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業績詳細


【論文】

"Temperature Effect on 1H Chemical Shift of Hydroxyl Groups in Zeolites and their Catalytic Activities as Solid Acids"
【全著者名】
Hajime Munakata, To-ru Koyama, Tatsuaki Yashima, Naoki Asakawa, Toshinori O-nuki, Ken Motokura, Akimitsu Miyaji, Toshihide Baba
【掲載雑誌名】
Journal of Physical Chemistry C
【巻・号・頁】
116(27): 14551-14560
【発表年月】
2012年06月
【単著、共著の別】
共著
【掲載雑誌種別】
学術雑誌
【論文の種別】
原著
【要旨】
The influence of temperature on the 1H chemical shift due to hydroxyl groups in H+-exchanged any kind of zeolites (ZSM-5 type zeolites including silicalite, mordenite and Y zeolites) was examined by variable temperature 1H magic-angle spinning nuclear magnetic resonance (1H MAS NMR) spectroscopy measured from 298 to 673 K. The 1H chemical shifts due to bridging hydroxyl groups (Si?(OH)?Al, Bronsted acid sites), which have a lower activation energy for proton jumping, terminal silanol groups, and nest silanol groups increased with temperature. The temperature dependence of the 1H chemical shift due to the bridging hydroxyl groups was more pronounced than that due to the terminal silanol groups and also the nest silanol groups. The relationship between the 1H chemical shift and the acid strength of the hydroxyl groups in zeolites was discussed on the basis of the variable temperature 1H MAS NMR measurements of zeolites, previously reported thermal analysis data, such as the heat of NH3 adsorption measured by NH3 temperature-programmed desorption, and also the catalytic activity for the conversion of ethanol and 1-hexene. It was found that the nest silanol groups of silicalite functioned as Bronsted acid sites and could catalyze the conversion of ethanol and 1-hexene with the same activity as the bridging hydroxyl groups in B-ZSM-5 at 673 K.

【研究者】

浅川 直紀