AN FT-IR AND FLOW REACTOR STUDY OF THE SELECTIVE CATALYTIC OXY-DEHYDROGENATION OF C3 ALCOHOLS ON MN3O4

The C3 alcohols 1-propanol, 2-propanol and prop-2-en-1-ol (allyl alcoh ol) are catalytically oxidized in He/oxygen to the corresponding carbo nyl compounds propanal, acetone and acrolein with high selectivities a nd yields over Mn3O4. The reaction occurs in the temperature range 400 -550 K and yields far over 85% are obtained in the synthesis of acrole in and acetone. The reaction rate is faster for the secondary alcohol 1-propanol, than for the primary ones. The oxidation of the unsaturate d allyl alcohol is faster than for the saturated one, l-propanol. Sele ctivity is limited by overoxidation of the carbonyl compounds. IR stud ies show that the high yields obtained in carbonyl compounds productio n over this catalyst are mainly due to their very weak adsorption. The main factor Limiting the selectivity to acetone and, mainly, propanal is their tendency to give enolate anions that further convert into ac etaldehyde in both cases. Overoxidation of aldehydes to the correspond ing carboxylate species is a less efficient mechanism limiting selecti vity, The selectivity/activity behavior is definitely different than t hat observed for stoichiometric alcohols oxidations with Mn(III) compo unds and also than that observed on other catalysts. This difference i s associated to the low surface acidity of the Mn3O4 catalyst. (C) 199 8 Elsevier Science B.V.