Contribution of HRTEM to the characterization of silica-incorporated copper-oxide catalysts prepared by the Sol-Gel technique

✍ Scribed by Benaïssa, M.; Diaz, G.

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 458 KB
• Volume: 40
• Category: Article
• ISSN: 1059-910X
• DOI: 10.1002/(sici)1097-0029(19980101)40:1<49::aid-jemt7>3.0.co;2-s

✦ Synopsis

The aim of the present work is a structural characterization study of silicaincorporated copper-oxide (CuO-SiO 2 ) catalysts using HRTEM. The catalysts were prepared by the sol-gel synthetic route. Two calcined catalysts (at 400°C and 800°C, respectively) were analyzed before and after the ''NO x ϩ H 2 '' catalytic reaction. It was found that in the 400°C calcined catalyst, the copper is present as CuO crystallites in a structureless form, while in the 800°C calcined catalyst, it was assumed that the copper is atomically dispersed into the silica matrix since no traces of crystalline copper were observed. Under a reducing atmosphere, i.e., after reaction, the former showed large crystallites of CuO, while in the latter a segregation of colloidal crystallites, a mixture of Cu 2 O and metallic Cu, was observed. It is worth noting that in the case of the 400°C ''after-reaction'' catalyst, a change in color was observed after a few minutes of air exposure. This result suggested that the reduced copper-oxide phase obtained after reduction was unstable.