Au/TiO2 as high efficient catalyst for the selective oxidative cyclization of 1,4-butanediol to γ-butyrolactone

Au/TiO2 catalysts prepared by the deposition–precipitation method showed excellent activity and selectivity in the oxidative cyclization of 1,4-butanediol to γ-butyrolactone, with high yields (>99%) under mild conditions (413 K, 1.25 MPa air). Catalysts with 3–8% gold loading and calcined at 573–673 K were all highly active for the formation of γ-butyrolactone, as demonstrated by XRD, TEM, XPS, ICP and UV–vis DRS results. It is concluded that highly dispersed small (2–10 nm) gold particles are formed with the surface enrichment of gold. The ratio of cationic gold to metallic gold depends on the treatment temperature. These findings, combined with those of the activity tests, lead to the conclusion that the surface metallic nanosized gold particles are active sites. The catalyst can be reused with no drop in activity or selectivity.