Catalysts

15 pages, 1122 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Biosynthesis of Furfurylamines in Batch and Continuous Flow by Immobilized Amine Transaminases

by Tobias Heinks, Luisa M. Merz, Jan Liedtke, Matthias Höhne, Luuk M. van Langen, Uwe T. Bornscheuer, Gabriele Fischer von Mollard and Per Berglund

Catalysts 2023, 13(5), 875; https://doi.org/10.3390/catal13050875 - 11 May 2023

Cited by 3 | Viewed by 3431

Abstract

Building blocks with amine functionality are crucial in the chemical industry. Biocatalytic syntheses and chemicals derived from renewable resources are increasingly desired to achieve sustainable production of these amines. As a result, renewable materials such as furfurals, especially furfurylamines like 5-(hydroxymethyl)furfurylamine (HMFA) and [...] Read more.

Building blocks with amine functionality are crucial in the chemical industry. Biocatalytic syntheses and chemicals derived from renewable resources are increasingly desired to achieve sustainable production of these amines. As a result, renewable materials such as furfurals, especially furfurylamines like 5-(hydroxymethyl)furfurylamine (HMFA) and 2,5-di(aminomethyl)furan (DAF), are gaining increasing attention. In this study, we identified four different amine transaminases (ATAs) that catalyze the reductive amination of 5-(hydroxymethyl)furfural (HMF) and 2,5-diformylfuran (DFF). We successfully immobilized these ATAs on glutaraldehyde-functionalized amine beads using multiple binding and on amine beads by site-selective binding of the unique Cα-formylglycine within an aldehyde tag. All immobilized ATAs were efficiently reused in five repetitive cycles of reductive amination of HMF with alanine as co-substrate, while the ATA from Silicibacter pomeroyi (ATA-Spo) also exhibited high stability for reuse when isopropylamine was used as an amine donor. Additionally, immobilized ATA-Spo yielded high conversion in the batch syntheses of HMFA and DAF using alanine (87% and 87%, respectively) or isopropylamine (99% and 98%, respectively) as amine donors. We further demonstrated that ATA-Spo was effective for the reductive amination of HMF with alanine or isopropylamine in continuous-flow catalysis with high conversion up to 12 days (48% and 41%, respectively). Full article

(This article belongs to the Special Issue Supported Biocatalysts for Sustainable Chemistry)

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15 pages, 7877 KiB

Open AccessEditor’s ChoiceArticle

Engineering Surface Properties of CuO/Ce_0.6Zr_0.4O₂ Catalysts for Efficient Low-Temperature Toluene Oxidation

by Mingyue Wang, Qiulin Zhang, Meilin Zou, Jingge Wang, Danrui Zhu, Jiaying Liu, Junwei Wang, Yang Zuo, Jianjun Chen and Ping Ning

Catalysts 2023, 13(5), 866; https://doi.org/10.3390/catal13050866 - 10 May 2023

Cited by 2 | Viewed by 1515

Abstract

The development of superior low-temperature catalytic performance and inexpensive catalysts for the removal of volatile organic compounds (VOCs) is crucial for their industrial application. Herein, CuO/Ce_0.6Zr_0.4O₂ catalysts calcinated at different temperatures (Cu/CZ-X, X represented calcination temperature) were prepared [...] Read more.

The development of superior low-temperature catalytic performance and inexpensive catalysts for the removal of volatile organic compounds (VOCs) is crucial for their industrial application. Herein, CuO/Ce_0.6Zr_0.4O₂ catalysts calcinated at different temperatures (Cu/CZ-X, X represented calcination temperature) were prepared and used to eliminate toluene. It can be found that Cu/CZ-550 presented the highest low-temperature catalytic activity, with the lowest temperature (220 °C) 50% conversion of toluene, the highest normalized reaction rate (3.1 × 10⁻⁵ mol·g⁻¹·s⁻¹ at 180 °C) and the lowest apparent activation energy value (86.3 ± 4.7 kJ·mol⁻¹). Systematically, the surface properties analysis results showed that the optimum redox property, abundant oxygen vacancies, and plentiful surface Ce³⁺ species over Cu/CZ-550 were associated with the strong interaction between Cu and support could significantly favor the adsorption and activation of toluene, thus resulting in its superior catalytic performance. Full article

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

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12 pages, 2144 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Improving the Kinetics of H₂-Fueled Biological Methanation with Quinone-Based Redox Mediators

by Matteo Tucci, Simone Colantoni, Carolina Cruz Viggi and Federico Aulenta

Catalysts 2023, 13(5), 859; https://doi.org/10.3390/catal13050859 - 9 May 2023

Cited by 2 | Viewed by 1840

Abstract

The biomethanation process involves the conversion of CO₂ into a valuable energy carrier (i.e., methane) by methanogenic archaea. Since it can be operated at mild conditions, it is more sustainable than traditional chemical approaches. Nevertheless, the efficacy of biomethanation is limited by [...] Read more.

The biomethanation process involves the conversion of CO₂ into a valuable energy carrier (i.e., methane) by methanogenic archaea. Since it can be operated at mild conditions, it is more sustainable than traditional chemical approaches. Nevertheless, the efficacy of biomethanation is limited by the low kinetics of the microbiological reaction and the poor solubility of H₂ in water. Herein, the effect of soluble (i.e., AQDS) and insoluble (i.e., biochar) quinone-based redox mediators on the kinetics of H₂-fueled biological methanation in bench-scale microcosms was investigated. Microcosms were set up in 120 mL serum bottles and were initially inoculated with a methanogenic sludge deriving from a lab-scale anaerobic digester treating food waste. As a result, the kinetics of H₂ consumption and CH₄ generation were greatly increased (p < 0.05) in presence of AQDS as compared to the control, accounting for up to +160% and +125% in the last experimental cycle, respectively. These findings could be explained by a two-step mechanism, whereby microbes used H₂ to quickly reduce AQDS into the highly soluble AH₂QDS, which in turn served as a more efficient electron donor for methanogenesis. In contrast, the used biochar had apparently an adverse effect on the biomethanation process. Full article

(This article belongs to the Special Issue Biocatalytic Processes: A Multidisciplinary Platform for Future Biorefineries and Energy Conversion Systems)

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14 pages, 698 KiB

Open AccessEditor’s ChoiceReview

Research Progress in Gas Separation and Purification Based on Zeolitic Materials

by Kai Qi, Lili Gao, Xuelian Li and Feng He

Catalysts 2023, 13(5), 855; https://doi.org/10.3390/catal13050855 - 8 May 2023

Cited by 5 | Viewed by 2717

Abstract

The characteristics and preparation methods of zeolite-based adsorbents and membranes were reviewed and their applications in gas separation and purification were introduced according to classification. The effects of framework structure, equilibrium cations and pore size of zeolites as well as temperature and pressure [...] Read more.

The characteristics and preparation methods of zeolite-based adsorbents and membranes were reviewed and their applications in gas separation and purification were introduced according to classification. The effects of framework structure, equilibrium cations and pore size of zeolites as well as temperature and pressure of the system on gas adsorption and separation were discussed, and the separation mechanisms were also summarized. The main defects and improved methods of zeolite-based adsorbents and membranes were briefly described, and their future trend for gas separation and purification was finally prospected. 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, 3619 KiB

Open AccessEditor’s ChoiceArticle

Cobalt-/pH-Modified V₂O₅-MoO₃/TiO₂ Catalyst with Enhanced Activity for the Low-Temperature Selective Catalytic Reduction Process

by Ruonan Wang, Yanli Zhang, Xing Fan and Jian Li

Catalysts 2023, 13(5), 844; https://doi.org/10.3390/catal13050844 - 6 May 2023

Cited by 5 | Viewed by 1688

Abstract

Currently, the elimination of gaseous pollutants—particularly nitrogen oxides—has emerged as a significant concern. Among various deNO_x technologies, selective catalytic reduction (SCR) has gained prominence as the primary approach for NO_x abatement, owing to its superior performance. In this study, novel low-temperature [...] Read more.

Currently, the elimination of gaseous pollutants—particularly nitrogen oxides—has emerged as a significant concern. Among various deNO_x technologies, selective catalytic reduction (SCR) has gained prominence as the primary approach for NO_x abatement, owing to its superior performance. In this study, novel low-temperature SCR catalysts were developed by regulating the pH value and doping cobalt based on a V₂O₅-MoO₃/TiO₂ (VMT) catalyst. The results show an increased SCR performance with 82.8% and 91.1% for catalysts after pH (=10) modification (VMT-10) and (1 wt%) Co/pH (=10) modification (1CoVMT-10), respectively. H₂-TPR, NH₃-TPD, XPS and DRIFTS confirmed that the pH regulation transformed polymerization V species into isolated V⁵⁺=O, thus leading to an increase in the number of acid sites, which enhanced the NH₃ and NO₂ adsorption capacity. Furthermore, the DRIFTS study indicated that the NH₃-SCR reaction over 1CoVMT-10 followed the E–R and L–H mechanism. Full article

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

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18 pages, 11875 KiB

Open AccessEditor’s ChoiceArticle

Catalytic Oxidation of VOC over Cobalt-Loaded Hierarchical MFI Zeolite

by Bozhidar Grahovski, Ralitsa Velinova, Pavletta Shestakova, Anton Naydenov, Hristo Kolev, Iliyana Yordanova, Georgi Ivanov, Krasimir Tenchev and Silviya Todorova

Catalysts 2023, 13(5), 834; https://doi.org/10.3390/catal13050834 - 3 May 2023

Cited by 3 | Viewed by 2172

Abstract

The zeolites ZSM-5 with different Si/Al ratios were modified with a buffer solution of HF and NH₄F. This acidic treatment led to the obtaining of a material with secondary mesoporosity. The deposition of cobalt from an aqueous solution of cobalt acetate [...] Read more.

The zeolites ZSM-5 with different Si/Al ratios were modified with a buffer solution of HF and NH₄F. This acidic treatment led to the obtaining of a material with secondary mesoporosity. The deposition of cobalt from an aqueous solution of cobalt acetate on the surface of treated samples generates the formation of different cobalt oxide species: bulk-like Co₃O₄ phases strongly interacting with the support, Co²⁺ in ion exchange positions (γ and β sites) and silicate-like phases. The mechanism of cobalt silicate phase formation is proposed here and includes a replacement of silanol groups and the bridging hydrogens by Co and the inclusion of the Co atoms in tetrahedral framework positions. The catalysts, obtained through use of the treated ZSM-5, exhibit higher activity in the reactions of propane, and n-hexane completes oxidation compared with the catalyst samples containing un-treated zeolite. Both the finer dispersion of metal oxide particles on the hierarchical sample and the presence of secondary mesoporosity improve the effectiveness of the active phase utilization via access to larger number of active sites. Full article

(This article belongs to the Special Issue Catalysts for Air Pollution Control: Present and Future)

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24 pages, 12609 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Recent Achievements in the Copper-Catalyzed Arylation of Adamantane-Containing Amines, Di- and Polyamines

by Alexei D. Averin, Svetlana P. Panchenko, Arina V. Murashkina, Varvara I. Fomenko, Daria S. Kuliukhina, Anna S. Malysheva, Alexei A. Yakushev, Anton S. Abel and Irina P. Beletskaya

Catalysts 2023, 13(5), 831; https://doi.org/10.3390/catal13050831 - 1 May 2023

Cited by 5 | Viewed by 2853

Abstract

Rapid development of the copper-catalyzed amination of aryl halides in the beginning of the 21st century, known as the Renaissance of the Ullmann chemistry, laid foundations for the use of this method as a powerful tool for the construction of the C(sp² [...] Read more.

Rapid development of the copper-catalyzed amination of aryl halides in the beginning of the 21st century, known as the Renaissance of the Ullmann chemistry, laid foundations for the use of this method as a powerful tool for the construction of the C(sp²)-N bond and became a rival of the Buchwald–Hartwig amination reaction. Various applications of this approach are well-documented in a number of comprehensive and more specialized reviews, and this overview in the form of a personal account of the Cu-catalyzed arylation and heteroarylation of the adamantane-containing amines, and di- and polyamines, covers a more specific area, showing the possibilities of the method and outlining general regularities, considering reagents structure, copper source and ligands, scope, and limitations. The material of the last decade is mainly considered, and recent data on the application of the unsupported copper nanoparticles and possibilities of the Chan-Lam reaction as an alternative to the use of aryl halides are also discussed. Full article

(This article belongs to the Special Issue Synthesis and Applications of Copper-Based Catalysts)

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15 pages, 3660 KiB

Open AccessEditor’s ChoiceArticle

Atmospheric and Efficient Selective Oxidation of Ethylbenzene Catalyzed by Cobalt Oxides Supported on Mesoporous Carbon Nitride

by Ye Zhu, Xue-Wen Zhang, Fei Wang, Bing Xue and Jie Xu

Catalysts 2023, 13(5), 828; https://doi.org/10.3390/catal13050828 - 30 Apr 2023

Cited by 6 | Viewed by 1656

Abstract

Mesoporous carbon nitride (mpg-C₃N₄) was prepared by using cyanamide as a precursor and colloidal nanosilica as a template. Then, the mpg-C₃N₄ was used as a catalytic support to load CoO_x. The physicochemical properties of [...] Read more.

Mesoporous carbon nitride (mpg-C₃N₄) was prepared by using cyanamide as a precursor and colloidal nanosilica as a template. Then, the mpg-C₃N₄ was used as a catalytic support to load CoO_x. The physicochemical properties of the synthesized CoO_x/mpg-C₃N₄ materials were elucidated by multiple characterization methods, and the catalytic activities were examined in the selective oxidation of ethylbenzene (EB) under atmospheric pressure by using tert-butyl hydrogen peroxide (TBHP) as an oxidant. It was found that mpg-C₃N₄ possessed a higher specific surface area than other carbon nitride materials, and its abundant N_b species were able to interact with Co (II) species. When the dosages of EB and TBHP were 10 mmol and 30 mmol, respectively, the reaction temperature was 100 °C, and the reaction time was 10 h, the conversion rate of ethylbenzene was 62%, and the selectivity of AP was 84.7%. Full article

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

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16 pages, 2948 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Production of Human Milk Fat Substitutes by Lipase-Catalyzed Acidolysis: Immobilization, Synthesis, Molecular Docking and Optimization Studies

by Cleide M. F. Soares, Milson S. Barbosa, Samuel B. Santos, Silvana Mattedi, Álvaro S. Lima, Matheus M. Pereira, Carla Tecelão and Suzana Ferreira-Dias

Catalysts 2023, 13(5), 825; https://doi.org/10.3390/catal13050825 - 29 Apr 2023

Cited by 3 | Viewed by 1950

Abstract

Human milk fat (HMF) triacylglycerols (TAGs) mainly contain palmitic acid esterified at the sn-2 position while oleic and other unsaturated fatty acids are located at positions sn-1,3. This study aimed at the production of HMF substitutes (HMFS) by lipase-catalyzed acidolysis of [...] Read more.

Human milk fat (HMF) triacylglycerols (TAGs) mainly contain palmitic acid esterified at the sn-2 position while oleic and other unsaturated fatty acids are located at positions sn-1,3. This study aimed at the production of HMF substitutes (HMFS) by lipase-catalyzed acidolysis of tripalmitin with oleic acid, in a solvent-free medium. Burkholderia cepacia lipase (BCL) was immobilized in silica (prepared with protic or aprotic ionic liquids) by covalent binding or encapsulation and used as biocatalyst. The supports and immobilized biocatalysts were characterized by FTIR, TGA, and SEM. Molecular docking analysis showed that BCL preferentially attacks oleic acid rather than tripalmitin, due to the lower free energy of hydrophobic binding with this acid (−6.5 kcal·mol⁻¹) than with tripalmitin (5.4 kcal·mol⁻¹). Therefore, the tripalmitin attack by BCL and subsequent HMFS production only occurs after the binding to most of the oleic acid molecules. The highest acidolysis activity was obtained with BCL immobilized by covalent binding in prepared silica with aprotic ionic liquid. A central composite rotatable design, as a function of temperature (58–72 °C) and oleic acid/tripalmitin molar ratio (MR = 2:1–6.8:1), was performed for acidolysis optimization. Under optimized conditions (58 °C and MR = 4:1 or 60 °C and MR = 2:1), the oleic acid incorporation of 28 mol.% was achieved after 48 h. Full article

(This article belongs to the Special Issue Enzyme Engineering for Improving the Enzymatic Catalysis, Stability and Substrate Specificity and Application)

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11 pages, 982 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Regioselective Esterification of Cardiac Glycosides Catalyzed by Novozym 435 and Lipase PS in Organic Solvents

by Ivan Bassanini, Lucia Roncaglia, Bruno Danieli and Sergio Riva

Catalysts 2023, 13(5), 819; https://doi.org/10.3390/catal13050819 - 28 Apr 2023

Viewed by 1530

Abstract

The enzymatic acetylation in the organic solvents of a number of the important bioactive cardiac glycosides was investigated. With the bufanolide proscillaridin A and the cardenolide lanatoside C, acylation, as expected, occurred at the secondary 4′-OH of the rhamnopyranosyl unit of the former [...] Read more.

The enzymatic acetylation in the organic solvents of a number of the important bioactive cardiac glycosides was investigated. With the bufanolide proscillaridin A and the cardenolide lanatoside C, acylation, as expected, occurred at the secondary 4′-OH of the rhamnopyranosyl unit of the former (by the action of Novozym 435 lipase) and the primary 6′′′′-OH of the terminal glucopyranosyl unit of the latter (best results obtained by the action of the lipase PS). Only lipase PS was found to be able to acylate the cardenolides digitoxin and digoxin at the 4‴-OH of their terminal digitoxose unit. The corresponding monoacetyl derivatives, both of which are commercialized drugs, could be isolated with good yields. The investigation of the Novozym 435-catalyzed acetylation of free D-digitoxose provided a possible explanation for the inability of this lipase to acylate digitoxin and digoxin. Full article

(This article belongs to the Special Issue Biocatalysis in Non-conventional Media)

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22 pages, 2726 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Electrocatalysts for Ammonia Oxidation Reaction

by Ji Hee Jang, So Young Park, Duck Hyun Youn and Youn Jeong Jang

Catalysts 2023, 13(5), 803; https://doi.org/10.3390/catal13050803 - 26 Apr 2023

Cited by 11 | Viewed by 7512

Abstract

Ammonia (NH₃) is a clean energy source that can either be directly used as fuel or a hydrogen carrier due to its high energy density and high hydrogen content. The NH₃ electro-oxidation reaction (AOR) is the main reaction in both [...] Read more.

Ammonia (NH₃) is a clean energy source that can either be directly used as fuel or a hydrogen carrier due to its high energy density and high hydrogen content. The NH₃ electro-oxidation reaction (AOR) is the main reaction in both direct NH₃ fuel cells and NH₃ electrolysis. The AOR is thermodynamically favorable; however, the sluggish kinetics of the reaction can result in issues such as high overpotential, slow reaction rate, deactivation, etc. To overcome this, multiple strategies have been discussed to develop electrocatalysts that maintain a robust reaction rate in low overpotential regions. In this review, the fundamentals of AOR, including thermodynamics, kinetics, and experimental techniques, are studied. This review also focused on recent progress for catalyst modifications and their effects, with a particular focus on Pt- or Ni-based electrocatalysts. Additionally, vacant rooms needed to be developed was pointed, and a way to overcome the limitations was suggested. The fundamentals and efforts to prepare catalysts reviewed in this work will be effective in proposing and designing new robust electrocatalysts leading to advance AOR in practice. Full article

(This article belongs to the Special Issue Theme Issue in Honor of Prof. Dr. Jae Sung Lee)

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15 pages, 4810 KiB

Open AccessEditor’s ChoiceArticle

Tuning Electrochemical Hydrogen-Evolution Activity of CoMoO₄ through Zn Incorporation

by Sanaz Chamani, Ebrahim Sadeghi, Ugur Unal, Naeimeh Sadat Peighambardoust and Umut Aydemir

Catalysts 2023, 13(5), 798; https://doi.org/10.3390/catal13050798 - 24 Apr 2023

Cited by 9 | Viewed by 1973

Abstract

Designing cheap, efficient, and durable electrocatalysts on three-dimensional (3D) substrates such as nickel foam (NF) for the hydrogen-evolution reaction (HER) is in high demand for the practical application of electrochemical water splitting. In this work, we adopted a simple one-step hydrothermal method to [...] Read more.

Designing cheap, efficient, and durable electrocatalysts on three-dimensional (3D) substrates such as nickel foam (NF) for the hydrogen-evolution reaction (HER) is in high demand for the practical application of electrochemical water splitting. In this work, we adopted a simple one-step hydrothermal method to realize the incorporation of Zn into the lattice of CoMoO₄ with various atomic concentrations—Co_1-xZn_xMoO₄ (x = 0, 0.1, 0.3, 0.5, and 0.7). The morphological studies demonstrated that parent CoMoO₄ consists of nanoflowers and nanorods. However, as the concentration of Zn increases within the host CoMoO₄, the portion of nanoflowers decreases and simultaneously the portion of nanorods increases. Moreover, the substitution of Zn²⁺ in place of Co²⁺/Co³⁺ creates oxygen vacancies in the host structure, especially in the case of Co_0.5Zn_0.5MoO₄, giving rise to lower charge-transfer resistance and a higher electrochemically active surface area. Therefore, among the prepared samples, Co_0.5Zn_0.5MoO₄ on NF showed an improved HER performance, reaching 10 mA cm⁻² at an overpotential as low as 204 mV in a 1.0 M KOH medium. Finally, the Co_0.5Zn_0.5MoO₄ electrode exhibited robust long-term stability at an applied current density of 10 mA cm⁻² for 20 h. The Faradaic efficiency determined by a gas chromatograph found that the hydrogen-production efficiency varied from 94% to 84%. Full article

(This article belongs to the Special Issue Electrocatalytic Hydrogen Evolution Reaction through Water Splitting)

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16 pages, 2236 KiB

Open AccessEditor’s ChoiceArticle

β-Sitosterol Oleate Synthesis by Candida rugosa Lipase in a Solvent-Free Mini Reactor System: Free and Immobilized on Chitosan-Alginate Beads

by Adejanildo da S. Pereira, Jully L. Fraga, Camila P. L. Souza, Alexandre G. Torres and Priscilla F. F. Amaral

Catalysts 2023, 13(4), 780; https://doi.org/10.3390/catal13040780 - 21 Apr 2023

Cited by 2 | Viewed by 1798

Abstract

Candida rugosa lipase (CRL) was immobilized by the ionic gelling technique using alginate and chitosan as encapsulating agents. An immobilization yield of 99% and an immobilization efficiency of 51% were obtained. Maximum hydrolytic activity for free and immobilized CRL was detected at 40 [...] Read more.

Candida rugosa lipase (CRL) was immobilized by the ionic gelling technique using alginate and chitosan as encapsulating agents. An immobilization yield of 99% and an immobilization efficiency of 51% were obtained. Maximum hydrolytic activity for free and immobilized CRL was detected at 40 °C and for synthesis activity at 35 °C. The optimum pH for immobilized and free CRL hydrolysis activity was 8.0. The V_max obtained for the hydrolysis reaction was higher for free CRL (4121.4 μmol/min/g) compared to immobilized CRL (2359.13 μmol/min/g). A Vmax of 2.24 μmol/min/g was detected for the synthetic activity of free CRL. The K_m obtained for the hydrolysis reaction was higher (660.02 μmol/L) for immobilized CRL than for free CRL (403.06 μmol/L). For the synthetic activity, a K_m of 234.44 μmol/L was calculated. The conversion of β-sitosterol oleate ranged from 80.85 to 96.84% for free CRL, higher than the maximum found for immobilized CRL (32%). The scale-up (scale factor: 50) with the free CRL was successfully performed, achieving a high conversion value (92%) in a 500 mL bioreactor. This conversion value was within the range predicted by the mathematical model obtained using mini reactors. These mini reactors are good models to test several conditions of enzyme reactions that are intended for large scales. Full article

(This article belongs to the Special Issue Lipase: A Multi-Purpose Biocatalyst at the Forefront of Biotechnology)

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22 pages, 2956 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Recent Progress in the Use of SnO₂ Quantum Dots: From Synthesis to Photocatalytic Applications

by Babu Bathula, Thirumala Rao Gurugubelli, Jihyung Yoo and Kisoo Yoo

Catalysts 2023, 13(4), 765; https://doi.org/10.3390/catal13040765 - 17 Apr 2023

Cited by 13 | Viewed by 3678

Abstract

This review article provides current developments in SnO₂ quantum dots (QDs) as effective catalysts over the last five years. SnO₂ QDs are exceptional prospects for catalytic applications because of their high surface area, compact size, and tunable optical features. SnO₂ [...] Read more.

This review article provides current developments in SnO₂ quantum dots (QDs) as effective catalysts over the last five years. SnO₂ QDs are exceptional prospects for catalytic applications because of their high surface area, compact size, and tunable optical features. SnO₂ QDs have recently made strides in their production and functionalization, which has enabled successful use of them as photocatalytic catalysts. The basic concepts of SnO₂ QDs, including their electrical and optical characteristics, are described in this review paper, along with the most current findings on their production and functionalization. Additionally, it covers the fundamental mechanisms that support SnO₂ QDs’ catalytic activity and emphasizes the difficulties involved in using them as catalysts. Lastly, it offers a forecast for the direction of research in this quickly evolving topic. Overall, our analysis demonstrates SnO₂ QDs’ potential as a successful and cutting-edge catalytic system in recent years. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis II)

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20 pages, 9329 KiB

Open AccessEditor’s ChoiceReview

Application of Laccase Catalysis in Bond Formation and Breakage: A Review

by Huan Lin, Zongjiang Yu, Qian Wang, Yaojie Liu, Long Jiang, Chao Xu and Mo Xian

Catalysts 2023, 13(4), 750; https://doi.org/10.3390/catal13040750 - 14 Apr 2023

Cited by 8 | Viewed by 2544

Abstract

Laccase belongs to the superfamily of multicopper oxidases and has been widely investigated in recent decades. Due to its mild and efficient oxidation of substrates, laccase has been successfully applied in organic catalytic synthesis, the degradation of harmful substances, and other green catalytic [...] Read more.

Laccase belongs to the superfamily of multicopper oxidases and has been widely investigated in recent decades. Due to its mild and efficient oxidation of substrates, laccase has been successfully applied in organic catalytic synthesis, the degradation of harmful substances, and other green catalytic fields. Nevertheless, there are few reports on the green catalysis with laccase. This review focuses on reporting and collating some of the latest interesting laccase-catalyzed bond formation and breakage research. This is discussed with a focus on the effects of the medium system on the laccase-catalyzed reaction, as well as the formation and the breakage of C–N, C–C, and C–O bonds catalyzed by laccase. It provides abundant references and novel insights for furthering the industrial applications of laccase. Full article

(This article belongs to the Special Issue Advances in Biocatalysis and Enzyme Engineering)

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16 pages, 3838 KiB

Open AccessEditor’s ChoiceArticle

Feasibility Assessment on Remanufacturing of Ni–Mo/γ–Al₂O₃ Catalyst for Residue Hydrodesulfurization

by Seon-Yong Ahn, Woo-Jin Na, Kyoung-Jin Kim, Beom-Jun Kim, Hea-Kyung Park and Hyun-Seog Roh

Catalysts 2023, 13(4), 738; https://doi.org/10.3390/catal13040738 - 13 Apr 2023

Cited by 4 | Viewed by 1864

Abstract

Residue hydrodesulfurization (RHDS) is a critical process in the petroleum refining industry for removing sulfur compounds from heavy residual oils. However, catalysts used in RHDS can easily be deactivated by numerous factors, leading to reduced process efficiency and economic benefits. The remanufacturing of [...] Read more.

Residue hydrodesulfurization (RHDS) is a critical process in the petroleum refining industry for removing sulfur compounds from heavy residual oils. However, catalysts used in RHDS can easily be deactivated by numerous factors, leading to reduced process efficiency and economic benefits. The remanufacturing of spent catalysts can be a useful strategy for extending the lifespan of catalysts, reducing waste, and improving process sustainability. This paper proposes an effective catalyst remanufacturing process for commercial RHDS catalysts. In detail, sequential unit processes including oil washing (OW), complete incineration (CI), and acid leaching (AL) were conducted to remanufacture the spent RHDS catalysts. We also highlight some of the key challenges in remanufacturing catalysts, such as the key factors involved in catalyst deactivation. Finally, we provide future perspectives on the development of an effective catalyst remanufacturing process for RHDS, with the goal of improving the efficiency, sustainability, and competitiveness of the petroleum refining industry. Full article

(This article belongs to the Special Issue Ni-Based Catalysts: Synthesis and Applications)

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22 pages, 9647 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Photocatalytic Degradation of Diclofenac by Nitrogen-Doped Carbon Quantum Dot-Graphitic Carbon Nitride (CNQD)

by Huzaikha Awang, Tim Peppel and Jennifer Strunk

Catalysts 2023, 13(4), 735; https://doi.org/10.3390/catal13040735 - 13 Apr 2023

Cited by 10 | Viewed by 3450

Abstract

In this study nitrogen-doped carbon quantum dots/graphitic carbon nitride nanosheet (CNQD) composites with different contents of nitrogen-doped carbon quantum dots (NCQDs; 2, 4, 6, and 8 wt%) were synthesized. The morphological, physicochemical, and photoelectrochemical properties were investigated using complementary methods such as scanning [...] Read more.

In this study nitrogen-doped carbon quantum dots/graphitic carbon nitride nanosheet (CNQD) composites with different contents of nitrogen-doped carbon quantum dots (NCQDs; 2, 4, 6, and 8 wt%) were synthesized. The morphological, physicochemical, and photoelectrochemical properties were investigated using complementary methods such as scanning electron microscopy (SEM), powder X-ray diffraction (pXRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), UV/Vis spectroscopy in diffuse reflectance (DRS), photoluminescence (PL), nitrogen physisorption (BET), photocurrent response, and electrochemical impedance spectroscopy (EIS). The photocatalytic activity of the synthesized materials was assessed during diclofenac (DCF) degradation in an aqueous solution under visible light irradiation. As a result, improved photocatalytic efficiency in DCF degradation was observed for all the CNQD composites compared with bulk graphitic carbon nitride (bCN) and nanosheet g-C₃N₄ (CNS). The fastest DCF degradation was observed for the 6 wt% NCQD on the surface of CNS (CNQD-6), which removed 62% of DCF in 3 h, with an associated k value of 5.41 × 10⁻³ min⁻¹. The performance test results confirmed the contribution of NCQDs to enhancing photocatalytic activity, leading to an improvement factor of 1.24 over bCN. The morphology of the CNS and the synergistic interaction between NCQDs and CNS were essential elements for enhancing photocatalytic activity. The photoelectrochemical data and photoluminescence analyses showed the efficient migration of photoexcited electrons from NCQDs to the CNS. The reduced charge recombination rates in CNQD photocatalysts might be due to the synergistic interaction between NCQDs and CNS and the unique up-conversion photoluminescence properties of NCQDs. Further investigations revealed that the photogenerated superoxide radicals (•O₂⁻) predominated in the degradation of DCF, and this photocatalyst had good reusability and toxicity reduction abilities. This work provides insight into the effects of NCQDs on the CNS surface to enhance its potential to remove emerging organic pollutants from water and wastewater. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis II)

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23 pages, 2957 KiB

Open AccessEditor’s ChoiceReview

Enabling Catalysts for Biodiesel Production via Transesterification

by Baohua Wang, Bingquan Wang, Sudheesh K. Shukla and Rui Wang

Catalysts 2023, 13(4), 740; https://doi.org/10.3390/catal13040740 - 13 Apr 2023

Cited by 33 | Viewed by 12070

Abstract

With the rapid development of industry and the increasing demand for transportation, traditional sources of energy have been excessively consumed. Biodiesel as an alternative energy source has become a research focus. The most common method for biodiesel production is transesterification, in which lipid [...] Read more.

With the rapid development of industry and the increasing demand for transportation, traditional sources of energy have been excessively consumed. Biodiesel as an alternative energy source has become a research focus. The most common method for biodiesel production is transesterification, in which lipid and low carbon alcohol are commonly used as raw materials, in the presence of a catalyst. In the process of transesterification, the performance of the catalyst is the key factor of the biodiesel yield. This paper reviews the recent research progress on homogeneous and heterogeneous catalysts in biodiesel production. The advantages and disadvantages of current homogeneous acid catalysts and homogeneous base catalysts are discussed, and heteropolyacid heterogeneous catalysts and biomass-derived base catalysts are described. The applications of the homogeneous and heterogeneous catalyst derivatives ionic liquids/deep eutectic solvents and nanocatalysts/magnetic catalysts in biodiesel production are reviewed. The mechanism and economic cost of current homogeneous acid catalysts and homogeneous base catalysts are also analyzed. The unique advantages of each type of catalyst are compared to better understand the microscopic details behind biodiesel. Finally, some challenges of current biodiesel catalysts are summarized, and future research directions are presented. This review will provide general and in-depth knowledge on the achievements, directions, and research priorities in developing novel homogeneous/heterogeneous catalysts for the green and cost-effective production of biodiesel. Full article

(This article belongs to the Special Issue Catalysis for Bitumen/Heavy Oil Upgrading and Petroleum Refining)

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30 pages, 4982 KiB

Open AccessEditor’s ChoiceReview

Recent Advances on Small Band Gap Semiconductor Materials (≤2.1 eV) for Solar Water Splitting

by Hefeng Zhang, Jiaqi Liu, Ting Xu, Wenqian Ji and Xu Zong

Catalysts 2023, 13(4), 728; https://doi.org/10.3390/catal13040728 - 12 Apr 2023

Cited by 35 | Viewed by 8283

Abstract

The conversion of solar energy into renewable H₂ fuel via photoelectrochemical and photocatalytic water splitting approaches has attracted considerable attention due to its potential to solve significant energy and environmental issues. To achieve reasonable energy conversion efficiency of 10%, which is amenable [...] Read more.

The conversion of solar energy into renewable H₂ fuel via photoelectrochemical and photocatalytic water splitting approaches has attracted considerable attention due to its potential to solve significant energy and environmental issues. To achieve reasonable energy conversion efficiency of 10%, which is amenable to the economic feasibility of this technology, semiconductor materials, which are the main carrier for solar H₂ production, must fulfill several important criteria. One of the most important criteria is the band gap of the semiconductor material, which should be low enough to allow the efficient absorption of incident light. This is because the band gap of semiconductor material fundamentally determines the upper limit of the theoretical energy conversion efficiency of the solar conversion system. In this work, recent advances in utilizing semiconductor material with a band gap smaller than 2.1 eV instead of the simply-defined visible-light-responsive semiconductor materials toward solar H₂ production from water splitting was reviewed. Full article

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

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11 pages, 2434 KiB

Open AccessEditor’s ChoiceArticle

Hydrothermally Synthesized Ag@MoS₂ Composite for Enhanced Photocatalytic Hydrogen Production

by Anuja A. Yadav, Yuvaraj M. Hunge, Ananta G. Dhodamani and Seok-Won Kang

Catalysts 2023, 13(4), 716; https://doi.org/10.3390/catal13040716 - 10 Apr 2023

Cited by 23 | Viewed by 2722

Abstract

Photocatalytic hydrogen production is a green, cost-effective, simple, and pollution-free technology for the supply of clean energy, which plays an important role in alleviating the fossil fuel crisis caused by exponentially grown energy consumption. Therefore, designing highly visible-light-active novel photocatalyst materials for photocatalytic [...] Read more.

Photocatalytic hydrogen production is a green, cost-effective, simple, and pollution-free technology for the supply of clean energy, which plays an important role in alleviating the fossil fuel crisis caused by exponentially grown energy consumption. Therefore, designing highly visible-light-active novel photocatalyst materials for photocatalytic hydrogen production is a promising task. The production efficiency of photocatalyst can be improved by using noble metals, which are useful for the effective transfer of charge carriers. This study highlights the synergistic effect of the noble co-catalyst Ag on MoS₂ during the investigation of photocatalytic hydrogen production. The hydrothermal method was used for the preparation of an Ag-MoS₂ composite, and their structural and morphological characterizations were carried out using different physiochemical characterization techniques. The Ag-MoS₂ composite shows an enhanced visible light absorption capacity and photocatalytic hydrogen production rate, as compared to that of pure MoS₂, which proves that Ag nanoparticles (NPs) can act as efficient co-catalyst materials for photocatalytic hydrogen production with an improved rate of hydrogen production. Along with this, a possible working mechanism was proposed for visible-light-driven photocatalytic hydrogen production using the Ag@MoS₂ composite. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis II)

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16 pages, 5687 KiB

Open AccessEditor’s ChoiceReview

Progress on the Cu-Catalyzed 1,4-Conjugate Addition to Thiochromones

by Fenghai Guo, Jayla A. Young, Mina S. Perez, Holden A. Hankerson and Alex M. Chavez

Catalysts 2023, 13(4), 713; https://doi.org/10.3390/catal13040713 - 8 Apr 2023

Cited by 4 | Viewed by 4123

Abstract

Carbon–carbon bond formation is one of the most important tools in synthetic organic chemists’ toolbox. It is a fundamental transformation that allows synthetic chemists to synthesize the carbon framework of complex molecules from inexpensive simple starting materials. Among the many synthetic methodologies developed [...] Read more.

Carbon–carbon bond formation is one of the most important tools in synthetic organic chemists’ toolbox. It is a fundamental transformation that allows synthetic chemists to synthesize the carbon framework of complex molecules from inexpensive simple starting materials. Among the many synthetic methodologies developed for the construction of carbon–carbon bonds, organocopper reagents are one of the most reliable organometallic reagents for this purpose. The versatility of organocuprate reagents or the reactions catalyzed by organocopper reagents were demonstrated by their applications in a variety of synthetic transformations including the 1,4-conjugate addition reactions. Sulfur-containing heterocyclic compounds are a much less studied area compared to oxygen-containing heterocycles but have gained more and more attention in recent years due to their rich biological activities and widespread applications in pharmaceuticals, agrochemicals, and material science. This paper will provide a brief review on recent progress on the synthesis of an important class of sulfur-heterocycles-2-alkylthiochroman-4-ones and thioflavanones via the conjugate additions of Grignard reagents to thiochromones catalyzed by copper catalysts. Recent progress on the synthesis of 2-substituted thiochroman-4-ones via alkynylation and alkenylation of thiochromones will also be covered in this review. Full article

(This article belongs to the Special Issue Synthesis and Applications of Copper-Based Catalysts)

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27 pages, 3192 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Advances in Catalysts for Water–Gas Shift Reaction Using Waste-Derived Synthesis Gas

by Ru-Ri Lee, I-Jeong Jeon, Won-Jun Jang, Hyun-Seog Roh and Jae-Oh Shim

Catalysts 2023, 13(4), 710; https://doi.org/10.3390/catal13040710 - 7 Apr 2023

Cited by 9 | Viewed by 3878

Abstract

Hydrogen is mainly produced by steam reforming of fossil fuels. Thus, research has been continuously conducted to produce hydrogen by replacing fossil fuels. Among various alternative resources, waste is attracting attention as it can produce hydrogen while reducing the amount of landfill and [...] Read more.

Hydrogen is mainly produced by steam reforming of fossil fuels. Thus, research has been continuously conducted to produce hydrogen by replacing fossil fuels. Among various alternative resources, waste is attracting attention as it can produce hydrogen while reducing the amount of landfill and incineration. In order to produce hydrogen from waste, the water–gas shift reaction is one of the essential processes. However, syngas obtained by gasifying waste has a higher CO concentration than syngas produced by steam reforming of fossil fuels, and therefore, it is essential to develop a suitable catalyst. Research on developing a catalyst for producing hydrogen from waste has been conducted for the past decade. This study introduces various catalysts developed and provides basic knowledge necessary for the rational design of catalysts for producing hydrogen from waste-derived syngas. Full article

(This article belongs to the Special Issue Advances in Catalysts for Water-Gas Shift Reaction)

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18 pages, 3129 KiB

Open AccessEditor’s ChoiceArticle

Tuning the Structure and Acidity of Pt/Hierarchical SSZ-32 Catalysts to Boost the Selective Hydroisomerization of n-Hexadecane

by Xinyue Yang, Wenli Zhao, Linlin Liu, Xiaopo Niu and Qingfa Wang

Catalysts 2023, 13(4), 702; https://doi.org/10.3390/catal13040702 - 5 Apr 2023

Cited by 2 | Viewed by 1596

Abstract

Developing highly selective and efficient bifunctional catalysts is an important issue for the hydroisomerization of long-chain n-alkanes. It is vital to tailor the balance of isomerization and cracking reactions in hydroisomerization. Herein, a bifunctional Pt/hierarchical SSZ-32 catalyst was fabricated with a sequential [...] Read more.

Developing highly selective and efficient bifunctional catalysts is an important issue for the hydroisomerization of long-chain n-alkanes. It is vital to tailor the balance of isomerization and cracking reactions in hydroisomerization. Herein, a bifunctional Pt/hierarchical SSZ-32 catalyst was fabricated with a sequential desilication–dealumination treatment to boost the selective hydroisomerization of n-hexadecane (C₁₆). The pore structure and acid sites of SSZ-32 zeolite were tailored. More mesopore and Brønsted acid sites were generated, and the ratio of weak to strong Brønsted acidity (B_w/B_s) was increased by the sequential desilication–dealumination. The generated hierarchical structure had little effect on the selectivity of the reaction pathways of hydroisomerization versus cracking. The ratio of isomers/cracking products increased almost linearly with the increase in the B_w/B_s ratios. Meanwhile, the synergetic effect of the hierarchical structure and acidity regulation promoted the selectivity of monobranched i-C16 products. Therefore, the resulting Pt/SSZ-0.6AS exhibited the highest activity with a total isomer yield of 71.5% at 255 °C and the enhanced formation mechanism of monobranched isomers occurred via the pore mouth. Full article

(This article belongs to the Special Issue Zeolites and Porous Materials: Insight into Catalysis and Adsorption Processes)

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24 pages, 3466 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Some Insights into the Use of Heterogeneous Copper Catalysts in the Hydroprocessing of Levulinic Acid

by Denise Cavuoto, Leandro Ardemani, Nicoletta Ravasio, Federica Zaccheria and Nicola Scotti

Catalysts 2023, 13(4), 697; https://doi.org/10.3390/catal13040697 - 4 Apr 2023

Cited by 4 | Viewed by 2612

Abstract

Levulinic acid and its esters are close to being extensively produced through consolidated industrial processes, thus playing a central role in biobased industries producing commodities within the principles of the circular economy. One of the main pathways of levulinic acid and ester valorization [...] Read more.

Levulinic acid and its esters are close to being extensively produced through consolidated industrial processes, thus playing a central role in biobased industries producing commodities within the principles of the circular economy. One of the main pathways of levulinic acid and ester valorization is their transformation with hydrogen to obtain γ-valerolactone, valeric esters, 1,4-pentanediol and 2-methyl tetrahydrofuran. These reactions are catalyzed by noble and non-noble metal-based heterogeneous catalysts. The use of an abundant and non-toxic element, such as copper, is advantageous with respect to expensive or harmful metals, such as Rh, Ru, Pt or Ni. In this critical review, we wish to give a deeper insight into research advancements in the last ten years regarding the processing of levulinic acid and its esters with hydrogen using heterogeneous copper catalysts. Full article

(This article belongs to the Special Issue Advances on Catalysts Based on Copper, 2nd Edition)

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11 pages, 1637 KiB

Open AccessEditor’s ChoiceArticle

Enzymatic Synthesis of Ascorbic Acid-Ketone Body Hybrids

by Valentina Venturi, Lindomar Alberto Lerin, Francesco Presini, Pier Paolo Giovannini, Martina Catani, Alessandro Buratti, Nicola Marchetti, Latha Nagamani Dilliraj and Simona Aprile

Catalysts 2023, 13(4), 691; https://doi.org/10.3390/catal13040691 - 1 Apr 2023

Cited by 2 | Viewed by 1928

Abstract

Molecular hybrids obtained by connecting two or more bioactive molecules through a metabolizable linker are used as multi-target drugs for the therapy of multifactorial diseases. Ascorbic acid, as well as the ketone bodies acetoacetate and (R)-3-hydroxybutyrate, are bioactive molecules that have [...] Read more.

Molecular hybrids obtained by connecting two or more bioactive molecules through a metabolizable linker are used as multi-target drugs for the therapy of multifactorial diseases. Ascorbic acid, as well as the ketone bodies acetoacetate and (R)-3-hydroxybutyrate, are bioactive molecules that have common fields of application in the treatment and prevention of neurodegenerative diseases and cardiac injuries as well. In spite of this, the preparation of ascorbic acid ketone body hybrids is uncovered by the literature. Herein, we report the lipase-catalyzed condensation of methyl acetoacetate with ascorbic acid, which affords the 6-O-acetoacetyl ascorbic acid in quantitative yield. The same approach, employing the methyl (R)-3-hydroxybutyrate in place of the methyl acetoacetate, allows the preparation of the 6-O-(R)-3-hydroxybutyryl ascorbic acid in 57% yield. A better result (90% overall yield) is achieved through the lipase-catalyzed coupling of ascorbic acid with methyl (R)-3-O-methoxymethyl-3-hydroxybutyrate followed by the cleavage of the MOM protecting group. The two novel products are fully characterized and additional information on the antioxidant activity of the new products is also given. Full article

(This article belongs to the Special Issue Enzyme Catalysis: Advances, Techniques and Outlooks)

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16 pages, 5432 KiB

Open AccessEditor’s ChoiceArticle

Simultaneous Photocatalytic Sugar Conversion and Hydrogen Production Using Pd Nanoparticles Decorated on Iron-Doped Hydroxyapatite

by Chitiphon Chuaicham, Yuto Noguchi, Sulakshana Shenoy, Kaiqian Shu, Jirawat Trakulmututa, Assadawoot Srikhaow, Karthikeyan Sekar and Keiko Sasaki

Catalysts 2023, 13(4), 675; https://doi.org/10.3390/catal13040675 - 30 Mar 2023

Cited by 3 | Viewed by 2042

Abstract

Pd nanoparticles (PdNPs) were successfully deposited on the surface of Fe(III)-modified hydroxyapatite (HAp), which was subsequently used as a photocatalyst for simultaneous photocatalytic H₂ evolution and xylose conversion. The structural phase and morphology of the pristine HAp, FeHAp, and Pd@FeHAp were examined [...] Read more.

Pd nanoparticles (PdNPs) were successfully deposited on the surface of Fe(III)-modified hydroxyapatite (HAp), which was subsequently used as a photocatalyst for simultaneous photocatalytic H₂ evolution and xylose conversion. The structural phase and morphology of the pristine HAp, FeHAp, and Pd@FeHAp were examined using XRD, SEM, and TEM instruments. At 20 °C, Pd@FeHAp provided a greater xylose conversion than pristine HAp and FeHAp, about 2.15 times and 1.41 times, respectively. In addition, lactic acid and formic acid production was increased by using Pd@FeHAp. The optimal condition was further investigated using Pd@FeHAp, which demonstrated around 70% xylose conversion within 60 min at 30 °C. Moreover, only Pd@FeHAp produced H₂ under light irradiation. To clarify the impact of Fe(III) doping in FeHAp and heterojunction between PdNPs and FeHAp in the composite relative to pure Hap, the optical and physicochemical properties of Pd@FeHAp samples were analyzed, which revealed the extraordinary ability of the material to separate and transport photogenerated electron-hole pairs, as demonstrated by a substantial reduction in photoluminescence intensity when compared to Hp and FeHAp. In addition, a decrease in electron trap density in the Pd@FeHAp composite using reversed double-beam photoacoustic spectroscopy was attributed to the higher photocatalytic activity rate. Furthermore, the development of new electronic levels by the addition of Fe(III) to the structure of HAp in FeHAp may improve the ability to absorb light by lessening the energy band gap. The photocatalytic performance of the Pd@FeHAp composite was improved by lowering charge recombination and narrowing the energy band gap. As a result, a newly developed Pd@FeHAp composite might be employed as a photocatalyst to generate both alternative H₂ energy and high-value chemicals. Full article

(This article belongs to the Special Issue Memorial Issue Dedicated to Prof. King-Chuen Lin: Palladium-Based Nanocomposites for Photocatalysts, Sensors, and Energy Storage)

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39 pages, 6102 KiB

Open AccessFeature PaperEditor’s ChoiceReview

From Fenton and ORR 2e⁻-Type Catalysts to Bifunctional Electrodes for Environmental Remediation Using the Electro-Fenton Process

by Edgar Fajardo-Puerto, Abdelhakim Elmouwahidi, Esther Bailón-García, Agustín Francisco Pérez-Cadenas and Francisco Carrasco-Marín

Catalysts 2023, 13(4), 674; https://doi.org/10.3390/catal13040674 - 30 Mar 2023

Cited by 10 | Viewed by 3673

Abstract

Currently, the presence of emerging contaminants in water sources has raised concerns worldwide due to low rates of mineralization, and in some cases, zero levels of degradation through conventional treatment methods. For these reasons, researchers in the field are focused on the use [...] Read more.

Currently, the presence of emerging contaminants in water sources has raised concerns worldwide due to low rates of mineralization, and in some cases, zero levels of degradation through conventional treatment methods. For these reasons, researchers in the field are focused on the use of advanced oxidation processes (AOPs) as a powerful tool for the degradation of persistent pollutants. These AOPs are based mainly on the in-situ production of hydroxyl radicals (OH^•) generated from an oxidizing agent (H₂O₂ or O₂) in the presence of a catalyst. Among the most studied AOPs, the Fenton reaction stands out due to its operational simplicity and good levels of degradation for a wide range of emerging contaminants. However, it has some limitations such as the storage and handling of H₂O₂. Therefore, the use of the electro-Fenton (EF) process has been proposed in which H₂O₂ is generated in situ by the action of the oxygen reduction reaction (ORR). However, it is important to mention that the ORR is given by two routes, by two or four electrons, which results in the products of H₂O₂ and H₂O, respectively. For this reason, current efforts seek to increase the selectivity of ORR catalysts toward the 2e⁻ route and thus improve the performance of the EF process. This work reviews catalysts for the Fenton reaction, ORR 2e⁻ catalysts, and presents a short review of some proposed catalysts with bifunctional activity for ORR 2e⁻ and Fenton processes. Finally, the most important factors for electro-Fenton dual catalysts to obtain high catalytic activity in both Fenton and ORR 2e⁻ processes are summarized. Full article

(This article belongs to the Special Issue Exclusive Review Papers in Catalytic Materials)

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13 pages, 7456 KiB

Open AccessEditor’s ChoiceArticle

One-Pot Synthesis of Benzoxazole/Benzothiazole-Substituted Esters by Michael Addition: A Selective Construction of C-N/C-S Bonds

by Zhi-Ying Gong, Cheng-Li Yang, Dan Wang, Lang Huang and Zhi-Bing Dong

Catalysts 2023, 13(4), 658; https://doi.org/10.3390/catal13040658 - 27 Mar 2023

Cited by 1 | Viewed by 1973

Abstract

An efficient and convenient synthesis of benzoxazole/benzothiazole-substituted esters in a one-pot strategy is reported. In this investigation, a selective construction of C-N and C-S bonds via simple addition is performed. Thus, using substituted 2-aminophenols/2-aminobenzenethiols, TMTD (tetramethylthiuram disulfide) and α,β-unsaturated esters [...] Read more.

An efficient and convenient synthesis of benzoxazole/benzothiazole-substituted esters in a one-pot strategy is reported. In this investigation, a selective construction of C-N and C-S bonds via simple addition is performed. Thus, using substituted 2-aminophenols/2-aminobenzenethiols, TMTD (tetramethylthiuram disulfide) and α,β-unsaturated esters as starting substrates, C-N and C-S bonds can be selectively constructed by means of the Michael addition reaction. This protocol features high selectivity, high atomic economy, mild conditions, good functional tolerance and good to excellent yields, showing the potential value for the preparation of some biologically and pharmaceutically active compounds. Full article

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

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20 pages, 5132 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Catalytic Performance and Reaction Mechanisms of Ethyl Acetate Oxidation over the Au–Pd/TiO₂ Catalysts

by Minming Bao, Yuxi Liu, Jiguang Deng, Lin Jing, Zhiquan Hou, Zhiwei Wang, Lu Wei, Xiaohui Yu and Hongxing Dai

Catalysts 2023, 13(4), 643; https://doi.org/10.3390/catal13040643 - 23 Mar 2023

Cited by 4 | Viewed by 3765

Abstract

The development of efficient and stable catalysts is of great importance for the elimination of volatile organic pollutants (VOCs). In this work, AuPd_x nanoparticles (NPs) were loaded on TiO₂ through the electrostatic adsorption approach to generate the yAuPd_x/TiO [...] Read more.

The development of efficient and stable catalysts is of great importance for the elimination of volatile organic pollutants (VOCs). In this work, AuPd_x nanoparticles (NPs) were loaded on TiO₂ through the electrostatic adsorption approach to generate the yAuPd_x/TiO₂ (i.e., 0.35AuPd_0.46/TiO₂, 0.34AuPd_2.09/TiO₂, and 0.37AuPd_2.72/TiO₂; x and y are Pd/Au molar ratio and AuPd_x loading, respectively; x = 0.46–2.72; and y = 0.34–0.37 wt%) catalysts, and their catalytic activities for the oxidation of ethyl acetate were determined. The results showed that the 0.37AuPd_2.72/TiO₂ sample exhibited the best activity (T_50% = 217 °C and T_90% = 239 °C at SV = 40,000 mL/(g h), E_a = 37 kJ/mol, specific reaction rate at 220 °C = 113.8 µmol/(g_Pd s), and turnover frequency (TOF_{Noble metal}) at 220 °C = 109.7 × 10⁻³ s⁻¹). The high catalytic performance of the 0.37AuPd_2.72/TiO₂ sample was attributed to the good dispersion of AuPd_2.72 NPs, the strong redox ability, the large ethyl acetate adsorption capacity, and the strong interaction between AuPd_x and TiO₂. Acetaldehyde, ethanol, and acetic acid are the main intermediates in the oxidation of ethyl acetate, and the loading of AuPd_x NPs effectively reduces the formation of the toxic by-product acetaldehyde. The oxidation of ethyl acetate over the 0.34AuPd_2.09/TiO₂ sample might occur via the pathway of ethyl acetate → ethanol → acetic acid → acetate → CO₂ and H₂O. We believe that the obtained results may provide a useful idea for the design of bimetallic catalysts under industrial conditions and for understanding the VOCs oxidation mechanisms. Full article

(This article belongs to the Special Issue Exclusive Papers in Environmentally Friendly Catalysis in China)

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14 pages, 5092 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Straightforward and Efficient Deuteration of Terminal Alkynes with Copper Catalysis

by Xènia Tarrach, Jingzhou Yang, Mohammad Soleiman-Beigi and Silvia Díez-González

Catalysts 2023, 13(4), 648; https://doi.org/10.3390/catal13040648 - 23 Mar 2023

Cited by 1 | Viewed by 2172

Abstract

The mild and effective preparation of deuterated organic molecules is an active area of research due to their important applications. Herein, we report an air-stable and easy to access copper(I) complex as catalyst for the deuteration of mono-substituted alkynes. Reactions were carried out [...] Read more.

The mild and effective preparation of deuterated organic molecules is an active area of research due to their important applications. Herein, we report an air-stable and easy to access copper(I) complex as catalyst for the deuteration of mono-substituted alkynes. Reactions were carried out in technical solvents and in the presence of air, to obtain excellent deuterium incorporation in a range of functionalised alkynes. Full article

(This article belongs to the Special Issue Feature Papers in Catalysis in Organic and Polymer Chemistry)

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24 pages, 3558 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Giving New Life to Waste Cigarette Butts: Transformation into Platinum Group Metal-Free Electrocatalysts for Oxygen Reduction Reaction in Acid, Neutral and Alkaline Environment

by Davide Testa, Giovanni Zuccante, Mohsin Muhyuddin, Roberto Landone, Axel Scommegna, Roberto Lorenzi, Maurizio Acciarri, Elisabetta Petri, Francesca Soavi, Lorenzo Poggini, Laura Capozzoli, Alessandro Lavacchi, Niccolò Lamanna, Andrea Franzetti, Luca Zoia and Carlo Santoro

Catalysts 2023, 13(3), 635; https://doi.org/10.3390/catal13030635 - 22 Mar 2023

Cited by 9 | Viewed by 2768

Abstract

Following the core theme of a circular economy, a novel strategy to upcycle cigarette butt waste into platinum group metal (PGM)-free metal nitrogen carbon (M-N-C) electrocatalysts for oxygen reduction reaction (ORR) is presented. The experimental route was composed of (i) the transformation of [...] Read more.

Following the core theme of a circular economy, a novel strategy to upcycle cigarette butt waste into platinum group metal (PGM)-free metal nitrogen carbon (M-N-C) electrocatalysts for oxygen reduction reaction (ORR) is presented. The experimental route was composed of (i) the transformation of the powdered cigarette butts into carbonaceous char via pyrolysis at 450 °C, 600 °C, 750 °C and 900 °C, (ii) the porosity activation with KOH and (iii) the functionalization of the activated chars with iron (II) phthalocyanine (FePc). The electrochemical outcomes obtained by the rotating disk electrode (RRDE) technique revealed that the sample pyrolyzed at 450 °C (i.e., cig_450) outperformed the other counterparts with its highest onset (E_on) and half-wave potentials (E_1/2) and demonstrated nearly tetra-electronic ORR in acidic, neutral and alkaline electrolytes, all resulting from the optimal surface chemistry and textural properties. Full article

(This article belongs to the Special Issue Non-noble Metal Electrocatalysts for the Oxygen Reduction Reaction)

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20 pages, 14135 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

BiPO₄/Ov-BiOBr High-Low Junctions for Efficient Visible Light Photocatalytic Performance for Tetracycline Degradation and H₂O₂ Production

by Minghui Tang, Xibao Li, Fang Deng, Lu Han, Yu Xie, Juntong Huang, Zhi Chen, Zhijun Feng and Yingtang Zhou

Catalysts 2023, 13(3), 634; https://doi.org/10.3390/catal13030634 - 22 Mar 2023

Cited by 12 | Viewed by 2406

Abstract

Through a two-step solvothermal method, different molar ratios of BiPO₄ were grown in situ on the surface of oxygen-vacancy-rich BiOBr (Ov-BiOBr), successfully constructing a BiPO₄/Ov-BiOBr heterojunction composite material. By constructing a novel type I high-low junction between the semiconductor BiPO [...] Read more.

Through a two-step solvothermal method, different molar ratios of BiPO₄ were grown in situ on the surface of oxygen-vacancy-rich BiOBr (Ov-BiOBr), successfully constructing a BiPO₄/Ov-BiOBr heterojunction composite material. By constructing a novel type I high-low junction between the semiconductor BiPO₄ and Ov-BiOBr, stronger oxidative holes or reductive electrons were retained, thereby improving the redox performance of the photocatalyst. The composite catalyst with a 10% molar content of BiPO₄ demonstrated the highest degradation rate of tetracycline (TC), degrading over 95% within 90 min, with a rate constant of 0.02534 min⁻¹, which is 2.3 times that of Ov-BiOBr and 22 times that of BiPO₄. The 10% BiPO₄/Ov-BiOBr sample displayed the best photocatalytic activity, producing 139 μmol·L⁻¹ H₂O₂ in 120 min, which is 3.6 times the efficiency of Ov-BiOBr and 19 times that of BiPO₄. This was due to the appropriate bandgap matching between BiPO₄ and Ov-BiOBr, the photo-generated electron transfer channel via Bi-bridge, and efficient charge separation. It was inferred that the free radical species ·OH and ·O₂⁻ played the dominant role in the photocatalytic process. Based on experimental and theoretical results, a possible photocatalytic mechanism was proposed. Full article

(This article belongs to the Special Issue Photocatalytic Nanomaterials for Environmental Purification)

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14 pages, 1700 KiB

Open AccessEditor’s ChoiceArticle

Four-Component Synthesis of 9H-Pyrimido[4,5-b]indoles Using Ammonium Iodide as the Nitrogen Source

by Yufeng Chen, Ruitong Yang, Fuhong Xiao, Tong Li, Guojiang Mao and Guo-Jun Deng

Catalysts 2023, 13(3), 623; https://doi.org/10.3390/catal13030623 - 20 Mar 2023

Cited by 5 | Viewed by 1551

Abstract

A four-component synthesis of 2-phenyl-9H-pyrimido[4,5-b]indoles was developed using indole-3-carboxaldehydes, aromatic aldehyde and ammonium iodide as the raw materials under transition-metal-free conditions. The pyrimidine ring was formed in one pot through [4 + 2] annulation reaction. Four C–N bonds were [...] Read more.

A four-component synthesis of 2-phenyl-9H-pyrimido[4,5-b]indoles was developed using indole-3-carboxaldehydes, aromatic aldehyde and ammonium iodide as the raw materials under transition-metal-free conditions. The pyrimidine ring was formed in one pot through [4 + 2] annulation reaction. Four C–N bonds were formed in one pot promoted by iodine and iodide additives. This work is highlighted by using two ammonium iodides as the sole nitrogen source. Full article

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

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18 pages, 8367 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Pt_1−xNi_x Alloy Nanoparticles Embedded in Self-Grown Carbon Nanofibers: Synthesis, Properties and Catalytic Activity in HER

by Anton A. Popov, Sofya D. Afonnikova, Andrey D. Varygin, Yury I. Bauman, Mikhail V. Trenikhin, Pavel E. Plyusnin, Yury V. Shubin, Aleksey A. Vedyagin and Ilya V. Mishakov

Catalysts 2023, 13(3), 599; https://doi.org/10.3390/catal13030599 - 16 Mar 2023

Cited by 13 | Viewed by 2109

Abstract

The development of new heterogeneous Pt-containing catalysts has retained its relevance over the past decades. The present paper describes the method to produce metal–carbon composites, Pt_1−xNi_x/CNF, with an adjustable Pt/Ni ratio. The composites represent Pt_1−xNi_x (x [...] Read more.

The development of new heterogeneous Pt-containing catalysts has retained its relevance over the past decades. The present paper describes the method to produce metal–carbon composites, Pt_1−xNi_x/CNF, with an adjustable Pt/Ni ratio. The composites represent Pt_1−xNi_x (x = 0.0–1.0) nanoparticles embedded within a structure of carbon nanofibers (CNF). The synthesis of the composites is based on a spontaneous disintegration of Pt_1−xNi_x alloys in an ethylene-containing atmosphere with the formation of CNF. The initial Pt_1−xNi_x alloys were prepared by thermolysis of multicomponent precursors. They possess a porous structure formed by fragments of 100–200 nm. As was shown by X-ray diffraction analysis, the crystal structure of the alloys containing 0–30 and 60–100 at.% Ni corresponds to a fcc lattice based on platinum (Fm-3m), while the Pt_0.50Ni_0.50 sample is an intermetallic compound with the tetragonal structure (P4/mmm). The impact of the Ni content in the Pt_1−xNi_x samples on their activity in ethylene decomposition was studied as well. As was revealed, the efficiency of Pt_1−xNi_x alloys in this process increases with the rise of Ni concentration. The composite samples were examined in an electrochemical hydrogen evolution reaction. The synthesized Pt_1-xNi_x/CNF composites demonstrated superior activity if compared with the Pt/Vulcan commercial catalyst. Full article

(This article belongs to the Special Issue Ni-Based Catalysts: Synthesis and Applications)

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16 pages, 5833 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Highly Efficient Au/ZnO−ZrO₂ Catalysts for CO Oxidation at Low Temperature

by Roberto Camposeco, Viridiana Maturano-Rojas and Rodolfo Zanella

Catalysts 2023, 13(3), 590; https://doi.org/10.3390/catal13030590 - 15 Mar 2023

Cited by 2 | Viewed by 1648

Abstract

A series of gold catalysts on ZnO−ZrO₂ featuring nominal ZnO loads of 3, 5, and 10 wt. % were synthesized by the sol–gel method using Zn(NO₃)₂ and zirconium (IV) propoxide aqueous solutions. In addition, gold catalysts with nominal loads [...] Read more.

A series of gold catalysts on ZnO−ZrO₂ featuring nominal ZnO loads of 3, 5, and 10 wt. % were synthesized by the sol–gel method using Zn(NO₃)₂ and zirconium (IV) propoxide aqueous solutions. In addition, gold catalysts with nominal loads between 1 and 3 wt. % were produced by the method of deposition-precipitation with urea, and their performance in the CO oxidation reaction at low temperature was evaluated. HRTEM outcomes revealed high gold dispersion on the 3Au/5ZnO−ZrO₂ catalyst with Zn/Zr atomic ratio of (5/95) and 3 wt. % of gold, which showed the highest CO conversion at low temperature (−5 °C) under air treatment when the CO oxidation was carried out with a space velocity of ~46,000 h⁻¹. The incorporation of ZnO to ZrO₂ provoked high dispersion of the gold nanoparticles on the support and close size distribution; moreover, the presence of Au¹⁺ and Zr³⁺ species was increased by the Zr−O−Zn interaction, which was stronger than in the single Au/ZrO₂ and Au/ZnO catalysts. DRIFT/GC−MS confirmed that the Au¹⁺/Au⁰ ratio and formation of carbonate species played an important role in determining the CO conversion; likewise, the 3Au/5ZnO–ZrO₂ catalyst was stable at 10 °C for 24 h. Full article

(This article belongs to the Special Issue Catalysts for Air Pollution Control: Present and Future)

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12 pages, 2442 KiB

Open AccessEditor’s ChoiceArticle

Semi-Rational Design of Diaminopimelate Dehydrogenase from Symbiobacterium thermophilum Improved Its Activity toward Hydroxypyruvate for D-serine Synthesis

by Ziyao Wang, Haojie Qu, Wenqi Li, Yan Xu and Yao Nie

Catalysts 2023, 13(3), 576; https://doi.org/10.3390/catal13030576 - 13 Mar 2023

Cited by 2 | Viewed by 2081

Abstract

D-serine plays an essential role in the field of medicine and cosmetics. Diaminopimelate dehydrogenase (DAPDH) is a kind of oxidoreductase that can reduce keto acid into the corresponding D-amino acid. Because of its high stereoselectivity and lack of by-product production, DAPDH has become [...] Read more.

D-serine plays an essential role in the field of medicine and cosmetics. Diaminopimelate dehydrogenase (DAPDH) is a kind of oxidoreductase that can reduce keto acid into the corresponding D-amino acid. Because of its high stereoselectivity and lack of by-product production, DAPDH has become the preferred enzyme for the efficient one-step synthesis of D-amino acids. However, the types of DAPDH with a reductive amination function reported so far are limited. Although the DAPDH from Symbiobacterium thermophilum (StDAPDH) demonstrates reductive amination activity toward a series of macromolecular keto acids, activity toward hydroxypyruvate (HPPA) for D-serine synthesis has not been reported. In this study, we investigated the activity of the available StDAPDH/H227V toward HPPA by measuring the desired product D-serine. After homologous structure modeling and docking analysis concerning the substrate-binding pocket, four residues, D92, D122, M152, and N253, in the active pocket were predicted for catalyzing HPPA. Through single-point saturation mutation and iterative mutation, a mutant D92E/D122W/M152S was obtained with an 8.64-fold increase in enzyme activity, exhibiting a specific activity of 0.19 U/mg and k_cat value of 3.96 s⁻¹ toward HPPA. Using molecular dynamics simulation, it was speculated that the increase in enzyme activity might be related to the change in substrate pocket size and the enhancement of the interactions between the substrate and key residues. Full article

(This article belongs to the Special Issue Biocatalysis in Organic Chemistry and Enzyme Engineering)

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11 pages, 4508 KiB

Open AccessEditor’s ChoiceArticle

Methane Activation and Coupling Pathways on Ni₂P Catalyst

by Abdulrahman Almithn, Salem N. Alghanim, Abdullah A. Mohammed, Abdullah K. Alghawinim, Mazen A. Alomaireen, Zaid Alhulaybi and SK Safdar Hossain

Catalysts 2023, 13(3), 531; https://doi.org/10.3390/catal13030531 - 6 Mar 2023

Cited by 3 | Viewed by 2044

Abstract

The direct catalytic conversion of methane (CH₄) to higher hydrocarbons has attracted considerable attention in recent years because of the increasing supply of natural gas. Efficient and selective catalytic conversion of methane to value-added products, however, remains a major challenge. Recent [...] Read more.

The direct catalytic conversion of methane (CH₄) to higher hydrocarbons has attracted considerable attention in recent years because of the increasing supply of natural gas. Efficient and selective catalytic conversion of methane to value-added products, however, remains a major challenge. Recent studies have shown that the incorporation of phosphorus atoms in transition metals improves their selectivity and resistance to coke formation for many catalytic reactions. In this work, we report a density function theory-based investigation of methane activation and C₂ product formation on Ni₂P(001). Our results indicate that, despite the lower reactivity of Ni₂P relative to Ni, the addition of phosphorus atoms hinders excessive dehydrogenation of methane to CH* and C* species, thus reducing carbon deposition on the surface. CH₃* and CH₂* moieties, instead, are more likely to be the most abundant surface intermediates once the initial C–H bond in methane is activated with a barrier of 246 kJ mol⁻¹. The formation of ethylene from 2CH₂* on Ni₂P is facile with a barrier of 56 kJ mol⁻¹, which is consistent with prior experimental studies. Collectively, these findings suggest that Ni₂P may be an attractive catalyst for selective methane conversion to ethylene. Full article

(This article belongs to the Special Issue The Role of Catalysts in Functionalization of C-H and C-C Bonds II)

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31 pages, 8801 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in the Efficient Synthesis of Useful Amines from Biomass-Based Furan Compounds and Their Derivatives over Heterogeneous Catalysts

by Jia Zhang, Jian Yang, Xuemei Li, Hailong Liu, Xiaolan Yao, Chungu Xia and Zhiwei Huang

Catalysts 2023, 13(3), 528; https://doi.org/10.3390/catal13030528 - 5 Mar 2023

Cited by 8 | Viewed by 3614

Abstract

Bio-based furanic oxygenates represent a well-known class of lignocellulosic biomass-derived platform molecules. In the presence of H₂ and different nitrogen sources, these versatile building blocks can be transformed into valuable amine compounds via reductive amination or hydrogen-borrowing amination mechanisms, yet they still [...] Read more.

Bio-based furanic oxygenates represent a well-known class of lignocellulosic biomass-derived platform molecules. In the presence of H₂ and different nitrogen sources, these versatile building blocks can be transformed into valuable amine compounds via reductive amination or hydrogen-borrowing amination mechanisms, yet they still face many challenges due to the co-existence of many side-reactions, such as direct hydrogenation, polymerization and cyclization. Hence, catalysts with specific structures and functions are required to achieve satisfactory yields of target amines. In recent years, heterogeneous catalytic synthesis of amines from bio-based furanic oxygenates has received extensive attention. In this review, we summarize and discuss the recent significant progress in the generation of useful amines from bio-based furanic oxygenates with H₂ and different nitrogen sources over heterogeneous catalysts, according to various raw materials and reaction pathways. The key factors affecting catalytic performances, such as active metals, supports, promoters, reaction solvents and conditions, as well as the possible reaction routes and catalytic reaction mechanisms are studied and discussed in depth. Special attention is paid to the structure–activity relationship, which would be helpful for the development of more efficient and stable heterogeneous catalysts. Moreover, the future research direction and development trend of the efficient synthesis for bio-based amines are prospected. Full article

(This article belongs to the Special Issue Catalytic Conversion of Biomass to Furan Compounds)

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13 pages, 3407 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Continuous Flow Photochemical Synthesis of 3-Methyl-4-arylmethylene Isoxazole-5(4H)-ones through Organic Photoredox Catalysis and Investigation of Their Larvicidal Activity

by Ana Beatriz S. Sampaio, Mônica Shigemi S. Mori, Lorena C. Albernaz, Laila S. Espindola, Carlos Eduardo M. Salvador and Carlos Kleber Z. Andrade

Catalysts 2023, 13(3), 518; https://doi.org/10.3390/catal13030518 - 3 Mar 2023

Cited by 4 | Viewed by 1977

Abstract

Isoxazole-5(4H)-ones are heteropentacycle compounds found in several bioactive molecules with pharmaceutical and agrochemical properties. A well-known multicomponent reaction between β-ketoester, hydroxylamine, and aromatic aldehydes leads to 3-methyl-4-arylmethylene isoxazole-5(4H)-ones, in mild conditions. The initial purpose of this work was to investigate whether the reaction [...] Read more.

Isoxazole-5(4H)-ones are heteropentacycle compounds found in several bioactive molecules with pharmaceutical and agrochemical properties. A well-known multicomponent reaction between β-ketoester, hydroxylamine, and aromatic aldehydes leads to 3-methyl-4-arylmethylene isoxazole-5(4H)-ones, in mild conditions. The initial purpose of this work was to investigate whether the reaction might be induced by light, as described in previous works. Remarkable results were obtained using a high-power lamp, reducing reaction times compared to methodologies that used heating or catalysis. Since there are many examples of successful continuous flow heterocycle synthesis, including photochemical reactions, the study evolved to run the reaction in flow conditions and scale up the synthesis of isoxazolones using a photochemical reactor set-up. Eight different compounds were obtained, and among them, three showed larvicidal activity on immature forms of Aedes aegypti in tests that investigated its growth inhibitory character. Mechanistic investigations indicate that the reactions occur through organic photoredox catalysis. Full article

(This article belongs to the Special Issue Multicomponent Catalytic Reactions under Green Conditions)

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13 pages, 1946 KiB

Open AccessEditor’s ChoiceArticle

Photocatalytic Removal of Thiamethoxam and Flonicamid Pesticides Present in Agro-Industrial Water Effluents

by Michalis K. Arfanis, George V. Theodorakopoulos, Christos Anagnostopoulos, Irene Georgaki, Evangelos Karanasios, George Em. Romanos, Emilia Markellou and Polycarpos Falaras

Catalysts 2023, 13(3), 516; https://doi.org/10.3390/catal13030516 - 3 Mar 2023

Cited by 7 | Viewed by 1905

Abstract

Pesticide residues, when present in agricultural wastewater, constitute a potential risk for the environment and human health. Hence, focused actions for their abatement are of high priority for both the industrial sectors and national authorities. This work evaluates the effectiveness of the photocatalytic [...] Read more.

Pesticide residues, when present in agricultural wastewater, constitute a potential risk for the environment and human health. Hence, focused actions for their abatement are of high priority for both the industrial sectors and national authorities. This work evaluates the effectiveness of the photocatalytic process to decompose two frequently detected pesticides in the water effluents of the fruit industry: thiamethoxam-a neonicotinoid compound and flonicamid-a pyridine derivative. Their photocatalytic degradation and mineralization were evaluated in a lab-scale photocatalytic batch reactor under UV-A illumination with the commercial photocatalyst Evonik P25 TiO₂ by employing different experimental conditions. The complete degradation of thiamethoxam was achieved after 90 min, when the medium was adjusted to natural or alkaline pH. Flonicamid was proven to be a more recalcitrant substance and the removal efficiency reached ~50% at the same conditions, although the degradation overpassed 75% in the acidic pH medium. Overall, the pesticides’ degradation follows the photocatalytic reduction pathways, where positive charged holes and hydroxyl radicals dominate as reactive species, with complete mineralization taking place after 4 h, regardless of the pH medium. Moreover, it was deduced that the pesticides’ degradation kinetics followed the Langmuir-Hinshelwood (L-H) model, and the apparent rate constant, the initial degradation rate, as well as the L-H model parameters, were determined for both pesticides. Full article

(This article belongs to the Special Issue Trends in Environmental Applications of Advanced Oxidation Processes)

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16 pages, 2615 KiB

Open AccessEditor’s ChoiceArticle

Improving Effects of Laccase-Mediated Pectin–Ferulic Acid Conjugate and Transglutaminase on Active Peptide Production in Bovine Lactoferrin Digests

by Mingxia Xing, Ying Ji, Lianzhong Ai, Fan Xie, Yan Wu and Phoency F. H. Lai

Catalysts 2023, 13(3), 521; https://doi.org/10.3390/catal13030521 - 3 Mar 2023

Viewed by 1735

Abstract

Bovine lactoferrin (bLf) is a multifunctional glycoprotein and a good candidate for producing diverse bioactive peptides, which are easily lost during over-digestion. Accordingly, the effects of laccase-mediated pectin–ferulic acid conjugate (PF) and transglutaminase (TG) on improving the production of bLf active peptides by [...] Read more.

Bovine lactoferrin (bLf) is a multifunctional glycoprotein and a good candidate for producing diverse bioactive peptides, which are easily lost during over-digestion. Accordingly, the effects of laccase-mediated pectin–ferulic acid conjugate (PF) and transglutaminase (TG) on improving the production of bLf active peptides by in vitro gastrointestinal digestion were investigated. Using ultra-high-performance liquid chromatography tandem mass spectroscopy (UPLC-MS-MS), the digests of bLf alone, PF-encapsulated bLf complex (LfPF), and TG-treated LfPF complex (LfPFTG) produced by conditioned in vitro gastric digestion (2000 U/mL pepsin, pH 3.0, 37 °C, 2 h) were identified with seven groups of active peptide-related fragments, including three common peptides (VFEAGRDPYKLRPVAAE, FENLPEKADRDQYEL, and VLRPTEGYL) and four differential peptides (GILRPYLSWTE, ARSVDGKEDLIWKL, YLGSRYLT, and FKSETKNLL). The gastric digest of LfPF contained more diverse and abundant detectable peptides of longer lengths than those of bLf and LfPFTG. After further in vitro intestinal digestion, two active peptide-related fragments (FEAGRDPYK and FENLPEKADRDQYE) remained in the final digest of LfPFTG; one (EAGRDPYKLRPVA) remained in that of bLf alone, but none remained in that of LfPF. Conclusively, PF encapsulation enhanced the production of bLf active peptide fragments under the in vitro gastric digestion applied. TG treatment facilitated active peptide FENLPEKADRDQYE being kept in the final gastrointestinal digest. Full article

(This article belongs to the Special Issue Enzymes in Biomedical, Cosmetic and Food Application)

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15 pages, 62227 KiB

Open AccessEditor’s ChoiceArticle

Effect of pH on Microstructure and Catalytic Oxidation of Formaldehyde in MnO₂ Catalyst

by Wenrui Zhang, Meilu Hao, Yonghui Wang, Pengfei Sun, Dongjuan Zeng, Xinya Wang and Peng Liang

Catalysts 2023, 13(3), 490; https://doi.org/10.3390/catal13030490 - 28 Feb 2023

Cited by 1 | Viewed by 2231

Abstract

Layered δ-MnO₂ catalysts were prepared using the one-step redox method in precursor solutions with five different pH values (pH = 7, 9, 11, 13, and 14). The effects of pH on the physical properties and catalytic activity of the catalyst were investigated [...] Read more.

Layered δ-MnO₂ catalysts were prepared using the one-step redox method in precursor solutions with five different pH values (pH = 7, 9, 11, 13, and 14). The effects of pH on the physical properties and catalytic activity of the catalyst were investigated through XRD, SEM, TEM, BET, XPS, H₂-TPR, and HCHO degradation tests at room temperature. The results showed that the layer spacing, manganese vacancy content, Mn⁴⁺/Mn³⁺ ratio, and surface-reactive oxygen species content of MnO₂ increased with the increase in pH value in the alkaline range. When the catalyst was prepared at pH = 13, the above characteristics of the catalyst reached the optimal value which contributed to the high catalytic activity. Combined with the related characterization results, it was proved that changing the pH can affect the degree of oxidation in the catalyst synthesis process, increase the number of active oxygen and the oxygen mobility of the catalyst, and effectively improve the catalytic activity of the manganese dioxide catalyst for HCHO. This work represents a giant step toward the preparation of an effective catalyst for practical applications of HCHO removal at room temperature at a low concentration and high velocity. Full article

(This article belongs to the Special Issue Effect of the Modification of Catalysts on the Catalytic Performance, 2nd Edition)

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18 pages, 3309 KiB

Open AccessEditor’s ChoiceArticle

Effect of Fe on Calcined Ni(OH)₂ Anode in Alkaline Water Electrolysis

by Tae-Hyun Kim, Kee-Young Koo, Chu-Sik Park, Seong-Uk Jeong, Ji-Eun Kim, Su-Han Lee, Young-Ho Kim and Kyoung-Soo Kang

Catalysts 2023, 13(3), 496; https://doi.org/10.3390/catal13030496 - 28 Feb 2023

Cited by 4 | Viewed by 2753

Abstract

Ni (hydr)oxide is a promising and inexpensive material for oxygen evolution reaction (OER) catalysts and is known to dramatically increase the activity when used with Fe. Herein, we basified a Ni(II) solution and coated layered Ni(OH)₂ on Ni coins to prepare a [...] Read more.

Ni (hydr)oxide is a promising and inexpensive material for oxygen evolution reaction (OER) catalysts and is known to dramatically increase the activity when used with Fe. Herein, we basified a Ni(II) solution and coated layered Ni(OH)₂ on Ni coins to prepare a template with high stability and activity. To evaluate the stability and catalytic activity during high-current-density operation, we analyzed the electrochemical and physicochemical properties before and after constant current (CC) operation. The electrode with a Ni(OH)₂ surface exhibited higher initial activity than that with a NiO surface; however, after the OER operation at a high-current density, degradation occurred owing to structural destruction. The activity of the electrodes with a NiO surface improved after the CC operation because of the changes on the electrode-surface caused by the CC operation and the subsequent Fe incorporation from the Fe impurity in the electrolyte. After confirming the improvement in activity due to Fe, we prepared NiFe-oxide electrodes with improved catalytic activity and optimized the Ni precursor and Fe loading solution concentrations. The Ni-Fe oxide electrode prepared under the optimal concentrations exhibited an overpotential of 287 mV at a current density of 10 mA/cm², and a tafel slope of 37 mV dec⁻¹, indicating an improvement in the OER activity. Full article

(This article belongs to the Topic Hydrogen Energy Technologies, 2nd Volume)

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15 pages, 3670 KiB

Open AccessEditor’s ChoiceArticle

Influence of the Valence of Iron on the NO Reduction by CO over Cu-Fe-Mordenite

by Yulia Kotolevich, Trino Zepeda-Partida, Rosario Yocupicio-Gaxiola, Joel Antúnez-Garcia, Luis Pelaez, Miguel Avalos-Borja, Pedro Jovanni Vázquez-Salas, Sergio Fuentes-Moyado and Vitalii Petranovskii

Catalysts 2023, 13(3), 484; https://doi.org/10.3390/catal13030484 - 27 Feb 2023

Cited by 2 | Viewed by 1337

Abstract

A comprehensive study of the catalytic properties of the copper-iron binary system supported on mordenite, depending on the iron valence—CuFe2MOR and CuFe3MOR—was carried out, and redox ability has been considered as a decisive factor in determining catalytic efficiency. Acidity was studied by TPD-NH [...] Read more.

A comprehensive study of the catalytic properties of the copper-iron binary system supported on mordenite, depending on the iron valence—CuFe2MOR and CuFe3MOR—was carried out, and redox ability has been considered as a decisive factor in determining catalytic efficiency. Acidity was studied by TPD-NH₃, DRIFT-OH, and DRT methods. The total acidity of both samples was high. The Brönsted acidity is similar for both bimetallic samples and is explained by the acidity of zeolite; Lewis acidity varies greatly and depends on the exchange cations. A screening DRIFT study of CO and NO has shown redox capacity and demonstrated a potential for using these materials as catalysts for ambient protection. CuFe2MOR demonstrated stable Cu and Fe species, while CuFe3MOR showed redox dynamic species. As expected, CuFe3MOR displayed higher catalytic performance in NO reduction via CO oxidation, because of the easily reduced intermediate NO-complex adsorbed on the metallic Cu and Fe sites, which were observed through in situ DRIFT study. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Catalytic Environment, Energy, and Sustainability)

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11 pages, 6043 KiB

Open AccessEditor’s ChoiceArticle

AAO-Assisted Nanoporous Platinum Films for Hydrogen Sensor Application

by Melike Sener, Orhan Sisman and Necmettin Kilinc

Catalysts 2023, 13(3), 459; https://doi.org/10.3390/catal13030459 - 22 Feb 2023

Cited by 5 | Viewed by 2187

Abstract

The effects of the porosity and the thickness on the ability of hydrogen sensing is demonstrated through a comparison of compact and nanoporous platinum film sensors. The synthesis of anodic aluminum oxide (AAO) nanotubes with an average pore diameter of less than 100 [...] Read more.

The effects of the porosity and the thickness on the ability of hydrogen sensing is demonstrated through a comparison of compact and nanoporous platinum film sensors. The synthesis of anodic aluminum oxide (AAO) nanotubes with an average pore diameter of less than 100 nm served as the template for the fabrication of nanoporous Pt films using an anodization method. This was achieved by applying a voltage of 40 V in 0.4 M of a phosphoric acid solution at 20 °C. To compare the film and nanoporous Pt, layers of approximately 3 nm and 20 nm were coated on both glass substrates and AAO templates using a sputtering technique. FESEM images monitored the formation of nanoporosity by observing the Pt layers covering the upper edges of the AAO nanotubes. Despite their low thickness and the poor long-range order, the EDX and XRD measurements confirmed and uncovered the crystalline properties of the Pt films by comparing the bare and the Pt deposited AAO templates. The nanoporous Pt and Pt thin film sensors were tested in the hydrogen concentration range between 10–50,000 ppm H₂ at room temperature, 50 °C, 100 °C and 150 °C. The results reveal that nanoporous Pt performed higher sensitivity than the Pt thin film and the surface scattering phenomenon can express the hydrogen sensing mechanism of the Pt sensors. Full article

(This article belongs to the Special Issue Advanced Materials for Application in Catalysis)

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16 pages, 4415 KiB

Open AccessEditor’s ChoiceArticle

An Efficient Strategy for Chemoenzymatic Conversion of Corn Stover to Furfuryl Alcohol in Deep Eutectic Solvent ChCl:PEG10000−Water Medium

by Daozhu Xu, Wei Tang, Zhengyu Tang and Yucai He

Catalysts 2023, 13(3), 467; https://doi.org/10.3390/catal13030467 - 22 Feb 2023

Cited by 4 | Viewed by 1854

Abstract

As a versatile and valuable intermediate, furfuryl alcohol (FOL) is widely utilized in manufacturing vitamin C, perfume, fruit acid, lubricant, lysine, plasticizer, dispersing agent, resin, fuel additive, and biofuel. This study aimed at the establishment of a cascade catalysis of biomass to FOL [...] Read more.

As a versatile and valuable intermediate, furfuryl alcohol (FOL) is widely utilized in manufacturing vitamin C, perfume, fruit acid, lubricant, lysine, plasticizer, dispersing agent, resin, fuel additive, and biofuel. This study aimed at the establishment of a cascade catalysis of biomass to FOL via a hybrid approach in a deep eutectic solvent medium. The catalysis of corn stover (75 g/L) with solid acid AT-Sn-WLS (1.2 wt%) produced 110.5 mM FAL in a ChCl:PEG10000–water (20:80, wt/wt) system at 170 °C for 30 min, and then the formed FAL was biologically transformed into FOL with recombinant E. coli SF harboring aldehyde reductase at pH 7.0 and 35 °C. This established hybrid strategy could efficiently valorize corn stover into FOL, with the productivity of 0.41 g FOL per g xylan in corn stover. Consequently, one combination of chemocatalytic and biocatalytic reactions leading to a one-pot catalytic process was shown as an attractive approach in the valorization of lignocellulose into valuable biobased chemicals. Full article

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

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13 pages, 14234 KiB

Open AccessEditor’s ChoiceArticle

The Quick Removal of Toxic Dye Molecules by an Efficient Adsorptive BiOI/Bi₂MoO₆ Heterostructure

by Tasie Ebenezer Onyedika, Mengying Xu, Yichao Deng, Yang Liu, Lian Li, Pier-Luc Tremblay and Tian Zhang

Catalysts 2023, 13(3), 457; https://doi.org/10.3390/catal13030457 - 21 Feb 2023

Cited by 3 | Viewed by 1891

Abstract

Adsorption is a low-energy, economical, and efficient method for pollutant removal from water. Because of their unique structure, large specific surface area (SSA), and non-toxicity, bismuth-based semiconductors, usually researched for the photodegradation of organic molecules, are also excellent for dark adsorption processes. Here, [...] Read more.

Adsorption is a low-energy, economical, and efficient method for pollutant removal from water. Because of their unique structure, large specific surface area (SSA), and non-toxicity, bismuth-based semiconductors, usually researched for the photodegradation of organic molecules, are also excellent for dark adsorption processes. Here, a three-dimensional adsorbent with a heterostructure with a hydrangea-like shape made of Bi₂MoO₆ (BMO) and BiOI (BOI) was synthesized by a one-pot solvothermal process and investigated for the adsorption of toxic dyes. BOI/BMO with an I-to-Mo ratio of 2.0 adsorbed 98.9% of the model pollutant rhodamine B (RhB) within 5 min with a maximum adsorption capacity of 72.72 mg/g in the dark at room temperature. When compared to pure BMO, the BOI₂/BMO heterostructure was 14.1 times more performant because of its flower-like morphology with multiple planes, an SSA that was 1.6-fold larger, increased porosity, the formation of heterojunctions, and a negative surface charge attracting RhB. Further investigation indicated that adsorption by BOI₂/BMO fitted the pseudo-second-order kinetic and the Langmuir isotherm models. In addition, the thermodynamic analysis showed that it was a spontaneous exothermic process probably relying on physisorption. Thus, the BOI/BMO adsorbent developed here is promising for the fast removal of toxic dyes from industrial wastewater. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis for Environmentally Compatible Reactions and Processes)

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14 pages, 2856 KiB

Open AccessEditor’s ChoiceArticle

Role of N-Terminal Extensional Long α-Helix in the Arylesterase from Lacticaseibacillus rhamnosus GG on Catalysis and Stability

by Bin-Chun Li, Tongtong Guo, Xue Li, Xueting Hou and Guo-Bin Ding

Catalysts 2023, 13(2), 441; https://doi.org/10.3390/catal13020441 - 18 Feb 2023

Viewed by 1499

Abstract

In the α/β hydrolases superfamily, the extra module modulated enzymatic activity, substrate specificity, and stability. The functional role of N-terminal extensional long α-helix (Ala2-Glu29, designated as NEL-helix) acting as the extra module in the arylesterase LggEst from Lacticaseibacillus rhamnosus GG had been systemically [...] Read more.

In the α/β hydrolases superfamily, the extra module modulated enzymatic activity, substrate specificity, and stability. The functional role of N-terminal extensional long α-helix (Ala2-Glu29, designated as NEL-helix) acting as the extra module in the arylesterase LggEst from Lacticaseibacillus rhamnosus GG had been systemically investigated by deletion mutagenesis, biochemical characterization, and biophysical methods. The deletion of the NEL-helix did not change the overall structure of this arylesterase. The deletion of the NEL-helix led to the shifting of optimal pH into the acidity and the loss of thermophilic activity. The deletion of the NEL-helix produced a 10.6-fold drop in catalytic activity towards the best substrate pNPC10. NEL-Helix was crucial for the thermostability, chemical resistance, and organic solvents tolerance. The deletion of the NEL-helix did not change the overall rigidity of enzyme structure and only reduced the local rigidity of the active site. Sodium deoxycholate might partially replenish the loss of activity caused by the deletion of the NEL-helix. Our research further enriched the functional role of the extra module on catalysis and stability in the α/β hydrolase fold superfamily. Full article

(This article belongs to the Special Issue Advances in Enzyme Engineering, Biocatalysis and Biosynthesis)

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18 pages, 3805 KiB

Open AccessEditor’s ChoiceArticle

Ni₂P-Modified P-Doped Graphitic Carbon Nitride Hetero-Nanostructures for Efficient Photocatalytic Aqueous Cr(VI) Reduction

by Evangelos K. Andreou, Eirini D. Koutsouroubi, Ioannis Vamvasakis and Gerasimos S. Armatas

Catalysts 2023, 13(2), 437; https://doi.org/10.3390/catal13020437 - 17 Feb 2023

Cited by 4 | Viewed by 2497

Abstract

Targeting heterostructures with modulated electronic structures and efficient charge carrier separation and mobility is an effective strategy to improve photocatalytic performance. In this study, we report the synthesis of 2D/3D hybrid heterostructures comprising P-doped graphitic carbon nitride (g-C₃N₄) nanosheets [...] Read more.

Targeting heterostructures with modulated electronic structures and efficient charge carrier separation and mobility is an effective strategy to improve photocatalytic performance. In this study, we report the synthesis of 2D/3D hybrid heterostructures comprising P-doped graphitic carbon nitride (g-C₃N₄) nanosheets (ca. 50–60 nm in lateral size) and small-sized Ni₂P nanoparticles (ca. 10–12 nm in diameter) and demonstrate their prominent activity in the photocatalytic reduction of Cr(VI). Utilizing a combination of spectroscopic and electrochemical characterization techniques, we unveil the reasons behind the distinct photochemical performance of these materials. We show that Ni₂P modification and P doping of the g-C₃N₄ effectively improve the charge-carrier transportation and spatial separation through the interface of Ni₂P/P-doped g-C₃N₄ junctions. As a result, the catalyst containing 15 wt.% Ni₂P exhibits superior photocatalytic activity in the detoxification of Cr(VI)-contaminated effluents under UV-visible light illumination, presenting an apparent quantum yield (QY) of 12.5% at 410 nm, notably without the use of sacrificial additives. This study marks a forward step in understanding and fabricating cost-effective photocatalysts for photochemical applications. Full article

(This article belongs to the Special Issue Feature Papers in Environmental Catalysis)

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13 pages, 1601 KiB

Open AccessEditor’s ChoiceArticle

Chlorobenzene Mineralization Using Plasma/Photocatalysis Hybrid Reactor: Exploiting the Synergistic Effect

by N’Zanon Aly KONE, Nacer Belkessa, Youcef Serhane, Sandotin Lassina Coulibaly, Mahamadou Kamagate, Lotfi Mouni, Sivachandiran Loganathan, Lacina Coulibaly, Abdelkrim Bouzaza, Abdeltif Amrane and Aymen Amine Assadi

Catalysts 2023, 13(2), 431; https://doi.org/10.3390/catal13020431 - 16 Feb 2023

Cited by 4 | Viewed by 2121

Abstract

Mineralization of gaseous chlorobenzene (major VOC from cement plants) was studied in a continuous reactor using three advanced oxidation processes: (i) photocatalysis, (ii) Dielectric Barrier Discharge (DBD) plasma and (iii) DBD/TiO₂-UV coupling. The work showed an overproduction of OH * and [...] Read more.

Mineralization of gaseous chlorobenzene (major VOC from cement plants) was studied in a continuous reactor using three advanced oxidation processes: (i) photocatalysis, (ii) Dielectric Barrier Discharge (DBD) plasma and (iii) DBD/TiO₂-UV coupling. The work showed an overproduction of OH * and O * radicals in the reaction medium due to the interaction of Cl * and O₃. A parametric study was carried out in order to determine the evolution of the removal efficiency as a function of the concentration, the flow rate and the applied voltage. Indeed, a variation of the flow rate from 0.25 to 1 m³/h resulted in a decrease in the degradation rate from 18 to 9%. Similarly, an increase in concentration from 13 to 100 mg/m³ resulted in a change in degradation rate from 18 to 4%. When the voltage was doubled from 6 to 12 kV, the degradation rate varied from 22 to 29 % (plasma) and from 53 to 75% (coupling) at 13 mg/m³. The evolution of CO_X and O₃ was monitored during the experiments. When the voltage was doubled, the selectivity increased from 28 to 37% in the plasma alone and from 48 to 62 % in the coupled process. In addition, at this same voltage range, the amount of ozone formed varied from 10 to 66 ppm in plasma and 3 to 29 ppm in coupling. This degradation performance can be linked to a synergistic effect, which resulted in an increase in the intensity of the electric field of plasma by the TiO₂ and the improvement in the performance of the catalyst following the bombardment of various high-energy particles of the plasma. Full article

(This article belongs to the Special Issue Catalysts for Air Pollution Control: Present and Future)

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