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Catalysts, Volume 14, Issue 7 (July 2024) – 60 articles

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17 pages, 4066 KiB  
Article
Strong Magnetic p-n Heterojunction Fe3O4-FeWO4 for Photo-Fenton Degradation of Tetracycline Hydrochloride
by Binger Bai, Guanrong Cheng, Jian Chen, Xiaoping Chen and Qizhao Wang
Catalysts 2024, 14(7), 453; https://doi.org/10.3390/catal14070453 (registering DOI) - 14 Jul 2024
Viewed by 133
Abstract
With the abuse of antibiotics, its pollution poses an increasing threat to the environment and human health. Effective degradation of organic pollutants in water bodies is urgent. Compared to traditional treatment methods, advanced oxidation processes that have developed rapidly in recent years are [...] Read more.
With the abuse of antibiotics, its pollution poses an increasing threat to the environment and human health. Effective degradation of organic pollutants in water bodies is urgent. Compared to traditional treatment methods, advanced oxidation processes that have developed rapidly in recent years are more environmentally friendly, efficient and applicable to a wider range of organic compounds. FeWO4 was used in this study as the iron-based semiconductor material to modify and optimize the material design. Fe3O4/FeWO4 composites were prepared by a two-step hydrothermal method. The crystal structure, surface morphology, electrochemical properties and separability of the composite semiconductor were analyzed by XRD, XPS, UV-vis, SEM, EDS and Mott-Schottky. The results showed that, when the initial contaminant concentration was 30 mg/L, the initial solution pH was 4, the dosage of the catalyst was 25 mg and the dosage of hydrogen peroxide was 30 μL, the degradation efficiency of tetracycline hydrochloride (TCH) could reach 91% within 60 min, which was significantly improved compared to the performance of the single semiconductors Fe3O4 and FeWO4. In addition, the catalyst prepared in this experiment can be easily recovered by magnetic separation technology in practical application, which will not affect the turbidity of water while reducing the cost of catalyst separation and recovery. Full article
(This article belongs to the Special Issue Two-Dimensional Materials in Photo(electro)catalysis)
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27 pages, 2109 KiB  
Review
Catalytic Applications in the Production of Hydrotreated Vegetable Oil (HVO) as a Renewable Fuel: A Review
by Nur-Sultan Mussa, Kainaubek Toshtay and Mickael Capron
Catalysts 2024, 14(7), 452; https://doi.org/10.3390/catal14070452 (registering DOI) - 14 Jul 2024
Viewed by 151
Abstract
The significance and challenges of hydrotreatment processes for vegetable oils have recently become apparent, encompassing various reactions like decarbonylation, decarboxylation, and hydrogenation. Heterogeneous noble or transition metal catalysts play a crucial role in these reactions, offering high selectivity in removing oxygen and yielding [...] Read more.
The significance and challenges of hydrotreatment processes for vegetable oils have recently become apparent, encompassing various reactions like decarbonylation, decarboxylation, and hydrogenation. Heterogeneous noble or transition metal catalysts play a crucial role in these reactions, offering high selectivity in removing oxygen and yielding desired hydrocarbons. Notably, both sulphided and non-sulphided catalysts exhibit effectiveness, with the latter gaining attention due to health and toxicity concerns associated with sulphiding agents. Nickel-based catalysts, such as NiP and NiC, demonstrate specific properties and tendencies in deoxygenation reactions, while palladium supported on activated carbon catalysts shows superior activity in hydrodeoxygenation. Comparisons between the performances of different catalysts in various hydrotreatment processes underscore the need for tailored approaches. Transition metal phosphides (TMP) emerge as promising catalysts due to their cost-effectiveness and environmental friendliness. Ultimately, there is an ongoing pursuit of efficient catalysts and the importance of further advancements in catalysis for the future of vegetable oil hydrotreatment. Full article
(This article belongs to the Section Biomass Catalysis)
20 pages, 2772 KiB  
Review
Enhancing Trace Pb2⁺ Detection via Novel Functional Materials for Improved Electrocatalytic Redox Processes on Electrochemical Sensors: A Short Review
by Duowen Yang, Xinyu Wang and Hao Xu
Catalysts 2024, 14(7), 451; https://doi.org/10.3390/catal14070451 (registering DOI) - 14 Jul 2024
Viewed by 155
Abstract
The efficient detection of lead ions (Pb2⁺) is significant for environmental protection and public health. Electrochemical detection has emerged as one of the most promising technologies due to its low detection limits, high sensitivity, and cost-effectiveness. However, significant challenges remain, including [...] Read more.
The efficient detection of lead ions (Pb2⁺) is significant for environmental protection and public health. Electrochemical detection has emerged as one of the most promising technologies due to its low detection limits, high sensitivity, and cost-effectiveness. However, significant challenges remain, including issues related to sensitivity, selectivity, interference, and the stability of electrode materials. This review explores recent advancements in the field, focusing on integrating novel catalytic materials and innovative sensor construction methods. Particular emphasis is placed on enhancing the electrocatalytic redox processes on sensor surfaces using advanced nanomaterials such as MXenes, ferrite-based nanomaterials, carbon nanomaterials, and metal–organic frameworks (MOFs). Additionally, the role of biomaterials and enzymes in improving electrochemical sensors’ selectivity and anti-interference capabilities is discussed. Despite the impressive low detection limits achieved, real-world applications present additional challenges due to the complex composition of environmental samples. The review concludes with future perspectives on overcoming these challenges by leveraging the unique properties of catalytic materials to develop more effective and reliable electrochemical sensors for trace Pb2⁺ detection. Full article
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48 pages, 3240 KiB  
Review
Advancing Plastic Recycling: A Review on the Synthesis and Applications of Hierarchical Zeolites in Waste Plastic Hydrocracking
by Muhammad Usman Azam, Waheed Afzal and Inês Graça
Catalysts 2024, 14(7), 450; https://doi.org/10.3390/catal14070450 - 12 Jul 2024
Viewed by 267
Abstract
The extensive use of plastics has led to a significant environmental threat due to the generation of waste plastic, which has shown significant challenges during recycling. The catalytic hydrocracking route, however, is viewed as a key strategy to manage this fossil-fuel-derived waste into [...] Read more.
The extensive use of plastics has led to a significant environmental threat due to the generation of waste plastic, which has shown significant challenges during recycling. The catalytic hydrocracking route, however, is viewed as a key strategy to manage this fossil-fuel-derived waste into plastic-derived fuels with lower carbon emissions. Despite numerous efforts to identify an effective bi-functional catalyst, especially metal-loaded zeolites, the high-performing zeolite for hydrocracking plastics has yet to be synthesized. This is due to the microporous nature of zeolite, which results in the diffusional limitations of bulkier polymer molecules entering the structure and reducing the overall cracking of plastic and catalyst cycle time. These constraints can be overcome by developing hierarchical zeolites that feature shorter diffusion paths and larger pore sizes, facilitating the movement of bulky polymer molecules. However, if the hierarchical modification process of zeolites is not controlled, it can lead to the synthesis of hierarchical zeolites with compromised functionality or structural integrity, resulting in reduced conversion for the hydrocracking of plastics. Therefore, we provide an overview of various methods for synthesizing hierarchical zeolites, emphasizing significant advancements over the past two decades in developing innovative strategies to introduce additional pore systems. However, the objective of this review is to study the various synthesis approaches based on their effectiveness while developing a clear link between the optimized preparation methods and the structure-activity relationship of the resulting hierarchical zeolites used for the hydrocracking of plastics. Full article
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23 pages, 5531 KiB  
Article
Novel Starch-Modified NiCrMn-LDH-Based Composite for Photocatalytic Degradation of Reactive Orange 13
by Muhammad Usman, Muhammad Babar Taj, Afaf Almasoudi, Doaa F. Baamer, Omar Makram Ali, Muhammad Imran Khan, Ismat Bibi, Mobeen Ur Rehman, Rabia Rasheed, Ahmad Raheel, Mushtaq Hussain Lashari, Abdallah Shanableh and Javier Fernandez-Garcia
Catalysts 2024, 14(7), 449; https://doi.org/10.3390/catal14070449 - 12 Jul 2024
Viewed by 210
Abstract
Water pollution has become a great challenge today. To address this problem regarding wastewater treatment by removing toxic synthetic dyes from wastewater, this research focused on the synthesis of a novel starch-modified NiCrMn-layered double hydroxide composite through the coprecipitation method and applied it [...] Read more.
Water pollution has become a great challenge today. To address this problem regarding wastewater treatment by removing toxic synthetic dyes from wastewater, this research focused on the synthesis of a novel starch-modified NiCrMn-layered double hydroxide composite through the coprecipitation method and applied it as a photocatalyst for the degradation of reactive orange 13 dye. The synthesized photocatalyst was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), point of zero charges (PZC), dynamic light scattering (DLS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Zeta potential techniques. These techniques revealed different characteristics of photocatalysts, like surface and structural properties. According to BET analysis, the final composite had 2.5 × 102 m2/g BET-specific surface area with a 45.56 nm pore radius value, and the overall composite found as mesoporous. Similarly, in DLS analysis, bare NiCrMn-LDH had 404 nm hydrodynamic size, which increased for the final starch composite up to 667 nm. Zeta potential value changed from −14.56 mV to 0.95 mV after the incorporation of starch with NiCrMn-LDH. They confirmed the incorporation of starch with trimetallic NiCrMn-layered double hydroxide (2:1:2). Starch association improved the properties of the photocatalyst like surface area. Different parameters like pH value, initial dye concentration, photocatalyst dose, hydrogen peroxide concentration, effect of sacrificial reagent, and effect of inorganic anions were studied for degradation of RO13. Overall, the photocatalysis process for RO13 followed pseudo-first-order kinetics. Photocatalytic degradation reactions for reactive orange 13 were conducted with an initial dye concentration of 10 mg/L, photocatalyst dosage of 20 mg/50 mL, and pH value at 3 in the presence of sunlight, resulting in an impressive degradation removal rate of 86.68%. This remarkable degradation ability of the photocatalyst for reactive orange 13 proves this composite was highly efficient. Full article
(This article belongs to the Section Photocatalysis)
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19 pages, 859 KiB  
Article
The Influence of Au Loading and TiO2 Support on the Catalytic Wet Air Oxidation of Glyphosate over TiO2+Au Catalysts
by Gregor Žerjav, Alen Albreht and Albin Pintar
Catalysts 2024, 14(7), 448; https://doi.org/10.3390/catal14070448 - 12 Jul 2024
Viewed by 158
Abstract
This study aimed to explore the impact of varying amounts of added Au (0.5 to 2 wt.%) and the structural characteristics of anatase TiO2 supports (nanoparticles (TP, SBET = 88m2/g) and nanorods (TR, SBET = 105 m2 [...] Read more.
This study aimed to explore the impact of varying amounts of added Au (0.5 to 2 wt.%) and the structural characteristics of anatase TiO2 supports (nanoparticles (TP, SBET = 88m2/g) and nanorods (TR, SBET = 105 m2/g)) on the catalytic efficiency of TiO2+Au catalysts in eliminating the herbicide glyphosate from aqueous solutions via the catalytic wet air oxidation (CWAO) process. The investigation was conducted using a continuous-flow trickle-bed reactor. Regardless of the TiO2 support and the amount of Au added, the addition of Au has a positive effect on the glyphosate degradation rate. Regarding the amount of Au added, the highest catalytic activity was observed with the TP + 1% Au catalyst, which had a higher Schottky barrier (SB) than the TP + 2% Au catalyst, which helped the charge carriers in the TiO2 conduction band to increase their reduction potential by preventing them from returning to the Au. The role of glyphosate degradation product adsorption on the catalyst surface is crucial for sustaining the long-term catalytic activity of the investigated TiO2+Au materials. This was particularly evident in the case of the TR + 1% Au catalyst, which had the highest glyphosate degradation rate at the beginning of the CWAO experiment, but its catalytic activity then decreased over time due to the adsorption of glyphosate degradation products, which was favoured by the presence of strong acidic sites. In addition, the TR + 1% Au solid had the smallest average Au particle size of all analyzed materials, which were more easily deactivated by the adsorption of glyphosate degradation products. The analysis of the degradation products of glyphosate shows that the oxidation of glyphosate in the liquid phase involves the rupture of C–P and C–N bonds, as amino-methyl-phosphonic acid (AMPA), glyoxylic acid and sarcosine were detected. Full article
(This article belongs to the Special Issue Environmental Catalysis in Advanced Oxidation Processes, 2nd Edition)
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36 pages, 3154 KiB  
Review
Photocatalytic Application of Polymers in Removing Pharmaceuticals from Water: A Comprehensive Review
by Sanja J. Armaković, Stevan Armaković and Maria M. Savanović
Catalysts 2024, 14(7), 447; https://doi.org/10.3390/catal14070447 - 12 Jul 2024
Viewed by 242
Abstract
This comprehensive review covers recent advancements in utilizing various types of polymers and their modifications as photocatalysts for the removal of pharmaceutical contaminants from water. It also considers polymers that enhance the photocatalytic properties of other materials, highlighting their dual role in improving [...] Read more.
This comprehensive review covers recent advancements in utilizing various types of polymers and their modifications as photocatalysts for the removal of pharmaceutical contaminants from water. It also considers polymers that enhance the photocatalytic properties of other materials, highlighting their dual role in improving water purification efficiency. Over the past decades, significant progress has been made in understanding the photocatalytic properties of polymers, including organic, inorganic, and composite materials, and their efficacy in degrading pharmaceuticals. Some of the most commonly used polymers, such as polyaniline, poly(p-phenylene vinylene), polyethylene oxide, and polypyrole, and their properties have been reviewed in detail. Physical modification techniques (mechanical blending and extrusion processing) and chemical modification techniques (nanocomposite formation, plasma modification techniques, surface functionalization, and cross-linking) have been discussed as appropriate for modifying polymers in order to increase their photocatalytic activity. This review examines the latest research findings, including the development of novel polymer-based photocatalysts and their application in the removal of pharmaceutical compounds, as well as optimization strategies for enhancing their performance. Additionally, challenges and future directions in this field are discussed to guide further research efforts. Full article
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19 pages, 2772 KiB  
Article
Staphylococcus aureus Alkaline Protease: A Promising Additive for Industrial Detergents
by Mona Alonazi
Catalysts 2024, 14(7), 446; https://doi.org/10.3390/catal14070446 - 12 Jul 2024
Viewed by 190
Abstract
A novel alkaline serine protease, derived from the Staphylococcus aureus strain ALA1 previously isolated from dromedary milk, was subjected to purification and characterization. Optimal protease production occurred under specific culture conditions. The purified protease, designated S. aureus Pr with a molecular mass of [...] Read more.
A novel alkaline serine protease, derived from the Staphylococcus aureus strain ALA1 previously isolated from dromedary milk, was subjected to purification and characterization. Optimal protease production occurred under specific culture conditions. The purified protease, designated S. aureus Pr with a molecular mass of 23,662 Da and an N-terminal sequence, showed an approximately 89% similar identity with those of other Staphylococcus strains. It exhibited its highest enzymatic activity at a pH of 10.0 and 60 °C in the presence of 3 mM Ca2+. Remarkable thermostability was observed at temperatures up to 70 °C and within a pH range of 6.0 to 10.0 for 2 h. The presence of Ca2+ or Mg2+ and Zn2+ significantly enhanced both enzymatic activity and thermal stability. Additionally, notable stability was demonstrated in the presence of reducing and chaotropic agents as well as in surfactants, oxidizing agents, and organic solvents commonly found in detergent compositions. This highlights the enzyme’s potential as a versatile biocatalyst, especially in detergents. Its stability and compatibility with laundry detergents matched Alcalase 2.5 L, type Dx, and the Stearothermophilus protease, used as controls. Collectively, this study investigated the potential utilization of S. aureus Pr in industrial detergents as an excellent candidate for incorporation as an additive in detergent formulations. Full article
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12 pages, 1017 KiB  
Article
Mixed Oxides as Catalysts for the Condensation of Cyclohexanol and Benzaldehyde to Obtain a Claisen–Schmidt Condensation Product
by Tanya Stoylkova, Tsveta Stanimirova, Christo D. Chanev, Petya Petrova and Kristina Metodieva
Catalysts 2024, 14(7), 445; https://doi.org/10.3390/catal14070445 - 11 Jul 2024
Viewed by 242
Abstract
Acid–base M2+MgAlO and M2+AlO mixed oxides (where M2+ = Mg, Cu, Co, Zn, and Ni) were obtained by thermal decomposition of the corresponding layered double hydroxide (LDH) precursors and used as catalysts for cyclohexanol and benzaldehyde condensation under [...] Read more.
Acid–base M2+MgAlO and M2+AlO mixed oxides (where M2+ = Mg, Cu, Co, Zn, and Ni) were obtained by thermal decomposition of the corresponding layered double hydroxide (LDH) precursors and used as catalysts for cyclohexanol and benzaldehyde condensation under solvent-free conditions. The catalysts were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and temperature-programmed desorption of CO2 (TPD-CO2). Gas chromatography–mass spectroscopy (GC/MS) was used for the identification and quantification of the product mixtures. In the reaction of cyclohexanol and benzaldehyde on M2+MgAlO and MgAlO catalysts, a 2,6-dibenzylidene-cyclohexanone was obtained as the main product as a result of consecutive one-pot dehydrogenation of cyclohexanol to cyclohexanone and subsequent Claisen–Schmidt condensation. In the reaction mixture obtained in the presence of NiAlO, CoAlO, and ZnAlO catalysts, a cyclohexyl ester of 6-hydroxyhexanoic acid was detected together with the main product. This is most likely a by-product obtained after the oxidation, ring opening, and subsequent esterification of the cyclohexanol. Full article
4 pages, 164 KiB  
Editorial
Nanocatalysts for the Degradation of Refractory Pollutants
by Sheng Guo, Yazi Liu and Jun Li
Catalysts 2024, 14(7), 444; https://doi.org/10.3390/catal14070444 - 11 Jul 2024
Viewed by 174
Abstract
The rapid development of industrialization has resulted in the excessive emission of hazardous contaminants into our water and air resources, adversely affecting both health and the environment [...] Full article
(This article belongs to the Special Issue Nanocatalysts for the Degradation of Refractory Pollutants)
16 pages, 17079 KiB  
Article
Structural Effect of Cu-Mn/Al2O3 Catalysts on Enhancing Toluene Combustion Performance: Molecular Structure of Polyols and Hydrothermal Treatment
by Junjie Li, Wenjing Chen, Chenghua Xu, Xiaoxiao Hou and Xiaodong Hu
Catalysts 2024, 14(7), 443; https://doi.org/10.3390/catal14070443 - 11 Jul 2024
Viewed by 207
Abstract
This study presents a series of Cu-Mn/Al2O3 catalysts prepared by the polyol method to improve the toluene combustion process. The catalytic activity evaluation results showed that the different polyols have a great influence on catalyst activity, in which the catalyst [...] Read more.
This study presents a series of Cu-Mn/Al2O3 catalysts prepared by the polyol method to improve the toluene combustion process. The catalytic activity evaluation results showed that the different polyols have a great influence on catalyst activity, in which the catalyst prepared with glycerol through a hydrothermal reaction at 90 °C displayed the highest catalytic activity. The lowest T90 and T50 values could be achieved by CMA-GL-90 with 260 and 237 °C, respectively. Moreover, the XRD and BET results showed that the hydrothermal treatment was more favorable with Cu-Mn crystal formation, and an abundance of mesopores remained in all catalysts with a high specific surface area from 94.37 to 123.03 m2·g−1. The morphology analysis results by SEM and TEM indicated that employing glycerol coupled with hydrothermal treatment at 90 °C could enhance the formation of CuMn2O4 spinel. The toluene catalytic combustion mechanism of Cu-Mn/Al2O3 catalysts was discussed based on XPS and H2-TPR, and a high atomic ratio of Mn3+ could be obtained with 51.03%, and the ratio of Oads/Olatt also increased to 2.85 in CMA-GL-90. The increase in Mn3+ species and oxygen vacancies on the surface of catalysts exhibited excellent activity and stability for toluene combustion. These findings offer valuable insights for optimizing the design and application of Cu-Mn/Al2O3 catalysts in addressing the catalytic oxidation reactions of organic volatile compounds. Full article
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15 pages, 9817 KiB  
Article
Enhanced Photocatalytic Performances of SnS2/TiO2 Composites via a Charge Separation Following Z-Scheme at the SnS2/TiO2{101} Facets
by Nkenku Carl, Muhammad Fiaz, Hyun-Seok Oh and Yu-Kwon Kim
Catalysts 2024, 14(7), 442; https://doi.org/10.3390/catal14070442 - 10 Jul 2024
Viewed by 264
Abstract
The formation of heterojunctions for efficient charge separation has been practiced for the preparation of efficient semiconductor-based photocatalysts for applications such as hydrogen production and environmental remediation. In this study, we synthesized a composite structure with a heterojunction between SnS2 and TiO [...] Read more.
The formation of heterojunctions for efficient charge separation has been practiced for the preparation of efficient semiconductor-based photocatalysts for applications such as hydrogen production and environmental remediation. In this study, we synthesized a composite structure with a heterojunction between SnS2 and TiO2 through a microwave-assisted hydrothermal process, in which SnS2 nanoparticles grew on nanocrystalline TiO2 nanosheets preferentially at the exposed {101} facets. Appropriate exposure of the {001} and {101} facets of the TiO2 nanosheet in the composite with a preferential growth of SnS2 nanoparticles at the {101} facets was the origin of the charge separation following a direct Z-scheme mechanism to result in enhanced photocatalytic performances in photodegradation of organic dyes such as methylene blue (MB) and rhodamine B (RhB) compared to that of SnS2 and TiO2 alone. A plot of photodegradation rates vs. SnS2 ratios in the composites gave an overall volcano-shaped curve with a maximum at the SnS2 ratio of about 33% at which small SnS2 nanoparticles were populated at the {101} facets of the TiO2 nanosheets with a high surface area (118.2 m2g−1). Our results suggest the microwave-assisted hydrothermal process can be a good synthetic approach for composite-based photocatalysts with a preferential heterojunction structure. Full article
(This article belongs to the Special Issue Recent Advances in Environment and Energy Catalysis)
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11 pages, 2358 KiB  
Article
Tuning a Cr-Catalyzed Ethylene Oligomerization Product Profile via a Rational Design of the N-aryl PNP Ligands
by Samir Barman, E. A. Jaseer, Nestor Garcia, Mohamed Elanany, Motaz Khawaji, Niladri Maity and Abdulrahman Musa
Catalysts 2024, 14(7), 441; https://doi.org/10.3390/catal14070441 - 10 Jul 2024
Viewed by 267
Abstract
An approach towards incorporating varied degrees of steric profiles around the ligand’s backbone, which were envisaged to alter the catalytic paths leading to targeted 1-C8/1-C6 olefin products, were explored. Cr-pre-catalysts designed with PNP ligands comprising a fused aryl moiety were [...] Read more.
An approach towards incorporating varied degrees of steric profiles around the ligand’s backbone, which were envisaged to alter the catalytic paths leading to targeted 1-C8/1-C6 olefin products, were explored. Cr-pre-catalysts designed with PNP ligands comprising a fused aryl moiety were delivered at a relatively higher C8 olefin selectivity (up to 74.6 wt% and C8/C6 of 3.4) when the N-connection to the aromatic unit was placed at the 2-position. A relatively higher C6 olefin selectivity (up to 33.7 wt% and C8/C6 of 1.9) was achieved with the PNP unit anchored at the 1- or 6-position. Based on detailed catalytic studies, we confirm the fact that by introducing a controlled degree of bulkiness on the N-site through a judicious selection of the N-aryl moiety of different sizes, the selectivity of the targeted olefin product could be tuned in a rational manner. Full article
(This article belongs to the Special Issue Advanced Catalysis for Energy and Environmental Applications)
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11 pages, 2861 KiB  
Article
Theoretical Study of Reversible Hydrogenation of CO2 to Formate Catalyzed by Ru(II)–PN5P, Fe(II)–PN5P, and Mn(I)–PN5P Complexes: The Effect of the Transition Metal Center
by Lingqiang Meng, Lihua Yao and Jun Li
Catalysts 2024, 14(7), 440; https://doi.org/10.3390/catal14070440 - 9 Jul 2024
Viewed by 315
Abstract
In 2022, Beller and coworkers achieved the reversible hydrogenation of CO2 to formic acid using a Mn(I)–PN5P complex with excellent activity and reusability of the catalyst . To understand the detailed mechanism for the reversible hydrogen release–storage process, especially the [...] Read more.
In 2022, Beller and coworkers achieved the reversible hydrogenation of CO2 to formic acid using a Mn(I)–PN5P complex with excellent activity and reusability of the catalyst . To understand the detailed mechanism for the reversible hydrogen release–storage process, especially the effects of the transition metal center in this process, we employed DFT calculations according to which Ru(II) and Fe(II) are considered as two alternatives to the Mn(I) center. Our computational results showed that the production of formic acid from CO2 hydrogenation is not thermodynamically favorable. The reversible hydrogen release–storage process actually occurs between CO2/H2 and formate rather than formic acid. Moreover, Mn(I) might not be a unique active metal for the reversible hydrogenation of CO2 to formate; Ru(II) would be a better option. Full article
(This article belongs to the Special Issue Catalysis for Selective Hydrogenation of CO and CO2, 2nd Edition)
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2 pages, 153 KiB  
Editorial
Exclusive Review Papers in Catalytic Materials
by Carolina Belver
Catalysts 2024, 14(7), 439; https://doi.org/10.3390/catal14070439 (registering DOI) - 9 Jul 2024
Viewed by 213
Abstract
Catalytic materials exist in several forms and can be prepared using different methodologies and protocols [...] Full article
(This article belongs to the Special Issue Exclusive Review Papers in Catalytic Materials)
3 pages, 154 KiB  
Editorial
Advances in Transition Metal Catalysis—Preface to the Special Issue
by Alessia Ciogli and Antonia Iazzetti
Catalysts 2024, 14(7), 438; https://doi.org/10.3390/catal14070438 (registering DOI) - 9 Jul 2024
Viewed by 220
Abstract
Over the years, transition metal catalysis has had a significant impact on science and technology [...] Full article
(This article belongs to the Special Issue Advances in Transition Metal Catalysis)
12 pages, 1667 KiB  
Article
Autocatalyzed Kinetics of 6-Electron Electroreduction of Iodic Acid Studied by Rotating Disk Electrode Technique
by Liliya Antipova, Oleg Tripachev, Alexandra Rybakova, Vladimir Andreev, Roman Pichugov, George Sudarev, Anatoly Antipov and Alexander Modestov
Catalysts 2024, 14(7), 437; https://doi.org/10.3390/catal14070437 (registering DOI) - 9 Jul 2024
Viewed by 281
Abstract
The 6-electron electrochemical reduction of IO3 to I represents a breakthrough for the development of next-generation redox flow batteries, offering substantially higher energy densities for oxidizer storage. Our study reveals that on a glassy carbon (GC) electrode in acidic electrolytes, [...] Read more.
The 6-electron electrochemical reduction of IO3 to I represents a breakthrough for the development of next-generation redox flow batteries, offering substantially higher energy densities for oxidizer storage. Our study reveals that on a glassy carbon (GC) electrode in acidic electrolytes, HIO3 undergoes an autocatalyzed electrochemical reduction to I. This process is mediated by the formation of a thin iodine layer on the electrode, acting as an intermediate and a catalyst. Under steady-state conditions, the iodine layer forms via a comproportionation reaction (HIO3 + I + 5H+ = I2 (s) + 3H2O). Initially, the iodine layer is generated through the slow direct electrochemical reduction of HIO3 on pristine GC. Once established, this layer significantly enhances the rate of iodate reduction. On voltammetry curves, it is clearly observable as a step-wise current surge to reach a plateau. The limiting current density on the GC seemingly aligns with the Levich equation, varying with the RDE rotation rate. Earlier, we demonstrated the electrochemical oxidation of I back to HIO3 using an H2/HIO3 flow cell, showcasing a full cycle that underpins the feasibility of this approach for energy storage. This study advances the understanding of iodate electroreduction and underscores its role in enhancing the capacity of next-generation energy storage systems. Full article
(This article belongs to the Section Electrocatalysis)
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13 pages, 1545 KiB  
Article
La-Modified SBA-15 Prepared by Direct Synthesis: Importance of Determining Actual Composition
by Gloribel Morales Hernández, José Escobar, José G. Pacheco Sosa, Mario A. Guzmán Cruz, José G. Torres Torres, Paz del Ángel Vicente, María C. Barrera, Carlos E. Santolalla Vargas and Hermicenda Pérez Vidal
Catalysts 2024, 14(7), 436; https://doi.org/10.3390/catal14070436 - 8 Jul 2024
Viewed by 329
Abstract
Lanthanum (La) integration (at various nominal contents) in SBA-15 prepared under acidic medium was intended from corresponding direct nitrate addition during mesoporous silica formation. Materials were impregnated with Pt (1.5 wt%) and studied through several textural (N2 physisorption), structural (XRD, TG-DTG), and [...] Read more.
Lanthanum (La) integration (at various nominal contents) in SBA-15 prepared under acidic medium was intended from corresponding direct nitrate addition during mesoporous silica formation. Materials were impregnated with Pt (1.5 wt%) and studied through several textural (N2 physisorption), structural (XRD, TG-DTG), and surface (FTIR, STEM-HAADF, SEM-EDS, NH3, and CO2 TPD) instrumental techniques. Pt-impregnated solids were tested in phenol hydrodeoxygenation (HDO, T = 250 °C, 3.2 MPa, batch reactor, n-decane as solvent). Catalytic activity (in pseudo-first-order kinetic constant, kHDO basis) was not directly related to Pt dispersion, which was not determined by nominal rare earth content. Determining the actual composition of modified SBA-15 materials is crucial in reaching sound conclusions regarding their physicochemical properties, especially when La modifier is directly added during mesoporous matrix formation, where efficient interaction among constituents could be difficult to get. Otherwise, results from some characterization techniques (N2 physisorption and FTIR, for instance) could be misleading and even contradictory. Indeed, extant modifier precursors, when under SBA-15 synthesis conditions, could affect the properties of prepared materials even though they were absent in obtained formulations. Performing simple compositional analysis could eliminate uncertainties regarding the role of various modifiers on characteristics of final catalysts. However, several groups have failed in doing so. Full article
(This article belongs to the Section Catalytic Materials)
27 pages, 3430 KiB  
Article
Effect of TiO2 on Acidity and Dispersion of H3PW12O40 in Bifunctional Cu-ZnO(Al)-H3PW12O40/TiO2 Catalysts for Direct Dimethyl Ether Synthesis
by Elena Millán Ordóñez, Noelia Mota Toledo, Bertrand Revel, Olivier Lafon and Rufino M. Navarro Yerga
Catalysts 2024, 14(7), 435; https://doi.org/10.3390/catal14070435 - 8 Jul 2024
Viewed by 283
Abstract
The performance of bifunctional hybrid catalysts based on phosphotungstic acid (H3PW12O40, HPW) supported on TiO2 combined with a Cu-ZnO(Al) catalyst in the direct synthesis of dimethyl ether (DME) from syngas has been investigated. In this work, [...] Read more.
The performance of bifunctional hybrid catalysts based on phosphotungstic acid (H3PW12O40, HPW) supported on TiO2 combined with a Cu-ZnO(Al) catalyst in the direct synthesis of dimethyl ether (DME) from syngas has been investigated. In this work, different types of TiO2 were used as a support to study the effect of changes in the structure of the TiO2 support on the acidity and dispersion of HPW. Various TiO2 supports with different structural and surface characteristics have been studied and the results indicate that: (i) the crystallinity and crystallite size of the primary particles of the HPW units depend on the TiO2 support; (ii) the pore size distribution of the TiO2 support affects the surface segregation of the heteropolyacids; and (iii) changes in the supported HPW acid catalysts do not significantly alter the crystal structure of the CuO and ZnO phases after contact with CZA in bifunctional catalysts. The activity results indicate that the variation in the intrinsic activity of the Cu-ZnOx centers in the bifunctional catalysts for direct DME synthesis is minimal due to the limited alteration of the crystal structure of the centers. Full article
(This article belongs to the Special Issue Polyoxometalates (POMs) as Catalysts for Biomass Conversion)
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4 pages, 183 KiB  
Editorial
Editorial: Air and Water Purification Processes through Photocatalysis—Scale-Up Perspectives, 2nd Edition
by Maria Laura Tummino and Rufino M. Navarro Yerga
Catalysts 2024, 14(7), 434; https://doi.org/10.3390/catal14070434 - 8 Jul 2024
Viewed by 352
Abstract
In the face of escalating environmental challenges, innovative solutions for purifying air and water are more critical than ever [...] Full article
19 pages, 3796 KiB  
Article
Photocatalytic Degradation of Losartan with BiOCl/Sepiolite Nanocomposites
by Konstantinos Kouvelis, Evangelia E. Karavaka, Dionisios Panagiotaras, Dimitrios Papoulis, Zacharias Frontistis and Athanasia Petala
Catalysts 2024, 14(7), 433; https://doi.org/10.3390/catal14070433 - 7 Jul 2024
Viewed by 459
Abstract
Developing highly active and available, environmentally friendly, and low-cost photocatalytic materials is one of the most popular topics in photocatalytic degradation systems. In the present study, a series of BiOCl/Sepiolite composite photocatalysts were prepared (in the range of 5%BiOCl/Sepiolite–30%BiOCl/Sepiolite). Their characterization was conducted [...] Read more.
Developing highly active and available, environmentally friendly, and low-cost photocatalytic materials is one of the most popular topics in photocatalytic degradation systems. In the present study, a series of BiOCl/Sepiolite composite photocatalysts were prepared (in the range of 5%BiOCl/Sepiolite–30%BiOCl/Sepiolite). Their characterization was conducted using X-ray diffraction, diffuse reflectance spectroscopy, scanning electron microscopy, nitrogen physical physisorption at the temperature of liquid nitrogen (77 K), and attenuated total reflectance-Fourier transform infrared spectroscopy. Results showed that composite photocatalysts possess superior efficiency than the parent materials for losartan, an antihypertensive agent, degradation in water, with the sample with only 10%wt. BiOCl shows the highest performance. The beneficial effect of the addition of sepiolite to BiOCl is derived from the increase in surface area, the prevention of particle aggregation, and the efficient separation of photogenerated species. Increasing catalyst concentration from 125 mg/L up to 500 mg/L was accompanied by an increase in the apparent kinetic constant from 0.077 min−1 to 0.197 min−1 while varying losartan concentration from 0.25 to 5.00 mg/L slowed down the removal efficiency. In addition, losartan degradation was only partially hampered in the case of bottled water, whereas it was practically stopped in a secondary wastewater effluent. Overall, this study serves as a useful guide for using geopolymers in photocatalytic applications. Full article
(This article belongs to the Section Environmental Catalysis)
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18 pages, 2366 KiB  
Article
Dependence of the Fluidizing Condition on Operating Parameters for Sorption-Enhanced Methanol Synthesis Catalyst and Adsorbent
by Simona Renda, Javier Lasobras, Jaime Soler, Javier Herguido and Miguel Menéndez
Catalysts 2024, 14(7), 432; https://doi.org/10.3390/catal14070432 - 7 Jul 2024
Viewed by 457
Abstract
The fluidization of two different solids was investigated by varying the temperature and pressure conditions and the fluidizing gas. The solids are a novel catalyst and a water sorbent that could be used to perform sorption-enhanced methanol synthesis; the operating conditions were selected [...] Read more.
The fluidization of two different solids was investigated by varying the temperature and pressure conditions and the fluidizing gas. The solids are a novel catalyst and a water sorbent that could be used to perform sorption-enhanced methanol synthesis; the operating conditions were selected accordingly to this process. The aim of this investigation was to find an expression for predicting the minimum fluidization conditions of a methanol synthesis catalyst and an adsorbent in the presence of their process stream and operating conditions. The findings of this study highlighted how umf (STP) decreases with a rise in temperature and increases with a rise in pressure, according to other works in the literature with different solids. Furthermore, the type of gas was found to influence the minimum fluidization velocity significantly. The experimental results agreed well with a theoretical expression of the minimum fluidization velocity adjusted for temperature, pressure, and viscosity. The choice of the expression for viscosity calculation in the case of gas mixtures was found to be of key importance. These results will be useful for researchers aiming to calculate the minimum fluidization velocity of a catalyst or other solids under reaction conditions using results obtained at ambient conditions with air or inert gas. Full article
(This article belongs to the Special Issue Fluidizable Catalysts for Novel Chemical Processes)
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15 pages, 4840 KiB  
Article
(La1−xCax)MnO3−δ (x = 0, 0.2, 0.3, 0.4) Perovskites as Redox Catalysts in Chemical Looping Hydrogen Production Process: The Relation between Defect Chemistry and Redox Performance
by Moschos Moschos, Antigoni Evdou and Vassilios Zaspalis
Catalysts 2024, 14(7), 431; https://doi.org/10.3390/catal14070431 - 6 Jul 2024
Viewed by 332
Abstract
The interaction between point defects in (La1−xCax)MnO3−δ (x = 0, 0.2, 0.3, 0.4) perovskites and their redox catalytic properties in a three-reactor chemical looping hydrogen production process is investigated. During the reduction step with CH4, the [...] Read more.
The interaction between point defects in (La1−xCax)MnO3−δ (x = 0, 0.2, 0.3, 0.4) perovskites and their redox catalytic properties in a three-reactor chemical looping hydrogen production process is investigated. During the reduction step with CH4, the behavior of the materials is extrinsically determined and strongly depends on the Ca content. At small oxygen deficiencies, CH4 becomes oxidized to CO2. As the deficiency increases, partial oxidation to CO and H2 at a molar ratio of approximately 2 is favored. During the water-splitting step, the dependency on the Ca content is much weaker since it is intrinsically determined by the Mn2+→Mn3+ oxidation with simultaneous annihilation of oxygen vacancies that are not required to compensate for the extra negative charge of the Ca dopant. Hydrogen productivities in the order of 13 cm3 (STP) H2/g solid could be achieved during the water-splitting step at 1000 °C. The materials exhibited reproducible catalytic behavior during 10 cycles of the complete three-step process and were found to retain their perovskite structure. Full article
(This article belongs to the Section Nanostructured Catalysts)
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16 pages, 3610 KiB  
Article
Copper- and Manganese-Based Bimetallic Layered Double Hydroxides for Catalytic Reduction of Methylene Blue
by Muhammad Altaf Nazir, Aziz ur Rehman, Tayyaba Najam, Mohamed Farouk Elsadek, M. Ajmal Ali, Ismail Hossain, Muhammad Khurram Tufail and Syed Shoaib Ahmad Shah
Catalysts 2024, 14(7), 430; https://doi.org/10.3390/catal14070430 - 5 Jul 2024
Viewed by 411
Abstract
In this study, copper (Cu)- and manganese (Mn)-based layered double hydroxide (LDH) nanosheets were produced by modest and low-cost hydrothermal technique to display an improved photocatalytic performance toward the degradation of aqueous methylene blue (MB). The morphological and structural properties of the as-prepared [...] Read more.
In this study, copper (Cu)- and manganese (Mn)-based layered double hydroxide (LDH) nanosheets were produced by modest and low-cost hydrothermal technique to display an improved photocatalytic performance toward the degradation of aqueous methylene blue (MB). The morphological and structural properties of the as-prepared photocatalysts were characterized through various techniques comprising XRD, FT-IR, SEM, EDS, and their MB degradation activity was evaluated under visible light irradiation. SEM results explore that the synthesized LDH materials have a sheet-like morphology and are stacked layer by layer. Various analysis parameters, such as the effect of the contact time, concentration and pH of MB solutions were performed to optimize the performance of fabricated LDH materials. The results revealed that the as-synthesized CuAl-LDH and MnAl-LDH exhibited a 74.95 and 70.93% removal of MB under solar light within 180 min. Moreover, synthesized photocatalysts showed an excellent performance of up to four regeneration cycles. We believe that this study provides novel mechanistic insights into the design and preparation of highly competent photocatalysts using low-cost materials, with applications in environmental remediation. Full article
(This article belongs to the Section Photocatalysis)
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18 pages, 4331 KiB  
Review
Photocatalytic Production of Hydrogen Peroxide from Covalent-Organic-Framework-Based Materials: A Mini-Review
by Jiayi Meng, Yamei Huang, Xinglin Wang, Yifan Liao, Huihui Zhang and Weilin Dai
Catalysts 2024, 14(7), 429; https://doi.org/10.3390/catal14070429 - 5 Jul 2024
Viewed by 367
Abstract
Hydrogen peroxide (H2O2) is one of the most environmentally friendly and versatile chemical oxidizing agents, with only O2 and H2O as reaction products. It is widely used in environmental protection, industrial production, and medical fields. At [...] Read more.
Hydrogen peroxide (H2O2) is one of the most environmentally friendly and versatile chemical oxidizing agents, with only O2 and H2O as reaction products. It is widely used in environmental protection, industrial production, and medical fields. At present, most of the industrial production of H2O2 adopts anthraquinone oxidation, but there are shortcomings such as pollution of the environment and large energy consumption. Covalent organic frameworks (COFs) are a class of porous crystalline materials formed by organic molecular building blocks connected by covalent bonds. The ordered conjugated structure of COFs not only facilitates the absorption of light energy but also promotes the transport of excited-state electrons. Therefore, the photochemical synthesis of H2O2 from water and oxygen using photocatalysts based on COFs as a green route has attracted much attention. In this review, we provide an overview of recent studies on COFs as photocatalysts and the different mechanisms involved in the photocatalytic production of hydrogen peroxide. Then, we summarize the various strategies to improve the performance. Finally, we outline the challenges and future directions of COFs in practical applications. This review highlights the potential and application prospects of COFs in the photochemical synthesis of H2O2, aiming to provide guidance for the design of COF-based catalysts and the optimization for photocatalytic production of H2O2, in order to promote scientific development and application in this field. Full article
(This article belongs to the Special Issue Exclusive Papers in Green Photocatalysis from China)
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11 pages, 1444 KiB  
Article
Selective Hydrogenolysis of Tetrahydrofurfuryl Alcohol to 1,5-Pentanediol over MgAl2O4-Modified Pt/WO3/γ-Al2O3 Catalyst
by Weiying Wang and Changlin Chen
Catalysts 2024, 14(7), 428; https://doi.org/10.3390/catal14070428 - 5 Jul 2024
Viewed by 298
Abstract
Tetrahydrofurfuryl alcohol, a cost-effective biomass derivative, offers a sustainable path for synthesizing 1,5-pentanediol through hydrogenolysis. To develop the efficient production of 1,5-pentanediol from this alcohol, we have prepared a series of MgAl2O4-modified Pt/WOx/γ-Al2O3 catalysts [...] Read more.
Tetrahydrofurfuryl alcohol, a cost-effective biomass derivative, offers a sustainable path for synthesizing 1,5-pentanediol through hydrogenolysis. To develop the efficient production of 1,5-pentanediol from this alcohol, we have prepared a series of MgAl2O4-modified Pt/WOx/γ-Al2O3 catalysts with varying compositions via impregnation–calcination methods. The physicochemical properties of these catalysts were subsequently characterized using diverse techniques. Characterization revealed that magnesia–alumina spinel modification enhanced Pt particle dispersion, CO adsorption on Pt/WOx/γ-Al2O3, reduced Pt particle reduction temperature, diminished the acid content in the catalysts, and increased the surface oxygen vacancy concentration. These alterations appear to influence the catalyst performance, though other factors cannot be ruled out. Catalytic activity tests demonstrated that magnesia–alumina spinel modification improved tetrahydrofurfuryl alcohol hydrogenolysis activity and the 1,5-pentanediol selectivity of Pt/WOx/γ-Al2O3. Optimal performance was achieved at 12% magnesia–alumina spinel loading, with a tetrahydrofurfuryl alcohol conversion of 47.3% and 1,5-pentanediol selectivity of 88.4%. Full article
(This article belongs to the Section Biomass Catalysis)
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23 pages, 3489 KiB  
Article
Investigating the Potential of Green-Fabricated Zinc Oxide Nanoparticles to Inhibit the Foodborne Pathogenic Bacteria Isolated from Spoiled Fruits
by Amr Fouda, Mohammed Ali Abdel-Rahman, Ahmed M. Eid, Samy Selim, Hasan Ejaz, Muharib Alruwaili, Emad Manni, Mohammed S. Almuhayawi, Soad K. Al Jaouni and Saad El-Din Hassan
Catalysts 2024, 14(7), 427; https://doi.org/10.3390/catal14070427 - 4 Jul 2024
Viewed by 740
Abstract
In the current investigation, the antibacterial activity of zinc oxide nanoparticles (ZnO-NPs) formed by an aqueous extract of Psidium guajava leaves against foodborne pathogenic bacterial strains was investigated. To achieve this goal, 33 bacterial isolates were obtained from spoiled fruits. Among these isolates, [...] Read more.
In the current investigation, the antibacterial activity of zinc oxide nanoparticles (ZnO-NPs) formed by an aqueous extract of Psidium guajava leaves against foodborne pathogenic bacterial strains was investigated. To achieve this goal, 33 bacterial isolates were obtained from spoiled fruits. Among these isolates, 79% showed cellulase activity, 82% showed amylase activity, 81% exhibited xylanase potential, and 65% exhibited lipase activity. Moreover, 12 isolates showed complete hemolysis (β-hemolysis). The identification of these isolates was done using sequencing and amplification of 16s rRNA as Staphylococcus aureus (two strains), Pseudomonas syringae (one strain), E. coli (two strains), Salmonella typhimurium (two strains), Listeria monocytogenes (one isolate), Bacillus cereus (two isolates), and Bacillus subtilis (two isolates). The formed ZnO-NPs by aqueous Psidium guajava leaf extract were characterized using UV, FT-IR, TEM, EDX, XRD, DLS, and Zeta potential. The data revealed the successful formation of a spherical shape, crystallographic structure, and well-arranged ZnO-NPs. FT-IR showed the effect of different functional groups in the plant extract in the formation of ZnO-NPs through reducing, capping, and stabilizing of end products. Moreover, EDX analysis showed that the Zn ion occupied the main component of the produced NPs. Interestingly, the obtained bacterial strains showed varied sensitivity toward green-synthesized ZnO-NPs. The growth inhibition of foodborne pathogenic strains by ZnO-NPs was concentration dependent, forming a zone of inhibition in the range of 20–23 mm at a concentration of 200 µg mL−1, which decreased to 15–18 mm at 100 µg mL−1. Moreover, the values of MIC were 25 and 50 µg mL−1 based on the bacterial strain. Overall, the green-synthesized ZnO-NPs can be a useful approach for inhibiting the growth of spoilage bacterial strains that destroy fruits and hence reduce the harmful effects of traditional treatment methods on the environment and human health. Full article
(This article belongs to the Section Biocatalysis)
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15 pages, 3488 KiB  
Article
The Direct Formation of an Iron Citrate Complex Using a Metallurgical Slag as an Iron Source for Micropollutant Removal via the Photo-Fenton Process
by Sandra Yazmin Arzate Salgado, Ana Yañez-Aulestia and Rosa-María Ramírez-Zamora
Catalysts 2024, 14(7), 426; https://doi.org/10.3390/catal14070426 - 4 Jul 2024
Viewed by 410
Abstract
Following the goals of the circular economy, this work demonstrates that an industrial by-product can be used in environmental remediation. Metallurgical slag and citric acid were used to form an Fe:Cit complex by simultaneously carrying out the lixiviation of the iron and the [...] Read more.
Following the goals of the circular economy, this work demonstrates that an industrial by-product can be used in environmental remediation. Metallurgical slag and citric acid were used to form an Fe:Cit complex by simultaneously carrying out the lixiviation of the iron and the chelating stages with an 87% iron recovery. This complex was evaluated in the photo-Fenton process to produce HO through salicylic acid dosimetry or salicylic acid hydroxylation, producing 0.13 ± 0.1 mM HO after 30 min of operation; such a value is three orders of magnitude higher than the one reported for the metallurgical slag (as a heterogeneous catalyst, 22 μM) in the photo-Fenton-like process. The system was tested for its ability to degrade a mixture of drugs, including dexamethasone (DEX), naproxen (NAP), and ketorolac (KTR), which are often used to treat the symptoms of COVID-19. The drug degradation tests were performed in two stages. In the first stage, the Fe:Cit complex from the metallurgical slag was compared to the one formed by analytical-grade reactants; the drug degradation was faster for the former, with the major difference being observed at 5 cm and 500 W/m2. Here, 85–90% of the drugs was degraded in 5 min using Fe:Cit from slag, while at least 20 min was necessary to achieve such degradation with the analytical reagent, conceivably because of the trace compounds being lixiviated from the slag. Then, the effects of the liquid depth (5, 10, and 15 cm) and irradiance (250, 500, and 750 W/m2) were tested; the pseudo-first-order kinetic degradation constants for the three model pollutants were in the range of 0.009 > kD > 0.09 min−1, showing that degradation is more feasible for DEX than for NAP and KRT because the radical attack feasibility is related to the molecular structures. Full article
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22 pages, 20446 KiB  
Article
Patterns of Formation of Binary Cobalt–Magnesium Oxide Combustion Catalysts of Various Composition
by Bolatbek Khussain, Alexandr Sass, Alexandr Brodskiy, Kenzhegul Rakhmetova, Ivan Torlopov, Magira Zhylkybek, Tolkyn Baizhumanova, Svetlana Tungatarova, Atabek Khussain, Murat Zhurinov, Abzal Kenessary, Ranida Tyulebayeva, Alexandr Logvinenko and Yernar Narimanov
Catalysts 2024, 14(7), 425; https://doi.org/10.3390/catal14070425 - 3 Jul 2024
Viewed by 387
Abstract
In order to establish the formation patterns of the Co–Mg oxide system, samples with different Co:Mg ratios and heat treatment temperatures were synthesized and studied. A study of the samples confirmed the phase transition of MgxCo2–xO4 spinels [...] Read more.
In order to establish the formation patterns of the Co–Mg oxide system, samples with different Co:Mg ratios and heat treatment temperatures were synthesized and studied. A study of the samples confirmed the phase transition of MgxCo2–xO4 spinels into the corresponding solid solutions at 800–900 °C. The similarity of the formation patterns for different compositions is shown. The rocksalt oxide in low-temperature samples is an anion-modified paracrystalline phase that forms a “true” solid solution only upon spinel decomposition. The TPR profiles of the decomposed Co3O4 spinel show surface Co3O4 peaks and a wide peak corresponding to the well-crystallized CoO, while partial Co3O4 TPR up to 380 °C results in dispersed and amorphous CoO. The high-temperature non-stoichiometric samples are poorly reduced, indicating their low oxygen reactivity. Spinel reoxidation after heat treatment to 1100 °C by calcination at 750 °C showed complete regeneration for MgCo2O4–Co3O4 samples and its absence in case of an excess of MgO relative to stoichiometry. Full article
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15 pages, 16489 KiB  
Article
Catalytic Dechlorination of Three Organochlorides by Recyclable Nano-Palladium-Engineered Natural Sponge with Formic Acid
by Mingyue Liu, Gang Chen, Zhenjun Song, Zhicai He, Aiguo Zhong and Mei Cui
Catalysts 2024, 14(7), 424; https://doi.org/10.3390/catal14070424 - 3 Jul 2024
Viewed by 570
Abstract
Catalytic dechlorination of organic chlorides by palladium (Pd) with HCOOH represents one of the most effective and promising techniques for environmental remediation. In this study, we adopted alkaline-modified porous natural sponge as support of a Pd nanocatalyst (Pd@M-Sponge) and HCOOH as a hydrogen [...] Read more.
Catalytic dechlorination of organic chlorides by palladium (Pd) with HCOOH represents one of the most effective and promising techniques for environmental remediation. In this study, we adopted alkaline-modified porous natural sponge as support of a Pd nanocatalyst (Pd@M-Sponge) and HCOOH as a hydrogen source for the hydrodechlorination of florfenicol (FF), o-chlorophenol (o-CP), and p-chlorophenol (p-CP). Favorable conversion efficiency of FF, o-CP, and p-CP was achieved at 25 °C and atmospheric pressure attributed to the small diameter and high catalytic reactivity of the prepared Pd NPs, in addition to the slight internal mass transfer limitation of the prepared Pd@M-Sponge. High reaction rate constants were obtained even in the conditions of a low molar ratio of HCOOH to p-CP (10:1) and a high concentration of p-CP (500 mg/L). The prepared catalyst also demonstrated superior recyclability without any obvious decrease in catalytic reactivity in 20 successive p-CP dechlorination cycles. This work provides an ideal recyclable and cost-effective catalyst based on renewable and biocompatible natural material for the catalytic hydrodechlorination of chlorinated organic pollutants with formic acid and a new view for the exploration and designing of highly reactive and stable catalysts for hydrodechlorination. Full article
(This article belongs to the Section Environmental Catalysis)
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