APPLIED ORGANOMETALLIC CHEMISTRY Appl. Organometal. Chem. 2006; 20: 775–783 Published online 1 September 2006 in Wiley InterScience (www.interscience.wiley.com) DOI:10.1002/aoc.1131 Materials, Nanoscience and Catalysis Preparation of uniform and nano-sized NaA zeolite using silatrane and alumatrane precursors N. Kuanchertchoo 1 , S. Kulprathipanja 2 , P. Aungkavattana 3 , D. Atong 3 , K. Hemra 3 , T. Rirksomboon 1 and S. Wongkasemjit 1 * 1 The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok, Thailand 2 UOP LLC, Illinois, USA 3 National Metal and Materials Technology Center (MTEC), Thailand Science park, Patumthani, Thailand Received 5 February 2006; Revised 7 March 2006; Accepted 26 May 2006 Nano-sized Na A zeolite was successfully synthesized via the sol–gel process and microwave techniques. The synthesis parameters, such as hydroxide ion concentration, seed amount, as well as heating time and temperature, were studied to obtain the most uniform and very small sized NaA zeolite using the composition of SiO 2 :Al 2 O 3 : xNa 2 O:410H 2 O; 3 ≤ x ≤ 6. It was found that hydroxide ion concentration affects the crystal size and heating time, whereas a higher amount of seed provides smaller sized NaA zeolite. The zeolite product can be synthesized using a higher temperature for a shorter time or lower temperature for a longer time. The best conditions for synthesizing the smallest size, 0.1–0.2 μm, and the most homogeneous NaA zeolite is to use the composition of SiO 2 :Al 2 O 3 :3Na 2 O:410H 2 O and 3 wt% crystal seed at 80 ◦ C microwave heating for 6 h. The synthesized NaA zeolite was characterized using XRD and SEM. Copyright  2006 John Wiley & Sons, Ltd. KEYWORDS: NaA zeolite; sol-gel process; silatrane and alumatrane; nano-sized INTRODUCTION Zeolite A, an aluminosilicate having a small pore size of 4 ˚ A and containing aluminum in the framework, results in requiremed balancing cations. The common form generally used as a membrane is the sodium form, NaA. NaA zeolite has also been employed in gas separation membranes to enhance the selectivity of the support. 1 In addition, NaA zeolites are used in many applications such as household products, aquaculture, agriculture, water treatment, etc., due to their adsorption, ion exchange and size selectivity properties. 2 Commercial NaA zeolite is synthesized by both conventional and microwave heating techniques. The microwave technique is used in NaA zeolite synthesis due to its homogeneous heating, resulting in tiny hot spots throughout the synthesis mixture, which reduce synthesis time. 3 The hydrothermal synthesis of aluminosilicate zeolite corresponds to the conversion of a mixture of silicon and aluminum compounds, alkali metal cation, organic molecules and water via an alkaline supersaturated solution into *Correspondence to: S. Wongkasemjit, The Petroleum and Petro- chemical College, Chulalongkorn University, Bangkok, Thailand. E-mail: dsujitra@chula.ac.th microporous crystalline aluminosilicate. 4 The variables, such as the composition of reaction mixture, temperature and time, have a major influence on zeolite structure crystallized. When the reactants are mixed, these solid phases are dissolved, mediated by the mineralizing agent or alkali. The solution is filled with silicate and aluminate monomer and oligomer which are organized into a more extended structure and finally into the crystalline phase. The crystallization process is thermally activated and allows a high yield of crystal to be achieved in an acceptable period of time. The crystallization period of zeolite can be subdivided into two steps: nucleation of the new population of zeolite crystals and growth of the existing population of crystals. Seeding is a technique in which the supersaturated system is inoculated with small particles of material to be crystallized. Using this operation, the nucleation stage is by-passed and the induction period is eliminated. 4 Seed crystals are added to a synthesis mixture which may act as pure seeds in that mass is deposited upon them and they grow or give rise to secondary nuclei and hence a new crop of crystals. In the absence of seed crystals, the reaction gives either very low yield or products heavily contaminated with impurity phases. 5 Recently, Wongkasemjit et al. 6–8 have developed a method to produce uniform zeolites using synthesis silatrane and Copyright  2006 John Wiley & Sons, Ltd.