Catalysts

17 pages, 5500 KiB

Open AccessArticle

Optimization of Palladium-Catalyzed One-Pot Synthesis of Functionalized Furans for High-Yield Production: A Study of Catalytic and Reaction Parameters

by Kheira Haiouani, Sherif Hegazy, Huda Alsaeedi, Mikhael Bechelany and Ahmed Barhoum

Catalysts 2024, 14(10), 712; https://doi.org/10.3390/catal14100712 - 11 Oct 2024

Abstract

This study investigates the palladium-catalyzed one-pot synthesis of functionalized furans from 1,3-Dicarbonyl compounds and alkenyl bromides, focusing on various catalysts and reaction parameters. Different catalysts, including PdCl₂(CH₃CN)₂, Pd(OAc)₂, and Pd(acac)₂ as well as solvents, bases, and oxidants, were systematically evaluated. PdCl₂(CH₃CN)₂ emerged [...] Read more.

This study investigates the palladium-catalyzed one-pot synthesis of functionalized furans from 1,3-Dicarbonyl compounds and alkenyl bromides, focusing on various catalysts and reaction parameters. Different catalysts, including PdCl₂(CH₃CN)₂, Pd(OAc)₂, and Pd(acac)₂ as well as solvents, bases, and oxidants, were systematically evaluated. PdCl₂(CH₃CN)₂ emerged as the most effective catalyst, achieving a remarkable yield of 94%. Optimal reaction conditions were identified as PdCl₂(CH₃CN)₂ in dioxane at 80 °C with K₂CO₃ as the base and CuCl₂ as the oxidant. This study also explored various 1,3-diketones including Cyclohexane-1,3-dione, 5,5-Dimethylcyclohexane-1,3-dione, 2H-Pyran-3,5(4H,6H)-dione, Cyclopentane-1,3-dione, Pentane-2,4-dione, Ethyl 3-oxobutanoate, 1,3-Diphenylpropane-1,3-dione, 1,3-Dip-tolylpropane-1,3-dione, 1,3-Bis(4-chlorophenyl)propane-1,3-dione, and 1,3-Bis(4-bromo- phenyl)propane-1,3-dione, alongside different alkenyl bromides such as allyl bromide, (E)-1-Bromo-3,4-dimethylpent-2-ene, 1-Bromo-3-methylbut-2-ene, 3-Bromocyclohex-1-ene, and (E)-1-Bromohex-2-ene. These variations demonstrated the method’s versatility and the significant impact of substituents on reactivity and reaction yield. These findings highlight the importance of optimizing reaction conditions to maximize efficiency and provide insights into improving catalytic processes for enhanced product yields. Full article

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

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14 pages, 2649 KiB

Open AccessArticle

Enhanced Photocatalytic Activity in Photocatalytic Concrete: Synthesis, Characterization, and Comprehensive Performance Assessment of Nano-TiO₂-Modified Recycled Aggregates

by Xiucheng Zhang, Weizhi Chen, Wencong Lin, Jiansheng Zheng, Guohui Yan and Xuefei Chen

Catalysts 2024, 14(10), 711; https://doi.org/10.3390/catal14100711 - 11 Oct 2024

Abstract

This study presents an exhaustive exploration into the development and rigorous evaluation of nano-TiO₂-modified recycled aggregates (NT@RAs) as an environmentally sustainable substitute for natural aggregates in concrete applications. A methodical framework was devised for the synthesis and thorough characterization of NT@RAs, [...] Read more.

This study presents an exhaustive exploration into the development and rigorous evaluation of nano-TiO₂-modified recycled aggregates (NT@RAs) as an environmentally sustainable substitute for natural aggregates in concrete applications. A methodical framework was devised for the synthesis and thorough characterization of NT@RAs, emphasizing the optimization of nano-TiO₂ loading onto the RA surface and within its intricate porous structure. The investigation encompassed three distinct types of recycled aggregates: recycled glass sands (RGSs), recycled clay brick sands (RCBSs), and recycled concrete sands (RCSs). Of particular interest, NT@RGS, with its properties of an inherently smooth surface texture and low water absorption, was found to exert a favorable influence on the rheological behavior of concrete, manifested in reduced yield stress, thereby underscoring the potential for fine-tuning mix designs to enhance workability. As the substitution levels of NT@RGS and NT@RCBS escalated, an initial decrement in compressive strength was discernible, which subsequently reversed to strength restoration at optimized substitution ratios. This phenomenon is attributed to the synergistic interplay among NT@RA components. Remarkably, NT@RA-incorporated concrete demonstrated unparalleled self-cleaning abilities, surpassing the performance of concrete with direct nano-TiO₂ powder incorporation. This comprehensive research contributes significantly to the advancement in sustainable, high-performance photocatalytic construction materials within the realm of concrete technology. It underscores the potential for enhancing not only the rheological and mechanical properties but also the environmental responsiveness of concrete through the innovative utilization of NT@RAs. Full article

(This article belongs to the Special Issue Catalytic Purification of Pollutants and Catalytic Conversion of Solid Wastes, 2nd Edition)

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11 pages, 1431 KiB

Open AccessFeature PaperArticle

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

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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11 pages, 2189 KiB

Open AccessArticle

Nano-TiO₂-Enhanced Surface Functionalization of Recycled Concrete Aggregates for Improved Degradation Efficiency of Low-Concentration Sulfur Dioxide

by Xue-Fei Chen, Wei-Zhi Chen, Xiu-Cheng Zhang, Wen-Cong Lin, Jian-Sheng Zheng and Guo-Hui Yan

Catalysts 2024, 14(10), 709; https://doi.org/10.3390/catal14100709 - 10 Oct 2024

Abstract

This study investigates the enhancement of recycled concrete aggregate (RCA) surfaces with nano-TiO₂ for an improved degradation of low-concentration sulfur dioxide (SO₂). Nano-TiO₂ particles, known for their photocatalytic properties, were uniformly deposited on RCA surfaces. Upon exposure to SO [...] Read more.

This study investigates the enhancement of recycled concrete aggregate (RCA) surfaces with nano-TiO₂ for an improved degradation of low-concentration sulfur dioxide (SO₂). Nano-TiO₂ particles, known for their photocatalytic properties, were uniformly deposited on RCA surfaces. Upon exposure to SO₂ under light irradiation, the functionalized RCA exhibited significantly improved degradation efficiency. This was attributed to the photo-induced oxidation of SO₂ by nano-TiO₂. Enhanced degradation was further observed under UV light due to increased photoactivation. The nano-TiO₂ coating also showed good durability and stability, ensuring long-term effectiveness. The experimental outcomes reveal that TiO₂-treated recycled aggregates exhibit an 85% retained photocatalytic activity post five cycles of reuse. Furthermore, the investigation employs a second-order polynomial-based mathematical fitting function to generate a three-dimensional trend surface, visually illustrating the inverse relationships between sulfur dioxide degradation and environmental variables, such as initial concentration and flow rates. Finally, this study demonstrates the potential of nano-TiO₂-modified RCA for mitigating the environmental impact of low-concentration SO₂, contributing to the development of more sustainable construction materials and broadening RCA’s applications in environmental remediation. Full article

(This article belongs to the Special Issue Designing Catalytic Desulfurization Processes to Prepare Clean Fuels, 2nd Edition)

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12 pages, 2675 KiB

Open AccessFeature PaperArticle

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

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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12 pages, 6564 KiB

Open AccessArticle

Tailoring Mesoporosity of Multi-Hydroxyls Hyper-Crosslinked Organic Polymers for Reinforced Ambient Chemical Fixation of CO₂

by Zengjing Guo, Shuguang Ning, Shicheng Xu, Yongying Zhang, Yifan Dong and Hongjing Han

Catalysts 2024, 14(10), 707; https://doi.org/10.3390/catal14100707 - 10 Oct 2024

Abstract

Ambient condition-determined chemical CO₂ fixation affords great promise for remitting the pressure of CO₂ release. The construction of a microporous environment easily captures CO₂ molecules around the reactive sites of the catalyst to reinforce the reaction process. Herein, multi-hydroxyl-containing hyper-crosslinked [...] Read more.

Ambient condition-determined chemical CO₂ fixation affords great promise for remitting the pressure of CO₂ release. The construction of a microporous environment easily captures CO₂ molecules around the reactive sites of the catalyst to reinforce the reaction process. Herein, multi-hydroxyl-containing hyper-crosslinked organic polymers (HCPs-OH-n) are synthesized by the polymerization of 1,4-dichlorobenzyl (DCX) and m-trihydroxybenzene in the monosaccharide form in a Friedel–Crafts alkylation hypercrosslinking process (FCAHP). By tuning the DCX ratio in the FCAHP, the structural properties can be regulated to create a more microporous surface in the HCPs-OH-n; meanwhile, the formed multi-hydroxyl species in the microporous environment could induce the easy interaction between hydroxyls and epoxides by forming a hydrogen bond, which improves the activation of epoxides during the cycloaddition reaction to synthesize the cyclic carbonates at ambient conditions. The structural properties suggest that HCPs-OH-n possess a large surface area with appreciable microporous and mesoporous distribution. As expected, the HCPs-OH-3 bearing the most abundant mesoporosity affords the highest reactivity in the chemical CO₂ fixation to cyclic carbonates and is endowed with rational recoverability. Full article

(This article belongs to the Section Catalytic Materials)

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11 pages, 4066 KiB

Open AccessArticle

Engineering the C-Terminal Region to Enhance the Thermal Stability of Streptomyces hygroscopicus Transglutaminase

by Zhaoxiang Wang, Kangkang Chen, Song Liu, Jianghua Li and Guocheng Du

Catalysts 2024, 14(10), 706; https://doi.org/10.3390/catal14100706 - 10 Oct 2024

Abstract

To enhance the applied value of transglutaminase (TGase), various methods have been employed to improve its catalytic properties. However, most modifications have targeted the N-terminus, while the role of the C-terminus in determining TGase properties has been overlooked. In this study, we focused [...] Read more.

To enhance the applied value of transglutaminase (TGase), various methods have been employed to improve its catalytic properties. However, most modifications have targeted the N-terminus, while the role of the C-terminus in determining TGase properties has been overlooked. In this study, we focused on enhancing the thermal stability of Streptomyces hygroscopicus TGase by engineering its C-terminal region. Modeling revealed that the C-terminal loop interacts with the N-terminal loop through hydrogen bonds between Trp331 and N-terminal residues (Asp19, Ala20, Tyr21). Removing the last C-terminal residue (Ser322) had no significant effect on TGase stability, but deleting additional residues (Trp331, Gly330, Gln299) led to inactivation. Substituting Trp331 with Ala reduced TGase’s half-life at 50 °C and specific activity by 50% and 70%, respectively, highlighting the importance of C-terminal interactions in TGase stability. We also attempted to fuse three self-assembling amphipathic peptides (SAPs) (EAK16, KL15, ELK16) and a C-terminal sequence (IGCIILT) from Sulfolobus tokodaii RNase HI to TGase. The fusion of IGCIILT increased TGase’s half-life by 1.5-fold without affecting specific activity, while the three SAPs had little effect on stability. Structural analysis showed that the fusion of IGCIILT raised TGase’s melting temperature by 5.2 °C and altered its tertiary structure. Our results indicate that the C-terminus is important for modulating TGase properties, and fusing “stabilization tags” like IGCIILT at the C-terminus is a promising strategy to enhance thermal stability. Full article

(This article belongs to the Section Biocatalysis)

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17 pages, 4252 KiB

Open AccessArticle

Novel Biochar-Modified ZIF-8 Metal–Organic Frameworks as a Potential Material for Optoelectronic and Electrochemical Energy Storage Applications

by Sarah Al-atawi, Meshari M. Aljohani, Taymour A. Hamdalla, S. A. Al-Ghamdi, Abdulrhman M. Alsharari and Syed Khasim

Catalysts 2024, 14(10), 705; https://doi.org/10.3390/catal14100705 - 10 Oct 2024

Abstract

Herein, we report the preparation of nanocomposites using activated biochar derived from rice husk (RHBC) by doping with a metal–organic framework, namely the zeolitic imidazolate framework (ZIF-8). The morphological and structural characterization of the prepared nanocomposite was performed using SEM, BET, XRD, FTIR, [...] Read more.

Herein, we report the preparation of nanocomposites using activated biochar derived from rice husk (RHBC) by doping with a metal–organic framework, namely the zeolitic imidazolate framework (ZIF-8). The morphological and structural characterization of the prepared nanocomposite was performed using SEM, BET, XRD, FTIR, TGA, and UV–Vis spectroscopy. The average particle sizes as observed from SEM micrographs for ZIF-8 and ZIF-8@RHBC were 67 nm and 78 nm, respectively. The BET surface analysis of the ZIF-8@RHBC composite showed a value of 308 m²/g and a pore diameter of about 42.56 A°. The inclusion of RHBC in ZIF-8 resulted in a 4% increase in the optical band gap and a 5% increase in the optical conductivity. The electrochemical properties of this nanocomposite were investigated through cyclic voltammetry, and it was observed that ZIF-8@RHBC showed improved CV curves in comparison to bare ZIF-8. The specific capacitance of ZIF-8@RHBC was significantly enhanced from 348 F/g to 452 F/g at a 1 A/g current density after incorporating ZIF-8 into the RHBC matrix. The formation of a mesoporous structure in the ZIF-8@RHBC composite contributed to the improved diffusion rate at the electrode surface, resulting in excellent electrochemical features in the composite. Furthermore, the EIS studies confirmed the reduced charge transfer resistance and increased conduction at the electrode surface in the case of the ZIF-8@RHBC composite. Owing to the ease of its green synthesis and its excellent structural and morphological features and optical and electrochemical properties, this ZIF@RHBC nanocomposite could represent a novel multifunctional material to be used in optoelectronics and energy storage applications. Full article

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

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3 pages, 183 KiB

Open AccessEditorial

Catalysts: Advances in the Catalytic Behavior of Ion-Exchange Resins

by Eliana Ramírez, Montserrat Iborra and Javier Tejero

Catalysts 2024, 14(10), 704; https://doi.org/10.3390/catal14100704 - 9 Oct 2024

Abstract

Ion-exchange resins have been embraced as a relevant scientific development of the 20th century [...] Full article

(This article belongs to the Special Issue Advances in the Catalytic Behavior of Ion-Exchange Resins)

36 pages, 6366 KiB

Open AccessReview

Catalyst for the Generation of OH Radicals in Advanced Electrochemical Oxidation Processes: Present and Future Perspectives

by Raciel Jaimes-López, Adriana Jiménez-Vázquez, Samuel Pérez-Rodríguez, Luis Alberto Estudillo-Wong and Nicolas Alonso-Vante

Catalysts 2024, 14(10), 703; https://doi.org/10.3390/catal14100703 - 9 Oct 2024

Abstract

Heterogeneous Advanced Oxidation Processes (H-AOPs) are considered a new process for removing emerging pollutants. In this case, the high reactivity of hydroxyl radicals is used to degrade persistent organic pollutants. This review explores the state-of-the-art catalyst for hydroxyl radical generation in AOPs. As [...] Read more.

Heterogeneous Advanced Oxidation Processes (H-AOPs) are considered a new process for removing emerging pollutants. In this case, the high reactivity of hydroxyl radicals is used to degrade persistent organic pollutants. This review explores the state-of-the-art catalyst for hydroxyl radical generation in AOPs. As a parasite reaction, chloride ions appear in alkaline conditions and compete with the active sites. The theoretical foundation of catalyst performance is explored, focusing on the fundamental principles that govern the efficiency and mechanism of hydroxyl or chloride radical production. The synthesis and electronic modification sections explore the modifications of catalysts. It discusses key methodologies for catalyst preparation, with a particular emphasis on electronic modification that enhances both activity and stability. Finally, laboratory and pilot applications highlight the effectiveness of novel or modified catalysts in different scenarios. These last findings provide insights into the future directions for research and application, aiming to draw attention to the gap between laboratory studies and real-world implementations. Full article

(This article belongs to the Section Environmental Catalysis)

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15 pages, 1600 KiB

Open AccessArticle

Microwave-Assisted Synthesis of Symmetrical 1,4-Disubstituted Bis-1H-1,2,3-triazoles Using Copper N-Heterocyclic Carbene Catalysts

by Loren Taylor Mitchell, Erin Barnett, Max Hexom, Alexander Ruiz and Allen Schoffstall

Catalysts 2024, 14(10), 702; https://doi.org/10.3390/catal14100702 - 9 Oct 2024

Abstract

Bis-triazoles separated by a symmetrical linking group are joined at C4 of each triazole or at N1 of each triazole. Preparation of a series of bis-1H-1,2,3-triazoles derived from o-bis(azidomethyl)benzene and an alkyne is reported with use of copper N-heterocyclic carbene [...] Read more.

Bis-triazoles separated by a symmetrical linking group are joined at C4 of each triazole or at N1 of each triazole. Preparation of a series of bis-1H-1,2,3-triazoles derived from o-bis(azidomethyl)benzene and an alkyne is reported with use of copper N-heterocyclic carbene catalysis with microwave-assisted heating in an aqueous solvent. The products were symmetrical N1–N1′-bis-1H-1,2,3-triazoles. Additional syntheses utilized dialkynes and organic azides to prepare symmetrical C4–C4′-bis-1H-1,2,3-triazoles. Pure products were often obtained directly when water was used as the solvent with microwave-assisted heating. Results are given for experiments using conventional heating or no heating. Sonication results are given for a reaction where microwave-assisted heating was unsatisfactory. Full article

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

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52 pages, 6874 KiB

Open AccessReview

Aspects of Reaction Engineering for Biodiesel Production

by Afsanehsadat Larimi, Adam P. Harvey, Anh N. Phan, Mehdi Beshtar, Karen Wilson and Adam F. Lee

Catalysts 2024, 14(10), 701; https://doi.org/10.3390/catal14100701 - 8 Oct 2024

Abstract

Biodiesel is a non-toxic, drop-in liquid transportation fuel that is amenable to continuous production from sustainable biomass resources using catalytic technologies. A diverse range of catalysts and reactor technologies have been experimentally investigated and computationally modelled, for producing biodiesel (fatty acid methyl esters) [...] Read more.

Biodiesel is a non-toxic, drop-in liquid transportation fuel that is amenable to continuous production from sustainable biomass resources using catalytic technologies. A diverse range of catalysts and reactor technologies have been experimentally investigated and computationally modelled, for producing biodiesel (fatty acid methyl esters) from oil feedstocks by their esterification or transesterification with short-chain alcohols. Solid-acid and base catalysts are attractive for biodiesel production from renewable oil feedstocks due to their ease of separation from the desired biodiesel and glycerol by-product, use of Earth’s abundant elements, and suitability in continuous processes. Here, we review the technical challenges and opportunities in designing catalytic reactor systems for biodiesel production. Full article

(This article belongs to the Section Nanostructured Catalysts)

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5 pages, 172 KiB

Open AccessEditorial

Advanced Oxidation Catalysts—Innovative Approaches and Emerging Trends

by Meng Li and Chenxi Li

Catalysts 2024, 14(10), 700; https://doi.org/10.3390/catal14100700 - 8 Oct 2024

Abstract

Novel oxidation catalysts in water treatment and purification have garnered major attention due to the growing demand for clean water resources [...] Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysts)

4 pages, 199 KiB

Open AccessEditorial

Applications of Heterogeneous Catalysts in Green Chemistry

by Anand Kumar, Mohammed Ali H. S. Saad and Siham Y. Al-Qaradawi

Catalysts 2024, 14(10), 699; https://doi.org/10.3390/catal14100699 - 8 Oct 2024

Abstract

In our day-to-day lives, the utilization of industrial products, including chemicals and fuels, is essential [...] Full article

(This article belongs to the Special Issue Applications of Heterogeneous Catalysts in Green Chemistry)

11 pages, 7775 KiB

Open AccessArticle

Particle Conditioning for Improving Blockage Resistance of Denitration Catalysts in Sintering Flue Gas

by Deshan Sun, Peiyuan Li, Can Zhou, Linghong Chen, Yang Yang, Zhengda Yang, Yifan Wang and Chenghang Zheng

Catalysts 2024, 14(10), 698; https://doi.org/10.3390/catal14100698 - 8 Oct 2024

Abstract

The stability and safety of selective catalytic reduction (SCR) systems are threatened by potential catalyst blockages caused by fly ash deposition. This paper proposes to improve the blockage resistance of denitration catalysts for sintered fly ash through particle conditioning. X-ray fluorescence spectroscopy, scanning [...] Read more.

The stability and safety of selective catalytic reduction (SCR) systems are threatened by potential catalyst blockages caused by fly ash deposition. This paper proposes to improve the blockage resistance of denitration catalysts for sintered fly ash through particle conditioning. X-ray fluorescence spectroscopy, scanning electron microscopy, and laser particle analyzer were combined with laboratory heating experiments and field tests for systematic research. The results indicate that the composition and morphology of sintered fly ash are intrinsic factors contributing to catalyst blockage, while heating conditions act as external triggers. The sintered fly ash primarily exhibits a fluffy, branched cotton-like structure. Its main components are K₂O, Fe₂O₃, Na₂O, and CaO, with the alkali metal oxides of potassium and sodium comprising 20% to 50%. At ambient temperature, sintered fly ash presents no agglomeration, but significant agglomeration occurs as temperature increases. Particle conditioning effectively inhibits the agglomeration tendency of sintered fly ash. Field tests show that catalyst activity remains unaffected even under severe blockage conditions. The pressure drop across the catalyst layers increases progressively, with the first layer displaying the least pressure drop and the third displaying the most. After particle conditioning, the pressure drop across the catalyst is stabilized at values below 600 Pa, effectively mitigating the blockage issue in the denitrification catalyst for sintering flue gas. This research provides critical technical support for the stable ultra-low emission of NO_x from sintering flue gas. Full article

(This article belongs to the Section Industrial Catalysis)

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16 pages, 2920 KiB

Open AccessArticle

Seeds Combining Pyrrolidine Control the Framework Al Distribution of FER Zeolite to Enhance Its Performance in the Skeletal Isomerization of n-Butene

by Jinlong Fan, Xuedong Zhu, Fan Yang, Yarong Xu and Lantian Chen

Catalysts 2024, 14(10), 697; https://doi.org/10.3390/catal14100697 - 7 Oct 2024

Abstract

FER zeolites have a unique framework structure and acid distribution, and are widely studied as a catalyst for reactions such as n-butene skeletal isomerization and dimethyl ether carbonylation. The Brönsted acid site (BAS) located in the 10-member ring (10-MR) of FER zeolites [...] Read more.

FER zeolites have a unique framework structure and acid distribution, and are widely studied as a catalyst for reactions such as n-butene skeletal isomerization and dimethyl ether carbonylation. The Brönsted acid site (BAS) located in the 10-member ring (10-MR) of FER zeolites serves as the active site for the isomerization reaction of skeletal n-butene to produce isobutene. This study prepared five types of FER zeolites using different methods: using pyrrolidine (PY) alone as a template; using Na-form FER as seeds (SN) or H-form FER as seeds without organic structure directing agents (OSDAs); and combining the seeds of SN or SH with PY as OSDAs. The differences in the structure and acid distribution of the five zeolites were investigated, as well as their catalytic performance for the skeletal isomerization of n-butene. Experiments and characterization results showed that under hydrothermal synthesis conditions, the FER-PY+SH zeolites synthesized by using both H-form zeolites seeds and pyridine exhibited the highest aluminum concentrations at T1 and T3 sites, along with the greatest BAS located in the 10-MR. This unique composition contributed to the highest selectivity of isobutene. The FER-PY+SH catalyst was continuously used for 720 h at 350 °C, 0.1 MPa, and an n-butene mass space velocity of 2.0 h⁻¹ for three cycles of 2160 h. During this period, the conversion of n-butene was over 39%, while the selectivity of isobutene exceeded 95%. The FER-PY+SH catalyst exhibited excellent stability and activity. Full article

(This article belongs to the Special Issue Catalysis on Zeolites and Zeolite-Like Materials, 3rd Edition)

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13 pages, 3773 KiB

Open AccessFeature PaperArticle

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

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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15 pages, 4948 KiB

Open AccessArticle

Cobalt-Doped Hydrochar Derived from Microalgae as an Efficient Peroxymonosulfate Activator for Paraben Degradation

by Chenyan Hu, Suxin Wu, Jiali Wang and Lianguo Chen

Catalysts 2024, 14(10), 695; https://doi.org/10.3390/catal14100695 - 6 Oct 2024

Abstract

Hydrochar, an attractive member of the carbonaceous materials, is derived from biomass and projects great potential in peroxymonosulfate (PMS) activation, but has not been studied much. Herein, by using the large-scale cultured Chlorella vulgaris and field-collected bloom algae, a series of porous hydrochar [...] Read more.

Hydrochar, an attractive member of the carbonaceous materials, is derived from biomass and projects great potential in peroxymonosulfate (PMS) activation, but has not been studied much. Herein, by using the large-scale cultured Chlorella vulgaris and field-collected bloom algae, a series of porous hydrochar was synthesized via a facile hydrothermal carbonization reaction, while Co doping significantly increased their specific surface areas, carbonization degree, and surface functional groups. These Co-doped hydrochar (xCo-HC, x: amount of the Co precursor) could efficiently activate the PMS, resulting in nearly 100% removal of five common paraben pollutants within 40 min. A dosage of 0.2Co-HC of 0.15 g/L, a PMS concentration of 0.6 g/L, and an unadjusted pH of 6.4 were verified more appropriately for paraben degradation. The coexistence of Cl⁻, SO₄²⁻, and humic acid inhibited the degradation, while HCO₃⁻ showed an enhancing effect. No observable change was found at the presence of NO₃⁻. Quenching results illustrated that the produced •SO₄⁻ during the conversion of doped Co³⁺/Co²⁺ acted as the dominant active species for paraben degradation, while •O₂⁻, ¹O₂, and •OH contributed relatively less. The algae-based hydrochar potentially facilitated the electron transfer in the xCo-HC/PMS system. Overall, this study develops a new strategy for resource utilization of the abundant algae. Full article

(This article belongs to the Special Issue Porous Materials as Efficient Catalysts: Synthesis, Characterization and Applications)

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20 pages, 4361 KiB

Open AccessArticle

Site-Directed Mutagenesis of Two-Domain Laccase ScaSL for Obtaining a Biocatalyst with Improved Characteristics

by Liubov Trubitsina, Ivan Trubitsin, Azat Gabdulkhakov, Azat Abdullatypov, Anna Larionova, Marina Petrakova, Vladimir Trubitsyn, Konstantin Egorov, Svetlana Tishchenko, Alexey Leontievsky, Sergey Alferov and Olga Ponamoreva

Catalysts 2024, 14(10), 694; https://doi.org/10.3390/catal14100694 - 5 Oct 2024

Abstract

Analysis of the structure of two-domain laccase ScaSL from Streptomyces carpinensis VKM Ac-1300 (with a middle-redox potential) revealed determinants that could affect the increased potential of ScaSL. Site-directed mutagenesis of the ScaSL laccase was carried out, and mutants H286A, H286T, H286W, and F232Y/F233Y [...] Read more.

Analysis of the structure of two-domain laccase ScaSL from Streptomyces carpinensis VKM Ac-1300 (with a middle-redox potential) revealed determinants that could affect the increased potential of ScaSL. Site-directed mutagenesis of the ScaSL laccase was carried out, and mutants H286A, H286T, H286W, and F232Y/F233Y were obtained. Replacement of His 286 with Ala led to a decrease in redox potential (0.45 V) and an increase in stability at pH 9 and 11; replacement with Thr led to an increase in redox potential (0.51 V) but to a decrease in the thermal stability of the protein; replacement with Trp did not affect the enzyme properties. Replacement of Phe residues 232 and 233 with Tyr led to a shift in enzyme activity to the acidic pH range without changing the redox potential and a decrease in the thermostability and pH stability of the enzyme. All mutants more efficiently oxidized phenolic substrate 2,6-DMP and were able to participate in direct electron transfer (DET) with MWCNT-modified electrodes. The F232Y/F233/Y mutant was unable to degrade triphenylmethane dyes without a mediator but showed a greater degree of decolorization of azo dyes in the presence of the mediator. The crystal structure of laccase with the highest potential was determined with high resolution. Full article

(This article belongs to the Section Biocatalysis)

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