Process of producing C2 and C3 olefins from hydrocarbons

A process of producing C2- and C3-olefins from feed hydrocarbons, characterized in that the feed hydrocarbon together with steam is passed as vapor through a thermal steam cracking in which it is heated to temperatures in the range from 700 to 1000° C., where a cracking mixture is produced which contains C2- to C6-olefins and C4- to C6-diolefins, that a first fraction, which contains C2- and C3-olefins, and a second fraction, which contains olefins and diolefins of the range C4 to C6, are separated from the cracking mixture, that the diolefins are at least partly removed from the second fraction and an intermediate product is produced which consists of C4-to C6-olefins for at least 30 wt-%, that a feed mixture containing C4- to C6-olefins and steam is introduced into a reactor with an inlet temperature of 300 to 700° C., which reactor contains a bed of granular, form-selective catalyst, where a product mixture containing C2- to C4-olefins is withdrawn from the bed, and C2- to C3-olefins are separated from the product mixture.