Kinetic study of thermal and catalytic degradation of polypropylene over mesoporous catalysts type AlMCM-48

Abstract

The plastic waste has suffered a dramatically increase and has become one of the biggest environmental problems of the 21st century. Thermal and catalytic degradation of plastics is one of the viable solutions to this problem since it can lead to both environmental protection benefits and economically advantageous processes in terms of energy expenditure. In this article a thermogravimetric study of the conversion of polypropylene (PP) in the presence of AlMCM-48 mesoporous catalysts (Si/Al=50 and 100) is presented. The catalytic performance showed that the PP degradation reaction occurs in complex reaction steps in the heating rates 5, 10 and 20 °C min^-1. Moreover, the pore volume of the catalysts in the different molar ratios Si/Al influenced the degradation process under non-isothermal conditions and played an important role in decreasing the degradation temperature of the PP. The apparent activation energy (E_a) was determined by the Vyazovkin isoconversion method. The kinetic parameters obtained revealed a reduction in E_a, showing an average of 89, 66 and 59 kJ mol^-1 for the degradation of pure PP, PP + AlMCM-48(50) and PP + AlMCM-48(100), respectively. As shown by the average values, it was evidenced that the greatest efficiency was of the AlMCM-48(100) that had a decrease of the activation energy of about 30 kJ mol^-1 when compared with the pure PP.