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

Abstract

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 exsitu pyrolysis-catalysis approach. This study explored the impact of operating parameters, T 1-T 2- C/P mass ratio, namely pyrolysis temperature, catalytic vapor upgrading temperature, and the catalyst/plastic mass ratio, on pyrolysis product yields and distributions. Higher T 2 benefited gas production, accompanied by a notable decrease in C 4 content in gaseous products. A larger C/P mass ratio provided more active sites for pyrolysis reactions, but higher T 2 induced coke formation on the catalyst, leading to ZSM-5(50) deactivation and inhibiting further gas production. Positive effects of T 2 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 C 2 yield of 30.3 wt%, the 500 -350 -0.4 run obtained the highest yield of C 3 and C 4 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.