Abstract:
Process for preparing a vinylidenecarboxylic acid or ester thereof, wherein a reaction gas comprising gaseous formaldehyde, molecular oxygen and an alkycarboxylic acid or ester thereof is brought into contact with a solid catalyst whose active composition comprises a vanadium-phosphorus oxide having an average oxidation state of vanadium of from +4.40 to +5.0 to give a product gas comprising the vinylidenecarboxylic acid or ester thereof.
Abstract:
In a process for preparing acrylic acid, a reaction gas which comprises a gaseous formaldehyde source and gaseous acetic acid and in which the partial pressure of the formaldehyde source, calculated as formaldehyde equivalents, is at least 85 mbar and in which the molar ratio of the acetic acid to the formaldehyde source, calculated as formaldehyde equivalents, is at least 1 is contacted with a solid condensation catalyst. The space-time yield can be enhanced significantly by increasing the partial pressure of the reactants. The space-time yield remains high even after prolonged process duration.