Abstract:
Proposed is a method for purifying a recycle stream (1) from a system for producing polyarylene ether sulfones by the polycondensation of aromatic bis-halogen compounds and aromatic bisphenols or salts thereof in the presence of at least one alkali metal- or ammonium carbonate or -hydrogen carbonate in an N-alkyl-2-pyrrolidone as a solvent, containing 60 to 90% by weight water, 10 to 40% by weight N-alkyl-2-pyrrolidone and, as a specification-detrimental impurity, up to 5000 ppm by weight of the alkyl succinimide corresponding to the N-alkyl-2-pyrrolidone and, in addition, up to 1000 ppm by weight additional high boilers relative to N-alkyl-2-pyrrolidone, in particular inorganic salts, each relative to the total weight of the recycle stream (1), the sum of the components being 100% by weight, to obtain a purified N-alkyl-2-pyrrolidone stream (2) that can be fed back into the system for producing polyarylene ether sulfones by purification by distillation in a purification column (K). Said method is characterized in that a prepurification step by evaporation in one or more evaporator stages is provided upstream of the purification by distillation in order to reduce the content of inorganic salts, one or more vapor streams (3, 4, 5) being obtained which are fed to the purification column (K) as feed streams. The bottom stream is discharged from the last evaporator stage and the bottom stream from the purification column (K) is entirely recycled into the last evaporator stage. The vapor stream (5) from the last evaporator stage is partially or entirely fed to an additional column (ZK) from which a top stream is removed, which is is fed to the purification column (K), and a bottom stream, which is discharged.
Abstract:
Die vorliegende Erfindung bezieht sich auf ein Verfahren zur Rückgewinnung von Acrylsäure, umfassend die Schritte a) Teilen eines temperierten Muttersäurestroms aus einer Kristallisationsvorrichtung in Richtung einer Absorptionskolonne (201) und in Richtung einer Spaltkolonne (205), b) Zuführen des ersten temperierten Muttersäure-Teilstroms als Rücklauf zu dem obersten Boden der Spaltkolonne (205), c) Zuführen zumindest eines Stripgasstroms unterhalb des untersten Bodens der Spaltkolonne (205), d) Zuführen eines oligomere Acrylsäure umfassenden Nebenkomponentenstroms aus der Kondensationskolonne (201) zu einem mittleren Boden der Spaltkolonne (205), e) Aufspalten zumindest eines Teils der oligomeren Acrylsäure aus dem Nebenkomponentenstrom in der Spaltkolonne (205) unter Erhalt von monomerer Acrylsäure, f) Abtrennen der im Nebenkomponentenstrom enthaltenen Nebenkomponenten durch Gegenstromrektifikation in der aufgesetzten Spaltkolonne (205) g) Abführen der monomeren Acrylsäure ohne Kondensation als Gasgemisch mit dem zugeführten Stripkreisgasstrom am Kopf der Spaltkolonne (205) und h) Zuführen des Gasgemischs unterhalb des untersten Bodens der Kondensationskolonne (201). Die vorliegende Erfindung betrifft ferner eine Anlage (1) zur Rückgewinnung von Acrylsäure.
Abstract:
An aqueous solution comprising acrylic acid and the conjugate base thereof in a total amount of at least 10% by weight, based on the weight of the aqueous solution, and propionic acid and the conjugate base thereof, formic acid and the conjugate base thereof, acetic acid and the conjugate base thereof, benzoic acid and the conjugate base thereof, maleic anhydride, maleic acid and the conjugate bases thereof, phthalic anhydride, phthalic acid and the conjugate bases thereof, acrolein, benzaldehyde, 2-furaldehyde, and at least 20 mol % of at least one alkali metal cation; process for preparing this solution; and the use of this solution for preparation of polymer by free-radical polymerization.
Abstract:
A process for preparing acrylic acid from ethanol and formaldehyde, in which, in a reaction zone A, the ethanol is partially oxidized to acetic acid in a heterogeneously catalyzed gas phase reaction, the product gas mixture A obtained and a formaldehyde source are used to obtain a reaction gas input mixture B which comprises acetic acid and formaldehyde and has the acetic acid in excess over the formaldehyde, and the formaldehyde present in reaction gas input mixture B is aldol-condensed with acetic acid present in reaction gas input mixture B to acrylic acid under heterogeneous catalysis in a reaction zone B, and unconverted acetic acid still present along-side the acrylic acid target product in the product gas mixture B obtained is removed therefrom, and the acetic acid removed is recycled into the production of reaction gas input mixture B.