Enhanced catalytic upgrading of biomass wastes pyrolysis vapors over Ni-Co modified HZSM-5 catalyst derived from spent ternary lithium-ion batteries

Spent ternary lithium-ion batteries (NCM) are rich in catalytically active transition metals (such as Ni and Co) and have high potential for constructing a catalyst used for the catalytic reforming of biomass pyrolysis volatiles. Therefore, in this study, a novel Ni-Co bimetallic catalyst (MPyNCM/HZSM-5) was fabricated by simultaneously recovering the Ni and Co components from the magnetic components of pyrolysis products of spent NCM (MPyNCM) and loading them on HZSM-5 support. The catalytic reforming performance and mechanism of MPyNCM/HZSM-5 for wheat straw (WS) pyrolysis volatiles were explored for the first time. The results showed that the MPyNCM/HZSM-5 catalyst had a mesoporous structure (average pore size around 5 nm), with the uniform distribution of the active metals Ni and Co on its surface. The MPyNCM/HZSM-5 catalytic reforming had the highest syngas yield, H₂ yield and H₂ concentration, with the H₂ yield reaching 1.19 mmol/g WS and 1.38 times higher than that of the HZSM-5 support. In addition, the MPyNCM/HZSM-5 significantly boosted the generation of aromatic hydrocarbons compounds and reduced the oxygen content of the obtained bio-oils, with the content of aromatic hydrocarbons reaching 29.36 %, which was 48.6 % higher than that of the HZSM-5 support. The synergistic effect between the Ni and Co metals made MPyNCM/HZSM-5 have comparable acid sites amount, high-temperature oxygen defects and reducibility to those of the Ni-Co/HZSM-5 catalysts. These chemical properties jointly promoted the deoxygenation and aromatization reactions of volatile macromolecules under MPyNCM/HZSM-5 catalysis. This study provides a novel approach to constructing a highly efficient catalyst from spent lithium-ion batteries for catalytic pyrolysis of biomass.