Cocracking Kinetics of PE/PP and PE/Hydrocarbon Mixtures (I) PE/PP Mixtures

Abstract

Cocracking behaviors of polyethylene/polypropylene and polyethylene/hydrocarbon mixtures have been investigated using a closed batch reactor/tube reactor, followed by Thermogravimetric Analysis (TGA) at certain heating rate from ambient temperature to 873 K. In part I, the cocracking of HDPE, LDPE, and PP was divided into two stages for intensive study: polyolefin cracking at closed batch/tube reactor was performed using nonisothermal/isothermal method, and further, the thermogravimetric study of polyolefin and the cracked products from polyolefin cracking was realized using nonisothermal method. Presence of synergistic effect is observed for cocracking of polyolefin mixtures, and such synergistic effect not only exists in mild cracking using closed batch reactor/tube reactor but also exists in the thermal degradation process of thermogravimetric analysis. The kinetic studies were performed according to Coats and Redfern method for first-order reaction. It is found that the pyrolysis process can be described by one first-order reaction and PE/PP mixture can decompose at a lower temperature than PE, where the activation energy of PE/PP can significantly decreased compared with that of HDPE. The results also indicate that interactions between HDPE and PP are mainly related to experimental conditions: temperature, residence time, and the degree of mixing for PE/PP. Thus, closed batch reactor with agitation equipment is useful for thermal cracking of polyolefin to produce more light oils.