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13 pages, 3904 KiB

Open AccessArticle

Structural Changes of Highly Active Pd/MeO_x (Me = Fe, Co, Ni) during Catalytic Methane Combustion

by Dominik Seeburg¹, Dongjing Liu^1,2, Joerg Radnik^1,3

, Hanan Atia¹, Marga-Martina Pohl¹, Matthias Schneider¹, Andreas Martin¹ and Sebastian Wohlrab^1,*

¹ Leibniz Institute for Catalysis at the University of Rostock, Albert-Einstein-Str. 29a, D-18059 Rostock, Germany

² School of Energy and Power Engineering, Jiangsu University, Xuefu Str. 301, Zhenjiang 212013, China

³ Federal Institute of Materials Testing and Research (BAM), Unter den Eichen 44-46, D-12203 Berlin, Germany

Catalysts 2018, 8(2), 42; https://doi.org/10.3390/catal8020042 - 23 Jan 2018

Cited by 21 | Viewed by 5250

Abstract

Fe₂O₃, Co₃O₄ and NiO nanoparticles were prepared via a citrate method and further functionalized with Pd by impregnation. The pure oxides as well as Pd/Fe₂O₃, Pd/Co₃O₄, and Pd/NiO [...] Read more.

Fe₂O₃, Co₃O₄ and NiO nanoparticles were prepared via a citrate method and further functionalized with Pd by impregnation. The pure oxides as well as Pd/Fe₂O₃, Pd/Co₃O₄, and Pd/NiO (1, 5 and 10 wt % Pd) were employed for catalytic methane combustion under methane lean (1 vol %)/oxygen rich (18 vol %, balanced with nitrogen) conditions. Already, the pure metal oxides showed a high catalytic activity leading to complete conversion temperature of T₁₀₀ ≤ 500 °C. H₂-TPR (Temperature-programmed reduction) experiments revealed that Pd-functionalized metal oxides exhibited enhanced redox activity compared to the pure oxides leading to improved catalytic combustion activity at lower temperatures. At a loading of 1 wt % Pd, 1Pd/Co₃O₄ (T₁₀₀ = 360 °C) outperforms 1Pd/Fe₂O₃ (T₁₀₀ = 410 °C) as well as 1Pd/NiO (T₁₀₀ = 380 °C). At a loading of 10 wt % Pd, T₁₀₀ could only be slightly reduced in all cases. 1Pd/Co₃O₄ and 1Pd/NiO show reasonable stability over 70 h on stream at T₁₀₀. XPS (X-ray photoelectron spectroscopy) and STEM (Scanning transmission electron microscopy) investigations revealed strong interactions between Pd and NiO as well as Co₃O₄, respectively, leading to dynamic transformations and reoxidation of Pd due to solid state reactions, which leads to the high long-term stability. Full article

(This article belongs to the Special Issue Commemorative Issue in Honor of Professor Emeritus Calvin H. Bartholomew in Anticipation of His 75th Birthday)

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13 pages, 5361 KiB

Open AccessArticle

Continuous-Flow Photocatalytic Degradation of Organics Using Modified TiO₂ Nanocomposites

by Imran Ali

and Jong-Oh Kim^*

Department of Civil and Environmental Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04763, Korea

Catalysts 2018, 8(2), 43; https://doi.org/10.3390/catal8020043 - 24 Jan 2018

Cited by 26 | Viewed by 6153

Abstract

In this study, TiO₂ nanotubes (TNTs) were fabricated on a Ti sheet following the anodic oxidation method and were decorated with reduced graphene oxide (RGO), graphene oxide (GO), and bismuth (Bi) via electrodeposition. The surface morphologies, crystal structures, and compositions of the [...] Read more.

In this study, TiO₂ nanotubes (TNTs) were fabricated on a Ti sheet following the anodic oxidation method and were decorated with reduced graphene oxide (RGO), graphene oxide (GO), and bismuth (Bi) via electrodeposition. The surface morphologies, crystal structures, and compositions of the catalyst were characterized by field emission scanning electron microscopy, Auger electron spectroscopy, X-ray diffraction, photoluminance spectra, X-ray photoelectron spectroscopy, and energy dispersive X-ray spectroscopy. The TNTs loaded with RGO, GO, and Bi were used in a continuous-flow system as photocatalysts for the degradation of methylene blue (MB) dye. It was found that the TNTs are efficient photocatalysts for the removal of color from water; upon UV irradiation on TNTs, the MB removal ratio was ~89%. Moreover, the photocatalytic activities of the decorated TNTs were higher than that of pristine TNTs in visible light. In comparison with TNTs, the rate of MB removal in visible light was increased by a factor of 3.4, 3.2, and 2.9 using RGO-TNTs, Bi-TNTs, and GO-TNTs, respectively. The reusability of the catalysts were investigated, and their quantum efficiencies were also calculated. The cylindrical anodized TNTs were excellent photocatalysts for the degradation of organic pollutants. Thus, it was concluded that the continuous-flow photocatalytic reactor comprising TNTs and modified TNTs is suitable for treating wastewater in textile industries. Full article

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15 pages, 9012 KiB

Open AccessArticle

Synthesis of Ag₃PO₄/G-C₃N₄ Composite with Enhanced Photocatalytic Performance for the Photodegradation of Diclofenac under Visible Light Irradiation

by Wei Zhang, Li Zhou, Jun Shi^* and Huiping Deng^*

State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China

Catalysts 2018, 8(2), 45; https://doi.org/10.3390/catal8020045 - 25 Jan 2018

Cited by 97 | Viewed by 8622

Abstract

A new visible-light-driven heterojunction Ag₃PO₄/g-C₃N₄ was prepared by a simple deposition-precipitation method for the degradation analysis of diclofenac (DCF), a model drug component, under visible-light irradiation. The heterojunction photocatalysts were characterized by a suite of tools. [...] Read more.

A new visible-light-driven heterojunction Ag₃PO₄/g-C₃N₄ was prepared by a simple deposition-precipitation method for the degradation analysis of diclofenac (DCF), a model drug component, under visible-light irradiation. The heterojunction photocatalysts were characterized by a suite of tools. The results revealed that the introduction of Ag₃PO₄ on the surface of g-C₃N₄ greatly promoted its stability and light absorption performance. In addition, the effects of the heterojunction mixing ratios were studied, when the molar ratio of Ag₃PO₄ to g-C₃N₄ in the composite was 30%, the as-prepared photocatalyst Ag₃PO₄/g-C₃N₄ (30%) possessed the best photocatalytic activity toward the photodegradation of DCF, and the optimal photocatalyst showed a DCF degradation rate of 0.453 min⁻¹, which was almost 34.8 and 6.4 times higher than those of pure g-C₃N₄ (0.013 min⁻¹) and Ag₃PO₄ (0.071 min⁻¹) under visible light irradiation (λ ≥ 400 nm). The trapping experimental results showed that h⁺, ·OH, and ·O₂⁻ were the main reactive oxygen species during the photocatalytic reaction. The improved performance of the composites was induced by the high charge separation efficiency of the photogeneration electron-hole pairs as well as the surface plasmon resonance (SPR) endowed in the Ag⁰ nanoparticles, and ultimately enhanced the DCF photodegradation. Full article

(This article belongs to the Special Issue Organic Photoredox Catalysis)

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9 pages, 906 KiB

Open AccessCommunication

Synthesis of New C₂-Symmetric Six-Membered NHCs and Their Application for the Asymmetric Diethylzinc Addition of Arylaldehydes

by Jie Li¹, Bihui Zhou¹, Yajie Jiang¹ and Xiaoming Liu^2,*

¹ School of Medicine, Zhejiang University City College, No. 48, Huzhou Road, Hangzhou 310015, China

² Department of Dermatologry, The Third Affiliated Hospital of Soochow University, No. 185, Juqian Street, Changzhou 213000, China

Catalysts 2018, 8(2), 46; https://doi.org/10.3390/catal8020046 - 26 Jan 2018

Cited by 7 | Viewed by 3637

Abstract

A concise method for the preparation of new 3,4,5,6-tetrahydropyrimidinium salts was presented in this paper. Further application of these salts in asymmetric diethylzinc addition of arylaldehydes was explored, giving the corresponding chiral second alcohols in good yields and moderate enantioselectivities. Full article

(This article belongs to the Special Issue Asymmetric Catalysis in Organic Synthesis)

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14 pages, 1644 KiB

Open AccessArticle

EPR Investigations of G-C₃N₄/TiO₂ Nanocomposites

by Dana Dvoranová¹, Milan Mazúr¹, Ilias Papailias²

, Tatiana Giannakopoulou²

, Christos Trapalis² and Vlasta Brezová^1,*

¹ Institute of Physical Chemistry and Chemical Physics, Faculty of Chemical and Food Technology, Slovak University of Technology in Bratislava, Radlinského 9, SK-812 37 Bratislava, Slovakia

² Institute of Nanoscience and Nanotechnology, National Center for Scientific Research “Demokritos”, 153 43 Agia Paraskevi, Attikis, Greece

Catalysts 2018, 8(2), 47; https://doi.org/10.3390/catal8020047 - 26 Jan 2018

Cited by 43 | Viewed by 9995

Abstract

The g-C₃N₄/TiO₂ nanopowders prepared by the annealing of melamine and TiO₂ P25 at 550 °C were investigated under dark and upon UV or visible-light photoactivation using X- and Q-band electron paramagnetic resonance (EPR) spectroscopy. The EPR spectra [...] Read more.

The g-C₃N₄/TiO₂ nanopowders prepared by the annealing of melamine and TiO₂ P25 at 550 °C were investigated under dark and upon UV or visible-light photoactivation using X- and Q-band electron paramagnetic resonance (EPR) spectroscopy. The EPR spectra of powders monitored at room temperature and 100 K showed the impact of the initial loading ratio of melamine/TiO₂ on the character of paramagnetic centers observed. For the photocatalysts synthesized using a lower titania content, the paramagnetic signals characteristic for the g-C₃N₄/TiO₂ nanocomposites were already found before exposure. The samples annealed using the higher TiO₂ loading revealed the photoinduced generation of paramagnetic nitrogen bulk centers (g-tensor components g₁ = 2.005, g₂ = 2.004, g₃ = 2.003 and hyperfine couplings from the nitrogen A₁ = 0.23 mT, A₂ = 0.44 mT, A₃ = 3.23 mT) typical for N-doped TiO₂. The ability of photocatalysts to generate reactive oxygen species (ROS) upon in situ UV or visible-light photoexcitation was tested in water or dimethyl sulfoxide by EPR spin trapping using 5,5-dimethyl 1-pyrroline N-oxide. The results obtained reflect the differences in photocatalyst nanostructures caused by the differing initial ratio of melamine/TiO₂; the photocatalyst prepared by the high-temperature treatment of melamine/TiO₂ wt. ratio of 1:3 revealed an adequate photoactivity in both spectral regions. Full article

(This article belongs to the Special Issue Photocatalytic materials alternative to TiO₂ for environmental remediation, sustainable chemistry and energy conversion)

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10 pages, 2991 KiB

Open AccessArticle

Highly Efficient Acetalization and Ketalization Catalyzed by Cobaloxime under Solvent-Free Condition

by Yang Zong^1,2, Liting Yang¹, Shanyu Tang¹, Longjia Li¹, Wanjie Wang², Bingxin Yuan^1,* and Guanyu Yang¹

¹ College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou 450001, China

² School of Material Science and Engineering, Zhengzhou University, Zhengzhou 450001, China

Catalysts 2018, 8(2), 48; https://doi.org/10.3390/catal8020048 - 26 Jan 2018

Cited by 14 | Viewed by 5171

Abstract

An efficient catalytic system was developed for the acetalization and ketalization of carbonyl compounds with polyhydric alcohols under mild solvent-free conditions. In the presence of 0.1 mol% CoCl₂ and 0.2 mol% dimethylglyoxime at 70 °C under 5 KPa pressure for 1 h, [...] Read more.

An efficient catalytic system was developed for the acetalization and ketalization of carbonyl compounds with polyhydric alcohols under mild solvent-free conditions. In the presence of 0.1 mol% CoCl₂ and 0.2 mol% dimethylglyoxime at 70 °C under 5 KPa pressure for 1 h, 95.3% conversion of cyclohexanone and 100% selectivity of the corresponding cyclic ketal could be obtained, where TOF reached as high as 953 h⁻¹. It is proposed that the in situ generated planartetracoordinate cobaloxime played the key role in the catalytic cycle and was responsible for the excellent catalytic performance. Full article

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14 pages, 3914 KiB

Open AccessArticle

Direct Hydroxylation of Benzene to Phenol over TS-1 Catalysts

by Yuecheng Luo, Jiahui Xiong, Conglin Pang, Guiying Li^* and Changwei Hu^*

Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064, Sichuan, China

Catalysts 2018, 8(2), 49; https://doi.org/10.3390/catal8020049 - 26 Jan 2018

Cited by 33 | Viewed by 7159

Abstract

We synthesized a TS-1 catalyst to directly hydroxylate benzene to phenol with H₂O₂ as oxidant and water as solvent. The samples were characterized by FT-IR (Fourier Transform Infrared), DR UV-Vis (Diffused Reflectance Ultraviolet Visible), XRD (X-ray diffraction), SEM(scanning electron microscope), [...] Read more.

We synthesized a TS-1 catalyst to directly hydroxylate benzene to phenol with H₂O₂ as oxidant and water as solvent. The samples were characterized by FT-IR (Fourier Transform Infrared), DR UV-Vis (Diffused Reflectance Ultraviolet Visible), XRD (X-ray diffraction), SEM(scanning electron microscope), TEM (Transmission Electron Microscope), XPS (X-ray photoelectron spectroscopy), ICP (inductively coupled plasma spectrum), and N₂ adsorption-desorption. A desirable phenol yield of 39% with 72% selectivity was obtained under optimized conditions: 0.15 g (0.34 to the mass of benzene) TS-1, 5.6 mmol C₆H₆, reaction time 45 min, 0.80 mL H₂O₂ (30%), 40.0 mL H₂O, and reaction temperature 70 °C. The reuse of the TS-1 catalyst illustrated that the catalyst had a slight loss of activity resulting from slight Ti leaching from the first run and then kept stable. Almost all of the Ti species added in the preparation were successfully incorporated into the TS-1 framework, which were responsible for the good catalytic activity. Extraframework Ti species were not selective for hydroxylation. Full article

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14 pages, 2215 KiB

Open AccessFeature PaperArticle

Vine Shoots and Grape Stalks as Carbon Sources for Hydrogen Evolution Reaction Electrocatalyst Supports

by J.A.S.B. Cardoso¹

, B. Šljukić¹

, M. Erdem²

, C.A.C. Sequeira¹

and D.M.F. Santos^1,*

¹ Center of Physics and Engineering of Advanced Materials (CeFEMA), Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisbon, Portugal

² Department of Environmental Engineering, Fırat University, 23279 Elazığ, Turkey

Catalysts 2018, 8(2), 50; https://doi.org/10.3390/catal8020050 - 27 Jan 2018

Cited by 11 | Viewed by 4930

Abstract

Activated bio-based carbons produced from vine shoots (VSAC) and grape stalks (GSAC), which have larger surface area and total pore volume than most of the commercially available activated carbons, are used as supports for palladium nanoparticles (Pd NPs). The prepared materials are characterised [...] Read more.

Activated bio-based carbons produced from vine shoots (VSAC) and grape stalks (GSAC), which have larger surface area and total pore volume than most of the commercially available activated carbons, are used as supports for palladium nanoparticles (Pd NPs). The prepared materials are characterised by elemental analysis, N₂-sorption, X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, and transmission electron microscopy analysis and are then assessed as potential cathodes for the hydrogen evolution reaction (HER) in alkaline media. The electrocatalysts’ performance for HER is evaluated from cathodic polarisation curves at different temperatures and compared to that of Vulcan XC72-supported Pd NPs. Additional chronoamperometry studies helped to assess the electrocatalysts’ activity stability. The novel VSAC-supported Pd electrocatalyst exhibits good HER activity in terms of high current density at low overpotentials, leading to the best performance. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis & Hydrogen Storage)

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17 pages, 4638 KiB

Open AccessArticle

An MM and QM Study of Biomimetic Catalysis of Diels-Alder Reactions Using Cyclodextrins

by Wei Chen¹, Lipeng Sun³, Zhiye Tang¹, Zulfikhar A. Ali², Bryan M. Wong^2,*

and Chia-en A. Chang^1,*

¹ Department of Chemistry, University of California, Riverside, CA 92521, USA

² Department of Chemical & Environmental Engineering and Materials Science & Engineering Program, University of California, Riverside, CA 92521, USA

³ Illinois Rocstar LLC, P.O. Box 3001, Champaign, IL 61826, USA

Catalysts 2018, 8(2), 51; https://doi.org/10.3390/catal8020051 - 29 Jan 2018

Cited by 8 | Viewed by 4970

Abstract

We performed a computational investigation of the mechanism by which cyclodextrins (CDs) catalyze Diels-Alder reactions between 9-anthracenemethanol and N-cyclohexylmaleimide. Hydrogen bonds (Hbonds) between N-cyclohexylmaleimide and the hydroxyl groups of cyclodextrins were suggested to play an important role in this catalytic process. [...] Read more.

We performed a computational investigation of the mechanism by which cyclodextrins (CDs) catalyze Diels-Alder reactions between 9-anthracenemethanol and N-cyclohexylmaleimide. Hydrogen bonds (Hbonds) between N-cyclohexylmaleimide and the hydroxyl groups of cyclodextrins were suggested to play an important role in this catalytic process. However, our free energy calculations and molecular dynamics simulations showed that these Hbonds are not stable, and quantum mechanical calculations suggested that the reaction is not promoted by these Hbonds. The binding of 9-anthracenemethanol and N-cyclohexylmaleimide to cyclodextrins was the key to the catalytic process. Cyclodextrins act as a container to hold the two reactants in the cavity, pre-organize them for the reactions, and thus reduce the entropy penalty to the activation free energy. Dimethyl-β-CD was a better catalyst for this specific reaction than β-CD because of its stronger van der Waals interaction with the pre-organized reactants and its better performance in reducing the activation energy. This computational work sheds light on the mechanism of the catalytic reaction by cyclodextrins and introduces new perspectives of supramolecular catalysis. Full article

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16 pages, 5115 KiB

Open AccessArticle

Relations between Structure, Activity and Stability in C₃N₄ Based Photocatalysts Used for Solar Hydrogen Production

by Ramesh P. Sivasankaran¹, Nils Rockstroh¹

, Dirk Hollmann¹

, Carsten R. Kreyenschulte¹

, Giovanni Agostini¹, Henrik Lund¹

, Amitava Acharjya², Jabor Rabeah¹

, Ursula Bentrup¹, Henrik Junge¹, Arne Thomas² and Angelika Brückner^1,*

¹ Leibniz Institute for Catalysis at the University of Rostock, Albert-Einstein-Str. 29a, 18059 Rostock, Germany

² Department of Chemistry, Technical University Berlin, Hardenbergstr. 40, 10623 Berlin, Germany

Catalysts 2018, 8(2), 52; https://doi.org/10.3390/catal8020052 - 29 Jan 2018

Cited by 14 | Viewed by 6583

Abstract

Solar hydrogen production from water could be a sustainable and environmentally friendly alternative to fossil energy carriers, yet so far photocatalysts active and stable enough for large-scale applications are not available, calling for advanced research efforts. In this work, H₂ evolution rates [...] Read more.

Solar hydrogen production from water could be a sustainable and environmentally friendly alternative to fossil energy carriers, yet so far photocatalysts active and stable enough for large-scale applications are not available, calling for advanced research efforts. In this work, H₂ evolution rates of up to 1968 and 5188 μmol h⁻¹ g⁻¹ were obtained from aqueous solutions of triethanolamine (TEOA) and oxalic acid (OA), respectively, by irradiating composites of AgIn₅S₈ (AIS), mesoporous C₃N₄ (CN, surface area >150 m²/g) and ≤2 wt.% in-situ photodeposited Pt nanoparticles (NPs) with UV-vis (≥300 nm) and pure visible light (≥420 nm). Structural properties and electron transport in these materials were analyzed by XRD, STEM-HAADF, XPS, UV-vis-DRS, ATR-IR, photoluminescence and in situ-EPR spectroscopy. Initial H₂ formation rates were highest for Pt/CN, yet with TEOA this catalyst deactivated by inclusion of Pt NPs in the matrix of CN (most pronounced at λ ≥ 300 nm) while it remained active with OA, since in this case Pt NPs were enriched on the outermost surface of CN. In Pt/AIS-CN catalysts, Pt NPs were preferentially deposited on the surface of the AIS phase which prevents them from inclusion in the CN phase but reduces simultaneously the initial H₂ evolution rate. This suggests that AIS hinders transport of separated electrons from the CN conduction band to Pt NPs but retains the latter accessible by protons to produce H₂. Full article

(This article belongs to the Special Issue Photocatalytic materials alternative to TiO₂ for environmental remediation, sustainable chemistry and energy conversion)

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16 pages, 4513 KiB

Open AccessArticle

Carbon-Supported Copper-Based Nitrogen-Containing Supramolecule as an Efficient Oxygen Reduction Reaction Catalyst in Neutral Medium

by Yuanyuan Zhao¹, Ya Chu¹, Xiuping Ju², Jinsheng Zhao^1,*

, Lingqian Kong² and Yan Zhang¹

¹ Department of Chemistry, Liaocheng University, Liaocheng 252059, China

² Dongchang College, Liaocheng University, Liaocheng 252059, China

Catalysts 2018, 8(2), 53; https://doi.org/10.3390/catal8020053 - 30 Jan 2018

Cited by 30 | Viewed by 6177

Abstract

In this work, a nitrogen-containing bidentate ligand named 5,5′-(9-octyl-9H-carbazole-2,7-diyl)bis(1,10-phenanthroline) (OCBP) was synthesized as a nitrogen precursor for making an oxygen reduction catalyst. The 1,10-phenanthroline unit provides a coordination site for copper ions, and the resulting Cu-N_x unit may be responsible for the [...] Read more.

In this work, a nitrogen-containing bidentate ligand named 5,5′-(9-octyl-9H-carbazole-2,7-diyl)bis(1,10-phenanthroline) (OCBP) was synthesized as a nitrogen precursor for making an oxygen reduction catalyst. The 1,10-phenanthroline unit provides a coordination site for copper ions, and the resulting Cu-N_x unit may be responsible for the catalytic activities of the catalyst. Carbon black was selected as a support to improve the electroconductibility of the resulting catalyst. The metallo-supramolecule (Cu-SOCBP) was dispersed on the surface of Vulcan XC-72 carbon and was used as a catalyst (designated as Cu-SOCBP/C) for the oxygen reduction reaction (ORR). The microscope structure and surface components of the catalyst were acquired via scanning electron microscopy and X-ray photoelectron spectroscopy, as well as X-ray powder diffraction. The electrochemical property and ORR mechanism of Cu-SOCBP/C were analyzed using a variety of electroanalytical methods including cyclic voltammetry, electrochemical impedance spectroscopy, and linear sweep voltammetry. These results show that Cu-SOCBP/C was successfully synthesized and that ORR was achieved mainly via a four-electron transfer process to water. Thus, Cu-SOCBP/C was an effective catalyst and might have potential application as a cathodic catalyst in microbial fuel cells, which operate in an aqueous medium. Full article

(This article belongs to the Special Issue Platinum-Free Electrocatalysts)

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13 pages, 2739 KiB

Open AccessFeature PaperArticle

Exploring the Effect of Au/Pt Ratio on Glycerol Oxidation in Presence and Absence of a Base

by Alberto Villa^1,*

, Andrea Jouve¹, Felipe J. Sanchez Trujillo², Davide Motta², Laura Prati¹

and Nikolaos Dimitratos^2,*

¹ Dipartimento di Chimica, Università degli Studi di Milano, via Golgi 19, I-20133 Milano, Italy

² Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK

Catalysts 2018, 8(2), 54; https://doi.org/10.3390/catal8020054 - 31 Jan 2018

Cited by 25 | Viewed by 5690

Abstract

Bimetallic AuPt nanoparticles with different Au:Pt ratios (molar ratio: 9-1, 8-2, 6-4, 2-8, 1-9) and the corresponding Au and Pt monometallic ones were prepared by sol immobilization and immobilized on commercial TiO₂ (P25). The catalytic activity was evaluated in the liquid phase [...] Read more.

Bimetallic AuPt nanoparticles with different Au:Pt ratios (molar ratio: 9-1, 8-2, 6-4, 2-8, 1-9) and the corresponding Au and Pt monometallic ones were prepared by sol immobilization and immobilized on commercial TiO₂ (P25). The catalytic activity was evaluated in the liquid phase glycerol oxidation in presence and absence of a base (NaOH). It was found that the Au:Pt molar ratio and reaction conditions strongly influence the catalytic performance. In the presence of NaOH, Au-rich catalysts were more active than Pt-rich ones, with the highest activity observed for Au₉Pt₁/TiO₂ (6575 h⁻¹). In absence of a base, a higher content of Pt is needed to produce the most active catalyst (Au₆Pt₄/TiO₂, 301 h⁻¹). In terms of selectivity, in presence of NaOH, Au-rich catalysts showed a high selectivity to C3 products (63–72%) whereas Pt-rich catalysts promote the formation of formic and glycolic acids. The opposite trend was observed in absence of a base with Pt-rich catalysts showing higher selectivity to C3 products (83–88%). Full article

(This article belongs to the Special Issue Glycerol Conversion by Heterogeneous Catalysis)

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12 pages, 2297 KiB

Open AccessFeature PaperEditor’s ChoiceCommunication

Whole-Cell Biocatalyst for Chemoenzymatic Total Synthesis of Rivastigmine

by Paola Vitale^1,2,*

, Filippo Maria Perna^1,2

, Gennaro Agrimi^3,4

, Isabella Pisano^3,4, Francesco Mirizzi¹, Roberto Vito Capobianco¹ and Vito Capriati^1,2,*

¹ Dipartimento di Farmacia-Scienze del Farmaco, Università degli Studi di Bari «Aldo Moro», Via E. Orabona 4, I-70125 Bari, Italy

² Consorzio C.I.N.M.P.I.S., Dipartimento di Farmacia-Scienze del Farmaco, Via E. Orabona 4, I-70125 Bari, Italy

³ Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari «Aldo Moro», Via E. Orabona 4, I-70125 Bari, Italy

⁴ Consorzio CIRCC, Via Celso Ulpiani 27, I-70126 Bari, Italy

Catalysts 2018, 8(2), 55; https://doi.org/10.3390/catal8020055 - 31 Jan 2018

Cited by 49 | Viewed by 7523

Abstract

Biocatalytic processes are increasingly playing a key role in the development of sustainable asymmetric syntheses, which are central to pharmaceutical companies for the production of chiral enantiopure drugs. This work describes a simple and economically viable chemoenzymatic process for the production of ( [...] Read more.

Biocatalytic processes are increasingly playing a key role in the development of sustainable asymmetric syntheses, which are central to pharmaceutical companies for the production of chiral enantiopure drugs. This work describes a simple and economically viable chemoenzymatic process for the production of (S)-rivastigmine, which is an important drug for the treatment of mild to moderate dementia of the Alzheimer’s type. The described protocol involves the R-regioselective bioreduction of an aromatic ketone by Lactobacillus reuteri DSM 20016 whole cells in phosphate buffered saline (PBS) (37 °C, 24 h) as a key step. Biocatalytic performance of baker’s yeast whole cells in water and in aqueous eutectic mixtures have been evaluated and discussed as well. The route is scalable, environmentally friendly, and the target drug is obtained via four steps in overall 78% yield and 98% ee. Full article

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18 pages, 4707 KiB

Open AccessArticle

Catalytic Activity Studies of Vanadia/Silica–Titania Catalysts in SVOC Partial Oxidation to Formaldehyde: Focus on the Catalyst Composition

by Niina Koivikko^1,*, Tiina Laitinen¹, Anass Mouammine^1,2, Satu Ojala¹ and Riitta L. Keiski¹

¹ Environmental and Chemical Engineering (ECE), Faculty of Technology, University of Oulu, P.O. Box 4300, FI-90014 Oulu, Finland

² Laboratory of Catalysis and Corrosion of Materials (LCCM), Department of Chemistry, Faculty of Sciences, University of Chouaïb Doukkali, 20 Route de Ben Maachou, 24000 El Jadida, Morocco

Catalysts 2018, 8(2), 56; https://doi.org/10.3390/catal8020056 - 2 Feb 2018

Cited by 19 | Viewed by 6811

Abstract

In this work, silica–titania supported catalysts were prepared by a sol–gel method with various compositions. Vanadia was impregnated on SiO₂-TiO₂ with different loadings, and materials were investigated in the partial oxidation of methanol and methyl mercaptan to formaldehyde. The materials [...] Read more.

In this work, silica–titania supported catalysts were prepared by a sol–gel method with various compositions. Vanadia was impregnated on SiO₂-TiO₂ with different loadings, and materials were investigated in the partial oxidation of methanol and methyl mercaptan to formaldehyde. The materials were characterized by using N₂ physisorption, X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), X-ray photoelectron spectroscopy (XPS), Scanning transmission electron microscope (STEM), NH₃-TPD, and Raman techniques. The activity results show the high importance of an optimized SiO₂-TiO₂ ratio to reach a high reactant conversion and formaldehyde yield. The characteristics of mixed oxides ensure a better dispersion of the active phase on the support and in this way increase the activity of the catalysts. The addition of vanadium pentoxide on the support lowered the optimal temperature of the reaction significantly. Increasing the vanadia loading from 1.5% to 2.5% did not result in higher formaldehyde concentration. Over the 1.5%V₂O₅/SiO₂ + 30%TiO₂ catalyst, the optimal selectivity was reached at 415 °C when the maximum formaldehyde concentration was ~1000 ppm. Full article

(This article belongs to the Special Issue New Concepts in Oxidation Processes)

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19 pages, 6432 KiB

Open AccessArticle

Ag₃PO₄-TiO₂-Graphene Oxide Ternary Composites with Efficient Photodegradation, Hydrogen Evolution, and Antibacterial Properties

by Fu-Jye Sheu¹, Chun-Pei Cho^1,*

, Yu-Ting Liao² and Chang-Tze Yu²

¹ Department of Applied Materials and Optoelectronic Engineering, National Chi Nan University, Nantou County 54561, Taiwan

² Department of Applied Chemistry, National Chi Nan University, Nantou County 54561, Taiwan

Catalysts 2018, 8(2), 57; https://doi.org/10.3390/catal8020057 - 2 Feb 2018

Cited by 45 | Viewed by 6026

Abstract

Ag₃PO₄-TiO₂-graphene oxide ternary composite photocatalysts were fabricated by the photocatalytic reduction and ion exchange methods. The properties and photocatalytic activity of the composites were examined, and the photodegradation mechanism was investigated. More TiO₂ nanoparticles in the [...] Read more.

Ag₃PO₄-TiO₂-graphene oxide ternary composite photocatalysts were fabricated by the photocatalytic reduction and ion exchange methods. The properties and photocatalytic activity of the composites were examined, and the photodegradation mechanism was investigated. More TiO₂ nanoparticles in the composites were found to improve light absorption, but caused a larger impedance and inferior charge transport. Excess TiO₂ nanoparticles distributed over the surfaces of Ag₃PO₄ and graphene oxide decreased the specific surface area and thus lowered light absorbance. An appropriate TiO₂ content enhanced photocatalytic performance. When the molar ratio of Ag₃PO₄ to TiO₂ was 0.6, the highest efficiency in photodegradation, hydrogen production (with a quantum efficiency of 8.1% and a hydrogen evolution rate of 218.7 μmole·g⁻¹·h⁻¹) and bacterial inactivation was achieved. Trapping experiments demonstrated that superoxide radicals and holes are the major active species involved in the photodegradation process. Full article

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18 pages, 9708 KiB

Open AccessArticle

Highly Selective Continuous Flow Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol in a Pt/SiO₂ Coated Tube Reactor

by Yang Bai¹, Nikolay Cherkasov^1,2

, Steven Huband³, David Walker³

, Richard I. Walton⁴ and Evgeny Rebrov^1,2,5,*

¹ Stoli Catalysts Ltd., Coventry CV3 4DS, UK

² School of Engineering, University of Warwick, Coventry CV4 7AL, UK

³ Department of Physics, University of Warwick, Coventry CV4 7AL, UK

⁴ Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK

⁵ Department of Biotechnology and Chemistry, Tver State Technical University, Nab. A. Nikitina 22, Tver 170026, Russia

Catalysts 2018, 8(2), 58; https://doi.org/10.3390/catal8020058 - 2 Feb 2018

Cited by 35 | Viewed by 9754

Abstract

A novel continuous flow process for selective hydrogenation of α, β-unsaturated aldehyde (cinnamaldehyde, CAL) to the unsaturated alcohol (cinnamyl alcohol, COL) has been reported in a tube reactor coated with a Pt/SiO₂ catalyst. A 90% selectivity towards the unsaturated alcohol was obtained [...] Read more.

A novel continuous flow process for selective hydrogenation of α, β-unsaturated aldehyde (cinnamaldehyde, CAL) to the unsaturated alcohol (cinnamyl alcohol, COL) has been reported in a tube reactor coated with a Pt/SiO₂ catalyst. A 90% selectivity towards the unsaturated alcohol was obtained at the aldehyde conversion of 98.8%. This is a six-fold improvement in the selectivity compared to a batch process where acetals were the main reaction products. The increased selectivity in the tube reactor was caused by the suppression of acid sites responsible for the acetal formation after a short period on stream in the continuous process. In a fixed bed reactor, it had a similar acetal suppression phenomenon but showed lower product selectivity of about 47–72% due to mass transfer limitations. A minor change in selectivity and conversion caused by product inhibition was observed during the 110 h on stream with a turnover number (TON) reaching 3000 and an alcohol production throughput of 0.36 kg g_Pt⁻¹ day⁻¹ in the single tube reactor. The catalysts performance after eight reaction cycles was fully restored by calcination in air at 400 °C. The tube reactors provide an opportunity for process intensification by increasing the reaction rates by a factor of 2.5 at the reaction temperature of 150 °C compared to 90 °C with no detrimental effects on catalyst stability or product selectivity. Full article

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16 pages, 4414 KiB

Open AccessArticle

Co-Processing of Jatropha-Derived Bio-Oil with Petroleum Distillates over Mesoporous CoMo and NiMo Sulfide Catalysts

by Shih-Yuan Chen^1,*

, Masayasu Nishi¹, Takehisa Mochizuki¹, Hideyuki Takagi¹, Akira Takatsuki¹, Wuttichai Roschat^2,3, Makoto Toba¹ and Yuji Yoshimura⁴

¹ Research Institute of Energy Frontier (RIEF), Department of Energy and Environment, National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba, Ibaraki 305-8569, Japan

² Program of Chemistry, Faculty of Science and Technology, Sakon Nakhon Rajabhat University, 680 Nittayo Rd., Mueang District, Sakon Nakhon 47000, Thailand

³ Center of Excellence on Alternative Energy, Research and Development Institute, Sakon Nakhon Rajabhat University, 680 Nittayo Rd., Mueang District, Sakon Nakhon 47000, Thailand

⁴ Materials for Energy Research Unit, National Metal and Materials Technology Center (MTEC), Pahonyothin Rd. Klong 1, Klong Luang Pathumtani 12120, Thailand

Catalysts 2018, 8(2), 59; https://doi.org/10.3390/catal8020059 - 2 Feb 2018

Cited by 23 | Viewed by 5738

Abstract

The co-processing of an unconventional type of Jatropha bio-oil with petroleum distillates over mesoporous alumina-supported CoMo and NiMo sulfide catalysts (denoted CoMo/γ-Al₂O₃ and NiMo/γ-Al₂O₃) was studied. Either a stainless-steel high-pressure batch-type reactor or an up-flow fixed-bed [...] Read more.

The co-processing of an unconventional type of Jatropha bio-oil with petroleum distillates over mesoporous alumina-supported CoMo and NiMo sulfide catalysts (denoted CoMo/γ-Al₂O₃ and NiMo/γ-Al₂O₃) was studied. Either a stainless-steel high-pressure batch-type reactor or an up-flow fixed-bed reaction system was used under severe reaction conditions (330–350 °C and 5–7 MPa), similar to the conditions of the conventional diesel hydrodesulfurization (HDS) process. To understand the catalytic performance of the mesoporous sulfide catalysts for co-processing, we prepared two series of oil feedstocks. First, model diesel oils, consisting of hydrocarbons and model molecules with various heteroatoms (sulfur, oxygen, and nitrogen) were used for the study of the reaction mechanisms. Secondly, low-grade oil feedstocks, which were prepared by dissolving of an unconventional type of Jatropha bio-oil (ca. 10 wt %) in the petroleum distillates, were used to study the practical application of the catalysts. Surface characterization by gas sorption, spectroscopy, and electron microscopy indicated that the CoMo/γ-Al₂O₃ sulfide catalyst, which has a larger number of acidic sites and coordinatively unsaturated sites (CUS) on the mesoporous alumina framework, was associated with small Co-incorporated MoS₂-like slabs with high stacking numbers and many active sites at the edges and corners. In contrast, the NiMo/γ-Al₂O₃ sulfide catalyst, which had a lower number of acidic sites and CUS on mesoporous alumina framework, was associated with large Ni-incorporated MoS₂-like slabs with smaller stacking numbers, yielding more active sites at the brims and corresponding to high hydrogenation (HYD) activity. Concerning the catalytic performance, the mesoporous CoMo/γ-Al₂O₃ sulfide catalyst with large CUS number was highly active for the conventional diesel HDS process; unfortunately, it was deactivated when oxygen- and nitrogen-containing model molecules or Jatropha bio-oil were present in the oil feedstock. In contrast, the mesoporous NiMo/γ-Al₂O₃ sulfide catalyst, which had a high HYD activity and low affinity for heteroatoms, was efficient in the simultaneous removal of those heteroatoms from model diesel oils, and, in particular, Jatropha bio-oil co-fed with petroleum distillates. This could allow the production of a drop-in diesel-like fuel, which would be a greener fuel and reduce the CO₂ emissions and hazardous exhaust gases produced by the transport sector, reducing the burden on the environment. Full article

(This article belongs to the Special Issue Porous Materials in Catalysis)

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13 pages, 3222 KiB

Open AccessArticle

Selective Hydrogenation of Cinnamaldehyde Catalyzed by ZnO-Fe₂O₃ Mixed Oxide Supported Gold Nanocatalysts

by Wei Wang^1,2, Yan Xie^1,*, Shaohua Zhang¹, Xing Liu¹, Masatake Haruta^1,3 and Jiahui Huang^1,*

¹ Gold Catalysis Research Center, State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian 116023, China

² University of Chinese Academy of Sciences, Beijing 100049, China

³ Research Center for Gold Chemistry, Department of Applied Chemistry, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University, 1-1 Minami-osawa, Hachioji, Tokyo 192-0379, Japan

Catalysts 2018, 8(2), 60; https://doi.org/10.3390/catal8020060 - 3 Feb 2018

Cited by 26 | Viewed by 6156

Abstract

ZnO-Fe₂O₃ mixed oxides and supported gold nanocatalysts were prepared by using coprecipitation and deposition–precipitation methods, respectively. Cinnamaldehyde hydrogenation over various ZnO-Fe₂O₃ mixed oxides supported gold nanocatalysts have been investigated at 140 °C and a hydrogen pressure of [...] Read more.

ZnO-Fe₂O₃ mixed oxides and supported gold nanocatalysts were prepared by using coprecipitation and deposition–precipitation methods, respectively. Cinnamaldehyde hydrogenation over various ZnO-Fe₂O₃ mixed oxides supported gold nanocatalysts have been investigated at 140 °C and a hydrogen pressure of 1.0 MPa. The molar ratio of Fe to Zn was found to greatly affect the selective hydrogenation catalytic activity of ZnO-Fe₂O₃ mixed oxide supported gold nanocatalysts. Among these supported gold nanocatalysts in this work, Au/Zn_0.7Fe_0.3O_x (Au loading of 1.74 wt %) exhibited the highest conversion of cinnamaldehyde and high selectivity to cinnamal alcohol. The excellent catalytic activity of Au/Zn_0.7Fe_0.3O_x was tightly associated with a large surface area, small gold nanoparticles, and good H₂ dissociation ability at low temperature. Full article

(This article belongs to the Collection Gold Catalysts)

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21 pages, 4778 KiB

Open AccessEditor’s ChoiceArticle

1,3-Diene Polymerization Mediated by Homoleptic Tetramethylaluminates of the Rare-Earth Metals

by Christoph O. Hollfelder, Lars N. Jende, Dominic Diether, Theresa Zelger, Rita Stauder, Cäcilia Maichle-Mössmer and Reiner Anwander^*

Institut für Anorganische Chemie, Eberhard-Karls-Universität Tübingen, 72076 Tübingen, Germany

Catalysts 2018, 8(2), 61; https://doi.org/10.3390/catal8020061 - 3 Feb 2018

Cited by 25 | Viewed by 6157

Abstract

During the past two decades homoleptic tetramethylaluminates of the trivalent rare-earth metals, Ln(AlMe₄)₃, have emerged as useful components for efficient catalyst design in the field of 1,3-diene polymerization. Previous work had focused on isoprene polymerization applying Ln(AlMe₄) [...] Read more.

During the past two decades homoleptic tetramethylaluminates of the trivalent rare-earth metals, Ln(AlMe₄)₃, have emerged as useful components for efficient catalyst design in the field of 1,3-diene polymerization. Previous work had focused on isoprene polymerization applying Ln(AlMe₄)₃ precatalysts with Ln = La, Ce, Pr, Nd, Gd and Y, in the presence of Et₂AlCl as an activator. Polymerizations employing Ln(AlMe₄)₃ with Ln = La, Y and Nd along with borate/borane co-catalysts [Ph₃C][B(C₆F₅)₄], [PhNMe₂H][B(C₆F₅)₄] and [B(C₆F₅)₃] were mainly investigated for reasons of comparison with ancillary ligand-supported systems (cf. half-sandwich complexes). The present study investigates into a total of eleven rare-earth elements, namely Ln = La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Y, Er and Lu. A full overview on the polymerization behavior of Ln(AlMe₄)₃ in the presence of perfluorinated borate/borane cocatalysts and R₂AlCl-type activators (R = Me, Et) is provided, probing the monomers isoprene and 1,3-butadiene (and preliminary ethylene). Virtually complete cis-1,4-selectivities are obtained for several catalyst/cocatalyst combinations (e.g., Gd(AlMe₄)₃/Me₂AlCl, >99.9%). Insights into the ‘black box’ of active species are obtained by indirect observations via screening of pre-reaction time and cocatalyst concentration. The microstructure of the polydienes is investigated by combined ¹H/¹³C NMR and ATR-IR spectroscopies. Furthermore, the reaction of [LuMe₆(Li(thf)_x)₃] with AlMe₃ has been applied as a new strategy for the efficient synthesis of Lu(AlMe₄)₃. The solid-state structures of Gd(AlMe₄)₃ and Tb(AlMe₄)₃ are reported. Full article

(This article belongs to the Special Issue Catalysts for the Controlled Polymerization of Conjugated Dienes)

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11 pages, 1215 KiB

Open AccessArticle

In-Situ Liquid Hydrogenation of m-Chloronitrobenzene over Fe-Modified Pt/Carbon Nanotubes Catalysts

by Feng Li^1,2, Jinrong Liang¹, Wenxi Zhu¹, Hua Song^1,*, Keliang Wang² and Cuiqin Li¹

¹ Provincial Key Laboratory of Oil & Gas Chemical Technology, College of Chemistry & Chemical Engineering, Northeast Petroleum University, Daqing 163318, China

² Key Laboratory of Enhanced oil & Gas Recovery of Education Ministry, College of Petroleum Engineering, Northeast Petroleum University, Daqing 163318, China

Catalysts 2018, 8(2), 62; https://doi.org/10.3390/catal8020062 - 4 Feb 2018

Cited by 14 | Viewed by 4736

Abstract

In-situ liquid-phase hydrogenation of m-chloronitrobenzene (m-CNB) based on aqueous-phase reforming (APR) of ethanol and catalytic hydrogenation was carried out over Fe-modified Pt/carbon nanotubes (CNTs) catalysts. The effects of Pt loading over CNTs and Fe modification on the catalytic performance of [...] Read more.

In-situ liquid-phase hydrogenation of m-chloronitrobenzene (m-CNB) based on aqueous-phase reforming (APR) of ethanol and catalytic hydrogenation was carried out over Fe-modified Pt/carbon nanotubes (CNTs) catalysts. The effects of Pt loading over CNTs and Fe modification on the catalytic performance of Pt/CNTs catalysts were studied. In-tube loading of Pt particles, compared with out-tube loading, considerably improved the catalytic activity. With in-tube loading, Fe-modified Pt/CNTs catalysts further improved the m-CNB in-situ hydrogenation performance. After Fe modification, Pt–Fe/CNTs catalysts formed, inside CNTs, a Pt–Fe alloy and iron oxides, which both improved catalytic hydrogenation performance and significantly enhanced ethanol APR hydrogen producing performance, thereby increasing the m-CNB in-situ hydrogenation reactivity. Full article

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20 pages, 6047 KiB

Open AccessFeature PaperArticle

In Situ UV-Visible Assessment of Iron-Based High-Temperature Water-Gas Shift Catalysts Promoted with Lanthana: An Extent of Reduction Study

by Basseem B. Hallac^1,†, Jared C. Brown^1,‡, Eli Stavitski², Roger G. Harrison³ and Morris D. Argyle^1,*

¹ Department of Chemical Engineering, Ira A. Fulton School of Engineering and Technology, Brigham Young University, 350 CB, Provo, UT 84602, USA

² Brookhaven National Laboratory, NSLS-II Building 743, Upton, NY 11973, USA

³ Department of Chemistry and Biochemistry, College of Physical and Mathematical Sciences, Brigham Young University, C209 BNSN, Provo, UT 84602, USA

^† Current address: Phillips 66, US Highway 60 & State Highway 123, Bartlesville, OK 74003, USA.

^‡ Current address: Micron Technology, 8000 S. Federal Way, P.O. Box 6, Boise, ID 83707, USA.

Catalysts 2018, 8(2), 63; https://doi.org/10.3390/catal8020063 - 4 Feb 2018

Cited by 8 | Viewed by 5497

Abstract

The extent of reduction of unsupported iron-based high-temperature water-gas shift catalysts with small (<5 wt %) lanthana contents was studied using UV-visible spectroscopy. Temperature- programmed reduction measurements showed that lanthana content higher than 0.5 wt % increased the extent of reduction to metallic [...] Read more.

The extent of reduction of unsupported iron-based high-temperature water-gas shift catalysts with small (<5 wt %) lanthana contents was studied using UV-visible spectroscopy. Temperature- programmed reduction measurements showed that lanthana content higher than 0.5 wt % increased the extent of reduction to metallic Fe, while 0.5 wt % of lanthana facilitated the reduction to Fe₃O₄. In situ measurements on the iron oxide catalysts using mass and UV-visible spectroscopies permitted the quantification of the extent of reduction under temperature-programmed reduction and high-temperature water-gas shift conditions. The oxidation states were successfully calibrated against normalized absorbance spectra of visible light using the Kubelka-Munk theory. The normalized absorbance relative to the fully oxidized Fe₂O₃ increased as the extent of reduction increased. XANES suggested that the average bulk iron oxidation state during the water-gas shift reaction was Fe^+2.57 for the catalyst with no lanthana and Fe^+2.54 for the catalysts with 1 wt % lanthana. However, the UV-vis spectra suggest that the surface oxidation state of iron would be Fe^+2.31 for the catalyst with 1 wt % lanthana if the oxidation state of iron in the catalyst with 0 wt % lanthana were Fe^+2.57. The findings of this paper emphasize the importance of surface sensitive UV-visible spectroscopy for determining the extent of catalyst reduction during operation. The paper highlights the potential to use bench-scale UV-visible spectroscopy to study the surface chemistry of catalysts instead of less-available synchrotron X-ray radiation facilities. Full article

(This article belongs to the Special Issue Commemorative Issue in Honor of Professor Emeritus Calvin H. Bartholomew in Anticipation of His 75th Birthday)

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20 pages, 2744 KiB

Open AccessFeature PaperArticle

The CoAlCeO Mixed Oxide: An Alternative to Palladium-Based Catalysts for Total Oxidation of Industrial VOCs

by Julien Brunet^1,*, Eric Genty^1,2

, Cédric Barroo²

, Fabrice Cazier³, Christophe Poupin¹

, Stéphane Siffert¹, Diane Thomas⁴, Guy De Weireld⁴, Thierry Visart de Bocarmé²

and Renaud Cousin^1,*

¹ Unité de Chimie Environnementale et Interactions sur le Vivant, Université du Littoral Côté d’Opale, MREI1—145 Avenue Maurice Schumann, 59140 Dunkerque, France

² Chemical Physics of Materials and Catalysis, Université Libre de Bruxelles, Faculty of Sciences, Campus Plaine CP 243, 1050 Brussels, Belgium

³ Centre Commun de Mesures, Université du Littoral Côté d’Opale, MREI1—145 Avenue Maurice Schumann, 59140 Dunkerque, France

⁴ Faculté Polytechnique de Mons, Université de Mons, 20 Place du Parc, B-7000 Mons, Belgium

Catalysts 2018, 8(2), 64; https://doi.org/10.3390/catal8020064 - 6 Feb 2018

Cited by 28 | Viewed by 5702

Abstract

Catalytic total oxidation is an effective technique for the treatment of industrial VOCs principally resulting from industrial processes using solvents, and usually containing mono-aromatics (BTEX) and oxygenated compounds (acetone, ethanol, butanone). The catalytic total oxidation of VOCs on noble metal materials is effective. [...] Read more.

Catalytic total oxidation is an effective technique for the treatment of industrial VOCs principally resulting from industrial processes using solvents, and usually containing mono-aromatics (BTEX) and oxygenated compounds (acetone, ethanol, butanone). The catalytic total oxidation of VOCs on noble metal materials is effective. However, the cost of catalysts is a main obstacle for the industrial application of these VOC removal processes. Therefore, the aim of this work is to propose an alternative material to palladium-based catalysts (which are suitable for VOCs’ total oxidation): a mixed oxide synthesized in the hydrotalcite way, namely CoAlCeO. This material was compared to four catalytic materials containing palladium, selected according to the literature: Pd/α-Al₂O₃, Pd/HY, Pd/CeO₂ and Pd/γAl₂O₃. These materials have been studied for the total oxidation of toluene, butanone, and VOCs mixtures. Catalysts’ performances were compared, taking into account the oxidation byproducts emitted from the process. This work highlight that the CoAlCeO catalyst presents better efficiency than Pd-based materials for the total oxidation of a VOCs mixture. Full article

(This article belongs to the Special Issue New Concepts in Oxidation Processes)

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19 pages, 10341 KiB

Open AccessArticle

Active and Stable Methane Oxidation Nano-Catalyst with Highly-Ionized Palladium Species Prepared by Solution Combustion Synthesis

by Mahmoud M. Khader^*, Mohammed J. Al-Marri, Sardar Ali and Ahmed G. Abdelmoneim

Gas Processing Centre, College of Engineering, Qatar University, Doha 2713, Qatar

Catalysts 2018, 8(2), 66; https://doi.org/10.3390/catal8020066 - 7 Feb 2018

Cited by 21 | Viewed by 6021

Abstract

We report on the synthesis and testing of active and stable nano-catalysts for methane oxidation. The nano-catalyst was palladium/ceria supported on alumina prepared via a one-step solution-combustion synthesis (SCS) method. As confirmed by X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HTEM), [...] Read more.

We report on the synthesis and testing of active and stable nano-catalysts for methane oxidation. The nano-catalyst was palladium/ceria supported on alumina prepared via a one-step solution-combustion synthesis (SCS) method. As confirmed by X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HTEM), SCS preparative methodology resulted in segregating both Pd and Ce on the surface of the Al₂O₃ support. Furthermore, HTEM showed that bigger Pd particles (5 nm and more) were surrounded by CeO₂, resembling a core shell structure, while smaller Pd particles (1 nm and less) were not associated with CeO₂. The intimate Pd-CeO₂ attachment resulted in insertion of Pd ions into the ceria lattice, and associated with the reduction of Ce⁴⁺ into Ce³⁺ ions; consequently, the formation of oxygen vacancies. XPS showed also that Pd had three oxidation states corresponding to Pd⁰, Pd²⁺ due to PdO, and highly ionized Pd ions (Pd^(2+x)+) which might originate from the insertion of Pd ions into the ceria lattice. The formation of intrinsic Ce³⁺ ions, highly ionized (Pd²⁺ species inserted into the lattice of CeO₂) Pd ions (Pd^(2+x)+) and oxygen vacancies is suggested to play a major role in the unique catalytic activity. The results indicated that the Pd-SCS nano-catalysts were exceptionally more active and stable than conventional catalysts. Under similar reaction conditions, the methane combustion rate over the SCS catalyst was ~18 times greater than that of conventional catalysts. Full methane conversions over the SCS catalysts occurred at around 400 °C but were not shown at all with conventional catalysts. In addition, contrary to the conventional catalysts, the SCS catalysts exhibited superior activity with no sign of deactivation in the temperature range between ~400 and 800 °C. Full article

(This article belongs to the Special Issue Catalytic Oxidation of Methane)

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8 pages, 1094 KiB

Open AccessArticle

Catalytic Wet Oxidation of Pharmaceutical Sludge by Molecular Sieve Loaded with Cu/Ce

by Xu Zeng^1,*, Jun Liu^1,2 and Jianfu Zhao¹

¹ State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China

² Shanghai Electric Power Generatoin Environment Protection Engineering Co., Ltd., Shanghai 201612, China

Catalysts 2018, 8(2), 67; https://doi.org/10.3390/catal8020067 - 8 Feb 2018

Cited by 14 | Viewed by 4701

Abstract

In the present study, the catalytic wet oxidation of pharmaceutical sludge by molecular sieve loaded with Cu/Ce as catalyst was investigated. Experiments were performed in an experimental batch reactor. Reaction parameters including catalyst dose, temperature, time, and oxygen pressure were discussed. The results [...] Read more.

In the present study, the catalytic wet oxidation of pharmaceutical sludge by molecular sieve loaded with Cu/Ce as catalyst was investigated. Experiments were performed in an experimental batch reactor. Reaction parameters including catalyst dose, temperature, time, and oxygen pressure were discussed. The results showed that the catalysts prepared by co-precipitating method have good catalytic performance. Under optimum conditions, the highest volatile suspended solids (VSS) removal rate approximately 92% and chemical oxygen demand (COD) removal rate of 75% were obtained at 260 °C for 60 min with initial oxygen pressure 1.0 MPa and the catalyst 10 g/L. These results implied that the catalytic wet oxidation of pharmaceutical sludge by molecular sieve loaded with Cu/Ce is a promising method for the highly efficient degradation of the sludge. Full article

(This article belongs to the Special Issue Catalytic Wet-Air Oxidation Processes)

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11 pages, 1863 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

New Trendy Magnetic C-Scorpionate Iron Catalyst and Its Performance towards Cyclohexane Oxidation

by Ana P. C. Ribeiro^1,*

, Inês A. S. Matias¹

, Elisabete C. B. A. Alegria^1,2

, Ana M. Ferraria³

, Ana M. Botelho do Rego³, Armando J. L. Pombeiro¹

and Luísa M. D. R. S. Martins^1,*

¹ Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal

² Departamento de Engenharia Química, Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa, R. Conselheiro Emídio Navarro, 1959-007 Lisboa, Portugal

³ Centro de Química-Física Molecular and Institute of Nanoscience and Nanotechnology, DEQ, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal

Catalysts 2018, 8(2), 69; https://doi.org/10.3390/catal8020069 - 8 Feb 2018

Cited by 15 | Viewed by 5316

Abstract

For the first time, a magnetic C-scorpionate catalyst was prepared from the iron(II) complex [FeCl₂{κ³-HC(pz)₃}] (pz = pyrazol-1-yl) and ferrite, using the sustainable mechanochemical synthetic procedure. Its catalytic activity for the cyclohexane oxidation with tert-butyl hydroperoxide [...] Read more.

For the first time, a magnetic C-scorpionate catalyst was prepared from the iron(II) complex [FeCl₂{κ³-HC(pz)₃}] (pz = pyrazol-1-yl) and ferrite, using the sustainable mechanochemical synthetic procedure. Its catalytic activity for the cyclohexane oxidation with tert-butyl hydroperoxide (TBHP) was evaluated in different conditions, namely under microwave irradiation and under the effect of an external magnetic field. The use of such magnetic conditions significantly shifted the catalyst alcohol/ketone selectivity, thus revealing a promising, easy new protocol for tuning selectivity in important catalytic processes. Full article

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10 pages, 3890 KiB

Open AccessArticle

Low Temperature Synthesis of Nest-Like Microsphere with Exposed (001) Facets and Its Enhanced Photocatalytic Performance by NaOH Alkalization

by Chentao Hou^*

, Jiaming Zhu and Qiaoqiao Song

College of Geology and Environment, Xi’an University of Science and Technology, Xi’an 710054, China

Catalysts 2018, 8(2), 70; https://doi.org/10.3390/catal8020070 - 8 Feb 2018

Cited by 10 | Viewed by 3916

Abstract

In this study, we completed a simple low-temperature synthesis of nest-like titanium oxide (TiO₂) microspheres with exposed (001) facets. For the first time, the photocatalytic performance was enhanced by sodium hydroxide (NaOH) alkalization. The characterization of as-synthesized F-TiO₂ and OH-TiO [...] Read more.

In this study, we completed a simple low-temperature synthesis of nest-like titanium oxide (TiO₂) microspheres with exposed (001) facets. For the first time, the photocatalytic performance was enhanced by sodium hydroxide (NaOH) alkalization. The characterization of as-synthesized F-TiO₂ and OH-TiO₂ were analyzed by field emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, fourier transform infrared spectroscopic analysis, ultraviolet-vis diffuse reflection spectra and Raman spectroscopy. The photocatalytic activity of the as-prepared catalyst was evaluated through the photocatalytic degradation of methylene blue (MB) and Rhodamine B (RhB) under simulated solar light. The results showed that modification using NaOH can lead to an increase in the percentage of (001) facets from 27.8% for F-TiO₂ to 39.2% for OH-TiO₂. OH-TiO₂ showed superior catalytic photoactivity toward MB. The mechanism of NaOH on TiO₂ is also discussed. Full article

(This article belongs to the Special Issue Organic Photoredox Catalysis)

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11 pages, 2865 KiB

Open AccessArticle

Effect of Dopant Loading on the Structural and Catalytic Properties of Mn-Doped SrTiO₃ Catalysts for Catalytic Soot Combustion

by Santiago Iván Suárez-Vázquez^1,*

, Arquímedes Cruz-López¹, Carlos Eduardo Molina-Guerrero¹, Astrid Iriana Sánchez-Vázquez²

and Carlos Macías-Sotelo¹

¹ Universidad Autónoma de Nuevo León, Facultad de Ingeniería Civil, Av. Universidad S/N, Cd. Universitaria, San Nicolás de los Garza 66455, Nuevo León, Mexico

² Universidad Autónoma de Nuevo León, Facultad de Ciencias Químicas, Av. Universidad S/N, Cd. Universitaria, San Nicolás de los Garza 66455, Nuevo León, Mexico

Catalysts 2018, 8(2), 71; https://doi.org/10.3390/catal8020071 - 9 Feb 2018

Cited by 27 | Viewed by 5058

Abstract

Soot particles have been associated with respiratory diseases and cancer. To decrease these emissions, perovskite-mixed oxides have been proposed due to their thermal stability and redox surface properties. In this work, SrTiO₃ doped with different amounts of Mn were synthesized by the [...] Read more.

Soot particles have been associated with respiratory diseases and cancer. To decrease these emissions, perovskite-mixed oxides have been proposed due to their thermal stability and redox surface properties. In this work, SrTiO₃ doped with different amounts of Mn were synthesized by the hydrothermal method and tested for soot combustion. Results show that at low Mn content, structural distortion, and higher O_ads/O_lat ratio were observed which was attributed to the high content of Mn³⁺ in Ti sites. On the other hand, increasing the Mn content led to surface segregation of manganese oxide. All synthesized catalysts showed mesopores in the range of 32–47 nm. In the catalytic combustion of soot, the samples synthesized in this work lowered the combustion temperature by more than 100 °C compared with the uncatalyzed reaction. The sample doped with 1 wt % of Mn showed the best catalytic activity. The activation energy of these samples was also calculated, and the order of decreasing activation energy is as follows: uncatalyzed > Mn0 > Mn8 > Mn4 > Mn1. The best catalytic activity for Mn1 was attributed to its physicochemical properties and the mobility of the oxygen from the bulk to the surface at temperatures higher than 500 °C. Full article

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13 pages, 1432 KiB

Open AccessArticle

Modeling of a Pilot-Scale Fixed-Bed Reactor for Dehydration of 2,3-Butanediol to 1,3-Butadiene and Methyl Ethyl Ketone

by Daesung Song

Global Technology, SK Innovation, 325 Exporo, Yuseong-gu, Daejeon 305-712, Korea

Catalysts 2018, 8(2), 72; https://doi.org/10.3390/catal8020072 - 9 Feb 2018

Cited by 10 | Viewed by 6037

Abstract

A 1D heterogeneous reactor model accounting for interfacial and intra-particle gradients was developed to simulate the dehydration of 2,3-Butanediol (2,3-BDO) to 1,3-Butadiene (1,3-BD) and Methyl Ethyl Ketone (MEK) over an amorphous calcium phosphate (a-CP) catalyst in a pilot-scale fixed-bed reactor. The developed model [...] Read more.

A 1D heterogeneous reactor model accounting for interfacial and intra-particle gradients was developed to simulate the dehydration of 2,3-Butanediol (2,3-BDO) to 1,3-Butadiene (1,3-BD) and Methyl Ethyl Ketone (MEK) over an amorphous calcium phosphate (a-CP) catalyst in a pilot-scale fixed-bed reactor. The developed model was validated with experimental data in terms of a fluid temperature profile along with the length of the catalyst bed, 2,3-BDO conversion, and selectivity for the major products, 1,3-BD and MEK, at the outlet of the reactor. The fluid temperature profile obtained from the model along the length of the catalyst bed coincides satisfactorily with the experimental observations. The difference between the experimental data and the 1D heterogeneous reactor model prediction for 2,3-BDO conversion and selectivity of 1,3-BD and MEK were 0.1%, 9 wt %, and 2 wt %, respectively. In addition, valuable insights related to the feeding system of a commercial-scale plant were made through troubleshooting of the pilot tests. Notably, if the feed including only 2,3-BDO and furnaces that increase the temperature of the feed to the reaction temperature were used in a commercial plant, the feeding system could not be operational because of the presence of heavy chemicals considered oligomers of 2,3-BDO. Full article

(This article belongs to the Special Issue Multiscale and Innovative Kinetic Approaches in Heterogeneous Catalysis)

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13 pages, 3912 KiB

Open AccessArticle

Wood-Biochar-Supported Magnetite Nanoparticles for Remediation of PAH-Contaminated Estuary Sediment

by Cheng-Di Dong¹, Chiu-Wen Chen¹, Chih-Ming Kao², Chuan-Chi Chien³ and Chang-Mao Hung^1,*

¹ Department of Marine Environmental Engineering, National Kaohsiung Marine University, Kaohsiung City 81157, Taiwan

² Institute of Environmental Engineering, National Sun Yat-sen University, Kaohsiung City 80424, Taiwan

³ Industrial Technology Research Institute, Hsinchu 31057, Taiwan

Catalysts 2018, 8(2), 73; https://doi.org/10.3390/catal8020073 - 9 Feb 2018

Cited by 90 | Viewed by 6902

Abstract

In this study, we investigated the ability of a magnetic wood biochar (WB)-based composite catalyst (Fe₃O₄–WB) to catalyze sodium persulfate (PS) for the remediation of estuary sediment contaminated with polycyclic aromatic hydrocarbons (PAHs). The effects of various critical parameters, [...] Read more.

In this study, we investigated the ability of a magnetic wood biochar (WB)-based composite catalyst (Fe₃O₄–WB) to catalyze sodium persulfate (PS) for the remediation of estuary sediment contaminated with polycyclic aromatic hydrocarbons (PAHs). The effects of various critical parameters, including the catalyst dose and initial pH, were investigated. The degradation of the PAHs was found to be related to the number of rings in their structure. The results showed that Fe₃O₄–WB is an efficient catalyst for the removal of high-ring PAHs (HPAHs), with the highest degradation rates for the 6-, 5-, and 4-ringed PAHs being 90%, 84%, and 87%, respectively, for a PS concentration of 2 × 10⁻⁵ M, catalyst concentration of 3.33 g/L, and pH of 3.0. That the reduction rate of the HPAHs was greater than that of the low-ring PAHs can be attributed to the strong affinity of the HPAHs for biochar derived from wood biomass. Overall, this study revealed that the WB-mediated electron transfer catalysis of the surface functional groups in a wide range of pH in the Fe₃O₄–WB/PS system and potentially application in the remediation of sediments contaminated with PAHs. Full article

(This article belongs to the Special Issue Catalytic Oxidation in Environmental Protection)

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14 pages, 3032 KiB

Open AccessArticle

Mn-Ce-V-WO_x/TiO₂ SCR Catalysts: Catalytic Activity, Stability and Interaction among Catalytic Oxides

by Xuteng Zhao¹

, Lei Mao¹ and Guojun Dong^1,2,*

¹ School of Material Science and Chemical Engineering, Harbin Engineering University, Harbin 150001, China

² Key Laboratory of Superlight Material and Surface Technology of Ministry of Education, College of Material Science and Chemical Engineering, Harbin Engineering University, Harbin 150001, China

Catalysts 2018, 8(2), 76; https://doi.org/10.3390/catal8020076 - 12 Feb 2018

Cited by 28 | Viewed by 6232

Abstract

A series of Mn-Ce-V-WO_x/TiO₂ composite oxide catalysts with different molar ratios (active components/TiO₂ = 0.1, 0.2, 0.3, 0.6) have been prepared by wet impregnation method and tested in selective catalytic reduction (SCR) of NO by NH₃ in a [...] Read more.

A series of Mn-Ce-V-WO_x/TiO₂ composite oxide catalysts with different molar ratios (active components/TiO₂ = 0.1, 0.2, 0.3, 0.6) have been prepared by wet impregnation method and tested in selective catalytic reduction (SCR) of NO by NH₃ in a wide temperature range. These catalysts were also characterized by X-ray diffraction (XRD), Transmission Electron Microscope (TEM), in situ Fourier Transform infrared spectroscopy (in situ FTIR), H₂-Temperature programmed reduction (H₂-TPR) and X-ray photoelectron spectroscopy (XPS). The results show the catalyst with a molar ratio of active components/TiO₂ = 0.2 exhibits highest NO conversion value between 150 °C to 400 °C and good resistance to H₂O and SO₂ at 250 °C with a gas hourly space velocity (GHSV) value of 40,000 h⁻¹. Different oxides are well dispersed and interact with each other. NH₃ and NO are strongly adsorbed on the catalyst surface and the adsorption of the reactant gas leads to a redox cycle with the valence state change among the surface oxides. The adsorption of SO₂ on Mn⁴⁺ and Ce⁴⁺ results in good H₂O and SO₂ resistance of the catalyst, but the effect of Mn and Ce are more than superior water and sulfur resistance. The diversity of valence states of the four active components and their high oxidation-reduction performance are the main reasons for the high NO conversion in this system. Full article

(This article belongs to the Special Issue Selective Catalytic Reduction of NO_x)

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17 pages, 3581 KiB

Open AccessArticle

Effect of Support Pretreatment Temperature on the Performance of an Iron Fischer–Tropsch Catalyst Supported on Silica-Stabilized Alumina

by Kamyar Keyvanloo^1,*, Baiyu Huang², Trent Okeson¹, Hussein H. Hamdeh³ and William C. Hecker¹

¹ Department of Chemical Engineering, Brigham Young University, Provo, UT 84602, USA

² Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA

³ Department of Physics, Wichita State University, Wichita, KS 67260, USA

Catalysts 2018, 8(2), 77; https://doi.org/10.3390/catal8020077 - 12 Feb 2018

Cited by 18 | Viewed by 5351

Abstract

The effect of support material pretreatment temperature, prior to adding the active phase and promoters, on Fischer–Tropsch activity and selectivity was explored. Four iron catalysts were prepared on silica-stabilized alumina (AlSi) supports pretreated at 700 °C, 900 °C, 1100 °C or 1200 °C. [...] Read more.

The effect of support material pretreatment temperature, prior to adding the active phase and promoters, on Fischer–Tropsch activity and selectivity was explored. Four iron catalysts were prepared on silica-stabilized alumina (AlSi) supports pretreated at 700 °C, 900 °C, 1100 °C or 1200 °C. Addition of 5% silica to alumina made the AlSi material hydrothermally stable, which enabled the unusually high support pretreatment temperatures (>900 °C) to be studied. High-temperature dehydroxylation of the AlSi before impregnation greatly reduces FeO·Al₂O₃ surface spinel formation by removing most of the support-surface hydroxyl groups leading to more effectively carbided catalyst. The activity increases more than four-fold for the support calcined at elevated temperatures (1100–1200 °C) compared with traditional support calcination temperatures of <900 °C. This unique pretreatment also facilitates the formation of ε′-Fe_2.2C rather than χ-Fe_2.5C on the AlSi support, which shows an excellent correlation with catalyst productivity. Full article

(This article belongs to the Special Issue Commemorative Issue in Honor of Professor Emeritus Calvin H. Bartholomew in Anticipation of His 75th Birthday)

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11 pages, 3418 KiB

Open AccessArticle

Photocatalytic Reduction of CO₂ from Simulated Flue Gas with Colored Anatase

by Yebin Guan^1,2, Ming Xia¹, Alessandro Marchetti¹

, Xiaohong Wang², Weicheng Cao¹, Hanxi Guan¹ and Xueqian Kong^1,*

¹ Center for Chemistry of Novel & High-Performance Materials, and Department of Chemistry, Zhejiang University, Hangzhou 310027, China

² Anhui Key Laboratory of Functional Coordination Compounds, School of Chemistry and Chemical Engineering, Anqing Normal University, Anqing 246011, China

Catalysts 2018, 8(2), 78; https://doi.org/10.3390/catal8020078 - 13 Feb 2018

Cited by 10 | Viewed by 5042

Abstract

Photocatalytic reduction with sunlight is an economical and promising advanced approach for reducing the excessive emissions of CO₂ from the combustion of fossil fuels. Aimed at practical applications, a type of inexpensive colored anatase material was used to evaluate CO₂ photoreduction [...] Read more.

Photocatalytic reduction with sunlight is an economical and promising advanced approach for reducing the excessive emissions of CO₂ from the combustion of fossil fuels. Aimed at practical applications, a type of inexpensive colored anatase material was used to evaluate CO₂ photoreduction performance on a platform with a continuous flow of gas mixtures (10 vol % CO₂, 90% N₂), which resembles realistic flue gas conditions. The results showed an enhanced photocatalytic activity compared with standard P25 and significant improvement over pristine anatase. Based on a series of characterization techniques, we propose that the oxygen vacancies and surface hydroxyl groups on colored anatase can reduce the bandgap and assist the binding of CO₂ molecules. Our results showed that photoreduction of CO₂ is feasible under practical conditions, and the efficiency could be improved through modification of catalysts. Full article

(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)

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14 pages, 900 KiB

Open AccessArticle

Heterogeneous Catalysis by Tetraethylammonium Tetrachloroferrate of the Photooxidation of Toluene by Visible and Near-UV Light

by Kelsie R. Barnard, Valerie R. Bright, Robert J. Enright, Kira M. Fahy

, Adam C. Liu

and Patrick E. Hoggard^*

Department of Chemistry and Biochemistry, Santa Clara University, Santa Clara, CA 95053, USA

Catalysts 2018, 8(2), 79; https://doi.org/10.3390/catal8020079 - 13 Feb 2018

Cited by 15 | Viewed by 5050

Abstract

Titanium dioxide is the most extensively used heterogeneous catalyst for the photooxidation of toluene and other hydrocarbons, but it has low utility for the synthesis of benzyl alcohol, of which little is produced, or benzaldehyde, due to further oxidation to benzoic acid and [...] Read more.

Titanium dioxide is the most extensively used heterogeneous catalyst for the photooxidation of toluene and other hydrocarbons, but it has low utility for the synthesis of benzyl alcohol, of which little is produced, or benzaldehyde, due to further oxidation to benzoic acid and cresol, among other oxidation products, and eventually complete mineralization to CO₂. Et₄N[FeCl₄] functions as a photocatalyst through the dissociation of chlorine atoms, which abstract hydrogen from toluene, and the photooxidation of toluene proceeds only as far as benzyl alcohol and benzaldehyde. Unlike TiO₂, which requires ultraviolet (UV) irradiation, Et₄N[FeCl₄] catalyzes the photooxidation of toluene with visible light alone. Even under predominantly UV irradiation, the yield of benzyl alcohol plus benzaldehyde is greater with Et₄N[FeCl₄] than with TiO₂. Et₄N[FeCl₄] photocatalysis yields benzyl chloride as a side product, but it can be minimized by restricting irradiation to wavelengths above 360 nm and by the use of long irradiation times. The photonic efficiency of oxidation in one experiment was found to be 0.042 mol/einstein at 365 nm. The use of sunlight as the irradiation source was explored. Full article

(This article belongs to the Special Issue Photocatalytic materials alternative to TiO₂ for environmental remediation, sustainable chemistry and energy conversion)

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16 pages, 3830 KiB

Open AccessArticle

Optimization of Biodiesel Production from Waste Cooking Oil Using Waste Eggshell as a Base Catalyst under a Microwave Heating System

by Yen-Ping Peng¹, Kassian T. T. Amesho²

, Chin-En Chen², Syu-Ruei Jhang², Feng-Chih Chou² and Yuan-Chung Lin^2,3,*

¹ Department of Environmental Science and Engineering, Tunghai University, Taichung 40704, Taiwan

² Institute of Environmental Engineering, National Sun Yat-sen University, Kaohsiung 804, Taiwan

³ Program in Toxicology, College of Pharmacy, Kaohsiung Medical University, Kaohsiung 807, Taiwan

Catalysts 2018, 8(2), 81; https://doi.org/10.3390/catal8020081 - 14 Feb 2018

Cited by 58 | Viewed by 8541

Abstract

This paper intends to explore the most affordable and environmentally friendly method for the synthesis of biodiesel. Substitute fuel is presently a significant topic all over the world, attributable to the efforts of reducing global warming, which is the result arising from the [...] Read more.

This paper intends to explore the most affordable and environmentally friendly method for the synthesis of biodiesel. Substitute fuel is presently a significant topic all over the world, attributable to the efforts of reducing global warming, which is the result arising from the combustion of petroleum or petrol diesel fuel. Due to its advantages of being renewable and environmentally friendly, biodiesel production has the potential to become the major substitute of petrol diesel fuel. Biodiesel is non-toxic, biodegradable, is produced from renewable sources, and contributes a small amount of greenhouse gas (e.g., CO₂ and SO₂) emissions to the atmosphere. Research has established that one of the key obstacles to the commercialization of biodiesel is the high price of biodiesel production due to the shortage of suitable raw materials. However, waste-cooking-oil (WCO) is one of the most cost-effective sources of biodiesel synthesis, and can practically minimize the raw material cost. The research was carried out to produce biodiesel from waste cooking oil in order to reduce the cost, waste, and pollution associated with biodiesel production. The application of a microwave heating system towards enhancing the production of biodiesel from waste cooking oil has been given little consideration in the preceding research, particularly with the application of eggshell as a heterogeneous catalyst. However, the tentative results in this study show significant performance in terms of biodiesel production, as follows: (1) the increasing of the reaction time from 120 to 165 min considerably increased the biodiesel production, which declined with a further rise to 210 min; (2) the results of this study reveal that a methanol-to-oil molar ratio of nine is appropriate and can be used for the best production of biodiesel; (3) the production of biodiesel in this study demonstrated a significant increase in response to the further increasing of power; (4) a 120 min response time, a ratio of 9:1 methanol-to-oil molar fraction, 65 °C temperature; (5) and 5 wt % catalyst were found to be the most ideal reaction conditions during this study. In summary, recycled eggshell was re-used as a suitable catalyst to produce new biodiesel from waste cooking oil, applicable to diesel engines. Full article

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13 pages, 5112 KiB

Open AccessArticle

Catalytic Fast Pyrolysis of Kraft Lignin over Hierarchical HZSM-5 and Hβ Zeolites

by Yadong Bi¹, Xiaojuan Lei¹, Guihua Xu¹, Hui Chen^1,* and Jianli Hu²

¹ Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384, China

² Department of Chemical and Biomedical Engineering, West Virginia University, Morgantown, WV 26506, USA

Catalysts 2018, 8(2), 82; https://doi.org/10.3390/catal8020082 - 14 Feb 2018

Cited by 49 | Viewed by 5426

Abstract

The hierarchical HZSM-5 and Hβ zeolites were prepared by alkaline post-treatment methods adopting Na₂CO₃, TMAOH/NaOH mixture, and NaOH as desilication sources, respectively. More mesopores are produced over two kinds of zeolites, while the micropores portion is well preserved. The [...] Read more.

The hierarchical HZSM-5 and Hβ zeolites were prepared by alkaline post-treatment methods adopting Na₂CO₃, TMAOH/NaOH mixture, and NaOH as desilication sources, respectively. More mesopores are produced over two kinds of zeolites, while the micropores portion is well preserved. The mesopores formed in hierarchical Hβ zeolites were directly related to the basicity of the alkaline solution, indicating that Hβ zeolite is more sensitive to the alkaline post-treatment. The hierarchical HZSM-5 and Hβ zeolites are more active than the parent one for catalytic fast pyrolysis (CFP) of Kraft lignin. Hierarchical zeolites retained the function of acid catalysis, while additionally creating larger mesopores to ensure the entry of bulkier reactant molecules. The increase of the condensable volatiles yield can be attributed to the improvement of the mass transfer performance, which correlates well with the change of mesoporous surface area. In particular, the condensable volatiles yield for the optimized hierarchical Hβ reached approximately two times that of the parent Hβ zeolites. In contrast to the parent HZSM-5, the optimized hierarchical HZSM-5 zeolite significantly reduced the selectivity of oxygenates from 27.2% to 3.3%. Full article

(This article belongs to the Special Issue Catalytic Pyrolysis)

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10 pages, 3223 KiB

Open AccessArticle

Aerobic Oxidation of Benzyl Alcohol on a Strontium-Based Gold Material: Remarkable Intrinsic Basicity and Reusable Catalyst

by Karla Patrícia R. Castro¹, Marco Aurélio S. Garcia¹, Wiury C. de Abreu^1,2, Samuel Anderson A. de Sousa¹, Carla Verônica R. de Moura¹, Jean Cláudio S. Costa¹ and Edmilson M. de Moura^1,*

¹ Chemistry Department, Federal University of Piauí, Teresina 64049-550, PI, Brazil

² Federal Institute of Maranhão, Buriticupu 65393-000, MA, Brazil

Catalysts 2018, 8(2), 83; https://doi.org/10.3390/catal8020083 - 15 Feb 2018

Cited by 19 | Viewed by 4725

Abstract

The development of stable and active gold catalysts has arisen as a significant strategy for oxidation of alcohols. Nano-size PVA-stabilized gold nanoparticles immobilized on Sr(OH)₂ by colloidal deposition presented high catalytic activity for benzyl alcohol oxidation. In 2.5 h, 2 bar of [...] Read more.

The development of stable and active gold catalysts has arisen as a significant strategy for oxidation of alcohols. Nano-size PVA-stabilized gold nanoparticles immobilized on Sr(OH)₂ by colloidal deposition presented high catalytic activity for benzyl alcohol oxidation. In 2.5 h, 2 bar of O₂ and without extra-base addition, the calcined support reached 54.6% (100 °C) and 67.4% (140 °C) of conversion, presenting the remarkable and unexplored intrinsic basicity that strontium-based materials retain. With sub-stoichiometric K₂CO₃ adding, under the same catalytic conditions, the catalyst conducted the reaction with similar activity, but with excellent reusability in the process, without any gold leaching. We investigated the influence that the support synthesis method and the solvent used for the NPs stabilization have on the oxidation activity. The produced materials were fully characterized by XPS, Rietveld refinement, and TEM. Full article

(This article belongs to the Special Issue New Developments in Heterogeneous Partial and Total Oxidation Catalysis)

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17 pages, 3305 KiB

Open AccessArticle

Immobilization Effects on the Catalytic Properties of Two Fusarium Verticillioides Lipases: Stability, Hydrolysis, Transesterification and Enantioselectivity Improvement

by Fernanda Dell Antonio Facchini¹, Marita Gimenez Pereira², Ana Claudia Vici², Marco Filice³, Benevides Costa Pessela⁴, Jose Manuel Guisan⁵

, Glória Fernandez-Lorente⁴ and Maria De Lourdes Teixeira de Moraes Polizeli^2,*

¹ Departamento de Medicina, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, 14040-900 Sao Paulo, Brazil

² Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, 14040-901 Sao Paulo, Brazil

³ Nanobiotechnology, Molecular Imaging and Metabolomics Group, Spanish National Centre for Cardiovascular Research–CNIC, 28029 Madrid, Spain

⁴ Departamento de Biotecnología y Microbiologia de los Alimentos, Instituto de Ciencias de la Alimentación, CIAL-CSIC, Calle Nicolás Cabrera 9, CampusUAM, 28049 Cantoblanco, Spain

⁵ Departamento de Biocatálisis, Instituto de Catálisis y Petroleoquímica—CSIC, Campus UAM, Cantoblanco, 28049 Madrid, Spain

Catalysts 2018, 8(2), 84; https://doi.org/10.3390/catal8020084 - 16 Feb 2018

Cited by 20 | Viewed by 4838

Abstract

Fusarium verticillioides lipases were purified in a “cascade” method using octadecyl Sepabeads and octyl Sepharose resins, which led to the isolation of two proteins with lipolytic activities. Lip 1 was purified after octyl Sepharose adsorption presenting 30.3 kDa and, Lip 2 presented 68.0 [...] Read more.

Fusarium verticillioides lipases were purified in a “cascade” method using octadecyl Sepabeads and octyl Sepharose resins, which led to the isolation of two proteins with lipolytic activities. Lip 1 was purified after octyl Sepharose adsorption presenting 30.3 kDa and, Lip 2 presented 68.0 kDa after octadecyl adsorption. These immobilization processes resulted in an increase of 3-fold in activity of each immobilized enzyme. These enzymes presented optima of pH of 5.0 and 6.0, respectively and temperature at 40 °C. They were thermostable at 40 °C and both remained more than 50% of its activity at the pH range of 5.0 to 7.0, with 180 min of incubation. The sardine oil hydrolysis showed higher EPA/DHA ratio. Concerning the ethanolysis reaction, Lip 2 showed higher conversion (5.5%) and both lipases showed activity in the release of the S enantiomers from 2-O-butyryl-2-phenylacetic acid (mandelic butyrate acid) and HPBE hydrolysis. Lip 2 also demonstrated capacity of transesterification. These applications made these enzymes attractive for industrial application. Full article

(This article belongs to the Special Issue Immobilized Biocatalysts)

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18 pages, 4975 KiB

Open AccessArticle

Influence of an Electronic Structure of N-TiO₂ on Its Photocatalytic Activity towards Decomposition of Acetaldehyde under UV and Fluorescent Lamps Irradiation

by Beata Tryba^1,*

, Magdalena Wozniak¹, Grzegorz Zolnierkiewicz², Nikos Guskos², Antoni Morawski¹, Christophe Colbeau-Justin³, Rafał Wrobel¹, Akio Nitta⁴ and Bunsho Ohtani^4,5

¹ Institute of Chemical Technology and Environment Engineering, West Pomeranian University of Technology, ul. Pulaskiego 10, 70-322 Szczecin, Poland

² Institute of Physics, West Pomeranian University of Technology, Al. Piastow 17, 70-310 Szczecin, Poland

³ Laboratoire de Chimie Physique, CNRS UMR 8000, Univ Paris-Sud - Université Paris-Saclay, 91405 Orsay, France

⁴ Graduate School of Environmental Science, Hokkaido University, Sapporo 060-0810, Japan

⁵ Institute for Catalysis, Hokkaido University, Sapporo 001-0021, Japan

Catalysts 2018, 8(2), 85; https://doi.org/10.3390/catal8020085 - 20 Feb 2018

Cited by 41 | Viewed by 5373

Abstract

The electronic structure of N-TiO₂ samples prepared by a sol-gel method was investigated by EPR (Electronic Paramagnetic Resonance) measurements and the energy-resolved distribution of electron traps. In EPR spectra, some of the resonance lines assigned to paramagnetic species of nitrogen and Ti [...] Read more.

The electronic structure of N-TiO₂ samples prepared by a sol-gel method was investigated by EPR (Electronic Paramagnetic Resonance) measurements and the energy-resolved distribution of electron traps. In EPR spectra, some of the resonance lines assigned to paramagnetic species of nitrogen and Ti³⁺ were detected. Sample prepared at 300 °C revealed the highest intensity line of the nitrogen paramagnetic centers, whereas that prepared at 400 °C showed a paramagnetic line for Ti³⁺. Measurements of the electron trap distribution showed higher density of electron traps for sample prepared at 400 °C than that at 300 °C. Sample prepared at 300 °C, which revealed the highest amount of nitrogen built in the titania in the interstitial position was the most active under visible light. It was evidenced that photocatalytic decomposition of acetaldehyde was dependent strongly on the BET surface area and electrokinetic potential of the photocatalyst surface. The UV content in the fluorescent lamp affected the yield of acetaldehyde decomposition. Full article

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14 pages, 11223 KiB

Open AccessFeature PaperArticle

Improved Kinetic Data Acquisition Using An Optically Accessible Catalytic Plate Reactor with Spatially-Resolved Measurement Techniques. Case of Study: CO₂ Methanation

by Jose A. Hernandez Lalinde, Kevin Kofler, Xuejie Huang and Jan Kopyscinski^*

Department of Chemical Engineering, McGill University, 3610 University Street, Montreal, QC H3A 0C5, Canada

Catalysts 2018, 8(2), 86; https://doi.org/10.3390/catal8020086 - 21 Feb 2018

Cited by 12 | Viewed by 6077

Abstract

Modelling and optimization of chemical reactors require a good understanding of the reactions mechanism with the corresponding kinetic description. Therefore, high quality kinetic data are needed, which can be challenging to obtain, especially for fast and highly exothermic reactions such as the CO [...] Read more.

Modelling and optimization of chemical reactors require a good understanding of the reactions mechanism with the corresponding kinetic description. Therefore, high quality kinetic data are needed, which can be challenging to obtain, especially for fast and highly exothermic reactions such as the CO₂ methanation. Traditionally, kinetic studies rely on measuring the exit gas composition (1 data point per species and experiment) using differential reactors with diluted catalyst beds and reactants to avoid temperature change. Therefore, an optically accessible catalytic channel reactor was designed, which allowed for the chance to gather spatially-resolved information on axial gas composition and catalyst surface temperature, specifically by means of a movable sampling capillary and shortwave infrared-thermography (SWIR), respectively. A catalyst coated plate was placed at the bottom of the channel, while a set of two quartz glass plates covers the top. In the current study 35 data points per gas species were collect for 1 experiment conducted under laminar flow conditions at 425 °C. Catalyst surface temperature determined via a SWIR camera was not influenced by polyatomic molecules partaking in the reaction and thus did not falsify the kinetic data. The catalyst mass distribution along the reactor axis was determined, enabling the development of a correct reactor model for kinetic parameter estimation and model discrimination. Full article

(This article belongs to the Special Issue Design Challenges for Catalytic and Photocatalytic Reactors)

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12 pages, 2406 KiB

Open AccessArticle

The H₂-Treated TiO₂ Supported Pt Catalysts Prepared by Strong Electrostatic Adsorption for Liquid-Phase Selective Hydrogenation

by Sasithorn Kuhaudomlap¹, Okorn Mekasuwandumrong², Piyasan Praserthdam¹, Shin-Ichiro Fujita³, Masahiko Arai³ and Joongjai Panpranot^1,*

¹ Center of Excellence on Catalysis and Catalytic Reaction Engineering, Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand

² Department of Chemical Engineering, Faculty of Engineering and Industrial Technology, Silpakorn University, Nakorn Pathom 73000, Thailand

³ Division of Applied Chemistry, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan

Catalysts 2018, 8(2), 87; https://doi.org/10.3390/catal8020087 - 22 Feb 2018

Cited by 15 | Viewed by 5997

Abstract

The H₂-treated TiO₂ supported Pt catalysts were prepared by strong electrostatic adsorption method and tested in the liquid-phase selective hydrogenation of various organic compounds such as 3-nitrostyrene to vinylaniline (VA) and furfural to furfuryl alcohol (FA). A combination of high [...] Read more.

The H₂-treated TiO₂ supported Pt catalysts were prepared by strong electrostatic adsorption method and tested in the liquid-phase selective hydrogenation of various organic compounds such as 3-nitrostyrene to vinylaniline (VA) and furfural to furfuryl alcohol (FA). A combination of high Pt dispersion, strong interaction of Pt-TiO_x, and the presence of low coordination Pt sites was necessary for high hydrogenation activity. However, while the selectivity of VA in 3-nitrostyrene hydrogenation did not depend much on the catalyst preparation method used, the selectivity of FA in furfural hydrogenation was much higher when the catalysts were prepared by SEA, comparing to those obtained by impregnation in which the solvent product was formed, due probably to the non-acidic conditions used during Pt loading by SEA method. Full article

(This article belongs to the Special Issue Active Sites in Catalytic Reaction)

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10 pages, 5790 KiB

Open AccessArticle

Ruthenium(II)-Arene Complexes of the Water-Soluble Ligand CAP as Catalysts for Homogeneous Transfer Hydrogenations in Aqueous Phase

by Antonella Guerriero¹, Maurizio Peruzzini^1,2,* and Luca Gonsalvi^1,*

¹ Consiglio Nazionale delle Ricerche (CNR), Istituto di Chimica dei Composti OrganoMetallici (ICCOM), Via Madonna del Piano 10, 50019 Sesto Fiorentino (Florence), Italy

² Consiglio Nazionale delle Ricerche (CNR), Dipartimento di Scienze Chimiche e Tecnologia dei Materiali (DSCTM), Via dei Taurini 19, 00185 Rome, Italy

Catalysts 2018, 8(2), 88; https://doi.org/10.3390/catal8020088 - 22 Feb 2018

Cited by 18 | Viewed by 5538

Abstract

The neutral Ru(II) complex κP-[RuCl₂(η⁶-p-cymene)(CAP)] (1), and the two ionic complexes κP-[RuCl(η⁶-p-cymene)(MeCN)(CAP)]PF₆ (2) and κP-[RuCl(η⁶-p-cymene)(CAP)₂]PF₆ [...] Read more.

The neutral Ru(II) complex κP-[RuCl₂(η⁶-p-cymene)(CAP)] (1), and the two ionic complexes κP-[RuCl(η⁶-p-cymene)(MeCN)(CAP)]PF₆ (2) and κP-[RuCl(η⁶-p-cymene)(CAP)₂]PF₆ (3), containing the water-soluble phosphine 1,4,7-triaza-9-phosphatricyclo[5.3.2.1]tridecane (CAP), were tested as catalysts for homogeneous hydrogenation of benzylidene acetone, selectively producing the saturated ketone as product. The catalytic tests were carried out in aqueous phase under transfer hydrogenation conditions, at mild temperatures using sodium formate as hydrogen source. Complex 3, which showed the highest stability under the reaction conditions applied, was also tested for C=N bond reduction from selected cyclic imines. Preliminary NMR studies run under pseudo-catalytic conditions starting from 3 showed the formation of κP-[RuH(η⁶-p-cymene)(CAP)₂]PF₆ (4) as the pivotal species in catalysis. Full article

(This article belongs to the Special Issue Homogeneous Catalysis and Mechanisms in Water and Biphasic Media)

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10 pages, 3439 KiB

Open AccessCommunication

Composites of Laminar Nanostructured ZnO and VOx-Nanotubes Hybrid as Visible Light Active Photocatalysts

by Eglantina Benavente^1,*

, Daniel Navas¹, Sindy Devis¹, Marjorie Segovia², Clivia Sotomayor-Torres^3,4

and Guillermo González^2,5

¹ Departamento de Química, Universidad Tecnológica Metropolitana, P.O. Box 9845, Santiago, Chile

² Department of Chemistry, Faculty of Sciences, Universidad de Chile, P.O. Box 653, Santiago, Chile

³ Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB Bellaterra, 08193 Barcelona, Spain

⁴ ICREA, Pg. Lluís Companys 23, 08010 Barcelona, Spain

⁵ Center for the Development of Nanoscience and Nanotechnology, CEDENNA, Av. Ecuador 3493, Santiago, Chile

Catalysts 2018, 8(2), 93; https://doi.org/10.3390/catal8020093 - 24 Feb 2018

Cited by 13 | Viewed by 4784

Abstract

A series of hybrid heterostructured nanocomposites of ZnO with V₂O₅ nanotubes (VOx-NTs) in different mixing ratios were synthesized, with the aim of reducing the recombination of photoinduced charge carriers and to optimize the absorption of visible light. The study was [...] Read more.

A series of hybrid heterostructured nanocomposites of ZnO with V₂O₅ nanotubes (VOx-NTs) in different mixing ratios were synthesized, with the aim of reducing the recombination of photoinduced charge carriers and to optimize the absorption of visible light. The study was focused on the use of heterostructured semiconductors that can extend light absorption to the visible range and enhance the photocatalytic performance of ZnO in the degradation of methylene blue as a model pollutant. The addition of VOx-NTs in the synthesis mixture led to a remarkable performance in the degradation of the model dye, with hybrid ZnO (stearic acid)/VOx-NTs at a ratio of 1:0.06 possessing the highest photocatalytic activity, about seven times faster than pristine zinc oxide. Diffuse reflectance spectroscopic measurements and experiments in the presence of different trapping elements allowed us to draw conclusions regarding the band positions and photocatalytic degradation mechanism. The photocatalytic activity measured in three subsequent cycles showed good reusability as no significant loss in efficiency of dye degradation was observed. Full article

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Review

Jump to: Research

27 pages, 4494 KiB

Open AccessReview

Navigating Glycerol Conversion Roadmap and Heterogeneous Catalyst Selection Aided by Density Functional Theory: A Review

by Bin Liu^1,*

and Feng Gao²

¹ Department of Chemical Engineering, Kansas State University, Manhattan, KS 66506, USA

² College of Medicine, Pennsylvania State University, Hershey, PA 17033, USA

Catalysts 2018, 8(2), 44; https://doi.org/10.3390/catal8020044 - 24 Jan 2018

Cited by 30 | Viewed by 12059

Abstract

Glycerol has been utilized in an extremely diversified manner throughout human civilization—ranging from food, to various consumer products, to pharmaceuticals, and even explosives. Large surplus in glycerol supply thanks to biodiesel production and biomass processing has created a demand to further boost its [...] Read more.

Glycerol has been utilized in an extremely diversified manner throughout human civilization—ranging from food, to various consumer products, to pharmaceuticals, and even explosives. Large surplus in glycerol supply thanks to biodiesel production and biomass processing has created a demand to further boost its utility. One growing area is to expand the use of glycerol as an alternative feedstock to supplement fuels and chemicals production. Various catalytic processes have been developed. This review summarizes catalytic materials for glycerol reforming, hydrodeoxygenation, and oxidation. In particular, rationale for catalyst selection and new catalyst design will be discussed aided by the knowledge of reaction mechanisms. The role of theoretical density functional theory (DFT) in elucidating complex glycerol conversion chemistries is particularly emphasized. Full article

(This article belongs to the Special Issue Glycerol Conversion by Heterogeneous Catalysis)

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18 pages, 2723 KiB

Open AccessReview

Oxygen Reduction Reaction Catalyzed by Noble Metal Clusters

by Zhenghua Tang^1,2,*

, Wen Wu¹ and Kai Wang¹

¹ Guangzhou Key Laboratory for Surface Chemistry of Energy Materials, New Energy Research Institute, School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006, China

² Guangdong Provincial Key Laboratory of Atmospheric Environment and Pollution Control, Guangdong Provincial Engineering and Technology Research Center for Environmental Risk Prevention and Emergency Disposal, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006, China

Catalysts 2018, 8(2), 65; https://doi.org/10.3390/catal8020065 - 7 Feb 2018

Cited by 69 | Viewed by 12005

Abstract

Highly-efficient catalysts for the oxygen reduction reaction (ORR) have been extensively investigated for the development of proton exchange membrane fuel cells (PEMFCs). The state-of-the-art Pt/C catalysts suffer from high price, limited accessibility of Pt, sluggish reaction kinetics, as well as undesirable long-term durability. [...] Read more.

Highly-efficient catalysts for the oxygen reduction reaction (ORR) have been extensively investigated for the development of proton exchange membrane fuel cells (PEMFCs). The state-of-the-art Pt/C catalysts suffer from high price, limited accessibility of Pt, sluggish reaction kinetics, as well as undesirable long-term durability. Engineering ultra-small noble metal clusters with high surface-to-volume ratios and robust stabilities for ORR represents a new avenue. After a simple introduction regarding the significance of ORR and the recent development of noble metal clusters, the general ORR mechanism in both acidic and basic media is firstly discussed. Subsequently, we will summarize the recent efforts employing Pt, Au, Ag, Pd and Ru clusters, as well as the alloyed bi-metallic clusters for acquiring highly efficient catalysts to enhance both the activity and stability of ORR. Molecular noble metal clusters with definitive composition to reveal the relevant ORR mechanism will be particularly highlighted. Finally, the current challenges, the future outlook, as well as the perspectives in this booming field will be proposed, featuring the great opportunities and potentials to engineering noble metal clusters as highly-efficient and durable cathodic catalysts for fuel cell applications. Full article

(This article belongs to the Special Issue Catalysts for Oxygen Reduction Reaction)

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13 pages, 1128 KiB

Open AccessReview

Nano-Immobilized Biocatalysts for Biodiesel Production from Renewable and Sustainable Resources

by Keon Hee Kim, Ok Kyung Lee and Eun Yeol Lee^*

Department of Chemical Engineering, Kyung Hee University, Gyeonggi-do 17104, Korea

Catalysts 2018, 8(2), 68; https://doi.org/10.3390/catal8020068 - 8 Feb 2018

Cited by 88 | Viewed by 10513

Abstract

The cost of biodiesel production relies on feedstock cost. Edible oil is unfavorable as a biodiesel feedstock because of its expensive price. Thus, non-edible crop oil, waste oil, and microalgae oil have been considered as alternative resources. Non-edible crop oil and waste cooking [...] Read more.

The cost of biodiesel production relies on feedstock cost. Edible oil is unfavorable as a biodiesel feedstock because of its expensive price. Thus, non-edible crop oil, waste oil, and microalgae oil have been considered as alternative resources. Non-edible crop oil and waste cooking oil are more suitable for enzymatic transesterification because they include a large amount of free fatty acids. Recently, enzymes have been integrated with nanomaterials as immobilization carriers. Nanomaterials can increase biocatalytic efficiency. The development of a nano-immobilized enzyme is one of the key factors for cost-effective biodiesel production. This paper presents the technology development of nanomaterials, including nanoparticles (magnetic and non-magnetic), carbon nanotubes, and nanofibers, and their application to the nano-immobilization of biocatalysts. The current status of biodiesel production using a variety of nano-immobilized lipase is also discussed. Full article

(This article belongs to the Special Issue Nanobiotechnology for Biofuel Production: Renewable and Sustainable Sources)

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47 pages, 13106 KiB

Open AccessReview

g-C₃N₄-Based Nanomaterials for Visible Light-Driven Photocatalysis

by Santosh Kumar¹

, Sekar Karthikeyan¹ and Adam F. Lee^2,*

¹ European Bioenergy Research Institute, Aston University, Birmingham B4 7ET, UK

² School of Science, RMIT University, Melbourne, VIC 3000, Australia

Catalysts 2018, 8(2), 74; https://doi.org/10.3390/catal8020074 - 9 Feb 2018

Cited by 236 | Viewed by 32142

Abstract

Graphitic carbon nitride (g-C₃N₄) is a promising material for photocatalytic applications such as solar fuels production through CO₂ reduction and water splitting, and environmental remediation through the degradation of organic pollutants. This promise reflects the advantageous photophysical properties [...] Read more.

Graphitic carbon nitride (g-C₃N₄) is a promising material for photocatalytic applications such as solar fuels production through CO₂ reduction and water splitting, and environmental remediation through the degradation of organic pollutants. This promise reflects the advantageous photophysical properties of g-C₃N₄ nanostructures, notably high surface area, quantum efficiency, interfacial charge separation and transport, and ease of modification through either composite formation or the incorporation of desirable surface functionalities. Here, we review recent progress in the synthesis and photocatalytic applications of diverse g-C₃N₄ nanostructured materials, and highlight the physical basis underpinning their performance for each application. Potential new architectures, such as hierarchical or composite g-C₃N₄ nanostructures, that may offer further performance enhancements in solar energy harvesting and conversion are also outlined. Full article

(This article belongs to the Special Issue Photocatalytic materials alternative to TiO₂ for environmental remediation, sustainable chemistry and energy conversion)

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28 pages, 6004 KiB

Open AccessFeature PaperEditor’s ChoiceReview

One-Pot Combination of Metal- and Bio-Catalysis in Water for the Synthesis of Chiral Molecules

by Nicolás Ríos-Lombardía^1,*, Joaquín García-Álvarez^2,*

and Javier González-Sabín^1,*

¹ EntreChem SL, Vivero Ciencias de la Salud, Santo Domingo de Guzmán, 33011 Oviedo, Spain

² Laboratorio de Compuestos Organometálicos y Catálisis (Unidad Asociada al CSIC), Centro de Innovación en Química Avanzada (ORFEO-CINQA), Departamento de Química Orgánica e Inorgánica, Universidad de Oviedo, E-33006 Oviedo, Spain

Catalysts 2018, 8(2), 75; https://doi.org/10.3390/catal8020075 - 10 Feb 2018

Cited by 54 | Viewed by 8894

Abstract

During the last decade, the combination of different metal- and bio-catalyzed organic reactions in aqueous media has permitted the flourishing of a variety of one-pot asymmetric multi-catalytic reactions devoted to the construction of enantiopure and high added-value chemicals under mild reaction conditions (usually [...] Read more.

During the last decade, the combination of different metal- and bio-catalyzed organic reactions in aqueous media has permitted the flourishing of a variety of one-pot asymmetric multi-catalytic reactions devoted to the construction of enantiopure and high added-value chemicals under mild reaction conditions (usually room temperature) and in the presence of air. Herein, a comprehensive account of the state-of-the-art in the development of catalytic networks by combining metallic and biological catalysts in aqueous media (the natural environment of enzymes) is presented. Among others, the combination of metal-catalyzed isomerizations, cycloadditions, hydrations, olefin metathesis, oxidations, C-C cross-coupling and hydrogenation reactions, with several biocatalyzed transformations of organic groups (enzymatic reduction, epoxidation, halogenation or ester hydrolysis), are discussed. Full article

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30 pages, 7088 KiB

Open AccessReview

Oriented Decoration in Metal-Functionalized Ordered Mesoporous Silicas and Their Catalytic Applications in the Oxidation of Aromatic Compounds

by Shijian Zhou^†, Fu Yang^†, Bangbang Wang, Hang Su, Kangchao Lu, Yun Ding, Kai Lei, Man Xu, Bo Shao, Yun Wang and Yan Kong^*

¹ State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing 210009, China

^† These authors contributed equally to this work.

Catalysts 2018, 8(2), 80; https://doi.org/10.3390/catal8020080 - 13 Feb 2018

Cited by 11 | Viewed by 5576

Abstract

Ordered mesoporous silicas (OMSs) attract considerable attention due to their advanced structural properties. However, for the pristine silica materials, the inert property greatly inhibits their catalytic applications. Thus, to contribute to the versatile surface of OMSs, different metal active sites, including acidic/basic sites [...] Read more.

Ordered mesoporous silicas (OMSs) attract considerable attention due to their advanced structural properties. However, for the pristine silica materials, the inert property greatly inhibits their catalytic applications. Thus, to contribute to the versatile surface of OMSs, different metal active sites, including acidic/basic sites and redox sites, have been introduced into specific locations (mesoporous channels and framework) of OMSs and the metal-functionalized ordered mesoporous silicas (MOMSs) show great potential in the catalytic applications. In this review, we first present the categories of metal active sites. Then, the synthesized processes of MOMSs are thoroughly discussed, in which the metal active sites would be introduced with the assistance of organic groups into the specific locations of OMSs. In addition, the structural morphologies of OMSs are elaborated and the catalytic applications of MOMSs in the oxidation of aromatic compounds are illustrated in detail. Finally, the prospects for the future development in this field are proposed. Full article

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22 pages, 5845 KiB

Open AccessReview

Catalysis and Downsizing in Mg-Based Hydrogen Storage Materials

by Jianding Li¹, Bo Li¹, Huaiyu Shao^1,*

, Wei Li² and Huaijun Lin^2,*

¹ Institute of Applied Physics and Materials Engineering (IAPME), University of Macau, Macau SAR, China

² Institute of Advanced Wear & Corrosion Resistance and Functional Materials, Jinan University, Guangzhou 510632, China

Catalysts 2018, 8(2), 89; https://doi.org/10.3390/catal8020089 - 23 Feb 2018

Cited by 66 | Viewed by 8697

Abstract

Magnesium (Mg)-based materials are promising candidates for hydrogen storage due to the low cost, high hydrogen storage capacity and abundant resources of magnesium for the realization of a hydrogen society. However, the sluggish kinetics and strong stability of the metal-hydrogen bonding of Mg-based [...] Read more.

Magnesium (Mg)-based materials are promising candidates for hydrogen storage due to the low cost, high hydrogen storage capacity and abundant resources of magnesium for the realization of a hydrogen society. However, the sluggish kinetics and strong stability of the metal-hydrogen bonding of Mg-based materials hinder their application, especially for onboard storage. Many researchers are devoted to overcoming these challenges by numerous methods. Here, this review summarizes some advances in the development of Mg-based hydrogen storage materials related to downsizing and catalysis. In particular, the focus is on how downsizing and catalysts affect the hydrogen storage capacity, kinetics and thermodynamics of Mg-based hydrogen storage materials. Finally, the future development and applications of Mg-based hydrogen storage materials is discussed. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis & Hydrogen Storage)

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33 pages, 18969 KiB

Open AccessReview

Advances in Enantioselective C–H Activation/Mizoroki-Heck Reaction and Suzuki Reaction

by Shuai Shi¹

, Khan Shah Nawaz¹

, Muhammad Kashif Zaman¹ and Zhankui Sun^1,2,*

¹ School of Pharmacy, Shanghai Jiao Tong University, No. 800 Dongchuan Rd., Shanghai 200240, China

² Huzhou Research and Industrialization Center for Technology, Chinese Academy of Sciences, 1366 Hongfeng Road, Huzhou 313000, China

Catalysts 2018, 8(2), 90; https://doi.org/10.3390/catal8020090 - 23 Feb 2018

Cited by 20 | Viewed by 9181

Abstract

Traditional cross-coupling reactions, like Mizoroki-Heck Reaction and Suzuki Reaction, have revolutionized organic chemistry and are widely applied in modern organic synthesis. With the rapid development of C–H activation and asymmetric catalysis in recent years, enantioselective C–H activation/cross-coupling reactions have drawn much attention from [...] Read more.

Traditional cross-coupling reactions, like Mizoroki-Heck Reaction and Suzuki Reaction, have revolutionized organic chemistry and are widely applied in modern organic synthesis. With the rapid development of C–H activation and asymmetric catalysis in recent years, enantioselective C–H activation/cross-coupling reactions have drawn much attention from researchers. This review summarizes recent advances in enantioselective C–H activation/Mizoroki-Heck Reaction and Suzuki Reaction, with emphasis on the structures and functions of chiral ligands utilized in different reactions. Full article

(This article belongs to the Special Issue Catalyzed Mizoroki–Heck Reaction or C–H activation)

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32 pages, 4795 KiB

Open AccessEditor’s ChoiceReview

The Design of MnO_x Based Catalyst in Post-Plasma Catalysis Configuration for Toluene Abatement

by Zhiping Ye^1,2, Jean-Marc Giraudon^1,*

, Nathalie De Geyter²

, Rino Morent² and Jean-François Lamonier¹

¹ Univ. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181—UCCS—Unité de Catalyse et Chimie du Solide, F-59000 Lille, France

² Research Unit Plasma Technology, Department of Applied Physics, Faculty of Engineering and Architecture, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Ghent, Belgium

Catalysts 2018, 8(2), 91; https://doi.org/10.3390/catal8020091 - 23 Feb 2018

Cited by 46 | Viewed by 10536

Abstract

This review provides an overview of our present state of knowledge using manganese oxide (MnO_x)-based catalysts for toluene abatement in PPC (Post plasma-catalysis) configuration. The context of this study is concisely sum-up. After briefly screening the main depollution methods, the principles [...] Read more.

This review provides an overview of our present state of knowledge using manganese oxide (MnO_x)-based catalysts for toluene abatement in PPC (Post plasma-catalysis) configuration. The context of this study is concisely sum-up. After briefly screening the main depollution methods, the principles of PPC are exposed based on the coupling of two mature technologies such as NTP (Non thermal plasma) and catalysis. In that respect, the presentation of the abundant manganese oxides will be firstly given. Then in a second step the main features of MnO_x allowing better performances in the reactions expected to occur in the abatement of toluene in PPC process are reviewed including ozone decomposition, toluene ozonation, CO oxidation and toluene total oxidation. Finally, in a last part the current status of the applications of PPC using MnO_x on toluene abatement are discussed. In a first step, the selected variables of the hybrid process related to the experimental conditions of toluene abatement in air are identified. The selected variables are those expected to play a role in the performances of PPC system towards toluene abatement. Then the descriptors linked to the performances of the hybrid process in terms of efficiency are given and the effects of the variables on the experimental outcomes (descriptors) are discussed. The review would serve as a reference guide for the optimization of the PPC process using MnO_x-based oxides for toluene abatement. Full article

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27 pages, 1154 KiB

Open AccessReview

A General Overview of Support Materials for Enzyme Immobilization: Characteristics, Properties, Practical Utility

by Jakub Zdarta^1,2,*, Anne S. Meyer²

, Teofil Jesionowski¹

and Manuel Pinelo²

¹ Institute of Chemical Technology and Engineering, Faculty of Chemical Technology, Poznan University of Technology, Berdychowo 4, PL-60965 Poznan, Poland

² Center for BioProcess Engineering, Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads 229, DK-2800 Kgs. Lyngby, Denmark

Catalysts 2018, 8(2), 92; https://doi.org/10.3390/catal8020092 - 24 Feb 2018

Cited by 778 | Viewed by 40368

Abstract

In recent years, enzyme immobilization has been presented as a powerful tool for the improvement of enzyme properties such as stability and reusability. However, the type of support material used plays a crucial role in the immobilization process due to the strong effect [...] Read more.

In recent years, enzyme immobilization has been presented as a powerful tool for the improvement of enzyme properties such as stability and reusability. However, the type of support material used plays a crucial role in the immobilization process due to the strong effect of these materials on the properties of the produced catalytic system. A large variety of inorganic and organic as well as hybrid and composite materials may be used as stable and efficient supports for biocatalysts. This review provides a general overview of the characteristics and properties of the materials applied for enzyme immobilization. For the purposes of this literature study, support materials are divided into two main groups, called Classic and New materials. The review will be useful in selection of appropriate support materials with tailored properties for the production of highly effective biocatalytic systems for use in various processes. Full article

(This article belongs to the Special Issue Immobilized Biocatalysts)

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