Mechanism of synergistic effects and kinetic analysis in bamboo-LDPE waste ex-situ catalytic co-pyrolysis for enhanced aromatic hydrocarbon production via CeZrAl and HZSM-5 dual catalyst

Abstract

Thermocatalytic co-pyrolysis of agro-forestry residue and LDPE waste was used to improve aromatic-rich bio-oil with combining CeZrAl and HZSM-5 dual catalyst. The influence of pyrolysis parameters on pyrolysis characteristics, kinetics, aromatic yield and selectivity was investigated; the synergistic effect and additive effect for promoting aromatic hydrocarbons with and without catalysts were determined based on the experimental and theoretical hydrocarbon content; and the reaction mechanism was also described by analyzing the free radicals. Experimental results showed that LDPE with a higher H/Ceff ratio promoted biomass pyrolysis to produce aromatic-rich bio-oil with mass transfer and radical explanation. Dual catalytic co-pyrolysis remarkably increased hydrocarbon and aromatic hydrocarbon (AHs) contents. When the proportion of HZSM-5 was greater than 50%, the layered mode was more conducive to the formation of aromatics and more conducive to the conversion of alkyl benzene, while the mixed mode was more conducive to the conversion of olefins with a higher CeZrAl ratio, which facilitated the formation of toluene, xylene, BTXE and MAHs. The optimum aromatic, BTXE and MAH yields and selectivity (88.49%, 59.48% and 68.00%) were observed at 500/550 °C for a 1:2 CeZrAl to HZSM-5 ratio and a biomass to LDPE ratio. Abundant free radicals were produced and improved the mechanism’s synergistic effect.