Three iron Fischer-Tropsch (F-T) catalysts (100 Fe/3 Cu/5 K/16 SiO2 in parts by weight) in the form of micro-spherical particles were prepared by spray drying. Their particle size distribution was rather broad, ranging from 5 to 40 mu m in diameter, regardless of the source of silica (colloidal silica, tetraethyl orthosilicate, or potassium silicate) employed in their preparation. Catalyst prepared employing colloidal silica had the highest attrition strength among all catalysts studied. After 345 h of testing in a stirred tank slurry reactor its morphology remained essentially unchanged, and it experienced small reductions in the volume mean diameter (5.4%) and generation of particles smaller than 10 pm in diameter was very small (0.7%). Catalytic performance of these catalysts during F-T synthesis was excellent. Syngas conversion was between 71 and 76%, whereas methane selectivity was between 2.0 and 3.5% and that of C-5(+) hydrocarbons was 78-89% (on C-atom basis). (C) 2010 Elsevier B.V. All rights reserved.