Unusual behaviour of Au/ZnO catalysts in selective hydrogenation of butadiene due to the formation of a AuZn nanoalloy

Abstract

The reaction of selective hydrogenation of butadiene performed in an excess of propene, which has been extensively studied over gold supported on different oxides and exhibited high selectivity to butenes, has been applied to the case of gold (1 wt%) supported on zinc oxide (8 m² g⁻¹), a strongly basic oxide, in order to try to thwart deactivation. Our results revealed, for the first time, a catalytic behaviour drastically different from what was previously observed over gold catalysts supported on alumina or titania, i.e. a much poorer activity when the catalyst was activated under usual conditions under hydrogen but a “normal” activity when it was activated in air. An in-depth characterisation study based on different hypotheses to explain the unusual result revealed that at variance with the other catalysts, Au₁Zn₁ alloy particles formed during activation under hydrogen at 300 °C and were responsible for the loss of activity.