Generating Basic Sites on Zeolite Y by Potassium Species Modification: Effect of Base Precursor
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Generating Basic Sites on Zeolite Y by Potassium Species Modification: Effect of Base Precursor Lin Bing Sun Æ Lu Gong Æ Xiao Qin Liu Æ Fang Na Gu Æ Yuan Chun Æ Jian Hua Zhu
Received: 13 May 2009 / Accepted: 9 July 2009 / Published online: 21 July 2009 Ó Springer Science+Business Media, LLC 2009
Abstract The zeolite Y was modified by a series of potassium compounds including KNO3, K2CO3, KHCO3, KOH, and KF. The obtained microporous materials exhibited quite different structural and basic properties. Such differences can be attributed to their different guest–host interaction. These materials displayed different catalytic activity on the vapor phase methylation of cyclopentadiene with methanol. The activity is well correlated with the basicity and surface areas of catalysts. Keywords Base precursor Basicity Guest–host interaction Zeolite
1 Introduction Solid strong bases are particularly desirable from the environmental and economical point of view, since they can catalyze diverse reactions under mild conditions and minimize the production of pollutants [1]. Various solid bases have been reported up to now [2–4]. In contrast to the single-component solid bases (e.g., alkaline earth metal oxides), those with double component (e.g., basic species supported on porous hosts) seem more attractive. For
L. B. Sun (&) L. Gong X. Q. Liu State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology, 210009 Nanjing, China e-mail: [email protected] F. N. Gu Y. Chun J. H. Zhu (&) Key Laboratory of Mesoscopic Chemistry of MOE, School of Chemistry and Chemical Engineering, Nanjing University, 210093 Nanjing, China e-mail: [email protected]
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double-component bases, the strength and amount of basic sites can be well controlled by adjusting the type and content of guest basic species. The porous hosts generally possess large surface areas and pore volumes, which provides suitable accommodation for the dispersion of basic guests. Therefore, double-component bases combine the advantages of guest and host, and basic materials with different properties can be obtained by adjusting guest or host [5, 6]. Porous oxides such as Al2O3 and ZrO2 are widely used hosts for the synthesis of solid strong bases [7, 8]. By introducing base precursor KNO3, superbasic sites can be generated on Al2O3 and ZrO2 after activation [9, 10]. Unfortunately, this type of basic materials possesses relatively small surface areas and disordered pore arrangement, since they are derived from oxide hosts. Ordered mesoporous silicas such as MCM-41 and SBA-15 were also employed as the hosts for solid bases [11–13]. However, their stability was relatively poor due to the amorphous walls; also, the silica hosts may react with strongly basic guest and sometimes lead to the destruction of mesoporous structure [5, 13]. These drawbacks may hinder their applications in catalysis and adsorption. It is known that zeolites have relatively large surface areas and unique shape sel
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