The present disclosure relates to an additive and a catalyst composition for a catalytic cracking process of vacuum gas oil for preparing cracked run naphtha having reduced liquid olefin content, and increased propylene and butylene yields in the LPG fraction. The process makes use of a catalyst composition which is a mixture of an FCC equilibrated catalyst and an additive comprising a zeolite, phosphorus and a combination of metal promoters. The process is successful in achieving high propylene and butylene yields in the LPG fraction along with a lower liquid olefin content and increased aromatic content with increase in RON unit in the resultant cracked run naphtha, as compared to that achieved using an FCC equilibrated catalyst alone.