Analysis of pyrolysis index and reaction mechanism in microwave-assisted ex-situ catalytic co-pyrolysis of agro-residual and plastic wastes

Catalytic and non-catalytic microwave-assisted co-pyrolysis of biomass with plastics was performed to understand the interactions. An ex-situ configuration was adopted for performing catalytic co-pyrolysis experiments with ZSM-5 as a catalyst. Co-pyrolysis promoted cracking of vapors resulting in enhanced gas yields. ZSM-5 further enhanced the secondary cracking which resulted in low oil yields. The oil fraction collected from the pyrolysis of plastics was rich in hydrocarbons, whereas biomass pyrolysis led to the formation of oxygenated compounds in the oil. A plausible reaction mechanism scheme is proposed to understand the formation of major pyrolysis products via different pathways during different pyrolysis processes investigated. Also, a new parameter, the pyrolysis index is introduced to understand the pyrolysis intensity by utilizing the feedstock conversion, pyrolysis time, heating value, mass of feedstock, and energy consumption. The value of the pyrolysis index was found to be higher for plastics pyrolysis than biomass pyrolysis. Co-pyrolysis further increased the pyrolysis index due to the synergistic interactions.

Automated summary

Catalytic and non-catalytic microwave-assisted co-pyrolysis of biomass with plastics was conducted to investigate their interactions. The results showed that co-pyrolysis increased gas yields but reduced oil yields. The oil fraction derived from plastic pyrolysis contained more hydrocarbons, while biomass pyrolysis resulted in the formation of oxygenated compounds in the oil. A new parameter, the pyrolysis index, was introduced to measure pyrolysis intensity, and it was found to be higher for plastic pyrolysis than biomass pyrolysis, further increased by co-pyrolysis due to synergistic interactions.