Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/42—Separation; Purification; Stabilisation; Use of additives
  • C07C51/48—Separation; Purification; Stabilisation; Use of additives by liquid-liquid treatment

Definitions

• the present invention relates to a process for the extraction of an aqueous solution containing (meth) acrylic acid by contacting it with a solution containing at least one extracting agent which can be converted into (meth) acrylic acid in one or more stages, and with the aqueous Solution forms a mixture gap.
• (meth) acrylic acid used in the context of this application denotes both acrylic acid and methacrylic acid.
• methacrylic acid forms a valuable monomer for the production of polymers, e.g. for aqueous polymer dispersions suitable as adhesives. This also applies to acrylic acid.
• methacrylic acid is accessible by gas phase oxidation of 1-butene, isobutene, isobutyraldehyde, isobutyric acid, isobutene, MTBE and / or methacrolein with oxygen or gases containing oxygen in the presence of catalysts, such as multimetal oxides, which contain the elements molybdenum and vanadium in oxidic form contain.
• the oxidation is carried out at elevated temperature and as a result of the high heat of reaction, preferably by diluting the reactants with inert gases such as N 2 , CO 2 and / or carbon. hydrogen and / or water vapor.
• a reaction gas mixture which, in addition to methacrylic acid, contains the starting materials, e.g. unreacted methacrolein, water vapor, inert diluent gas (e.g. nitrogen), and by-products (e.g. carbon oxides), lower aldehydes such as formaldehyde, high-boiling components. such as citraconic acid, and in particular contains acetic acid, from which the methacrylic acid must subsequently be separated (see, for example, EP-A 253 409 and DE-A 19 62 431).
• starting compounds are also conceivable from which the actual C starting compound, for example methacrolein, only forms intermediately during the gas phase oxidation.
• the methyl ether of tert-butanol (MTBE) may be mentioned as an example.
• Acrylic acid can be obtained analogously starting from the corresponding C 3 compounds, in particular propene and / or acrolein.
• (meth) acrylic acid is to be separated from the reaction gas mixture obtained by extraction
• the reaction gas mixture is first subjected to a condensation stage and then extracted.
• EP-B 345 083 describes a process of this type which comprises a methacrylic acid extraction stage in which methacrylic acid is extracted with a saturated hydrocarbon having 6 to 9 carbon atoms.
• an aqueous methacrylic acid solution obtained by cooling and condensing the reaction gas is obtained by adding an organic solvent, preferably an aliphatic hydrocarbon having 5 to 9 carbon atoms, an aromatic hydrocarbon, an ester or within a process for purifying methacrylic acid a mixture thereof, extracted from the aqueous solution.
• Japanese patent JP 57 095 938 describes the extraction of acrylic acid from a dilute aqueous solution by extraction using an oxygen-containing solvent and a tertiary amine.
• examples include trioctylamine and 2,6-dimethyl-4-heptanol.
• the present invention relates to a process for extracting an aqueous solution containing (meth) acrylic acid by contacting it with a solution containing at least one extracting agent which can be converted into (meth) acrylic acid and forming a mixture gap with the aqueous solution , whereby an organic phase containing (meth) acrylic acid and extracting agent and an aqueous phase is obtained.
• extraction extract includes, as i.a. defined in the claims, all substances which can be converted into (meth) acrylic acid in one or more stages and at the same time form a miscibility gap with the aqueous solution which contains (meth) acrylic acid.
• Alkanes, alkanols, alkenes or alkenals with 3 or 4 carbon atoms or mixtures of two or more thereof, which can be converted into (meth) acrylic acid and form a miscibility gap with the aqueous solution defined above, are to be mentioned in particular.
• the substances which are suitable for this purpose are preferably (meth) acrolein, isobutene, propene, propane, butane, isobutyraldehyde, the methyl ether of tert-butanol (MTBE) or a mixture of two or more thereof.
• (Meth) acrolein is particularly preferably used.
• the solution which contains at least one extractant that can be converted into (meth) acrylic acid, either consists entirely of this extractant or contains it as a mixture with other substances, such as water and / or acetic acid.
• the solution can also have impurities due to the manufacturing process of the components, so it does not have to be cleaned before the extraction.
• This solution can also be mixed with additives which improve the extraction action. Examples include defoamers such as talc fatty alcohol and other polyalcohols, de-emulsifiers such as alkali metal chlorides and surfactants and substances that widen the miscibility gap, such as higher alkanes, especially those with 4 to 14 carbon atoms.
• concentration of the extractant contained in this solution which can be converted into meth (acrylic acid)
• concentration of this extractant in the solution is preferably in a range from approximately 50 to 100% by weight, more preferably approximately Is 70 to about 99.9% by weight, and especially about 90 to about 97% by weight.
• the solution defined above must have a miscibility gap with the aqueous solution containing (meth) acrylic acid.
• the at least one extraction agent contains, which can be converted into (meth) acrylic acid, to use a solution which can be used as a starting material for the (meth) acrylic acid synthesis and preferably contains a concentration of extracting agent from 50 to 100 wt .-%. It is more preferably a solution which contains (meth) acrolein.
• reaction gas mixture obtained by oxidation of the C 3 / C compounds in the first stage which still contains starting material, after condensation thereof, can also be used as a solution which contains at least one extractant, which can be converted into (meth) acrylic acid can be used for the extraction of (meth) acrylic acid.
• the extractant contained in the solution which is to some extent in the aqueous phase after extraction, is preferably recovered by a thermal separation process, e.g. by stripping with water vapor or an intergas, e.g. Nitrogen, air, carbon dioxide, exhaust gas from the (meth) acrylic acid production or a mixture of two or more thereof, or by recovery by distillation.
• the extractant is almost completely converted into the gas phase and can then be used to produce (meth) acrylic acid, if appropriate after passing through further (work-up) steps.
• concentration of (meth) acrylic acid in the aqueous solution there are also no restrictions with regard to the concentration of (meth) acrylic acid in the aqueous solution.
• the content of (meth) acrylic acid in this solution is preferably from about 0.01 to about 80% by weight, more preferably from about 1 to about 40% by weight and in particular from about 5 to about 20% by weight.
• this solution especially if it is obtained industrially from the production of (meth) acrylic acid, can contain a small amount, usually less than about 3% by weight, which is used to prepare (meth) acrylic acid used educt and a small amount, usually less than 10 wt .-%, contain acetic acid.
• an organic phase is obtained during the extraction, which contains (meth) acrylic acid and extractant.
• the extraction is preferably carried out so that the total amount or almost the total amount of (meth) acrylic acid used is in this phase.
• the organic phase contains extractants as well as small amounts of water, acetic acid and high-boiling Components.
• the aqueous phase obtained may still contain small amounts of (meth) acrylic acid, extractant and acetic acid, but most of them can be removed by thermal separation processes.
• the organic phase which contains (meth) acrylic acid and extracting agent
• a thermal separation process such as e.g. stripping with water vapor or an intergas, e.g. Nitrogen, air, carbon dioxide, an exhaust gas, which is formed in the oxidation of the starting materials for the production of (meth) acrylic acid, or a mixture of these intergases, or a distillation of the extractant AVasser mixture.
• an intergas e.g. Nitrogen, air, carbon dioxide, an exhaust gas, which is formed in the oxidation of the starting materials for the production of (meth) acrylic acid, or a mixture of these intergases, or a distillation of the extractant AVasser mixture.
• the (meth) acrylic acid together with the high-boiling constituents and the acetic acid are separated from the predominant part of the extractant and water.
• the temperature at which the method according to the invention can be carried out there are no particular restrictions with regard to the temperature at which the method according to the invention can be carried out. The only requirement is that it is possible at the selected temperature and pressure that two phases, an organic and an aqueous phase, form.
• the process according to the invention is carried out at a temperature of approximately 0 to approximately 150 ° C., preferably approximately 30 to approximately 80 ° C. and in particular approximately 50 to approximately 70 ° C., with (meth) acrolein being used as the extracting agent at temperatures above from about 68 ° C at superatmospheric pressure.
• temperature and / or pressure must be modified depending on this.
• the aqueous solution which contains (meth) acrylic acid and the solution which contains at least one extractant which can be converted into (meth) acrylic acid can be brought into contact with one another either in cocurrent, crosscurrent or countercurrent, wherein contacting in countercurrent is preferred.
• the extraction can be carried out in one or more stages, and combinations of extraction devices can also be used.
• the process according to the invention can be carried out continuously or batchwise, with the continuous procedure being preferred.
• the amount of (meth) acrylic acid to be extracted generally corresponds to the amount of (meth) acrylic acid which was not condensed during the condensation of the reaction mixture obtained directly in the production of (meth) acrylic acid by gas phase oxidation.
• the extractant used for extraction is preferably recovered after going through the extraction.
• thermal separation processes are particularly suitable, such as stripping with steam or an intergas such as nitrogen, air, carbon dioxide, an exhaust gas which is used in the oxidation of the starting materials for production of (meth) acrylic acid, or a mixture of these intergases or the distillation of the extractant / water mixture.
• the stripping process is generally carried out at a temperature of about 30 to about 100 ° C, preferably about 50 to about 80 ° C and a pressure of about 1 to about 1.5 x 10 5 Pa. carried out.
• the temperatures must be modified accordingly for other pressures.
• stripping device there is no particular restriction on the type of stripping device used, and any conventional stripping devices which allow gas-liquid contact, e.g. Packing, sieve tray, bubble tray or spray towers. Further usable spray devices are described under the keyword “absorption column” in EP-A 706 986 in column 3, lines 11 to 38 and the prior art cited therein, which is incorporated by reference in its entirety into the present application.
• the (meth) acrylic acid contained in the organic phase is also recovered by a thermal separation process, preferably by subjecting the organic phase to a stage for the condensation of (meth) acrylic acid.
• a condensate is obtained which contains the main amount of the (meth) acrylic acid in the organic phase and the main amount of acetic acid, while the extracting agent usually contained in the organic phase changes into the gaseous state.
• the organic phase is fed to a thermal separation process which is operated at a temperature at which the above objective, namely the separation of the main amount of (meth) acrylic acid from the main amount of extractant, is achieved.
• solutions used in the present process to avoid or reduce the tendency to polymerize (meth) acrylic acid and / or extracting agent can also be a stabilizer, such as e.g. Phenothiazine, hydroquinone and its derivatives are added.
• the (meth) acrylic acid-water azeotrope can be overcome in a simple manner by adding extraction agents which can be converted to (meth) acrylic acid by means of the process according to the invention. This saves time-consuming, energy-intensive, distillative separation steps. Furthermore, pollution problems caused by the processing of the auxiliary are avoided.
• the organic phase obtained contained the total amount of (meth) acrylic acid introduced and had a concentration of 17.6% by weight. 361 g (meth) acrylic acid were extracted.
• 630 g of aqueous solution with 10.3% by weight of methacrylic acid and 2.2% by weight of acetic acid were extracted in one step with 300 g of an organic methacrolein solution.
• the methacrolein solution contained 7% by weight of water.
• 580 g of aqueous phase with 1.7% by weight of methacrylic acid and 1.2% by weight of acetic acid were obtained.
• the methacrolein solution was loaded with 14.4% by weight methacrylic acid and 1.1% by weight acetic acid in the extraction step.
• Acetic acid was extracted in one step with 212 g of an organic methacrolein solution.
• the methacrolein solution contained 7% by weight of water.
• the methacrolein solution was loaded with 2.9% by weight methacrylic acid and 0.73% by weight acetic acid in the extraction step.
• 328 g of aqueous solution with 0.37% by weight of methacrylic acid and 1.2% by weight of acetic acid were extracted in one stage with 156 g of an organic methacrolein solution.
• the methacrolein solution contained 7% by weight of water.
• 325 g of aqueous phase with 0.06% by weight of methacrylic acid and 0.68% by weight of acetic acid were obtained.
• the methacrolein solution was loaded with 0.65% by weight methacrylic acid and 0.56% by weight acetic acid in the extraction step.
• the second aqueous solution running out of the first settier was brought into contact with a second methacrolein solution running out of a third settier.
• the third aqueous solution running out of the second settler was brought into contact with the first methacroline solution in the third stage.
• 3 kg / h of fourth aqueous phase were obtained from the third settier.
• This fourth aqueous solution contained 0.8% by weight methacrylic acid and 1.5% by weight acetic acid.
• From the first settier 2 kg / h fourth methacrolein solution were obtained.
• This fourth methacrolein solution contained 17.6% by weight of methacrolein and 1.6% by weight of acetic acid.
• phase separation between the aqueous solutions and the methacrol solutions was complete in less than 3 minutes in all examples.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Cosmetics (AREA)

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Cited By (9)

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Citations (4)

• 1997
  • 1997-03-07 DE DE19709392A patent/DE19709392A1/de not_active Withdrawn
• 1998
  • 1998-03-05 AU AU68276/98A patent/AU6827698A/en not_active Abandoned
  • 1998-03-05 CA CA002282492A patent/CA2282492A1/en not_active Abandoned
  • 1998-03-05 ID IDW990963A patent/ID22758A/id unknown
  • 1998-03-05 CN CN98803154A patent/CN1249739A/zh active Pending
  • 1998-03-05 WO PCT/EP1998/001256 patent/WO1998040342A1/de not_active Application Discontinuation
  • 1998-03-05 EP EP98913652A patent/EP0973718A1/de not_active Withdrawn
  • 1998-03-05 JP JP53918298A patent/JP2001514643A/ja active Pending
  • 1998-03-05 BR BR9808158-6A patent/BR9808158A/pt not_active Application Discontinuation
  • 1998-03-05 KR KR1019997008075A patent/KR20000075989A/ko not_active Application Discontinuation
  • 1998-03-06 TW TW087103308A patent/TW438760B/zh active

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