Hydrogen assisted catalytic biomass pyrolysis. Effect of temperature and pressure

Beech wood has been converted into a mixture of oxygen-free naphtha and diesel boiling point range hydrocarbons by using catalytic hydropyrolysis in a fluid bed reactor with a CoMoS/MgAl2O4 catalyst, followed by deep hydrodeoxygenation (HDO) in a fixed bed reactor loaded with a NiMoS/Al₂O₃ catalyst. The effect of varying the temperature (365–511 °C) and hydrogen pressure (1.6–3.6 MPa) on the product yield and organic composition was studied. The mass balance closed by a mass fraction between 90 and 101% dry ash free basis (daf). The yield of the combined condensed organics and C4+ varied between a mass fraction of 17 and 22% daf, corresponding to an energy recovery of between 40 and 53% in the organic product. The yield of the non-condensable gases varied between a mass fraction of 24 and 32% daf and the char yield varied between 9.6 and 18% daf. The condensed organics contained a mass fraction of 42–75% aromatics, based on GC × GC-FID chromatographic peak area, and the remainder was primarily naphthenes with minor amounts of paraffins. The condensed organics were essentially oxygen free (mass fraction below 0.001%) when both reactors were used. Bypassing the HDO reactor increased the oxygen concentration in the condensed liquid to a mass fraction of 1.8%. The results show that catalytic hydropyrolysis may be a viable way to process solid biomass into liquid and gaseous fuels.