Catalysts

11 pages, 5358 KiB

Open AccessArticle

Preparation of Rh/Ni Bimetallic Nanoparticles and Their Catalytic Activities for Hydrogen Generation from Hydrolysis of KBH₄

by Liqiong Wang, Liang Huang, Chengpeng Jiao, Zili Huang, Feng Liang, Simin Liu, Yuhua Wang and Haijun Zhang

Catalysts 2017, 7(4), 125; https://doi.org/10.3390/catal7040125 - 23 Apr 2017

Cited by 25 | Viewed by 6308

Abstract

ISOBAM-104 protected Rh/Ni bimetallic nanoparticles (BNPs) of 3.1 nm in diameter were synthesized by a co-reduction method with a rapid injection of KBH₄ solution. The catalytic activities of as-prepared BNPs for hydrogen generation from hydrolysis of a basic KBH₄ solution were [...] Read more.

ISOBAM-104 protected Rh/Ni bimetallic nanoparticles (BNPs) of 3.1 nm in diameter were synthesized by a co-reduction method with a rapid injection of KBH₄ solution. The catalytic activities of as-prepared BNPs for hydrogen generation from hydrolysis of a basic KBH₄ solution were evaluated. Ultraviolet-visible spectrophotometry (UV-Vis), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) were employed to characterize the structure, particle size, and chemical composition of the resultant BNPs. Catalytic activities for hydrolysis of KBH₄ and catalytic kinetics of prepared BNPs were also investigated. It was shown that Rh/Ni BNPs displayed much higher catalytic activities than that of Rh or Ni monometallic nanoparticles (MNPs), and the prepared Rh₁₀Ni₉₀ BNPs possessed the highest catalytic activities with a value of 11580 mol-H₂·h⁻¹·mol-Rh⁻¹. The high catalytic activities of Rh/Ni BNPs could be attributed to the electron transfer effect between Rh and Ni atoms, which was confirmed by a density functional theory (DFT) calculation. The apparent activation energy for hydrogen generation of the prepared Rh₁₀Ni₉₀ BNPs was about 47.2 ± 2.1 kJ/mol according to a kinetic study. Full article

(This article belongs to the Special Issue Small Molecule Activation and Catalysis)

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11 pages, 4749 KiB

Open AccessArticle

In Search of Governing Gas Flow Mechanism through Metal Solid Foams

by Anna Gancarczyk, Marcin Piątek, Marzena Iwaniszyn, Przemysław J. Jodłowski, Joanna Łojewska, Jolanta Kowalska and Andrzej Kołodziej

Catalysts 2017, 7(4), 124; https://doi.org/10.3390/catal7040124 - 21 Apr 2017

Cited by 7 | Viewed by 4961

Abstract

Solid foams have been intensely studied as promising structured catalytic internals. However, mechanisms governing flow and transport phenomena within the foam structures have not been properly addressed in the literature. The aim of this study was to consider such flow mechanisms based on [...] Read more.

Solid foams have been intensely studied as promising structured catalytic internals. However, mechanisms governing flow and transport phenomena within the foam structures have not been properly addressed in the literature. The aim of this study was to consider such flow mechanisms based on our experimental results on flow resistance. Two mechanisms were considered: developing laminar flow in a short capillary channel (flow-through model), and flow around an immersed solid body, either a cylinder or sphere (flow-around model). Flow resistance experiments were performed on three aluminum foams of 10, 20, and 40 PPI (pores per inch), using a 57 mm ID test column filled with the foams studied. The foam morphology was examined using microtomography and optical microscopy to derive the geometric parameters applied in the model equations. The flow-through model provided an accuracy of 25% for the experiments. The model channel diameter was the foam cell diameter, and the channel length was the strut thickness. The accuracy of the flow-around model was only slightly worse (35%). It was difficult to establish the geometry of the immersed solid body (sphere or cylinder) because experiment characteristics tended to change from sphere to cylinder with increasing PPI value. Full article

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

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12 pages, 1491 KiB

Open AccessArticle

A Simple and Efficient Process for Large Scale Glycerol Oligomerization by Microwave Irradiation

by Rémi Nguyen, Nicolas Galy, Abhishek K. Singh, Florian Paulus, Daniel Stöbener, Cathleen Schlesener, Sunil K. Sharma, Rainer Haag and Christophe Len

Catalysts 2017, 7(4), 123; https://doi.org/10.3390/catal7040123 - 19 Apr 2017

Cited by 21 | Viewed by 8117

Abstract

Herein, an optimized method for 100 g scale synthesis of glycerol oligomers using a microwave multimode source and the low priced K₂CO₃ as catalyst is reported. This method allows the complete conversion of glycerol to its oligomers in only 30 [...] Read more.

Herein, an optimized method for 100 g scale synthesis of glycerol oligomers using a microwave multimode source and the low priced K₂CO₃ as catalyst is reported. This method allows the complete conversion of glycerol to its oligomers in only 30 min, yielding molecular weights up to 1000 g mol⁻¹. Furthermore, a simple iterative purification process, involving the precipitation of the crude product in acetone and methanol, affords a final product composed of larger oligomers with a narrow dispersity (D < 1.5). Full article

(This article belongs to the Special Issue Catalysis of Biomass-Derived Molecules)

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11 pages, 3741 KiB

Open AccessArticle

Promotive Effect of Sn²⁺ on Cu⁰/Cu⁺ Ratio and Stability Evolution of Cu/SiO₂ Catalyst in the Hydrogenation of Dimethyl Oxalate

by Chuancai Zhang, Denghao Wang and Bin Dai

Catalysts 2017, 7(4), 122; https://doi.org/10.3390/catal7040122 - 19 Apr 2017

Cited by 10 | Viewed by 6271

Abstract

The influence of Sn²⁺doping on the structure and performance of silica supported copper catalyst was systematically investigated and characterised. Catalytic evaluation showed that the suitable content of Sn²⁺ introduced into a Cu/SiO₂ catalyst evidently improved the catalytic activity and [...] Read more.

The influence of Sn²⁺doping on the structure and performance of silica supported copper catalyst was systematically investigated and characterised. Catalytic evaluation showed that the suitable content of Sn²⁺ introduced into a Cu/SiO₂ catalyst evidently improved the catalytic activity and stability of ethylene glycol synthesis from dimethyl oxalate. X-ray diffraction and X-ray auger electron spectroscopy indicated that the Cu⁰/Cu⁺ ratio gradually increased with increasing Sn²⁺ content, and an appropriate proportion of Cu⁰/Cu⁺ ratio played a very significant role in this reaction. Transmission electron microscopy revealed that the active copper particles in the Cu-xSn/SiO₂ catalyst were smaller than those of the Cu/SiO₂ catalyst. This result may be due to the introduction of Sn²⁺ species transformed into SnO₂. Furthermore, SnO₂ effectively segregated the active copper. These effects are beneficial in inhibiting the aggregation of copper in the catalysts, thereby improving the stability of the catalyst and prolonging the life span. Full article

(This article belongs to the Special Issue Small Molecule Activation and Catalysis)

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29 pages, 8874 KiB

Open AccessFeature PaperReview

Merging Metallic Catalysts and Sonication: A Periodic Table Overview

by Claudia E. Domini, Mónica B. Álvarez, Gustavo F. Silbestri, Giancarlo Cravotto and Pedro Cintas

Catalysts 2017, 7(4), 121; https://doi.org/10.3390/catal7040121 - 19 Apr 2017

Cited by 15 | Viewed by 8009

Abstract

This account summarizes and discusses recent examples in which the combination of ultrasonic waves and metal-based reagents, including metal nanoparticles, has proven to be a useful choice in synthetic planning. Not only does sonication often enhance the activity of the metal catalyst/reagent, but [...] Read more.

This account summarizes and discusses recent examples in which the combination of ultrasonic waves and metal-based reagents, including metal nanoparticles, has proven to be a useful choice in synthetic planning. Not only does sonication often enhance the activity of the metal catalyst/reagent, but it also greatly enhances the synthetic transformation that can be conducted under milder conditions relative to conventional protocols. For the sake of clarity, we have adopted a structure according to the periodic-table elements or families, distinguishing between bulk metal reagents and nanoparticles, as well as the supported variations, thus illustrating the characteristics of the method under consideration in target synthesis. The coverage focuses essentially on the last decade, although the discussion also strikes a comparative balance between the more recent advancements and past literature. Full article

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

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15 pages, 2047 KiB

Open AccessArticle

Quantitative Structure-Thermostability Relationship of Late Transition Metal Catalysts in Ethylene Oligo/Polymerization

by Wenhong Yang, Zhifeng Ma, Jun Yi and Wen-Hua Sun

Catalysts 2017, 7(4), 120; https://doi.org/10.3390/catal7040120 - 18 Apr 2017

Cited by 12 | Viewed by 5308

Abstract

Quantitative structure–thermostability relationship was carried out for four series of bis(imino)pyridine iron (cobalt) complexes and α-diimine nickel complexes systems in ethylene oligo/polymerization. Three structural parameters were correlated with thermal stability, including bond order of metal-nitrogen (B), minimum distance (D [...] Read more.

Quantitative structure–thermostability relationship was carried out for four series of bis(imino)pyridine iron (cobalt) complexes and α-diimine nickel complexes systems in ethylene oligo/polymerization. Three structural parameters were correlated with thermal stability, including bond order of metal-nitrogen (B), minimum distance (D) between central metal and ortho-carbon atoms on the aryl moiety and dihedral angle (α) of a central five-membered ring. The variation degree of catalytic activities between optimum and room temperatures (A_T) was calculated to describe the thermal stability of the complex. By multiple linear regression analysis (MLRA), the thermal stability presents good correlation with three structural parameters with the correlation coefficients (R²) over 0.95. Furthermore, the contributions of each parameter were evaluated. Through this work, it is expected to help the design of a late transition metal complex with thermal stability at the molecular level. Full article

(This article belongs to the Special Issue Computational Methods and Their Application in Catalysis)

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11 pages, 5322 KiB

Open AccessArticle

Microwave-Assisted Synthesis of Co₃(PO₄)₂ Nanospheres for Electrocatalytic Oxidation of Methanol in Alkaline Media

by Prabhakarn Arunachalam, Maged N. Shaddad, Abdullah Salah Alamoudi, Mohamed A. Ghanem and Abdullah M. Al-Mayouf

Catalysts 2017, 7(4), 119; https://doi.org/10.3390/catal7040119 - 17 Apr 2017

Cited by 71 | Viewed by 8098

Abstract

Low-cost and high-performance advanced electrocatalysts for direct methanol fuel cells are of key significance for the improvement of environmentally-pleasant energy technologies. Herein, we report the facile synthesis of cobalt phosphate (Co₃(PO₄)₂) nanospheres by a microwave-assisted process and [...] Read more.

Low-cost and high-performance advanced electrocatalysts for direct methanol fuel cells are of key significance for the improvement of environmentally-pleasant energy technologies. Herein, we report the facile synthesis of cobalt phosphate (Co₃(PO₄)₂) nanospheres by a microwave-assisted process and utilized as an electrocatalyst for methanol oxidation. The phase formation, morphological surface structure, elemental composition, and textural properties of the synthesized (Co₃(PO₄)₂) nanospheres have been examined by powder X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), field emission-scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption-desorption isotherm investigations. The performance of an electrocatalytic oxidation of methanol over a Co₃(PO₄)₂ nanosphere-modified electrode was evaluated in an alkaline solution using cyclic voltammetry (CV) and chronopotentiometry (CP) techniques. Detailed studies were made for the methanol oxidation by varying the experimental parameters, such as catalyst loading, methanol concentration, and long-term stability for the electro-oxidation of methanol. The good electrocatalytic performances of Co₃(PO₄)₂ should be related to its good surface morphological structure and high number of active surface sites. The present investigation illustrates the promising application of Co₃(PO₄)₂ nanospheres as a low-cost and more abundant electrocatalyst for direct methanol fuel cells. Full article

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

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14 pages, 4627 KiB

Open AccessArticle

SO₄²⁻/Sn-MMT Solid Acid Catalyst for Xylose and Xylan Conversion into Furfural in the Biphasic System

by Qixuan Lin, Huiling Li, Xiaohui Wang, Longfei Jian, Junli Ren, Chuanfu Liu and Runcang Sun

Catalysts 2017, 7(4), 118; https://doi.org/10.3390/catal7040118 - 17 Apr 2017

Cited by 45 | Viewed by 7561

Abstract

A sulphated tin ion-exchanged montmorillonite (SO₄²⁻/Sn-MMT) was successfully prepared by the ion exchange method of montmorillonite (MMT) with SnCl₄, followed by the sulphation. This catalysis was applied as a solid acid catalyst for the heterogeneous catalytic transformations of [...] Read more.

A sulphated tin ion-exchanged montmorillonite (SO₄²⁻/Sn-MMT) was successfully prepared by the ion exchange method of montmorillonite (MMT) with SnCl₄, followed by the sulphation. This catalysis was applied as a solid acid catalyst for the heterogeneous catalytic transformations of xylose and xylan into furfural in the bio-based 2-methyltetrahydrofuran/H₂O biphasic system. These prepared catalysts were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), temperature programmed desorption of ammonia (NH₃-TPD), pyridine adsorbed Fourier transform infrared spectroscopy (Py-FTIR), element analysis (EA) and Brunauer-Emmett-Teller (BET) method. Their catalytic performance for xylose and xylan into furfural was also investigated. The reaction parameters such as the initial xylose and xylan concentration, the amounts of catalyst, the organic-to-aqueous phase volume ratio, the reaction temperature and time were studied to optimize the reaction conditions. Results displayed that SO₄²⁻/Sn-MMT contained both Brønsted acid and Lewis acid sites, and SO₄²⁻ ions were contributive to the formation of stronger Brønsted acid sites, which could improve the reaction efficiency. Reaction parameters had significant influence on the furfural production. The substitution of water by the saturated NaCl solution in the aqueous phase also had an important effect on the xylose and xylan conversion. The highest furfural yields were achieved up to 79.64% from xylose and 77.35% from xylan under the optimized reaction conditions (160 °C, 120 min; 160 °C, 90 min). Moreover, the prepared catalyst was stable and was reused five times with a slight decrease (10.0%) of the furfural yield. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis for Environmental Remediation)

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14 pages, 4812 KiB

Open AccessArticle

Novel Synthesis of Plasmonic Ag/AgCl@TiO₂ Continues Fibers with Enhanced Broadband Photocatalytic Performance

by Nan Bao, Xinhan Miao, Xinde Hu, Qingzhe Zhang, Xiuyan Jie and Xiyue Zheng

Catalysts 2017, 7(4), 117; https://doi.org/10.3390/catal7040117 - 17 Apr 2017

Cited by 59 | Viewed by 7175

Abstract

The plasmonic Ag/AgCl@TiO₂ fiber (S-CTF) photocatalyst was synthesized by a two-step approach, including the sol-gel and force spinning method for the preparation of TiO₂ fibers (TF), and the impregnation-precipitation-photoreduction strategy for the deposition of Ag/AgCl onto the fibers. NaOH aqueous solution [...] Read more.

The plasmonic Ag/AgCl@TiO₂ fiber (S-CTF) photocatalyst was synthesized by a two-step approach, including the sol-gel and force spinning method for the preparation of TiO₂ fibers (TF), and the impregnation-precipitation-photoreduction strategy for the deposition of Ag/AgCl onto the fibers. NaOH aqueous solution was utilized to hydrolyze TiCl₄, to synthesize TF and remove the byproduct HCl, and the produced NaCl was recycled for the formation and deposition of Ag/AgCl. The surface morphology, specific surface area, textural properties, crystal structure, elemental compositions and optical absorption of S-CTF were characterized by a series of instruments. These results revealed that the AgCl and Ag⁰ species were deposited onto TF successfully, and the obtained S-CTF showed improved visible light absorption due to the surface plasmon resonance of Ag⁰. In the photocatalytic degradation of X-3B, S-CTF exhibited significantly enhanced activities under separate visible or UV light irradiation, in comparison to TF. Full article

(This article belongs to the Special Issue Titanium Dioxide Photocatalysis)

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15 pages, 8654 KiB

Open AccessArticle

Hydrothermal Fabrication of High Specific Surface Area Mesoporous MgO with Excellent CO₂ Adsorption Potential at Intermediate Temperatures

by Wanlin Gao, Tuantuan Zhou, Benoit Louis and Qiang Wang

Catalysts 2017, 7(4), 116; https://doi.org/10.3390/catal7040116 - 15 Apr 2017

Cited by 50 | Viewed by 8692

Abstract

In this work, we report on a novel sodium dodecyl sulfate (SDS)-assisted magnesium oxide (MgO)-based porous adsorbent synthesized by hydrothermal method for intermediate CO₂ capture. For industrial MgO, its CO₂ adsorption capacity is normally less than 0.06 mmol g⁻¹, [...] Read more.

In this work, we report on a novel sodium dodecyl sulfate (SDS)-assisted magnesium oxide (MgO)-based porous adsorbent synthesized by hydrothermal method for intermediate CO₂ capture. For industrial MgO, its CO₂ adsorption capacity is normally less than 0.06 mmol g⁻¹, with a specific surface area as low as 25.1 m² g⁻¹. Herein, leaf-like MgO nanosheets which exhibited a disordered layer structure were fabricated by the introduction of SDS surfactants and the control of other synthesis parameters. This leaf-like MgO adsorbent showed an excellent CO₂ capacity of 0.96 mmol g⁻¹ at moderate temperatures (~300 °C), which is more than ten times higher than that of the commercial light MgO. This novel mesoporous MgO adsorbent also exhibited high stability during multiple CO₂ adsorption/desorption cycles. The excellent CO₂ capturing performance was believed to be related to its high specific surface area of 321.3 m² g⁻¹ and abundant surface active adsorption sites. This work suggested a new synthesis scheme for MgO based CO₂ adsorbents at intermediate temperatures, providing a competitive candidate for capturing CO₂ from certain sorption enhanced hydrogen production processes. Full article

(This article belongs to the Special Issue C1 Chemistry—C1-Platform Chemicals as Cornerstone for a Sustainable Energy)

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9 pages, 6938 KiB

Open AccessCommunication

Lipase-Mediated Amidation of Anilines with 1,3-Diketones via C–C Bond Cleavage

by Liu Zhang, Fengxi Li, Chunyu Wang, Lu Zheng, Zhi Wang, Rui Zhao and Lei Wang

Catalysts 2017, 7(4), 115; https://doi.org/10.3390/catal7040115 - 14 Apr 2017

Cited by 14 | Viewed by 6828

Abstract

In this work, an efficient and green lipase-mediated technique has been mined for the amidation of anilines with 1,3-diketones via C–C bond cleavage. Under the optimal conditions, high yields (64.3%–96.2%) could be obtained when Novozym 435 was used as the catalyst. Furthermore, Novozym [...] Read more.

In this work, an efficient and green lipase-mediated technique has been mined for the amidation of anilines with 1,3-diketones via C–C bond cleavage. Under the optimal conditions, high yields (64.3%–96.2%) could be obtained when Novozym 435 was used as the catalyst. Furthermore, Novozym 435 exhibited a satisfying reusability and more than 80% of yield can be obtained after seven cycles. This work provides a more rapid and mild strategy for amide synthesis with high yield and expands the application of enzyme in organic synthesis. Full article

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18 pages, 5611 KiB

Open AccessArticle

Steam Reforming of Bio-Compounds with Auto-Reduced Nickel Catalyst

by Feng Cheng and Valerie Dupont

Catalysts 2017, 7(4), 114; https://doi.org/10.3390/catal7040114 - 13 Apr 2017

Cited by 16 | Viewed by 5537

Abstract

As an extension of chemical looping combustion, chemical looping steam reforming (CLSR) has been developed for H2 production. During CLSR, a steam reforming (SR) process occurs following the reduction of catalysts by the reforming feedstock itself (termed “auto-reduction”), as opposed to a separate, [...] Read more.

As an extension of chemical looping combustion, chemical looping steam reforming (CLSR) has been developed for H2 production. During CLSR, a steam reforming (SR) process occurs following the reduction of catalysts by the reforming feedstock itself (termed “auto-reduction”), as opposed to a separate, dedicated reducing agent like H2. This paper studied SR performances of four common bio-compounds (ethanol, acetone, furfural, and glucose) with a nickel catalyst that had undergone auto-reduction. A packed bed reactor was used to carry out the experiment of auto-reduction and subsequent SR. The effects of temperature and steam to carbon ratio (S/C) on the carbon conversions of the bio-compounds to gases and yields of gaseous products were investigated. The carbon deposition on spent catalysts was characterized by CHN elemental analysis and Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDX). The SR performance with the auto-reduced catalyst was close to that with the H2-reduced catalyst. In general, an increase in temperature or S/C would lead to an increase in H2 yields. The dependence of SR performance on temperature or S/C was specific to the type of bio-compounds. Accordingly, the main bottlenecks for SR of each bio-compound were summarized. A large amount of CH4 existed in the reforming product of ethanol. Severe carbon deposition was observed for SR of acetone at temperatures below 650 °C. A high thermal stability of furfural molecules or its derivatives restricted the SR of furfural. For SR of glucose, the main problem was the severe agglomeration of catalyst particles due to glucose coking. Full article

(This article belongs to the Special Issue Reforming Catalysts)

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33 pages, 2436 KiB

Open AccessFeature PaperReview

Abatement of VOCs Using Packed Bed Non-Thermal Plasma Reactors: A Review

by Savita K. P. Veerapandian, Christophe Leys, Nathalie De Geyter and Rino Morent

Catalysts 2017, 7(4), 113; https://doi.org/10.3390/catal7040113 - 12 Apr 2017

Cited by 113 | Viewed by 11035

Abstract

Non thermal plasma (NTP) reactors packed with non-catalytic or catalytic packing material have been widely used for the abatement of volatile organic compounds such as toluene, benzene, etc. Packed bed reactors are single stage reactors where the packing material is placed directly in [...] Read more.

Non thermal plasma (NTP) reactors packed with non-catalytic or catalytic packing material have been widely used for the abatement of volatile organic compounds such as toluene, benzene, etc. Packed bed reactors are single stage reactors where the packing material is placed directly in the plasma discharge region. The presence of packing material can alter the physical (such as discharge characteristics, power consumption, etc.) and chemical characteristics (oxidation and destruction pathway, formation of by-products, etc.) of the reactor. Thus, packed bed reactors can overcome the disadvantages of NTP reactors for abatement of volatile organic compounds (VOCs) such as lower energy efficiency and formation of unwanted toxic by-products. This paper aims at reviewing the effect of different packing materials on the abatement of different aliphatic, aromatic and chlorinated volatile organic compounds. Full article

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12 pages, 629 KiB

Open AccessReview

Improving the Stability of Cold-Adapted Enzymes by Immobilization

by ChangWoo Lee, Sei-Heon Jang and Hye-Shin Chung

Catalysts 2017, 7(4), 112; https://doi.org/10.3390/catal7040112 - 12 Apr 2017

Cited by 45 | Viewed by 8956

Abstract

Cold-adapted enzymes have gained considerable attention as biocatalysts that show high catalytic activity at low temperatures. However, the use of cold-adapted enzymes at ambient temperatures has been hindered by their low thermal stabilities caused by their inherent structural flexibilities. Accordingly, protein engineering and [...] Read more.

Cold-adapted enzymes have gained considerable attention as biocatalysts that show high catalytic activity at low temperatures. However, the use of cold-adapted enzymes at ambient temperatures has been hindered by their low thermal stabilities caused by their inherent structural flexibilities. Accordingly, protein engineering and immobilization have been employed to improve the thermal stability of cold-adapted enzymes. Immobilization has been shown to increase the thermal stability of cold-adapted enzymes at the critical temperatures at which denaturation begins. This review summarizes progress in immobilization of cold-adapted enzymes as a strategy to improve their thermal and organic solvent stabilities. Full article

(This article belongs to the Special Issue Immobilized Enzymes: Strategies for Enzyme Stabilization)

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14 pages, 3955 KiB

Open AccessFeature PaperArticle

Unprecedented Multifunctionality of Grubbs and Hoveyda–Grubbs Catalysts: Competitive Isomerization, Hydrogenation, Silylation and Metathesis Occurring in Solution and on Solid Phase

by Maitena Martinez-Amezaga, Carina M. L. Delpiccolo, Luciana Méndez, Ileana Dragutan, Valerian Dragutan and Ernesto G. Mata

Catalysts 2017, 7(4), 111; https://doi.org/10.3390/catal7040111 - 9 Apr 2017

Cited by 9 | Viewed by 12188

Abstract

This contribution showcases the interplay of several non-metathetic reactions (isomerization, silylation and “hydrogen-free” reduction) with metathesis in systems comprising a functionalized olefin and a soluble or resin-immobilized silane. These competing, one-pot reactions occur under activation by second-generation Ru-alkylidene catalysts. Different olefinic substrates were [...] Read more.

This contribution showcases the interplay of several non-metathetic reactions (isomerization, silylation and “hydrogen-free” reduction) with metathesis in systems comprising a functionalized olefin and a soluble or resin-immobilized silane. These competing, one-pot reactions occur under activation by second-generation Ru-alkylidene catalysts. Different olefinic substrates were used to study the influence of the substitution pattern on the reaction outcome. Emphasis is placed upon the rarely reported yet important transformations implying a solid phase-supported silane reagent. Catalytic species involved in and reaction pathways accounting for these concurrent processes are evidenced. An unexpected result of this research was the clearly proved partial binding of the olefin to the resin, thereby removing it from the reacting ensemble. Full article

(This article belongs to the Special Issue Ruthenium Catalysts)

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13 pages, 1867 KiB

Open AccessArticle

Study of the V₂O₅-WO₃/TiO₂ Catalyst Synthesized from Waste Catalyst on Selective Catalytic Reduction of NO_x by NH₃

by Chunping Qi, Weijun Bao, Liguo Wang, Huiquan Li and Wenfen Wu

Catalysts 2017, 7(4), 110; https://doi.org/10.3390/catal7040110 - 8 Apr 2017

Cited by 65 | Viewed by 8028

Abstract

V₂O₅-WO₃/TiO₂ catalysts were synthesized from waste selective catalytic reduction (SCR) catalyst through oxalic acid leaching and impregnating with various V₂O₅ mass loadings. The denitration (deNO_x) activity and physiochemical properties of the [...] Read more.

V₂O₅-WO₃/TiO₂ catalysts were synthesized from waste selective catalytic reduction (SCR) catalyst through oxalic acid leaching and impregnating with various V₂O₅ mass loadings. The denitration (deNO_x) activity and physiochemical properties of the catalysts were investigated. All the catalysts were characterized by N₂ adsorption/desorption, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and H₂-temperature programmed reduction. The evaluation result revealed that the deNO_x activity of newly synthesized catalyst with 1.0% V₂O₅ was almost recovered to the level of fresh catalyst, with NO conversion being recovered to 91% at 300 °C, and it also showed a good resistance to SO₂ and H₂O. The characterization results showed that the decrease of impurities, partial recovery of the V⁴⁺/V⁵⁺ ratio, and increased reducibility were mainly responsible for the recovery of catalytic activity. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis for Environmental Remediation)

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15 pages, 2586 KiB

Open AccessFeature PaperReview

Characterization of MoVTeNbO_x Catalysts during Oxidation Reactions Using In Situ/Operando Techniques: A Review

by Soe Lwin, Weijian Diao, Chinmoy Baroi, Anne M. Gaffney and Rebecca R. Fushimi

Catalysts 2017, 7(4), 109; https://doi.org/10.3390/catal7040109 - 8 Apr 2017

Cited by 21 | Viewed by 7448

Abstract

Light alkanes are abundant in shale gas resources. The bulk mixed metal oxide MoVTe(Sb)NbO_x catalysts play a very important role in dehydrogenation and selective oxidation reactions of these short hydrocarbons to produce high-value chemicals. This catalyst system mainly consists of M1 and [...] Read more.

Light alkanes are abundant in shale gas resources. The bulk mixed metal oxide MoVTe(Sb)NbO_x catalysts play a very important role in dehydrogenation and selective oxidation reactions of these short hydrocarbons to produce high-value chemicals. This catalyst system mainly consists of M1 and less-active M2 crystalline phases. Due to their ability to directly monitor the catalysts under the relevant industrial conditions, in situ/operando techniques can provide information about the nature of active sites, surface intermediates, and kinetics/mechanisms, and may help with the synthesis of new and better catalysts. Sophisticated catalyst design and understanding is necessary to achieve the desired performance (activity, selectivity, lifetime, etc.) at reasonable reaction conditions (temperature, pressure, etc.). This article critically reviews the progress made in research of these MoVTe(Sb)NbO_x catalysts in oxidation reactions mainly through in situ/operando techniques and suggests the future direction needed to realize the industrialization of these catalysts. Full article

(This article belongs to the Special Issue In Situ and Operando Characterization in Catalysis)

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9 pages, 2372 KiB

Open AccessArticle

Efficient Hydrolysis of Lignocellulose by Acidic Ionic Liquids under Low-Toxic Condition to Microorganisms

by Kosuke Kuroda, Ken Inoue, Kyohei Miyamura, Heri Satria, Kenji Takada, Kazuaki Ninomiya and Kenji Takahashi

Catalysts 2017, 7(4), 108; https://doi.org/10.3390/catal7040108 - 7 Apr 2017

Cited by 4 | Viewed by 4974

Abstract

Lignocellulose is known as a renewable resource, and acidic ionic liquids have been highlighted as efficient catalysts for hydrolysis of cellulose. To achieve successive hydrolysis and fermentation, efficient hydrolysis with sufficiently diluted acidic ionic liquids is necessary because acidic ionic liquids are toxic [...] Read more.

Lignocellulose is known as a renewable resource, and acidic ionic liquids have been highlighted as efficient catalysts for hydrolysis of cellulose. To achieve successive hydrolysis and fermentation, efficient hydrolysis with sufficiently diluted acidic ionic liquids is necessary because acidic ionic liquids are toxic to fermentative microorganisms. Escherichia coli was confirmed to grow in 0.05 M dilute acidic ionic liquid—1-(1-butylsulfonic)-3-methylimidazolium hydrogen sulfate ([Sbmim][HSO₄])—although the growth was suppressed in more concentrated solutions. Therefore, we applied the 0.05 M [Sbmim][HSO₄] solution to hydrolysis of bagasse, leading to a glucose yield of 48% at 190 °C. This value is greater than that obtained with a concentrated [Sbmim][HSO₄] solution, which is not suitable for the growth of Escherichia coli (yield: 40% in a 1.0 M solution). Efficient hydrolysis with acidic ionic liquids under low-toxic condition was achieved. Full article

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

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8 pages, 2229 KiB

Open AccessArticle

Recyclable Polymer-Supported Terpyridine–Palladium Complex for the Tandem Aminocarbonylation of Aryl Iodides to Primary Amides in Water Using NaN₃ as Ammonia Equivalent

by Toshimasa Suzuka, Hiromu Sueyoshi and Kazuhito Ogihara

Catalysts 2017, 7(4), 107; https://doi.org/10.3390/catal7040107 - 7 Apr 2017

Cited by 11 | Viewed by 5764

Abstract

Primary aromatic amides are valuable compounds, which are generally prepared via Beckmann rearrangement of oximes and the hydration of nitriles in organic solvents. We investigated the environmentally friendly catalytic aminocarbonylation in water. Thus, a novel heterogeneous transition-metal catalyst, a polymer-supported terpyridine–palladium(II) complex, was [...] Read more.

Primary aromatic amides are valuable compounds, which are generally prepared via Beckmann rearrangement of oximes and the hydration of nitriles in organic solvents. We investigated the environmentally friendly catalytic aminocarbonylation in water. Thus, a novel heterogeneous transition-metal catalyst, a polymer-supported terpyridine–palladium(II) complex, was prepared and found to promote azidocarbonylation of aryl iodides with NaN₃ and to reduce the generated benzoyl azides in water under CO gas to yield primary aryl amides with high to excellent yield in a one-pot reaction. The catalyst was recovered and reused several times with no loss of catalytic activity. Full article

(This article belongs to the Special Issue Organometallic Catalysis for Organic Synthesis)

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11 pages, 4393 KiB

Open AccessArticle

Thermal Activation of CuBTC MOF for CO Oxidation: The Effect of Activation Atmosphere

by Xiuling Zhang, Zhibin Zhan, Zhuang Li and Lanbo Di

Catalysts 2017, 7(4), 106; https://doi.org/10.3390/catal7040106 - 7 Apr 2017

Cited by 34 | Viewed by 8511

Abstract

High performance catalysts for carbon monoxide (CO) oxidation were obtained through thermal activation of a CuBTC (BTC: 1,3,5-benzenetricarboxylic acid) metal–organic framework (MOF) in various atmospheres. X-ray diffraction (XRD), X-ray photonelectron spectroscopy (XPS), N₂ adsorption–desorption measurement, and field emission scanning electron microscopy (FESEM) [...] Read more.

High performance catalysts for carbon monoxide (CO) oxidation were obtained through thermal activation of a CuBTC (BTC: 1,3,5-benzenetricarboxylic acid) metal–organic framework (MOF) in various atmospheres. X-ray diffraction (XRD), X-ray photonelectron spectroscopy (XPS), N₂ adsorption–desorption measurement, and field emission scanning electron microscopy (FESEM) were adopted to characterize the catalysts. The results show that thermal activation by reductive H₂ may greatly destroy the structure of CuBTC. Inert Ar gas has a weak influence on the structure of CuBTC. Therefore, these two catalysts exhibit low CO oxidation activity. Activating with O₂ is effective for CuBTC catalysts, since active CuO species may be obtained due to the slight collapse of CuBTC structure. The highest activity is obtained when activating with CO reaction gas, since many pores and more effective Cu₂O is formed during the thermal activation process. These results show that the structure and chemical state of coordinated metallic ions in MOFs are adjustable by controlling the activation conditions. This work provides an effective method for designing and fabricating high performance catalysts for CO oxidation based on MOFs. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis for Environmental Remediation)

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16 pages, 3596 KiB

Open AccessArticle

Environmental Benign Synthesis of Lithium Silicates and Mg-Al Layered Double Hydroxide from Vermiculite Mineral for CO₂ Capture

by Yu Zhang, Tuantuan Zhou, Benoit Louis, Feng Yu, Jianming Dan and Qiang Wang

Catalysts 2017, 7(4), 105; https://doi.org/10.3390/catal7040105 - 3 Apr 2017

Cited by 20 | Viewed by 6872

Abstract

This research introduces a completely new environmental benign synthesis route for obtaining two kinds of inter-mediate and high temperature CO₂ sorbents, Mg-Al layered double hydroxide (LDH) and Li₄SiO₄, from vermiculite. The mineral vermiculite was leached with acid, from [...] Read more.

This research introduces a completely new environmental benign synthesis route for obtaining two kinds of inter-mediate and high temperature CO₂ sorbents, Mg-Al layered double hydroxide (LDH) and Li₄SiO₄, from vermiculite. The mineral vermiculite was leached with acid, from which the obtained SiO2 was used for the synthesis of Li₄SiO₄ and the leaching waste water was used for the synthesis of Mg-Al LDH. Therefore, no waste was produced during the whole process. Both Li₄SiO₄ and Mg-Al LDH sorbents were carefully characterized using XRD, SEM, and BET analyses. The CO₂ capturing performance of these two sorbents was comprehensively evaluated. The influence of the Li/Si ratio, calcination temperature, calcination time, and sorption temperature on the CO₂ sorption capacity of Li₄SiO₄, and the sorption temperature on the CO2 sorption capacity of LDH, were investigated. The optimal leaching acid concentration for vermiculite and the CO₂ sorption/desorption cycling performance of both the Li₄SiO₄ and Mg-Al LDH sorbents were determined. In sum, this demonstrated a unique and environment-friendly scheme for obtaining two CO₂ sorbents from cheap raw materials, and this idea is applicable to the efficient utilization of other minerals. Full article

(This article belongs to the Special Issue C1 Chemistry—C1-Platform Chemicals as Cornerstone for a Sustainable Energy)

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13 pages, 3418 KiB

Open AccessArticle

Methanation of Carbon Dioxide over Ni–Ce–Zr Oxides Prepared by One-Pot Hydrolysis of Metal Nitrates with Ammonium Carbonate

by Wangxin Nie, Xiujing Zou, Chenju Chen, Xueguang Wang, Weizhong Ding and Xionggang Lu

Catalysts 2017, 7(4), 104; https://doi.org/10.3390/catal7040104 - 31 Mar 2017

Cited by 20 | Viewed by 5593

Abstract

Ni–Ce–Zr mixed oxides were prepared through one-pot hydrolysis of mixed metal nitrates with ammonium carbonate for CO₂ methanation. The effects of Ce/Zr molar ratio and Ni content on catalysts’ physical and chemical properties, reduction degree of Ni²⁺, and catalytic properties [...] Read more.

Ni–Ce–Zr mixed oxides were prepared through one-pot hydrolysis of mixed metal nitrates with ammonium carbonate for CO₂ methanation. The effects of Ce/Zr molar ratio and Ni content on catalysts’ physical and chemical properties, reduction degree of Ni²⁺, and catalytic properties were systematically investigated. The results showed that Zr could lower metallic Ni particle sizes and alter interaction between Ni and supports, resulting in enhancements in the catalytic activity for CO₂ methanation. The Ni–Ce–Zr catalyst containing 40 wt % Ni and Ce/Zr molar ratio of 9:1 exhibited the optimal catalytic properties, with 96.2% CO₂ conversion and almost 100% CH₄ selectivity at a low temperature of 275 °C. During the tested period of 500 h, CO₂ conversion and CH₄ selectivity over Ni–Ce–Zr catalyst kept constant under 300 °C. Full article

(This article belongs to the Special Issue C1 Chemistry—C1-Platform Chemicals as Cornerstone for a Sustainable Energy)

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10 pages, 1372 KiB

Open AccessArticle

Dicyclopentadiene Hydroformylation to Value-Added Fine Chemicals over Magnetically Separable Fe₃O₄-Supported Co-Rh Bimetallic Catalysts: Effects of Cobalt Loading

by Yubo Ma, Jie Fu, Zhixian Gao, Libo Zhang, Chengyang Li and Tianfu Wang

Catalysts 2017, 7(4), 103; https://doi.org/10.3390/catal7040103 - 30 Mar 2017

Cited by 25 | Viewed by 5883

Abstract

Six Co-Rh/Fe₃O₄ catalysts with different cobalt loadings were prepared by the co-precipitation of RhCl₃, Co(NO₃)₂, and Fe(NO₃)₃ using Na₂CO₃ as the precipitant. These catalysts were tested for dicyclopentadiene [...] Read more.

Six Co-Rh/Fe₃O₄ catalysts with different cobalt loadings were prepared by the co-precipitation of RhCl₃, Co(NO₃)₂, and Fe(NO₃)₃ using Na₂CO₃ as the precipitant. These catalysts were tested for dicyclopentadiene (DCPD) hydroformylation to monoformyltricyclodecenes (MFTD) and diformyltricyclodecanes (DFTD). The results showed that the MFTD formation rate increased with increasing cobalt loading, whereas the DFTD formation rate initially increased and then decreased when the cobalt loading was greater than twice that of Rh. The DFTD selectivity was only 21.3% when monometallic Rh/Fe₃O₄ was used as the catalyst. In contrast, the selectivity was 90.6% at a similar DCPD conversion when the bimetallic 4Co-2Rh/Fe₃O₄ catalyst was employed. These catalysts were characterized by temperature-programmed reduction (TPR), temperature-programmed desorption (TPD), and thermogravimetric and differential thermal analyses (TG-DTA). The results obtained by these complimentary characterization techniques indicated that adding cobalt to the Rh/Fe₃O₄ catalyst enhanced the Rh reducibility and dispersion; the Rh reducibility was easily altered, and increasing the cobalt loading improved the Rh dispersion. It was concluded that the enhanced catalytic performance with increasing cobalt loading might be due to the formation of a more reactive Rh species with a different Rh–phosphine interaction strength on the catalyst surface. Full article

(This article belongs to the Special Issue Magnetic Nanocatalysts)

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10 pages, 3290 KiB

Open AccessArticle

Caprolactam-Based Brønsted Acidic Ionic Liquids for Biodiesel Production from Jatropha Oil

by Hui Luo, Heng Yin, Rui Wang, Weiyu Fan and Guozhi Nan

Catalysts 2017, 7(4), 102; https://doi.org/10.3390/catal7040102 - 27 Mar 2017

Cited by 11 | Viewed by 6493

Abstract

Caprolactam-based ionic liquids show many advantages, such as the lower toxicity, lower cost, and a simple preparation process. In this work, caprolactam-based ionic liquids were prepared and adopted as catalysts for the transesterification of Jatropha oil with methanol. The results demonstrated that the [...] Read more.

Caprolactam-based ionic liquids show many advantages, such as the lower toxicity, lower cost, and a simple preparation process. In this work, caprolactam-based ionic liquids were prepared and adopted as catalysts for the transesterification of Jatropha oil with methanol. The results demonstrated that the SO₃H-functional caprolactam‐based ionic liquids have higher catalytic activity than those of the caprolactam-based ionic liquids without sulfonic group or the SO₃H-functional pyridine-based ionic liquids, attributed to their stronger Brønsted acidity. By optimizing the reaction parameter, the biodiesel yield catalyzed by 1-(4-sulfonic group) butylcaprolactamium hydrogen sulfate ([HSO₃-bCPL][HSO₄]) could reach above 95% at 140 °C for 3 h. Furthermore, the ionic liquid had a good reusability. Full article

(This article belongs to the Special Issue Organocatalysis in Ionic Liquids)

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18 pages, 5775 KiB

Open AccessArticle

High Catalytic Activity of Heterometallic (Fe₆Na₇ and Fe₆Na₆) Cage Silsesquioxanes in Oxidations with Peroxides

by Alexey I. Yalymov, Alexey N. Bilyachenko, Mikhail M. Levitsky, Alexander A. Korlyukov, Victor N. Khrustalev, Lidia S. Shul’pina, Pavel V. Dorovatovskii, Marina A. Es’kova, Frédéric Lamaty, Xavier Bantreil, Benoît Villemejeanne, Jean Martinez, Elena S. Shubina, Yuriy N. Kozlov and Georgiy B. Shul’pin

Catalysts 2017, 7(4), 101; https://doi.org/10.3390/catal7040101 - 27 Mar 2017

Cited by 36 | Viewed by 6453

Abstract

Two types of heterometallic (Fe(III),Na) silsesquioxanes—[Ph₅Si₅O₁₀]₂[Ph₁₀Si₁₀O₂₁]Fe₆(O^2‒)₂Na₇(H₃O⁺)(MeOH)₂(MeCN)_4.5.1.25(MeCN), I, and [Ph₅Si₅ [...] Read more.

Two types of heterometallic (Fe(III),Na) silsesquioxanes—[Ph₅Si₅O₁₀]₂[Ph₁₀Si₁₀O₂₁]Fe₆(O^2‒)₂Na₇(H₃O⁺)(MeOH)₂(MeCN)_4.5.1.25(MeCN), I, and [Ph₅Si₅O₁₀]₂[Ph₄Si₄O₈]₂Fe₆Na₆(O^2‒)₃(MeCN)_8.5(H₂O)_8.44, II—were obtained and characterized. X-ray studies established distinctive structures of both products, with pair of Fe(III)-O-based triangles surrounded by siloxanolate ligands, giving fascinating cage architectures. Complex II proved to be catalytically active in the formation of amides from alcohols and amines, and thus becoming a rare example of metallasilsesquioxanes performing homogeneous catalysis. Benzene, cyclohexane, and other alkanes, as well as alcohols, can be oxidized in acetonitrile solution to phenol—the corresponding alkyl hydroperoxides and ketones, respectively—by hydrogen peroxide in air in the presence of catalytic amounts of complex II and trifluoroacetic acid. Thus, the cyclohexane oxidation at 20 °C gave oxygenates in very high yield of alkanes (48% based on alkane). The kinetic behaviour of the system indicates that the mechanism includes the formation of hydroxyl radicals generated from hydrogen peroxide in its interaction with di-iron species. The latter are formed via monomerization of starting hexairon complex with further dimerization of the monomers. Full article

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33 pages, 7351 KiB

Open AccessFeature PaperReview

Visible-Light-Active TiO₂-Based Hybrid Nanocatalysts for Environmental Applications

by Alessandra Truppi, Francesca Petronella, Tiziana Placido, Marinella Striccoli, Angela Agostiano, Maria Lucia Curri and Roberto Comparelli

Catalysts 2017, 7(4), 100; https://doi.org/10.3390/catal7040100 - 25 Mar 2017

Cited by 108 | Viewed by 10995

Abstract

Photocatalytic nanomaterials such as TiO₂ are receiving a great deal of attention owing to their potential applications in environmental remediation. Nonetheless, the low efficiency of this class of materials in the visible range has, so far, hampered their large-scale application. The increasing [...] Read more.

Photocatalytic nanomaterials such as TiO₂ are receiving a great deal of attention owing to their potential applications in environmental remediation. Nonetheless, the low efficiency of this class of materials in the visible range has, so far, hampered their large-scale application. The increasing demand for highly efficient, visible-light-active photocatalysts can be addressed by hybrid nanostructured materials in which two or more units, each characterised by peculiar physical properties, surface chemistry and morphology, are combined together into a single nano-object with unprecedented chemical–physical properties. The present review intends to focus on hybrid nanomaterials, based on TiO₂ nanoparticles able to perform visible-light-driven photocatalytic processes for environmental applications. We give a brief overview of the synthetic approaches recently proposed in the literature to synthesise hybrid nanocrystals and discuss the potential applications of such nanostructures in water remediation, abatement of atmospheric pollutants (including NO_x and volatile organic compounds (VOCs)) and their use in self-cleaning surfaces. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis for Environmental Remediation)

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12 pages, 3555 KiB

Open AccessArticle

Fivefold Enhanced Photoelectrochemical Properties of ZnO Nanowire Arrays Modified with C₃N₄ Quantum Dots

by Hao Yang, Zhiliang Jin, Hongyan Hu, Gongxuan Lu and Yingpu Bi

Catalysts 2017, 7(4), 99; https://doi.org/10.3390/catal7040099 - 24 Mar 2017

Cited by 34 | Viewed by 6828

Abstract

A facile and effective growing strategy of graphite-like carbon nitride quantum dots (CNQDs) modified on ZnO nanowire array composite electrodes has been successfully designed and prepared for the first time. The remarkable quantum enhanced properties were carefully studied by means of scanning electron [...] Read more.

A facile and effective growing strategy of graphite-like carbon nitride quantum dots (CNQDs) modified on ZnO nanowire array composite electrodes has been successfully designed and prepared for the first time. The remarkable quantum enhanced properties were carefully studied by means of scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscope (XPS), UV-vis diffuse reflectance, PEC performance, and photocatalytic hydrogen production, and the results were in good agreement. Fivefold enhanced photoelectrochemical performances of this novel hierarchical hetero-array prepared in this paper compared with pure ZnO nanowire arrays were obtained under UV-light. The effect was attributed to the remarkable charge separation between CNQDs and ZnO nanowire arrays. Additional investigations revealed that the particular structure of CNQDs/ZnO composites contributed to the separation of a photon-generation carrier and an enhanced photoelectric current. Moreover, the absorption edge of CNQD-modified ZnO nanowire arrays was slightly broadened, and the diameter was reduced as well. The photoelectrochemistry hydrogen evolution splitting water using simulated solar irradiation exhibited the foreground of a possible application of a mechanism of photoelectrochemistry hydrogen evolution over CNQDs/ZnO composite electrodes. Full article

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80 pages, 32185 KiB

Open AccessReview

Eco-Friendly Physical Activation Methods for Suzuki–Miyaura Reactions

by Katia Martina, Maela Manzoli, Emanuela Calcio Gaudino and Giancarlo Cravotto

Catalysts 2017, 7(4), 98; https://doi.org/10.3390/catal7040098 - 23 Mar 2017

Cited by 35 | Viewed by 12848

Abstract

Eco-compatible activation methods in Suzuki–Miyaura cross-coupling reactions offer challenging opportunities for the design of clean and efficient synthetic processes. The main enabling technologies described in the literature are microwaves, ultrasound, grinding (mechanochemistry) and light. These methods can be performed in water or other [...] Read more.

Eco-compatible activation methods in Suzuki–Miyaura cross-coupling reactions offer challenging opportunities for the design of clean and efficient synthetic processes. The main enabling technologies described in the literature are microwaves, ultrasound, grinding (mechanochemistry) and light. These methods can be performed in water or other green solvents with phase-transfer catalysis or even in solventless conditions. In this review, the authors will summarize the progress in this field mainly from 2010 up to the present day. Full article

(This article belongs to the Special Issue Suzuki–Miyaura Cross-Coupling Reaction and Potential Applications)

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11 pages, 3670 KiB

Open AccessArticle

Three-Dimensional TiO₂ Structures Incorporated with Tungsten Oxide for Treatment of Toxic Aromatic Volatile Compounds

by Joon Yeob Lee and Wan-Kuen Jo

Catalysts 2017, 7(4), 97; https://doi.org/10.3390/catal7040097 - 23 Mar 2017

Cited by 9 | Viewed by 4500

Abstract

This study assessed 3D WO₃–TiO₂ nanoflowers (WTNF) synthesized by a combined hydrothermal–ultrasonication–impregnation method for their applicability to the treatment of aromatic volatile compounds under visible-light illumination. The scanning electron microscopy exhibited the formation of 3D structures in the prepared WTNF [...] Read more.

This study assessed 3D WO₃–TiO₂ nanoflowers (WTNF) synthesized by a combined hydrothermal–ultrasonication–impregnation method for their applicability to the treatment of aromatic volatile compounds under visible-light illumination. The scanning electron microscopy exhibited the formation of 3D structures in the prepared WTNF samples. The X-ray diffraction patterns and energy dispersive X-ray results indicated a successful incorporation of WO₃ into TNF structures. The UV-visible spectroscopy showed that the prepared WTNF samples can be functioned under visible light irradiation. The output-to-input concentration ratios of toluene and o-xylene with WTNF samples were lower than those of TiO₂ nanoflowers. These findings were illustrated on the basis of charge separation ability, adsorption capability, and light absorption of the sample photocatalysts. The input-to-output concentration ratios of the target chemicals were lowest for 10 M NaOH and highest for 5 M NaOH. The photocatalytic degradation efficiencies of WTNF sample photocatalysts increased with increasing WO₃ content from 0.1% to 1.0%, and dropped gradually with increasing WO₃ content further to 4.0%. Light-emitting-diodes (LEDs) are a more highly energy-efficient light source compared to a conventional lamp for the photocatalytic degradation of toluene and o-xylene, although the photocatalytic activity is higher for the conventional lamp. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis for Environmental Remediation)

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14 pages, 2710 KiB

Open AccessArticle

Total Oxidation of Propane Using CeO₂ and CuO-CeO₂ Catalysts Prepared Using Templates of Different Nature

by Benjamin Solsona, Rut Sanchis, Ana M. Dejoz, Tomas García, Lidia Ruiz-Rodríguez, José Manuel López Nieto, Juan Antonio Cecilia and Enrique Rodríguez-Castellón

Catalysts 2017, 7(4), 96; https://doi.org/10.3390/catal7040096 - 23 Mar 2017

Cited by 49 | Viewed by 7363

Abstract

Several CeO₂ and CuO-CeO₂ catalysts were prepared using different methods, i.e., a homogeneous precipitation with urea, a nanocasting route using CMK-3 carbon as a hard template and a sol–gel process using Poly(methyl methacrylate) (PMMA) polymer as a soft template, and tested [...] Read more.

Several CeO₂ and CuO-CeO₂ catalysts were prepared using different methods, i.e., a homogeneous precipitation with urea, a nanocasting route using CMK-3 carbon as a hard template and a sol–gel process using Poly(methyl methacrylate) (PMMA) polymer as a soft template, and tested in the total oxidation of propane. The catalysts were characterized by a number of physicochemical techniques (XRD, N₂ adsorption, TPR, XPS, Raman spectroscopy) showing distinct characteristics. For each series, Cu-Ce-O catalysts with low Cu-loadings (5 wt % CuO) showed the highest activity, higher than those samples either without copper or with high Cu-loading (13 wt % CuO). The incorporation of copper leads to an increase of the concentration of bulk defects but if the Cu-loading is too high the surface area drastically falls. The highest activity in the total oxidation of propane was achieved by Cu-containing ceria catalysts synthesized using a polymer as a template, as this method yields high surface area materials. The surface area and the number of bulk/sub-surface defects of the ceria seem to be the main properties determining the catalytic activity. Full article

(This article belongs to the Special Issue Ceria-based Catalysts)

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