CaO as a cheap, eco-friendly material for the continuous-flow, gas-phase, catalytic transfer hydrogenation of furfural with methanol

The hydrogenation of biomass-derived molecules is a key reaction in upgrading these compounds into chemicals and fuels. The use of catalytic transfer hydrogenation, employing alcohols as hydrogen sources, offers an alternative approach to this process, avoiding the use of H2 under high pressure and precious noble metal catalysts. In this work, the continuous-flow, selective conversion of biomass-derived furfural (FU) into furfuryl alcohol (FAL) was investigated, using methanol as the H-transfer agent and CaO-based catalysts. CaO is easily prepared by thermal decomposition of the carbonate precursor and has proved to be a suitable material for the reduction of furfural into its unsaturated alcohol, thus allowing selective H-transfer from methanol to the substrate with relatively good conversion and very high selectivity. The decomposition temperature of the precursor is one of the fundamental parameters which allows the obtainment of the catalyst, albeit with a low surface area, which maintains an adequate number of defects and basic sites on the surface. The feed composition rich in methanol allows to avoid saturation of the active sites by the substrate to minimize the oligomerization reactions which decrease the selectivity and deactivate the catalyst. Dedicated characterizations have proven the in-situ formation of a partially carbonated CaO phase during the first hour of time on stream. The presence of the two phases improves the catalyst activity and stability leading, in the best reaction conditions, to high FAL productivity (5.37•10-4 molFAL/h m2).