Iron salts-catalyzed biomass hydropyrolysis for production of bio-oil and gaseous hydrocarbons

The catalytic hydropyrolysis of pine wood was conducted in a fixed bed reactor under a H₂ pressure of 5 MPa at different temperatures (600-700 ℃) to investigate the effects of two iron salts, Fe(NO₃)₃ and FeSO₄, on the upgrading of bio-oil and gaseous products. Fe(NO₃)₃ is found to promote the conversion of biomass to bio-oil and gaseous products, with a carbon conversion rate as high as 97.4%, a CH₄ yield of 21.2%, and a bio-oil yield of 32.8% (daf. biomass basis). Moreover, the oxygen content in the bio-oil decreases, the yield of light aromatic hydrocarbon increases and the yield of BTX (benzene, toluene and xylene) reaches 2.6%. In contrast, FeSO₄ has an inhibitory effect on the production of gaseous hydrocarbons and bio-oil. The XRD analysis shows that Fe(NO₃)₃ is transformed to α-Fe during hydropyrolysis, with the amorphous and porous structures of bio-char being formed. This is highly conducive to the catalytic hydrogenation and methanation of bio-char. But FeSO₄ is converted to Fe₂S₃ during the hydropyrolysis, which might poison the catalytic activity.