Shape selective cracking of polypropylene on an H-MFI type zeolite catalyst with recovery of cyclooctane solvent†

Abstract

The use of hydrocarbon solvents for zeolite-catalyzed polyolefin cracking narrows the molecular weight distribution of the products, which enhances the efficiency of polyolefin chemical recycling to naphtha, a key precursor to polyolefins. However, solvent consumption remains a challenge. In this study, zeolite microporosity was used to achieve shape-selective polyolefin cracking while allowing solvent recovery. With an H-MFI type zeolite catalyst combined with cyclooctane as the solvent, polypropylene was selectively converted without cyclooctane reactivity. In a typical case, 84% of polypropylene was converted into C3-27 aliphatic and monocyclic aromatic compounds (equivalent to liquid petroleum gas, naphtha, kerosene, jet and diesel) with 79% selectivity, while 95% of cyclooctane was recovered. This study is the first to demonstrate solvent recyclability in polyolefin cracking on an acidic zeolite, contributing to the chemical recycling of polyolefin into its precursor, naphtha, with high selectivity facilitated by the presence of solvent but without solvent consumption.