Patent ID: 7589236

Claim:
A process for separating acrylic acid and benzoic acid present as the main product and bi-product as well as other product gas mixture constituents in a product gas mixture of a partial heterogeneously catalyzed gas phase oxidation of a C 3 precursor compound of acrylic acid, in which the acrylic acid and the benzoic acid, together with other constituents of the product gas mixture which have lower and higher boiling points than acrylic acid, are converted from the product gas mixture to a liquid phase P, and constituents having a lower boiling point than benzoic acid and acrylic acid are removed from the resulting liquid phase P using at least one thermal separating process to leave a liquid phase P* which comprises at least 80% by weight of acrylic acid and, based on the amount of acrylic acid present, at least 0.1 per mille by weight of benzoic acid, which comprises separating the benzoic acid from the acrylic acid by crystallization out of the liquid phase P*, the acrylic acid accumulating in the crystals formed and the benzoic acid in the remaining mother liquor.