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Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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25 pages, 1711 KiB  
Review
Bimetallic and Trimetallic Catalysts Advancements in the Conventional and MW-Assisted Propane Dehydrogenation Process
by Olga Muccioli, Concetta Ruocco and Vincenzo Palma
Catalysts 2024, 14(12), 950; https://doi.org/10.3390/catal14120950 - 22 Dec 2024
Viewed by 1409
Abstract
A huge variety of chemical commodities are built from propylene molecules, and its conventional production technologies (naphtha steam cracking and fluid catalytic cracking) are unable to satisfy C3H6’s increasing requirements. In this scenario, Direct Propane Dehydrogenation (PDH) provides a [...] Read more.
A huge variety of chemical commodities are built from propylene molecules, and its conventional production technologies (naphtha steam cracking and fluid catalytic cracking) are unable to satisfy C3H6’s increasing requirements. In this scenario, Direct Propane Dehydrogenation (PDH) provides a practical and reliable route for supplying this short demand due to the economic availability of the raw material (C3H8) and the high propylene selectivities. The main challenges of propane dehydrogenation technology are related to the design of very active catalysts with negligible byproduct formation. In particular, the issue of catalyst deactivation by coke deposition still requires further development. In addition, PDH is a considerable endothermic reaction, and the efficiency of this technology is strictly related to heat transfer management. Thus, this current review specifically discusses the recent advances in highly dispersed bimetallic and trimetallic catalysts proposed for the PDH reaction in both conventional-heated and microwave-heated reactors. From the point of view of catalyst development, the recent research is mainly addressed to obtain nanometric and single-atom catalysts and core–shell alloys: atomically dispersed metal atoms promote the desorption of surface-bonded propylene and inhibit its further dehydrogenation. The discussion is focused on the alternative formulations proposed in the last few years, employing active species and supports different from the classical Pt-Sn/Al2O3 catalyst. Concerning the conventional route of energy-supply to the catalytic bed, the advantage of using a membrane as well as fluidized bed reactors is highlighted. Recent developments in alternative microwave-assisted dehydrogenation (PDH) employing innovative catalytic systems based on silicon carbide (SiC) facilitate selective heating of the catalyst. This advancement leads to improved catalytic activity and propylene selectivity while effectively reducing coke formation. Additionally, it promotes environmental sustainability in the ongoing electrification of chemical processes. Full article
(This article belongs to the Special Issue Current Status and Future Aspects of Bimetallic and Trimetallic Catalysts)
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31 pages, 4435 KiB  
Review
Carbon Materials Application in Heterogeneous Catalysis for Water Treatment: A Pathway to Process Intensification
by Ana Sofia G. G. Santos, Carla A. Orge, Manuel Fernando R. Pereira and Olívia Salomé G. P. Soares
Catalysts 2024, 14(12), 947; https://doi.org/10.3390/catal14120947 - 21 Dec 2024
Viewed by 1065
Abstract
Over the past few years, heterogeneous catalysis has been recognized as a versatile and efficient approach for applications in environmental remediation systems. The water treatment field is one of the most prominent beneficiaries of these various catalytic processes due to the crucial need [...] Read more.
Over the past few years, heterogeneous catalysis has been recognized as a versatile and efficient approach for applications in environmental remediation systems. The water treatment field is one of the most prominent beneficiaries of these various catalytic processes due to the crucial need to promote water reuse. However, there are still shortcomings related to the efficiency of these processes when applied to increasingly complex water matrices composed of different classes of contaminants. The present review aims to address the advantages associated with the application of catalytic processes and the diverse catalysts for water treatment while exploring how to take advantage of process integration as a solution to address the challenges posed by the growing complexity of environmental matrices. Full article
(This article belongs to the Special Issue Featured Papers in “Environmental Catalysis” Section)
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56 pages, 24168 KiB  
Review
The Synthesis, Characteristics, and Application of Hierarchical Porous Materials in Carbon Dioxide Reduction Reactions
by Ze-Long Guan, Yi-Da Wang, Zhao Wang, Ying Hong, Shu-Lin Liu, Hao-Wen Luo, Xian-Lin Liu and Bao-Lian Su
Catalysts 2024, 14(12), 936; https://doi.org/10.3390/catal14120936 - 18 Dec 2024
Cited by 1 | Viewed by 2041
Abstract
The reduction of carbon dioxide to valuable chemical products could favor the establishment of a sustainable carbon cycle, which has attracted much attention in recent years. Developing efficient catalysts plays a vital role in the carbon dioxide reduction reaction (CO2RR) process, [...] Read more.
The reduction of carbon dioxide to valuable chemical products could favor the establishment of a sustainable carbon cycle, which has attracted much attention in recent years. Developing efficient catalysts plays a vital role in the carbon dioxide reduction reaction (CO2RR) process, but with great challenges in achieving a uniform distribution of catalytic active sites and rapid mass transfer properties. Hierarchical porous materials with a porous hierarchy show great promise for application in CO2RRs owing to the high specific surface area and superior porous connection. Plenty of breakthroughs in recent CO2RR studies have been recently achieved regarding hierarchical porous materials, indicating that a summary of hierarchical porous materials for carbon dioxide reduction reactions is highly desired and significant. In this paper, we summarize the recent breakthroughs of hierarchical porous materials in CO2RRs, including classical synthesis methods, advanced characterization technologies, and novel CO2RR strategies. Moreover, by highlighting several significant works, the advantages of hierarchical porous materials for CO2RRs are analyzed and revealed. Additionally, a perspective on hierarchical porous materials for CO2RRs (e.g., challenges, potential catalysts, promising strategies, etc.) for future study is also presented. It can be anticipated that this comprehensive review will provide valuable insights for further developing efficient alternative hierarchical porous catalysts for CO2 reduction reactions. Full article
(This article belongs to the Special Issue Research Advances in Zeolites and Zeolite-Based Catalysts)
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15 pages, 4408 KiB  
Article
Cu/MOF-808 Catalyst for Transfer Hydrogenation of 5-Hydroxymethylfurfural to 2, 5-Furandimethanol with Formic Acid Mediation
by Jingxin Tan, Mengqi Li, Lingtao Liu, Lijian Wang, Haocun Wang, Junjie Bian and Chunhu Li
Catalysts 2024, 14(12), 929; https://doi.org/10.3390/catal14120929 - 17 Dec 2024
Viewed by 1031
Abstract
Biomass platform compound 5-Hydroxymethylfurfural (HMF), with its low price and abundant source, can be used as a renewable resource to replace traditional petrochemicals. MOF-808(Zr) has tunable active sites and excellent stability under high temperatures and acidic as well as basic environments, and the [...] Read more.
Biomass platform compound 5-Hydroxymethylfurfural (HMF), with its low price and abundant source, can be used as a renewable resource to replace traditional petrochemicals. MOF-808(Zr) has tunable active sites and excellent stability under high temperatures and acidic as well as basic environments, and the unsaturated coordination of metal ions within its framework structure can exhibit Lewis acidity, facilitating catalytic transfer hydrogenation from HMF to 2, 5-Furandimethanol (BHMF). The hydrothermal–impregnation–reduction method was used to prepare Cu/MOF-808 catalysts with high catalytic performance. Formic acid was chosen as the hydrogen donor solvent. The selectivity and yield of BHMF were 75.65% and 71%, respectively, at 150 °C for 4 h. A reaction pathway for the catalytic hydrogen transfer of HMF to BHMF was proposed. The high activity and stability of the Cu/MOF-808 catalyst with dual active sites provide a viable method for feasible hydrogenation of HMF to high value-added compounds. Full article
(This article belongs to the Special Issue Zeolites as Catalysts: Applications in Chemical Engineering, Energy Sources and Environmental Protection, 2nd Edition)
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31 pages, 10015 KiB  
Review
The Enantiopure 1,2-Diphenylethylenediamine (DPEDA) Motif in the Development of Organocatalysts for Asymmetric Reactions: Advances in the Last 20 Years
by Shilashi Badasa Oljira, Martina De Angelis, Andrea Sorato, Giulia Mazzoccanti, Simone Manetto, Ilaria D’Acquarica and Alessia Ciogli
Catalysts 2024, 14(12), 915; https://doi.org/10.3390/catal14120915 - 12 Dec 2024
Viewed by 4222
Abstract
1,2-Diphenylethylenediamine (DPEDA) is a privileged chiral scaffold being used in the construction of a broad variety of organocatalysts and ligands for enantioselective organic reactions. This molecule gave a significant contribution in the synthesis of structurally different bi/multifunctional organocatalysts. DPEDA played an essential role [...] Read more.
1,2-Diphenylethylenediamine (DPEDA) is a privileged chiral scaffold being used in the construction of a broad variety of organocatalysts and ligands for enantioselective organic reactions. This molecule gave a significant contribution in the synthesis of structurally different bi/multifunctional organocatalysts. DPEDA played an essential role in the development of organocatalysts capable of yielding important information on the different reaction mechanisms, like enamine, iminium, hydrogen-bonding and anion-binding catalysis. The aim of the present review is to highlight and summarize the achievements reached in the last 20 years (2004–2024) in the chemistry of DPEDA-based organocatalysts for asymmetric synthesis. Full article
(This article belongs to the Section Catalysis in Organic and Polymer Chemistry)
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15 pages, 4188 KiB  
Article
Role of the Solvent and Ultrasound Irradiation in the Preparation of TiO2 for the Photocatalytic Degradation of Sulfamethoxazole in Water
by Alessandro Di Michele, Paola Sassi, Riccardo Vivani, Alessandro Minguzzi, Laura Prati and Carlo Pirola
Catalysts 2024, 14(12), 910; https://doi.org/10.3390/catal14120910 - 11 Dec 2024
Viewed by 758
Abstract
The preparation of titania-based photocatalysts has been largely investigated in the literature. Nevertheless, the study of the influence of different solvents in the synthesis mixture requires further analysis. Addressing this issue, we explored the potential of heterogeneous photocatalysis with nano-sized titanium dioxide (TiO [...] Read more.
The preparation of titania-based photocatalysts has been largely investigated in the literature. Nevertheless, the study of the influence of different solvents in the synthesis mixture requires further analysis. Addressing this issue, we explored the potential of heterogeneous photocatalysis with nano-sized titanium dioxide (TiO2) synthesized via the sol–gel method with and without ultrasound for the degradation of sulfamethoxazole (SMX) in water. Specifically, we engineered TiO2 nanoparticles within the 20–30 nm range, in order to work in the same particle size range of Evonik P25. The synthesis was conducted in five distinct solvents, n-hexane, decane, isopropanol, ethanol, and 1-octanol, and it was evaluated with the presence and absence of ultrasound. Following synthesis, the powders were thoroughly characterized. When nonpolar solvents were used, the photocatalysts were characterized by the presence of both anatase and brookite phases, while with polar solvents, the only polymorph present was anatase. A different behavior was shown by 1-octanol, where the role of the solvent was so important that US did not affect the final sample features. The samples prepared in ethanol and isopropanol exhibited superior activity compared to those synthesized in other solvents in the SMX photodegradation (about 35% after 6 h), and the effect of US during preparation resulted positive for all solvents (an average increase of SMX photodegradation in the range of 5–10% for the different photocatalysts for each degradation time). Full article
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16 pages, 7075 KiB  
Article
Synthesis of Bimetallic Pd/Pt Truncated Nanocubes and Their Catalytic Performance in Selective Hydrogenation of Acetophenone
by Jingjing Bai, Xinkai Yang, Jianyu Chen, Bin Yue, Xueying Chen and Heyong He
Catalysts 2024, 14(12), 900; https://doi.org/10.3390/catal14120900 - 8 Dec 2024
Viewed by 783
Abstract
A series of bimetallic Pd/Pt truncated nanocube catalysts with similar morphologies and particle sizes but different platinum contents were successfully synthesized using a colloidal method without using any capping agents. Their hydrogenation properties were systematically studied and compared with their monometallic Pd or [...] Read more.
A series of bimetallic Pd/Pt truncated nanocube catalysts with similar morphologies and particle sizes but different platinum contents were successfully synthesized using a colloidal method without using any capping agents. Their hydrogenation properties were systematically studied and compared with their monometallic Pd or Pt nanocrystal counterparts. The results of EDX-mapping and line scanning show that platinum was relatively uniformly distributed on the surface of the Pd/Pt bimetallic nanocrystals and was not selectively deposited at the corners of the nanocrystals. The results of the selective hydrogenation of acetophenone demonstrate that the hydrogenation rate and the carbonyl selectivity of bimetallic Pd/Pt truncated nanocube catalysts are generally much higher than those of their monometallic Pd or Pt nanocrystal counterparts. It was found that the electronic interaction between palladium and platinum in the bimetallic Pd/Pt truncated nanocube catalysts and the corresponding hydrogenation activity in the selective hydrogenation of acetophenone are closely related to the molar ratio between platinum and palladium and the thickness of the platinum layer in the bimetallic Pd/Pt truncated nanocube catalyst. With an increase in the Pt/Pd molar ratio in the bimetallic Pd/Pt truncated nanocube catalysts, the activity and carbonyl selectivity in the acetophenone hydrogenation reaction increase first, reach a maximum when the molar ratio of Pt/Pd is 0.02 and the theoretical thickness of Pt is 1.3 atomic layers, and then decrease with a further increase in the Pt/Pd ratio. The hydrogenation rate of acetophenone on the Pd/Pt0.02 catalyst reaches 1.07 × 103 mmol·h−1·gcat.−1, which is 79 and 75 times larger than that of the monometallic Pd and Pt nanocrystal catalysts, respectively. The maximum yield of the target product 1-phenylethanol on the Pd/Pt0.02 truncated nanocube catalyst reaches 97.2%, which is 6.6% and 16.7% higher than that of the monometallic Pd and Pt nanocrystal catalysts, respectively. Full article
(This article belongs to the Special Issue Design and Synthesis of Nanostructured Catalysts, 2nd Edition)
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21 pages, 2890 KiB  
Review
Visible-Light-Activated TiO2-Based Photocatalysts for the Inactivation of Pathogenic Bacteria
by Farhana Haque, Allison Blanchard, Baileigh Laipply and Xiuli Dong
Catalysts 2024, 14(12), 855; https://doi.org/10.3390/catal14120855 - 25 Nov 2024
Viewed by 1400
Abstract
Pathogenic bacteria in the environment pose a significant threat to public health. Titanium dioxide (TiO2)-based photocatalysts have emerged as a promising solution due to their potent antimicrobial effects under visible light and their generally eco-friendly properties. This review focuses on the [...] Read more.
Pathogenic bacteria in the environment pose a significant threat to public health. Titanium dioxide (TiO2)-based photocatalysts have emerged as a promising solution due to their potent antimicrobial effects under visible light and their generally eco-friendly properties. This review focuses on the antibacterial properties of visible-light-activated, TiO2-based photocatalysts against pathogenic bacteria and explores the factors influencing their efficacy. Various TiO2 modification strategies are discussed, including doping with non-metals, creating structure defects, combining narrow-banded semiconductors, etc., to extend the light absorption spectrum from the UV to the visible light region. The factors affecting bacterial inactivation, and the underlying mechanisms are elucidated. Although certain modified TiO2 nanoparticles (NPs) show antibacterial activities in the dark, they exhibit much higher antibacterial efficacies under visible light, especially with higher light intensity. Doping TiO2 with elements such as N, S, Ce, Bi, etc., or introducing surface defects in TiO2 NPs without doping, can effectively inactivate various pathogenic bacteria, including multidrug-resistant bacteria, under visible light. These surface modifications are advantageous in their simplicity and cost-effectiveness in synthesis. Additionally, TiO2 can be coupled with narrow-banded semiconductors, resulting in narrower band gaps and enhanced photocatalytic efficiency and antibacterial activities under visible light. This information aids in understanding the current technologies for developing visible-light-driven, TiO2-based photocatalysts and their application in inactivating pathogenic bacteria in the environment. Full article
(This article belongs to the Special Issue Photocatalysis towards a Sustainable Future)
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15 pages, 1855 KiB  
Article
Mechanistic and Kinetic Analysis of Complete Methane Oxidation on a Practical PtPd/Al2O3 Catalyst
by Min Wang, Hai-Ying Chen, Yuliana Lugo-Jose, Joseph M. Fedeyko, Todd J. Toops and Jacqueline Fidler
Catalysts 2024, 14(12), 847; https://doi.org/10.3390/catal14120847 - 23 Nov 2024
Cited by 1 | Viewed by 1095
Abstract
A PtPd/Al2O3 catalyst developed for the complete oxidation of methane from the ventilation air of underground coal mines is compared against a model PdO/Al2O3 catalyst. Although the PtPd/Al2O3 catalyst is substantially more active and [...] Read more.
A PtPd/Al2O3 catalyst developed for the complete oxidation of methane from the ventilation air of underground coal mines is compared against a model PdO/Al2O3 catalyst. Although the PtPd/Al2O3 catalyst is substantially more active and stable than the model catalyst, the nature of active sites between the two catalysts is deemed to be fundamentally the same based on their response to different feed gas compositions and the evolution of surface CO adsorption complexes during time-resolved CO adsorption DRIFTS experiment. For both catalysts, coordinatively unsaturated Pd sites are considered the active centers for methane activation and the subsequent oxidation reaction. H2O competes with CH4 for the same active sites, resulting in severe inhibition. Additionally, the CH4 oxidation reaction also causes self-inhibition. Taking both inhibition effects into consideration, a relatively simple kinetic model is developed. The model provides a good fit of the 72 sets of kinetic data collected on the PtPd/Al2O3 catalyst under practically relevant reaction conditions with CH4 concentration in the range of 0.05–0.4%, H2O concentration of 1.0–5.0%, and reaction temperatures of 450–700 °C. Kinetic parameters based on the model suggest that the CH4 activation energy on the PtPd/Al2O3 catalyst is 96.7 kJ/mol, and the H2O adsorption energy is −31.0 kJ/mol. Both values are consistent with the parameters reported in the literature. The model can be used to develop catalyst sizing guidelines and be incorporated into the control algorithm of the catalytic system. 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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14 pages, 4037 KiB  
Article
Hydrogen and Oxygen Evolution on Flexible Catalysts Based on Nickel–Iron Coatings
by Dmytro Shyshkin, Loreta Tamašauskaitė-Tamašiūnaitė, Dijana Šimkūnaitė, Aldona Balčiūnaitė, Zita Sukackienė, Jūratė Vaičiūnienė, Birutė Šimkūnaitė-Stanynienė, Antanas Nacys and Eugenijus Norkus
Catalysts 2024, 14(12), 843; https://doi.org/10.3390/catal14120843 - 22 Nov 2024
Viewed by 943
Abstract
The electrolysis of water is one of low-cost green hydrogen production technologies. The main challenge regarding this technology is designing and developing low-cost and high-activity catalysts. Herein, we present a strategy to fabricate flexible electrocatalysts based on nickel–iron (NiFe) alloy coatings. NiFe coatings [...] Read more.
The electrolysis of water is one of low-cost green hydrogen production technologies. The main challenge regarding this technology is designing and developing low-cost and high-activity catalysts. Herein, we present a strategy to fabricate flexible electrocatalysts based on nickel–iron (NiFe) alloy coatings. NiFe coatings were plated on the flexible copper-coated polyimide surface (Cu/PI) using the low-cost and straightforward electroless metal-plating method, with morpholine borane as a reducing agent. It was found that Ni90Fe10, Ni80Fe20, Ni60Fe40, and Ni30Fe70 coatings were deposited on the Cu/PI surface; then, the concentration of Fe2+ in the plating solution was 0.5, 1, 5, and 10 mM, respectively. The morphology, structure, and composition of NixFey/Cu/PI catalysts have been examined using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and inductively coupled plasma–optical emission spectroscopy (ICP-OES), whereas their activity has been investigated for hydrogen evolution (HER) and oxygen evolution (OER) reactions in 1 M KOH using linear sweep voltammetry (LSVs). It was found that the Ni80Fe20/Cu/PI catalyst exhibited the lowest overpotential value of −202.7 mV for the HER, obtaining a current density of 10 mA cm−2 compared to Ni90Fe10/Cu/PI (−211.9 mV), Ni60Fe40/Cu/PI (−276.3 mV), Ni30Fe70/Cu/PI (−278.4 mV), and Ni (−303.4 mV). On the other hand, the lowest OER overpotential (344.7 mV) was observed for the Ni60Fe40/Cu/PI catalyst, obtaining a current density of 10 mA cm−2 compared to the Ni35Fe65 (369.9 mV), Ni80Fe20 (450.2 mV), and Ni90Fe10 (454.2 mV) coatings, and Ni (532.1 mV). The developed Ni60Fe40/Cu/PI catalyst exhibit a cell potential of 1.85 V at 10 mA cm−2. The obtained catalysts seem to be suitable flexible catalysts for HER and OER in alkaline media. Full article
(This article belongs to the Section Catalytic Materials)
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18 pages, 4983 KiB  
Article
Understanding the Negative Apparent Activation Energy for Cu2O and CoO Oxidation Kinetics at High Temperature near Equilibrium
by Yang Wang, Haiyang Liu, Qiwei Duan and Zhenshan Li
Catalysts 2024, 14(11), 832; https://doi.org/10.3390/catal14110832 - 19 Nov 2024
Viewed by 1135
Abstract
The pairs of Cu2O/CuO and CoO/Co3O4 as the carriers of transferring oxygen and storing heat are essential for the recently emerged high-temperature thermochemical energy storage (TCES) system. Reported research results of Cu2O and CoO oxidation kinetics [...] Read more.
The pairs of Cu2O/CuO and CoO/Co3O4 as the carriers of transferring oxygen and storing heat are essential for the recently emerged high-temperature thermochemical energy storage (TCES) system. Reported research results of Cu2O and CoO oxidation kinetics show that the reaction rate near equilibrium decreases with the temperature, which leads to the negative activation energy obtained using the Arrhenius equation and apparent kinetics models. This study develops a first-principle-based theoretical model to analyze the Cu2O and CoO oxidation kinetics. In this model, the density functional theory (DFT) is adopted to determine the reaction pathways and to obtain the energy barriers of elementary reactions; then, the DFT results are introduced into the transition state theory (TST) to calculate the reaction rate constants; finally, a rate equation is developed to describe both the surface elemental reactions and the lattice oxygen concentration in a grain. The reaction mechanism obtained from DFT and kinetic rate constants obtained from TST are directly implemented into the rate equation to predict the oxidation kinetics of Cu2O without fitting experimental data. The accuracy of the developed theory is validated by experimental data obtained from the thermogravimetric analyzer (TGA). Comparing the developed theory with the traditional apparent models, the reasons why the latter cannot appropriately predict the true oxidation characteristics are explained. The reaction rate is jointly controlled by thermodynamics (reaction driving force) and kinetics (reaction rate constant). Without considering the effect of the reaction driving force, the negative apparent activation energy of Cu2O oxidation is obtained. However, for CoO oxidation, the negative apparent activation energy is still obtained although the effect of the reaction driving force is considered. According to the DFT results, the activation energy of the overall CoO oxidation reaction is negative, but the energy barriers of the elementary reactions are positive. Moreover, according to the first-principle-based rate equation theory, the pre-exponential factor in the kinetic model is dependent on the partition function ratio and decreases with the temperature for the Cu2O and CoO oxidation near equilibrium, which results in the apparent activation energy being slightly lower than the actual value. Full article
(This article belongs to the Section Computational Catalysis)
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19 pages, 3816 KiB  
Article
Optimizing Fe-N-C Electrocatalysts for PEMFCs: Influence of Constituents and Pyrolysis on Properties and Performance
by Ilias Maniatis, Georgios Charalampopoulos, Fotios Paloukis and Maria K. Daletou
Catalysts 2024, 14(11), 780; https://doi.org/10.3390/catal14110780 - 4 Nov 2024
Cited by 4 | Viewed by 1307
Abstract
Proton exchange membrane fuel cells (PEMFCs) are promising alternative technologies with applications in stationary power systems, vehicles, and portable electronics due to their low temperature operation, fast start-up, and environmental advantages. However, the high cost of platinum-based catalysts, in particular for the oxygen [...] Read more.
Proton exchange membrane fuel cells (PEMFCs) are promising alternative technologies with applications in stationary power systems, vehicles, and portable electronics due to their low temperature operation, fast start-up, and environmental advantages. However, the high cost of platinum-based catalysts, in particular for the oxygen reduction reaction (ORR) of the cathode side, prevents their widespread incorporation. Fe-N-C electrocatalysts have emerged as viable alternatives to platinum. In this study, different precursor components were investigated for the way that they affect the pyrolysis process, which is crucial for tailoring the final catalyst properties. In particular, carbon allotropes such as carbon Vulcan, Ketjenblack, and carbon nanotubes were selected for their unique structures and properties. In addition, various sources of iron (FeCl2, FeCl3, and K[Fe(SCN)4]) were evaluated. The influence of the pyrolysis atmosphere on the resulting Fe-N-C catalyst structures was also assessed. Through an integrated structure and surface chemistry analyses, as well as electrochemical tests with rotating disk electrode experiments in acidic media, the ORR performance and stability of these catalysts were defined. By examining the relationships between carbon sources and iron precursors, this research provides valuable information for the optimization of Fe-N-C catalysts in fuel cell applications. Full article
(This article belongs to the Special Issue Advanced Catalysis for Energy and Environmental Applications)
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15 pages, 3350 KiB  
Article
Innovative Black TiO2 Photocatalyst for Effective Water Remediation Under Visible Light Illumination Using Flow Systems
by Mahzad Yaghmaei, Daliane R. C. da Silva, Nelson Rutajoga, Sara Currie, Yiran Li, Morgan Vallieres, Maria Jazmin Silvero, Neeraj Joshi, Bowen Wang and Juan C. Scaiano
Catalysts 2024, 14(11), 775; https://doi.org/10.3390/catal14110775 - 1 Nov 2024
Cited by 1 | Viewed by 4883
Abstract
Contaminated drinking water is a major health hazard in large urban areas as well as remote communities. Several pollutants detected in rivers and lakes are hormone disruptors that are harmful to consumers as well as aquatic life. In this contribution, we present a [...] Read more.
Contaminated drinking water is a major health hazard in large urban areas as well as remote communities. Several pollutants detected in rivers and lakes are hormone disruptors that are harmful to consumers as well as aquatic life. In this contribution, we present a new material, synthesized using novel green technologies, designed for solar- or LED-driven degradation of pollutants. This material is based on a glass fiber support, loaded with black TiO2, a modified form of TiO2 with strong visible light absorption and without any toxic metal or non-metal dopants. This photocatalyst is fully compatible with flow applications. The effectiveness of the catalyst is demonstrated with crocin and 17β-estradiol, the former being a natural carotenoid used as a screening tool and the latter being a common hormonal disruptor. Our work shows that under visible light illumination, our supported black TiO2 can degrade these water contaminants with greater efficiency than conventional TiO2. We envision that our findings can contribute to the production of inexpensive, large-scale solar or LED-based water decontamination systems that could be rapidly deployed to sites in need. Operation of such systems would require minimal training and could be monitored remotely. In addition to the catalyst’s non-toxicity and inflow compatibility, the material also has a long shelf life and is easy and inexpensive to produce, making it an attractive candidate for developing water treatment devices. Full article
(This article belongs to the Special Issue Remediation of Natural Waters by Photocatalysis)
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12 pages, 8618 KiB  
Article
Hydrogen and CO Over-Equilibria in Catalytic Reactions of Methane Reforming
by Vitaliy R. Trishch, Mykhailo O. Vilboi, Gregory S. Yablonsky and Dmytro O. Kovaliuk
Catalysts 2024, 14(11), 773; https://doi.org/10.3390/catal14110773 - 31 Oct 2024
Cited by 1 | Viewed by 890
Abstract
Hydrogen and carbon monoxide over-equilibria have been found computationally in kinetic dependencies of methane-reforming catalytic reactions (steam and dry reforming) using the conditions of the conservatively perturbed equilibrium (CPE) phenomenon, i.e., at the initial equilibrium concentration of hydrogen or carbon monoxide. The influence [...] Read more.
Hydrogen and carbon monoxide over-equilibria have been found computationally in kinetic dependencies of methane-reforming catalytic reactions (steam and dry reforming) using the conditions of the conservatively perturbed equilibrium (CPE) phenomenon, i.e., at the initial equilibrium concentration of hydrogen or carbon monoxide. The influence of the pressure, temperature, flow rate and composition of the initial mixture on the position of the CPE point (the extremum point) was investigated over a wide domain of parameters. The CPE phenomenon significantly increases the product concentration (H2 and CO) at the reactor length, which is significantly less than the reactor length required to reach equilibrium. The CPE point is interpreted as the “turning point” in kinetic behaviour. Recommendations on temperature and pressure regimes are different from the traditional ones related to Le Chatelier’s law. The obtained results provide valuable information on optimal reaction conditions for complex reversible chemical transformations, offering potential applications in chemical engineering processes. Full article
(This article belongs to the Special Issue Catalytic Reforming and Hydrogen Production: From the Past to the Future)
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35 pages, 4527 KiB  
Review
Biocatalysis with Unconventional Yeasts
by Cecilia Andreu and Marcel·lí del Olmo
Catalysts 2024, 14(11), 767; https://doi.org/10.3390/catal14110767 - 30 Oct 2024
Cited by 1 | Viewed by 1274
Abstract
Biocatalysis is a green and sustainable technology based on the use of natural substances to catalyze chemical reactions. Humans have been unconsciously using biocatalysis for thousands of years to produce food and alcoholic beverages, but it is only since the 19th century that [...] Read more.
Biocatalysis is a green and sustainable technology based on the use of natural substances to catalyze chemical reactions. Humans have been unconsciously using biocatalysis for thousands of years to produce food and alcoholic beverages, but it is only since the 19th century that we have begun to understand its fundamentals and its enormous potential. In fact, advances in our knowledge of enzymes and metabolic pathways and, in recent decades, the introduction of tools such as bioinformatics, DNA sequencing and protein engineering have made biocatalysis a key strategy in fine chemistry and for the production of active pharmaceutical ingredients. In addition, the discovery of new microorganisms adapted to adverse conditions has also been crucial in advancing this avenue. The present review focuses on the use of unconventional yeasts and their enzymes in the most interesting reactions where biocatalysis is applied. It highlights the advantages of using these microorganisms in industrial chemical processes due to their particular phenotypes, such as their ability to withstand high temperatures and pressures, as well as acidic or alkaline environments, high substrate loads, presence of organic solvents, etc. All this results in a wider range of possible substrates and higher efficiency. Examples of the most important reactions in which their use has been described are included, considering both catalysis by wild-type whole cells or their isolated enzymes and their genetically modified variants. All this information will help to understand the current relevance of unconventional yeasts and their enzymes in biocatalysis. Full article
(This article belongs to the Special Issue Feature Review Papers in Biocatalysis and Enzyme Engineering)
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29 pages, 11136 KiB  
Article
Oxidative Steam Reforming of Methanol over Cu-Based Catalysts
by Matteo Tommasi, Davide Ceriotti, Alice Gramegna, Simge Naz Degerli, Gianguido Ramis and Ilenia Rossetti
Catalysts 2024, 14(11), 759; https://doi.org/10.3390/catal14110759 - 28 Oct 2024
Viewed by 1374
Abstract
Several Cu and Ni-based catalysts were synthetized over Ce-based supports, either pure or mixed with different amounts of alumina (1:2 and 1:3 mol/mol). Different metal loadings (10–40 wt%) and preparation methods (wet impregnation, co-precipitation, and flame-spray pyrolysis—FSP) were compared for the oxidative steam [...] Read more.
Several Cu and Ni-based catalysts were synthetized over Ce-based supports, either pure or mixed with different amounts of alumina (1:2 and 1:3 mol/mol). Different metal loadings (10–40 wt%) and preparation methods (wet impregnation, co-precipitation, and flame-spray pyrolysis—FSP) were compared for the oxidative steam reforming of methanol. Characterization of the catalysts has been performed, e.g., through XRD, BET, XPS, TPR, SEM, and EDX analyses. All the catalysts have been tested in a bench-scale continuous setup. The hydrogen yield and methanol conversion obtained have been correlated with the operating conditions, metal content, crystallinity of the catalyst particles, total surface area, and with the interaction of the metal with the support. A Cu loading of 20% wt/wt was optimal, while the presence of alumina was not beneficial, decreasing catalyst activity at low temperatures compared with catalysts supported on pure CeO2. Ni-based catalysts were a possible alternative, but the activity towards the methanation reaction at relatively high temperatures decreased inevitably the hydrogen yield. Durability and deactivation tests showed that the best-performing catalyst, 20% wt. Cu/CeO2 prepared through coprecipitation was stable for a long period of time. Full methanol conversion was achieved at 280 °C, and the highest yield of H2 was ca. 80% at 340 °C, higher than the literature data. Full article
(This article belongs to the Section Catalytic Reaction Engineering)
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13 pages, 14099 KiB  
Article
One-Step Scalable Synthesis of 3D Self-Supported Superaerophobic Ce-Coupled Ni3S2/NiS@NF Nanobud Catalyst for Efficient Oxygen Evolution Reaction
by Mengjie Lu, Run Cheng, Li Wang, Dandan Liang, Meng Qin, Bili Wang, Rui Song and Duo Chen
Catalysts 2024, 14(11), 752; https://doi.org/10.3390/catal14110752 - 26 Oct 2024
Viewed by 1056
Abstract
The elaborate design of inexpensive, high-performance electrocatalysts from earth-abundant elements toward oxygen evolution reaction (OER) is critical in various (electro)chemical processes. Herein, a novel binder-free catalyst of Ce-coupled Ni3S2/NiS supported on Ni foam (Ce-Ni3S2/NiS@NF) is [...] Read more.
The elaborate design of inexpensive, high-performance electrocatalysts from earth-abundant elements toward oxygen evolution reaction (OER) is critical in various (electro)chemical processes. Herein, a novel binder-free catalyst of Ce-coupled Ni3S2/NiS supported on Ni foam (Ce-Ni3S2/NiS@NF) is successfully synthesized via a facile one-step hydrothermal method that enables practical feasibility with a significant enhancement of OER activity through anchoring Ce dopants on an Ni3S2/NiS nanobud host. Ce species coupling can modulate electronic structure, which reduces the reaction energy barrier and optimizes OER catalytic activity. More profoundly, the superhydrophilic and superaerophobic properties of the Ce-Ni3S2/NiS@NF electrode further promote mass transfer. As a result, the Ce-Ni3S2/NiS@NF electrode exhibits excellent OER activity with a low overpotential of 236 and 350 mV to achieve current densities of 10 and 100 mA cm−2, respectively, and long-term durability for 24 h in alkaline medium. These results could supply valuable guidelines for the design of other OER catalysts and beyond. Full article
(This article belongs to the Special Issue Recent Advances in Electrocatalysis and Future Perspective)
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12 pages, 2999 KiB  
Article
Ordered Mesoporous Nitrogen Dope Carbon Synthesized from Aniline for Stabilization of Ruthenium Species in CO2 Hydrogenation to Formate
by Arsalan Haider, Ahmad Masudi, Sunghee Ahn, Kwangho Park, Kyung Rok Lee and Kwang-Deog Jung
Catalysts 2024, 14(10), 720; https://doi.org/10.3390/catal14100720 - 15 Oct 2024
Viewed by 1456
Abstract
The hydrogenation of CO2 to produce formic acid has garnered increasing interest as a means to address climate change and promote the hydrogen economy. This research investigates the nanocasting technique for the synthesis of ordered mesoporous nitrogen-doped carbon (MNC-An). KIT-6 functioned as [...] Read more.
The hydrogenation of CO2 to produce formic acid has garnered increasing interest as a means to address climate change and promote the hydrogen economy. This research investigates the nanocasting technique for the synthesis of ordered mesoporous nitrogen-doped carbon (MNC-An). KIT-6 functioned as the silica template, while aniline served as the nitrogen–carbon precursor. The resultant MNC-An exhibits cubic Ia3D geometry, possesses significant mesoporosity, and has a high nitrogen content, which is essential for stabilizing ruthenium single atoms. The catalyst exhibited a specific activity of 252 mmolFAgcat−1 following a 2 h reaction at 120 °C. Moreover, the catalyst exhibited exceptional relative activity during five recycling experiments while preserving its catalytic efficacy. The atomically dispersed ruthenium and its Ru3+ oxidation state demonstrated perseverance both before and after the treatment. The results indicated that the synthesized catalyst possesses potential for the expedited commercialization of CO2 hydrogenation to produce formic acid. The elevated carbon yield, along with excellent thermal stability, renders it a viable substrate for attaching and stabilizing atomically dispersed ruthenium catalysts. Full article
(This article belongs to the Special Issue Catalysis and Catalytic Processes for Valuable Chemical Production from CO2)
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11 pages, 1431 KiB  
Article
Efficient Catalytic Conversion of Acetate to Citric Acid and Itaconic Acid by Engineered Yarrowia lipolytica
by Yuchen Ning, Renwei Zhang, Huan Liu, Yue Yu, Li Deng and Fang Wang
Catalysts 2024, 14(10), 710; https://doi.org/10.3390/catal14100710 - 10 Oct 2024
Viewed by 1466
Abstract
The bioconversion of agricultural and industrial wastes is considered a green and sustainable alternative method for producing high-value biochemicals. As a major catalytic product of greenhouse gases and a by-product in the fermentation and lignocellulose processing industries, acetate is a promising bioconversion raw [...] Read more.
The bioconversion of agricultural and industrial wastes is considered a green and sustainable alternative method for producing high-value biochemicals. As a major catalytic product of greenhouse gases and a by-product in the fermentation and lignocellulose processing industries, acetate is a promising bioconversion raw material. In this work, endogenous and heterologous enzymes were manipulated in Yarrowia lipolytica to achieve the conversion of acetate to high-value citric acid and itaconic acid, respectively. After the combinational expression of the key enzymes in the acetate metabolic pathway, the citric acid synthesis pathway, and the mitochondrial transport system, acetate could be efficiently converted to citric acid. Coupled with the down-regulation of fatty acid synthase expression in the competitive pathway, more acetyl-CoA flowed into the synthesis of citric acid, and the titer reached 15.11 g/L with a productivity of 0.51 g/g acetate by the engineered Y. lipolytica, which is comparable to the results using glucose as the substrate. On this basis, the heterologous cis-aconitate decarboxylase from Aspergillus terreus was introduced into the engineered Y. lipolytica to achieve the catalytic synthesis of itaconic acid from acetate. Combined with investigating the effects of multiple enzymes in the synthesis pathway, the titer of itaconic acid reached 1.87 g/L with a yield of 0.43 g/g DCW by the final engineered strain, which is the highest reported titer of itaconic acid derived from acetate by engineered microbes in shake flasks. It is demonstrated that acetate has the potential to replace traditional starch-based raw materials for the synthesis of high-value organic acids and our work lays a foundation for the rational utilization of industrial wastes and the catalytic products of greenhouse gases. Full article
(This article belongs to the Special Issue Recent Advances in Biocatalysis and Enzyme Engineering)
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12 pages, 2675 KiB  
Article
Vertically Ti3CN@NiFe LDH Nanoflakes as Self-Standing Catalysts for Enhanced Oxygen Evolution Reaction
by Lei He, Qing Tang, Qi Fan, Haizheng Zhuang, Shengchao Wang, Yifan Pang and Kun Liang
Catalysts 2024, 14(10), 708; https://doi.org/10.3390/catal14100708 - 10 Oct 2024
Viewed by 1620
Abstract
Hydrogen production from water electrolysis is gaining interest as a source of renewable energy storage due to its high efficiency and low environmental impact. However, the slow kinetics of the oxygen evolution reaction (OER) limits the overall efficiency of electrolyzer systems. This study [...] Read more.
Hydrogen production from water electrolysis is gaining interest as a source of renewable energy storage due to its high efficiency and low environmental impact. However, the slow kinetics of the oxygen evolution reaction (OER) limits the overall efficiency of electrolyzer systems. This study presents the synthesis and characterization of a novel electrocatalyst with a vertical structure, composed of Ti3CN MXene-modified NiFe-layered double hydroxides (LDHs) supported on nickel foam (NF) for efficient OER applications. The 1.0-LDH/3MXNF catalyst exhibits excellent electrocatalytic activity, achieving a low overpotential of 247 mV at a current density of 100 mA cm−2 and a favorable Tafel slope of 67.7 mV/dec. This can be attributed to the transfer of excess electrons from Ti3CN MXene to NiFe-LDH, which reduces the oxidation states of Ni and Fe, resulting in a strong interfacial coupling between Ti3CN MXene and NiFe-LDHs. Additionally, the electrode exhibited exceptional stability, maintaining constant performance with minimal potential degradation over prolonged operation. These findings underscore the potential of hybrid LDH-MXene systems as advanced electrocatalysts for renewable energy applications, paving the way for further innovations in energy conversion technologies. Full article
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13 pages, 3773 KiB  
Article
Self-Assembled PDI-COOH/PDINH Supramolecular Composite Photocatalysts for Highly Efficient Photodegradation of Organic Pollutants
by Guodong Zhou, Zetian He, Zeyu Jia, Shiqing Ma, Daimei Chen and Yilei Li
Catalysts 2024, 14(10), 696; https://doi.org/10.3390/catal14100696 - 7 Oct 2024
Viewed by 1220
Abstract
Photocatalytic degradation of organic pollutants is one of the green ways to solve environmental problems. In this study, the PDI-COOH/PDINH composite photocatalysts were successfully synthesized by electrostatic self-assembly. Under visible light irradiation, the degradation efficiency of the optimal PDI-COOH/PDINH sample reached 67%, which [...] Read more.
Photocatalytic degradation of organic pollutants is one of the green ways to solve environmental problems. In this study, the PDI-COOH/PDINH composite photocatalysts were successfully synthesized by electrostatic self-assembly. Under visible light irradiation, the degradation efficiency of the optimal PDI-COOH/PDINH sample reached 67%, which was 1.7 and 1.6 times higher than that of the self-assembled PDINH supramolecule and PDI-COOH supramolecule, respectively. The excellent photocatalytic performance of PDI-COOH/PDINH can be attributed to the enhancement of the separation and transport efficiency of photogenerated carriers by the construction of a heterojunction and the expanded electronic conjugated structure by the combination of organic–organic semiconductors. This study offers a new idea for the preparation of organic–organic composite photocatalysts. Full article
(This article belongs to the Special Issue Exclusive Papers in Green Photocatalysis from China)
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16 pages, 3640 KiB  
Article
Cobalt Molybdenum Telluride as an Efficient Trifunctional Electrocatalyst for Seawater Splitting
by Rajarshi Kar, Amideddin Nouralishahi, Harish Singh and Manashi Nath
Catalysts 2024, 14(10), 684; https://doi.org/10.3390/catal14100684 - 2 Oct 2024
Cited by 1 | Viewed by 1349
Abstract
A mixed-metal ternary chalcogenide, cobalt molybdenum telluride (CMT), has been identified as an efficient tri-functional electrocatalyst for seawater splitting, leading to enhanced oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR). The CMT was synthesized by a single step [...] Read more.
A mixed-metal ternary chalcogenide, cobalt molybdenum telluride (CMT), has been identified as an efficient tri-functional electrocatalyst for seawater splitting, leading to enhanced oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR). The CMT was synthesized by a single step hydrothermal technique. Detailed electrochemical studies of the CMT-modified electrodes showed that CMT has a promising performance for OER in the simulated seawater solutions, exhibiting a small overpotential of 385 mV at 20 mA cm−2, and superior catalyst durability for prolonged period of continuous oxygen evolution. Interestingly, while gas chromatography analysis confirmed the evolution of oxygen in an anodic chamber, it showed that there was no chlorine evolution from these electrodes in alkaline seawater, highlighting the novelty of this catalyst. CMT also displayed remarkable ORR activity in simulated seawater as indicated by its four-electron reduction pathway forming water as the dominant product. One of the primary challenges of seawater splitting is chlorine evolution from the oxidation of dissolved chloride salts. The CMT catalyst successfully and significantly lowers the water oxidation potential, thereby separating the chloride and water oxidation potentials by a larger margin. These results suggest that CMT can function as a highly active tri-functional electrocatalyst with significant stability, making it suitable for clean energy generation and environmental applications using seawater. Full article
(This article belongs to the Special Issue Electrocatalytic Water Oxidation, 2nd Edition)
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14 pages, 2887 KiB  
Article
Renewable Diesel Production over Mo-Ni Catalysts Supported on Silica
by John Zafeiropoulos, George Petropoulos, Eleana Kordouli, Labrini Sygellou, Alexis Lycourghiotis and Kyriakos Bourikas
Catalysts 2024, 14(10), 662; https://doi.org/10.3390/catal14100662 - 24 Sep 2024
Viewed by 1450
Abstract
Nickel catalysts promoted with Mo and supported on silica were studied for renewable diesel production from triglyceride biomass, through the selective deoxygenation process. The catalysts were prepared by wet co-impregnation of the SiO2 with different Ni/(Ni + Mo) atomic ratios (0/0.84/0.91/0.95/0.98/1) and [...] Read more.
Nickel catalysts promoted with Mo and supported on silica were studied for renewable diesel production from triglyceride biomass, through the selective deoxygenation process. The catalysts were prepared by wet co-impregnation of the SiO2 with different Ni/(Ni + Mo) atomic ratios (0/0.84/0.91/0.95/0.98/1) and a total metal content equal to 50%. They were characterized by XRD, XPS, N2 physisorption, H2-TPR, and NH3-TPD. Evaluation of the catalysts for the transformation of sunflower oil to renewable (green) diesel took place in a high-pressure semi-batch reactor, under solvent-free conditions. A very small addition of Mo, namely the synergistic Ni/(Ni + Mo) atomic ratio equal to 0.95, proved to be the optimum one for a significant enhancement of the catalytic performance of the metallic Ni/SiO2 catalyst, achieving 98 wt.% renewable diesel production. This promoting action of Mo has been attributed to the significant increase of the metallic Ni active phase surface area, the suitable regulation of surface acidity, the acceleration of the hydro-deoxygenation pathway (HDO), the creation of surface oxygen vacancies, and the diminution of coke formation provoked by Mo addition. Full article
(This article belongs to the Special Issue Catalytic Conversion of Biomass to Chemicals)
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16 pages, 4499 KiB  
Article
Modular Photocatalytic Reactor for the Removal of Estrogens from Aqueous Solutions
by Liliana Bobirică, Cristina Orbeci, Cristian Pîrvu, Alexandra Constantinescu, Elena Iuliana Bîru, Giovanina Iuliana Ionică, Ecaterina Matei, Andrei Constantin Berbecaru and Constantin Bobirică
Catalysts 2024, 14(10), 661; https://doi.org/10.3390/catal14100661 - 24 Sep 2024
Viewed by 1112
Abstract
Estrogens, widely used for therapeutic or contraceptive purposes, act as endocrine disruptors in aquatic systems and have adverse effects on a wide range of living organisms. Wastewater insufficiently treated by conventional methods is the main way for estrogens to enter aquatic systems. Therefore, [...] Read more.
Estrogens, widely used for therapeutic or contraceptive purposes, act as endocrine disruptors in aquatic systems and have adverse effects on a wide range of living organisms. Wastewater insufficiently treated by conventional methods is the main way for estrogens to enter aquatic systems. Therefore, the purpose of this paper is to develop a novel photocatalytic system for the removal of the estrogenic mixture estradiol valerate/norgestrel from wastewater. The photocatalytic modules are operated in a plug flow reactor system under a UV-A radiation field, and the photocatalyst (TiO2, ZnO or TiO2/ZnO) is immobilized on an inert support of glass balls that are strung on stainless-steel wire and arranged in rows along the photocatalytic modules. The photocatalysts were synthesized by the sol–gel method and then deposited on the inert glass support by the hot method, after which it was calcined for two hours at a temperature of 500 °C. The experimental results showed that the efficiency of photocatalytic degradation largely depends on the dose of photocatalyst. The dose of photocatalyst can be adjusted by adding or removing photocatalytic modules, each of which have an approximately equal amount of photocatalyst. The best result was obtained for the TiO2/ZnO photocatalyst, the organic substrate being practically mineralized in 120 min, for which only two photocatalytic modules are needed. Full article
(This article belongs to the Special Issue Photocatalytic Nanomaterials for Environmental Purification)
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14 pages, 1493 KiB  
Article
The [PdCl2(Xantphos)] Complex Efficiently Catalyzed the Methoxycarbonylation of Iodobenzene to Methyl Benzoate
by Luca Pietrobon, Lucio Ronchin and Andrea Vavasori
Catalysts 2024, 14(10), 660; https://doi.org/10.3390/catal14100660 - 24 Sep 2024
Viewed by 1053
Abstract
The [PdCl2(Xantphos)] complex, in comparison with several [PdCl2(P–P)] complexes having different diphosphine chelating ligands (P–P), is very active as a catalyst for the carbonylation of iodobenzene to methyl benzoate. The run conditions and the influence of several cocatalysts have [...] Read more.
The [PdCl2(Xantphos)] complex, in comparison with several [PdCl2(P–P)] complexes having different diphosphine chelating ligands (P–P), is very active as a catalyst for the carbonylation of iodobenzene to methyl benzoate. The run conditions and the influence of several cocatalysts have been also studied to further improve the catalytic activity. The optimization of the catalytic system allowed to obtain TOFs of ca. 260,000 h−1. The addition of some additives able to reduce the possible catalyst deactivation allowed to increase the TOF of ca. 15%. The best positive results were obtained by adding reducing agents such as ferrocene, which leads to a TOF higher than 300,000 h−1. Full article
(This article belongs to the Special Issue Recent Applications of Metal Catalysts in Organic Synthesis, 2nd Edition)
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15 pages, 8013 KiB  
Article
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 - 21 Sep 2024
Viewed by 1023
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, 2130 KiB  
Article
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
Cited by 2 | Viewed by 1507
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 (DTinitial = 29 °C) and stable over the 5-day run (DTfinal = 22 °C), whereas the attenuated activity of c-cat (DTinitial = 16 °C) decayed steadily over 3 days until it was barely active (DTfinal < 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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31 pages, 3833 KiB  
Article
Transition Metal-Promoted LDH-Derived CoCeMgAlO Mixed Oxides as Active Catalysts for Methane Total Oxidation
by Marius C. Stoian, Cosmin Romanitan, Katja Neubauer, Hanan Atia, Constantin Cătălin Negrilă, Ionel Popescu and Ioan-Cezar Marcu
Catalysts 2024, 14(9), 625; https://doi.org/10.3390/catal14090625 - 17 Sep 2024
Cited by 1 | Viewed by 1274
Abstract
A series of M(x)CoCeMgAlO mixed oxides with different transition metals (M = Cu, Fe, Mn, and Ni) with an M content x = 3 at. %, and another series of Fe(x)CoCeMgAlO mixed oxides with Fe contents x ranging from 1 to 9 at. [...] Read more.
A series of M(x)CoCeMgAlO mixed oxides with different transition metals (M = Cu, Fe, Mn, and Ni) with an M content x = 3 at. %, and another series of Fe(x)CoCeMgAlO mixed oxides with Fe contents x ranging from 1 to 9 at. % with respect to cations, while keeping constant in both cases 40 at. % Co, 10 at. % Ce and Mg/Al atomic ratio of 3 were prepared via thermal decomposition at 750 °C in air of their corresponding layered double hydroxide (LDH) precursors obtained by coprecipitation. They were tested in a fixed bed reactor for complete methane oxidation with a gas feed of 1 vol.% methane in air to evaluate their catalytic performance. The physico-structural properties of the mixed oxide samples were investigated with several techniques, such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX), elemental mappings, inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction under hydrogen (H2-TPR) and nitrogen adsorption–desorption at −196 °C. XRD analysis revealed in all the samples the presence of Co3O4 crystallites together with periclase-like and CeO2 phases, with no separate M-based oxide phase. All the cations were distributed homogeneously, as suggested by EDX measurements and elemental mappings of the samples. The metal contents, determined by EDX and ICP-OES, were in accordance with the theoretical values set for the catalysts’ preparation. The redox properties studied by H2-TPR, along with the surface composition determined by XPS, provided information to elucidate the catalytic combustion properties of the studied mixed oxide materials. The methane combustion tests showed that all the M-promoted CoCeMgAlO mixed oxides were more active than the M-free counterpart, the highest promoting effect being observed for Fe as the doping transition metal. The Fe(x)CoCeMgAlO mixed oxide sample, with x = 3 at. % Fe displayed the highest catalytic activity for methane combustion with a temperature corresponding to 50% methane conversion, T50, of 489 °C, which is ca. 40 °C lower than that of the unpromoted catalyst. This was attributed to its superior redox properties and lowest activation energy among the studied catalysts, likely due to a Fe–Co–Ce synergistic interaction. In addition, long-term tests of Fe(3)CoCeMgAlO mixed oxide were performed, showing good stability over 60 h on-stream. On the other hand, the addition of water vapors in the feed led to textural and structural changes in the Fe(3)CoCeMgAlO system, affecting its catalytic performance in methane complete oxidation. At the same time, the catalyst showed relatively good recovery of its catalytic activity as soon as the water vapors were removed from the feed. Full article
(This article belongs to the Collection Nanocatalysis Towards Energy Transition and Environmental Sustainability)
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12 pages, 5519 KiB  
Article
Biomass-Derived Co/MPC Nanocomposites for Effective Sensing of Hydrogen Peroxide via Electrocatalysis Reduction
by Mei Wang, Jin Cai, Lihua Jiao and Quan Bu
Catalysts 2024, 14(9), 624; https://doi.org/10.3390/catal14090624 - 16 Sep 2024
Viewed by 1167
Abstract
Utilizing the full potential of reproducible biomass resources is crucial for the sustainable development of humanity. In this study, biochar (MPC) was prepared through the microwave-assisted pyrolysis of sugarcane bagasse. Subsequently, Co nanoparticles were introduced by microwave-assisted hydrothermal treatment to form a highly [...] Read more.
Utilizing the full potential of reproducible biomass resources is crucial for the sustainable development of humanity. In this study, biochar (MPC) was prepared through the microwave-assisted pyrolysis of sugarcane bagasse. Subsequently, Co nanoparticles were introduced by microwave-assisted hydrothermal treatment to form a highly dispersive Co/MPC material. Characterization results indicated that Co nanoparticles were wrapped by thin carbon layers and uniformly dispersed on a carbon-based skeleton via a microwave-assisted hydrothermal synthesis approach, providing high-activity space. Thus, the prepared material was limited to glassy carbon; on the electrode surface, a cobalt-based sensing platform (Co/MPC/GCE) was built. On the basis of this constructed sensing platform, a linear equation was fitted by the concentration change of current signal I and H2O2. The linear range was 0.55–100.05 mM; the detection limit was 1.38 μM (S/N = 3); and the sensitivity was 103.45 μA cm−2 mM−1. In addition, the effect this sensor had on H2O2 detection of actual water samples was conducted by using a standard addition recovery method; results disclosed that the recovery rate and RSD of H2O2 in tap water samples were 94.0–97.6% and 4.1–6.5%, respectively. Full article
(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)
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18 pages, 4620 KiB  
Article
Fractal Behavior of Nanostructured Pt/TiO2 Catalysts: Synthesis, Characterization and Evaluation of Photocatalytic Hydrogen Generation
by Anca Vasile, Gianina Dobrescu, Veronica Bratan, Mircea Teodorescu, Cornel Munteanu, Irina Atkinson, Catalin Negrila, Florica Papa and Ioan Balint
Catalysts 2024, 14(9), 619; https://doi.org/10.3390/catal14090619 - 13 Sep 2024
Viewed by 1388
Abstract
The fractal characterization of supported nanoparticles is a useful tool for obtaining structural and morphological information that strongly impacts catalytic properties. We have synthesized and characterized Pt supported on TiO2 nanostructures. Triblock copolymers with thermosensitive properties were used as templating agents during [...] Read more.
The fractal characterization of supported nanoparticles is a useful tool for obtaining structural and morphological information that strongly impacts catalytic properties. We have synthesized and characterized Pt supported on TiO2 nanostructures. Triblock copolymers with thermosensitive properties were used as templating agents during the synthesis process. In addition to the several techniques used for the characterization of the materials, we carried out fractal analysis. The prepared materials showed a reduction in the band gap of TiO2 from 3.44 to 3.01 eV. The extended absorption in the 500–700 nm regions is mostly attributed to the presence of supported Pt nanoparticles. The ability of the nanostructured Pt/TiO2 catalysts to generate H2 in an aqueous solution was evaluated. The test reaction was carried out in the presence of methanol, as a hole scavenger, under simulated solar light. Pt/TiO2-3TB shows the highest rate of H2 (4.17 mmol h−1 gcat−1) when compared to Pt/TiO2-0TB (3.65 mmol h−1 gcat−1) and Pt/TiO2-6TB (2.29 mmol h−1 gcat−1) during simulated solar light irradiation. Pt/TiO2-3TB exhibits a more structured organization (fractal dimensions of 1.65–1.74 nm at short scales, 1.27–1.30 nm at long scales) and a distinct fractal behavior. The generation of hydrogen via photocatalysis can be linked to the fractal characteristics. Full article
(This article belongs to the Special Issue Effect of the Modification of Catalysts on the Catalytic Performance, 2nd Edition)
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11 pages, 1981 KiB  
Article
Continuous Flow Synthesis of Furfuryl Ethers over Pd/C Catalysts via Reductive Etherification of Furfural in Ethanol
by Ayoub Hassine, Anas Iben Ayad, Aïssa Ould Dris, Denis Luart and Erwann Guénin
Catalysts 2024, 14(9), 617; https://doi.org/10.3390/catal14090617 - 13 Sep 2024
Cited by 1 | Viewed by 1448
Abstract
Furfural has become one of the most promising building blocks directly derived from biomass. It can be transformed into numerous important biobased chemicals. Among them, furfuryl ethers such as furfuryl ethyl ether (FEE) and tetrahydrofurfuryl ethyl ether (THFEE) are considered to be attractive [...] Read more.
Furfural has become one of the most promising building blocks directly derived from biomass. It can be transformed into numerous important biobased chemicals. Among them, furfuryl ethers such as furfuryl ethyl ether (FEE) and tetrahydrofurfuryl ethyl ether (THFEE) are considered to be attractive derivatives, notably as fuel components, due to their high stability and high octane numbers. Therefore, the production of furfuryl ethers from furfural via a hydrogenation route is an important academic and industrial challenge and requires the deployment of new catalytic processes under green and competitive reaction conditions. The existing processes are based on a two-step process combining hydrogenation and reaction with a strong Bronsted acid catalyst in batch conditions. For the first time, a continuous flow one-step process has been elaborated for the conversion of furfural directly into furfuryl ethers based on reductive etherification. The present work explores the catalytic performance in a continuous flow of commercial palladium catalysts supported on activated carbon for the catalytic reductive etherification of furfural with ethanol in the presence of trifluoroacetic acid. The chemical and engineering aspects, such as the mechanisms and reaction conditions, will be discussed. Full article
(This article belongs to the Special Issue Industrial Applications of High-Value Added Biomass Conversion)
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12 pages, 3636 KiB  
Article
Improving the Catalytic Efficiency of an AA9 Lytic Polysaccharide Monooxygenase MtLPMO9G by Consensus Mutagenesis
by Yao Meng, Wa Gao, Xiaohua Liu, Tang Li, Kuikui Li and Heng Yin
Catalysts 2024, 14(9), 614; https://doi.org/10.3390/catal14090614 - 12 Sep 2024
Viewed by 799
Abstract
Cellulose is one of the most abundant renewable resources in nature. However, its recalcitrant crystalline structure hinders efficient enzymatic depolymerization. Unlike cellulases, lytic polysaccharide monooxygenases (LPMOs) can oxidatively cleave glycosidic bonds in the crystalline regions of cellulose, playing a crucial role in its [...] Read more.
Cellulose is one of the most abundant renewable resources in nature. However, its recalcitrant crystalline structure hinders efficient enzymatic depolymerization. Unlike cellulases, lytic polysaccharide monooxygenases (LPMOs) can oxidatively cleave glycosidic bonds in the crystalline regions of cellulose, playing a crucial role in its enzymatic depolymerization. An AA9 LPMO from Myceliophthora thermophila was previously identified and shown to exhibit a highly efficient catalytic performance. To further enhance its catalytic efficiency, consensus mutagenesis was applied. Compared with the wild-type enzyme, the oxidative activities of mutants A165S and P167N increased by 1.8-fold and 1.4-fold, respectively, and their catalytic efficiencies (kcat/Km) improved by 1.6-fold and 1.2-fold, respectively. The mutants also showed significantly enhanced activity in the synergistic degradation of cellulose with cellobiohydrolase. Additionally, the P167N mutant exhibited better H2O2 tolerance. A molecular dynamics analysis revealed that the increased activity of mutants A165S and P167N was due to the closer proximity of the active center to the substrate post-mutation. This study demonstrates that selecting appropriate mutation sites via a semi-rational design can significantly improve LPMO activity, providing valuable insights for the protein engineering of similar enzymes. Full article
(This article belongs to the Section Biocatalysis)
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33 pages, 6114 KiB  
Article
Roles of Catalysts and Feedstock in Optimizing the Performance of Heavy Fraction Conversion Processes: Fluid Catalytic Cracking and Ebullated Bed Vacuum Residue Hydrocracking
by Dicho Stratiev, Ivelina Shishkova, Georgi Argirov, Rosen Dinkov, Mihail Ivanov, Sotir Sotirov, Evdokia Sotirova, Veselina Bureva, Svetoslav Nenov, Krassimir Atanassov, Denis Stratiev and Svetlin Vasilev
Catalysts 2024, 14(9), 616; https://doi.org/10.3390/catal14090616 - 12 Sep 2024
Viewed by 1397
Abstract
Petroleum refining has been, is still, and is expected to remain in the next decades the main source of energy required to drive transport for mankind. The demand for automotive and aviation fuels has urged refiners to search for ways to extract more [...] Read more.
Petroleum refining has been, is still, and is expected to remain in the next decades the main source of energy required to drive transport for mankind. The demand for automotive and aviation fuels has urged refiners to search for ways to extract more light oil products per barrel of crude oil. The heavy oil conversion processes of ebullated bed vacuum residue hydrocracking (EBVRHC) and fluid catalytic cracking (FCC) can assist refiners in their aim to produce more transportation fuels and feeds for petrochemistry from a ton of petroleum. However, a good understanding of the roles of feed quality and catalyst characteristics is needed to optimize the performance of both heavy oil conversion processes. Three knowledge discovery database techniques—intercriteria and regression analyses, and artificial neural networks—were used to evaluate the performance of commercial FCC and EBVRHC in processing 19 different heavy oils. Seven diverse FCC catalysts were assessed using a cascade and parallel fresh catalyst addition system in an EBVRHC unit. It was found that the vacuum residue conversion in the EBVRHC depended on feed reactivity, which, calculated on the basis of pilot plant tests, varied by 16.4%; the content of vacuum residue (VR) in the mixed EBVRHC unit feed (each 10% fluctuation in VR content leads to an alteration in VR conversion of 1.6%); the reaction temperature (a 1 °C deviation in reaction temperature is associated with a 0.8% shift in VR conversion); and the liquid hourly space velocity (0.01 h-1 change of LHSV leads to 0.85% conversion alteration). The vacuum gas oil conversion in the FCC unit was determined to correlate with feed crackability, which, calculated on the basis of pilot plant tests, varied by 8.2%, and the catalyst ΔCoke (each 0.03% ΔCoke increase reduces FCC conversion by 1%), which was unveiled to depend on FCC feed density and equilibrium FCC micro-activity. The developed correlations can be used to optimize the performance of FCC and EBVRHC units by selecting the appropriate feed slate and catalyst. Full article
(This article belongs to the Section Catalytic Reaction Engineering)
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20 pages, 4832 KiB  
Review
Green Catalysts and/or Green Solvents for Sustainable Multi-Component Reactions
by Gatien Messire, Emma Caillet and Sabine Berteina-Raboin
Catalysts 2024, 14(9), 593; https://doi.org/10.3390/catal14090593 - 4 Sep 2024
Cited by 3 | Viewed by 2704
Abstract
Here, we describe some well-known multicomponent reactions and the progress made over the past decade to make these processes even more environmentally friendly. We focus on the Mannich, Hantzsch, Biginelli, Ugi, Passerini, Petasis, and Groebke–Blackburn–Bienaymé reactions. After describing the origin of the reactions [...] Read more.
Here, we describe some well-known multicomponent reactions and the progress made over the past decade to make these processes even more environmentally friendly. We focus on the Mannich, Hantzsch, Biginelli, Ugi, Passerini, Petasis, and Groebke–Blackburn–Bienaymé reactions. After describing the origin of the reactions and their mechanisms, we summarize some advances in terms of the eco-compatibility of these different MCRs. These are followed by examples of some reactions, considered as variants, which are less well documented but which are promising in terms of structures generated or synthetic routes. Full article
(This article belongs to the Special Issue Recent Applications of Metal Catalysts in Organic Synthesis, 2nd Edition)
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34 pages, 3135 KiB  
Review
The Role of Catalysts in Life Cycle Assessment Applied to Biogas Reforming
by Sergio Nogales-Delgado and Juan Félix González González
Catalysts 2024, 14(9), 592; https://doi.org/10.3390/catal14090592 - 3 Sep 2024
Cited by 1 | Viewed by 1223
Abstract
The real implementation of biogas reforming at an industrial scale to obtain interesting products (like hydrogen or syngas) is a developing research field where multidisciplinary teams are continuously adding improvements and innovative technologies. These works can contribute to the proliferation of green technologies [...] Read more.
The real implementation of biogas reforming at an industrial scale to obtain interesting products (like hydrogen or syngas) is a developing research field where multidisciplinary teams are continuously adding improvements and innovative technologies. These works can contribute to the proliferation of green technologies where the circular economy and sustainability are key points. To assess the sustainability of these processes, there are different tools like life cycle assessment (LCA), which involves a complete procedure where even small details count to consider a certain technology sustainable or not. The aim of this work was to review works where LCA is applied to different aspects of biogas reforming, focusing on the role of catalysts, which are essential to improve the efficiency of a certain process but can also contribute to its environmental impact. In conclusion, catalysts have an influence on LCA through the improvement of catalytic performance and the impact of their production, whereas other aspects related to biogas or methane reforming could equally affect their catalytic durability or reusability, with a subsequent effect on LCA. Further research about this subject is required, as this is a continuously changing technology with plenty of possibilities, in order to homogenize this research field. Full article
(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)
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11 pages, 1027 KiB  
Article
Catalytic Valorization of Organic Solid Waste: A Pilot-Scale Run of Sugarcane Bagasse
by Zhaofei Li, Ali Omidkar and Hua Song
Catalysts 2024, 14(9), 568; https://doi.org/10.3390/catal14090568 - 28 Aug 2024
Viewed by 1185
Abstract
Organic solid waste treatment is crucial for enhancing environmental sustainability, promoting economic growth, and improving public health. Following our previous organic solid waste upgrading technique, a further two-step pilot-scale run, using sugarcane bagasse as the feedstock, has been successfully conducted with long-term stability. [...] Read more.
Organic solid waste treatment is crucial for enhancing environmental sustainability, promoting economic growth, and improving public health. Following our previous organic solid waste upgrading technique, a further two-step pilot-scale run, using sugarcane bagasse as the feedstock, has been successfully conducted with long-term stability. Firstly, the sugarcane bagasse was treated under mild conditions (400 °C and 1 bar of CH4), and this catalytic Methanolysis treatment resulted in a bio-oil with a yield of 60.5 wt.%. Following that, it was subjected to a catalytic Methano-Refining process (400 °C and 50 bar of CH4) to achieve high-quality renewable fuel with a liquid yield of 95.0 wt.%. Additionally, this renewable fuel can be regarded as an ideal diesel component with a high cetane number, high heating values, a low freezing point, low density and viscosity, and low oxygen, nitrogen, and sulfur contents. The successful pilot-scale catalytic upgrading of sugarcane bagasse further verified the effectiveness of this methane-assisted organic solid waste upgrading technique and confirmed the high flexibility of this innovative technology for processing a wide spectrum of agricultural and forestry residues. This study will shed light on the further valorization of organic solid waste and other carbonaceous materials. Full article
(This article belongs to the Special Issue Catalyzing the Sustainable Process Paradigm)
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15 pages, 2562 KiB  
Article
Sludge Recycling from Non-Lime Purification of Electrolysis Wastewater: Bridge from Contaminant Removal to Waste-Derived NOX SCR Catalyst
by Ju Gao, Fucheng Sun, Pei Liu, Jizhi Zhou and Yufeng Zhang
Catalysts 2024, 14(8), 535; https://doi.org/10.3390/catal14080535 - 17 Aug 2024
Viewed by 4341
Abstract
Catalysts for the selective catalytic reduction (NOX SCR) of nitrogen oxides can be obtained from sludge in industrial waste treatment, and, due to the complex composition of sludge, NOX SCR shows various SCR efficiencies. In the current work, an SCR catalyst [...] Read more.
Catalysts for the selective catalytic reduction (NOX SCR) of nitrogen oxides can be obtained from sludge in industrial waste treatment, and, due to the complex composition of sludge, NOX SCR shows various SCR efficiencies. In the current work, an SCR catalyst developed from the sludge produced with Fe/C micro-electrolysis Fenton technology (MEF) in wastewater treatment was investigated, taking into account various sludge compositions, Fe/C ratios, and contaminant contents. It was found that, at about 300 °C, the NOX removal rate could reach 100% and there was a wide decomposition temperature zone. The effect of individual components of electroplating sludge, i.e., P, Fe and Ni, on NOX degradation performance of the obtained solids was investigated. It was found that the best effect was achieved when the Fe/P was 8/3 wt%, and variations in the Ni content had a limited effect on the NOX degradation performance. When the Fe/C was 1:2 and the Fe/C/P was 1:2:0.4, the electroplating sludge formed after treatment with Fe/C MEF provided the best NOX removal rate at 100%. Moreover, the characterization results show that the activated carbon was also involved in the catalytic reduction degradation of NOX. An excessive Fe content may cause agglomeration on the catalyst surface and thus affect the catalytic efficiency. The addition of P effectively reduces the catalytic reaction temperature, and the formation of phosphate promotes the generation of adsorbed oxygen, which in turn contributes to improvements in catalytic efficiency. Therefore, our work suggests that controlling the composition in the sludge is an efficient way to modulate SCR catalysis, providing a bridge from contaminant-bearing waste to efficient catalyst. Full article
(This article belongs to the Special Issue Homogeneous and Heterogeneous Catalytic Oxidation and Reduction)
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49 pages, 2859 KiB  
Review
Recent Advances in Layered MX2-Based Materials (M = Mo, W and X = S, Se, Te) for Emerging Optoelectronic and Photo(electro)catalytic Applications
by Felipe M. Pinto, Mary C. M. D. de Conti, Wyllamanney S. Pereira, Júlio C. Sczancoski, Marina Medina, Patricia G. Corradini, Juliana F. de Brito, André E. Nogueira, Márcio S. Góes, Odair P. Ferreira, Lucia H. Mascaro, Fernando Wypych and Felipe A. La Porta
Catalysts 2024, 14(6), 388; https://doi.org/10.3390/catal14060388 - 17 Jun 2024
Cited by 7 | Viewed by 4019
Abstract
Transition metal dichalcogenides (TMDCs), represented by MX2 (where M = Mo, W and X = S, Se, and Te), and more recently, their moiré superlattices (i.e., formed by superimposing layers of TMDCs with different rotation angles) have attracted considerable interest due to [...] Read more.
Transition metal dichalcogenides (TMDCs), represented by MX2 (where M = Mo, W and X = S, Se, and Te), and more recently, their moiré superlattices (i.e., formed by superimposing layers of TMDCs with different rotation angles) have attracted considerable interest due to their excellent physical properties and unique nanoscale functionalities. Compared to graphene, the literature indicates that TMDCs offer a competitive advantage in optoelectronic technologies, primarily owing to their compositionally controlled non-zero bandgap. These two-dimensional (2D) nanostructured single or multiple layers exhibit remarkable properties that differ from their bulk counterparts. Moreover, stacking different TMDC monolayers also forms heterostructures and introduces unique quantum effects and extraordinary electronic properties, which is particularly promising for next-generation optoelectronic devices and photo(electro)catalytic applications. Therefore, in this review, we also highlight the new possibilities in the formation of 2D/2D heterostructures of MX2-based materials with moiré patterns and discuss the main critical challenges related to the synthesis and large-scale applications of layered MX2 and MX2-based composites to spur significant advances in emerging optoelectronic and photo(electro)catalytic applications. Full article
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38 pages, 7801 KiB  
Review
Ethylene Oligomerization Catalyzed by Different Homogeneous or Heterogeneous Catalysts
by Anfeng Peng, Zheng Huang and Gang Li
Catalysts 2024, 14(4), 268; https://doi.org/10.3390/catal14040268 - 17 Apr 2024
Cited by 5 | Viewed by 4003
Abstract
Linear α-olefins (LAOs) are linear alkenes with double bonds at the ends of the molecular chains. LAOs with different chain lengths can be widely applied in various fields. Ethylene oligomerization has become the main process for producing LAOs. In this review, different homogeneous [...] Read more.
Linear α-olefins (LAOs) are linear alkenes with double bonds at the ends of the molecular chains. LAOs with different chain lengths can be widely applied in various fields. Ethylene oligomerization has become the main process for producing LAOs. In this review, different homogeneous or heterogeneous catalysts recently reported in ethylene oligomerization with Ni, Fe, Co, Cr, etc., as active centers will be discussed. In the homogeneous catalytic system, we mainly discuss the effects of the molecular structure and the electronic and coordination states of complexes on their catalytic activity and selectivity. The Ni, Fe, and Co homogeneous catalysts are discussed separately based on different ligand types, while the Cr-based homogeneous catalysts are discussed separately for ethylene trimerization, tetramerization, and non-selective oligomerization. In heterogeneous catalytic systems, we mainly concentrate on the influence of various supports (metal–organic frameworks, covalent organic frameworks, molecular sieves, etc.) and different ways to introduce active centers to affect the performance in ethylene oligomerization. Finally, a summary and outlook on ethylene oligomerization catalysts are provided based on the current research. The development of highly selective α-olefin formation processes remains a major challenge for academia and industry. Full article
(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members and Topical Advisory Panel Members of Catalysts in Section "Catalytic Materials")
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24 pages, 6903 KiB  
Review
Review of Mechanism Investigations and Catalyst Developments for CO2 Hydrogenation to Alcohols
by Guoqing Cui, Yingjie Lou, Mingxia Zhou, Yuming Li, Guiyuan Jiang and Chunming Xu
Catalysts 2024, 14(4), 232; https://doi.org/10.3390/catal14040232 - 31 Mar 2024
Cited by 6 | Viewed by 3807
Abstract
Heterogeneous thermal-catalytic CO2 hydrogenation to alcohols using renewable energy is a highly attractive approach for recycling greenhouse gases into high-value chemicals and fuels, thereby reducing the dependence on fossil fuels, while simultaneously mitigating the CO2 emission and environmental problems. Currently, great [...] Read more.
Heterogeneous thermal-catalytic CO2 hydrogenation to alcohols using renewable energy is a highly attractive approach for recycling greenhouse gases into high-value chemicals and fuels, thereby reducing the dependence on fossil fuels, while simultaneously mitigating the CO2 emission and environmental problems. Currently, great advances have been made on the heterogeneous catalysts, but an in-depth and more comprehensive understanding to further promote this reaction process is still lacking. Herein, we highlight the thermodynamic and kinetic analysis of CO2 hydrogenation reaction firstly. Then, various reaction pathways for CO2 hydrogenation to methanol and higher alcohols (C2+ alcohols) have been discussed in detail, respectively, by combining the experimental studies and density functional theory calculations. On this basis, the key factors influencing the reaction performance, such as metal dispersion, support modification, promoter addition and their structural optimization, are summarized on the metal-based and metal-oxide-based catalysts. In addition, the catalytic performance of CO2 hydrogenation to alcohols and the relationship between structure and properties are mainly summarized and analyzed in the past five years. To conclude, the current challenges and potential strategies in catalyst design, structural characterization and reaction mechanisms are presented for CO2 hydrogenation to alcohols. Full article
(This article belongs to the Section Industrial Catalysis)
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24 pages, 5671 KiB  
Article
Reduced Siderite Ore Combined with Magnesium Oxide as Support Material for Ni-Based Catalysts; An Experimental Study on CO2 Methanation
by Kamonrat Suksumrit, Christoph A. Hauzenberger, Srett Santitharangkun and Susanne Lux
Catalysts 2024, 14(3), 206; https://doi.org/10.3390/catal14030206 - 20 Mar 2024
Viewed by 2520
Abstract
Ni-based catalysts play a fundamental role in catalytic CO2 methanation. In this study, the possibility of using siderite ore as a catalyst or catalytic support material for nickel-based catalysts was investigated, aiming at the exploitation of an abundant natural resource. The catalytic [...] Read more.
Ni-based catalysts play a fundamental role in catalytic CO2 methanation. In this study, the possibility of using siderite ore as a catalyst or catalytic support material for nickel-based catalysts was investigated, aiming at the exploitation of an abundant natural resource. The catalytic performance of Ni-based catalysts with reduced siderite ore as a support was evaluated and compared to MgO as a support material. MgO is known as an effective support material, as it provides access to bifunctional catalysts because of its basicity and high CO2 adsorption capacity. It was shown that undoped and Ni-doped reduced siderite ore have comparable catalytic activity for CO2 hydrogenation (20−23%) at 648 K, but show limited selectivity toward methane (<20% for sideritereduced and 60.2% for Ni/sideritereduced). When MgO was added to the support material (Ni/sideritereduced/MgO), both the CO2 conversion and the selectivity toward methane increased significantly. CO2 conversions were close to the thermodynamic equilibrium, and methane selectivities of ≥99% were achieved. Full article
(This article belongs to the Special Issue Heterogeneous Catalysis: From Nano- and Cluster-Catalysts to Single-Atom Catalysts)
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19 pages, 21509 KiB  
Article
Ru/Attapulgite as an Efficient and Low-Cost Ammonia Decomposition Catalyst
by Qingfeng Teng, Junkang Sang, Guoxin Chen, Haoliang Tao, Yunan Wang, Hua Li, Wanbing Guan, Changsheng Ding, Fenghua Liu and Liangzhu Zhu
Catalysts 2024, 14(3), 197; https://doi.org/10.3390/catal14030197 - 16 Mar 2024
Cited by 2 | Viewed by 2442
Abstract
On-site hydrogen generation from ammonia decomposition is a promising technology to address the challenges of direct transportation and storage of hydrogen. The main problems with the existing support materials for ammonia decomposition catalysts are their high cost and time-consuming preparation process. In this [...] Read more.
On-site hydrogen generation from ammonia decomposition is a promising technology to address the challenges of direct transportation and storage of hydrogen. The main problems with the existing support materials for ammonia decomposition catalysts are their high cost and time-consuming preparation process. In this work, ammonia decomposition catalysts consisting of in situ-formed nano-Ru particles supported on a naturally abundant mineral fiber, attapulgite (ATP), were proposed and studied. Also, 1 wt.% Ru was uniformly dispersed and anchored onto the surface of ATP fibers via the chemical method. We found that the calcination temperatures of the ATP support before the deposition of Ru resulted in little difference in catalytic performance, while the calcination temperatures of the 1Ru/ATP precursor were found to significantly influence the catalytic performance. The prepared 1 wt.% Ru/ATP catalyst (1Ru/ATP) without calcination achieved an ammonia conversion efficiency of 51% at 500 °C and nearly 100% at 600 °C, with the flow rate of NH3 being 10 sccm (standard cubic centimeter per minute). A 150 h continuous test at 600 °C showed that the 1Ru/ATP catalyst exhibited good stability with a degradation rate of about 0.01% h−1. The 1Ru/ATP catalyst was integrated with proton ceramic fuel cells (PCFCs). We reported that PCFCs at 650 °C offered 433 mW cm−2 under H2 fuel and 398 mW cm−2 under cracked NH3 fuel. The overall results suggest low-level Ru-loaded ATP could be an attractive, low-cost, and efficient ammonia decomposition catalyst for hydrogen production. Full article
(This article belongs to the Special Issue Recent Advances and Strategies in the Development of Sustainable Metal Catalysts for Energy, Environment and Generation of High-Value Products)
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19 pages, 10744 KiB  
Review
Air-Stable and Highly Active Transition Metal Phosphide Catalysts for Reductive Molecular Transformations
by Takato Mitsudome
Catalysts 2024, 14(3), 193; https://doi.org/10.3390/catal14030193 - 12 Mar 2024
Cited by 1 | Viewed by 3150
Abstract
This review introduces transition metal phosphide nanoparticle catalysts as highly efficient and reusable heterogeneous catalysts for various reductive molecular transformations. These transformations include the hydrogenation of nitriles to primary amines, reductive amination of carbonyl compounds, and biomass conversion, specifically, the aqueous hydrogenation reaction [...] Read more.
This review introduces transition metal phosphide nanoparticle catalysts as highly efficient and reusable heterogeneous catalysts for various reductive molecular transformations. These transformations include the hydrogenation of nitriles to primary amines, reductive amination of carbonyl compounds, and biomass conversion, specifically, the aqueous hydrogenation reaction of mono- and disaccharides to sugar alcohols. Unlike traditional air-unstable non-precious metal catalysts, these are stable in air, eliminating the need for strict anaerobic conditions or pre-reduction. Moreover, when combined with supports, metal phosphides exhibit significantly enhanced activity, demonstrating high activity, selectivity, and durability in these hydrogenation reactions. Full article
(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members and Topical Advisory Panel Members of Catalysts in Section "Catalysis in Organic and Polymer Chemistry")
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15 pages, 4717 KiB  
Article
Ni Doped Co-MOF-74 Synergized with 2D Ti3C2Tx MXene as an Efficient Electrocatalyst for Overall Water-Splitting
by Ke Yu, Jingyuan Zhang, Yuting Hu, Lanqi Wang, Xiaofeng Zhang and Bin Zhao
Catalysts 2024, 14(3), 184; https://doi.org/10.3390/catal14030184 - 7 Mar 2024
Cited by 12 | Viewed by 3313
Abstract
Metal-organic framework (MOF)-based materials with abundant pore structure, large specific surface area, and atomically dispersed metal centers are considered as potential electrocatalysts for oxygen-evolution reaction (OER), while their ligand-saturated metal nodes are inert to electrocatalysis. In this work, heteroatom doping and interface engineering [...] Read more.
Metal-organic framework (MOF)-based materials with abundant pore structure, large specific surface area, and atomically dispersed metal centers are considered as potential electrocatalysts for oxygen-evolution reaction (OER), while their ligand-saturated metal nodes are inert to electrocatalysis. In this work, heteroatom doping and interface engineering are proposed to improve the OER performance of Co-MOF-74. Using two-dimensional Ti3C2Tx MXene as a conductive support, Ni-doped Co-MOF-74 (CoNi-MOF-74/MXene/NF) was in situ synthesized through a hydrothermal process, which exhibits excellent OER and hydrogen evolution reaction (HER) properties. For OER, the CoNi-MOF-74/MXene/NF achieves a current density of 100 mA/cm2 at an overpotential of only 256 mV, and a Tafel slope of 40.21 mV/dec. When used for HER catalysis, the current density of 10 mA/cm2 is reached at only 102 mV for the CoNi-MOF-74/MXene/NF. In addition, the two-electrode electrolyzer with CoNi-MOF-74/MXene/NF as both the cathode and anode only requires 1.49 V to reach the current density of 10 mA/cm2. This work provides a new approach for the development of bimetallic MOF-based electrocatalysts. Full article
(This article belongs to the Special Issue Green Energy and New Functional Materials through Catalysis for Carbon Neutrality)
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17 pages, 20527 KiB  
Article
Preparation of Proline-Modified UIO−66 Nanomaterials and Investigation of Their Potential in Lipase Immobilization
by Xiaoxiao Dong, Chengnan Zhang, Prasanna J. Patil, Weiwei Li and Xiuting Li
Catalysts 2024, 14(3), 180; https://doi.org/10.3390/catal14030180 - 4 Mar 2024
Cited by 2 | Viewed by 2574
Abstract
Metal–organic frameworks (MOFs) are regarded as excellent carriers for immobilized enzymes due to their substantial specific surface area, high porosity, and easily tunable pore size. Nevertheless, the use of UIO−66 material is significantly limited in immobilized enzymes due to the absence of active [...] Read more.
Metal–organic frameworks (MOFs) are regarded as excellent carriers for immobilized enzymes due to their substantial specific surface area, high porosity, and easily tunable pore size. Nevertheless, the use of UIO−66 material is significantly limited in immobilized enzymes due to the absence of active functional groups on its surface. This study comprised the synthesis of UIO−66 and subsequent modification of the proline (Pro) on UIO−66 through post-synthetic modification. UIO−66 and UIO−66/Pro crystals were employed as matrices to immobilize Rhizopus oryzae lipase (ROL). The contact angle demonstrated that the introduction of Pro onto UIO−66 resulted in favorable conformational changes in the structure of ROL. The immobilized enzyme ROL@UIO−66/Pro, produced via the covalent-bonding method, exhibited greater activity (0.064715 U/mg (about 1.73 times that of the free enzyme)) and stability in the ester hydrolysis reaction. The immobilized enzymes ROL@UIO−66 (131.193 mM) and ROL@UIO−66/Pro (121.367 mM), which were synthesized using the covalent-bonding approach, exhibited a lower Km and higher substrate affinity compared to the immobilized enzyme ROL@UIO−66/Pro (24.033 mM) produced via the adsorption method. This lays a solid foundation for the industrialization of immobilized enzymes. Full article
(This article belongs to the Special Issue Metal–Organic Framework Materials as Catalysts, 2nd Edition)
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12 pages, 3215 KiB  
Article
Advanced Alkaline Water Electrolysis Stack with Non-Noble Catalysts and Hybrid Electrical Connections of the Single Cells
by Galin Borisov, Vasil Bachvarov, Rashko Rashkov and Evelina Slavcheva
Catalysts 2024, 14(3), 179; https://doi.org/10.3390/catal14030179 - 4 Mar 2024
Cited by 2 | Viewed by 3879
Abstract
In this research, a thin layer of multi-metallic non-precious catalyst is prepared by electroplating from an electrolyte bath containing Ni, Co, and Fe sulfates over pressed commercial nickel foam electrode. The composition of the deposited catalytic film and its morphology are characterized by [...] Read more.
In this research, a thin layer of multi-metallic non-precious catalyst is prepared by electroplating from an electrolyte bath containing Ni, Co, and Fe sulfates over pressed commercial nickel foam electrode. The composition of the deposited catalytic film and its morphology are characterized by scanning electron microscopy (SEM) with energy dispersion X-ray (EDX) techniques. The efficiency of the prepared binder-free electrodes for electrochemical water splitting is investigated in a self-designed short water electrolysis stack with zero-gap configuration of the integrated single cells and hybrid electrical connections. The separator used is a commercial Zirfon Perl 500 membrane, doped with 25% KOH. The performance of the catalyst, the single cells, and the developed electrolyzer stack are examined by steady state polarization curves and stationery galvanostatic stability tests in the temperature range 20 °C to 80 °C. The NiFeCoP multi-metallic alloy demonstrates superior catalytic efficiency compared to the pure nickel foam electrodes and reliable stability with time. The single cells in the stack show identical performance and the cumulative stack parameters strictly follow the theoretical considerations. The applied hybrid electrical connections enable scaling of both the stack voltage and the passing current, which in turn ensures flexibility with regard to the input power and the hydrogen production capacity. Full article
(This article belongs to the Section Electrocatalysis)
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40 pages, 5127 KiB  
Review
Recent Advances in Coke Management for Dry Reforming of Methane over Ni-Based Catalysts
by Zhenchao Xu and Eun Duck Park
Catalysts 2024, 14(3), 176; https://doi.org/10.3390/catal14030176 - 1 Mar 2024
Cited by 18 | Viewed by 5257
Abstract
The dry reforming of methane (DRM) is a promising method for controlling greenhouse gas emissions by converting CO2 and CH4 into syngas, a mixture of CO and H2. Ni-based catalysts have been intensively investigated for their use in the [...] Read more.
The dry reforming of methane (DRM) is a promising method for controlling greenhouse gas emissions by converting CO2 and CH4 into syngas, a mixture of CO and H2. Ni-based catalysts have been intensively investigated for their use in the DRM. However, they are limited by the formation of carbonaceous materials on their surfaces. In this review, we explore carbon-induced catalyst deactivation mechanisms and summarize the recent research progress in controlling and mitigating carbon deposition by developing coke-resistant Ni-based catalysts. This review emphasizes the significance of support, alloy, and catalyst structural strategies, and the importance of comprehending the interactions between catalyst components to achieve improved catalytic performance and stability. Full article
(This article belongs to the Special Issue Heterogeneous Catalysis for Clean Energy Production and Carbon Dioxide Utilization)
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17 pages, 11501 KiB  
Article
Estimating the Anti-Viral Performance of Photocatalytic Materials: The Correlation between Air Purification Efficiency and Severe Acute Respiratory Syndrome Coronavirus 2 Inactivation
by Tsuyoshi Ochiai, Takeshi Nagai, Kengo Hamada, Tomoyuki Tobe, Daisuke Aoki, Kayano Sunada and Hitoshi Ishiguro
Catalysts 2024, 14(3), 163; https://doi.org/10.3390/catal14030163 - 23 Feb 2024
Cited by 2 | Viewed by 4023
Abstract
The coronavirus disease 2019 pandemic has increased the demand for anti-viral products. Photocatalytic materials are used to develop coatings and air purifiers that inactivate severe acute respiratory syndrome coronavirus 2. However, the methods for evaluating the anti-viral performance of photocatalytic materials are time-consuming. [...] Read more.
The coronavirus disease 2019 pandemic has increased the demand for anti-viral products. Photocatalytic materials are used to develop coatings and air purifiers that inactivate severe acute respiratory syndrome coronavirus 2. However, the methods for evaluating the anti-viral performance of photocatalytic materials are time-consuming. To address this problem, herein, we propose a screening test for the anti-viral performance of photocatalytic materials based on the ‘acetaldehyde decomposition test’—an air purification efficiency test used to evaluate the decomposition performance of photocatalytic materials. This test is suitable for screening multiple samples and conditions in a short period. The temporal variation in the acetaldehyde concentration was approximated using an exponential function, similar to the temporal variation in the viral infection values. Thereafter, the slope of the regression line for the acetaldehyde concentration over time was used as an indicator in the screening tests. When the anti-viral performance and acetaldehyde decomposition tests were conducted on the same photocatalytic material, a correlation was observed between the slopes of the regression lines. Overall, the proposed screening test shows good potential for evaluating the anti-viral performance of photocatalytic materials. Full article
(This article belongs to the Special Issue Surface Microstructure Design for Advanced Catalysts)
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32 pages, 4789 KiB  
Review
Recent Advances in Electrocatalytic Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid by Heterogeneous Catalysts
by Zhiming Ma, Lei Wang, Guangyu Li and Tao Song
Catalysts 2024, 14(2), 157; https://doi.org/10.3390/catal14020157 - 19 Feb 2024
Cited by 10 | Viewed by 4194
Abstract
The utilization and development of biomass resources is an efficient solution to mitigate the fossil energy crisis. Based on the advantages of mild reaction conditions, rapid reaction, and high conversion, the synthesis of 2,5-furandicarboxylic acid (FDCA) by the electrocatalytic oxidation of 5-hydroxymethylfurfural (HMFOR) [...] Read more.
The utilization and development of biomass resources is an efficient solution to mitigate the fossil energy crisis. Based on the advantages of mild reaction conditions, rapid reaction, and high conversion, the synthesis of 2,5-furandicarboxylic acid (FDCA) by the electrocatalytic oxidation of 5-hydroxymethylfurfural (HMFOR) has attracted considerable attention. This review will summarize the recent advances of HMFOR to FDCA, including the reaction pathway and mechanism, as well as the catalytic performance of various heterogeneous electrocatalysts. The challenges and prospects for HMFOR are also focused on. Finally, it is expected that this work may provide guidance for the design of high-efficiency electrocatalysts and thereby accelerate the industrialization process of biomass utilization. Full article
(This article belongs to the Section Catalysis in Organic and Polymer Chemistry)
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26 pages, 5714 KiB  
Review
Influence of Impurities in the Chemical Processing Chain of Biomass on the Catalytic Valorisation of Cellulose towards γ-Valerolactone
by Preeti Kashyap, Magdalena Brzezińska, Nicolas Keller and Agnieszka M. Ruppert
Catalysts 2024, 14(2), 141; https://doi.org/10.3390/catal14020141 - 12 Feb 2024
Cited by 5 | Viewed by 3258
Abstract
The conversion of lignocellulosic biomass to valuable chemicals such as levulinic acid and γ-valerolactone is a promising approach for achieving a sustainable circular economy. However, the presence of impurities during the stepwise chemical processing chain of the biomass feedstock can significantly impact both [...] Read more.
The conversion of lignocellulosic biomass to valuable chemicals such as levulinic acid and γ-valerolactone is a promising approach for achieving a sustainable circular economy. However, the presence of impurities during the stepwise chemical processing chain of the biomass feedstock can significantly impact both the hydrolysis and hydrogenation steps implemented to convert the cellulosic feedstock to levulinic acid and further to γ-valerolactone, respectively. This review article explores the effects of those impurities by classifying them into two groups, namely endogenous and exogenous types, based on whether they originate directly from the raw lignocellulosic biomass or arise during its multi-step chemical processing. Endogenous impurities include heavy metals, alkali metals, alkaline earth metals, proteins, and side products from the downstream treatment of cellulose, while exogenous impurities are introduced during physical pre-treatments such as ball milling or during the hydrolysis step, or they might originate from the reactor setup. The specific catalyst deactivation by carbonaceous species such as humins and coke is considered. The mechanisms of impurity-induced catalyst deactivation and by-product formation are thoroughly discussed. Additionally, strategies for minimizing the detrimental effects of impurities on biomass conversion and enhancing catalytic efficiency and stability are also proposed. Full article
(This article belongs to the Section Biomass Catalysis)
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