Catalysis Letters最新文献

Conversion of a short alkane such as ethane into chemical feedstocks instead of alkene becomes important for efficient use of natural gas and refinery off-gas. Here direct ethylation of benzene with ethane into ethylbenzene was attempted. Preceding studies clarified catalytic activity of Pt-loaded MFI-type zeolite. In addition, for a similar reaction, i.e., methylation of benzene with methane, we previously found catalytic activity of Co/MFI. Based on these backgrounds, various metal elements supported by zeolites were investigated as catalysts for a reaction between ethane and benzene. Pt, Pb, Zn, Mo, Co, and Ga/MFI showed high activity for ethylation of benzene with ethane. Among them, Pb/MFI showed high reaction rate for formation of desired products (ethylbenzene, styrene and diethylbenzene), while the others brought side reactions, i.e., formation of C₃₋₅ aliphatic hydrocarbons, toluene, naphthalene, and its derivatives. Pb/MFI showed stable activity, while Pt, Zn, and Mo/MFI showed deactivation due to carbonaceous formed by the side reactions.

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Graphene with high-density defects was generated by one-step gaseous detonation method, designated as DG. The DG exhibits a highly hydrogen evolution reaction (HER) performance in terms of its lower onset potential of 223 mV and smaller Tafel slope of 120 mV·dec⁻¹, which are superior to those of commercial counterpart (CG). Furthermore, the value of DG acted as an excellent support of active materials was verified by successfully hybridizing the MoS₂ with DG and the improvement of DG on the HER performance of MoS₂. This work provides a simple, economical, energy-saving and high yield to prepared DG with highly HER electrocatalytic activity and advantages as an excellent support material, making it of great value in practical applications.

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Promotional role of basic ligands on the combination of cupric ions and 2,2,6,6-tetramethyl-piperidine-N-noxyl (Cu²⁺/TEMPO) was tried in the previous publications for selective aerobic oxidation of benzyl alcohol but a lack of a detailed investigation encourages us to perform further work. Here, Cu²⁺/TEMPO was used to catalyze selective aerobic oxidation of benzyl alcohol to benzaldehyde in the presence of bases, and triethylamine was found to be the best additive. A conversion of benzyl alcohol of 92.9% and a selectivity to benzaldehyde of 100% was observed in the presence of Cu²⁺/TEMPO/triethylamine. The promotion of triethylamine on Cu²⁺/TEMPO can be related to its capability in electron-donor and deprotonation. The speciation of the ternary catalyst combination was partially observed by the means of high-resolution mass spectroscopy (HRMS) and some key intermediates such as N-hydroxyl-2,2,6,6-tetramethylperidine (TEMPOH) and ethyl-substituted ammonium ions were confirmed. This study might provide some insights into the highly efficient transformation from benzyl alcohol to benzaldehyde and the promotion of bases on this transformation.

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Despite thorough exploration of the acidity properties and pore structure effects of zeolite catalysts on catalytic conversion, a comprehensive understanding of how these factors influence reaction pathways is still lacking. Herein, three common zeolites (ZSM-5, ZSM-22 and ZSM-48) of different shapes and size dimensions were introduced into catalytic conversion of isobutane, with combination of X-ray diffraction (XRD), transmission electron microscopy (TEM), N₂ adsorption and desorption, solid-state ²⁹Si and ²⁷Al MAS NMR, ammonia temperature programmed desorption (NH₃-TPD) and pyridine adsorption infrared spectroscopy (Py-FTIR) to characterize their structure and acidity. And channels and topologies were associated with stability and catalytic activity. ZSM-5 performed best, showing the most active sites. Furthermore, ZSM-48 led to an increase in the propene yield by suppressing inhibitory secondary reactions in the monomolecular reaction pathway. Moreover, the amount of Brønsted acid sites (BASs) of ZSM-22 were a key factor in promoting light alkene formation. However, 1D channels contributed to the deactivation of ZSM-22 and ZSM-48. The detailed reaction pathways of zeolite catalysts with diverse pore structures and acidities are crucial for optimizing their catalytic performance.

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In this work, the catalytic conversion of furfural was found to follow both CTHs and etherification pathways in one-pot over multicationic inorganic perovskites (LaNi_1-xMo_xO_3±δ) as heterogeneous catalysts. The conversion of furfural (FA) into alcohols and ether functionalities using the as-synthesized perovskite catalysts showed good conversions that are above 80% and excellent selectivity towards the desired product. The LaMoO₃ catalyst was found to achieve the highest percentage conversion of 83%. Simple and multicationic inorganic perovskites were successfully employed in the transformation of furfural to produce β-methoxy-2-furanethanol. Furthermore, we postulate the hydrogenation of the keto-group to be the first step in the mechanism of the formation of β-methoxy-2-furanethanol and that its formation is characterized by rearrangement of the intermediate over the surface of the catalyst.

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Enhancing the performance of ruthenium (Ru)-based electrocatalysts for the alkaline hydrogen evolution reaction (HER) presents a significant challenge. Herein, titanium dioxide nanowire arrays decorated with ruthenium clusters were grown on carbon cloth (Ru-TiO₂ NWAs/CC) via a two-step hydrothermal method. The nanowire array structure increases the surface area of the substrate, allowing for more Ru clusters to be decorated, thereby improving catalytic activity. The resulting Ru₃–TiO₂ NWAs/CC catalyst exhibits prominent HER performance in 1.0 M KOH with overpotentials of 61 at 10 mA cm⁻² and a Tafel slope of only 47.4 mV dec⁻¹. Furthermore, it maintains outstanding stability under alkaline conditions for more than 10 h. The Ru clusters decoration enhances the TiO₂/CC kinetic, more active sites were exposed on nanowires of the surface and accelerated electron transport, thus reducing the charge transfer barrier. After the electrochemical test, the morphology and structure of Ru₃–TiO₂/CC remained largely unchanged, and the valence states of the elements remained stable. This work paves the road to exploiting highly active and cost-efficient electrocatalysts for alkaline hydrogen evolution.

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In this study, silicon carbide (SiC) was prepared from sol–gel process combined with subsequent carbothermal reaction. Then through hydrothermal method synthesized xFe/SiC-700 and 30Fe/SiC-T catalysts. The catalysts were characterized by XRD, SEM/TEM, XPS, and H₂-TPR. The ammonia decomposition performances of the catalysts were assessed in a fixed-bed reactor. Tests revealed that SiC has a high specific surface area and can evenly diffuse Fe₂O₃ nanoparticles, thus exposing more active sites and raising the adsorption capacity of catalysts surface. The interaction of Fe₂O₃ and SiC is stronger, the catalyst activity is better. The surface basicity of catalyst is higher, decomposition ability of ammonia is stronger. 30Fe/SiC-700 catalyst has the best activity among the synthesized catalysts for hydrogen production by ammonia decomposition. The ammonia conversion rate can reach up to 90.16%, and the hydrogen generation can rate reach up to 30.19 mmol·min⁻¹·gcat⁻¹ at 600 °C at 30,000 mL·gcat⁻¹·h⁻¹. Moreover, the catalytic activity is efficient and stable after continuous reaction at 600 °C for 160 h.

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Ammonia decomposition: The silicon carbide supported iron oxide catalyst was prepared, which effectively cracked ammonia to produce CO_X-free H₂.

The first zinc(II)-catalyzed approach towards an array of 2-aminobenzothiazole derivatives was successfully developed. In this process, the substrate 2-bromophenyl isothiocyanate was reacted with a range of amines, including aromatic and aliphatic (primary and secondary) and cyclic secondary amines, yielding the products in reasonably good amounts. The reactivity analyses of different amines revealed that cyclic secondary amines performed exceptionally well, providing excellent outcomes. Additionally, aliphatic amines also exhibited the capability to undergo the transformation successfully.

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We use density functional theory (DFT) to calculate the optimal parameters of atomic arrangement, energy level and electronic structure of sawtooth (n, 0) nanotubes in this paper. The strain energy and formation energy data show that the coiled process of nanotubes is endothermic, and the correlation value decreases with the increase of the radius. Our study shows that the band gap width of SiI₂ nanotubes first increases and then decreases with the increase of the nanotube radius. The band gap of SiI₂ nanotubes changes from indirect to direct after the single layer is rolled into nanotubes and have appropriate band gaps for absorbing visible light. In addition, it is speculated that the disparity between the effective mass of electrons and holes can reduce charge carrier recombination. Among them, the n value 10 ~ 50 nanotubes showed redox capacity between pH = 7 and 0, and the reducing capacity increased with the increase of tube radius. In conclusion, we believe that SiI₂ nanotubes have great application potential in photocatalytic water splitting.

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Visible light absorption indicate that SiI₂ nanotube should be effective photocatalysis for production of H₂ from splitting water