Effect of vanadium pentoxide (and other transition metal oxides) on gas‐phase combustion. IV. oxidation of isobutyraldehyde and related compounds

Abstract

AbstractThe slow combustion of isobutyraldehyde at 290–330° in a static system, using vessels coated with vanadium pentoxide, molybdenum oxide and bismuthphosphomolybdate, has been studied. Some results have also been obtained with isobutene oxide, isobutyric acid, propionaldehyde and n‐butyraldehyde. A rapid oxidation of isobutyraldehyde occurred at 320°, the initial rate with the phosphomolybdate coating depending markedly on both the aldehyde and oxygen pressures and the overall activation energy being 23 kcal/mole. High yields of methacrolein were obtained using this coating, but much lower ones with the V2O5 and MoO3 surfaces, considerable quantities of other products such as acetone being formed. Using the phosphomolybdate‐coated vessel much the same analytical results were obtained with isobutene oxide (as with isobutyraldehyde) and quite a high initial yield of methacrylic acid was obtained from isobutyric acid oxidation. However, with the straight‐chain aldehydes, little of the corresponding unsaturated aldehydes was formed.The oxidative dehydrogenation probably occurred on the surface and involved an allyl type intermediate. The reaction was most likely with carbonyl compounds of the structure R1R2CHC(R3)CO. With isobutyraldehyde, bismuth phosphomolybdate was an active catalyst and specific towards methacrolein formation, while MoO3 was not very active but probably quite specific and V2O5 was active but not very specific.