In the hydrogenation of CO at atmospheric pressure, unsupported molybdenum carbide catalyst produced mostly C1-C5 paraffins. Promotion of the catalyst with K2CO3 yielded C2-C5 hydrocarbons consisting of 80-100% olefins and reduced the methane selectivity. The selectivity of C2-C5 olefins among all hydrocarbon products was 50-70 wt% at CO conversions up to 70%