CATALYTIC ACTIVITY OF CO, MO AND COMO SUPPORTED ON NAY ZEOLITE - HYDRODESULFURIZATION OF GAS OIL AT HIGH-PRESSURE

Three series of Co/NaY, Mo/NaY and CoMo/NaY zeolite catalysts with var iable metal content, prepared by a conventional impregnation method, w ere characterized by XRD, IR spectroscopy (oxide state) and acidity me asurements (sulfide state), and tested in hydrodesulfurization (HDS) o f gas oil at high pressure in the temperature range 275-350-degrees-C. The combined results of surface area, XRD and IR showed that in the c atalysts with high metal loading a small loss in crystallinity and a p artial blockage of the zeolite supercages were produced by Mo oxide sp ecies. The number of acid sites, which was lower for the Co/NaY than f or the Mo/NaY catalysts, increased with increasing Co or Mo loading, b ut the strength of the acid sites was stronger for the Co/NaY series. HDS specific activities of the Co/NaY and Mo/NaY monometallic catalyst s reached a maximum at very low loadings of Co(approximately 0.10 at. nm-2) or Mo(approximately 0.16 at. nm-2) by the double action of the m etal sulfide species and the strong acid sites generated on the zeolit e by the Co or Mo incorporation. In the binary CoMo/NaY catalysts, the synergy between Co and Mo species was significant for high Mo content s only.