Centimeter-sized zeolite bodies of intergrown crystals: Preparation, characterization and study of binder evolution Lama Itani a , Valentin Valtchev a , Joël Patarin a,⇑ , Séverinne Rigolet a , Feifei Gao a , Gérard Baudin b a Equipe Matériaux à Porosité Contrôlée (MPC), Institut de Science des Matériaux de Mulhouse (IS2M), LRC-CNRS 7228, Université de Haute Alsace (UHA), Ecole Nationale Supérieure de Chimie de Mulhouse (ENSCMu), 68093 Mulhouse, France b Commissariat aux Énergies Atomiques et Alternatives (CEA), Direction des Applications Militaires (DAM), Gramat, F46500 Gramat, France article info Article history: Received 22 July 2010 Received in revised form 15 September 2010 Accepted 16 September 2010 Available online 21 September 2010 Keywords: Zeolite bodies Inter-particle pores Secondary growth treatment abstract The control of the inter-particle porosity in polycrystalline zeolite bodies remains a challenge. The pres- ent study reports on the preparation of centimeter-sized zeolite bodies (32  2 mm pellets) with reduced inter-particle porosity. The bodies were prepared by assembling zeolite colloidal nanocrystals with monomodal particle size distribution and sub-colloidal aluminum hydroxide binder. A secondary growth treatment under hydrothermal conditions was performed in order to fill up the inter-particle voids and obtain polycrystalline zeolite materials with textural characteristics close to those of single zeolite crystals. Initial material, intermediates and ultimate product were studied with a combination of comple- mentary methods revealing a substantial reduction even an elimination of the inter-particle porosity. Particular attention was paid to the chemical evolution of the binder and the migration of aluminum species, employing X-ray powder diffraction, 27 Al-MAS, 27 Al-3QMAS NMR and X-ray fluorescence spectroscopy analyses. Evidences for insertion of aluminum from the binder into the zeolite framework during secondary growth step were found. Consequently the ultimate pellets comprised aluminum- rich zeolite beta crystals and very low binder content. Ó 2010 Elsevier Inc. All rights reserved. 1. Introduction Zeolites are crystalline microporous materials with uniform pore size ranging between 0.3 and 2 nm. Stereo selectivity com- bined with surface activity make zeolites indispensable for numer- ous chemical processes. Zeolite synthesis is usually performed in alkaline media under hydrothermal conditions and leads typically to powder of micrometer-sized crystals. These crystals are difficult to handle and use in liquid and gas phase reactions. On the other hand, the synthesis of larger zeolite crystals is difficult to be achieved on a larger than a laboratory scale. The application of such crystals is limited to fundamental studies of zeolite structure, diffusion properties and growth process [1–4]. Large zeolite crys- tals might also find applications as hosts for guest molecules (alignments of dye molecules), ions, and clusters for optical, elec- tric and magnetic microdevices [5–7]. Generally fairly exotic meth- ods that is difficult to be used in an industrial scale are employed [8,9]. In addition, such synthesis suffer from other limitations such as long synthesis time laying usually between several days and several weeks, the formation of co-crystalline phases, and low yield. Thus most of the industrial applications require shaping the zeolite powders in larger constructs where in most cases a binder is used [10]. Traditionally employed binders are alumina, silica and natural clays (kaolin, kaolinite, montmorillonite, benton- ite, etc.) [11]. In general it is accepted that these binders are chemically inert and do not contribute to the performance of zeolite-binder composite. However, there are studies revealing that the catalytic properties of the zeolite might be strongly influ- enced by the binder. For instance, many studies show that the use of aluminosilicate clays decreased strongly the number of strong acid sites in the catalyst [11–14]. The influence of the binder on the deactivation of the zeolite catalyst by coking was also observed [15–17]. On the other hand, when using an alumina binder, Shihabi et al. showed that the activity for acid catalyzed reactions of high- silica ZSM-5 was enhanced [18]. They attributed this result to the formation of new acid sites during the catalyst preparation. Namely, the higher activity was attributed to incorporation of alu- minum species released from the binder into zeolite framework. Kubicek et al. has also reported enhancement of zeolite beta cata- lytic properties after embedding in alumina and alumino-silicate amorphous matrixes [19]. These studies confirmed the possible aluminum incorporation into zeolite frameworks of species issued from the binder. Another important feature of binder-containing zeolite constructs is the presence of secondary porosity due to the uncontrolled aggregation of zeolite crystals and the binder. In some applications, particularly in catalysis, this porosity can have a positive effect for the diffusion of the reactants and products. 1387-1811/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.micromeso.2010.09.011 ⇑ Corresponding author. Tel.: +33 3 89 33 68 80; fax: +33 3 89 33 68 85. E-mail addresses: j.patarin@univ-mulhouse.fr, joel.patarin@uha.fr (J. Patarin). Microporous and Mesoporous Materials 138 (2011) 157–166 Contents lists available at ScienceDirect Microporous and Mesoporous Materials journal homepage: www.elsevier.com/locate/micromeso