Catalyzed pyrolysis of plastics: A thermogravimetric study

Abstract

Thermal or catalytic pyrolysis processes have attracted much attention for the conversion of plastic wastes to a mixture of their basic hydrocarbons, which can be valuable either as fuels or as raw chemicals. The effect of different catalysts on the thermal degradation of propylene (PP) has been studied by thermogravimetric analysis (TGA). TGA experiments were used to compare the activity of different catalysts towards PP degradation. All the hydrocracking (HC) catalysts enhanced the pyrolysis of PP. The reaction rates were found to increase with increasing catalyst fraction, acidity of catalyst and decreasing particle size. The temperatures of onset (Ton), of maximum-rate (Tmax) and of end (Tend) of the degradation also shifted to lower values. Among HC catalysts, it seems that Z-713 performed better at all three weight fractions; Z-713 reduced both T1% and T99% better than others. On the other hand, the FCC catalyst (RCD-8) performed poorly for the degradation of PP. Various titania based catalysts prepared in our laboratory, performed well. The number of acid sites and catalyst pore size along with impregnation with transition metals such as W/ Ni and Ni/ Mo are found as the key factors for the energy efficient degradation of polymers. The details of the research are presented in this paper. Key words: Thermogravimetric analysis (TGA), DSC, pyrolysis, catalytic degradation, polypropylene, waste plastics, catalysts.