In-situ catalytic pyrolysis of waste tires over clays for high quality pyrolysis products

This paper aims to evaluate the effect of low-cost clays (kaolin with different particle size and montmorillonite (MTT) modified with ZnCl2 and HCl) as catalysts on the pyrolysis products from waste tire. The results show that clays can improve the quality and yield of pyrolysis products. Different particle size and modification conditions have significant influence on the distribution and component of pyrolysis products. Compared with blank group, the content of combustible gas (including CH4 of 56.35%, H2 of 35.67% and CO of 7.98%) in ZnCl2 group is increased. Moreover, the hydrocarbon content of pyrolysis oil in each group exceed 90%. The N-containing compounds can be removed by hydrodenitrogenation (HDN) reaction and convert into aromatics through ring-opening reaction. Meanwhile, the yield of the O-containing compounds in each group is less than 3%, and the lowest content is ZnCl2 group. ZnCl2-modified MTT have high specific surface area and rich mesoporous structure, which can promote deoxidation and aromatization to reach the highest aromatics content (90.23%). In addition, the content of C11–C20 in addition groups can be increased by small molecule polymerization. The catalysts promote the formation of diesel fraction through alkylation of benzene and naphthalene.