The effect of different particle sizes and HCl-modified kaolin on catalytic pyrolysis characteristics of reworked polypropylene plastics

Abstract

At present, the catalysts used to produce high value products by catalytic pyrolysis of high calorific value waste plastics are expensive. In this study, the catalytic pyrolysis characteristics of reworked polypropylene (PP) plastics were studied by using low-cost kaolin with different particle sizes and HCl-modified kaolin. The results show that the catalysts reduced the condensate oil yield and increased the gas yield. C6–C20 was the major components of condensate oil ranging from 90% to 97% in catalyst pyrolysis by significantly decreasing the heavy components (above C20). Kaolin has high cracking efficiency of heavy components into alkanes and alkenes (the range of diesel components). The stronger acid sites on the modified kaolin further promoted the secondary cracking of diesel components, resulting in a great increase in the C6–C11 content. Moreover, HCl-modified kaolin significantly increased the aromaticity of the condensate oil because of the aromatization and Diels-Alder reaction of alkanes and alkenes. Meanwhile, kaolin significantly increased the yield of H2, and the H2 yield was increased with the decrease of kaolin particle size. HCl-modified kaolin further promoted the yield and quality of gas. It is found that kaolin is a potential cheap and efficient pyrolysis catalyst.