Catalytic cracking of low-density polyethylene over H-Beta and HZSM-5 zeolites:: Influence of the external surface.: Kinetic model

The effect of the addition of H-Beta and HZSM-5 zeolites on the pyrolysis of commercial LDPE has been Studied using dynamic experiments in a thermobalance. The H-Beta zeolite shows an important influence on the decomposition of the polymer even at a very low zeolite concentration. A remarkable effect in the first steps of LDPE decomposition on increasing the catalyst loading has been observed and a two-step process occurs in the presence of H-Beta zeolite. A pseudo-kinetic model has been proposed in order to adequately reproduce this behaviour. The model developed has been applied to simultaneously correlate the TG and DTG curves obtained under dynamic conditions at beating rates of 5, 10 and 35 degrees C/min and at several catalyst concentrations. The model is capable of simultaneously correlating all the experiments, thus demonstrating the validity of the hypothesis suggested and revealing a notable ability as a predictive model. (c) 2006 Elsevier Ltd. All rights reserved.