Oxidation of propionaldehyde in aged boric-acid-coated vessels. Part 2.—Analytical results

Abstract

The main products in the oxidation of C₂H₅CHO + O₂ mixtures at temperatures around 440°C are C₂H₄, CO and H₂O₂. About 80 % of the C₂H₅CHO oxidized appears as C₂H₄. CH₃CHO and CO₂ appear in 10–20 % yield, and there are smaller but significant amounts of C₂H₄O, CH₄, C₂H₆ and H₂. Mechanisms to account for these products have been suggested, and velocity constants obtained where possible. Formation of acetaldehyde is attributed to attack by OH or HO₂ at the secondary CH₂ position rather than the CHO group. The [CO]/[CO₂] ratio is about 10, and its variation with mixture composition suggests a competition between the reactions, C₂H₅CO + M′→ C₂H₅+ CO + M, C₂H₅CO + O₂→ C₂H₅CO₃→ CO₂. Measurement of the relative rates of formation of C₂H₆ and C₂H₄ gives the ratio k(C₂H₅+ O₂= C₂H₄+ HO₂)/k(C₂H₅+ C₂H₅CHO)= 41 at 440°C.