Production of biofuel intermediates from furfural via aldol condensation over K2O clusters containing N-doped porous carbon materials with shape selectivity

Abstract

Upgrading biochemicals to the high energy density intermediates is the promising way to produce renewable diesel and jet fuel range alkanes. In this work, K2O clusters containing N-doped microporous and mesoporous carbon materials were prepared by a one-pot method and used as base catalysts to produce the key biofuel intermediate derived from furfural through its solvent-free aldol condensation with acetone. It is found that K2O clusters, which are stabilized by nitrogen and carbon atoms of N-doped porous carbon materials due to their strong interactions, are located inside the micropores, existing in the form of extra framework K2O clusters. The presence of K2O clusters inside micropores endows N-doped microporous and mesoporous carbon catalysts exceptional catalytic activity and shape selectivity in aldol condensation, almost full furfural conversion and over 90% selectivity to the monomer aldol product 4-(2-furyl)-3-buten-2-one (FAc) can be achieved within 2 h reaction time at 100 °C over these two types of N-doped carbon catalysts, which can be attributed to the synergetic effect between strong basic K2O clusters and N-doped carbon materials, and the micropores, which hinder the second condensation step to form the dimer aldol product 1, 5-di-2-furanyl-1, 4-pentadien-3-one (F2Ac). In addition, all the catalysts exhibited excellent regeneration capability and their catalytic activities can be well recovered by calcination under N2.