Catalytic degradation of polyethylene over solid acid catalysts

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 r ange of 450-500 degrees C. The degradation products of PE, especially a liq uid fraction, formed over solid acid catalysts, were analyzed by gas chroma tography-mass spectroscopy (GC-MS). Compared with those obtained by thermal degradation, the catalytic degradation products are distributed in a narro w range of carbon numbers. The liquid fraction contained large amounts of i so-paraffins and aromatics, as are present in the gasoline fraction of petr oleum. The NZ catalyst (clinoptilolite structure, occurring in the Youngil area of Korea) aias an efficient catalyst for the PE degradation. The acidi ty and characteristic pore structure of zeolites appear to be responsible f or 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. (C) 1999 Elsevier Science Ltd. All rights rese rved.