期刊
MICROPOROUS AND MESOPOROUS MATERIALS
卷 196, 期 -, 页码 341-348出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.micromeso.2014.05.043
关键词
CHA-type zeolite; OSDA-free synthesis; Alkali cations; Seed crystals; Boron species
类别
资金
- Tokyo Institute of Technology and Mitsubishi Chemical Company (MCC)
Highly crystalline CHA-type aluminosilicate zeolites with the Si/Al ratio of around 4-5 were successfully synthesized by a seed-assisted method in the absence of organic-structure-directing agents (OSDAs); a method for so-called OSDA-free synthesis of the CHA zeolite has been newly developed. In this OSDA-free system, in addition to the seeds with the CHA topology, a judicious use of potassium or cesium cations together with sodium cations is a crucial key to the crystallization of the amorphous aluminosilicate gel into the CHA structure. The Si/Al ratio of the CHA zeolite was increased by decreasing the total amount of alkali cations added and/or the use of cesium cations in place of potassium ones. Furthermore, the employment of the amorphous aluminosilicate gel containing boron species led to the formation of the CHA zeolite with a high Si/Al ratio of 6.1 compared with the synthetic chabazite crystallized through the interzeolite conversion of the FAU zeolite (Si/Al: 2.0). The catalytic performance of the prepared CHA zeolites was also evaluated. In the methanol-to-olefins reaction, the catalyst life was improved by increasing the Si/Al ratio of the CHA zeolite. (C) 2014 Elsevier Inc. All rights reserved.
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