Catalysts, Volume 13, Issue 12 (December 2023) – 64 articles

The stable activity of catalysts is an important characteristic, which determines their suitability for industrial applications. The purpose of this study was to investigate the stability of ruthenium systems deposited on carbon under conditions simulating long-term operation in CO methanation. Two series of Ru/carbon catalysts were prepared and studied during CO methanation in a hydrogen-rich gas stream. Two graphitized carbons substantially differing in their surface area (23 and 1457 m²/g) were used as supports, and Ru loadings of 3 and 6 wt.% were applied. The stability of Ru/C catalysts was examined in a 240 h time-on-stream test. The samples were characterized by CO chemisorption, XRD, TEM, Raman spectroscopy, TG–MS studies and CO-TPD. The stability of the catalysts over 240 h in the CO + H₂ mixture depended on the support type and Ru loading. The highest CO conversion and increased activity was observed for both catalysts with Ru dispersion above 80%. The tested systems were also resistant to carbon deposition. Interestingly, a similar level of activity was obtained for 3 wt.% Ru supported on the low surface area carbon. It is presumed that the similar activity observed for systems with such different ruthenium dispersion is related to the presence of active sites of different strength and structure on the surface of both small and large Ru particles. Full article

Hierarchical Beta zeolites with interconnected intracrystalline mesopores and high structural stability are highly attractive for catalytic applications involving bulky reactants. Here, by introducing a suitable amount of polydiallyldimethylammonium chloride into the initial synthesis system, micron-sized Beta zeolite crystals with abundant hierarchical porosity (Beta-H) were hydrothermally synthesized. The sample named Beta-H_1 exhibited very high catalytic activity and durability for the Friedel–Crafts acylation of anisole with acetic anhydride. A 92% conversion rate of acetic anhydride could be achieved after 1 h of reaction in a fixed bed reactor, and 71% conversion still remained after 10 h, much better than the rate for conventional Beta zeolite (which decreased rapidly from 85% to 37% within 10 h). The enhanced catalytic performance of Beta-H zeolites could be mainly attributed to the relatively lower strong acid density and the faster transport rate of the hierarchical zeolites. In addition, Beta-H showed high structural stability and could be easily regenerated via high-temperature calcination without obvious loss in catalytic activity, demonstrating its great potential for catalytic applications in the industrially important Friedel–Crafts acylation process. Full article

Zirconia–silica monolithic catalysts with hierarchical micro/macroporous structure were obtained in a sol-gel process combined with phase separation using inorganic salts, i.e., oxychloride, oxynitrate and sulphate, as a zirconium source. It was found that the use of zirconium oxychloride and prehydrolysis of tetraethoxysilane (TEOS) resulted in materials characterized by a well-developed continuous structure of macropores with a diameter of ca. 10 μm. For zirconium oxynitrate and sulfate modified materials, the prehydrolysis hardly affected the macropore size. The micropores with a diameter of 1.5 nm in the skeleton of all materials provided a large surface area of 550–590 m²/g. A high dispersion of zirconia in the silica skeleton in all studied materials was shown. However, the largest surface concentration of Lewis and Brönsted acid sites was found in the monolith synthesized with zirconium oxychloride. The monoliths were used as a core for continuous-flow microreactors and high catalytic activity was confirmed in the deacetalization of benzylaldehyde dimethyl acetal. The process was characterized by a high efficiency at low temperature, i.e., 35 °C. Full article

d-Tagatose is a rare sugar with low calories, and is extensively used in food, beverage, and drug additives. In this study, an in vitro multienzyme cascade route for d-tagatose synthesis from sucrose (MCTS) was designed, which contains five enzymes (sucrose phosphorylase, fructokinase, d-fructose 6-phosphate 4-epimerase, d-tagatose 6-phosphate phosphatase, and polyphosphate kinase). The whole MCTS route comprised a sucrose phosphorylation reaction, and a phosphorylation–dephosphorylation reaction coupled with an ATP regeneration system. After optimization, the conversion of d-tagatose from 10 mM sucrose reached 82.3%. At an elevated sucrose concentration of 50 mM, 72.4% of d-tagatose conversion and 0.27 g·L^–1·h⁻¹ of space–time yield were obtained. Furthermore, ADP consumption decreased to 1% of the sucrose concentration after introducing the ATP regeneration system. The MCTS strategy is an efficient and cost-effective approach for d-tagatose production. Full article

CO₂ methanation offers a promising route for converting CO₂ into valuable chemicals and energy fuels at the same time as hydrogen is stored in methane, so the development of suitable catalysts is crucial. In this review, the performance of catalysts for CO₂ methanation is presented and discussed, including noble metal-based catalysts and non-noble metal-based catalysts. Among the noble metal-based catalysts (Ru, Rh, and Pd), Ru-based catalysts show the best catalytic performance. In the non-noble metal catalysts, Ni-based catalysts are the best among Ni-, Co-, and Fe-based catalysts. The factors predominantly affecting catalytic performance are the dispersion of the active metal; the synergy of the active metal with support; and the addition of dopants. Further comprehensive investigations into (i) catalytic performance under industrial conditions, (ii) stability over a much longer period and (iii) activity enhancement at low reaction temperatures are anticipated to meet the industrial applications of CO₂ methanation. Full article

This article discusses the potential applications of the Fuel Shot liquid catalyst in compression ignition (CI) engines for reducing toxic substances in exhaust gases. Incorporating catalysts into fuel can optimize the combustion process, consequently reducing the emission of toxic substances into the atmosphere. Toxic compounds, such as nitrogen oxides, particulate matter, and hydrocarbons, adversely affect flora and fauna. Various methods are known for reducing their concentration in engine exhaust gases, one of which is the Fuel Shot liquid catalyst. The authors conducted experiments on a Fiat 1.3 JTD engine with a Common Rail system. The results indicate that the application of the liquid catalyst reduces the content of nitrogen oxides and hydrocarbons in the exhaust gases and slightly decreases fuel consumption. Additionally, investigations were carried out on the engine’s injection apparatus, which was fueled with modified fuel. The findings demonstrate that the fuel additive does not affect the wear of precision parts of fuel injectors and high-pressure pumps. Full article

With the development of coal chemical technology, a large amount of gasification slag and wastewater are produced through coal gasification. Efficient gasification slag utilization and wastewater treatment have attracted much attention. In this study, gasification slag was modified and used as a low-cost and efficient catalyst to activate persulfate for acetaminophen degradation. Via the analysis of high-resolution X-ray photoelectron spectroscopy, the surfaces of nitric acid and calcined modified gasification slag retained a considerable number of carbonyl and graphite N functional groups. These proved to be effective active sites for the activation of persulfate. X-ray diffraction analysis revealed that the gasification slag was composed of carbon and SiO₂. The evaluation of catalytic activity and application of density functional theory proved that the interaction between carbonyl and graphitic nitrogen significantly affected the catalyst activity. When the ratio of graphitic nitrogen to carbonyl was 1:3, the adsorption and activation of persulfate were significantly enhanced. The results of the quenching experiments also confirmed that the non-free radical pathway is the main pathway to activate persulfate using the gasification slag. This study provides a new approach to industrial waste utilization in wastewater treatment. Full article

Series of ceria-zirconia (CZ)-based nano-materials with a d₅₀ in the range of 0.2 to 1.3 microns were made using the jar milling, Eiger milling, and steam jet milling (SJM) techniques. The effect of the milling conditions on the morphology and textural properties was studied. High-energy steam jet milling in a quasi-hydrothermal environment (with potential local temperature spikes over 500 °C) significantly impacted the CZ crystal structure by inducing lattice distortions. It was shown that the acquired lattice stress resulted in a significant increase in oxygen mobility, which was manifested by a TPR-H₂ T_max shift from 450–550 to 150–250 °C. CZ materials with fast oxygen mobility are metastable phases, and re-slurring nano-CZ powders in water and impregnation with precious metals had stabilizing effects on fast oxygen mobility. Efficiently enhancing the CZ redox activity milling process took place in the following order: Steam jet milling > Eiger milling > jar milling. Full article

The molecular complexes of Re(4,4′-dcbpy)(CO)₃Cl (dcbpy = dicarboxylicacid-2,2’-bipyridyl) and [Ru(dcbpy)₃]²⁺ are co-assembled into UiO-66 scaffolds as structural imperfects for CO₂ photocatalytic reduction (named as Re-Ru@U). The prepared catalysts are characterized by XRD, Fourier-Transform infrared (FTIR) spectra, X-ray photoelectron spectra (XPS) and N₂ adsorption–desorption isotherms. The intact structure of molecular complexes within the matrix are monitored by ¹H nuclear magnetic resonance (NMR) spectra through a totally digesting catalyst. The optical properties are studied via absorption and photoluminescence spectra, and the single-electron reduction in Re and Ru complexes is detected by electron paramagnetic resonance (EPR) spectra. An excellent photocatalytic performance is obtained with steady and sustained CO evolution and a turnover number (TON) value of 15 (11 h). The CO activity irradiating by single wavelength presents the absorption-intensity-dependent changing tendency, where the absorption intensity is superposed by Re and Ru complexes. The two radicals related to Re and Ru, respectively, are simultaneously detected in the Re-Ru@U catalyst. It is suggested that the ReC₂ component serves as both a photosensitizer and a catalyst, and the RuC₂ component works as an additional photosensitizer to supply the second electron for CO₂ reduction. The co-assembling of dual metals Re and Ru in the matrix promotes the electron transfer from the reductive Ru centres to one-electron-reduced Re centres and accounts for the superior activity of CO evolution. Our results demonstrate a strategy to develop the multimetallic catalysts via facile assembling into MOF scaffolds to promote photocatalytic performance. Full article

In this work, ZnO, SnO₂, and their mixed ZnO-SnO₂(25%) nanoparticles (NPs) were successfully green synthesized in a straightforward manner with a low-cost and environmentally friendly approach using a banana peel extract. The synthesized nanophotocatalysts were characterized using various techniques including FTIR, XRD, UV-Vis, TEM, SEM, BET, PL, EDS, and TGA. The characterization results showed that the ZnO and SnO₂ powders were crystallized in a hexagonal wurtzite and rutile-type tetragonal structures, respectively, and their mixed ZnO-SnO₂(25%) NPs contain both structures. Also, it was found that the addition of SnO₂ into the ZnO structure reduces the PL intensity of the latter, confirming better separation of electron/hole pairs. The average particle size of a ZnO-SnO₂(25%) NP photocatalyst was found to be 7.23 nm. The cationic dyes methylene blue (MB) and crystal violet (CV) as well as the anionic dyes naphthol blue black (NBB) and Coomassie brilliant blue R 250 (CBB) were employed as model dyes to assess the dye removal efficiencies of the biosynthesized nanophotocatalysts under sunlight. In all cases, the mixed ZnO-SnO₂(25%) NP photocatalyst showed much better photocatalytic activity than individual photocatalysts. The degradation percent of dyes using ZnO-SnO₂(25%) NPs ranged between 92.2% and 98%. The efficient photocatalytic activity of ZnO-SnO₂(25%) NPs is attributed to the effective charge separation and reduced electron/hole recombination rate. The kinetic study results conformed to a pseudo first-order reaction rationalized in terms of the Langmuir–Hinshelwood model. Furthermore, the results showed that the ZnO-SnO₂(25%) NP photocatalyst is highly stable and could be recycled several times without a noticeable reduction in its catalytic activity towards dye removal. Full article

A prepared FeZnNa@SiO₂-C catalyst with graphitized carbon (C)-modified mesoporous SiO₂ supports metal nanoparticles with the sol–gel method. The effect of adding metal Na and Zn promoters as a dispersion on the CO₂ hydrogenation to low olefins was systematically studied. The results showed that Zn–Na, as a combination, could promote the absorption of CO₂ and improved the conversion rate of CO₂. Na as an alkaline substance can improve the absorption of more acidic CO₂, which could increase the conversion rate of CO₂ to 59.03%. Meanwhile, the addition of secondary metal Zn to Fe-based catalysts to form a surface alloy could alter the adsorption of CO₂ and the activation of C-O bonds, inhibit the subsequent hydrogenation of olefins to paraffins, and facilitate the reduction of Fe₂O₃ and the formation of active Fe₅C₂ species. The formation of active Fe₅C₂ species was found in TEM and XRD, and the selectivity of the target product was 41.07%. The deep hydrogenation of olefins was inhibited, and the space–time yield (STY) of low olefins was raised again by inhibiting their deep hydrogenations, up to 0.0436. However, the corresponding STY did not increase infinitely with the increase of Na doping, and higher catalytic performance for CO₂ hydrogenation could be exhibited when the Na doping reached 6.4%. Compared with Fe@SiO₂-C catalyst, Na- and Zn-promoted Fe-based catalysts, prepared by the modified sol-gel method, can be used directly for highly efficient CO₂ hydrogenation to low olefins and thus has a more promising application prospect in the future. Full article

In this work, the activity of various alcohols in the hexene-1 hydroalkoxycarbonylation reaction in the presence of two catalytic systems was investigated for the first time: (1) Pd(PPh₃)₄-PPh₃-TsOH (menthol, cyclohexanol, ethanol, propanol, iso-propanol, butanol, isobutanol and benzyl alcohol) and (2) PdCl₂(PPh₃)₂-PPh₃-AlCl₃ (ethanol, propanol-1, butanol-1, isoamyl alcohol, isobutanol, pentanol-1, allyl alcohol and tert-butyl alcohol). The optimal process parameters (temperature, pressure and reaction time) for the reactions of the hydropropoxycarbonylation and hydrobutoxycarbonylation of hexene-1, at which the yields of target products reached 91.8% and 91.5%, respectively, were determined. Full article

The recent advancement in the production of nanomaterials with novel architectures and functionality has allowed for the effective treatment of industrial wastewaters and contaminated soil and, in that view, the current study aimed to investigate the catalytic efficacy of biopolymer-loaded titanium nanocomposite. Therefore, Cerium (Ce)-titanium dioxide (TiO₂) loaded chitosan nanocomposite was formed and studied its catalytic efficacy towards the degradation of an industrial dye pollutant. For the production of Ce-TiO₂/chitosan nanocomposite, we followed the hydrothermal synthesis route and the formed nanocomposite was thoroughly analyzed for the crystallinity (using powdered X-ray diffraction, XRD), surface bonding, and nature (using Fourier transform infrared, FTIR spectroscopy), morphology (scanning electron microscopy, SEM), elemental composition (electron diffraction analysis by X-rays, EDAX), porosity (Brunauer–Emmett–Teller, BET), and particles size in powdered form (transmission electron microscopy, TEM). Then the efficiency of synthesized nanocomposite was tested towards the photocatalytic degradation of Rhodamine B (Rh B) dye by applying various parameters such as the irradiation time, solution pH, catalyst dosage, and the dye concentration. Further, the Langmuir–Hinshelwood model was employed to investigate the kinetics of RhB degradation and provided a conceivable photocatalytic mechanism. It was indicated based on the catalyst mechanism that the modification of TiO₂ nanoparticles with Ce and loading onto chitosan biopolymer may have accelerated the photocurrent transport due to an increase in the number of electrons and holes generated by the photon’s irradiation. In this way, the study has witnessed the excellent photocatalytic performance of Ce-TiO₂/chitosan with 95% Rh B degradation as against the pure TiO₂ nanoparticles thus stressing the importance of developing novel composite photocatalysts. Full article

With the advances in engine technology, the exhaust gas temperature of automobiles has further reduced, which in turn leads to an increase in the emissions of carbon monoxide (CO) and hydrocarbons (HCs). In order to understand the influence of CeO₂-based catalysts loaded with different noble metals on the catalytic oxidation activity of CO and HCs, this study constructed catalyst models of Ce_0.875Zr_0.125O₂ (100) surfaces loaded with Pt, Pd, Ag, and Au. The electronic density and state density structures of the catalysts were analyzed, and the reaction energy barriers for CO oxidation and C₃H₆ dehydrogenation oxidation on the catalyst surfaces were also calculated. Furthermore, the activity sequences of the catalysts were explored. The results revealed that after loading Pt, Pd, Ag, and Au atoms onto the catalyst surfaces, these noble metal atoms exhibited strong interactions with the catalyst surfaces, and electron transfer occurred between the noble metal atoms and the catalyst surfaces. Loading with noble metals can enhance the catalytic activity of CO oxidation, but it has little effect on the dehydrogenation oxidation of C₃H₆. Of the different noble metals, loading with Pd exhibits the best catalytic activity for both CO and C₃H₆ oxidation. This study elucidated the influence of noble metal doping on the catalytic activity of catalysts at the molecular level, providing theoretical guidance for the design of a new generation of green and efficient catalysts. Full article

The novel ternary composites BiOBr-TiO₂-attapulgite (BTA) were synthesized using a simple hydrothermal and water-bath method, exhibiting excellent photocatalytic performance to multiple xanthates. For the BTA photocatalyst, TiO₂ and BiOBr were uniformly loaded onto the surface of acid-activated attapulgite. As a widely used collector in mining processes, sodium ethyl-xanthate (SEX) was selected as the target pollutant due to its high toxicity. The BTA ternary photocatalyst demonstrated significantly higher adsorption and photocatalytic degradation performance compared to TiO₂ nanoparticles, BiOBr nanosheets, and BiOBr-TiO₂ heterojunction. Structural characterization and experimental results indicated that the exceptional photocatalytic degradation efficiency of BTA was mainly attributed to the formation of a heterojunction between BiOBr and TiO₂, as well as the presence of additional active adsorption sites provided by attapulgite. Free radical scavenging experiments and EPR results confirmed that the photogenerated holes were the predominant active species in photodegrading SEX throughout the entire experiment. The LC-MS results provided insight into potential degradation pathways of SEX. This research demonstrates that BTA, as a novel triple composite material, achieves rapid and complete degradation to 20 mg/L SEX within 20 min. This work presents a novel approach to synthesize mineral-based photocatalysts, which have broad prospects for application in flotation wastewater treatment. Full article

The usability of glass fibers as immobilization support with a porous open structure was investigated. We developed a method to immobilize the enzyme β-galactosidase on special glass fiber rolls. The new method is simple, non-expensive and industrially applicable. Glutaraldehyde was used as a non-specific cross-linking agent for the covalent binding of β-galactosidase on modified glass fibers. The efficiency of immobilization was tested with the known hydrolysis of lactose. All experiments were performed in a continuous laboratory reactor. The influence of the reaction temperature (20, 25 and 30 °C), the substrate flow rate (1, 2 and 3 mL/min) and the pH of the reaction medium (6, 7 and 8) on the conversion was investigated. The reaction efficiency was monitored by measuring the glucose concentration with a spectrophotometer. High immobilization efficiency, enzyme activity and stability were obtained. The optimal reaction temperature, substrate flow rate and pH were found. The activity and stability of the enzyme entrapped on the glass fiber rolls remained almost unchanged during reuse, which is promising for potential industrial applications. Full article

The glycine motif is widely prevalent in bioactive peptides. Thus, the direct and precise modification of glycine derivatives has attracted significant attention over the past few decades. Among various protocols for the modification of glycine derivatives, the visible-light-driven direct α-C(sp³)–H bond functionalization of glycine derivatives has emerged as a powerful tool to achieve this objective, owing to its merits in atom economy, selectivity, reaction simplicity, and sustainability. This review summarizes the recent advancements in visible-light-driven direct α-C(sp³)–H bond functionalization of glycine derivatives. The contents of this review are organized based on the photocatalysts employed and the various reaction modes in the functionalization process. The mechanism, the challenges encountered, and future trends are also discussed, enabling readers to understand the current developmental status in this field. Full article

Rotating packed beds (RPB) facilitate the mixing of heterogeneous substrates, and promote high mass transfer efficiency in heterogeneous reactions. For the enzymatic reactions, traditional porous particles with immobilized enzymes are sensitive to the strong sheer force of the RPB, thus limiting its application. This work offers a strategy for enzyme immobilization on the surface of stainless-steel fleece, to improve the shear strength resistance of immobilized enzymes. Lipase was applied to investigate and optimize the immobilization. Finally, a fatty acid hydratase (FAH) was applied for immobilization based on the optimized method, which was further applied for evaluating its performance in RPB. The results indicated that metal immobilized enzymes resist a higher shear force than their particle-immobilized alternatives. Operating at a centrifugal force factor (β) of 30, the hydration conversion rate of 96% is achieved after 8 h, which was from nearly 38% faster than in a stirrer tank reactor (hydration yield of 60%). The metal immobilization, moreover, efficiently improved the enzyme reusability, as demonstrated by a conversion rate remaining above 90% after 15 batches. These results indicated that a metal immobilization method combined with an RPB reactor significantly increases the efficiency of enzymatic reactions. Full article

Transition metal carbides have emerged as an attractive alternative to conventional catalysts in hydrodeoxygenation (HDO) reactions due to surface reactivity, catalytic activity, and thermodynamic stability similar to those of noble metals. In this study, the impact of varying Mo concentration in carbon nanofiber-supported catalysts for the supercritical ethanol-assisted HDO of bio-oils in an autoclave batch reactor is discussed. Raw bio-oils derived from agave bagasse and corncob through solar hydrothermal liquefaction were treated at 350 °C. Our findings indicate that the presence of Mo has a strong impact on both product yield and chemical properties. Thus, a Mo concentration of 10 wt.% is enough to obtain high deoxygenation values (69–72%), resulting in a yield of upgraded bio-oil ranging between 49.9 and 60.4%, depending on the feedstock used, with an energy content of around 35 MJ/kg. A further increase in the Mo loadings (20 and 30 wt.%) reduced the loss of carbon due to gasification and improved the bio-oil yields up to 62.6 and 67.4%, without compromising the product quality. Full article

The selective hydrogenation of CO₂ for the production of net-zero fuels and essential chemical building blocks is a promising approach to combat climate change. Key to this endeavor is the development of catalysts with high activity and selectivity for desired hydrocarbon products in the C2–C5 range. The process involves a two-step reaction, starting with the reverse water–gas shift (RWGS) reaction and proceeding to the Fischer–Tropsch reactions under high pressure. Understanding the catalyst features that control the selectivity of these pathways is crucial for product formation, as well as identifying morphological changes in the catalysts during the reaction to optimize their performance. In this study, an innovative method for synthesizing iron–ruthenium bimetallic catalysts is introduced, capitalizing on the synergistic effects of these metals as active phases. This method leverages ionic liquids as solvents, allowing for the precise and uniform distribution of active metal phases. Advanced characterizations and extensive catalytic tests have demonstrated that the use of ionic liquids outperformed traditional colloid-based techniques, resulting in superior selectivity for target hydrocarbons. The success of this inventive approach not only advances the field of CO₂ hydrogenation catalysis, but also represents a significant stride towards sustainable e-fuel production. Full article

Hydrogen has emerged as an important candidate for clean energy, owing to its environmentally friendly advantages. Electrolytic hydrogen production stands out as the most promising technology for hydrogen production. Therefore, the design of highly efficient electrocatalysts is significant to drive the application of hydrogen technologies. Platinum (Pt)-based catalysts are famous for their outstanding performance in the hydrogen evolution reaction (HER). However, the expensive cost limits its wide application. Ruthenium (Ru)-based catalysts have received extensive attention due to their relatively lower cost and HER performance similar to that of Pt. Nevertheless, the performance of Ru-based catalysts is still unable to meet industrial demands. Therefore, improving HER performance through the modification of Ru-based catalysts remains significant. In this review, the reaction mechanism of HER is analyzed and the latest research progress in the modification of Ru-based electrocatalysts is summarized. From the reaction mechanism perspective, addressing the adsorption of intermediates on the Ru-based electrocatalyst surface, the adsorption–activation of interface water molecules, and the behavior of interface water molecules and proposing solutions to enhance performance of Ru-based electrocatalyst are the main findings, ultimately contributing to promoting their application in the field of electrocatalysis. Full article

This article presents an efficient iron(III) molecular catalyst for the production of biodiesel from waste vegetable oils. The approach involved an initial screening of eight salophen complexes with various substituents on the arene rings, leading to the selection of the simplest unsubstituted species as the most active catalyst. Under optimized conditions, this catalyst demonstrated the capability to achieve complete conversion of the oil at a low catalyst loading (0.10% mol/mol) and convenient conditions (160 °C, 20/1 MeOH/oil ratio). Full article

Flavin-dependent monooxygenases (FMOs) have raised substantial interest as catalysts in monooxygenation reactions, impacting diverse fields such as drug metabolism, environmental studies, and natural product synthesis. Their application in biocatalysis boasts several advantages over conventional chemical catalysis, such as heightened selectivity, safety, sustainability, and eco-friendliness. In the realm of biomedicine, FMOs are pivotal in antibiotic research, significantly influencing the behavior of natural products, antimicrobial agents, and the pathways critical to drug synthesis They are also underscored as potential pharmaceutical targets, pivotal in opposing disease progression and viable for therapeutic intervention. Additionally, FMOs play a substantial role in environmental science, especially in pesticide processing and in preserving plant vitality. Their involvement in the biosynthesis of compounds like polyethers, tropolones, and ω-hydroxy fatty acids, with remarkable regio- and stereoselectivity, renders them indispensable in drug discovery and development. As our comprehension of FMOs’ catalytic mechanisms and structures advances, through the use of cutting-edge biotechnologies like computational design and directed evolution, FMOs are poised to occupy an increasingly significant role in both scientific exploration and industrial applications. Full article

In this work, Sn-Si mixed oxide microspheres with concave hollow morphologies were first synthesized by a simple aerosol method using the very common commercial surfactant cetyl trimethyl ammonium bromide (CTAB) as a template, and then highly interconnected mesoporous and hollow Sn-Si mixed oxide microspheres were synthesized via an alkali (NaOH) treatment in the presence of CTAB. The results show that CTAB plays a crucial role not only in forming hollow morphologies during the aerosol process, but also protecting the amorphous framework and thus preventing the excessive loss of Sn species during the NaOH treatment. More importantly, it widens mesoporous distribution and forms interconnected mesoporous channels. The catalytic performance of Baeyer–Villiger oxidation on the interconnected mesoporous and hollow Sn-Si mixed oxide microspheres with 2-adamantanone and hydrogen peroxide was 9.4 times higher than that of the sample synthesized without the addition of CTAB; 2.3 times that of the untreated parent, which was due to the excellent diffusion properties derived from the hollow and interconnected mesopore structure. This method is mild, simple, low-cost, and can be continuously produced, which has the prospect of industrial application. Furthermore, the fundamentals of this study provide new insights for the rational design and preparation of highly interlinked mesoporous and hollow metal-oxides with unique catalytic performances. Full article

Disulfides, as fundamental scaffolds, are widely present in peptides, natural products, and pharmaceutical molecules. However, traditional synthesis of disulfides often involves the utilization of toxic reagents or environmentally unfriendly reaction conditions. In this work, a green and efficient method was developed for synthesizing pyrrole disulfides using β-ketothioamides and ethyl cyanoacetate as substrates, with lipase serving as a catalyst. Under the optimal conditions (β-Ketothioamides (1 mmol), ethyl cyanoacetate (1 mmol), PPL (200 U), and EtOH (5 mL)), lipase leads to the formation of pyrrole disulfides in yields of up to 88% at 40 °C. The related mechanism is also speculated in this paper. This approach not only presents a new application of lipase in enzyme catalytic promiscuity, but also offers a significant advancement in the synthetic pathway for pyrrole disulfides and aligns with the current mainstream research direction of green chemistry, contributing to the further development of environmentally friendly biocatalytic processes. Full article

In this study, coal fly ash was functionalized, using a simple one-step process (loading with Al³⁺ and sulfonation), to yield a solid acid catalyst (S/Al-CFA) with strong acid sites. The catalyst was then used to produce furfural from xylose in a biphasic system (H₂O_(NaCl)/tetrahydrofuran). The furfural yield reached 82% at 180 °C–60 min with catalyst/xylose ratio of 0.2:1.0 (w/w). With the reaction completed, all of the components could be effectively separated, and the furfural was 97.6% pure. The cycle and regeneration of the catalyst were evaluated, and the catalyst deactivation mechanism was investigated. Full article

Catalytic ozonation, with enhanced efficiency and reduced byproduct formation at lower temperatures, proved to be efficient in ethyl acetate (EA) degradation. In this work, MMn₂O₄ (M = Cu, Co, Ni, Mg) catalysts were prepared via a redox-precipitation method to explore the catalytic ozonation mechanism of EA. Among all the catalysts, CuMn exhibited superior catalytic activity at 120 °C, achieving nearly 100% EA conversion and above 90% CO₂ selectivity with an O₃/EA molar ratio of 10. Many characterizations were conducted, such as SEM, BET and XPS, for revealing the properties of the catalysts. Plentiful active sites, abundant oxygen vacancies, more acid sites and higher reduction ability contributed to the excellent performance of CuMn. Moreover, the addition of NO induced a degree of inhibition to EA conversion due to its competition for ozone. H₂O had little effect on the catalytic ozonation of CuMn, as the conversion of EA could reach a stable platform at ~89% even with 5.0 vol.% of H₂O. The presence of SO₂ usually caused catalyst deactivation. However, the conversion could gradually recover once SO₂ was discontinued due to the reactivation of ozone. A detailed reaction mechanism for catalytic ozonation was proposed via in situ DRIFTS measurements and DFT calculations. Full article

The influence of mass transfer intensity on the kinetics of the catalytic oxidation of flax shives with oxygen in alkaline media to aromatic aldehydes and pulp was studied. The process was carried out in two autoclaves, with moderate stirring (stirrer engine of 8 W) and intense stirring (stirrer engine of 200 W). The oxidation of flax shives into vanillin, syringaldehyde, and pulp was shown to proceed as a completely diffusion-controlled process under the studied conditions, both moderate and intense stirring. Depending on the process conditions, it can be limited by stages of oxygen transfer through the diffusion boundary layer near the gas–liquid interface (low intensity of mass transfer) as well as by reagents’ inner diffusion in the porous and solid matter of the flax shive particle (high intensity of mass transfer). The results on the influence of the stirring speed and volume of the reaction mass on the rates of oxygen consumption and vanillin accumulation were obtained. They were described using a known simple model connecting the intensity of mass transfer and the stirring power density in the bulk of the liquid phase in terms of algebra equations. Full article

Carbon dioxide is ideal for carboxylation reactions as a renewable and sustainable C1 feedstock and has significant recognition owing to its low cost, non-toxicity, and high abundance. To depreciate the environmental concentration of CO₂, which causes the greenhouse gas effect, developing new catalytic protocols for organic synthesis in CO₂ utilization is of great importance. This review focuses on carboxylation reactions using CO₂ as a C1 feedstock to synthesize value-added functionalized carboxylic acids and their corresponding derivatives via catalytically generated allyl metal intermediates, photoredox catalysis, and electrocatalysis with a focus on recent developments and opportunities in catalyst design for carboxylation reactions. In this article, we describe recent developments in the carboxylation of C–H bonds, alkenes, and alkynes using CO₂ as the C1 source for various reactions under different conditions, as well as the potential direction for the further development of CO₂ utilization in organic synthesis. Full article