Microwave co-pyrolysis of PET bottle waste and rice husk: effect of plastic waste loading on product formation

Abstract

This research work is focused to understand the role of microwave susceptor-assisted pyrolysis on polyethylene terephthalate (PET) bottle waste with rice husk (RH) valorization. Microwave pyrolysis/co-pyrolysis experiments were conducted at 450 W microwave power using a graphite susceptor. Effects of PET: RH ratio and total mass of co-pyrolysis feed mixture were thoroughly investigated. Mass and energy yields of bio-crude, char, and gas were evaluated. Microwave energy consumption and energy efficiency of pyrolysis were also evaluated. Pyrolysis energy efficiency is higher at 40 g (73–76%) compared to 20 g (53–75%) of co-pyrolysis feed mixture. The heating value of bio-crude was high (34–36 MJ/kg) due to carbon (79–83 wt%) and hydrogen (5–6 wt%) rich compounds. Bio-crude composition significantly varied with PET: RH ratios. Co-pyrolysis promoted the formation of aromatic oxygenates and biphenyl hydrocarbons. The selectivity of biphenyl hydrocarbons (29.2%) is high at an equal PET: RH ratio. The selectivity of hydrocarbons obtained at the 20:20 (PET: RH) ratio is found to be 47.5%. The selectivity of aromatic hydrocarbons obtained in microwave pyrolysis (47.9%) of PET is higher compared to conventional pyrolysis (8%). In microwave pyrolysis of RH, the high selectivity of aromatic oxygenates (73%) was obtained. Whereas, in conventional pyrolysis, the formation of aliphatic oxygenates (36.5%) was observed. This research would provide an understanding of waste valorization using the co-pyrolysis platform.