Interaction of titanium and iron oxide with ZSM-5 to tune the catalytic cracking of hydrocarbons

• Published in: Applied catalysis. A, General General, 2010-03, Vol.375 (2), p.222-229
• Main Authors: Li, Xianfeng, Shen, Baojian, Xu, Chunming
• Format: Article
• Language: English
• Subjects: Benzene; Catalysis; Catalysts; Catalytic cracking; Catalytic pyrolysis catalyst; Chemistry; Colloidal state and disperse state; Exact sciences and technology; Fe 2O 3; General and physical chemistry; Ion-exchange; Iron; Light olefins; Porous materials; Reduction; Surface physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; TiO 2; Titanium; Titanium dioxide; Zeolites: preparations and properties; ZSM-5
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2009.12.033

After modification by Fe 2O 3 and TiO 2, the acidity and reduction properties of Fe–Ti/ZSM-5 improved. As a result, catalyst Fe–Ti/ZSM-5 showed a better catalytic cracking performance of n-decane and isopropyl benzene than catalysts Ti/ZSM-5, Fe/ZSM-5 or ZSM-5, such superiority indicates that Fe–Ti/ZSM-5 has potential application in the catalytic pyrolysis of heavy oil to light olefins (ethylene and propylene). In order to increase the yield of ethylene and propylene in the catalytic pyrolysis of heavy oil, ZSM-5 zeolite was modified by Fe 2O 3 and TiO 2 via pore volume impregnation. XRD, SEM, and TEM analysis indicated that the structure of the ZSM-5 remained intact after modification, and that the Ti and Fe partially entered the channels of the ZSM-5. Measurement of the number of Brønsted acid sites by n-propylamine temperature-programmed reaction and FTIR measurements showed that the Brønsted acid sites of Ti/ZSM-5 (TiO 2 loaded ZSM-5) and Fe–Ti/ZSM-5 (Fe 2O 3 and TiO 2 loaded ZSM-5) catalysts increased through the polarization function of Ti 4+. DRS, XPS, and TPR results showed that the presence of Ti species improved the dispersion of Fe species on the surface of ZSM-5, whereas Fe 2O 3 promoted the reduction of TiO 2. After modification by Fe 2O 3 and TiO 2, the acidity and reduction properties of Fe–Ti/ZSM-5 improved; such improvement led to a decrease of the apparent activation energy of isopropyl benzene cracking over Fe–Ti/ZSM-5 by about 21 kJ/mol compared with that over ZSM-5. As a result, catalyst Fe–Ti/ZSM-5 showed a better catalytic cracking performance of n-decane and isopropyl benzene than catalysts Ti/ZSM-5, Fe/ZSM-5 (Fe 2O 3 loaded ZSM-5) or ZSM-5.