Catalysts

15 pages, 3350 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Innovative Black TiO₂ Photocatalyst for Effective Water Remediation Under Visible Light Illumination Using Flow Systems

by Mahzad Yaghmaei, Daliane R. C. da Silva, Nelson Rutajoga, Sara Currie, Yiran Li, Morgan Vallieres, Maria Jazmin Silvero, Neeraj Joshi, Bowen Wang and Juan C. Scaiano

Catalysts 2024, 14(11), 775; https://doi.org/10.3390/catal14110775 - 1 Nov 2024

Cited by 1 | Viewed by 5242

Abstract

Contaminated drinking water is a major health hazard in large urban areas as well as remote communities. Several pollutants detected in rivers and lakes are hormone disruptors that are harmful to consumers as well as aquatic life. In this contribution, we present a [...] Read more.

Contaminated drinking water is a major health hazard in large urban areas as well as remote communities. Several pollutants detected in rivers and lakes are hormone disruptors that are harmful to consumers as well as aquatic life. In this contribution, we present a new material, synthesized using novel green technologies, designed for solar- or LED-driven degradation of pollutants. This material is based on a glass fiber support, loaded with black TiO₂, a modified form of TiO₂ with strong visible light absorption and without any toxic metal or non-metal dopants. This photocatalyst is fully compatible with flow applications. The effectiveness of the catalyst is demonstrated with crocin and 17β-estradiol, the former being a natural carotenoid used as a screening tool and the latter being a common hormonal disruptor. Our work shows that under visible light illumination, our supported black TiO₂ can degrade these water contaminants with greater efficiency than conventional TiO₂. We envision that our findings can contribute to the production of inexpensive, large-scale solar or LED-based water decontamination systems that could be rapidly deployed to sites in need. Operation of such systems would require minimal training and could be monitored remotely. In addition to the catalyst’s non-toxicity and inflow compatibility, the material also has a long shelf life and is easy and inexpensive to produce, making it an attractive candidate for developing water treatment devices. Full article

(This article belongs to the Special Issue Remediation of Natural Waters by Photocatalysis)

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12 pages, 8618 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Hydrogen and CO Over-Equilibria in Catalytic Reactions of Methane Reforming

by Vitaliy R. Trishch, Mykhailo O. Vilboi, Gregory S. Yablonsky and Dmytro O. Kovaliuk

Catalysts 2024, 14(11), 773; https://doi.org/10.3390/catal14110773 - 31 Oct 2024

Cited by 1 | Viewed by 1034

Abstract

Hydrogen and carbon monoxide over-equilibria have been found computationally in kinetic dependencies of methane-reforming catalytic reactions (steam and dry reforming) using the conditions of the conservatively perturbed equilibrium (CPE) phenomenon, i.e., at the initial equilibrium concentration of hydrogen or carbon monoxide. The influence [...] Read more.

Hydrogen and carbon monoxide over-equilibria have been found computationally in kinetic dependencies of methane-reforming catalytic reactions (steam and dry reforming) using the conditions of the conservatively perturbed equilibrium (CPE) phenomenon, i.e., at the initial equilibrium concentration of hydrogen or carbon monoxide. The influence of the pressure, temperature, flow rate and composition of the initial mixture on the position of the CPE point (the extremum point) was investigated over a wide domain of parameters. The CPE phenomenon significantly increases the product concentration (H₂ and CO) at the reactor length, which is significantly less than the reactor length required to reach equilibrium. The CPE point is interpreted as the “turning point” in kinetic behaviour. Recommendations on temperature and pressure regimes are different from the traditional ones related to Le Chatelier’s law. The obtained results provide valuable information on optimal reaction conditions for complex reversible chemical transformations, offering potential applications in chemical engineering processes. Full article

(This article belongs to the Special Issue Catalytic Reforming and Hydrogen Production: From the Past to the Future)

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35 pages, 4527 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Biocatalysis with Unconventional Yeasts

by Cecilia Andreu and Marcel·lí del Olmo

Catalysts 2024, 14(11), 767; https://doi.org/10.3390/catal14110767 - 30 Oct 2024

Cited by 3 | Viewed by 1825

Abstract

Biocatalysis is a green and sustainable technology based on the use of natural substances to catalyze chemical reactions. Humans have been unconsciously using biocatalysis for thousands of years to produce food and alcoholic beverages, but it is only since the 19th century that [...] Read more.

Biocatalysis is a green and sustainable technology based on the use of natural substances to catalyze chemical reactions. Humans have been unconsciously using biocatalysis for thousands of years to produce food and alcoholic beverages, but it is only since the 19th century that we have begun to understand its fundamentals and its enormous potential. In fact, advances in our knowledge of enzymes and metabolic pathways and, in recent decades, the introduction of tools such as bioinformatics, DNA sequencing and protein engineering have made biocatalysis a key strategy in fine chemistry and for the production of active pharmaceutical ingredients. In addition, the discovery of new microorganisms adapted to adverse conditions has also been crucial in advancing this avenue. The present review focuses on the use of unconventional yeasts and their enzymes in the most interesting reactions where biocatalysis is applied. It highlights the advantages of using these microorganisms in industrial chemical processes due to their particular phenotypes, such as their ability to withstand high temperatures and pressures, as well as acidic or alkaline environments, high substrate loads, presence of organic solvents, etc. All this results in a wider range of possible substrates and higher efficiency. Examples of the most important reactions in which their use has been described are included, considering both catalysis by wild-type whole cells or their isolated enzymes and their genetically modified variants. All this information will help to understand the current relevance of unconventional yeasts and their enzymes in biocatalysis. Full article

(This article belongs to the Special Issue Feature Review Papers in Biocatalysis and Enzyme Engineering)

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29 pages, 11136 KiB

Open AccessEditor’s ChoiceArticle

Oxidative Steam Reforming of Methanol over Cu-Based Catalysts

by Matteo Tommasi, Davide Ceriotti, Alice Gramegna, Simge Naz Degerli, Gianguido Ramis and Ilenia Rossetti

Catalysts 2024, 14(11), 759; https://doi.org/10.3390/catal14110759 - 28 Oct 2024

Cited by 3 | Viewed by 1628

Abstract

Several Cu and Ni-based catalysts were synthetized over Ce-based supports, either pure or mixed with different amounts of alumina (1:2 and 1:3 mol/mol). Different metal loadings (10–40 wt%) and preparation methods (wet impregnation, co-precipitation, and flame-spray pyrolysis—FSP) were compared for the oxidative steam [...] Read more.

Several Cu and Ni-based catalysts were synthetized over Ce-based supports, either pure or mixed with different amounts of alumina (1:2 and 1:3 mol/mol). Different metal loadings (10–40 wt%) and preparation methods (wet impregnation, co-precipitation, and flame-spray pyrolysis—FSP) were compared for the oxidative steam reforming of methanol. Characterization of the catalysts has been performed, e.g., through XRD, BET, XPS, TPR, SEM, and EDX analyses. All the catalysts have been tested in a bench-scale continuous setup. The hydrogen yield and methanol conversion obtained have been correlated with the operating conditions, metal content, crystallinity of the catalyst particles, total surface area, and with the interaction of the metal with the support. A Cu loading of 20% wt/wt was optimal, while the presence of alumina was not beneficial, decreasing catalyst activity at low temperatures compared with catalysts supported on pure CeO₂. Ni-based catalysts were a possible alternative, but the activity towards the methanation reaction at relatively high temperatures decreased inevitably the hydrogen yield. Durability and deactivation tests showed that the best-performing catalyst, 20% wt. Cu/CeO₂ prepared through coprecipitation was stable for a long period of time. Full methanol conversion was achieved at 280 °C, and the highest yield of H₂ was ca. 80% at 340 °C, higher than the literature data. Full article

(This article belongs to the Section Catalytic Reaction Engineering)

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13 pages, 14099 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

One-Step Scalable Synthesis of 3D Self-Supported Superaerophobic Ce-Coupled Ni₃S₂/NiS@NF Nanobud Catalyst for Efficient Oxygen Evolution Reaction

by Mengjie Lu, Run Cheng, Li Wang, Dandan Liang, Meng Qin, Bili Wang, Rui Song and Duo Chen

Catalysts 2024, 14(11), 752; https://doi.org/10.3390/catal14110752 - 26 Oct 2024

Viewed by 1234

Abstract

The elaborate design of inexpensive, high-performance electrocatalysts from earth-abundant elements toward oxygen evolution reaction (OER) is critical in various (electro)chemical processes. Herein, a novel binder-free catalyst of Ce-coupled Ni₃S₂/NiS supported on Ni foam (Ce-Ni₃S₂/NiS@NF) is [...] Read more.

The elaborate design of inexpensive, high-performance electrocatalysts from earth-abundant elements toward oxygen evolution reaction (OER) is critical in various (electro)chemical processes. Herein, a novel binder-free catalyst of Ce-coupled Ni₃S₂/NiS supported on Ni foam (Ce-Ni₃S₂/NiS@NF) is successfully synthesized via a facile one-step hydrothermal method that enables practical feasibility with a significant enhancement of OER activity through anchoring Ce dopants on an Ni₃S₂/NiS nanobud host. Ce species coupling can modulate electronic structure, which reduces the reaction energy barrier and optimizes OER catalytic activity. More profoundly, the superhydrophilic and superaerophobic properties of the Ce-Ni₃S₂/NiS@NF electrode further promote mass transfer. As a result, the Ce-Ni₃S₂/NiS@NF electrode exhibits excellent OER activity with a low overpotential of 236 and 350 mV to achieve current densities of 10 and 100 mA cm⁻², respectively, and long-term durability for 24 h in alkaline medium. These results could supply valuable guidelines for the design of other OER catalysts and beyond. Full article

(This article belongs to the Special Issue Recent Advances in Electrocatalysis and Future Perspective)

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12 pages, 2999 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Ordered Mesoporous Nitrogen Dope Carbon Synthesized from Aniline for Stabilization of Ruthenium Species in CO₂ Hydrogenation to Formate

by Arsalan Haider, Ahmad Masudi, Sunghee Ahn, Kwangho Park, Kyung Rok Lee and Kwang-Deog Jung

Catalysts 2024, 14(10), 720; https://doi.org/10.3390/catal14100720 - 15 Oct 2024

Viewed by 1661

Abstract

The hydrogenation of CO₂ to produce formic acid has garnered increasing interest as a means to address climate change and promote the hydrogen economy. This research investigates the nanocasting technique for the synthesis of ordered mesoporous nitrogen-doped carbon (MNC-An). KIT-6 functioned as [...] Read more.

The hydrogenation of CO₂ to produce formic acid has garnered increasing interest as a means to address climate change and promote the hydrogen economy. This research investigates the nanocasting technique for the synthesis of ordered mesoporous nitrogen-doped carbon (MNC-An). KIT-6 functioned as the silica template, while aniline served as the nitrogen–carbon precursor. The resultant MNC-An exhibits cubic Ia3D geometry, possesses significant mesoporosity, and has a high nitrogen content, which is essential for stabilizing ruthenium single atoms. The catalyst exhibited a specific activity of 252 mmol_FAg_cat⁻¹ following a 2 h reaction at 120 °C. Moreover, the catalyst exhibited exceptional relative activity during five recycling experiments while preserving its catalytic efficacy. The atomically dispersed ruthenium and its Ru³⁺ oxidation state demonstrated perseverance both before and after the treatment. The results indicated that the synthesized catalyst possesses potential for the expedited commercialization of CO₂ hydrogenation to produce formic acid. The elevated carbon yield, along with excellent thermal stability, renders it a viable substrate for attaching and stabilizing atomically dispersed ruthenium catalysts. Full article

(This article belongs to the Special Issue Catalysis and Catalytic Processes for Valuable Chemical Production from CO₂)

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12 pages, 2675 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Vertically Ti₃CN@NiFe LDH Nanoflakes as Self-Standing Catalysts for Enhanced Oxygen Evolution Reaction

by Lei He, Qing Tang, Qi Fan, Haizheng Zhuang, Shengchao Wang, Yifan Pang and Kun Liang

Catalysts 2024, 14(10), 708; https://doi.org/10.3390/catal14100708 - 10 Oct 2024

Cited by 2 | Viewed by 2144

Abstract

Hydrogen production from water electrolysis is gaining interest as a source of renewable energy storage due to its high efficiency and low environmental impact. However, the slow kinetics of the oxygen evolution reaction (OER) limits the overall efficiency of electrolyzer systems. This study [...] Read more.

Hydrogen production from water electrolysis is gaining interest as a source of renewable energy storage due to its high efficiency and low environmental impact. However, the slow kinetics of the oxygen evolution reaction (OER) limits the overall efficiency of electrolyzer systems. This study presents the synthesis and characterization of a novel electrocatalyst with a vertical structure, composed of Ti₃CN MXene-modified NiFe-layered double hydroxides (LDHs) supported on nickel foam (NF) for efficient OER applications. The 1.0-LDH/3MXNF catalyst exhibits excellent electrocatalytic activity, achieving a low overpotential of 247 mV at a current density of 100 mA cm⁻² and a favorable Tafel slope of 67.7 mV/dec. This can be attributed to the transfer of excess electrons from Ti₃CN MXene to NiFe-LDH, which reduces the oxidation states of Ni and Fe, resulting in a strong interfacial coupling between Ti₃CN MXene and NiFe-LDHs. Additionally, the electrode exhibited exceptional stability, maintaining constant performance with minimal potential degradation over prolonged operation. These findings underscore the potential of hybrid LDH-MXene systems as advanced electrocatalysts for renewable energy applications, paving the way for further innovations in energy conversion technologies. Full article

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11 pages, 1431 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Efficient Catalytic Conversion of Acetate to Citric Acid and Itaconic Acid by Engineered Yarrowia lipolytica

by Yuchen Ning, Renwei Zhang, Huan Liu, Yue Yu, Li Deng and Fang Wang

Catalysts 2024, 14(10), 710; https://doi.org/10.3390/catal14100710 - 10 Oct 2024

Cited by 1 | Viewed by 1755

Abstract

The bioconversion of agricultural and industrial wastes is considered a green and sustainable alternative method for producing high-value biochemicals. As a major catalytic product of greenhouse gases and a by-product in the fermentation and lignocellulose processing industries, acetate is a promising bioconversion raw [...] Read more.

The bioconversion of agricultural and industrial wastes is considered a green and sustainable alternative method for producing high-value biochemicals. As a major catalytic product of greenhouse gases and a by-product in the fermentation and lignocellulose processing industries, acetate is a promising bioconversion raw material. In this work, endogenous and heterologous enzymes were manipulated in Yarrowia lipolytica to achieve the conversion of acetate to high-value citric acid and itaconic acid, respectively. After the combinational expression of the key enzymes in the acetate metabolic pathway, the citric acid synthesis pathway, and the mitochondrial transport system, acetate could be efficiently converted to citric acid. Coupled with the down-regulation of fatty acid synthase expression in the competitive pathway, more acetyl-CoA flowed into the synthesis of citric acid, and the titer reached 15.11 g/L with a productivity of 0.51 g/g acetate by the engineered Y. lipolytica, which is comparable to the results using glucose as the substrate. On this basis, the heterologous cis-aconitate decarboxylase from Aspergillus terreus was introduced into the engineered Y. lipolytica to achieve the catalytic synthesis of itaconic acid from acetate. Combined with investigating the effects of multiple enzymes in the synthesis pathway, the titer of itaconic acid reached 1.87 g/L with a yield of 0.43 g/g DCW by the final engineered strain, which is the highest reported titer of itaconic acid derived from acetate by engineered microbes in shake flasks. It is demonstrated that acetate has the potential to replace traditional starch-based raw materials for the synthesis of high-value organic acids and our work lays a foundation for the rational utilization of industrial wastes and the catalytic products of greenhouse gases. Full article

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

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13 pages, 3773 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Self-Assembled PDI-COOH/PDINH Supramolecular Composite Photocatalysts for Highly Efficient Photodegradation of Organic Pollutants

by Guodong Zhou, Zetian He, Zeyu Jia, Shiqing Ma, Daimei Chen and Yilei Li

Catalysts 2024, 14(10), 696; https://doi.org/10.3390/catal14100696 - 7 Oct 2024

Viewed by 1355

Abstract

Photocatalytic degradation of organic pollutants is one of the green ways to solve environmental problems. In this study, the PDI-COOH/PDINH composite photocatalysts were successfully synthesized by electrostatic self-assembly. Under visible light irradiation, the degradation efficiency of the optimal PDI-COOH/PDINH sample reached 67%, which [...] Read more.

Photocatalytic degradation of organic pollutants is one of the green ways to solve environmental problems. In this study, the PDI-COOH/PDINH composite photocatalysts were successfully synthesized by electrostatic self-assembly. Under visible light irradiation, the degradation efficiency of the optimal PDI-COOH/PDINH sample reached 67%, which was 1.7 and 1.6 times higher than that of the self-assembled PDINH supramolecule and PDI-COOH supramolecule, respectively. The excellent photocatalytic performance of PDI-COOH/PDINH can be attributed to the enhancement of the separation and transport efficiency of photogenerated carriers by the construction of a heterojunction and the expanded electronic conjugated structure by the combination of organic–organic semiconductors. This study offers a new idea for the preparation of organic–organic composite photocatalysts. Full article

(This article belongs to the Special Issue Exclusive Papers in Green Photocatalysis from China)

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16 pages, 3640 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Cobalt Molybdenum Telluride as an Efficient Trifunctional Electrocatalyst for Seawater Splitting

by Rajarshi Kar, Amideddin Nouralishahi, Harish Singh and Manashi Nath

Catalysts 2024, 14(10), 684; https://doi.org/10.3390/catal14100684 - 2 Oct 2024

Cited by 2 | Viewed by 1688

Abstract

A mixed-metal ternary chalcogenide, cobalt molybdenum telluride (CMT), has been identified as an efficient tri-functional electrocatalyst for seawater splitting, leading to enhanced oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR). The CMT was synthesized by a single step [...] Read more.

A mixed-metal ternary chalcogenide, cobalt molybdenum telluride (CMT), has been identified as an efficient tri-functional electrocatalyst for seawater splitting, leading to enhanced oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR). The CMT was synthesized by a single step hydrothermal technique. Detailed electrochemical studies of the CMT-modified electrodes showed that CMT has a promising performance for OER in the simulated seawater solutions, exhibiting a small overpotential of 385 mV at 20 mA cm⁻², and superior catalyst durability for prolonged period of continuous oxygen evolution. Interestingly, while gas chromatography analysis confirmed the evolution of oxygen in an anodic chamber, it showed that there was no chlorine evolution from these electrodes in alkaline seawater, highlighting the novelty of this catalyst. CMT also displayed remarkable ORR activity in simulated seawater as indicated by its four-electron reduction pathway forming water as the dominant product. One of the primary challenges of seawater splitting is chlorine evolution from the oxidation of dissolved chloride salts. The CMT catalyst successfully and significantly lowers the water oxidation potential, thereby separating the chloride and water oxidation potentials by a larger margin. These results suggest that CMT can function as a highly active tri-functional electrocatalyst with significant stability, making it suitable for clean energy generation and environmental applications using seawater. Full article

(This article belongs to the Special Issue Electrocatalytic Water Oxidation, 2nd Edition)

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14 pages, 1493 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The [PdCl₂(Xantphos)] Complex Efficiently Catalyzed the Methoxycarbonylation of Iodobenzene to Methyl Benzoate

by Luca Pietrobon, Lucio Ronchin and Andrea Vavasori

Catalysts 2024, 14(10), 660; https://doi.org/10.3390/catal14100660 - 24 Sep 2024

Viewed by 1322

Abstract

The [PdCl₂(Xantphos)] complex, in comparison with several [PdCl₂(P–P)] complexes having different diphosphine chelating ligands (P–P), is very active as a catalyst for the carbonylation of iodobenzene to methyl benzoate. The run conditions and the influence of several cocatalysts have [...] Read more.

The [PdCl₂(Xantphos)] complex, in comparison with several [PdCl₂(P–P)] complexes having different diphosphine chelating ligands (P–P), is very active as a catalyst for the carbonylation of iodobenzene to methyl benzoate. The run conditions and the influence of several cocatalysts have been also studied to further improve the catalytic activity. The optimization of the catalytic system allowed to obtain TOFs of ca. 260,000 h⁻¹. The addition of some additives able to reduce the possible catalyst deactivation allowed to increase the TOF of ca. 15%. The best positive results were obtained by adding reducing agents such as ferrocene, which leads to a TOF higher than 300,000 h⁻¹. Full article

(This article belongs to the Special Issue Recent Applications of Metal Catalysts in Organic Synthesis, 2nd Edition)

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14 pages, 2887 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Renewable Diesel Production over Mo-Ni Catalysts Supported on Silica

by John Zafeiropoulos, George Petropoulos, Eleana Kordouli, Labrini Sygellou, Alexis Lycourghiotis and Kyriakos Bourikas

Catalysts 2024, 14(10), 662; https://doi.org/10.3390/catal14100662 - 24 Sep 2024

Viewed by 1650

Abstract

Nickel catalysts promoted with Mo and supported on silica were studied for renewable diesel production from triglyceride biomass, through the selective deoxygenation process. The catalysts were prepared by wet co-impregnation of the SiO₂ with different Ni/(Ni + Mo) atomic ratios (0/0.84/0.91/0.95/0.98/1) and [...] Read more.

Nickel catalysts promoted with Mo and supported on silica were studied for renewable diesel production from triglyceride biomass, through the selective deoxygenation process. The catalysts were prepared by wet co-impregnation of the SiO₂ with different Ni/(Ni + Mo) atomic ratios (0/0.84/0.91/0.95/0.98/1) and a total metal content equal to 50%. They were characterized by XRD, XPS, N₂ physisorption, H₂-TPR, and NH₃-TPD. Evaluation of the catalysts for the transformation of sunflower oil to renewable (green) diesel took place in a high-pressure semi-batch reactor, under solvent-free conditions. A very small addition of Mo, namely the synergistic Ni/(Ni + Mo) atomic ratio equal to 0.95, proved to be the optimum one for a significant enhancement of the catalytic performance of the metallic Ni/SiO₂ catalyst, achieving 98 wt.% renewable diesel production. This promoting action of Mo has been attributed to the significant increase of the metallic Ni active phase surface area, the suitable regulation of surface acidity, the acceleration of the hydro-deoxygenation pathway (HDO), the creation of surface oxygen vacancies, and the diminution of coke formation provoked by Mo addition. Full article

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

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16 pages, 4499 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Modular Photocatalytic Reactor for the Removal of Estrogens from Aqueous Solutions

by Liliana Bobirică, Cristina Orbeci, Cristian Pîrvu, Alexandra Constantinescu, Elena Iuliana Bîru, Giovanina Iuliana Ionică, Ecaterina Matei, Andrei Constantin Berbecaru and Constantin Bobirică

Catalysts 2024, 14(10), 661; https://doi.org/10.3390/catal14100661 - 24 Sep 2024

Cited by 1 | Viewed by 1283

Abstract

Estrogens, widely used for therapeutic or contraceptive purposes, act as endocrine disruptors in aquatic systems and have adverse effects on a wide range of living organisms. Wastewater insufficiently treated by conventional methods is the main way for estrogens to enter aquatic systems. Therefore, [...] Read more.

Estrogens, widely used for therapeutic or contraceptive purposes, act as endocrine disruptors in aquatic systems and have adverse effects on a wide range of living organisms. Wastewater insufficiently treated by conventional methods is the main way for estrogens to enter aquatic systems. Therefore, the purpose of this paper is to develop a novel photocatalytic system for the removal of the estrogenic mixture estradiol valerate/norgestrel from wastewater. The photocatalytic modules are operated in a plug flow reactor system under a UV-A radiation field, and the photocatalyst (TiO₂, ZnO or TiO₂/ZnO) is immobilized on an inert support of glass balls that are strung on stainless-steel wire and arranged in rows along the photocatalytic modules. The photocatalysts were synthesized by the sol–gel method and then deposited on the inert glass support by the hot method, after which it was calcined for two hours at a temperature of 500 °C. The experimental results showed that the efficiency of photocatalytic degradation largely depends on the dose of photocatalyst. The dose of photocatalyst can be adjusted by adding or removing photocatalytic modules, each of which have an approximately equal amount of photocatalyst. The best result was obtained for the TiO₂/ZnO photocatalyst, the organic substrate being practically mineralized in 120 min, for which only two photocatalytic modules are needed. Full article

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

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15 pages, 8013 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Shining a Light on Sewage Treatment: Building a High-Activity and Long-Lasting Photocatalytic Reactor with the Elegance of a “Kongming Lantern”

by Xiaohan Xu, Yi Wang, Zhuo Deng, Jin Wang, Xile Wei, Peng Wang and Dun Zhang

Catalysts 2024, 14(9), 645; https://doi.org/10.3390/catal14090645 - 21 Sep 2024

Viewed by 1182

Abstract

Photocatalysis is a promising technology for efficient sewage treatment, and designing a reactor with a stable loading technique is crucial for achieving long-term stability. However, there is a need to improve the current state of the art in both reactor design and loading [...] Read more.

Photocatalysis is a promising technology for efficient sewage treatment, and designing a reactor with a stable loading technique is crucial for achieving long-term stability. However, there is a need to improve the current state of the art in both reactor design and loading techniques to ensure reliable and efficient performance. In this study, we propose an innovative solution by employing polydimethylsiloxane as a bonding layer on a substrate of 3D-printed polyacrylic resin. By means of mechanical extrusion, the active layer interacts with the bonding layer, ensuring a stable loading of the active layer onto the substrate. Simultaneously, 3D printing technology is utilized to construct a photocatalytic reactor resembling a “Kongming Lantern”, guaranteeing both high activity and durability. The reactor exhibited remarkable performance in degrading organic dyes and eliminating microbes and displayed a satisfactory purification effect on real water samples. Most significantly, it maintained its catalytic activity even after 50 weeks of cyclic degradation. This study contributes to the development of improved photocatalysis technologies for long-term sewage treatment applications. Full article

(This article belongs to the Special Issue Catalysts for Water and Air Pollution Control: Present and Future, 2nd Edition)

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12 pages, 2130 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Superhydrophobic Surface Modification of a Co-Ru/SiO₂ Catalyst for Enhanced Fischer-Tropsch Synthesis

by Pawarat Bootpakdeetam, Oluchukwu Virginia Igboenyesi, Brian H. Dennis and Frederick M. MacDonnell

Catalysts 2024, 14(9), 638; https://doi.org/10.3390/catal14090638 - 19 Sep 2024

Cited by 2 | Viewed by 1713

Abstract

Commercial silica support pellets were impregnated and calcined to contain cobalt oxide and ruthenium oxide for Fischer-Tropsch synthesis (FTS). The precatalyst pellets were split evenly into two groups, the control precatalyst (c-precat) and silylated precatalyst (s-precat), which were treated with 1H,1H, 2H, 2H-perfluorooctyltriethoxysilane [...] Read more.

Commercial silica support pellets were impregnated and calcined to contain cobalt oxide and ruthenium oxide for Fischer-Tropsch synthesis (FTS). The precatalyst pellets were split evenly into two groups, the control precatalyst (c-precat) and silylated precatalyst (s-precat), which were treated with 1H,1H, 2H, 2H-perfluorooctyltriethoxysilane (PFOS) in toluene. The samples of powderized s-precat were superhydrophobic, as determined by the water droplet contact angle (>150°) and sliding angle (<1°). Thermal analysis revealed the PFOS groups to be thermally stable up to 400 °C and temperature programmed reduction (TPR) studies showed that H₂ reduction of the cobalt oxide to cobalt was enhanced at lower temperatures relative to the untreated c-precat. The two active catalysts were examined for their FTS performance in a tubular fixed-bed reactor after in situ reduction at 400 °C for 16 h in flowing H₂ to give the active catalysts c-cat and s-cat. The FTS runs were performed under identical conditions (255 °C, 2.1 MPa, H₂/CO = 2.0, gas hourly space velocity (GHSV) 510 h^–1) for 5 days. Each catalyst was examined in three runs (n = 3) and the mean values with error data are reported. S-cat showed a higher selectivity for C₅₊ products (64 vs. 54%) and lower selectivity for CH₄ (11 vs. 17%), CO₂ (2 % vs. 4 %), and olefins (8% vs. 15%) than c-cat. S-cat also showed higher CO conversion, at 37% compared to 26%, leading to a 64% increase in the C₅₊ productivity measured as g C₅₊ products per g catalyst per hour. An analysis of the temperature differential between the catalyst bed and external furnace temperature showed that s-cat was substantially more active (DT_initial = 29 °C) and stable over the 5-day run (DT_final = 22 °C), whereas the attenuated activity of c-cat (DT_initial = 16 °C) decayed steadily over 3 days until it was barely active (DT_final < 5 °C). A post-run surface analysis of s-cat revealed no change in the water contact angle or sliding angle, indicating that the FTS operation did not degrade the PFOS surface treatment. Full article

(This article belongs to the Special Issue Catalysis for Selective Hydrogenation of CO and CO₂, 2nd Edition)

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31 pages, 3833 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Transition Metal-Promoted LDH-Derived CoCeMgAlO Mixed Oxides as Active Catalysts for Methane Total Oxidation

by Marius C. Stoian, Cosmin Romanitan, Katja Neubauer, Hanan Atia, Constantin Cătălin Negrilă, Ionel Popescu and Ioan-Cezar Marcu

Catalysts 2024, 14(9), 625; https://doi.org/10.3390/catal14090625 - 17 Sep 2024

Cited by 2 | Viewed by 1521

Abstract

A series of M(x)CoCeMgAlO mixed oxides with different transition metals (M = Cu, Fe, Mn, and Ni) with an M content x = 3 at. %, and another series of Fe(x)CoCeMgAlO mixed oxides with Fe contents x ranging from 1 to 9 at. [...] Read more.

A series of M(x)CoCeMgAlO mixed oxides with different transition metals (M = Cu, Fe, Mn, and Ni) with an M content x = 3 at. %, and another series of Fe(x)CoCeMgAlO mixed oxides with Fe contents x ranging from 1 to 9 at. % with respect to cations, while keeping constant in both cases 40 at. % Co, 10 at. % Ce and Mg/Al atomic ratio of 3 were prepared via thermal decomposition at 750 °C in air of their corresponding layered double hydroxide (LDH) precursors obtained by coprecipitation. They were tested in a fixed bed reactor for complete methane oxidation with a gas feed of 1 vol.% methane in air to evaluate their catalytic performance. The physico-structural properties of the mixed oxide samples were investigated with several techniques, such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX), elemental mappings, inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction under hydrogen (H₂-TPR) and nitrogen adsorption–desorption at −196 °C. XRD analysis revealed in all the samples the presence of Co₃O₄ crystallites together with periclase-like and CeO₂ phases, with no separate M-based oxide phase. All the cations were distributed homogeneously, as suggested by EDX measurements and elemental mappings of the samples. The metal contents, determined by EDX and ICP-OES, were in accordance with the theoretical values set for the catalysts’ preparation. The redox properties studied by H₂-TPR, along with the surface composition determined by XPS, provided information to elucidate the catalytic combustion properties of the studied mixed oxide materials. The methane combustion tests showed that all the M-promoted CoCeMgAlO mixed oxides were more active than the M-free counterpart, the highest promoting effect being observed for Fe as the doping transition metal. The Fe(x)CoCeMgAlO mixed oxide sample, with x = 3 at. % Fe displayed the highest catalytic activity for methane combustion with a temperature corresponding to 50% methane conversion, T₅₀, of 489 °C, which is ca. 40 °C lower than that of the unpromoted catalyst. This was attributed to its superior redox properties and lowest activation energy among the studied catalysts, likely due to a Fe–Co–Ce synergistic interaction. In addition, long-term tests of Fe(3)CoCeMgAlO mixed oxide were performed, showing good stability over 60 h on-stream. On the other hand, the addition of water vapors in the feed led to textural and structural changes in the Fe(3)CoCeMgAlO system, affecting its catalytic performance in methane complete oxidation. At the same time, the catalyst showed relatively good recovery of its catalytic activity as soon as the water vapors were removed from the feed. Full article

(This article belongs to the Collection Nanocatalysis Towards Energy Transition and Environmental Sustainability)

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12 pages, 5519 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Biomass-Derived Co/MPC Nanocomposites for Effective Sensing of Hydrogen Peroxide via Electrocatalysis Reduction

by Mei Wang, Jin Cai, Lihua Jiao and Quan Bu

Catalysts 2024, 14(9), 624; https://doi.org/10.3390/catal14090624 - 16 Sep 2024

Viewed by 1292

Abstract

Utilizing the full potential of reproducible biomass resources is crucial for the sustainable development of humanity. In this study, biochar (MPC) was prepared through the microwave-assisted pyrolysis of sugarcane bagasse. Subsequently, Co nanoparticles were introduced by microwave-assisted hydrothermal treatment to form a highly [...] Read more.

Utilizing the full potential of reproducible biomass resources is crucial for the sustainable development of humanity. In this study, biochar (MPC) was prepared through the microwave-assisted pyrolysis of sugarcane bagasse. Subsequently, Co nanoparticles were introduced by microwave-assisted hydrothermal treatment to form a highly dispersive Co/MPC material. Characterization results indicated that Co nanoparticles were wrapped by thin carbon layers and uniformly dispersed on a carbon-based skeleton via a microwave-assisted hydrothermal synthesis approach, providing high-activity space. Thus, the prepared material was limited to glassy carbon; on the electrode surface, a cobalt-based sensing platform (Co/MPC/GCE) was built. On the basis of this constructed sensing platform, a linear equation was fitted by the concentration change of current signal I and H₂O₂. The linear range was 0.55–100.05 mM; the detection limit was 1.38 μM (S/N = 3); and the sensitivity was 103.45 μA cm⁻² mM⁻¹. In addition, the effect this sensor had on H₂O₂ detection of actual water samples was conducted by using a standard addition recovery method; results disclosed that the recovery rate and RSD of H₂O₂ in tap water samples were 94.0–97.6% and 4.1–6.5%, respectively. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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11 pages, 1981 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Continuous Flow Synthesis of Furfuryl Ethers over Pd/C Catalysts via Reductive Etherification of Furfural in Ethanol

by Ayoub Hassine, Anas Iben Ayad, Aïssa Ould Dris, Denis Luart and Erwann Guénin

Catalysts 2024, 14(9), 617; https://doi.org/10.3390/catal14090617 - 13 Sep 2024

Cited by 1 | Viewed by 1866

Abstract

Furfural has become one of the most promising building blocks directly derived from biomass. It can be transformed into numerous important biobased chemicals. Among them, furfuryl ethers such as furfuryl ethyl ether (FEE) and tetrahydrofurfuryl ethyl ether (THFEE) are considered to be attractive [...] Read more.

Furfural has become one of the most promising building blocks directly derived from biomass. It can be transformed into numerous important biobased chemicals. Among them, furfuryl ethers such as furfuryl ethyl ether (FEE) and tetrahydrofurfuryl ethyl ether (THFEE) are considered to be attractive derivatives, notably as fuel components, due to their high stability and high octane numbers. Therefore, the production of furfuryl ethers from furfural via a hydrogenation route is an important academic and industrial challenge and requires the deployment of new catalytic processes under green and competitive reaction conditions. The existing processes are based on a two-step process combining hydrogenation and reaction with a strong Bronsted acid catalyst in batch conditions. For the first time, a continuous flow one-step process has been elaborated for the conversion of furfural directly into furfuryl ethers based on reductive etherification. The present work explores the catalytic performance in a continuous flow of commercial palladium catalysts supported on activated carbon for the catalytic reductive etherification of furfural with ethanol in the presence of trifluoroacetic acid. The chemical and engineering aspects, such as the mechanisms and reaction conditions, will be discussed. Full article

(This article belongs to the Special Issue Industrial Applications of High-Value Added Biomass Conversion)

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18 pages, 4620 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Fractal Behavior of Nanostructured Pt/TiO₂ Catalysts: Synthesis, Characterization and Evaluation of Photocatalytic Hydrogen Generation

by Anca Vasile, Gianina Dobrescu, Veronica Bratan, Mircea Teodorescu, Cornel Munteanu, Irina Atkinson, Catalin Negrila, Florica Papa and Ioan Balint

Catalysts 2024, 14(9), 619; https://doi.org/10.3390/catal14090619 - 13 Sep 2024

Cited by 1 | Viewed by 1680

Abstract

The fractal characterization of supported nanoparticles is a useful tool for obtaining structural and morphological information that strongly impacts catalytic properties. We have synthesized and characterized Pt supported on TiO₂ nanostructures. Triblock copolymers with thermosensitive properties were used as templating agents during [...] Read more.

The fractal characterization of supported nanoparticles is a useful tool for obtaining structural and morphological information that strongly impacts catalytic properties. We have synthesized and characterized Pt supported on TiO₂ nanostructures. Triblock copolymers with thermosensitive properties were used as templating agents during the synthesis process. In addition to the several techniques used for the characterization of the materials, we carried out fractal analysis. The prepared materials showed a reduction in the band gap of TiO₂ from 3.44 to 3.01 eV. The extended absorption in the 500–700 nm regions is mostly attributed to the presence of supported Pt nanoparticles. The ability of the nanostructured Pt/TiO₂ catalysts to generate H₂ in an aqueous solution was evaluated. The test reaction was carried out in the presence of methanol, as a hole scavenger, under simulated solar light. Pt/TiO₂-3TB shows the highest rate of H₂ (4.17 mmol h⁻¹ g_cat⁻¹) when compared to Pt/TiO₂-0TB (3.65 mmol h⁻¹ g_cat⁻¹) and Pt/TiO₂-6TB (2.29 mmol h⁻¹ g_cat⁻¹) during simulated solar light irradiation. Pt/TiO₂-3TB exhibits a more structured organization (fractal dimensions of 1.65–1.74 nm at short scales, 1.27–1.30 nm at long scales) and a distinct fractal behavior. The generation of hydrogen via photocatalysis can be linked to the fractal characteristics. 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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33 pages, 6114 KiB

Open AccessEditor’s ChoiceArticle

Roles of Catalysts and Feedstock in Optimizing the Performance of Heavy Fraction Conversion Processes: Fluid Catalytic Cracking and Ebullated Bed Vacuum Residue Hydrocracking

by Dicho Stratiev, Ivelina Shishkova, Georgi Argirov, Rosen Dinkov, Mihail Ivanov, Sotir Sotirov, Evdokia Sotirova, Veselina Bureva, Svetoslav Nenov, Krassimir Atanassov, Denis Stratiev and Svetlin Vasilev

Catalysts 2024, 14(9), 616; https://doi.org/10.3390/catal14090616 - 12 Sep 2024

Cited by 3 | Viewed by 1779

Abstract

Petroleum refining has been, is still, and is expected to remain in the next decades the main source of energy required to drive transport for mankind. The demand for automotive and aviation fuels has urged refiners to search for ways to extract more [...] Read more.

Petroleum refining has been, is still, and is expected to remain in the next decades the main source of energy required to drive transport for mankind. The demand for automotive and aviation fuels has urged refiners to search for ways to extract more light oil products per barrel of crude oil. The heavy oil conversion processes of ebullated bed vacuum residue hydrocracking (EBVRHC) and fluid catalytic cracking (FCC) can assist refiners in their aim to produce more transportation fuels and feeds for petrochemistry from a ton of petroleum. However, a good understanding of the roles of feed quality and catalyst characteristics is needed to optimize the performance of both heavy oil conversion processes. Three knowledge discovery database techniques—intercriteria and regression analyses, and artificial neural networks—were used to evaluate the performance of commercial FCC and EBVRHC in processing 19 different heavy oils. Seven diverse FCC catalysts were assessed using a cascade and parallel fresh catalyst addition system in an EBVRHC unit. It was found that the vacuum residue conversion in the EBVRHC depended on feed reactivity, which, calculated on the basis of pilot plant tests, varied by 16.4%; the content of vacuum residue (VR) in the mixed EBVRHC unit feed (each 10% fluctuation in VR content leads to an alteration in VR conversion of 1.6%); the reaction temperature (a 1 °C deviation in reaction temperature is associated with a 0.8% shift in VR conversion); and the liquid hourly space velocity (0.01 h-1 change of LHSV leads to 0.85% conversion alteration). The vacuum gas oil conversion in the FCC unit was determined to correlate with feed crackability, which, calculated on the basis of pilot plant tests, varied by 8.2%, and the catalyst ΔCoke (each 0.03% ΔCoke increase reduces FCC conversion by 1%), which was unveiled to depend on FCC feed density and equilibrium FCC micro-activity. The developed correlations can be used to optimize the performance of FCC and EBVRHC units by selecting the appropriate feed slate and catalyst. Full article

(This article belongs to the Section Catalytic Reaction Engineering)

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12 pages, 3636 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Improving the Catalytic Efficiency of an AA9 Lytic Polysaccharide Monooxygenase MtLPMO9G by Consensus Mutagenesis

by Yao Meng, Wa Gao, Xiaohua Liu, Tang Li, Kuikui Li and Heng Yin

Catalysts 2024, 14(9), 614; https://doi.org/10.3390/catal14090614 - 12 Sep 2024

Viewed by 952

Abstract

Cellulose is one of the most abundant renewable resources in nature. However, its recalcitrant crystalline structure hinders efficient enzymatic depolymerization. Unlike cellulases, lytic polysaccharide monooxygenases (LPMOs) can oxidatively cleave glycosidic bonds in the crystalline regions of cellulose, playing a crucial role in its [...] Read more.

Cellulose is one of the most abundant renewable resources in nature. However, its recalcitrant crystalline structure hinders efficient enzymatic depolymerization. Unlike cellulases, lytic polysaccharide monooxygenases (LPMOs) can oxidatively cleave glycosidic bonds in the crystalline regions of cellulose, playing a crucial role in its enzymatic depolymerization. An AA9 LPMO from Myceliophthora thermophila was previously identified and shown to exhibit a highly efficient catalytic performance. To further enhance its catalytic efficiency, consensus mutagenesis was applied. Compared with the wild-type enzyme, the oxidative activities of mutants A165S and P167N increased by 1.8-fold and 1.4-fold, respectively, and their catalytic efficiencies (k_cat/K_m) improved by 1.6-fold and 1.2-fold, respectively. The mutants also showed significantly enhanced activity in the synergistic degradation of cellulose with cellobiohydrolase. Additionally, the P167N mutant exhibited better H₂O₂ tolerance. A molecular dynamics analysis revealed that the increased activity of mutants A165S and P167N was due to the closer proximity of the active center to the substrate post-mutation. This study demonstrates that selecting appropriate mutation sites via a semi-rational design can significantly improve LPMO activity, providing valuable insights for the protein engineering of similar enzymes. Full article

(This article belongs to the Section Biocatalysis)

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20 pages, 4832 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Green Catalysts and/or Green Solvents for Sustainable Multi-Component Reactions

by Gatien Messire, Emma Caillet and Sabine Berteina-Raboin

Catalysts 2024, 14(9), 593; https://doi.org/10.3390/catal14090593 - 4 Sep 2024

Cited by 8 | Viewed by 3586

Abstract

Here, we describe some well-known multicomponent reactions and the progress made over the past decade to make these processes even more environmentally friendly. We focus on the Mannich, Hantzsch, Biginelli, Ugi, Passerini, Petasis, and Groebke–Blackburn–Bienaymé reactions. After describing the origin of the reactions [...] Read more.

Here, we describe some well-known multicomponent reactions and the progress made over the past decade to make these processes even more environmentally friendly. We focus on the Mannich, Hantzsch, Biginelli, Ugi, Passerini, Petasis, and Groebke–Blackburn–Bienaymé reactions. After describing the origin of the reactions and their mechanisms, we summarize some advances in terms of the eco-compatibility of these different MCRs. These are followed by examples of some reactions, considered as variants, which are less well documented but which are promising in terms of structures generated or synthetic routes. Full article

(This article belongs to the Special Issue Recent Applications of Metal Catalysts in Organic Synthesis, 2nd Edition)

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34 pages, 3135 KiB

Open AccessFeature PaperEditor’s ChoiceReview

The Role of Catalysts in Life Cycle Assessment Applied to Biogas Reforming

by Sergio Nogales-Delgado and Juan Félix González González

Catalysts 2024, 14(9), 592; https://doi.org/10.3390/catal14090592 - 3 Sep 2024

Cited by 2 | Viewed by 1549

Abstract

The real implementation of biogas reforming at an industrial scale to obtain interesting products (like hydrogen or syngas) is a developing research field where multidisciplinary teams are continuously adding improvements and innovative technologies. These works can contribute to the proliferation of green technologies [...] Read more.

The real implementation of biogas reforming at an industrial scale to obtain interesting products (like hydrogen or syngas) is a developing research field where multidisciplinary teams are continuously adding improvements and innovative technologies. These works can contribute to the proliferation of green technologies where the circular economy and sustainability are key points. To assess the sustainability of these processes, there are different tools like life cycle assessment (LCA), which involves a complete procedure where even small details count to consider a certain technology sustainable or not. The aim of this work was to review works where LCA is applied to different aspects of biogas reforming, focusing on the role of catalysts, which are essential to improve the efficiency of a certain process but can also contribute to its environmental impact. In conclusion, catalysts have an influence on LCA through the improvement of catalytic performance and the impact of their production, whereas other aspects related to biogas or methane reforming could equally affect their catalytic durability or reusability, with a subsequent effect on LCA. Further research about this subject is required, as this is a continuously changing technology with plenty of possibilities, in order to homogenize this research field. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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11 pages, 1027 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Catalytic Valorization of Organic Solid Waste: A Pilot-Scale Run of Sugarcane Bagasse

by Zhaofei Li, Ali Omidkar and Hua Song

Catalysts 2024, 14(9), 568; https://doi.org/10.3390/catal14090568 - 28 Aug 2024

Viewed by 1345

Abstract

Organic solid waste treatment is crucial for enhancing environmental sustainability, promoting economic growth, and improving public health. Following our previous organic solid waste upgrading technique, a further two-step pilot-scale run, using sugarcane bagasse as the feedstock, has been successfully conducted with long-term stability. [...] Read more.

Organic solid waste treatment is crucial for enhancing environmental sustainability, promoting economic growth, and improving public health. Following our previous organic solid waste upgrading technique, a further two-step pilot-scale run, using sugarcane bagasse as the feedstock, has been successfully conducted with long-term stability. Firstly, the sugarcane bagasse was treated under mild conditions (400 °C and 1 bar of CH₄), and this catalytic Methanolysis treatment resulted in a bio-oil with a yield of 60.5 wt.%. Following that, it was subjected to a catalytic Methano-Refining process (400 °C and 50 bar of CH₄) to achieve high-quality renewable fuel with a liquid yield of 95.0 wt.%. Additionally, this renewable fuel can be regarded as an ideal diesel component with a high cetane number, high heating values, a low freezing point, low density and viscosity, and low oxygen, nitrogen, and sulfur contents. The successful pilot-scale catalytic upgrading of sugarcane bagasse further verified the effectiveness of this methane-assisted organic solid waste upgrading technique and confirmed the high flexibility of this innovative technology for processing a wide spectrum of agricultural and forestry residues. This study will shed light on the further valorization of organic solid waste and other carbonaceous materials. Full article

(This article belongs to the Special Issue Catalyzing the Sustainable Process Paradigm)

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15 pages, 2562 KiB

Open AccessEditor’s ChoiceArticle

Sludge Recycling from Non-Lime Purification of Electrolysis Wastewater: Bridge from Contaminant Removal to Waste-Derived NO_X SCR Catalyst

by Ju Gao, Fucheng Sun, Pei Liu, Jizhi Zhou and Yufeng Zhang

Catalysts 2024, 14(8), 535; https://doi.org/10.3390/catal14080535 - 17 Aug 2024

Viewed by 4472

Abstract

Catalysts for the selective catalytic reduction (NO_X SCR) of nitrogen oxides can be obtained from sludge in industrial waste treatment, and, due to the complex composition of sludge, NO_X SCR shows various SCR efficiencies. In the current work, an SCR catalyst [...] Read more.

Catalysts for the selective catalytic reduction (NO_X SCR) of nitrogen oxides can be obtained from sludge in industrial waste treatment, and, due to the complex composition of sludge, NO_X SCR shows various SCR efficiencies. In the current work, an SCR catalyst developed from the sludge produced with Fe/C micro-electrolysis Fenton technology (MEF) in wastewater treatment was investigated, taking into account various sludge compositions, Fe/C ratios, and contaminant contents. It was found that, at about 300 °C, the NO_X removal rate could reach 100% and there was a wide decomposition temperature zone. The effect of individual components of electroplating sludge, i.e., P, Fe and Ni, on NO_X degradation performance of the obtained solids was investigated. It was found that the best effect was achieved when the Fe/P was 8/3 wt%, and variations in the Ni content had a limited effect on the NO_X degradation performance. When the Fe/C was 1:2 and the Fe/C/P was 1:2:0.4, the electroplating sludge formed after treatment with Fe/C MEF provided the best NO_X removal rate at 100%. Moreover, the characterization results show that the activated carbon was also involved in the catalytic reduction degradation of NO_X. An excessive Fe content may cause agglomeration on the catalyst surface and thus affect the catalytic efficiency. The addition of P effectively reduces the catalytic reaction temperature, and the formation of phosphate promotes the generation of adsorbed oxygen, which in turn contributes to improvements in catalytic efficiency. Therefore, our work suggests that controlling the composition in the sludge is an efficient way to modulate SCR catalysis, providing a bridge from contaminant-bearing waste to efficient catalyst. Full article

(This article belongs to the Special Issue Homogeneous and Heterogeneous Catalytic Oxidation and Reduction)

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49 pages, 2859 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Layered MX₂-Based Materials (M = Mo, W and X = S, Se, Te) for Emerging Optoelectronic and Photo(electro)catalytic Applications

by Felipe M. Pinto, Mary C. M. D. de Conti, Wyllamanney S. Pereira, Júlio C. Sczancoski, Marina Medina, Patricia G. Corradini, Juliana F. de Brito, André E. Nogueira, Márcio S. Góes, Odair P. Ferreira, Lucia H. Mascaro, Fernando Wypych and Felipe A. La Porta

Catalysts 2024, 14(6), 388; https://doi.org/10.3390/catal14060388 - 17 Jun 2024

Cited by 13 | Viewed by 4613

Abstract

Transition metal dichalcogenides (TMDCs), represented by MX₂ (where M = Mo, W and X = S, Se, and Te), and more recently, their moiré superlattices (i.e., formed by superimposing layers of TMDCs with different rotation angles) have attracted considerable interest due to [...] Read more.

Transition metal dichalcogenides (TMDCs), represented by MX₂ (where M = Mo, W and X = S, Se, and Te), and more recently, their moiré superlattices (i.e., formed by superimposing layers of TMDCs with different rotation angles) have attracted considerable interest due to their excellent physical properties and unique nanoscale functionalities. Compared to graphene, the literature indicates that TMDCs offer a competitive advantage in optoelectronic technologies, primarily owing to their compositionally controlled non-zero bandgap. These two-dimensional (2D) nanostructured single or multiple layers exhibit remarkable properties that differ from their bulk counterparts. Moreover, stacking different TMDC monolayers also forms heterostructures and introduces unique quantum effects and extraordinary electronic properties, which is particularly promising for next-generation optoelectronic devices and photo(electro)catalytic applications. Therefore, in this review, we also highlight the new possibilities in the formation of 2D/2D heterostructures of MX₂-based materials with moiré patterns and discuss the main critical challenges related to the synthesis and large-scale applications of layered MX₂ and MX₂-based composites to spur significant advances in emerging optoelectronic and photo(electro)catalytic applications. Full article

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38 pages, 7801 KiB

Open AccessEditor’s ChoiceReview

Ethylene Oligomerization Catalyzed by Different Homogeneous or Heterogeneous Catalysts

by Anfeng Peng, Zheng Huang and Gang Li

Catalysts 2024, 14(4), 268; https://doi.org/10.3390/catal14040268 - 17 Apr 2024

Cited by 8 | Viewed by 5126

Abstract

Linear α-olefins (LAOs) are linear alkenes with double bonds at the ends of the molecular chains. LAOs with different chain lengths can be widely applied in various fields. Ethylene oligomerization has become the main process for producing LAOs. In this review, different homogeneous [...] Read more.

Linear α-olefins (LAOs) are linear alkenes with double bonds at the ends of the molecular chains. LAOs with different chain lengths can be widely applied in various fields. Ethylene oligomerization has become the main process for producing LAOs. In this review, different homogeneous or heterogeneous catalysts recently reported in ethylene oligomerization with Ni, Fe, Co, Cr, etc., as active centers will be discussed. In the homogeneous catalytic system, we mainly discuss the effects of the molecular structure and the electronic and coordination states of complexes on their catalytic activity and selectivity. The Ni, Fe, and Co homogeneous catalysts are discussed separately based on different ligand types, while the Cr-based homogeneous catalysts are discussed separately for ethylene trimerization, tetramerization, and non-selective oligomerization. In heterogeneous catalytic systems, we mainly concentrate on the influence of various supports (metal–organic frameworks, covalent organic frameworks, molecular sieves, etc.) and different ways to introduce active centers to affect the performance in ethylene oligomerization. Finally, a summary and outlook on ethylene oligomerization catalysts are provided based on the current research. The development of highly selective α-olefin formation processes remains a major challenge for academia and industry. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members and Topical Advisory Panel Members of Catalysts in Section "Catalytic Materials")

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24 pages, 6903 KiB

Open AccessEditor’s ChoiceReview

Review of Mechanism Investigations and Catalyst Developments for CO₂ Hydrogenation to Alcohols

by Guoqing Cui, Yingjie Lou, Mingxia Zhou, Yuming Li, Guiyuan Jiang and Chunming Xu

Catalysts 2024, 14(4), 232; https://doi.org/10.3390/catal14040232 - 31 Mar 2024

Cited by 9 | Viewed by 4551

Abstract

Heterogeneous thermal-catalytic CO₂ hydrogenation to alcohols using renewable energy is a highly attractive approach for recycling greenhouse gases into high-value chemicals and fuels, thereby reducing the dependence on fossil fuels, while simultaneously mitigating the CO₂ emission and environmental problems. Currently, great [...] Read more.

Heterogeneous thermal-catalytic CO₂ hydrogenation to alcohols using renewable energy is a highly attractive approach for recycling greenhouse gases into high-value chemicals and fuels, thereby reducing the dependence on fossil fuels, while simultaneously mitigating the CO₂ emission and environmental problems. Currently, great advances have been made on the heterogeneous catalysts, but an in-depth and more comprehensive understanding to further promote this reaction process is still lacking. Herein, we highlight the thermodynamic and kinetic analysis of CO₂ hydrogenation reaction firstly. Then, various reaction pathways for CO₂ hydrogenation to methanol and higher alcohols (C₂₊ alcohols) have been discussed in detail, respectively, by combining the experimental studies and density functional theory calculations. On this basis, the key factors influencing the reaction performance, such as metal dispersion, support modification, promoter addition and their structural optimization, are summarized on the metal-based and metal-oxide-based catalysts. In addition, the catalytic performance of CO₂ hydrogenation to alcohols and the relationship between structure and properties are mainly summarized and analyzed in the past five years. To conclude, the current challenges and potential strategies in catalyst design, structural characterization and reaction mechanisms are presented for CO₂ hydrogenation to alcohols. Full article

(This article belongs to the Section Industrial Catalysis)

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24 pages, 5671 KiB

Open AccessEditor’s ChoiceArticle

Reduced Siderite Ore Combined with Magnesium Oxide as Support Material for Ni-Based Catalysts; An Experimental Study on CO₂ Methanation

by Kamonrat Suksumrit, Christoph A. Hauzenberger, Srett Santitharangkun and Susanne Lux

Catalysts 2024, 14(3), 206; https://doi.org/10.3390/catal14030206 - 20 Mar 2024

Cited by 1 | Viewed by 2801

Abstract

Ni-based catalysts play a fundamental role in catalytic CO₂ methanation. In this study, the possibility of using siderite ore as a catalyst or catalytic support material for nickel-based catalysts was investigated, aiming at the exploitation of an abundant natural resource. The catalytic [...] Read more.

Ni-based catalysts play a fundamental role in catalytic CO₂ methanation. In this study, the possibility of using siderite ore as a catalyst or catalytic support material for nickel-based catalysts was investigated, aiming at the exploitation of an abundant natural resource. The catalytic performance of Ni-based catalysts with reduced siderite ore as a support was evaluated and compared to MgO as a support material. MgO is known as an effective support material, as it provides access to bifunctional catalysts because of its basicity and high CO₂ adsorption capacity. It was shown that undoped and Ni-doped reduced siderite ore have comparable catalytic activity for CO₂ hydrogenation (20−23%) at 648 K, but show limited selectivity toward methane (<20% for siderite_reduced and 60.2% for Ni/siderite_reduced). When MgO was added to the support material (Ni/siderite_reduced/MgO), both the CO₂ conversion and the selectivity toward methane increased significantly. CO₂ conversions were close to the thermodynamic equilibrium, and methane selectivities of ≥99% were achieved. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis: From Nano- and Cluster-Catalysts to Single-Atom Catalysts)

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19 pages, 21509 KiB

Open AccessEditor’s ChoiceArticle

Ru/Attapulgite as an Efficient and Low-Cost Ammonia Decomposition Catalyst

by Qingfeng Teng, Junkang Sang, Guoxin Chen, Haoliang Tao, Yunan Wang, Hua Li, Wanbing Guan, Changsheng Ding, Fenghua Liu and Liangzhu Zhu

Catalysts 2024, 14(3), 197; https://doi.org/10.3390/catal14030197 - 16 Mar 2024

Cited by 4 | Viewed by 2634

Abstract

On-site hydrogen generation from ammonia decomposition is a promising technology to address the challenges of direct transportation and storage of hydrogen. The main problems with the existing support materials for ammonia decomposition catalysts are their high cost and time-consuming preparation process. In this [...] Read more.

On-site hydrogen generation from ammonia decomposition is a promising technology to address the challenges of direct transportation and storage of hydrogen. The main problems with the existing support materials for ammonia decomposition catalysts are their high cost and time-consuming preparation process. In this work, ammonia decomposition catalysts consisting of in situ-formed nano-Ru particles supported on a naturally abundant mineral fiber, attapulgite (ATP), were proposed and studied. Also, 1 wt.% Ru was uniformly dispersed and anchored onto the surface of ATP fibers via the chemical method. We found that the calcination temperatures of the ATP support before the deposition of Ru resulted in little difference in catalytic performance, while the calcination temperatures of the 1Ru/ATP precursor were found to significantly influence the catalytic performance. The prepared 1 wt.% Ru/ATP catalyst (1Ru/ATP) without calcination achieved an ammonia conversion efficiency of 51% at 500 °C and nearly 100% at 600 °C, with the flow rate of NH₃ being 10 sccm (standard cubic centimeter per minute). A 150 h continuous test at 600 °C showed that the 1Ru/ATP catalyst exhibited good stability with a degradation rate of about 0.01% h⁻¹. The 1Ru/ATP catalyst was integrated with proton ceramic fuel cells (PCFCs). We reported that PCFCs at 650 °C offered 433 mW cm⁻² under H₂ fuel and 398 mW cm⁻² under cracked NH₃ fuel. The overall results suggest low-level Ru-loaded ATP could be an attractive, low-cost, and efficient ammonia decomposition catalyst for hydrogen production. Full article

(This article belongs to the Special Issue Recent Advances and Strategies in the Development of Sustainable Metal Catalysts for Energy, Environment and Generation of High-Value Products)

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19 pages, 10744 KiB

Open AccessEditor’s ChoiceReview

Air-Stable and Highly Active Transition Metal Phosphide Catalysts for Reductive Molecular Transformations

by Takato Mitsudome

Catalysts 2024, 14(3), 193; https://doi.org/10.3390/catal14030193 - 12 Mar 2024

Cited by 5 | Viewed by 3581

Abstract

This review introduces transition metal phosphide nanoparticle catalysts as highly efficient and reusable heterogeneous catalysts for various reductive molecular transformations. These transformations include the hydrogenation of nitriles to primary amines, reductive amination of carbonyl compounds, and biomass conversion, specifically, the aqueous hydrogenation reaction [...] Read more.

This review introduces transition metal phosphide nanoparticle catalysts as highly efficient and reusable heterogeneous catalysts for various reductive molecular transformations. These transformations include the hydrogenation of nitriles to primary amines, reductive amination of carbonyl compounds, and biomass conversion, specifically, the aqueous hydrogenation reaction of mono- and disaccharides to sugar alcohols. Unlike traditional air-unstable non-precious metal catalysts, these are stable in air, eliminating the need for strict anaerobic conditions or pre-reduction. Moreover, when combined with supports, metal phosphides exhibit significantly enhanced activity, demonstrating high activity, selectivity, and durability in these hydrogenation reactions. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members and Topical Advisory Panel Members of Catalysts in Section "Catalysis in Organic and Polymer Chemistry")

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15 pages, 4717 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Ni Doped Co-MOF-74 Synergized with 2D Ti₃C₂T_x MXene as an Efficient Electrocatalyst for Overall Water-Splitting

by Ke Yu, Jingyuan Zhang, Yuting Hu, Lanqi Wang, Xiaofeng Zhang and Bin Zhao

Catalysts 2024, 14(3), 184; https://doi.org/10.3390/catal14030184 - 7 Mar 2024

Cited by 17 | Viewed by 4076

Abstract

Metal-organic framework (MOF)-based materials with abundant pore structure, large specific surface area, and atomically dispersed metal centers are considered as potential electrocatalysts for oxygen-evolution reaction (OER), while their ligand-saturated metal nodes are inert to electrocatalysis. In this work, heteroatom doping and interface engineering [...] Read more.

Metal-organic framework (MOF)-based materials with abundant pore structure, large specific surface area, and atomically dispersed metal centers are considered as potential electrocatalysts for oxygen-evolution reaction (OER), while their ligand-saturated metal nodes are inert to electrocatalysis. In this work, heteroatom doping and interface engineering are proposed to improve the OER performance of Co-MOF-74. Using two-dimensional Ti₃C₂T_x MXene as a conductive support, Ni-doped Co-MOF-74 (CoNi-MOF-74/MXene/NF) was in situ synthesized through a hydrothermal process, which exhibits excellent OER and hydrogen evolution reaction (HER) properties. For OER, the CoNi-MOF-74/MXene/NF achieves a current density of 100 mA/cm² at an overpotential of only 256 mV, and a Tafel slope of 40.21 mV/dec. When used for HER catalysis, the current density of 10 mA/cm² is reached at only 102 mV for the CoNi-MOF-74/MXene/NF. In addition, the two-electrode electrolyzer with CoNi-MOF-74/MXene/NF as both the cathode and anode only requires 1.49 V to reach the current density of 10 mA/cm². This work provides a new approach for the development of bimetallic MOF-based electrocatalysts. Full article

(This article belongs to the Special Issue Green Energy and New Functional Materials through Catalysis for Carbon Neutrality)

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17 pages, 20527 KiB

Open AccessEditor’s ChoiceArticle

Preparation of Proline-Modified UIO−66 Nanomaterials and Investigation of Their Potential in Lipase Immobilization

by Xiaoxiao Dong, Chengnan Zhang, Prasanna J. Patil, Weiwei Li and Xiuting Li

Catalysts 2024, 14(3), 180; https://doi.org/10.3390/catal14030180 - 4 Mar 2024

Cited by 5 | Viewed by 2771

Abstract

Metal–organic frameworks (MOFs) are regarded as excellent carriers for immobilized enzymes due to their substantial specific surface area, high porosity, and easily tunable pore size. Nevertheless, the use of UIO−66 material is significantly limited in immobilized enzymes due to the absence of active [...] Read more.

Metal–organic frameworks (MOFs) are regarded as excellent carriers for immobilized enzymes due to their substantial specific surface area, high porosity, and easily tunable pore size. Nevertheless, the use of UIO−66 material is significantly limited in immobilized enzymes due to the absence of active functional groups on its surface. This study comprised the synthesis of UIO−66 and subsequent modification of the proline (Pro) on UIO−66 through post-synthetic modification. UIO−66 and UIO−66/Pro crystals were employed as matrices to immobilize Rhizopus oryzae lipase (ROL). The contact angle demonstrated that the introduction of Pro onto UIO−66 resulted in favorable conformational changes in the structure of ROL. The immobilized enzyme ROL@UIO−66/Pro, produced via the covalent-bonding method, exhibited greater activity (0.064715 U/mg (about 1.73 times that of the free enzyme)) and stability in the ester hydrolysis reaction. The immobilized enzymes ROL@UIO−66 (131.193 mM) and ROL@UIO−66/Pro (121.367 mM), which were synthesized using the covalent-bonding approach, exhibited a lower K_m and higher substrate affinity compared to the immobilized enzyme ROL@UIO−66/Pro (24.033 mM) produced via the adsorption method. This lays a solid foundation for the industrialization of immobilized enzymes. Full article

(This article belongs to the Special Issue Metal–Organic Framework Materials as Catalysts, 2nd Edition)

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12 pages, 3215 KiB

Open AccessEditor’s ChoiceArticle

Advanced Alkaline Water Electrolysis Stack with Non-Noble Catalysts and Hybrid Electrical Connections of the Single Cells

by Galin Borisov, Vasil Bachvarov, Rashko Rashkov and Evelina Slavcheva

Catalysts 2024, 14(3), 179; https://doi.org/10.3390/catal14030179 - 4 Mar 2024

Cited by 2 | Viewed by 4435

Abstract

In this research, a thin layer of multi-metallic non-precious catalyst is prepared by electroplating from an electrolyte bath containing Ni, Co, and Fe sulfates over pressed commercial nickel foam electrode. The composition of the deposited catalytic film and its morphology are characterized by [...] Read more.

In this research, a thin layer of multi-metallic non-precious catalyst is prepared by electroplating from an electrolyte bath containing Ni, Co, and Fe sulfates over pressed commercial nickel foam electrode. The composition of the deposited catalytic film and its morphology are characterized by scanning electron microscopy (SEM) with energy dispersion X-ray (EDX) techniques. The efficiency of the prepared binder-free electrodes for electrochemical water splitting is investigated in a self-designed short water electrolysis stack with zero-gap configuration of the integrated single cells and hybrid electrical connections. The separator used is a commercial Zirfon Perl 500 membrane, doped with 25% KOH. The performance of the catalyst, the single cells, and the developed electrolyzer stack are examined by steady state polarization curves and stationery galvanostatic stability tests in the temperature range 20 °C to 80 °C. The NiFeCoP multi-metallic alloy demonstrates superior catalytic efficiency compared to the pure nickel foam electrodes and reliable stability with time. The single cells in the stack show identical performance and the cumulative stack parameters strictly follow the theoretical considerations. The applied hybrid electrical connections enable scaling of both the stack voltage and the passing current, which in turn ensures flexibility with regard to the input power and the hydrogen production capacity. Full article

(This article belongs to the Section Electrocatalysis)

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40 pages, 5127 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Coke Management for Dry Reforming of Methane over Ni-Based Catalysts

by Zhenchao Xu and Eun Duck Park

Catalysts 2024, 14(3), 176; https://doi.org/10.3390/catal14030176 - 1 Mar 2024

Cited by 22 | Viewed by 7024

Abstract

The dry reforming of methane (DRM) is a promising method for controlling greenhouse gas emissions by converting CO₂ and CH₄ into syngas, a mixture of CO and H₂. Ni-based catalysts have been intensively investigated for their use in the [...] Read more.

The dry reforming of methane (DRM) is a promising method for controlling greenhouse gas emissions by converting CO₂ and CH₄ into syngas, a mixture of CO and H₂. Ni-based catalysts have been intensively investigated for their use in the DRM. However, they are limited by the formation of carbonaceous materials on their surfaces. In this review, we explore carbon-induced catalyst deactivation mechanisms and summarize the recent research progress in controlling and mitigating carbon deposition by developing coke-resistant Ni-based catalysts. This review emphasizes the significance of support, alloy, and catalyst structural strategies, and the importance of comprehending the interactions between catalyst components to achieve improved catalytic performance and stability. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis for Clean Energy Production and Carbon Dioxide Utilization)

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17 pages, 11501 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Estimating the Anti-Viral Performance of Photocatalytic Materials: The Correlation between Air Purification Efficiency and Severe Acute Respiratory Syndrome Coronavirus 2 Inactivation

by Tsuyoshi Ochiai, Takeshi Nagai, Kengo Hamada, Tomoyuki Tobe, Daisuke Aoki, Kayano Sunada and Hitoshi Ishiguro

Catalysts 2024, 14(3), 163; https://doi.org/10.3390/catal14030163 - 23 Feb 2024

Cited by 3 | Viewed by 4385

Abstract

The coronavirus disease 2019 pandemic has increased the demand for anti-viral products. Photocatalytic materials are used to develop coatings and air purifiers that inactivate severe acute respiratory syndrome coronavirus 2. However, the methods for evaluating the anti-viral performance of photocatalytic materials are time-consuming. [...] Read more.

The coronavirus disease 2019 pandemic has increased the demand for anti-viral products. Photocatalytic materials are used to develop coatings and air purifiers that inactivate severe acute respiratory syndrome coronavirus 2. However, the methods for evaluating the anti-viral performance of photocatalytic materials are time-consuming. To address this problem, herein, we propose a screening test for the anti-viral performance of photocatalytic materials based on the ‘acetaldehyde decomposition test’—an air purification efficiency test used to evaluate the decomposition performance of photocatalytic materials. This test is suitable for screening multiple samples and conditions in a short period. The temporal variation in the acetaldehyde concentration was approximated using an exponential function, similar to the temporal variation in the viral infection values. Thereafter, the slope of the regression line for the acetaldehyde concentration over time was used as an indicator in the screening tests. When the anti-viral performance and acetaldehyde decomposition tests were conducted on the same photocatalytic material, a correlation was observed between the slopes of the regression lines. Overall, the proposed screening test shows good potential for evaluating the anti-viral performance of photocatalytic materials. Full article

(This article belongs to the Special Issue Surface Microstructure Design for Advanced Catalysts)

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32 pages, 4789 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Electrocatalytic Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid by Heterogeneous Catalysts

by Zhiming Ma, Lei Wang, Guangyu Li and Tao Song

Catalysts 2024, 14(2), 157; https://doi.org/10.3390/catal14020157 - 19 Feb 2024

Cited by 13 | Viewed by 4722

Abstract

The utilization and development of biomass resources is an efficient solution to mitigate the fossil energy crisis. Based on the advantages of mild reaction conditions, rapid reaction, and high conversion, the synthesis of 2,5-furandicarboxylic acid (FDCA) by the electrocatalytic oxidation of 5-hydroxymethylfurfural (HMFOR) [...] Read more.

The utilization and development of biomass resources is an efficient solution to mitigate the fossil energy crisis. Based on the advantages of mild reaction conditions, rapid reaction, and high conversion, the synthesis of 2,5-furandicarboxylic acid (FDCA) by the electrocatalytic oxidation of 5-hydroxymethylfurfural (HMFOR) has attracted considerable attention. This review will summarize the recent advances of HMFOR to FDCA, including the reaction pathway and mechanism, as well as the catalytic performance of various heterogeneous electrocatalysts. The challenges and prospects for HMFOR are also focused on. Finally, it is expected that this work may provide guidance for the design of high-efficiency electrocatalysts and thereby accelerate the industrialization process of biomass utilization. Full article

(This article belongs to the Section Catalysis in Organic and Polymer Chemistry)

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26 pages, 5714 KiB

Open AccessEditor’s ChoiceReview

Influence of Impurities in the Chemical Processing Chain of Biomass on the Catalytic Valorisation of Cellulose towards γ-Valerolactone

by Preeti Kashyap, Magdalena Brzezińska, Nicolas Keller and Agnieszka M. Ruppert

Catalysts 2024, 14(2), 141; https://doi.org/10.3390/catal14020141 - 12 Feb 2024

Cited by 8 | Viewed by 3528

Abstract

The conversion of lignocellulosic biomass to valuable chemicals such as levulinic acid and γ-valerolactone is a promising approach for achieving a sustainable circular economy. However, the presence of impurities during the stepwise chemical processing chain of the biomass feedstock can significantly impact both [...] Read more.

The conversion of lignocellulosic biomass to valuable chemicals such as levulinic acid and γ-valerolactone is a promising approach for achieving a sustainable circular economy. However, the presence of impurities during the stepwise chemical processing chain of the biomass feedstock can significantly impact both the hydrolysis and hydrogenation steps implemented to convert the cellulosic feedstock to levulinic acid and further to γ-valerolactone, respectively. This review article explores the effects of those impurities by classifying them into two groups, namely endogenous and exogenous types, based on whether they originate directly from the raw lignocellulosic biomass or arise during its multi-step chemical processing. Endogenous impurities include heavy metals, alkali metals, alkaline earth metals, proteins, and side products from the downstream treatment of cellulose, while exogenous impurities are introduced during physical pre-treatments such as ball milling or during the hydrolysis step, or they might originate from the reactor setup. The specific catalyst deactivation by carbonaceous species such as humins and coke is considered. The mechanisms of impurity-induced catalyst deactivation and by-product formation are thoroughly discussed. Additionally, strategies for minimizing the detrimental effects of impurities on biomass conversion and enhancing catalytic efficiency and stability are also proposed. Full article

(This article belongs to the Section Biomass Catalysis)

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21 pages, 6492 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Recent Modification Strategies of MoS₂ towards Electrocatalytic Hydrogen Evolution

by Lei Liu, Ning Liu, Biaohua Chen, Chengna Dai and Ning Wang

Catalysts 2024, 14(2), 126; https://doi.org/10.3390/catal14020126 - 5 Feb 2024

Cited by 10 | Viewed by 3582

Abstract

Hydrogen production by the electrolysis of water is a green and efficient method, which is of great significance for achieving sustainable development. Molybdenum disulfide (MoS₂) is a promising electrocatalyst for hydrogen evolution reaction (HER) due to its high electrochemical activity, low [...] Read more.

Hydrogen production by the electrolysis of water is a green and efficient method, which is of great significance for achieving sustainable development. Molybdenum disulfide (MoS₂) is a promising electrocatalyst for hydrogen evolution reaction (HER) due to its high electrochemical activity, low cost, and abundant reserves. In comparison to the noble metal Pt, MoS₂ has poorer hydrogen evolution performance in water electrolysis. Therefore, further modifications of MoS₂ need to be developed aiming at improving its catalytic performance. The present work summarizes the modification strategies that have been developed in the past three years on hydrogen evolution from water electrolysis by utilizing MoS₂ as the electrocatalyst and following the two aspects of internal and external modifications. The former includes the strategies of interlayer spacing, sulfur vacancy, phase transition, and element doping, while the latter includes the heterostructure and conductive substrate. If the current gap in this paper’s focus on modification strategies for electrocatalytic hydrogen evolution in water electrolysis is addressed, MoS₂ will perform best in acidic or alkaline media. In addition to that, the present work also discusses the challenges and future development directions of MoS₂ catalysts. Full article

(This article belongs to the Special Issue Recent Advances in Environment and Energy Catalysis)

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16 pages, 3614 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Deep Eutectic Solvents as Catalysts in the Synthesis of Active Pharmaceutical Ingredients and Precursors

by Chiara Falcini and Gonzalo de Gonzalo

Catalysts 2024, 14(2), 120; https://doi.org/10.3390/catal14020120 - 2 Feb 2024

Cited by 11 | Viewed by 4747

Abstract

Deep Eutectic Solvents (DESs) have appeared in recent years as an appealing alternative to classical organic solvents, due to their valuable environmental properties. In addition, these compounds, formed by the combination of one hydrogen bond donor with a hydrogen bond acceptor at a [...] Read more.

Deep Eutectic Solvents (DESs) have appeared in recent years as an appealing alternative to classical organic solvents, due to their valuable environmental properties. In addition, these compounds, formed by the combination of one hydrogen bond donor with a hydrogen bond acceptor at a defined stoichiometric ratio, present other valuable activities not only as a reaction medium. DESs can also be employed as catalysts through hydrogen-bond interactions in different chemical transformations, thus substituting hazardous reagents and solvents. The search for novel and more environmentally friendly catalysts is an area of interest of pharmaceutical chemists, and therefore, the efforts made in the application of DESs as catalysts in the synthesis of APIs or its precursors are described, focusing mainly on condensations, nucleophilic additions to carbonyl moieties, and multicomponent reactions. Full article

(This article belongs to the Special Issue Catalytic Procedures for the Synthesis of Pharmaceutical Active Compounds in Deep Eutectic Solvents)

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20 pages, 1654 KiB

Open AccessEditor’s ChoiceReview

Aldolase: A Desirable Biocatalytic Candidate for Biotechnological Applications

by Moloko G. Mathipa-Mdakane and Lucia Steenkamp

Catalysts 2024, 14(2), 114; https://doi.org/10.3390/catal14020114 - 31 Jan 2024

Cited by 1 | Viewed by 4368

Abstract

The utilization of chemical reactions is crucial in various industrial processes, including pharmaceutical synthesis and the production of fine chemicals. However, traditional chemical catalysts often lack selectivity, require harsh reaction conditions, and lead to the generation of hazardous waste. In response, biocatalysis has [...] Read more.

The utilization of chemical reactions is crucial in various industrial processes, including pharmaceutical synthesis and the production of fine chemicals. However, traditional chemical catalysts often lack selectivity, require harsh reaction conditions, and lead to the generation of hazardous waste. In response, biocatalysis has emerged as a promising approach within green chemistry, employing enzymes as catalysts. Among these enzymes, aldolases have gained attention for their efficiency and selectivity in catalyzing C-C bond formation, making them versatile biocatalysts for diverse biotechnological applications. Despite their potential, challenges exist in aldolase-based biocatalysis, such as limited availability of natural aldolases with desired catalytic properties. This review explores strategies to address these challenges, including immobilization techniques, recombinant expression, and protein engineering approaches. By providing valuable insights into the suitability of aldolases as biocatalysts, this review lays the groundwork for future research and the exploration of innovative strategies to fully harness the potential of aldolases in biotechnology. This comprehensive review aims to attract readers by providing a comprehensive overview of aldolase-based biocatalysis, addressing challenges, and proposing avenues for future research and development. Full article

(This article belongs to the Section Biocatalysis)

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33 pages, 1682 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Mechanistic and Compositional Aspects of Industrial Catalysts for Selective CO₂ Hydrogenation Processes

by Guido Busca, Elena Spennati, Paola Riani and Gabriella Garbarino

Catalysts 2024, 14(2), 95; https://doi.org/10.3390/catal14020095 - 24 Jan 2024

Cited by 13 | Viewed by 4524

Abstract

The characteristics of industrial catalysts for conventional water-gas shifts, methanol syntheses, methanation, and Fischer-Tropsch syntheses starting from syngases are reviewed and discussed. The information about catalysts under industrial development for the hydrogenation of captured CO₂ is also reported and considered. In particular, [...] Read more.

The characteristics of industrial catalysts for conventional water-gas shifts, methanol syntheses, methanation, and Fischer-Tropsch syntheses starting from syngases are reviewed and discussed. The information about catalysts under industrial development for the hydrogenation of captured CO₂ is also reported and considered. In particular, the development of catalysts for reverse water-gas shifts, CO₂ to methanol, CO₂-methanation, and CO₂-Fischer-Tropsch is analyzed. The difference between conventional catalysts and those needed for pure CO₂ conversion is discussed. The surface chemistry of metals, oxides, and carbides involved in this field, in relation to the adsorption of hydrogen, CO, and CO₂, is also briefly reviewed and critically discussed. The mechanistic aspects of the involved reactions and details on catalysts’ composition and structure are critically considered and analyzed. Full article

(This article belongs to the Special Issue Application of Catalysts in CO₂ Capture, Production and Utilization)

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29 pages, 9554 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Biocatalysis for the Synthesis of Active Pharmaceutical Ingredients in Deep Eutectic Solvents: State-of-the-Art and Prospects

by Ningning Zhang, Pablo Domínguez de María and Selin Kara

Catalysts 2024, 14(1), 84; https://doi.org/10.3390/catal14010084 - 19 Jan 2024

Cited by 28 | Viewed by 8809

Abstract

Biocatalysis holds immense potential for pharmaceutical development as it enables synthetic routes to various chiral building blocks with unparalleled selectivity. Therein, solvent and water use account for a large contribution to the environmental impact of the reactions. In the spirit of Green Chemistry [...] Read more.

Biocatalysis holds immense potential for pharmaceutical development as it enables synthetic routes to various chiral building blocks with unparalleled selectivity. Therein, solvent and water use account for a large contribution to the environmental impact of the reactions. In the spirit of Green Chemistry, a transition from traditional highly diluted aqueous systems to intensified non-aqueous media to overcome limitations (e.g., water shortages, recalcitrant wastewater treatments, and low substrate loadings) has been observed. Benefiting from the spectacular advances in various enzyme stabilization techniques, a plethora of biotransformations in non-conventional media have been established. Deep eutectic solvents (DESs) emerge as a sort of (potentially) greener non-aqueous medium with increasing use in biocatalysis. This review discusses the state-of-the-art of biotransformations in DESs with a focus on biocatalytic pathways for the synthesis of active pharmaceutical ingredients (APIs). Representative examples of different enzyme classes are discussed, together with a critical vision of the limitations and discussing prospects of using DESs for biocatalysis. Full article

(This article belongs to the Special Issue Catalytic Procedures for the Synthesis of Pharmaceutical Active Compounds in Deep Eutectic Solvents)

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16 pages, 5344 KiB

Open AccessEditor’s ChoiceArticle

Surface Modification of Fe-ZSM-5 Using Mg for a Reduced Catalytic Pyrolysis Temperature of Low-Density Polyethylene to Produce Light Olefin

by Yincui Li, Ting Liu, Shengnan Deng, Xiao Liu, Qian Meng, Mengxue Tang, Xueying Wu and Huawei Zhang

Catalysts 2024, 14(1), 78; https://doi.org/10.3390/catal14010078 - 18 Jan 2024

Cited by 4 | Viewed by 3107

Abstract

Although the catalytic pyrolysis of low-density polyethylene (LDPE) to produce light olefin has shown potential industrial application advantages, it has generally suffered when using higher pyrolysis temperatures. In this work, Mg-modified Fe-ZSM-5 was used for catalytic conversion of LDPE to obtain light olefin [...] Read more.

Although the catalytic pyrolysis of low-density polyethylene (LDPE) to produce light olefin has shown potential industrial application advantages, it has generally suffered when using higher pyrolysis temperatures. In this work, Mg-modified Fe-ZSM-5 was used for catalytic conversion of LDPE to obtain light olefin in a fixed bed reactor. The effects of catalyst types, pyrolysis temperatures, and Mg loading on the yield of light olefin were investigated. The 1 wt% Mg loading slightly improved the yield of light olefin to 38.87 wt% at 395 °C, lowering the temperature of the pyrolysis reaction. We considered that the higher light olefin yield of Fe-Mg-ZSM-5 was attributed to the introduction of Mg, where Mg regulated the surface acidity of the catalyst, inhibited the secondary cracking reaction, and reduced coking during the pyrolysis process. Furthermore, the addition of Mg also dramatically reduced the average particle size of Fe oxides from 40 nm to 10 nm, which is conducive to a lower catalytic reaction temperature. Finally, the spent catalyst could be easily regenerated at the conditions of 600 °C in airflow with a heating rate of 10 °C/min for 1 h, and the light olefin yield remained higher than 36.71 wt% after five cycles, indicating its excellent regeneration performance. Full article

(This article belongs to the Topic Valorizing Waste through Thermal and Biological Processes for Sustainable Energy Production)

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19 pages, 3920 KiB

Open AccessEditor’s ChoiceReview

Preparation of Mesoporous Zeolites and Their Applications in Catalytic Elimination of Atmospheric Pollutants

by Chuchen Miao, Lanyi Wang, Shengran Zhou, Di Yu, Chunlei Zhang, Siyu Gao, Xuehua Yu and Zhen Zhao

Catalysts 2024, 14(1), 75; https://doi.org/10.3390/catal14010075 - 17 Jan 2024

Cited by 6 | Viewed by 3113

Abstract

With increasing environmental awareness, the issue of atmospheric pollution has gained significant attention. Specifically, three types of atmospheric pollutants, namely, nitrogen oxides, volatile organic compounds, and carbon monoxide, have become the focus of widespread concern. In addressing these pollutants, mesoporous zeolites have emerged [...] Read more.

With increasing environmental awareness, the issue of atmospheric pollution has gained significant attention. Specifically, three types of atmospheric pollutants, namely, nitrogen oxides, volatile organic compounds, and carbon monoxide, have become the focus of widespread concern. In addressing these pollutants, mesoporous zeolites have emerged as promising materials due to their large specific surface area, which enables effective dispersion of active sites, and their large pore volume, which facilitates efficient diffusion. This article provides a comprehensive overview of the preparation methods of mesoporous zeolites and their applications in removing nitrogen oxides, volatile organic compounds, and carbon monoxide. It also highlights the challenges and limitations faced by the application of mesoporous zeolites in pollutant removal and emphasizes their potential as efficient catalysts. Full article

(This article belongs to the Special Issue Catalysts for Mobile Source: Low-Carbon and Pollution Emission Control)

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23 pages, 11426 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Platinum Alloys for Methanol Oxidation Electrocatalysis: Reaction Mechanism and Rational Design of Catalysts with Exceptional Activity and Stability

by Renqin Yu, Yifan Zhang, Sixu Deng, Rongying Zhu, Shiming Zhang, Jiujun Zhang, Yufeng Zhao and Zhonghong Xia

Catalysts 2024, 14(1), 60; https://doi.org/10.3390/catal14010060 - 12 Jan 2024

Cited by 14 | Viewed by 3572

Abstract

Direct methanol fuel cells have emerged as highly promising energy conversion devices in the past few decades. However, some challenges, such as carbon monoxide (CO) poisoning and unsatisfactory long-term stability, remain for platinum (Pt) as a methanol oxidation reaction (MOR) catalyst. This review [...] Read more.

Direct methanol fuel cells have emerged as highly promising energy conversion devices in the past few decades. However, some challenges, such as carbon monoxide (CO) poisoning and unsatisfactory long-term stability, remain for platinum (Pt) as a methanol oxidation reaction (MOR) catalyst. This review covers recent advances in Pt alloy MOR catalysts and provides some insights. This review presents MOR catalytic mechanisms based on CO or non-CO pathways. Typical dimension-based designs of MOR catalysts, such as anisotropic nanowires, metallene, nanoframes, and corresponding rationales for performance enhancements, are introduced. More importantly, some key tuning strategies are elaborated, including intermetallic compound synthesis, interface engineering, and surface facet engineering. High-entropy alloys as an intriguing class of MOR catalysts with favorable prospects are also discussed. Finally, future directions and opportunities are outlined. Full article

(This article belongs to the Special Issue Noble Metal-Based Nanomaterials for Heterogeneous Catalysis)

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34 pages, 12422 KiB

Open AccessEditor’s ChoiceReview

Ultradurable Pt-Based Catalysts for Oxygen Reduction Electrocatalysis

by Ziting Li, Peng Zhou, Yuxin Zhao, Wenyue Jiang, Bingxin Zhao, Xiaoshuang Chen and Menggang Li

Catalysts 2024, 14(1), 57; https://doi.org/10.3390/catal14010057 - 12 Jan 2024

Cited by 15 | Viewed by 5071

Abstract

An oxygen reduction reaction (ORR) is the key half reaction of proton exchange membrane fuel cells (PEMFCs), and is highly dependent on Pt-based nanocrystals as core electrocatalysts. Despite the exceptional ORR activity from adjusting the electronic structures of surface or near-surface atoms, several [...] Read more.

An oxygen reduction reaction (ORR) is the key half reaction of proton exchange membrane fuel cells (PEMFCs), and is highly dependent on Pt-based nanocrystals as core electrocatalysts. Despite the exceptional ORR activity from adjusting the electronic structures of surface or near-surface atoms, several serious issues, including the corrosion of carbon supports, the preferential leaching of active metal elements, the instability of surface low-coordinated atoms and the sintering/agglomeration of nanocrystals, still exist, challenging the ORR durability of developed Pt-based ORR catalysts. From the point of view of the catalyst structure design, in this review, we summarized the state-of-the-art structural regulation strategies for improving the ORR durability of Pt-based catalysts. The current limitation of Pt-based binary catalysts for ORR electrocatalysis is firstly discussed, and the detailed strategies are further classified into the optimization of supports, metal-doped alloys, core/shell structures, intermetallics and high-entropy alloys, etc. The structure–performance relationship is detailedly explained, especially emphasizing the elimination of the above restrictions. Finally, the existing challenges and future research direction are further presented, aiming at practicing the PEMFC devices of the ultradurable Pt-based catalysts. Full article

(This article belongs to the Special Issue Noble Metal-Based Nanomaterials for Heterogeneous Catalysis)

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12 pages, 5442 KiB

Open AccessEditor’s ChoiceArticle

Structure Robustness of Highly Dispersed Pt/Al₂O₃ Catalyst for Propane Dehydrogenation during Oxychlorination Regeneration Process

by Lu Dong, Yitong Sun, Yifan Zhou, Zhijun Sui, Yunsheng Dai, Yian Zhu and Xinggui Zhou

Catalysts 2024, 14(1), 48; https://doi.org/10.3390/catal14010048 - 10 Jan 2024

Cited by 3 | Viewed by 2942

Abstract

The structure and performance stability of a Pt-based catalyst for propane dehydrogenation during its reaction–regeneration cycles is one of the key factors for its commercial application. A 0.3% Pt/Al₂O₃ catalyst with a sub-nanometric particle size was prepared and two different [...] Read more.

The structure and performance stability of a Pt-based catalyst for propane dehydrogenation during its reaction–regeneration cycles is one of the key factors for its commercial application. A 0.3% Pt/Al₂O₃ catalyst with a sub-nanometric particle size was prepared and two different types of regeneration processes, long-term dichloroethane oxychlorination and a reaction–oxidation–oxychlorination cycle, were investigated on this catalyst. The fresh, sintered and regenerated catalyst was characterized by HAADF-STEM, CO-DRIFTS, XPS, CO chemisorption and N₂ physisorption, and its catalytic performance for propane dehydrogenation was also tested. The results show that the catalysts tend to have a similar particle size, coordination environment and catalytic performance with the extension of the regeneration time or an increase in the number of cycles in the two regeneration processes, and a common steady state could be achieved on the catalysts. This indicates that structure of the catalyst tends to approach its equilibrium state in the regeneration process, during which the utilization efficiency of Pt is maximized by increasing the dispersion of Pt and its intrinsic activity, and the structural robustness is secured. The performance of the catalyst is comparable to that of a single-atom Pt/Al₂O₃ catalyst. Full article

(This article belongs to the Topic Surface Chemistry of Catalysis)

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21 pages, 7105 KiB

Open AccessEditor’s ChoiceArticle

Density Functional Theory Study of Mechanism of Reduction of N₂O by CO over Fe-ZSM-5 Zeolites

by Ning Yuan, Congru Gao, Xiuliang Sun and Jianwei Li

Catalysts 2024, 14(1), 49; https://doi.org/10.3390/catal14010049 - 10 Jan 2024

Cited by 5 | Viewed by 2468

Abstract

Nitrous oxide (N₂O) is an industrial waste gas (e.g., from the production of adipic acid), which damages the ozone layer and causes the greenhouse effect. Density functional theory calculations were employed to investigate the mechanism of direct catalytic decomposition of N [...] Read more.

Nitrous oxide (N₂O) is an industrial waste gas (e.g., from the production of adipic acid), which damages the ozone layer and causes the greenhouse effect. Density functional theory calculations were employed to investigate the mechanism of direct catalytic decomposition of N₂O and selective catalytic reduction (SCR) of N₂O by CO over Fe-ZSM-5 zeolites. Two stable Fe-active sites with six-membered ring structures on Fe-ZSM-5 were considered. The calculations indicate that the decomposition of N₂O is affected by the coordination environment around Fe and can occur through two reaction pathways. However, there is invariably a more considerable energy hurdle for the initiation of the second stage of N₂O decomposition. When CO participated in the reaction, it showed good reactivity and stability, the reaction energy barriers of the rate-limiting step were reduced by roughly 20.57 kcal/mol compared to the direct catalytic decomposition of N₂O. CO exhibited a superior electron-donating ability and orbital hybridization performance during the reaction, which enhanced the cyclicity of the N₂O reduction catalytic process. Our calculations confirmed the significant role of CO in N₂O reduction over Fe-ZSM-5 observed in previous studies. This study provides a valuable theoretical reference for exploring CO-SCR methods for N₂O reduction over Fe-based zeolite catalysts. Full article

(This article belongs to the Section Computational Catalysis)

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20 pages, 6106 KiB

Open AccessEditor’s ChoiceArticle

Reaction Kinetics and Mechanism for the Synthesis of Glycerol Carbonate from Glycerol and Urea Using ZnSO₄ as a Catalyst

by Huajun Wang and Jingjing Ma

Catalysts 2024, 14(1), 41; https://doi.org/10.3390/catal14010041 - 6 Jan 2024

Cited by 5 | Viewed by 3724

Abstract

A series of Zn salts were used as catalysts for the reaction of glycerol and urea to produce glycerol carbonate and it was found that ZnSO₄ showed the highest catalytic activity. Furthermore, the effects of reaction parameters on the glycerol conversion and [...] Read more.

A series of Zn salts were used as catalysts for the reaction of glycerol and urea to produce glycerol carbonate and it was found that ZnSO₄ showed the highest catalytic activity. Furthermore, the effects of reaction parameters on the glycerol conversion and glycerol carbonate yield were studied in detail. The results indicated that the glycerol conversion and glycerol carbonate yield were increased with the reaction temperature, reaction time, and catalyst amount while the optimal reaction conditions were 140 °C, 240 min, catalyst amount of 5 wt% (based on the glycerol weight), and urea-to-glycerol molar ratio of 1.1:1. During the reaction, the ZnSO₄ catalyst is transformed into Zn(NH₃)₂SO₄ at the initial stage of the reaction and then further transformed into Zn(C₃H₆O₃). Zn(C₃H₆O₃) and (NH₄)₂SO₄ may be the true active species for the activation of urea and glycerol, respectively. The reaction mechanism is proposed in this article. Based on the experimental results, a reaction kinetics model considering the change in volume of the reaction system was also established, and the model parameters were obtained by fitting the experimental data. The statistical results showed that the established kinetics model is accurate. Full article

(This article belongs to the Section Catalytic Reaction Engineering)

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