The effect of 10 typical biomass-derived synthesis gas impurities on cobalt Fischer-Tropsch catalyst performance was investigated at industrially relevant conditions. Impurities (0-1000 ppmw) were introduced ex situ by incipient wetness impregnation to give 23 different compositions. The presence of alkali (Na, K) and alkaline earth elements (Ca, Mg) did not affect the ex situ-measured cobalt surface area but decreased the in situ activity, thereby decreasing the apparent turnover frequency. The C(5+) selectivity increased and decreased upon addition of alkali and alkaline earth metals, respectively. Mn, Fe, and P had minor effects on catalyst performance. The presence of Cl decreased cobalt surface without affecting activity, thus increasing the turnover frequency. The changes in turnover frequency correlated with element electronegativity. In situ addition of H(2)S and (CH(3))(2)S (2.5-10 ppm) decreased activity at all concentrations. However, product selectivity was not affected. Addition of NH(3) (4 ppm) did not change catalytic performance. (C) 2011 Elsevier Inc. All rights reserved.