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Catalysts, Volume 14, Issue 5 (May 2024) – 50 articles

Cover Story (view full-size image): Automotive three-way catalysts (TWCs) reduce toxic emissions but need replacing after 8–10 years of use, resulting in substantial amounts of palladium-rich waste. Current pyrometallurgical routes to recycle this precious metal content are very energy-intensive and require the use of hazardous chemicals. More recently, a mild, low-energy process has been reported that can transform model TWC material into the palladium dimer [NnBu4]2[Pd2I6] in high yields and purity. In this contribution, we demonstrate that this dimeric recovery product, and its derivative PdI2(dppf), can be employed as effective (pre)catalysts for the formation of new C-O and C-N bonds in low-impact solvents. [NnBu4]2[Pd2I6] can also be recovered and re-used multiple times after the reaction, providing additional sustainability benefits. View this paper
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16 pages, 7610 KiB  
Article
Enhancing the Visible Light Photocatalytic Activity of TiO2-Based Coatings by the Addition of Exfoliated g-C3N4
by Ilias Papailias, Nadia Todorova, Tatiana Giannakopoulou, Niki Plakantonaki, Michail Vagenas, Panagiotis Dallas, George C. Anyfantis, Ioannis Arabatzis and Christos Trapalis
Catalysts 2024, 14(5), 333; https://doi.org/10.3390/catal14050333 - 20 May 2024
Viewed by 432
Abstract
In the last few years, increasing interest from researchers and companies has been shown in the development of photocatalytic coatings for air purification and self-cleaning applications. In order to maintain the photocatalyst’s concentration as low as possible, highly active materials and/or combinations of [...] Read more.
In the last few years, increasing interest from researchers and companies has been shown in the development of photocatalytic coatings for air purification and self-cleaning applications. In order to maintain the photocatalyst’s concentration as low as possible, highly active materials and/or combinations of them are required. In this work, novel photocatalytic formulations containing g-C3N4/TiO2 composites were prepared and deposited in the form of coatings on a-block substrates. The obtained photocatalytic surfaces were tested for NOx and acetaldehyde removal from model air. It was found that the addition of only 0.5 wt% g-C3N4 towards TiO2 content results in over 50% increase in the photocatalytic activity under visible light irradiation in comparison to pure TiO2 coating, while the activity under UV light was not affected. The result was related to the creation of a g-C3N4/TiO2 heterojunction that improves the light absorption and the separation of photogenerated electron-hole pairs, as well as to the inhibition of TiO2 particles’ agglomeration due to the presence of g-C3N4 sheets. Full article
(This article belongs to the Special Issue Recent Advances in g-C3N4-Based Photocatalysts)
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17 pages, 8900 KiB  
Article
Glucose Isomerization to Fructose Catalyzed by MgZr Mixed Oxides in Aqueous Solution
by Xiongxiong Zuo and Xing Tang
Catalysts 2024, 14(5), 332; https://doi.org/10.3390/catal14050332 - 18 May 2024
Viewed by 380
Abstract
The catalytic isomerization of glucose to fructose plays a pivotal role in the application of biomass as a feedstock for chemicals. Herein, we propose a facile solid-state-grinding strategy to construct ZrO2/MgO mixed oxides, which offered an excellent fructose yield of over [...] Read more.
The catalytic isomerization of glucose to fructose plays a pivotal role in the application of biomass as a feedstock for chemicals. Herein, we propose a facile solid-state-grinding strategy to construct ZrO2/MgO mixed oxides, which offered an excellent fructose yield of over 34.55% and a high selectivity of 80.52% (80 °C, 2 h). The co-mingling of amphiphilic ZrO2 with MgO improved the unfavorable moderate/strongly basic site distribution on MgO, which can prohibit the side reactions during the reaction and enhance the fructose selectivity. Based on the catalyst characterizations, MgO was deposited on the ZrO2 surface by plugging the pores, and the addition of ZrO2 lessened the quantity of strongly basic sites of MgO. Additionally, the presence of ZrO2 largely enhanced the catalyst stability in comparison with pure MgO by recycling experiments. Full article
(This article belongs to the Section Biomass Catalysis)
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2 pages, 136 KiB  
Editorial
Nanotechnology in Catalysis, 2nd Edition
by Maria J. Sabater
Catalysts 2024, 14(5), 331; https://doi.org/10.3390/catal14050331 - 17 May 2024
Viewed by 383
Abstract
Catalysis is considered a central field in nanoscience and nanotechnology, given that the use of nanoscale structures has played a central role in the development of nanomaterials such as catalysts (nanocatalysts) for decades [...] Full article
(This article belongs to the Special Issue Nanotechnology in Catalysis, 2nd Edition)
17 pages, 7249 KiB  
Article
Investigating the Inhibitory Factors of Sucrose Hydrolysis in Sugar Beet Molasses with Yeast and Invertase
by Mikael Sjölin, Maria Djärf, Mohamed Ismail, Herje Schagerlöf, Ola Wallberg, Rajni Hatti-Kaul and Mahmoud Sayed
Catalysts 2024, 14(5), 330; https://doi.org/10.3390/catal14050330 - 17 May 2024
Viewed by 375
Abstract
Sugar beet molasses is a low-value byproduct from the sugar industry. It contains significant amounts of sucrose (approx. 50% (w/w)), which can be used for many different applications, for example, as feedstock for the production of fuel (as ethanol) [...] Read more.
Sugar beet molasses is a low-value byproduct from the sugar industry. It contains significant amounts of sucrose (approx. 50% (w/w)), which can be used for many different applications, for example, as feedstock for the production of fuel (as ethanol) and biobased chemicals such as 5-hydoxymethyl furfural (HMF). To produce platform chemicals, sucrose is hydrolyzed into its monomeric C6 sugars: glucose and fructose. When comparing the hydrolysis rates of molasses with a pure sucrose solution, the specific reaction rate is much slower (Qp/x,60min = 93 and 70 gprod L−1 h−1 gcell−1 for pure sucrose and crude molasses, respectively) at the same sucrose concentration (300 g/L) and process conditions. To clarify why molasses inhibits the enzymatic hydrolysis rate, the influence of its viscosity and inorganic and organic composition was investigated. Also, the effects of molasses and treated molasses on pure enzymes, invertase (from Saccharomyces cerevisiae, 0.05 mg/mL), compared with hydrolysis using whole cells of Baker’s yeast (3 mg/mL), were tested. The results indicate an inhibitory effect of potassium (Qp/x,60min = 76 gprod L−1 h−1 gcell−1), generally at high salt concentrations (Qp/x,60min = 67 gprod L−1 h−1 gcell−1), which could be correlated to the solution’s high salt concentrations and possibly the synergistic effects of different ions when applying concentrations that were four times that in the molasses. Also, the viscosity and sucrose purity seem to have an effect, where pure sucrose solutions and thick juice from the sugar mill yielded higher hydrolysis rates (Qp/x,60min = 97 gprod L−1 h−1 gcell−1) than molasses-type solutions with a higher viscosity (Qp/x,60min = 70–74 gprod L−1 h−1 gcell−1). Attempting to further understand the effects of different components on the invertase activity, an in silico investigation was performed, indicating that high salt concentrations affected the binding of sucrose to the active site of the enzyme, which can result in a lower reaction rate. This knowledge is important for future scale-up of the hydrolysis process, since reduced hydrolysis rates require larger volumes to provide a certain productivity, requiring larger process equipment and thereby higher investment costs. Full article
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22 pages, 6470 KiB  
Article
Controllable Synthesis of Fe2O3/Nickel Cobaltite Electrocatalyst to Enhance Oxidation of Small Molecules
by Fowzia S. Alamro, Shymaa S. Medany, Nada S. Al-Kadhi, Ayman M. Mostafa, Walaa F. Zaher, Hoda A. Ahmed and Mahmoud A. Hefnawy
Catalysts 2024, 14(5), 329; https://doi.org/10.3390/catal14050329 - 17 May 2024
Viewed by 409
Abstract
Nickel-based catalysts have been widely recognized as highly promising electrocatalysts for oxidation. Herein, we designed a catalyst surface based on iron oxide electrodeposited on NiCo2O4 spinel oxide. Nickel foam was used as a support for the prepared catalysts. The modified [...] Read more.
Nickel-based catalysts have been widely recognized as highly promising electrocatalysts for oxidation. Herein, we designed a catalyst surface based on iron oxide electrodeposited on NiCo2O4 spinel oxide. Nickel foam was used as a support for the prepared catalysts. The modified surface was characterized by different techniques like electron microscopy and X-ray photon spectroscopy. The activity of the modified surface was investigated through the electrochemical oxidation of different organic molecules such as urea, ethanol, and ethylene glycol. Therefore, the modified Fe@ NiCo2O4/NF current in 1.0 M NaOH and 1.0 M fuel concentrations reached 31.4, 27.1, and 17.8 mA cm−2 for urea, ethanol, and ethylene glycol, respectively. Moreover, a range of kinetic characteristics parameters were computed, such as the diffusion coefficient, Tafel slope, and transfer coefficient. Chronoamperometry was employed to assess the electrode’s resistance to long-term oxidation. Consequently, the electrode’s activity exhibited a reduction ranging from 17% to 30% over a continuous oxidation period of 300 min. Full article
(This article belongs to the Special Issue Recent Advances in Energy-Related Materials in Catalysts, 2nd Edition)
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27 pages, 44489 KiB  
Review
Recent Developments on CO2 Hydrogenation Performance over Structured Zeolites: A Review on Properties, Synthesis, and Characterization
by Methene Briones Cutad, Mohammed J. Al-Marri and Anand Kumar
Catalysts 2024, 14(5), 328; https://doi.org/10.3390/catal14050328 - 17 May 2024
Viewed by 511
Abstract
This review focuses on an extensive synopsis of the recent improvements in CO2 hydrogenation over structured zeolites, including their properties, synthesis methods, and characterization. Key features such as bimodal mesoporous structures, surface oxygen vacancies, and the Si/Al ratio are explored for their [...] Read more.
This review focuses on an extensive synopsis of the recent improvements in CO2 hydrogenation over structured zeolites, including their properties, synthesis methods, and characterization. Key features such as bimodal mesoporous structures, surface oxygen vacancies, and the Si/Al ratio are explored for their roles in enhancing catalytic activity. Additionally, the impact of porosity, thermal stability, and structural integrity on the performance of zeolites, as well as their interactions with electrical and plasma environments, are discussed in detail. The synthesis of structured zeolites is analyzed by comparing the advantages and limitations of bottom-up methods, including hard templating, soft templating, and non-templating approaches, to top-down methods, such as dealumination, desilication, and recrystallization. The review addresses the challenges associated with these synthesis techniques, such as pore-induced diffusion limitations, morphological constraints, and maintaining crystal integrity, highlighting the need for innovative solutions and optimization strategies. Advanced characterization techniques are emphasized as essential for understanding the catalytic mechanisms and dynamic behaviors of zeolites, thereby facilitating further research into their efficient and effective use. The study concludes by underscoring the importance of continued research to refine synthesis and characterization methods, which is crucial for optimizing catalytic activity in CO2 hydrogenation. This effort is important for achieving selective catalysis and is paramount to the global initiative to reduce carbon emissions and address climate change. Full article
(This article belongs to the Special Issue Applications of Heterogeneous Catalysts in Green Chemistry)
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21 pages, 3032 KiB  
Article
Study of Oxygen Reduction Reaction on Polycrystalline Rhodium in Acidic and Alkaline Media
by Jelena Golubović, Miroslava Varničić and Svetlana Štrbac
Catalysts 2024, 14(5), 327; https://doi.org/10.3390/catal14050327 - 16 May 2024
Viewed by 385
Abstract
This study examines the kinetics and mechanism of the oxygen reduction reaction (ORR) on a polycrystalline rhodium electrode (Rh(poly)) in acidic and alkaline media, using rotating disc electrode measurements. This study found that the ORR activity of the Rh(poly) electrode decreases in the [...] Read more.
This study examines the kinetics and mechanism of the oxygen reduction reaction (ORR) on a polycrystalline rhodium electrode (Rh(poly)) in acidic and alkaline media, using rotating disc electrode measurements. This study found that the ORR activity of the Rh(poly) electrode decreases in the order of 0.1 M NaOH > 0.1 M HClO4 > 0.05 M H2SO4 concerning the half-wave potentials. The Tafel slopes for ORR on Rh(poly) in the cathodic direction are 60 and 120 mV dec−1 at low and high overpotentials, respectively, in perchloric acid and alkaline solutions. However, strongly adsorbed sulfate anions hinder the ORR on Rh(poly) in sulfuric acid, leading to higher Tafel slopes. The highest ORR activity of Rh(poly) in an alkaline media suggests the promoting role of the specifically adsorbed OH anions and RhOH. In all cases, ORR on Rh(poly) proceeds through the 4e-series reaction pathway. Full article
(This article belongs to the Special Issue Exploring the Mechanisms and Kinetics of Electrocatalytic Reactions)
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11 pages, 1788 KiB  
Article
Optimization of Desulfurization Process via Choline Phosphotungstate Coupled with Persulfate Using Response Surface Methodology
by Yinke Zhang and Hang Xu
Catalysts 2024, 14(5), 326; https://doi.org/10.3390/catal14050326 - 16 May 2024
Viewed by 327
Abstract
Using a simple acid-base neutralization method, a Ch-PW solid catalyst was synthesized by mixing choline hydroxide (ChOH) and phosphotungstic acid (HPW) at a 2:1 molar ratio in an aqueous solution. This catalyst was combined with a 20 wt.% potassium peroxymonosulfate (PMS) solution, using [...] Read more.
Using a simple acid-base neutralization method, a Ch-PW solid catalyst was synthesized by mixing choline hydroxide (ChOH) and phosphotungstic acid (HPW) at a 2:1 molar ratio in an aqueous solution. This catalyst was combined with a 20 wt.% potassium peroxymonosulfate (PMS) solution, using acetonitrile (ACN) as the extraction solvent to create an extraction catalytic oxidative desulfurization system. The optimal desulfurization conditions were determined through response surface methodology, targeting the highest desulfurization rate: 0.99 g of Ch-PW, 1.07 g of PMS, 2.5 g of extraction solvent, at a temperature of 50.48 °C. The predicted desulfurization rate was 90.79%, compared to an experimental rate of 93.64%, with a deviation of 3.04%. A quadratic model correlating the desulfurization rate with the four conditions was developed and validated using ANOVA, which also quantified the impact of each factor on the desulfurization rate: PMS > ACN > Ch-PW > temperature. GC-MS analysis identified the main oxidation product as DBTO2, and the mechanism of desulfurization in this system was further explored. Full article
(This article belongs to the Section Catalytic Materials)
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16 pages, 6714 KiB  
Article
Nano-Sheets of CsNiVF6 Pyrochlore Electrocatalyst for Enhanced Urea Oxidation and Hydrogen Green Production Reactions
by Mohamed A. Ghanem, Abdullah M. Al-Mayouf, Khalaf A. Alfudhayli and Mohamed O. Abdelkader
Catalysts 2024, 14(5), 325; https://doi.org/10.3390/catal14050325 - 16 May 2024
Viewed by 380
Abstract
This study presents the successful synthesis of a cesium–nickel–vanadium fluoride (CsNiVF6) pyrochlore nano-sheet catalyst via solid-phase synthesis and its electrochemical performance in green hydrogen production through urea electrolysis in alkaline media. The physicochemical characterizations revealed that the CsNiVF6 exhibits a [...] Read more.
This study presents the successful synthesis of a cesium–nickel–vanadium fluoride (CsNiVF6) pyrochlore nano-sheet catalyst via solid-phase synthesis and its electrochemical performance in green hydrogen production through urea electrolysis in alkaline media. The physicochemical characterizations revealed that the CsNiVF6 exhibits a pyrochlore-type structure consisting of a disordered cubic corner-shared (Ni, V)F6 octahedra structure and nano-sheet morphology with a thickness ranging from 10 to 20 nm. Using the CsNiVF6 catalyst, the electrochemical analysis, conducted through cyclic voltammetry, demonstrates a current mass activity of ~1500 mA mg−1, recorded at 1.8 V vs. RHE, along with low-resistance (3.25 ohm) charge transfer and good long-term stability for 0.33 M urea oxidation in an alkaline solution. Moreover, the volumetric hydrogen production rate at the cathode (bare nickel foam) is increased from 12.25 to 39.15 µmol/min upon the addition of 0.33 M urea to a 1.0 KOH solution and at a bias potential of 2.0 V. The addition of urea to the electrolyte solution enhances hydrogen production at the cathode, especially at lower voltages, surpassing the volumes produced in pure 1.0 M KOH solution. This utilization of a CsNiVF6 pyrochlore nano-sheet catalyst and renewable urea as a feedstock contributes to the development of a green and sustainable hydrogen economy. Overall, this research underscores the potential use of CsNiVF6 as a cost-effective nickel-based pyrochlore electrocatalyst for advancing renewable and sustainable urea electrolysis processes toward green hydrogen production. Full article
(This article belongs to the Special Issue Electrocatalysis for Hydrogen/Oxygen Evolution Reactions)
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12 pages, 2402 KiB  
Article
One-Step Synthesis of High-Efficiency Oxygen Evolution Reaction Catalyst FeSx(Y/MB) with High Temperature Resistance and Strong Alkali
by Jing Wang, Lingling Feng, Zikang Zhao, Yan Wang, Ying Zhang, Shan Song, Shengwei Sun, Junshuang Zhou and Faming Gao
Catalysts 2024, 14(5), 324; https://doi.org/10.3390/catal14050324 - 16 May 2024
Viewed by 399
Abstract
Given the energy crisis and escalating environmental pollution, the imperative for developing clean new energy is evident. Hydrogen has garnered significant attention owing to its clean properties, high energy density, and ease of storage and transportation. This study synthesized four types of catalysts—FeS(DI/MB), [...] Read more.
Given the energy crisis and escalating environmental pollution, the imperative for developing clean new energy is evident. Hydrogen has garnered significant attention owing to its clean properties, high energy density, and ease of storage and transportation. This study synthesized four types of catalysts—FeS(DI/MB), FeS(ET/MB), Fe(DI/MB), and Fe(ET/MB)—using two distinct solution systems: DI/MB and ET/MB. The FeS(DI/MB) catalyst, synthesized using the layered solution system (DI/MB), demonstrates a uniformly distributed and dense nanosheet structure, exhibiting excellent resistance to strong bases and superior catalytic properties. The FeS(DI/MB) electrode showed OER overpotentials of 460 mV and 318 mV in 1 M and 6 M, respectively, at current densities of up to 500 mA cm−2. Under industrial electrolysis test conditions, the FeS(DI/MB) electrode required only 262 mV to achieve a current density of 500 mA cm−2, operating in a high-temperature, strong alkaline environment of 6 M at 60 °C. Furthermore, the FeS(DI/MB) electrode exhibited excellent OER catalytic activity and stability, as evidenced by a 60 h stability test These findings provide valuable insights into the preparation of iron nickel sulfide-based catalysts, and further in-depth and comprehensive exploration is anticipated to yield the excellent catalytic performance of these catalysts in the realm of electrolytic water hydrogen production. Full article
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9 pages, 3273 KiB  
Article
Lithium Polysulfide Catalytic Mechanism of AlN/InN Heterojunction by First-Principles Calculation
by Lingfeng Ye, Jin Wang, Zhiping Lin, Huafeng Dong and Fugen Wu
Catalysts 2024, 14(5), 323; https://doi.org/10.3390/catal14050323 - 14 May 2024
Viewed by 381
Abstract
To solve the shuttling effect and transformations of LiPSs in lithium–sulfur batteries, heterostructures have been designed to immobilize LiPSs and boost their reversible conversions. In this paper, we have constructed AlN/InN heterojunctions with AlN with a wide band gap and InN with a [...] Read more.
To solve the shuttling effect and transformations of LiPSs in lithium–sulfur batteries, heterostructures have been designed to immobilize LiPSs and boost their reversible conversions. In this paper, we have constructed AlN/InN heterojunctions with AlN with a wide band gap and InN with a narrow band gap. The heterojunctions show metallic properties, which are primarily composed of 2s, 2p N atoms and 5s, 5p In atoms. InN has relatively higher adsorptivity for LiPSs than AlN. Reaction profiles show that on the surface of AlN, there is a lower rate-limiting step than on that of InN, from S8 to Li2S6, and a higher rate-limiting step from Li2S4 to Li2S2, which is more favorable for InN during the reduction from Li2S4 to Li2S2. The heterojunction can realize the synergistic reaction of trapping–diffusion–conversion for LiPSs, in which AlN traps large Li2S8 and Li2S6, the heterojunction causes the diffusion of Li2S4, and InN completes the conversion of Li2S4 to Li2S. Full article
(This article belongs to the Section Computational Catalysis)
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21 pages, 7423 KiB  
Article
Performance Evaluation and Durability Analysis of NiFeCoOx Catalysts for Alkaline Water Electrolysis in Anion Exchange Membrane Electrolyzers
by Khaja Wahab Ahmed and Michael Fowler
Catalysts 2024, 14(5), 322; https://doi.org/10.3390/catal14050322 - 14 May 2024
Viewed by 529
Abstract
This study examines the catalytic activity of NiFeCoOx catalysts for anion exchange membrane (AEM) water electrolysis. The catalysts were synthesized with a Ni to Co ratio of 2:1 and Fe content ranges from 2.5 to 12.5 wt%. The catalysts were characterized using [...] Read more.
This study examines the catalytic activity of NiFeCoOx catalysts for anion exchange membrane (AEM) water electrolysis. The catalysts were synthesized with a Ni to Co ratio of 2:1 and Fe content ranges from 2.5 to 12.5 wt%. The catalysts were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The catalytic activity of the NiFeCoOx catalysts was evaluated through linear sweep voltammetry (LSV) and chronoamperometry (CA) experiments for the oxygen evolution reaction (OER). The catalyst with 5% Fe content exhibited the highest catalytic activity, achieving an overpotential of 228 mV at a current density of 10 mA cm−2. Long-term catalyst testing for the OER at 50 mA cm−2 showed stable electrolysis operation for 100 h. The catalyst was further analyzed in an AEM water electrolyzer in a single-cell test, and the NiFeCoOx catalyst with 5% Fe at the anode demonstrated the highest current densities of 1516 mA cm−2 and 1620 mA cm−2 at 55 °C and 70 °C at 2.1 V. The maximum current density of 1880 mA cm−2 was achieved at 2.2 V and 70 °C. The Nyquist plot analysis of electrolysis at 55 °C showed that the NiFeCoOx catalyst with 5% Fe had lower activation resistance compared with the other Fe loadings, indicating enhanced performance. The durability test was performed for 8 h, showing stable AEM water electrolysis with minimum degradation. An overall cell efficiency of 70.5% was achieved for the operation carried out at a higher current density of 0.8 A cm−2. Full article
(This article belongs to the Section Electrocatalysis)
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0 pages, 3605 KiB  
Article
Facile Asymmetric Syntheses of Non-Natural Amino Acid (S)-Cyclopropylglycine by the Developed NADH-Driven Biocatalytic System
by Qian Tang, Shanshan Li, Liping Zhou, Lili Sun, Juan Xin and Wei Li
Catalysts 2024, 14(5), 321; https://doi.org/10.3390/catal14050321 - 13 May 2024
Viewed by 491
Abstract
A self-sufficient bifunctional enzyme integrating reductive amination and coenzyme regeneration activities was developed and successfully employed to synthesize (S)-cyclopropylglycine with an improved reaction rate 2.1-fold over the native enzymes and a short bioconversion period of 6 h at a high substrate [...] Read more.
A self-sufficient bifunctional enzyme integrating reductive amination and coenzyme regeneration activities was developed and successfully employed to synthesize (S)-cyclopropylglycine with an improved reaction rate 2.1-fold over the native enzymes and a short bioconversion period of 6 h at a high substrate concentration of 120 g·L−1 and space–time yield of (S)-cyclopropylglycine up to 377.3 g·L−1·d−1, higher than that of any previously reported data. Additionally, (S)-cyclopropylglycine could be continuously synthesized for 90 h with the enzymes packed in a dialysis tube, providing 634.6 g of (S)-cyclopropylglycine with >99.5% ee and over 95% conversion yield up to 12 changes. These results confirmed that the newly developed NADH-driven biocatalytic system could be utilized as a self-sufficient biocatalyst for industrial application in the synthesis of (S)-cyclopropylglycine, which provides a chiral center and cyclopropyl fragment for the frequent synthesis of preclinical/clinical drug molecules. Full article
(This article belongs to the Section Biocatalysis)
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13 pages, 1873 KiB  
Article
Liquid–Liquid Equilibrium Behavior of Ternary Systems Comprising Biodiesel + Glycerol and Triglyceride + Methanol: Experimental Data and Modeling
by Lingmei Yang, Shiyou Xing, Xianbin Teng, Rukuan Liu, Zhongming Wang, Baining Lin, Pengmei Lv, Akram Ali Nasser Mansoor Al-Haimi, Fatma Yehia and Wen Luo
Catalysts 2024, 14(5), 320; https://doi.org/10.3390/catal14050320 - 12 May 2024
Viewed by 546
Abstract
Having a comprehensive knowledge of phase equilibrium is advantageous for industrial simulation and design of chemical processes. For further acquisition of primary data to facilitate the separation and purification of waste oil biodiesel systems, a liquid–liquid equilibrium (LLE) tank is deployed for the [...] Read more.
Having a comprehensive knowledge of phase equilibrium is advantageous for industrial simulation and design of chemical processes. For further acquisition of primary data to facilitate the separation and purification of waste oil biodiesel systems, a liquid–liquid equilibrium (LLE) tank is deployed for the ternary system of waste oil biodiesel + methanol + glycerin, thereby enhancing the precision and efficiency of the process. The phase equilibrium system was constructed under the influence of atmospheric pressure at precise temperatures of 303.15 K, 313.15 K, and 323.15 K. The equilibrium components of each substance were analyzed by employing high-temperature gas chromatography, a sophisticated analytical method that enables the identification and quantification of individual components of a sample. Moreover, the ternary liquid–liquid equilibrium data were correlated by implementing the NRTL and UNIQUAC activity coefficient models. Subsequently, the binary interaction parameters of the ternary system were derived by conducting regression analysis. The experimental data demonstrated that the presence of lower methanol content in the system resulted in nearly immiscible biodiesel and glycerol phases, which ultimately facilitated the separation of biodiesel and glycerol. Conversely, with the increase in methanol content, the mutual solubility of biodiesel and glycerol was observed to increase gradually. The results showed that the calculated values of the NRTL and UNIQUAC models aligned well with the experimental values. The root-mean-square deviations of the NRTL and UNIQUAC models at 313.15 K were 2.76% and 3.56%, respectively. Full article
(This article belongs to the Section Biomass Catalysis)
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25 pages, 4329 KiB  
Article
Methane Combustion Kinetics over Palladium-Based Catalysts: Review and Modelling Guidelines
by Roshni Sajiv Kumar, Joseph P. Mmbaga, Natalia Semagina and Robert E. Hayes
Catalysts 2024, 14(5), 319; https://doi.org/10.3390/catal14050319 - 11 May 2024
Viewed by 511
Abstract
Fugitive methane emissions account for a significant proportion of greenhouse gas emissions, and their elimination by catalytic combustion is a relatively easy way to reduce global warming. New and novel reactor designs are being considered for this purpose, but their correct and efficient [...] Read more.
Fugitive methane emissions account for a significant proportion of greenhouse gas emissions, and their elimination by catalytic combustion is a relatively easy way to reduce global warming. New and novel reactor designs are being considered for this purpose, but their correct and efficient design requires kinetic rate expressions. This paper provides a comprehensive review of the current state of the art regarding kinetic models for precious metal catalysts used for the catalytic combustion of lean methane mixtures. The primary emphasis is on relatively low-temperature operation at atmospheric pressure, conditions that are prevalent in the catalytic destruction of low concentrations of methane in emission streams. In addition to a comprehensive literature search, we illustrate a detailed example of the methodology required to determine an appropriate kinetic model and the constants therein. From the wide body of literature, it is seen that the development of a kinetic model is not necessarily a trivial matter, and it is difficult to generalize. The model, especially the dependence on the water concentration, is a function of not only the active ingredients but also the nature of the support. Kinetic modelling is performed for six catalysts, one commercial and five that were manufactured in our laboratory, for illustration purposes. Full article
(This article belongs to the Section Computational Catalysis)
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15 pages, 4179 KiB  
Article
Direct Synthesis of Calcium Lactate through the Reaction of Glycerol with Calcium Hydroxide Catalyzed by Bimetallic AuCu/SiO2 Nanocatalysts
by Changqing Li, Xinyue Cui, Aili Wang, Hengbo Yin, Yuting Li, Qiao Lin and Junjie Guo
Catalysts 2024, 14(5), 318; https://doi.org/10.3390/catal14050318 - 11 May 2024
Viewed by 387
Abstract
Bimetallic AuCu/SiO2 nanosized catalysts were prepared using the wet chemical reduction technique. From among Au0.1–1.5Cu10/SiO2 catalysts, the Au0.5Cu10/SiO2 catalyst gave the highest yield of calcium lactate of 87% at a glycerol conversion [...] Read more.
Bimetallic AuCu/SiO2 nanosized catalysts were prepared using the wet chemical reduction technique. From among Au0.1–1.5Cu10/SiO2 catalysts, the Au0.5Cu10/SiO2 catalyst gave the highest yield of calcium lactate of 87% at a glycerol conversion of 96% when the reaction of glycerol with calcium hydroxide at a mole ratio of calcium hydroxide to glycerol of 0.8:1 was conducted under an anaerobic atmosphere at 200 °C for 2 h. The interactions between metallic Au0 and Cu0 nanoparticles facilitate calcium lactate formation. The simulation of glycerol consumption rate with an empirical power-function reaction kinetics equation yielded a reaction activation energy of 44.3 kJ∙mol−1, revealing that the catalytic reaction of glycerol with calcium hydroxide to calcium lactate can be conducted by overcoming a mild energy barrier. The synthesis of calcium lactate through the catalytic reaction of glycerol with calcium hydroxide on a bimetallic AuCu/SiO2 nanosized catalyst under a safe anaerobic atmosphere is an alternative to the conventional calcium lactate production technique through the reaction of expensive lactic acid with calcium hydroxide. Full article
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41 pages, 1777 KiB  
Review
A Comprehensive Review of Fine Chemical Production Using Metal-Modified and Acidic Microporous and Mesoporous Catalytic Materials
by Joseph Lantos, Narendra Kumar and Basudeb Saha
Catalysts 2024, 14(5), 317; https://doi.org/10.3390/catal14050317 - 10 May 2024
Viewed by 497
Abstract
Fine chemicals are produced in small annual volume batch processes (often <10,000 tonnes per year), with a high associated price (usually >USD 10/kg). As a result of their usage in the production of speciality chemicals, in areas including agrochemicals, fragrances, and pharmaceuticals, the [...] Read more.
Fine chemicals are produced in small annual volume batch processes (often <10,000 tonnes per year), with a high associated price (usually >USD 10/kg). As a result of their usage in the production of speciality chemicals, in areas including agrochemicals, fragrances, and pharmaceuticals, the need for them will remain high for the foreseeable future. This review article assesses current methods used to produce fine chemicals with heterogeneous catalysts, including both well-established and newer experimental methods. A wide range of methods, utilising microporous and mesoporous catalysts, has been explored, including their preparation and modification before use in industry. Their potential drawbacks and benefits have been analysed, with their feasibility compared to newer, recently emerging catalysts. The field of heterogeneous catalysis for fine chemical production is a dynamic and ever-changing area of research. This deeper insight into catalytic behaviour and material properties will produce more efficient, selective, and sustainable processes in the fine chemical industry. The findings from this article will provide an excellent foundation for further exploration and a critical review in the field of fine chemical production using micro- and mesoporous heterogeneous catalysts. Full article
(This article belongs to the Special Issue Microporous and Mesoporous Materials for Catalytic Applications)
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21 pages, 3761 KiB  
Article
Promoter Impact on 5Ni/SAPO-5 Catalyst for H2 Production via Methane Partial Oxidation
by Abdulaziz Al-Anazi, Omer Bellahwel, Kavitha C., Jehad Abu-Dahrieh, Ahmed A. Ibrahim, S. Santhosh, Ahmed E. Abasaeed, Anis H. Fakeeha and Ahmed S. Al-Fatesh
Catalysts 2024, 14(5), 316; https://doi.org/10.3390/catal14050316 - 10 May 2024
Viewed by 435
Abstract
Compared to steam reforming techniques, partial oxidation of methane (POM) is a promising technology to improve the efficiency of synthesizing syngas, which is a mixture of CO and H2. In this study, partial oxidation of methane (POM) was used to create [...] Read more.
Compared to steam reforming techniques, partial oxidation of methane (POM) is a promising technology to improve the efficiency of synthesizing syngas, which is a mixture of CO and H2. In this study, partial oxidation of methane (POM) was used to create syngas, a combination of CO and H2, using the SAPO-5-supported Ni catalysts. Using the wetness impregnation process, laboratory-synthesized Ni promoted with Sr, Ce, and Cu was used to modify the SAPO-5 support. The characterization results demonstrated that Ni is appropriate for the POM due to its crystalline structure, improved metal support contact, and increased thermal stability with Sr, Ce, and Cu promoters. During POM at 600 °C, the synthesized 5Ni+1Sr/SAPO-5 catalyst sustained stability for 240 min on stream. While keeping the reactants stoichiometric ratio of (CH4:O2 = 2:1), the addition of Sr promoter and active metal Ni to the SAPO-5 increased the CH4 conversion from 41.13% to 49.11% and improved the H2/CO ratio of 3.33. SAPO-5-supported 5Ni+1Sr catalysts have great potential for industrial catalysis owing to their unique combination of several oxides. This composition not only boosts the catalyst’s activity but also promotes favorable physiochemical properties, resulting in improved production of syngas. Syngas is a valuable intermediate in various industrial processes. Full article
(This article belongs to the Section Catalytic Materials)
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20 pages, 7989 KiB  
Article
Au Nanoparticles Supported on Hydrotalcite-Based MMgAlOx (M=Cu, Ni, and Co) Composite: Influence of Dopants on the Catalytic Activity for Semi-Hydrogenation of C2H2
by Xun Sun, Wenrui Lv, Yanan Cheng, Huijuan Su, Libo Sun, Lijun Zhao, Zifan Wang and Caixia Qi
Catalysts 2024, 14(5), 315; https://doi.org/10.3390/catal14050315 - 10 May 2024
Viewed by 513
Abstract
Semi-hydrogenation of acetylene to ethylene over metal oxide-supported Au nanoparticles is an interesting topic. Here, a hydrotalcite-based MMgAlOx (M=Cu, Ni, and Co) composite oxide was exploited by introducing different Cu, Ni, and Co dopants with unique properties, and then used as support [...] Read more.
Semi-hydrogenation of acetylene to ethylene over metal oxide-supported Au nanoparticles is an interesting topic. Here, a hydrotalcite-based MMgAlOx (M=Cu, Ni, and Co) composite oxide was exploited by introducing different Cu, Ni, and Co dopants with unique properties, and then used as support to obtain Au/MMgAlOx catalysts via a modified deposition–precipitation method. XRD, BET, ICP-OES, TEM, Raman, XPS, and TPD were employed to investigate their physic-chemical properties and catalytic performances for the semi-hydrogenation of acetylene to ethylene. Generally, the catalytic activity of the Cu-modified Au/CuMgAlOx catalyst was higher than that of the other modified catalysts. The TOR for Au/CuMgAlOx was 0.0598 h−1, which was 30 times higher than that of Au/MgAl2O4. The SEM and XRD results showed no significant difference in structure or morphology after introducing the dopants. These dopants had an unfavorable effect on the Au particle size, as confirmed by the TEM studies. Accordingly, the effects on catalytic performance of the M dopant of the obtained Au/MMgAlOx catalyst were improved. Results of Raman, NH3-TPD, and CO2-TPD confirmed that the Au/CuMgAlOx catalyst had more basic sites, which is beneficial for less coking on the catalyst surface after the reaction. XPS analysis showed that gold nanoparticles exhibited a partially oxidized state at the edges and surfaces of CuMgAlOx. Besides an increased proportion of basic sites on Au/CuMgAlOx catalysts, the charge transfer from nanogold to the Cu-doped matrix support probably played a positive role in the selective hydrogenation of acetylene. The stability and deactivation of Au/CuMgAlOx catalysts were also discussed and a possible reaction mechanism was proposed. Full article
(This article belongs to the Special Issue Nanomaterials in Catalysis: Design, Characterization and Applications)
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12 pages, 2032 KiB  
Article
Metal–Organic Framework Fe-BTC as Heterogeneous Catalyst for Electro-Fenton Treatment of Tetracycline
by Taylor Mackenzie Fisher, Alexsandro J. dos Santos and Sergi Garcia-Segura
Catalysts 2024, 14(5), 314; https://doi.org/10.3390/catal14050314 - 10 May 2024
Viewed by 523
Abstract
This study explores the use of the iron-containing metal–organic framework (MOF), Basolite®F300, as a heterogeneous catalyst for electrochemically-driven Fenton processes. Electrochemical advanced oxidation processes (EAOPs) have shown promise on the abatement of recalcitrant organic pollutants such as pharmaceuticals. Tetracyclines (TC) are [...] Read more.
This study explores the use of the iron-containing metal–organic framework (MOF), Basolite®F300, as a heterogeneous catalyst for electrochemically-driven Fenton processes. Electrochemical advanced oxidation processes (EAOPs) have shown promise on the abatement of recalcitrant organic pollutants such as pharmaceuticals. Tetracyclines (TC) are a frequently used class of antibiotics that are now polluting surface water and groundwater sources worldwide. Acknowledging the fast capability of EAOPs to treat persistent pharmaceutical pollutants, we propose an electrochemical Fenton treatment process that is catalyzed by the use of a commercially available MOF material to degrade TC. The efficiency of H2O2 generation in the IrO2/carbon felt setup is highlighted. However, electrochemical oxidation with H2O2 production (ECO-H2O2) alone is not enough to achieve complete TC removal, attributed to the formation of weak oxidant species. Incorporating Basolite®F300 in the heterogeneous electro-Fenton (HEF) process results in complete TC removal within 40 min, showcasing its efficacy. Additionally, this study explores the effect of varying MOF concentrations, indicating optimal removal rates at 100 mg L−1 due to a balance of kinetics and limitation of active sites of the catalysts. Furthermore, the impact of the applied current on TC removal is investigated, revealing a proportional relationship between current and removal rates. The analysis of energy efficiency emphasizes 50 mA as the optimal current, however, balancing removal efficiency with electrical energy consumption. This work highlights the potential of Basolite®F300 as an effective catalyst in the HEF process for pollutant abatement, providing valuable insights into optimizing electrified water treatment applications with MOF nanomaterials to treat organic pollutants. Full article
(This article belongs to the Section Environmental Catalysis)
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17 pages, 5003 KiB  
Article
Perovskite Oxide Catalysts for Enhanced CO2 Reduction: Embroidering Surface Decoration with Ni and Cu Nanoparticles
by Andrea Osti, Lorenzo Rizzato, Jonathan Cavazzani, Ambra Meneghello and Antonella Glisenti
Catalysts 2024, 14(5), 313; https://doi.org/10.3390/catal14050313 - 10 May 2024
Viewed by 520
Abstract
The imperative reduction of carbon dioxide into valuable fuels stands as a crucial step in the transition towards a more sustainable energy system. Perovskite oxides, with their high compositional and property adjustability, emerge as promising catalysts for this purpose, whether employed independently or [...] Read more.
The imperative reduction of carbon dioxide into valuable fuels stands as a crucial step in the transition towards a more sustainable energy system. Perovskite oxides, with their high compositional and property adjustability, emerge as promising catalysts for this purpose, whether employed independently or as a supporting matrix for other active metals. In this study, an A-site-deficient La0.9FeO3 perovskite underwent surface decoration with Ni, Cu or Ni + Cu via a citric acid-templated wet impregnation method. Following extensive characterization through XRD, N2 physisorption, H2-TPR, SEM-EDX, HAADF STEM-EDX mapping, CO2-TPD and XPS, the prepared powders underwent reduction under diluted H2 to yield metallic nanoparticles (NPs). The prepared catalysts were then evaluated for CO2 reduction in a CO2/H2 = 1/4 mixture. The deposition of Ni or Cu NPs on the perovskite support significantly enhanced the conversion of CO2, achieving a 50% conversion rate at 500 °C, albeit resulting in only CO as the final product. Notably, the catalyst featuring Ni-Cu co-deposition outperformed in the intermediate temperature range, exhibiting high selectivity for CH4 production around 350 °C. For this latter catalyst, a synergistic effect of the metal–support interaction was evidenced by H2-TPR and CO2-TPD experiments as well as a better nanoparticle dispersion. A remarkable stability in a 20 h time-span was also demonstrated for all catalysts, especially the one with Ni-Cu co-deposition. Full article
(This article belongs to the Special Issue Advanced Research of Perovskite Materials as Catalysts)
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20 pages, 8018 KiB  
Article
Highly Efficient PtSn/Al2O3 and PtSnZnCa/Al2O3 Catalysts for Ethane Dehydrogenation: Influence of Catalyst Pretreatment Atmosphere
by Seetharamulu Podila, Abdulrahim A. Al-Zahrani, Muhammad A. Daous and Hesham Alhumade
Catalysts 2024, 14(5), 312; https://doi.org/10.3390/catal14050312 - 9 May 2024
Viewed by 421
Abstract
Increased demand for ethylene has motivated direct ethane dehydrogenation over Pt-based catalysts. PtSn/γ-Al2O3 and PtSnZnCa/γ-Al2O3 catalysts were investigated with the aim of understanding the effect of the pretreatment environment on the state of dispersed Pt for ethane [...] Read more.
Increased demand for ethylene has motivated direct ethane dehydrogenation over Pt-based catalysts. PtSn/γ-Al2O3 and PtSnZnCa/γ-Al2O3 catalysts were investigated with the aim of understanding the effect of the pretreatment environment on the state of dispersed Pt for ethane dehydrogenation. The catalysts were prepared by the impregnation method and pretreated in different environments like static air (SA), flowing air (FA), and nitrogen (N2) atmospheres. A comprehensive characterization of the catalysts was performed using Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), Temperature-Programmed Reduction (TPR), NH3 Temperature-Programmed Desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), and Transmission Electron Microscopy (TEM) techniques. The results reveal that the PtSn on Al2O3 catalyst pretreated in the static air environment (PtSn-SA) exhibits 21% ethylene yield with 95% selectivity at 625 °C. XPS analysis found more platinum and tin on the catalyst surface after static air treatment. The overall acidity of the catalysts decreased after thermal treatment in static air. Elemental mapping demonstrated that Pt agglomeration was pronounced in catalysts calcined under flowing air and nitrogen. These factors are responsible for the enhanced activity of the PtSn-SA catalyst compared to the other catalysts. The addition of Zn and Ca to the PtSn catalysts increases the yield of the catalyst calcined in static air (PtSnZnCa-SA). The PtSnZnCa-SA catalyst showed the highest ethylene yield of 27% with 99% selectivity and highly stable activity at 625 °C for 10 h. Full article
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22 pages, 9063 KiB  
Article
Remediation of Polycyclic Aromatic Hydrocarbon-Contaminated Soil by Using Activated Persulfate with Carbonylated Activated Carbon Supported Nanoscale Zero-Valent Iron
by Changzhao Chen, Zhe Yuan, Shenshen Sun, Jiacai Xie, Kunfeng Zhang, Yuanzheng Zhai, Rui Zuo, Erping Bi, Yufang Tao and Quanwei Song
Catalysts 2024, 14(5), 311; https://doi.org/10.3390/catal14050311 - 8 May 2024
Viewed by 537
Abstract
Soil contamination by polycyclic aromatic hydrocarbons (PAHs) has been an environmental issue worldwide, which aggravates the ecological risks faced by animals, plants, and humans. In this work, the composites of nanoscale zero-valent iron supported on carbonylated activated carbon (nZVI-CAC) were prepared and applied [...] Read more.
Soil contamination by polycyclic aromatic hydrocarbons (PAHs) has been an environmental issue worldwide, which aggravates the ecological risks faced by animals, plants, and humans. In this work, the composites of nanoscale zero-valent iron supported on carbonylated activated carbon (nZVI-CAC) were prepared and applied to activate persulfate (PS) for the degradation of PAHs in contaminated soil. The prepared nZVI-CAC catalyst was characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). It was found that the PS/nZVI-CAC system was superior for phenanthrene (PHE) oxidation than other processes using different oxidants (PS/nZVI-CAC > PMS/nZVI-CAC > H2O2/nZVI-CAC) and it was also efficient for the degradation of other six PAHs with different structures and molar weights. Under optimal conditions, the lowest and highest degradation efficiencies for the selected PAHs were 60.8% and 90.7%, respectively. Active SO4−• and HO were found to be generated on the surface of the catalysts, and SO4−• was dominant for PHE oxidation through quenching experiments. The results demonstrated that the heterogeneous process using activated PS with nZVI-CAC was effective for PAH degradation, which could provide a theoretical basis for the remediation of PAH-polluted soil. Full article
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12 pages, 208 KiB  
Correction
Correction: Zhou et al. Removal of Emerging Organic Pollutants by Zeolite Mineral (Clinoptilolite) Composite Photocatalysts in Drinking Water and Watershed Water. Catalysts 2024, 14, 216
by Pengfei Zhou, Fei Wang, Yanbai Shen, Xinhui Duan, Sikai Zhao, Xiangxiang Chen and Jinsheng Liang
Catalysts 2024, 14(5), 310; https://doi.org/10.3390/catal14050310 - 8 May 2024
Viewed by 356
Abstract
There was an error in the original publication [...] Full article
14 pages, 7462 KiB  
Article
Strong and Hierarchical Ni(OH)2/Ni/rGO Composites as Multifunctional Catalysts for Excellent Water Splitting
by Lixin Wang, Ailing Song, Yue Lu, Manman Duanmu, Zhipeng Ma, Xiujuan Qin and Guangjie Shao
Catalysts 2024, 14(5), 309; https://doi.org/10.3390/catal14050309 - 7 May 2024
Viewed by 424
Abstract
The lack of efficient and non-precious metal catalysts poses a challenge for electrochemical water splitting in hydrogen and oxygen evolution reactions. Here, we report on the preparation of growing Ni(OH)2 nanosheets in situ on a Ni and graphene hybrid using supergravity electrodeposition [...] Read more.
The lack of efficient and non-precious metal catalysts poses a challenge for electrochemical water splitting in hydrogen and oxygen evolution reactions. Here, we report on the preparation of growing Ni(OH)2 nanosheets in situ on a Ni and graphene hybrid using supergravity electrodeposition and the hydrothermal method. The obtained catalyst displays outstanding performance with small overpotentials of 161.7 and 41 mV to acquire current densities of 100 and 10 mA cm−2 on hydrogen evolution reaction, overpotentials of 407 and 331 mV to afford 100 and 50 mA cm−2 on oxygen evolution reaction, and 10 mA·cm−2 at a cell voltage of 1.43 V for water splitting in 1 M KOH. The electrochemical activity of the catalyst is higher than most of the earth-abundant materials reported to date, which is mainly due to its special hierarchical structure, large surface area, and good electrical conductivity. This study provides new tactics for enhancing the catalytic performance of water electrolysis. Full article
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29 pages, 3152 KiB  
Review
Dehydration of Methanol to Dimethyl Ether—Current State and Perspectives
by Lucjan Chmielarz
Catalysts 2024, 14(5), 308; https://doi.org/10.3390/catal14050308 - 7 May 2024
Viewed by 694
Abstract
The main groups of catalytic materials used in the conversion of methanol to dimethyl ether (the MTD process) were presented with respect to their advantages, disadvantages, and the methods of their modifications, resulting in catalysts with improved activity, selectivity, and stability. In particular, [...] Read more.
The main groups of catalytic materials used in the conversion of methanol to dimethyl ether (the MTD process) were presented with respect to their advantages, disadvantages, and the methods of their modifications, resulting in catalysts with improved activity, selectivity, and stability. In particular, the effects of strength, surface concentration, and the type of acid sites, the porous structure and morphology of the catalytic materials, the role of catalyst activators, and others, were considered. The prosed mechanisms of the MTD process over various types of catalysts are presented. Moreover, the advantages of membrane reactors for the MTD process are presented and analysed. The perspectives in the development of effective catalysts for the dehydration of methanol to dimethyl ether are presented and discussed. Full article
(This article belongs to the Section Catalytic Materials)
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23 pages, 6273 KiB  
Article
Influence of Power Fluctuation on Ni-Based Electrode Degradation and Hydrogen Evolution Reaction Performance in Alkaline Water Splitting: Probing the Effect of Renewable Energy on Water Electrolysis
by Congying Liu, Bing Lin, Hailong Zhang, Yingying Wang, Hangzhou Wang, Junlei Tang and Caineng Zou
Catalysts 2024, 14(5), 307; https://doi.org/10.3390/catal14050307 - 6 May 2024
Viewed by 528
Abstract
The combination of water electrolysis and renewable energy to produce hydrogen is a promising way to solve the climate and energy crisis. However, the fluctuating characteristics of renewable energy not only present a significant challenge to the use of water electrolysis electrodes, but [...] Read more.
The combination of water electrolysis and renewable energy to produce hydrogen is a promising way to solve the climate and energy crisis. However, the fluctuating characteristics of renewable energy not only present a significant challenge to the use of water electrolysis electrodes, but also limit the development of the hydrogen production industry. In this study, the effects of three different types of waveforms (square, step, and triangle, which were used to simulate the power input of renewable energy) on the electrochemical catalysis behavior of Ni plate cathodes for HER was investigated. During the test, the HER performance of the Ni cathode increased at first and then slightly decreased. The fluctuating power led to the degradation of the Ni cathode surface, which enhanced the catalysis effect by increasing the catalytic area and the active sites. However, prolonged operation under power fluctuations could have damaged the morphology of the electrode surface and the substances comprising this surface, potentially resulting in a decline in catalytic efficiency. In addition, the electrochemical catalysis behavior of the prepared FeNiMo-LDH@NiMo/SS cathode when subjected to square-wave potential with different fluctuation amplitudes was also extensively studied. A larger amplitude of fluctuating power led to a change in the overpotential and stability of the LDH electrode, which accelerated the degradation of the cathode. This research provides a technological basis for the coupling of water electrolysis and fluctuating renewable energy and thus offers assistance to the development of the “green hydrogen” industry. Full article
(This article belongs to the Section Electrocatalysis)
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14 pages, 6216 KiB  
Article
Study on NH3-SCR Activity and HCl/H2O Tolerance of Titanate-Nanotube-Supported MnOx-CeO2 Catalyst at Low Temperature
by Qiulin Wang, Feng Liu, Zhihao Wu, Jing Jin, Xiaoqing Lin, Shengyong Lu and Juan Qiu
Catalysts 2024, 14(5), 306; https://doi.org/10.3390/catal14050306 - 5 May 2024
Viewed by 505
Abstract
Manganese oxide-cerium oxide supported on titanate nanotubes (i.e., MnCe/TiNTs) were prepared and their catalytic activities towards NH3-SCR of NO were tested. The results indicated that the MnCe/TiNT catalyst can achieve a high NO removal efficiency above 95% within the temperature range [...] Read more.
Manganese oxide-cerium oxide supported on titanate nanotubes (i.e., MnCe/TiNTs) were prepared and their catalytic activities towards NH3-SCR of NO were tested. The results indicated that the MnCe/TiNT catalyst can achieve a high NO removal efficiency above 95% within the temperature range of 150–350 °C. Even after exposure to a HCl-containing atmosphere for 2 h, the NO removal efficiency of the MnCe/TiNT catalyst maintains at approximately 90% at 150 °C. This is attributed to the large specific surface area as well as the unique hollow tubular structure of TiNTs that exposes more Ce atoms, which preferentially react with HCl and thus protect the active Mn atoms. Moreover, the abundant OH groups on TiNTs serve as Brønsted acid sites and provide H protons to expel Cl atom from the catalyst surface. The irreversible deactivation caused by HCl can be alleviated by H2O. That is because the dissociated adsorption of H2O on TiNTs forms additional OH groups and relieves HCl poisoning. Full article
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13 pages, 4005 KiB  
Article
Binuclear Dioxomolybdenum(VI) Complex Based on Bis(2-pyridinecarboxamide) Ligand as Effective Catalyst for Fuel Desulfurization
by Fátima Mirante, Catarina N. Dias, André Silva, Sandra Gago and Salete S. Balula
Catalysts 2024, 14(5), 305; https://doi.org/10.3390/catal14050305 - 4 May 2024
Viewed by 548
Abstract
A binuclear dioxomolybdenum catalyst [(MoO2Cl2)2(L)] (1) (with L (1S,2S)-N,N′-bis(2-pyridinecarboxamide)-1,2-cyclohexane) was prepared and used as catalyst for the desulfurization of a multicomponent model fuel containing the most refractory [...] Read more.
A binuclear dioxomolybdenum catalyst [(MoO2Cl2)2(L)] (1) (with L (1S,2S)-N,N′-bis(2-pyridinecarboxamide)-1,2-cyclohexane) was prepared and used as catalyst for the desulfurization of a multicomponent model fuel containing the most refractory sulfur compounds in real fuels. This complex was shown to have a high efficiency to oxidize the aromatic benzothiophene derivative compounds present in fuels, mainly using a biphasic 1:1 model fuel/MeOH system. This process conciliates catalytic oxidative and extractive desulfurization, resulting in the oxidation of the sulfur compounds in the polar organic solvent. The oxidative catalytic performance of (1) was shown to be influenced by the presence of water in the system. Using 50% aq. H2O2, it was possible to reuse the catalyst and the extraction solvent, MeOH, during ten consecutive cycles without loss of desulfurization efficiency. Full article
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15 pages, 5279 KiB  
Article
Functionalized Chitosan and Alginate Composite Hydrogel-Immobilized Laccase with Sustainable Biocatalysts for the Effective Removal of Organic Pollutant Bisphenol A
by Hong Zhang, Xin Zhang, Lei Wang, Bo Wang, Xu Zeng and Bo Ren
Catalysts 2024, 14(5), 304; https://doi.org/10.3390/catal14050304 - 3 May 2024
Viewed by 628
Abstract
The immobilization of enzymes is an important strategy to improve their stability and reusability. Enzyme immobilization technology has broad application prospects in biotechnology, biochemistry, environmental remediation, and other fields. In this study, composites of chitosan (CS) and sodium alginate (SA) with Cu2+ [...] Read more.
The immobilization of enzymes is an important strategy to improve their stability and reusability. Enzyme immobilization technology has broad application prospects in biotechnology, biochemistry, environmental remediation, and other fields. In this study, composites of chitosan (CS) and sodium alginate (SA) with Cu2+ forming a double-network crosslinked structure of hydrogels were prepared and used for the immobilization of laccase. Fourier infrared spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy tests revealed that laccase molecules were immobilized on the composite hydrogel surface by a covalent bonding method. Compared to free laccase, the pH, temperature, and storage stability of the immobilized laccase were markedly improved. In addition, the immobilized laccase could be easily separated from the reaction system and reused, and it maintained 81.6% of its initial viability after six cycles of use. Bisphenol A (BPA) in polluted water was efficiently degraded using immobilized laccase, and the factors affecting the degradation efficiency were analyzed. Under the optimal conditions, the BPA removal was greater than 82%, and the addition of a small amount of ABTS had a significant effect on BPA degradation, with a removal rate of up to 99.1%. Experimental results indicated that immobilized laccases had enormous potential in actual industrial applications. Full article
(This article belongs to the Section Biocatalysis)
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