Parametric investigation of water gas shift over Pd based catalysts

The purpose of this study is to investigate WGS reaction over Pd based catalysts, cheaper alternatives of Au and Pt, and explore the impact of reactor structuring on CO conversion. The Pd based catalysts used in this research, which contains 1.5wt.% active metal, were prepared by incipient to wetness impregnation method with various types of support materials, including CeO2, Al2O3 and TiO2. The effects of reaction temperature and feed composition on WGS activity comparatively studied in conventional packed bed reactor and a packed microchannel reactor in the temperature and molar steam to carbon (S/C) ratio ranges of 250-325 °C and 1-5, respectively. Experimental studies revealed that among the prepared catalysts WGS activity, measured in terms of CO conversion, followed the order of Pd/CeO2>Pd-CeO2/Al2O3>Pd/TiO2. CO conversion was improved at higher temperatures and molar steam to carbon ratios in the feed. Additionally, when compared with conventional fixed bed reactor, microchannel configuration involving less amount of catalyst exhibited better reactor productivity expressed in terms of per cent conversion per unit mass of catalyst. Scanning electron microscopy (SEM) analyses were conducted over CeO2 and Al2O3 supported catalyst samples and uniform Pd dispersion was observed in both cases. SEM analysis on catalysts exposed to reaction detected no coke formation and agglomeration of Pd particles.