Abstract: In a process for the purification of a crude acrylic acid melt, the crude acrylic acid melt is converted, under the action of low temperatures, into a crude acrylic acid suspension consisting of acrylic acid crystals and residual melt, and the acrylic acid crystals of the crude acrylic acid suspension are freed from remaining residual melt in a wash column, the production of the acrylic acid crystals of the crude acrylic acid suspension being carried out in the presence of water, the wash column being a wash column with forced transport of the acrylic acid crystals and the wash liquid used being the melt of acrylic acid crystals purified in the wash column.

Abstract: (Meth)acrylic acid is purified by crystallization by a process in which the (meth)acrylic acid is purified by a combination of at least two different dynamic crystallization processes, in particular a suspension crystallization and a layer crystallization.

Abstract: A process for the preparation of acrylic acid by: (a) preparation of a gaseous product mixture which essentially has the composition of a reaction mixture of catalytic gas-phase oxidation of C3-alkanes, C3-alkenes, C3-alkanols and/or C3-alkanals and/or intermediates thereof to acrylic acid, which comprises (b) condensation of the gaseous product mixture, (c) crystallization of the acrylic acid from the solution obtained in stage (b), with partial evaporation of the solution under reduced pressure, (d) isolation of the resulting crystals from the mother liquor, (e) recycling of at least a part of the mother liquor from stage (d) to stage (b) and (f) recycling of at least a part of the evaporated solution from stage (c) to stage (b).

Abstract: In a process for purifying acrylic acid by crystallization by means of vacuum evaporation, a solution which contains acrylic acid and water and may contain further components is crystallized by means of vacuum evaporation with formation of a liquid phase, consisting of a mother liquor containing more than 10% by weight of water and of the crystals, and a vapor phase, the vapor phase is introduced into a liquid material in a condensation zone with formation of a liquid condensation mixture, and the liquid condensation mixture is recycled at least partly to the condensation zone, the operating conditions in the condensation zone being established so that no solid is precipitated.

Abstract: In a process for purifying acrylic acid by crystallization by means of vacuum evaporation, a solution which contains acrylic acid and water and may contain further components is crystallized by means of vacuum evaporation with formation of a liquid phase, consisting of a mother liquor containing more than 10% by weight of water and of the crystals, and a vapor phase, the vapor phase is introduced into a liquid material in a condensation zone with formation of a liquid condensation mixture, and the liquid condensation mixture is recycled at least partly to the condensation zone, the operating conditions in the condensation zone being established so that no solid is precipitated.

Abstract: The invention is directed toward preparation of (meth)acrylic acid, comprising condensation of a gas comprising (meth)acrylic acid, absorption with water, and extraction with an aqueous solution forming a miscibility gap.

Abstract: In a process for crystallizing material to be isolated, fluid is vaporized from a melt or a solution comprising the material to be isolated and the fluid and the vaporized fluid is condensed or absorbed in a liquid material to form a liquid mixture, wherein the fluid components to be condensed/absorbed have partial pressures over the liquid mixture which are smaller than the partial pressures of these components over the crystallizing solution/melt and the freezing point of the liquid mixture is lower than the condensation/absorption temperature in the liquid mixture.

Abstract: A process for separating a liquid eutectic mixture by crystallization of one eutectic forming substance of the mixture on a cold surface to which seed crystals of the eutectic forming substance have been applied in the form of a seed crystal layer, and subsequent removal of the eutectic forming substance in liquid form after heating of the surface.