In the first section of this paper, the activity of an iron-chromium-based catalyst for the water-gas-shift reaction is studied at laboratory scale. The influence on the activity of the sweet shift catalyst of the main operating parameters-temperature, space velocity, excess steam, pressure, and gas composition-is evaluated. Base case gas composition M1 was set according to that of the IGCC Power Plant of Puertollano, Spain (ELCOGAS): N-2 13.4 vol%, CO 60.7 vol%, H-2 22.3 vol%, and CO2 3.6 vol%. The effect of gas hourly space velocity GHSV (2000-5000 h(-1)), steam to CO ratio R, (1-3 mol mol(-1)), pressure P (0.1-2 MPa), and temperature (523-653 K) has been determined. In order to study the effect of gas composition on the activity of the WGS catalyst, the following gas mixtures have been evaluated: M2 (CO 60.7 vol%, H-2 22.3 vol%, and CO2 17 vol%); M3 (CO 60 vol%, N-2 40 vol%); and M4 (CO 60 vol%, and CO2 40 vol%). The second part of this paper deals with subsequent WGS testing at bench-scale level, based on the results obtained at laboratory scale. Tests were performed using a gas composition according to that of ELCOGAS IGCC plant. The operating temperature was 583 K, pressure was set at 1 MPa, and gas space velocity was 4715 h(-1). The effect of steam to CO ratio was evaluated. (C) 2012 Elsevier Ltd. All rights reserved.