title: Improved description of the surface acidity of eta-alumina.
abstract: The surface acidity of an activated eta-alumina catalyst has been investigated by examining the interaction of pyridine with the catalyst by a combination of gravimetric and volumetric adsorption isotherms, infrared spectroscopy (diffuse reflectance and transmission), inelastic neutron scattering spectroscopy, temperature-programmed desorption spectroscopy, and gravimetric desorption experiments. From previous work, this surface was considered to contain three types of Lewis acid sites of increasing acidity: weak, medium, and strong. However, this multitechnique approach reveals the presence of an additional type of Lewis acid site. Although the traditional pyridine ring modes about 1580 cm(-1) are consistent with previous studies, temperature-programmed infrared spectroscopy of the surface hydroxyl groups and mass-selective temperature-programmed desorption experiments establish that the medium-strength Lewis acid category can be subdivided into two components. In this way, the surface structure of the activated catalyst is redefined as comprising (i) weak, (ii) medium-weak, (iii) medium-strong and (iv) strong Lewis acid sites. The (O-H) stretching mode of surface hydroxyl groups provides information on the local structure of the distinct sites, and schematic descriptions for these sites are proposed.
authors.affiliation: Department of Chemistry, Joseph Black Building, The University of Glasgow, Glasgow, G12 8QQ, UK.
authors.forename: David T
authors.initials: DT
authors.lastname: Lundie
authors.forename: Alastair R
authors.initials: AR
authors.lastname: McInroy
authors.forename: Robert
authors.initials: R
authors.lastname: Marshall
authors.forename: John M
authors.initials: JM
authors.lastname: Winfield
authors.forename: Peter
authors.initials: P
authors.lastname: Jones
authors.forename: Chris C
authors.initials: CC
authors.lastname: Dudman
authors.forename: Stewart F
authors.initials: SF
authors.lastname: Parker
authors.forename: Chris
authors.initials: C
authors.lastname: Mitchell
authors.forename: David
authors.initials: D
authors.lastname: Lennon