Parametric study of water-gas shift reaction over Pt-based catalysts

Abstract

In this study, parametric investigation of low temperature water-gas shift reaction over Pt-based catalysts is carried out. Effects of reaction temperature, feed composition, catalyst particle size and reactor geometry on CO conversion are examined. The catalysts, 1.5 wt% Pt-5 wt% CeO2/Al2O3 and 1 wt% Pt/MIL-53(Al), are prepared by the incipient-to-wetness method using deionized water as solvent. It is observed that CO conversion increases with temperature significantly, whereas it varies slightly with the feed composition. Highest CO conversion of 84 % is obtained at 325 °C and at feed composition including the highest CO2 content. CO conversions obtained over Pt/MIL-53(Al) remained less than 5 % due to the change in the crystal structure of MIL-53(Al) after impregnation of Pt. XRD analyses reveal that storage conditions of MIL-53(Al) is important to prevent degeneracy in crystal structure and incipient-to-wetness method for catalyst preparation is not suitable for MIL-53(Al). It is found that CO conversion increases from 1 % to 4 % by decreasing the reactor diameter from 10 mm to 2 mm. A similar effect is noted by decreasing particle size of the Pt/CeO2/Al2O3 catalyst from 3.02x10-1 mm to 3x10-3 mm which increased CO conversion from 1 % to 12 %. These findings indicate that running WGS in a microchannel reactor configuration involving reactor diameters in the sub-millimeter range can improve CO conversion. This hypothesis is also tested in the context of studies in which the reaction is carried out in microchannel reactor configurations involving washcoated and packed forms of the Pt/CeO2/Al2O3 catalysts. However, no net findings are obtained due to problems in coating of the catalyst and by-passing of the reactive mixture.