CHARACTERIZATION AND DEACTIVATION STUDIES OF SPENT RESID CATALYST FROM EBULLATING BED SERVICE

Two series of bimodal CoMo/Al2O3 catalyst samples have been analyzed a nd characterized using porosimetry, temperature-programmed oxidation a nd NMR spectroscopy. The samples are withdrawn after varying times on stream of up to 120 days. The results show that coke and metals are de posited rather rapidly and that the pore volume of the catalyst at equ ilibrium is almost filled with coke and/or metals. With increasing tim e on stream, the coke in both the first- and third-stage samples becom es more hydrogen and sulfur deficient as evidenced by increasing conce ntration of aromatic carbon and a lowering in concentration of S assoc iated with the coke. There is evidence that the sulfur in the coke is associated with the upper layers of coke and that nitrogen may adsorb preferentially during the initial coke laydown. Furthermore, it is sho wn that vanadium catalyzes the oxidation of coke. Model compound activ ity measurements show that the HDS activity is less sensitive to the e ffects of coke deposition than the HDN and hydrogenation activities. I t is also shown that the initial metals deposits have a stronger effec t on the loss of activity for HDS than for HDN and hydrogenation, indi cating that different sites are involved in these hydrotreating reacti ons.