Search Results (444)

Improving the separation efficiency between methyldichlorosilane (CH₃SiHCl₂) and trichlorosilane (SiHCl₃) is one of the key urgent problems to be solved for the quality improvement and consumption reduction in high-purity polysilicon. In this work, three types of porous supported catalysts were prepared via an in situ reaction method, taking aluminum chloride (AlCl₃) as the active component and activated carbon, silica gel and activated alumina as support; the catalytic reaction mechanisms of CH₃SiHCl₂ and silicon tetrachloride (SiCl₄) over the as-prepared porous supported catalysts were investigated, based on density functional theory (DFT). The results reveal that among the three supported catalysts, the activated carbon-supported aluminum chloride catalyst (C@AlCl₃) possesses the maximum binding energy (−3.20 eV) between the active component and support. CH₃SiHCl₂ and SiCl₄ possess the lowest co-adsorption energy (−1.8 eV) and the minimum reaction energy barrier (0.8 eV) on C@AlCl₃, accompanied by the maximum charge transfer to the catalyst surface (−2.65 e and −2.80 e), thus exhibiting the highest catalytic activity, with the maximum single-pass conversion of CH₃SiHCl₂ exceeding 90%. This work provides material basis and theoretical guidance for constructing a reactive distillation strategy for high-efficiency and low-energy separation of CH₃SiHCl₂ from SiHCl₃. Full article

Dry reforming of methane (DRM) represents a promising route for the valorization of CO₂ captured from industrial emissions through high-temperature catalytic conversion. In this work, a LaMn_1−xNi_xO₃ perovskite catalyst (x = 0.25, 6 wt% Ni) was synthesized as a powder by solution combustion synthesis and subsequently deposited onto γ-alumina supports to obtain a structured catalyst. X-ray diffraction confirmed the formation of the perovskite structure, characterized by corner-sharing BO₆ octahedra with Ni substitution at the B-site. H₂-temperature-programmed reduction (H₂-TPR) revealed the reduction of Mn⁴⁺ and Mn³⁺ species to MnO, accompanied by the complete reduction of oxidized Ni species to metallic Ni over the investigated temperature range. Raman spectroscopy of the spent catalyst indicated negligible carbon deposition after DRM. Moreover, the Mn–O stretching band shifted from 657 cm⁻¹ in the fresh catalyst to 643 cm⁻¹ after reaction, consistent with changes in the manganese oxidation state associated with the collapse of the perovskite structure and the formation of MnO. During a 25 h stability test at 700 °C, the powdered LaMn_1−xNi_xO₃ catalyst achieved a CH₄ conversion of 75% at a WHSV of 60 L g⁻¹ h⁻¹. DRM tests performed with the structured catalyst confirmed the catalytic performance under larger-scale operating conditions and different reaction parameters, including temperature, residence time, and CH₄/CO₂ feed ratio, reaching CH₄ conversions of up to 94% at 800 °C. Full article

Electrified steam methane reforming (eSMR) is emerging as a promising technology for the decarbonization of the chemical industry and low-carbon hydrogen production by coupling renewable electricity with renewable gaseous feedstocks such as biomethane. In this work, structured Ni-based catalysts washcoated on highly thermally conductive SiC open-cell foams (OCFs) were developed and evaluated for biomethane steam-reforming operating conditions. Two catalyst formulations, 30 wt.% Al₂O₃_30 wt.% CeO₂_20 wt.%Ni and SiC_30 wt.% Al₂O₃_30 wt.%Ce_0.25Zr0.75 O₂_20 wt.%Ni, were tested in a laboratory-scale indirectly electrically heated reformer. The high thermal conductivity of the SiC-structured support ensured efficient heat transfer throughout the reactor, limiting radial temperature gradients to below 10 °C. Both catalyst formulations exhibited excellent catalytic performance; however, the Ce_0.25Zr0.75O₂-promoted catalyst achieved the best results, maintaining equilibrium methane conversion at a gas hourly space velocity above 7000 h⁻¹ while reaching a specific electrical energy consumption of 2.06 kWh/Nm³ of produced H₂ projected for industrial-scale efficiency. Notably, these performances were obtained with a catalyst loading approximately 20–50% lower than that of conventional commercial alumina pellet catalysts. XRD characterization did not reveal the formation of crystalline graphitic carbon after catalytic operation. Furthermore, the structural evolution of the Ce–Zr–O highlights the active role of the mixed oxide in promoting redox processes and maintaining catalytic activity under reaction conditions. Overall, these results demonstrate that the combination of highly conductive SiC-structured supports and Ce–Zr-promoted Ni catalysts significantly enhances both the thermal and catalytic efficiency of eSMR. The proposed catalyst provides a promising route toward compact, energy-efficient, and decentralized hydrogen production from biomethane, supporting the electrification and decarbonization of future hydrogen generation technologies. Full article

Metal centralizers suffer high frictional resistance, high self-weight, and severe pore shrinkage after perforation in deep, highly deviated, and horizontal wells. Targeting the performance demands of adhesive casing centralizers, this study uses epoxy resin as the matrix, introduces amino modification, and regulates inorganic filler composites to prepare an amino-modified epoxy resin composite centralizer material, followed by systematic property tests. The optimal formula of modified epoxy resin:curing agent:UR300 accelerator:amino-modified silica:silicon carbide:alumina is 100:10:1:1:35:20 and delivers superior comprehensive performance. Its compressive strength reaches 136.61 MPa with a Shore hardness of 92.32 HD, low linear expansion, and favorable thermal compatibility with steel casings. Hardness remains stable after 168 h of aging at 150 °C, and the material maintains low friction at ambient and elevated temperatures. After 30-day immersion in acidic, alkaline, and high-salinity fluids, its compressive strength retention exceeds 86% with a slight variation in volume and mass, while adhesion strength reaches 2.667 MPa at a pipe-wall roughness of 12.12 μm. Combining high strength, heat resistance, corrosion resistance, and strong adhesion, the material suits complex downhole conditions and supports the field application of resin composite centralizers. Full article

Bauxite residue (red mud) is a highly alkaline byproduct of the alumina refining process generated in large volumes worldwide. Most alumina operations currently rely on long-term storage facilities due to the high costs and technical constraints of residue reuse technologies. Therefore, understanding the mechanical behaviour of bauxite residue is critical to minimising environmental contamination risks, preventing structural failures, and ensuring the long-term stability of storage facilities. However, obtaining reliable geotechnical parameters is challenging due to the residue’s complex composition and chemical characteristics, particularly given the current fragmented state of the literature. This review compiles an extensive database of bauxite residue parameters across alumina operations worldwide, synthesising existing knowledge and research needs. The database encompasses 940 data points extracted from 63 studies across 25 countries. The findings reveal considerable variability in parameter values across countries, potentially exacerbated by inconsistencies in experimental methodologies. Few studies have integrated geochemical conditions, such as pH and salinity, with geomechanical behaviour, thereby limiting understanding of the mechanisms that govern key parameters, including strength and deformability. Enhancing the predictability of bauxite residue behaviour requires the development of standardised experimental protocols that explicitly account for the coupled effects of chemistry and mechanics to support reliable risk assessments of storage facilities. Full article

Partial oxidation of methane (POM) is a thermodynamically favorable process for hydrogen and syngas production. Cerium oxide (CeO₂) was investigated as a textural promoter for nickel (Ni)-based catalysts in POM. In this study, CeO₂ was incorporated into Ni/Al₂O₃ catalysts with varying cerium loadings (1–3 wt.%) to examine its role as a structural and functional promoter. Comprehensive physicochemical characterization using BET, XRD, H₂-TPR, and TEM analyses indicated that incorporation of ceria influenced the textural and structural properties, leading to reduced Ni crystallite size from 10 nm to 2.9–3.3 nm, and modified metal-support interactions. The 2 wt.% CeO₂-modified Ni/Al₂O₃ (Ni/2Ce-Al) catalyst demonstrated superior catalytic performance, achieving 70% methane (CH₄) conversion and 64% hydrogen (H₂) yield at 650 °C with stable performance over 275 min time-on-stream with minimal deactivation. Temperature-programmed reduction studies revealed a non-monotonic trend in reduction behavior with an optimal 2 wt.% cerium loading exhibiting the lowest reduction temperature (865 °C). The H₂/CO ratio of 2.92 indicates favorable syngas composition under the conditions studied. Raman spectroscopy showed a decrease in the D/G intensity ratio from 1.55 to 1.33 with increasing cerium loading, indicating enhanced structural ordering and improved coke resistance. The improved catalytic performance may be associated with redox properties of ceria (Ce³⁺/Ce⁴⁺ cycling), its enhanced oxygen storage capacity, and modified Ni-support interactions which can contribute to improved resistance to carbon deposition and Ni sintering. Response surface methodology (RSM) was also successfully used to model the interaction of temperature, space velocity and feed ratio and to confirm the significant positive effect of temperature on conversion. The long-term performance of the optimized catalyst, over a 20 h period, demonstrated the excellent durability of the catalyst, resulting in a stable H₂ yield of ca. 87% and CH₄ conversion of ca. 90%. This work demonstrates that optimized cerium promotion on alumina-supported Ni catalysts can improve catalytic activity and stability, providing a potentially cost-effective, thermally stable catalyst system for industrial hydrogen and syngas production from (CH₄). Full article

This work reports the design and validation of a reusable platinum (Pt) electrode platform (ST-E) for green electrochemical analysis. The device integrates Pt working and counter electrodes with an external Ag/AgCl reference and is engineered for repeated regeneration and refunctionalization. Surface renewal by alumina polishing followed by electrochemical activation in 0.5 M H₂SO₄ restores a clean, reproducible Pt surface, as confirmed by diffusion-controlled, reversible ferricyanide voltammetry over 5–150 mV s⁻¹ with near-Nernstian peak separation and i_pa/ipc ≈ 1. Platform versatility is demonstrated in two applications. First, ST-E is functionalized with PFOA-selective molecularly imprinted nanoparticles on an APTES layer, enabling trace determination of perfluorooctanoic acid (1–5 pg mL⁻¹), with a detection limit of 0.50 pg mL⁻¹ and sensitivity of 3.16 μA (pg mL⁻¹)⁻¹. Responses correlate with an equivalently modified commercial screen-printed electrode (r = 0.990, p < 0.005), with Bland–Altman analysis confirming concordance. Second, after regeneration, electropolymerization of o-phenylenediamine yields an insulating poly(o-phenylenediamine) film that attenuates redox currents and increases ΔE_p, illustrating compatibility with diverse surface chemistries. Green metrics (AGREE, AGREEprep ≈ 0.80; BAGI = 75.0) highlight reduced waste and solvent use versus single-use transducers and compatibility with portable potentiostats, supporting circular electrochemical sensing. Full article

Methane partial oxidation (POM) offers a promising pathway for syngas production, but achieving optimal catalyst performance requires precise control of promoter loading. We systematically investigated cerium (Ce) promotion on nickel-based catalysts supported on aluminum oxide (Ni/Al₂O₃) catalysts across 1–3 wt.% loadings and identified a critical discovery: catalyst performance exhibits a pronounced non-monotonic response to Ce concentration. The 1 wt.% Ce-promoted catalyst (Ni+1Ce/Al) achieved the superior performance with 65% methane conversion and 60% hydrogen yield at 650 °C, maintaining stable output over 275 min time-on-stream. This smaller Ce amount tunes NiO reducibility, oxygen mobility, and metal–support interactions, resulting in improved activity performance of Ni+1Ce/Al. Notably, Ce promotion shifts the H₂/CO ratio from 2.5 to 2.9, with the increased hydrogen yield arising from enhanced water–gas shift chemistry and indirect oxidation pathways. Excess cerium (2–3 wt.%) causes performance deterioration, Ni particle agglomeration, and thus loss of Ni active sites, demonstrating that Ce operates as a structural promoter with a well-defined appropriate concentration window. Moreover, the best performing catalyst (Ni+1Ce/Al) remained stable during 20-h long-term POM. An artificial neural network model achieved exceptional predictive accuracy (R = 0.9758 overall), validating the experimental findings. These results indicate that the best Ce loading for industrial application is 1 wt.% and the traditional alumina supports can be competitive in performance with the advantage of thermal stability and cost-effectiveness when doped with rare-earth elements. Full article

The electrification of high-temperature industrial processes requires refractory materials that combine thermal stability with tailored electrical functionality. In this study, Ta/Nb-Al₂O₃ composites were prepared by spark plasma sintering (SPS) to investigate densification, metal-phase deformation, electrical conductivity and percolation behavior. Coarse, fine and superfine alumina powders were combined with tantalum or niobium and sintered at 1300–1600 °C for 5 min with 50 MPa uniaxial pressure. The results show that the alumina particle size and morphology strongly influence the formation of conductive metal networks. Coarse alumina promotes deformation and elongation of the metallic phase, thereby improving metal-phase connectivity and lowering the operational percolation threshold. Fine and superfine alumina enhance densification but can delay percolation by embedding metal particles in a dense ceramic matrix. Combining these fractions, both effects can be balanced, enabling improved densification while maintaining effective conductive pathways. An operational percolation threshold of 7.5 vol.-% was obtained for Ta/coarse alumina, indicating highly effective metal-phase connectivity after SPS. Microstructural analysis supports the interpretation that matrix-controlled metal-particle deformation and spatial distribution govern the electrical response. Tailored alumina matrix design can reduce the refractory metal content required for conductive ceramic–metal composites. Full article

Molecular transport membranes are promising alternatives to conventional cryogenic separation processes. Here, solvent polarity effects were investigated by varying the DMF/MeOH ratio during the solvothermal synthesis of supported ZIF-7 membranes. A DMF:MeOH ratio of 1:3 preserved the characteristic sodalite topology while suppressing dense-phase formation. Methanol incorporation modified heterogeneous crystallization behavior, intercrystalline organization, membrane morphology, and film densification on α-alumina supports while reducing DMF consumption by approximately 75%. These effects are associated with solvent-mediated precursor solvation, Zn²⁺–benzimidazole coordination equilibria, and heterogeneous nucleation at the support–solution interface. Although low BET surface areas were obtained from N₂ adsorption at 77 K, these values were interpreted cautiously considering the known limitations of nitrogen physisorption in flexible ultramicroporous frameworks. Overall, the results support solvent polarity engineering as a physicochemical strategy for regulating membrane microstructural evolution under reduced DMF conditions. Accordingly, the transport behavior discussed herein is interpreted primarily from a solvent-mediated microstructural perspective rather than as a direct quantitative descriptor of accessible porosity. Full article

Piezoelectric pressure sensors for dynamic monitoring face a trade-off between charge output and measurement range, and existing high-sensitivity designs are largely confined to narrow ranges. This study presents a composite layered piezoelectric pressure sensor in which a 316L stainless-steel diaphragm drives a centrally suspended PZT-5H wafer supported by a perforated alumina gasket, with the wafer thickness and cavity radius optimized under a 10 MPa full-scale stress constraint. Over 0–10 MPa, quasi-static calibration gave a highly repeatable quadratic pressure–charge relationship ($R^2=0.99995$) with a maximum residual below 1% FS. The sensitivity is pressure-dependent: the secant sensitivity increased monotonically from 3.16 pC/kPa at 1 MPa to 5.36 pC/kPa at 10 MPa, reflecting a stress-stiffening response rather than a measurement tolerance band. The output deviation remained within 3% from 25 °C to 150 °C. Shock-tube testing yielded a resonance of ∼50 kHz and a mutually consistent 10–90% leading-edge interval of 10.12 $\mathsf{\mu }$s. Combining high charge sensitivity over a wide 0–10 MPa range with a fast transient response and stable operation up to 150 °C, the proposed sensor is suited to dynamic pressure-pulsation monitoring in fluid-power and thermal and power-plant fluid systems. Full article

Rhodamine B (RhB) is a typical xanthene-based cationic dye. Its widespread application has brought serious safety and environmental risks. Heterogeneous Fenton systems based on zero-valent iron (Fe⁰) are promising for RhB degradation. However, bare Fe⁰ suffers from severe agglomeration and surface passivation. In this study, alumina with a large pore volume and high specific surface area was employed as a support to enhance Fe⁰ dispersion and stability. The catalyst was prepared via a glucose-assisted carbothermal reduction method, and the formation of Fe⁰ was confirmed by X-ray diffraction and electron microscopy analyses. Under optimal conditions (pH = 3.58, catalyst dosage = 0.8 g·L⁻¹, H₂O₂ = 10 mM), 10 mg·L⁻¹ RhB was completely degraded within 25 min, with a pseudo-first-order rate constant of 0.432 min⁻¹. This exhibits a faster degradation rate and efficiency advantage. Radical quenching experiments indicated that hydroxyl radicals (•OH) were the dominant reactive species, while singlet oxygen (¹O₂) also contributed to the degradation process. Two primary degradation pathways, including N-deethylation and hydroxylation, were identified. The catalyst showed moderate reusability with slight deactivation after repeated cycles. This study demonstrates that tailoring the pore structure of alumina supports is an effective strategy to enhance Fe⁰ dispersion, mass transfer, and catalytic performance in heterogeneous Fenton systems. Full article

Methods for the preparation of aluminum hydroxides and alumina-supported catalysts through the interaction of activated Al–In–Ga alloys with water were developed. Bayerite was obtained from an alloy containing 99.0% Al + 0.5% In + 0.5% Ga at 303 K, while pseudoboehmite was synthesized from 90% Al + 5% In + 5% Ga at 363 K. The maximum specific surface area of aluminum oxide reached 700 m²/g. Dehydration of aluminum hydroxides proceeds via a sigmoidal mechanism with induction, acceleration, and deceleration stages. The dehydration rate increases with calcination temperature. Kinetic analysis revealed both kinetic and diffusion-controlled transformation regions for pseudoboehmite and bayerite. Transformation of pseudoboehmite into γ-Al₂O₃ at 523–673 K preserves a high specific surface area of 630–640 m²/g. Two platinum deposition methods were proposed: synthesis in the presence of soluble platinum salts and incorporation of Pt into the Al–Ga–In alloy followed by reaction with water. Alongside metallic Pt, Ptδ⁺, Pt²⁺, and Pt⁴⁺ species were detected and reduced to Pt⁰ at 900 K. Alumina–platinum catalysts showed high activity in cyclohexane dehydrogenation. A Zn–Al catalyst for methanol decomposition was developed, providing up to 70% H₂ in gaseous fuel and complete methanol conversion at 573 K. Full article

Fine-paste earthenware held symbolic significance in Hindu and Buddhist rituals and domestic use in Southeast Asia. Despite the influx of Chinese glazed ceramics from the ninth century onward, these locally produced vessels continued to circulate widely until the fourteenth century along maritime trade routes extending from northern Sumatra and Java to the southern Philippines and the Thai–Malay Peninsula. Integrated petrographic, Field Emission Scanning Electron Microscopy (FESEM), and Energy Dispersive X-ray Spectroscopy (EDS) analyses were employed to compare fine-paste earthenware from the Kok Moh production center in Songkhla Province, Thailand, and the Kota Cina consumption site in northern Sumatra, Indonesia. Petrographic observations indicate broadly similar mineralogical compositions in samples from both sites, consistent with the use of kaolin-rich clay materials. FESEM reveals that Kok Moh samples exhibit relatively dense and homogeneous microstructures with more continuous matrices, whereas Kota Cina specimens display coarser textures, more distinct mineral inclusions, and less consolidated matrices. EDS elemental mapping further demonstrates a more uniform distribution of major elements in the Kok Moh samples. Although both groups share broadly similar silica–alumina compositions, the observed microstructural differences suggest variations in clay preparation and firing practices rather than major differences in raw material selection. Comparison with published data from Nakhon Si Thammarat supports an association with kaolin-rich clay resources in southern Thailand. In contrast, the examined ceramics differ from fine-paste wares reported from northeastern Thailand, Myanmar, and India. These findings suggest that maritime Southeast Asian fine-paste ware developed as a localized technological tradition shaped by regional resources, production practices, and maritime exchange networks. Full article

Tetracycline-class antibiotics are persistent contaminants in aquatic environments and are difficult to remove by conventional treatment processes. In this study, a recoverable granular MIL-101(Fe)/γ-Al₂O₃ catalyst was prepared through ligand anchoring followed by secondary Fe-MOF growth on spherical γ-Al₂O₃ and applied to catalytic ozonation of tetracycline (TC) under ordinary-bubble and microbubble-assisted operation. Structural characterization supported the formation of Fe-containing MOF domains on the alumina support, accompanied by an increase in BET surface area from 164.28 to 210.05 m² g⁻¹ and enhanced Lewis-acid-related pyridine-IR signals. Under conventional bubbling ozonation, the optimized catalyst achieved 67.93% apparent UV–Vis-based TC removal during an overall 50 min run consisting of 30 min dark adsorption followed by 20 min ozonation. In a 12 L microbubble reactor, the catalyst-assisted system reached 93.74% apparent UV–Vis-based TC removal at pH 6 with 100 g catalyst and 6 mg min⁻¹ fed ozone, showing higher apparent removal than ordinary ozonation, microbubble ozonation, and ordinary-bubble catalytic ozonation under the tested configuration. Phosphate-blocking and radical-quenching experiments were consistent with the involvement of Lewis-acid-related sites, hydroxyl radicals, and superoxide-related pathways, but these tests are interpreted as indirect mechanistic evidence. LC-MS analysis suggested possible hydroxylation, demethylation, deamidation, ring opening, and low-molecular-weight product formation. The system also transformed chlortetracycline, oxytetracycline, and doxycycline and reduced COD and TOC in a simulated mixed-antibiotic matrix. Because parent-compound HPLC/LC-MS time-series quantification, ozone utilization/off-gas ozone measurement, bubble-size/kLa analysis, and ICP-based Fe loading/leaching data were not available, the present work is positioned as an apparent catalyst–reactor coupling study rather than a complete catalytic, hydrodynamic, or process-level demonstration. Full article