Abstract: The present invention relates to a process for the preparation of solid acylphosphine oxides by converting an acylphosphine oxide which is in the form of a melt or in dispersed form into the solid state of aggregation with mechanical stress, shearing/internal agitation of the melt.

Abstract: A process for heterogeneously catalyzed partial gas phase oxidation of propylene to acrylic acid, in which the starting reaction gas mixture comprises cyclopropane as an impurity and the acrylic acid, after conversion from the product gas mixture into the condensed phase, is removed with the aid of a crystallative removal.

Abstract: A process for operating a hydraulic wash column, in which the position of the buildup front in the wash column is positioned by means of the flow rates of control liquor conducted into the wash column and/or by means of the flow rate of the suspension conducted into the wash column, and the flow rate determination is with the aid of the pressure difference which exists in the column between points in the suspension zone disposed upstream of the buildup front and points in the zone projecting from the buildup front up to the end of the crystal bed.

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: A process for removing methacrylic acid from liquid phase P comprising acrylic acid as a main constituent and target product, and methacrylic acid as a secondary component in which the removal is effected by crystallization, the acrylic acid accumulating in the crystals formed and the methacrylic acid in the remaining mother liquor.

Abstract: A process for removing methacrolein from liquid phase P comprising acrylic acid as a main constituent and target product, and methacrolein as a secondary component in which the removal is effected by crystallization, the acrylic acid accumulating in the crystals formed and the methacrolein in the remaining mother liquor.

Abstract: In a process for preparing acrylic acid, an acrylic acid-containing product gas mixture obtained by catalytic gas phase partial oxidation of a C3 precursor of acrylic acid, after direct cooling with a quench liquid, is fractionally condensed in a separating column provided with internals, rising into itself with sidestream takeoff of crude acrylic acid, and the acrylic acid oligomers which form are dissociated and the resulting dissociation gas is subjected to a countercurrent rectification before it is recycled.

Abstract: Acrylic acid or methacrylic acid is purified by crystallization to obtain crystals and a mother liquor, by a process in which the crystals are washed with a wash liquid containing the acid and having a temperature from 15 to 40° C. Furthermore, a process for the preparation of acrylic acid or methacrylic acid comprises the abovementioned purification process.

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: An apparatus for separating crystals from their suspension in contaminated crystal melt with purification, in which a hydraulic wash column has distributor aids in a distributor space.

Abstract: A process for purifying removal of crystals from their suspension in mother liquor by means of a washing column having forced transport in which the process chamber is encased by a metal wall which, on its side facing away from the process chamber, is heated at least along the length of the pure melt zone.

Abstract: The invention relates to a method for the production of a purified melt of a monomer melt obtained by condensation, absorption or extraction in a crystallizer, wherein the inlet to the crystallizer is subjected to a mechanical solid/liquid separation operation.

Abstract: The invention relates to a method for purifying a raw melt of at least one monomer by crystallization, wherein suspension crystallization is initially used and the resulting remaining melt or the suspension crystals that have been molten once again and separated are subjected to a mechanical separation operation before undergoing subsequent purification by crystallization.

Abstract: In a process for preparing acrylic acid, an acrylic acid-containing product gas mixture obtained by catalytic gas phase partial oxidation of a C3 precursor of acrylic acid, after direct cooling with a quench liquid, is fractionally condensed in a separating column provided with internals, rising into itself with sidestream takeoff of crude acrylic acid, and the acrylic acid oligomers which form are dissociated and the resulting dissociation gas is subjected to a countercurrent rectification before it is recycled.

Abstract: The invention describes a process for the isolation of pure N-vinylpyrrolidone from N-vinylpyrrolidone-containing crude products, comprising a single-stage or multistage crystallization process, which comprises passing the mother liquor from the first crystallization stage either to a distillative and/or extractive purification, or returning it to an N-vinylpyrrolidone-containing product stream of the preparation process.

Abstract: Acrylic acid or methacrylic acid is purified be crystallization to obtain crystals and a mother liquor, by a process in which the crystals are washed with a was liquid containing the acid and having a temperature from 15 to 40° C. Furthermore, a process for the preparation of acrylic acid or methacrylic acid comprises the abovementioned purification process.

Abstract: A process for the production of tablet-shaped granular material from a melt, in which (i) a melt is prepared, (ii) the prepared melt is shaped to droplets, (iii) the droplets are deposited on a cooling surface, and (iv) the deposited droplets solidify to give the granular material, wherein the melt comprises an alcohol, and the melt has a melting point of 30° C. or above.

Abstract: The present invention relates to the use of an optical line detector for regulating the position of the wash front and/or of the build-up front of the crystal bed of a wash column in a melt crystallization process and a corresponding regulation method. The line detector, for example a CCD camera or a linear array of reflection probes, is arranged in such a way that optical properties of the crystal bed can be detected continuously in a region running parallel to the longitudinal axis of the wash column, this region covering the desired setpoint position of the wash front or of the build-up front.

Abstract: The invention describes a process for the isolation of pure N-vinylpyrrolidone from N-vinylpyrrolidone-containing crude products, comprising a single-stage or multistage crystallization process, which comprises passing the mother liquor from the first crystallization stage either to a distillative and/or extractive purification, or returning it to an N-vinylpyrrolidone-containing product stream of the preparation process.

Abstract: Crude acrylic acid is purified batchwise by crystallization by a process which comprises at least one purification stage and at least one stripping stage and in which at least the first stripping stage is carried out in a different crystallizer from the first purification stage.