Novel Cu-Zn-Al catalysts obtained from hydrotalcite-type precursors for middle-temperature water-gas shift applications

Abstract Water gas shift (WGS) reaction is a key step in the steam reforming industrial processes, allowing to increase the H 2 production reducing the CO content in the exiting stream. Currently the WGS reaction is performed in two steps, at high and low temperature, but in recent years, the possibility to perform it in only one step using one reactor operating at middle temperature (about 300 °C) has received increasing interest. Cu/Zn/Al hydrotalcite-type (HT) compounds having a Cu-content lower than 30 wt% showed to be useful precursors of highly active and stable catalysts for the WGS reaction in the 250–350 °C temperature range. The best performances were observed for a catalyst containing 20 wt% of copper and a M(II)/M(III) atomic ratio equal to 2.0 that reached the equilibrium values of CO conversion in all the temperature range with a behaviour similar to one of the most widely employed commercial catalyst, associated to a very good stability with time-on-stream. The catalytic behaviour may be rationalized considering both the Cu 0 surface area and the Cu/ZnO interactions, which are promoted by the homogeneous distribution of the cations in the brucite-type layers of the HT precursors.