Search Results (587)

The efficient conversion of CO₂ into valuable chemicals using highly efficient, environmentally friendly, and renewable heterogeneous catalysts is paramount for the progression of a carbon circular economy. In pursuit of this goal, this study introduces a metal-free, scalable melamine-based organic polymer catalyst designed to integrate CO₂ adsorption with customizable functional properties. Employing both solid-state thermal synthesis (SST) and hydrothermal methods, we synthesized three amine-based hydrogen bond donor catalysts, thereby balancing environmentally conscious practices with scalable synthesis: MCA, a high-nitrogen-content polymer derived from trichlorocyanuric acid; MCA-SST; and MTAB, a triazine-trichlorocyanuric acid polymer. Under mild conditions (100 °C, 0.1 MPa, 24 h), MCA demonstrated superior catalytic performance in the CO₂ cycloaddition of epichlorohydrin, achieving a 99% conversion rate, significantly surpassing MCA-SST (60%) and MTAB (78%). MCA’s high specific surface area and structural integrity facilitate efficient catalysis under mild conditions, and it retains 79% of its initial activity after five cycles, indicating exceptional stability. These results suggest that while the incorporation of secondary amines and increased nitrogen content generally promote the reaction, densely packed adjacent secondary amine linkages can induce repulsion between nitrogen atoms, thereby weakening active sites and reducing catalytic activity. Consequently, this study not only presents MCA as a novel metal-free catalyst exhibiting remarkable performance in catalyzing CO₂ cycloaddition under ambient pressure and mild conditions, but also elucidates the structure–activity relationship between secondary amine density and catalytic activity. This work provides a deeper mechanistic understanding and offers a theoretical foundation for future rational catalyst design. Full article

The industrial preparation via solid-state polymerization (SSP) of high-viscosity copolyamides 6/66 (PA6/66) addresses the challenges, including prolonged reaction times, high energy consumption, and uneven viscosity distribution. In this study, sodium hypophosphite was introduced into the PA6/66 copolymerization system as a solid-state polymerization catalyst. The effects of this catalyst on the solid-state viscosity-increasing rate and relative viscosity were systematically investigated, and the extraction process was optimized to solve the loss of catalyst and controllable extractable content. The results showed that the relative viscosity of PA6/66 increased linearly with the SSP time, and the apparent viscosity increase rate could be stably maintained at 0.14 h⁻¹ at 160 °C due to the catalytic action. Based on the phosphorus (P) content in the chips, the viscosity increase rate is not further large when the P content is 25 ppm at 150 °C and 30 ppm at 160 °C, which can be added as a “control concentration” as a catalyst. The extraction kinetics showed that the catalyst concentration of the chip could be kept higher than the control concentration, and the extractable content can satisfy the requirements for processing. The catalyst of sodium hypophosphite was utilized on the 4500 tons/year PA6/66 continuous polymerization test line, and the high-viscosity PA6/66 chips with uniform viscosity were stably prepared. This study provides a reliable theoretical basis and process route for the large-scale continuous preparation of high-quality and high-viscosity PA6/66 resin. Full article

A series of catalytic oxides (Fe₂O₃, CuO, ZnO, and Cu₂O) were investigated as prospective additives shaping the thermal features of a model solid rocket propellant (SRP) formulation utilising ammonium nitrate as the oxidising agent. An extensive investigation of the thermal behaviour (DSC and ignition/explosion temperature studies) of the model and catalyst-bearing SRP formulations was conducted, providing insights into both the thermodynamics and mechanism of combustion of these systems. XRD analysis of post-combustion residues was used to validate the mechanistic claims, as well as to provide information about the behaviour of copper oxides in the SRP system. In addition, the linear combustion velocity was experimentally determined, and the power output was estimated from density, linear combustion velocity and DSC data, in order to assess the potential motor performance of the tested formulations. The obtained results show that the utilisation of metal oxides significantly improves the combustion performance of ammonium nitrate-based SRP formulations relative to the unmodified ammonium nitrate-based propellants. Full article

Solid base catalysts hold significant promise for replacing traditional homogeneous bases with green chemical processes. However, the construction of their strong basic sites typically relies on high-temperature calcination, which often leads to the collapse of the carrier structure and high energy consumption. This study proposes a novel “carrier reducibility tuning” strategy, which involves endowing the carrier with intrinsic reducibility to induce the low-temperature decomposition of alkali precursors via a redox pathway, thereby enabling the mild construction of strong basic sites. Low-valence Cr³⁺ was doped into a mesoporous zirconia framework, successfully fabricating an MCZ carrier with a mesostructure and reducible characteristics. Characterization results indicate that a significant redox interaction between the Cr³⁺ in the carrier and the supported KNO₃ occurs at 500 °C. This interaction facilitates the complete conversion of KNO₃ into highly dispersed, strongly basic K₂O species, while Cr³⁺ is predominantly oxidized to Cr⁶⁺. This activation temperature is approximately 300 °C lower than that required for the conventional thermal decomposition pathway and effectively preserves the structural integrity of the material. In the transesterification reaction for synthesizing dimethyl carbonate, the prepared catalyst exhibits superior catalytic activity, significantly outperforming classic solid bases like MgO and other reference catalysts. Full article

One-dimensional ZnO nanowires offer significant potential for optoelectronic applications, though their controlled synthesis remains challenging. This study optimized ZnO nanowire growth via carbothermal reduction vapor transport based on the vapor–liquid–solid mechanism. Key parameters investigated were gold catalyst thickness and annealing, source temperature, system pressure, and oxygen concentration. Results show that thinner Au films promote high-density, small-diameter nanowires. An optimal source temperature window (950–1000 °C) was identified, while pressure and oxygen content critically influenced growth mode by modulating vapor supersaturation. Under optimized conditions, aligned single-crystalline ZnO nanowires with hexagonal wurtzite structure were achieved. Structural and optical characterization confirmed high crystallinity and strong near-band-edge emission, demonstrating the efficacy of the developed approach for tailored nanowire synthesis. Full article

This study focuses on the development and physicochemical evaluation of an alternative liquid carrier for coal dust combustion modifiers containing solid catalyst particles. A commercially used acrylic-polymer-based carrier, whose viscosity is regulated by sodium hydroxide addition, was investigated and compared with a proposed safer substitute based on an aqueous sodium carboxymethyl cellulose (Na-CMC) solution. Rheological properties were measured in the shear-rate range relevant to industrial transport and injection systems, while sedimentation behavior was assessed using image-based analysis. The results show that the Na-CMC carrier exhibits shear-thinning behavior and viscosity levels comparable to the commercial formulation, enabling stable suspension of catalyst particles without the need for alkali additives. Unlike the reference system, the alternative carrier does not generate gas during storage, eliminating potential safety hazards associated with hydrogen evolution. Although no direct combustion experiments were performed, the obtained rheological and stability characteristics indicate that the proposed Na-CMC-based carrier is suitable for short-term storage and injection of catalyst-containing modifiers in coal dust combustion systems. Direct validation of combustion performance is planned in future work. Full article

Biodiesel, which is a blend of fatty acid methyl esters (FAME), has garnered significant attention as a promising alternative to petroleum-based diesel fuel. Nevertheless, the commercial production of biodiesel faces challenges due to the high costs associated with feedstock and the non-recyclable homogeneous catalyst system. To address these issues, a solid catalyst derived from construction industry waste cement was synthesized and utilized for biodiesel production from waste cooking oil (WCO). The catalyst’s surface and physical characteristics were analyzed through various techniques, including Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier Transform Infrared Spectroscopy (FTIR). The waste-cement catalyst demonstrated remarkable catalytic performance and reusability in the transesterification of WCO with methanol for biodiesel synthesis. A maximum biodiesel yield of 98.1% was obtained under the optimal reaction conditions of reaction temperature 65 °C; methanol/WCO molar ratio 16:1; calcined cement dosage 3 g; and reaction time 8 h. The apparent activation energy (Ea) from the reaction kinetic study is 35.78 KJ·mol⁻¹, suggesting that the transesterification reaction is governed by kinetic control rather than diffusion. The biodiesel produced exhibited high-quality properties and can be utilized in existing diesel engines without any modifications. This research presents a scalable, environmentally benign pathway for WCO transesterification, thereby contributing significantly to the economic viability and long-term sustainability of the global biodiesel industry. Full article

Magnesium hydride (MgH₂) is a promising solid-state hydrogen storage material owing to its high hydrogen capacity and low cost, yet its practical application is limited by sluggish kinetics, high operating temperatures, and poor cycling stability. Among various catalytic approaches, Fe-based catalysts have emerged as attractive candidates due to their abundance, compositional tunability, and effective promotion of hydrogen sorption reactions in MgH₂ systems. This review critically summarizes recent progress in Fe-based catalysts for MgH₂ hydrogen storage, encompassing elemental Fe, iron oxides, Fe-based alloys, and advanced composite catalysts with nanostructured and multicomponent architectures. Mechanistic insights into catalytic enhancement are discussed, with particular emphasis on interfacial electron transfer, catalytic phase evolution, hydrogen diffusion pathways, and synergistic effects between Fe-containing species and MgH₂, supported by experimental and theoretical studies. In addition to catalytic activity, key stability challenges—including catalyst agglomeration, phase segregation, interfacial degradation, and performance decay during cycling—are analyzed in relation to structural evolution and kinetic–thermodynamic trade-offs. Finally, a roadmap for the scalable design of Fe-based catalysts is proposed, highlighting rational catalyst selection, interface engineering, and compatibility with large-scale synthesis. This review aims to bridge fundamental mechanisms with practical design considerations for developing durable and high-performance MgH₂-based hydrogen storage materials. Full article

The expansion of green hydrogen requires technologies that are both manufacturable at a GW-to-TW power scale and adaptable for decentralized, renewable-driven energy systems. Recent advances in proton exchange membrane, alkaline, and solid oxide electrolysis reveal persistent bottlenecks in catalysts, membranes, porous transport layers, bipolar plates, sealing, and high-temperature ceramics. Emerging fabrication strategies, including roll-to-roll coating, spatial atomic layer deposition, digital-twin-based quality assurance, automated stack assembly, and circular material recovery, enable high-yield, low-variance production compatible with multi-GW power plants. At the same time, these developments support decentralized hydrogen systems that demand compact, dynamically operated, and material-efficient electrolyzers integrated with local renewable generation. The analysis underscores the need to jointly optimize material durability, manufacturing precision, and system-level controllability to ensure reliable and cost-effective hydrogen supply. This paper outlines a convergent approach that connects critical-material reduction, high-throughput manufacturing, a digitalized balance of plant, and circularity with distributed energy architectures and large-scale industrial deployment. Full article

Efficient conversion of biomass-based platform molecules into high-value derivatives is recognized as one formidable challenge in biomass upgrading. In this work, a one-pot deep eutectic solvents-assisted solvothermal method was developed for the modification of the commercial Pt/C catalysts by introducing a secondary metal (M = Sn, Bi, Ge, Sb, Pb). The structural and electronic properties of the catalysts were precisely tuned. Among the screened metals, the addition of Sn yielded the most significant improvement in catalytic activity. The optimized PtSn_0.5/C-140 catalyst achieved superior furfural (FAL) conversion and furfuryl alcohol (FOL) selectivity under mild conditions (20 °C, 2 MPa H₂). Comprehensive characterizations, including XRD, HRTEM, XPS, and H₂-TPD, confirmed the formation of Pt-Sn solid-solution phase. Furthermore, Characterization and reaction results revealed that the electronic and geometric effects induced by Sn modulated Pt active sites, significantly enhancing the adsorption of the active H species. Additionally, the SnO_x species adjacent to the Pt-Sn sites served as hydrogen spillover acceptors, further accelerating the hydrogenation process. The synergy between the Pt-Sn solid-solution phase and SnO_x species is identified as the origin of the superior performance at room temperature. These findings provide a new strategy for the design of high-performance biomass conversion catalysts by upgrading commercial noble metal catalysts. Full article

Rhenium is one of the rarest and most strategically important metals, indispensable in high-temperature superalloys and platinum–rhenium catalysts used across the aerospace and petrochemical industries. Owing to its limited primary reserves, recovering rhenium from secondary sources, such as spent catalysts, superalloy residues, and metallurgical dusts, has become vital to ensuring supply security. This review examines technological developments between 1998 and 2025, focusing on how operational parameters, including temperature, leaching time, reagent concentration, and solid-to-liquid ratio, govern dissolution kinetics and overall process efficiency. Comparative evaluation of hydrometallurgical, alkaline, and hybrid processes indicates that modern systems can achieve recovery rates exceeding 98% through selective oxidation, alkaline activation, or combined pyro and hydrometallurgical mechanisms. Acid–chlorine leaching facilitates rapid, low-temperature dissolution; alkaline sintering stabilises rhenium as soluble perrhenates; and hybrid smelting routes enable the concurrent separation of rhenium and osmium. Sustainable aqueous systems employing nitric and ammonium media have also demonstrated near-complete recovery at ambient temperature under closed-loop recycling conditions. Collectively, these findings highlight a technological transition from energy-intensive, acid-based pathways towards low-impact, recyclable, and digitally optimised hydrometallurgical processes. The integration of selective oxidants, phase engineering, circular reagent management, and artificial intelligence-assisted modelling is defining the next generation of rhenium recovery, combining high extraction yields with reduced environmental impact and alignment with global sustainability goals. Full article

The continuous tightening of emission regulations and the escalating costs of palladium (Pd) and rhodium (Rh) have renewed interest in platinum (Pt)-based three-way catalysts (TWCs) as cost-effective alternatives for gasoline aftertreatment. However, despite extensive studies on Pt/CeO₂ and Pt/Ba-based formulations, the cooperative roles of Ba and Ce and, in particular, the fundamental influence of the Ba/Ce ratio on oxygen mobility, NO_x storage behavior, and Pt–support interactions remain poorly understood. In this work, we address this gap by systematically tuning the Ba/Ce molar ratio in a series of Pt–Ba–Ce/Al₂O₃ catalysts prepared from Ba(CH₃COO)₂ and CeO₂ precursors, and evaluating their structure–function relationships in both fresh and hydrothermally aged states. Through comprehensive characterization (N₂ physisorption, XRD, XPS, H₂-TPR, NO_x-TPD, SEM, CO pulse adsorption, and dynamic light-off testing), we establish previously unrecognized correlations between Ba/Ce ratio–dependent structural evolution and TWC performance. The results reveal that the Ba/Ce ratio exerts a decisive control over catalyst textural properties, Pt dispersion, and interfacial Pt–CeO₂ oxygen species. Low Ba/Ce ratios uniquely promote Pt–Ce interfacial oxygen and O₂ spillover—providing a new mechanistic basis for enhanced low-temperature oxidation and reduction reactions—while higher Ba loading selectively drives BaCO₃ formation and boosts NO_x storage capacity. A clear volcano-type dependence of NO_x storage on the Ba/Ce ratio is demonstrated for the first time. Hydrothermal aging at 850 °C induces PtO_x decomposition, BaCO₃–Al₂O₃ solid-state reactions forming inactive BaAl₂O₄, and Pt sintering, collectively suppressing Pt–Ce interactions and reducing TWC activity. Importantly, an optimized Ba/Ce ratio is shown to mitigate these degradation pathways, offering a new design principle for thermally durable Pt-based TWCs. Overall, this study provides new mechanistic insight into Ba–Ce cooperative effects, establishes the Ba/Ce ratio as a critical and previously overlooked parameter governing Pt–support interactions and NO_x storage, and presents a rational strategy for designing cost-effective, hydrothermally robust Pt-based alternatives to Pd/Rh commercial TWCs. Full article

This study presents a one-dimensional numerical simulation of particulate matter (PM) oxidation and regeneration behavior in gasoline particulate filters (GPFs) under Worldwide Harmonized Light Vehicles Test Cycle (WLTC) conditions. The model incorporates both catalyst activity—represented by activation energy (E) and pre-exponential factor (A)—and exhaust control strategies involving forced fuel cut (FC). PM deposition and oxidation were simulated based on solid-state and gas-phase reactions, with the effects of oxygen concentration and temperature analyzed in detail. The results show that under high catalyst activity (E = 100 kJ mol⁻¹, A = 6.2 × 10⁷), PM oxidation proceeds efficiently even during medium-speed phases, achieving a 98.8% oxidation rate after one WLTC. Conversely, conventional catalysts (E = 120 kJ mol⁻¹, A = 6.2 × 10⁶) exhibited limited regeneration, leaving 0.11 g of residual PM. Introducing forced FC effectively enhanced oxidation by increasing oxygen concentration to 20% and sustaining heat release. A single continuous 100 s FC yielded the highest oxidation (96% reduction), while split FCs reduced peak PM accumulation. These findings demonstrate that optimizing the balance between catalyst activity and FC control can significantly improve GPF regeneration performance, providing a practical strategy for PM reduction in GDI vehicles under real driving conditions. Full article

As a widely sourced solid waste rich in metallic elements such as Fe, Zn, Mn and Ca, electric furnace dust serves as a crucial raw material for preparing catalytic materials. This study employed a three-step process—“acid/alkali modification–impregnation–calcination”—to synthesise an electric furnace dust-based magnetic heterogeneous catalyst for biodiesel production. The catalyst prepared via CH₃ONa modification combined with Na₂CO₃ impregnation achieved stable cycling performance at low temperatures, with 14 cycles yielding a consistent conversion exceeding 93.44 wt%, demonstrating exceptional catalytic activity. The CH₃ONa modification generates abundant reactive oxygen species on the furnace dust surface, facilitating the binding of hydroxyl oxygen from the active component (Na⁺) to the modified surface (EFD/CH₃ONa) and thereby anchoring the active species. However, the decline in catalytic performance of the Na₂CO₃&(EFD/CH₃ONa) catalyst after calcination at 600 °C (yield decreasing to 69.77 wt% after 11 stable cycles) was attributed to the detachment and agglomeration of the active component sodium at elevated temperatures. This paper employed electric furnace dust as feedstock to synthesise highly active and stable magnetic multiphase catalysts, thereby not only providing an environmentally sound pathway for industrial solid waste recycling but also offering novel insights for the industrial-scale production of biodiesel. Full article

Titania catalysts containing cerium, copper, or iron were obtained using the sol–gel method and tested in the selective reduction of nitrogen oxide. Samples with cerium and iron showed high activity at temperatures ranging from 200 to 400 °C, without the formation of N₂O. The materials crystallized in anatase structure, and only a small amount of ceria was detected by XRD. Their crystallites were nanometric in size. The solids were mesoporous, with a specific surface area between 74 and 160 m²/g, determined based on nitrogen sorption at low temperature. The optimum Ce/Ti and Fe/Ti atomic ratio was 0.1 to 0.9, and such catalysts were composed of small anatase crystallites, although the presence of ceria also resulted in high catalytic activity. This activity was due to the presence of Fe³⁺ or Ce³⁺ ions on the surface of the material. Full article