The effect of acidity behaviour of Y zeolites on the catalytic degradation of polyethylene Isabel C. Neves a, * , Gabriela Botelho a , Ana V. Machado b , Patrı ´cia Rebelo b a Departamento de Quı ´mica, Centro de Quı ´mica, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal b Departamento de Engenharia de Polı ´meros, Universidade do Minho, Campus de Azure ´m, 4800-058 Guimara ˜es, Portugal Received 11 November 2005; received in revised form 18 January 2006; accepted 24 January 2006 Available online 15 March 2006 Abstract Thermogravimetric (TGA) and differential scanning calorimetric (DSC) analyses were used to investigate the effect of the acidity behaviour of Y zeolites on the catalytic degradation of polyethylene (PE). The acidity behaviour of these zeo- lites was modified by ion exchange treatments. Two Y zeolites with similar Si/Al atomic ratios were subjected to an ion exchange treatment using NaNO 3 for H-form (HY) and NH 4 NO 3 for Na-form (NaY). The activity and the deactivation behaviour of the Y zeolites were determined in the samples by TGA measurements, using a polymer/catalyst ratio of 9:1. The sample residues obtained after an isothermic TGA, were analysed by DSC, in order to evaluate the crystallinity of each mixture. The HY zeolite, which has the strongest acidity, reduced the onset temperature resulting in more rapid deg- radation of the polymer. It is shown that the ion exchange treatment over Y zeolites enhances the selective catalytic deg- radation of polymer in detriment of the rapid deactivation. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Y Zeolite; Ion exchange; Polymer degradation; Catalytic cracking; Deactivation 1. Introduction Nowadays, plastic waste is one of the major con- cerns for the scientific community as well as envi- ronmentalists. In 2000 the plastic consumption was 45 Mt in Europe, and the consumption is grow- ing annually by 4–8%. On the other hand, the amount of waste from plastics was about 30 Mt in 2000 [1,2]. Plastic waste can be regarded as a poten- tially cheap source of chemicals and energy. The conventional waste process (landfill and incinera- tion) is becoming progressively expensive and often generates problems with unacceptable emissions. Polymer recycling has been suggested as the only sustainable solution to the problem of rapidly increasing amounts of plastic waste. Alternative processes for the conversion of plastic waste to use- ful products have attracted research in the area of thermal degradation [3,4]. Pure thermal degradation of plastic waste though requires high temperatures and produces heavy products. However, the thermal degradation of polymers to low molecular weight material has a major drawback in that a very broad product range is obtained. This method can be improved by using zeolites catalysts due to their 0014-3057/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.eurpolymj.2006.01.021 * Corresponding author. Fax: +351 253678983. E-mail address: ineves@quimica.uminho.pt (I.C. Neves). European Polymer Journal 42 (2006) 1541–1547 www.elsevier.com/locate/europolj EUROPEAN POLYMER JOURNAL