This work deals with the direct synthesis of branched hydrocarbons from synthesis gas using a two-component catalyst : a Fischer-Tropsch synthesis catalyst (RuKY) and a sulfated zirconia (SO42-/ZrO2) strong acid catalyst. The composition of C-7 hydrocarbons was used to gauge the effect of the acid catalyst on hydrocarbon product selectivity. Over RuKY alone, C-7 olefins prevail in C-7 hydrocarbons while the content of branched C-7 paraffins is very low. The use of SO42-/ZrO2 as a cocatalyst for Fischer-Tropsch synthesis causes significant changes in the composition of hydrocarbon products, particularly in the early stages of the reaction. It increases the content of branched paraffins and decreases that of olefins. However, this catalyst suffers serious deactivation. Addition of small amounts of Pt to SO42-/ZrO2 is an effective way for stabilizing its activity under FTS reaction conditions. CO in the synthesis gas has a suppressing effect on the catalytic activity of SO42-/ZrO2 catalysts. This effect becomes weaker as the reaction temperature increases due to a less competitive CO adsorption. Our data reveal that CO adsorption occurs not only on Lewis acid sites of SO42-/ZrO2 but also on Pt particles.