(293b) Investigation of the Effect of Commercial ZSM-5 Catalysts and Their Modified Forms in the Pyrolysis Reaction of Polyethylene.

The use of plastic is justified thanks to its physical-chemical qualities, low production costs, and its diverse industrial applications, such as Packaging, Building & Construction, etc. However, as a result of its use, plastic wastes can have harmful effects on human health and the environment. In Europe only 57% of the plastic used was collected, 19% in Recycling, 24% in Energy Recovery, 14% Landfill. In the last decade, catalytic pyrolysis in plastic wastes has been proposed as an alternative for plastic waste valorization by converting it into a pyrolysis oil of high quality.

A key point to obtain a high-value liquid phase derived from main factors that have an effect on the catalytic pyrolysis process, such as, the temperature, retention time, quantity and type of catalyst, etc. In this work the effect of catalysts and performance of ZSM-5 zeolite and its modifications in the catalytic pyrolysis of polyethylene at 450°C and atmosphere pressure was evaluated. Three ZSM-5 commercial catalysts with different ratios of Si/Al, and three doped ZSM-5 zeolites were selected. In this manner the effects of catalyst porosity and acidity was particularly examined.
The acidity of zeolites increases when the Si/Al ratio decreases. We demonstrated that as the acidity increases, the aromatic content (benzene, toluene and xylene) of the oil increased. This result could be explained by the high number of strong acid sites which favour the aromatization reaction. In the case of doped zeolites, the liquid yield increases with a major external surface, but the nature of the acid sites was determinant in the selectivity to aromatic compounds.
The optimization of the main factors that affect catalytic pyrolysis can lead to the second phase of research on the regeneration and reuse of catalysts to carry out a process with economic and environmental sustainability.