Abstract A number of catalysts have been tested on coal under hydropyrolysis conditions. For tin(II) chloride and zinc chloride, the most effective catalysts, the influences of hydrogen pressure, heating rate and loading on the total conversion and the conversion rates have been examined. The results can be interpreted as a thermally induced formation of free radicals in the first step and a catalysed stabilization of free radicals by hydrogen in the second step. The influence of the tin and zinc chlorides also on the first reaction step is obvious. Zinc chloride is observed to undergo a deactivation caused by a still unknown side reaction.