Effect of the Nature, the Content and the Preparation Method of Zeolite-Polymer Mixtures on the Pyrolysis of Linear Low-Density Polyethylene

Abstract

The effect of the preparation method of the mixture catalyst/polymer on the linear low-density polyethylene (LLDPE) pyrolysis is studied by comparing the results obtained when the polymer and the catalyst (Hβ or HZSM-5) are extruded or simply mixed in powder form. By improving the polymer/catalyst contact through extrusion, the polymer degradation took place at lower temperature. The effect of extrusion is more pronounced with Hβ compared to HZSM-5 owing to the highest external surface of Hβ. While the yields of gas/liquid/coke do not differ with the preparation method when HZSM-5 is used as catalyst, more significant amount of liquid phase and high production of paraffins are observed when Hβ/LLDPE mixture is extruded, according to random scission pathway reactions. The subsequent reactions are limited by the size of the pore, which impede hydrogenation reactions, producing high molecular weight molecules. Regardless of zeolite type, the micropores of the zeolite are more affected by deactivation by coke when extrusion method is used, this effect being much more important for HZSM-5. This result is a consequence of a polymer pre-degradation during the extrusion process in which the first cracks of the polymer at low temperature and the first pore blockages can be generated.