Impact of acid zeolites as additives in Pd-loaded HBETA and HY catalysts on waste tire pyrolysis products

Abstract

Addition of one or two acid zeolites as additives into catalysts used in catalytic pyrolysis of waste tire was studied in this work. Pd/HBETA and Pd/HY were used as the main catalysts because of their ability on improving the quality and quantity of light fractions (full range naphtha, and kerosene). Taking advantages of their large pore size, HBETA and HY were selected as a first additive in the main catalysts, aiming to improve cracking performance for the high production of lighter fraction, namely full range naphtha. HZSM-5 zeolite, which has smaller pore diameter and high acid strength, favors the aromatization reaction of light molecules. Therefore, it was used as a second additive in the main pyrolysis catalysts. The amount of Pd was fixed at 1% wt., whereas the additive, varied at 10 % wt., and 20 % wt., was physically mixed with the main catalyst. The obtained products were analyzed via gas chromatograph, liquid chromatograph, and SIMDIST GC, whereas the catalysts were analyzed by SAA and TG-DTA. The results indicated that the addition of HY in Pd/HBETA cannot improve the naphtha fraction because the cracking activity was reduced. However, it can improve the gas oil fractions instead by increasing saturated hydrocarbons in these fractions. On the other hand, the addition of 10 % wt., HBETA in Pd/HY can improve the cracking performance of Pd/HY, resulting in the high production of naphtha fraction and valuable gaseous products. The further mixing with the second additive, HZSM-5, in the selected catalysts can improve both quantity and quality of naphtha fraction. These results revealed that the acid properties and pore sizes of zeolites were two important factors influencing the products.