Selective Deoxygenation of Aqueous Furfural to 2-Methylfuran over Cu⁰/Cu₂O·SiO₂ Sites via a Copper Phyllosilicate Precursor without Extraneous Gas

Furfural (FUL) is substantially produced by the polymeric xylan fraction of hemicellulose with the presence of acids, and 2-methyl furan (2-MF) produced from FUL is an important biogasoline additive. Here, we report that 2-MF can be selectively formed from FUL with a 90% yield at 220 °C within 2 h over Cu⁰/Cu₂O·SiO₂ sites via a copper phyllosilicate precursor without extraneous gas. Methanol is used for in situ generating of highly pure hydrogen (92% content), and the almost CO free atmosphere avoids the poison on the Cu sites. The structure-activity relationship shows that Cu⁰ or Cu₂O or physically mixed Cu⁰ and Cu₂O is inactive, but the hydrogen-reduced copper phyllosilicate sample comprising abundant Cu⁰/Cu₂O·SiO₂ sites with interfaces demonstrates high activities in both reactions of methanol decomposition and FUL hydrodeoxygenation (HDO). The network for converting FUL to 2-MF includes tandem steps of FUL hydrogenation and furfural alcohol (FOL) hydrogenolysis to target 2-MF, accompanied by the side-reactions of hydrogenation of furan rings and ring opening of 2-MF. The kinetics modeling shows that the rational manipulation of reaction parameters of temperatures, reaction times, and H₂ amounts is the key for attaining high yields of 2-MF. Eventually, the crude aqueous FUL solution with 10 wt % water can be selectivity hydrodeoxygenated to 2-MF (close to 90% yield) at the used catalytic conditions.