Study on the reusability of kaolin as catalysts for catalytic pyrolysis of low-density polyethylene

Abstract

The commonly used pyrolytic catalysts (molecular sieves, metals, etc.) are expensive and easily inactivated, which is a major difficulty in the catalytic pyrolysis technology. In this work, the effect of low-cost kaolin with different particle sizes on the catalytic pyrolysis of low-density polyethylene (LDPE) in fixed furnace and its reusability are studied. The results show that the liquid oil mainly contains aliphatics and aromatics. The carbon number of liquid oils is mainly in the range of C6-C20, accounting for 90%-95%. The first addition of 1250 mesh kaolin (K1250) produces the highest contents of aliphatics (64.66%) and hydrocarbons (93.91%) and H2 (30.07%). During the repeated use of K1250, the increasing trend of aromatics content was consistent with the results of particle size increase. The presence of carbon deposition after the use of the catalyst causes slight coking, which increases the acidity and particle size of the catalyst. K1250 is suitable for the production of liquid oil with better quality (more hydrocarbons, more aliphatic groups) and higher yield in the early stage of use. However, it is suitable to produce pyrolysis gas with high quality (more hydrogen and methane) and high yield in the later stage of reuse.