Infrared Study of Surface Properties of Alumina Supported Chromia: Nitric Oxide Adsorption

✍ Scribed by H. Batis; M. K. Younes; A. Ghorbel

• Publisher: Wiley (John Wiley & Sons)
• Year: 2010
• Weight: 384 KB
• Volume: 99
• Category: Article
• ISSN: 0037-9646
• DOI: 10.1002/bscb.19900990403

✦ Synopsis

Infrared study of NO adsorption on chromia/alumina catalysts gives interesting information concerning both the surface heterogeneity and the reactivity of alumina-supported Cr ions.

On a preoxidized surface NO interacts with oxygen ligands to form nitrite and nitrate species. However in the presence of chemisorbed NH3 on oxidized catalyst the mobility of oxygen is strongly increased and can be displaced by NO molecules to form surface complexes with bands at 1 7 1 5 and 1855 cm-l.

On a prereduced surface, coordinatively insaturated Cr ions are created. A small fraction of theseions with one coordination vacancy adsorb weakly one NO molecule giving rise to a band at 1810 cm-l. These ions are poisoned by most strongly adsorbed NH3 as would be expected for Cr4' ions. Most of the Cr ions coordinate a couple of NO molecules to form stable Cr(N0)2 complexes with bands at 1125 and 1 8 6 5 cm-l.