The nature of the active sites in the catalytic cracking of gas—oil

The kinetics of gasoil cracking over an HY zeolite catalyst have been studied at atmospheric pressure and temperatures of 482°, 503° and 524°C, using a fixedbed integral reactor. The total conversion of gas‐oil, the yield of gasoline, of various gaseous products, and the influence of temperature on conversion, gasoline and minor product yield are presented here. The various primary reaction rate constants, the constants describing the decay of catalyst activity, and the refractoriness of the feed, have been determined for this system and are compared with those obtained using a LaY zeolite catalyst. The observed differences between these two catalysts are discussed in terms of the nature and number of active sites present on the two catalysts. We conclude that the initial reaction of a saturated gas‐oil feed occurs on a range of Lewis acid sites of various strengths. Such sites are more numerous on LaY than on HY, and this disparity is larger for weak sites than it is for strong sites.