Process for preparing acrylic acid from ethanol and formaldehyde

Abstract

A process for preparing acrylic acid from ethanol and formaldehyde, in which, in a reaction zone A, the ethanol is partially oxidized to acetic acid in a heterogeneously catalyzed gas phase reaction, the product gas mixture A obtained and a formaldehyde source are used to obtain a reaction gas input mixture B which comprises acetic acid and formaldehyde and has the acetic acid in excess over the formaldehyde, and the formaldehyde present in reaction gas input mixture B is aldol-condensed with acetic acid present in reaction gas input mixture B to acrylic acid under heterogeneous catalysis in a reaction zone B, and unconverted acetic acid still present along-side the acrylic acid target product in the product gas mixture B obtained is removed therefrom, and the acetic acid removed is recycled into the production of reaction gas input mixture B.

1 - 21 . (canceled) 
     
     
         22 . Acrylic acid for which the ratio V of the molar amount n 14 C of  14 C atomic nuclei present in this acrylic acid to the molar amount n 12 C of  12 C atomic nuclei present in the same acrylic acid, V=n 14 C:n 12 C, is greater than 0 and less than the corresponding molar ratio V* of  14 C atomic nuclei to  12 C atomic nuclei present in the carbon dioxide in the earth's atmosphere. 
     
     
         23 . Acrylic acid according to  claim 22 , wherein V=(2/3)·V*. 
     
     
         24 . A liquid phase P comprising at least 1 kg of acrylic acid, wherein the acrylic acid present is an acrylic acid according to  claim 22 .