Abstract: A process for extractively removing nickel(0) complexes having phosphorus ligands and/or free phosphorus ligands from a reaction effluent of a hydrocyanation of unsaturated mononitriles to dinitriles by extraction by means of a hydrocarbon, a phase separation of the hydrocarbon and of the reaction effluent into two phases being effected at a temperature T (in ° C.), wherein the content of nickel(0) complexes having phosphorus ligands and/or free phosphorus ligands in the reaction effluent of the hydrocyanation, depending on the temperature T, is at least y % by weight and, irrespective of the temperature T, is a maximum of 60% by weight, where the numerical value of the minimum content y is given by the equation y=0.5·T+20 and T is to be used in the equation as a dimensionless numerical value.

Abstract: A process for extractively removing homogeneously dissolved catalysts from a reaction effluent of a hydrocyanation of unsaturated mononitriles to dinitriles, by extraction by means of a hydrocarbon H, which comprises a) adding a nonpolar aprotic liquid L to the reaction effluent to obtain a stream I, and b) extracting the stream I at a temperature T with the hydrocarbon H to obtain a stream II comprising the hydrocarbon H enriched with the catalyst and a stream III having a low catalyst content.

Abstract: The present invention relates to a process for extracting 2-keto-L-gulonic acid (KGA) from a polar, preferably aqueous, solvent, preferably from a solvent which comprises a mixture of ascorbic acid and 2-keto-L-gulonic acid, by means of liquid/liquid extraction using an extractant which comprises a tertiary amine and a polar organic diluent. The process of the invention preferably also comprises steps for back-extraction of the KGA and recycling of the extractant. The present invention likewise relates to a process for preparing ascorbic acid from KGA and isolating the prepared ascorbic acid.

Abstract: The invention relates to a method for the separation of ascorbic acid from a mixture containing ascorbic acid and 2-keto-L-gulonic acid in a polar, preferably aqueous solvent, by means of liquid/liquid extraction using an amide. The method preferably also comprises steps for the back-extraction of the ascorbic acid, recycling of the extraction solvent and/or the back extraction solvent and for isolation of the ascorbic acid from the back extraction solvent. The invention further relates to a method for the production of ascorbic acid from KGA and isolation of the ascorbic acid so produced.

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.