Applied Catalysis, 17 (1985) 233-259 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands 233 zyxwvutsr CHARACTERIZATION OF INTERMEDIATE TPA-ZSM-5 TYPE STRUCTURES DURING CRYSTALLIZATION K.F.M.G.J. SCHOLLEI, W.S. VEEMANI, P. FRENKEN2 and G.P.M. van der VELDEN2 1 Department of Physical Chemistry, Faculty of Science, University of Nijmegen, Toernooiveld, 6525 ED Nijmegen, The Netherlands 2 DSM, Research and Patents, P.O. Box 18, 6160 MD Geleen, The Netherlands (Received 18 February 1985, accepted 9 April 1985) ABSTRACT A wide range of analytical techniques (XRD, DTA/TGA, I.R., texture, SEM/TEM, I3C, 27A1, 29Si MAS NMR) has been used to characterize intermediate products formed during the crystallization process of the zeolite Tetrapropylammonium ZSM-5 (TPA- ZSM-5). In the beginning of the crystallization process the solid products are XRD- amorphous and consist of an aluminum-rich phase next to an increasing amount of TPA-ZSM-5 entities with dimensions of the order of the unit cell of ZSM-5. In the final stage of the crystallization process (here up to 8 days) the TPA-ZSM-5 entities recombine to a crystalline ZSM-5 framework. A large amount of framework defects are then still present in the XRD-crystalline TPA-ZSM-5 framework as evidenced by 29Si MAS NMR. These defects disappear upon calcination. INTRODUCTION Zeolites are of great interest for the petrochemical industry. Especially the zeolite ZSM-5 receives much attention due to its special catalytic properties[l,21. Zeolite ZSM-5 can be synthesized by a hydrothermal method described by Mobil in US patent no. 3702886. An essential step during the synthesis is thought to be the use of Tetrapropylammonium (TPA) cations which are believed to act as templates during crystal growth of ZSM-5 131.However, in the patent literature the successful use of several other organic compounds in the synthesis is claimed as well. When the crystallization has been finished, the TPA-cation is removed from the pore system of the zeolite by calcination at e.g. 540°C. The acidic form, H-ZSM-5, is obtained by cation exchange and then the zeolite is ready for use as a catalyst. In this report we deal mainly with the first part of this procedure, the synthesis of TPA-ZSM-5. The primary goal of our investigation was to study and to characterize the solid products from the hydrothermal synthesis process as a function of time, using a widerange of characterization techniques in order to obtain a better understanding of the crystallization process. The characterization techniques used are: X-ray diffraction (XRD), texture measurements, differential thermal analysis (DTA), thermogravimetric analysis (TGA), 0166-9834/85:$03.30 0 1985 Elsevier Science Publishers B.V.