Abstract A gravimetric study of the catalytic activity of alkali metal hydridotetracarbonylferrates on steam gasification of oil coke at 800°C revealed the following order with respect to the cation: Na > Li > K > Rb > Cs. This order was not consistent with that of the catalytic activity of alkali metal carbonates. The most reactive rubidium and potassium carbonates at a higher loading level exhibited poor binary effect when they were used with iron in the form of alkali metal ferrate. This offered important information for interpreting the mechanism of steam gasification of coal using the Fe-Na binary catalyst. The reactivity of the oil coke was slightly enhanced by preoxidation. The sodium ferrate gave a remarkable difference in the catalytic reactivity of gasification between the original and pre-oxidized cokes. The increase in oxygen content rather than that in surface area may play an important role in the pre-oxidized coke impregnated with the catalyst.