Catalytic degradation of polyethylene over solid acid catalysts

摘要

In this study we investigated the catalytic degradation of polyethylene (PE) in a fixed-bed reactor composed of a melter and a catalytic cracking bed. Solid acid catalysts, silica-alumina and zeolites [HZSM-5, natural zeolite (NZ), Y zeolite, etc.] were screened for polyethylene degradation in the range of 450-500℃. The degradation products of PE, especially a liquid fraction, formed over solid acid catalysts, were analyzed by gas chromatography-mass spectroscopy (GC-MS). Compared with those obtained by ther- mal degradation, the catalytic degradation products are distributed in a narrow range of carbon numbers. The liquid fraction contained large amounts of iso-paraffins and aromatics, as are present in the gasoline fraction of petroleum. The NZ catalyst (clinoptilolite structure, occurring in the Youngil area of Korea) was an efficient catalyst for the PE degradation. The acidity and characteristic pore structure of zeolites appear to be responsible for the good performance. The effects of temperature, contact time, and the presence of nickel metal on the product distribution in PE degradation are also discussed in this work.