Catalyst addition in polyethylene pyrolysis - Thermogravimetric study

The effect of catalyst addition on the thermal decomposition of low-density polyethylene has been studied. The pyrolysis has been studied in a thermob alance, using polyethylene mixed with different catalysts, such as MCM41, U SY and ZSM-5. The study comprises the analysis of various effects, includin g the amount of catalyst added and the type of catalyst. It has been observ ed that almost all the catalytic effect is obtained for a given amount of a dded catalyst, and a further increase in the catalyst added does not produc e a further reduction in the decomposition temperature. A kinetic model has been applied which allows a very good correlation of all the runs performe d using the same catalyst. The model involves two different ways for the de composition, one catalysed and the other non-catalysed. The order of the no n-catalysed reaction has been allowed to vary, yielding reaction orders clo se to zero (i.e. very similar to that found in several thermogravimetric st udies of polyethylene decomposition). On the other hand, the catalysed reac tion has a rate constant with a saturating dependence with the concentratio n of the catalyst. (C) 2001 Elsevier Science B.V. All rights reserved.