Investigation of dealuminated mordenites by x-ray photoelectron spectroscopy

Abstract

Mg Ka X-ray photoelectron spectroscopy (XPS) was used to establish the relative concentration and the chemical state of aluminum at the surface of dealuminated mordenites. A method for the binding energy calibration is proposed. Modified Auger parameters of AI have been determined for different zeolites and clay minerals as well as for dealuminated mordenites. The data are compared with those available in the literature. Ranges of values for modified Auger parameter of octahedral and tetrahedral aluminum are reported. The results obtained on highly dealuminated mordenites are consistent with the presence of surface tricoordinated AI. IntroductionMordenite is used in several industrial catalytic processes.'v2 Dealumination of mordenite is nowadays a common way to improve the catalytic performances as well as the catalyst life.3-4

α-Alumina-Supported Nickel Catalysts Prepared with Nickel Acetylacetonate. 2. A Study of the Thermolysis of the Metal Precursor

“…Both Al VI and Al IV could be discriminated in the support calcined at 500 °C, with α‘ values of 1462.4 eV for Al VI (BE of Al 2p = 74.4 eV, fwhm = 1.97 eV) and 1461.4 eV for Al IV (BE of Al 2p = 73.2, fwhm = 2.01 eV). These values are close to those established for zeolites. − No good fit with the experimental curve was obtained when the Al VI /Al IV ratio determined from the 27 Al MAS NMR measurement (4.5:1) was imposed for the Al 2p and Al KLL peak decomposition. A good fit was only obtained for a ratio of 1.5:1, thus indicating a greater proportion of Al IV in the surface than in the bulk.…”

Calibration of the X‐Ray Photoelectron Spectroscopy Binding Energy Scale for the Characterization of Heterogeneous Catalysts: Is Everything Really under Control?

“…This appears more consistent with the fact that the chemical environment of these elements should not vary significantly in the sample panel. Even potential changes in symmetry (octahedral versus tetrahedral coordination) are not expected to yield any shift in the Al 2p BE 15b. In contrast, as expected, the BE of the C (C,H) component of the C 1s peak (Figure 1 f) decreased if the SiO 2 content was increased, because the conductivity of the substrate decreased.…”

X ‐Ray Photoelectron and Auger Electron Spectroscopy

“…Poncelet and co-workers characterized the Al coordination at the outer surface of dealuminated mordenites [45,46] and beta zeolites [47] by XPS using a careful analysis of the Al 2p and the Al KLL Auger transitions excited by X-rays. The basis of their analysis was the Al Auger parameter defined as α Al = E b (Al 2p) + E k (Al KLL).…”