EFFECT OF CALCINATION CONDITIONS OF THE OXIDIZED PRECURSOR ON THE STRUCTURE OF A SULFIDED K-MO/GAMMA-AL2O3 CATALYST FOR MIXED ALCOHOL SYNTHESIS

The effect of the calcination temperature and time of the oxidized precursor on the structure of a sulfided K-Mo/gamma-Al2O3 catalyst was investigated by surface area analysis, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and energy dispersive spectroscopy. The experimental results show that calcination of the oxidized precursor at high temperature leads to a surface sintering, whereby the surface areas of the samples decrease sharply. Because of the strong K-Mo interaction, various K-Mo-O phases are formed. These K-Mo-O phases are transformed to K-Mo-O-S and K-Mo-S phases during sulfidation. The K-Mo interaction species retard, to some extent, the sulfidation and reduction of molybdenum and result in an increase in Mo-VI content in the samples. The surface K+ ions are enriched and surface Cl- ions are partially lost after calcination. Three kinds of surface sulfur species are formed on the sulfided samples. Some sulfur species might be unstable and might be lost in the reactant stream. The synthesis of mixed alcohols was measured in a micro-reactor. It was found that calcination at 700 degrees C-800 degrees C of the oxidized precursor is more beneficial for alcohol formation. The correlation between the activity, selectivity of mixed alcohols and the structures of the samples are discussed.