Phase and surface composition and dispersion of MoO 3 in MoO 3/Al 2O 3—SiO 2 catalysts

• Published in: Applied catalysis Vol. 61; no. 1; pp. 253 - 263
• Main Authors: Henker, Matthias, Wendlandt, Klaus-Peter, Shpiro, Efim Sergejevich, Tkachenko, Olga Petrovna
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 1990
• Subjects: catalyst characterization (XPS; composition; dispersion; molybdenum/alumina-silica; XRD; composition; catalyst characterization (XPS; XRD; dispersion; molybdenum/alumina-silica
• ISSN: 0166-9834
• DOI: 10.1016/S0166-9834(00)82148-X

MoO 3/Al 2O 3-SiO 2 catalysts containing between 1 and 30 wt.-% MoO 3 and O and 100 wt.-% Al 2O 3 in the support are studied by means of X-ray diffraction and X-ray photoelectron spectroscopic (XPS) techniques. In contrast to the SiO 2 support, where the X-ray pattern of the 15 wt.- % MoO 3 sample shows evidence for the formation of MoO 3 crystals, in catalysts containing alumina Al 2(MoO 4) 3 formation is preferred. Al 2(MoO 4) 3 formation is enhanced by increasing the content of alumina in the support and by raising the amount of MoO 3. The XPS results show a high dispersion of MoO 3 in the alumina-rich catalysts (≥30 wt.-% Al 2O 3). At lower Al 2O 3 content the preferential formation of polylayers and microcrystals of MoO 3 takes place. On an alumina-rich carrier, an increase in the Al-to-Si ratio on the catalyst surface could be observed with increasing MoO 3 content up to 15 wt.-%.