Effect of Calcination Temperature of Kaolin Microspheres on the In situ Synthesis of ZSM-5
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Effect of Calcination Temperature of Kaolin Microspheres on the In situ Synthesis of ZSM-5 Hui Feng Æ Chunyi Li Æ Honghong Shan
Received: 23 June 2008 / Accepted: 20 November 2008 / Published online: 4 December 2008 Ó Springer Science+Business Media, LLC 2008
Abstract ZSM-5 zeolite has been successfully synthesized in-situ on calcined kaolin microspheres by the hydrothermal method using n-butylamine as a template. The supported ZSM-5 was characterized by X-ray diffraction and scanning electron microscopy. The effect of calcination temperature of kaolin microspheres on the insitu synthesis of ZSM-5 was investigated. The influence of the pretreatment temperature on the properties of kaolin microspheres including phase transformation, amounts of active SiO2 and Al2O3, and pore structures, was studied using fourier transform infrared (FT-IR), nitrogen adsorption and chemical analysis. The results showed that when the calcination temperature increased from 300 to 900 °C, the amount of active SiO2 in the kaolin microspheres increased slightly and the amount of active Al2O3 initially increased rapidly and then decreased steadily. The surface area and pore volume of the kaolin calcined at both low and high temperatures was less than those of kaolin calcined at a medium temperature. The property changes of kaolin caused the relative crystallinity of in situ synthesized ZSM-5 to vary. Keywords Calcination temperature Kaolin microspheres In situ synthesis ZSM-5 H. Feng C. Li (&) H. Shan State Key Laboratory of Heavy Oil Processing, China University of Petroleum, 257061 Dongying, China e-mail: [email protected] H. Shan e-mail: [email protected] H. Feng Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USA e-mail: [email protected]
1 Introduction Propylene is an important industrial chemical; however, the supply is not keeping pace with its demand, as a result, research on increasing propylene production has become a topic of interest. ZSM-5 zeolite with threedimensional sinusoidal and straight channels of molecular dimension was first used by Mobil in 1990s to increase the yield of propylene [1]. This zeolite selectively conducts cracking of C7–C13 straight and short branched chain hydrocarbons to C3–C5 olefins. Thus, it enhances the octane of gasoline, increases the yield of light olefins and has become the preferred catalyst or additive for enhancing the yield of propylene in the field of petrochemical processing [2]. The method for in situ synthesis of ZSM-5 has significant advantages compared to the additive’s traditional preparation. In the traditional method of preparation, the active component ZSM-5 is embedded in a binder or matrix which greatly reduces the contact between the feedstock and the active component. Consequently, the efficiency of ZSM-5 zeolite is decreased. Using the method of in situ synthesis, ZSM-5 zeolite can be synthesized on the surfaces of kaolin microspheres, thus allowing the feed oil easy access to the active component. Furthermore, if the shape of microspheres is pr
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