Catalysts

17 pages, 2756 KiB

Open AccessFeature PaperCommunication

Halide-Enhanced Catalytic Activity of Palladium Nanoparticles Comes at the Expense of Catalyst Recovery

by Azzedine Bouleghlimat¹, Mazin A. Othman², Louis V. Lagrave^1,3

, Soichiro Matsuzawa⁴, Yoshinobu Nakamura^5,6, Syuji Fujii^5,6,*

and Niklaas J. Buurma^1,*

¹ Physical Organic Chemistry Centre, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK

² Chemistry Department, College of Science, Salahaddin University-Erbil, Kirkuk Road, Kurdistan Region 44002, Iraq

³ ENSIACET-INP Toulouse, 4 Allée Emile Monso, 31030 Toulouse, France

⁴ Division of Applied Chemistry, Graduate School of Engineering, Osaka Institute of Technology, 5-16-1 Omiya, Asahi-ku, Osaka 535-8585, Japan

⁵ Department of Applied Chemistry, Faculty of Engineering, Osaka Institute of Technology, 5-16-1 Omiya, Asahi-ku, Osaka 535-8585, Japan

⁶ Nanomaterials Microdevices Research Center, Osaka Institute of Technology, 5-16-1 Omiya, Asahi-ku, Osaka 535-8585, Japan

Catalysts 2017, 7(9), 280; https://doi.org/10.3390/catal7090280 - 19 Sep 2017

Cited by 12 | Viewed by 6033

Abstract

In this communication, we present studies of the oxidative homocoupling of arylboronic acids catalyzed by immobilised palladium nanoparticles in aqueous solution. This reaction is of significant interest because it shares a key transmetallation step with the well-known Suzuki-Miyaura cross-coupling reaction. Additives can have [...] Read more.

In this communication, we present studies of the oxidative homocoupling of arylboronic acids catalyzed by immobilised palladium nanoparticles in aqueous solution. This reaction is of significant interest because it shares a key transmetallation step with the well-known Suzuki-Miyaura cross-coupling reaction. Additives can have significant effects on catalysis, both in terms of reaction mechanism and recovery of catalytic species, and our aim was to study the effect of added halides on catalytic efficiency and catalyst recovery. Using kinetic studies, we have shown that added halides (added as NaCl and NaBr) can increase the catalytic activity of the palladium nanoparticles more than 10-fold, allowing reactions to be completed in less than half a day at 30 °C. However, this increased activity comes at the expense of catalyst recovery. The results are in agreement with a reaction mechanism in which, under conditions involving high concentrations of chloride or bromide, palladium leaching plays an important role. Considering the evidence for analogous reactions occurring on the surface of palladium nanoparticles under different reaction conditions, we conclude that additives can exert a significant effect on the mechanism of reactions catalyzed by nanoparticles, including switching from a surface reaction to a solution reaction. The possibility of this switch in mechanism may also be the cause for the disagreement on this topic in the literature. Full article

(This article belongs to the Special Issue Catalysis in Innovative Solvents)

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18 pages, 10954 KiB

Open AccessArticle

Surface Oxidation of Supported Ni Particles and Its Impact on the Catalytic Performance during Dynamically Operated Methanation of CO₂

by Benjamin Mutz^1,2, Andreas Martin Gänzler¹, Maarten Nachtegaal³, Oliver Müller^4,5, Ronald Frahm⁴, Wolfgang Kleist^1,2,6 and Jan-Dierk Grunwaldt^1,2,*

¹ Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology (KIT), D-76131 Karlsruhe, Germany

² Institute of Catalysis Research and Technology, Karlsruhe Institute of Technology (KIT), D-76344 Eggenstein-Leopoldshafen, Germany

³ Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland

⁴ Department of Physics, University of Wuppertal, D-42119 Wuppertal, Germany

⁵ Stanford Synchrotron Radiation Lightsource (SSRL), SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA

⁶ Laboratory of Industrial Chemistry, Ruhr-University Bochum, D-44801 Bochum, Germany

Catalysts 2017, 7(9), 279; https://doi.org/10.3390/catal7090279 - 18 Sep 2017

Cited by 61 | Viewed by 10234

Abstract

The methanation of CO₂ within the power-to-gas concept was investigated under fluctuating reaction conditions to gather detailed insight into the structural dynamics of the catalyst. A 10 wt % Ni/Al₂O₃ catalyst with uniform 3.7 nm metal particles and a [...] Read more.

The methanation of CO₂ within the power-to-gas concept was investigated under fluctuating reaction conditions to gather detailed insight into the structural dynamics of the catalyst. A 10 wt % Ni/Al₂O₃ catalyst with uniform 3.7 nm metal particles and a dispersion of 21% suitable to investigate structural changes also in a surface-sensitive way was prepared and characterized in detail. Operando quick-scanning X-ray absorption spectroscopy (XAS/QEXAFS) studies were performed to analyze the influence of 30 s and 300 s H₂ interruptions during the methanation of CO₂ in the presence of O₂ impurities (technical CO₂). These conditions represent the fluctuating supply of H₂ from renewable energies for the decentralized methanation. Short-term H₂ interruptions led to oxidation of the most reactive low-coordinated metallic Ni sites, which could not be re-reduced fully during the subsequent methanation cycle and accordingly caused deactivation. Detailed evaluation of the extended X-ray absorption fine structure (EXAFS) spectra showed surface oxidation/reduction processes, whereas the core of the Ni particles remained reduced. The 300-s H₂ interruptions resulted in bulk oxidation already after the first cycle and a more pronounced deactivation. These results clearly show the importance and opportunities of investigating the structural dynamics of catalysts to identify their mechanism, especially in power-to-chemicals processes using renewable H₂. Full article

(This article belongs to the Special Issue Catalytic, Photocatalytic and Electrocatalytic Processes for the Valorisation of CO₂)

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12 pages, 1937 KiB

Open AccessArticle

S- and N-Doped Graphene Nanomaterials for the Oxygen Reduction Reaction

by Luis Miguel Rivera, Sergio Fajardo, María Del Carmen Arévalo, Gonzalo García

and Elena Pastor^*

Departamento de Química, Instituto Universitario de Materiales y Nanotecnología (IMN), Universidad de La Laguna (ULL), Apartado 456, 38200 La Laguna, Tenerife, Spain

Catalysts 2017, 7(9), 278; https://doi.org/10.3390/catal7090278 - 18 Sep 2017

Cited by 60 | Viewed by 8924

Abstract

In the current work, heteroatom-doped graphene materials containing different atomic ratios of nitrogen and sulphur were employed as electrocatalysts for the oxygen reduction reaction (ORR) in acidic and alkaline media. To this end, the hydrothermal route and different chemical reducing agents were employed [...] Read more.

In the current work, heteroatom-doped graphene materials containing different atomic ratios of nitrogen and sulphur were employed as electrocatalysts for the oxygen reduction reaction (ORR) in acidic and alkaline media. To this end, the hydrothermal route and different chemical reducing agents were employed to synthesize the catalytic materials. The physicochemical characterization of the catalysts was performed by several techniques, such as X-ray diffraction, Raman spectroscopy and elemental analysis; meanwhile, the electrochemical performance of the materials toward the ORR was analyzed by linear sweep voltammetry (LSV), rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) techniques. The main results indicate that the ORR using heteroatom-doped graphene is a direct four-electron pathway, for which the catalytic activity is higher in alkaline than in acidic media. Indeed, a change of the reaction mechanism was observed with the insertion of N into the graphenic network, by the rate determining step changes from the first electrochemical step (formation of adsorbed OOH) on glassy carbon to the removal of adsorbed O (O_ad) from the N-graphene surface. Moreover, the addition of sulphur atoms into the N-graphene structure increases the catalytic activity toward the ORR, as the desorption of O_ad is accelerated. Full article

(This article belongs to the Special Issue Graphene-Based Materials for Energy Conversion)

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12 pages, 2540 KiB

Open AccessArticle

A New Homo-Hexamer Mn-Containing Catalase from Geobacillus sp. WCH70

by Hai-Chao Li¹, Qing Yu¹, Hui Wang¹, Xin-Yu Cao¹, Li Ma^1,2,* and Zheng-Qiang Li^1,*

¹ Key Laboratory for Molecular Enzymology & Engineering, the Ministry of Education, School of Life Sciences, Jilin University, 2699 Qianjin Street, Changchun 130012, Jilin, China

² Department of Physics, Georgia Southern University, Statesboro, GA 30460, USA

Catalysts 2017, 7(9), 277; https://doi.org/10.3390/catal7090277 - 18 Sep 2017

Cited by 8 | Viewed by 7853

Abstract

Catalase is an effective biocatalyst to degrade hydrogen peroxide to water and oxygen that can serve in textile effluent treatment to remove residual H₂O₂. Thermostable catalases are needed to withstand both the high temperature and pH of textile wastewater. [...] Read more.

Catalase is an effective biocatalyst to degrade hydrogen peroxide to water and oxygen that can serve in textile effluent treatment to remove residual H₂O₂. Thermostable catalases are needed to withstand both the high temperature and pH of textile wastewater. We have cloned the Mn-containing catalase gene ACS24898.1 from Geobacillus sp. WCH70, which originated from thermophilic organisms, and expressed it in Escherichia coli in activated form. The recombinant protein has been purified to homogeneity and identified to be a new homo-hexamer Mn-containing catalase. The native molecular mass of the catalase has been measured to be 138 kDa by size-exclusion chromatography. The new enzyme has optimum catalyzed activity at pH 9.0 and a temperature of 75 °C. It is thermostable up to 70 °C for 8 h incubation and maintains 80% and 50% activity, respectively, at 80 °C after 5 h and 90 °C after 1 h. At 75 °C and pH 9.0, the K_m is 67.26 mM for substrate H₂O₂ and the rate of reaction at H₂O₂ saturation, V_max, is 75,300 U/mg. The thermophilic and alkaline preferred properties of this new Mn-catalase are valuable features in textile wastewater treatment. Full article

(This article belongs to the Special Issue Biocatalysis and Biotransformations)

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20 pages, 8983 KiB

Open AccessArticle

The Preparation of a Highly Efficient Ag₃PO₄/Ag/Bi₂O₂CO₃ Photo-Catalyst and the Study of Its Photo-Catalytic Organic Synthesis Reaction Driven by Visible Light

by Zhi Guo, Hui Xin, Jingjing Ma, Meifen Bai, Yan Wang and Jingyi Li^*

College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot 010021, China

Catalysts 2017, 7(9), 276; https://doi.org/10.3390/catal7090276 - 17 Sep 2017

Cited by 10 | Viewed by 6125

Abstract

Ag₃PO₄/Ag/Bi₂O₂CO₃ composites were prepared by a hydrothermal and precipitation method. The morphology, structure, and valence state of the photo-catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Scanning [...] Read more.

Ag₃PO₄/Ag/Bi₂O₂CO₃ composites were prepared by a hydrothermal and precipitation method. The morphology, structure, and valence state of the photo-catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface areas, and UV-vis diffuse reflectance spectra (UV-vis DRS). They were applied as heterogeneous catalysts in the synthesis of esters from aldehydes (or alcohols) and alcohols and the synthesis of imines from alcohols and amines under visible light irradiation. The photo-catalytic activities of the esterification reactions of aldehydes and alcohols were heavily dependent on the loading of Ag₃PO₄/Ag/Bi₂O₂CO₃ as well as the intensity and wavelength of the visible light. Furthermore, their conversion under visible light irradiation was superior to that in the dark. Herein a reaction mechanism from aldehydes and alcohols to esters was proposed, and the Ag₃PO₄/Ag/Bi₂O₂CO₃ catalysts could be used six times without a significant decrease in activity. Using these catalysts under visible light could motivate future studies to develop efficient recyclable photo-catalysts and facilitate many synthetic organic reactions. 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, 2593 KiB

Open AccessArticle

Improving the Indigo Carmine Decolorization Ability of a Bacillus amyloliquefaciens Laccase by Site-Directed Mutagenesis

by Jiayi Wang, Lei Lu^*

and Fujuan Feng

College of Life Sciences, Northeast Forestry University, Harbin 150040, China

Catalysts 2017, 7(9), 275; https://doi.org/10.3390/catal7090275 - 15 Sep 2017

Cited by 63 | Viewed by 10730

Abstract

Indigo carmine is a typical recalcitrant dye which is widely used in textile dyeing processes. Laccases are versatile oxidases showing strong ability to eliminate hazardous dyes from wastewater. However, most laccases require the participation of mediators for efficient decolorization of indigo carmine. Here [...] Read more.

Indigo carmine is a typical recalcitrant dye which is widely used in textile dyeing processes. Laccases are versatile oxidases showing strong ability to eliminate hazardous dyes from wastewater. However, most laccases require the participation of mediators for efficient decolorization of indigo carmine. Here we describe the improvement of the decolorization ability of a bacterial laccase through site-directed mutagenesis. A D501G variant of Bacillus amyloliquefaciens laccase was constructed and overexpressed in Escherichia coli. The laccase activity in the culture supernatant achieved 3374 U·L⁻¹ for the mutant. Compared with the wild-type enzyme, the D501G exhibited better stability and catalytic efficiency. It could decolorize more than 92% of indigo carmine without additional mediators in 5 h at pH 9.0, which was 3.5 times higher than the wild-type laccase. Isatin sulfonic acid was confirmed to be the main product of indigo carmine degradation by UV-vis and LC-MS analyses. Full article

(This article belongs to the Special Issue Biocatalysis and Biotransformations)

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11 pages, 1320 KiB

Open AccessArticle

Electrocarboxylation of Dichlorobenzenes on a Silver Electrode in DMF

by Pei-Pei Luo¹, Ying-Tian Zhang¹, Bao-Li Chen^1,*

, Shu-Xian Yu¹, Hua-Wei Zhou¹, Kong-Gang Qu¹, Yu-Xia Kong¹, Xian-Qiang Huang¹, Xian-Xi Zhang^1,* and Jia-Xing Lu^2,*

¹ Shandong Provincial Key Laboratory of Chemical Energy Storage and Novel Cell Technology, College of Chemistry and Chemical Engineering, Liaocheng University, Liaocheng 252059, China

² Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China

Catalysts 2017, 7(9), 274; https://doi.org/10.3390/catal7090274 - 15 Sep 2017

Cited by 18 | Viewed by 6096

Abstract

Carbon dioxide (CO₂) is the largest contributor to the greenhouse effect, and fixing and using this greenhouse gas in a facile manner is crucial. This work investigates the electrocarboxylation of dichlorobenzenes with the atmospheric pressure of CO₂ in an undivided [...] Read more.

Carbon dioxide (CO₂) is the largest contributor to the greenhouse effect, and fixing and using this greenhouse gas in a facile manner is crucial. This work investigates the electrocarboxylation of dichlorobenzenes with the atmospheric pressure of CO₂ in an undivided cell with an Ag cathode and an Mg sacrificial anode. The corresponding carboxylic acids and their derivatives, which are important industrial and fine chemicals, are obtained. To deeply understand this reaction, we investigate the influence of various reaction conditions, such as supporting electrolyte, current density, electric charge, and reaction temperature, on the electrocarboxylation yield by using 1,4-dichlorobenzene as the model compound. The electrochemical behavior of dichlorobenzenes is studied through cyclic voltammetry. The relation among the distinct electronic effects of dichlorobenzenes, the electrochemical characteristics of their reduction, and the distribution law of target products is also established. Full article

(This article belongs to the Special Issue Advances in Electrocatalysis)

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14 pages, 1862 KiB

Open AccessArticle

The Isomerization of Limonene over the Ti-SBA-15 Catalyst—The Influence of Reaction Time, Temperature, and Catalyst Content

by Monika Retajczyk and Agnieszka Wróblewska^*

West Pomeranian University of Technology Szczecin, Faculty of Chemical Technology and Engineering, Institute of Organic Chemical Technology, Pulaskiego 10, 70-322 Szczecin, Poland

Catalysts 2017, 7(9), 273; https://doi.org/10.3390/catal7090273 - 14 Sep 2017

Cited by 20 | Viewed by 9310

Abstract

The isomerization of limonene over the Ti-SBA-15 catalyst, which was prepared by the hydrothermal method, was studied. The main products of limonene isomerization were terpinolene, α-terpinene, γ-terpinene, and p-cymene—products with numerous applications. The amount of these products depended on reaction time, temperature, and [...] Read more.

The isomerization of limonene over the Ti-SBA-15 catalyst, which was prepared by the hydrothermal method, was studied. The main products of limonene isomerization were terpinolene, α-terpinene, γ-terpinene, and p-cymene—products with numerous applications. The amount of these products depended on reaction time, temperature, and catalyst content. These parameters changed in the following range: reaction time 30–1380 min, temperature 140–160 °C, and catalyst content 5–15 wt %. Finally, the most favorable conditions for the limonene isomerization process were established: a reaction time of 180 min, temperature of 160 °C, and amount of the catalyst 15 wt %. In order to obtain p-cymene (dehydroaromatization product), the most favorable conditions are similar but the reaction time should be 1380 min. The application of such conditions allowed us to obtain the highest amounts of the desired products in the shortest time. Full article

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15 pages, 2226 KiB

Open AccessArticle

The Catalytic Hydrogenation of Maleic Anhydride on CeO_2−δ-Supported Transition Metal Catalysts

by Xin Liao^1,2, Yin Zhang¹, Junqiu Guo², Lili Zhao¹, Martyn Hill²

, Zheng Jiang^1,2,* and Yongxiang Zhao^1,*

¹ Engineering Research Center of Ministry of Education for Fine Chemicals, School of Chemistry and Chemical Engineering, Shanxi University, Taiyuan 030006, China

² Faculty of Engineering and the Environment, University of Southampton, Highfield, Southampton SO17 1BJ, UK

Catalysts 2017, 7(9), 272; https://doi.org/10.3390/catal7090272 - 14 Sep 2017

Cited by 38 | Viewed by 7888

Abstract

The proper selection of transition metals and support is pivotal to the design of active and selective catalysts for maleic anhydride hydrogenation (MAH). Herein, the M/CeO_2−δ (M = Co, Ni, Cu, respectively) catalysts with pre-optimised metal loading of 10 wt % were [...] Read more.

The proper selection of transition metals and support is pivotal to the design of active and selective catalysts for maleic anhydride hydrogenation (MAH). Herein, the M/CeO_2−δ (M = Co, Ni, Cu, respectively) catalysts with pre-optimised metal loading of 10 wt % were prepared via a wet impregnation method and well characterized to corroborate their MAH performance with the properties of metal, support and the M/CeO_2−δ catalysts. The results revealed that the metal dispersion on the catalyst declines in the order of Ni/CeO_2−δ > Co/CeO_2−δ > Cu/CeO_2−δ, similar to the apparent activity for maleic anhydride (MA) transformation to succinic anhydride (SA). The hydrogenolysis of SA to γ-butyrolactone (GBL) occurs on Ni/CeO_2−δ and Co/CeO_2−δ only when the MA → SA transformation completing. The Ni/CeO_2−δ displays superior activity and selectivity to Co/CeO_2−δ in both MA → SA and SA → GBL reactions, while the Cu/CeO_2−δ and CeO_2−δ are both inert for SA → GBL hydrogenolysis. The MA hydrogenation to SA follows the first order kinetic law on the Ni/CeO_2−δ and Co/CeO_2−δ catalysts yet a more complex kinetic characteristics observed on the Cu/CeO_2−δ. The distinct catalytic hydrogenation behaviours of the M/CeO_2−δ catalysts are assigned to the synergism of dispersion and electronic configuration of the transition metals and oxygen vacancies. Full article

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14 pages, 9788 KiB

Open AccessArticle

Catalytic Characteristics of New Antibacterials Based on Hexahistidine-Containing Organophosphorus Hydrolase

by Olga Maslova^*

, Aysel Aslanli, Nikolay Stepanov, Ilya Lyagin

and Elena Efremenko^*

Faculty of Chemistry, Lomonosov Moscow State University, Moscow 119991, Russia

Catalysts 2017, 7(9), 271; https://doi.org/10.3390/catal7090271 - 14 Sep 2017

Cited by 18 | Viewed by 6179

Abstract

Catalytic characteristics of hexahistidine-containing organophosphorus hydrolase (His₆-OPH) and its enzyme-polyelectrolyte complexes with poly-l-glutamic acid or poly-l-aspartic acid (His₆-OPH/PLD₅₀), hydrolyzing organophosphorous compounds, and N-acyl homoserine lactones were studied in the presence of various [...] Read more.

Catalytic characteristics of hexahistidine-containing organophosphorus hydrolase (His₆-OPH) and its enzyme-polyelectrolyte complexes with poly-l-glutamic acid or poly-l-aspartic acid (His₆-OPH/PLD₅₀), hydrolyzing organophosphorous compounds, and N-acyl homoserine lactones were studied in the presence of various antibiotics (ampicillin, gentamicin, kanamycin, and rifampicin). The antibiotics at concentrations below 1 g·L⁻¹ had a negligible inhibiting effect on the His₆-OPH activity. Mixed inhibition of His₆-OPH was established for higher antibiotic concentrations, and rifampicin was the most potent inhibitor. Stabilization of the His₆-OPH activity was observed in the presence of antibiotics at a concentration of 0.2 g·L⁻¹ during exposure at 25–41 °C. Molecular docking of antibiotics to the surface of His₆-OPH dimer revealed the antibiotics binding both to the area near active centers of the enzyme subunits and to the region of contact between subunits of the dimer. Such interactions between antibiotics and His₆-OPH were verified with Fourier-transform infrared (FTIR) spectroscopy. Considering all the results of the study, the combination of His₆-OPH/PLD₅₀ with β-lactam antibiotic ampicillin was established as the optimal one in terms of exhibition and persistence of maximal lactonase activity of the enzyme. Full article

(This article belongs to the Special Issue Biocatalysis and Biotransformations)

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23 pages, 4972 KiB

Open AccessArticle

Promotion of Ca-Co Bifunctional Catalyst/Sorbent with Yttrium for Hydrogen Production in Modified Chemical Looping Steam Methane Reforming Process

by Samira Akbari-Emadabadi, Mohammad Reza Rahimpour^*, Ali Hafizi and Peyman Keshavarz

Department of Chemical Engineering, Shiraz University, Shiraz 71345, Iran

Catalysts 2017, 7(9), 270; https://doi.org/10.3390/catal7090270 - 13 Sep 2017

Cited by 22 | Viewed by 6185

Abstract

In this study, the application of a calcium-based bifunctional catalyst/sorbent is investigated in modified chemical looping steam methane reforming (CLSMR) process for in situ CO₂ sorption and H₂ production. The yttrium promoted Ca-Co samples were synthesized and applied as bifunctional catalysts/sorbent. [...] Read more.

In this study, the application of a calcium-based bifunctional catalyst/sorbent is investigated in modified chemical looping steam methane reforming (CLSMR) process for in situ CO₂ sorption and H₂ production. The yttrium promoted Ca-Co samples were synthesized and applied as bifunctional catalysts/sorbent. The influence of reduction temperature (500–750 °C), Ca/Co and Ca/Y ratios (1.5–∞ and 3–18, respectively) and catalyst life time are determined in CLSMR process. The physicochemical transformation of fresh, used and regenerated samples after 16 redox cycles are determined using X-ray powder diffraction (XRD), N₂ adsorption–desorption, field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM) techniques. The effect of yttrium promoter on the structure of catalyst and regeneration step on the reversibility of bifunctional catalyst/sorbent was two important factors. The characterization results revealed that the presence of yttrium in the structure of Ca-9Co sample could improve the morphology and textural properties of catalyst/sorbents. The suitable reversibility of bifunctional catalyst/sorbents during the repeated cycles is confirmed by characterization of calcined samples. The Ca-9Co-4.5Y as optimal catalyst illustrated superior performance and stability. It showed about 95.8% methane conversion and 82.9% hydrogen yield at 700 °C and stable activity during 16 redox cycles. Full article

(This article belongs to the Special Issue Reforming Catalysts)

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13 pages, 9291 KiB

Open AccessArticle

Selective Acetylation of Small Biomolecules and Their Derivatives Catalyzed by Er(OTf)₃

by Monica Nardi^1,2,*

, Maria Luisa Di Gioia^3,*

, Paola Costanzo⁴

, Antonio De Nino¹

, Loredana Maiuolo¹

, Manuela Oliverio⁴

, Fabrizio Olivito⁴ and Antonio Procopio⁴

¹ Dipartimento di Chimica, Università della Calabria Cubo 12C, 87036 Arcavacata di Rende CS, Italy

² Dipartimento di Agraria, Università Telematica San Raffaele, Roma, Via di Val Cannuta, 247, 00166 Rome, Italy

³ Dipartimento di Farmacia e Scienze della Salute e della Nutrizione, Edificio Polifunzionale, Università della Calabria, Arcavacata di Rende, 87030 Cosenza, Italy

⁴ Dipartimento di Scienze della Salute, Università Magna Graecia, Viale Europa, Germaneto, 88100 Catanzaro CZ, Italy

Catalysts 2017, 7(9), 269; https://doi.org/10.3390/catal7090269 - 12 Sep 2017

Cited by 28 | Viewed by 5156

Abstract

It is of great significance to develop sustainable processes of catalytic reaction. We report a selective procedure for the synthesis of acetylated bioactive compounds in water. The use of 1-acetylimidazole combined with Er(OTf)₃ as a Lewis acid catalyst gives high regioselectivity and [...] Read more.

It is of great significance to develop sustainable processes of catalytic reaction. We report a selective procedure for the synthesis of acetylated bioactive compounds in water. The use of 1-acetylimidazole combined with Er(OTf)₃ as a Lewis acid catalyst gives high regioselectivity and good yields for the acetylation of primary hydroxyl groups, as well as amino groups. The protection is achieved in short reaction times under microwave irradiation, and is successful even in the case of base-sensitive substrates. Full article

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11 pages, 2032 KiB

Open AccessArticle

Pulse Microcalorimetry Study of Methane Dry Reforming Reaction on Ni/Ceria-Zirconia Catalyst

by Mikhail N. Simonov^1,2

, Vladimir A. Rogov^1,2, Marina Yu. Smirnova^1,2 and Vladislav A. Sadykov^1,2,*

¹ Boreskov Institute of Catalysis, Prospekt Akademika Lavrentieva, 5, Novosibirsk 630090, Russia

² Novosibirsk State University, Pirogova Street, 2, Novosibirsk 630090, Russia

Catalysts 2017, 7(9), 268; https://doi.org/10.3390/catal7090268 - 12 Sep 2017

Cited by 15 | Viewed by 6172

Abstract

For Ni/CeZrO catalyst prepared in supercritical isopropanol main features of methane dry reforming reaction mechanism were studied by the pulse microcalorimetric technique. The reaction scheme is described by a step-wise redox mechanism with independent stages of CH₄ transformation on Ni/support interface producing [...] Read more.

For Ni/CeZrO catalyst prepared in supercritical isopropanol main features of methane dry reforming reaction mechanism were studied by the pulse microcalorimetric technique. The reaction scheme is described by a step-wise redox mechanism with independent stages of CH₄ transformation on Ni/support interface producing syngas with participation of support oxygen bridging species (the rate-limiting stage) and fast reoxidation of support sites by CO₂ yielding CO regenerating reactive oxygen species. Full article

(This article belongs to the Special Issue Conversion of CO₂ into CO Using Heterogeneous Catalysis)

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53 pages, 10451 KiB

Open AccessReview

Heck Reaction—State of the Art

by Sangeeta Jagtap

Department of Chemistry, Baburaoji Gholap College, Sangvi, Pune 411027, India

Catalysts 2017, 7(9), 267; https://doi.org/10.3390/catal7090267 - 11 Sep 2017

Cited by 184 | Viewed by 34549

Abstract

The Heck reaction is one of the most studied coupling reactions and is recognized with the Nobel Prize in Chemistry. Thousands of articles, hundreds of reviews and a number of books have been published on this topic. All reviews are written exhaustively describing [...] Read more.

The Heck reaction is one of the most studied coupling reactions and is recognized with the Nobel Prize in Chemistry. Thousands of articles, hundreds of reviews and a number of books have been published on this topic. All reviews are written exhaustively describing the various aspects of Heck reaction and refer to the work done hitherto. Looking at the quantum of the monographs published, and the reviews based on them, we found a necessity to summarize all reviews on Heck reaction about catalysts, ligands, suggested mechanisms, conditions, methodologies and the compounds formed via Heck reaction in one review and generate a resource of information. One can find almost all the catalysts used so far for Heck reaction in this review. Full article

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

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13 pages, 5763 KiB

Open AccessArticle

Flower-Like Au–CuO/Bi₂WO₆ Microsphere Catalysts: Synthesis, Characterization, and Their Catalytic Performances for CO Oxidation

by Lili Wang¹, Baolin Zhu^1,2, Shoumin Zhang^1,2 and Weiping Huang^1,2,3,*

¹ College of Chemistry, Nankai University, Tianjin 300071, China

² The Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), Nankai University, Tianjin 300071, China

³ Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300071, China

Catalysts 2017, 7(9), 266; https://doi.org/10.3390/catal7090266 - 11 Sep 2017

Cited by 1 | Viewed by 4918

Abstract

The flower-like Bi₂WO₆ microsphere was synthesized through a simple hydrothermal route, and three catalysts, Au/Bi₂WO₆, CuO/Bi₂WO₆, and Au–CuO/Bi₂WO₆, were prepared by a deposition–precipitation method. The morphology and structure [...] Read more.

The flower-like Bi₂WO₆ microsphere was synthesized through a simple hydrothermal route, and three catalysts, Au/Bi₂WO₆, CuO/Bi₂WO₆, and Au–CuO/Bi₂WO₆, were prepared by a deposition–precipitation method. The morphology and structure of the catalysts were characterized by X-ray powder diffraction, surface area analyzer, inductively coupled plasma optical emission spectrometer, scanning electron microscope, transmission electron microscopy, UV/Vis spectrometer, as well as X-ray photoelectron spectroscopy. Their catalytic performances in catalytic CO oxidation were evaluated. For Au/Bi₂WO₆ and CuO/Bi₂WO₆, Au and CuO nanoparticles highly dispersed on Bi₂WO₆ are 3 and 10 nm, respectively, in average size. For Au–CuO/Bi₂WO₆, a part of the Au nanoparticles (Au NPs) strongly adheres to the CuO, due to the strong interaction between Au NPs and CuO, which has a positive effect on catalytic activity of Au–CuO/Bi₂WO₆. Au–CuO/Bi₂WO₆ can convert CO into CO₂ completely at 40 °C, as the contents of Au and Cu are 0.438 wt % and 4.85 wt %, respectively. Full article

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40 pages, 10246 KiB

Open AccessFeature PaperReview

Hydrodeoxygenation of Lignin-Derived Phenols: From Fundamental Studies towards Industrial Applications

by Päivi Mäki-Arvela and Dmitry Yu. Murzin^*

Johan Gadolin Process Chemistry Centre, Åbo Akademi University, 20500 Turku/Åbo, Finland

Catalysts 2017, 7(9), 265; https://doi.org/10.3390/catal7090265 - 7 Sep 2017

Cited by 96 | Viewed by 12587

Abstract

Hydrodeoxygenation (HDO) of bio-oils, lignin and their model compounds is summarized in this review. The main emphasis is put on elucidating the reaction network, catalyst stability and time-on-stream behavior, in order to better understand the prerequisite for industrial utilization of biomass in HDO [...] Read more.

Hydrodeoxygenation (HDO) of bio-oils, lignin and their model compounds is summarized in this review. The main emphasis is put on elucidating the reaction network, catalyst stability and time-on-stream behavior, in order to better understand the prerequisite for industrial utilization of biomass in HDO to produce fuels and chemicals. The results have shown that more oxygenated feedstock, selection of temperature and pressure as well as presence of certain catalyst poisons or co-feed have a prominent role in the HDO of real biomass. Theoretical considerations, such as density function theory (DFT) calculations, were also considered, giving scientific background for the further development of HDO of real biomass. Full article

(This article belongs to the Special Issue Catalytic Sustainable Processes in Biorefineries)

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15 pages, 4929 KiB

Open AccessArticle

Mechanistic Insight into the 2° Alcohol Oxidation Mediated by an Efficient Cu^I/L-Proline-TEMPO Catalyst—A Density Functional Theory Study

by Siyu Li¹, Lin Cheng^1,*

, Qi Wu², Qiancheng Zhang¹, Jucai Yang¹ and Juming Liu^1,*

¹ College of Chemical Engineering, Inner Mongolia University of Technology, Inner Mongolia Key Laboratory of Theoretical and Computational Chemistry Simulation, Hohhot 010051, China

² High Performance Computing Center of Jilin University, Changchun 130022, China

Catalysts 2017, 7(9), 264; https://doi.org/10.3390/catal7090264 - 5 Sep 2017

Cited by 3 | Viewed by 6364

Abstract

Density functional theory (DFT) calculations have been performed to investigate the 2° alcohol oxidation to acetophenone catalyzed by the Cu^I/L-Proline-2,2,6,6- tetramethylpiperidinyloxy (TEMPO) catalyst system. Seven possible pathways (paths A→F) are presented. Our calculations show that two pathways (path A and path [...] Read more.

Density functional theory (DFT) calculations have been performed to investigate the 2° alcohol oxidation to acetophenone catalyzed by the Cu^I/L-Proline-2,2,6,6- tetramethylpiperidinyloxy (TEMPO) catalyst system. Seven possible pathways (paths A→F) are presented. Our calculations show that two pathways (path A and path B) are the potential mechanisms. Furthermore, by comparing with experimental observation, it is found that path A—in which substrate alcohol provides the proton to ⁻O^tBu to produce HO^tBu followed by the oxidation of substrate directly to product acetophenone by O₂—is favored in the absence of TEMPO. Correspondingly, path B is likely to be favored when TEMPO is involved. In path B, the O–O bond cleavage of Cu^I–OOH to Cu^II–OH species occurs, followed by acetophenone formation assisted by ligand (L)²ˉ. It is also found that the cooperation of ligand (L)²ˉ and TEMPO plays an important role in assisting the formation of the product acetophenone in path B. Full article

(This article belongs to the Special Issue Catalysis Assisted by Calculations: From Organic and Metal Catalysts to Enzymes)

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15 pages, 6658 KiB

Open AccessArticle

Regioselective Synthesis of Lactulose Esters by Candida antarctica and Thermomyces lanuginosus Lipases

by Luis F. Chávez-Flores¹, Hiram Isaac Beltran², Daniel Arrieta-Baez³

and Dolores Reyes-Duarte^4,*

¹ Posgrado en Ciencias Naturales e Ingeniería, Universidad Autónoma Metropolitana-Unidad Cuajimalpa, Av. Vasco de Quiroga 4871, Col. Santa Fe Cuajimalpa, Deleg. Cuajimalpa de Morelos 05348 CDMX, Mexico

² Departamento de Ciencias Naturales, Universidad Autónoma Metropolitana-Unidad Cuajimalpa, Av. Vasco de Quiroga 4871, Col. Santa Fe Cuajimalpa, Deleg. Cuajimalpa de Morelos 05348 CDMX, Mexico

³ Instituto Politécnico Nacional - CNMN, Calle Luis Enrique Erro s/n, Unidad Profesional Adolfo López Mateos, Col. Zacatenco, México D.F. CP 07738, Mexico

⁴ Departamento de Procesos y Tecnología, Universidad Autónoma Metropolitana-Unidad Cuajimalpa, Av. Vasco de Quiroga 4871, Col. Santa Fe Cuajimalpa, Deleg. Cuajimalpa de Morelos 05348 CDMX, Mexico

Catalysts 2017, 7(9), 263; https://doi.org/10.3390/catal7090263 - 3 Sep 2017

Cited by 19 | Viewed by 7042

Abstract

The interest in sugar esters as emulsifiers has been increasing in recent years because they have tunable surfactant properties that depend on the chain length of the fatty acid and the type of the sugar, covering a wide range of hydrophilic-lipophilic balance (HLB). [...] Read more.

The interest in sugar esters as emulsifiers has been increasing in recent years because they have tunable surfactant properties that depend on the chain length of the fatty acid and the type of the sugar, covering a wide range of hydrophilic-lipophilic balance (HLB). In this work, ten biocatalysts were used for the transesterification reaction screening of lactulose, a prebiotic sugar, with vinyl laurate. The reactions were followed by thin layer chromatography (TLC) analysis, identifying two major monoesters mixtures defined as monoester fraction 1 and monoester fraction 2. Candida antarctica lipase B (Novozym 435) produces “monoester fraction 1”, while Thermomyces lanuginosus lipase (Lipozyme^® TL IM) and Mucor miehei lipase (Lipozyme^®) seem to produce the same “monoester fraction 2”. These three enzymes were selected as model biocatalysts for a kinetic study, and monoester fractions 1 and 2 from Novozym 435 and Lipozyme^® TL IM, respectively, were used for product characterization. Monoester fraction 1 contained 86.9% of the major monoester in position 1-O-, and monoester fraction 2 contained 91.4% of 6′-O-. Although these lipases acylated three positions of lactulose, they mainly synthesize a monoester presenting regioselectivity. These results contribute to the study of the chemical structure diversity of biosurfactants to enhance their applications in foods, pharmaceutical products, and cosmetics. Full article

(This article belongs to the Special Issue Biocatalysis and Biotransformations)

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14 pages, 2044 KiB

Open AccessFeature PaperArticle

Expanding the Scope of Cu(I) Catalyzed “Click Chemistry” with Abnormal NHCs: Three-Fold Click to Tris-Triazoles

by Nga Kim T. Ho², Sven O. Reichmann³, Dennis Rottschäfer^1,2, Regine Herbst-Irmer³ and Rajendra S. Ghadwal^1,2,*

¹ Anorganische Molekülchemie und Katalyse, Lehrstuhl für Anorganische Chemie und Strukturchemie, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, D-33615 Bielefeld, Germany

² Centrum für Molekulare Materialien, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, D-33615 Bielefeld, Germany

³ Institut für Anorganische Chemie der Georg-August-Universität Göttingen, Tammannstraße 4, D-37077 Göttingen, Germany

Catalysts 2017, 7(9), 262; https://doi.org/10.3390/catal7090262 - 1 Sep 2017

Cited by 18 | Viewed by 6711

Abstract

Cationic copper(I) complexes [Cu(aIPr^Ph)(IPr)]I (3) and [Cu(aIPr^Ph)₂]I (4) featuring an abnormal N-heterocyclic carbene (aNHC) (aIPr^Ph = 1,3-bis(2,6-diisopropylphenyl)-2-phenyl- imidazol-4-ylidene) and/or an NHC (IPr = 1,3-Bis(2,6-diisopropylphenyl)imidazol-2-ylidene) ligand(s) are reported. Treatment of Cu(aIPr^Ph [...] Read more.

Cationic copper(I) complexes [Cu(aIPr^Ph)(IPr)]I (3) and [Cu(aIPr^Ph)₂]I (4) featuring an abnormal N-heterocyclic carbene (aNHC) (aIPr^Ph = 1,3-bis(2,6-diisopropylphenyl)-2-phenyl- imidazol-4-ylidene) and/or an NHC (IPr = 1,3-Bis(2,6-diisopropylphenyl)imidazol-2-ylidene) ligand(s) are reported. Treatment of Cu(aIPr^Ph)I (2) with IPr affords complex 3. Reaction of (IPrPh)I (1) (IPrPh = 1,3-bis(2,6-diisopropylphenyl)-2-phenyl-imidazolium) with CuI in the presence of K{N(SiMe₃)₂} leads to the formation of 4. Complexes 3 and 4 represent rare examples of mixed aNHC-NHC and bis-aNHC metal complexes, respectively. They are characterized by elemental analysis, NMR spectroscopic, and mass spectrometric studies. The solid-state molecular structures of 3 and 4 have been determined by single crystal X-ray diffraction analyses. The catalytic activity of 2, 3, and 4 has been investigated in the [3+2] cycloaddition of alkynes and organic azides, affording triazole derivatives in an almost quantitative yield. Notably, complexes 2, 3, and 4 are excellent catalysts for the three-fold cycloaddition of a tris-azide with various alkynes. This catalytic protocol offers a high yield access to tris-triazoles in a shorter reaction time and considerably reduces the experimental work-up compared to the classical synthetic method. Full article

(This article belongs to the Special Issue Tailor-Made NHC Ligands)

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57 pages, 15147 KiB

Open AccessFeature PaperReview

The Beneficial Sinergy of MW Irradiation and Ionic Liquids in Catalysis of Organic Reactions

by Barbara Floris, Federica Sabuzi

, Pierluca Galloni

and Valeria Conte^*

Dipartimento di Scienze e Tecnologie Chimiche, Università degli Studi di Roma “Tor Vergata”, via della Ricerca Scientifica snc, 00133 Rome, Italy

Catalysts 2017, 7(9), 261; https://doi.org/10.3390/catal7090261 - 1 Sep 2017

Cited by 24 | Viewed by 8701

Abstract

The quest for sustainable processes is becoming more and more important, with catalysis playing a major role in improving atom economy and reducing waste. Organic syntheses with less need of protecting/de-protecting steps are highly desirable. The combination of microwave irradiation, as energy source, [...] Read more.

The quest for sustainable processes is becoming more and more important, with catalysis playing a major role in improving atom economy and reducing waste. Organic syntheses with less need of protecting/de-protecting steps are highly desirable. The combination of microwave irradiation, as energy source, with ionic liquids, as both solvents and catalysts, offered interesting solutions in recent years. The literature data of the last 15 years concerning selected reactions are presented, highlighting the importance of microwave (MW) technology coupled with ionic liquids. Full article

(This article belongs to the Special Issue Enabling Technologies toward Green Catalysis)

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17 pages, 6936 KiB

Open AccessReview

Polyoxometalate (POM)-Layered Double Hydroxides (LDH) Composite Materials: Design and Catalytic Applications

by Tengfei Li¹, Haralampos N. Miras^2,*

and Yu-Fei Song^1,3,*

¹ State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China

² WestCHEM, School of Chemistry, the University of Glasgow, Glasgow G12 8QQ, UK

³ Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China

Catalysts 2017, 7(9), 260; https://doi.org/10.3390/catal7090260 - 1 Sep 2017

Cited by 105 | Viewed by 16752

Abstract

Layered double hydroxides (LDHs) are an important large class of two-dimensional (2D) anionic lamellar materials that possess flexible modular structure, facile exchangeability of inter-lamellar guest anions and uniform distribution of metal cations in the layer. Owing to the modular accessible gallery and unique [...] Read more.

Layered double hydroxides (LDHs) are an important large class of two-dimensional (2D) anionic lamellar materials that possess flexible modular structure, facile exchangeability of inter-lamellar guest anions and uniform distribution of metal cations in the layer. Owing to the modular accessible gallery and unique inter-lamellar chemical environment, polyoxometalates (POMs) intercalated with LDHs has shown a vast array of physical properties with applications in environment, energy, catalysis, etc. Here we describe how polyoxometalate clusters can be used as building components for the construction of systems with important catalytic properties. This review article mainly focuses on the discussion of new synthetic approaches developed recently that allow the incorporation of the element of design in the construction of a fundamentally new class of materials with pre-defined functionalities in catalytic applications. Introducing the element of design and taking control over the finally observed functionality we demonstrate the unique opportunity for engineering materials with modular properties for specific catalytic applications. Full article

(This article belongs to the Special Issue Recent Advances in Polyoxometalate-Catalyzed Reactions)

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12 pages, 6510 KiB

Open AccessFeature PaperArticle

The Role of Non-Framework Lewis Acidic Al Species of Alkali-Treated HZSM-5 in Methanol Aromatization

by Po-Chen Lai¹, Chi-Ying Hsieh¹, Chao-Huang Chen² and Yu-Chuan Lin^1,*

¹ Department of Chemical Engineering, National Cheng Kung University, Tainan 70101, Taiwan

² Division of Chemical Engineering, Material and Chemical Research Laboratories, Industrial Technology Research Institute, Hsinchu 30011, Taiwan

Catalysts 2017, 7(9), 259; https://doi.org/10.3390/catal7090259 - 1 Sep 2017

Cited by 13 | Viewed by 4930

Abstract

Mesoporous HZSM-5 prepared by alkaline treatment (also termed desilication) has drawn significant attention due to its potential in large-scale production and in versatile applications, such as separation and catalysis. Alkali-treated HZSM-5 contains considerable amounts of non-framework (amorphous) Lewis acidic Al species on the [...] Read more.

Mesoporous HZSM-5 prepared by alkaline treatment (also termed desilication) has drawn significant attention due to its potential in large-scale production and in versatile applications, such as separation and catalysis. Alkali-treated HZSM-5 contains considerable amounts of non-framework (amorphous) Lewis acidic Al species on the external surface, and is deemed to be essential in affecting its catalytic performances. This study intends to clarify the catalytic nature of amorphous Al species of alkali-treated HZSM-5 in methanol aromatization. Physicochemical characterizations, including N₂ adsorption, scanning electron microscopy (SEM), X-ray diffraction (XRD), magic-angle-spinning nuclear magnetic resonance (MAS NMR), inductively coupled plasma (ICP) analysis, NH₃ temperature-programmed desorption (TPD), and methanol-TPD, were performed. The outcomes showed that non-framework Al promotes the hydride transfer in mesoporous HZSM-5, thereby facilitating the aromatization reaction. Among aromatic products, durene can be promoted by non-framework Al through methylation/transalkylation of other aromatics, particularly xylenes, instead of being promoted by reduced space confinement in mesoporous HZSM-5. Full article

(This article belongs to the Special Issue Zeolites and Catalysis)

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17 pages, 2189 KiB

Open AccessArticle

Experimental Research of an Active Solution for Modeling In Situ Activating Selective Catalytic Reduction Catalyst

by Tuo Ye¹, Donglin Chen^1,*, Yanshan Yin¹, Jing Liu² and Xi Zeng¹

¹ School of Energy and Power Engineering, Changsha University of Science and Technology, Changsha 410114, China

² School of Electric Power, South China University of Technology, Guangzhou 510640, China

Catalysts 2017, 7(9), 258; https://doi.org/10.3390/catal7090258 - 31 Aug 2017

Cited by 13 | Viewed by 6006

Abstract

The effect of active solutions suitable for the in situ activation of selective catalytic reduction (SCR) catalysts was experimentally investigated using a designed in situ activation modeling device. To gain further insight, scanning electron microscopy (SEM), specific surface area analysis (BET), Fourier transform [...] Read more.

The effect of active solutions suitable for the in situ activation of selective catalytic reduction (SCR) catalysts was experimentally investigated using a designed in situ activation modeling device. To gain further insight, scanning electron microscopy (SEM), specific surface area analysis (BET), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS) analyses were used to investigate the effects of different reaction conditions on the characteristics of the deactivated catalysts. The activation effect of loading V₂O₅, WO₃ and MoO₃ on the surface of the deactivated catalysts was analyzed and the correlation to the denitrification activity was determined. The results demonstrate that the prepared activating solution of 1 wt % vanadium (V), 9 wt % tungsten (W), and 6 wt % molybdenum (Mo) has a beneficial effect on the deactivation of the catalyst. The activated catalyst resulted in a higher NO removal rate when compared to the deactivated catalyst. Furthermore, the NO removal rate of the activated catalyst reached a maximum of 32%. The activity of the SCR catalyst is closely linked to the concentration of the active ingredients. When added in optimum amounts, the active ingredients helped to restore the catalytic activity. In particular, the addition of active ingredients, the availability of labile surface oxygen, and the presence of small pores improved the denitrification efficiency. Based on these results, active solutions can effectively solve the problem of denitrification catalyst deactivation. These findings are a reference for the in-situ activation of the selective catalytic reduction of nitrogen oxides (SCR-DeNOx) catalyst. Full article

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

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10 pages, 1452 KiB

Open AccessArticle

Characterization of a Novel Nicotine Hydroxylase from Pseudomonas sp. ZZ-5 That Catalyzes the Conversion of 6-Hydroxy-3-Succinoylpyridine into 2,5-Dihydroxypyridine

by Tao Wei¹, Jie Zang¹, Yadong Zheng¹, Hongzhi Tang², Sheng Huang¹ and Duobin Mao^1,*

¹ School of Food and Biological Engineering, Zhengzhou University of Light Industry, Zhengzhou 450002, China

² State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China

Catalysts 2017, 7(9), 257; https://doi.org/10.3390/catal7090257 - 31 Aug 2017

Cited by 8 | Viewed by 4286

Abstract

A novel nicotine hydroxylase was isolated from Pseudomonas sp. ZZ-5 (HSPH_ZZ). The sequence encoding the enzyme was 1206 nucleotides long, and encoded a protein of 401 amino acids. Recombinant HSPH_ZZ was functionally overexpressed in Escherichia coli BL21-Codon Plus (DE3)-RIL cells [...] Read more.

A novel nicotine hydroxylase was isolated from Pseudomonas sp. ZZ-5 (HSPH_ZZ). The sequence encoding the enzyme was 1206 nucleotides long, and encoded a protein of 401 amino acids. Recombinant HSPH_ZZ was functionally overexpressed in Escherichia coli BL21-Codon Plus (DE3)-RIL cells and purified to homogeneity after Ni-NTA affinity chromatography. Liquid chromatography-mass spectrometry (LC-MS) analyses indicated that the enzyme could efficiently catalyze the conversion of 6-hydroxy-3-succinoylpyridine (HSP) into 2,5-dihydroxypyridine (2,5-DHP) and succinic acid in the presence of nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD). The kinetic constants (K_m, k_cat, and k_cat/K_m) of HSPH_ZZ toward HSP were 0.18 mM, 2.1 s⁻¹, and 11.7 s⁻¹ mM⁻¹, respectively. The optimum temperature, pH, and optimum concentrations of substrate and enzyme for 2,5-DHP production were 30 °C, 8.5, 1.0 mM, and 1.0 μM, respectively. Under optimum conditions, 85.3 mg/L 2,5-DHP was produced in 40 min with a conversion of 74.9%. These results demonstrated that HSPH_ZZ could be used for the enzymatic production of 2,5-DHP in biotechnology applications. Full article

(This article belongs to the Special Issue Biocatalysis and Biotransformations)

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21 pages, 7879 KiB

Open AccessReview

Controllable and Large-Scale Synthesis of Carbon Nanostructures: A Review on Bamboo-Like Nanotubes

by Zirui Jia¹, Kaichang Kou¹, Ming Qin², Hongjing Wu^1,*

, Fabrizio Puleo³ and Leonarda Francesca Liotta^3,*

¹ School of Science, Northwestern Polytechnical University, Xi’an 710072, China

² Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074, China

³ Institute for the Study of Nanostructured Materials (ISMN)-CNR, Via Ugo La Malfa 153, 90146 Palermo, Italy

Catalysts 2017, 7(9), 256; https://doi.org/10.3390/catal7090256 - 30 Aug 2017

Cited by 62 | Viewed by 8971

Abstract

Bamboo-like carbon nanotubes are members of the carbon nanotubes (CNTs) family, whose structure is made up of separated hollow compartments and bamboo knots. Due to the peculiar structure of the CNTs species, the growth mechanism and related features have been widely investigated. Bamboo-like [...] Read more.

Bamboo-like carbon nanotubes are members of the carbon nanotubes (CNTs) family, whose structure is made up of separated hollow compartments and bamboo knots. Due to the peculiar structure of the CNTs species, the growth mechanism and related features have been widely investigated. Bamboo-like carbon nanotubes are widely applied in several fields, such as sensors, adsorbents, catalysts, and lithium-ion battery electrodes materials. Different methods have been applied for the synthesis of carbon nanotubes, among them, catalytic chemical vapor deposition has been singled out as the most used procedure due to low cost with a high quality product. The present review is devoted to increasing the literature dealing with the design, synthesis, and characterization of bamboo-like carbon nanotubes grown over different catalysts. Results on the methane dry reforming reaction, hydrocarbon thermal decomposition, special chemical vapor deposition as well as other methods applied to the preparation of bamboo-like carbon nanotubes are discussed. The differences in the carbon deposits between the dry reforming reaction and other reaction methods are compared and possible formation mechanisms of bamboo-like carbon nanotubes are discussed. Full article

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

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10 pages, 5302 KiB

Open AccessArticle

Continuous-Flow Monolithic Silica Microreactors with Arenesulphonic Acid Groups: Structure–Catalytic Activity Relationships

by Agnieszka Ciemięga¹, Katarzyna Maresz¹, Janusz J. Malinowski¹ and Julita Mrowiec-Białoń^1,2,*

¹ Institute of Chemical Engineering Polish Academy of Sciences, Bałtycka 5, 44-100 Gliwice, Poland

² Department of Chemical Engineering and Process Design, Silesian University of Technology, Ks. M. Strzody 7, 44-100 Gliwice, Poland

Catalysts 2017, 7(9), 255; https://doi.org/10.3390/catal7090255 - 30 Aug 2017

Cited by 18 | Viewed by 5362

Abstract

The performance of monolithic silica microreactors activated with sulphonic acid groups and a packed bed reactor with Amberlyst 15 resin were compared in the esterification of acetic acid with n-butanol. The monolithic microreactors were made of single silica rods with complex pore architecture, [...] Read more.

The performance of monolithic silica microreactors activated with sulphonic acid groups and a packed bed reactor with Amberlyst 15 resin were compared in the esterification of acetic acid with n-butanol. The monolithic microreactors were made of single silica rods with complex pore architecture, differing in the size of mesopores, and in particular, flow-through macropores which significantly affected the flow characteristic of the continuous system. The highest ester productivity of 105.2 mol·mol_H⁺⁻¹·h⁻¹ was achieved in microreactor M1 with the largest porosity, characterized by a total pore volume of 4 cm³·g⁻¹, mesopores with 20 nm diameter, and large flow-through macropores 30–50 μm in size. The strong impact of the permeability of the monoliths on a reaction kinetics was shown. Full article

(This article belongs to the Special Issue Nanostructured Materials for Applications in Heterogeneous Catalysis)

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13 pages, 1155 KiB

Open AccessArticle

Nature and Location of Carbonaceous Species in a Composite HZSM-5 Zeolite Catalyst during the Conversion of Dimethyl Ether into Light Olefins

by María Ibáñez, Paula Pérez-Uriarte, Miguel Sánchez-Contador, Tomás Cordero-Lanzac

, Andrés T. Aguayo, Javier Bilbao and Pedro Castaño^*

Department of Chemical Engineering, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain

Catalysts 2017, 7(9), 254; https://doi.org/10.3390/catal7090254 - 30 Aug 2017

Cited by 47 | Viewed by 7068

Abstract

The deactivation of a composite catalyst based on HZSM-5 zeolite (agglomerated in a matrix using boehmite as a binder) has been studied during the transformation of dimethyl ether into light olefins. The location of the trapped/retained species (on the zeolite or on the [...] Read more.

The deactivation of a composite catalyst based on HZSM-5 zeolite (agglomerated in a matrix using boehmite as a binder) has been studied during the transformation of dimethyl ether into light olefins. The location of the trapped/retained species (on the zeolite or on the matrix) has been analyzed by comparing the properties of the fresh and deactivated catalyst after runs at different temperatures, while the nature of those species has been studied using different spectroscopic and thermogravimetric techniques. The reaction occurs on the strongest acid sites of the zeolite micropores through olefins and alkyl-benzenes as intermediates. These species also condensate into bulkier structures (polyaromatics named as coke), particularly at higher temperatures and within the meso- and macropores of the matrix. The critical roles of the matrix and water in the reaction medium have been proved: both attenuating the effect of coke deposition. Full article

(This article belongs to the Special Issue Zeolites and Catalysis)

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24 pages, 10361 KiB

Open AccessFeature PaperReview

Nano-Array Integrated Structured Catalysts: A New Paradigm upon Conventional Wash-Coated Monolithic Catalysts?

by Junfei Weng^†

, Xingxu Lu^† and Pu-Xian Gao^*

¹ Department of Materials Science and Engineering & Institute of Materials Science, University of Connecticut, Storrs, CT 06269-3136, USA

^† These authors contributed equally to this work.

Catalysts 2017, 7(9), 253; https://doi.org/10.3390/catal7090253 - 28 Aug 2017

Cited by 23 | Viewed by 7398

Abstract

The monolithic catalyst, namely the structured catalyst, is one of the important categories of catalysts used in various fields, especially in catalytic exhaust after-treatment. Despite its successful application in conventional wash-coated catalysts in both mobile and stationary catalytic converters, washcoat-based technologies are facing [...] Read more.

The monolithic catalyst, namely the structured catalyst, is one of the important categories of catalysts used in various fields, especially in catalytic exhaust after-treatment. Despite its successful application in conventional wash-coated catalysts in both mobile and stationary catalytic converters, washcoat-based technologies are facing multi-fold challenges, including: (1) high Pt-group metals (PGM) material loading being required, driving the market prices; (2) less-than ideal distribution of washcoats in typically square-shaped channels associated with pressure drop sacrifice; and (3) far from clear correlations between macroscopic washcoat structures and their catalytic performance. To tackle these challenges, the well-defined nanostructure array (nano-array)-integrated structured catalysts which we invented and developed recently have been proven to be a promising class of cost-effective and efficient devices that may complement or substitute wash-coated catalysts. This new type of structured catalysts is composed of honeycomb-structured monoliths, whose channel surfaces are grown in situ with a nano-array forest made of traditional binary transition metal oxide support such as Al₂O₃, CeO₂, Co₃O₄, MnO₂, TiO₂, and ZnO, or newer support materials including perovskite-type ABO₃ structures, for example LaMnO₃, LaCoO₃, LaNiO, and LaFeO₃. The integration strategy parts from the traditional washcoat technique. Instead, an in situ nanomaterial assembly method is utilized, such as a hydro (solva-) thermal synthesis approach, in order to create sound structure robustness, and increase ease and complex-shaped substrate adaptability. Specifically, the critical fabrication procedures for nano-array structured catalysts include deposition of seeding layer, in situ growth of nano-array, and loading of catalytic materials. The generic methodology utilization in both the magnetic stirring batch process and continuous flow reactor synthesis offers the nano-array catalysts with great potential to be scaled up readily and cost-effectively. The tunability of the structure and catalytic performance could be achieved through morphology and geometry adjustment and guest atoms and defect manipulation, as well as composite nano-array catalyst manufacture. Excellent stabilities under various conditions were also present compared to conventional wash-coated catalysts. Full article

(This article belongs to the Special Issue Structured and Micro-Structured Catalysts and Reactors)

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12 pages, 3854 KiB

Open AccessArticle

SnS_x (x = 1, 2) Nanocrystals as Effective Catalysts for Photoelectrochemical Water Splitting

by Po-Chia Huang¹

, Yu-Min Shen¹, Sanjaya Brahma¹, Muhammad Omar Shaikh², Jow-Lay Huang^1,3,4 and Sheng-Chang Wang^2,*

¹ Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan

² Department of Mechanical Engineering, Southern Taiwan University of Science and Technology, Tainan 710, Taiwan

³ Department of Chemical and Materials Engineering, National University of Kaohsiung, Kaohsiung 81148, Taiwan

⁴ Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 70101, Taiwan

Catalysts 2017, 7(9), 252; https://doi.org/10.3390/catal7090252 - 25 Aug 2017

Cited by 37 | Viewed by 8624

Abstract

Two-dimensional SnS_x (x = 1, 2) nanocrystals are attractive catalysts for photoelectrochemical water splitting as their components are earth abundant and environmentally friendly. We have fabricated SnS thin-film photoelectrodes by spin coating mixed-phase SnS nanocrystals synthesized via a hot-injection technique on glass/Cr/Au [...] Read more.

Two-dimensional SnS_x (x = 1, 2) nanocrystals are attractive catalysts for photoelectrochemical water splitting as their components are earth abundant and environmentally friendly. We have fabricated SnS thin-film photoelectrodes by spin coating mixed-phase SnS nanocrystals synthesized via a hot-injection technique on glass/Cr/Au substrates. The obtained SnS thin films can be transformed into SnS₂ by introducing structural phase changes via a facile low-vacuum annealing protocol in the presence of sulfur. This sulfurization process enables the insertion of sulfur atoms between layers of SnS and results in the generation of shallow donors that alter the mechanism for water splitting. The SnS₂ thin films are used as stable photocatalysts to drive the oxygen evolution reaction, and the light-current density of 0.195 mA/cm² at 0.8 V vs. Ag/AgCl can be achieved due to the high carrier density, lower charge transfer resistance, and a suitable reaction band position. Based on a combination of UV-Vis spectroscopy (ultraviolet and visible spectroscopy), cyclic voltammetry and Mott–Schottky analysis, the band positions and band gaps of SnS and SnS₂ relative to the electrolyte are determined and a detailed mechanism for water splitting is presented. Our results demonstrate the potential of layered tin sulfide compounds as promising photocatalysts for efficient and large-scale water splitting. Full article

(This article belongs to the Special Issue Advances in Electrocatalysis)

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13 pages, 2352 KiB

Open AccessArticle

The Kinetic Resolution of Racemic Amines Using a Whole-Cell Biocatalyst Co-Expressing Amine Dehydrogenase and NADH Oxidase

by Hyunwoo Jeon^1,†, Sanghan Yoon^1,†, Md Murshidul Ahsan²

, Sihyong Sung¹, Geon-Hee Kim¹, Uthayasuriya Sundaramoorthy¹, Seung-Keun Rhee² and Hyungdon Yun^1,*

¹ Department of Systems Biotechnology, Konkuk University, Seoul 05029, Korea

² School of Biotechnology, Yeungnam University, Kyongsan 38541, Korea

^† Hyunwoo Jeon and Sanghan Yoon have contributed equally to this work.

Catalysts 2017, 7(9), 251; https://doi.org/10.3390/catal7090251 - 25 Aug 2017

Cited by 21 | Viewed by 7127

Abstract

Amine dehydrogenase (AmDH) possesses tremendous potential for the synthesis of chiral amines because AmDH catalyzes the asymmetric reductive amination of ketone with high enatioselectivity. Although a reductive application of AmDH is favored in practice, the oxidative route is interesting as well for the [...] Read more.

Amine dehydrogenase (AmDH) possesses tremendous potential for the synthesis of chiral amines because AmDH catalyzes the asymmetric reductive amination of ketone with high enatioselectivity. Although a reductive application of AmDH is favored in practice, the oxidative route is interesting as well for the preparation of chiral amines. Here, the kinetic resolution of racemic amines using AmDH was first extensively studied, and the AmDH reaction was combined with an NADH oxidase (Nox) to regenerate NAD⁺ and to drive the reaction forward. When the kinetic resolution was carried out with 10 mM rac-2-aminoheptane and 5 mM rac-α-methylbenzylamine (α-MBA) using purified enzymes, the enantiomeric excess (ee) values were less than 26% due to the product inhibition of AmDH by ketone and the inhibition of Nox by the substrate amine. The use of a whole-cell biocatalyst co-expressing AmDH and Nox apparently reduces the substrate and product inhibition, and/or it increases the stability of the enzymes. Fifty millimoles (50 mM) rac-2-aminoheptane and 20 mM rac-α-MBA were successfully resolved into the (S)-form with >99% ee using whole cells. The present study demonstrates the potential of a whole-cell biocatalyst co-expressing AmDH and Nox for the kinetic resolution of racemic amines. Full article

(This article belongs to the Special Issue Biocatalysis and Biotransformations)

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