Catalytic pyrolysis of waste tire over KL-based catalysts: the effect of MoO₃ and Re

Abstract

Pyrolysis of waste tire is an interesting process to produce oil and solve the non-biodegradation problems of waste tire as the same time. The important products are the saturated hydrocarbons and the mono-aromatics which can be used as precursor in petrochemical industry and improve the octane number in gasoline range. MoO3 catalyst has an aromatization activity that is expected to produce mono- aromatics from light gases. Moreover, the hydrogenation activity of Re catalyst affects to the conversion of heavy products to light products. This research used the basic zeolite (KL zeolite) as a support catalyst in the study, of the two different sets of catalysts; individually loaded catalysts (%MoO3/K L and % Re/KL) and co-loaded catalysts (% Re -l% MoO3 /K L) for the pyrolysis of waste tire. The research issues were to investigate the effects of catalysts on the pyrolysis products, especially on the selectivity and yields of mono-aromatics. The results showed that both MoO3/K L and Re/KL catalysts significantly increased the amount of mono-aromatics in the oil products. However, the quantity of mono-aromatic obtained from Re/K L was higher than MoO3/KL catalysts. These results might occur from the hydrogen lysis activity of Re/KL catalysts to convert di- and poly -aromatics toward mono-aromatics. Moreover, Re/KL catalysts also produced the higher amount of naphtha fraction than MoO3/KL catalysts. 0.75 wt% of Re/KL was the optimum percentage to produce a high amount of naphtha fraction in maltene and a high amount of mono-aromatics yield. Co-loaded catalysts (% Re -l% MoO3/KL) gave the dilution effect on pyrolytic products. Moreover, it did not promote the production of mono -aromatics as the individually-loaded catalyst did, but increased saturated hydrocarbons. It was resulted from the promotion of the cracking and hydrogenation activity of co-loaded catalysts. In addition, all catalysts showed the dramatic reduction of alphaltene in the pyrolytic oil, resulting to the improvement of oil quality by partially breakdown the complex and high molecular weight structures of asphaltene on the active sites of catalysts to lighter molecular weight structures.