Partial removal of Al2O3 enhanced production of aromatic hydrocarbons from catalytic pyrolysis of waste lithium-ion battery separators

Abstract

A new method for the sustainable utilization of waste lithium-ion battery separators was developed, involving the hydrochloric acid washing to partially remove the Al₂O₃ coating, followed by catalytic pyrolysis to produce aromatic hydrocarbons with HZSM-5. The separators composed of polyethylene as base film were selected as the feedstock. The effects of acid washing pretreatment on the physicochemical properties and pyrolysis characteristics of the separators were studied. The results showed that the partial removal of Al₂O₃ coating not only enhanced the heat and mass transfer, improving the primary thermal decomposition of organic matter and increasing the formation of volatiles, but also promoted the contact between volatiles and Al₂O₃, resulting in the cracking of large molecular substances into small molecular olefins. This pretreatment process was conducive to the production of aromatic hydrocarbons during the catalytic pyrolysis over HZSM-5. The aromatic hydrocarbons yield, calculated based on the ash-free separator, reached a maximum value of 83.20 wt% under conditions of 1.5 mol/L hydrochloric acid concentration and a catalyst/separator ratio of 12 at 650℃. This yield surpassed the yields of 59.24 wt% from untreated separator and 64.39 wt% from pure polyethylene separator.