Utilization of Ni as a Non-Noble-Metal Co-catalyst for Ceria-Supported Rhenium Oxide in Combination of Deoxydehydration and Hydrogenation of Vicinal Diols
Kosuke Yamaguchi, Yoshinao Nakagawa, Congcong Li, Mizuho Yabushita, Keiichi Tomishige
Abstract
Removal of vicinal diols by combination of deoxydehydration and hydrogenation (DODH + HG) was carried out over the mixture of ReOx/CeO2 and CeO2-supported base metals with H2 as the reducing agent, in order to replace expensive Pd in the ReOx–Pd/CeO2 catalyst used in previous studies for the same reaction. Similar high activity and selectivity of the mixture catalysts of ReOx/CeO2 and pre-reduced Ni/CeO2 were observed for DODH + HG as those of Pd-based catalysts (co-loaded ReOx–Pd/CeO2 or mixture catalysts of ReOx/CeO2 + Pd/CeO2), while co-loaded ReOx–Ni/CeO2 catalyst showed almost no activity. The ReOx/CeO2 + Ni/CeO2 catalyst system gave 99% yield of tetrahydrofuran from 1,4-anhydroerythritol and could be applied to DODH + HG of other diols and polyols such as glycerol, erythritol, and xylitol. Unlike ReOx–Pd/CeO2, the activity of the ReOx/CeO2 + Ni/CeO2 catalyst decreased in the reuse test, especially before second or later reuses, even when the recovered catalyst was calcined as regeneration. The catalysts were characterized by various methods such as thermal gravimetry–differential thermal analysis, temperature-programmed reduction with H2, and X-ray absorption fine structure spectroscopy. The deactivated ReOx/CeO2 + Ni/CeO2 catalyst after use and the inactive ReOx–Ni/CeO2 catalyst after reduction had Re–Ni direct bonds, suggesting that the strong interaction between Re and Ni species decreased the activity of ReOx/CeO2 in the DODH reaction.