Low-Temperature Catalytic Transfer Hydrogenation of Biomass-Derived Furfural over Irreversibly Adsorbed and Highly Dispersed Zr(IV) Species.

Abstract

Developing pure inorganic catalysts for low-energy transfer hydrogenation of biomass-derived furfural and alcohols below 100 °C is still challenging. This work reports highly dispersed Zr(IV) species catalysts prepared by irreversible adsorption of different solvent-dissolved Zr(IV) cations such as Zr4+ or [Zr4(OH)8(H2O)16]8+ on/in SBA-15 through Zr-O coordination, without adding an alkaline precipitant and calcination treatment. In the transfer hydrogenation of furfural to furfuryl alcohol, the Zr(IV) species catalysts exhibited unexpectedly outstanding transfer hydrogenation activity at low temperatures of 70 and 85 °C, superior to other transition-metal (Zr4+, Hf4+, Fe3+, etc.)- and main-group metal (Al3+, etc.)-based inorganic catalysts, which need high reaction temperatures above 100 °C, and comparable to the best-performing metal-organic hybrid catalysts with precise defect engineering modification or specific macromolecular ligands, and had negligible Zr leaching amounts (<0.01%) in water and in the collected liquid reaction medium from 7 cycles of reactions. In addition, the large strong Lewis acidic site amount rather than the large total acidic amount is a crucial condition for the catalysts to obtain high transfer hydrogenation activity, and basic sites were also involved in catalysis, and their absence would induce the acetalization side reaction. Furthermore, the catalysts were universal for low-temperature transfer hydrogenation of other aldehydes.