Two-stage catalytic fast hydropyrolysis of biomass for the production of drop-in biofuel

The major obstacles for the production of drop-in fuel from traditional fast pyrolysis are low bio-oil yield, poor fuel heating value and high solid yield. To overcome these obstacles, we studied the introduction of high pressure hydrogen into the pyrolysis reactor, in a process known as catalytic fast hydropyrolysis (CFHP). CFHP of anisole, a bio-oil model compound, was performed at different temperatures and pressures, to determine the effects of those variables on the CFHP reaction network. Alkanes were observed at low temperature and high pressure, whereas aromatics were dominant at low pressure and high temperature. Aspen modelling and calculation of reaction equilibrium constants showed that there is a thermodynamic barrier for simultaneous pyrolysis and hydrogenation at 600 °C. Reduced heating rates and CFHP followed by second-stage hydroprocessing (SH) were proposed as a means to control reaction temperature and efficiently deoxygenate CFHP vapors. The two-stage CFHP followed by hydroprocessing produced nearly 18 mol% carbon yield to alkanes, and a total bio-oil carbon yield of 25 mol%. The approximate bio-oil higher heating value (HHV) and aromaticity were 43.4 MJ/kg and 28 wt%, respectively, both within the range of gasoline.