Determination of Acid Site Location in Dealuminated MCM-68 by 27Al MQMAS NMR and FT-IR Spectroscopy with Probe Molecules

Ryoichi Otomo, Toshiki Nishitoba, Ryota Osuga, Yusuke Kunitake, Yuichi Kamiya, Takashi Tatsumi, Toshiyuki Yokoi

研究成果: Article査読

6 被引用数 (Scopus)

抄録

A series of MCM-68 zeolites with different Si/Al ratios were prepared by treatment with nitric acid and compared with beta zeolites. Speciation of aluminum and location of acid sites changed depending on the Si/Al ratio. The location of Brønsted acid sites in MCM-68 samples was able to be classified by FT-IR measurements with pyridine and 2,6-di-tert-butylpyridine as probe molecules, and the number of Brønsted acid sites was quantified according to the locations. For high-aluminum MCM-68, Brønsted acid sites were broadly distributed in both the 12-ring channel and 10-ring windows as well as inside the supercage. The Brønsted acid sites in the 12-ring channel were easily removed by the acid treatment, and consequently, high-silica MCM-68 had Brønsted acid sites predominantly in the 10-ring windows and inside the supercage. 27Al MQMAS NMR spectra of high-silica MCM-68 showed two specific peaks assignable to T6 and T7 sites, which did not face the 12-ring channel, forming the Brønsted acid sites highly tolerant to the acid treatment. MCM-68 catalysts showed better catalytic performance in dehydration of sorbitol than beta, mordenite, and ZSM-5. Large void spaces at the intersection of 12- and 10-ring channels and inside the supercage for MCM-68 made it easy to take bulky transition states in the dehydration of sorbitol, resulting in its high catalytic performance.

本文言語English
ページ(範囲)1180-1191
ページ数12
ジャーナルJournal of Physical Chemistry C
122
2
DOI
出版ステータスPublished - 2018 1 18
外部発表はい

ASJC Scopus subject areas

  • 電子材料、光学材料、および磁性材料
  • エネルギー(全般)
  • 物理化学および理論化学
  • 表面、皮膜および薄膜

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