Dual-bed catalyst system for C-C coupling of biomass-derived oxygenated hydrocarbons to fuel-grade compounds

Mono-functional intermediates produced by catalytic conversion of sugars and polyols over Pt-Re/C catalysts (consisting of alcohols, ketones, carboxylic acids, and heterocyclic compounds) can be upgraded to fuel-grade compounds using two catalytic reactors operated in a cascade mode. The first reactor achieves C-C coupling of monofunctional intermediates using a dual-bed catalyst system, where the upstream catalyst bed (Ce1Zr1Ox) is employed to carry out ketonization of carboxylic acids, and the downstream catalyst bed (Pd/ZrO2) is used to achieve aldol condensation/hydrogenation of alcohols and ketones. This second bed is not significantly inhibited by CO2 and H2O produced during ketonization. The high molecular weight ketones produced by C-C coupling reactions in the dual-bed catalyst system are subsequently converted to alkanes by hydrodeoxygenation (i.e., dehydration/hydrogenation) over a Pt/SiO2-Al2O3 catalyst. Using the aforementioned approach, an aqueous feed containing 60 wt% sorbitol was converted to a liquid stream of alkanes, 53% of which consisted of C7+ alkanes with minimal branching, desirable for Diesel fuel.