Abstract
The oxidation of propylene with a large amount of propylene has been studied over vanadium and molecule oxide catalysts in a flow system. The relation temperature was 470°C; the partial pressure of oxygen was kept at 0.1 atm, while that of propylene was varied from 0.1 to 0.8 atm. The main oxidation products were carbon monoxide, carbon dioxide, and acrrolein. In the oxidation with a pure vanadium oxide catalyst, the yield of acrolein increased with the proplene partial pressure, and the selectivity to acrolein was about 30% at the propylene partial pressure, and the selectivity values of the selectivity to various reaction products at the contact time of 0 sec did not change even though the propylene partial pressure was changed from 0.1 to 0.8 atm. X-ray patterns of the catlyst used (free of carriers) show the presence (of V2O4 or a mixture) of V2O4and V2O3 according to the partial pressure of propylene. It is concluded that acrolein undergoes a secondary reaction more severly when a vanadium oxide catalyst is in the higher oxidative state, that is, when it is richer in V2O4. In the system of vanadium-molybedenum oxides, the three mixed catalysts, containing 10, 18 and 30 mol% moO3, acted in a similar way and raised the selectivity to acroline to some extent in coparison with a pure vanadium oxide catalyst, whatever was partial pressure of propylene. In the mixtures containing more than 50 mol% MnO3, MoO3 had a dilution effect on the catalytic activity. A pure molybenum oxide catalyst scarcely oxidized propylene at all 470°C. It has thus been found that the catalytic cativity of this system is closely related with the formation of solid solutions MoO3 in V2O5.
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