Influence of support surface basicity and gold particle size on catalytic activity of Au/γ-AlOOH and Au/γ-Al2O3 catalyst in aerobic oxidation of α,ω-diols to lactones

Abstract

Gold catalysts on inert support γ-AlOOH and γ-Al2O3 were used as catalysts for selective aerobic oxidation of α,ω-diols to the corresponding lactones. The support crystal phase and basicity can be adjusted by calcination. Support calcined at below 573K is in the γ-AlOOH phase and when calcined at above 773K it is in the form of γ-Al2O3. There are only weak or medium basic sites on γ-Al2O3, while γ-AlOOH has strong or medium basic sites. Both support surface acidic–basic properties and gold particle size have influence on the activity and selectivity of the catalysts. Highly active catalysts can be obtained on both of the support, and from the characterization results it was found that the strong basic sites of γ-AlOOH were beneficial for the reaction, while selectivity would be sacrificed due to the hydrolysis of the product or further oxidation to acids under basic conditions. By loading gold onto γ-Al2O3, average gold particle size small as 3.8nm can be obtained and it gives higher activity and selectivity than Au/γ-AlOOH.