Surface species on the oxidized K 2CO 3/MoS 2 and their effects on catalytic carbon monoxide hydrogenation

Abstract

The properties of K 2CO 3/MoS 2 oxidized at room temperature and the effects of thermal treatments of the sample on its catalytic activity and physicochemical properties were investigated by means of temperature-programmed desorption (TPD), X-ray photoelectron spectroscopy, infrared. X-ray dif- fraction and electron spin resonance. The TPD exhibited four peaks of SO 2 evolution. Among them, three peaks originated from the decomposition of surface SO 2− 4 species with C 2v and T d symmetries. The decomposition of sulfate by heat treatment resulted in the production of SO 2 and oxidized molybdenum species such as MoO 3+ which were converted to MoO 2 by further heat treatment. The thermal treatment of oxidized catalyst above 1013 K caused a solid-state reaction between potassium and molybdenum, producing K 2MoO 4. The treated catalyst on which the surface SO 2− 4 species had been removed, recovered their selectivity to alcohol formation in CO-H 2 reactions which had been lost when the catalysts were oxidized.