Catalytic properties of cobalt-promoted Pd/HAP catalyst for CO-cleanup of H2-rich stream

Abstract

The promoting effect of Co addition on the behaviour of the Pd/HAP system in WGS reaction has been investigated. Hydroxyapatite-supported bimetallic PdCo samples have been prepared by two consecutive impregnation steps with solutions of Co and Pd precursors, respectively. The resulting catalysts have been thoroughly characterised by BET, XRD, H2-TPR, XPS, OSCC and OSC techniques.The progressive addition of cobalt drives to an abundance of the Pd species exhibiting an intimate contact with Co and an eminent enhancement of the redox properties of the Pd/Co(x)/HAP catalysts. This results in an improvement of their performance in WGS reaction. The Pd species presenting an intimate contact with cobalt seems to be the responsible of the improvement of the CO conversion. However, this PdCo interaction leads to an increase in the methanation activity at the expense of WGS activity. When small amounts of O2 is added to the WGS mixture, the activity is exclusively enhanced in the presence of Co species exhibiting easier reducibility.