A comparative study of propene adsorption on total and partial oxidation catalysts

Abstract

A study of separate and successive adsorption of propene and oxygen on a total oxidation (the perovskite PrCoO 3) and on a partial oxidation (Mo-Pr-Bi-O) catalyst in the temperature range 195–511 K has been carried out. From the adsorption at 77 K, a cross-sectional area of propene of 0.38 nm 2 was calculated. The irreversibly adsorbed fraction of propene is significantly depressed by oxygen preadsorption while preadsorption of propene enhanced the irreversible adsorption of oxygen on both catalysts at 373 K. Whereas PrCoO 3 does not appear to activate the hydrocarbon molecule even at 500 K, activated adsorption of C 3H 6 on Mo-Pr-Bi-O does occur above 325 K. The adsorption heat of propene on PrCoO 3 was found to be substantially higher than that measured on Mo-Pr-Bi-O at 273–300 K where activated adsorption does not occur. The values of R (ratio between the irreversibly adsorbed and the reversibly adsorbed fractions) are considerably higher for PrCoO 3 than for Mo-Pr-Bi-O. These results reveal that Mo-Pr-Bi-O, which is a selective oxidation catalyst, yields a bond of moderate strength with propene while the perovskite, which is a total oxidation catalyst, gives rise to stronger interactions with the hydrocarbon. The activation of the olefin and the bond strength of propene with the adsorbent surface greatly influence the catalytic action for oxidation of these oxide materials.