Abstract: In a process for rectificative isolation of (meth)acrylic acid from a mixture containing, as main components, (meth)acrylic acid and an organic liquid having a higher boiling point than (meth)acrylic acid, the rectification is carried out with the addition of a surfactant.

Abstract: In a process for esterifying (meth)acrylic acid with an alkanol in the presence of an esterification catalyst, in which unconverted starting compounds and (meth)acrylic ester to be formed are separated off by distillation and an oxyester-containing bottom product is formed, the bottom product is first separated off and then the oxyesters contained in it are cleaved in the presence of a relatively long-chain alkylbenzenesulfonic acid at elevated temperatures.

Abstract: Plant parts which are used for the production or processing of (meth)acrylic esters are cleaned by (a) emptying the plant parts, (b) flushing the plant parts with aqueous 5 to 50% strength by weight alkali metal hydroxide solution, (c) removing the alkali metal hydroxide solution from the plant parts, (d) if required, washing the plant parts with water and (e) if required, drying the plant parts.

Abstract: A method is described of stabilizing (meth)acrylic esters against unwanted free-radical polymerization, in which the mixture to be stabilized has added to it a polymerization inhibitor mixture comprising at least one nitroxyl radical and/or at least one organic compound having at least one nitroso group, and at least one p-phenylenediamine.

Abstract: The process for the esterification of (meth)acrylic acid with an alkanol in the presence of an esterification catalyst, in which unconverted starting compounds and the (meth)acrylate to be formed are separated off by distillation and an oxyester-containing bottom product is formed and is separated off, and (a) in the bottom product separated off, the oxyesters present are cleaved, if required after the addition of (meth)acrylic acid and/or oligomeric (meth)acrylic acid, directly in the presence of acid catalysts differing from (meth)acrylic acid and/or oligomeric (meth)acrylic acid, and the cleavage products are removed, a cleavage residue remaining, or (b) the oxyesters are first removed by distillation from the cleavage product separated off, a distillation residue remaining, and the oxyesters removed are cleaved, if required after addition of (meth)acrylic acid and/or oligomeric (meth)acrylic acid, in the presence of acid catalysts differing from (meth)acrylic acid and/or oligomeric (meth)acrylic acid, a

Abstract: Plant parts which are used for the production or processing of (meth)acrylic esters are cleaned by

Abstract: A process for the continuous preparation of acrylates of (meth)acrylic acid by reaction of (meth)acrylic acid with alkanols of 4 to 8 carbon atoms in an esterification zone is proposed, in which the reaction mixture removed from the esterification zone is first fed to a three-stage prepurification and then worked up by rectification for isolating the desired ester.

Abstract: In a process for the preparation of (meth)acrylic acid from a mixture which contains (meth)acrylic acid and a solvent having a boiling point above the boiling point of (meth)acrylic acid by distillation of the mixture in a column which is connected to an evaporator and has a stripping section and a rectifying section, between which the mixture is fed in, and a side take-off for the (meth)acrylic acid, a polymeization inhibitor is fed into the column in the region of the top of the column and in the region of the side take-off, that amount of polymerization inhibitor which is introduced in the region of the top of the column being smaller than the amount introduced in the region of the side take-off.

Abstract: A method for continuous production of (meth)acrylic alkyl esters by reacting (meth)acrylic acid with alkanols containing 1-8 C-atoms, whereby raw (meth)acrylic acid containing acetic acid is used as a starting compound and the alkyl acetate that is formed as a by-product is evacuated in an appropriate area.

Abstract: In a process for esterifying (meth)acrylic acid with an alkanol, oxy ester formed as a byproduct of the esterification is recleaved under acid catalysis with addition of monomeric and/or oligomeric (meth)acrylic acid and water.

Abstract: In a process for the separation by rectification of (meth)acrylic acid from a mixture containing (meth)acrylic acid and an inert hydrophobic organic liquid having a boiling point higher than that of (meth)acrylic acid as main constituents and also lower aldehydes as secondary constituents, a primary amine and/or a salt thereof are added.

Abstract: Crude (meth)acrylic acid is purified by a process in which a primary amine compound and an organic sulfonic acid are added to the crude (meth)acrylic acid and the latter is then worked up by distillation.

Abstract: In a process for the continuous preparation of alkyl esters of (meth)acrylic acid by reacting (meth)acrylic acid with alkanols having from 1 to 8 carbon atoms in a homogeneous, liquid, solvent-free phase at elevated temperature and in the presence of an acid esterification catalyst, in which the (meth)acrylic acid, the alkanol and the acid catalyst are fed to a reaction zone, the water formed is removed by rectification during a residence time as constituent of a mixture comprising starting alkanol in a rectification unit (III) superposed on the reaction zone, the distillate obtained is separated into an organic phase comprising alkanol and an aqueous phase comprising water, the organic phase is essentially completely returned to the rectification unit (III), the reaction mixture is discharged from the reaction zone and conveyed into a distillative separation zone comprising further rectification units and in the latter the alkyl (meth)acrylate formed is separated off.

Abstract: A process for the separation by rectification of (meth)acrylic acid from a mixture containing (meth)acrylic acid and an inert hydrophobic organic liquid having a boiling point higher than that of (meth)acrylic acid as main constituents and also lower aldehydes as secondary constituents, a primary amine and/or a salt thereof are added.

Abstract: In a process and an apparatus for the continuous preparation of alkyl esters of (meth)acrylic acid by reacting (meth)acrylic acid with alkanols having from 1 to 5 carbon atoms in a homogeneous, liquid, solvent-free phase at elevated temperature and in the presence of an acid esterification catalyst, in which the (meth)acrylic acid, the alkanol and the catalyst are fed to a reaction zone, the water formed is removed by rectification during a residence time as constituent of a mixture comprising alkanol in a rectification unit superposed on the reaction zone, the distillate thus obtained is separated into an organic phase comprising alkanol and an aqueous phase comprising water, the organic phase is returned to the rectification unit, the reaction mixture is discharged from the reaction zone and conveyed into a distillative separation zone comprising further rectification units and in the latter the alkyl (meth)acrylate formed is separated off.

Abstract: 4-Acylaminopiperidine N-oxides IaA.sup.1 B.sup.1 (Ia)where A.sup.1 is hydrogen or an organic radical and B.sup.1 is a radical IIa ##STR1## where R.sup.1 -R.sup.4 are each C.sub.1 -C.sub.4 -alkyl and R.sup.1 and R.sup.2, on the one hand, and R.sup.3 and R.sup.4, on the other hand, may furthermore be bonded to form a 5-membered or 6-membered ring,R.sup.5 is H or C.sub.1 14 C.sub.4 -alkyl andR.sup.6 is H or C.sub.1 -C.sub.18 -alkyl,are used for stabilizing organic materials against the harmful effect of free radicals, particularly in the distillation of monomers which undergo free radical polymerization, especially styrene.

Abstract: In a process for esterifying (meth)acrylic acid with an alkanol in the presence of an acidic esterification catalyst, in which unconverted starting compounds and the (meth)acrylates to be formed are separated off by distillation and an oxyester-containing bottom product is formed, the bottom product is separated off and is heated in the presence of an acid to 150-250.degree. C. and the pressure is adjusted so that the cleavage products formed under the abovementioned conditions from the oxyesters contained in the bottom product evaporate directly. The process can be carried out in the presence of molecular oxygen. Mineral acids, for example sulfuric acid or phosphoric acid and/or alkanesulfonic or arylsulfonic acids, for example methanesulfonic acid or p-toluenesulfonic acid, can be added to the bottom product.

Abstract: In the process for the continuous preparation of alkyl esters of (meth)acrylic acid by reacting (meth)acrylic acid with monohydric alkanols having from 1 to 8 carbon atoms in the presence of an acid esterification catalyst in a reaction zone, there is discharged from the reaction zone a product mixture which comprises the alkyl (meth)acrylate formed, the catalyst and the by-products formed during the course of the esterification having boiling points higher than that of the alkyl (meth)acrylate, and from which the alkyl (meth)acrylate is separated by distillation in a separation zone. The product mixture discharged from the reaction zone is fed to a rectification unit (I), in this unit the product mixture discharged is separated by rectification into at least one product (I) comprising the alkyl ester of (meth)acrylic acid and a product (II) comprising the catalyst, the product (I) is fed to a further rectification unit (II) and in this the alkyl ester of (meth)acrylic acid is separated off by rectification.

Abstract: A process is provided for the isolation of (meth)acrylic acid from a mixture containing (meth)acrylic acid as the main component and lower aldehydes as secondary components by rectification in a rectification column having a stripping section and a rectification section, wherein the starting mixture containing the (meth)acrylic acid to be isolated by rectification is not fed directly to the rectification column but is first passed into a heated dwell vessel which is connected to the vapor side of the rectification section of the rectification column and in which the starting mixture is kept at the boil and, instead of the starting mixture as such, the bottom liquid of the dwell vessel is fed to the rectification column.

Abstract: A process for the fractional separation of (meth)acrylic acid from a mixture containing (meth)acrylic acid, in which (meth)acrylic acid is tapped off from the rectifying column at a point above the level at which the liquid mixture containing (meth)acrylic acid enters the rectifying column, and at at least one point of the rectifying column the reflux liquid descending therein is tapped off from the rectifying column, oligomerized and/or polymerized (meth)acrylic acid present therein is separated and the reflux liquid is subsequently recycled to the rectifying column.