Topics in Catalysis最新文献

In this study, the photocatalytic degradation of methylene blue (MB) was investigated using graphene oxide (GO)/CuBi₂O₄/TiO₂ catalysts under UV irradiation. The degradation kinetics were monitored as a function of GO loading in the system. It was observed that the optimal GO loading was 0.5 wt%, while higher GO loadings reduced the photocatalytic degradation of methylene blue (MB). The results also showed that increased surface modification of the sample enhanced the degradation kinetics. This study demonstrated that, with an appropriate GO loading and the formation of a heterojunction, GO/CuBi₂O₄/TiO₂ can serve as an effective UV photocatalyst.

One of the best ways to deal with solid waste is microwave-assisted pyrolysis. Extraction of valuable oils from date seed (DS) and Chelly seeds (CS) by MW-assisted catalytic co-pyrolysis has demonstrated encouraging results in this field of study. The CaO Nano catalyst served as the susceptor, while graphite was employed as the catalyst. A 1:1 CS: DS ratio was used as the feedstock. The production yields of oil (37.04 to 50.20 wt%), gas (38.14 to 28.39 wt%), and the char level (24.807 to 21.4 wt%) were different between the two groups when comparing co-pyrolysis with and without a CaO nano-catalyst. The average heating rate, feedstock conversion, and product yields concerning the nano-catalyst were all examined. The rate without the catalyst was 20.17.0 °C/min, but it climbed to 24.17.0 °C/min with the catalyst. The analysis focused on the synergistic impacts on product yields, average heating rates, and conversion factors. An increase in oil output is one prominent effect of co-pyrolysis synergy. Another is increased char and gas production when a CaO nano-catalyst is used. In addition, FTIR, NMR, and GC–MS were used to examine the oil produced during the catalytic co-pyrolysis of CS by DS. The catalyst facilitated the formation of aliphatic molecules, aromatic compounds, amides, and alkenes through co-pyrolysis.

The dry reforming of biogas provides a promising route for generating syngas sustainably by concurrently converting CH₄ and CO₂. However, the presence of trace H₂S in biogas streams can significantly influence catalyst stability and performance. In this study, Ni-based catalysts promoted with M (M = K, Mg, Ba, Y, Ce, La) and supported on commercial or sol-gel alumina were synthesized via wet impregnation. The physical and chemical characteristics of the catalysts were analyzed using XRD, N₂ adsorption–desorption, DRIFTS, TGA, Raman, XPS, SEM, TPR and ICP-OES techniques. All samples exhibited mesoporous structures, while DRIFTS results indicated that promoter addition reduced the surface acidity of Ni-based commercial alumina-supported catalyst in the following order: K > Mg > Y > Ce > Ba > La. In H₂-TPR profile of sol-gel alumina supported Ni-La catalyst, a broad reduction peak spanning from 700 °C to 900 °C were observed, indicating the reduction of nickel aluminate spinel (NiAl₂O₄) phases, which are associated with strong interactions between Ni species and the alumina support. XRD analysis showed that La incorporation increased the nickel crystal size, which may have enhanced the reducibility of nickel species in Ni-based alumina catalyst, particularly in commercial alumina-supported catalyst. Catalytic activity was tested at 750 °C under atmospheric conditions in the presence of 50 ppm H₂S. The incorporation of La decreased CH₄ conversion from 77% to 62% and significantly suppressed coke formation from 9% to 1.2% for the sol-gel alumina-supported catalyst. The results demonstrated that the effect of La strongly depended on the support type. For the commercial alumina-supported catalyst (CAL), La enhanced Ni reducibility and improved sulfur tolerance, whereas for the sol-gel alumina- supported catalyst (SGA), La decreased catalyst acidity, contributing to a substantial reduction in carbon deposition. These findings highlight the critical balance between promoter effects, catalytic activity, sulfur tolerance, and coke suppression in Ni-based systems.

Airborne nitrogen oxides (NOₓ) are among the most persistent urban pollutants, contributing to ozone formation, acid rain, and respiratory health issues. Beyond emission control at the source, photocatalytic NOₓ oxidation and storage (PHONOS) has emerged as a promising strategy for sustainable environmental remediation. This review systematically discusses the fundamental mechanisms, material developments, and practical aspects of photocatalytic NOₓ abatement. We first summarize the reaction pathways governing NO and NO₂ oxidation on TiO₂ and related semiconductors, emphasizing the roles of photogenerated holes, hydroxyl radicals, and surface-bound intermediates in determining selectivity toward nitrate. Next, we highlight advances in material design, including single-atom catalysts, doped TiO₂, g-C₃N₄ heterostructures, and oxygenate-modified surfaces that enhance visible-light activity and nitrate storage stability. The influence of environmental factors-such as humidity, reactant gas flow rate, and irradiation wavelength are also discussed. Existing scientific literature suggests that as a novel environmental airborne pollution abatement technology, PHONOS has the potential to evolve from a laboratory concept into a viable, sunlight-driven approach for actively improving urban air quality even far away from the point where pollution is generated.

Copper nanoparticles are widely studied for catalytic applications; however, controlling their aggregation during synthesis remains challenging due to the complex interplay of synthesis parameters. In this work, we systematically investigate the aggregation behavior of copper nanoparticles synthesized via a one-pot chemical reduction method at room temperature by independently varying key synthesis parameters, including copper precursor concentration, reducing agent concentration and injection rate, capping agent concentration, and overall component concentrations. Electron microscopy-based size analysis combined with statistical evaluation reveals that, under the studied conditions, the primary particle size remains largely insensitive to changes in copper precursor concentration, while aggregation is strongly promoted with increasing precursor concentration and total component concentrations. In contrast, the reducing agent plays a decisive role in both particle growth and aggregation. Increasing its concentration promotes the formation of larger primary particles and aggregates, whereas faster injection rates effectively suppress aggregation over a broad parameter window. The capping agent, poly(vinylpyrrolidone), exhibits a comparatively limited influence on aggregation and no pronounced effect on primary particle size under the conditions investigated. The direct impact of aggregation on catalytic performance is demonstrated using CO oxidation as a probe reaction, where a decrease in activity is observed with increasing aggregate size despite similar primary particle sizes. Overall, this study establishes aggregation as a highly sensitive and independently tunable outcome of copper nanoparticle synthesis, providing practical guidelines for controlling aggregate formation during scale-up and for the rational design of nanostructured copper catalysts where aggregate architecture is critical to performance.

The surplus glycerol produced as a byproduct of biodiesel manufacturing offers significant potential for valorization through its conversion into value-added chemicals such as solketal, a promising fuel additive and environmentally benign solvent. In this study, Fe-TPA nanoparticles were synthesized and immobilized onto SBA-15 and SBA-16 mesoporous supports at varying loadings (20%, 30% and 40%) to develop efficient solid acid catalysts for the acetalization of glycerol with acetone. The catalysts were systematically characterized using XRD, FT-IR, BET, pore size distribution, SEM-EDS, XRF, NH₃-TPD and DRIFT analyses, confirming successful incorporation of Fe-TPA and revealing correlations between mesostructural properties, acidity and catalytic behavior. Among the catalysts, 40% Fe-TPA/SBA-15 displayed the best performance, achieving 100% glycerol conversion and 97% solketal selectivity under mild conditions (35 °C, 1:6 glycerol-to-acetone molar ratio, 4 wt% catalyst). Its superior activity is attributed to its high surface area, well-ordered pore structure and enhanced total acidity. The catalyst also exhibited excellent stability and reusability over multiple cycles, showing minimal loss of activity. Thus, the results demonstrate that Fe-TPA/SBA-15 is a highly efficient and robust heterogeneous catalyst for sustainable solketal production, presenting a promising strategy for glycerol valorization within biodiesel-based biorefineries.

In this work, we report the synthesis of pristine and cobalt-doped nickel sulfide (Co-NiS) nanomaterials (NMs) via co-precipitation for dual applications in photocatalysis and gas sensing. FTIR, XRD, SEM-EDX, and HR-TEM analyses revealed vibrational modes, high crystallinity, significant reductions in particle size and morphology, and uniform incorporation of Co into NiS. UV-DRS analysis confirmed that Co-doping narrowed the band gap of NiS from 3.2 eV to 2.9 eV and enhanced visible-light absorption. The improved electronic composition facilitated higher photocatalytic degradation of Xylidine dye to 92% under simulated sunlight, exceeding the 87% achieved with pristine NiS, with superoxide radical anion (O₂⁻) as the chief reactive species. Co-doping also significantly altered the selectivity of gas sensing. NiS exhibited a gas-sensing sensitivity of 72% toward CO₂ at 120 °C; however, Co-NiS demonstrated excellent selectivity for liquefied petroleum gas (LPG), responding with 77% at 60 °C, which is highly energy-efficient. This performance enhancement results from a tailored morphology and Co-based electronic structure. Overall, our findings on Co-NiS as a bifunctional NMs are promising for advanced environmental remediation and low-energy gas sensors.

Graphical Abstract

The role of NH₃ adsorption and diffusion in the pores of the catalyst on the ammonia synthesis rates at elevated temperatures is investigated through pulse feeding of the reactants over two different catalysts. One of the catalysts was a 1 wt% Ru/SBA-15, offering a very high and porous surface area. The second catalyst was a very low surface area Co₃Mo₃N catalyst with well-defined bulk and surface properties. By sending alternative pulses of H₂ and N₂ mixed with Ar, it was possible to differentiate the role of a porous support and observe surface events. Through a pulse feeding strategy, both reactor hydrodynamics and some of the surface events could be monitored. The transients of Ar in an empty reactor and a reactor packed with Co₃Mo₃N exhibited similar behaviours. On the other hand, delayed signals as tails in the derivative response curves over Ru/SBA-15 packed reactor indicated pore diffusion effects, even for Ar. Time derivatives of the mass spectrometer signals represent the rates, revealing system-based responses of the reactive species. Ammonia signal from Ru/SBA15 catalyst was congruent with the pulses during the initial period, becoming erratic suggesting cycles of pore condensation, saturation and desorption and finally reaching a steady value reflecting a steady desorption from the pores. On the other hand, ammonia signal from Co₃Mo₃N revealed NH₃ signals congruent with the pulses, consistent with the absence of effects related to adsorption and diffusion in pores.