Homogeneous OH groups in dealuminated HY zeolite studied by IR spectroscopy

✍ Scribed by Jerzy Datka; Barbara Gil; Teresa Domagała; Kinga Góra-Marek

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 112 KB
• Volume: 47
• Category: Article
• ISSN: 1387-1811
• DOI: 10.1016/s1387-1811(01)00314-6

✦ Synopsis

The analysis of IR spectra of free OH groups in strongly dealuminated zeolite HY (Si/Al 100) restoring on desorption of ammonia or pyridine provides spectroscopic evidence for the homogeneity of SiO 1 HAl groups. The same conclusion is obtained by analysis of the IR spectra of OH and OD groups interacting (by hydrogen-bonding) with nitrogen at 170 K. The homogeneity of OH groups in strongly dealuminated HY is explained by the presence of only (SiO) 3 SiO 1 HAl(OSi) 3 groups. By contrast, heterogeneous OH groups are found in non-dealuminated HY (Si/Al 2:56) containing three kinds of OH groups of various acid strength: (SiO)(AlO) 2 SiO 1 HAl(OSi) 3 , (SiO) 2 (AlO)SiO 1 HAl(OSi) 3 and (SiO) 3 SiO 1 HAl(OSi) 3 . Our dealuminated sample is the only known example of a zeolite with strongly acidic homogeneous hydroxyls. It may be a model catalyst for strongly acidic homogeneous OH groups or a model system for spectroscopic studies (IR, NMR etc.).