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Catalysts, Volume 12, Issue 11 (November 2022) – 197 articles

Cover Story (view full-size image): Titania-based photocatalysts have been intensively studied for various applications during the last fifty years, including environmental purification, solar energy conversion and organic synthesis. Despite broad scientific interest and even commercial use, two shortcomings (charge-carriers’ recombination and UV-limited photoabsorption) should be overcome for successful commercialization of titania, and thus, various strategies have been proposed. Can defective (self-doped) titania be considered as UV/vis/NIR active photocatalysts? Is the type of defect important (charge carriers’ recombination center)? Does black titania mean an efficient photocatalytic material? This paper is an attempt to answer those crucial questions, based on the characterization and photocatalytic activity data for different (mainly black) titania samples. View this paper
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17 pages, 7619 KiB  
Article
Visible-Light-Active Vanadium and Copper Co-Doped gCN Nanosheets with Double Direct Z-Scheme Heterojunctions for Photocatalytic Removal of Monocrotophos Pesticide in Water
by Dhanapal Vasu, Arjunan Karthi Keyan, Subramanian Sakthinathan, Chung-Lun Yu, Yu-Feng You, Te-Wei Chiu, Liangdong Fan and Po-Chou Chen
Catalysts 2022, 12(11), 1489; https://doi.org/10.3390/catal12111489 - 21 Nov 2022
Cited by 6 | Viewed by 1764
Abstract
In this study, both vanadium and copper elements were anchored on graphitic carbon nitride (gCN) (denoted as V/Cu/gCN) via a thermal decomposition process as a novel nanosheet photocatalyst for the removal of monocrotophos (MCP). The prepared nanosheet features were studied by utilizing XRD, [...] Read more.
In this study, both vanadium and copper elements were anchored on graphitic carbon nitride (gCN) (denoted as V/Cu/gCN) via a thermal decomposition process as a novel nanosheet photocatalyst for the removal of monocrotophos (MCP). The prepared nanosheet features were studied by utilizing XRD, UV–Visible absorption spectrometry, PL, FE-SEM, TEM, and XPS techniques. These analytical techniques revealed the successful formation of direct Z-scheme heterojunctions of V/Cu/gCN nanosheets. The dopant materials significantly enhanced the electron–hole separation and enhanced the removal rate of MCP as compared with bulk gCN. The investigation of effective operating conditions confirmed that a higher removal of MCP could be obtained at a doping concentration of 0.3 wt% and a catalytic dosage of 8 mg with 80 min of visible-light irradiation. The generation of various reactive radicals during the degradation process of the photocatalyst was observed using a scavenging treatment process. Additionally, the scavenging process confirmed that e, OH•, h+, and O2•− played a major role in MCP degradation. The direct Z-scheme dual-heterojunction mechanism, as well as the possible pathway for the fragmentation of MCP by the V/Cu/gCN nanosheet photocatalyst, was derived in detail. This research article provides a novel perspective on the formation of excellent semiconductor photocatalysts, which exhibit enormous potential for environmental treatments. Full article
(This article belongs to the Special Issue Synthesis and Photocatalytic Activity of Composite)
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16 pages, 3470 KiB  
Article
Removal of Persistent Acid Pharmaceuticals by a Biological-Photocatalytic Sequential Process: Clofibric Acid, Diclofenac, and Indomethacin
by María J. Cruz-Carrillo, Rosa M. Melgoza-Alemán, Cecilia Cuevas-Arteaga and José B. Proal-Nájera
Catalysts 2022, 12(11), 1488; https://doi.org/10.3390/catal12111488 - 21 Nov 2022
Viewed by 1113
Abstract
The removal of three acid pharmaceuticals—clofibric acid (CLA), diclofenac (DCL), and indomethacin (IND)—by a biological-photocatalytic sequential system was studied. These pharmaceutical active compounds (PhACs) are considered to persist in the environment and have been found in water and sewage, producing adverse effects on [...] Read more.
The removal of three acid pharmaceuticals—clofibric acid (CLA), diclofenac (DCL), and indomethacin (IND)—by a biological-photocatalytic sequential system was studied. These pharmaceutical active compounds (PhACs) are considered to persist in the environment and have been found in water and sewage, producing adverse effects on the aquatic environment. For the biological process, in batch experiments, a fixed bed bioreactor and activated sludge (hybrid bioreactor), under aerobic conditions, was used as pretreatment. The pretreated effluent was exposed to a photocatalytic process employing TiO2 nanotubular films (NTF-TiO2) with the following characteristics: an internal diameter of 112 nm, a wall thickness of 26 nm, nanotube length of 15 µm, a roughness factor of 1840 points, and an anatase-rutile crystalline structure. In the hybrid bioreactor, 39% IND and 50% ACL and DCL were removed. The biological-photocatalysis sequential system achieved the degradation of up to 90% of the initial concentrations of the three acid pharmaceuticals studied. This approach appears to be a viable alternative for the treatment of these non-biodegradable effluents. Full article
(This article belongs to the Special Issue Advanced Oxidation Catalysts)
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30 pages, 6495 KiB  
Review
Critical Review of the Various Reaction Mechanisms for Glycerol Etherification
by Prakas Palanychamy, Steven Lim, Yeow Hong Yap and Loong Kong Leong
Catalysts 2022, 12(11), 1487; https://doi.org/10.3390/catal12111487 - 21 Nov 2022
Cited by 12 | Viewed by 4991
Abstract
This review provides in-depth coverage of numerous mechanisms available for the etherification process of glycerol, including alcohol solvent, olefin solvent and solvent-free routes along with products that are formed at various stages of the reaction. Mono tert-butyl glycerol ether (MTBG), di tert-butyl glycerol [...] Read more.
This review provides in-depth coverage of numerous mechanisms available for the etherification process of glycerol, including alcohol solvent, olefin solvent and solvent-free routes along with products that are formed at various stages of the reaction. Mono tert-butyl glycerol ether (MTBG), di tert-butyl glycerol ether (DTBG), and tri tert-butyl glycerol ether (TTBG) are the three general ether compounds obtained through tert-butyl alcohol (TBA) etherification. Glycerol etherification with n-butanol results in the formation of glycerol ether products that are linked to the substituted butyl groups. These products include two mono-butyl glycerol ethers, two di-butyl glycerol ethers and a tri-butyl glycerol ether. Two mono-benzyl glycerol ether isomers, two di-benzyl glycerol ether isomers and tri-benzyl glycerol ether are the most reported results when benzyl alcohol is used as a solvent in the etherification reaction. The etherification of glycerol with 1-butene involves a series of equilibrium reactions to produce mono-ethers, di-ethers, and tri-ethers, whereas the etherification of glycerol with isobutene is carried out via tert-butylation of glycerol, yielding similar glycerol ether products when TBA is used as a solvent. As the by-product may be easily removed, the solvent-free glycerol etherification approach may have several advantages over the other conventional methods. Therefore, further studies on base-catalyzed glycerol etherification that employs a solvent-free reaction route may reveal a method for improving the conversion, selectivity, and yield of reaction products. This review study is crucial in improving knowledge of numerous mechanisms and how they relate to the effectiveness of the product’s catalytic process. Full article
(This article belongs to the Special Issue Catalytic Conversion of Glycerol)
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17 pages, 5136 KiB  
Article
Hydrodeoxygenation–Isomerization of Methyl Palmitate over SAPO-11-Supported Ni-Phosphide Catalysts
by Ivan V. Shamanaev, Irina A. Shamanaeva, Ekaterina V. Parkhomchuk and Galina A. Bukhtiyarova
Catalysts 2022, 12(11), 1486; https://doi.org/10.3390/catal12111486 - 21 Nov 2022
Cited by 6 | Viewed by 1841
Abstract
Ni-phosphide catalysts on SAPO-11 were studied in the hydrodeoxygenation–isomerization of methyl palmitate (C15H31COOCH3—MP). The catalysts were synthesized using temperature-programmed reduction (TPR) of a phosphate precursor ((NH4)2HPO4 and Ni(CH3CH2COO) [...] Read more.
Ni-phosphide catalysts on SAPO-11 were studied in the hydrodeoxygenation–isomerization of methyl palmitate (C15H31COOCH3—MP). The catalysts were synthesized using temperature-programmed reduction (TPR) of a phosphate precursor ((NH4)2HPO4 and Ni(CH3CH2COO)2), TPR of a phosphite precursor (H3PO3 and Ni(OH)2), and using phosphidation of Ni/SAPO-11 by PPh3 in the liquid phase. The samples were characterized by ICP-AES chemical analysis, N2 physisorption, NH3-TPD, XRD, and TEM. First, the screening of the catalysts prepared by the TPR method was carried out in a semi-batch autoclave to determine the influence of the preparation method and conditions on one-pot HDO–isomerization (290–380 °C, 2–3 MPa). The precursor’s nature and the amount of phosphorus strongly influenced the activity of the catalysts and their surface area and acidity. Isomerization occurred only at a low P content (Ni/P = 2/1) and blocking of the SAPO-11 channels by unreduced phosphates at higher P contents did not allow us to obtain iso-alkanes. Experiments with liquid phosphidation samples in a continuous-flow reactor also showed the strong dependence of activity on phosphidation duration as well as on Ni content. The highest yield of isomerized products (66% iso-C15–16 hydrocarbons, at complete conversion of O-containing compounds, 340 °C, 2 MPa, and LHSV = 5.3 h−1) was obtained over 7% Ni2P/SAPO-11 prepared by the liquid phosphidation method. Full article
(This article belongs to the Special Issue Catalysis in Biomass Valorization for Fuel and Chemicals)
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13 pages, 3783 KiB  
Article
Exploring Deep Learning for Metalloporphyrins: Databases, Molecular Representations, and Model Architectures
by An Su, Chengwei Zhang, Yuan-Bin She and Yun-Fang Yang
Catalysts 2022, 12(11), 1485; https://doi.org/10.3390/catal12111485 - 21 Nov 2022
Cited by 3 | Viewed by 1861
Abstract
Metalloporphyrins have been studied as biomimetic catalysts for more than 120 years and have accumulated a large amount of data, which provides a solid foundation for deep learning to discover chemical trends and structure–function relationships. In this study, key components of deep learning [...] Read more.
Metalloporphyrins have been studied as biomimetic catalysts for more than 120 years and have accumulated a large amount of data, which provides a solid foundation for deep learning to discover chemical trends and structure–function relationships. In this study, key components of deep learning of metalloporphyrins, including databases, molecular representations, and model architectures, were systematically investigated. A protocol to construct canonical SMILES for metalloporphyrins was proposed, which was then used to represent the two-dimensional structures of over 10,000 metalloporphyrins in an existing computational database. Subsequently, several state-of-the-art chemical deep learning models, including graph neural network-based models and natural language processing-based models, were employed to predict the energy gaps of metalloporphyrins. Two models showed satisfactory predictive performance (R2 0.94) with canonical SMILES as the only source of structural information. In addition, an unsupervised visualization algorithm was used to interpret the molecular features learned by the deep learning models. Full article
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31 pages, 2750 KiB  
Review
Recent Progress of Hydrogenation and Hydrogenolysis Catalysts Derived from Layered Double Hydroxides
by Zhihui Wang, Wei Zhang, Cuiqing Li and Chen Zhang
Catalysts 2022, 12(11), 1484; https://doi.org/10.3390/catal12111484 - 20 Nov 2022
Cited by 6 | Viewed by 5083
Abstract
Layered double hydroxides (LDHs), also known as hydrotalcite-like compounds, are widely used in many fields due to their unique structural advantages. Based on LDHs, a wide range of metal catalysts could be synthesized with high metal dispersion, tunable acid-base properties, facile but flexible [...] Read more.
Layered double hydroxides (LDHs), also known as hydrotalcite-like compounds, are widely used in many fields due to their unique structural advantages. Based on LDHs, a wide range of metal catalysts could be synthesized with high metal dispersion, tunable acid-base properties, facile but flexible preparation methods, strong metal-support interaction, and thermal stability. Owing to these outstanding advantages, LDH-derived materials manifest great potential as catalysts, particularly in hydrogenation and hydrogenolysis reactions. More than 200 papers published in the past five years in this field clearly indicated the rapid development of these materials. In this respect, it is imperative and essential to provide a timely review to summarize the current progress and motivate greater research effort on hydrogenation and hydrogenolysis catalysts derived from LDHs. In this review, the applications of LDH-derived materials as heterogeneous catalysts in various hydrogenation and hydrogenolysis reactions were comprehensively discussed. Hydrogenation of unsaturated chemical bonds, hydrodeoxygenation of oxygenated compounds, hydrogenolysis of carbon–carbon bonds and hydrogenation of nitrites and nitriles were described. This review demonstrates the extraordinary potentials of LDH-derived catalysts in hydrogenation and hydrogenolysis reactions, and it is undoubted that LDH-derived catalysts will play an even more significant role in the foreseeable future. Full article
(This article belongs to the Section Catalytic Materials)
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10 pages, 1633 KiB  
Article
Sustainable Aromatic Production from Catalytic Fast Pyrolysis of 2-Methylfuran over Metal-Modified ZSM-5
by Shengpeng Xia, Chenyang Wang, Yu Chen, Shunshun Kang, Kun Zhao, Anqing Zheng, Zengli Zhao and Haibin Li
Catalysts 2022, 12(11), 1483; https://doi.org/10.3390/catal12111483 - 20 Nov 2022
Cited by 1 | Viewed by 1323
Abstract
The catalytic fast pyrolysis (CFP) of bio-derived furans offers a promising approach for sustainable aromatic production. ZSM-5 modified by different metal species (Zn, Mo, Fe, and Ga) was employed in the CFP of bio-derived furans for enhancing aromatic production. The effects of metal [...] Read more.
The catalytic fast pyrolysis (CFP) of bio-derived furans offers a promising approach for sustainable aromatic production. ZSM-5 modified by different metal species (Zn, Mo, Fe, and Ga) was employed in the CFP of bio-derived furans for enhancing aromatic production. The effects of metal species, metal loadings, and the weight hourly space velocity (WHSV) on the product distributions from the CFP of 2-methylfuran (MF) were systemically investigated. It is found that the introduction of Zn, Mo, Fe, and Ga on ZSM-5 significantly increases the MF conversion and aromatic yields. The maximum MF conversions of 75.49 and 69.03% are obtained, respectively, by Fe-ZSM-5 and Ga-ZSM-5, which boost the aromatic yield by 34.5 and 42.7% compared to ZSM-5. The optimal loading of Fe on ZSM-5 is 2%. Additionally, the highest aromatic yield of 40.03% is achieved by 2%Fe-ZSM-5 at a WHSV of 2 h−1. The catalyst characterization demonstrates that the synergistic effect of Brønsted and Lewis acid sites in Fe-ZSM-5 is responsible for achieving the efficient aromatization of MF. The key to designing improved zeolite catalysts for MF aromatization is the introduction of large numbers of new Lewis acid sites without a significant loss of Brønsted acid sites in ZSM-5. These findings can provide guidelines for the rational design of better zeolite catalysts used in the CFP of biomass and its derived furans. Full article
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17 pages, 4347 KiB  
Article
Heteroepitaxial Growth of GaP Photocathode by Hydride Vapor Phase Epitaxy for Water Splitting and CO2 Reduction
by Axel Strömberg, Yanqi Yuan, Feng Li, Balaji Manavaimaran, Sebastian Lourdudoss, Peng Zhang and Yanting Sun
Catalysts 2022, 12(11), 1482; https://doi.org/10.3390/catal12111482 - 20 Nov 2022
Cited by 3 | Viewed by 1577
Abstract
Heteroepitaxial Zn-doped p-GaP was grown on (001) GaAs, (001) Si and (111) Si substrates by hydride vapor phase epitaxy for solar-driven photoelectrochemical applications of hydrogen generation by water splitting and CO2 reduction. Growth of GaP on Si was realized through the implementation [...] Read more.
Heteroepitaxial Zn-doped p-GaP was grown on (001) GaAs, (001) Si and (111) Si substrates by hydride vapor phase epitaxy for solar-driven photoelectrochemical applications of hydrogen generation by water splitting and CO2 reduction. Growth of GaP on Si was realized through the implementation of a low-temperature buffer layer, and the morphology and crystalline quality were enhanced by optimizing the precursor flows and pre-heating ambient substrate. The p-GaP/GaAs and p-GaP/Si samples were processed to photoelectrodes with an amorphous TiO2 coating for CO2 reduction and a combination of TiO2 layer and mesoporous tungsten phosphide catalyst for water splitting. P-GaP/GaAs with suitable Zn-doping concentration exhibited photoelectrochemical performance comparable to homoepitaxial p-GaP/GaP for water splitting and CO2 reduction. Degradation of photocurrent in p-GaP/Si photoelectrodes is observed in PEC water splitting due to the high density of defects arising from heteroepitaxial growth. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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10 pages, 1573 KiB  
Article
Substrate-Dependent Selectivity in Sc(OTf)3-Catalyzed Cyclization of Alkenoic Acids and N-Protected Alkenamides
by Hailong Zhang, Romain Carlino, Régis Guillot, Richard Gil, Sophie Bezzenine and Jérôme Hannedouche
Catalysts 2022, 12(11), 1481; https://doi.org/10.3390/catal12111481 - 20 Nov 2022
Viewed by 2098
Abstract
Five- and six-membered ring lactones and lactams are ubiquitous frameworks in various natural and synthetic molecules and are key building blocks in organic synthesis. Catalytic addition of an O-H or N-H bond across an unactivated C–C double bond is an appealing approach to [...] Read more.
Five- and six-membered ring lactones and lactams are ubiquitous frameworks in various natural and synthetic molecules and are key building blocks in organic synthesis. Catalytic addition of an O-H or N-H bond across an unactivated C–C double bond is an appealing approach to rapidly access such highly valuable N- and O-containing skeletons in a waste-free and 100% atom efficient process. Herein, we report, for the first time, the efficient and high-yield cyclization of δ/ε-alkenoic acids and N-protected δ-alkenamides catalyzedby practical and easily accessible Lewis acid scandium(III) triflate under thermal and microwave conditions. The selectivity outcome of the reaction of δ/ε-alkenoic acids was dependent on the substitution patterns of the backbone chain and alkene moiety, leading to the exclusive formation of either the corresponding γ/δ-lactones via an O-selective cyclization or the Friedel–Crafts-type product by C-selective cyclization. An uncommon and rarely disclosed O-selective cyclization occurred preferentially or exclusively when N-protected δ-alkenamides were engaged in the reaction. The atom selectivity of the cyclization was unambiguously confirmed by single crystal X-ray crystallography. Full article
(This article belongs to the Special Issue New Frontiers in Organometallic Catalysis)
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16 pages, 24519 KiB  
Article
A Brønsted Acidic Deep Eutectic Solvent for N-Boc Deprotection
by Debora Procopio, Carlo Siciliano, Roberta De Rose, Sonia Trombino, Roberta Cassano and Maria Luisa Di Gioia
Catalysts 2022, 12(11), 1480; https://doi.org/10.3390/catal12111480 - 19 Nov 2022
Cited by 4 | Viewed by 3927
Abstract
The tert-butyloxycarbonyl (Boc) group is one of the most widely used amine-protecting groups in multistep reactions in synthetic organic chemistry as well as in peptide synthesis. Traditional methods to remove the Boc group have disadvantages in terms of high acidity, the use of [...] Read more.
The tert-butyloxycarbonyl (Boc) group is one of the most widely used amine-protecting groups in multistep reactions in synthetic organic chemistry as well as in peptide synthesis. Traditional methods to remove the Boc group have disadvantages in terms of high acidity, the use of expensive reagents, excessive amounts of catalysts and harmful solvents as well as high temperatures, making them environmentally unsustainable. Therefore, more efforts must be stepwise tightened to make Boc removal practical, clean, and minimize any potential impact. We describe an efficient and sustainable method for N-Boc deprotection by means of a choline chloride/p-toluenesulfonic acid deep eutectic solvent (DES), which is used as a reaction medium plus catalyst. The adopted conditions allow the deprotection of a wide variety of N-Boc derivatives in excellent yields. The strategy has found advantages in greening, simplicity, and short reaction times, resulting in a useful alternative to standard methods. Full article
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13 pages, 3829 KiB  
Article
Visible-Light-Driven CO2 Reduction into Methanol Utilizing Sol-Gel-Prepared CeO2-Coupled Bi2O3 Nanocomposite Heterojunctions
by Mohamed Mokhtar Mohamed Mostafa, Ahmed Shawky, Sharif Fakhruz Zaman, Katabathini Narasimharao, Mohamed Abdel Salam, Abdulmohsen Ali Alshehri, Nezar H. Khdary, Sulaiman Al-Faifi and Abhishek Dutta Chowdhury
Catalysts 2022, 12(11), 1479; https://doi.org/10.3390/catal12111479 - 19 Nov 2022
Cited by 13 | Viewed by 1966
Abstract
Carbon dioxide (CO2) photoreduction into renewable fuels over semiconductor photocatalysts has emerged as a green and sustainable alternative for energy production. Consequently, tremendous efforts are being performed to develop robust and sustainable photocatalysts. Therefore, visible-light active nanocomposite photocatalysts composed of 5.0–20.0 [...] Read more.
Carbon dioxide (CO2) photoreduction into renewable fuels over semiconductor photocatalysts has emerged as a green and sustainable alternative for energy production. Consequently, tremendous efforts are being performed to develop robust and sustainable photocatalysts. Therefore, visible-light active nanocomposite photocatalysts composed of 5.0–20.0 wt.% bismuth oxide (Bi2O3) and cerium oxide (CeO2) were synthesized by a sol-gel-based process. The prepared nanocomposites were evaluated for the promoted photocatalytic reduction of CO2 into methanol (CH3OH). Various characterizations of the obtained photocatalysts exposed an outstanding development of crystalline structure, morphology, and surface texture due to the presence of Bi2O3. Moreover, the absorbance of light in the visible regime was improved with enhanced charge separation, as revealed by the exploration of optical response, photoluminescence, and photocurrent measurements. The overall bandgap calculations revealed a reduction to 2.75 eV for 15% Bi2O3/CeO2 compared to 2.93 eV for pure CeO2. Moreover, the adjusted 2.8 g L−1 dose of 15% Bi2O3/CeO2 selectively produced 1300 μmol g−1 CH3OH after 9 h of visible light irradiation. This photocatalyst also exhibits bearable reusability five times. The improved progression of 15% Bi2O3/CeO2 is denoted by significant charge separation as well as enhanced mobility. This study suggests the application of metal oxide-based heterojunctions for renewable fuel production under visible light. Full article
(This article belongs to the Special Issue Nanoparticles in the Catalysis)
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11 pages, 5420 KiB  
Article
CdS Nanoparticles Decorated 1D CeO2 Nanorods for Enhanced Photocatalytic Desulfurization Performance
by Xiaowang Lu, Zhengwei Liu, Xiangping Zhao, Weiye Xu, Haijun Hou and Junchao Qian
Catalysts 2022, 12(11), 1478; https://doi.org/10.3390/catal12111478 - 19 Nov 2022
Cited by 3 | Viewed by 1390
Abstract
CdS nanoparticles were constructed onto one-dimensional (1D) CeO2 nanorods by a two-step hydrothermal method. The X-ray diffraction (XRD), transmission election microscopy (TEM), Raman spectra, X-ray photoelectron spectra (XPS) and UV-Vis diffuse reflection spectroscopy (DRS) techniques were used to characterize these CdS/CeO2 [...] Read more.
CdS nanoparticles were constructed onto one-dimensional (1D) CeO2 nanorods by a two-step hydrothermal method. The X-ray diffraction (XRD), transmission election microscopy (TEM), Raman spectra, X-ray photoelectron spectra (XPS) and UV-Vis diffuse reflection spectroscopy (DRS) techniques were used to characterize these CdS/CeO2 nanocomposites. It was concluded that when the molar ratio of CdS and CeO2 was 1:1, the nanocomposites exhibited the best photocatalytic desulfurization activity, reaching 92% in 3 h. Meanwhile, transient photocurrent (PT) measurement, photoluminescence (PL) spectra and electrochemical impedance spectroscopy (EIS) measurement indicated that the modification of CeO2 nanorods by CdS nanoparticles could significantly inhibit the recombination of photogenerated electrons and holes. In addition, the possible mechanism of photocatalytic oxidation desulfurization of the nanocomposites was proposed. This study may provide an effective CeO2-based photocatalyst for photocatalytic desulfurization applications. Full article
(This article belongs to the Special Issue Synthesis and Application of Composite Photocatalysts)
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15 pages, 2164 KiB  
Article
Methane-Assisted Iron Oxides Chemical Looping in a Solar Concentrator: A Real Case Study
by Luca Borghero, Maurizio Bressan, Domenico Ferrero, Massimo Santarelli and Davide Papurello
Catalysts 2022, 12(11), 1477; https://doi.org/10.3390/catal12111477 - 19 Nov 2022
Cited by 4 | Viewed by 1434
Abstract
Recent interest in hydrogen as an alternative fuel for lowering carbon emissions is funding the exploration of new ways to cleanly produce this molecule. Iron oxides can be used within a process of chemical looping. More specifically, they can lose oxygens at extremely [...] Read more.
Recent interest in hydrogen as an alternative fuel for lowering carbon emissions is funding the exploration of new ways to cleanly produce this molecule. Iron oxides can be used within a process of chemical looping. More specifically, they can lose oxygens at extremely high temperature in an inert atmosphere. An alumina receiver could not stand the extreme thermal stress, while steel (AISI 316 and Inconel Hastelloy c-276) lasted enough for the reaction to start, even if at the end of the process the receiver melted. Operating at a temperature above 1000 K helped the reaction switch from methane chemical looping combustion to chemical looping reforming, thus favouring H2 and CO yields. The gas flow outlet from the reactor reached a percentage up to 45% of H2 and 10% of CO. Carbon dioxide instead reached very low concentrations. While CO and CO2 reached a peak at the beginning of the experiment and then decreased, H2 was oscillating around a stable value. Unreacted methane was detected. The temperatures recorded in the reactor and the gas mixture obtained were used to validate a multiphysical model. The heat transfer and the chemistry of the experiment were simulated. Full article
(This article belongs to the Special Issue Advanced Catalysis for Green Fuel Synthesis and Energy Conversion)
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20 pages, 4016 KiB  
Article
A Stable and Reusable Supported Copper Catalyst for the Selective Liquid-Phase Hydrogenation of 5-Hydroxymethylfurfural to 2,5-Bis(hydroxymethyl)furan
by Juan Zelin, Camilo Ignacio Meyer, Hernán Antonio Duarte and Alberto Marchi
Catalysts 2022, 12(11), 1476; https://doi.org/10.3390/catal12111476 - 19 Nov 2022
Cited by 4 | Viewed by 1799
Abstract
Synthesis of 2,5-bis(hydroxymethyl)furan (BHMF) by selective 5-hydroxymethylfurfural (HMF) hydrogenation is ecofriendly and industrially important since HMF is obtained from renewable sources, and BHMF is a raw material used for production of biodegradable polymers. Four copper-based catalysts were prepared by incipient wetness impregnation (Cu/SiO [...] Read more.
Synthesis of 2,5-bis(hydroxymethyl)furan (BHMF) by selective 5-hydroxymethylfurfural (HMF) hydrogenation is ecofriendly and industrially important since HMF is obtained from renewable sources, and BHMF is a raw material used for production of biodegradable polymers. Four copper-based catalysts were prepared by incipient wetness impregnation (Cu/SiO2-I, Cu/Al2O3-I), precipitation–deposition (Cu/SiO2-PD) and coprecipitation (CuMgAl), and then tested in the liquid-phase hydrogenation of HMF. Metallic phases with large copper particles were obtained by incipient wetness impregnation, while precipitation methods gave highly dispersed metal copper nanoparticles. The pattern found for the concentration and strength of surface acid sites was: CuMgAl > Cu/Al2O3-I > Cu/SiO2-PD > Cu/SiO2-I. The copper-based catalysts active in HMF hydrogenation are all highly selective to BHMF, but the intrinsic activity and stability depend on metallic copper dispersion and support nature. The catalyst stability becomes poorer in the cases that the metallic phase is formed by large copper particles or interacts with high-acidity supports. Therefore, the catalyst with the highest activity, BHMF yield and stability was Cu/SiO2-PD. Furthermore, it was found that Cu/SiO2-PD is reusable in the selective liquid-phase HMF hydrogenation after being submitted to a two-step thermal treatment: (1) calcination under air flow at 673 K; (2) reduction under H2 flow at 523 K. Full article
(This article belongs to the Special Issue Catalysis in Green Chemistry and Organic Synthesis)
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18 pages, 6652 KiB  
Article
Highly Active Ag-Cu Nanocrystal Catalyst-Coated Brewer’s Spent Grain Biochar for the Mineralization of Methyl Orange and Methylene Blue Dye Mixture
by Lahcen Boubkr, Arvind K. Bhakta, Youssef Snoussi, Cora Moreira Da Silva, Laurent Michely, Mohamed Jouini, Souad Ammar and Mohamed M. Chehimi
Catalysts 2022, 12(11), 1475; https://doi.org/10.3390/catal12111475 - 18 Nov 2022
Cited by 9 | Viewed by 2586
Abstract
The aim of the present work is to valorise the brewing industry’s waste, i.e., brewer’s spent grain (BSG), into functional biocarbon for environmental catalysis applications. In this context, cost-effective and environmentally friendly biochar support coated with in-situ-generated Ag-Cu nanocrystals, was developed via the [...] Read more.
The aim of the present work is to valorise the brewing industry’s waste, i.e., brewer’s spent grain (BSG), into functional biocarbon for environmental catalysis applications. In this context, cost-effective and environmentally friendly biochar support coated with in-situ-generated Ag-Cu nanocrystals, was developed via the wet impregnation of BSG biomass powder with copper (II) nitrate trihydrate and silver nitrate aqueous solution prior to pyrolysis at moderate temperature (500 °C). Small-size homogenously distributed Ag-Cu nanocrystals (≤80 nm) on the surface of the biochar (Biochar@Ag-Cu) were observed by field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). Elemental compositions were determined by X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray analysis (EDX). The crystalline nature of the nanoparticles was confirmed by X-ray powder diffraction (XRD). Information about the thermal stability of the materials and quality were obtained by thermogravimetric analysis (TGA) and Raman, respectively. The potentiality of the Biochar@Ag-Cu catalyst in the field of pollutant removal is demonstrated by taking methyl orange and methylene blue as model dyes. A kinetics study was performed and analyzed by UV–vis spectroscopy. Its highly active catalytic nature is proved by the complete mineralization of the methyl orange dye (100%) through oxidative degradation. The reusability of the catalyst has shown 96% removal efficiency after 3 cycles. The linear plot of −Ln (CA/C0) vs. time (R2 = 0.9892) reveals that the mineralization of the methyl orange dye follows pseudo-first-order kinetics (k = 0.603 × 10−2 min−1). A methyl orange + methylene blue dye mixture degradation study has revealed the faster kinetics of the present catalyst towards methylene blue degradation. The current study suggests that BSG Biochar@Ag-Cu can be a potential candidate in contribution towards SDG 6. Full article
(This article belongs to the Special Issue Nanoparticles in the Catalysis)
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16 pages, 2625 KiB  
Article
Photocatalytic Degradation of Methyl Orange Dyes Using Green Synthesized MoS2/Co3O4 Nanohybrids
by Tsung-Mo Tien, Chao-Hsiang Chen, Chen-Tang Huang and Edward L. Chen
Catalysts 2022, 12(11), 1474; https://doi.org/10.3390/catal12111474 - 18 Nov 2022
Cited by 11 | Viewed by 2451
Abstract
In this work, a new binary MoS2/Co3O4 nanohybrids was successfully fabricated and the chemical structures, morphologies, electrochemical and optical characterizations were carried out. In addition, heterojunction nanoparticles present in S-scheme structures act as electron traps and promote light [...] Read more.
In this work, a new binary MoS2/Co3O4 nanohybrids was successfully fabricated and the chemical structures, morphologies, electrochemical and optical characterizations were carried out. In addition, heterojunction nanoparticles present in S-scheme structures act as electron traps and promote light absorption capacity for the degradation of Methyl orange (MO) with visible-light activity. MoS2/Co3O4 nanohybrids suggested excellent photocatalytic performance compared to bare MoS2 and Co3O4, where 95.6% of MO was degraded within 170 min, respectively. The results also showed excellent stability and recyclability over five consecutive cycles, without noticeable changes in the nanocomposite structure. The boosted photocatalytic degradation and redox activities of MoS2/Co3O4 can be attributed to the created S-scheme heterostructure to facilitate the separation of and to delay recombination of photoinduced charge carriers. We believe that this strategy of exploiting nanohybrid photocatalysts has great potential in the field of environmental catalysis and diverse applications. Full article
(This article belongs to the Special Issue Structured Semiconductors in Photocatalysis)
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19 pages, 3716 KiB  
Article
Heterologous Lignan Production in Stirred-Tank Reactors—Metabolomics-Assisted Bioprocess Development for an In Vivo Enzyme Cascade
by Andrea Steinmann, Maurice Finger, Christian Nowacki, Davide Decembrino, Georg Hubmann, Marco Girhard, Vlada B. Urlacher and Stephan Lütz
Catalysts 2022, 12(11), 1473; https://doi.org/10.3390/catal12111473 - 18 Nov 2022
Cited by 1 | Viewed by 1587
Abstract
Towards establishing a prospective industrial microbial lignan production process, we set up and investigated the biotransformation of coniferyl alcohol to secoisolariciresinol with recombinant Escherichia coli in a stirred-tank reactor (STR). Initially, we tested different cofactor concentrations and antifoam additions in shake flasks. Next, [...] Read more.
Towards establishing a prospective industrial microbial lignan production process, we set up and investigated the biotransformation of coniferyl alcohol to secoisolariciresinol with recombinant Escherichia coli in a stirred-tank reactor (STR). Initially, we tested different cofactor concentrations and antifoam additions in shake flasks. Next, we designed an STR batch bioprocess and tested aeration rates, pH regulation, and substrate-feeding strategies. Targeted metabolomics of phenylpropanoids and lignans assisted the bioprocess development by monitoring the lignan pathway activity. We found that the copper concentration and the substrate-feeding strategy had considerable impact on lignan production. Furthermore, time-resolved monitoring of pathway metabolites revealed two maximal intracellular lignan concentrations, the first shortly after induction of gene expression and the second after the cells entered the stationary growth phase. During STR cultivation, a maximal intracellular titer of 130.4 mg L−1 secoisolariciresinol was achieved, corresponding to a yield coefficient of 26.4 mg g−1 and a space–time yield of 2.6 mg L−1 h−1. We report for the first time the in-depth evaluation of microbially produced lignans in a well-controlled STR bioprocess. Monitoring of the lignan pathway activity showed that lignan accumulation is highly dynamic during the cultivation and points towards the need for a more efficient coniferyl alcohol dimerization system for optimal microbial production conditions. Full article
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37 pages, 11710 KiB  
Article
Kinetic Modelling of Esterification and Transesterification Processes for Biodiesel Production Utilising Waste-Based Resource
by M. A. Hazrat, Mohammad G. Rasul, Mohammad M. K. Khan, Nanjappa Ashwath, Arridina S. Silitonga, I. M. R. Fattah and T. M. Indra Mahlia
Catalysts 2022, 12(11), 1472; https://doi.org/10.3390/catal12111472 - 18 Nov 2022
Cited by 7 | Viewed by 3410
Abstract
Process optimisation and reaction kinetic model development were carried out for two-stage esterification-transesterification reactions of waste cooking oil (WCO) biodiesel. This study focused on these traditional processes due to their techno-economic feasibility, which is an important factor before deciding on a type of [...] Read more.
Process optimisation and reaction kinetic model development were carried out for two-stage esterification-transesterification reactions of waste cooking oil (WCO) biodiesel. This study focused on these traditional processes due to their techno-economic feasibility, which is an important factor before deciding on a type of feedstock for industrialisation. Four-factor and two-level face-centred central composite design (CCD) models were used to optimise the process. The kinetic parameters for the esterification and transesterification processes were determined by considering both pseudo-homogeneous irreversible and pseudo-homogeneous first-order irreversible processes. For the esterification process, the optimal conditions were found to be an 8.12:1 methanol to oil molar ratio, 1.9 wt.% of WCO for H2SO4, and 60 °C reaction temperature for a period of 90 min. The optimal process conditions for the transesterification process were a 6.1:1 methanol to esterified oil molar ratio, 1.2 wt.% of esterified oil of KOH, reaction temperature of 60 °C, and a reaction time of 110 min in a batch reactor system; the optimal yield was 99.77%. The overall process conversion efficiency was found to be 97.44%. Further research into reaction kinetics will aid in determining the precise reaction process kinetic analysis in future. Full article
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15 pages, 11405 KiB  
Article
Novel Indium Vanadium Oxide Nanosheet-Supported Nickel Iron Oxide Nanoplate Heterostructure for Synergistically Enhanced Photocatalytic Degradation of Tetracycline
by N. Sreeram, V. Aruna, Ravindranadh Koutavarapu, Dong-Yeon Lee and Jaesool Shim
Catalysts 2022, 12(11), 1471; https://doi.org/10.3390/catal12111471 - 18 Nov 2022
Cited by 6 | Viewed by 1706
Abstract
Semiconductor-based heterogeneous photocatalytic oxidation processes have received considerable attention for the remediation of toxic pollutants. Herein, InVO4/NiFe2O4 nanocomposites were synthesized using a facile hydrothermal technique. Furthermore, various characterization results revealed the successful loading of NiFe2O4 [...] Read more.
Semiconductor-based heterogeneous photocatalytic oxidation processes have received considerable attention for the remediation of toxic pollutants. Herein, InVO4/NiFe2O4 nanocomposites were synthesized using a facile hydrothermal technique. Furthermore, various characterization results revealed the successful loading of NiFe2O4 nanoplates over InVO4 nanosheets, thereby signifying the formation of a heterostructure. The performance of the synthesized photocatalyst was tested for tetracycline (TC) antibiotic removal. The optimized InVO4/NiFe2O4 nanocomposite exhibits maximum photodegradation of TC molecules (96.68%) in 96 min; this is approximately 6.47 and 4.93 times higher than that observed when using NiFe2O4 and InVO4, respectively. The strong interaction between the InVO4 nanosheets and NiFe2O4 nanoplates can improve the visible-light absorption and hinder the recombination of charge carriers, further enhancing the photocatalytic performance. Moreover, hydroxyl radicals play a crucial role in the photodegradation of TC antibiotics. Full article
(This article belongs to the Special Issue Synthesis and Photocatalytic Activity of Composite)
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12 pages, 4574 KiB  
Article
NiFe Layered Double Hydroxide Electrocatalyst Prepared via an Electrochemical Deposition Method for the Oxygen Evolution Reaction
by Murugesan Praveen Kumar, Moorthy Sasikumar, Arunachalam Arulraj, Venugopalan Rajasudha, Govindhasamy Murugadoss, Manavalan Rajesh Kumar, Shaik Gouse Peera and Ramalinga Viswanathan Mangalaraja
Catalysts 2022, 12(11), 1470; https://doi.org/10.3390/catal12111470 - 18 Nov 2022
Cited by 13 | Viewed by 3892
Abstract
Herein, we aimed to obtain NiFe layered double hydroxide (LDH) with a controlled phase and surface morphology as a highly active and stable oxygen evolution catalyst via the electrochemical deposition method, which was thermodynamically stable for the oxygen evolution reaction (OER) in an [...] Read more.
Herein, we aimed to obtain NiFe layered double hydroxide (LDH) with a controlled phase and surface morphology as a highly active and stable oxygen evolution catalyst via the electrochemical deposition method, which was thermodynamically stable for the oxygen evolution reaction (OER) in an alkaline medium. The NiFe-LDH sample was analyzed by sophisticated instruments and tested as an electrocatalyst on Toray carbon (TC). The NiFe-LDH electrocatalyst showed an excellent performance with lower overpotential of 0.27 V at 35 mA cm−2 and higher density of 125 mA cm−2 for OER in the 1 M KOH electrolyte solution. Moreover, the prepared catalyst exhibited unpredictable long-time stability for 700 h. From our knowledge, NiFe-LDH is a robust highly stable electrocatalyst compared to the recent reports. Full article
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18 pages, 3593 KiB  
Article
Application of Dithiocarbamate Chitosan Modified SBA-15 for Catalytic Reductive Removal of Vanadium(V)
by Yilin Huang, Jia Wang, Mengwei Li and Zhixiong You
Catalysts 2022, 12(11), 1469; https://doi.org/10.3390/catal12111469 - 18 Nov 2022
Cited by 5 | Viewed by 1554
Abstract
We have successfully synthesized dithiocarbamate chitosan modified SBA-15 (CS2C@SBA) composites, with promise in vanadium (V(V)) elimination. Among the three composites using different mass ratios of dithiocarbamate chitosan to SBA-15, CS2C@SBA−3, which had the highest CS2 substitution, showed the [...] Read more.
We have successfully synthesized dithiocarbamate chitosan modified SBA-15 (CS2C@SBA) composites, with promise in vanadium (V(V)) elimination. Among the three composites using different mass ratios of dithiocarbamate chitosan to SBA-15, CS2C@SBA−3, which had the highest CS2 substitution, showed the best performance on V(V) removal of which the maximum adsorption capacity could achieve 218.00 mg/g at pH 3.0. The adsorption kinetics were best fitted with a pseudo−second order reaction model, suggesting a chemisorption mechanism. Meanwhile, the Langmuir model fitted better with the adsorption isotherm, revealing a monolayer adsorption behavior. Through FTIR and XPS analysis, the functional group −SH was identified as dominating reduction sites on this composite, which reduced 73.1% of V(V) into V(IV) and V(III). The functional group −NH− was the main adsorption site for vanadium species. This reaction followed a catalytic reduction coupled adsorption mechanism reducing most of V(V) into less toxic vanadium species. Furthermore, CS2C@SBA−3 showed great selectivity towards V(V) in the presence of various co−existing ions in synthetic wastewater and real water samples. Moreover, CS2C@SBA−3 could retain a removal efficiency over 90% after five adsorption−desorption cycles. Based on the aforementioned results, we can conclude that CS2C@SBA−3 has great potential to be applied in efficient remediation of vanadium water−pollution. Full article
(This article belongs to the Special Issue Advanced Catalytic Material for Water Treatment)
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8 pages, 2647 KiB  
Article
Quinoline Derivatives with Different Functional Groups: Evaluation of Their Catecholase Activity
by Mohamed Moutaouakil, Said Tighadouini, Zainab M. Almarhoon, Maha I. Al-Zaben, Abir Ben Bacha, Vijay H. Masand, Jamal Jamaleddine and Rafik Saddik
Catalysts 2022, 12(11), 1468; https://doi.org/10.3390/catal12111468 - 18 Nov 2022
Cited by 8 | Viewed by 1891
Abstract
In this work, we are interested in finding new catalysts for catecholase, whose principle is based on the oxidation reaction of catechol to o-quinone. In this context, we have studied a series of seven quinoline-based compounds. The present work indicates that the [...] Read more.
In this work, we are interested in finding new catalysts for catecholase, whose principle is based on the oxidation reaction of catechol to o-quinone. In this context, we have studied a series of seven quinoline-based compounds. The present work indicates that the complexes formed between seven selected quinoline compounds and the copper salts viz. Cu(OAc)2, CuSO4, Cu(NO3)2, and CuCl2 elicit catalytic activities for the oxidation of catechol to o-quinone. The complexes formed with the Cu(OAc)2 salt show a much higher catalytic activity than the others, whereas the Cu(NO3)2 and CuCl2 salts formed complexes with low catalytic activity. This study also shows that the oxidation rate depends on two factors, namely the chemical structure of the ligands and the nature of the ions coordinated with the copper. Full article
(This article belongs to the Section Biocatalysis)
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16 pages, 3608 KiB  
Article
Magnetron Sputtered Al Co-Doped with Zr-Fe2O3 Photoanode with Fortuitous Al2O3 Passivation Layer to Lower the Onset Potential for Photoelectrochemical Solar Water Splitting
by Tae Sik Koh, Periyasamy Anushkkaran, Jun Beom Hwang, Sun Hee Choi, Weon-Sik Chae, Hyun Hwi Lee and Jum Suk Jang
Catalysts 2022, 12(11), 1467; https://doi.org/10.3390/catal12111467 - 18 Nov 2022
Cited by 1 | Viewed by 2067
Abstract
In this paper, we investigate the magnetron sputtering deposition of an Al-layer on Zr-doped FeOOH (Zr-FeOOH) samples to fabricate a Zr/Al co-doped Fe2O3 (Al-Zr/HT) photoanode. An Al-layer is deposited onto Zr-FeOOH through magnetron sputtering and the thickness of the Al [...] Read more.
In this paper, we investigate the magnetron sputtering deposition of an Al-layer on Zr-doped FeOOH (Zr-FeOOH) samples to fabricate a Zr/Al co-doped Fe2O3 (Al-Zr/HT) photoanode. An Al-layer is deposited onto Zr-FeOOH through magnetron sputtering and the thickness of the Al deposition is regulated by differing the sputtering time. Electrochemical impedance spectroscopy, intensity-modulated photocurrent spectroscopy, Mott-Schottky and time-resolved photoluminescence spectra analyses were used to study, in depth, the correlations between sputtered Al-layer thicknesses and PEC characteristics. High-temperature quenching (800 °C) assists in diffusing the Al3+ in the bulk of the Zr-doped Fe2O3 photoanode, whilst an unintended Al2O3 passivation layer forms on the surface. The optimized Al-Zr/HT photoelectrode achieved 0.945 mA/cm2 at 1.0 VRHE, which is 3-fold higher than that of the bare Zr/HT photoanode. The Al2O3 passivation layer causes a 100 mV cathodic shift in the onset potential. Al co-doping improved the donor density, thus reducing the electron transit time. In addition, the passivation effect of the Al2O3 layer ameliorated the surface charge transfer kinetics. The Al2O3 passivation layer suppressed the surface charge transfer resistance, consequently expediting the hole migration from photoanode to electrolyte. We believe that the thickness-controlled Al-layer sputtering approach could be applicable for various metal oxide photoanodes to lower the onset potential. Full article
(This article belongs to the Special Issue Theme Issue in Honor of Prof. Dr. Jae Sung Lee)
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9 pages, 4832 KiB  
Article
Application of a TEMPO-Polypyrrole Polymer for NOx-Mediated Oxygen Electroreduction
by Daniil A. Lukyanov, Arseniy Y. Kalnin, Lyubov G. Rubicheva, Vasiliy V. Potapenkov, Olga Y. Bakulina and Oleg V. Levin
Catalysts 2022, 12(11), 1466; https://doi.org/10.3390/catal12111466 - 18 Nov 2022
Cited by 6 | Viewed by 1626
Abstract
The oxygen reduction reaction (ORR) is one of the key processes for electrochemical energy storage, such as the cathode process in fuel cells and metal–air batteries. To date, the efficiency of the ORR half-reaction limits the overall performance of these energy storage devices. [...] Read more.
The oxygen reduction reaction (ORR) is one of the key processes for electrochemical energy storage, such as the cathode process in fuel cells and metal–air batteries. To date, the efficiency of the ORR half-reaction limits the overall performance of these energy storage devices. Traditional platinum-based materials are expensive and cannot provide the desired ORR efficiency. As an alternative, a new catalytic scheme for an ORR was proposed, which consisted of an electrode modified with a TEMPO-containing conductive polymer and a solution redox mediator system based on nitrogen oxides (NOx). NOx is perfect for oxygen reduction in solution, which, however, cannot be efficiently reduced onto a pristine electrode, while TEMPO is inactive in the ORR itself but catalyzes the electrochemical reduction of NO2 on the electrode surface. Together, these catalysts have a synergistic effect, enabling an efficient ORR in an acidic medium. In the present study, the synthesis of a novel TEMPO-containing conductive polymer and its application in the synergistic ORR system with a NOx mediator is described. The proposed mediator system may increase the performance of proton-exchange fuel cells and metal–air batteries. Full article
(This article belongs to the Special Issue Electrocatalysts for Oxidation-Reduction Reactions)
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14 pages, 3956 KiB  
Article
Effects of Ca-Compounds on the Gases Formation Behavior during Molten Salts Thermal Treatment of Bio-Waste
by Jing He, Chan Zou, Xuanzhi Zhou, Yuting Deng, Xi Li, Lu Dong and Hongyun Hu
Catalysts 2022, 12(11), 1465; https://doi.org/10.3390/catal12111465 - 18 Nov 2022
Viewed by 1428
Abstract
Bio-waste utilization is essential, and pyrolysis is a prominent way for its effective utilization. However, the gradual accumulation of ash compounds in the intermediate products probably affects the thermal conversion characteristics of bio-waste. In the present study, beech wood and disposable chopsticks were [...] Read more.
Bio-waste utilization is essential, and pyrolysis is a prominent way for its effective utilization. However, the gradual accumulation of ash compounds in the intermediate products probably affects the thermal conversion characteristics of bio-waste. In the present study, beech wood and disposable chopsticks were selected as bio-waste samples. The effects of typical ash components (Ca-compounds) on volatile formation behavior were investigated during the molten salts thermal treatment of bio-waste. Results demonstrated that about 80% mass of initial bio-waste was gasified into the volatiles at 300 °C. The introduction of Ca-compounds in the molten salts slightly decreased the total yield of gaseous products. More specifically, Ca2+ could improve the generation of CO2 and suppress the generation of other gases (CO, H2, and CH4), and this is accompanied by a reduction in the low heating value (LHV) of the gases. The possible reason is that Ca2+ might act on the -OH bonds, phenyl C-C bond, methoxy bond and carboxylic acid -COOH bonds of the bio-waste to promote CO2 release. In contrast, the introduction of CO32− and OH- tended to relieve the inhibition effect of Ca2+ on the generation of H-containing gases. Meanwhile, the introduction of Ca2+ can promote the conversion of bio-waste into liquid products as well as increase the saturation level of liquid products. Moreover, as a vital form of carbon storage, CO2 was found to be abundant in the pyrolysis gases from molten salts thermal treatment of bio-waste, and the concentration of CO2 was much higher than that of direct-combustion or co-combustion with coal. It’s a promising way for bio-waste energy conversion as well as synchronized CO2 capture by using molten salts thermal treatment, while the introduction of small amounts of Ca-compounds was found to have no significant effect on the change of CO2 concentration. Full article
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18 pages, 3684 KiB  
Article
Rapid Detection of Mercury Ions Using Sustainable Natural Gum-Based Silver Nanoparticles
by Samie Yaseen Sharaf Zeebaree, Osama Ismail Haji, Aymn Yaseen Sharaf Zeebaree, Dunya Akram Hussein and Emad Hameed Hanna
Catalysts 2022, 12(11), 1464; https://doi.org/10.3390/catal12111464 - 18 Nov 2022
Cited by 16 | Viewed by 3745
Abstract
Fabrication of metal nanostructures using natural products has attracted scientists and researchers due to its renewable and environmentally benign availability. This work has prepared an eco-friendly, low-cost, and rapid colorimetric sensor of silver nanoparticles using tree gum as a reducing and stabilizing agent. [...] Read more.
Fabrication of metal nanostructures using natural products has attracted scientists and researchers due to its renewable and environmentally benign availability. This work has prepared an eco-friendly, low-cost, and rapid colorimetric sensor of silver nanoparticles using tree gum as a reducing and stabilizing agent. Several characterization techniques have been exploited to describe the synthesized nanosensor morphology and optical properties. Ultraviolet−Visible (UV−Vis) spectroscopy has been used for monitoring the localized plasmon surface area. High-resolution transmission electron microscopy (HR-TEM) illustrated the size and shape of silver nanoparticles. X-ray diffraction spectra showed the crystallography and purity of the product. Silver nanoparticles decorated with almond gum molecules (AgNPs@AG) demonstrated high sensitivity and colorimetric detection of mercury ions in water samples. The method is based on the aggregation of AgNPs and the disappearing yellow color of AgNPs via a spectrophotometer. The detection limit of this method was reported to be 0.5 mg/L. This work aimed to synthesize a rapid, easy-preparation, eco-friendly, and efficient naked-eye colorimetric sensor to detect toxic pollutants in aqueous samples. Full article
(This article belongs to the Special Issue Recent Advances on Nano-Catalysts for Biological Processes)
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18 pages, 2920 KiB  
Article
Study of Photocatalytic Oxidation of Micropollutants in Water and Intensification Case Study
by Lucija Radetić, Jan Marčec, Ivan Brnardić, Tihana Čižmar and Ivana Grčić
Catalysts 2022, 12(11), 1463; https://doi.org/10.3390/catal12111463 - 18 Nov 2022
Cited by 2 | Viewed by 1548
Abstract
During the last decades, heterogenous photocatalysis has shown as the most promising advanced oxidation process for the removal of micropollutants due to degradation rate, sustainability, non-toxicity, and low-cost. Synergistic interaction of light irradiation, photocatalysts, and highly reactive species are used to break down [...] Read more.
During the last decades, heterogenous photocatalysis has shown as the most promising advanced oxidation process for the removal of micropollutants due to degradation rate, sustainability, non-toxicity, and low-cost. Synergistic interaction of light irradiation, photocatalysts, and highly reactive species are used to break down pollutants toward inert products. Even though titanium dioxide (TiO2) is the most researched photocatalyst, to overcome shortcomings, various modifications have been made to intensify photocatalytic activity in visible spectra range among which is modification with multiwalled carbon nanotubes (MWCNTs). Therefore, photocatalytic oxidation and its intensification by photocatalyst’s modification was studied on the example of four micropollutants (diclofenac, DF; imidacloprid, IMI; 1-H benzotriazole, BT; methylene blue, MB) degradation. Compound parabolic collector (CPC) reactor was used as, nowadays, it has been considered the state-of-the-art system due to its usage of both direct and diffuse solar radiation and quantum efficiency. A commercially available TiO2 P25 and nanocomposite of TiO2 and MWCNT were immobilized on a glass fiber mesh by sol-gel method. Full-spectra solar lamps with appropriate UVB and UVA irradiation levels were used in all experiments. Photocatalytic degradation of DF, IMI, BT, and MB by immobilized TiO2 and TiO2/CNT photocatalysts was achieved. Mathematical modelling which included mass transfer and photon absorption was applied and intrinsic reaction rate constants were estimated: kDF=3.56 × 1010s1W0.5m1.5, kIMI=8.90 × 1011s1W0.5m1.5, kBT=1.20 × 109s1W0.5m1.5, kMB=1.62 × 1010s1W0.5m1.5. Intensification of photocatalysis by TiO2/CNT was observed for DF, IMI, and MB, while that was not the case for BT. The developed model can be effectively applied for different irradiation conditions which makes it extremely versatile and adaptable when predicting the degradation extents throughout the year using sunlight as the energy source at any location. Full article
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11 pages, 2714 KiB  
Article
Metal-Organic Framework-Derived Atomically Dispersed Co-N-C Electrocatalyst for Efficient Oxygen Reduction Reaction
by Dongqi Ge, Longfei Liao, Mingyu Li and Yongli Yin
Catalysts 2022, 12(11), 1462; https://doi.org/10.3390/catal12111462 - 18 Nov 2022
Cited by 4 | Viewed by 1746
Abstract
In this work, an atomically dispersed cobalt-nitrogen-carbon (Co-N-C) catalyst is prepared for the oxygen reduction reaction (ORR) by using a metal-organic framework (MOF) as a self-sacrifice template under high-temperature pyrolysis. Spherical aberration-corrected electron microscopy is employed to confirm the atomic dispersion of high-density [...] Read more.
In this work, an atomically dispersed cobalt-nitrogen-carbon (Co-N-C) catalyst is prepared for the oxygen reduction reaction (ORR) by using a metal-organic framework (MOF) as a self-sacrifice template under high-temperature pyrolysis. Spherical aberration-corrected electron microscopy is employed to confirm the atomic dispersion of high-density Co atoms on the nitrogen-doped carbon scaffold. The X-ray photoelectron spectroscopy results verify the existence of Co-N-C active sites and their content changes with the Co content. The electrochemical results show that the electrocatalytic activity shows a volcano-shaped relationship, which increases with the Co content from 0 to 0.99 wt.% and then decreases when the presence of Co nanoparticles at 1.61 wt.%. The atomically dispersed Co-N-C catalyst with Co content of 0.99 wt.% shows an onset potential of 0.96 V vs. reversible hydrogen electrode (RHE) and a half-wave potential of 0.89 V vs. RHE toward ORR. The excellent ORR activity is attributed to the high density of the Co-N-C sites with high intrinsic activity and high specific surface area to expose more active sites. Full article
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12 pages, 4415 KiB  
Article
Removal of Tetracycline Hydrochloride from Water by Visible-Light Photocatalysis Using BiFeO3/BC Materials
by Zhengyang Fang, Honghui Jiang, Jiamin Gong, Hengrui Zhang, Xi Hu, Ke Ouyang, Yuan Guo, Xinjiang Hu, Hui Wang and Ping Wang
Catalysts 2022, 12(11), 1461; https://doi.org/10.3390/catal12111461 - 18 Nov 2022
Cited by 4 | Viewed by 1847
Abstract
It is widely considered that photocatalysis is an effective and eco-friendly method of dealing with organic pollutants dissolved in water. Nonetheless, photocatalysts still have some drawbacks, such as poor visible-light absorption, easy recombination of photogenerated charge carriers, and limited active sites. In this [...] Read more.
It is widely considered that photocatalysis is an effective and eco-friendly method of dealing with organic pollutants dissolved in water. Nonetheless, photocatalysts still have some drawbacks, such as poor visible-light absorption, easy recombination of photogenerated charge carriers, and limited active sites. In this study, bismuth ferrite coupled with biochar material (BiFeO3/BC) was simply synthesized, and its photocatalysis reactivity was systemically examined under an irradiation of λ > 400 nm. The experimental results showed that under a relatively acidic environment, the removal rate of tetracycline hydrochloride reached 95%. Using a variety of characterization investigations, we analyzed the morphology structure and chemical composition of BiFeO3/BC. In consideration of simple preparation and high respondence toward visible light, further explorations of BiFeO3/BC and its properties and optimized degradation conditions are worthwhile. Full article
(This article belongs to the Special Issue Carbon-Based Catalysts for Water and Wastewater Treatment)
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15 pages, 3246 KiB  
Article
Degradation of Safranin O in Water by UV/TiO2/IO4 Process: Effect of Operating Conditions and Mineralization
by Meriem Bendjama, Oualid Hamdaoui, Hamza Ferkous and Abdulaziz Alghyamah
Catalysts 2022, 12(11), 1460; https://doi.org/10.3390/catal12111460 - 18 Nov 2022
Cited by 9 | Viewed by 1930
Abstract
Hybrid advanced oxidation processes employed to degrade recalcitrant organic pollutants in water have been widely examined in recent years. In the present work, the potential of TiO2-mediated photocatalysis in the presence of the periodate anion (IO4) toward Safranin [...] Read more.
Hybrid advanced oxidation processes employed to degrade recalcitrant organic pollutants in water have been widely examined in recent years. In the present work, the potential of TiO2-mediated photocatalysis in the presence of the periodate anion (IO4) toward Safranin O (SO) removal from aqueous solutions was investigated. The findings revealed a high efficiency of the UV/TiO2/IO4 system due to the production of more reactive radicals (OH, IO3 and IO4) and non-radical species (O3, IO3 and IO4). Additionally, the presence of IO4 as an effective electron acceptor avoids electron-hole recombination, which induces more oxidative reactions at the hole level, increasing the degradation rate of SO. Kinetically, the involvement of IO4 anions in the UV/TiO2 system enhanced substantially the initial rate of degradation; from 0.295 to 12.07 mg L−1 min−1. The performance of both systems, i.e., UV/TiO2 and UV/TiO2/IO4, was examined under different conditions such as initial dye concentration, photocatalyst loading, periodate dosage, initial solution pH, temperature and dissolved gases. The SO degradation was found to be maximized at low concentration of pollutant at the optimum loading of catalyst (0.4 g L−1). The continuous increasing in periodate concentration over the range of 0.01–3 mM improved the system reactivity with no overdose effect. Both systems seemed to be insensitive to minor variations in temperature in the range of 15–45 °C, and showed a strong dependence on initial solution pH where the degradation rates increased proportionally with pH values up to pH 10 and decreased afterwards. A slight negative effect on the photocatalytic removal yield was noted under either aeration, nitrogen or argon atmospheres in the presence of periodate (UV/TiO2/IO4), with minor enhancement under aeration for the classical system (UV/TiO2). The mineralization of the organic substrate was also monitored. The depletion of organic matter with time was measured using total organic carbon (TOC) analysis. Despite the rapid decolorization of the dye solution in the UV/TiO2/IO4 system, a TOC removal efficiency of ~62% was obtained with both systems after 180 min of treatment. Full article
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