IR Characterization of Homogeneously Mixed Silica鈥揂lumina Samples and Dealuminated Y Zeolites by Using Pyridine, CO, and Propene Probe Molecules

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• 作者：Yuichi Matsunaga ; Hiroshi Yamazaki ; Toshiyuki Yokoi ; Takashi Tatsumi ; Junko N. Kondo
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：July 11, 2013
• 年：2013
• 卷：117
• 期：27
• 页码：14043-14050
• 全文大小：437K
• 年卷期：v.117,no.27(July 11, 2013)
• ISSN：1932-7455

文摘

Homogeneously mixed silica鈥揳lumina samples with various Si/Al ratios (Si/Al = 9/1, 7/3, 5/5, 3/7, and 1/9) were prepared and characterized by infrared spectroscopy. Pyridine, propene, and CO were used as probe molecules to detect Br酶nsted and Lewis acid sites. The homogeneity of Si and Al in mixed oxides was confirmed by comparison with a physical mixture of pure silica and alumina. The continuous change of spectral appeared by increasing or decreasing the Si/Al ratio in silica鈥揳lumina samples. The frequency of the broad band due to surface OH groups hydrogen-bonded to CO was found to be a measure of the Si/Al ratio in silica鈥揳lumina samples roughly. This information was used to characterize steam-treated HY and NH₄Y zeolites. Dealumination from the framework structure and generation of extra-framework silica鈥揳lumina were apparent for both steam-treated zeolites, which were not identified by X-ray diffraction patterns and microscope images. The Si/Al ratios of the formed silica鈥揳lumina on steam-treated YH and NH₄Y zeolites were roughly estimated to be 5/5 and 7/3, respectively, by the peak position of hydrogen-bonded OH bands when CO was adsorbed. The acid strength of both steam-treated samples was weakened, and it was more apparent for HY than NH₄Y zeolite.