Morphology control of ionic-liquid-templated ZSM-22 and ZSM-5 zeolites using a two-step process and its effect on toluene methylation
- Authors
- Li, Xuemin; Tsai, Shang-Tien; Wu, Kevin C-W; Curnow, Owen J.; Choi, Jungkyu; Yip, Alex C. K.
- Issue Date
- 12월-2021
- Publisher
- ELSEVIER
- Keywords
- Ionic liquid; Shape selectivity; Toluene methylation; ZSM-22; ZSM-5
- Citation
- MICROPOROUS AND MESOPOROUS MATERIALS, v.328
- Indexed
- SCIE
SCOPUS
- Journal Title
- MICROPOROUS AND MESOPOROUS MATERIALS
- Volume
- 328
- URI
- https://scholar.korea.ac.kr/handle/2021.sw.korea/135581
- DOI
- 10.1016/j.micromeso.2021.111475
- ISSN
- 1387-1811
- Abstract
- 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 agita-tion 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 Al-27 and Si-29 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 modi-fying 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.
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