A preliminary work on design and development of sour water gas shift catalysts for synthetic natural gas process

Abstract

The main goal of this study is to design and develop a model sour water gas shift catalyst showing high performance in terms of activity, stability & selectivity and conducting performance screening by mimicking the syngas composition of the potential coal gasifier under ideal, sulfur-free conditions. According to the literature, dry powder entrained-bed type gasifier seems potential gasifier for the Synthetic Natural Gas (SNG) production processes, and it contains low steam/CO ratio, below 0.8. On the other hand, classical sour water gas shift (SWGS) catalysts work under high steam/CO ratio, specifically, above 2 or 3. In this context, from literature, one of the potential SWGS catalysts which is suitable for dry-powder syngas composition was chosen as a reference. Activated carbon supported KCoRe as the model SWGS catalysts were developed and these catalysts were tested under ideal, sulfur-free syngas composition. The effect of reaction conditions (i.e., reaction temperature and steam to carbon monoxide ratio) and catalyst preparation & support pre treatment methods (i.e., impregnation method, air & nitric acid pre-treatment on the Activated Carbon support) were investigated on the prepared catalyst. Activity and selectivity were determined in terms of conversions of CO and H₂, respectively. Experimental results showed that reaction conditions are very important parameters on the performance of the catalysts. At low steam/CO ratios, it is necessary to increase the temperature in order to get high activity. The effect of the impregnation method may vary from support to support since impregnation depends on the surface chemistry of the support material. Co-impregnation method may not be suitable for air oxidized AC supported catalysts. Both air and nitric acid treatments are helpful to increase the performance of the catalysts by increasing the oxygen bearing surface groups on the AC support.