Catalysts

12 pages, 2452 KiB

Open AccessArticle

Isolation of a Bacillus Aryabhattai Strain for the Resolution of (R, S)-Ethyl Indoline-2-Carboxylate to Produce (S)-Indoline-2-Carboxylic Acid

by Yinjun Zhang, Jialin Chen, Changsheng Chen and Shijin Wu

Catalysts 2019, 9(2), 206; https://doi.org/10.3390/catal9020206 - 25 Feb 2019

Cited by 5 | Viewed by 3275

Abstract

The strain screened from sludge can selectively hydrolyze (S)-ethyl indoline-2-carboxylate to produce (S)-indoline-2-carboxylic acid. It was identified as the Bacillus aryabhattai strain based on its morphology, metabolism, and 16S rDNA sequence analysis. Glucose and yeast powder were used as [...] Read more.

The strain screened from sludge can selectively hydrolyze (S)-ethyl indoline-2-carboxylate to produce (S)-indoline-2-carboxylic acid. It was identified as the Bacillus aryabhattai strain based on its morphology, metabolism, and 16S rDNA sequence analysis. Glucose and yeast powder were used as the best carbon and nitrogen sources to cultured cells with an initial pH of seven. Subsequently, we optimized the key parameters for selective hydrolysis. Finally, when the substrate concentration had reached 3%, with a 35 °C water bath, a pH of seven, and a speed of 600 rpm, the e.e._p value attained 96% with a 33% yield. Thus, we had developed a new method for producing (S)-indoline-2-carboxylic acid that used whole microbial cells as the biocatalyst. Full article

(This article belongs to the Special Issue Biocatalysts: Design and Application)

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17 pages, 6822 KiB

Open AccessArticle

Selective Catalytic Reduction of Nitric Oxide with Propylene over Fe/Beta Catalysts Under Lean-Burn Conditions

by Hao Zhou, Mengyao Ge, Huishuang Zhao, Shiguo Wu, Mengyu Li and Yaxin Su

Catalysts 2019, 9(2), 205; https://doi.org/10.3390/catal9020205 - 23 Feb 2019

Cited by 14 | Viewed by 5253

Abstract

Fe/Beta catalysts were used for the selective catalytic reduction of nitric oxide with propylene (C₃H₆-SCR) under lean-burn conditions, which were prepared by liquid ion-exchange (LIE), solid-state ion-exchange (SIE), and incipient wet-impregnation (IWI) methods. The iron species on Fe/Beta were [...] Read more.

Fe/Beta catalysts were used for the selective catalytic reduction of nitric oxide with propylene (C₃H₆-SCR) under lean-burn conditions, which were prepared by liquid ion-exchange (LIE), solid-state ion-exchange (SIE), and incipient wet-impregnation (IWI) methods. The iron species on Fe/Beta were characterized and identified by a combination of several characterization techniques. The results showed preparation methods had a significant influence on the composition and distribution of iron species, LIE method inclined to produce more isolated Fe³⁺ ions at ion-exchanged sites than IWI and SIE method. C₃H₆-SCR activity tests demonstrated Fe/Beta(LIE) possessed remarkable catalytic activity and N₂ selectivity at temperature 300–450 °C. Kinetic studies of C₃H₆-SCR reaction suggested that isolated Fe³⁺ species were more active for NO reduction, whereas Fe₂O₃ nanoparticles enhanced the hydrocarbon combustion in excess of oxygen. According to the results of in situ DRIFTS, more isolated Fe³⁺ sites on Fe/Beta(LIE) would promote the formation of the key intermediates, i.e., NO₂ adspecies and formate species, then led to the superior C₃H₆-SCR activity. The slight decrease of SCR activity after hydrothermal aging of Fe/Beta(LIE) catalyst might be due to the migration of isolated Fe³⁺ ions into oligomeric clusters and/or Fe₂O₃ nanoparticles. Full article

(This article belongs to the Special Issue Catalysis for the Removal of Gas-Phase Pollutants)

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16 pages, 3589 KiB

Open AccessArticle

Radiative and Non-Radiative Recombination Pathways in Mixed-Phase TiO₂ Nanotubes for PEC Water-Splitting

by Rambabu Yalavarthi, Alberto Naldoni, Štěpán Kment, Luca Mascaretti, Hana Kmentová, Ondřej Tomanec, Patrik Schmuki and Radek Zbořil

Catalysts 2019, 9(2), 204; https://doi.org/10.3390/catal9020204 - 23 Feb 2019

Cited by 40 | Viewed by 7185

Abstract

Anatase and rutile mixed-phase TiO₂ with an ideal ratio has been proven to significantly enhance photoelectrochemical (PEC) activity in water-splitting applications due to suppressing the electron–hole recombination. However, the mechanism of this improvement has not been satisfactory described yet. The PEC water [...] Read more.

Anatase and rutile mixed-phase TiO₂ with an ideal ratio has been proven to significantly enhance photoelectrochemical (PEC) activity in water-splitting applications due to suppressing the electron–hole recombination. However, the mechanism of this improvement has not been satisfactory described yet. The PEC water oxidation (oxygen evolution) at the interface of TiO₂ photoanode and electrolyte solution is determined by the fraction of the photogenerated holes that reach the solution and it is defined as the hole transfer efficiency. The surface and bulk recombination processes in semiconductor photoanodes majorly influence the hole transfer efficiency. In this work, we study the hole transfer process involved in mixed-phase TiO₂ nanotube arrays/solution junction using intensity-modulated photocurrent and photovoltage spectroscopy (IMPS and IMVS); then, we correlate the obtained hole transfer rate constants to (photo)electrochemical impedance spectroscopy (PEIS) measurements. The results suggest that the enhanced performance of the TiO₂ mixed-phase is due to the improved hole transfer rate across the TiO₂/liquid interface as well as to the decrease in the surface trap recombination of the holes. Full article

(This article belongs to the Special Issue Nanostructured Materials for Photocatalysis)

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12 pages, 1793 KiB

Open AccessArticle

Aldol Condensation of Furfural with Acetone Over Mg/Al Mixed Oxides. Influence of Water and Synthesis Method

by Almudena Parejas, Daniel Cosano, Jesús Hidalgo-Carrillo, José Rafael Ruiz, Alberto Marinas, César Jiménez-Sanchidrián and Francisco J. Urbano

Catalysts 2019, 9(2), 203; https://doi.org/10.3390/catal9020203 - 23 Feb 2019

Cited by 26 | Viewed by 8502

Abstract

Aldol condensation of furfural and acetone (an important initial step to obtain diesel from biomass) was studied over MgAl mixed oxides. The influence of the utilization of microwaves and/or a surfactant (Pluronic 123) during the synthesis as well as the use of water [...] Read more.

Aldol condensation of furfural and acetone (an important initial step to obtain diesel from biomass) was studied over MgAl mixed oxides. The influence of the utilization of microwaves and/or a surfactant (Pluronic 123) during the synthesis as well as the use of water (either pre-hydrating the solids before catalytic studies or in water/toluene mixtures as the reaction medium) is discussed. The combined use of Pluronic 123 and microwaves led to solids with bigger pore sizes, exhibiting lower basicity and higher acidity than the conventional synthetic method, thus resulting in an increase in the yield of the desired product of condensation, comprising two molecules of furfural and one of acetone (F2Ac). As for the influence of water, re-hydration of the mixed oxides was detrimental to activity, probably as a result of the partial blocking (solvation) of active sites. On the contrary, the increase in water percentage in the reaction medium resulted in higher conversions, though selectivity to F2Ac decreased. The weakening of the C=O bond of furfural in the presence of water as well as the higher solubility of the first condensation product (FAc) in toluene, as compared to water, could account for that. A 44.5% yield of F2Ac (66% conversion) after 16 h was obtained with the most active solid, which maintained the activity for three consecutive reactions. Full article

(This article belongs to the Special Issue Catalysis for Global Development. Contributions around the Iberoamerican Federation of Catalysis)

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12 pages, 4031 KiB

Open AccessArticle

Hierarchical ZSM-5 Zeolite with Enhanced Catalytic Activity for Alkylation of Phenol with Tert-Butanol

by Ling Xu, Fan Wang, Zhiqiang Feng, Zongrui Liu and Jingqi Guan

Catalysts 2019, 9(2), 202; https://doi.org/10.3390/catal9020202 - 23 Feb 2019

Cited by 13 | Viewed by 3890

Abstract

Using polyethylene glycol as a mesoporous soft template, a series of hierarchically porous ZSM-5 zeolites were prepared. X-ray diffraction, infrared spectroscopy, N₂ adsorption–desorption, and transmission electron microscopy results demonstrated that the resultant materials contained a micro–mesoporous structure. Since the existence of mesoporous [...] Read more.

Using polyethylene glycol as a mesoporous soft template, a series of hierarchically porous ZSM-5 zeolites were prepared. X-ray diffraction, infrared spectroscopy, N₂ adsorption–desorption, and transmission electron microscopy results demonstrated that the resultant materials contained a micro–mesoporous structure. Since the existence of mesoporous structure favors the diffusion of large molecular reactants and products, the phenol conversion and selectivity to 2,4-Di-TBP on the hierarchical ZSM-5 zeolite can be improved for the alkylation of phenol with tert-butanol. Full article

(This article belongs to the Section Nanostructured Catalysts)

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22 pages, 7541 KiB

Open AccessReview

Titanium-Dioxide-Based Visible-Light-Sensitive Photocatalysis: Mechanistic Insight and Applications

by Shinya Higashimoto

Catalysts 2019, 9(2), 201; https://doi.org/10.3390/catal9020201 - 22 Feb 2019

Cited by 71 | Viewed by 10564

Abstract

Titanium dioxide (TiO₂) is one of the most practical and prevalent photo-functional materials. Many researchers have endeavored to design several types of visible-light-responsive photocatalysts. In particular, TiO₂-based photocatalysts operating under visible light should be urgently designed and developed, in [...] Read more.

Titanium dioxide (TiO₂) is one of the most practical and prevalent photo-functional materials. Many researchers have endeavored to design several types of visible-light-responsive photocatalysts. In particular, TiO₂-based photocatalysts operating under visible light should be urgently designed and developed, in order to take advantage of the unlimited solar light available. Herein, we review recent advances of TiO₂-based visible-light-sensitive photocatalysts, classified by the origins of charge separation photo-induced in (1) bulk impurity (N-doping), (2) hetero-junction of metal (Au NPs), and (3) interfacial surface complexes (ISC) and their related photocatalysts. These photocatalysts have demonstrated useful applications, such as photocatalytic mineralization of toxic agents in the polluted atmosphere and water, photocatalytic organic synthesis, and artificial photosynthesis. We wish to provide comprehension and enlightenment of modification strategies and mechanistic insight, and to inspire future work. Full article

(This article belongs to the Special Issue Emerging Trends in TiO₂ Photocatalysis and Applications)

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20 pages, 7432 KiB

Open AccessArticle

Effect of Pt Promotion on the Ni-Catalyzed Deoxygenation of Tristearin to Fuel-Like Hydrocarbons

by Ryan Loe, Kelsey Huff, Morgan Walli, Tonya Morgan, Dali Qian, Robert Pace, Yang Song, Mark Isaacs, Eduardo Santillan-Jimenez and Mark Crocker

Catalysts 2019, 9(2), 200; https://doi.org/10.3390/catal9020200 - 22 Feb 2019

Cited by 18 | Viewed by 4946

Abstract

Pt represents an effective promoter of supported Ni catalysts in the transformation of tristearin to green diesel via decarbonylation/decarboxylation (deCO_x), conversion increasing from 2% over 20% Ni/Al₂O₃ to 100% over 20% Ni-0.5% Pt/Al₂O₃ at 260 [...] Read more.

Pt represents an effective promoter of supported Ni catalysts in the transformation of tristearin to green diesel via decarbonylation/decarboxylation (deCO_x), conversion increasing from 2% over 20% Ni/Al₂O₃ to 100% over 20% Ni-0.5% Pt/Al₂O₃ at 260 °C. Catalyst characterization reveals that the superior activity of Ni-Pt relative to Ni-only catalysts is not a result of Ni particle size effects or surface area differences, but rather stems from several other phenomena, including the improved reducibility of NiO when Pt is present. Indeed, the addition of a small amount of Pt to the supported Ni catalyst dramatically increases the amount of reduced surface metal sites, which are believed to be the active sites for deCO_x reactions. Further, Pt addition curbs the adsorption of CO on the catalyst surface, which decreases catalyst poisoning by any CO evolved via decarbonylation, making additional active sites available for deoxygenation reactions and/or preventing catalyst coking. Specifically, Pt addition weakens the Ni-CO bond, lowering the binding strength of CO on surface Ni sites. Finally, analysis of the spent catalysts recovered from deCO_x experiments confirms that the beneficial effect of Pt on catalyst performance can be partially explained by decreased coking and fouling. Full article

(This article belongs to the Special Issue Development of Catalysts for Green Diesel Production)

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17 pages, 7266 KiB

Open AccessArticle

The Support Effects on the Direct Conversion of Syngas to Higher Alcohol Synthesis over Copper-Based Catalysts

by Xiaoli Li, Junfeng Zhang, Min Zhang, Wei Zhang, Meng Zhang, Hongjuan Xie, Yingquan Wu and Yisheng Tan

Catalysts 2019, 9(2), 199; https://doi.org/10.3390/catal9020199 - 21 Feb 2019

Cited by 19 | Viewed by 4931

Abstract

The types of supports employed profoundly influence the physicochemical properties and performances of as-prepared catalysts in almost all catalytic systems. Herein, Cu catalysts, with different supports (SiO₂, Al₂O₃), were prepared by a facile impregnation method and used [...] Read more.

The types of supports employed profoundly influence the physicochemical properties and performances of as-prepared catalysts in almost all catalytic systems. Herein, Cu catalysts, with different supports (SiO₂, Al₂O₃), were prepared by a facile impregnation method and used for the direct synthesis of higher alcohols from CO hydrogenation. The prepared catalysts were characterized using multiple techniques, such as X-ray diffraction (XRD), N₂ sorption, H₂-temperature-programmed reduction (H₂-TPR), temperature-programmed desorption of ammonia (NH₃-TPD), X-ray photoelectron spectroscopy (XPS) and in situ Fourier-transform infrared spectroscopy (FTIR), etc. Compared to the Cu/Al₂O₃ catalyst, the Cu/SiO₂ catalyst easily promoted the formation of a higher amount of C1 oxygenate species on the surface, which is closely related to the formation of higher alcohols. Simultaneously, the Cu/Al₂O₃ and Cu/SiO₂ catalysts showed obvious differences in the CO conversion, alcohol distribution, and CO₂ selectivity, which were probably originated from differences in the structural and physicochemical properties, such as the types of copper species, the reduction behaviors, acidity, and electronic properties. Besides, it was also found that the gap in performances in two kinds of catalysts with the different supports could be narrowed by the addition of potassium because of its neutralization to surface acidy of Al₂O₃ and the creation of new basic sites, as well as the alteration of electronic properties. Full article

(This article belongs to the Special Issue Rational Design of Non-precious Metal Oxide Catalysts by Means of Advanced Synthetic and Promotional Routes)

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11 pages, 1770 KiB

Open AccessArticle

First-Principles Study of Optoelectronic Properties of the Noble Metal (Ag and Pd) Doped BiOX (X = F, Cl, Br, and I) Photocatalytic System

by Shixiong Zhou, Tingting Shi, Zhihong Chen, Dmitri S. Kilin, Lingling Shui, Mingliang Jin, Zichuan Yi, Mingzhe Yuan, Nan Li, Xiaobao Yang, Qingguo Meng, Xin Wang and Guofu Zhou

Catalysts 2019, 9(2), 198; https://doi.org/10.3390/catal9020198 - 21 Feb 2019

Cited by 28 | Viewed by 4867

Abstract

To explore the photocatalytic performances and optoelectronic properties of pure and doped bismuth oxyhalides D-doped BiOX (D = Ag, Pd; X = F, Cl, Br, I) compounds, their atomic properties, electronic structures, and optical properties were systematically investigated using first-principles calculations. In previous [...] Read more.

To explore the photocatalytic performances and optoelectronic properties of pure and doped bismuth oxyhalides D-doped BiOX (D = Ag, Pd; X = F, Cl, Br, I) compounds, their atomic properties, electronic structures, and optical properties were systematically investigated using first-principles calculations. In previous experiments, the BiOX (X = Cl, Br) based system has been observed with enhanced visible light photocatalytic activity driven by the Ag dopant. Our calculations also show that the potential photocatalytic performance of Ag-doped BiOCl or BiOBr systems is enhanced greatly under visible light, compared with other Pd-doped BiOX (X = Cl, Br) compounds. Furthermore, it is intriguing to find that the Pd-doped BiOF compound has strong absorption over the infrared and visible light spectrum, which may offer an effective strategy for a promising full spectrum catalyst. Indicated by various Mulliken charge distributions and different impurity states in the gap when Ag or Pd was doped in the BiOX compounds, we notice that all D-doped BiOXs exhibit a p-type semiconductor, and all impurity levels originated from the D-4d state. The charge transfer, optoelectronic properties, and absorption coefficients for photocatalytic activities among D-doped BiOX photocatalysts caused by the electronegativity difference of halide elements and metal atoms will finally affect the photocatalytic activity of doped BiOX systems. Therefore, it is significant to understand the inside physical mechanism of the enhanced Ag/Pd-doped BiOX photocatalysts through density functional theory. Full article

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

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11 pages, 2528 KiB

Open AccessArticle

Theoretical Study on Influence of Cobalt Oxides Valence State Change for C₆H₅COOH Pyrolysis

by Si-Mei Fu, Yue Zhao, Jiang-Tao Liu, Wen-Sheng Liang, Gang-Sen Li, Wei Huang and Zhi-Jun Zuo

Catalysts 2019, 9(2), 197; https://doi.org/10.3390/catal9020197 - 21 Feb 2019

Cited by 2 | Viewed by 3950

Abstract

Benzoic acid (C₆H₅COOH) is selected as coal-based model compound with Co compounds (Co₃O₄, CoO and Co) as the catalysts, and the influence of the valence state change of the catalyst for pyrolysis process is investigated [...] Read more.

Benzoic acid (C₆H₅COOH) is selected as coal-based model compound with Co compounds (Co₃O₄, CoO and Co) as the catalysts, and the influence of the valence state change of the catalyst for pyrolysis process is investigated using density functional theory (DFT). DFT results shows that the highest energy barrier of C₆H₅COOH pyrolysis is in the following order: E_a(CoO) <E_a(Co₃O₄) <E_a(no catalyst) <E_a(Co). In general, Co₃O₄ catalyst accelerates C₆H₅COOH pyrolysis. Then, the catalytic activity further increases when Co₃O₄ is reduced to CoO. Finally, Co shows no activity for C₆H₅COOH pyrolysis due to the reduction of CoO to metallic Co. Full article

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

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5 pages, 184 KiB

Open AccessEditorial

Editorial Catalysts: Special Issue on Plasma Catalysis

by Annemie Bogaerts

Catalysts 2019, 9(2), 196; https://doi.org/10.3390/catal9020196 - 21 Feb 2019

Cited by 6 | Viewed by 4238

Abstract

Plasma catalysis is gaining increasing interest for various gas conversion applications, such as CO₂ conversion into value-added chemicals and fuels, N₂ fixation for the synthesis of NH₃ or NO_x, and CH₄ conversion into higher hydrocarbons or oxygenates [...] Full article

(This article belongs to the Special Issue Plasma Catalysis)

10 pages, 5550 KiB

Open AccessCommunication

Aerobic Epoxidation of Low-Molecular-Weight and Polymeric Olefins by a Supramolecular Manganese Porphyrin Catalyst

by Ivan Bernar, Floris P.J.T. Rutjes, Johannes A.A.W. Elemans and Roeland J.M. Nolte

Catalysts 2019, 9(2), 195; https://doi.org/10.3390/catal9020195 - 21 Feb 2019

Cited by 25 | Viewed by 5008

Abstract

We report on the highly efficient epoxidation of low-molecular-weight and polymeric olefins catalyzed by a supramolecular manganese porphyrin complex using molecular oxygen as an oxidant and an aldehyde as a co-reductant. At ambient temperature and under optimized reaction conditions, the catalyst showed high [...] Read more.

We report on the highly efficient epoxidation of low-molecular-weight and polymeric olefins catalyzed by a supramolecular manganese porphyrin complex using molecular oxygen as an oxidant and an aldehyde as a co-reductant. At ambient temperature and under optimized reaction conditions, the catalyst showed high activity and stereoselectivity. The efficiency of the supramolecular manganese porphyrin was higher than that of a reference porphyrin catalyst, possibly because it was more stable under the applied reaction conditions. Mechanistic studies suggest that a manganese oxo porphyrin complex may be an intermediate in the epoxidation reaction. Full article

(This article belongs to the Special Issue Transition Metal Complexes as Catalysts in Organic Chemistry)

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14 pages, 5935 KiB

Open AccessArticle

Alkali and Alkaline Earth Cation-Decorated TiO₂ Nanotube-Supported Rh Catalysts for Vinyl Acetate Hydroformylation

by Hongyuan Chuai, Penghe Su, Hongchi Liu, Baolin Zhu, Shoumin Zhang and Weiping Huang

Catalysts 2019, 9(2), 194; https://doi.org/10.3390/catal9020194 - 20 Feb 2019

Cited by 12 | Viewed by 3872

Abstract

Alkali and alkaline earth cation-decorated TiO₂ nanotube (TNT)-supported rhodium catalysts were synthesized and characterized by inductively-coupled plasma optical emission spectrometer, surface characterization analyzer, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier transforming infrared spectrum, respectively. Their catalytic performances were evaluated [...] Read more.

Alkali and alkaline earth cation-decorated TiO₂ nanotube (TNT)-supported rhodium catalysts were synthesized and characterized by inductively-coupled plasma optical emission spectrometer, surface characterization analyzer, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier transforming infrared spectrum, respectively. Their catalytic performances were evaluated by the hydroformylation of vinyl acetate. Results showed that both the conversion rate of vinyl acetate and selectivity for aldehyde were improved after Rh/TNTs were modified by alkali or alkali-earth cations. Such improved selectivity for aldehyde might be attributed to the presence of alkali or alkaline earth cations which enhanced CO adsorption, while the high conversion rate of vinyl acetate was likely due to the proper interaction of Lewis acid–base between cations modified TNTs and vinyl acetate. Full article

(This article belongs to the Special Issue Catalytic Carbonylation Reactions)

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13 pages, 3601 KiB

Open AccessReview

Photocatalytic Reversible Reactions Driven by Localized Surface Plasmon Resonance

by Zheng Gong, Jialong Ji and Jingang Wang

Catalysts 2019, 9(2), 193; https://doi.org/10.3390/catal9020193 - 20 Feb 2019

Cited by 10 | Viewed by 3898

Abstract

In this study, we review photocatalytic reversible surface catalytic reactions driven by localized surface plasmon resonance. Firstly, we briefly introduce the synthesis of 4,4′-dimercaptoazobenzene (DMAB) from 4-nitrobenzenethiol (4NBT) using surface-enhanced Raman scattering (SERS) technology. Furthermore, we study the photosynthetic and degradation processes of [...] Read more.

In this study, we review photocatalytic reversible surface catalytic reactions driven by localized surface plasmon resonance. Firstly, we briefly introduce the synthesis of 4,4′-dimercaptoazobenzene (DMAB) from 4-nitrobenzenethiol (4NBT) using surface-enhanced Raman scattering (SERS) technology. Furthermore, we study the photosynthetic and degradation processes of 4NBT to DMAB reduction, as well as factors associated with them, such as laser wavelength, reaction time, substrate, and pH. Last but not least, we reveal the competitive relationship between photosynthetic and degradation pathways for this reduction reaction by SERS technology on the substrate of Au film over a nanosphere. Full article

(This article belongs to the Special Issue Plasmonic Photocatalysts)

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22 pages, 1421 KiB

Open AccessArticle

NHC-Catalyzed Organocatalytic Asymmetric Approach to 2,2-Disubstituted Benzofuran-3(2H)-ones Containing Fully Substituted Quaternary Stereogenic Center

by Zbigniew Rafiński

Catalysts 2019, 9(2), 192; https://doi.org/10.3390/catal9020192 - 20 Feb 2019

Cited by 8 | Viewed by 3715

Abstract

A highly efficient and enantioselective approach to the synthesis of functionalized benzofuran-3(2H)-ones is presented. It proceeds via an intramolecular Stetter reaction using β,β-disubstituted Michael acceptors in the construction of five-membered rings with fully-substituted quaternary stereogenic centers and is promoted by terpene-derived [...] Read more.

A highly efficient and enantioselective approach to the synthesis of functionalized benzofuran-3(2H)-ones is presented. It proceeds via an intramolecular Stetter reaction using β,β-disubstituted Michael acceptors in the construction of five-membered rings with fully-substituted quaternary stereogenic centers and is promoted by terpene-derived triazolium salts. As a result, a series of chiral 2,2-disubstituted benzofuran-3(2H)-one derivatives with linear, branched, and cyclic aliphatic substitutions on the quaternary stereogenic center were obtained in high yields and with excellent enantioselectivities of up to 99% ee. Full article

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

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32 pages, 8851 KiB

Open AccessEditor’s ChoiceReview

Titanium Dioxide: From Engineering to Applications

by Xiaolan Kang, Sihang Liu, Zideng Dai, Yunping He, Xuezhi Song and Zhenquan Tan

Catalysts 2019, 9(2), 191; https://doi.org/10.3390/catal9020191 - 19 Feb 2019

Cited by 328 | Viewed by 23727

Abstract

Titanium dioxide (TiO₂) nanomaterials have garnered extensive scientific interest since 1972 and have been widely used in many areas, such as sustainable energy generation and the removal of environmental pollutants. Although TiO₂ possesses the desired performance in utilizing ultraviolet light, [...] Read more.

Titanium dioxide (TiO₂) nanomaterials have garnered extensive scientific interest since 1972 and have been widely used in many areas, such as sustainable energy generation and the removal of environmental pollutants. Although TiO₂ possesses the desired performance in utilizing ultraviolet light, its overall solar activity is still very limited because of a wide bandgap (3.0–3.2 eV) that cannot make use of visible light or light of longer wavelength. This phenomenon is a deficiency for TiO₂ with respect to its potential application in visible light photocatalysis and photoelectrochemical devices, as well as photovoltaics and sensors. The high overpotential, sluggish migration, and rapid recombination of photogenerated electron/hole pairs are crucial factors that restrict further application of TiO₂. Recently, a broad range of research efforts has been devoted to enhancing the optical and electrical properties of TiO₂, resulting in improved photocatalytic activity. This review mainly outlines state-of-the-art modification strategies in optimizing the photocatalytic performance of TiO₂, including the introduction of intrinsic defects and foreign species into the TiO₂ lattice, morphology and crystal facet control, and the development of unique mesocrystal structures. The band structures, electronic properties, and chemical features of the modified TiO₂ nanomaterials are clarified in detail along with details regarding their photocatalytic performance and various applications. Full article

(This article belongs to the Special Issue Emerging Trends in TiO₂ Photocatalysis and Applications)

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18 pages, 2615 KiB

Open AccessEditor’s ChoiceReview

Application of Cell-Free Protein Synthesis for Faster Biocatalyst Development

by Jascha Rolf, Katrin Rosenthal and Stephan Lütz

Catalysts 2019, 9(2), 190; https://doi.org/10.3390/catal9020190 - 19 Feb 2019

Cited by 37 | Viewed by 10904

Abstract

Cell-free protein synthesis (CFPS) has become an established tool for rapid protein synthesis in order to accelerate the discovery of new enzymes and the development of proteins with improved characteristics. Over the past years, progress in CFPS system preparation has been made towards [...] Read more.

Cell-free protein synthesis (CFPS) has become an established tool for rapid protein synthesis in order to accelerate the discovery of new enzymes and the development of proteins with improved characteristics. Over the past years, progress in CFPS system preparation has been made towards simplification, and many applications have been developed with regard to tailor-made solutions for specific purposes. In this review, various preparation methods of CFPS systems are compared and the significance of individual supplements is assessed. The recent applications of CFPS are summarized and the potential for biocatalyst development discussed. One of the central features is the high-throughput synthesis of protein variants, which enables sophisticated approaches for rapid prototyping of enzymes. These applications demonstrate the contribution of CFPS to enhance enzyme functionalities and the complementation to in vivo protein synthesis. However, there are different issues to be addressed, such as the low predictability of CFPS performance and transferability to in vivo protein synthesis. Nevertheless, the usage of CFPS for high-throughput enzyme screening has been proven to be an efficient method to discover novel biocatalysts and improved enzyme variants. Full article

(This article belongs to the Special Issue Biocatalysis for Industrial Applications)

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13 pages, 2279 KiB

Open AccessArticle

Synergistic Effect of Photocatalytic Degradation of Hexabromocyclododecane in Water by UV/TiO₂/persulfate

by Qiang Li, Lifang Wang, Xuhui Fang, Li Zhang, Jingjiu Li and Hongyong Xie

Catalysts 2019, 9(2), 189; https://doi.org/10.3390/catal9020189 - 18 Feb 2019

Cited by 31 | Viewed by 4241

Abstract

In this work, the elimination of hexabromocyclododecane (HBCD) is explored by using photodegradation of the UV/TiO₂ system, the UV/potassium persulfate (KPS) system, and the homo/heterogeneous UV/TiO₂/KPS system. The experimental results show that the dosages of TiO₂ and potassium persulfate [...] Read more.

In this work, the elimination of hexabromocyclododecane (HBCD) is explored by using photodegradation of the UV/TiO₂ system, the UV/potassium persulfate (KPS) system, and the homo/heterogeneous UV/TiO₂/KPS system. The experimental results show that the dosages of TiO₂ and potassium persulfate have optimum values to increase the degradation degree. HBCD can be almost completely degraded and 74.3% of the total bromine content is achieved in the UV/TiO₂/KPS homo/heterogeneous photocatalysis, much more than in the UV/persulfate system and the UV/TiO₂ system. Roles of radicals SO₄^•− and OH^• in the photocatalysis systems are discussed based on experimental measurements. The high yield of the concentration of bromide ions and decreased pH value indicates that synergistic effects exist in the UV/TiO₂/KPS homo/heterogeneous photocatalysis, which can mineralize HBCD into inorganic small molecules like carboxylic acids, CO₂ and H₂O, thus much less intermediates are formed. The possible pathways of degradation of HBCD in the UV/TiO₂/KPS system were also analyzed by GC/MS. This work will have practical application potential in the fields of pollution control and environmental management. Full article

(This article belongs to the Special Issue Emerging Trends in TiO₂ Photocatalysis and Applications)

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15 pages, 6777 KiB

Open AccessArticle

Combined Magnesia, Ceria and Nickel catalyst supported over γ-Alumina Doped with Titania for Dry Reforming of Methane

by Ahmed Sadeq Al-Fatesh, Samsudeen Olajide Kasim, Ahmed Aidid Ibrahim, Anis Hamza Fakeeha, Ahmed Elhag Abasaeed, Rasheed Alrasheed, Rawan Ashamari and Abdulaziz Bagabas

Catalysts 2019, 9(2), 188; https://doi.org/10.3390/catal9020188 - 18 Feb 2019

Cited by 21 | Viewed by 4413

Abstract

This study investigated dry reforming of methane (DRM) over combined catalysts supported on γ-Al₂O₃ support doped with 3.0 wt. % TiO₂. Physicochemical properties of all catalysts were determined by inductively coupled plasma/mass spectrometry (ICP-MS), nitrogen physisorption, X-ray diffraction, [...] Read more.

This study investigated dry reforming of methane (DRM) over combined catalysts supported on γ-Al₂O₃ support doped with 3.0 wt. % TiO₂. Physicochemical properties of all catalysts were determined by inductively coupled plasma/mass spectrometry (ICP-MS), nitrogen physisorption, X-ray diffraction, temperature programmed reduction/oxidation/desorption/pulse hydrogen chemisorption, thermogravimetric analysis, and scanning electron microscopy. Addition of CeO₂ and MgO to Ni strengthened the interaction between the Ni and the support. The catalytic activity results indicate that the addition of CeO₂ and MgO to Ni did not reduce carbon deposition, but improved the activity of the catalysts. Temperature programmed oxidation (TPO) revealed the formation of carbon that is mainly amorphous and small amount of graphite. The highest CH₄ and CO₂ conversion was found for the catalyst composed of 5.0 wt. % NiO-10.0 wt. % CeO₂/3.0 wt. %TiO₂-γ-Al₂O₃ (Ti-CAT-II), resulting in H₂/CO mole ratio close to unity. The optimum reaction conditions in terms of reactant conversion and H₂/CO mole ratio were achieved by varying space velocity and CO₂/CH₄ mole ratio. Full article

(This article belongs to the Special Issue Catalysts for Syngas Production)

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16 pages, 5086 KiB

Open AccessArticle

Z-Schemed WO₃/rGO/SnIn₄S₈ Sandwich Nanohybrids for Efficient Visible Light Photocatalytic Water Purification

by Pingfan Xu, Siyi Huang, Minghua Liu, Yuancai Lv, Zhonghui Wang, Jinlin Long, Wei Zhang and Haojun Fan

Catalysts 2019, 9(2), 187; https://doi.org/10.3390/catal9020187 - 17 Feb 2019

Cited by 24 | Viewed by 4573

Abstract

Semiconductor photocatalysis has received much attention as a promising technique to solve energy crisis and environmental pollution. This work demonstrated the rational design of “sandwich” WO₃/rGO/SnIn₄S₈ (WGS) Z-scheme photocatalysts for efficient purification of wastewater emitted from tannery and [...] Read more.

Semiconductor photocatalysis has received much attention as a promising technique to solve energy crisis and environmental pollution. This work demonstrated the rational design of “sandwich” WO₃/rGO/SnIn₄S₈ (WGS) Z-scheme photocatalysts for efficient purification of wastewater emitted from tannery and dyeing industries. Such materials were prepared by a combined protocol of the in situ precipitation method with hydrothermal synthesis, and structurally characterized by XRD, SEM, HRTEM, UV-vis DRS, and PL spectroscopy. Results showed that the Z-schemed nanohybrids significantly enhanced the photocatalytic activity compared to the single component photocatalysts. An optimized case of the WGS-2.5% photocatalysts exhibited the highest Cr(VI) reduction rate, which was ca. 1.8 and 12 times more than those of pure SnIn₄S₈ (SIS) and WO₃, respectively. Moreover, the molecular mechanism of the enhanced photocatalysis was clearly revealed by the radical-trapping control experiments and electron paramagnetic resonance (ESR) spectroscopy. The amount of superoxide and hydroxyl radicals as the major reactive oxygen species performing the redox catalysis was enhanced significantly on the Z-scheme WGS photocatalysts, where the spatial separation of photoinduced electron–hole pairs was therefore accelerated for the reduction of Cr(VI) and degradation of Rhodamine B (RhB). This study provides a novel strategy for the synthesis of all-solid-state Z-scheme photocatalysts for environmental remediation. Full article

(This article belongs to the Section Photocatalysis)

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12 pages, 2941 KiB

Open AccessArticle

Dehydration of Bioethanol to Ethylene over H-ZSM-5 Catalysts: A Scale-Up Study

by Sanggil Moon, Ho-Jeong Chae and Min Bum Park

Catalysts 2019, 9(2), 186; https://doi.org/10.3390/catal9020186 - 16 Feb 2019

Cited by 17 | Viewed by 5751

Abstract

Bioethanol dehydration was carried out in a bench scale reactor-loaded H-ZSM-5 molded catalyst, which increased by tens of times more than at lab scale (up to 60 and 24 times based on the amount of catalyst and ethanol flow rate, respectively). From the [...] Read more.

Bioethanol dehydration was carried out in a bench scale reactor-loaded H-ZSM-5 molded catalyst, which increased by tens of times more than at lab scale (up to 60 and 24 times based on the amount of catalyst and ethanol flow rate, respectively). From the results of the lab scale reaction, we confirmed the optimum Si/Al ratio (14) of H-ZSM-5, reaction temperature (~250 °C), and weight hourly space velocity (WHSV) (<5 h⁻¹) indicating high ethanol conversion and ethylene selectivity. Five types of cylindrical shaped molded catalysts were prepared by changing the type and/or amount of organic solid binder, inorganic solid binder, inorganic liquid binder, and H-ZSM-5 basis catalyst. Among them, the catalyst exhibiting the highest compression strength and good ethanol dehydration performance was selected. The bench scale reaction with varying reaction temperature of 245–260 °C and 1.2– 2.0 h⁻¹ WHSV according to reaction time showed that the conversion and ethylene selectivity were more than 90% after 400 h on stream. It was also confirmed that even after the successive catalyst regeneration and the reaction for another 400 h, both the ethanol conversion and ethylene selectivity were still maintained at about 90%. Full article

(This article belongs to the Special Issue Synthesis and Application of Zeolite Catalysts)

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25 pages, 15013 KiB

Open AccessArticle

Plasma Catalysis: Distinguishing between Thermal and Chemical Effects

by Guido Giammaria, Gerard van Rooij and Leon Lefferts

Catalysts 2019, 9(2), 185; https://doi.org/10.3390/catal9020185 - 16 Feb 2019

Cited by 21 | Viewed by 5797

Abstract

The goal of this study is to develop a method to distinguish between plasma chemistry and thermal effects in a Dielectric Barrier Discharge nonequilibrium plasma containing a packed bed of porous particles. Decomposition of CaCO₃ in Ar plasma is used as a [...] Read more.

The goal of this study is to develop a method to distinguish between plasma chemistry and thermal effects in a Dielectric Barrier Discharge nonequilibrium plasma containing a packed bed of porous particles. Decomposition of CaCO₃ in Ar plasma is used as a model reaction and CaCO₃ samples were prepared with different external surface area, via the particle size, as well as with different internal surface area, via pore morphology. Also, the effect of the CO₂ in gas phase on the formation of products during plasma enhanced decomposition is measured. The internal surface area is not exposed to plasma and relates to thermal effect only, whereas both plasma and thermal effects occur at the external surface area. Decomposition rates were in our case found to be influenced by internal surface changes only and thermal decomposition is concluded to dominate. This is further supported by the slow response in the CO₂ concentration at a timescale of typically 1 minute upon changes in discharge power. The thermal effect is estimated based on the kinetics of the CaCO₃ decomposition, resulting in a temperature increase within 80 °C for plasma power from 0 to 6 W. In contrast, CO₂ dissociation to CO and O₂ is controlled by plasma chemistry as this reaction is thermodynamically impossible without plasma, in agreement with fast response within a few seconds of the CO concentration when changing plasma power. CO forms exclusively via consecutive dissociation of CO₂ in the gas phase and not directly from CaCO₃. In ongoing work, this methodology is used to distinguish between thermal effects and plasma–chemical effects in more reactive plasma, containing, e.g., H₂. Full article

(This article belongs to the Special Issue Plasma Catalysis)

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15 pages, 2317 KiB

Open AccessArticle

Appraisal of Sulphonation Processes to Synthesize Palm Waste Biochar Catalysts for the Esterification of Palm Fatty Acid Distillate

by Shehu-Ibrahim Akinfalabi, Umer Rashid, Robiah Yunus and Yun Hin Taufiq-Yap

Catalysts 2019, 9(2), 184; https://doi.org/10.3390/catal9020184 - 15 Feb 2019

Cited by 17 | Viewed by 4318

Abstract

Palm waste biochar (PWB) catalysts were synthesized as bio-based catalysts using different sulphonation methods. (NH₄)₂SO₄, ClSO₃H, and H₂SO₄ were applied to functionalize PWB and appraise the discrepancies between the sulfonic agents, as [...] Read more.

Palm waste biochar (PWB) catalysts were synthesized as bio-based catalysts using different sulphonation methods. (NH₄)₂SO₄, ClSO₃H, and H₂SO₄ were applied to functionalize PWB and appraise the discrepancies between the sulfonic agents, as they affect the esterification reaction in terms of fatty acid methyl ester (FAME) yield and conversion while using palm fatty acid distillate (PFAD) as feedstock. The PWB was first soaked in phosphoric acid (H₃PO₄) for 24 h and then pyrolized at 400 °C for 2 h in tube furnace. Afterwards, sulphonation was done with different sulfonic agents and characterized with thermo-gravimetric analysis (TGA), Brunauer-Emmett-Teller (BET), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX), and temperature programmed desorption–ammonia (TPD-NH₃). The three synthesized catalysts showed high free fatty acid (FFA) conversions of 90.1% for palm waste biochar-ammonium sulfate (PWB-(NH₄)₂SO₄), 91.5% for palm waste biochar-chlorosulfonic acid (PWB-ClSO₃H), and 97.4% for palm waste biochar - sulphuric acid (PWB-H₂SO₄), whereas FAME yields were 88.6% (PWB-(NH₄)₂SO₄), 89.1% (PWB-ClSO₃H), and 96.1% (PWB-H₂SO₄). It was observed that PWB-H₂SO₄ has the best catalytic activity, which was directly linked to its high acid density (11.35 mmol/g), improved pore diameter (6.25 nm), and increased specific surface area (372.01 m² g⁻¹). PWB-H₂SO₄ was used for the reusability study, where it underwent eight reaction runs and was stable until the seventh run. PWB-H₂SO₄ has shown huge promise for biodiesel synthesis, owing to its easy synthetic process, recyclability, and high catalytic activity for waste oils and fats. Full article

(This article belongs to the Special Issue Sustainable Applications in Surface Chemistry and Catalysis)

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9 pages, 1705 KiB

Open AccessArticle

A Facile Fabrication of Supported Ni/SiO₂ Catalysts for Dry Reforming of Methane with Remarkably Enhanced Catalytic Performance

by Yan Xu, Qiang Lin, Bing Liu, Feng Jiang, Yuebing Xu and Xiaohao Liu

Catalysts 2019, 9(2), 183; https://doi.org/10.3390/catal9020183 - 15 Feb 2019

Cited by 17 | Viewed by 4142

Abstract

Ni catalysts supported on SiO₂ are prepared via a facile combustion method. Both glycine fuel and ammonium nitrate combustion improver facilitate the formation of much smaller Ni nanoparticles, which give excellent activity and stability, as well as a syngas with a molar [...] Read more.

Ni catalysts supported on SiO₂ are prepared via a facile combustion method. Both glycine fuel and ammonium nitrate combustion improver facilitate the formation of much smaller Ni nanoparticles, which give excellent activity and stability, as well as a syngas with a molar ratio of H₂/CO of about 1:1 due to the minimal side reaction toward revserse water gas shift (RWGS) in CH₄ dry reforming. Full article

(This article belongs to the Special Issue Catalysts for Syngas Production)

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14 pages, 2596 KiB

Open AccessArticle

Experimental Studies on Co-Combustion of Sludge and Wheat Straw

by Zeyu Xue, Zhaoping Zhong and Bo Zhang

Catalysts 2019, 9(2), 182; https://doi.org/10.3390/catal9020182 - 15 Feb 2019

Cited by 14 | Viewed by 3261

Abstract

This work presents studies on the co-combustion of sludge and wheat straw (30 wt % sludge + 70 wt % wheat straw). Prior to the combustion experiment, thermogravimetric analysis was performed to investigate the combustion characteristic of the blended fuel. Results indicated that [...] Read more.

This work presents studies on the co-combustion of sludge and wheat straw (30 wt % sludge + 70 wt % wheat straw). Prior to the combustion experiment, thermogravimetric analysis was performed to investigate the combustion characteristic of the blended fuel. Results indicated that the blended fuel could remedy the defect of each individual component and also promote the combustion. Co-combustion experiments were conducted in a lab-scale vertical tube furnace and the ash samples were analyzed by Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES), X-ray Diffraction (XRD), and Scanning Electron Microscope (SEM). Thermodynamic calculations were also made to study the interactions that occurred. Addition of sludge could raise the melting point of wheat straw ash and reduce the slagging tendency. Co-combustion also restrained the release of K and transferred it into aluminosilicate and phosphate. Transfer of Pb and Zn in the co-combustion was also studied. The release and leaching toxicity of the two heavy metals in the co-combustion were weakened effectively by wheat straw. PbCl₂(g) and ZnCl₂(g) could be captured by K₂SiO₃ in wheat straw ash particles and generate silicates. Interactions that possibly occurred between K, Zn, and Pb components were discussed at the end of the paper. Full article

(This article belongs to the Special Issue Catalytic Biomass to Renewable Biofuels and Biomaterials)

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10 pages, 1099 KiB

Open AccessArticle

Photocatalytic Degradation of Microcystins by TiO₂ Using UV-LED Controlled Periodic Illumination

by Olivia M. Schneider, Robert Liang, Leslie Bragg, Ivana Jaciw-Zurakowsky, Azar Fattahi, Shasvat Rathod, Peng Peng, Mark R. Servos and Y. Norman Zhou

Catalysts 2019, 9(2), 181; https://doi.org/10.3390/catal9020181 - 14 Feb 2019

Cited by 27 | Viewed by 5528

Abstract

Toxic microcystins (MCs) produced by freshwater cyanobacteria such as Microcystis aeruginosa are of concern because of their negative health and economic impacts globally. An advanced oxidation process using UV/TiO₂ offers a promising treatment option for hazardous organic pollutants such as microcystins. The [...] Read more.

Toxic microcystins (MCs) produced by freshwater cyanobacteria such as Microcystis aeruginosa are of concern because of their negative health and economic impacts globally. An advanced oxidation process using UV/TiO₂ offers a promising treatment option for hazardous organic pollutants such as microcystins. The following work details the successful degradation of MC-LA, MC-LR, and MC-RR using a porous titanium–titanium dioxide (PTT) membrane under UV-LED light. Microcystin quantitation was achieved by sample concentration and subsequent LC–MS/MS analysis. The PTT membrane offers a treatment option that eliminates the need for the additional filtration or separation steps required for traditional catalysts. Controlled periodic illumination was successfully used to decrease the total light exposure time and improve the photonic efficiency for a more cost-effective treatment system. Individual degradation rates were influenced by electrostatic forces between the catalyst and differently charged microcystins, which can potentially be adjusted by modifying the solution pH and the catalyst’s isoelectric point. Full article

(This article belongs to the Special Issue Emerging Trends in TiO₂ Photocatalysis and Applications)

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13 pages, 2155 KiB

Open AccessFeature PaperArticle

Kinetic Study of the Selective Hydrogenation of Acetylene over Supported Palladium under Tail-End Conditions

by Caroline Urmès, Jean-Marc Schweitzer, Amandine Cabiac and Yves Schuurman

Catalysts 2019, 9(2), 180; https://doi.org/10.3390/catal9020180 - 14 Feb 2019

Cited by 21 | Viewed by 6616

Abstract

The kinetics of the selective hydrogenation of acetylene in the presence of an excess of ethylene has been studied over a 0.05 wt. % Pd/α-Al₂O₃ catalyst. The experimental reaction conditions were chosen to operate under intrinsic kinetic conditions, free from [...] Read more.

The kinetics of the selective hydrogenation of acetylene in the presence of an excess of ethylene has been studied over a 0.05 wt. % Pd/α-Al₂O₃ catalyst. The experimental reaction conditions were chosen to operate under intrinsic kinetic conditions, free from heat and mass transfer limitations. The data could be described adequately by a Langmuir–Hinshelwood rate-equation based on a series of sequential hydrogen additions according to the Horiuti–Polanyi mechanism. The mechanism involves a single active site on which both the conversion of acetylene and ethylene take place. Full article

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

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20 pages, 4301 KiB

Open AccessArticle

Fluorinated and Platinized Titania as Effective Materials in the Photocatalytic Treatment of Dyestuffs and Stained Wastewater Coming from Handicrafts Factories

by Julie Joseane Murcia, Ángela Carolina Cely, Hugo Alfonso Rojas, María Carmen Hidalgo and José Antonio Navío

Catalysts 2019, 9(2), 179; https://doi.org/10.3390/catal9020179 - 14 Feb 2019

Cited by 15 | Viewed by 3247

Abstract

In this study, commercial and lab-prepared TiO₂ were modified by fluorination and platinum photodeposition; and the effect of these modifications over the physicochemical and photocatalytic properties of TiO₂ was evaluated. It was found that F and Pt addition leads to the [...] Read more.

In this study, commercial and lab-prepared TiO₂ were modified by fluorination and platinum photodeposition; and the effect of these modifications over the physicochemical and photocatalytic properties of TiO₂ was evaluated. It was found that F and Pt addition leads to the modification of the optical and textural properties of TiO₂. The materials prepared were tested in the photocatalytic degradation of different organic dyestuffs such as methylene blue (MB) and methyl orange (MO); the degradation of commercial anilines employed in the staining of natural fibers was also evaluated. Photocatalysis was also studied in this work as an eco-friendly treatment of wastewater coming from handicrafts factories. In general it was observed that the effectiveness of the photocatalytic treatment strongly depends on the substrate to be degraded, thus, fluorinated and platinized commercial Titania (Pt-F-P25) showed the best photocatalytic performance in the MB and MO photodegradation and in contrast, in the case of the anilines the highest degradation was obtained over commercial TiO₂ fluorinated (F-P25). These results can be explained by differences observed in the structure and in the adsorption of these dyestuffs over the photocatalysts surfaces. F-P25 photocatalyst also demonstrated to be the best material for the treatment of real wastewater coming from handicrafts factories. Full article

(This article belongs to the Special Issue New Trends in the Photocatalytic Removal of Organic Dyes)

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27 pages, 10021 KiB

Open AccessArticle

Strong Photo-Oxidative Capability of ZnWO₄ Nanoplates with Highly Exposed {0 1 1} Facets

by Bao-gai Zhai, Long Yang, Fu-fang Zhou, Jun-sheng Shi and Yuan Ming Huang

Catalysts 2019, 9(2), 178; https://doi.org/10.3390/catal9020178 - 14 Feb 2019

Cited by 19 | Viewed by 3602

Abstract

ZnWO₄ nanoplates with highly exposed {0

\bar{1}

1} facets were synthesized via a hydrothermal technique. The phase, morphology, and optical characteristics of ZnWO₄ nanoplates were characterized with scanning electron microscopy, transmission electron microscopy, X–ray diffraction, diffuse ultraviolet–visible light (UV–Vis) reflectance [...] Read more.

ZnWO₄ nanoplates with highly exposed {0

\bar{1}

1} facets were synthesized via a hydrothermal technique. The phase, morphology, and optical characteristics of ZnWO₄ nanoplates were characterized with scanning electron microscopy, transmission electron microscopy, X–ray diffraction, diffuse ultraviolet–visible light (UV–Vis) reflectance spectroscopy, photoluminescence (PL) spectrophotometry, and PL lifetime spectroscopy. Optical characterizations, along with the density functional calculations, confirm that the strong blue PL band of ZnWO₄ nanoplates originates from the intrinsic defects in ZnWO₄ nanoplates. Furthermore, photocatalytic tests show that ZnWO₄ nanoplates exhibit strong photo-oxidative capability of complete mineralization of the organic pollutant (methyl orange) in water, whereas ZnWO₄ nanoparticles can only cleave the organic molecules into fragments. The superior photo-oxidative capability of ZnWO₄ nanoplates can be attributed to the specific chemical bonding and stereochemistry on the exposed facets. This work demonstrates that crystal facet engineering is an efficient strategy to endow ZnWO₄ with strong photo-oxidative capability. Full article

(This article belongs to the Special Issue Nanostructured Materials for Photocatalysis)

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12 pages, 3957 KiB

Open AccessArticle

Preparation and Catalytic Performance of Metal-Rich Pd Phosphides for the Solvent-Free Selective Hydrogenation of Chloronitrobenzene

by Chunshan Lu, Qianwen Zhu, Xuejie Zhang, Qiangqiang Liu, Juanjuan Nie, Feng Feng, Qunfeng Zhang, Lei Ma, Wenfeng Han and Xiaonian Li

Catalysts 2019, 9(2), 177; https://doi.org/10.3390/catal9020177 - 13 Feb 2019

Cited by 15 | Viewed by 3837

Abstract

A facile synthesis method of palladium phosphide supported on the activated carbon was developed. The effects of Pd precursors for phosphatization, phosphatization temperature, and the ratio of hypophosphite/Pd on the generation of palladium phosphide were investigated, and a generation mechanism of the Pd [...] Read more.

A facile synthesis method of palladium phosphide supported on the activated carbon was developed. The effects of Pd precursors for phosphatization, phosphatization temperature, and the ratio of hypophosphite/Pd on the generation of palladium phosphide were investigated, and a generation mechanism of the Pd₃P crystal structure is proposed. The results demonstrate that only PdO, rather than Pd or PdCl₂, can transform into Pd phosphide without damage to the activated carbon. The penetration of P into the Pd particle can dramatically improve the dispersion of Pd species particles on the activated carbon. The generation of Pd phosphide greatly depends on the phosphatization temperature and the ratio of hypophosphite/Pd. An intact Pd₃P crystal structure was obtained when the ratio of hypophosphite/Pd reached 32 and the phosphatization temperature was above 400 °C. The Pd₃P supported on the activated carbon exhibited superior catalytic performance in terms of the hydrogenation of halonitrobenzenes to haloanilines because it had few L acids and B acids sites and could not generate deficient-electron active hydrogen atoms as electrophiles. Full article

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