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

In order to increase the yield of ethylene and propylene in the catalytic pyrolysis of heavy oil, ZSM-5 zeolite was modified by Fe2O3 and TiO2 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 (TiO2 loaded ZSM-5) and Fe–Ti/ZSM-5 (Fe2O3 and TiO2 loaded ZSM-5) catalysts increased through the polarization function of Ti4+. 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 Fe2O3 promoted the reduction of TiO2. After modification by Fe2O3 and TiO2, 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 (Fe2O3 loaded ZSM-5) or ZSM-5.