SURFACE SPECIES ON THE OXIDIZED K2CO3/MOS2 AND THEIR EFFECTS ON CATALYTIC CARBON-MONOXIDE HYDROGENATION

Abstract

The properties of K2CO3/MoS2 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 diffraction and electron spin resonance. The TPD exhibited four peaks of SO2 evolution. Among them, three peaks originated from the decomposition of surface SO42- species with C-2v and T-d symmetries. The decomposition of sulfate by heat treatment resulted in the production of SO2 and oxidized molybdenum species such as MoO3+ which were converted to MoO2 by further heat treatment. The thermal treatment of oxidized catalyst above 1013 K caused a solid-state reaction between potassium and molybdenum, producing K2MoO4. The treated catalyst on which the surface SO42- species had been removed, recovered their selectivity to alcohol formation in CO-H-2 reactions which had been lost when the catalysts were oxidized.