PRODUCTION OF HYDROCARBONS BY CATALYTIC DEGRADATION OF HIGH-DENSITY POLYETHYLENE IN A LABORATORY FLUIDIZED-BED REACTOR

High density polyethylene (HDPE) was pyrolysed over different catalyst s using an in-house designed laboratory fluidised-bed reactor operatin g in the 290-430 degrees C range under atmospheric pressure. The catal ysts used were HZSM-5, Silicalite, HMOR, HUSY and SAHA and the yield o f volatile hydrocarbons (based on the feed) was typically HZSM-5>HUSY approximate to HMOR>SAHA. Product streams varied markedly with catalys ts type and structure. The sodium form of siliceous ZSM-5, silicalite, containing very few or no catalytically active sites, gave very low c onversions of polymer to volatile hydrocarbons. HZSM-5 and SAHA produc ed more olefinic streams with HZSM-5 yielding over 80 wt% olefins in t he C-3-C-5 range compared with around 40 wt% with SAHA. However, both HMOR and HUSY produced more paraffinic streams with large amounts of C -4 (19 and 14 wt%, respectively) and both catalysts deactivated during the course of the degradation. Observed differences in product yields and product distributions under identical reaction conditions can be attributed to the microstructure of catalysts. (C) 1998 Elsevier Scien ce B.V.