Hydrogenation of Dimethyl Adipate to 1,6-Hexanediol on Supported Rh–Sn Catalysts

Abstract

Hydrogenation of dimethyl adipate (DMA) to 1,6-hexanediol (1,6-HDO) was studied on supported noble metal-Sn binary catalysts at 300 °C and 9.1 MPa of H₂ in an autoclave. Binary catalysts were prepared by the conventional impregnation method and characterized by XRD, TPR and XPS. Among the catalysts studied, Rh–Sn supported on α-Al₂O₃ gave the highest 1,6-HDO yield. A novel reaction scheme is proposed including 6-hydroxyhexyl methyl adipate produced by an ester-exchange reaction between DMA and 1,6-HDO. The molar ratio of Sn to Rh greatly affected the catalytic performance. The active site structure and valences of Rh and Sn are discussed. Comparison of the catalytic performance with reported catalysts suggested that Rh–Sn and previous Ru–Sn catalysts provided superior selectivity for 1,6-HDO to previous Cu–Cr catalyst at the same DMA conversion.