Hydrocarbon-Rich Bio-Oil Production from Ex Situ Catalytic Microwave Co-Pyrolysis of Peanut Shells and Low-Density Polyethylene over Zn-Modified Hierarchical Zeolite

Abstract

Peanut shells, a major economic and oil crop in China, boast an abundant availability and remarkably high lignin content compared to other agricultural residues. Previous work indicated that the modified hierarchical zeolite (Zn-ZSM-5/MCM41) was effective in promoting the conversion of intermediate macromolecules during the lignin pyrolysis reaction and enhancing the yield and selectivity of liquid products. Thereby, this study aims to improve the quality of liquid products in the ex situ catalytic microwave co-pyrolysis of peanut shells and LDPE by utilizing Zn-ZSM-5/MCM41. Employing a compound center experimental design, we optimized reaction conditions through response surface analysis. The impact of microwave pyrolysis temperature and the catalyst-to-feedstock ratio on yield distribution and liquid product selectivity was explored. Results indicated a marginal increase in liquid product yield with rising pyrolysis temperatures. Moreover, an initial increase followed by a subsequent decrease in liquid product yield was observed with an increase in the catalyst-to-feedstock ratio. Optimal conditions of 450 °C and a catalyst-to-peanut hull ratio of 2.34% yielded the highest bio-oil yield at 34.25%. GC/MS analysis of the bio-oil revealed a peak in hydrocarbon content at 68.36% under conditions of 450 °C and a catalyst-to-feedstock ratio of 13.66%. Additionally, the quadratic model effectively predicted bio-oil yield and the selectivity for major chemical components. This study underscores the potential of Zn-ZSM-5/MCM41 in optimizing liquid product quality during catalytic co-pyrolysis, offering insights into bio-oil production and its chemical composition.