The catalytic activity of a series of carbon-supported cobalt manganese oxide (CoMnOx) catalysts was investigated for the Fischer Tropsch synthesis reaction. The catalysts were compared with an unsupported CoMnOx catalyst under the same reaction conditions, and it was shown that the use of an activated carbon support increased both the catalyst activity and the selectivity to C2+ hydrocarbons, whilst lowering the selectivity to CH4 and CO2. Additionally, the effects of varying heat treatment temperatures and increasing the precursor ageing times were also investigated. Increasing the heat treatment temperature of the catalyst precursor between 300 and 500 degrees C led to an increase in activity, as well as an increase in selectivity to C2+ hydrocarbons, but it also increased the selectivity to CO2. At 600 degrees C there was a marked decrease in activity, and the main product was C5+ hydrocarbons. Ageing the initial precipitate led to a decrease in activity and also decreased the selectivity towards hydrocarbons. (C) 2015 Elsevier B.V. All rights reserved.