MO-USY ZEOLITES FOR HYDRODESULFURIZATION .2. SURFACE-PROPERTIES OF SULFIDED CATALYSTS AND ACTIVITY FOR THIOPHENE HYDRODESULFURIZATION

MolYbdena-containing ultrastable (USHY) zeolite catalysts were prepare d using different molybdenum precursors and activation Procedures and the sulphided catalysts were characterised by nitric oxide and pyridin e adsorption, X-ray photoelectron spectroscopy and tested in the hydro desulphurization (HDS) of thiophene at 3 MPa pressure and a reaction t emperature of 623 K. MoUSY catalyst exhibited decreasing conversions a s a function of time-on-stream due to coking while thiophene conversio n over MoNaY remained constant. No relationship between dispersion and HDS or hydrogenation selectivity was found. Differences between hydro genation selectivities over MoUSY and MoNaY catalysts were attributed to the low concentration of support bound molybdenum species in the ox ide form of the latter catalyst.