Catalytic depolymerization of polyethylene (PE) over several aluminosilicate catalysts was studied using thermogravimetric (TG) analysis. Procedure was proposed for decoupling mass loss related directly to the catalyst and that of PE depolymerization. The benefit of this approach is twofold: (1) It enables a more realistic kinetic analysis, and (2) reduces the total number of required experiments with the pure catalyst by more than 50 %. The activation energies of PE depolymerization over different catalysts were calculated from the treated PE-TG profiles using advanced isoconversional analysis and were compared to those obtained from raw TG profiles. The presented analysis reveals that neglecting the mass loss associated with the aluminosilicate catalyst results in underestimated values of calculated activation energies at low PE conversions, while at high conversions the values of calculated activation energies were overestimated. The apparent PE depolymerization activation energy in the presence of applied catalysts increases in the following order: amorphous silica alumina <heulandite/clinoptilolite (M300) <alumina grafted montmorillonite within the conversion range from 0 to 95 %.