Promotion of monocyclic aromatics by catalytic fast pyrolysis of biomass with modified HZSM-5

The present study proposes biomass torrefaction combined with catalytic pyrolysis to simplify the liquid products and selectively generate aromatic hydrocarbons. Cedarwood was selected as the representative biomass sample. The torrefaction of cedarwood at 250 degrees C and 300 degrees C (TB250 and TB300) was carried out to determine the solid product yield and its composition. It was shown that TB250 yielded the highest lignin feedstock and the yield of acetic acid was decreased to 1.88 %. Different transition metals (Ni/Cr) and Mo2N modified HZSM-5 catalysts with different Si/Al ratios were prepared for catalytic pyrolysis. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) experiments were performed to evaluate the effects of several factors on the final aromatic hydrocarbons yields. The results indicated that with a pyrolysis temperature of 700 degrees C, a catalyst-to-biomass ratio of 5, and 5% Ni-Mo2N/HZSM-5 (Si/Al ratio of 25) catalyzed, the yields of benzene, toluene and xylene could be increased to 2.10 %, 3.94 % and 5.54 %, respectively. Resulting from the excellent reduction ability of the modified catalyst, the yields of naphthalene and methylnaphthalene were reduced to 2.58 % and 0.70 %, respectively.