Search Results (235)

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

Linear alkylbenzene (LAB) is the main raw material used to make biodegradable detergents, and its production process is based on aromatic alkylation. HY zeolites that have undergone controlled dealumination and desilication have led industrial standards amongst solid acid catalysts because of their controllable acidity and hierarchical pore structure. Coke formation in such systems can assume a dual role, which is dependent on its condition. Though the over-deposition is known to cause deactivation by blocking the micropores, Bronsted acid-site masking, and diffusion collapse, the low-level deposition could also be done to increase the monoalkylate selectivity by the pore mouth catalysis, steric modulation, and selective suppression of secondary alkylation pathways. The critical review is done on the structural-kinetic interaction that determines the coke evolution in HY-based catalysts. In order to moderate the acid-site density and enhance hydrothermal stability, dealumination (Si/Al optimization of about 2.5 to 30–100) occurs, but to reduce deep-pore coke formation, desilication (interconnected mesopores) is created. The bimodal porosity and regulated acidity are found to be synergistic, as hierarchical HY zeolites produced through successive cycles of steam and alkaline treatments not only show LAB selectivity in excess of 90% but also exhibit much longer catalyst lifetimes. Quantitative research on the beneficial coke regime revealed that it was composed of about 36 wt% hydrogen-rich species, which were localized at the pore mouths, hence enhancing monoalkylation selectivity by 15–40%. Beyond a critical transition window (e.g., 8–12 wt.%), coke formation to condensed polyaromatic and graphitic products leads to fast deactivated coke formation, which is due to percolation limits and transport-controlled kinetics. More advanced techniques of characterization of the coke, e.g., temperature-programmed oxidation (TPO), ²⁷Al MAAS NMR, and UV-Raman spectroscopy, indicate how the coke is changed to highly structured graphitic deposits of high oxidation activation energy. Activity recovery of 85–98% is obtained in regeneration processes, including controlled oxidative calcination, microwave-based and plasma-based processes, and thermal management protocols, and it would be determined by the chemistry of the coke, its spatial distribution, and the regeneration protocols. This paper has developed a mechanistic coke control system by cross-tuning the acidity and development of an effective pore network, which led to a sustainable aromatic alkylation reaction with minimal activity loss, high selectivity, and long life. 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

The development of Sustainable Aviation Fuel (SAF) is a crucial pathway to achieving carbon neutrality goals in the aviation industry. In the preparation process of SAF, the performance of catalysts is a core factor determining reaction efficiency, product distribution, and selectivity. Among these, zeolite molecular sieves play an irreplaceable key role in catalytic systems. This paper, through an in-depth survey and systematic analysis of over 70 core literature pieces in related fields, primarily elucidates the structural regulation mechanisms of zeolite catalysts in key reaction steps such as deoxygenation, hydrocracking, and isomerization. Research indicates that differences in pore size, pore channel configuration, and acidity distribution of zeolite molecular sieves with different topological structures (one-dimensional channels such as SAPO-11 and ZSM-22; three-dimensional intersecting channel micropores such as ZSM-5; three-dimensional twelve-membered ring micropores such as Y-type and Beta zeolites) directly affect the selectivity of catalytic reactions and product quality. Full article

Pd-based catalysts with different Pd species (Pd ions, Pd clusters, and Pd nanoparticles) in USY were synthesized for naphthalene hydrogenation reaction. Among the catalysts, Pd clusters were prepared by controlled aggregation of Pd ions during the hydrogenation reaction with the assistance of physically adsorbed water in zeolite micropore. The coordination state and electronic structure of Pd species on these catalysts were analyzed to reveal the structure–performance relationship. Due to the high dispersion and optimized electronic structure, Pd clusters showed the highest activity for naphthalene hydrogenation compared to Pd ions and Pd nanoparticles. Full article

Continuous excessive CO₂ emissions have a negative impact on the environment. In order to address the issue of CO₂ emission control, its conversion to some valuable commodities is the way forward in dealing with this issue. Additionally, the conversion of CO₂ to some valuable product such as methanol fuel will not only tackle the issue but also result in producing energy. Here, the co-precipitation method was used to synthesize Cu-ZnO bimetallic catalysts based on TiO₂ support to be applied for CO₂ conversion to methanol fuel. To elucidate the role of potassium (K) as a promoter, varied concentrations of K were added to parent Cu-ZnO/TiO₂ catalysts. A number of analytical techniques were used to scrutinize the physico-chemical properties of calcined Cu-ZnO/TiO₂ catalysts. The crystalline nature of TiO₂ catalyst support with high metal oxide dispersion were the major findings disclosed based on X-ray diffraction examinations. The combination of the mesoporous and microporous character of the K-promoted Cu-ZnO/TiO₂ catalysts was discovered using the N₂ adsorption–desorption technique. Similarly, N₂ adsorption–desorption studies also revealed surface defects by K-promotion. The creation of surface defects was also endorsed by X-ray photoelectron spectroscopy (XPS) by showing additional XPS peaks for O1s in higher binding energy (BE) regions. XPS also showed the oxidation states of K-promoted Cu-ZnO/TiO₂ catalysts as well as metal–support interactions. Activity results demonstrated the active profile of K-promoted Cu-ZnO/TiO₂ catalysts for methanol synthesis via CO₂ reduction in a liquid phase slurry reactor. The methanol synthesis rate was accelerated from 35 to 53 g.MeOH/kg.cat.h by incorporating of K to parent Cu-ZnO/TiO₂ catalysts at reaction temperature and pressure of 210 °C and 30 bar, respectively. Structure–activity investigations revealed a promoting role of K by facilitating Cu reduction as well metal–support interaction. The comparative study further revealed the importance of K promotion for the title reaction. Full article

Aiming to obtain chemicals from renewable sources to mitigate global warming, the catalytic pyrolysis of tamarind pulp, obtained from juice industries, was studied. Catalysts based on HZSM-5 zeolite prepared from rice husk ash using ultrasound, microwaves, and a combination of both were used. The catalysts were characterized by elemental analysis, X-ray diffraction, specific surface area and porosity measurements, scanning electron microscopy, and acidity measurements. The specific surface areas and the micropore volumes were slightly affected by the treatments, with microwave alone or combined with ultrasound having the strongest effect. The number of acid sites increased, and the relative number of strong sites decreased with the treatments. The relative amount of Bronsted to Lewis sites was increased by ultrasound and decreased by microwave, alone or combined. These catalysts decreased oxygenated products and increased BTEX production during tamarind pulp pyrolysis. Product distribution was similar for all cases, meaning that HZSM-5 with the following characteristics is a selective catalyst for BTEX in tamarind pulp pyrolysis: specific surface area = 310–347 m²/g; micropore volume = 0.099–0.105 cm³ g⁻¹; acidity = 327 to 571 µmol NH₃ g_cat⁻¹; and ratio of Bronsted to Lewis acid sites = 0.034 to 0.044. Full article

Plastic streams dominated by polyethylene (PE) including PE HD/MD (High Density/Medium Density) and PE LD/LLD (Low Density/Linear Low Density), polypropylene (PP), and polyvinyl chloride (PVC) across Europe demand a design framework that links synthesis with end of life reactivity, supporting circular economic goals and European Union waste management targets. This work integrates polymerization derived chain architecture and depolymerization mechanisms to guide selective valorization of commercial plastic wastes in the European context. Catalytic topologies such as Bronsted or Lewis acidity, framework aluminum siting, micro and mesoporosity, initiators, and strategies for process termination are evaluated under relevant variables including temperature, heating rate, vapor residence time, and pressure as encountered in industrial practice throughout Europe. The analysis demonstrates that polymer chain architecture constrains reaction pathways and attainable product profiles, while additives, catalyst residues, and contaminants in real waste streams can shift radical populations and observed selectivity under otherwise similar operating windows. For example, strong Bronsted acidity and shape selective micropores favor the formation of C₂ to C₄ olefins and Benzene, Toluene, and Xylene (BTX) aromatics, while weaker acidity and hierarchical porosity help preserve chain length, resulting in paraffinic oils and waxes. Increasing mesopore content shortens contact times and limits undesired secondary cracking. The use of suitable initiators lowers the energy threshold and broadens processing options, whereas diffusion management and surface passivation help reduce catalyst deactivation. In the case of PVC, continuous hydrogen chloride removal and the use of basic or redox co catalysts or ionic liquids reduce the dehydrochlorination temperature and improve fraction purity. Staged dechlorination followed by subsequent residue cracking is essential to obtain high quality output and prevent the release of harmful by products within European Union approved processes. Framing process design as a sequence that connects chain architecture, degradation chemistry, and operating windows supports mechanistically informed selection of catalysts, severity, and residence time, while recognizing that reported selectivity varies strongly with reactor configuration and feed heterogeneity and that focused comparative studies are required to validate quantitative structure to selectivity links. In European post consumer sorting chains, PS and PC are frequently handled as separate fractions or appear in residues with distinct processing routes, therefore they are not included in the polymer set analyzed here. Polystyrene and polycarbonate are outside the scope of this review because they are commonly handled as separate fractions and are typically optimized toward different product slates than the gas, oil, and wax focused pathways emphasized here. Full article

Al-rich NH₄-ZSM-5 with highly oriented crystals was directly synthesized through a one-pot hydrothermal technique, using ammonium nitrate as a metal-free mineralizer. The samples were characterized by XRD, N₂ adsorption–desorption, SEM, FTIR, Py-FTIR, ²⁷Al MAS NMR, ²⁹Si MAS NMR, ¹H MAS NMR, and TGA techniques. The impact of aluminum source, ammonium source, and H₂O/SiO₂ molar ratio was studied. XRD results showed that the ZSM-5 catalyst with a low Si/Al ratio (13) was successfully synthesized without any amorphous phase, including a microporous/mesoporous structure. A low H₂O/SiO₂ molar ratio (75) resulted in coffin-shape surface morphology, large b-axis-oriented particles (ca. 19 µm), and high specific surface area (>300 m² g⁻¹), providing a large portion of straight channels (90.5%). The catalytic activity of the catalysts was evaluated in the CO₂ hydrogenation reaction in tandem configuration with a Na/Fe₂O₃ catalyst. The results confirmed that highly b-oriented crystals improved the product shape selectivity to p-xylene by affecting the diffusion resistance. Therefore, the developed catalyst provided high CO₂ conversion (45%) and high aromatic selectivity (77%), with p-xylene accounting for 82% of the produced xylene compounds, over a long-term time on stream (17 h). These results demonstrate the effectiveness of the direct synthesis strategy in producing Al-rich ZSM-5 catalysts with tailored textural and acidic properties for tandem and shape-selective catalysis. Full article

The selective hydrocracking of polycyclic aromatic hydrocarbons to BTX requires precise control over catalyst porosity and metal–acid balance. Hierarchical porosity, integrating microporous and mesoporous networks, is pivotal for enhancing mass transport and regulating reaction pathways. USY zeolites were engineered to create distinct hierarchical architectures via HCl, urea, and NaOH–surfactant treatments. HCl treatment constructed a gradient pore acidity system, urea treatment enhanced acidity while preserving microporosity, and NaOH–surfactant fabricated ordered mesopores with reduced acidity. The catalyst with the HCl-engineered gradient pore (NiMo/YH-1) achieved a 91% BTX yield at 425 °C in naphthalene hydrocracking, outperforming others. This performance is attributed to its gradient structure that enforces an optimal “hydrogenation-then-cracking” pathway, highlighting the critical role of tailored hierarchical porosity. Full article

Advanced alkaline water electrolysis (AWE) in “zero-gap” configuration is a promising approach for low-temperature hydrogen production, but its efficiency strongly depends on the design and surface chemistry of nickel-based electrodes. Here, we present a simple dip-and-drying method (DDM) to modify commercial nickel foam with a Ni–FeOOH/PTFE microporous catalytic layer and evaluate its electrochemical performance in 1 M KOH and in a laboratory zero-gap cell with a Zirfon^® Perl 500 UTP diaphragm, through circulating 25 wt.% KOH. The FeSO₄-assisted DDM treatment generates mixed Ni–Fe oxyhydroxide surface species, while PTFE imparts control hydrophobicity, enhancing both catalytic activity and gas-release behavior. Annealing the electrode (DDM-NF-CAT-A) results in a cell voltage of 2.45 V at 1 A·cm⁻² and 80 °C, demonstrating moderate performance comparable to other Ni-based electrodes prepared via low-complexity methods, though below that of optimized state-of-the-art zero-gap systems. Short-term durability tests (80 h at 0.5 A·cm⁻²) indicate stable operation, but long-term industrial performance was not assessed. These findings illustrate the potential of the DDM approach as a simple, low-cost route to structured nickel foam electrodes and provide a foundation for further optimization of catalyst loading, microstructure, and long-term stability for practical AWE applications. Full article

This study investigated the hierarchical structuring of *BEA zeolite using 0.2 M sodium hydroxide followed by 0.5 M hydrochloric acid (T-NaOH-HCl). Tungsten trioxide (WO₃) was then impregnated at different loadings (5, 10, 15, and 20 wt.%) onto the hierarchized materials (BEA-T). The modified zeolites were subsequently used as catalysts for the dehydration of ethanol (230 and 250 °C) and 1-propanol (230 °C). The hierarchization treatment increased the Si/Al ratio (from 13 to 39), decreased relative crystallinity by 15%, and reduced the average crystal-domain size (from 18 to 10 nm). After the NaOH–HCl treatment (BEA-T), the mesopore area increased by 7%, the mesopore volume by 19%, and the total pore volume by 12%. Conversely, the BET specific surface area and micropore volume decreased, indicating effective hierarchization of the *BEA zeolite. XRD, FT-IR and Raman confirmed the presence of monoclinic WO₃ on the BEA-T surface. MAS NMR analyses of ²⁷Al and ²⁹Si indicated that the T-NaOH-HCl treatment slightly increased the population of tetrahedral Al environments. The high conversion and selectivity from the dehydration of ethanol and 1-propanol can be attributed to a moderate reduction in the acidity of *BEA zeolite and tunned mesoporosity. Based on TON, catalysts with 10% and 20% WO₃ stood out in dehydration tests. Full article

Modification of zeolitic structures through the incorporation of transition metal oxides has proven to be a promising approach for heterogeneous catalysis. In the present study, *BEA zeolite was modified using the incipient wetness impregnation method with varying amounts (10, 20, and 40 wt.%) of iron(III) oxide to investigate its structural and physicochemical properties. Characterization techniques such as XRD, UV–Vis DRS, FT–IR, Raman spectroscopy, SEM/EDS, TEM/EDS, and SAED, as well as textural and thermal analyses, were employed to assess the main changes. Different iron species were detected, including isolated iron(III) and well-dispersed Fe₂O₃ nanoparticles coating the zeolite surface. Under the synthesis conditions, increased Fe₂O₃ loading promoted hematite nanocrystal growth and the formation of the α-Fe₂O₃ phase, as demonstrated by XRD, Raman, and SAED analyses. Key observations included the preservation of the zeolite framework, high relative crystallinity (ranging from 70% to 85%), and a band gap of approximately 2.0 eV. Furthermore, a general increase in mesoporosity and external surface area was observed, along with a reduction in the number of acidic sites. This decrease may be attributed to restricted accessibility of the probe molecule (pyridine) to Brønsted sites due to micropore blockage in *BEA. These results demonstrate that the adopted synthesis method effectively produced α-Fe₂O₃/BEA catalysts, with no other crystalline phases of iron(III) oxide detected. Full article

Fluoroquinolones are a major issue in aquatic ecosystems due to their persistence, potential to induce antibiotic resistance, and inability to be effectively removed using conventional treatment methods. Several advanced oxidation processes have been studied for their degradation; however, there is still a lack of knowledge about their degradation mechanisms and the precise roles played by reactive species. In this context, the study investigated the heterogeneous activation of persulfate (PS) to degrade fluoroquinolones (FQs), such as moxifloxacin (MFX), in iron-rich soil (Cat) under ultrasound irradiation (US). The analysis of the soil catalyst revealed the presence of quartz (35%), iron oxides (33%), and alumina (26%) as the predominant constituents of the sample. The mineral phase analysis indicated the presence of magnetite, hematite, and alumina. Then, the outcomes of the specific surface area, micropore volume, and total pore volume were determined to be 19 m² g⁻¹, 6 m³ g⁻¹ and 9.10 m³ g⁻¹, respectively. The MFX/PS/US/Cat system demonstrated 89% degradation and 56% mineralization after 300 min. However, the optimized concentrations of i-PrOH, t-BuOH, and CHCl₃ were 50, 100, and 50 mM, respectively, in order to trap the radicals SO₄^•−, OH^•, and O₂^•−. The study examined the individual contributions of SO₄^•−, OH^•, and O₂^•− radicals to the overall process of MFX degradation. The results indicated that SO₄^•− was the primary radical, with a contribution of 52%, followed by OH^• with 43%, and O₂^•− with 5%. Finally, the investigation revealed that laterite exhibited both good catalytic activity and reusability over several cycles. The development of this new process could stimulate the creation of cost-effective technology for water remediation through the effective removal of fluoroquinolones. Full article

The advancement of overall water-splitting technologies relies on the development of earth-abundant electrocatalysts that efficiently produce H₂ as a chemical fuel while offering high catalytic efficiency, structural robustness, and low-cost synthesis. Therefore, we aim to develop a cost-effective and durable non-noble electrocatalyst for overall water splitting. A straightforward hydrothermal approach was employed to fabricate freestanding polyhedral Co₃O₄ on a microporous Ni foam scaffold, followed by anion-exchange transformation in the presence of Na₂S solution to yield its conductive sulfide analog. The engineered Co₃S₄ electrode delivers remarkable HER activity in 1.0 M KOH, requiring a low overpotential (<100 mV) to drive 10 mA cm⁻², far outperforming its pristine oxide counterpart and even closely benchmarking with a commercial Pt/C catalyst. This exceptional performance is governed by the synergistic effects of enhanced electrical conductivity, abundant catalytic sites, and accelerated charge-transfer kinetics introduced through sulfur substitution. Furthermore, the optimized Co₃S₄ electrodes enable a bifunctional overall water-splitting device that achieves a cell voltage of >1.76 V at 100 mA cm⁻² and maintains prolonged operational stability for over 100 hrs. of continuous operation. Post-stability analyses confirm insignificant phase preservation during testing, ensuring sustained activity throughout the electrolysis process. This study highlights the potential of anion-exchanged Co₃S₄ as a cost-effective and durable catalyst for high-performance HER and full-cell water-splitting applications. Full article