Catalytic degradation of high density polyethylene over mesoporous and microporous catalysts in a fluidised-bed reactor

High density polyethylene (HDPE) was pyrolysed over various catalysts using a laboratory fluidised-bed reactor operating isothermally at ambient pressure. HZSM-5 catalysed degradation resulted in much larger amounts of volatile hydrocarbons compared with degradation over non-zeolitic catalysts (MCM-41 and SAHA). When an HZSM-5 was used as a cracking additive in combination with a non-zeolitic catalyst (MCM-41 and SiO2-Al2O3), the solid mixed catalysts produced less gas with a lower loss of gasoline than HZSM-5. MCM-41 with large mesopores and SAHA with weaker acid sites resulted in a highly olefinic product and gave rise to the broadest carbon range Of C-3-C-7. Both SAHA and MCM-41 materials allow bulky reactions to occur leading to the generation of coke and subsequently deactivation of the catalyst. This paper presents the conversion of polymers to useful hydrocarbons using various cracking catalysts and attempts to provide a basis for optimising the potential benefit of catalytic polymer recycling. (C) 2004 Elsevier Ltd. All rights reserved.