Abstract: A process for producing light olefins, especially ethylene, propylene, isobutylene and isoamylene, together with high octane gasoline as by-product, comprises that petroleum hydrocarbons are contacted with phosphorus and rare earth containing high silica zeolite having a structure of pentasil catalysts and catalytically converted at a temperature of 480.degree. to 680.degree. C. and a pressure of 1.2.times.10.sup.5 to 4.0.times.10.sup.5 Pa, with a contact time of 0.1 to 6 seconds, a weight ratio of catalyst to feedstock of 4:1 to 20:1 and a weight ratio of steam to feedstock of 0.01:1 to 0.5:1.

Abstract: A cracking catalyst for the production of light olefins comprises 0-70% (based on the weight of the catalyst) of clay, 5-99% of inorganic oxides, and 1-50% of zeolite. The zeolite in the catalyst is a mixture of 0-25 wt % of REY or high silica Y zeolite and 75-100 wt % of phosphorus and rare earth containing high silica zeolite having a structure of pentasil. The catalyst exhibits higher hydrothermal activity-stability, conversion level, and C.sub.2 -C.sub.4 olefin yields in cracking reaction, comparing with the catalyst using HZSM-5 zeolite as active component.