HZSM-5 and HY Zeolite Catalyst Performance in the Pyrolysis of Tires in a Conical Spouted Bed Reactor

• Published in: Industrial & engineering chemistry research Vol. 47; no. 20; pp. 7600 - 7609
• Main Authors: Arabiourrutia, Miriam, Olazar, Martin, Aguado, Roberto, López, Gartzen, Barona, Astrid, Bilbao, Javier
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15.10.2008
• Subjects: Applied sciences; Catalysis; Catalytic reactions; Chemical engineering; Chemistry; Exact sciences and technology; Fluidization; General and physical chemistry; Kinetics, Catalysis, and Reaction Engineering; Reactors; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Pyrolysis; Fluidization; Spouted bed; Zeolite; Reactor; Catalyst
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/ie800376d

A study has been carried out on the in situ use of two catalysts (prepared based on HZSM-5 and HY zeolites) in the pyrolysis of tires in a conical spouted bed reactor at 425 and 500 °C. Both catalysts significantly affect the yields and composition obtained in thermal pyrolysis for the fractions corresponding to C1−C4 gases, nonaromatic C5−C10, aromatic C10−, and tar. The shape selectivity characteristic of each zeolite has a considerable influence on catalyst performance. The HZSM-5 zeolite catalyst produces an increase in the yield of gases, with an increase in the yield of propene and the same yield of butadiene as in thermal pyrolysis, in which it is already high. Concerning the liquid fraction, the catalysts give way to a decrease in the yield of d-limonene (the conical spouted bed reactor performs very well in thermal pyrolysis for this purpose), whereas the yield of BTX aromatics increases, with an increase in the yield of xylenes. A positive fact to be noted is the decrease in the formation of tar (C10+) compared to thermal pyrolysis. As the reaction occurs, a carbonaceous material is deposited on the catalyst, in which the following are identified: (i) carbon black externally coating the particles and deposited on the catalyst macropores and mesopores and (ii) coke deposited on zeolite micropores, due to hydrocarbon condensation activated by catalyst active sites. This condensation preferably takes place in the HY zeolite due to both the larger size of intersections between micropore channels and to greater hydrogen-transfer capacity. Nevertheless, under the reaction conditions tested (up to 10.87 g of tire treated/g of catalyst), product yields remain almost constant, which is evidence that the catalyst does not undergo deactivation.