Selective generation of aromatic hydrocarbons from hydrotreating-cracking of bio-oil light fraction with MOx modified HZSM-5 (M = Ga, Mo and Zn)

The upgrading of highly unsaturated bio-oil by zeolite cracking suffers from severe catalyst deactivation due to the carbonaceous deposition. Therefore, the dual-stage hydrotreating-cracking process is developed for more stable operation. In this work, to further promote the generation of aromatic hydrocarbon in a hydrotreatingcracking process cofeeding bio-oil light fraction and methanol, the cracking catalyst HZSM-5 was modified by MOx (M = Ga, Mo and Zn). Compared with the blank HZSM-5, the promotion of aromatic hydrocarbon production by MoO3/HZSM-5 was mainly owing to the enhanced selective conversion of intermediate light alkenes to aromatics, while those by Ga2O3/HZSM-5 and ZnO/HZSM-5 were attributed to both the re-activation of hydrotreating-derived CH4 and the intensified selective aromatization of alkenes. Meanwhile, raising cracking temperature decreased the yield of aromatic hydrocarbon but favored the production of gases. Ga2O3/HZSM-5 was the most effective catalyst for aromatic hydrocarbon production and 400 degrees C was a suitable cracking temperature, under which the upgrading of a bio-oil aqueous fraction achieved the oil phase yield of above 22% with the aromatic hydrocarbon content of above 93%.