On the Nature of Nonframework Cations in a Zeolitic deNOx Catalyst: Cu-Mordenite

✍ Scribed by Martin P. Attfield; Scott J. Weigel; Anthony K. Cheetham

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 251 KB
• Volume: 170
• Category: Article
• ISSN: 0021-9517
• DOI: 10.1006/jcat.1997.1736

✦ Synopsis

The locations of extra-framework Cu 2+ cations in hydrated copper ion-exchanged mordenite (formula Cu 1.384 T 48 O 2 • 28H 2 O, space group Cmcm, a = 18.1659(4) Å, b = 20.375(1) Å, c = 7.495(1) Å, V = 2774.4(4) Å3 , Z = 1, R = 5.13%) and its partially dehydrated analog (formula Cu 1.468 T 48 O 2 • 4.04H 2 O, space group Cmcm, a = 18.0546(7) Å, b = 20.298(2) Å, c = 7.4772(3) Å, V = 2740.2(3) Å3 , Z = 1, R = 3.90%) have been determined from the analysis of roomtemperature single-crystal X-ray data. Two copper sites were found in the hydrated sample: one in the elliptical 8-ring and the other in the center of the main 12-ring channel. Upon dehydration three copper sites were determined; one in the elliptical 8-ring, one above the 6-ring in the main channel and the last in the circular 8-ring that leads into the main channel. The low coordination, but high accessibility, of the latter two cation sites in the partially dehydrated sample provides a possible explanation for the high activity of mordenite and its related pentasil family members for nitrogen oxide decomposition.