Hydrogenation of alkenes over supported gold

Abstract

Gold has been supported upon SiO₂ and γ-Al₂O₃ using an impregnation technique and HAuCl₄ solutions. The severity of the conditions required to effect the reduction/decomposition of the acid to metallic Au upon the support decreased and the activity per unit weight of metal in the hydrogenation of pent-1-ene at 373 K increased, as the concentration of Au decreased from 5.0 to 0.01%. Au supported upon SiO₂ at these concentrations could be atomically dispersed, but in lower dispersions when upon γ-Al₂O₃. An increase in Au dispersion as its concentration decreased, which would provide an explanation for the unusual activity of these catalysts, may have been detected only by electron spin resonance and not by more traditional methods of characterisation. Preliminary results for SiO₂-supported Ag and Pt are compared with Au.