A process for producing polypropylene from olefins selectively produced from a catalytically cracked or thermally cracked naphtha stream is disclosed herein. The naphtha stream is contacted with a catalyst containing from about 10 to 50 wt. % of a crystalline zeolite having an average pore diameter less than about 0.7 nanometers at reaction conditions which include temperatures from about 500° C. to 650° C. and a hydrocarbon partial pressure from about 10 to 40 psia. The catalyst may be pre-coked with a carbonaceous feed. Alternatively, the carbonaceous feed used to coke the catalyst may be co-fed with the naphtha feed.