TRANSITION-METAL OXIDES ADDITIVATED WITH SULFATE OR PHOSPHATE AS CATALYSTS FOR THE CRACKING OF CUMENE AND SUPPORTS FOR SULFIDED NICKEL-TUNGSTEN HYDROCRACKING CATALYSTS

Oxides of zirconium, titanium, niobium, tin, and a mixed zirconium-tin oxide, additivated with sulphate, were prepared by the adsorption of sulphate from a sulphuric acid solution on the corresponding hydrous o xides, followed by calcination at 773 K. An oxide of niobium, additiva ted with phosphate, was also prepared by a similar procedure using pho sphoric acid. The additivated oxides were characterized with respect t o the total acidity by n-butylamine chemisorption using a gravimetric method. The acid site strength distribution was measured by titrating them with n-butylamine using Hammett indicators. The catalytic activit ies of the materials for the cracking of cumene were determined using a pulse method at 573 K. Nickel and tungsten were supported by the add itivated oxides and the resulting catalysts were tested for the hydroc racking of cumene at 673 K and 3.1 MPa pressure, with carbon disulphid e as a sulphiding agent. With the exception of the niobium samples, al l oxides had their acid site density increased by the additivation. In all cases, except for the sulphated niobia, there was a marked shift in the acid site strength distribution towards the stronger and strong est sites (H-0 less than or equal to-8, 2), observed on the sulphated zirconia and phosphated niobia. These two samples also had activities, selectivities and stabilities, for the conversion of cumene, similar to those obtained with a zeolite containing sample, indicating the Bro nsted nature of their acidic sites. Only sulphided nickel-tungsten, su pported on sulphated zirconia and titania, and on phosphated niobia, d isplayed any significant activity in the hydrocracking of cumene at 67 3 K; but of these, only the phosphated niobia presented a good stabili ty for this reaction. An activation effect, during the first few hours of the reaction, was observed with the catalysts supported by the sul phated titania sample, suggestive of the generation of Bronsted acid s ites by a spill-over effect upon exposure to hydrogen.