ACID CATALYSIS OVER CUY ZEOLITES

Isobutane and n-pentane cracking were studied over Cu zeolite catalysts and these results were compared with their HY analogues at low conversions and at temperatures of 673 K and below. Three forms of the catalysts were used: those reduced in CO at 773 K; those reduced with H2 at 473 K; and those in the oxidic form (following flushing with He at 773 K). In contrast with an earlier publication (1), very little difference inactivity was found between the two reduced forms. The oxidic form that had not been investigated previously, however, was found to be considerably more active than either of the other two. The product distributions from the reduced forms of the catalysts did not differ significantly from each other nor from the H-form of the zeolite. They were typical ofa Brønsted acid catalysis. The oxidic form of the catalyst produced excess H2 in increasing amounts with time on stream. This could be quantitatively accounted for by the coking of the catalyst. These results negate the previous claim (1) that Lewis acid sites are effective in thecracking of light hydrocarbons over Cu zeolites. © 1993 Academic Press, Inc.