Conversion of low density polyethylene (LDPE) over ZSM-5 zeolite to liquid fuel

Abstract

Catalytic cracking of plastics waste to produce fuel is increasingly gaining the attention of researchers worldwide. The objective of this study is to assess the effects of temperature and liquid hourly space velocity (LHSV) on composition of liquid products from catalytic cracking of LDPE dissolved in benzene. A plausible reaction mechanism was also proposed. The catalytic cracking produced C1[sbnd]C8 hydrocarbons in all runs due to the effective heat exchange between polymer chains and catalysts. Analysis of products composition indicated that catalytic cracking of LDPE generally produced high amount of aliphatic branched-chain compounds, together with moderate amount of cyclic compounds. The reaction conditions also led to alkylation of benzene by the cracking products from LDPE. Hence, it is concluded that the catalytic cracking of LDPE is dominated by free radical mechanism, while the influence of carbenium ion is less pronounced due to low acidity of the catalyst. Overall, it is shown that catalytic cracking of LDPE solution in fixed bed reactor produced higher polymer conversion and liquid yield than conventional reactors and has the potential to extract hydrocarbon energy from recycled polymer waste.