Quantitative Determination of the Number of Active Surface Sites and the Turnover Frequency for Methanol over Metal Oxide Catalysts

LAURA E. BRIAND ; ISRAEL E. WACHS

Studies in Surface Science and Catalysis

Elsevier Science B.V.

Lugar: Amsterdam; Año: 2000; p. 305 - 310

Methanol chemisorption was successfully developed to quantify the number of surface active sites Ns and the methanol oxidation turnover frequency TOF of metal oxide catalysts (supported molybdenum oxides, bulk metal molybdates and bulk metal oxides). This is the first example in the catalysis literature where the Ns and TOF values of different types of metal oxide catalysts have been quantitatively compared for an oxidation reaction. Comparable values of Ns and TOF were obtained for the corresponding molybdate catalysts (e.g., MoO3/Al2O3 and Al2(MoO4)3), which reflect the influence of the cation ligands in these catalists (e.g., Al). Further comparison with the pure metal oxides (e.g., MoO3 and Al2O3) suggests that the bulk metal molybdate catalysts are enriched in surface Mo and may actually possess a surface molybdenum oxide overlayer. These new insights account for the special prperties of bulk metal molybdates during catalytic oxidation reactions.