Activity and selectivity of Ni–Cu bimetallic zeolites catalysts on biomass conversion for bio-aromatic and bio-phenols

To improve the quality of bio-oil and minimize coke formation, ex-situ catalytic biomass pyrolysis vapor upgrading to high-grade bio-aromatic and phenol compounds with Py-GC × GC/MS at different nickel-to-copper ratios was investigated. At the same time, the deoxygenation efficiency, structure-activity relationship, deactivation mechanism and possible pathways between combined mono- and bimetallic catalysts were also demonstrated. Ni and Cu species could be well dispersed, and the HZSM-5 support maintained the MFI crystal structure after bimetallic Ni–Cu modification, but the surface area, pore volume, and total acidity decreased. Bimetallic Ni–Cu catalysts showed better deoxygenation efficiency than monometallic catalysts, which had more advantages in the preparation of aliphatic hydrocarbons (29.86%) than mono- and bimetallic catalysts, which favored the production of aromatics (28.89%). Higher-Ni-loading catalysts promoted the formation of aliphatic hydrocarbons, aromatics and alkanes due to decarboxylation, decarbonylation and aromatization reactions, and higher-Cu-loading catalysts enhanced the olefin and phenol yields due to dehydration and demethylation reactions. Overall, the highest yields of bio-aromatic compounds and phenols were46.78% and 36.34%, respectively, at Ni-to-Cu ratios of 1:1 and 1:2, due to the high total acid amount and suitable average pore size for bio-aromatics and the low acidity and large pore size for phenols. The bimetallic Ni–Cu catalyst significantly increased the quality of bio-oil and reduced coke deposition.