Catalysts

16 pages, 2560 KiB

Open AccessArticle

Investigation into the Fuel Characteristics of Biodiesel Synthesized through the Transesterification of Palm Oil Using a TiO₂/CH₃ONa Nanocatalyst

by Cherng-Yuan Lin and Shun-Lien Tseng

Catalysts 2024, 14(9), 623; https://doi.org/10.3390/catal14090623 (registering DOI) - 16 Sep 2024

Abstract

Biodiesel is a renewable and sustainable alternative fuel to petrol-derived diesel. Decreasing the operating costs by improving the catalyst’s characteristics is an effective way to increase the competitiveness of biodiesel in the fuel market. An aqueous solution of sodium methoxide (CH₃ONa), [...] Read more.

Biodiesel is a renewable and sustainable alternative fuel to petrol-derived diesel. Decreasing the operating costs by improving the catalyst’s characteristics is an effective way to increase the competitiveness of biodiesel in the fuel market. An aqueous solution of sodium methoxide (CH₃ONa), which is a traditional alkaline catalyst, was immersed in nanometer-sized particles of titanium dioxide (TiO₂) powder to prepare the strong alkaline catalyst TiO₂/CH₃ONa. The immersion method was used to enhance the transesterification reaction. The mixture of TiO₂ and CH₃ONa was calcined in a high-temperature furnace in a range between 150 and 450 °C continuously for 4 h. The heterogeneous alkaline catalyst TiO₂/CH₃ONa was then used to catalyze the strong alkaline transesterification reaction of palm oil with methanol. The highest content of fatty acid methyl esters (FAMEs), which amounted to 95.9%, was produced when the molar ratio of methanol to palm oil was equal to 6, and 3 wt.% TiO₂/CH₃ONa was used, based on the weight of the palm oil. The FAMEs produced from the above conditions were also found to have the lowest kinematic viscosity of 4.17 mm²/s, an acid value of 0.32 mg KOH/g oil, and a water content of 0.031 wt.%, as well as the highest heating value of 40.02 MJ/kg and cetane index of 50.05. The lower catalyst amount of 1 wt.%, in contrast, resulted in the lowest cetane index of 49.31. The highest distillation temperature of 355 °C was found when 3 wt.% of the catalyst was added to the reactant mixture with a methanol/palm oil molar ratio of 6. The prepared catalyst is considered effective for improving the fuel characteristics of biodiesel. Full article

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

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11 pages, 2390 KiB

Open AccessFeature PaperArticle

Catalytic Decontamination of Carbon Monoxide Using Strong Metal–Support Interactions on TiO₂ Microparticles

by Avraham Dayan, Jacob Alter and Gideon Fleminger

Catalysts 2024, 14(9), 622; https://doi.org/10.3390/catal14090622 (registering DOI) - 15 Sep 2024

Abstract

The traditional catalytic oxidation of carbon monoxide (CO) using metal oxide catalysts often requires either high temperatures (thermocatalysis) or ultraviolet light (UV) excitation (photocatalysis), limiting practical applications under ambient conditions. Our research aimed to develop a catalytic system capable of oxidizing CO to [...] Read more.

The traditional catalytic oxidation of carbon monoxide (CO) using metal oxide catalysts often requires either high temperatures (thermocatalysis) or ultraviolet light (UV) excitation (photocatalysis), limiting practical applications under ambient conditions. Our research aimed to develop a catalytic system capable of oxidizing CO to CO₂ at room temperature and in the dark. Using the Strong Metal–Support Interaction (SMSI) methodology, several titanium oxide (TiO₂)-complexed metals were prepared (Ag, Au, Pd, and Pt). The highest catalytic efficiency of CO oxidation at room temperature was demonstrated for the TiO₂-Pt complex. Therefore, this complex was further examined structurally and functionally. Two modes of operation were addressed. The first involved applying the catalytic system to remove CO from an individual’s environment (environmental system), while the second involved the installation of the catalysis chamber as a part of a personal protection unit (e.g., a mask). The catalytic activity exhibited a significant reduction in CO levels in both the environmental and personal protection scenarios. The practical application of the system was demonstrated through efficient CO oxidation in air emitted from a controlled fire experiment conducted in collaboration with the Israel Fire and Rescue Authority. Full article

(This article belongs to the Special Issue Catalytic CO Oxidation and Preferential CO Oxidation (PROX) II)

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16 pages, 12097 KiB

Open AccessArticle

Insight into the Structural and Performance Correlation of Photocatalytic TiO₂/Cu Composite Films Prepared by Magnetron Sputtering Method

by Kun Lu, Miao Sun, Yaohong Jiang, Xinmeng Wu, Lijun Zhao and Junhua Xu

Catalysts 2024, 14(9), 621; https://doi.org/10.3390/catal14090621 (registering DOI) - 14 Sep 2024

Abstract

Photocatalysis technology, as an efficient and safe environmentally friendly purification technique, has garnered significant attention and interest. Traditional TiO₂ photocatalytic materials still face limitations in practical applications, hindering their widespread adoption. The research prepared TiO₂/Cu films with different Cu contents [...] Read more.

Photocatalysis technology, as an efficient and safe environmentally friendly purification technique, has garnered significant attention and interest. Traditional TiO₂ photocatalytic materials still face limitations in practical applications, hindering their widespread adoption. The research prepared TiO₂/Cu films with different Cu contents using a magnetron sputtering multi-target co-deposition technique. The incorporation of Cu significantly enhances the antibacterial properties and visible light response of the films. The effects of different Cu contents on the microstructure, surface morphology, wettability, antibacterial properties, and visible light response of the films were investigated using an X-ray diffractometer, X-ray photoelectron spectrometer, field emission scanning electron microscope, confocal laser scanning microscope, Ultraviolet–visible spectrophotometer, and contact angle goniometer. The results showed that the prepared TiO₂/Cu films were mainly composed of the rutile TiO₂ phase and face-center cubic Cu phase. The introduction of Cu affected the crystal orientation of TiO₂ and refined the grain size of the films. With the increase in Cu content, the surface roughness of the films first decreased and then increased. The water contact angle of the films first increased and then decreased, and the film exhibited optimal hydrophobicity when the Cu target power was 10 W. The TiO₂/Cu films showed good antibacterial properties against Escherichia coli and Staphylococcus aureus. The introduction of Cu shifted the absorption edge of the films to the red region, significantly narrowed the band gap width to 2.5 eV, and broadened the light response range of the films to the visible light region. Full article

(This article belongs to the Special Issue Tailored Nanosystems and Nanocatalysts for Photo-/Electrocatalytic Applications, 2nd Edition)

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20 pages, 1236 KiB

Open AccessArticle

Photo-Fenton Treatment under UV and Vis Light Reduces Pollution and Toxicity in Water from Madín Dam, Mexico

by Deysi Amado-Piña, Rubi Romero, Emmanuel Salazar Carmona, Armando Ramírez-Serrano, Leobardo Manuel Gómez-Oliván, Gustavo Elizalde-Velázquez and Reyna Natividad

Catalysts 2024, 14(9), 620; https://doi.org/10.3390/catal14090620 (registering DOI) - 14 Sep 2024

Abstract

Water from Madín Dam in Mexico has been shown to contain a wide variety of pollutants such as drugs, pesticides, personal care products and compounds that are released into the environment as waste from production processes. In this work, the effect of the [...] Read more.

Water from Madín Dam in Mexico has been shown to contain a wide variety of pollutants such as drugs, pesticides, personal care products and compounds that are released into the environment as waste from production processes. In this work, the effect of the main process variables on the percentage of total organic carbon (TOC) removal in water samples from the Madín reservoir was studied by applying a photo-Fenton treatment catalyzed with iron-pillared clays. The catalyst was characterized by XRD, N₂ physisorption, DRS and XPS. The sampling and characterization of the water from the Madín reservoir was carried out according to Mexican standards. The system for treatment tests was 0.1 L of reaction volume and a controlled temperature of 23–25 °C, and the reaction system was kept under constant stirring. After 4 h of treatment time under UV light, the TOC removal was 90%, and it was 60% under Vis light. The main ROS involved in the photo-Fenton process driven by UVC light were hydroxyl radicals, while hydroperoxyl radicals predominate in the Vis-light-driven process. Evidence of superoxide anion participation was not found. The toxicity of untreated and treated water was assessed on Danio rerio specimens, and it was observed to be reduced after the photo-Fenton treatment. Full article

(This article belongs to the Section Photocatalysis)

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18 pages, 4620 KiB

Open AccessFeature PaperArticle

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

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

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

Abstract

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

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

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

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47 pages, 6874 KiB

Open AccessReview

Nanoalchemy: Unveiling the Power of Carbon Nanostructures and Carbon–Metal Nanocomposites in Synthesis and Photocatalytic Activity

by Yalini Devi Neelan, Senthil Bakthavatchalam, Shanmugam Mahalingam, Krishnasamy Sreenivason Yoganand, Shunmuga Vadivu Ramalingam, Umamaheswari Rajendran, Rajasekaran Ramu, Tae-Youl Yang, Junghwan Kim and Raji Atchudan

Catalysts 2024, 14(9), 618; https://doi.org/10.3390/catal14090618 - 13 Sep 2024

Abstract

Due to a rise in industrial pollutants in modern life, the climate and energy crisis have grown more widespread. One of the best ways to deal with dye degradation, hydrogen production, and carbon dioxide reduction issues is the photocatalytic technique. Among various methods, [...] Read more.

Due to a rise in industrial pollutants in modern life, the climate and energy crisis have grown more widespread. One of the best ways to deal with dye degradation, hydrogen production, and carbon dioxide reduction issues is the photocatalytic technique. Among various methods, catalytic technology has demonstrated tremendous promise in recent years as a cheap, sustainable, and environmentally benign technology. The expeditious establishment of carbon-based metal nanoparticles as catalysts in the disciplines of materials and chemical engineering for catalytic applications triggered by visible light is largely attributed to their advancement. There have been many wonderful catalysts created, but there are still many obstacles to overcome, which include the cost of catalysts being reduced and their effectiveness being increased. Carbon-based materials exhibit a unique combination of characteristics that make them ideal catalysts for various reaction types. These characteristics include an exceptional electrical conductivity, well-defined structures at the nanoscale, inherent water repellency, and the ability to tailor surface properties for specific applications. This versatility allows them to be effective in diverse catalytic processes, encompassing organic transformations and photocatalysis. The emergence of carbon-based nanostructured materials, including fullerenes, carbon dots, carbon nanotubes, graphitic carbon nitride, and graphene, presents a promising alternative to conventional catalysts. This review focuses on the diverse functionalities of these materials within the realm of catalysis materials for degradation, hydrogen production, and carbon dioxide reduction. Additionally, it explores the potential for their commercialization, delving into the underlying mechanisms and key factors that influence their performance. It is anticipated that this review will spur more research to develop high-performance carbon-based materials for environmental applications. Full article

(This article belongs to the Special Issue Nanostructures for Catalysis: From Synthesis and Characterization to Applications)

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11 pages, 1981 KiB

Open AccessFeature PaperArticle

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

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

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

Abstract

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

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

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

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30 pages, 6114 KiB

Open AccessArticle

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

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

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

Abstract

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

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

(This article belongs to the Section Catalytic Reaction Engineering)

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20 pages, 6133 KiB

Open AccessArticle

Synthesis of In-Modified TiO₂ Composite Materials from Waste Tobacco Stem Silk and Study of Their Catalytic Performance under Visible Light

by Junyang Leng, Yi Zhao, Jindi Zhang, Xiaoli Bai, Anlong Zhang, Quanhui Li, Mengyang Huang and Jiaqiang Wang

Catalysts 2024, 14(9), 615; https://doi.org/10.3390/catal14090615 - 12 Sep 2024

Abstract

Titanium dioxide (TiO₂) catalysts are primarily utilized under ultraviolet light, and their potential in industrial applications remains largely untapped. To address this issue, our study uses a one-pot impregnation method to prepare a series of In-TiO₂/TSS(X) (TSS, Tobacco stem [...] Read more.

Titanium dioxide (TiO₂) catalysts are primarily utilized under ultraviolet light, and their potential in industrial applications remains largely untapped. To address this issue, our study uses a one-pot impregnation method to prepare a series of In-TiO₂/TSS(X) (TSS, Tobacco stem silk. X, the molar ratio of In/Ti) catalysts. Among them, the degradation performance of the In-TiO₂/TSS(2.0) material increased from 13.8% for TiO₂ to an impressive 92.9%. By establishing a first-order kinetic model, it was determined that the degradation performance of the In-TiO₂/TSS(2.0) material surpassed that of TiO₂ by a factor of 24. Structural characterization revealed that the introduction of tobacco stem silk templates did not alter the crystal phase of TiO₂ and that the main component of the catalyst remained TiO₂. Not only that, an O–In structure formed on the surface of the TiO₂, leading to a significant increase in the material’s specific surface area. Furthermore, principle tests were conducted, revealing significant enhancements in its light absorption capacity, intensity, and photocurrent density. Through active species trapping experiments, it was observed that, in the photocatalytic degradation process of this catalyst series, holes (h⁺) played the primary role, while the hydroxyl ion (·OH) and superoxide ion (·O²⁻) acted as auxiliary species. Full article

(This article belongs to the Special Issue Cutting-Edge Photocatalysis)

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13 pages, 3636 KiB

Open AccessFeature PaperArticle

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

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

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

Abstract

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

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

(This article belongs to the Section Biocatalysis)

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16 pages, 3343 KiB

Open AccessArticle

Exploring Enhanced Oxygen Reduction Reactions: A Study on Nanocellulose, Dopamine, and Cobalt Complex-Derived Non-Precious Electrocatalyst

by Md Mohsin Patwary, Shanzida Haque, Peter Szwedo, Ghada Hasan, Raja Shekhar Kondrapolu, Fumiya Watanabe, Krishna KC, Daoyuan Wang and Anindya Ghosh

Catalysts 2024, 14(9), 613; https://doi.org/10.3390/catal14090613 - 12 Sep 2024

Abstract

Cobalt-based catalysts are recognized as promising electrocatalysts for oxygen reduction reactions (ORRs) in fuel cells that operate within acidic electrolytes. A synthesis process involving a cobalt complex, nanocellulose, and dopamine, followed by pyrolysis at 500 °C under a nitrogen atmosphere, was used to [...] Read more.

Cobalt-based catalysts are recognized as promising electrocatalysts for oxygen reduction reactions (ORRs) in fuel cells that operate within acidic electrolytes. A synthesis process involving a cobalt complex, nanocellulose, and dopamine, followed by pyrolysis at 500 °C under a nitrogen atmosphere, was used to create a cobalt and nitrogen-doped carbonaceous material. Additionally, urea was incorporated to enhance nitrogen doping in the carbonaceous material. The morphology and structure of the material were examined using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD), where SEM unveiled dispersed metal oxides within the carbonaceous framework. Energy Dispersive X-ray Spectroscopy (EDS) analysis showed an even distribution of elements across the cobalt-doped carbonaceous material. X-ray Photoelectron Spectroscopy (XPS) analysis further highlighted significant alterations in the elemental composition due to pyrolysis. The electrochemical behavior of the cobalt-doped carbonaceous material, with respect to the oxygen reduction reaction (ORR) in an acidic medium, was investigated via cyclic voltammetry (CV), revealing an ORR peak at 0.30 V against a reversible hydrogen reference electrode, accompanied by a notably high current density. The catalyst’s performance was evaluated across different pH levels and with various layers deposited, showing enhanced effectiveness in acidic conditions and a more pronounced reduction peak with uniformly applied electrode layers. Rotating disk electrode (RDE) studies corroborated the mechanism of a four-electron reduction of oxygen to water, emphasizing the catalyst’s efficiency. Full article

(This article belongs to the Section Electrocatalysis)

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17 pages, 2942 KiB

Open AccessArticle

Color-Coordinated Photocatalysis of the One-Pot Synthesis of Schiff Bases from Benzyl Alcohol and Nitro Compounds Using a Hybrid Magnetic Catalyst

by Daliane Regis Correa da Silva, Melissa Cely-Pinto and Juan C. Scaiano

Catalysts 2024, 14(9), 612; https://doi.org/10.3390/catal14090612 - 12 Sep 2024

Abstract

The versatility and significance of imines (Schiff bases) make them highly attractive for many industrial applications. This study investigates photocatalytic routes for the one-pot synthesis of Schiff bases using alcohol and an aromatic nitro compound as reagents, rather than the more conventional amine [...] Read more.

The versatility and significance of imines (Schiff bases) make them highly attractive for many industrial applications. This study investigates photocatalytic routes for the one-pot synthesis of Schiff bases using alcohol and an aromatic nitro compound as reagents, rather than the more conventional amine and aldehyde or ketone. Utilizing photoirradiation at 370 nm with TiO₂ loaded with various metals, we demonstrate the exceptional efficiency of the one-pot synthesis of Schiff bases under an inert atmosphere. Notably, the Fe₃O₄@TiO₂ magnetic catalyst offers an excellent option for synthesizing the corresponding imine, achieving a remarkable production rate of 6.8 mmol h⁻¹ during the first 6 h of irradiation with UVA light and reaching over 99% yield after 20 h. This success is attributed to a series of reactions involving the photocatalytic oxidation of benzyl alcohol to benzaldehyde and the simultaneous in situ reduction of nitrobenzene to aniline. The subsequent catalytic condensation of these products, facilitated by the active sites at the TiO₂-metal interface, ultimately yields the desired imine. Additionally, while irradiation in the UVA region alone can photocatalyze the process, incorporating blue light (450 nm) accelerates it significantly. Dual-wavelength irradiation increased the production of the benzaldehyde to 77.9 mmol and more than doubled the Schiff base yield, from 7.5 mmol (with UVA light) to 17 mmol in 3 h of irradiation. Additionally, the reusability of the catalyst under simultaneous 450 nm and 370 nm light exposure significantly enhanced Schiff base production, which rose from 16.9 mmol to 48.9 mmol after adding fresh 0.1 M nitrobenzene for the second use. This highlights the effectiveness of color-coordinated catalysis in advancing sustainable chemistry through two-color photochemistry. The magnetic catalytic system not only demonstrates remarkable performance but also shows excellent reusability, representing a promising alternative for sustainable and efficient chemical transformations. Full article

(This article belongs to the Special Issue Applied Catalysis in Chemical Industry: Synthesis, Catalyst Design, and Evaluation, 2nd Edition)

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20 pages, 4634 KiB

Open AccessFeature PaperArticle

Comparative Assessment of First-Row 3d Transition Metals (Ti-Zn) Supported on CeO₂ Nanorods for CO₂ Hydrogenation

by Maria Lykaki, Sofia Stefa, Georgios Varvoutis, Vassilios D. Binas, George E. Marnellos and Michalis Konsolakis

Catalysts 2024, 14(9), 611; https://doi.org/10.3390/catal14090611 - 11 Sep 2024

Abstract

Herein, motivated by the excellent redox properties of rod-shaped ceria (CeO₂-NR), a series of TM/CeO₂ catalysts, employing the first-row 3d transition metals (Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) as active metal phases, were comparatively assessed under [...] Read more.

Herein, motivated by the excellent redox properties of rod-shaped ceria (CeO₂-NR), a series of TM/CeO₂ catalysts, employing the first-row 3d transition metals (Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) as active metal phases, were comparatively assessed under identical synthesis and reaction conditions to decipher the role of active metal in the CO₂ hydrogenation process. Notably, a volcano-type dependence of CO₂ hydrogenation activity/selectivity was disclosed as a function of metal entity revealing a maximum for the Ni-based sample. Ni/CeO₂ is extremely active and fully selective to methane (Y_CH4 = 90.8% at 350 °C), followed by Co/CeO₂ (Y_CH4 = 45.2%), whereas the rest of the metals present an inferior performance. No straightforward relationship was disclosed between the CO₂ hydrogenation performance and the textural, structural, and redox properties, whereas, on the other hand, a volcano-shaped trend was established with the relative concentration of oxygen vacancies and partially reduced Ce³⁺ species. The observed trend is also perfectly aligned with the previously reported volcano-type dependence of atomic hydrogen adsorption energy and CO₂ activation as a function of 3d-orbital electron number, revealing the key role of intrinsic electronic features of each metal in conjunction to metal–support interactions. Full article

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

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9 pages, 11507 KiB

Open AccessCommunication

Highly Efficient 1-Iodination of Terminal Alkynes Catalyzed by Inorganic or Organic Bases

by Yang Yang, Jian Zhang, Fang Wan, E Liu and Huaxin Zhang

Catalysts 2024, 14(9), 610; https://doi.org/10.3390/catal14090610 - 11 Sep 2024

Abstract

1-Iodoalkynes are one type of the most reactive and the most practical intermediates in organic synthesis. Here, some facile and efficient methods for the 1-iodination of terminal alkynes are developed using N-iodosuccinimide (NIS) as an iodination reagent and some inexpensive mild bases as [...] Read more.

1-Iodoalkynes are one type of the most reactive and the most practical intermediates in organic synthesis. Here, some facile and efficient methods for the 1-iodination of terminal alkynes are developed using N-iodosuccinimide (NIS) as an iodination reagent and some inexpensive mild bases as catalysts. K₂CO₃ and 4-dimethylaminopyridine (DMAP) have been proven to be the most suitable inorganic and organic bases, succeeding in 17 examples with excellent yields (up to 99%). Full article

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21 pages, 4751 KiB

Open AccessArticle

Green Synthesis of LaMnO₃-Ag Nanocomposites Using Citrus limon (L.) Burm Peel Aqueous Extract: Photocatalytic Degradation of Rose Bengal Dye and Antibacterial Applications

by Nazim Hasan

Catalysts 2024, 14(9), 609; https://doi.org/10.3390/catal14090609 - 11 Sep 2024

Abstract

Perovskites can absorb solar energy and are extensively used in various catalytic and photocatalytic reactions. However, noble metal particles may enhance the catalytic, photocatalytic, and antibacterial activities. This study demonstrates the cost-effective green synthesis of the photocatalyst perovskite LaMnO₃ and its modification [...] Read more.

Perovskites can absorb solar energy and are extensively used in various catalytic and photocatalytic reactions. However, noble metal particles may enhance the catalytic, photocatalytic, and antibacterial activities. This study demonstrates the cost-effective green synthesis of the photocatalyst perovskite LaMnO₃ and its modification with noble metal Ag nanoparticles. The green synthesis of nanocomposite was achieved through a hydrothermal method employing aqueous extract derived from Citrus limon (L.) Burm peels. The properties of fabricated perovskites LaMnO₃ and LaMnO₃-Ag nanocomposites were evaluated and characterized by Ultraviolet-Visible spectroscopy (UV-Vis), Diffuse Reflectance Spectroscopy (DRS), X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FT-IR), High-Resolution Transmission Electron Microscopy (HRTEM), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray spectroscopy (EDX) and Brunauer–Emmett–Teller (BET) surface area techniques. The particle size distribution % of LaMnO₃ and LaMnO₃-Ag was observed to be 20 to 60 nm after using TEM images. The maximum percentage size distribution was 37 nm for LaMnO₃ and 43 nm for LaMnO₃-Ag. In addition, LaMnO₃-Ag nanocomposite was utilized as a photocatalyst for the degradation of Rose Bengal (RB) dye and its antibacterial activities against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The surface area and band gap for perovskite LaMnO₃ nanoparticles were calculated as 12.642 m²/g and 3.44 eV, respectively. The presence of noble metal and hydrothermal-bio reduction significantly impacted the crystallinity. The BET surface area was found to be 16.209 m²/g, and band gap energy was calculated at 2.94 eV. The LaMnO₃ nanocomposite with noble metal shows enhanced photocatalytic effectiveness against RB dye (20 PPM) degradation (92%, R² = 0.995) with pseudo-first-order chemical kinetics (rate constant, k = 0.05057 min⁻¹) within 50 min due to the ultimate combination of the hydrothermal and bio-reduction technique. The photocatalytic activity of the LaMnO₃-Ag nanocomposite was optimized at different reaction times, photocatalyst doses (0.2, 0.4, 0.6, and 0.8 g/L), and various RB dye concentrations (20, 30, 40, and 50 ppm). The antibacterial activities of green synthesized LaMnO₃ and LaMnO₃-Ag nanoparticles were explored based on colony-forming unit (cfu) reduction and TEM images of bacterial and nanoparticle interactions for S. aureus and E. coli. An amount of 50 µg/mL LaMnO₃-Ag nanocomposite was sufficient to work as the highest antibacterial activity for both bacteria. The perovskite LaMnO₃-Ag nanocomposite synthesis process is economically and environmentally friendly. Additionally, it has a wide range of effective and exclusive applications for remediating pollutants. Full article

(This article belongs to the Special Issue Electrochemical and Photoelectrochemical Processes for Water Splitting)

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20 pages, 3471 KiB

Open AccessReview

Navigating Alkaline Hydrogen Evolution Reaction Descriptors for Electrocatalyst Design

by Samuel Akinlolu Ogunkunle, Fabien Mortier, Assil Bouzid, Jack Jon Hinsch, Lei Zhang, Zhenzhen Wu, Samuel Bernard, Yong Zhu and Yun Wang

Catalysts 2024, 14(9), 608; https://doi.org/10.3390/catal14090608 - 10 Sep 2024

Abstract

The quest for efficient green hydrogen production through Alkaline Water Electrolysis (AWE) is a critical aspect of the clean energy transition. The hydrogen evolution reaction (HER) in alkaline media is central to this process, with the performance of electrocatalysts being a determining factor [...] Read more.

The quest for efficient green hydrogen production through Alkaline Water Electrolysis (AWE) is a critical aspect of the clean energy transition. The hydrogen evolution reaction (HER) in alkaline media is central to this process, with the performance of electrocatalysts being a determining factor for overall efficiency. Theoretical studies using energy-based descriptors are essential for designing high-performance alkaline HER electrocatalysts. This review summarizes various descriptors, including water adsorption energy, water dissociation barrier, and Gibbs free energy changes of hydrogen and hydroxyl adsorption. Examples of how to apply these descriptors to identify the active site of materials and better design high-performance alkaline HER electrocatalysts are provided, highlighting the previously underappreciated role of hydroxyl adsorption-free energy changes. As research progresses, integrating these descriptors with experimental data will be paramount in advancing AWE technology for sustainable hydrogen production. Full article

(This article belongs to the Special Issue Feature Review Papers in Electrocatalysis)

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10 pages, 3581 KiB

Open AccessArticle

Improvement in the Photocatalytic Hydrogen Production of Flower-Shaped ZnIn₂S₄ by Surface Modification with Amino Silane

by Xiangyu Chen, Benliang Liang and Luting Yan

Catalysts 2024, 14(9), 607; https://doi.org/10.3390/catal14090607 - 10 Sep 2024

Abstract

ZnIn₂S₄ has attracted extensive attention in the field of photocatalytic hydrogen production because of its suitable band gap and excellent photoelectrochemical properties. However, its lower photogenerated carrier separation efficiency and high degree of photocorrosion severely restricts its photocatalytic activity. In [...] Read more.

ZnIn₂S₄ has attracted extensive attention in the field of photocatalytic hydrogen production because of its suitable band gap and excellent photoelectrochemical properties. However, its lower photogenerated carrier separation efficiency and high degree of photocorrosion severely restricts its photocatalytic activity. In this work, the photocatalytic hydrogen production performance of ZnIn₂S₄ modified with 3-aminopropylmethoxysilane was studied. Surface modification by amino silane not only regulated the band gap and enhanced the light absorption of ZnIn₂S₄ but it also increased the colloidal stability of the ZnIn₂S₄ suspension and enhanced the adsorption of H⁺ on the active surface sites, thereby improving the photocatalytic hydrogen production performance. Compared with that of unmodified ZnIn₂S₄, the photocatalytic hydrogen production rate of surface-modified ZnIn₂S₄ increased by 1.46 times, and after four cycles for 12 h, the hydrogen production efficiency remained at 75.14%. Full article

(This article belongs to the Section Photocatalysis)

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14 pages, 28964 KiB

Open AccessArticle

The Contradicting Influences of Silica and Titania Supports on the Properties of Au⁰ Nanoparticles as Catalysts for Reductions by Borohydride

by Gifty Sara Rolly, Alina Sermiagin, Krishnamoorthy Sathiyan, Dan Meyerstein and Tomer Zidki

Catalysts 2024, 14(9), 606; https://doi.org/10.3390/catal14090606 - 9 Sep 2024

Abstract

This study investigates the significant impact of metal–support interactions on catalytic reaction mechanisms at the interface of oxide-supported metal nanoparticles. The distinct and contrasting effects of SiO₂ and TiO₂ supports on reaction dynamics using NaBD₄ were studied and focused on [...] Read more.

This study investigates the significant impact of metal–support interactions on catalytic reaction mechanisms at the interface of oxide-supported metal nanoparticles. The distinct and contrasting effects of SiO₂ and TiO₂ supports on reaction dynamics using NaBD₄ were studied and focused on the relative yields of [HD]/[H₂] and [D₂]/[H₂]. The findings show a consistent increase in HD yields with rising [BD₄⁻] concentrations. Notably, the sequence of HD yield enhancement follows the order of TiO₂-Au⁰-NPs < Au⁰-NPs < SiO₂-Au⁰-NPs. Conversely, the rate of H₂ evolution during BH₄^- hydrolysis exhibits an inverse trend, with TiO₂-Au⁰-NPs outperforming the others, followed by Au⁰-NPs and SiO₂-Au⁰-NPs, demonstrating the opposing effects exerted by the TiO₂ and SiO₂ supports on the catalytic processes. Further, the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) confirms the catalytic mechanism, with TiO₂-Au⁰-NPs demonstrating superior activity. The catalytic activity observed aligns with the order of TiO₂-Au⁰-NPs > Au⁰-NPs > SiO₂-Au⁰-NPs, suggesting that SiO₂ donates electrons to Au⁰-NPs, while TiO₂ withdraws them. It is of interest to note that two very different processes, that clearly proceed via different mechanisms, are affected similarly by the supports. This study reveals that the choice of support material influences catalytic activity, impacting overall yield and efficiency. These findings underscore the importance of selecting appropriate support materials for tailored catalytic outcomes. Full article

(This article belongs to the Special Issue Novel Nanocatalysts for Sustainable and Green Chemistry)

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17 pages, 4445 KiB

Open AccessArticle

Influence of the Interaction of Nickel and Copper with Ceria on Ethanol Steam Reforming over Ni-Cu-CeO₂ Catalysts

by Karen C. Pájaro, Vicente Cortés Corberán and Arturo Martínez-Arias

Catalysts 2024, 14(9), 605; https://doi.org/10.3390/catal14090605 - 7 Sep 2024

Abstract

Catalysts of nickel-ceria, nickel-copper-ceria, and copper-ceria were explored with respect to their properties for hydrogen production through ethanol steam reforming (ESR). They were prepared by coprecipitation of the components within inverse microemulsions to achieve intimate contact between them, and the catalysts were characterized [...] Read more.

Catalysts of nickel-ceria, nickel-copper-ceria, and copper-ceria were explored with respect to their properties for hydrogen production through ethanol steam reforming (ESR). They were prepared by coprecipitation of the components within inverse microemulsions to achieve intimate contact between them, and the catalysts were characterized by N₂ adsorption measurements, XRD, Raman spectroscopy, TPR, and XPS. The catalysts were tested for the ESR reaction, and they were regenerated with oxygen when significant deactivation took place, as occurred for the copper-containing systems. In contrast, the nickel–ceria catalyst exhibits a high activity and stability despite the formation of an important amount of carbon deposits during the course of the ESR test. The presence of nickel sites, which strongly interact with the ceria support, and which are affected by the presence of copper, and the limitation of copper for C-C bond breaking are invoked to explain the results obtained on the whole. Full article

(This article belongs to the Section Catalysis for Sustainable Energy)

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