The kinetics of the water-gas shift (WGS) reaction over two iron-chromium based commercial catalysts has been studied. The experiments were performed in a differential reactor at a constant temperature of 450 degrees C and a space velocity of 1.9 m(3) g(cat)(-1) h(-1) at approximately atmospheric pressure. The effects of CO. CO2, H2O and H-2 concentration on WGS reaction rate were determined over both catalysts using selected gas compositions that might be encountered in coal based gasification system of the dry-feed and slurry-feed types and at the backend of conventional fixed-bed and catalytic membrane reactors. It was found that the rates of the WGS reaction (in mol g(cat)(-1)s(-1)) over two commercial catalysts (referred to as HTC1 and HTC2) at a reaction temperature of 450 degrees C can be expressed by the following power-law Fate models: For HTC1 [GRAPHICS] It was observed that HTC1 promotes (he Fate of WGS reaction when the in let gas consists of higher CO concentration, and lower CO2 and H-2 concentration. Due to the less-negative reaction order with respect to CO2, HTC2 was found to be more applicable to the gas streams with higher CO2 levels, which are likely to be found on the retentate side at the backend of a catalytic membrane reactor. Crown Copyright (c) 2008 Published by Elsevier B.V. All rights reserved.