Process for the preparation of hydrocarbons

A process for the preparation of linear C.sub.10 -C.sub.20 olefins, which comprises preparing a mixture of hydrocarbons substantially consisting of linear paraffins by:

• (a) Contacting a mixture of carbon monoxide and hydrogen at elevated temperature and pressure with a catalyst comprising 3-60 pbw of cobalt and 0.1-100 pbw of at least one other metal chosen from the group formed by zirconium, titanium and chromium per 100 pbw of silica, alumina or silica-alumina carrier, which catalyst has been prepared by kneading and/or impregnation,
• (b) Separating from the paraffin mixture thus prepared a heavy fraction which consists substantially of C.sub.20.sup.+ paraffins, and
• (c) Converting at least this heavy fraction by mild thermal cracking into a mixture of hydrocarbons which consists substantially of linear olefins and contains the desired C.sub.10 -C.sub.20 olefins.