Processing of mixed-plastic waste to fuel oil, carbon nanotubes and hydrogen using multi–core reactor

Abstract

Conversion of mixed–plastic waste into carbon nanotubes (CNTs) and hydrogen–rich hydrocarbon gases was carried out in a multi–core reactor using Ni/Mo/MgO catalyst. The mixed plastic waste consisted of HDPE (67.2 wt%), PP (11.2 wt%), PS (6.2 wt%), PVC (5.2 wt%) and PET (10.2 wt%). Optimization of process parameters such as pyrolysis temperature, CNT synthesis temperature, reaction time and recycle ratio were carried out using Box–Behnken 3–level and 4–factorial design method. The result shows that CNTs of 6.63 g and hydrocarbon gases containing 78% hydrogen would yield using 60 g plastic waste and 1 g of catalyst. Recycle ratio and pyrolysis temperature have shown the considerable effect over the yield of CNTs and product gases. The HRTEM analysis indicates that CNTs with aligned graphene walls can be produced at 50% recycle ratio, while 70% recycle ratio produces CNTs with bamboo like structure. High recycle ratio results in an increase of CO/CO2 concentration with reduction of CNTs and hydrogen yield.