Chitosan-derived NC support zirconia as highly efficient catalyst for the catalytic transfer hydrogenation of furfural to furfuryl alcohol

Developing green and efficient catalysts for converting biomass into high-value chemicals is of great significance in heterogeneous catalysis. Herein, we prepared a series of wZrO₂/NC_T with various ZrO₂ loading (w) and pyrolysis temperature (T) by a hydrothermal carbonization-pyrolysis method using green and inexpensive bio-chitosan as nitrogen-doped carbon materials (NC) precursor, and applied to the catalytic transfer hydrogenation (CTH) of furfural (FUR) to furfuryl alcohol (FAL). A 99.7 % FUR conversion and 96.5 % FAL selectivity was achieved over 33ZrO₂/NC_750 catalyst using 2-propanol as the hydrogen source under certain reaction conditions, which was much higher than that of ZrO₂ and ZrO₂/C catalyst. The nitrogen species in NC can not only enhance the dispersion of ZrO₂, but also provide a certain amount of Lewis base sites. The synergistic interaction of Lewis acid sites (Zr⁴⁺) and Lewis base sites (N species and O^2-) played important roles in the FUR to FAL reaction. Moreover, the absence of Brønsted acid sites reduced the occurrence of side reactions and thereby enhances the selectivity of FAL. The influence of acidic (benzoic acid) and basic (pyridine) additives on the catalytic performance further verified the synergistic acid-base catalytic mechanism. In addition, this catalyst can also catalyze other aldehydes to corresponding alcohols and was reused at least five times without any significant loss of catalytic active and selectivity.