Partial oxidation of H2S to sulfur on V-Cu-O mixed oxides bronzes

Insights into the mechanism of low-temperature H2S oxidation over Zn-Cu/Al2O3 catalyst

Odor pollution caused by toxic chemicals with low human olfactory thresholds, such as hydrogen sulfide (H₂S), has become a major cause of environmental grievance world-wide. Although the low-temperature (<180 °C) catalytic oxidation of H₂S using metal oxides has received widespread attention, desulfurization performance is not ideal. Herein, a series of Zn-Cu/Al₂O₃ catalysts were developed using an impregnation method based on the Al₂O₃ hydrophilicity and the effects of zinc loading on the catalyst physicochemical properties and performance were systematically studied. The catalysts were characterized using inductively coupled plasma-optical emission spectrometry (ICP-OES), N₂ adsorption-desorption isotherms, scanning electron microscopy with energy dispersive spectrometry (SEM-EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR) and electron paramagnetic resonance (EPR). It was found that optimization of zinc doping could improve the hydrophilicity of the catalyst, and hence its activity. Catalytic activity was also dependent on operational parameters such as temperature, humidity and space velocity. The Zn₃Cu₃ catalyst exhibited the highest breakthrough capacity of 353.91 mg/g at 50 °C and at a relative humidity of 50%. The excellent desulfurization performance was attributed to oxygen vacancies contributed by CuO, Cu₂O and ZnO, which facilitated the conversion of H₂O into hydroxyl radicals. Consequently, a hydroxyl radical-induced desulfurization mechanism over Zn-Cu/Al₂O₃ is proposed. This work provides a potential green and efficient catalyst for the selective oxidation of H₂S.

Phase-dependent photocatalytic selective oxidation of cyclohexane over copper vanadates

Three copper vanadates with different crystal phases show different abilities for selective oxidation of cyclohexane.

Precise control of heat-treatment conditions to improve the catalytic performance of V2O5/TiO2 for H2S removal

The purpose of this study is to investigate the influences of atmospheric gas and temperature while preparing V₂O₅/TiO₂ catalysts to find a suitable heat-treatment method to improve catalytic performance during the process of H₂S removal. The catalysts prepared by wet-impregnation were heat-treated at different temperatures (400 or 600 ℃) under various atmospheres (Air, N₂, or H₂). The catalytic tests demonstrated that the catalyst heat-treated at 400 ℃ under N₂ atmosphere (N-400) possessed excellent catalytic activities regarding H₂S conversion (96.4%) and sulfur yield (89.1%). The characterization results revealed that the mild reducing condition employed for N-400 led to the formation of partially reduced V₂O₅ crystals and a strong V-Ti interaction owing to the anatase TiO₂ phase, resulting in the high oxygen vacancies on the catalyst surface. However, severe reducing conditions (H₂ or N₂ with 600 ℃) or the higher temperature (600 ℃) induced highly reduced V₂O_5-x or rutile TiO₂ related to a weak V-Ti interaction, respectively, which facilitated lower oxygen vacancies. This study is the first to demonstrate the significance of a precisely controlled heat-treatment to enhance catalytic performance for H₂S removal.

Adipic acid formation from cyclohexanediol using platinum and vanadium catalysts: elucidating the role of homogeneous vanadium species

The applicability of platinum and vanadium catalysts for the production of adipic acid from cyclohexanediol is severely limited by the instability of the latter species in liquid phase reactions.