Process for producing propylene and ethylene from a light hydrocarbon stream comprising essentially ethane and butane The process involves a non catalytic cracking of ethane and normal butane followed by a metathesis of ethylene and 2 butene to increase the propylene yield Optionally the by produced iso butane is dehydrogenated and subsequently the produced iso butene is converted to other valuable products like di isobutylene, alkylate for gasoline blending, tertiary butyl ethers, polyisobutyle.