Unveiling the conditioning correlation in ex-situ catalytic pyrolysis of waste polyolefins towards designated conversion into valuable products

The ex-situ catalytic pyrolysis of waste polyolefin plastics holds promise for producing aromatics and light olefins, with potential integrations in the low-carbon olefin processing industry for producing ethylene, propylene, butadiene, or aromatic hydrocarbons. Employing ZSM-5(50) zeolite, selected for its substantial specific surface area and total pore volume, facilitated the catalytic pyrolysis of household plastic waste through an ex-situ pyrolysis-catalysis approach. This study explored the impact of operating parameters, T1-T2- C/P mass ratio, namely pyrolysis temperature, catalytic vapor upgrading temperature, and the catalyst/plastic mass ratio, on pyrolysis product yields and distributions. Higher T2 benefited gas production, accompanied by a notable decrease in C4 content in gaseous products. A larger C/P mass ratio provided more active sites for pyrolysis reactions, but higher T2 induced coke formation on the catalyst, leading to ZSM-5(50) deactivation and inhibiting further gas production. Positive effects of T2 and the C/P mass ratio were observed for the concentration of BTX in the produced oil. The quadratic fitting was engaged in characterising the reaction conditions. Specifically, the 500–550–0.25 run achieved the maximum C2 yield of 30.3 wt%, the 500–350–0.4 run obtained the highest yield of C3 and C4 of 75.4 wt%, and the run of 575–450–0.25 yielded the highest amount of BTX of 17.2 wt%. These findings provide valuable insights into the designated conditioning of catalytic pyrolysis for plastic waste valorisation. •Conditioning correlation of the household plastics ex-situ pyrolysis was unveiled.•The pyrolysis temperature engaged plastics pyrolysis and vapor formation.•A higher upgrading temperature benefited total gas yield but declined C4 content.•The elevated upgrading temperature and the catalyst ratio concentrated aromatics.