Fischer-Tropsch synthesis (FTS) was carried out over precipitated iron-based catalysts activated by syngas (H-2 + CO) with different amounts of CO2 (0%, 20%, 33%, and 50%). The activation using CO2-containing syngas significantly suppressed the production of undesired products, CH4 and C-2-C-4 hydrocarbons, but facilitated the production of valuable products, C5+ hydrocarbons. In particular, in the case of C19+ hydrocarbons, the target products of low-temperature FTS (<= 280 degrees C), both selectivity and productivity showed a great increase with an increased inlet CO2 content during activation. We attribute the advantageous performance of the catalysts activated by CO2-containing syngas to the improvement in the effective performance of active iron carbides, possibly induced by an increased ratio of epsilon'-carbide (Fe2.2C) to chi-carbide (Fe2.5C) and a decreased fraction of inactive bulk carbons. (C) 2014 The Authors. Published by Elsevier Inc.