Synthesis and Character of Nanosized ZSM-23 Zeolite

Bingchun Wang
Dalian Institute of Chemical Physics,Chinese Academy of Sciences

Zhijian Tian
Dalian Institute of Chemical Physics,Chinese Academy of Sciences

Peng Li
Dalian Institute of Chemical Physics,Chinese Academy of Sciences

Zhusheng Xu
Dalian Institute of Chemical Physics,Chinese Academy of Sciences

Guangqing Qu
Dalian Institute of Chemical Physics,Chinese Academy of Sciences

Yunpeng Xu
Dalian Institute of Chemical Physics,Chinese Academy of Sciences

Liwu Lin
Dalian Institute of Chemical Physics,Chinese Academy of Sciences

     Full text: Not available
     Last modified: March 13, 2006

Abstract
Synthesis and Character of Nanosized ZSM-23 Zeolite
Bingchun Wang1*, Zhijian Tian1*, Peng Li1, Zhusheng Xu1, Guangqing Qu1, Yunpeng Xu1, Liwu Lin2

1 Natural Gas Utilization and Applied Catalysis Laboratory, Dalian Institute of Chemical Physics,Chinese Academy of Sciences, P.O. Box 110, Dalian 116023, P. R. China.
2State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics,Chinese Academy of Sciences, P.O. Box 110, Dalian 116023, P. R. China.
* e-mail: wangbc@dicp.ac.cn, tianz@dicp.ac.cn

Recently in the nanotechnology era, Precise synthesis and control of materials at the nanometer scale has been directed toward ultimate goal. In the interdisciplinary field of zeolites and molecular sieves, the current impact of molecular sieve materials is indisputably significant, with applications ranging from petroleum refining for fuels and petrochemical processes for various chemicals to air separation and nuclear waste management.
ZSM-23 is a medium pore high silica zeolite with MTT topology, possessing the 10-ring nonintersecting channels of 0.56 nm×0.45 nm [1]. ZSM-23 exhibits catalytic properties for skeletal isomerization of paraffins. However, it often exhibits insufficient activity and/or fast deactivation, mainly due to poor diffusion efficiency. In order to benefit fully from the unique sorption and shape-selectivity effects, the diffusional path length in the micropores should be very short. During the last decade special attention has been drawn to the preparation of nanosized zeolites utilizing different methods [2,3].
In the present work, we focused on the synthesis of nanosized ZSM-23 zeolite under hydrothermal conditions using pyrrolidine as template. For comparison, the synthesis of normal-sized ZSM-23 was also investigated. The samples were characterized by Nitrogen adsorption/desorption analyses, SEM, TGA/DTA, and XRD et al.
The results show that nanosized zeolite ZSM-23 primary grains of 40–60 nm in size are obtained from SEM. The loose assemblies are formed by the primary grains with diameters about 1～2μm. The degree of crystallinity and phase homogeneity of the nano zeolite depend on the temperature and time of aging and crystallizing as well as on the amounts of alklies and salts in the initial mixture. And also the ratio of silica to alumina of initial gel is an influence factor. The main advantages of the nano ZSM-23 obtained via this method is the fast preparation and high conversion of the silica.

References
[1] R. Kumar, P. Ratnasamy, J. Catal. 121 (1990), 89
[2] G. Majano, S. Mintova , O. Ovsitser, et al, Micro. Meso. Mater. 80 (2005), 227
[3] M. Tsapatsis, M. Lovallo, T. Okubo, et al, Chem. Mater. 7 (1995), 1734