Catalytic degradation of polyethylene: An evaluation of the effect of dealuminated Y zeolites using thermal analysis

Commercial samples of high density polyethylene were degraded over Y zeolites with different Si/Al: ultrastable Y zeolite (USY) and three dealuminated Y zeolites (HY(4), HY(12) and HY(20)). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) was used aiming to evaluate the apparent activation energy of polymer cracking. The results obtained show that the efficiency of different zeolites was due to their acidity. A high Si/Al ratio gave a greater acidity to zeolites and the onset degradation temperature of the polymer and related activation energy decreased. The sample residues obtained after an isothermic TGA, were analysed by DSC and it was observed that the crystallinity decreases with the acidity of zeolites. HY(20) zeolite was the most active catalyst due to the isolation of the residual Brønsted acid sites which promote their strong acidity.