Selective upgrading of biomass pyrolysis oil into renewable p-xylene with multifunctional M/SiO2/HZSM-5 catalyst

This work indicated that p-xylene, an important bulk chemical in petrochemical industry, was able to be produced using the renewable biomass pyrolysis-derived bio-oil. The multifunctional catalysts (especially 3%Zn/20%SiO2/HZSM-5) simultaneously promoted the selectivity and yield of p-xylene in the catalytic upgrading of the bio-oil or bio-oil/methanol mixture. The SiO2 layer loaded on the catalysts significantly increased the selectivity of p-xylene by decreasing the external acidity of the catalyst surface. The addition of the active elements such as Zn and Ga into the HZSM-5 zeolite further improved the p-xylene yield by promoting the decarbonylation, decarboxylation and aromatization reactions. The optimized catalyst of 3%Zn/20%SiO2/HZSM-5 showed the maximum p-xylene yield of 18.7% with high p-xylene to xylenes ratio of 93.8%. The reaction pathways were proposed according to the detailed investigation for the catalytic cracking of different bio-oils and the functional groups in the products. Potentially, the resulting p-xylene product from the bio-oil can be used for high added value chemical or high octane gasoline additive.