EP1528961B1 - Method for cleaning apparatus in which organic solvents containing (meth)acrylic acid have been treated and/or produced - Google Patents

Method for cleaning apparatus in which organic solvents containing (meth)acrylic acid have been treated and/or produced Download PDF

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Publication number
EP1528961B1
EP1528961B1 EP03790831A EP03790831A EP1528961B1 EP 1528961 B1 EP1528961 B1 EP 1528961B1 EP 03790831 A EP03790831 A EP 03790831A EP 03790831 A EP03790831 A EP 03790831A EP 1528961 B1 EP1528961 B1 EP 1528961B1
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EP
European Patent Office
Prior art keywords
acrylic acid
column
meth
aqueous
water
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EP03790831A
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German (de)
French (fr)
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EP1528961A1 (en
Inventor
Volker Diehl
Ulrich JÄGER
Jürgen Schröder
Joachim Thiel
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BASF SE
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BASF SE
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B9/00—Cleaning hollow articles by methods or apparatus specially adapted thereto 
    • B08B9/02—Cleaning pipes or tubes or systems of pipes or tubes
    • B08B9/027—Cleaning the internal surfaces; Removal of blockages
    • B08B9/032—Cleaning the internal surfaces; Removal of blockages by the mechanical action of a moving fluid, e.g. by flushing
    • B08B9/0321—Cleaning the internal surfaces; Removal of blockages by the mechanical action of a moving fluid, e.g. by flushing using pressurised, pulsating or purging fluid
    • B08B9/0323—Arrangements specially designed for simultaneous and parallel cleaning of a plurality of conduits
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
    • B08B3/04—Cleaning involving contact with liquid
    • B08B3/08—Cleaning involving contact with liquid the liquid having chemical or dissolving effect
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B9/00—Cleaning hollow articles by methods or apparatus specially adapted thereto 
    • B08B9/02—Cleaning pipes or tubes or systems of pipes or tubes
    • B08B9/027—Cleaning the internal surfaces; Removal of blockages
    • B08B9/032—Cleaning the internal surfaces; Removal of blockages by the mechanical action of a moving fluid, e.g. by flushing
    • B08B9/0321—Cleaning the internal surfaces; Removal of blockages by the mechanical action of a moving fluid, e.g. by flushing using pressurised, pulsating or purging fluid
    • B08B9/0327—Cleaning the internal surfaces; Removal of blockages by the mechanical action of a moving fluid, e.g. by flushing using pressurised, pulsating or purging fluid the fluid being in the form of a mist

Definitions

  • the present invention relates to a process for purifying apparatus in which (meth) acrylic acid-containing organic solvents have been treated and / or produced and which contain undesired fouling and / or polymer and organic solvent residues.
  • (Meth) acrylic acid is particularly suitable for the preparation of polymers for a variety of applications, e.g. Use as adhesives, of importance.
  • (Meth) acrylic acid itself is obtainable primarily by heterogeneously catalyzed gas-phase oxidation of alkanes, alkanols, alkenes or alkenals which contain 3 or 4 C atoms.
  • Particularly advantageous is (meth) acrylic acid, e.g. by catalytic gas-phase oxidation of propane, propene, acrolein, tert-butanol, isobutene, isobutane, isobutyraldehyde or methacrolein.
  • these starting gases usually diluted with inert gases such as nitrogen, CO 2 , saturated hydrocarbons and / or water vapor, in admixture with oxygen at elevated temperatures (usually 200 to 400 ° C) and optionally elevated pressure via transition metal (eg Mo, V, W and / or Fe-containing) mixed oxide catalysts and oxidatively converted into (meth) acrylic acid (cf., for example, DE-A 4405059, EP-A 253409, EP-A 92097, DE-A 4431957 and DE-A 4431949).
  • inert gases such as nitrogen, CO 2 , saturated hydrocarbons and / or water vapor
  • the separation of (meth) acrylic acid usually takes place via absorptive, extractive, desorptive and / or rectificative separation processes with the concomitant use of organic solvents in a wide variety of apparatuses.
  • the formed (meth) acrylic acid from the reaction gas mixture of the gas phase oxidation optionally after indirect and / or direct cooling with an optionally organic solvent, first in a suitable absorbent (for example, water or, preferably high-boiling, organic solvent) is absorbed.
  • a suitable absorbent for example, water or, preferably high-boiling, organic solvent
  • desorptive, extractive and / or rectificative separation of the absorbate is then usually obtained a (meth) acrylic acid of high purity.
  • DE-A 4436243 relates, for example, to a process for the separation of (meth) acrylic acid from the reaction gas mixture of the catalytic gas phase oxidation by countercurrent absorption with a high-boiling inert organic liquid, in which the reaction gas mixture is passed in an absorption column to the descending high-boiling inert hydrophobic organic liquid in countercurrent in that the absorption process naturally undergoes a rectification process in the absorption column by removing from the absorption column an amount of energy exceeding its natural energy output due to its contact with the ambient temperature and from the (meth) acrylic acid and the absorbent (main) containing liquid effluent of the absorption column (absorbate) separates the (meth) acrylic acid over the top rectifying.
  • DE-A 4436243 hereby prefers all those organic liquids whose boiling point at normal pressure (1 atm) is above the boiling point of (meth) acrylic acid and which is at least 70% by weight of such molecules which do not contain an outward-acting polar group and thus are, for example, unable to form hydrogen bonds.
  • EP-A 117146 relates to a process for the separation of acrylic acid from the reaction gas mixture of the catalytic gas phase oxidation by absorbing the acrylic acid in a water-operated absorption column. By extraction with ethyl acetate the acrylic acid is separated from the liquid effluent and rectified from the extract acrylic acid over the bottom.
  • DE-A 19606877 discloses first to cool the reaction gas mixture containing acrylic acid from the gas-phase oxidation of propene and / or propane by partial evaporation of a high-boiling organic solvent in a direct condenser K9.
  • a direct condenser K9 the high-boiling secondary components of the reaction gas mixture condense in the non-evaporated solvent.
  • a partial flow from the direct condenser (quench) K9 is subjected to a solvent distillation, wherein the solvent is distilled over and the high-boiling secondary components remain.
  • the latter can be further thickened and disposed of, e.g. to be burned.
  • a column K10 which is preferably a valve-bottom column or a combination of valve trays (top) and a few dual-flow trays (in the lowest part of the column), is charged from above with the same solvent, while the in K9 evaporated solvent and the gaseous reaction product are introduced from below into the column K10 and then cooled to absorption temperature.
  • the cooling is expediently carried out by the absorption column reflux, which passes through external cooling circuits. After the reaction gas stream has cooled to the absorption temperature, the actual absorption takes place. In this case, the acrylic acid contained in the reaction gas and a part of the low-boiling secondary components are absorbed.
  • the unabsorbed, remaining reaction gas is further cooled to condense contained therein, relatively difficult to condense secondary components and water vapor contained and separate as sour water.
  • the then still remaining gas stream is advantageously partially disposed of and partially recirculated (circulating gas) as a diluent gas in the gas phase oxidation or used for stripping. From the bottom of the column K10, the solvent loaded with acrylic acid and secondary components is withdrawn and fed to a desorption column K20.
  • the low boilers which are contained in the cycle gas used as stripping gas are removed before it enters the K20.
  • a nearly low boiler-free, acrylic acid-laden solvent stream is withdrawn from the bottom of the desorption column K20 and the distillation column K30, which is preferably a dual-flow tray column, fed.
  • the distillation column K30 In the bottom of the column K30 condenses the high boiling solvent and minor components such. Maleic anhydride.
  • this low boiler fraction is advantageously reduced by extending the buoyancy part of the column K30 so far that the acrylic acid can be withdrawn as side draw from the column.
  • the lightly high-boiling stream drawn off at the top of the column K30, because it still contains acrylic acid, is advantageously returned to the absorption column K10.
  • the solvent substantially free of low-boiling components and of acrylic acid withdrawn from the bottom of the rectification column K30 is for the most part fed to the countercurrent washing column K19 in order, as already mentioned above, to wash the low-boiling components from the stripping gas stream which leads into the desorption column K20 , Subsequently, the solvent which is virtually free of acrylic acid, except for a small partial stream, is returned to the absorption column K10.
  • the small partial stream of the solvent, which is virtually free of acrylic acid the sour water, which still contains dissolved acrylic acid, is treated extractively. In this sour water extraction, a portion of the acrylic acid is recovered from the sour water, while at the same time the sour water extracts all polar components from the solvent substream. The remaining acid water can be pre-evaporated and then burned.
  • acrylic acid standard separation In the context of this standard separation, all columns used can also be dual-flow tray columns.
  • high-boiling organic solvents are suitable for the acrylic acid standard separation especially Mixtures of diphenyl ether (70 to 75 wt .-%) and diphenyl (25 to 30 wt .-%).
  • a particularly favorable high-boiling hydrophobic organic absorption liquid in this process is a mixture consisting of a mixture of 70 to 75% by weight of diphenyl ether and 25 to 30% by weight. Diphenyl, and, based on this mixture, 0.1 to 25 wt .-% o-dimethyl phthalate. In principle, however, it is also possible to use all other high-boiling organic liquids recommended in EP-A 722,926.
  • These apparatuses are, in particular, rectification columns, absorption columns, desorption columns and extraction columns.
  • columns usually columns are generally used with a variety of internals.
  • Such internals are e.g. Floors (such as dual-flow trays, sieve trays, valve trays, Thormann trays, tunnel trays and / or bubble trays), packs, Raschig rings and / or Pall rings.
  • Evaporators act as indispensable for the thermal separation processes and e.g. in EP-A 854120 or to capacitors or mixing devices.
  • (meth) acrylic acid even in the presence of polymerization inhibitors, e.g. N-oxyl radicals, phenothiazine, monomethyl ether of hydroquinone, hydroquinone, etc., especially in the liquid phase has a pronounced tendency to polymerize. This is particularly disadvantageous in the case of thermal separation processes, in which the (meth) acrylic acid monomers are exposed to comparatively high temperature loads.
  • polymerization inhibitors e.g. N-oxyl radicals, phenothiazine, monomethyl ether of hydroquinone, hydroquinone, etc.
  • DE-A 10213027 therefore recommends extractively removing from the fouling and / or polymer the residues of the organic solvent present in the same by means of (meth) acrylic acid from the same and the mixture of (meth) acrylic acid and residues of the organic solvent in the process the separation of the (meth) acrylic acid from the reaction gas mixture of the gas phase oxidation.
  • DE-A 10213027 recommends, in the event that the apparatus to be cleaned is a column, to pass a gas through the column in countercurrent to the rinsing liquid then conducted in descending direction (for example air or nitrogen or steam), water vapor is only then used as the same recommended if the rinse liquid itself is watery. However, the latter is only after extraction with (meth) acrylic acid, i. after removal of the residues of the organic solvent of the case.
  • a disadvantage of the aforementioned procedure is that the steam distillation and the rinsing are performed spatially separated with water.
  • a steam distillation of the apparatus contents contained in the apparatus is to be understood as meaning all processes in which, on the one hand, water vapor is generated in the apparatus to be cleaned and / or steam is supplied to the apparatus to be cleaned and, on the other hand, vapor phase is removed from the apparatus to be cleaned.
  • the apparatus normally drained to the formed fouling and / or polymer and organic solvent residues and small amounts of (meth) acrylic acid, is treated with water or an aqueous basic solution (i.e., with an aqueous rinsing liquid), e.g. an aqueous alkali hydroxide solution (preferably sodium hydroxide and / or potassium hydroxide), is filled (in particular columns is usually only partially filled, the amount is usually sized so that evaporator and pumps are operable), which may be preheated. Subsequently, the aqueous phase is added e.g. brought to boiling and thus the formation of water vapor by suitable heat exchangers and / or heated steam passed into the apparatus.
  • an aqueous basic solution i.e., with an aqueous rinsing liquid
  • an aqueous alkali hydroxide solution preferably sodium hydroxide and / or potassium hydroxide
  • the organic phase essentially consists of the organic solvent which, for example, can again be supplied to the separation of the (meth) acrylic acid from the product gas mixture of the gas-phase oxidation (for example, it can be recycled to the absorption column K10 in the standard acrylic acid separation below the supply of fresh absorbent , which reduces solvent losses).
  • the aqueous phase consists essentially of water. It can e.g.
  • the apparatus to be purified is a separation column (e.g., a rectification column), the aqueous phase may be recycled to the column as reflux) and / or supplied to the steam generator outside the apparatus to be cleaned.
  • a separation column e.g., a rectification column
  • the steam distillation according to the invention can be carried out in an extreme case, however, so that it passes through the emptied to be cleaned apparatus only hot water vapor.
  • the vapor phase removed from the apparatus can be treated in the same way as described above, ie condensed and separated into two phases.
  • the steam distillation according to the invention will be terminated when the vapor phase removed from the apparatus to be cleaned is largely or completely free of organic solvent. This is often the case for a period of application of the method according to the invention of 1 to 20 hours.
  • the case of the apparatus over the entire course taken vapor phase based on the capacity of the apparatus with water, 0.5 to 5 tons, often 1 to 2 tons per ton of capacity.
  • the filling amount is the amount that would be needed to completely fill the emptied apparatus with water.
  • aqueous rinsing liquid also removed from the apparatus to be cleaned and, optionally after heating outside of the apparatus to be cleaned (eg in a suitable heat exchanger), returned to the apparatus to be cleaned and so by the apparatus to be cleaned continuously be circulated.
  • aqueous rinsing liquid also removed from the apparatus to be cleaned and, optionally after heating outside of the apparatus to be cleaned (eg in a suitable heat exchanger), returned to the apparatus to be cleaned and so by the apparatus to be cleaned continuously be circulated.
  • aqueous rinsing liquid also removed from the apparatus to be cleaned and, optionally after heating outside of the apparatus to be cleaned (eg in a suitable heat exchanger), returned to the apparatus to be cleaned and so by the apparatus to be cleaned continuously be circulated.
  • For pumping pumps are used.
  • water vapor is supplied to the apparatus to be cleaned when carrying out the process according to the invention, its pressure, in particular when the apparatus to be purified is a separation column, is advantageously 1.0 to 16 bar, frequently 1.1 to 4 bar.
  • Saturated steam is preferably used as the steam. Saturated steam means that the water partial pressure makes up at least 99% of the total pressure.
  • aqueous rinsing liquid As basic aqueous rinsing liquid, all those which are also recommended by DE-A 19746688, DE-A 19536179, DE-A 1033359, DE-A 10211273 and DE-A 10213027 can be used for the process according to the invention.
  • aqueous alkali metal and / or alkaline earth metal hydroxide and / or oxide solutions these are in particular aqueous alkali metal and / or alkaline earth metal hydroxide and / or oxide solutions, above all, as already mentioned, the aqueous solutions of NaOH, KOH and Ca (OH) 2 .
  • the aqueous solution has a dissolved salt content of from 0.01 to 30% by weight, preferably from 0.5 to 10% by weight.
  • the aforementioned basic aqueous alkali solution in the ratio of> 0: 1 to 2: 1 is a substantially pH-neutral (based on its aqueous solution) and alkali / or alkaline earth salt added.
  • Particularly suitable for this purpose are the sulfates, acetates, oxalates, carbonates corresponding to the hydroxide / oxidic compounds. Hydrogen sulfates, bicarbonates and / or other salts.
  • an aqueous rinsing liquid is expediently used in the process according to the invention and if the point in time at which the vapor phase removed from the apparatus to be cleaned is substantially or completely free of organic substances is removed, the aqueous rinsing liquid is discarded and disposed of as described in the DE-OS. A 10211273 or DE-A 10213027 described.
  • an aqueous rinsing liquid used in this way can be renewed from time to time and / or exchanged for another aqueous rinsing liquid.
  • it expediently has boiling point.
  • the apparatus to be cleaned is usually rinsed with water (with prior use of alkali is rinsed alkali-free).
  • the inventive method can be carried out both at regular intervals as well as after detection of a specific formation of polymer.
  • the process according to the invention is particularly suitable when the boiling point of the organic solvent is above the boiling point of water (both at 1 atm). That is, it is particularly suitable when it is a high-boiling, preferably hydrophobic, organic absorption liquid, as recommended in DE-A 2136396 and DE-A 4308087. These are essentially liquids whose boiling point at normal pressure (1 atm) is above 160 ° C. Examples include middle oil fractions from the Paraffugillation, diphenyl ether, diphenyl or mixtures of the aforementioned liquids, such as a mixture of 70 to 75 wt .-% diphenyl ether and 25 to 30 wt .-% diphenyl.
  • the (meth) acrylic acid content of the (meth) acrylic acid-containing organic solvent may be ⁇ 5% by weight, or ⁇ 10% by weight, or ⁇ 25% by weight. , or ⁇ 35 wt .-%, or ⁇ 50 wt .-%, or ⁇ 65 wt .-%, or ⁇ 80 wt .-%, or ⁇ 90 wt .-%, or ⁇ 95 wt .-%, based to the solution.
  • this content is ⁇ 90% by weight, or ⁇ 80% by weight, or ⁇ 65% by weight.
  • Suitable apparatuses to be cleaned according to the invention are all apparatuses already mentioned in the document. This is especially true if they are made of stainless steel with the material number 1.4541 or 1.4571 (see standard DIN EN 10020).
  • the process of the invention is applicable to any form of separation columns (absorption, desorption, extraction and rectification columns).
  • separation columns may be tray columns, (e.g., bell, Thormann®, sieve, tunnel, dual-flow or valve trays), packed columns (with Raschig rings or with pall rings) or packed columns.
  • tray columns e.g., bell, Thormann®, sieve, tunnel, dual-flow or valve trays
  • packed columns with Raschig rings or with pall rings
  • packed columns with Raschig rings or with pall rings
  • the process according to the invention can be carried out in the apparatuses to be cleaned at reduced pressure (for example 10 to 100 mbar), elevated pressure or under other conditions.
  • the process according to the invention is expediently carried out by passing an aqueous basic rinse solution through the tray column from top to bottom and passing water vapor through the tray column in countercurrent to the rinsing solution in such a way that the Difference between the pressure in the vapor phase immediately below the bottom of the tray column and the vapor pressure immediately above the top tray, divided by the number of trays in the tray at least 0.5 mbar, often 0.5 to 6 mbar or 1 to 5 mbar, per floor.
  • the bubble layers thus produced cause an improved cleaning effect.
  • the rinse solution is removed from the column bottom expediently continuously and fed back via the return line of the tray column. Their temperature is in their boiling point.
  • the pressure in the vapor phase "immediately" below the lowest or above the uppermost bottom of the tray column in this document means that the measuring point should not be more than 15 cm below the bottom and at least 25 cm above the top soil.
  • the pressure measurement may e.g. via open tapping, in which a transmitter is connected via a wall socket with the column.
  • the advantage of the method according to the invention lies in the fact that the organic load of a co-used or subsequently applied aqueous rinse solution is so low that it can be fed directly to a sewage treatment plant for the purpose of aerobic degradation of the organic cargo.
  • the content of organic solvent is usually well below 100 ppm by weight. If final rinsing with water, the resulting wash water can usually be delivered directly into the natural environment.

Abstract

A process for cleaning apparatus in which (meth)acrylic acid-containing organic solvents have been treated and/or generated and contain fouling and/or polymer and residues of organic solvent, in which the apparatus contents are subjected to a steam distillation in the apparatus.

Description

Vorliegende Erfindung betrifft ein Verfahren zur Reinigung von Apparaten, in welchen (Meth)acrylsäure enthaltende organische Lösungsmittel behandelt und/oder erzeugt wurden und die in unerwünschter Weise gebildetes Fouling und/oder Polymerisat und Reste des organischen Lösungsmittels enthalten.The present invention relates to a process for purifying apparatus in which (meth) acrylic acid-containing organic solvents have been treated and / or produced and which contain undesired fouling and / or polymer and organic solvent residues.

(Meth)acrylsäure wird in dieser Schrift als verkürzte Schreibweise verwendet und steht für Acrylsäure oder Methacrylsäure.(Meth) acrylic acid is used in this document as a shortened notation and stands for acrylic acid or methacrylic acid.

(Meth)acrylsäure, entweder für sich oder in Form ihrer Ester, ist insbesondere zur Herstellung von Polymerisaten für die verschiedensten Anwendungsgebiete, z.B. Verwendung als Klebstoffe, von Bedeutung.(Meth) acrylic acid, either alone or in the form of their esters, is particularly suitable for the preparation of polymers for a variety of applications, e.g. Use as adhesives, of importance.

(Meth)acrylsäure selbst ist vornehmlich durch heterogen katalysierte Gasphasenoxidation von Alkanen, Alkanolen, Alkenen oder Alkenalen erhältlich, die 3 bzw. 4 C-Atome enthalten. Besonders vorteilhaft ist (Meth)acrylsäure z.B. durch katalytische Gasphasenoxidation von Propan, Propen, Acrolein, tert.-Butanol, isoButen, iso-Butan, iso-Butyraldehyd oder Methacrolein erhältlich.(Meth) acrylic acid itself is obtainable primarily by heterogeneously catalyzed gas-phase oxidation of alkanes, alkanols, alkenes or alkenals which contain 3 or 4 C atoms. Particularly advantageous is (meth) acrylic acid, e.g. by catalytic gas-phase oxidation of propane, propene, acrolein, tert-butanol, isobutene, isobutane, isobutyraldehyde or methacrolein.

Als Ausgangsverbindungen sind aber auch solche denkbar, aus welchen sich die eigentliche C3-/C4-Ausgangsverbindung während der Gasphasenoxidation erst intermediär bildet. Beispielhaft genannt sei der Methylether des tert.-Butanols.However, as starting compounds, those are also conceivable from which the actual C 3 - / C 4 starting compound first forms as an intermediate during the gas-phase oxidation. By way of example, the methyl ether of tert-butanol may be mentioned.

Dabei werden diese Ausgangsgase, in der Regel mit inerten Gasen wie Stickstoff, CO2, gesättigten Kohlenwasserstoffen und/oder Wasserdampf verdünnt, im Gemisch mit Sauerstoff bei erhöhten Temperaturen (üblicherweise 200 bis 400°C) sowie gegebenenfalls erhöhtem Druck über übergangsmetallische (z.B. Mo, V, W und/oder Fe enthaltende) Mischoxidkatalysatoren geleitet und oxidativ in (Meth)acrylsäure umgewandelt (vgl. z.B. DE-A 4405059, EP-A 253409, EP-A 92097, DE-A 4431957 und DE-A 4431949).In this case, these starting gases, usually diluted with inert gases such as nitrogen, CO 2 , saturated hydrocarbons and / or water vapor, in admixture with oxygen at elevated temperatures (usually 200 to 400 ° C) and optionally elevated pressure via transition metal (eg Mo, V, W and / or Fe-containing) mixed oxide catalysts and oxidatively converted into (meth) acrylic acid (cf., for example, DE-A 4405059, EP-A 253409, EP-A 92097, DE-A 4431957 and DE-A 4431949).

Aufgrund zahlreicher im Verlauf der katalytischen Gasphasenoxidation erfolgender Parallel- und Folgereaktionen sowie aufgrund der mitzuverwendenden inerten Verdünnungsgase wird bei der katalytischen Gasphasenoxidation jedoch keine reine (Meth)acrylsäure, sondern ein Reaktionsgasgemisch erhalten, das im wesentlichen (Meth)acrylsäure, die inerten Verdünnungsgase und Nebenprodukte enthält, aus welchem die (Meth)acrylsäure abgetrennt werden muß.Due to numerous parallel and subsequent reactions occurring in the course of the catalytic gas phase oxidation and due to the inert diluent gases to be used, however, in the catalytic gas phase oxidation no pure (meth) acrylic acid is obtained, but essentially a reaction gas mixture (Meth) acrylic acid containing inert diluent gases and by-products from which the (meth) acrylic acid must be separated.

Üblicherweise erfolgt die Abtrennung der (Meth)acrylsäure über absorptive, extraktive, desorptive und/oder rektifikative Trennverfahren unter Mitverwendung organischer Lösungsmittel in unterschiedlichsten Apparaten.The separation of (meth) acrylic acid usually takes place via absorptive, extractive, desorptive and / or rectificative separation processes with the concomitant use of organic solvents in a wide variety of apparatuses.

In der Regel wird die gebildete (Meth)acrylsäure aus dem Reaktionsgasgemisch der Gasphasenoxidation, gegebenenfalls nach indirekter und/oder direkter Kühlung mit einem gegebenenfalls organischen Lösungsmittel, zunächst in ein geeignetes Absorptionsmittel (z.B. Wasser oder ein, bevorzugt hochsiedendes, organisches Lösungsmittel) absorbiert. Durch desorptive, extraktive und/oder rektifikative Auftrennung des Absorbats wird dann üblicherweise eine (Meth)acrylsäure hoher Reinheit erhalten.In general, the formed (meth) acrylic acid from the reaction gas mixture of the gas phase oxidation, optionally after indirect and / or direct cooling with an optionally organic solvent, first in a suitable absorbent (for example, water or, preferably high-boiling, organic solvent) is absorbed. By desorptive, extractive and / or rectificative separation of the absorbate is then usually obtained a (meth) acrylic acid of high purity.

Die DE-A 4436243 betrifft beispielsweise ein Verfahren zur Abtrennung von (Meth)acrylsäure aus dem Reaktionsgasgemisch der katalytischen Gasphasenoxidation durch Gegenstromabsorption mit einer hochsiedenden inerten organischen Flüssigkeit, bei dem man das Reaktionsgasgemisch in einer Absorptionskolonne zu der absteigenden hochsiedenden inerten hydrophoben organischen Flüssigkeit im Gegenstrom führt, dem in der Absorptionskolonne in natürlicher Weise erfolgenden Absorptionsprozeß einen Rektifikationsprozeß überlagert, indem man der Absorptionskolonne eine über ihre, aufgrund ihres Kontaktes mit der Umgebungstemperatur erfolgende, natürliche Energieabgabe hinausgehende Energiemenge entzieht und aus dem (Meth)acrylsäure und das Absorptionsmittel (Absorgens) als Hauptbestandteile enthaltenden Flüssigkeitsablauf der Absorptionskolonne (Absorbat) die (Meth)acrylsäure über Kopf rektifikativ abtrennt.DE-A 4436243 relates, for example, to a process for the separation of (meth) acrylic acid from the reaction gas mixture of the catalytic gas phase oxidation by countercurrent absorption with a high-boiling inert organic liquid, in which the reaction gas mixture is passed in an absorption column to the descending high-boiling inert hydrophobic organic liquid in countercurrent in that the absorption process naturally undergoes a rectification process in the absorption column by removing from the absorption column an amount of energy exceeding its natural energy output due to its contact with the ambient temperature and from the (meth) acrylic acid and the absorbent (main) containing liquid effluent of the absorption column (absorbate) separates the (meth) acrylic acid over the top rectifying.

Als hochsiedende inerte hydrophobe organische Flüssigkeit (Absorbens) bevorzugt die DE-A 4436243 dabei alle diejenigen organischen Flüssigkeiten, deren Siedepunkt bei Normaldruck (1 atm) oberhalb der Siedetemperatur der (Meth)acrylsäure liegt und die zu wenigstens 70 Gew.-% aus solchen Molekülen bestehen, die keine nach außen wirkende polare Gruppe enthalten und somit beispielsweise nicht in der Lage sind, Wasserstoffbrücken zu bilden.As high-boiling inert hydrophobic organic liquid (absorbent), DE-A 4436243 hereby prefers all those organic liquids whose boiling point at normal pressure (1 atm) is above the boiling point of (meth) acrylic acid and which is at least 70% by weight of such molecules which do not contain an outward-acting polar group and thus are, for example, unable to form hydrogen bonds.

Die EP-A 117146 betrifft ein Verfahren zur Abtrennung von Acrylsäure aus dem Reaktionsgasgemisch der katalytischen Gasphasenoxidation durch Absorbieren der Acrylsäure in einer mit Wasser betriebenen Absorptionskolonne. Durch Extraktion mit Ethylacetat wird die Acrylsäure aus dem Flüssigkeitsablauf abgetrennt und aus dem Extrakt Acrylsäure über Sumpf rektifikativ gewonnen.EP-A 117146 relates to a process for the separation of acrylic acid from the reaction gas mixture of the catalytic gas phase oxidation by absorbing the acrylic acid in a water-operated absorption column. By extraction with ethyl acetate the acrylic acid is separated from the liquid effluent and rectified from the extract acrylic acid over the bottom.

Die DE-A 19606877 offenbart, das aus der Gasphasenoxidation von Propen und/oder Propan kommende, Acrylsäure enthaltende, Reaktionsgasgemisch durch Teilverdampfen eines hochsiedenden organischen Lösungsmittels in einem Direktkondensator K9 zunächst zu kühlen. Hierbei kondensieren die schwersiedenden Nebenkomponenten des Reaktionsgasgemisches in das nicht verdampfte Lösungsmittel. Ein Teilstrom aus dem Direktkondensator (Quench) K9 wird einer Lösungsmitteldestillation unterzogen, wobei das Lösungsmittel überdestilliert wird und die schwersiedenden Nebenkomponenten zurückbleiben. Letztere können weiter eingedickt und entsorgt, z.B. verbrannt werden.DE-A 19606877 discloses first to cool the reaction gas mixture containing acrylic acid from the gas-phase oxidation of propene and / or propane by partial evaporation of a high-boiling organic solvent in a direct condenser K9. In this case, the high-boiling secondary components of the reaction gas mixture condense in the non-evaporated solvent. A partial flow from the direct condenser (quench) K9 is subjected to a solvent distillation, wherein the solvent is distilled over and the high-boiling secondary components remain. The latter can be further thickened and disposed of, e.g. to be burned.

Eine Kolonne K10, bei der es sich vorzugsweise um eine Ventilboden-Kolonne bzw. um eine Kombination aus Ventilböden (oben) und wenigen Dual-Flow-Boden (im untersten Bereich der Kolonne) handelt, wird von oben mit demselben Lösungsmittel beaufschlagt, während das in K9 verdampfte Lösungsmittel und das gasförmige Reaktionsprodukt von unten in die Kolonne K10 eingeleitet und anschließend auf Absorptionstemperatur abgekühlt werden. Die Abkühlung erfolgt zweckmäßig durch der Absorptionskolonne entnommenen Rücklauf, der externe Kühlkreise durchläuft. Nachdem der Reaktionsgasstrom auf die Absortionstemperatur abgekühlt ist, erfolgt die eigentliche Absorption. Dabei werden die im Reaktionsgas enthaltene Acrylsäure sowie ein Teil der leichtsiedenden Nebenkomponenten absorbiert. Das nicht absorbierte, verbleibende Reaktionsgas wird weiter abgekühlt, um darin enthaltene, vergleichsweise schwer kondensierbare Nebenkomponenten sowie enthaltenen Wasserdampf zu kondensieren und als Sauerwaser abzutrennen. Der dann noch verbleibende Gasstrom wird vorteilhaft teilweise entsorgt und teilweise (Kreisgas) als Verdünnungsgas in die Gasphasenoxidation rückgeführt oder zum Strippen verwendet. Aus dem Sumpf der Kolonne K10 wird das mit Acrylsäure und Nebenkomponenten beladene Lösungsmittel abgezogen und einer Desorptionskolonne K20 zugeführt.A column K10, which is preferably a valve-bottom column or a combination of valve trays (top) and a few dual-flow trays (in the lowest part of the column), is charged from above with the same solvent, while the in K9 evaporated solvent and the gaseous reaction product are introduced from below into the column K10 and then cooled to absorption temperature. The cooling is expediently carried out by the absorption column reflux, which passes through external cooling circuits. After the reaction gas stream has cooled to the absorption temperature, the actual absorption takes place. In this case, the acrylic acid contained in the reaction gas and a part of the low-boiling secondary components are absorbed. The unabsorbed, remaining reaction gas is further cooled to condense contained therein, relatively difficult to condense secondary components and water vapor contained and separate as sour water. The then still remaining gas stream is advantageously partially disposed of and partially recirculated (circulating gas) as a diluent gas in the gas phase oxidation or used for stripping. From the bottom of the column K10, the solvent loaded with acrylic acid and secondary components is withdrawn and fed to a desorption column K20.

In der Desorptionskolonne K20 wird der größte Teil der Leichtsieder mit einem Teil des Kreisgases aus dem beladenen Lösungsmittel gestrippt. Da hierbei auch größere Mengen an Acrylsäure mitgestrippt werden, wird dieser Strom in zweckmäßiger Weise wieder in den Direktkondensator K9 rezirkuliert oder dem unteren Teil der Kolonne K10 unterhalb des Frischlösungsmittelzulaufs zugeführt.In the desorption column K20 most of the low boilers are stripped with a portion of the circulating gas from the loaded solvent. Since in this case larger amounts of acrylic acid are also stripped, this stream is recirculated expediently again in the direct condenser K9 or fed to the lower part of the column K10 below the Frischlösungsmittelzulaufs.

Zur Erhöhung der Desorptionsleistung der Kolonne K20 werden die Leichtsieder, die im als Strippgas verwendeten Kreisgas enthalten sind, vor dessen Eintritt in die K20 entfernt. Verfahrenstechnisch vorteilhaft erfolgt dies dadurch, daß das Strippgas mit aufgearbeitetem Lösungsmittel aus der unten näher beschriebenen Kolonne K30 in einer Gegenstromwaschkolonne K19 gereinigt wird.To increase the desorption capacity of the column K20, the low boilers which are contained in the cycle gas used as stripping gas are removed before it enters the K20. In terms of process technology, this advantageously takes place in that the stripping gas is purified with worked-up solvent from the column K30 described in more detail below in a countercurrent washing column K19.

Im nächsten Verfahrensschritt wird aus dem Sumpf der Desorptionskolonne K20 ein nahezu leichtsiederfreier, mit Acrylsäure beladener Lösungsmittelstrom abgezogen und der Destillationskolonne K30, bei der es sich bevorzugt um eine Dual-Flow-Bodenkolonne handelt, zugeführt. In den Sumpf der Kolonne K30 kondensiert das schwersiedende Lösungsmittel und Nebenkomponenten wie z.B. Maleinsäureanhydrid. Um zu vermeiden, daß die am Kopf der Kolonne K30 abgezogene Acrylsäure noch nennenswerte Mengen an leichtsiedenden Komponenten enthält, reduziert man diesen Leichtsiederanteil zweckmäßigerweise dadurch, daß man den Auftriebsteil der Kolonne K30 soweit verlängert, daß die Acrylsäure als Seitenabzug aus der Kolonne abgezogen werden kann. Der am Kopf der Kolonne K30 abgezogene leichtsiederreiche Strom wird, da er noch Acrylsäure enthält, vorteilhaft wieder in die Absorptionskolonne K10 rückgeführt. Das aus dem Sumpf der Rektifikationskolonne K30 abgezogene, an Leichtsiedern und an Acrylsäure im wesentlichen freie Lösungsmittel wird zum überwiegenden Teil der Gegenstromwaschkolonne K19 zugeführt, um, wie bereits weiter oben erwähnt, die Leichtsieder aus dem Strippgasstrom, der in die Desorptionskolonne K20 führt, zu waschen. Anschließend wird das nahezu an Acrylsäure freie Lösungsmittel, bis auf einen kleinen Teilstrom, wieder der Absorptionskolonne K10 zugeführt. Mit dem kleinen Teilstrom des nahezu an Acrylsäure freien Lösungsmittels wird das Sauerwasser, das noch Acrylsäure gelöst enthält, extraktiv behandelt. Bei dieser Sauerwasser-Extraktion wird ein Teil der Acrylsäure aus dem Sauerwasser zurückgewonnen, während gleichzeitig das Sauerwasser alle polaren Komponenten aus dem Lösungsmittelteilstrom extrahiert. Das dabei verbleibende Sauerwasser kann vorverdampft und anschließend verbrannt werden.In the next process step, a nearly low boiler-free, acrylic acid-laden solvent stream is withdrawn from the bottom of the desorption column K20 and the distillation column K30, which is preferably a dual-flow tray column, fed. In the bottom of the column K30 condenses the high boiling solvent and minor components such. Maleic anhydride. In order to avoid that the withdrawn at the top of the column K30 acrylic acid still contains appreciable amounts of low-boiling components, this low boiler fraction is advantageously reduced by extending the buoyancy part of the column K30 so far that the acrylic acid can be withdrawn as side draw from the column. The lightly high-boiling stream drawn off at the top of the column K30, because it still contains acrylic acid, is advantageously returned to the absorption column K10. The solvent substantially free of low-boiling components and of acrylic acid withdrawn from the bottom of the rectification column K30 is for the most part fed to the countercurrent washing column K19 in order, as already mentioned above, to wash the low-boiling components from the stripping gas stream which leads into the desorption column K20 , Subsequently, the solvent which is virtually free of acrylic acid, except for a small partial stream, is returned to the absorption column K10. With the small partial stream of the solvent, which is virtually free of acrylic acid, the sour water, which still contains dissolved acrylic acid, is treated extractively. In this sour water extraction, a portion of the acrylic acid is recovered from the sour water, while at the same time the sour water extracts all polar components from the solvent substream. The remaining acid water can be pre-evaporated and then burned.

Diese Verfahrensweise der DE-A 19606877 soll im weiteren Verlauf dieser Schrift als Acrylsäure-Standardabtrennung bezeichnet werden (im Rahmen dieser Standardabtrennung können alle verwendeten Kolonnen auch Dual-Flow-Bodenkolonnen sein.) Als hochsiedende organische Lösungsmittel eignen sich für die Acrylsäure-Standardabtrennung vor allem Gemische aus Diphenylether (70 bis 75 Gew.-%) und Diphenyl (25 bis 30 Gew.-%). Eine in diesem Verfahren besonders günstige hochsiedende hydrophobe organische Absorptionsflüssigkeit ist ein Gemisch, bestehend aus einer Mischung aus 70 bis 75 Gew.-% Diphenylether und 25 bis 30 Gew.-% Diphenyl, sowie, bezogen auf diese Mischung, 0,1 bis 25 Gew.-% o-Dimethylphthalat. Prinzipiell können aber auch alle anderen in der EP-A 722926 empfohlenen hochsiedenden organischen Flüssigkeiten angewendet werden.This procedure of DE-A 19606877 will be referred to in the further course of this document as acrylic acid standard separation (in the context of this standard separation, all columns used can also be dual-flow tray columns.) As high-boiling organic solvents are suitable for the acrylic acid standard separation especially Mixtures of diphenyl ether (70 to 75 wt .-%) and diphenyl (25 to 30 wt .-%). A particularly favorable high-boiling hydrophobic organic absorption liquid in this process is a mixture consisting of a mixture of 70 to 75% by weight of diphenyl ether and 25 to 30% by weight. Diphenyl, and, based on this mixture, 0.1 to 25 wt .-% o-dimethyl phthalate. In principle, however, it is also possible to use all other high-boiling organic liquids recommended in EP-A 722,926.

Sowohl der beschriebenen Acrylsäure-Standardabtrennung als auch den anderen in dieser Schrift zitierten oder in den Schriften WO 01/51159 A, DE-A 19810962, EP-A 1125912, EP-A 722926, DE-A 4308087, EP-A 297445, DE-A 2136396, EP-A 982288, EP-A 982289 und EP-A 982287 beschriebenen (Meth)acrylsäureabtrennungen aus den Produktgasgemischen der Gasphasenoxidation ist gemein, daß in ihrem Verlauf (Meth)acrylsäure enthaltende organische Lösungsmittel in Apparaten behandelt und/oder erzeugt (z.B. durch die Absorption der (Meth)acrylsäure aus der Gasphase in ein organisches Lösungsmittel) werden.Both the described acrylic acid standard separation and the other cited in this document or in the publications WO 01/51159 A, DE-A 19810962, EP-A 1125912, EP-A 722926, DE-A 4308087, EP-A 297445, DE -A 2136396, EP-A 982288, EP-A 982289 and EP-A 982287 described in the product gas mixtures of the gas phase oxidation is common that treated in their course (meth) acrylic acid containing organic solvents in apparatuses and / or generated ( for example, by the absorption of (meth) acrylic acid from the gas phase into an organic solvent).

Bei diesen Apparaten handelt es sich insbesondere um Rektifikationskolonnen, Absorptionskolonnen, Desorptionskolonnen und Extraktionskolonnen. Als solche Kolonnen werden üblicherweise ganz generell Kolonnen mit unterschiedlichsten Einbauten verwendet. Solche Einbauten sind z.B. Böden(wie Dual-Flow-Böden, Siebböden, Ventilböden, Thormann-Böden, Tunnelböden und/oder Glockenböden), Packungen, Raschig Ringe und/oder Pallringe.These apparatuses are, in particular, rectification columns, absorption columns, desorption columns and extraction columns. As such columns usually columns are generally used with a variety of internals. Such internals are e.g. Floors (such as dual-flow trays, sieve trays, valve trays, Thormann trays, tunnel trays and / or bubble trays), packs, Raschig rings and / or Pall rings.

Es kann sich aber auch um ganz andere Apparate, wie z.B. Verdampfer, handeln, wie sie für die thermischen Trennverfahren unverzichtbar und z.B. in der EP-A 854120 beschrieben sind, oder um Kondensatoren oder Mischvorrichtungen.But it can also be very different apparatus, such. Evaporators act as indispensable for the thermal separation processes and e.g. in EP-A 854120 or to capacitors or mixing devices.

Von Nachteil ist nun, daß (Meth)acrylsäure selbst im Beisein von Polymerisationsinhibitoren wie z.B. N-Oxyl Radikalen, Phenothiazin, Monomethylether des Hydrochinons, Hydrochinon, etc. insbesondere in flüssiger Phase befindlich eine ausgeprägte Polymerisationsneigung aufweist. Diese macht sich vor allem bei den thermischen Trennverfahren nachteilig bemerkbar, bei denen die (Meth)acrylsäuremonomeren vergleichsweise hohen Temperaturbelastungen ausgesetzt sind.It is disadvantageous that (meth) acrylic acid, even in the presence of polymerization inhibitors, e.g. N-oxyl radicals, phenothiazine, monomethyl ether of hydroquinone, hydroquinone, etc., especially in the liquid phase has a pronounced tendency to polymerize. This is particularly disadvantageous in the case of thermal separation processes, in which the (meth) acrylic acid monomers are exposed to comparatively high temperature loads.

Im Ergebnis kommt es daher in Apparaten, in welchen (Meth)acrylsäure enthaltende organische Lösungsmittel behandelt oder erzeugt werden, im Lauf der Zeit zur Bildung von unerwünschtem Belag, der aus Polymerisat und/oder anderen Foulingfeststoffen besteht und im Extremfall die Apparate verstopfen und ihre Durchlässigkeit bzw. ihr Wärmeübertragungsvermögen zu mindern vermag. Es ist deshalb von Zeit zu Zeit erforderlich, die vorstehend beschriebenen Apparate zu entleeren und zu reinigen.As a result, in apparatuses in which (meth) acrylic acid-containing organic solvents are treated or produced, over time, undesired scale is formed, which consists of polymer and / or other fouling solids and, in extreme cases, clogs the apparatus and its permeability or to be able to reduce their heat transfer capacity. It is therefore necessary from time to time to empty and clean the apparatuses described above.

Aus der DE-A 19746688, der DE-A 19536179, der EP-A 1033359, der DE-A 10211273 und der DE-A 10213027 sind solche Reinigungsverfahren bekannt.DE-A 19746688, DE-A 19536179, EP-A 1033359, DE-A 10211273 and DE-A 10213027 disclose such cleaning methods.

Sie bestehen darin, dass man den entleerten, im wesentlichen nur noch in unerwünschter Weise gebildetes Polymerisat und/oder Fouling und Reste des organischen Lösungsmittels sowie (Meth)acrylsäure enthaltenden Apparat, zunächst mit (Meth)acrylsäure oder Wasser und anschließend mit der wässrigen Lösung eines basischen Salzes behandelt. Spätestens bei letzterem Schritt löst sich das gebildete Polymerisat und/oder Fouling vollständig und die resultierende wässrige Lösung kann entsorgt werden.They consist in that the emptied, substantially only undesired formed polymer and / or fouling and residues of the organic solvent and (meth) acrylic acid containing apparatus, first with (meth) acrylic acid or water and then with the aqueous solution of a treated with basic salt. At the latest in the latter step, the polymer formed and / or fouling completely dissolves and the resulting aqueous solution can be disposed of.

Die Lösung der vorgenannten Entsorgungsfrage ist dabei nicht trivial. Da die wässrige Lösung salzhaltig ist, entstünde im Rahmen ihrer Verbrennung Rauch (salzhaltiges Abgas).The solution of the aforementioned disposal question is not trivial. Since the aqueous solution is salty, smoke (salty exhaust gas) would be produced as part of its combustion.

Ein Abbau der organischen Fracht der zu entsorgenden wässrigen Lösung durch aerobe (Sauerstoff atmende) Mikroorganismen (z.B. in einer Kläranlage) wäre daher wünschenswert. In der Regel ist dies jedoch mit Schwierigkeiten verbunden, da die organische Fracht der relevanten wässrigen Lösung für einen bakteriellen Abbau häufig zu hoch ist.Degradation of the organic cargo of the aqueous solution to be disposed by aerobic (oxygen-breathing) microorganisms (e.g., in a sewage treatment plant) would therefore be desirable. However, this is usually associated with difficulties because the organic load of the relevant aqueous solution is often too high for bacterial degradation.

Ausführliche Untersuchungen ergaben, dass dies unter anderem auch darauf zurückzuführen ist, dass die Polymerisat- und/oder Fouling-Schicht, von der die Apparateoberflächen gereinigt werden müssen, noch Lösungsmittel adsorbiert und/oder absorbiert enthält, weshalb die relevante wässrige Lösung im Normalfall nicht nur mit gelöstem Polymerisat und/oder Fouling, sondern auch mit dem organischen Lösungsmittel belastet ist. Dies gilt um so mehr dann, wenn die Apparate Toträume aufweisen, in welchen beim Leerlaufen organisches Lösungsmittel verbleiben und beim nachfolgenden Spülen in die wässrige Spüllösung gelangen kann. Letztlich resultieren aus vorgenanntem Sachverhalt auch Lösungsmittelverluste.Extensive investigations have shown that this is partly due to the fact that the polymer and / or fouling layer from which the surfaces of the apparatus must be cleaned still contains adsorbed and / or absorbed solvents, which is why the relevant aqueous solution is normally not only with dissolved polymer and / or fouling, but also charged with the organic solvent. This is all the more true when the apparatus have dead spaces in which remain at idling organic solvent and can enter the aqueous rinse solution during subsequent rinsing. Ultimately, resulting from the above facts also solvent losses.

Die DE-A 10213027 empfiehlt daher, aus dem Fouling und/oder Polymerisat die in selbigem enthaltenden Reste des organischen Lösungsmittels zunächst mittels (Meth)acrylsäure aus selbigem extraktiv zu entfernen und das Gemisch aus (Meth)acrylsäure und Resten des organischen Lösungsmittels in den Prozess der Abtrennung der (Meth)acrylsäure aus dem Reaktionsgasgemisch der Gasphasenoxidation rückzuführen.DE-A 10213027 therefore recommends extractively removing from the fouling and / or polymer the residues of the organic solvent present in the same by means of (meth) acrylic acid from the same and the mixture of (meth) acrylic acid and residues of the organic solvent in the process the separation of the (meth) acrylic acid from the reaction gas mixture of the gas phase oxidation.

Nachteilig an dieser Verfahrensweise ist jedoch, dass bereits abgetrennte (Meth)acrylsäure wieder mit organischem Lösungsmittel vermischt wird.A disadvantage of this procedure, however, is that already separated (meth) acrylic acid is mixed again with organic solvent.

Zwar empfiehlt die DE-A 10213027 für den Fall, dass der zu reinigende Apparat eine Kolonne ist, im Gegenstrom zur dann absteigend geführten Spülflüssigkeit ein Gas durch die Kolonne zu führen (z.B. Luft oder Stickstoff oder Wasserdampf), als selbiges wird Wasserdampf jedoch nur dann empfohlen, wenn die Spülflüssigkeit selbst wässrig ist. Letzteres ist jedoch erst nach der Extraktion mit (Meth)acrylsäure, d.h. nach Entfernung der Reste des organischen Lösungsmittels der Fall.Although DE-A 10213027 recommends, in the event that the apparatus to be cleaned is a column, to pass a gas through the column in countercurrent to the rinsing liquid then conducted in descending direction (for example air or nitrogen or steam), water vapor is only then used as the same recommended if the rinse liquid itself is watery. However, the latter is only after extraction with (meth) acrylic acid, i. after removal of the residues of the organic solvent of the case.

In ähnlicher Weise wird in der DE-A 10211273 der Apparat (eine Bodenkolonne) zunächst mit Wasser weitestgehend lösungsmittelfrei gespült und die im anfallenden Spülwasser enthaltenen Reste an organischem Lösungsmittel durch nachträgliche Wasserdampfdestillation rückgewonnen.Similarly, in DE-A 10211273 the apparatus (a tray column) is first rinsed with water as far as possible without solvent and the residues of organic solvent contained in the resulting rinse water are recovered by subsequent steam distillation.

Erst für die nachfolgende Spülung mittels einer basischen Flüssigkeit wird empfohlen, im Gegengstrom zur Spülflüssigkeit ein Gas durch die Bodenkolonne zu führen. Im Ausführungsbeispiel wird als solches Gas Luft verwendet.Only for the subsequent rinsing by means of a basic liquid is it recommended to pass a gas through the tray column in countercurrent to the rinsing liquid. In the embodiment, air is used as such gas.

Nachteilig an der vorgenannten Verfahrensweise ist, dass die Wasserdampfdestillation und die Spülung mit Wasser räumlich getrennt durchgeführt werden.A disadvantage of the aforementioned procedure is that the steam distillation and the rinsing are performed spatially separated with water.

Aufgabe der vorliegenden Erfindung war es daher, ein Verfahren zur Reinigung von Apparaten, in welchen (Meth)acrylsäure enthaltende organische Lösungsmittel behandelt und/oder erzeugt wurden und die in unerwünschter Weise gebildetes Fouling und/oder Polymerisat und Reste des organischen Lösungsmittels (z.B. in Toträumen) enthalten, zur Verfügung zu stellen, das die Nachteile der Verfahren des Standes der Technik nicht aufweist.It was therefore an object of the present invention to provide a process for purifying apparatus in which (meth) acrylic acid-containing organic solvents were treated and / or produced and the undesired fouling and / or polymer and residues of the organic solvent (eg in dead spaces ), which does not have the disadvantages of the prior art methods.

Demgemäß wurde ein Verfahren zur Reinigung von Apparaten, in welchen (Meth)acrylsäure enthaltende organische Lösungsmittel behandelt und/oder erzeugt wurden und die in unerwünschter Weise gebildetes Fouling und/oder Polymerisat und Reste des organischen Lösungsmittels enthalten, gefunden, das dadurch gekennzeichnet ist, dass man den Apparateinhalt im Apparat befindlich einer Wasserdampfdestillation unterwirft, die dem Apparat dabei entnommene Dampfphase kondensiert und das dabei anfallende Kondensat in eine wässrige sowie in eine organische, Reste des organischen Lösungsmittels enthaltende, Phase auftrennt.Accordingly, there has been found a process for purifying apparatuses in which organic solvents containing (meth) acrylic acid have been treated and / or produced and which contain undesired fouling and / or polymer and organic solvent residues, characterized in that: the apparatus contents in the apparatus are subjected to a steam distillation, the vapor phase taken off the apparatus is condensed and the resulting condensate is separated into an aqueous phase and an organic phase containing residues of the organic solvent.

Unter einer Wasserdampfdestillation des im Apparat befindlichen Apparateinhalts sollen dabei alle Verfahren verstanden werden, bei denen man einerseits im zu reinigenden Apparat Wasserdampf erzeugt und/oder dem zu reinigenden Apparat Wasserdampf zuführt und andererseits dem zu reinigenden Apparat Dampfphase entnimmt.A steam distillation of the apparatus contents contained in the apparatus is to be understood as meaning all processes in which, on the one hand, water vapor is generated in the apparatus to be cleaned and / or steam is supplied to the apparatus to be cleaned and, on the other hand, vapor phase is removed from the apparatus to be cleaned.

Dabei kann z.B. wie folgt vorgegangen werden. Der normalerweise bis auf das gebildete Fouling und/oder Polymerisat und Reste des organischen Lösungsmittels sowie geringe Mengen an (Meth)acrylsäure entleerte Apparat wird mit Wasser oder einer wässrigen basischen Lösung (d.h. mit einer wässrigen Spülflüssigkeit), z.B. einer wässrigen Alkalihydroxidlösung (bevorzugt Natriumhydroxid und/oder Kaliumhydroxid), befüllt (insbesondere bei Kolonnen wird in der Regel nur teilbefüllt; die Menge wird normalerweise so bemessen, dass Verdampfer und Pumpen betreibbar sind), die vorerwärmt sein kann. Anschließend wird die wässrige Phase z.B. durch geeignete Wärmetauscher zum Sieden und somit zur Ausbildung von Wasserdampf gebracht und/oder erhitzter Wasserdampf in den Apparat geführt.In this case, e.g. proceed as follows. The apparatus, normally drained to the formed fouling and / or polymer and organic solvent residues and small amounts of (meth) acrylic acid, is treated with water or an aqueous basic solution (i.e., with an aqueous rinsing liquid), e.g. an aqueous alkali hydroxide solution (preferably sodium hydroxide and / or potassium hydroxide), is filled (in particular columns is usually only partially filled, the amount is usually sized so that evaporator and pumps are operable), which may be preheated. Subsequently, the aqueous phase is added e.g. brought to boiling and thus the formation of water vapor by suitable heat exchangers and / or heated steam passed into the apparatus.

Dadurch bildet sich eine Dampfphase aus, die sowohl Wasserdampf als auch Dampf des organischen Lösungsmittels enthält. Dieser Mischdampf wird aus dem Apparat herausgeführt, kondensiert und das dabei anfallende Kondensat in eine wässrige und in eine organische Phase aufgetrennt. Die organische Phase besteht im wesentlichen aus dem organischen Lösungsmittel, welches beispielsweise wieder der Abtrennung der (Meth)acrylsäure aus dem Produktgasgemisch der Gasphasenoxidation zugeführt werden kann (beispielsweise kann sie bei der Acrylsäure-Standardabtrennung unterhalb der Zufuhr von frischem Absorptionsmittel in die Absorptionskolonne K10 rückgeführt werden, was Lösungsmittelverluste verringert). Die wässrige Phase besteht im wesentlichen aus Wasser. Sie kann z.B. in den zu reinigenden Apparat rückgeführt (ist der zu reinigende Apparat beispielsweise eine Trennkolonne (z.B. eine Rektifikationskolonne), kann die wässrige Phase beispielsweise als Rücklauf in die Kolonne rückgeführt werden) und/oder der Wasserdampferzeugung außerhalb des zu reinigenden Apparates zugeführt werden.This forms a vapor phase containing both water vapor and organic solvent vapor. This mixed steam is led out of the apparatus, condensed and the resulting condensate is separated into an aqueous and an organic phase. The organic phase essentially consists of the organic solvent which, for example, can again be supplied to the separation of the (meth) acrylic acid from the product gas mixture of the gas-phase oxidation (for example, it can be recycled to the absorption column K10 in the standard acrylic acid separation below the supply of fresh absorbent , which reduces solvent losses). The aqueous phase consists essentially of water. It can e.g. recycled to the apparatus to be purified (for example, if the apparatus to be purified is a separation column (e.g., a rectification column), the aqueous phase may be recycled to the column as reflux) and / or supplied to the steam generator outside the apparatus to be cleaned.

Die erfindungsgemäße Wasserdampfdestillation kann im Extremfall aber auch so durchgeführt werden, dass man durch den entleerten zu reinigenden Apparat nur heißen Wasserdampf leitet. Die dabei dem Apparat entnommene Dampfphase kann in gleicher Weise wie vorstehend beschrieben behandelt, d.h. kondensiert und in zwei Phasen aufgetrennt, werden.The steam distillation according to the invention can be carried out in an extreme case, however, so that it passes through the emptied to be cleaned apparatus only hot water vapor. The vapor phase removed from the apparatus can be treated in the same way as described above, ie condensed and separated into two phases.

In der Regel wird man die erfindungsgemäße Wasserdampfdestillation dann beenden, wenn die dem zu reinigenden Apparat entnommene Dampfphase weitgehend oder vollständig frei von organischem Lösungsmittel ist. Häufig ist dies nach einer Anwendungsdauer des erfindungsgemäßen Verfahrens von 1 bis 20 Stunden der Fall. Die dabei dem Apparat über den Gesamtverlauf insgesamt entnommene Dampfphase beträgt, bezogen auf die Füllmenge des Apparates mit Wasser, 0,5 bis 5 Tonnen, häufig 1 bis 2 Tonnen pro Tonne Füllmenge. Die Füllmenge ist dabei diejenige Menge, die benötigt würde, um den entleerten Apparat vollständig mit Wasser zu füllen. Selbstverständlich kann eine im Rahmen des erfindungsgemäßen Verfahrens mitverwendete wässrige Spülflüssigkeit dem zu reinigenden Apparat auch kontinuierlich entnommen und, gegebenenfalls nach Erwärmung außerhalb des zu reinigenden Apparates (z.B. in einem geeigneten Wärmetauscher), in den zu reinigenden Apparat rückgeführt und so durch den zu reinigenden Apparat kontinuierlich zirkuliert werden. Zur Förderung werden dabei Pumpen eingesetzt. Bevorzugt führt man zugeführten Wasserdampf und mitverwendete wässrige Spülflüssigkeit im Fall einer solchen Zirkulation im Gegenstrom durch den zu reinigenden Apparat.In general, the steam distillation according to the invention will be terminated when the vapor phase removed from the apparatus to be cleaned is largely or completely free of organic solvent. This is often the case for a period of application of the method according to the invention of 1 to 20 hours. The case of the apparatus over the entire course taken vapor phase, based on the capacity of the apparatus with water, 0.5 to 5 tons, often 1 to 2 tons per ton of capacity. The filling amount is the amount that would be needed to completely fill the emptied apparatus with water. Of course, a co-used in the process according to the invention aqueous rinsing liquid also removed from the apparatus to be cleaned and, optionally after heating outside of the apparatus to be cleaned (eg in a suitable heat exchanger), returned to the apparatus to be cleaned and so by the apparatus to be cleaned continuously be circulated. For pumping pumps are used. In the case of such a circulation, it is preferred to introduce supplied steam and aqueous flushing liquid in countercurrent flow through the apparatus to be cleaned.

Wird dem zu reinigenden Apparat bei der Durchführung des erfindungsgemäßen Verfahrens Wasserdampf zugeführt, beträgt dessen Druck, insbesondere dann, wenn es sich bei dem zu reinigenden Apparat um eine Trennkolonne handelt, zweckmäßig 1,0 bis 16 bar, häufig 1,1 bis 4 bar. Bevorzugt wird dabei als Wasserdampf Sattdampf verwendet. Sattdampf bedeutet, dass der Wasserpartialdruck wenigstens 99 % des Gesamtdruckes ausmacht.If water vapor is supplied to the apparatus to be cleaned when carrying out the process according to the invention, its pressure, in particular when the apparatus to be purified is a separation column, is advantageously 1.0 to 16 bar, frequently 1.1 to 4 bar. Saturated steam is preferably used as the steam. Saturated steam means that the water partial pressure makes up at least 99% of the total pressure.

Als basische wässrige Spülflüssigkeit können für das erfindungsgemäße Verfahren alle diejenigen eingesetzt werden, die auch die DE-A 19746688, die DE-A 19536179, die DE-A 1033359, die DE-A 10211273 und die DE-A 10213027 empfehlen.As basic aqueous rinsing liquid, all those which are also recommended by DE-A 19746688, DE-A 19536179, DE-A 1033359, DE-A 10211273 and DE-A 10213027 can be used for the process according to the invention.

Das sind im besonderen wässrige Alkali- und/oder Erdalkalihydroxid- und/oder -oxidlösungen, vor allem, wie bereits erwähnt, die wässrigen Lösungen von NaOH, KOH und Ca(OH)2. In der Regel weist dabei die wässrige Lösung einen gelösten Salzgehalt von 0,01 bis 30 Gew.-%, vorzugsweise von 0,5 bis 10 Gew.-% auf.These are in particular aqueous alkali metal and / or alkaline earth metal hydroxide and / or oxide solutions, above all, as already mentioned, the aqueous solutions of NaOH, KOH and Ca (OH) 2 . As a rule, the aqueous solution has a dissolved salt content of from 0.01 to 30% by weight, preferably from 0.5 to 10% by weight.

Gemäß einer vorteilhaften Weiterbildung der Erfindung wird der vorgenannten basischen wässrigen Alkalilösung im Verhältnis von > 0:1 bis 2:1 (Gewichtsverhältnis von Neutralsalz zu Hydroxid und/oder Oxid) ein im wesentlichen ph-neutrales (bezogen auf seine wässrige Lösung) Alkali- und/oder Erdalkalisalz zugesetzt. Hierfür eignen sich besonders die den hydroxidischen/oxidischen Verbindungen entsprechenden Sulfate, Acetate, Oxalate, Carbonate, Hydrogensulfate, Hydrogencarbonate und/oder andere Salze. Durch einen solchen Zusatz lässt sich das Lösungsverhalten der basischen Lösung für das erfindungsgemäße Verfahren weiter verbessern.According to an advantageous embodiment of the invention, the aforementioned basic aqueous alkali solution in the ratio of> 0: 1 to 2: 1 (weight ratio of neutral salt to hydroxide and / or oxide) is a substantially pH-neutral (based on its aqueous solution) and alkali / or alkaline earth salt added. Particularly suitable for this purpose are the sulfates, acetates, oxalates, carbonates corresponding to the hydroxide / oxidic compounds. Hydrogen sulfates, bicarbonates and / or other salts. By such an addition, the solution behavior of the basic solution for the inventive method can be further improved.

Wird beim erfindungsgemäßen Verfahren in zweckmäßiger Weise eine wässrige Spülflüssigkeit mitverwendet und ist der Zeitpunkt erreicht, bei dem die dem zu reinigenden Apparat entnommene Dampfphase im wesentlichen oder vollständig frei an organischen Substanzen ist, lässt man die wässrige Spülflüssigkeit ab und entsorgt sie wie in der DE-A 10211273 bzw. der DE-A 10213027 beschrieben.If an aqueous rinsing liquid is expediently used in the process according to the invention and if the point in time at which the vapor phase removed from the apparatus to be cleaned is substantially or completely free of organic substances is removed, the aqueous rinsing liquid is discarded and disposed of as described in the DE-OS. A 10211273 or DE-A 10213027 described.

Selbstverständlich kann eine solchermaßen mitverwendete wässrige Spülflüssigkeit im Rahmen der Durchführung des erfindungsgemäßen Verfahrens von Zeit zu Zeit erneuert und/oder gegen eine andere wässrige Spülflüssigkeit ausgetauscht werden. Innerhalb des zu reinigenden Apparates weist sie erfindungsgemäß zweckmäßig Siedetemperatur auf.Of course, in the context of carrying out the method according to the invention, an aqueous rinsing liquid used in this way can be renewed from time to time and / or exchanged for another aqueous rinsing liquid. Within the apparatus to be cleaned, according to the invention, it expediently has boiling point.

Zum Abschluss des erfindungsgemäßen Verfahrens wird der zu reinigende Apparat in der Regel mit Wasser gespült (bei vorheriger Mitverwendung von Alkali wird alkalifrei gespült).To complete the process of the invention, the apparatus to be cleaned is usually rinsed with water (with prior use of alkali is rinsed alkali-free).

Bei Bedarf kann zuvor wie in den DE-A 10211273 und DE-A 10213027 beschrieben nochmals mit wässriger basischer Spülflüssigkeit gespült werden, ohne dass gleichzeitig eine Wasserdampfdestillation durchgeführt wird. Diese Spülflüssigkeit weist bei Bedarf ebenfalls eine erhöhte Temperatur auf.If required, it is possible, as described in DE-A 10211273 and DE-A 10213027, to rinse again with aqueous basic rinsing liquid without simultaneously carrying out a steam distillation. If necessary, this rinsing liquid also has an elevated temperature.

Das erfindungsgemäße Verfahren kann sowohl in regelmäßigen Zeitabständen wie auch nach Feststellung einer bestimmten Polymerisatbildung durchgeführt werden.The inventive method can be carried out both at regular intervals as well as after detection of a specific formation of polymer.

Das erfindungsgemäße Verfahren ist insbesondere dann geeignet, wenn der Siedepunkt des organischen Lösungsmittels oberhalb des Siedepunktes von Wasser liegt (beide bei 1 atm). D.h., es eignet sich insbesondere dann, wenn es sich um eine hochsiedende, vorzugsweise hydrophobe, organische Absorptionsflüssigkeit handelt, wie sie in der DE-A 2136396 und in der DE-A 4308087 empfohlen werden. Dies sind im wesentlichen Flüssigkeiten, deren Siedepunkt bei Normaldruck (1 atm) oberhalb von 160°C liegt. Beispielhaft genannt seien Mittelölfraktionen aus der Paraffindestillation, Diphenylether, Diphenyl oder Mischungen der vorgenannten Flüssigkeiten, wie z.B. ein Gemisch aus 70 bis 75 Gew.-% Diphenylether und 25 bis 30 Gew.-% Diphenyl. Günstig ist die Verwendung eines Gemisches bestehend aus einer Mischung aus 70 bis 75 Gew.-% Diphenylether und 25 bis 30 Gew.-% Diphenyl sowie bezogen auf diese Mischung 0,1 bis 25 Gew.-% o-Dimethylphthalat.The process according to the invention is particularly suitable when the boiling point of the organic solvent is above the boiling point of water (both at 1 atm). That is, it is particularly suitable when it is a high-boiling, preferably hydrophobic, organic absorption liquid, as recommended in DE-A 2136396 and DE-A 4308087. These are essentially liquids whose boiling point at normal pressure (1 atm) is above 160 ° C. Examples include middle oil fractions from the Paraffindestillation, diphenyl ether, diphenyl or mixtures of the aforementioned liquids, such as a mixture of 70 to 75 wt .-% diphenyl ether and 25 to 30 wt .-% diphenyl. It is advantageous to use a mixture consisting of a mixture of 70 to 75 wt .-% diphenyl ether and 25 to 30 wt .-% diphenyl and based on this mixture, 0.1 to 25 wt .-% o-dimethyl phthalate.

Der (Meth)acrylsäuregehalt des (Meth)acrylsäure enthaltenden organischen Lösungsmittels, wie es in den erfindungsgemäßen zu reinigenden Apparaten behandelt oder erzeugt wurde, kann ≥ 5 Gew.-%, oder ≥ 10 Gew.-%, oder ≥ 25 Gew.-%, oder ≥ 35 Gew.-%, oder ≥ 50 Gew.-%, oder ≥ 65 Gew.-%, oder ≥ 80 Gew.-%, oder ≥ 90 Gew.-%, oder ≥ 95 Gew.-%, bezogen auf die Lösung, betragen. In der Regel liegt dieser Gehalt bei Werten ≤ 90 Gew.-%, bzw. ≤ 80 Gew.-%, oder ≤ 65 Gew.-%.The (meth) acrylic acid content of the (meth) acrylic acid-containing organic solvent, as it has been treated or produced in the apparatuses to be cleaned according to the invention, may be ≥5% by weight, or ≥10% by weight, or ≥25% by weight. , or ≥ 35 wt .-%, or ≥ 50 wt .-%, or ≥ 65 wt .-%, or ≥ 80 wt .-%, or ≥ 90 wt .-%, or ≥ 95 wt .-%, based to the solution. As a rule, this content is ≦ 90% by weight, or ≦ 80% by weight, or ≦ 65% by weight.

Als erfindungsgemäß zu reinigende Apparate kommen alle in der Schrift bereits genannten Apparate in Betracht. Dies gilt insbesondere dann, wenn sie aus Edelstahl mit der Werkstoffnummer 1.4541 oder 1.4571 gefertigt wurden (vgl. Norm DIN EN 10020).Suitable apparatuses to be cleaned according to the invention are all apparatuses already mentioned in the document. This is especially true if they are made of stainless steel with the material number 1.4541 or 1.4571 (see standard DIN EN 10020).

Insbesondere ist das erfindungsgemäße Verfahren auf jedwede Form von Trennkolonnen (Absorptions-, Desorptions-, Extraktions- und Rektifikationskolonnen) anwendbar. Dies können Bodenkolonnen, (z.B. Glocken-, Thormann®-, Sieb-, Tunnel-, Dual-Flow- oder Ventilböden), Füllkörperkolonnen (mit Raschigringen oder mit Pallringen) oder Kolonnen mit Packungen sein. Es ist aber auch auf jedwede Form von Wärmetauschern anwendbar.In particular, the process of the invention is applicable to any form of separation columns (absorption, desorption, extraction and rectification columns). These may be tray columns, (e.g., bell, Thormann®, sieve, tunnel, dual-flow or valve trays), packed columns (with Raschig rings or with pall rings) or packed columns. But it is also applicable to any form of heat exchangers.

Das erfindungsgemäße Verfahren kann in den zu reinigenden Apparaten bei reduziertem Druck (z.B. 10 bis 100 mbar), erhöhtem Druck oder unter sonstigen Bedingungen durchgeführt werden.The process according to the invention can be carried out in the apparatuses to be cleaned at reduced pressure (for example 10 to 100 mbar), elevated pressure or under other conditions.

Handelt es sich bei dem erfindungsgemäß zu reinigendem Apparat um eine Bodenkolonne, führt man das erfindungsgemäße Verfahren zweckmäßig so aus, dass man durch die Bodenkolonne von oben nach unten eine wässrige basische Spüllösung fördert und im Gegenstrom zur Spüllösung Wasserdampf so durch die Bodenkolonne führt, dass der Unterschied zwischen dem Druck in der Dampfphase unmittelbar unterhalb des untersten Bodens der Bodenkolonne und dem Druck in der Dampfphase unmittelbar oberhalb des obersten Bodens, geteilt durch die Anzahl der in der Kolonne befindlichen Böden wenigstens 0,5 mbar, häufig 0,5 bis 6 mbar oder 1 bis 5 mbar, pro Boden beträgt. Die so erzeugten Sprudelschichten bewirken eine verbesserte Reinigungswirkung.If the apparatus to be cleaned according to the invention is a tray column, the process according to the invention is expediently carried out by passing an aqueous basic rinse solution through the tray column from top to bottom and passing water vapor through the tray column in countercurrent to the rinsing solution in such a way that the Difference between the pressure in the vapor phase immediately below the bottom of the tray column and the vapor pressure immediately above the top tray, divided by the number of trays in the tray at least 0.5 mbar, often 0.5 to 6 mbar or 1 to 5 mbar, per floor. The bubble layers thus produced cause an improved cleaning effect.

Die Spüllösung wird dem Kolonnensumpf dabei zweckmäßig kontinuierlich entnommen und über die Rücklaufleitung der Bodenkolonne wieder zugeführt. Ihre Temperatur liegt in ihrem Siedepunkt.The rinse solution is removed from the column bottom expediently continuously and fed back via the return line of the tray column. Their temperature is in their boiling point.

Der Druck in der Dampfphase "unmittelbar" unterhalb des untersten bzw. oberhalb des obersten Bodens der Bodenkolonne soll in dieser Schrift bedeuten, dass die Meßstelle nicht mehr als 15 cm unterhalb des untersten und wenigstens 25 cm oberhalb des obersten Bodens liegen soll. Die Druckmessung kann z.B. via offene Anbohrung erfolgen, bei der ein Meßumformer über einen Wandstutzen mit der Kolonne verbunden ist.The pressure in the vapor phase "immediately" below the lowest or above the uppermost bottom of the tray column in this document means that the measuring point should not be more than 15 cm below the bottom and at least 25 cm above the top soil. The pressure measurement may e.g. via open tapping, in which a transmitter is connected via a wall socket with the column.

Analog kann selbstredend auch bei Kolonnen gearbeitet werden, die andere Einbauten als Böden (z.B. Raschigringe, Pallringe oder Packungen) enthalten.Analogously, it is of course also possible to use columns which contain internals other than trays (for example Raschig rings, Pall rings or packings).

Der Vorteil des erfindungsgemäßen Verfahrens liegt darin begründet, dass die organische Fracht einer mitverwendeten oder nachfolgend angewandten wässrigen Spüllösung so gering ist, so dass sie unmittelbar zum Zwecke des aeroben Abbaus der organischen Fracht einer Kläranlage zugeführt werden kann. Der Gehalt an organischem Lösungsmittel liegt üblicherweise weit unter 100 gew.ppm. Wird abschließend mit Wasser nachgespült, so kann das resultierende Waschwasser in der Regel unmittelbar in die natürliche Umgebung abgegeben werden.The advantage of the method according to the invention lies in the fact that the organic load of a co-used or subsequently applied aqueous rinse solution is so low that it can be fed directly to a sewage treatment plant for the purpose of aerobic degradation of the organic cargo. The content of organic solvent is usually well below 100 ppm by weight. If final rinsing with water, the resulting wash water can usually be delivered directly into the natural environment.

BeispieleExamples Beispiel 1example 1

In einem 1 1 Vierhalskolben

Figure imgb0001
mit Bodenventil, mechanischem Rührer, Gaseinleitungsrohr, Thermometer und Destillationsbrücke wurden 600 g einer wässrigen Spülnatronlauge vorgelegt, die gelöste Polyacrylsäure und eine geringe Menge eines Gemisches (Diphyl genannt) aus Diphenyl und Diphenylether enthielt. In einem zweiten 1 1 Vierhalskolben
Figure imgb0002
mit Tropftrichter wurden 600 g Wasser vorgelegt (Dampferzeuger). Das Wasser im Vierhalskolben
Figure imgb0003
wurde erhitzt und der Wasserdampf über das Gaseinleitungsrohr durch die Spüllauge geleitet. Über den Tropftrichter wurde das verdampfte Wasser nachdosiert. Die Füllstände beider Vierhalskolben wurden konstant gehalten.In a 1 liter four-necked flask
Figure imgb0001
with bottom valve, mechanical stirrer, gas inlet tube, thermometer and distillation bridge 600 g of an aqueous Spülnatronlauge were submitted, the dissolved polyacrylic acid and a small amount of a mixture (called Diphyl) of diphenyl and diphenyl ether contained. In a second 1 1 four-necked flask
Figure imgb0002
with dropping funnel, 600 g of water were submitted (steam generator). The water in the four-necked flask
Figure imgb0003
was heated and the water vapor passed through the gas inlet tube through the flushing eye. About the dropping funnel, the evaporated water was added. The fill levels of both four-necked flasks were kept constant.

Stündlich wurden aus dem Vierhalskolben mit der simulierten Spüllauge über das Bodenventil Proben gezogen. Diese wurden gaschromatographisch auf Diphyl untersucht. Die Spüllauge enthielt noch 1,75 Gew.-% freie Natronlauge (bezogen auf die Spüllaugenmenge).Hourly samples were taken from the four-necked flask with the simulated rinsing eye via the bottom valve. These were analyzed by gas chromatography for diphyl. The rinsing solution still contained 1.75% by weight of free sodium hydroxide solution (based on the amount of rinsing agent).

Das Ergebnis zeigt die folgende Tabelle: Laufzeit Wasserdampfmenge W verwendet Verhältnis von W zur Spüllaugenmengen Diphyl in Probe 0 h 0 g 0 2,2 Gew.-% 1 h 260 g 0,43 1,3 Gew.-% 2 h 550 g 0,92 0,5 Gew.-% 3 h 920 g 1,53 < 0,01 Gew.-% 4 h 1290 g 2,15 < 0,01 Gew.-% The result is shown in the following table: running time Water vapor amount W used Ratio of W to purging liquor levels Diphyl in sample 0 h 0 g 0 2.2% by weight 1 h 260 g 0.43 1.3% by weight 2 h 550 g 0.92 0.5% by weight 3 h 920 g 1.53 <0.01% by weight 4 h 1290 g 2.15 <0.01% by weight

Nach drei Stunden bzw. der 1,5-fachen Wasserdampfmenge bezogen auf eingesetzt Spüllauge wurde der Wert von 100 gew.ppm Diphyl im Abwasser unterschritten.After three hours or 1.5 times the amount of water vapor, based on the rinse liquor used, the value of 100 ppm by weight of diphyl in the wastewater was not reached.

Beispiel 2Example 2

In einem 10 1 Doppelmantelplanschliffreaktiongefäß mit Bodenventil, magnetgekuppeltem Rührer, Gaseinleitungsrohr, Thermometer und Destillationsbrücke mit Schlangenkühler wurden 6000 g der Spüllauge aus Beispiel 1 vorgelegt. Das Reaktionsgefäß wurde mit Wärmeträgeröl auf 110°C erwärmt. In einem 2 1 Vierhalskolben mit Tropftrichter wurden 1000 g Wasser vorgelegt (Dampferzeuger). Das Wasser wurde zum Sieden erhitzt und der Wasserdampf wurde über das Gaseinleitungsrohr durch die Spüllauge geleitet. Über den Tropftrichter wurde Wasser in den Dampferzeuger dosiert. Die Füllstände der beiden Behälter wurden konstant gehalten.6000 g of the rinsing liquor from Example 1 were initially taken in a 10 l jacketed planer reaction vessel with bottom valve, magnetically coupled stirrer, gas inlet tube, thermometer and distillation bridge with snake cooler. The reaction vessel was heated to 110 ° C. with heat transfer oil. In a 2 1 four-necked flask with dropping funnel 1000 g of water were submitted (steam generator). The water was boiled and the water vapor was passed through the bubbler through the bubbler. Water was metered into the steam generator via the dropping funnel. The levels of the two containers were kept constant.

Innerhalb von 12 h wurden insgesamt 9000 g Wasserdampf durch die Spüllauge geleitet. Anschließend wurde der Reaktorinhalt auf Diphyl untersucht (gaschromatographisch). Der Diphylgehalt lag unter 100 gew.ppm.Within 12 hours, a total of 9000 g of water vapor were passed through the rinsing liquor. Subsequently, the reactor contents were examined for Diphyl (gas chromatographic). The Diphylgehalt was below 100 ppm by weight.

Claims (6)

  1. A process for cleaning apparatus in which (meth)acrylic acid-comprising organic solvents have been treated and/or generated and comprise fouling and/or polymer formed in an undesired manner and residues of the organic solvent, which comprises subjecting the apparatus contents to a steam distillation in the apparatus, condensing the vapor phase removed from the apparatus and separating the resulting condensate into an aqueous and an organic phase, the organic phase comprising residues of the organic solvent.
  2. The process according to claim 1, wherein the apparatus is a rectification column, an absorption column, a desorption column or an extraction column.
  3. The process according to claim 1 or 2, wherein the apparatus comprises an aqueous purging liquid while the process is carried out.
  4. The process according to any of claims 1 to 3, wherein the aqueous purging solution is an aqueous solution of KOH and/or NaOH.
  5. The process according to any of claims 1 to 4, wherein steam is fed to the apparatus to be cleaned.
  6. The process according to any of claims 1 to 5, wherein the amount of steam fed during the process, based on the amount of water, which is required to fill the empty apparatus with water is from 1 to 2 metric tons per metric ton.
EP03790831A 2002-08-09 2003-07-30 Method for cleaning apparatus in which organic solvents containing (meth)acrylic acid have been treated and/or produced Expired - Lifetime EP1528961B1 (en)

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