Water–gas shift catalyst development for energy efficient applications

Abstract

The water–gas shift (WGS) is a reversible, moderately exothermic reaction (1) and is used for the production of hydrogen from CO rich gas streams (synthesis gas). CO + H2O ? CO2 + H2 ?H°= –41 kJ mol?1 (1) This research has focused on the catalyst development of water–gas shift (WGS) reaction and understanding the catalytic activity contributions by different elements present in the catalyst formulation. The motivation for the catalyst development was to improve the energy efficiency in the process of hydrogen production by WGS for an integrated gasification combined cycle (IGCC) power generation for which a CO2 capture unit is foreseen. The WGS process requirements for a more efficient process are that the newly developed catalysts have to operate at low H¬2O/CO ratio (< 3), medium temperature range (523–673 K), to be resistant or reversible to H2S, and should have similar activity, selectivity, and lifetime to that of the current commercial catalysts. A highly active catalyst Rh/Fe2O3/ZrO2 was developed which outperformed currently available commercial high temperature shift catalyst. The rhodium was investigated to mostly promote the redox mechanism dominant in iron oxide and the presence of rhodium in Rh/Fe2O3/ZrO2 however also led to small amounts of methane produced as a side product.