Search Results (337)

The fast growth of the aviation sector has intensified the need for sustainable alternatives to conventional fossil-based jet fuels. Sustainable aviation fuel (SAF) has emerged as one of the most promising strategies to reduce greenhouse gas emissions while remaining compatible with existing aviation infrastructure. Among the different feedstocks explored for SAF production, lipid-based resources such as vegetable oils, animal fats, and waste cooking oil have received considerable attention due to their high content of triglycerides and free fatty acids. Additionally, the increasing generation of plastic waste has stimulated interest in its catalytic valorization as an alternative carbon source for hydrocarbon fuel production. This mini-review summarizes recent advances in catalytic pathways for producing jet-fuel-range hydrocarbons (C₈–C₁₆) from lipid-based feedstocks and polyolefins. Particular emphasis is given on hydroprocessing reactions, including deoxygenation, cracking, and isomerization, which are essential to adjust fuel properties and meet aviation specifications. In this context, bifunctional heterogeneous catalysts play a crucial role, particularly regarding the influence of the metal phase and catalyst support on catalytic activity and stability. Different support classes, including metal oxides, mesoporous silicas, and zeolites, are discussed. Carbon-based materials, especially carbon nanotubes (CNT), are also highlighted due to their outstanding chemical and textural properties. Full article

Ce-Ni@WSA (WSA = water-resistant silica–alumina gel) ozone catalyst was prepared with an impregnation–calcination method using WSA as the support and characterized by SEM, XRD, BET, XRF, and XPS analyses. The operating conditions and reaction mechanism of the Ce-Ni@WSA catalytic ozonation of norfloxacin (Nor)-simulated wastewater were systematically studied. A data-envelopment analysis model (DEA-B²C) was then established to evaluate the catalytic ozonation process. Under the optimal conditions of initial pH 7.42 (raw water), ozone dosage = 0.4 g/L/h, catalyst-filling ratio = 5%, humic acid dosage = 0 mg/L, the removal rates of chemical oxygen demand (COD) and Nor reached 84.95% and 93.52%, respectively. Ce-Ni@WSA retained its high catalytic performance and mechanical strength after 50 cycles of repeated use. Mechanistic studies showed that •OH oxidation was dominant in the catalytic-ozonation system, and Nor can be degraded into small molecules through three different pathways and eventually mineralized. The DEA-B²C model analysis showed that the treatment cost was low and the catalytic efficiency was high under the optimal operating conditions. Full article

Albendazole (ABZ) exhibits poor oral absorption; therefore, ABZ was conjugated to cholic acid to engage the apical sodium-dependent bile acid transporter (ASBT) and promote ileal uptake. ABZ–linker–CA conjugates bearing amino-alcohol linkers (C4–C8) were evaluated by integrating synthetic feasibility, purification selectivity, and ex vivo performance. Thermal aminolysis in DMF (95 °C) produced ABZ–linkers in ~50% reaction yields (HPLC-assayed), with a minor ABZ-amine by-product consistent with a workup-sensitive isocyanate route. Immobilized-lipase screening identified Lipozyme RM IM as the most effective catalyst for CA esterification in CHCl₃, showing a pronounced linker-length dependence (31% yield for C4, 25% for C6, and C8 ≤ 2.6% yield). Docking and molecular dynamics supported this trend by indicating productive binding geometries for C4/C6 but not for C8. A polarity-guided workup and silica-gel protocol enabled retrieval of unreacted intermediates and CA recycling, with cleaner separation for the C6 series. Ex vivo transport studies confirmed ASBT-mediated, linerixibat-sensitive ileal uptake, and protoscolex assays showed improved antiparasitic efficacy versus ABZ. Overall, ABZ-C6-CA offered the best balance of uptake, near-maximal efficacy, enzymatic accessibility, and separability, supporting its prioritization for scalable biocatalytic manufacturing. Full article

The redox mechanisms of silica-supported Ni particles were investigated using their in situ X-ray absorption fine structure, providing mechanistic insights into partially reduced NiO and partially oxidized metallic Ni. The results of surface oxidation of partially reduced NiO particles at room temperature revealed that the surface was not fully covered with metallic Ni and that metallic Ni had also formed within the particle interior. During NiO particle reduction, the process initiates at specific surface sites, and before the metallic Ni phase fully covers the surface, O²⁻ ions are expelled from the particle. Conversely, the oxidation of metallic Ni particles progresses inward from the surface, with an accompanying increase in the thickness of the NiO layer that forms upon O₂ exposure at room temperature. This mechanism is supported by observations that the reduction of a thin NiO shell on metallic Ni particles was completed below 200 °C, while reduction temperatures shifted to higher values as the NiO layer thickness increased. The distinct oxidation and reduction mechanisms are attributed to differences in the migration direction of O²⁻ ions. During reduction, it is proposed that O²⁻ ions within the particles migrate to the surface along the interface between the NiO phase and the metallic Ni phase. This study elucidates the detailed mechanism behind the redox interconversion between NiO and metallic Ni in solid catalyst particles. Full article

This review explores the catalytic conversion of carbon dioxide (CO₂) into glycerol carbonate (GC), positioning this pathway as a sustainable strategy that couples environmental mitigation with the valorization of surplus glycerol from biodiesel production. Glycerol carbonate maintains extensive industrial utility as a green solvent, chemical intermediate, and functional component in polymers, cosmetics, and packaging. Distinct from prior literature, this study specifically evaluates the use of amorphous silica from rice husk ash (RHA) as a sustainable, low-cost support, analyzing the synergistic effect between Nb₂O₅, NiO, and ionic liquids in hybrid catalyst architectures. The review evaluates diverse catalytic frameworks, with a primary focus on heterogeneous systems. Silica-based materials are highlighted, particularly those synthesized from rice husk ash, which is an abundant amorphous silica source. The sol–gel method is identified as a robust route for engineering porous matrices with high surface areas and tunable structural properties. Furthermore, the doping of silica with metal oxides, such as niobium oxide (Nb₂O₅) and nickel oxide (NiO), is discussed as a strategic approach to introduce synergistic acid–base sites and redox properties that facilitate CO₂ activation. The integration of ionic liquids into hybrid systems is also examined as a promising frontier to enhance reaction kinetics and selectivity. Finally, this review delineates the nexus between agro-industrial waste management and the reduction in greenhouse gas emissions, proposing a circular economy framework for the biodiesel value chain. Full article

The rational design of supported ruthenium catalysts for sustainable energy applications requires precise control over metal nanoparticle size, dispersion, and metal–support interactions. This study investigates the influence of mesoporous silica support topology—SBA-15 (2D hexagonal, cylindrical pores), SBA-12 (3D hexagonal structure), and SBA-3 (2D hexagonal)—on the structure and catalytic performance of 1 wt% ruthenium catalysts in CO₂ methanation and gas-phase toluene hydrogenation. Comprehensive characterization by nitrogen physisorption, low- and high-angle X-ray diffraction (XRD), H₂ temperature-programmed reduction (H₂-TPR), CO chemisorption, and transmission electron microscopy (TEM) revealed that support pore architecture dictates ruthenium particle size (1.2 nm for Ru/SBA-15, 2.8 nm for Ru/SBA-3, 4.3 nm for Ru/SBA-12) and dispersion (80%, 35%, 23%, respectively) through geometric confinement effects. Catalytic testing demonstrated contrasting structure–activity relationships: CO₂ methanation exhibited strong structure sensitivity with turnover frequency (TOF) increasing with particle size (Pearson’s r = 0.96), favoring Ru/SBA-3 and Ru/SBA-12 with near-optimal 3–4 nm particles, while toluene hydrogenation showed weaker structure sensitivity, with Ru/SBA-12 achieving the highest TOF owing to its larger particle size and higher crystallinity. These findings underscore the critical importance of tailoring mesoporous support topology to match reaction-specific structure sensitivity, providing fundamental insights for the design of bifunctional catalysts for hydrogenation reactions. Full article

Silica-supported zinc (II)–Schiff-base complexes were prepared through a simple and high-yield immobilization strategy and evaluated as heterogeneous catalysts for the ring-opening polymerization (ROP) of lactide. Silica gel and silica nanoparticles were employed as supports to assess the influence of support morphology and textural properties on catalytic performance. Comprehensive characterization by AAS, BET, SEM, and SEM–EDS confirmed effective anchoring of the Zn complexes, homogeneous metal distribution, and support-dependent textural modifications. The supported catalysts were active in the bulk ROP of racemic and enantiopure lactide, affording PLA with high conversions and moderate dispersities. Silica-gel-supported systems exhibited high and reproducible activity over a wide range of conditions, whereas catalysts supported on silica nanoparticles showed a stronger dependence on reaction time and ligand electronic effects, highlighting the key role of the support in modulating active site accessibility and chain growth. Microstructural and thermal analyses confirmed the formation of atactic PLA from rac-lactide and stereoregular PLLA from L-lactide. Overall, this study demonstrates that silica-supported zinc(II)–Schiff-base complexes constitute an effective and versatile heterogeneous platform for lactide ROP and underscore the importance of support properties in the rational design of sustainable catalysts for biodegradable polyester synthesis. Full article

This study addresses the challenges posed by weakly cemented strata in mine tunnels, where surrounding rock softens and deforms upon water exposure, which promotes the development of seepage pathways, and exhibits insufficient stability in bolt (cable) support systems. This study conducts laboratory grouting tests using silica sol on typical weakly cemented sandstone from Xinjiang mining areas. The mineral composition and pore structure were characterized using XRD, SEM, and mercury porosimetry. The injectable mixing ratio parameters for silica sol and the catalyst were determined through viscosity-time evolution tests. Grouting was performed using a custom-built constant-pressure grouting apparatus. After curing, unconfined compressive strength (UCS) and porosity-permeability tests were conducted to evaluate the micro-mechanism of grouting effects on the mechanical and permeability properties of weakly cemented sandstone. The results indicate: (1) The sandstone exhibits a high clay mineral content of 39.8%, dominated by illite. Its pores are primarily small-scale (10–100 nm), accounting for 79.31% of the total pore volume. This scale matches that of silica sol nanoparticles (approximately 9–20 nm), facilitating slurry penetration into micro-pores; (2) microscopic analyses reveal that silica sol effectively reconstructs pore structures through permeation filling and surface coating. Compared to KCl-induced gelation (with approximately 8% gel coverage), NaCl-induced gelation forms a more continuous gel film with more complete pore filling, achieving coverage of around 22%. Furthermore, the larger surface area of the gel aggregates indicates a more thorough filling of micro- and nano-pores, effectively enhancing rock mass compactness. (3) Permeability decreased from 6.91 mD to 3.55 mD, a reduction of 48.6%, while porosity decreased from 16.94% to 13.55%, showing a phased reduction during the grouting process; (4) following pressure grouting stabilization, the uniaxial compressive strength of sandstone increased appropriately by approximately 7–14%, while the elastic modulus rose by about 18–28%. The failure mechanism shifted from shear brittleness to a shear-tension composite state, with enhanced post-peak bearing capacity. These findings provide support for optimizing silica sol grouting parameters in weakly cemented strata tunnels and for the synergistic reinforcement of rock mass permeability and strength. Full article

This work presents the synthesis, characterization, and application of zirconium oxide (ZrO₂)-based catalysts, modified with macro (silica nanospheres, NSP-SiO₂) and mesopore templates (Pluronic 123), impregnated with tungstophosphoric acid (TPA), in the catalytic pyrolysis of tomato agro-industrial residues. The NSP-SiO₂ (SXX) and P123 (PYY) amount mainly influences the ZrO₂SXXPYY-specific surface area (S_BET) and average pore diameter (D_p). ³¹P MAS NMR and FT-IR characterization results show that TPA (H₃PW₁₂O₄₀) was partially transformed into [P₂W₂₁O₇₁]⁶⁻ and [PW₁₁O₃₉]⁷⁻ during the synthesis steps. The acidic properties of ZrO₂SXXPYY samples containing 25 and 50 wt% of TPA (ZrO₂SXXPYYT25 and ZrO₂SXXPYYT50, respectively) are dependent on both the TPA content and the support nature. Bio-oil composition and product selectivity were strongly influenced by the textural and acid-based properties of the catalysts. Notably, non-catalytic pyrolysis favored pathways leading to C2 compounds, with a high content of acetic acid and hydroxyacetone. In contrast, the use of catalysts promoted the formation of higher molecular weight oxygenated compounds (C5–C6), specifically furans, aldehydes, and ketones. Full article

Reforming processes are key technologies for the production of hydrogen and synthesis gas from hydrocarbon feedstocks, with steam reforming and dry reforming being the most extensively studied routes. Steam reforming remains the dominant industrial process due to its high efficiency and economic viability; however, its associated CO₂ emissions raise environmental concerns, partially mitigated through an integration with carbon capture and storage technologies. Dry reforming has emerged as an attractive alternative, although it requires high operating temperatures and suffers from catalyst deactivation. Catalyst design is therefore critical for improving process efficiency and stability. Supported metal catalysts, particularly Ni-based systems, are widely employed, with the support material playing a decisive role in metal dispersion, resistance to sintering and coking, and reaction selectivity. Microporous and mesoporous silica-based materials, including zeolites and ordered mesoporous silicas, offer tunable structural and surface properties that enhance catalytic performance. The novelty of this work lies in its holistic approach to reforming catalysis, where the catalytic performance is not discussed solely in terms of active metals, but is systematically correlated with the surface properties, chemical composition, and structural features of silica-based supports. Moreover, this study expands the perspective to alternative and less-explored feedstocks. By considering multiple fuels and support types, the study provides new design guidelines for developing more efficient and sustainable reforming catalysts. Full article

In the present work, 1.92 wt% Pd/9.68 wt% CeO₂/spherical mesoporous silica (denoted as 1.92Pd/9.68CeO₂/KCC-1) and 1.96 wt% Pd/KCC-1 (denoted as 1.96Pd/KCC-1) catalysts were prepared. It was found that the 1.92Pd/9.68CeO₂/KCC-1 sample exhibited an excellent catalytic activity for methane combustion, which was much better than that of the 1.96Pd/KCC-1 sample. In addition, the 1.92Pd/9.68CeO₂/KCC-1 sample possessed good high-temperature stability and water resistance. The enhanced methane combustion performance of 1.92Pd/9.68CeO₂/KCC-1 was mainly attributed to the good dispersion of Pd species and the stabilization of the active Pd²⁺ species and generation of more reactive oxygen species by CeO₂ modification. This work offers new insights into developing methane combustion catalysts with low-temperature catalytic performance and high-temperature stability. Full article

The catalytic hydrogenation of carbon dioxide (CO₂) represents a transformative approach for reducing greenhouse gas emissions while producing sustainable fuels and chemicals, with ethanol being particularly promising due to its compatibility with existing energy infrastructure. Despite significant progress in converting CO₂ to C₁ products (e.g., methane, methanol), selective synthesis of C₂₊ compounds like ethanol remains challenging because of competing reaction pathways and byproduct formation. Recent advances in thermo-catalytic CO₂ hydrogenation have explored diverse catalyst systems including noble metals (Rh, Pd, Au, Ir, Pt) and non-noble metals (Co, Cu, Fe), supported on zeolites, metal oxides, perovskites, silica, metal–organic frameworks, and carbon-based materials. These studies reveal that catalytic performance hinges on the synergistic effects of multimetallic sites, tailored support properties and controlled reaction micro-environments to optimize CO₂ activation, controlled hydrogenation and C−C coupling. Mechanistic insights highlight the critical balance between CO₂ reduction steps and selective C−C bond formation, supported by thermodynamic analysis, advanced characterization techniques and theoretical calculations. However, challenges persist, such as low ethanol yields and undesired byproducts, necessitating innovative catalyst designs and optimized reactor configurations. Future efforts must integrate computational modeling, in situ/operando studies, and renewable hydrogen sources to advance scalable and economically viable processes. This review consolidates key findings, proposes potential reaction mechanisms, and outlines strategies for designing high-efficiency catalysts, ultimately providing reference for industrial application of CO₂-to-ethanol technologies. Full article

A series of silica-supported, nitrogen-doped carbon-encapsulated cobalt–nickel alloy catalysts (Co_xNi_y@NC/SiO₂) was successfully synthesized and systematically evaluated for the liquid-phase hydrogenation of 1-nitronaphthalene to 1-naphthylamine. Physicochemical characterization confirmed that the incorporation of nickel promotes the formation of Co–Ni alloys and modulates the electronic structure of the catalysts. The catalytic performance was found to be highly sensitive to the Co/Ni ratio, with Co₂Ni₁@NC/SiO₂ exhibiting the most outstanding activity. Under optimized reaction conditions (90 °C, 0.6 MPa H₂, 5.5 h), both the conversion of 1-nitronaphthalene and the selectivity toward 1-naphthylamine reached approximately 99%. The catalyst also demonstrated excellent stability and recyclability, attributed to the protective nitrogen-doped carbon shell and the synergistic interaction between the Co–Ni alloy and M–N_x active sites. This work provides a new strategy for designing efficient and robust non-noble-metal catalysts for hydrogenation reactions. Full article

Photo-Fenton advanced oxidation processes are promising and sustainable approaches for water treatment, particularly under visible-light irradiation. In this study, Cu-Fe bimetallic catalysts supported on silica and γ-alumina were developed for visible-light-driven photo-Fenton reactions, with emphasis on the influence of metal ratios and support-metal interactions on charge–carrier dynamics and hydroxyl radical formation. Comprehensive characterization (XRD, TEM, UV-Vis DRS, PL, TCSPC, and EPR) revealed stronger metal–support interactions and higher metal dispersion on γ-alumina, while silica-supported catalysts showed CuO aggregation at higher Cu loadings. Catalytic performance was evaluated using coumarin oxidation as both a model reaction and a quantitative probe for ^•OH radical generation. Alumina-supported catalysts exhibited superior activity, and ^•OH production increased with increasing Cu content on both supports. Importantly, iron was found to play a dual role: low Fe loading enhances photo-Fenton activity, whereas higher Fe content promotes charge–carrier recombination, leading to reduced activity under visible-light irradiation. These results highlight how the interplay between Fe/Cu ratio and support material governs charge dynamics and provides clear guidelines for the rational design of efficient heterogeneous photo-Fenton catalysts. Full article

The efficient generation of structurally diverse rare ginsenosides from abundant precursors remains a significant challenge. In this study, a heterogeneous catalyst, 12-tungstosilicic acid supported on mesoporous silica (HSiW@mSiO₂), was developed for the transformation of ginsenoside Re in aqueous ethanol solution. The reaction was conducted under mild conditions, and the products were systematically analyzed using high-performance liquid chromatography coupled with multistage tandem mass spectrometry and high-resolution mass spectrometry. A total of 24 transformation products were identified, arising from deglycosylation, epimerization, dehydration, cyclization, and nucleophilic addition reactions. Structural elucidation revealed the formation of deglycosylated, hydrated and dehydrated derivatives, C-20 epimers, and novel ethoxylated protopanaxatriol-type ginsenosides resulting from solvent incorporation at the C-24(25) or C-20 position. Product distribution varied with reaction parameters, including solvent composition, reaction time, temperature, and catalyst dosage. The synthesized HSiW@mSiO₂ catalyst could be readily recovered by centrifugation and reused for five consecutive cycles, with complete conversion of ginsenoside Re maintained in the first two runs and a gradual decline in conversion to approximately 50% by the fifth cycle. This work demonstrates the efficacy of solid acid catalysts in enabling the structural diversification of ginsenosides through solvent-involved pathways. Full article