https://scholars.lib.ntu.edu.tw/handle/123456789/633330
標題: | Morphology control of ionic-liquid-templated ZSM-22 and ZSM-5 zeolites using a two-step process and its effect on toluene methylation | 作者: | Li, Xuemin Tsai, Shang Tien KEVIN CHIA-WEN WU Curnow, Owen J. Choi, Jungkyu Yip, Alex C.K. |
關鍵字: | Ionic liquid | Shape selectivity | Toluene methylation | ZSM-22 | ZSM-5 | 公開日期: | 1-十二月-2021 | 卷: | 328 | 來源出版物: | Microporous and Mesoporous Materials | 摘要: | ZSM-22 (TON) and ZSM-5 (MFI) zeolites were synthesized using 1-ethyl-3-methylimidazolium bromide ([EMIM]Br) and 1-butyl-3-methylimidazolium bromide ([BMIM]Br), respectively, as structure-directing agents. A two-step crystallization method, i.e., crystallizing at different temperatures under static conditions and/or agitation by rotation, was used to tune the zeolite particle size. X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images show good crystallinity and a variety of particle sizes of the zeolites. Temperature programmed desorption of ammonia (NH3-TPD) along with 27Al and 29Si solid-state NMR indicate that the acid site concentration and the acid strength were similar for all the zeolite samples and that Al was incorporated into the framework. The shape-selective capability of the zeolites was evaluated by toluene methylation. All of the ZSM-22 zeolites showed higher para-xylene (p-xylene) selectivity than the ZSM-5 zeolites. The ZSM-22 sample with a smaller particle size exhibited the highest para-xylene (p-xylene) selectivity of up to 92%. In contrast, the highest p-xylene selectivity among the ZSM-5 zeolites only reached 53%. The enhancement of the p-xylene selectivity is ascribed to the one-dimensional structure of the ZSM-22 zeolite. This work provides an alternative method of promoting high p-xylene selectivity in toluene methylation. Furthermore, as an alternative to modifying MFI zeolites by post-treatments, rational design of ZSM-22 zeolites, e.g., incorporating mesopores and uniform nanosized particles, is a promising way to achieve high selectivity during toluene methylation. |
URI: | https://scholars.lib.ntu.edu.tw/handle/123456789/633330 | ISSN: | 13871811 | DOI: | 10.1016/j.micromeso.2021.111475 |
顯示於: | 化學工程學系 |
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