The activity and structure of methanol synthesis catalysts derived from silver, copper, and cerium alloys in relation to Frost's hypothesis

Abstract

The structure and methanol synthesis activity of systems derived from binary cerium-silver and ternary cerium-silver-copper intermetallic precursors have been studied in the light of Frost's hypothesis according to which methanol synthesis occurs on a metal-promoted oxide phase. Results were obtained by in situ powder X-ray diffraction (XRD) with concurrent analysis of the exit gas stream by gas chromatography. To attain extensive metal/cerium oxide interaction, activation in N 20 and CO/H 2, with and without hydrogen pretreatment, was investigated; pressures up to 50 bar and temperatures up to 500°C were used. No methanol synthesis activity was observed from Ag/CeO 2 systems derived from binary cerium-silver alloys. Furthermore, the activity of the Cu/Ag catalyst derived from the ternary precursor was very significantly reduced relative to that expected by comparison with CeCu 2-derived catalysts on the basis of its copper content. Thus at least for methanol synthesis catalysts derived from these intermetallic precursors, the identity of the transition metal does indeed appear to be crucial.