Kinetic study of polypropylene pyrolysis using ZSM-5 and an equilibrium fluid catalytic cracking catalyst

Abstract

The effect of the addition of ZSM-5 zeolite and an equilibrium fluid catalytic cracking (FCC) catalyst in the pyrolysis of polypropylene has been studied, using dynamic thermogravimetry at a heating rate of 10 K min −1, with N 2 at 1 atm and using different contents of catalyst. Results obtained have shown the important effect of the presence of these catalysts—especially for the equilibrium FCC catalyst (E-cat)—in reducing the temperature of the complete degradation process as compared to the non-catalysed process. The saturating effect observed when using other catalysts such as MCM-41 was not observed when using E-cat or ZSM-5, which shows a linear tendency, with a higher decrease of decomposition temperature at higher catalyst loads. The differences between both catalysts indicate the important role of the selective matrix of the active alumina and other oxides of the FCC catalyst. A quantitative mechanistic kinetic model has been applied and the corresponding kinetic constants have been obtained by simultaneously correlating all the thermogravimetric experiments with different contents of catalyst. The kinetic parameters obtained have revealed a reduction in the activation energy of the catalytic decomposition as compared to the thermal process.