Abstract
A robust method is needed to achieve high yield all-catalytic conversion of recalcitrant lignocellulosic biomass to transportation fuels while maximizing carbon utilization from raw substrates. To accomplish this, we developed an integrated strategy that combines homogeneous and heterogeneous reactions with a treatment-extraction step to coproduce 2-methylfuran (MF) and 2,5-dimethylfuran (DMF) directly from hardwood poplar while maintaining high catalyst activity. In the first step, poplar wood chips were treated with dilute FeCl3 in THF–water at subpyrolytic temperature to yield 93.5% furfural (FF) from xylan and 66.0% 5-hydroxymethylfurfural (HMF) from glucan. Concurrently, a highly pure lignin powder was obtained from the liquor by precipitation upon room temperature vacuum recovery of THF from the water. Afterward, FF and HMF were extracted from water into an organic phase consisting of toluene and 1,4-dioxane treated with Ca(OH)2. A second hydrodeoxygenation reaction using Cu–Ni/TiO2 catalyst yielded 87.8% MF from FF and 85.6% DMF from HMF. Characterization of the lignin product showed its molecular weight to be reduced by an order of magnitude from its native state as well as complete removal of its native β-aryl ether linkages without hydrogen input or further heterogeneous catalytic processing. A 60% cumulative yield of MF, DMF, and lignin products from the available carbon (xylan+glucan+lignin) in poplar was achieved, rivaling more mature cellulosic ethanol strategies.
