Study by synchrotron radiation of the structure of a working catalyst at high temperatures and pressures

A relation among activity, composition, and structure was determined for a working catalyst by means of a stainless-steel reactor cell of novel design that permitted operation at temperatures and pressures similar to those in industrial reactors. Molybdenum K-edge x-ray absorption spectra were used to probe the structural environment of molybdenum in CoMoS/[unknown]-alumina catalysts while hydro-desulfurization of benzothiophene was proceeding at high temperature and pressure. For catalyst samples with different contents of cobalt, radial structure functions obtained from extended x-ray absorption fine structure data presented the same features as those obtained from the spectra of MoS(2)/[unknown]-alumina reference samples. Moreover, Mo-S and Mo-Mo coordination numbers were maximum for the sample with an atomic ratio of Co to (Co + Mo) of 0.33; this sample was also the most active catalyst tested.