(208a) Production of Jet and Diesel Fuel Range Alkanes From Waste Hemicellulose-Derived Aqueous Solutions

We present a novel four-step process for the production of jet and diesel fuel range straight chain alkanes from hemicellulose-derived aqueous solutions which are byproducts from a Kraft mill located in the Northeastern U.S. The hemicelluloses extract contains xylose oligomers (21.2 g/l xylose after the acid hydrolysis) as well as 0.79 g/l glucose, 1.1 g/l arabinose, 9.77 g/l acetic acid, 0.32 g/l formic acid, and other minor products. The first step in this process is an acid-catalyzed biphasic dehydration to produce furfural in yields up to 87%. The furfural is extracted from the aqueous solution into a tetrahydrofuran (THF) phase which is then fed into an aldol condensation step. The furfural-acetone-furfural (F-Ac-F) dimer is produced in this step by reaction of furfural with acetone with yields of 96% for the F-Ac-F dimer. The F-Ac-F dimer is then subjected to a low temperature hydrogenation to form hydrogenated dimer (H-FAF) at 110-130 °C and 800 psig with a 5 wt% Ru/C catalyst. Finally the H-FAF undergoes hydrodeoxygenation to make large straight chain alkanes primarily C13 and C12 in yields up to 91%. The theoretical yield for this process is 0.61 kg of alkane per kg of xylose (monomer or oligomers) in the hemicelluloses extract. Experimentally we were able to obtain 76% of the theoretical yield for the overall process. We estimate that the jet fuel range alkanes can be produced from between $2.06/gal to $4.39/gal depending on the feed xylose concentration, the size of the biorefinery, and the overall yields. Sensitivity analysis shows that the prices of raw materials, the organic to aqueous mass ratio in biphasic dehydration, and the feed xylose concentration in the hemicellulose extract significantly affect the product cost.