Beneficial effects of hydrogen pressure in the pyrolysis of biomass: a study of Euphorbia Rigida

Abstract

Abstract Fixed-bed pyrolysis and hydropyrolysis experiments at different temperatures and pressures have been conducted on a sample of Euphorbia Rigida extracted with n-hexane and methanol to remove low molecular mass terpenoids and saccharides to elucidate the extent of oil formation from the remaining predominantly cellulosic structure. The trends in yield and product composition are markedly different to those found previously for coals. Primary oil yields reached a maximum of ca 35% (daf basis corresponding to ca 60% on a carbon basis) at a hydrogen pressure of 50 bar and 500°C. Raising the temperature and hydrogen pressure decreased the oxygen contents and increased the aromaticities of the oils but also increased hydrocarbon gas yields. The relatively high nitrogen contents of the oils (2–3%) were not markedly affected by hydrogen pressure and present the major obstacle to producing light hydrocarbon oils via two-stage hydropyrolysis.