na Li

Promotion effect of Fe in mordenite zeolite on carbonylation of dimethyl ether to methyl acetate

A series of Fe-modified mordenite zeolite samples were synthesized by a template-free method and employed in dimethyl ether (DME) carbonylation reaction for the production of methyl acetate (MAc). XRD, UV-Vis, and UV-Raman characterization studies proved that Fe atoms have been introduced into the mordenite zeolite framework by partial substitution of Al atoms, which led to evident changes of activity and MAc selectivity. With the increase of iron content (as metal) from 0.0 to 3.6 wt%, DME conversion first increased and then decreased. MAc selectivity and catalyst stability were enhanced for all Fe-modified samples. TG and GC-MS analysis of deactivated catalysts showed that the amount of coke retained in the catalysts decreased as the iron content of the zeolites increased. The enhancement effects were expounded in terms of the decrease of the acid strength and acid density in the 12MR channels of mordenite after introduction of Fe, resulting in the reduction of carbon deposition.

Phosphorous-modified ordered mesoporous carbon for catalytic dehydrogenation of propane to propylene

Phosphorous (P)-modified ordered mesoporous carbon CMK-3 was used as a catalyst for the direct dehydrogenation (DH) of propane to propylene without any auxiliary stream, and this catalyst exhibited better activity and selectivity than the pristine ordered mesoporous carbon. The prepared samples were characterized by N2 adsorption and desorption, temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS). After the introduction of P using an impregnation method, PO groups formed on the surface of the materials and substantially improved the activity and selectivity. The PO groups are believed to be electron donors for CO active centers, or independent active centers for catalytic DH of propane.

The effect of ethanol on the performance of CrOx/SiO2 catalysts during propane dehydrogenation

Abstract The effects of ethanol vapor pretreatment on the performance of CrO x /SiO 2 catalysts during the dehydrogenation of propane to propylene were studied with and without the presence of CO 2 . The catalyst pretreated with ethanol vapor exhibited better catalytic activity than the pristine CrO x /SiO 2 , generating 41.4% propane conversion and 84.8% propylene selectivity. The various catalyst samples prepared were characterized by X-ray diffraction, transmission electron microscopy, temperature-programmed reduction, X-ray photoelectron spectroscopy and reflectance UV-Vis spectroscopy. The data show that coordinative Cr 3+ species represent the active sites during the dehydrogenation of propane and that these species serve as precursors for the generation of Cr 3+ . Cr 3+ is reduced during the reaction, leading to a decrease in catalytic activity. Following ethanol vapor pretreatment, the reduced CrO x in the catalyst is readily re-oxidized to Cr 6+ by CO 2 . The pretreated catalyst thus exhibits high activity during the propane dehydrogenation reaction by maintaining the active Cr 3+ states.

A highly efficient Nafion-H catalyst for vapour phase carbonylation of dimethoxymethane

A highly active Nafion-H catalyst is developed for vapour phase carbonylation of dimethoxymethane (DMM) to methyl methoxyacetate (MMAc) with a significant MMAc selectivity as high as 90%. The excellently catalytic performance is because of the unique structure and high acid strength of the Nafion-H catalyst.