Process for the preparation of alpha, beta unsaturated aldehydes by oxidation of alcohols in the presence of a liquid phase

A process for the preparation of alpha, beta unsaturated aldehydes of general formula (I)

• wherein R1, R2 and R3, independently of one another, are selected from
• hydrogen;
• C1-C6-alkyl, which optionally carry 1, 2, 3, or 4 identical or different substituents which are selected from NO2, CN, halogen, C1-C6 alkoxy, (C1-C6-alkoxy)carbonyl, C1-C6 acyl, C1-C6 acyloxy and aryl;
• and C2-C6-alkenyl, which optionally carry 1, 2, 3, or 4 identical or different substituents which are selected from NO2, CN, halogen, C1-C6 alkoxy, (C1-C6-alkoxy)carbonyl, C1-C6 acyl, C1-C6 acyloxy and aryl;
• by oxidation of alcohols of general formula (II) out at a temperature of 20° C. to 100° C.,
• wherein R1, R2 and R3 have the meaning as given above
• in the presence of a catalyst and in the presence of a liquid phase,
• wherein the liquid phase contains 0.1 to less than 25 weight-% water and
• wherein the liquid phase contains at least 25 weight-% of alcohol(s) of general formula (II) and alpha, beta unsaturated aldehyde(s) of general formula (I) and
• wherein the oxidant is oxygen and/or hydrogen peroxide,
• wherein the oxidation is carried out at a temperature of 20° C. to 100° C.,
• all weight-% based on the total weight of the liquid phase determined at a temperature of 20° C. and a pressure of 1 bar.