Effects of Water Addition to Isopropanol for Hydrogenation of Compounds Derived from 5-Hydroxymethyl Furfural over Pd, Ru, and Cu Catalysts

We have developed lumped reaction schemes to optimize the yields of products from selective hydrogenations of HAH, a biomass-derived platform chemical produced by two-step aldol condensations of 5-hydroxymethyl furfural (H) with acetone (A). Reaction schemes consisting of 7, 9, and 11 steps were examined to describe the rates of formation of the observed products and reaction intermediates for hydrogenation of HAH over Ru and Pd catalysts, and a 3-step scheme was studied over Cu catalysts. Rate constants and activation energies were calculated using these reaction schemes, and we then apply the schemes to explore the effects of water addition on the hydrogenation pathways. The effects of water addition to isopropanol (IPA) solvents on the hydrogenation of HAH were markedly different over Pd, Ru, and Cu catalysts. Over the Pd catalyst, the addition of water to IPA increased hydrogenation rates and promoted the hydrogenation of furan rings. The addition of water to IPA yielded significant carbon losses over the Ru catalyst, and slowed hydrogenation steps over Cu, while significantly inhibiting hydrogenation of the ketone group. This behavior opened routes toward increased production rates of PHAH═O (a partially hydrogenated, P, form of HAH containing a C═O bond), a product in which the diene groups of the furan rings were not hydrogenated. The addition of water also allowed increased feed concentrations of HAH that were previously not possible in pure IPA solvents. The insights presented in this work provide a more mechanistic description of the hydrogenation of HAH, the behavior of specific intermediates, and the reactivity of key functional groups.