Ultrafast batch preparation and efficient continuous-flow preparation of biomass-derived furfural acetals over a TiO2 nanoparticle/exfoliated montmorillonite composite catalyst.

Furfural acetals with high octane value, high calorific value and high oxidation resistance are considered as a promising biofuel or fuel precursor with potential huge demand. However, there are few studies on efficient scalable catalytic systems such as continuous-flow catalytic systems for preparation of furfural acetals. In this work, TiO 2 nanoparticle/exfoliated montmorillonite composite with strong Lewis acid sites and abundant accessible Brønsted acid sites, was prepared to catalyze the acetalation reactions of biomass-derived furfural and alcohols. Low dosage of catalyst made the reaction reach equilibrium in a very short time (TOF = 690 ~ 1305 min -1 ) at room temperature with the acetal as the only product. In continuous-flow reactions, the catalyst showed a stable product output with the conversion close to that in the batch reaction in a short catalyst-reactant contact time of 150 s. The contrast experiments revealed that both Lewis and Brønsted acid sites on the catalyst were indispensable for maximizing the catalytic performance, and simultaneously activating both furfural and alcohol on the adjacent Lewis and Brønsted acid sites was speculated to be responsible for the high catalytic performance.