Catalysts

13 pages, 2534 KiB

Open AccessArticle

Engineering of Substrate Tunnel of P450 CYP116B3 though Machine Learning

by Yiheng Liu, Zhongyu Li, Chenqi Cao, Xianzhi Zhang, Shuaiqi Meng, Mehdi D. Davari, Haijun Xu, Yu Ji, Ulrich Schwaneberg and Luo Liu

Catalysts 2023, 13(8), 1228; https://doi.org/10.3390/catal13081228 - 21 Aug 2023

Cited by 1 | Viewed by 1146

Abstract

The combinatorial complexity of the protein sequence space presents a significant challenge for recombination experiments targeting beneficial positions. To overcome these difficulties, a machine learning (ML) approach was employed, which was trained on a limited literature dataset and combined with iterative generation and [...] Read more.

The combinatorial complexity of the protein sequence space presents a significant challenge for recombination experiments targeting beneficial positions. To overcome these difficulties, a machine learning (ML) approach was employed, which was trained on a limited literature dataset and combined with iterative generation and experimental data implementation. The PyPEF method was utilized to identify existing variants and predict recombinant variants targeting the substrate channel of P450 CYP116B3. Through molecular dynamics simulations, eight multiple-substituted improved variants were successfully validated. Specifically, the RMSF of variant A86T/T91H/M108S/A109M/T111P was decreased from 3.06 Å (wild type) to 1.07 Å. Additionally, the average RMSF of the variant A86T/T91P/M108V/A109M/T111P decreased to 1.41 Å, compared to the wild type’s 1.53 Å. Of particular significance was the prediction that the variant A86T/T91H/M108G/A109M/T111P exhibited an activity approximately 15 times higher than that of the wild type. Furthermore, during the selection of the regression model, PLS and MLP regressions were compared. The effect of data size and data relevance on the two regression approaches has been summarized. The aforementioned conclusions provide evidence for the feasibility of the strategy that combines ML with experimental approaches. This integrated strategy proves effective in exploring potential variations within the protein sequence space. Furthermore, this method facilitates a deeper understanding of the substrate channel in P450 CYP116B3. Full article

(This article belongs to the Section Biocatalysis)

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13 pages, 2796 KiB

Open AccessArticle

Efficient Regioselective Synthesis of Novel Ensembles of Organylselanyl-Functionalized Divinyl Sulfides and 1,3-Thiaselenoles under Phase Transfer Catalysis Conditions

by Andrey S. Filippov, Svetlana V. Amosova, Nataliya A. Makhaeva, Alexander I. Albanov and Vladimir A. Potapov

Catalysts 2023, 13(8), 1227; https://doi.org/10.3390/catal13081227 - 21 Aug 2023

Viewed by 666

Abstract

Efficient regioselective synthesis of novel ensembles of organylselanyl-functionalized 1,3-thiaselenoles and divinyl sulfides in high yields under phase transfer catalysis conditions was developed. The methodology is based on the generation of sodium [(Z)-2-(vinylsulfanyl)ethenyl]selenolate and 1,3-thiaselenol-2-ylmethylselenolate, which were involved in a nucleophilic addition [...] Read more.

Efficient regioselective synthesis of novel ensembles of organylselanyl-functionalized 1,3-thiaselenoles and divinyl sulfides in high yields under phase transfer catalysis conditions was developed. The methodology is based on the generation of sodium [(Z)-2-(vinylsulfanyl)ethenyl]selenolate and 1,3-thiaselenol-2-ylmethylselenolate, which were involved in a nucleophilic addition reaction with activated alkenes such as acrylonitrile, acrylamide, methyl vinyl ketone, methyl, and ethyl acrylates. In the case of methyl vinyl ketone, the reaction was accompanied by the hydrogenation of the carbonyl group. Methylene chloride was involved in the nucleophilic substitution reaction with sodium [(Z)-2-(vinylsulfanyl)ethenyl]selenolate and 1,3-thiaselenol-2-ylmethylselenolate to afford new polyunsaturated compounds with several sulfur and selenium atoms. Full article

(This article belongs to the Special Issue Recent Advances in Catalytic Synthesis and Application of Heterocyclic and Heteroatom Compounds)

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28 pages, 16466 KiB

Open AccessReview

Rational Design of the Catalysts for the Direct Conversion of Methane to Methanol Based on a Descriptor Approach

by Zhi Li, Yanjun Chen, Zean Xie, Weiyu Song, Baijun Liu and Zhen Zhao

Catalysts 2023, 13(8), 1226; https://doi.org/10.3390/catal13081226 - 21 Aug 2023

Viewed by 1635

Abstract

The direct oxidation of methane to methanol as a liquid fuel and chemical feedstock is arguably the most desirable methane conversion pathway. Currently, constructing and understanding linear scaling relationships between the fundamental physical or chemical properties of catalysts and their catalytic performance to [...] Read more.

The direct oxidation of methane to methanol as a liquid fuel and chemical feedstock is arguably the most desirable methane conversion pathway. Currently, constructing and understanding linear scaling relationships between the fundamental physical or chemical properties of catalysts and their catalytic performance to explore suitable descriptors is crucial for theoretical research on the direct conversion of methane to methanol. In this review, we summarize the energy, electronic, and structural descriptors used to predict catalytic activity. Fundamentally, these descriptors describe the redox properties of active sites from different dimensions. We further explain the moderate principle of descriptors in methane-to-methanol catalyst design and provide related application work. Simultaneously, the underlying activity limitation of methane activation and active species generation is revealed. Based on the selectivity descriptor, the inverse scaling relationship limitation between methane conversion and methanol selectivity is quantitatively understood. Finally, multiscale strategies are proposed to break the limitation and achieve the simultaneous enhancement of activity and selectivity. This descriptor-based review provides theoretical insights and guidance to accelerate the understanding, optimization, and design of efficient catalysts for direct methane-to-methanol conversion. Full article

(This article belongs to the Special Issue Advances in Catalytic Oxidation of Methane and Carbon Monoxide, 2nd Edition)

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18 pages, 7370 KiB

Open AccessArticle

Zeolitic Imidazolium Frameworks-Derived Ru-Based Composite Materials Enable the Catalytic Dehydrogenation of Alcohols to Carboxylic Acids

by Zhan Chen, Jing Hang, Song Zhang, Ye Yuan, Francis Verpoort and Cheng Chen

Catalysts 2023, 13(8), 1225; https://doi.org/10.3390/catal13081225 - 20 Aug 2023

Viewed by 966

Abstract

The metal-catalyzed dehydrogenation of alcohols without any oxidant or additive has been demonstrated as an atom-economic and environmentally friendly strategy for carboxylic acid synthesis. Among the various catalysts applied to this transformation, Ru-based homogeneous ones have been the most extensively studied owing to [...] Read more.

The metal-catalyzed dehydrogenation of alcohols without any oxidant or additive has been demonstrated as an atom-economic and environmentally friendly strategy for carboxylic acid synthesis. Among the various catalysts applied to this transformation, Ru-based homogeneous ones have been the most extensively studied owing to their remarkable catalytic activity. However, these catalysts required multiple complicated synthesis steps. In addition, they were either difficult to recycle or their recovery processes were relatively tedious. Therefore, a series of Ru-containing heterogeneous catalysts with zeolitic imidazolium frameworks (ZIFs)-derived materials were designed and fabricated. A thorough screening of various parameters was conducted, and it was found that the material obtained by loading a Ru concentration of 0.05 mol/L into Co species embedded in porous N-doped carbon (Ru_0.05@Co-NC) had the best catalytic performance in this transformation, affording a handful of carboxylic acid products from the corresponding aromatic or aliphatic alcohols in moderate to high yields. Additionally, the catalyst showed remarkable recyclability as it could be recycled eight times with stable activity fluctuation (45–52%). It is noteworthy that catalyst recycling was convenient and fast, which could be realized simply by an external magnet. Moreover, the stable morphology and structure of Ru_0.05@Co-NC, along with its high specific surface area, hierarchical pore structure, high porosity, and other properties, jointly contributed to its high catalytic activity and good recyclability. Furthermore, the stability and activity of Ru_0.05@Co-NC were further evaluated through acid etching experiments, which revealed that some Ru species could stably exist in concentrated acids and play a pivotal role in promoting this catalytic process. Full article

(This article belongs to the Special Issue Zeolites and Zeolite-Based Catalysts in Industrial Catalysis)

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18 pages, 3231 KiB

Open AccessArticle

Highly Efficient RGO-Supported Pd Catalyst for Low Temperature Hydrocarbon Oxidation

by Ralitsa Velinova, Anton Naydenov, Diana Kichukova, Ventsislav Tumbalev, Genoveva Atanasova, Daniela Kovacheva and Ivanka Spassova

Catalysts 2023, 13(8), 1224; https://doi.org/10.3390/catal13081224 - 20 Aug 2023

Cited by 1 | Viewed by 883

Abstract

The work presents Pd-containing catalysts for practical application with enhanced low-temperature activity in the complete oxidation of volatile organic compounds (VOCs) using innovative combinations of reduced graphene oxide (RGO) and alumina. The catalysts were characterized by XRD, SEM, TEM, XPS, low-temperature N₂ [...] Read more.

The work presents Pd-containing catalysts for practical application with enhanced low-temperature activity in the complete oxidation of volatile organic compounds (VOCs) using innovative combinations of reduced graphene oxide (RGO) and alumina. The catalysts were characterized by XRD, SEM, TEM, XPS, low-temperature N₂-adsorption, and CO chemisorption. The tests on complete catalytic oxidation of different VOC (propane, butane, hexane, dimethyl ether, toluene, propylene) and CO were carried out. The reaction kinetics and the mechanism of the reaction of complete oxidation of toluene are being investigated in detail. The results show that the new catalyst design makes it able to completely oxidize the studied VOCs and CO at low temperatures (100–350 °C) with long-term stability. Using a variety of instrumental methods, it was established that for high activity and long-term stability, the optimal ratio Pd/PdO should be close to 1:1. The most probable mechanism of complete toluene oxidation is the mechanism of Langmuir–Hinshelwood. The high activity and the weak effect of water on the catalyst performance leads to further perspectives for the application of the currently developed approach for the preparation of large-scale monolithic catalytic systems for air pollution control. Full article

(This article belongs to the Special Issue Catalytic Combustion - From Laboratory Tests to Practical Applications)

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14 pages, 2539 KiB

Open AccessArticle

Catalytic Cracking of Fischer-Tropsch Wax on Different Zeolite Catalysts

by Chao Yang, Lingtao Liu, Genquan Zhu, Chaogang Xie, Xiance Zhang and Xiaoqiao Zhang

Catalysts 2023, 13(8), 1223; https://doi.org/10.3390/catal13081223 - 18 Aug 2023

Viewed by 1254

Abstract

Fisher-Tropsch synthesis (FTS) is a promising method to make alternative hydrocarbons from biomass or other resources. Upgrading the primary FTS products is of considerable interest. Cracking FT wax is economically attractive to produce light olefins. Herein, the effects of the zeolite type, Si/Al [...] Read more.

Fisher-Tropsch synthesis (FTS) is a promising method to make alternative hydrocarbons from biomass or other resources. Upgrading the primary FTS products is of considerable interest. Cracking FT wax is economically attractive to produce light olefins. Herein, the effects of the zeolite type, Si/Al ratio of ZSM-5, and reaction condition on the catalytic cracking of FT wax were investigated. It was found that the pore structure and acid properties of zeolites had a significant impact on the product selectivity. USY was beneficial for the production of gasoline and diesel, while β was suitable for the production of propylene and butenes, and ZSM-5 was conductive to producing ethylene and propylene. Increasing the Si/Al ratio of ZSM-5 can suppress the hydrogen transfer reaction and increase the selectivity of light olefins. When the Si/Al ratio of ZSM-5 was 140, the mass yields of ethylene, propylene, and butenes were 6.40%, 26.83%, and 20.10%, respectively. Full article

(This article belongs to the Special Issue Zeolites and Zeolite-Based Catalysts in Industrial Catalysis)

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24 pages, 9281 KiB

Open AccessArticle

Excellent Performance and Feasible Mechanism of ErOx-Boosted MnOx-Modified Biochars Derived from Sewage Sludge and Rice Straw for Formaldehyde Elimination: In Situ DRIFTS and DFT

by Jiajie Wang, Lei Gao, Dong Xie, Caiting Li, Liping Xiang, Yun Jiang, Qing Xu, Huiyu Xiong, Lei Yi, Jie Liu and Jiajun Wu

Catalysts 2023, 13(8), 1222; https://doi.org/10.3390/catal13081222 - 17 Aug 2023

Viewed by 1003

Abstract

To avoid resource waste and environmental pollution, a chain of ErO_x-boosted MnO_x-modified biochars derived from rice straw and sewage sludge (Er_yMn_1-y/BACs, where biochars derived from rice straw and sewage sludge were defined as BACs) were [...] Read more.

To avoid resource waste and environmental pollution, a chain of ErO_x-boosted MnO_x-modified biochars derived from rice straw and sewage sludge (Er_yMn_1-y/BACs, where biochars derived from rice straw and sewage sludge were defined as BACs) were manufactured for formaldehyde (HCHO) elimination. The optimal 15%Er_0.5Mn_0.5/BAC achieved a 97.2% HCHO removal efficiency at 220 °C and exhibited favorable E_HCHO and thermal stability in a wide temperature window between 180 and 380 °C. The curbed influences of H₂O and SO₂ offset the boosting effect of O₂ in a certain range. Er–Mn bimetallic-modified BACs offered a superior HCHO removal performance compared with that of BACs boosted using Er or Mn separately, owing to the synergistic effect of ErO_x and MnO_x conducive to improving the samples’ total pore volume and surface area, surface active oxygen species, promoting redox ability, and inhibiting the crystallization of MnO_x. Moreover, the support’s hierarchical porous structure not only expedited the diffusion and mass transfer of reactants and their products but also elevated the approachability of adsorption and catalytic sites. Notably, these prominent features were partly responsible for the outstanding performance and excellent tolerance to H₂O and SO₂. Using in situ DRIFTS characterization analysis, it could be inferred that the removal process of HCHO was HCHO_ad → dioxymethylene (DOM) → formate species → CO₂ + H₂O, further enhanced with reactive oxygen species. The DFT calculation once again proved the removal process of HCHO and the strengthening effect of Er doping. Furthermore, the optimal catalytic performance of 15%Er_0.5Mn_0.5/BAC demonstrated its vast potential for practical applications. Full article

(This article belongs to the Section Biomass Catalysis)

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20 pages, 4342 KiB

Open AccessReview

Recent Advances in Design and Synthesis of 1,3-Thiaselenolane and 1,3-Thiaselenole Derivatives

by Svetlana V. Amosova and Nataliya A. Makhaeva

Catalysts 2023, 13(8), 1221; https://doi.org/10.3390/catal13081221 - 17 Aug 2023

Viewed by 855

Abstract

Recent advances in the design and synthesis of five-membered heterocycles containing both sulfur and selenium atoms—1,3-thiaselenolane and 1,3-thiaselenole derivatives—are discussed in this review. These heterocyclic systems are of interest as intermediates for organic synthesis and compounds that can exhibit various useful properties, including [...] Read more.

Recent advances in the design and synthesis of five-membered heterocycles containing both sulfur and selenium atoms—1,3-thiaselenolane and 1,3-thiaselenole derivatives—are discussed in this review. These heterocyclic systems are of interest as intermediates for organic synthesis and compounds that can exhibit various useful properties, including biological activity and electrical conductivity. The main focus of the review is on the works of the last 20 years that make use of catalytic reactions. Synthetic methods for the preparation of structurally related 1,4,5,8-diselenadithiafulvalenes based on catalytic cross-coupling reactions are also presented. To date, the design and synthesis of 1,3-thiaselenolane and 1,3-thiaselenole derivatives have not been discussed in a separate review. Full article

(This article belongs to the Special Issue Recent Advances in Catalytic Synthesis and Application of Heterocyclic and Heteroatom Compounds)

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11 pages, 2717 KiB

Open AccessArticle

Microbial Transformation of Pimavanserin by Cunninghamella blakesleeana AS 3.970

by Ming Song, Qi Yu, Yuqi Liu, Sulan Cai, Xuliang Jiang, Weizhuo Xu and Wei Xu

Catalysts 2023, 13(8), 1220; https://doi.org/10.3390/catal13081220 - 17 Aug 2023

Viewed by 764

Abstract

Pimavanserin is an approved selective 5-HT_2A receptor inverse agonist for treating Parkinson’s disease psychosis. However, few studies on its metabolism in vitro have been investigated. In this research, eight strains of fungi are used to study the pimavanserin metabolism profiles in vitro [...] Read more.

Pimavanserin is an approved selective 5-HT_2A receptor inverse agonist for treating Parkinson’s disease psychosis. However, few studies on its metabolism in vitro have been investigated. In this research, eight strains of fungi are used to study the pimavanserin metabolism profiles in vitro and six of them demonstrated positive transformation results. Factors influencing the transformation rate, like substrate concentration, culture time, initial media pH value, culture temperature, and shaking speed, were evaluated and optimized. Cunninghamella blakesleeana AS3.970 provided the best transformation rate of 30.31%, and 10 unreported metabolites were screened by LC-MS/MS. Among these metabolites, M1 is the major one and identified as 1-(4-fluorobenzyl)-3-(4-(2-hydroxy-2-methylpropoxy)benzyl)-1-(1-methylpiperidin-4-yl)urea, which is a hydroxylation product of the pimavanserin. A preliminary molecular docking simulation was performed, which indicated that M1 exhibits similar binding properties with pimavanserin and may become a potential candidate for Parkinson’s disease treatment. Full article

(This article belongs to the Special Issue Microbial Biocatalysis, 2nd Edition)

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17 pages, 8326 KiB

Open AccessFeature PaperArticle

Effect of Different Zinc Species on Mn-Ce/CuX Catalyst for Low-Temperature NH₃-SCR Reaction: Comparison of ZnCl₂, Zn(NO₃)₂, ZnSO₄ and ZnCO₃

by Lin Chen, Shan Ren, Tao Chen, Xiaodi Li, Zhichao Chen, Mingming Wang, Qingcai Liu and Jie Yang

Catalysts 2023, 13(8), 1219; https://doi.org/10.3390/catal13081219 - 17 Aug 2023

Viewed by 863

Abstract

The effects of four distinct zinc species (ZnCl₂, Zn(NO₃)₂, ZnSO₄, and ZnCO₃) on a Mn-Ce co-doped CuX (MCCX)catalyst were investigated and contrasted in the low-temperature NH₃-SCR process. Aqueous solutions of ZnCl [...] Read more.

The effects of four distinct zinc species (ZnCl₂, Zn(NO₃)₂, ZnSO₄, and ZnCO₃) on a Mn-Ce co-doped CuX (MCCX)catalyst were investigated and contrasted in the low-temperature NH₃-SCR process. Aqueous solutions of ZnCl₂, Zn(NO₃)₂, ZnSO₄, and ZnCO₃ were used to poison the catalysts. The catalytic activity of all catalysts was assessed, and their physicochemical properties were studied. There was a notable drop trend in catalytic activity in the low temperature range (200 °C) after zinc species poisoning on MCCX catalyst. Interestingly, ZnSO₄ and ZnCO₃ on MCCX catalyst had more serious effect on catalytic activity than Zn(NO₃)₂ and ZnCl₂ from 150 °C to 225 °C, in which NO conversion of the MCCX-Zn-S and MCCX-Zn-C catalysts dropped about 20–30% below 200 °C compared with the fresh MCCX catalyst. The zeolite X structure was impacted by Zn species doping on the MCCX catalyst, and the Zn-poisoned catalysts had less acidic and lower redox ability than fresh Mn-Ce/CuX catalysts. Through the results of in situ DRIFTS spectroscopy experiments, all catalysts were governed by both Langmuir–Hinshelwood (L–H) and Eley–Rideal (E–R) mechanisms, and the possible mechanism for poisoning the Mn-Ce/CuX catalyst using various zinc species was revealed. Full article

(This article belongs to the Special Issue Zeolites as Catalysts: Applications in Chemical Engineering, Energy Sources and Environmental Protection)

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15 pages, 9873 KiB

Open AccessArticle

The Structure–Activity Relationship of CuO in the Catalytic Conversion Reaction of Glycerol to Lactic Acid

by Cheng Tang, Shuangming Li, Shanqi Li, Yiwen Wang, Mingyue He, Mengyuan Huang and Sansan Yu

Catalysts 2023, 13(8), 1218; https://doi.org/10.3390/catal13081218 - 17 Aug 2023

Cited by 2 | Viewed by 1205

Abstract

Three types of CuO with different micro–structures were applied to catalyze the conversion of glycerol to lactic acid. The structure–activity relationship between CuO and its catalytic performance was investigated by combining experiments and theoretical calculations. We demonstrated that two CuO samples (CuO–BCC and [...] Read more.

Three types of CuO with different micro–structures were applied to catalyze the conversion of glycerol to lactic acid. The structure–activity relationship between CuO and its catalytic performance was investigated by combining experiments and theoretical calculations. We demonstrated that two CuO samples (CuO–BCC and CuO–CA), as prepared by calcining copper salts, show larger lattice spacing than that of commercial CuO (CuO–COM). In the catalytic experiments, CuO–BCC, which had the largest lattice spacing (d = 0.2480 nm), exhibited the highest yield of 78.54% for lactic acid. The lattice strain caused by lattice expansion was considered more favorable for CuO–BCC in adsorbing glycerol molecules, thereby improving the conversion of glycerol to lactic acid. The DFT simulation calculation results further prove that CuO–BCC has a larger adsorption energy for glycerol and a smaller thermodynamic energy barrier for the dehydrogenation of glycerol to form the key intermediate products (glyceraldehyde and 1,3-dihydroxyacetone) than CuO–COM. This study demonstrates the role of lattice strain effects in the development of catalysts and provides ideas for catalytic glycerol-selective oxidation studies. Full article

(This article belongs to the Section Biomass Catalysis)

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17 pages, 7953 KiB

Open AccessArticle

Hard Template-Assisted Trans-Crystallization Synthesis of Hierarchically Porous Cu-SSZ-13 with Enhanced NH₃-SCR Performance

by Fuzhen Yang, Ying Xin, Xiaoli Zhu, Ahui Tang, Long Yu, Dongxu Han, Junxiu Jia, Yaning Lu and Zhaoliang Zhang

Catalysts 2023, 13(8), 1217; https://doi.org/10.3390/catal13081217 - 16 Aug 2023

Cited by 1 | Viewed by 1230

Abstract

Small porous Cu-SSZ-13 catalysts have recently been commercialized for the selective catalytic reduction of NO_x with ammonia (NH₃-SCR) on diesel vehicles. Unfortunately, the conventional Cu-SSZ-13 catalyst still confronts the challenge of diffusion limitations, which represent a major obstacle that reduces [...] Read more.

Small porous Cu-SSZ-13 catalysts have recently been commercialized for the selective catalytic reduction of NO_x with ammonia (NH₃-SCR) on diesel vehicles. Unfortunately, the conventional Cu-SSZ-13 catalyst still confronts the challenge of diffusion limitations, which represent a major obstacle that reduces the catalyst’s SCR performance. Herein, a hierarchically porous SSZ-13 zeolite was synthesized via a trans-crystallization method assisted by the use of carbon black as a hard template in a short synthetic period, and the corresponding Cu-SSZ-13 catalysts with mesopores exhibited improved low-temperature activity and hydrothermal stability when compared with their microporous counterpart. A series of characterizations revealed that the mesopores are conducive to an increase in Cu loading while helping to stabilize the CHA structure and maintain the Cu species in their ionic form. More importantly, intra-particle diffusion limitations are reduced via the introduction of the mesopores owing to the shortened diffusion path inside the SSZ-13 zeolite, thus not only enhancing the active sites’ accessibility but also promoting the diffusion of the reactants and products. This work contributes to the design and synthesis of a high-performance Cu-SSZ-13 zeolite SCR catalyst for the removal of NO_x emitted from diesel vehicles. Full article

(This article belongs to the Special Issue Catalysts for Selective Catalytic Reduction (SCR) and Related Reactions)

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13 pages, 7302 KiB

Open AccessArticle

Efficient Conversion of Monosaccharides into 5-Hydroxymethylfurfural Using Acidic Deep Eutectic Solvents

by Linh Ngoc To, Trinh Hao Nguyen, Thien Phuoc Nguyen, Ha Bich Phan, Linh Ho Thuy Nguyen, Tan Le Hoang Doan, Chinh Van Dang and Phuong Hoang Tran

Catalysts 2023, 13(8), 1216; https://doi.org/10.3390/catal13081216 - 16 Aug 2023

Viewed by 1098

Abstract

In this study, a quick, simple, green method of converting carbohydrates into 5-hydroxymethylfurfural (HMF) with the use of deep eutectic solvents (DESs) was reported on. We synthesized 12 DESs for HMF conversion from carbohydrates which were studied under different conditions. Under optimal conditions, [...] Read more.

In this study, a quick, simple, green method of converting carbohydrates into 5-hydroxymethylfurfural (HMF) with the use of deep eutectic solvents (DESs) was reported on. We synthesized 12 DESs for HMF conversion from carbohydrates which were studied under different conditions. Under optimal conditions, oxalic acid and citric acid with a choline chloride-based DES produced a maximum yield of HMF at 59 ± 2% and 62 ± 3% in 5 min at 120 °C, respectively. The efficiency of converting glucose to HMF in a short time (5 min) at 140 °C using CrCl₃ with a choline chloride-based DES was around 37 ± 1%, which was higher than in previous work. This study demonstrates the significant potential of DESs as a combination for the continuous catalytic transformation of biomass in the synthesis of platform chemicals. Full article

(This article belongs to the Special Issue Catalysts in Neoteric Solvents II)

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25 pages, 3664 KiB

Open AccessReview

Fischer–Tropsch Synthesis Catalysts for Selective Production of Diesel Fraction

by Kristina Mazurova, Albina Miyassarova, Oleg Eliseev, Valentine Stytsenko, Aleksandr Glotov and Anna Stavitskaya

Catalysts 2023, 13(8), 1215; https://doi.org/10.3390/catal13081215 - 16 Aug 2023

Cited by 1 | Viewed by 3177

Abstract

The Fischer–Tropsch process is considered one of the most promising eco-friendly routes for obtaining synthetic motor fuels. Fischer–Tropsch synthesis is a heterogeneous catalytic process in which a synthesis gas (CO/H₂) transforms into a mixture of aliphatic hydrocarbons, mainly linear alkanes. Recently, [...] Read more.

The Fischer–Tropsch process is considered one of the most promising eco-friendly routes for obtaining synthetic motor fuels. Fischer–Tropsch synthesis is a heterogeneous catalytic process in which a synthesis gas (CO/H₂) transforms into a mixture of aliphatic hydrocarbons, mainly linear alkanes. Recently, an important direction has been to increase the selectivity of the process for the diesel fraction. Diesel fuel synthesized via the Fischer–Tropsch method has a number of advantages over conventional fuel, including the high cetane number, the low content of aromatic, and the practically absent sulfur and nitrogen impurities. One of the possible ways to obtain a high yield of diesel fuel via the Fischer–Tropsch process is the development of selective catalysts. In this review, the latest achievements in the field of production of diesel via Fischer–Tropsch synthesis using catalysts are reviewed for the first time. Catalytic systems based on Al₂O₃ and mesoporous silicates, such as MCM-41, SBA-15, and micro- and mesoporous zeolites, are observed. Together with catalytic systems, the main factors that influence diesel fuel selectivity such as temperature, pressure, CO:H₂ ratio, active metal particle size, and carrier pore size are highlighted. The motivation behind this work is due to the increasing need for alternative processes in diesel fuel production with a low sulfur content and better exploitation characteristics. Full article

(This article belongs to the Special Issue Heterogeneous Catalysts for Petrochemical Synthesis and Oil Refining, 2nd Edition)

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11 pages, 1482 KiB

Open AccessCommunication

Zinc Iodide-Metal Chloride-Organic Base: An Efficient Catalytic System for Synthesis of Cyclic Carbonates from Carbon Dioxide and Epoxides under Ambient Conditions

by Masatoshi Mihara, Shuichi Nakao, Takeo Nakai and Takumi Mizuno

Catalysts 2023, 13(8), 1214; https://doi.org/10.3390/catal13081214 - 16 Aug 2023

Viewed by 1317

Abstract

Development of an effective catalytic system for the cycloaddition of carbon dioxide to epoxides for the preparation of cyclic carbonates under mild conditions is of great importance. Herein, a mixture of zinc iodide, metal chlorides, and strong organic bases is demonstrated to be [...] Read more.

Development of an effective catalytic system for the cycloaddition of carbon dioxide to epoxides for the preparation of cyclic carbonates under mild conditions is of great importance. Herein, a mixture of zinc iodide, metal chlorides, and strong organic bases is demonstrated to be a useful catalytic system that works at room temperature under atmospheric pressure. The most efficient combination, zinc iodide-niobium chloride-7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (1.2-0.3-3.0 mol%), gave styrene carbonate (95%) from styrene oxide and CO₂ (balloon) at 25 °C for 24 h. Another combination, zinc iodide-zinc chloride-1,8-diazabicyclo[5.4.0]undec-7-ene (1.2-0.8-4.0 mol%), kept the catalytic activity for the preparation of propylene carbonate until the fourth run. Therefore, the reaction system was operationally simple, highly efficient, and proceeded under ambient conditions. The catalyst is composed of readily available reagents and is reusable. Thus, the method presented is a powerful tool for utilizing CO₂ as the starting material for the production of valuable chemicals. Full article

(This article belongs to the Special Issue Recent Progress of Catalysis in “Dual Carbon Targets”)

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49 pages, 16582 KiB

Open AccessReview

Recent Progress in Pd-Catalyzed Tandem Processes

by Linda Z. Nikoshvili and Valentina G. Matveeva

Catalysts 2023, 13(8), 1213; https://doi.org/10.3390/catal13081213 - 15 Aug 2023

Cited by 2 | Viewed by 1339

Abstract

In recent years, Pd-containing catalytic systems for tandem processes have gained special attention due to their enhanced catalytic properties and their possibility of performing several reactions without the necessity of separating the intermediates. In this review, recent progress in Pd-catalyzed tandem processes is [...] Read more.

In recent years, Pd-containing catalytic systems for tandem processes have gained special attention due to their enhanced catalytic properties and their possibility of performing several reactions without the necessity of separating the intermediates. In this review, recent progress in Pd-catalyzed tandem processes is considered. Three types of catalytic systems are described: homogeneous catalysts (including immobilized Pd complexes); heterogeneous catalysts supported on oxides, MOFs, COFs, etc., with particular attention to the supports containing acid/base sites; and metal-enzyme catalysts for chemoenzymatic tandem processes applied in fine organic synthesis and biotechnology. For homogeneous Pd-catalyzed reactions, different tandem reactions were considered, i.e., cross-coupling, cyclization, carbonylation, isomerization, alkylation, arylation, etc. Full article

(This article belongs to the Special Issue Transition-Metal-Containing Bifunctional Catalysts: Design and Catalytic Applications)

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13 pages, 4294 KiB

Open AccessFeature PaperArticle

Mechanistic Insight into the Propane Oxidation Dehydrogenation by N₂O over Cu-BEA Zeolite with Diverse Active Site Structures

by Ruiqi Wu, Ning Liu, Chengna Dai, Ruinian Xu, Gangqiang Yu, Ning Wang and Biaohua Chen

Catalysts 2023, 13(8), 1212; https://doi.org/10.3390/catal13081212 - 15 Aug 2023

Viewed by 955

Abstract

The present work theoretically investigated propane oxidation dehydrogenation by utilizing N₂O as an oxidant (N₂O-ODHP) over Cu-BEA with three different types of active site, including monomeric Cu ([Cu]⁺), dimeric Cu ([Cu−Cu]²⁺), and distant monomeric Cu [...] Read more.

The present work theoretically investigated propane oxidation dehydrogenation by utilizing N₂O as an oxidant (N₂O-ODHP) over Cu-BEA with three different types of active site, including monomeric Cu ([Cu]⁺), dimeric Cu ([Cu−Cu]²⁺), and distant monomeric Cu sites ([Cu]⁺—[Cu]⁺). Energetically, we calculated that the monomeric [Cu]⁺ is favorable for the αH dehydrogenation step (∆E = 0.05 eV), which, however, suffers from high barriers of N₂O dissociation and βH dehydrogenation steps of 1.40 and 1.94 eV, respectively. Although the dimeric [Cu−Cu]²⁺ site with a Cu—Cu distance of 4.91 Å is much more favorable for N₂O dissociation (0.95 eV), it still needs to overcome an extremely high barrier (∆E = 2.15 eV) for βH dehydrogenation. Interestingly, the distant [Cu]⁺—[Cu]⁺ site with the Cu—Cu distance of 5.82 Å exhibits low energy barriers for N₂O dissociation (0.89 eV) and ODHP steps (0.01 and 0.33 eV) due to the synergistic effect of distant [Cu]⁺. The microkinetic analyses quantitatively verified the superior activity of the distant [Cu]⁺—[Cu]⁺ site with a reaction rate being eight to nine orders of magnitude higher than those of the monomeric and the dimeric Cu sites, and this is related to its ready charge-transfer ability, as shown by the partial Density of State (PDOS) analysis and the static charge differential density analysis in this study. Generally, the present work proposes that the distance between the [Cu]⁺ sites plays a significant and important role in N₂O-ODHP over the Cu-based zeolite catalyst and modulates Cu—Cu distance, and this constitutes a promising strategy for highly-efficient Cu-zeolite catalyst design for N₂O-ODHP. Full article

(This article belongs to the Special Issue Zeolites as Catalysts: Applications in Chemical Engineering, Energy Sources and Environmental Protection)

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16 pages, 4398 KiB

Open AccessFeature PaperArticle

Photocatalytic Degradation of 1,4-Dioxane by Heterostructured Bi₂O₃/Cu-MOF Composites

by Wen-Min Wang, Lu Zhang, Wen-Long Wang, Jin-Yi Huang, Qian-Yuan Wu and Jerry J. Wu

Catalysts 2023, 13(8), 1211; https://doi.org/10.3390/catal13081211 - 15 Aug 2023

Cited by 1 | Viewed by 1134

Abstract

Photocatalysts exhibiting high activity for the degradation of 1,4-dioxane (1,4-D) have been a subject of intense focus due to their high toxicity and challenging degradability. Bismuth oxide (Bi₂O₃) is recognized as an ideal photocatalyst; however, there have been limited [...] Read more.

Photocatalysts exhibiting high activity for the degradation of 1,4-dioxane (1,4-D) have been a subject of intense focus due to their high toxicity and challenging degradability. Bismuth oxide (Bi₂O₃) is recognized as an ideal photocatalyst; however, there have been limited studies on its effectiveness in 1,4-D degradation. It is crucial to address the issue of low photocatalytic efficiency attributed to the instability and easy recombination of photogenerated electrons and holes in Bi₂O₃ upon photoexcitation. In this study, Cu-MOF and oxygen vacancy were utilized to improve the 1,4-D photocatalytic degradation efficiency of Bi₂O₃ by preparing Bi₂O₃, Bi₂O₃/Cu-MOF, Bi₂O_3−x, and Bi₂O_3−x/Cu-MOF. The results revealed that the incorporation of Cu-MOF induced a larger specific surface area, a well-developed pore structure, and a smaller particle size in Bi₂O₃, facilitating enhanced visible light utilization and an improved photoelectron transfer rate, leading to the highest photocatalytic activity observed in Bi₂O₃/Cu-MOF. In addition, oxygen vacancies were found to negatively affect the photocatalytic activity of Bi₂O₃, mainly due to the transformation of the β-Bi₂O₃ crystalline phase into α-Bi₂O₃ caused by oxygen vacancies. Further, the synergistic effect of MOF and oxygen vacancies did not positively affect the photocatalytic activity of Bi₂O₃. Therefore, the construction of heterojunctions using Cu-MOF can significantly enhance the efficiency of degradation of 1,4-D, and Bi₂O₃/Cu-MOF appears to be a promising photocatalyst for 1,4-D degradation. This study opens new avenues for the design and optimization of advanced photocatalytic materials with improved efficiency for the treatment of recalcitrant organic pollutants. Full article

(This article belongs to the Section Environmental Catalysis)

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21 pages, 9011 KiB

Open AccessArticle

Comparison of the Mechanisms of deNOx and deN₂O Processes on Bimetallic Cu–Zn and Monometallic Cu–Cu Dimers in Clinoptilolite Zeolite—A DFT Study Simulating Industrial Conditions

by Izabela Kurzydym, Weronika Magnuszewska and Izabela Czekaj

Catalysts 2023, 13(8), 1210; https://doi.org/10.3390/catal13081210 - 14 Aug 2023

Viewed by 1104

Abstract

This paper presents two mechanisms for the deNOx process and for the deN₂O process (in two variants). The processes were carried out on a clinoptilolite zeolite catalyst with a deposited Cu–Cu monometallic dimer and Cu–Zn bimetallic dimer with bridged oxygen between [...] Read more.

This paper presents two mechanisms for the deNOx process and for the deN₂O process (in two variants). The processes were carried out on a clinoptilolite zeolite catalyst with a deposited Cu–Cu monometallic dimer and Cu–Zn bimetallic dimer with bridged oxygen between the metal atoms. Analyses were performed for hydrated forms of the catalyst with a hydrated bridging oxygen on one of the metal atoms. Calculations were performed using DFT (density functional theory) based on an ab initio method. The analyses included calculations of the energies of individual reaction steps and analysis of charges, bond orders and bond lengths as well as HOMO, SOMO and LUMO orbitals of selected steps in the mechanism. Based on the results obtained, it was determined that the most efficient catalyst for both processes is a Cu–Zn bimetallic catalyst with a bridged hydroxyl group. It shows higher efficiency in the limiting step (formation of the -N₂H intermediate product) than the previously studied FAU and MFI zeolites with a Cu–Zn bimetallic dimer. In addition, the possibility of using the catalytic system from the deNOx process in the deN₂O process was presented, which can benefit SCR installations. In addition, it was proved that the order of adsorption of NO and N₂O has significance for further steps of the deN₂O process. In order to improve the comparison of FAU, MFI and CLI zeolite catalysts with a Cu–Zn dimer, further studies on the deN₂O mechanism for the first two zeolites are needed. This study allows us to propose a bimetallic catalyst for the deNOx and deN₂O processes. Full article

(This article belongs to the Special Issue Zeolites and Zeolite-Based Catalysts in Industrial Catalysis)

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15 pages, 1742 KiB

Open AccessArticle

Two-Stage Conversion of Used Cooking Oil to Biodiesel Using Ion Exchange Resins as Catalysts

by Sumaiya Zainal Abidin, Misbahu Ladan Mohammed and Basudeb Saha

Catalysts 2023, 13(8), 1209; https://doi.org/10.3390/catal13081209 - 14 Aug 2023

Cited by 1 | Viewed by 1184

Abstract

This study focuses on the development of a novel two-stage (esterification–transesterification) synthesis of biodiesel from used cooking oil (UCO) using ion exchange resins as catalysts. Esterification of the UCO has been conducted using various types of ion exchange resin catalysts. Purolite D5081, a [...] Read more.

This study focuses on the development of a novel two-stage (esterification–transesterification) synthesis of biodiesel from used cooking oil (UCO) using ion exchange resins as catalysts. Esterification of the UCO has been conducted using various types of ion exchange resin catalysts. Purolite D5081, a hyper cross-linked resin, showed the best catalytic performance among all the catalysts investigated, with 92% of free fatty acid (FFA) conversion. The transesterification of pre-treated used cooking oil (P-UCO) was carried out sequentially using several acidic and basic ion exchange resin catalysts. In the screening process, the Diaion PA306s catalyst showed the best catalytic performance and was selected for the optimisation study. A triglyceride conversion of ca. 75% was recorded at the optimum reaction conditions (9% (w/w) catalyst loading, 328 K reaction temperature, 18:1 methanol to P-UCO feed mole ratio, and 350 rpm stirring speed). Furthermore, the reusability study of the Diaion PA306s catalyst gave a similar triglyceride conversion after a couple of cycles without losing its catalytic activity. A dry purification technique was found to give the lowest percentage of glycerides and glycerine content and, therefore, was chosen as the best biodiesel purification route. Full article

(This article belongs to the Special Issue Advances in the Catalytic Behavior of Ion-Exchange Resins)

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3 pages, 174 KiB

Open AccessEditorial

Editorial: Special Issue on Advanced Functional Materials for Photo/Electro-Catalysts for Environmental and Energy Applications

by Boopathy Ramasamy and Karthikeyan Sekar

Catalysts 2023, 13(8), 1208; https://doi.org/10.3390/catal13081208 - 13 Aug 2023

Viewed by 767

Abstract

In the last three decades, it has become clearly evident that a sustainable approach to environmental issues and non-fossil energy production is impossible without functional materials [...] Full article

(This article belongs to the Special Issue Advanced Functional Materials for Photo/Electro-Catalysts for Environmental and Energy Applications)

3 pages, 187 KiB

Open AccessEditorial

Editorial: Special Issue on “Photocatalysts for Pollutants Disposals, CO₂ Reduction, Hydrogen Evolution Reaction”

by Kai Yang and Changlin Yu

Catalysts 2023, 13(8), 1207; https://doi.org/10.3390/catal13081207 - 13 Aug 2023

Viewed by 652

Abstract

The global energy and environmental crisis are some of the most pressing challenges facing mankind [...] Full article

(This article belongs to the Special Issue Photocatalysts for Pollutants Disposals, CO₂ Reduction, Hydrogen Evolution Reaction)

16 pages, 6449 KiB

Open AccessArticle

Effects of Difluorophenyl Substituents on Structural, Redox, and Magnetic Properties of Blatter Radicals

by Dmitry Gulyaev, Andrey Serykh, Evgeny Tretyakov, Anna Akyeva, Mikhail Syroeshkin, Dmitry E. Gorbunov, Svetlana V. Maltseva, Nina P. Gritsan, Galina Romanenko and Artem Bogomyakov

Catalysts 2023, 13(8), 1206; https://doi.org/10.3390/catal13081206 - 12 Aug 2023

Cited by 2 | Viewed by 1197

Abstract

Blatter radicals 1-(3,4-difluorophenyl)-(1a) and 1-(2,4-difluorophenyl)-3-phenyl-1,4-dihydrobenzo[e][1,2,4]triazin-4-yl (1b) were prepared in good yields through oxidation of the corresponding amidrazones using MnO₂ in dry CH₂Cl₂. Cyclic voltammetry showed that both radicals are oxidized and reduced [...] Read more.

Blatter radicals 1-(3,4-difluorophenyl)-(1a) and 1-(2,4-difluorophenyl)-3-phenyl-1,4-dihydrobenzo[e][1,2,4]triazin-4-yl (1b) were prepared in good yields through oxidation of the corresponding amidrazones using MnO₂ in dry CH₂Cl₂. Cyclic voltammetry showed that both radicals are oxidized and reduced chemically and electrochemically reversibly in accordance with −1/0 and 0/+1 processes. EPR spectroscopy indicated that spin density is mainly delocalized on the triazinyl moiety of the heterocycle. The structure of all paramagnets was unambiguously confirmed by single-crystal X-ray diffraction, and two different 1D chains of alternating radicals were identified. 3,4-difluorophenyl-derivatives 1a are packed into columns composed of two kinds of alternating centrosymmetric dimers, having comparatively short intermolecular distances. In crystals of 2,4-difluorophenyl-derivative 1b, the parallel arrangement of bicyclic moieties and phenyl rings favors the formation of 1D regular chains wherein the radicals are related by translation parallel to the crystallographic stacking axis. Magnetic susceptibility measurements in the 2–300 K region showed that in crystals of the radicals, strong antiferromagnetic interactions are dominant. Subsequent fitting of the dependence of χT on T with 12-membered looped stacks gave the following best-fit parameters: for 1a, g = 2.01 ± 0.05, J₁/k_B = −292 ± 10 K (according to BS-DFT calculations J₂ = 0.12 × J₁ and J₃ = 0.61 × J₁); for 1b, g = 2.04 ± 0.01 J₁/k_B = −222 ± 17 K. For comparison, in a nonfluorinated related radical, there are only very weak intermolecular interactions along the columns (J/k_B = −2.2 ± 0.2 K). These results illustrate the magnitude of the influence of the difluorophenyl substituents introduced into Blatter radicals on their structure and magnetic properties. Full article

(This article belongs to the Special Issue Free Radicals in Catalysis, Organic Synthesis, and Material Science)

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11 pages, 2874 KiB

Open AccessArticle

Facile Synthesis of Ni-Doped WO_3-x Nanosheets with Enhanced Visible-Light-Responsive Photocatalytic Performance for Lignin Depolymerization into Value-Added Biochemicals

by Hao Wang, Yuan Li and Xintong Xiao

Catalysts 2023, 13(8), 1205; https://doi.org/10.3390/catal13081205 - 12 Aug 2023

Viewed by 837

Abstract

Lignin is the only renewable resource composed of aromatic hydrocarbons in nature that can be used as raw materials for preparing chemicals. However, due to the existence of stable C–O bonds and C−C bonds in the lignin, the high-value resource utilization of lignin [...] Read more.

Lignin is the only renewable resource composed of aromatic hydrocarbons in nature that can be used as raw materials for preparing chemicals. However, due to the existence of stable C–O bonds and C−C bonds in the lignin, the high-value resource utilization of lignin is still challenging work. Herein, we reported efficient lignin depolymerization using a Ni-doped WO_3-x nanosheet photocatalyst that was prepared via the two-step hydrothermal treatment. The optimized catalyst (Ni-doped WO_3-x) successfully depolymerized sodium lignosulfonate to vanillic acid and guaiacol under visible-light irradiation. The active radicals of photocatalytic depolymerization of sodium lignosulfonate were superoxide radicals, photogenic holes, and hydroxyl radicals under visible-light irradiation. Furthermore, the introduction of Ni significantly decreased the activation energy barrier for selective cleavage of the C−C bond, which was the essential step to promote lactic acid production. This work presented an effective and promising strategy for lignin depolymerization and value-added biochemical production. Full article

(This article belongs to the Special Issue Nanocatalysts for the Degradation of Refractory Pollutants)

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33 pages, 4979 KiB

Open AccessFeature PaperReview

Which Configuration of Photocatalytic Membrane Reactors Has a Major Potential to Be Used at an Industrial Level in Tertiary Sewage Wastewater Treatment?

by Raffaele Molinari, Angela Severino, Cristina Lavorato and Pietro Argurio

Catalysts 2023, 13(8), 1204; https://doi.org/10.3390/catal13081204 - 11 Aug 2023

Cited by 2 | Viewed by 2657

Abstract

Photocatalytic membrane reactors (PMRs) have been found to be very effective in the removal of organic pollutants (particularly recalcitrant compounds) from wastewater because they allow for the mineralization of organic pollutants to innocuous by-products, thus achieving high-quality treated water. Owing to the very [...] Read more.

Photocatalytic membrane reactors (PMRs) have been found to be very effective in the removal of organic pollutants (particularly recalcitrant compounds) from wastewater because they allow for the mineralization of organic pollutants to innocuous by-products, thus achieving high-quality treated water. Owing to the very high volumes of water involved, treated sewage wastewater could be reused if a very efficient tertiary stage, like a PMR, can be foreseen. In this review, the two main PMR configurations (photocatalytic membranes and slurry PMRs) were analyzed as requirements of a tertiary treatment of sewage wastewater considering six design and operational parameters of such plants: (i) continuous wastewater flow rate from the secondary stage; (ii) the self-control of the photodegradation rate related to wastewater chemical–physical parameters; (iii) ability to handle variations of wastewater concentration and flow rate; (iv) the control of the quality of treated wastewater; (v) low plant footprint; and (vi) easy maintenance. In this analysis, some characteristics of photocatalysis (which involves three phases: solid (the photocatalyst), liquid (the wastewater), and gas (oxygen or air)) and those of membranes (they can be produced using different materials and configurations, different processes (pressure-driven or not pressure-driven), etc.) were considered. The obtained results show that slurry PMRs seem more suitable than photocatalytic membranes for such applications. We believe this review can trigger a shift in research from the laboratory to industry in using photocatalytic membrane reactors. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Catalytic and Photocatalytic Membrane Reactors)

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23 pages, 4699 KiB

Open AccessFeature PaperArticle

ZnO/TiO₂ Composite Thin-Film Photocatalysts for Gas-Phase Oxidation of Ethanol

by Ibrahim Sanusi and Catherine B. Almquist

Catalysts 2023, 13(8), 1203; https://doi.org/10.3390/catal13081203 - 11 Aug 2023

Cited by 1 | Viewed by 1412

Abstract

The aim of this project is to investigate the photocatalytic activity of ZnO/TiO₂ composite films for the gas-phase oxidation of ethanol. Pure TiO₂, pure ZnO, and their composites were formulated using a sol-gel synthesis method, and the resulting powders were [...] Read more.

The aim of this project is to investigate the photocatalytic activity of ZnO/TiO₂ composite films for the gas-phase oxidation of ethanol. Pure TiO₂, pure ZnO, and their composites were formulated using a sol-gel synthesis method, and the resulting powders were cast and dried as thin films in a flat-plate ultraviolet light-emitting diode (UV LED) reactor. P25 TiO₂ and commercially available ZnO were also used for comparison. The structural, morphological, and optical characteristics of the materials were characterized. The photocatalytic oxidation of ethanol vapors in air after 24 h of reactor operation was used to assess the relative photocatalytic activity of the ZnO/TiO₂ composite films. Our results show that as ZnO content increased in the coupled semiconductor materials, the apparent photocatalytic activity decreased. In this study, pure ZnO (both sol-gel and purchased) had the least photocatalytic activity for vapor-phase ethanol oxidation in our test apparatus. For gas-phase photocatalysis, surface area was shown to be a critical feature for photocatalytic activity. However, the inherent photocatalytic activity of the materials was not decoupled from the effects of surface area in this study. Full article

(This article belongs to the Special Issue Photocatalysis in Air Purification)

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18 pages, 4451 KiB

Open AccessFeature PaperArticle

Organic Acids from Glucose—Heterogeneous Catalysis with the Participation of Natural Zeolite

by Natalia Sobuś, Igor Łabaj and Magdalena Król

Catalysts 2023, 13(8), 1202; https://doi.org/10.3390/catal13081202 - 11 Aug 2023

Viewed by 966

Abstract

In this paper, we present the results of a one-pot process for converting, utilizing a modified clinoptilolite catalyst. Iron, cobalt, and copper were introduced into the zeolite structure as active centers. The modified clinoptilolite catalyst was characterized in terms of phase composition, structure, [...] Read more.

In this paper, we present the results of a one-pot process for converting, utilizing a modified clinoptilolite catalyst. Iron, cobalt, and copper were introduced into the zeolite structure as active centers. The modified clinoptilolite catalyst was characterized in terms of phase composition, structure, and microstructure (using XRD, BET, FT-IR, and DRS UV-VIS), as well as the speciation of introduced metals. The catalytic process was conducted at a temperature of 250 °C for 1–5 h. Depending on the catalyst used and the specific process conditions, the reaction mixture exhibited the formation of various organic acids, including lactic acid (100% yield after 1 h using CLI), levulinic acid (40.3% yield after 5 h using Fe-H-CLI), formic acid (15.8% yield after 3 h using Fe-H-CLI), and acrylic acid (11.9% yield after 5 h using Fe-CLI). Full article

(This article belongs to the Special Issue Zeolites and Zeolite-Based Catalysts in Industrial Catalysis)

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24 pages, 8751 KiB

Open AccessReview

The Behavior of Carbon Dots in Catalytic Reactions

by Lerato L. Mokoloko, Roy P. Forbes and Neil J. Coville

Catalysts 2023, 13(8), 1201; https://doi.org/10.3390/catal13081201 - 11 Aug 2023

Cited by 1 | Viewed by 1111

Abstract

Since their discovery in 2004, carbon dots (CDs), with particle sizes < 10 nm, have found use in various applications, mainly based on the material’s fluorescent properties. However, other potential uses of CDs remain relatively unexplored when compared to other carbon-based nanomaterials. In [...] Read more.

Since their discovery in 2004, carbon dots (CDs), with particle sizes < 10 nm, have found use in various applications, mainly based on the material’s fluorescent properties. However, other potential uses of CDs remain relatively unexplored when compared to other carbon-based nanomaterials. In particular, the use of CDs as catalysts and as supports for use in catalytic reactions, is still in its infancy. Many studies have indicated the advantages of using CDs in catalysis, but there are difficulties associated with their stability, separation, and aggregation due to their small size. This small size does however allow for studying the interaction of small catalyst particles with small dimensional supports, including the inverse support interaction. However, recent studies have indicated that CDs are not stable under high temperature conditions (especially >250 °C; with and without a catalyst) suggesting that the CDs may agglomerate and transform under some reaction conditions. The agglomeration of the metal in a CD/metal catalyst, especially because of the CDs agglomeration and transformation at high temperature, is not always considered in studies using CDs as catalysts, as post-reaction analysis of a catalyst is not always undertaken. Further, it appears that under modest thermal reaction conditions, CDs can react with some metal ions to change their morphology, a reaction that relates to the metal reducibility. This review has thus been undertaken to indicate the advantages, as well as the limitations, of using CDs in catalytic studies. The various techniques that have been used to evaluate these issues is given, and some examples from the literature that highlight the use of CDs in catalysis are described. Full article

(This article belongs to the Special Issue Catalytic Methods for the Synthesis of Carbon Nanodots and Their Applications)

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19 pages, 7934 KiB

Open AccessArticle

Photocatalytic and Antibacterial Activities of a Nickel(II)-Bipyridine Complex-Modified Graphene Oxide Nanocomposite: Synthesis and Characterization

by Ganeshraja Ayyakannu Sundaram, Prasanth Ravikumar, Lavanya Ramesh, Hema Kesavan, Siva Padma Devi Sadhasivam, Santhana Krishna Kumar Alagarsamy and Junhu Wang

Catalysts 2023, 13(8), 1200; https://doi.org/10.3390/catal13081200 - 10 Aug 2023

Cited by 2 | Viewed by 1318

Abstract

In this study, we aimed to synthesize and characterize a nickel(II) complex-modified graphene oxide (Ni-GO) nanocomposite with enhanced photocatalytic and antimicrobial properties. The nanocomposite was prepared through a modified Hummer’s method, followed by an adsorption technique using the precursor complex [Ni(bipy)₃]Cl [...] Read more.

In this study, we aimed to synthesize and characterize a nickel(II) complex-modified graphene oxide (Ni-GO) nanocomposite with enhanced photocatalytic and antimicrobial properties. The nanocomposite was prepared through a modified Hummer’s method, followed by an adsorption technique using the precursor complex [Ni(bipy)₃]Cl₂·5H₂O, which was preferentially adsorbed onto the graphene oxide (GO) surface. The surface interaction between the nickel complex ions and GO was characterized using various analytical techniques, including FTIR, XRD, SEM-EDX, DRS, and XPS analyses. Photoluminescence analysis demonstrated the fluorescence property of the prepared composite. The DRS spectra indicated that the adsorption of composite particles extended to the visible region, making it excitable by visible light. The photocatalytic activity of the Ni-GO nanocomposite was tested by studying the degradation of an organic model pollutant, Rhodamine B dye, under real sunlight irradiation. The introduction of the Ni(II) complex onto the GO surface matrix intensified the photocatalytic property, making it more efficient under direct sunlight exposure. Comparisons with pristine graphite and GO revealed that Ni-GO exhibited enhanced photocatalytic potential. Additionally, we have evaluated the antimicrobial property of the Ni(II) complex-modified GO against Klebsiella pneumoniae. The results demonstrated that both the Ni(II) precursor complex and Ni-GO nanocomposite possessed an excellent antimicrobial efficacy, suggesting their potential use in antimicrobial applications. The synthesis and characterization of the Ni(II) complex-modified GO nanocomposite presented in this study showed promising results for both ameliorative photocatalytic and antimicrobial activities. These findings indicated the potential utility of Ni-GO as an efficient photocatalyst and antimicrobial agent, surpassing the performance of pristine graphite and GO. This research opens up new avenues for the development of advanced nanocomposites with diverse applications in environmental remediation and biomedical fields. Full article

(This article belongs to the Special Issue Air and Water Purification Processes through Photocatalysis: Scale Up Perspectives, 2nd Edition)

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16 pages, 3259 KiB

Open AccessFeature PaperArticle

Influence of Vacancy Defects on the Interfacial Structural and Optoelectronic Properties of ZnO/ZnS Heterostructures for Photocatalysis

by Sajjad Hussain, Lingju Guo and Tao He

Catalysts 2023, 13(8), 1199; https://doi.org/10.3390/catal13081199 - 10 Aug 2023

Viewed by 847

Abstract

Hybrid density functional theory has been employed to study the influence of interfacial oxygen (O), sulfur (S) and zinc (Zn) vacancies on the optoelectronic properties of ZnO/ZnS heterostructure. The results show that the O, S, and Zn vacancies can decrease cell volume of [...] Read more.

Hybrid density functional theory has been employed to study the influence of interfacial oxygen (O), sulfur (S) and zinc (Zn) vacancies on the optoelectronic properties of ZnO/ZnS heterostructure. The results show that the O, S, and Zn vacancies can decrease cell volume of the ZnO/ZnS heterostructure, leading to slight deformation from the perfect heterostructure. The quasi-band gap of ZnO/ZnS heterostructure is remarkably reduced compared to the ZnO surface. Hence, the visible light response is enhanced in ZnO/ZnS heterostructure, which can be further improved by creating an interfacial S or O vacancy. Moreover, the removal of S or O atoms can generate lone electrons in the system, which can enhance n-type conductivity of the heterostructure. The O and S vacancies improve the contribution of the atomic orbitals of Zn_ZnO (Zn atom in ZnO), Zn_ZnS (Zn atom in ZnS), S and O to the valence band maximum (VB) of the heterostructure; while the Zn-vacancy remarkably improves the contribution of S states to the conduction band minimum (CB). The resultant type-II band alignment and large difference between the migration speed of electrons and holes can efficiently separate the photogenerated electron-hole pairs. The CB edge positions are more negative than the redox potentials of CO₂/CO and H₂O/H₂, and the VB edge positions are more positive than the redox potential of O₂/H₂O. Hence, all the systems under investigation can be potentially used as efficient photocatalysts for various applications like CO₂ reduction and water splitting. Full article

(This article belongs to the Special Issue 50 Years of Research in Photocatalysis: Scientific Advances, Discoveries and New Perspectives)

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Catalysts, Volume 13, Issue 8 (August 2023) – 81 articles

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