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Volume 12
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Catalysts, Volume 12, Issue 2 (February 2022) – 137 articles

Cover Story (view full-size image): Hydrogen and oxygen production from water splitting is a green and clean energy production method. Efficient water decomposition catalysts are the key to the wide use of water decomposition. In this work, six manganese containing polyoxometalate (Mnx-POMs) with different structures of Mn-O clusters and Mn oxidation states were selected from the literature, and their electrocatalytic water oxidation properties in solution and composite membrane were compared. The results show that Mn14-POM has the best catalytic performance because it has a Mn-O cluster cubic structure, which is similar to the photocatalytic active center (PSII), and their Mn have the same oxidation state. These two laws are conducive to further screening high-performance water oxidation catalysts. View this paper
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24 pages, 1749 KiB  
Review
Research Progress and Reaction Mechanism of CO2 Methanation over Ni-Based Catalysts at Low Temperature: A Review
by Li Li, Wenqing Zeng, Mouxiao Song, Xueshuang Wu, Guiying Li and Changwei Hu
Catalysts 2022, 12(2), 244; https://doi.org/10.3390/catal12020244 - 21 Feb 2022
Cited by 42 | Viewed by 7734
Abstract
The combustion of fossil fuels has led to a large amount of carbon dioxide emissions and increased greenhouse effect. Methanation of carbon dioxide can not only mitigate the greenhouse effect, but also utilize the hydrogen generated by renewable electricity such as wind, solar, [...] Read more.
The combustion of fossil fuels has led to a large amount of carbon dioxide emissions and increased greenhouse effect. Methanation of carbon dioxide can not only mitigate the greenhouse effect, but also utilize the hydrogen generated by renewable electricity such as wind, solar, tidal energy, and others, which could ameliorate the energy crisis to some extent. Highly efficient catalysts and processes are important to make CO2 methanation practical. Although noble metal catalysts exhibit higher catalytic activity and CH4 selectivity at low temperature, their large-scale industrial applications are limited by the high costs. Ni-based catalysts have attracted extensive attention due to their high activity, low cost, and abundance. At the same time, it is of great importance to study the mechanism of CO2 methanation on Ni-based catalysts in designing high-activity and stability catalysts. Herein, the present review focused on the recent progress of CO2 methanation and the key parameters of catalysts including the essential nature of nickel active sites, supports, promoters, and preparation methods, and elucidated the reaction mechanism on Ni-based catalysts. The design and preparation of catalysts with high activity and stability at low temperature as well as the investigation of the reaction mechanism are important areas that deserve further study. Full article
(This article belongs to the Special Issue Carbon Dioxide Utilization: From Homogeneous to Heterogeneous Catalysis)
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11 pages, 5878 KiB  
Article
Hg0 Removal by V2O5 Modified Palygorskite in Simulated Flue Gas at Low Temperature
by Junwei Wang, Huan Wang, Caihong Jiang, Xie Wang and Jianli Zhang
Catalysts 2022, 12(2), 243; https://doi.org/10.3390/catal12020243 - 21 Feb 2022
Cited by 2 | Viewed by 1437
Abstract
The V2O5-modified palygorskite (V2O5/PG catalysts) were prepared and used for Hg0 removal in simulated flue gas at low temperature. It was found that the V2O5/PG catalyst had excellent performance for [...] Read more.
The V2O5-modified palygorskite (V2O5/PG catalysts) were prepared and used for Hg0 removal in simulated flue gas at low temperature. It was found that the V2O5/PG catalyst had excellent performance for Hg0 removal at 150 °C. O2 exhibited a positive effect on Hg0 removal over V2O5/PG, while SO2 and H2O showed an inhibiting effect. However, Hg0 removal efficiency showed a promotion trend in the presence of H2O, SO2, and O2. The Brunauer–Emmett–Teller (BET) method, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were applied to characterize the physicochemical properties of the V2O5/PG catalyst. Mercury temperature-programmed desorption (Hg-TPD) experiments were also conducted to identify the mercury species adsorbed on the V2O5/PG catalyst, and the pathway of Hg0 removal over V2O5/PG was also discussed. The used V2O5/PG catalyst after Hg0 removal was regenerated, and its capability for Hg0 removal can be completely recovered. The V2O5/PG-Re-300 °C catalyst showed excellent performance and good stability for Hg0 removal after regeneration. Full article
(This article belongs to the Special Issue Frontiers in Catalytic Emission Control)
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12 pages, 2819 KiB  
Article
Immobilization of Lipases on Modified Silica Clay for Bio-Diesel Production: The Effect of Surface Hydrophobicity on Performance
by Youdan Duan, Ting Zou, Sijin Wu and Haiming Cheng
Catalysts 2022, 12(2), 242; https://doi.org/10.3390/catal12020242 - 21 Feb 2022
Cited by 5 | Viewed by 1520
Abstract
The hydrophobicity of a support plays a critical role in the catalytic efficiency of immobilized lipases. 3-aminopropyltriethoxysilane (APTES)-modified silica clay (A-SC) was coupled with silane coupling agents of different alkyl chains (methyl triethoxysilane, vinyl triethoxysilane, octyl triethoxysilane, and dodecyl triethoxysilane) to prepare a [...] Read more.
The hydrophobicity of a support plays a critical role in the catalytic efficiency of immobilized lipases. 3-aminopropyltriethoxysilane (APTES)-modified silica clay (A-SC) was coupled with silane coupling agents of different alkyl chains (methyl triethoxysilane, vinyl triethoxysilane, octyl triethoxysilane, and dodecyl triethoxysilane) to prepare a series of hydrophobic support for lipase immobilization. The lipases were immobilized onto the support by conducting glutaraldehyde cross-linking processes. The results showed that the activity of the immobilized biocatalyst increased with hydrophobicity. The hydrolytic activity of Lip-Glu-C12-SC (contact angle 119.8°) can reach 5900 U/g, which was about three times that of Lip-Glu-A-SC (contact angle 46.5°). The immobilized lipase was applied as a biocatalyst for biodiesel production. The results showed that the catalytic yield of biodiesel with highly hydrophobic Lip-Glu-C12-SC could be as high as 96%, which is about 30% higher than that of Lip-Glu-A-SC. After being recycled five times, the immobilized lipase still maintained good catalytic activity and stability. This study provides a good strategy to improve the efficiency of immobilized lipases, showing great potential for future industrial application on biodiesel production. Full article
(This article belongs to the Topic Catalysis for Sustainable Chemistry and Energy)
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16 pages, 5169 KiB  
Article
The Inorganic Perovskite-Catalyzed Transfer Hydrogenation of Cinnamaldehyde Using Glycerol as a Hydrogen Donor
by Tafadzwa Precious Mabate, Reinout Meijboom and Ndzondelelo Bingwa
Catalysts 2022, 12(2), 241; https://doi.org/10.3390/catal12020241 - 21 Feb 2022
Cited by 8 | Viewed by 2102
Abstract
Catalytic transfer hydrogenation reactions (CTHs) produce value-added chemicals in the most economical, safe, green, and sustainable way. However, understanding the reaction mechanism and developing stable, selective, and cheap catalysts has been a significant challenge. Herein, we report on the hydrogenation of cinnamaldehyde utilizing [...] Read more.
Catalytic transfer hydrogenation reactions (CTHs) produce value-added chemicals in the most economical, safe, green, and sustainable way. However, understanding the reaction mechanism and developing stable, selective, and cheap catalysts has been a significant challenge. Herein, we report on the hydrogenation of cinnamaldehyde utilizing glycerol as a hydrogen donor and metal-oxides (SnO2, LaFeO3, and LaSnO3) as heterogeneous catalysts. The perovskite types were used because they are easy to synthesize, the metal components are readily available, and they are good alternatives to noble metals. The catalysts were synthesized through the nanocasting (hard-template) method with SiO2 (KIT-6) as a template. The template was synthesized using the soft-template (sol-gel) method resulting in a high surface area of 624 m2/g. Furthermore, catalytic evaluations gave high cinnamaldehyde percentage conversions of up to 99%. Interestingly, these catalysts were also found to catalyze the etherification of glycerol in one pot. Therefore, we propose competitive surface catalytic reactions driven by the transition metal cations as the binding sites for the cinnamaldehyde and the sacrificial glycerol. Full article
(This article belongs to the Special Issue Catalytic Conversion of Glycerol)
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14 pages, 3050 KiB  
Article
Highly Efficient Hierarchical Porous Carbon Supported Pd-Based Catalysts for Additive-Free Dehydrogenation of Formic Acid
by Xinyi Miao, Fengwu Tian, Miaomiao Bai, Yujia Zhang, Wei Wang, Zuoping Zhao, Xianzhao Shao and Xiaohui Ji
Catalysts 2022, 12(2), 240; https://doi.org/10.3390/catal12020240 - 20 Feb 2022
Cited by 7 | Viewed by 2240
Abstract
Formic acid (FA) is one of the most prospective hydrogen carriers for renewable energy transformation. In this context, the addition of extra-amine is always required for promoting the reactivity of FA, which is still a key challenge. Herein, we report a simple but [...] Read more.
Formic acid (FA) is one of the most prospective hydrogen carriers for renewable energy transformation. In this context, the addition of extra-amine is always required for promoting the reactivity of FA, which is still a key challenge. Herein, we report a simple but effective strategy to synthesize Pd nanoparticles, supported on NH2-functionalized, phosphorous-doped glucose-based porous carbon (NH2-P-GC). The introduction of NH2- groups on the support acts as an immobilized amine-additive for FA dehydrogenation, while phosphorus not only serves as an electronic promoter to keep Pd in the electronic deficient state for FA dehydrogenation, but also as an enlarger of the aperture size of the carbon. As a result, the Pd/NH2-P-GC has exceptional catalytic activity, 100% H2 selectivity, CO generation that is undetectable, and good reusability for hydrogen production from FA. In the additive-free dehydrogenation of aqueous FA solution, the initial turnover frequency (TOF) can reach 5126 h−1 at room temperature, which is substantially higher than the best heterogeneous catalyst so far recorded. Overall, the system’s high activity, selectivity, stability, and simplicity in producing CO-free H2/CO2 gas from FA, without the need for any additive, makes it attractive for practical deployment. Full article
(This article belongs to the Topic Catalysis for Sustainable Chemistry and Energy)
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19 pages, 4222 KiB  
Article
Modelling and Optimisation of the Sol-Gel Conditions for Synthesis of Semi-Hexagonal Titania-Based Nano-Catalyst for Esterification Reaction
by Hamed Nayebzadeh, Abbas Rohani, Aliakbar Sistani, Ali Hassanpour and Jabbar Gardy
Catalysts 2022, 12(2), 239; https://doi.org/10.3390/catal12020239 - 20 Feb 2022
Cited by 1 | Viewed by 2011
Abstract
Design and fabrication of a catalyst with the highest activity can be achieved by optimising the synthesis conditions. In this study, the sol-gel synthesis conditions of citric acid concentration, gelling temperature, complex time, and calcination temperature were studied for the preparation of a [...] Read more.
Design and fabrication of a catalyst with the highest activity can be achieved by optimising the synthesis conditions. In this study, the sol-gel synthesis conditions of citric acid concentration, gelling temperature, complex time, and calcination temperature were studied for the preparation of a novel semi-hexagonal calcium/titania-zirconia nano-catalyst used in the esterification reaction. After synthesis of around 24 samples at various conditions, their activity was tested in the esterification reaction and the results were analysed by multi-layer perceptron (MLP) and support vector machine (SVM) models. Both models predicted the actual data with high coefficients of determination, and indicated that the calcination temperature has the most influence on the activity of the prepared semi-hexagonal calcium/titania-zirconia nano-catalyst for the esterification reaction. Moreover, the genetic algorithm (GA) was utilised for optimising the preparation conditions based on the SVM model, due to its higher generalisation capability for prediction. The prepared nano-catalysts under the optimum conditions of 1.42 acid ratio, gelling temperature of 72 °C, complex time of 2.65 h, and calcination temperature of 487 °C showed good crystalline structure and metal–metal and metal–oxygen cation bonding. Finally, the fabricated catalyst had a high surface area (276.5 m2/g) with 3.5 nm pore diameter and almost uniform particle size (80–110 nm) distribution, leading to a high conversion of 97.6% in the esterification reaction, with good catalytic stability up to five times. Full article
(This article belongs to the Special Issue Solid Acid Catalysts for Biodiesel Production)
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17 pages, 1735 KiB  
Article
Assessment of Pretreatments for Highly Concentrated Leachate Waters to Enhance the Performance of Catalytic Wet Peroxide Oxidation with Sustainable Low-Cost Catalysts
by Gabriel de Freitas Batista, Fernanda F. Roman, Jose L. Diaz de Tuesta, Raquel Vieira Mambrini, Paulo Praça and Helder T. Gomes
Catalysts 2022, 12(2), 238; https://doi.org/10.3390/catal12020238 - 20 Feb 2022
Cited by 7 | Viewed by 1928
Abstract
Matured compost, derived from a mechanical and biological treatment (MBT) plant, was used as a precursor to produce catalysts through hydrothermal and thermal carbonization, HC and PC, respectively. HC and PC displayed suitable properties to act as catalysts in the catalytic wet peroxide [...] Read more.
Matured compost, derived from a mechanical and biological treatment (MBT) plant, was used as a precursor to produce catalysts through hydrothermal and thermal carbonization, HC and PC, respectively. HC and PC displayed suitable properties to act as catalysts in the catalytic wet peroxide oxidation (CWPO) treatment of the highly polluted leachate waters generated in the same MBT plant (TOC0 = 27 g L−1; COD0 = 60 g L−1; BOD5,0 = 23 g L−1). The influence of catalyst loading and pH were studied, considering multiple additions of H2O2. The best experimental conditions found were T = 80 °C, pH0 = 3.0, 7.2 g L−1 of HC catalyst, 85.7 g L−1 of H2O2, added in five batches in one-hour intervals between each addition. Under these experimental conditions, removals of 43%, 52%, 93%, 82%, 35%, 95% and 93% for the COD, TOC, BOD5, aromaticity, chlorides, turbidity and color number (CN) were, respectively, observed. Ion exchange resins and coagulation–flocculation were studied as pretreatment options to reduce the complexity of the leachate waters and enhance the CWPO results. Both strategies resulted in higher mineralization and enhanced the consumption efficiency of H2O2 (ηH2O2). The sequential treatment using coagulation–flocculation and CWPO with PC catalyst showed the best results, achieving abatement of 94%, 70%, 98%, 93%, 31%, 96% and 95% for COD, TOC, BOD5, aromaticity, chlorides, turbidity and CN, respectively. Full article
(This article belongs to the Special Issue Catalysis and Carbon-Based Materials)
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24 pages, 2146 KiB  
Review
Production of Jet Biofuels by Catalytic Hydroprocessing of Esters and Fatty Acids: A Review
by Rodolpho R. C. Monteiro, Isabela A. dos Santos, Maria R. A. Arcanjo, Célio L. Cavalcante, Jr., Francisco M. T. de Luna, Roberto Fernandez-Lafuente and Rodrigo S. Vieira
Catalysts 2022, 12(2), 237; https://doi.org/10.3390/catal12020237 - 20 Feb 2022
Cited by 19 | Viewed by 8365
Abstract
The transition from fossil to bio-based fuels is a requisite for reducing CO2 emissions in the aviation sector. Jet biofuels are alternative aviation fuels with similar chemical composition and performance of fossil jet fuels. In this context, the Hydroprocessing of Esters and [...] Read more.
The transition from fossil to bio-based fuels is a requisite for reducing CO2 emissions in the aviation sector. Jet biofuels are alternative aviation fuels with similar chemical composition and performance of fossil jet fuels. In this context, the Hydroprocessing of Esters and Fatty Acids (HEFA) presents the most consolidated pathway for producing jet biofuels. The process for converting esters and/or fatty acids into hydrocarbons may involve hydrodeoxygenation, hydrocracking and hydroisomerization, depending on the chemical composition of the selected feedstock and the desired fuel properties. Furthermore, the HEFA process is usually performed under high H2 pressures and temperatures, with reactions mediated by a heterogeneous catalyst. In this framework, supported noble metals have been preferably employed in the HEFA process; however, some efforts were reported to utilize non-noble metals, achieving a similar performance of noble metals. Besides the metallic site, the acidic site of the catalyst is crucial for product selectivity. Bifunctional catalysts have been employed for the complete process of jet biofuel production with standardized properties, with a special remark for using zeolites as support. The proper design of heterogeneous catalysts may also reduce the consumption of hydrogen. Finally, the potential of enzymes as catalysts for intermediate products of the HEFA pathway is highlighted. Full article
(This article belongs to the Topic Catalysis for Sustainable Chemistry and Energy)
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15 pages, 2786 KiB  
Article
Oxygen Vacancy-Mediated Selective H2S Oxidation over Co-Doped LaFexCo1−xO3 Perovskite
by Xinlei Yu, Xun Tao, Yunfei Gao, Lu Ding, Yanqin Wang, Guangsuo Yu and Fuchen Wang
Catalysts 2022, 12(2), 236; https://doi.org/10.3390/catal12020236 - 19 Feb 2022
Cited by 6 | Viewed by 2095
Abstract
Compared to the Claus process, selective H2S catalytic oxidation to sulfur is a promising reaction, as it is not subject to thermodynamic limitations and could theoretically achieve ~100% H2S conversion to sulfur. In this study, we investigated the effects [...] Read more.
Compared to the Claus process, selective H2S catalytic oxidation to sulfur is a promising reaction, as it is not subject to thermodynamic limitations and could theoretically achieve ~100% H2S conversion to sulfur. In this study, we investigated the effects of Co and Fe co-doping in ABO3 perovskite on H2S selective catalytic oxidation. A series of LaFexCo1−xO3 (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) perovskites were synthesized by the sol-gel method. Compared to LaFeO3 and LaCoO3, co-doped LaFexCo1−xO3 significantly improved the H2S conversion and sulfur selectivity at a lower reaction temperature. Nearly 100% sulfur yield was achieved on LaFe0.4Co0.6O3 under 220 °C with exceptional catalyst stability (above 95% sulfur yield after 77 h). The catalysts were characterized by XRD, BET, FTIR, XPS, and H2-TPR. The characterization results showed that the structure of LaFexCo1−xO3 changed from the rhombic phase of LaCoO3 to the cubic phase of LaFeO3 with Fe substitution. Doping with appropriate iron (x = 0.4) facilitates the reduction of Co ions in the catalyst, thereby promoting the H2S selective oxidation. This study demonstrates a promising approach for low-temperature H2S combustion with ~100% sulfur yield. Full article
(This article belongs to the Special Issue Catalytic Reaction for High-Temperature and Low-Emission Combustion Technologies)
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17 pages, 4638 KiB  
Article
Noble Metal Promoted TiO2 from Silver-Waste Valorisation: Synergism between Ag and Au
by Marta Stucchi, Daniela Meroni, György Safran, Alberto Villa, Claudia L. Bianchi and Laura Prati
Catalysts 2022, 12(2), 235; https://doi.org/10.3390/catal12020235 - 19 Feb 2022
Cited by 4 | Viewed by 1763
Abstract
Wastewaters from precious metal industries contain high amounts of noble metals, but their efficient recycling is hindered by the wastewater complex composition. Here, we propose an innovative approach for the efficient recovery of noble metals contained in these metal-enriched wastewaters as precursors for [...] Read more.
Wastewaters from precious metal industries contain high amounts of noble metals, but their efficient recycling is hindered by the wastewater complex composition. Here, we propose an innovative approach for the efficient recovery of noble metals contained in these metal-enriched wastewaters as precursors for the synthesis of noble metal nanoparticles (NPs) and supported metal catalysts. Silver NPs were synthesized from Ag-enriched wastewater and then deposited on TiO2 to prepare photocatalysts. Then, further promotion of the photocatalytic activity of Ag-modified TiO2 was achieved by the addition of as little as 0.5 wt.% of Au. STEM-EDS analyses proved that Au NPs were located on Ag or AgOx nanoparticles. The contact between the two metal-containing NPs results in charge transfer effects, appreciable both in terms of oxidation states determined by XPS and of optical properties. In particular, the plasmon band of Au NPs shows photochromic effects: under UV light irradiation, bimetallic samples exhibit a blue-shift of the plasmon band, which is reversible under dark storage. The activity of the materials was tested towards ethanol photodegradation under UV light. Adding 0.5 wt.% Au NPs resulted in a promoted activity compared to Ag-TiO2, thus showing synergistic effects between Au and Ag. Ethanol was completely converted already after 1 h of UV irradiation, acetaldehyde was formed as the main oxidation product and fully degraded in less than 180 min. Notably, bimetallic samples showed ethylene formation by a parallel dehydration mechanism. Full article
(This article belongs to the Special Issue Catalytic Processes of Bimetallic Nanoparticles)
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23 pages, 726 KiB  
Review
State of the Art on the Microbial Production of Industrially Relevant Organic Acids
by Raffaella Desirè Di Lorenzo, Immacolata Serra, Danilo Porro and Paola Branduardi
Catalysts 2022, 12(2), 234; https://doi.org/10.3390/catal12020234 - 19 Feb 2022
Cited by 8 | Viewed by 3532
Abstract
The industrial relevance of organic acids is high; because of their chemical properties, they can be used as building blocks as well as single-molecule agents with a huge annual market. Organic acid chemical platforms can derive from fossil sources by petrochemical refining processes, [...] Read more.
The industrial relevance of organic acids is high; because of their chemical properties, they can be used as building blocks as well as single-molecule agents with a huge annual market. Organic acid chemical platforms can derive from fossil sources by petrochemical refining processes, but most of them also represent natural metabolites produced by many cells. They are the products, by-products or co-products of many primary metabolic processes of microbial cells. Thanks to the potential of microbial cell factories and to the development of industrial biotechnology, from the last decades of the previous century, the microbial-based production of these molecules has started to approach the market. This was possible because of a joint effort of microbial biotechnologists and biochemical and process engineers that boosted natural production up to the titer, yield and productivity needed to be industrially competitive. More recently, the possibility to utilize renewable residual biomasses as feedstock not only for biofuels, but also for organic acids production is further augmenting the sustainability of their production, in a logic of circular bioeconomy. In this review, we briefly present the latest updates regarding the production of some industrially relevant organic acids (citric fumaric, itaconic, lactic and succinic acid), discussing the challenges and possible future developments of successful production. Full article
(This article belongs to the Section Biocatalysis)
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58 pages, 15719 KiB  
Review
Tetramethylammonium Fluoride: Fundamental Properties and Applications in C-F Bond-Forming Reactions and as a Base
by Vladimir Iashin, Tom Wirtanen and Jesus E. Perea-Buceta
Catalysts 2022, 12(2), 233; https://doi.org/10.3390/catal12020233 - 18 Feb 2022
Cited by 9 | Viewed by 10449
Abstract
Nucleophilic ionic sources of fluoride are essential reagents in the synthetic toolbox to access high added-value fluorinated building blocks unattainable by other means. In this review, we provide a concise description and rationale of the outstanding features of one of these reagents, tetramethylammonium [...] Read more.
Nucleophilic ionic sources of fluoride are essential reagents in the synthetic toolbox to access high added-value fluorinated building blocks unattainable by other means. In this review, we provide a concise description and rationale of the outstanding features of one of these reagents, tetramethylammonium fluoride (TMAF), as well as disclosing the different methods for its preparation, and how its physicochemical properties and solvation effects in different solvents are intimately associated with its reactivity. Furthermore, herein we also comprehensively describe its historic and recent utilization, up to December 2021, in C-F bond-forming reactions with special emphasis on nucleophilic aromatic substitution fluorinations with a potential sustainable application in industrial settings, as well as its use as a base capable of rendering unprecedented transformations. Full article
(This article belongs to the Special Issue Organohalogen Chemistry and Catalysis)
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17 pages, 8233 KiB  
Article
Microflowery, Microspherical, and Fan-Shaped TiO2 Crystals via Hierarchical Self-Assembly of Nanorods with Exposed Specific Crystal Facets and Enhanced Photocatalytic Performance
by Yi-en Du, Xianjun Niu, Kai Hou, Xinru He and Caifeng Zhang
Catalysts 2022, 12(2), 232; https://doi.org/10.3390/catal12020232 - 18 Feb 2022
Cited by 2 | Viewed by 1372
Abstract
In this paper, khaki titanium dioxide (TiO2) crystals via hierarchical self-assembly of nanorods with different morphologies and specific exposed crystal facets were prepared for the first time by using a TiCl3 treatment process in the presence and absence of morphology-controlling [...] Read more.
In this paper, khaki titanium dioxide (TiO2) crystals via hierarchical self-assembly of nanorods with different morphologies and specific exposed crystal facets were prepared for the first time by using a TiCl3 treatment process in the presence and absence of morphology-controlling agents. The crystal structure, morphology, microstructure, specific surface area, and separation efficiency of photogenerated electron-hole pairs of the synthesized TiO2 crystals were characterized. The photocatalytic and recycled performances of the synthesized TiO2 crystals in the presence of shape-controlling agents, such as ammonium sulfate (AS), ammonium carbonate (AC), and urea, and the absence of shape-controlling agents (the obtained TiO2 crystals were expressed as AS-TiO2, AC-TiO2, urea-TiO2, and No-TiO2, respectively) were evaluated and compared with the commercial TiO2 (CM-TiO2) crystals. The AS-TiO2 microspheres with exposed uncertain facets exhibited enhanced photocatalytic activity for the degradation of methylene blue solution, which can be attributed to the combined effect of the anatase phase structure, relatively larger specific surface area, and the effective separation of the photogenerated electron-holes. Full article
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2 pages, 165 KiB  
Editorial
The Merit and the Context of Hydrogen Production from Water and Its Effect on Global CO2 Emission
by Hicham Idriss
Catalysts 2022, 12(2), 231; https://doi.org/10.3390/catal12020231 - 18 Feb 2022
Viewed by 1709
Abstract
For a green economy to be possible in the near future, hydrogen production from water is a sought-after alternative to fossil fuels [...] Full article
(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members (EBMs) of Catalysts)
13 pages, 1062 KiB  
Article
Effects of Soil Surface Chemistry on Adsorption and Activity of Urease from a Crude Protein Extract: Implications for Biocementation Applications
by Rayla Pinto Vilar and Kaoru Ikuma
Catalysts 2022, 12(2), 230; https://doi.org/10.3390/catal12020230 - 18 Feb 2022
Cited by 2 | Viewed by 1751
Abstract
In the bacterial enzyme-induced calcite precipitation (BEICP) technique for biocementation, the spatial distribution of adsorbed and catalytically active urease dictates the location where calcium carbonate precipitation and resulting cementation will occur. This study investigated the relationships between the amount of urease and total [...] Read more.
In the bacterial enzyme-induced calcite precipitation (BEICP) technique for biocementation, the spatial distribution of adsorbed and catalytically active urease dictates the location where calcium carbonate precipitation and resulting cementation will occur. This study investigated the relationships between the amount of urease and total bacterial proteins adsorbed, the retained enzymatic activity of adsorbed urease, and the overall loss of activity upon adsorption, and how these relationships are influenced by changes in soil surface chemistry. In soils with hydrophobic contents higher than 20% (w/w) ratio, urease was preferentially adsorbed compared to the total amount of proteins present in the crude bacterial protein extract. Conversely, adsorption of urease onto silica sand and soil mixtures, including iron-coated sand, was much lower compared to the total proteins. Higher levels of urease activity were retained in hydrophobic-containing samples, with urease activity decreasing with lower hydrophobic content. These observations suggest that the surface manipulation of soils, such as treatments to add hydrophobicity to soil surfaces, can potentially be used to increase the activity of adsorbed urease to improve biocementation outcomes. Full article
(This article belongs to the Special Issue Enzymes and Biocatalysis)
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3 pages, 175 KiB  
Editorial
Advance in Selective Alcohol and Polyol Oxidation Catalysis
by Werner Oberhauser
Catalysts 2022, 12(2), 229; https://doi.org/10.3390/catal12020229 - 18 Feb 2022
Cited by 1 | Viewed by 1404
Abstract
The aerobic oxidation of organic molecules and in particular alcohols and bio-derived poly alcohols to value-added commodity molecules is under continuous investigation, due to the importance of oxidation products (aldehydes, ketones carboxylic acids and esters) and the challenging nature of this chemical transformation, [...] Read more.
The aerobic oxidation of organic molecules and in particular alcohols and bio-derived poly alcohols to value-added commodity molecules is under continuous investigation, due to the importance of oxidation products (aldehydes, ketones carboxylic acids and esters) and the challenging nature of this chemical transformation, since rather harsh reaction conditions (T > 100 °C) are needed to gain a significant substrate conversion [...] Full article
(This article belongs to the Special Issue Advance in Selective Alcohol and Polyol Oxidation Catalysis)
30 pages, 6749 KiB  
Review
Recent Progress in Two-Dimensional Materials for Electrocatalytic CO2 Reduction
by Song Lu, Fengliu Lou and Zhixin Yu
Catalysts 2022, 12(2), 228; https://doi.org/10.3390/catal12020228 - 17 Feb 2022
Cited by 24 | Viewed by 5573
Abstract
Electrocatalytic CO2 reduction (ECR) is an attractive approach to convert atmospheric CO2 to value-added chemicals and fuels. However, this process is still hindered by sluggish CO2 reaction kinetics and the lack of efficient electrocatalysts. Therefore, new strategies for electrocatalyst design [...] Read more.
Electrocatalytic CO2 reduction (ECR) is an attractive approach to convert atmospheric CO2 to value-added chemicals and fuels. However, this process is still hindered by sluggish CO2 reaction kinetics and the lack of efficient electrocatalysts. Therefore, new strategies for electrocatalyst design should be developed to solve these problems. Two-dimensional (2D) materials possess great potential in ECR because of their unique electronic and structural properties, excellent electrical conductivity, high atomic utilization and high specific surface area. In this review, we summarize the recent progress on 2D electrocatalysts applied in ECR. We first give a brief description of ECR fundamentals and then discuss in detail the development of different types of 2D electrocatalysts for ECR, including metal, graphene-based materials, transition metal dichalcogenides (TMDs), metal–organic frameworks (MOFs), metal oxide nanosheets and 2D materials incorporated with single atoms as single-atom catalysts (SACs). Metals, such as Ag, Cu, Au, Pt and Pd, graphene-based materials, metal-doped nitric carbide, TMDs and MOFs can mostly only produce CO with a Faradic efficiencies (FE) of 80~90%. Particularly, SACs can exhibit FEs of CO higher than 90%. Metal oxides and graphene-based materials can produce HCOOH, but the FEs are generally lower than that of CO. Only Cu-based materials can produce high carbon products such as C2H4 but they have low product selectivity. It was proposed that the design and synthesis of novel 2D materials for ECR should be based on thorough understanding of the reaction mechanism through combined theoretical prediction with experimental study, especially in situ characterization techniques. The gap between laboratory synthesis and large-scale production of 2D materials also needs to be closed for commercial applications. Full article
(This article belongs to the Special Issue Catalysis for CO2 Conversion)
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28 pages, 14478 KiB  
Review
Recent Advances in Catalytic [3,3]-Sigmatropic Rearrangements
by Huijin Lee, Ki Tae Kim, Min Kim and Cheoljae Kim
Catalysts 2022, 12(2), 227; https://doi.org/10.3390/catal12020227 - 16 Feb 2022
Cited by 10 | Viewed by 4377
Abstract
Carbon–carbon bond formation by [3,3]-sigmatropic rearrangement is a fundamental and powerful method that has been used to build organic molecules for a long time. Initially, Claisen and Cope rearrangements proceeded at high temperatures with limited scopes. By introducing catalytic systems, highly functionalized substrates [...] Read more.
Carbon–carbon bond formation by [3,3]-sigmatropic rearrangement is a fundamental and powerful method that has been used to build organic molecules for a long time. Initially, Claisen and Cope rearrangements proceeded at high temperatures with limited scopes. By introducing catalytic systems, highly functionalized substrates have become accessible for forming complex structures under mild conditions, and asymmetric synthesis can be achieved by using chiral catalytic systems. This review describes recent breakthroughs in catalytic [3,3]-sigmatropic rearrangements since 2016. Detailed reaction mechanisms are discussed to enable an understanding of the reactivity and selectivity of the reactions. Finally, this review is inspires the development of new cascade reaction pathways employing catalytic [3,3]-sigmatropic rearrangement as related methodologies for the synthesis of complex functional molecules. Full article
(This article belongs to the Section Catalysis in Organic and Polymer Chemistry)
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11 pages, 2624 KiB  
Article
MgO Catalysts for FAME Synthesis Prepared Using PEG Surfactant during Precipitation and Calcination
by Valdis Kampars, Ruta Kampare and Aija Krumina
Catalysts 2022, 12(2), 226; https://doi.org/10.3390/catal12020226 - 16 Feb 2022
Cited by 5 | Viewed by 2154
Abstract
To develop a method for the preparation of MgO nanoparticles, precatalyst synthesis from magnesium nitrate with ammonia and calcination was performed in presence of PEG in air. Without PEG, the catalysts are inactive. The conversion to hydroxide was performed using a PEG/MgO molar [...] Read more.
To develop a method for the preparation of MgO nanoparticles, precatalyst synthesis from magnesium nitrate with ammonia and calcination was performed in presence of PEG in air. Without PEG, the catalysts are inactive. The conversion to hydroxide was performed using a PEG/MgO molar ratio of 1, but, before the calcination, excess of PEG was either saved (PEG1) or increased to 2, 3, or 4 (PEG 2–4). Catalysts were calcined at 400–660 °C and characterized using XRD, N2 adsorption-desorption, TGA, FTIR, and SEM. The FAME yield in the reactions with methanol depend on the PEG ratio used and the calcination temperature. The optimal calcination temperature and highest FAME yield in the 6 h reactions for catalysts PEG1, PEG2, PEG3 and PEG4 were 400 °C, 74%; 500 °C, 80%; 500 °C, 51% and 550 °C, 31%, respectively. The yield dependence on calcination temperature for catalysts with a constant PEG ratio is similar to that of a bell curve, which becomes wider and flatters with an increase in PEG ratio. For most catalysts, the FAME yield increases as the size of the crystallites decreases. The dependence of FAME and the intermediate yield on oil conversion confirms that all catalysts have strong base sites. Full article
(This article belongs to the Special Issue Advances in the Catalytic Conversion of Biomass Components to Ester Derivatives: Challenges and Opportunities)
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15 pages, 9829 KiB  
Article
Effect of Pd/Ce Loading and Catalyst Components on the Catalytic Abatement of Toluene
by Wenjun Liang, Xiujuan Shi, Qinglei Li, Sida Ren and Guobin Yin
Catalysts 2022, 12(2), 225; https://doi.org/10.3390/catal12020225 - 16 Feb 2022
Cited by 2 | Viewed by 2173
Abstract
Monolithic catalysts are widely used in industrial catalysis. However, in the preparation of a monolithic catalyst, the traditional methods have some drawbacks such as low washcoat uploading ratio and poor uniformity. In the present work, the effects of Pd/Ce loading and catalyst components [...] Read more.
Monolithic catalysts are widely used in industrial catalysis. However, in the preparation of a monolithic catalyst, the traditional methods have some drawbacks such as low washcoat uploading ratio and poor uniformity. In the present work, the effects of Pd/Ce loading and catalyst components on the catalytic abatement of toluene were investigated. The acid treatment of the substrate, the particle size of the slurry and the dispersant on the uniformity of the washcoat and the catalytic performance were also explored. Characterisation was achieved via BET, SEM, zeta potential and laser grain-size analyses. The results showed that the catalytic activity of the catalyst increased with the increasing of the Ce content. It was found that the 0.2Pd-0.3Ce/γ-Al2O3 catalysts had the best toluene catalytic activity. The pretreatment of the cordierite with 20% HCl could improve the properties of the cordierite. It was also found that reducing the particle size of the washcoat and adding dispersant PAA could effectively improve the stability of the suspension and the uniformity of the washcoat. When 20% HCl pretreatment was used, the toluene catalytic activity of the monolith catalyst prepared by cordierite increased, in which T10 and T90 decreased by about 5 °C. Decreasing the particle size and dispersant also promoted the efficiency of catalytic degradation. Full article
(This article belongs to the Special Issue Advances in Catalytic Surface Reactions, Kinetics and Mechanism)
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16 pages, 4803 KiB  
Article
Studies of Clinoptilolite-Rich Zeolitic Tuffs from Different Regions and Their Activity in Photodegradation of Methylene Blue
by Jelena Pavlović, Andraž Šuligoj, Mojca Opresnik, Nataša Novak Tušar, Nataša Zabukovec Logar and Nevenka Rajić
Catalysts 2022, 12(2), 224; https://doi.org/10.3390/catal12020224 - 16 Feb 2022
Cited by 5 | Viewed by 1919
Abstract
The present study focuses on clinoptilolite (CLI)-rich natural zeolitic tuffs and their photocatalytic activity in the degradation of cationic organic dyes. CLI from different regions was tested in the photocatalytic degradation of methylene blue (MB) as a model cationic dye. The photocatalytic tests [...] Read more.
The present study focuses on clinoptilolite (CLI)-rich natural zeolitic tuffs and their photocatalytic activity in the degradation of cationic organic dyes. CLI from different regions was tested in the photocatalytic degradation of methylene blue (MB) as a model cationic dye. The photocatalytic tests were performed at room temperature and atmospheric pressure under visible light irradiation. For all the CLI samples, the highest activity was observed at pH = 6. Total MB degradation varied between 70 and 91% (C0 = 10 mg dm–3, 0.2 g dm–3 of photocatalyst, during 300 min). It is suggested that the presence of Fe species in the studied tuffs is responsible for the photocatalytic activity. The activity increases linearly with the Fe content in the tuffs. The MB photodegradation follows the Langmuir–Hinshelwood kinetic model. The recyclability tests showed good stability and efficiency of the photocatalyst. The degradation rate decreased from 91 to 69% during three reaction cycles, indicating a promising potential of natural zeolites in the treatment of textile industry wastewater. Full article
(This article belongs to the Special Issue Engineering Materials for Catalysis)
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23 pages, 41826 KiB  
Review
The Role of Sulfated Materials for Biodiesel Production from Cheap Raw Materials
by Brandon Lowe, Jabbar Gardy and Ali Hassanpour
Catalysts 2022, 12(2), 223; https://doi.org/10.3390/catal12020223 - 16 Feb 2022
Cited by 11 | Viewed by 3287
Abstract
There is an urgent need to reduce global greenhouse gas emissions, yet to date the decarbonization of the transportation industry has been slow and of particular difficulty. While fossil fuel replacements such as biodiesel may aid the transition to a less polluting society, [...] Read more.
There is an urgent need to reduce global greenhouse gas emissions, yet to date the decarbonization of the transportation industry has been slow and of particular difficulty. While fossil fuel replacements such as biodiesel may aid the transition to a less polluting society, production at the industrial scales required is currently heavily dependent on chemical catalysis. Conventional two-step homogenous routes require the challenging separation of catalyst from the obtained product; however, heterogenous solid catalysts bring new considerations such as material stability, surface area, porosity, deactivation effects, and reduced reactivities under mild conditions. Nanomaterials present an attractive solution, offering the high reactivity of homogenous catalysts without complex recyclability issues. Slightly less reactive, acidic sulfated nanomaterials may also demonstrate greater stability to feedstock impurity, extending lifetime and improved versatility to a range of starting feeds. There remains, however, much work to be done in demonstrating the full-scale feasibility of such catalysts. This review explores recent developments over time in acidic sulfated nanocatalysis for biodiesel production, with particular focus on metal oxides, magnetic nanoparticles, silica-supported nanomaterials, and acidic carbon nanocatalysts. Included are various summaries of current progress in the literature, as well as recommendations for future research. Full article
(This article belongs to the Special Issue Solid Acid Catalysts for Biodiesel Production)
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12 pages, 6612 KiB  
Article
Surface Modification towards Integral Bulk Catalysts of Transition Metal Borides for Hydrogen Evolution Reaction
by Wei Zhao, Dan Xu, Yanli Chen, Jiaen Cheng, Cun You, Xin Wang, Shushan Dong, Qiang Tao and Pinwen Zhu
Catalysts 2022, 12(2), 222; https://doi.org/10.3390/catal12020222 - 16 Feb 2022
Cited by 4 | Viewed by 2429
Abstract
Transition metal borides (TMBs) are promising catalysts for hydrogen evolution reaction (HER). While the commercially available TMBs indicate poor HER performance due to powder electrode and low activity sites density, optimizing commercial TMBs for better HER performance is urgent. To break through the [...] Read more.
Transition metal borides (TMBs) are promising catalysts for hydrogen evolution reaction (HER). While the commercially available TMBs indicate poor HER performance due to powder electrode and low activity sites density, optimizing commercial TMBs for better HER performance is urgent. To break through the challenge, a new strategy is proposed to compose integral bulk electrodes with needle surfaces in TMBs. The integral bulk electrodes in TiB2, ZrB2, and HfB2 are formed under high pressure and high temperature (HPHT), and the nanoneedle morphology is constructed by chemical etching. In the three materials, the smallest overpotential is 346 mV at 10 mA cm−2 in the HCl etched bulk TiB2 electrode, which is about 61.9% higher than commercial TiB2 powder. Better performance arises from better conductivity of the integral bulk electrode, and the nano morphology exposes the edge sides of the structure which have high activity site density. This work is significant for developing new kinds of bulk TMBs catalysts. Full article
(This article belongs to the Special Issue Catalytic Hydrogen Production, Storage and Application)
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14 pages, 28849 KiB  
Article
Facile Synthesis of Sillén-Aurivillius Layered Oxide Bi7Fe2Ti2O17Cl with Efficient Photocatalytic Performance for Degradation of Tetracycline
by Yan Gu, Fang Yu, Jikun Chen and Qinfang Zhang
Catalysts 2022, 12(2), 221; https://doi.org/10.3390/catal12020221 - 15 Feb 2022
Cited by 7 | Viewed by 2260
Abstract
The development of an efficient and environment-friendly photocatalyst for antibiotics degradation is of great significance and still remains a major challenge. Herein, a novel Sillén-Aurivillius layered oxide Bi7Fe2Ti2O17Cl is successfully synthesized via a one-step flux [...] Read more.
The development of an efficient and environment-friendly photocatalyst for antibiotics degradation is of great significance and still remains a major challenge. Herein, a novel Sillén-Aurivillius layered oxide Bi7Fe2Ti2O17Cl is successfully synthesized via a one-step flux route (noted as F-BFTOC) and solid-state reaction (noted as S-BFTOC). The as-prepared F-BFTOC manifests the enhanced visible-light photocatalytic performance towards tetracycline (TC) degradation compared with Bi4NbO8Cl and its degradation efficiency reaches 90% within 90 min. Additionally, the proposed degradation pathway and photocatalytic mechanism are systematically investigated by liquid chromatography tandem-mass spectrometry (HPLC-MS), active species trapping test, electron spin resonance (ESR) and first-principles calculations. The superior degradation of antibiotics is primarily derived from the photo-generated h+, and radical ·O2− as the dominant active species. More importantly, the F-BFTOC exhibits excellent cycle stability and TC is ultimately transformed into non-toxic open-loop products. Simultaneously, Rhodamine B (RhB) as a typical organic pollutant is further employed to evaluate the photocatalytic activity of F-BFTOC, and 98% of the degradation efficiency is achieved. BFTOC as a multifunctional photocatalyst for pollutant degradation offers a new insight for Sillén-Aurivillius photocatalytic in the field of water purification. Full article
(This article belongs to the Topic Catalysis for Sustainable Chemistry and Energy)
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10 pages, 1329 KiB  
Article
Tuning the Catalytic Activity of Recyclable Heterogeneous Catalysts for the Direct Etherification Reaction of Glycerol Using Antagonistic Additives
by Je Seung Lee, Eunji Jang, Dae Won Kim and Seo Kyung Park
Catalysts 2022, 12(2), 220; https://doi.org/10.3390/catal12020220 - 15 Feb 2022
Cited by 2 | Viewed by 1902
Abstract
Using zeolite as a heterogeneous catalyst, the reaction conditions were optimized to increase the yield and selectivity of diglycerol (DG) and triglycerol (TG) in the direct etherification reaction of glycerol. By the addition of weakly acidic alkali metal-based inorganic salts (NaHSO4 and [...] Read more.
Using zeolite as a heterogeneous catalyst, the reaction conditions were optimized to increase the yield and selectivity of diglycerol (DG) and triglycerol (TG) in the direct etherification reaction of glycerol. By the addition of weakly acidic alkali metal-based inorganic salts (NaHSO4 and KHSO4), the selectivities and yields of DG and TG increased. Although the conversion of glycerol was lowered due to the role of the additive as an inhibitor, the reaction conditions were optimized by controlling the amounts and reaction times of the additives to increase the yields of DG and TG. Under the optimized condition, the glycerol conversion was as high as 85.4%, and the highest yields of DG and TG were observed as 54.1% and 21.3%, respectively. The recyclability of the catalysts was much enhanced by the influence of the additives suppressing the formation of oligomers. Full article
(This article belongs to the Special Issue Catalytic Conversion of Glycerol)
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19 pages, 6021 KiB  
Article
Toluene Steam Reforming over Ni/CeZrO2—The Influence of Steam to Carbon Ratio and Contact Time on the Catalyst Performance and Carbon Deposition
by Agata Łamacz
Catalysts 2022, 12(2), 219; https://doi.org/10.3390/catal12020219 - 15 Feb 2022
Cited by 5 | Viewed by 2389
Abstract
The formation of tars during coal or biomass gasification is a serious issue resulting in decreasing efficiency of the process and increased maintenance costs. The decomposition of tars can be conducted via catalytic steam reforming that enriches the produced gas in hydrogen. Nevertheless, [...] Read more.
The formation of tars during coal or biomass gasification is a serious issue resulting in decreasing efficiency of the process and increased maintenance costs. The decomposition of tars can be conducted via catalytic steam reforming that enriches the produced gas in hydrogen. Nevertheless, the catalyst should be characterized by high activity, stability, and resistance towards carbon deposition. Ceria-zirconia supported nickel (Ni/CeZrO2) is a very good candidate to catalyze tar removal—Ni is an active phase for reforming reactions, while CeZrO2 provides the active sites that play important roles in protecting the catalyst from carbon deposition. Ni/CeZrO2 shows high activity in the steam reforming of model tar compounds. In this paper, its performance in the steam reforming of toluene and carbon deposition is discussed considering the changing parameters of the reaction: the temperature, steam to carbon ratio, and the contact time. Full article
(This article belongs to the Special Issue Catalysts in Environmental and Climate Protection)
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25 pages, 33737 KiB  
Article
Evaluation of Au/ZrO2 Catalysts Prepared via Postsynthesis Methods in CO2 Hydrogenation to Methanol
by Tatiparthi Vikram Sagar, Janez Zavašnik, Matjaž Finšgar, Nataša Novak Tušar and Albin Pintar
Catalysts 2022, 12(2), 218; https://doi.org/10.3390/catal12020218 - 14 Feb 2022
Cited by 13 | Viewed by 3450
Abstract
Au nanoparticles supported on ZrO2 enhance its surface acidic/basic properties to produce a high yield of methanol via the hydrogenation of CO2. Amorphous ZrO2-supported 0.5–1 wt.% Au catalysts were synthesized by two methods, namely deposition precipitation (DP) and [...] Read more.
Au nanoparticles supported on ZrO2 enhance its surface acidic/basic properties to produce a high yield of methanol via the hydrogenation of CO2. Amorphous ZrO2-supported 0.5–1 wt.% Au catalysts were synthesized by two methods, namely deposition precipitation (DP) and impregnation (IMP), characterized by a variety of techniques, and evaluated in the process of CO2 hydrogenation to methanol. The DP-method catalysts were highly advantageous over the IMP-method catalyst. The DP method delivered samples with a large surface area, along with the control of the Au particle size. The strength and number of acidic and basic sites was enhanced on the catalyst surface. These surface changes attributed to the DP method greatly improved the catalytic activity when compared to the IMP method. The variations in the surface sites due to different preparation methods exhibited a huge impact on the formation of important intermediates (formate, dioxymethylene and methoxy) and their rapid hydrogenation to methanol via the formate route, as revealed by means of in situ DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) analysis. Finally, the rate of formation of methanol was enhanced by the increased synergy between the metal and the support. Full article
(This article belongs to the Topic Catalysis for Sustainable Chemistry and Energy)
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20 pages, 1276 KiB  
Review
Partial Methane Oxidation in Fuel Cell-Type Reactors for Co-Generation of Energy and Chemicals: A Short Review
by Rodrigo F. B. de Souza, Daniel Z. Florio, Ermete Antolini and Almir O. Neto
Catalysts 2022, 12(2), 217; https://doi.org/10.3390/catal12020217 - 14 Feb 2022
Cited by 13 | Viewed by 4362
Abstract
The conversion of methane into chemicals is of interest to achieve a decarbonized future. Fuel cells are electrochemical devices commonly used to obtain electrical energy but can be utilized either for chemicals’ production or both energy and chemicals cogeneration. In this work, the [...] Read more.
The conversion of methane into chemicals is of interest to achieve a decarbonized future. Fuel cells are electrochemical devices commonly used to obtain electrical energy but can be utilized either for chemicals’ production or both energy and chemicals cogeneration. In this work, the partial oxidation of methane in fuel cells for electricity generation and valuable chemicals production at the same time is reviewed. For this purpose, we compile different types of methane-fed fuel cells, both low- and high-temperature fuel cells. Despite the fact that few studies have been conducted on this subject, promising results are driving the development of fuel cells that use methane as a fuel source for the cogeneration of power and valuable chemicals. Full article
(This article belongs to the Section Catalytic Materials)
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13 pages, 2604 KiB  
Article
Influence of Supports on the Catalytic Activity and Coke Resistance of Ni Catalyst in Dry Reforming of Methane
by Da Hye Song, Un Ho Jung, Young Eun Kim, Hyo Been Im, Tae Ho Lee, Ki Bong Lee and Kee Young Koo
Catalysts 2022, 12(2), 216; https://doi.org/10.3390/catal12020216 - 14 Feb 2022
Cited by 6 | Viewed by 2939
Abstract
The dependence of the catalytic activity and coke resistance of Ni-based catalysts on the support type was investigated in the dry reforming of methane (DRM). Catalysts were prepared using incipient wetness impregnation and analyzed using ICP-OES, BET-BJH, XRD, H2-chemisorption, H2 [...] Read more.
The dependence of the catalytic activity and coke resistance of Ni-based catalysts on the support type was investigated in the dry reforming of methane (DRM). Catalysts were prepared using incipient wetness impregnation and analyzed using ICP-OES, BET-BJH, XRD, H2-chemisorption, H2-TPR, and CO2-TPD. DRM was performed at 600–750 °C at 144,000 mL/gcat∙h of GHSV (CH4/CO2/N2 = 1/1/1). Ni/Al2O3 and Ni/MgO catalysts formed NiAl2O4 and NiO-MgO solid solutions, respectively, owing to strong binding between the metal and support. In contrast, MgO-Al2O3 and MgAl2O4 supports suppressed NiAl2O4 and NiO-MgO solid solution formation, due to Mg addition, with high metal dispersions of 4.6 and 6.6%, respectively. In the DRM reaction, the Ni/MgO-Al2O3 and Ni/MgAl2O4 catalysts showed high CH4 conversions of 78.1 and 76.8%, respectively, compared with Ni/Al2O3 and Ni/MgO at 750 °C. A stability test was performed at 600 °C for 20 h. A coke study of the spent catalysts was performed using SEM and TGA. Alkaline-earth metal-containing catalysts Ni/MgO-Al2O3 and Ni/MgAl2O4 with strong CO2 adsorption properties showed 20 wt% reduction in carbon deposition compared to commercial catalysts. Therefore, the support and basic properties of the catalyst significantly influenced the catalyst performance and coke resistance in the DRM. Full article
(This article belongs to the Special Issue Advances in Reforming Catalysts for Hydrogen Production)
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18 pages, 7602 KiB  
Article
Experimental and Theoretical Investigations of Low-Dimensional BiFeO3 System for Photocatalytic Applications
by Manal Benyoussef, Sébastien Saitzek, Nitul S. Rajput, Matthieu Courty, Mimoun El Marssi and Mustapha Jouiad
Catalysts 2022, 12(2), 215; https://doi.org/10.3390/catal12020215 - 12 Feb 2022
Cited by 15 | Viewed by 3542
Abstract
We report on the fabrication of sub-20 nm BiFeO3 (BFO) nanoparticles using a solid-state approach and preferential leching process. The nanoparticles were subsequently used to deposit, through spray pyrolysis, BFO thin films in a rhombohedral (R3c) crystallographic structure. Then, systematic investigations of [...] Read more.
We report on the fabrication of sub-20 nm BiFeO3 (BFO) nanoparticles using a solid-state approach and preferential leching process. The nanoparticles were subsequently used to deposit, through spray pyrolysis, BFO thin films in a rhombohedral (R3c) crystallographic structure. Then, systematic investigations of the optical and the photocatalytic properties were conducted to determine the effects of the particles size, the microstructure and the increased surface area on their catalytic performances. Especially, improved optical properties were observed, with an optical bandgap energy of 2.20 eV compared to reported 2.7 eV for the bulk system. In addition, high optical absorption was obtained in the UV–visible light region reaching up to 90% at 400 nm. The photoelectrochemical measurements revealed a high photocurrent density under visible light irradiation. Besides, density functional theory calculations were performed on both bulk and thin film BFO structures, revealing an interesting comparison of the electronic, magnetic, ferroelectric and optical properties for bulk and thin film BFO systems. Both theoretical and experimental findings show that the alignment of the band edges of BFO thin film is coherent with good photocatalytic water splitting potential, making them desirable photoanode materials. Full article
(This article belongs to the Special Issue Selective Catalysis for the Sustainable Energies)
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