Catalysis Letters最新文献

Cleaning up carbon monoxide (CO) in water gas shift feedstocks is crucial for fuel cell applications. The catalytic transformation of CO in hydrogen-rich feeds poses a significant challenge in environmental catalysis. To address this issue, a range of Cu–Mn-based monometallic and bimetallic catalysts with diverse supports (such as alumina, silica, zirconia, and titania) were employed. Temperature programming techniques were utilised to observe the reduction and oxidation behaviours of these catalysts. The investigation involved testing CO oxidation at various temperatures over copper and manganese-based supported catalysts in the presence of H₂O and CO₂ (simulating realistic conditions). A positive impact of H₂O on catalytic performance was noted, whereas CO₂ had a suppressive effect. Furthermore, the specific support materials (Al₂O₃, SiO₂, TiO₂, and ZrO₂) were studied to understand their roles in CO oxidation under realistic conditions. In the presence of water, alumina catalysts containing bimetallic metals (Cu–Mn) exhibited 100% CO conversion even at a lower temperature of 160 °C. Conversely, under the predominant influence of CO₂, alumina catalyst (Cu–Mn) showed 55% CO conversion. The exceptional performance was attributed to CO preferential adsorption on highly active Cu–Mn sites and a small H₂-oxidative atmosphere of the catalysts. The activity results highlighted the strong dependence of CO conversion on reaction temperatures, the presence of metals, and the types of supports. Overall, these findings suggest the potential use of these catalysts for H₂ purification under realistic conditions.

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Selective catalytic conversion of ammonia to nitrogen is an effective method for reducing ammonia emissions from both stationary and mobile sources. In this study, CeO₂-based catalysts (M/CeO₂, M = Co, Cu, Fe, Zr) were synthesized using the sol–gel method and subsequently tested on a simulated gas experimental platform to assess their performance in NH₃ selective catalytic oxidation (NH₃-SCO). Results showed that Co/CeO₂ and Cu/CeO₂ catalysts exhibited high ammonia oxidation activity at respectively low temperatures, with T₅₀ 196.8 and 229.5 °C, and T₉₀ 239.2 and 292.1 °C. However, it was observed that while Co/CeO₂ displayed poor N₂ selectivity, Cu/CeO₂ demonstrated good N₂ selectivity. The superior catalytic performance of Cu/CeO₂ and Co/CeO₂ catalysts compared to Fe/CeO₂ and Zr/CeO₂ can be attributed to their distinct interactions with Ce. Subsequent characterization experiments were conducted to elucidate these interactions. BET and SEM analyses revealed that all M/CeO₂ catalysts possessed a typical mesoporous structure. XRD and XPS results indicated that the primary phase of each catalyst was CeO₂, and the incorporation of M transition metals did not alter the cubic fluorite structure. The interaction between the M metal and Ce varied, impacting the Ce³⁺ content on the catalyst surface, which in turn influenced oxygen species adsorption and ammonia oxidation activity. H₂-TPR and Raman spectroscopy analyses demonstrated that M metal incorporation shifted the CeO₂ reduction peak, thereby altering reduction properties and affecting oxidation performance. In particular, the Co-metal composite shifted the reduction peak to a lower temperature, thereby enhancing the reduction properties and indirectly increasing oxidation activity.

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The electrolytic division of water into hydrogen (H₂) and oxygen (O₂) presents a sustainable solution for meeting escalating demands in renewable energy sources. Yet, this process faces formidable challenges due to its energy-intensive nature. Our study introduces efficient electrocatalysts formed from chromium sulphide nanoparticles integrated with tin oxide via a straightforward solvothermal approach, enabling water splitting in both acidic and alkaline settings. The resulting SnO₂@CrS₂ heterostructure exhibits notable performance by requiring lower overpotentials 142 and 99 mV for achieving a current density of 10 mA cm⁻² during the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in 1 M KOH, and 157 and 165 mV for OER and HER in 0.1 M HClO₄, respectively. Correspondingly, Tafel slopes of 30 and 45 mVdec⁻¹ in 1.0 M KOH and 52 and 32 mVdec⁻¹ in 0.1 M HClO₄ were observed for OER and HER respectively. These catalysts display promising efficiency at reduced overpotentials, demonstrating exceptional performance for overall water splitting. This approach of integrating an active heterostructure through interfacial tuning offers a novel pathway for developing economically viable and efficient electrocatalyst systems crucial for water splitting and H₂ production.

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Graphical abstract of synthesized catalyst

This work reports the synthesis and characterization of Nanosized-Ni doped montmorillonite heterocatalyst and its application for Suzuki Miyaura cross coupling of aryl iodides with aryl boronic acids. The catalyst is highly selective and did not give any other byproducts. The reaction was complete within 24 h with > 98% yield. Nickel was uniformly dispersed on the catalyst with approximately 4.0 ± 2 nm clusters of Ni. The solvent, base, catalyst loading, and catalyst precursors were varied to obtain optimum reaction conditions for highest yield. The catalyst was recovered and reused for reactions demonstrating excellent recyclability with high yield. Ni doped montmorillonite catalyst is very effective for Suzuki Miyaura cross coupling reactions and can be used to replace expensive Pd-based catalysts with earth abundant and inexpensive Ni-based catalysts.

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Photocatalytic hydrogen production by semiconductors is an optimal path to achieve solar energy conversion. In this work, Cu₂O/ZnFe₂O₄ type II heterostructure is composed of ZnFe₂O₄ nanoparticles loaded on the surface of Cu₂O microspheres, the photocatalytic hydrogen evolution performance is studied. Under the irradiation 5 h of 5 w LED lamp, the hydrogen production of Cu₂O/ZnFe₂O₄ composites was 30.8 and 12.7 times higher than pure Cu₂O and pure ZnFe₂O₄, respectively. In addition, after four cycles of experiments for 20 h, the hydrogen production is still maintained at 67.4% of the initial activity, indicating the relatively stable hydrogen evolution activity of the composite material. The electron transfer mechanism of the photocatalyst was confirmed through the utilization of density functional theory (DFT) and in-situ irradiation X-ray photoelectron spectroscopy. The effective interfacial contact between Cu₂O and ZnFe₂O₄ nanoparticles forms a type II heterojunction, which makes the effective separation of photogenerated charges, facilitates the reduction of protons to H₂, and achieves efficient hydrogen production. This work presents a strategy for simple design and fabrication of highly efficient composite photocatalysts.

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The majority of reaction conditions employed in SF₆ conversion research are characterized by elevated temperatures and pressures, resulting in a considerable expenditure of energy. The transformation of SF₆ under mild conditions represents a viable methodology at this time. It has been demonstrated that the conditions required for the photoconversion of SF₆ are relatively mild. Furthermore, the defect engineering of catalysts has been shown to be an effective strategy for enhancing the photocatalytic performance of photocatalysis. Thus, we utilized two-dimensional materials as a model for our research. These materials have active sites that are highly dense and uniform, allowing us to thoroughly examine how defects affect the SF₆ photoconversion process. By synthesizing ZnO atomic layers with oxygen vacancies and confirming their presence using various techniques, we found that these vacancies enhanced light absorption and promoted the separation of charge carriers. These results suggest that the oxygen-deficient ZnO atomic layers have superior SF₆ photoconversion performance compared to the pristine ZnO atomic layers. Overall, the findings of this study indicate that the incorporation of defects in photocatalysts is a crucial strategy for optimizing pivotal photocatalytic processes and enhancing the efficacy of SF₆ photoconversion.

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We initially built clear models of two-dimensional atomic layers with defect concentrations, and hence directly disclose the defect type and distribution at atomic level. As a prototype, defective ZnO nanosheets with atomic thickness are successfully synthesized. Also, we use defective ZnO atomic layers to achieve light conversion of SF₆ under mild conditions, which provides a new path to solve the environmental pollution of perfluorinated compounds.

Chemical looping gasification (CLG) is an effective technology for efficient utilization of coal, biomass and other fuels. In this work, the detailed mechanism of catalytic decomposition during CLG for toluene, a tar model compound, was studied by using reactive force field molecular dynamics (ReaxFF MD) method. Results show that toluene hardly decomposes at temperature lower than 2000 K. Improving temperature could significantly improve decomposition efficiency but also enhances the polymerization to produce PAHs and soot precursor, with largest molecule weight of 2175 (C₁₇₇H₅₁, 3000 K, 400 ps). Fe₂O₃ nanocluster, as oxygen carrier, could improve the decomposition efficiency of toluene and reduce the decomposition temperature. At 2000 K and 200 ps, the catalytic conversion of toluene reaches 60%. A large amount of H₂, CO, C₂H₂ and other small molecular gases are generated during the catalytic decomposition of toluene. At 3000 K, the yield of H₂, CO and C₂H₂ reached 132 %mole, 117 %mole and 40 %mole of toluene, respectively. Meanwhile, polymerization reactions are largely inhibited by Fe₂O₃ nanocluster and the largest molecule is C₂₀H₉O, the weight of which is much lower than soot precursor in thermal decomposition. Kinetic results show that the activated energy of catalytic decomposition is about 74 kJ/mole, which is much lower than thermal decomposition (382 kJ/mole). Detailed reaction mechanism reveals that lattice oxygen on Fe₂O₃ nanocluster act as the active sites, which enhance the decomposition of toluene.

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WVO_x bi-metal oxides supported on the cost-effective industrial mesoprous Al₂O₃, SiO₂, active carbon (AC), and TiO₂–Al₂O₃ with different specific surface areas (WVO/Al₂O₃, WVO/SiO₂, WVO/AC, and WVO/TiO₂–Al₂O₃) were designed and prepared through co-impregnation method for large-scale bio-glycerol dehydration to acrolein. The XRD, BET, SEM–EDS, XPS, and NH₃-TPD characterization results revealed the WO₃–VO_x (V⁴⁺/V⁵⁺) species existed with better dispersion, lower molar ratio of V⁴⁺/V⁵⁺, and enhanced strength of surface acid sites on the developed mesoporous TiO₂–Al₂O₃ in comparison with that on the mesoporous Al₂O₃, SiO₂, and AC, demonstrating strong interaction of WO₃–VO_x species with the TiO₂–Al₂O₃ support and accounting for the acrolein selectivity over catalysts following the order of WVO/TiO₂–Al₂O₃ (75.8%) > WVO/AC (71.2%) > WVO/SiO₂ (55.3%) > WVO/Al₂O₃ (42.8%). Over the WVO/TiO₂–Al₂O₃, gas-glycerol conversion reached above 97.0% with acrolein selectivity of about 75.0% under the gas hourly space velocity (GHSV) of 120–360 h⁻¹, and maintained an improved catalytic stability.

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The acrolein selectivity over the prepared catalysts followed the order of WVO/TiO₂–Al₂O₃ > WVO/AC > WVO/SiO₂ > WVO/Al₂O₃, Among them, the WVO/TiO₂–Al₂O₃ catalyst demonstrated a low V⁴⁺/V⁵⁺ ratio, surface acid sites, and exceptional catalytic performance with a gas-glycerol conversion rate of 97.2% and an acrolein selectivity of 75.8%. Even after continuous reaction for 16 h, both gas-glycerol conversion and acrolein selectivity remained above 75% and 90%, respectively. This study presents a remarkable advancement in the development of industrial catalysts with outstanding performance in terms of efficiency, stability, and cost-effectiveness. Moreover, this catalyst shows great promise for its utilization in acrolein synthesis via glycerol dehydration.

Residual chlorine has a bactericidal effect, but it may react with natural organic matter in water to produce harmful substances. In this work, we report an efficient residual chlorine removal filter with activated carbon fiber (ACF) as adsorption carrier and CuO as residual chlorine degradation catalyst. Experimental results show that CuO has high catalytic efficiency and no attenuation of catalytic performance in 2924 h. The CuO is loaded on the surface of ACF by dipping-calcinating method. When the loading rate is 1.5%, the CuO distribution is uniform without defects and agglomeration. Continuous-flow experiment result shows that 1.5%-CuO/ACF filter can treat water amount 2.2 times as long as that for single ACF filter (residual chlorine concentration < 0.1 mg/L). Weak acidity and rising temperature can improve the reaction activity and increase the degradation amount of residual chlorine. The composite filter has excellent adsorption performance for Cu²⁺, showing the Cu²⁺ concentration in the produced water is less than 0.1 mg/L after filter treatment, which is in line with the National Drinking Water Standards, and in agreement with the Standard for Safety Assessment of Water Transmission and Distribution Equipment and Protective Materials for Drinking Water (GB/T17219-1998) of Immersion Experiment, indicating that 1.5%-CuO/ACF filter has good stability and safety.

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Efficient production of H₂ by combined (steam/CO₂; steam/O₂) reforming of CH₄ was comparatively studied over perovskite-derived promoted Ni catalysts. The process performance was improved by regulating the redox and structural properties of the LaNi_0.99M_0.01O₃ catalysts through promotion (M = Pt, Pd, Re, Mo, Sn). The catalysts were synthesized using the citrate sol–gel method, tested in combined reforming of methane and studied by X-ray fluorescence analysis, thermal analysis, N₂ adsorption, X-ray diffraction, electron microscopy, temperature-programed hydrogen reduction to elucidate the impact of catalyst properties on their activity and resistance to re-oxidation and formation of carbon deposits under reaction conditions. It was shown that LaNi_0.99M_0.01O₃ catalysts after calcination at 850 °C in air have a perovskite structure that was destroyed after reductive activation with formation of metal Ni^o particles with an average size of ~ 25 nm on the surface of lanthanum oxide/hydroxide. The resistance to re-oxidation of Ni^o particles depends on the type of promoter and is maximum in the case of M = Re. It was established that the type of promoter affects the conversion of reagents (CH₄, CO₂) and the H₂ yield, which at 700 °C increases in the series of promoters Sn < Mo < Pt < Pd < Re in the case of steam/CO₂ reforming and Pt < Sn < Mo < Pd < Re with steam/O₂ reforming. The optimal composition of catalyst was identified: among the studied samples, LaNi_0.99Re_0.01O₃ is characterized by a higher specific surface area, average reduction ability and high resistance to re-oxidation and coking. At 850 °C it provides the H₂ yield of 95 and 50% at complete CH₄ conversion in steam/CO₂ and steam/O₂ reforming, respectively.

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