Synthesis of zeolite beta in fluoride media under microwave irradiation Dae Sung Kim a , Jong-San Chang a, * , Jin-Soo Hwang a , Sang-Eon Park b, * , Ji Man Kim a,1 a Catalysis Center for Molecular Engineering, Korea Research Institute of Chemical Technology (KRICT), P.O. Box 107, Yusung, Taejon 305-600, South Korea b Department of Chemistry, Inha University, Incheon 402-751, South Korea Received 9 June 2003; received in revised form 28 November 2003; accepted 29 November 2003 Abstract Zeolite beta has been successfully prepared at 150 °C within 4 h by direct synthesis under microwave irradiation. Addition of seeds into the synthesis solution under microwave irradiation did not affect overall synthesis time of the material significantly, while addition of ammonium fluoride accelerated the crystallization of zeolite beta. In particular, microwave technique combined with fluoride species and seeding led to more rapid synthesis of crystalline zeolite beta. Upon microwave irradiation fluoride species and the microwave-activated water in the synthesis solution might be ascribed to shortening an induction period at the nucleation step, resulting in the rapid synthesis of the material. Ó 2003 Elsevier Inc. All rights reserved. Keywords: Microwave synthesis; Zeolite beta; Fluoride mineralization; Rapid synthesis; Nucleation and crystallization 1. Introduction Microwave techniques have attracted growing atten- tion for the rapid synthesis of nanoporous materials requiring several days to prepare under hydrothermal conditions [1–14]. Potential advantages include a rapid and more simultaneous nucleation and growth, homo- geneous heating throughout the reaction vessel, super- heating, and suppression of undesired phases compared with conventional hydrothermal techniques. To date, several types of mesoporous materials as well as microporous zeolites such as zeolite A [1], zeolite Y [2], ZSM-5 [1,3], AlPO-5 [4,5], SAPO-5/SAPO-34 [6], MCM-41 [7–10], SBA-15 [11], SBA-16 [12] etc. have been synthesized by microwave irradiation. Microwave techniques in the synthesis of inorganic materials are generally known to be faster and simpler than conven- tionalmethods[15].Energytransferfrommicrowavesto the materials is believed to occur either through reso- nance or relaxation, which results in rapid heating. Furthermore, the employment of the microwave tech- nique in the synthesis of nanoporous materials have been shown to provide versatile effects, for instance, short heating times, inductive heating through the con- ducting properties of the synthesis mixture, specific en- ergy dissipation via microwave energization of the hydroxylated surface or associated water molecules in the boundary layer, and formation of the high potential of the active water molecules [1,8,13,14]. Zeolite beta (BEA) is a wide-pore and high-silica microporous material where the structure consists of an intergrowth of two or more polymorphs comprising a three-dimensional system of 12-membered ring chan- nels [15–17]. It has recently been recognized as an interesting catalyst for chemical synthesis due to its high thermal and chemical stability, strong acid sites, hydrophobicity and large pore size. One of polymorphs in zeolite beta shows chirality, making it an attractive material from the view of its potential for catalytic con- versions and separation of chiral components [18,19]. * Corresponding authors. Tel.: +82-42-860-7673; fax: +82-42-860- 7676 (J.-S. Chang); Tel.: +82-32-860-7675; fax: +82-32-874-7674 (S.-E. Park). E-mail addresses: jschang@krict.re.kr (J.-S. Chang), separk@inha. ac.kr (S.-E. Park). 1 Permanent address: Department of Molecular Science and Tech- nology, Ajou University, Suwon 442-749, South Korea. 1387-1811/$ - see front matter Ó 2003 Elsevier Inc. All rights reserved. doi:10.1016/j.micromeso.2003.11.017 www.elsevier.com/locate/micromeso Microporous and Mesoporous Materials 68 (2004) 77–82