Study of the polymer-catalyst contact effectivity and the heating rate influence on the HDPE pyrolysis

This paper studies the effect of two different parameters on the different fractions obtained in the catalytic pyrolysis of HDPE using HZSM-5. On one hand, the influence of the heating rate on the results obtained has been studied by selecting two totally different heating rates: flash and slow (5 degrees C/min) pyrolysis. On the other hand, two different types of samples have been pyrolyzed at each heating rate: dry catalyst-polymer blend and melted blend (prepared in an extruder). The results obtained allow us to evaluate the influence of the contact effectivity between polymer and catalyst, as well as the effect of the type of heating on the product distribution. In general, catalytic pyrolysis leads to higher volatiles yields than thermal degradation and the pyrolysis of a melted blend reaches always higher yields than a dry blend. It seems than a better contact between polymer and catalyst implies a more noticeable activity of the catalyst although both parameters, heating rate and polymer-catalyst contact, are interconnected and the grade of influence of the type of blend used depends, in many cases, on the heating rate of the process. A detailed quantitative analysis of the compounds generated under these different conditions has been performed. (C) 2006 Elsevier B.V. All rights reserved.