Integrated Catalytic Process for Biomass Conversion and Upgrading to C12 Furoin and Alkane Fuel

Report herein is an integrated catalytic process for conversion and upgrading of biomass feedstocks into 5,5′-dihydroxymethyl furoin (DHMF), through self-coupling of 5-hydroxymethyl furfural (HMF) via organocatalysis, and subsequently into n-C12H26 alkane fuel via metal–acid tandem catalysis. The first step of the process involves semicontinuous organocatalytic conversion of biomass (fructose, in particular) to the high-purity HMF. N-Heterocyclic carbenes (NHCs) are found to catalyze glucose-to-fructose isomerization, and the relatively inexpensive thiazolium chloride [TM]Cl, a Vitamin B1 analog, catalyzes fructose dehydration to HMF of good purity (>99% by HPLC), achieving a constant HMF yield of 72% over 10 semicontinuous extraction batch runs. Crystallization of the crude HMF from toluene yields the spectroscopically and analytically pure HMF as needle crystals. The second step of the process is the NHC-catalyzed coupling of C6 HMF produced by the semicontinuous process to C12 DHMF; the most effective organic NHC catalyst produces DHMF in 93% or 91% isolated yield with an NHC loading of 0.70 mol % or 0.10 mol % at 60 °C for 3 h under solvent-free conditions. The third step of the process converts C12 DHMF to linear alkanes via hydrodeoxygenation. With a bifunctional catalyst system consisting of Pd/C + acetic acid + La(OTf)3 at 250 °C and 300 psi H2 for 16 h, DHMF has been transformed to liquid hydrocarbon fuel (78% alkanes), with a 64% selectivity to n-C12H26 and an overall C/H/O % ratio of 84/11/5.0.