Catalysts

17 pages, 1600 KiB

Open AccessArticle

Comparative Studies on Methyl Ester Production from Pretreated Sludge Palm Oil Using Homogeneous and Heterogeneous Base Catalysts

by Ye Min Oo, Panupong Juera-Ong, Kritsakon Pongraktham and Krit Somnuk

Catalysts 2024, 14(9), 647; https://doi.org/10.3390/catal14090647 (registering DOI) - 22 Sep 2024

Abstract

A heterogeneous base catalyst transesterification process with a calcium oxide (CaO) catalyst was performed to produce high-purity methyl ester (ME) from pretreated sludge palm oil (PSPO) derived from sludge palm oil (SPO). Additionally, a comparative analysis was conducted with potassium hydroxide (KOH) as [...] Read more.

A heterogeneous base catalyst transesterification process with a calcium oxide (CaO) catalyst was performed to produce high-purity methyl ester (ME) from pretreated sludge palm oil (PSPO) derived from sludge palm oil (SPO). Additionally, a comparative analysis was conducted with potassium hydroxide (KOH) as a homogeneous base catalyst to assess the distinctions between heterogeneous and homogeneous base catalysts. The response surface methodology (RSM) was utilized to determine the optimal and recommended conditions for both transesterification processes. For heterogeneous transesterification, a varying CaO catalyst loading (10–60 wt.%), methanol (25–65 wt.%), and reaction time (60–180 min) were essential parameters. Meanwhile, homogeneous transesterification involved investigating the KOH catalyst loading (1–3 wt.%), methanol (1.8–5.5 wt.%), and reaction time (20–60 min). For the heterogeneous-base-catalyzed reaction, the recommended conditions were as follows: a molar ratio of methanol to oil of 5.83:1 (41.61 wt.%), 31.3 wt.% CaO, and a reaction time of 119.0 min, which resulted in a ME purity of 96.51 wt.%. The optimal conditions for homogeneous transesterification were a molar ratio of methanol to oil of 0.49:1 (3.45 wt.%), a 40 min reaction time, and a 1.39 wt.% KOH concentration, which achieved 96.59 wt.% ME and met the standard. Full article

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

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30 pages, 17190 KiB

Open AccessArticle

Synthesis, Performance Measurement of Dy₂EuSbO₇/ZnBiDyO₄ Heterojunction Composite Catalyst and Photocatalytic Degradation of Chlorpyrifos within Pesticide Wastewater under Visible Light Irradiation

by Jingfei Luan, Yang Xiao, Liang Hao, Ye Yao, Bowen Niu, Guangmin Yang and Yichun Wang

Catalysts 2024, 14(9), 646; https://doi.org/10.3390/catal14090646 (registering DOI) - 21 Sep 2024

Abstract

For the first time, a novel catalyst named Dy₂EuSbO₇ was successfully synthesized via the high-temperature solid-state sintering method (HTSSM). Dy₂EuSbO₇/ZnBiDyO₄ heterojunction photocatalyst (DZHP) was fabricated through the HTSSM for degrading chlorpyrifos (CPS) in the pesticide [...] Read more.

For the first time, a novel catalyst named Dy₂EuSbO₇ was successfully synthesized via the high-temperature solid-state sintering method (HTSSM). Dy₂EuSbO₇/ZnBiDyO₄ heterojunction photocatalyst (DZHP) was fabricated through the HTSSM for degrading chlorpyrifos (CPS) in the pesticide wastewater under visible light irradiation (VSLID). Under VSLID, DZHP could effectively degrade CPS in pesticide wastewater. The experimental outcomes suggested that the kinetic curve with the Dy₂EuSbO₇/ZnBiDyO₄ heterojunction (DZH) as a photocatalyst for the reduction of CPS under VSLID conformed to the first-order kinetics (FOKT). After VSLID of 156 min, the photocatalytic degradation (PTD) removal rate of CPS using DZH as photocatalyst was 1.12 times, 1.21 times, or 2.96 times that using Dy₂EuSbO₇ as a photocatalyst, ZnBiDyO₄ as a photocatalyst, or nitrogen-doped titanium dioxide as a photocatalyst. After VSLID of 156 min for four cycle degradation tests (FCDTS) with DZH as a photocatalyst, the removal rate of CPS reached 98.78%, 97.66%, 96.59%, and 95.69%, respectively. Above results indicated that the DZHP possessed high stability. Experiments with the addition of trapping agents showed that hydroxyl radicals (•OH) owned the strongest oxidative removal ability for degrading CPS compared with superoxide anions (•O₂⁻) or holes (h⁺). The oxidation capacity of three oxidation radicals for eliminating CPS was ranked in the ascending order as follows: h⁺ < •OH < •O₂⁻. Lastly, the possible degradation pathway and degradation mechanism of CPS were discussed in detail. A visible light responsive heterojunction catalyst with high catalytic activity and a photocatalytic reaction system which were capable of efficiently removing toxic organic pollutants from pesticide wastewater were obtained. Full article

(This article belongs to the Section Photocatalysis)

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15 pages, 4313 KiB

Open AccessFeature PaperArticle

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

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

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

Abstract

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

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

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

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12 pages, 2397 KiB

Open AccessArticle

Kinetic Evaluation and Catalytic Efficiency of Sebacic Acid as a Novel Catalyst in Hydrogen Generation via NaBH₄ Alcoholysis Reactions

by Savas Gurdal

Catalysts 2024, 14(9), 644; https://doi.org/10.3390/catal14090644 - 20 Sep 2024

Abstract

This study explores the use of sebacic acid, a catalyst not previously examined in the literature, for hydrogen production from NaBH₄ through methanolysis and ethanolysis reactions. Solutions of sebacic acid with concentrations ranging from 0.1 M to 0.4 M were prepared and [...] Read more.

This study explores the use of sebacic acid, a catalyst not previously examined in the literature, for hydrogen production from NaBH₄ through methanolysis and ethanolysis reactions. Solutions of sebacic acid with concentrations ranging from 0.1 M to 0.4 M were prepared and tested. At a concentration of 0.3 M, 90% of the hydrogen from a 0.33 M NaBH₄ solution was released within 3 s, and full release was achieved in 4 s. Hydrogen production rates reached 4500 mL/min for ethanolysis and 4845 mL/min for methanolysis, with methanolysis reactions proving faster. The activation energies for methanolysis and ethanolysis were calculated as 7.17 kJ/mol and 52.3 kJ/mol, respectively. These results demonstrate that sebacic acid enables rapid and efficient hydrogen production, offering a new approach that significantly advances current hydrogen production methods. Full article

(This article belongs to the Special Issue Advanced Catalysis for Green Fuel Synthesis and Energy Conversion, 2nd Edition)

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14 pages, 2231 KiB

Open AccessArticle

Biodiesel Synthesis from Date Seed Oil Using Camel Dung as a Novel Green Catalyst: An Experimental Investigation

by Raiedhah A. Alsaiari, Esraa M. Musa and Moustafa A. Rizk

Catalysts 2024, 14(9), 643; https://doi.org/10.3390/catal14090643 - 20 Sep 2024

Abstract

Biodiesel is seen as more environmentally benign than petroleum-based fuels. It is also cheaper and capable of creating cleaner energy, which has a good impact on increasing the bioeconomy. An investigation was conducted on a novel heterogeneous catalyst system utilized in the synthesis [...] Read more.

Biodiesel is seen as more environmentally benign than petroleum-based fuels. It is also cheaper and capable of creating cleaner energy, which has a good impact on increasing the bioeconomy. An investigation was conducted on a novel heterogeneous catalyst system utilized in the synthesis of eco-friendly biodiesel from date seed oil, a non-edible feedstock obtained through the calcination of desiccated camel manure at varying temperatures. X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) analysis, and scanning electron microscopy (SEM) were utilized to characterize this catalyst. As a result of raising the calcination temperature, the results showed that the pore size of the catalyst decreased. The biodiesel production was optimized to be 86% by using the transesterification method. The optimal reaction parameters included a catalyst with 4% loading, a molar ratio of 1:8 between date seed oil and ethanol, and a temperature of 75 °C for a reaction period of three hours. The confirmation of FAME generation was achieved by gas chromatography–mass spectrometry (GC–MS). The fuel qualities of fatty acid ethyl ester are in accordance with ASTM, suggesting that it is a suitable alternative fuel option. Utilizing biodiesel derived from waste and untamed resources to establish and execute a more sustainable and ecologically conscious energy plan is praiseworthy. The adoption and integration of green energy practices could potentially yield positive environmental outcomes, thereby fostering enhanced societal and economic development for the biodiesel sector on a broader scale. Full article

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

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4 pages, 179 KiB

Open AccessEditorial

Advances in Catalytic Oxidation of Methane and Carbon Monoxide (2nd Edition)

by Hongxing Dai and Junhu Wang

Catalysts 2024, 14(9), 642; https://doi.org/10.3390/catal14090642 - 20 Sep 2024

Abstract

The catalytic removal of carbon monoxide and methane produced from human activities is an important method for eliminating these pollutants, and can solve their associated environmental problems [...] Full article

(This article belongs to the Special Issue Advances in Catalytic Oxidation of Methane and Carbon Monoxide, 2nd Edition)

21 pages, 9630 KiB

Open AccessArticle

Enhancing Biomedical and Photocatalytic Properties: Synthesis, Characterization, and Evaluation of Copper–Zinc Oxide Nanoparticles via Co-Precipitation Approach

by Maha M. Almoneef, Manal A. Awad, Haia H. Aldosari, Awatif A. Hendi, Horiah A. Aldehish, Nada M. Merghani, Saad G. Alshammari, Latifah M. Alsuliman, Alhanouf A. Alghareeb and Magd S. Ahmed

Catalysts 2024, 14(9), 641; https://doi.org/10.3390/catal14090641 - 20 Sep 2024

Abstract

In this work, researchers synthesized copper–zinc oxide nanoparticles (NPs) of different shapes and sizes and tested their antibacterial and anticancer effects. The current research used a straightforward method to synthesize copper-doped zinc oxide nanoparticles (Cu-ZnO NPs). Next, the photocatalytic, antibacterial, and anticancer properties [...] Read more.

In this work, researchers synthesized copper–zinc oxide nanoparticles (NPs) of different shapes and sizes and tested their antibacterial and anticancer effects. The current research used a straightforward method to synthesize copper-doped zinc oxide nanoparticles (Cu-ZnO NPs). Next, the photocatalytic, antibacterial, and anticancer properties of the Cu-ZnO NPs were ascertained. Nanoparticles of Cu-doped ZnO were synthesized using co-precipitation technology. The physicochemical characterization was carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet–visible (UV-Vis) and Fourier-transform infrared (FTIR) spectroscopy, and other imaging techniques. The SEM analysis confirmed that the particles observed by SEM were found to be below 100 nm in size, which aligns with the results obtained from XRD. The size histogram in the figure inset shows that the nanoparticles are mostly round and have a size range of 5 to 50 nm. The XRD diffractograms revealed the classic structure of wurtzite-phase crystalline Cu-ZnO, and the crystallite size is 26.48 nm. Differences in the principal absorption peaks between the FTIR and UV-vis spectra suggest that varying ZnO NP morphologies might lead to spectrum shifts. We used the agar diffusion method to determine how effective Cu-doped ZnO NPs were against bacteria and the MTT assay to see how well they worked against cancer. The photocatalytic disintegration capacity of Cu-doped ZnO NPs was investigated by degrading crystal violet (CV) and methylene blue (MB) dyes under ultraviolet lamp irradiation. A value of 1.32 eV was recorded for the band gap energy. All peaks conformed to those of the Zn, O, and Cu atoms, and there were no impurities, according to the EDS study. Additionally, the nanoparticles had anticancer properties, indicating that the NPs were specifically targeting cancer cells by inducing cell death. At a 100 µg/mL concentration of the synthesized Cu-doped ZnO NPs, the cell availability percentages for the SW480, MDA-231, and HeLa cell lines were 29.55, 30.15, and 28.2%, respectively. These findings support the idea that Cu-doped ZnO NPs might be a new cancer treatment. Moreover, the results show the percentage of dye degradation over different time durations. After 180 h, the degradation of CV dye reached 79.6%, while MB dye exhibited a degradation of 69.9%. Based on these findings, Cu-doped ZnO NPs have the potential to be effective photocatalysts, antibacterial agents, and cancer fighters. This bodes well for their potential applications in the fields of ecology, medicine, and industry in the future. Full article

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

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4 pages, 409 KiB

Open AccessEditorial

New Catalysts and Reactors for the Synthesis or Conversion of Methanol

by Jaime Soler

Catalysts 2024, 14(9), 640; https://doi.org/10.3390/catal14090640 (registering DOI) - 20 Sep 2024

Abstract

Energy storage is a critical issue in the development of an economy based on the use of renewable energy [...] Full article

(This article belongs to the Special Issue New Catalysts and Reactors for the Synthesis or Conversion of Methanol)

16 pages, 6912 KiB

Open AccessArticle

Enhanced Photoelectrochemical Water Splitting Performance of Ce-Doped TiO₂ Nanorod Array Photoanodes for Efficient Hydrogen Production

by Bi-Li Lin, Rui Chen, Mei-Ling Zhu, Ao-Sheng She, Wen Chen, Bai-Tong Niu, Yan-Xin Chen and Xiu-Mei Lin

Catalysts 2024, 14(9), 639; https://doi.org/10.3390/catal14090639 - 20 Sep 2024

Abstract

In this study, original titanium dioxide (TiO₂) and cerium (Ce)-doped TiO₂ nanorod array photoanodes are prepared by hydrothermal method combined with high-temperature annealing, and their morphology, photoelectrochemical properties, and photocatalytic hydrogen production ability are systematically evaluated. X-ray diffraction (XRD) analysis [...] Read more.

In this study, original titanium dioxide (TiO₂) and cerium (Ce)-doped TiO₂ nanorod array photoanodes are prepared by hydrothermal method combined with high-temperature annealing, and their morphology, photoelectrochemical properties, and photocatalytic hydrogen production ability are systematically evaluated. X-ray diffraction (XRD) analysis shows that as the Ce content increases, the diffraction peak of the rutile phase (110) shifts towards lower angles, indicating the successful doping of different contents of Ce into the TiO₂ lattice. Photoelectric performance test results show that Ce doping significantly improves the photocurrent density of TiO₂, especially for the 0.54wt% Ce-doped TiO₂ (denoted as CR5). The photocurrent density of CR5 reaches 1.98 mA/cm² at a bias voltage of 1.23 V (relative to RHE), which is 2.6 times that of undoped TiO₂ (denoted as R). Photoelectrochemical hydrolysis test results show that the hydrogen yield performance under full-spectrum testing conditions of Ce-doped TiO₂ photoanodes is better than that of original TiO₂ as well, which are 37.03 and 12.64 µmol·cm⁻²·h⁻¹ for CR5 and R, respectively. These results indicate that Ce doping can effectively promote charge separation and improve hydrogen production efficiency by reducing resistance, accelerating charge transfer, and introducing new electronic energy levels. Our findings provide a new strategy for designing efficient photocatalysts with enhanced photoelectrochemical (PEC) water-splitting performance. Full article

(This article belongs to the Section Photocatalysis)

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12 pages, 2130 KiB

Open AccessFeature PaperArticle

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

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

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

Abstract

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

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

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

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18 pages, 5834 KiB

Open AccessArticle

Hydrogen-Ignited-Methanol Catalytic Co-Combustion of Aromatic Volatile Organic Compounds over PdPt/Al₂O₃ Bimetallic Catalyst

by Sehrish Munsif, Lutf Ullah, Long Cao, Palle Ramana Murthy, Jing-Cai Zhang and Wei-Zhen Li

Catalysts 2024, 14(9), 637; https://doi.org/10.3390/catal14090637 - 19 Sep 2024

Abstract

Electric heating is frequently employed to treat volatile organic compounds (VOCs) through catalytic combustion. However, it is associated with problems such as slow heating, high energy consumption, and low efficiency. This study explores PdPt/Al₂O₃ catalysts for igniting methanol (MeOH) through [...] Read more.

Electric heating is frequently employed to treat volatile organic compounds (VOCs) through catalytic combustion. However, it is associated with problems such as slow heating, high energy consumption, and low efficiency. This study explores PdPt/Al₂O₃ catalysts for igniting methanol (MeOH) through H₂ catalytic combustion, providing internal on-site heating of catalyst active sites. It also investigates VOCs’ abatement using H₂-ignited-MeOH combustion without H₂ and external heating. Bimetallic catalysts enhance activity and reduce thermal aging. Hydrogen gas (H₂) can initiate the MeOH combustion at room temperature with the addition of very small amounts, even below its low explosive limit of 4%. This process optimizes MeOH ignition at approximately 350 °C, even when the concentration of H₂ is as low as 0.01%. This method enhances combustion kinetics, converting MeOH and VOCs into CO₂ and water. Catalytic performance is independent of PdPt nanoparticle sizes in fresh and spent catalysts, represented in XRD and STEM. Using hydrogen as an igniting agent provides a clean, effective method to initiate catalytic reactions, addressing traditional challenges and enhancing VOCs’ decomposition efficiency. 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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32 pages, 6561 KiB

Open AccessReview

Recent Research Progress on Surface Modified Graphite Carbon Nitride Nanocomposites and Their Photocatalytic Applications: An Overview

by Shuhan Li, Juntao Tan, Jiatong Liu, Yang Li, Liang Sun, Zhijie Huang and Jiaming Li

Catalysts 2024, 14(9), 636; https://doi.org/10.3390/catal14090636 - 19 Sep 2024

Abstract

Semiconductors with visible light catalytic characteristics can realize the degradation of pollutants, CO₂ reduction, and hydrogen preparation in sunlight. They have huge application value in the fields of environmental repair and green energy. Graphite phase nitride (g-C₃N₄, CN) [...] Read more.

Semiconductors with visible light catalytic characteristics can realize the degradation of pollutants, CO₂ reduction, and hydrogen preparation in sunlight. They have huge application value in the fields of environmental repair and green energy. Graphite phase nitride (g-C₃N₄, CN) is widely used in various fields such as photocatalytic degradation of pollutants due to its suitable gap width, easy preparation, low cost, fast visible light response, and rich surface activity sites. However, the absorption rate of ordinary CN on visible light is low, and the carriers are easy to recombination, making the lower optical catalytic activity. Therefore, in order to improve the photocatalytic characteristics of the CN, it is necessary to make the surface modification. This article first introduces several main methods for the current surface modification of CN, including size regulation, catalyst embedding, defect introduction, heterostructure construction, etc., and then summarizes the optical catalytic application and related mechanisms of CN. Finally, some challenges and development prospects of CN in preparation and photocatalytic applications are proposed. Full article

(This article belongs to the Special Issue Two-Dimensional Materials in Photo(electro)catalysis)

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10 pages, 2078 KiB

Open AccessArticle

Microwave-Assisted Oxidation of N₂ into NO_x over a La-Ce-Mn-O Perovskite Yielding Plasmas in a Quartz Flow Reactor at Atmospheric Pressure

by Frederic C. Meunier and Akim Kaddouri

Catalysts 2024, 14(9), 635; https://doi.org/10.3390/catal14090635 - 19 Sep 2024

Abstract

N₂ oxidation to NO_x is a challenging reaction, and alternative routes to the industrial Ostwald process are of interest. A perovskite under flowing O₂-N₂ mixtures at atmospheric pressure in a quartz tube reactor was irradiated by microwaves (MW), [...] Read more.

N₂ oxidation to NO_x is a challenging reaction, and alternative routes to the industrial Ostwald process are of interest. A perovskite under flowing O₂-N₂ mixtures at atmospheric pressure in a quartz tube reactor was irradiated by microwaves (MW), leading to the formation of hot spots and plasmas within the catalyst bed. NO_x concentrations up to 2.5 vol.% in one pass were obtained at 600 W. Using a lower MW power of 100 W led to a pulsed mode yielding lower NO_x concentrations and no noticeable damage to the quartz reactor. The formation of plasma was strongly dependent on the perovskite bed packing. The perovskite acted primarily as a susceptor and likely also as a catalyst, although the proportion of heterogeneous and homogenous reactions could not be determined in the present study. The simple reactor layout allowing operation at atmospheric pressure is promising for the development of practical MW-assisted N₂ fixation technologies. Full article

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

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13 pages, 3743 KiB

Open AccessArticle

Deactivation of Cu/ZSM-5 Catalysts during the Conversion of 2,3-Butanediol to Butenes

by Ziyuan Wang, Pawel Chmielniak and Carsten Sievers

Catalysts 2024, 14(9), 634; https://doi.org/10.3390/catal14090634 - 19 Sep 2024

Abstract

This work determines the deactivation mechanisms of Cu/ZSM-5 catalysts used for the conversion of 2,3-butanediol to butene as part of an alcohol-to-jet route. The deactivation of the catalyst, reflected by a drop in the rate of the limiting hydrogenation step by over 90% [...] Read more.

This work determines the deactivation mechanisms of Cu/ZSM-5 catalysts used for the conversion of 2,3-butanediol to butene as part of an alcohol-to-jet route. The deactivation of the catalyst, reflected by a drop in the rate of the limiting hydrogenation step by over 90% in 24 h at a weight hourly space velocity of 5.92 h⁻¹, proceeds via both the agglomeration of copper particles and the obstruction of copper surfaces due to carbonaceous deposits, although the former has less impact on the decrease in the hydrogenation rate. To reduce the detrimental effect of carbonaceous deposits on catalytic activity, ZMS-5 is modified through desilication of the HZSM-5 support with NaOH and CsOH solutions to generate a hierarchical structure with mesopores. The catalyst with the CsOH-treated support generates the highest overall yield of desired olefin products and experiences the slowest deactivation. This is a result of the lower Brønsted acidity and larger mesopores found in the CsOH-treated catalyst, leading to the slower formation of carbonaceous deposits and the faster diffusion of their precursors out of the pores. Full article

(This article belongs to the Special Issue Zeolites and Zeolite-Based Catalysis)

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14 pages, 4880 KiB

Open AccessArticle

Enhancement Study of the Photoactivity of TiO₂ Photocatalysts during the Increase of the WO₃ Ratio in the Presence of Ag Metal

by Sharah H. Aldirham, Ahmed Helal, Mohd Shkir, M. A. Sayed and Atif Mossad Ali

Catalysts 2024, 14(9), 633; https://doi.org/10.3390/catal14090633 - 18 Sep 2024

Abstract

Nanocomposites (NCs) consisting of 4%Ag/x%WO₃/TiO₂, with varied concentrations (x = 1, 3, 5, 7 wt.%) of WO₃, were successfully synthesized using the sol-gel process to examine their photocatalytic performance. The synthesized 4%Ag/x%WO [...] Read more.

Nanocomposites (NCs) consisting of 4%Ag/x%WO₃/TiO₂, with varied concentrations (x = 1, 3, 5, 7 wt.%) of WO₃, were successfully synthesized using the sol-gel process to examine their photocatalytic performance. The synthesized 4%Ag/x%WO₃/TiO₂ nanopowder was characterized using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectra (UV–vis DRS), photoluminescence (PL), and Brunauer–Emmett–Teller (BET) surface area analysis to elucidate its physicochemical properties. The photocatalytic evaluation revealed that the Ag/1%WO₃/TiO₂ nanocomposite exhibits 98% photoreduction efficiency for Cr(VI) after 2 h under visible light due to the impact of the plasmonic effect of Ag atoms. In addition, the Ag/4%WO₃/TiO₂ shows about 95% photooxidation efficiency for methylene blue (MB) dye after 4 h. Full article

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

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14 pages, 2131 KiB

Open AccessArticle

Influence of Current Collector Design and Combination on the Performance of Passive Direct Methanol Fuel Cells

by Weibin Yu, Zhiyuan Xiao, Weiqi Zhang, Qiang Ma, Zhuo Li, Xiaohui Yan, Huaneng Su, Lei Xing and Qian Xu

Catalysts 2024, 14(9), 632; https://doi.org/10.3390/catal14090632 - 18 Sep 2024

Abstract

In this work, an anode current collector with a scaled step-hole structure (called SF-type) and a cathode current collector with a perforated cross-tilt structure (called X-type) were designed and fabricated for application in passive direct methanol fuel cells (DMFCs). A whole-cell test showed [...] Read more.

In this work, an anode current collector with a scaled step-hole structure (called SF-type) and a cathode current collector with a perforated cross-tilt structure (called X-type) were designed and fabricated for application in passive direct methanol fuel cells (DMFCs). A whole-cell test showed that the combination of an anode SF-type current collector and cathode conventional current collector increased the optimal methanol concentration from 6 M to 8 M and the maximum power density to 5.40 mW cm⁻², which improved the cell performance by 51.6% compared to that of the conventional design under ambient testing conditions. The combination of the anode conventional current collector and cathode X-type current collector achieved a maximum power density of 5.65 mW cm⁻² with a 58.7% performance improvement, while the optimal methanol concentration was increased to 10 M. Furthermore, the combination of anode SF-type and cathode X-type obtained the highest power density at 6.22 mW cm⁻². Notably, the anode and cathode catalyst loadings used in this study were 2.0 mg cm⁻², which is lower than the commonly used loading, thus reducing the fuel cell cost. Full article

(This article belongs to the Special Issue Advances in Catalyst Design and Application for Fuel Cells)

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18 pages, 5608 KiB

Open AccessArticle

Production of Bio-Oil from Sugarcane Bagasse through Hydrothermal Liquefaction Processes with Modified Zeolite Socony Mobil-5 Catalyst

by Thandiswa Jideani, Ntalane Sello Seroka and Lindiwe Khotseng

Catalysts 2024, 14(9), 631; https://doi.org/10.3390/catal14090631 - 18 Sep 2024

Abstract

In response to the increasing global demand for sustainable energy alternatives, this research explores the efficient conversion of sugarcane bagasse to bio-oil through hydrothermal liquefaction (HTL) processes with modified Zeolite Socony Mobil-5 catalysts (ZSM-5). The study systematically investigates the impact of feedstock quantity, [...] Read more.

In response to the increasing global demand for sustainable energy alternatives, this research explores the efficient conversion of sugarcane bagasse to bio-oil through hydrothermal liquefaction (HTL) processes with modified Zeolite Socony Mobil-5 catalysts (ZSM-5). The study systematically investigates the impact of feedstock quantity, reaction temperature, duration, and catalyst loading on bio-oil yield and quality. Optimisation experiments revealed that a feedstock amount of 10 grammes, an HTL temperature of 340 °C for 60 min and a ZSM-5 catalyst loading of 3 grammes resulted in the highest bio-oil yield. Furthermore, the introduction of Ni and Fe metals to ZSM-5 exhibited enhanced catalytic activity without compromising the structure of the zeolites. Comprehensive characterisation of modified catalysts using SEM-EDS, XRD, TGA, TEM, and FTIR provided insight into their structural and chemical properties. The successful incorporation of Ni and Fe into ZSM-5 was confirmed, highlighting promising applications in hydrothermal liquefaction. Gas chromatography–mass spectrometry (GC-MS) analysis of bio-oils demonstrated the effectiveness of the 2% Fe/ZSM-5 catalyst, highlighting a significant increase in hydrocarbon content. FTIR analysis of the produced bio-oils indicated a reduction in functional groups and intensified aromatic peaks, suggesting a shift in chemical composition favouring aromatic hydrocarbons. This study provides valuable information on HTL optimisation, catalyst modification, and bio-oil characterisation, advancing the understanding of sustainable biofuel production. The findings underscore the catalytic prowess of modified ZSM-5, particularly with iron incorporation, in promoting the formation of valuable hydrocarbons during hydrothermal liquefaction. Full article

(This article belongs to the Section Catalytic Reaction Engineering)

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14 pages, 4307 KiB

Open AccessArticle

PEDOT: PSS Doped Activated Biochar as a Novel Composite Material for Photocatalytic and Efficient Energy Storage Application

by Taymour A. Hamdalla, Saleh A. Al-Ghamdi, Shahd Alfadhli, Abdulrhman M. Alsharari, M. Chiesa and Syed Khasim

Catalysts 2024, 14(9), 630; https://doi.org/10.3390/catal14090630 - 18 Sep 2024

Abstract

Herein, we report the synthesis of activated biochar from green algae and the effect of its doping on the structural, photocatalytic, and energy storage properties of PEDOT-PSS. The morphology of pure and doped samples was investigated with Fourier Transform Infrared Spectroscopy (FTIR), Atomic [...] Read more.

Herein, we report the synthesis of activated biochar from green algae and the effect of its doping on the structural, photocatalytic, and energy storage properties of PEDOT-PSS. The morphology of pure and doped samples was investigated with Fourier Transform Infrared Spectroscopy (FTIR), Atomic Force Microscopy (AFM), Brunauer–Emmett–Teller (BET) analysis, and thermogravimetric analysis (TGA). AFM results for PEDOT-PSS@6wt.% of BC indicate that the calculated average peak height, particle size, and roughness were 283 nm, 136 nm, and 71 nm, respectively. Adding biochar to PEDOT-PSS significantly improved the thermal stability of PEDOT-PSS up to 550 °C. The novel photocatalyst PEDOT-PSS@6wt.% BC improved photocatalytic performance by approximately 17% in Methylene Blue (MB) dye removal. The electrochemical performance in terms of supercapacitors for the synthesized samples was investigated using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), specific capacitance, stability, and electrochemical impedance spectra (EIS). PEDOT-PSS@6wt.% of BC as a novel electrode material in supercapacitors exhibits an initial specific capacitance of 1300 Fg⁻¹. Moreover, the PEDOT-PSS@6wt.% of BC electrode shows excellent stability up to 1000 cycles of operation. The EIS studies suggest the presence of charge transfer resistance. Considering the economical biosynthesis and multifunctional features, the PEDOT-PSS@6wt.% of BC could potentially be used as a photocatalyst to remove organic dyes and supercapacitors in energy storage applications. Full article

(This article belongs to the Special Issue Advances in Catalysis for Sustainable Energy and Environmental Remediation)

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14 pages, 4623 KiB

Open AccessArticle

Synergic Effects of Ordered Mesoporous Bifunctional Ionic Liquid: A Recyclable Catalyst to Access Chemoselective N-Protected Indoline-2,3-dione Analogous

by Gouthaman Siddan and Viswas Raja Solomon

Catalysts 2024, 14(9), 629; https://doi.org/10.3390/catal14090629 - 17 Sep 2024

Abstract

SBA-15 and organic ionic liquid were incorporated in a post-grafting technique for generating a bifunctional ionic liquid embedded mesoporous SBA-15. The prepared heterogeneous catalyst was employed for the first time to synthesize N-alkylated indoline-2,3-dione at mild conditions to afford excellent yields in [...] Read more.

SBA-15 and organic ionic liquid were incorporated in a post-grafting technique for generating a bifunctional ionic liquid embedded mesoporous SBA-15. The prepared heterogeneous catalyst was employed for the first time to synthesize N-alkylated indoline-2,3-dione at mild conditions to afford excellent yields in a short reaction time. The synthesized DABCOIL@SBA-15 catalyst was meticulously characterized by various techniques, such as FT-IR, solid-state ¹³C NMR, solid-state ²⁹Si NMR, small-angle X-ray diffraction (XRD), and N₂ adsorption–desorption. Further, the morphological behavior of the catalyst was studied by SEM and TEM. The thermal stability and number of active sites were determined by thermogravimetric analysis (TGA). The Hammett equation was used to analyze the synergetic effect of the catalyst and substituent effects on the N-alkylated products of 5-substituted isatin derivatives, which resulted in a negative slope. This negative slope indicates a positive charge in the transition state. Notably, the DABCOIL@SBA-15 catalyst demonstrated its practicality by being reused for seven cycles with consistently high catalytic activity. Full article

(This article belongs to the Special Issue Mesoporous Nanostructured Materials for Heterogeneous Catalysis)

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