Production of renewable C4–C6 monoalcohols from waste biomass-derived carbohydrate via aqueous-phase hydrodeoxygenation over Pt-ReO_x/Zr-P

A bifunctional catalyst, Pt-ReO_x supported on zirconium phosphate (Pt-ReO_x/Zr-P), was prepared and tested for aqueous-phase hydrodeoxygenation (APHDO) of waste biomass-derived carbohydrate (e.g., sorbitol) to produce C4–C6 monoalcohols such as butanol, pentanol, and hexanol in a high-pressure continuous flow reactor. For steady-state operation, the reaction parameters were optimized to achieve the highest yield of C4–C6 monoalcohols from APHDO of sorbitol. Approximately 30% yield of C4–C6 monoalcohols was reached at optimal reaction conditions (temperature: 453 K, pressure: 6.21 MPa, weight hourly space velocity (WHSV): 0.16 h⁻¹) for APHDO of sorbitol over the Pt-ReO_x/Zr-P catalyst. The effect of catalyst support for monoalcohol production was also evaluated by comparison between the Pt-ReO_x/Zr-P and carbon supported Pt-ReO_x (Pt-ReO_x/C) catalysts. The Zr-P supported catalyst exhibited a four times higher yield of C4–C6 monoalcohols than the carbon supported catalyst, suggesting that acid sites atomically separated from metal sites play a crucial role in producing monoalcohols via C–O bond cleavage of chemical intermediates produced during APHDO of sorbitol.