PROMOTING EFFECT OF CO_2 ON THE DEGRADATION OF POLYETHYLENE TO ETHYLENE AND PROPYLENE OVER HZSM-5 CATALYST

概要

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As a part of the recycling of waste plastics, degradation of polyethylene to ethylene and propylene with HZSM-5 catalyst was studied by using a two-step process (thermal cracking and catalytic cracking). In the first stage, thermal cracking of high density polyethylene (HDPE) was carried out at 450-500℃. Yields of the cracked oil from HDPE were 79% at 450℃ and 88% at 500℃, respectively. Hydrocarbons of C7-C20 were the predominant products in the cracked oil. Higher hydrocarbons (>C20) increased with increasing reaction temperature. In the second stage, in order to obtain lower alkenes (mainly C_2H_4 and C_3H_6), the catalytic cracking of the thermally-cracked oil obtained in the first stage was carried out using a HZSM-5 catalyst at 600℃ in N_2 and CO_2 atmospheres. Since the cracked oil was difficult to handle, n-C_<16>H_<34>, which was a representative product in the thermal cracking of HDPE, was employed as a model compound. HZSM-5 catalyst increased the C1-C4 gas yield to 50% and C_2H_4 + C_3H_6 yield to 12% in N_2 atmosphere. On the other hand, in CO_2 atmosphere the gas yield reached 61% and C_2H_4 + C_3H_6 yield reached 30%, respectively. Addition of CO_2 promoted the catalytic cracking of n-C_<16>H_^<34> with HZSM-5 to give C_2H_4 + C_3H_6.
関西大学の論文
2006-03-21