Product distributions and reaction rates were measured for the reaction of a mixture of 66.7% H2-33.3% CO over a commercial promoted, fused iron catalyst. Data are presented for a pressure of 2.0 MPa, over the temperature range 523-588 K, for a range of conversion up to 70%. The results are used for the preliminary design of an energy storage system based on the Fischer-Tropsch synthesis. Product distributions over a cobalt-silica catalyst are also presented.