Catalytic partial oxidation of propane to acrolein

Results are discussed on the direct oxidation of propane to acrolein on Me(x)O(y)-supported Ag0.01Bi0.85V0.54Mo0.45Ox (Me(x)O(y) = gamma-Al2O3, TiO2, SiO2) and on Me(7)Bi(5)Mo(12)O(x) (Me = Mg, Ca, Zn) catalysts. Almost no formation of acrolein was observed over Me(x)O(y)-supported catalysts although active phases for oxidative dehydrogenation of propane (dispersed y VOx species) and oxygen insertion in propene (scheelite structure) were present. For Me-Bi-Mo-O, selectivities to acrolein and CO, depended on the nature of the third cation and reaction mixture used. The acrolein selectivities amounted to 34 and 20% (yields of 3.2 and 2.7%) when using Ca(7)Bi(5)Wo(12)O(x) and Mg7Bi5Mo12Ox, respectively. Redox properties were found to be an important factor determining the reaction pathways. Tentatively it can be concluded that different types of lattice oxygen are involved in propane dehydrogenation to propene and consecutive reactions towards acrolein and COx. Under conditions of effective propane dehydrogenation to propene a competitive reaction between an allylic intermediate and propane forming propene and propyl radical can be assumed as the reason for low acrolein formation in favour to propene. Applying a two layer fixed bed reactor an acrolein yield of 7.4% (S = 20%) was obtained.