Abstract: A process for production of acrylic acid includes preparing a product gas mixture by a catalytic gas-phase oxidation of a C3 precursor; cooling and contacting the cooled product gas mixture in an absorption column having at least two cooling loops in countercurrent with an absorbent to obtain an absorbate A, containing the absorbent and absorbed acrylic acid; condensing a high boiler fraction of the product gas mixture in a first cooling loop; condensing a low boiler fraction of the product gas mixture in a second cooling loop; maintaining a temperature of the absorbate A in the second cooling loop at a value of at least 56° C.; removing an acid water stream comprising glyoxal from the absorption column at a side take-off located above the second cooling loop; and removing a stream F of absorbate A from the absorption column at a side take-off, located at a height of the absorption column between the first cooling loop and the second cooling loop.

Abstract: The invention is related to a process for production of acrylic acid comprising the following steps: a) preparation of a product gas mixture by a catalytic gas-phase oxidation of at least one C3 precursor compound to acrylic acid, wherein acrylic acid is formed as a main product of the catalytic gas-phase oxidation and glyoxal is formed as a by-product and the product gas mixture comprises acrylic acid and glyoxal, b) cooling of the product gas mixture, c) contacting the product gas mixture in countercourrent with an absorbent, wherein an absorbate A, comprising the absorbent and absorbed acrylic acid, is formed, d) introducing a feed stream F (2) comprising at least part of the absorbate A into a rectification column comprising a rectifying section and a stripping section, e) enriching the absorbent in the stripping section and enriching acrylic acid in the rectifying section, f) withdrawing a stream C of crude acrylic acid comprising at least 90% by weight of acrylic acid out of the rectifying section as a

Abstract: A process for inhibiting unwanted free-radical polymerization of acrylic acid present in a liquid phase P whose acrylic acid content is at least 10% by weight and which, based on the weight of the acrylic acid present therein, additionally comprises at least 100 ppm by weight of propionic acid and at least 100 ppm by weight of glyoxal, in which at least one chemical compound of the element copper is added to the liquid phase P, and the resulting liquid phases P to which a chemical compound of the element copper has been added.

Abstract: A process for inhibiting unwanted free-radical polymerization of acrylic acid present in a liquid phase P whose acrylic acid content is at least 10% by weight and which, based on the weight of the acrylic acid present therein, additionally comprises at least 100 ppm by weight of propionic acid and at least 100 ppm by weight of glyoxal, in which at least one chemical compound of the element copper is added to the liquid phase P, and the resulting liquid phases P to which a chemical compound of the element copper has been added.

Abstract: A process for transporting a liquid monomer phase which has been withdrawn from a storage vessel and comprises methacrylic monomers to an extent of ?90% by weight, in a tank truck or in a tanker ship, in which the liquid monomer phase is subjected to a separating operation on the route from the storage vessel into the tank of a tank truck or of a tanker ship in order to separate polymer of the monomer present in dissolved form in the liquid monomer phase.

Abstract: A process for preparing oligomers by continuous oligomerization of butenes is described, wherein a) a feed stream 1) comprising 1-butene and 2-butene in a total concentration of from 10 to 70% by weight and from 10 to 60% by weight of isobutane is reacted until more than 60% by weight of the 1-butene comprised in the feed stream 1 but less than 50% by weight of the 2-butene comprised in feed stream 1 have been converted into oligomers. b) The oligomers obtained in a) are separated off and optionally passed to a further work-up and the remaining residual stream is fed to work-up by distillation. c) Isobutane is separated off by distillation from the residual stream, and d) the isobutane-depleted stream obtained after the work-up by distillation c) is reacted to form oligomers.

Abstract: Process for preparing oligomers by continuous oligomerization of butenes, wherein a) a feed stream comprising 1-butene and 2-butene in a total concentration of from 10 to 70% by weight and from 10 to 60% by weight of isobutane is used (hereinafter referred to as feed stream 1), b) this feed stream 1 is reacted until more than 60% by weight of the 1-butene comprised in the feed stream 1 but less than 50% by weight of the 2-butene comprised in feed stream 1 have been converted into oligomers, c) the oligomers obtained in b) are separated off and optionally passed to a further work-up and the remaining residual stream is fed to work-up by distillation, d) isobutane is separated off by distillation from the residual stream, e) the isobutane-depleted stream obtained after the work-up by distillation d) (hereinafter referred to as feed stream 2) is reacted to form oligomers.

Abstract: A process for separating acrylic acid present as a main product and glyoxal present as a by-product in a product gas mixture of a partial gas phase oxidation of a C3 precursor compound, in which a liquid phase P is obtained, which consists of acrylic acid to an extent of at least 70% of its weight and, based on the molar amount of acrylic acid present therein, comprises at least 200 molar ppm of glyoxal, in which the glyoxal is separated from the acrylic acid in the liquid phase P by crystallization.

Abstract: A redissociating apparatus to carry out a process for redissociating Michael adducts which are present in a liquid F with a proportion by weight of ?10% by weight and have been formed in the preparation of acrylic acid or esters thereof is provided. The apparatus comprises a pump P, a separating column K with separating internals and a circulation heat exchanger UW, wherein, for the purpose of supplying the cleavage energy, the pump P sucks in bottoms liquid from the bottom space of the separating column K and, via the circulation heat exchanger UW, continually recycles it into the bottom space above the level of the bottoms liquid, and wherein the pump P is a radial circulation pump with an open impeller.

Abstract: A process for redissociating Michael adducts which are present in a liquid F with a proportion by weight of ?10% by weight and have been formed in the preparation of acrylic acid or esters thereof in a redissociating apparatus which comprises a pump P, a separating column K with separating internals and a circulation heat exchanger UW, wherein, for the purpose of supplying the cleavage energy, the pump P sucks in bottoms liquid from the bottom space of the separating column K and, via the circulation heat exchanger UW, continually recycles it into the bottom space above the level of the bottoms liquid, and wherein the pump P is a radial circulation pump with an open impeller.

Abstract: A process for inhibiting unwanted free-radical polymerization of acrylic acid present in a liquid phase P whose acrylic acid content is at least 10% by weight and which, based on the weight of the acrylic acid present therein, additionally comprises at least 100 ppm by weight of propionic acid and at least 100 ppm by weight of glyoxal, in which at least one chemical compound of the element copper is added to the liquid phase P, and the resulting liquid phases P to which a chemical compound of the element copper has been added.

Abstract: A process for storing a monomer phase which is liquid under the conditions of storage and comprises methacrylic monomers to an extent of ?95% by weight and has been obtained by condensation out of a gaseous phase or by melting a crystalline phase, in a storage vessel, in which polymer of the monomer present in dissolved form in the liquid monomer phase is removed therefrom on the route from its generation into the storage vessel, and also a process for withdrawing liquid monomer phase from the storage vessel in which polymer of the monomer present in dissolved form in the monomer phase is likewise removed.

Abstract: A process for removal of a crude acrylic acid from a product gas mixture which comprises glyoxal as a by-product from a heterogeneously catalyzed partial gas phase oxidation of at least one C3 precursor compound, which comprises the absorption of the acrylic acid in a high-boiling absorbent and the rectificative workup of the resulting adsorbate, and in which absorbent present in the bottoms liquid withdrawn from the bottom space of the absorption column is distilled off in a distillation unit and recycled into the absorption, before high boilers which remain are discharged, and in which the glyoxal content of the crude acrylic acid is reduced by restricting the high boiler residence time in the distillation unit.

Abstract: A process for redissociating Michael adducts which are present in a liquid F with a proportion by weight of ?10% by weight and have been formed in the preparation of acrylic acid or esters thereof in a redissociating apparatus which comprises a pump P, a separating column K with separating internals and a circulation heat exchanger UW, wherein, for the purpose of supplying the cleavage energy, the pump P sucks in bottoms liquid from the bottom space of the separating column K and, via the circulation heat exchanger UW, continually recycles it into the bottom space above the level of the bottoms liquid, and wherein the pump P is a radial circulation pump with an open impeller.

Abstract: A process for separating acrylic acid present as a main product and glyoxal present as a by-product in a product gas mixture of a partial gas phase oxidation of a C3 precursor compound, in which a liquid phase P is obtained, which consists of acrylic acid to an extent of at least 70% of its weight and, based on the molar amount of acrylic acid present therein, comprises at least 200 molar ppm of glyoxal, in which the glyoxal is separated from the acrylic acid in the liquid phase P by crystallization.

Abstract: A process for transferring heat to a liquid F comprising dissolved monomeric acrylic acid, Michael acrylic acid oligomers, and acrylic acid polymer with the aid of an indirect heat exchanger to which are supplied the liquid F with a temperature TF of ?150° C. and a fluid heat carrier W with a temperature of TW>TF, wherein the formation of gas bubbles and/or of thin layers of liquid F adjoining a gas phase is brought about in the liquid F during the flow through the heat exchanger.

Abstract: A process for storing a monomer phase which is liquid under the conditions of storage and comprises methacrylic monomers to an extent of ?95% by weight and has been obtained by condensation out of a gaseous phase or by melting a crystalline phase, in a storage vessel, in which polymer of the monomer present in dissolved form in the liquid monomer phase is removed therefrom on the route from its generation into the storage vessel, and also a process for withdrawing liquid monomer phase from the storage vessel in which polymer of the monomer present in dissolved form in the monomer phase is likewise removed.

Abstract: The invention relates to a composition containing at least one piperidine compound of formula (I) as a stabiliser. In said formula (I) the variables R1, R2, R3, R4, R5, R6, R7, R8, Y and the index n have the meanings cited in claim 1 and the description. Said composition also comprises a polymer component and a colouring agent. The invention further relates to a method for producing pigment-containing polymer compositions and to the use of the compounds of formula (I) as dispersing auxiliary agents.

Abstract: A process for transporting a liquid monomer phase which has been withdrawn from a storage vessel and comprises methacrylic monomers to an extent of ?90% by weight, in a tank truck or in a tanker ship, in which the liquid monomer phase is subjected to a separating operation on the route from the storage vessel into the tank of a tank truck or of a tanker ship in order to separate polymer of the monomer present in dissolved form in the liquid monomer phase.