Genesis, nature and dispersion of active phase in sulphided CoMo/γ-Al2O3 hydrodesulphurization catalysts. Investigation by analytical electron microscopy and X-ray photoelectron spectroscopy

A series of CoMo/γ-Al2O3 catalysts with a varying Co/(Co + Mo) atomic ratio has been investigated by analytical electron microscopy (a.e.m.) and X-ray photoelectron spectroscopy (X.p.s.) after sulphidation and catalytic testing by hydrodesulphurization and hydrogenation reactions. The crystalline nature of the active species has been characterized by dark field and high resolution imaging. Their dispersion has been measured in more detail using electron probe microanalysis and X.p.s. Comparison with the results of previous work on oxide precursors allows us to describe the transformations brought about by sulphidation. The complementary aspects of a.e.m. and X.p.s. for the study of supported catalysts are discussed.