Bi-Metal-Supported Activated Carbon Monolith Catalysts for Selective Hydrogenation of Furfural

Activated carbon monolith (ACM) catalysts were impregnated with Pd, Pd–Cu, and Pd–Fe for continuous hydrogenation of aqueous furfural (FUR). The effect of temperature, pressure, and liquid residence time on product selectivity and space-time yield (STY) was determined. Adding a second metal to Pd/ACM shifted the selectivity of the catalyst from 2-methylfuran (2MF) and 2-methyltetrahydrofuran (2MTHF) to furfuryl alcohol (FA) and tetrahydrofurfuryl alcohol (THFA), respectively, over the range of tested temperatures and pressures. High STYs of 272 g/Lcat/h (1089 g/kg-cat/h) for THFA and 143 g/Lcat/h (574 g/kg-cat/h) for FA were achieved using Pd–Fe/ACM at 180 °C and 300 psig. Similarly, adding Fe increased the FUR, FA, and THFA turnover frequency by a factor of 3, 4, and 60, respectively. The effect was not as pronounced when adding Cu. The effect of acetic acid, an impurity present in crude FUR, on FUR conversion and product selectivity was determined. The surface area analysis indicated a relatively low loss of surface area over 13 hydrogenation reactions on each catalyst. The presence of a second metal on the monolith catalyst stabilized the Pd particles, reduced the leaching, and altered the product selectivity.