Catalytic pyrolysis of waste tire over Ag-loaded catalysts

Abstract

Waste tire can cause the environmental problems because it is hard to degrade. Pyrolysis is an interesting alternative for waste tire elimination because it is well known for low emissions to the environment and can produce highly valuable products from wastes. The limitation of waste tire pyrolysis is a complex mixture of hydrocarbons and high concentration of sulfur compounds in the pyrolysis products. Sulfur-containing compounds in the oils obtained from waste tire pyrolysis are largely present in the forms of polar-aromatic compounds. The objectives of this research were to improve the pyrolysis products and reduce the amount of sulfur in the oil products. Ag-modified zeolites were promising to improve the pyrorysis products and reduce sulfur content in the pylolytic oils. It was found that 1 wt% of Ag loading gave the highest desulfurization activity. Also, this work was to investigate the effect of different zeolites. 1% Ag loaded on various zeolites, namely HMOR, BETA, KL, and Y zeolites has been investigated for its effect on the pyrolysis products. 1%Ag/HMOR zeolite was a selective catalyst to produce cooking gas. Additionally, 1%Ag/HMOR catalyst showed the highest performance in sulfur removal, since it gave the lowest concentration of sulfur in the oil product as compared to the other Ag-loaded catalysts. The presence of Ag on HMOR zeolite helps promote desulfurization reaction resulting in the decrease of sulfur concentration in the oil product. It can be suggested that the Ag metal has hydrogenolysis activity since it enhances C-S-C bond breaking. The co-loading of Pd with Ag (Pd-Ag/HMOR catalysts) had the negative effect on the liquid products, and the bimetallic catalysts had a lower desulfurization activity than the monometallic catalysts. 1%Ag/HMOR was the best among all catalysts in removing sulfur compounds from the tire-derived oil.