Two different kinds of γ-Al2O3 precursors: stick-like ammonium aluminum carbonate hydroxide and willow leaf-like boehmite could be selectively synthesized via a facile hydrothermal method by just adjusting reaction temperature. After heat treatment, γ-Al2O3 with two different morphologies (stick-like and willow leaf-like) were synthesized and used as supports for CoMo hydrodesulfurization catalysts. Fourier transform infrared spectroscopy of pyridine adsorption and NH3-temperature-programmed desorption showed that stick-like γ-Al2O3 (ACH) and willow leaf-like γ-Al2O3 (AOH) exhibited a lower Lewis acidity than commercial γ-Al2O3. X-ray diffraction indicated that CoMo oxidic catalysts supported on ACH and AOH contained more β-CoMoO4 phase. X-ray photoelectron spectroscopy and high resolution transmission electron microscopy revealed that after presulfurization, more CoMoS active sites and multilayered (Co)MoS2 slabs formed on ACH and AOH supports, thereby creating catalysts with a higher hydrodesulfurization activity in the hydrodesulfurization of thiophene and 4,6-dimethyldibenzothiophene.

In the present study, density functional theory (DFT) calculations were performed to investigate the reaction mechanism of methane oxidation catalyzed by ZSM-5-supported binuclear iron species. A variety of binuclear iron sites such as [Fe(μ-O)Fe]2+, [Fe(μ-O)2Fe]2+, [Fe(μ-O)(μ-OH)Fe]+, and [HOFe(μ-O)FeOH]2+ were considered. The conversion of methane to methanol is decomposed into two processes: C–H activation and methanol formation. It is found that the anhydrous [Fe(μ-O)Fe]2+ sites exhibit the lowest reactivity for methane oxidation due to high energy barriers for both C–H activation and methanol formation steps, while the [Fe(μ-O)(μ-OH)Fe]+ and [HOFe(μ-O)FeOH]2+ sites are found to exhibit higher reactivity for methane oxidation in comparison with the anhydrous sites. This high reactivity is mainly attributed to the presence of the terminal or bridged hydroxyls, which can either provide a significant coordination effect or act as an oxidant for methane oxidation. Moreover, we find that on both [Fe(μ-O)Fe]2+ and [Fe(μ-O)2Fe]2+ sites the existence of solvent water molecule can effectively enhance the reactivity of the methanol formation step. Our results confirm the experimental observation of methane oxidation at the low-temperature range (<500 K) and suggest a significant role of water in methane oxidation in Fe/ZSM5 catalyst. This may provide an important guide in designing catalysts with high activity of methane oxidation.

•Dimethyl disulfide in liquefied petroleum gas was adsorbed by the modified zeolites.•The adsorption mechanism was studied by FT-IR spectroscopy.•The regenerability of adsorbent Ag2O/NaY was also studied.The removal of dimethyl disulfide from model liquefied petroleum gas using metal salt impregnated zeolite as the adsorbent was studied in a fixed-bed adsorption equipment. Effects of different carrier, metal iron species and content of active component, mass space velocity, temperature, as well as adsorption selectivity and regeneration performance were all investigated by performing the breakthrough experiment. Among all these adsorbents, 5 wt.%Ag2O/NaY showed the highest breakthrough sulfur capacity. The adsorption selectivity of Ag2O/NaY was studied by the infrared spectra. It was found that the direct S–Ag(I) interaction was the essential reason for the evidently improved adsorption ability and selectivity of Ag2O/NaY for removing disulfide from solutions containing olefin. Regeneration study indicated that the saturated adsorbent was regenerated under the temperature of 550 °C for 8 h in the air atmosphere. After five times regeneration, the adsorbent Ag2O/NaY still shows high breakthrough sulfur capacity.Adsorbent Ag2O/NaY which was prepared by equivalent-volume impregnation method was selected and used for separation of dimethyl disulfide from model liquefied petroleum gas. The separation ability of NaY and Ag2O/NaY for removing dimethyl disulfide from model liquefied petroleum gas with or without 1-hexene was compared. The adsorption strength of dimethyl disulfide on NaY and Ag2O/NaY as well as the competitive adsorption of dimethyl disulfide and olefin on NaY and Ag2O/NaY were investigated detailedly by FT-IR spectroscopy.

In this work, a series of acidic montmorillonite/cordierite monolithic catalysts were prepared by a coating method using silica sol as the binder. The morphology and structure of the acidic montmorillonite/cordierite samples were characterized by means of X-ray diffraction (XRD), N2 adsorption/desorption isotherms, and scanning electron microscope (SEM). The cleavage of cumene hydroperoxide (CHP) in a conventional fixed-bed reactor was chosen as a model reaction to evaluate the catalytic activity of the monolithic catalysts. The influences of acidic montmorillonite loading, reaction temperature, CHP concentration, and weight hourly space velocity (WHSV) on the catalytic activity and selectivity of phenol were studied. The results indicated that the obtained acidic montmorillonite/cordierite monolithic catalysts were firm and compact, and the loading of acidic montmorillonite was found to reach 40% (by mass) after three coating operations. The surface area of acidic montmorillonite/cordierite catalysts increases greatly as acidic montmorillonite loading increases due to higher surface area of acidic montmorillonite. Under the optimal reaction conditions (acidic montmorillonite loading of 32.5% (by mass), temperature of 80 °C, a mass ratio of CHP to acetone of 1: 3, and WHSV of CHP of 90 h− 1), the conversion of CHP can reach 100%, and the selectivity of phenol is up to 99.8%.The monolithic catalyst as a novel kind of catalyst with the internal structure of a regular honeycomb structure exhibits some advantages compared with the conventional particulate catalyst. A series of acidic montmorillonite/cordierite monolithic catalysts are prepared in this work, and then the samples are characterized by analytic methods. The preliminary study shows that the catalysts exhibit excellent catalytic performance, which makes monolithic catalysts become more competitive.Download full-size image

Two different kinds of γ-Al2O3 precursors: stick-like ammonium aluminum carbonate hydroxide and willow leaf-like boehmite could be selectively synthesized via a facile hydrothermal method by just adjusting reaction temperature. After heat treatment, γ-Al2O3 with two different morphologies (stick-like and willow leaf-like) were synthesized and used as supports for CoMo hydrodesulfurization catalysts. Fourier transform infrared spectroscopy of pyridine adsorption and NH3-temperature-programmed desorption showed that stick-like γ-Al2O3 (ACH) and willow leaf-like γ-Al2O3 (AOH) exhibited a lower Lewis acidity than commercial γ-Al2O3. X-ray diffraction indicated that CoMo oxidic catalysts supported on ACH and AOH contained more β-CoMoO4 phase. X-ray photoelectron spectroscopy and high resolution transmission electron microscopy revealed that after presulfurization, more CoMoS active sites and multilayered (Co)MoS2 slabs formed on ACH and AOH supports, thereby creating catalysts with a higher hydrodesulfurization activity in the hydrodesulfurization of thiophene and 4,6-dimethyldibenzothiophene.