Thermo-chemical disposal of plastic waste from end-of-life vehicles (ELVs) using CO2

Abstract

The source reduction of plastic waste could be an effective means to attenuate hazardous environmental problems triggered by microplastics. Energy recovery from plastic waste through thermochemical processes is a desirable valorization route. To realize the grand challenges, plastic waste derived from end-of-life vehicles (ELVs) was pyrolyzed. To propose a greener feature, CO2 was introduced as a mediator to maximize carbon allocation to the gaseous pyrogenic product (syngas) by CO2 reduction to CO and concurrent oxidation of volatile matter (VM) that was evolved from the thermolysis of plastic waste. As such, fundamental and systematic works were conducted to delineate the CO2 effects on conversion of VMs. This study experimentally proved that CO2 promotes thermal cracking in line with C–C bond scissions. However, the reaction rate for the conversion of CO2 and VM into CO via homogeneous reaction was not fast. Therefore, a Ni-based catalyst was employed to accelerate the reaction rate. However, there was coke deposition on the catalyst surface. To prevent coke formation, we chose a method to enhance CO2 reduction to CO and the oxidation of VM. Thus, three bimetallic catalysts were used for catalytic pyrolysis. Among the three bimetallic catalysts, Rh0.1Ni1/SiO2 was the most effective.