Conversion of low-density polyethylene into monocyclic aromatic hydrocarbons by catalytic pyrolysis: Comparison of HZSM-5, Hβ, HY and MCM-41

Abstract

The catalytic properties of different catalytic materials on the pyrolysis of plastics have been extensively investigated. In order to better understand the relevant mechanism of catalytic pyrolysis of plastic waste, the effect of different acidity and pore size of catalytic material on its pyrolysis kinetic parameters and the distribution of pyrolysis products needs to be studied to provide a stronger theoretical basis for its resource utilization. This study aims to study the effects of HZSM-5, Hβ, HY and MCM-41 on the thermodynamic properties , kinetic parameters and pyrolysis characteristics of low-density polyethylene (LDPE), analyze the relationship between the specific catalytic pyrolysis products and the properties of the catalyst. Among the four catalysts, HZSM-5 obtained the most concentrated product distribution and the highest yield of monocyclic aromatic hydrocarbons , and it was found that the cracking of LDPE mainly occurred in its pores. Due to the large pore size and low concentration of acid sites, the main product type obtained by MCM-41 was olefins . In addition, it was found that HY reduced the pyrolysis temperature of LDPE and the activation energy of the reaction to the greatest extent. The different catalytic effects were mainly caused by different pore structures and acid site concentration. Moreover, it was found that the addition of catalyst changed the cracking mechanism of LDPE. Under the comprehensive consideration with the goal of producing monocyclic aromatic hydrocarbons, HZSM-5 is the most suitable catalyst among them. • The catalytic effects of HZSM-5, Hβ, HY and MCM-41 were studied. • HZSM-5 is the most suitable catalyst for the production of MAHs from LDPE. • Different pore structures and acid sites cause the changes of catalytic effects. • Partial LDPE scission sites changed from random-chain to end-chain due to catalysis. • The cracking reaction of LDPE occurs in the pores of HZSM-5.