(237c) Woody Biomass to Liquid Hydrocarbon Fuel

This work describes the production of jet fuel range hydrocarbons from woody biomass. Both untreated yellow poplar (Liriodendron tulipifera) and commercially available 100-mesh wood flour were used in experiments. A novel, low temperature process was developed in which the lignocellulosic feedstock, particularly the lignin fraction, is minimally broken down into processable fragments through liquid phase hydro-pyrolysis in the presence of a base and a solid catalyst. The resulting fuel precursors mainly consist of phenol, cyclohexanol, alkyl-phenols and alkyl-cyclohexanols, derived from the lignin fragments of the biomass. The hydropyrolysis process was carried out in a 0.5-L Inconel stirred autoclave. The precursor yield was studied at temperatures of 200 °C to 300 °C and at wood/base mass ratios of 0.27 to 3 in the presence of hydrogen. The results showed that low temperatures and a low wood/base ratio favored higher precursor yield. The maximum fuel precursor yield achieved was 55.1%. The hydropyrolysis process was also carried out in a 1.8 L autoclave to scale up the process. The results of the scale-up process will be presented. 

      The fuel precursors were separated from the unconverted biomass, mainly cellulose and organic acid byproducts, and were coupled into C₉-C₁₆ hydrocarbons in the presence of a solid catalyst and hydrogen. Both precious metal and base metal catalysts were studied for the precursor coupling reaction. With a model compound mixture, such as phenol and cyclohexanol (2:1 by weight), a maximum C₁₁+ yield of 68% was achieved at 275 °C and the major product was 2-cyclohexylcyclohexanol. With increasing coupling temperatures, a more hydrogenated product, 1,1’-bicyclohexyl, was produced with a slight decrease in overall C₁₁+ yield.  Water was also found to inhibit the yield of the coupling process. Cobalt-based catalysts showed more resistance to water inhibition than palladium-based catalysts. Using solvent-extracted (water-free) fuel precursors obtained from the hydro-pyrolysis of a hardwood flour mixture, a 30% yield of C₉-C₁₂ hydrocarbons was obtained with a Pd-based catalyst. The produced fuel was composed of hydrocarbons in the C₈ to C₁₆ range. The estimated density of the fuel sample was about 0.802 g/cm³ and the average boiling point was approximately 159 °C.

      In the presentation, the different steps of the proposed biomass to fuel process and associated experimental results will be discussed. Techno-economic analysis results based on a HYSYS material and energy balance process model for fuel production from wood will also be presented.