Procedure for generation of catalyst-free PE-TG profiles and its consequence on calculated activation energies
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 %.
KeywordsActivation energy Catalytic depolymerization Extracted TG profiles Predicted TG profiles Smoothing Isoconversional analysis
The authors gratefully acknowledge the financial support of the Ministry of Education, Science and Sport of the Republic of Slovenia through Research Project L2-5465 and the Slovenian Research Agency (ARRS) for financing the Research Program P2-0152. The authors kindly acknowledge Mrs. Špela Božič for performing the TG experiments.
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