JP6029669B2 - Method for producing methacrylic acid and methacrylic acid ester - Google Patents

Description

  The present invention relates to a method for producing methacrylic acid, a method for producing a methacrylic acid ester, and a method for treating an aqueous phase containing at least one organic compound.

  Methacrylic acid (MMA) and methacrylic acid esters, such as methyl methacrylate (MMA) and butyl methacrylate, are used in a wide range of applications. Commercial production of methacrylic acid is carried out, inter alia, by heterogeneously catalyzed gas phase oxidation of isobutylene, tert-butanol, methacrolein or isobutyraldehyde. The gaseous reaction phase so obtained is converted into aqueous methacrylic acid solution by cooling and condensation, optionally separated from low-boiling substances such as acetaldehyde, acetone, acetic acid, acrolein and methacrolein, followed by solvent extraction Introduced into the column, methacrylic acid is extracted and separated using a suitable extractant, such as a short chain hydrocarbon. The separated methacrylic acid is further purified, for example by distillation, to separate high boiling impurities such as benzoic acid, maleic acid and terephthalic acid to obtain pure methacrylic acid. Such known methods are described, for example, in EP 0710443, US 4618709, US 4956493, EP 386117 and US 5248819.

  Such known methods produce a large amount of wastewater at various process steps, most often in the form of an aqueous phase remaining after extraction of methacrylic acid from the quenched phase. The water comes primarily from the steam or water added to the gas phase oxidation stage, and the use of water as a quenching agent in the cooling and condensation stages, as well as its own oxidation reaction. This wastewater contains significant amounts of organic compounds and cannot be reused or disposed of safely without further processing to at least partially remove those organic compounds. Such organic compounds generally contain the desired product, such as methacrylic acid, and other byproducts of the oxidation stage, such as acrylic acid, acetic acid and propionic acid, due to incomplete extraction into an organic extractant, They are also of commercial value. The organic content in this wastewater is generally high to accommodate water treatment methods such as biological treatments such as activated sludge processes without the need for significant dilution, significant time and very large treatment facilities. Thus, in commercial methacrylic acid production, wastewater is often burned, for example as described in US Pat. No. 4,618,709. However, combustion of wastewater is environmentally and economically undesirable, requires high energy input, results in emissions that may require further treatment before being released into the environment, and wastewater This also results in the loss of potentially valuable organic compounds present in the wastewater as well as the wastewater itself.

  It is therefore advantageous to be able to at least partially recover the organic compounds present in the wastewater. Optionally at a sufficiently low organic content to be subjected to biological treatment without further treatment and / or discharged into the environment, or for example as industrial process water or in the reaction itself, for example oxidation and It may also be advantageous to recover at least some of the wastewater itself with sufficient purity so that the water can be reused in the quenching stage. CN1903738 proposes using a membrane separator and then purifying the wastewater from the production of acrylic acid using a rectifying column and recovering acrylic acid, toluene and acetic acid. The disadvantage of membrane filtration is that a large amount of water (usually wastewater itself is often used) is generally required to wash away components that do not pass through the filter. In this case, this wash water with an increased concentration of organic compounds must itself be further processed or burned.

  The object of the present invention is generally to overcome as much as possible the aforementioned drawbacks of the prior art methods.

  A further challenge is to improve the overall efficiency and / or yield of the methacrylic acid production process by recovering organic compounds from the process wastewater.

  A further object of the present invention is to reduce the contamination of wastewater by organic compounds as much as possible, rather than combusting with organic compounds, the water can be reused and subjected to biological purification processes, or optionally It is to be able to be discharged into the environment after a biological purification step or other type of purification step.

In order to solve the above problems, at least one method for producing methacrylic acid and methacrylic acid esters comprising the following process steps contributes:
a1) gas phase oxidation of at least one C ₄ compound to obtain a reaction phase containing methacrylic acid;
a2) quenching the reaction phase to obtain a crude aqueous phase containing methacrylic acid;
a3) Extracting at least part of methacrylic acid from a crude aqueous phase containing methacrylic acid into an organic solvent to obtain a crude organic phase containing methacrylic acid and a first aqueous phase;
Here, the first aqueous phase comprises the following components:
i. Water in the range of at least 65% by weight, preferably in the range of 65% to 99.9% by weight, more preferably in the range of 70% to 99.8% by weight, based on the total weight of the first aqueous phase, and even more. Preferably in the range of 75% to 99% by weight, more preferably in the range of 76% to 98.5% by weight, more preferably in the range of 77% to 98% by weight, even more preferably 78% to 97%. Water in the range of 5% by weight, even more preferably in the range of 79% to 95% by weight, even more preferably in the range of 80% to 90% by weight, and ii. 35 mass% or less, preferably in the range of 0.1 mass% to 35 mass%, preferably in the range of 0.2 mass% to 30 mass%, more preferably 1 mass, relative to the total mass of the first aqueous phase. % To 25% by mass, even more preferably 1.5% to 24% by mass, more preferably 2% to 23% by mass, and even more preferably 2.5% to 22% by mass. At least one other than the organic solvent used as extractant in process step a3), in the range of 5% to 21% by weight, even more preferably in the range of 10% to 20% by weight. Organic compounds,
Here, the sum of the masses of i and ii is 100% by mass;
a4) separating and optionally purifying at least part of the methacrylic acid from the crude organic phase obtained in process step a3);
a5) optionally esterifying at least a portion of the methacrylic acid obtained in step a4);
b) extracting at least part, preferably all, of the first aqueous phase obtained in step a3) with an extractant to form an extracted phase comprising component ii and a second aqueous phase; Here, the second aqueous phase has a reduced component ii compared to the first aqueous phase;
c) at least partially separating the second aqueous phase obtained in step b) from the extracted phase obtained in step b);
d) Optionally, at least one organic compound is at least partially separated from the second aqueous phase obtained in step c) and at least one organic compound is reduced compared to the second aqueous phase. Obtaining a third aqueous phase;
e) optionally separating at least a portion of the extractant from the extraction phase to obtain an extract comprising at least one component ii.

In order to solve the above-mentioned problems, a method for treating an aqueous phase comprising at least one organic compound comprising the following process steps also contributes:
a) providing a first aqueous phase comprising the following components:
i. Water in the range of at least 65% by weight, preferably in the range of 65% to 99.9% by weight, more preferably in the range of 70% to 99.8% by weight, based on the total weight of the first aqueous phase, and even more. Preferably in the range of 75% to 99% by weight, more preferably in the range of 76% to 98.5% by weight, more preferably in the range of 77% to 98% by weight, even more preferably 78% to 97%. Water in the range of 5% by weight, even more preferably in the range of 79% to 95% by weight, even more preferably in the range of 80% to 90% by weight, and ii. 35 mass% or less, preferably in the range of 0.1 mass% to 35 mass%, preferably in the range of 0.2 mass% to 30 mass%, more preferably 1 mass, relative to the total mass of the first aqueous phase. % To 25% by mass, even more preferably 1.5% to 24% by mass, more preferably 2% to 23% by mass, and even more preferably 2.5% to 22% by mass. At least one organic compound, more preferably in the range 5% to 21% by weight, even more preferably in the range 10% to 20% by weight,
Here, the sum of the masses of i and ii is 100% by mass;
b) extracting at least a portion, preferably all, of the first aqueous phase with an extractant to form an extracted phase comprising at least one component ii and a second aqueous phase, wherein The second aqueous phase has a reduction in at least one component ii compared to the first aqueous phase;
c) at least partially separating the second aqueous phase from the extraction phase;
d) Optionally, at least one organic compound is at least partially separated from the second aqueous phase obtained in step c) and at least one organic compound is reduced compared to the second aqueous phase. Obtaining a third aqueous phase;
e) optionally separating at least a portion of the extractant from the extraction phase to obtain an extract comprising at least one component ii.

The C ₄ compound subjected to gas phase oxidation in step a1) of the process according to the invention is preferably a C ₄ compound selected from isobutylene, tert-butyl alcohol, isobutyraldehyde and methacrolein, or two or more thereof More mixture. In a preferred embodiment of the present invention, C ₄ compound is derived from dissociation of methyl tert- butyl ether (MTBE) or ethyl tert- butyl ether (ETBE).

The gas phase oxidation in step a1) of the process according to the invention is preferably carried out in the presence of at least one oxidation catalyst. When the C ₄ compound is isobutylene or tert-butyl alcohol, the gas phase oxidation to obtain a gas phase containing methacrylic acid can be carried out in one step, in which case one step in the context of the present application is methacrolein It is taken to mean that the initial oxidation to and further oxidation to methacrylic acid takes place in the presence of at least one catalyst in substantially the same reaction zone. Optionally, the gas phase oxidation in stage a1) can be carried out in more than one stage, preferably in two stages, preferably in two or more reaction zones separated from each other, Two or more catalysts are preferably present, and each catalyst is preferably present in a reaction zone separate from each other. In the two-stage gas phase oxidation, in the first stage, preferably the C ₄ compound is at least partially oxidized to methacrolein, followed by at least partial oxidation of methacrolein to methacrylic acid. Thus, for example, in the first reaction stage, preferably there is at least one catalyst suitable for the oxidation of at least one C ₄ compound to methacrolein, and in the second reaction stage, methacrolein. There is at least one catalyst suitable for the oxidation of to methacrylic acid.

Suitable reaction conditions for gas phase catalytic oxidation are, for example, a temperature of about 250 ° C to about 450 ° C, preferably about 250 ° C to about 390 ° C, and a pressure of about 1 atm to about 5 atm. The space velocity can vary from about 100 to about 6000 (NTP) per hour, and preferably from about 500 to about 3000 per hour. C ₄ feedstock, for example isobutylene, methacrolein and / or oxidation to methacrylic acid, for example gas phase catalytic oxidation, as well as catalysts therefor, literature, e.g. Nos US5248819, Patent US5231226, Patent US5276178, Patent US6596901, Patent US4652673, US6498270 No., US Pat. No. 5,1985,579, US Pat.

  Particularly preferred catalysts and methods suitable for the oxidation of isobutylene or tert-butanol to methacrolein and / or methacrylic acid are described in EP 0 267 556 and suitable for the oxidation of methacrolein to methacrylic acid. Particularly preferred catalysts and methods are described in EP 0376117. These references are included within this application by reference and form part of the disclosure of the present invention.

  The gas phase oxidation of methacrolein to methacrylic acid in the process according to the present invention preferably comprises a temperature of about 250 to about 350 ° C. and below, a pressure of about 1 to about 3 atm, and a volumetric load of about 800 to about 1800 Nl / l / h. Done in

As an oxidant, oxygen is generally diluted, for example in the form of air, or with pure oxygen, or at least one gas inert under the reaction conditions, such as at least one of nitrogen, carbon monoxide and carbon dioxide. It is used in the form of oxygen, with air being preferred as the oxidant and nitrogen and / or carbon dioxide being preferred as the diluent gas. Where carbon dioxide is used as the diluent gas, preferably it is carbon dioxide recycled from combustion, preferably catalytic or thermal combustion of the reaction gas and / or by-products. The gas subjected to gas phase oxidation in step a1) of the process according to the invention preferably also comprises water, which is generally present in the form of water vapor. Oxygen, one or more inert gases, and water can be introduced into the reaction phase or mixed with the C ₄ compound prior to or during the gas phase reaction or before and during the gas phase reaction.

In a preferred embodiment of the process according to the invention, a mixture comprising at least one C ₄ compound, air or oxygen and a recycled oxidation reactor effluent gas, preferably an oxidation reactor effluent burned before recycling, is obtained in step a1. ). The reactor effluent gas preferably contains at least one unreacted C ₄ compound, at least one carbon oxide, nitrogen and oxygen, and water, depending on the separation conditions and the presence of the combustion stage and the action of the combustion stage. Including.

In the two-stage gas phase oxidation according to the present invention, the preferred volume ratio of C ₄ compound: O ₂ : H ₂ O: inert gas in the first stage is generally from 1: 0.5 to 5: 1 to 20: 3 to 30, preferably 1: 1 to 3: 2 to 10: 7 to 20. The volume ratio of methacrolein: O ₂ : H ₂ O: inert gas in the second stage is preferably 1: 1-5: 2-20: 3-30, preferably 1: 1-4: 3-10. : 7-18.

In step a2) of the process according to the invention, the gas phase containing methacrylic acid is cooled and condensed (commonly known as quenching) to obtain a condensate in the form of a crude aqueous solution containing methacrylic acid. Cooling the condensation by any means known to those skilled in the art and considered suitable, for example, cooling the methacrylic acid-containing gas phase to a temperature below the dew point of at least one of its components, in particular water and methacrylic acid. Can be done. Suitable cooling methods are known to the person skilled in the art, for example using at least one heat exchanger or by quenching, for example liquids in the gas phase, for example water, aqueous compositions or organic solvents, for example aromatic or aliphatic Cooling by spraying with an organic solvent selected from hydrocarbons, or at least two mixtures thereof, wherein preferred organic solvents have a relatively low vapor pressure under quenching conditions, such as heptane, toluene or Xylene, wherein water is preferred as the quench liquid according to the present invention, and at least a portion of the condensate formed in the quench stage itself is even more preferred. Suitable quenching methods are known to the person skilled in the art, for example from DE 2136396, EP 297445, EP 297788, JP01193240, JP01242433, JP01006233, US2001 / 0007043, US6596901, US4956493, US4618709, US52448819, acrylics The disclosure of acid and methacrylic acid quenching is included herein and forms part of this disclosure. According to the invention, it is preferable to cool the gas phase to a temperature of 40-80 ° C. and wash with water and / or condensate from the quenching stage to obtain an aqueous solution containing methacrylic acid, which contains said methacrylic acid Aqueous solutions include various amounts of impurities such as acetic acid, maleic acid, fumaric acid, citraconic acid, acrylic acid and formic acid, and aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, acrolein, methacrolein, ketones and unreacted singular or plural. The C ₄ compound may also be included. In order to obtain high purity methacrylic acid, these impurities as well as water must be separated from methacrylic acid to the maximum extent possible.

The extraction of at least a portion of the methacrylic acid from the crude methacrylic acid-containing aqueous solution is carried out in process step a3) with an organic extractant, for example at least one organic solvent, preferably at least one solvent essentially immiscible with water. Can be used to form an aqueous phase and an organic phase. Process step a3) also includes the separation of the aqueous and organic phases from each other. Preferred organic solvents which can be used in step c) of the process according to the invention have a boiling point which is different from, preferably lower than that of methacrylic acid. Preferably, in the process according to the invention, the organic extractant used in process step a3) has a boiling point of less than 161 ° C., measured at atmospheric pressure. The organic extractant can in this case be separated in principle from methacrylic acid, for example by distillation, preferably at least partly, preferably to a substantial extent in step a4) of the process according to the invention, where it is preferably Is at least partially removed as a low boiler in the distillation apparatus at a higher level than pure methacrylic acid. The separated organic extractants or parts thereof can optionally be returned to process step a3) after at least one cooling and / or purification step. Preferred organic solvents for this stage are in particular selected from alkanes and aromatics, preferably alkyl aromatics, hydrocarbons, wherein at least one organic solvent selected from C ₆ -C ₈ -hydrocarbons Are preferred, with heptane, toluene and xylene being particularly preferred and heptane, preferably n-heptane being most preferred. Process step a3) may be carried out by any means known to the person skilled in the art and considered suitable, preferably as countercurrent extraction, for example as solvent extraction tower, pulse packed or packed tower, rotary extractor, washing tower, It can be carried out using a phase separator or other apparatus suitable for extraction of the aqueous phase using the organic phase and separation of the organic phase from the aqueous phase. According to the invention, at least partly, preferably at least 50% by weight, preferably at least about 70% by weight, preferably at least about 80% by weight, more preferably at least about 90% by weight, contained in an aqueous methacrylic acid solution. It is preferred to extract methacrylic acid into the organic phase.

Two phases: a methacrylic acid-containing crude organic phase led to step a4) of the process according to the invention and a first aqueous phase comprising components i and ii (water and at least one organic compound) in the amounts described above. It is thus obtained in step a3) of the process according to the invention. The organic compound that may be included as component ii in the first aqueous phase is described above in connection with any organic compound formed during the gas phase oxidation reaction, such as the crude aqueous phase obtained in the quenching step. As well as any unreacted C ₄ compound and any methacrylic acid remaining in the aqueous phase. The first aqueous phase may contain a small amount of organic solvent used for extraction in process step a2), for example due to incomplete separation of the organic phase from the first aqueous phase. This solvent is not considered as component ii.

  In step a4) of the process according to the invention, the crude organic phase containing methacrylic acid obtained in step a3) is separated, preferably subjected to a thermal separation method, from the organic solvent used as extractant in process step a3). , Separating at least a portion of the methacrylic acid contained therein. If thermal separation is used, this is preferably distillation, whereby the organic solvent used for extraction in process step a3) is preferably as the top product of the distillation column or from the distillation column. While removed at a high level, methacrylic acid or a phase rich in methacrylic acid is removed as the bottom product of the distillation column or at a lower level than the extraction solvent. For example, using a fractionation column or a rectification column, impurities having a higher boiling point than methacrylic acid are left in the bottom product, and higher purity methacrylic acid is at a higher level than the bottom product. It is also possible to be able to take it out. If the organic solvent used for extraction has a boiling point higher than that of methacrylic acid, it is also possible to remove the methacrylic acid phase at the top of the column and / or at a higher level of the column. Further purification of the methacrylic acid or methacrylic acid-rich phase so obtained may be by further thermal steps, such as distillation or rectification, or by other means, for example by crystallization. In the process according to the invention, before or during process step a4), intermediate steps, for example one or more stripping or distillation to separate low or high boilers, removing solid impurities Such as filtration, crystallization, washing and the like. The number of purification and other separation steps depends on the amount of contamination and the desired purity of the methacrylic acid end product. When methacrylic acid is used as such, for example as a monomer or comonomer for the preparation of methacrylic acid polymers, higher purity may be preferred, especially depending on the end use. If methacrylic acid is esterified, lower purity methacrylic acid is acceptable, for example if the final product of the ester can be purified more simply, more effectively or more efficiently than methacrylic acid. .

Esterification of at least a portion of the methacrylic acid so obtained in process step a5) is optionally carried out in any manner known and considered suitable for the person skilled in the art and optionally methacrylic acid and / or methyl methacrylate. In the presence of a polymerization inhibitor to prevent polymerization of The means for carrying out the esterification in step a5) is not particularly limited. Esterification can be performed, for example, as described in US6469202, JP1249743, EP1254887, US4748268, US4474981, US49556493 or US44464229, the disclosures of which are related to the esterification of acrylic acid and methacrylic acid in this application. And is part of the present disclosure. Liquid phase esterification is preferred. Where esterification occurs by a direct reaction between methacrylic acid and an alcohol, it is preferred to catalyze the reaction with a suitable catalyst. Esterification catalysts are known to those skilled in the art and include, for example, heterogeneous or homogeneous catalysts, such as solid state or liquid catalysts. The esterification catalyst is preferably an acidic ion exchange resin, such as those described in US Pat. No. 6,469,292, JP 1249743, EP1254887, or Amberlyst® (Rohm and Haas Corp.), Dowex® (Dow) Corp.) or Lewertit® (Lanxess AG), or an acid that can catalyze esterification, such as sulfuric acid, H ₂ SO ₄ .

The methacrylate ester prepared in process step a5) according to the invention preferably has the formula [CH ₂ ═C (CH ₃ ) C (═O) O] _n —R, and methacrylic acid and the formula R (OH ) _M can be formed by esterification with alcohol, wherein n and m are 1 to 10, preferably 1 to 6, more preferably 1 to 5, more preferably 1 to 4, more preferably 1 to 3. And R is linear or branched, saturated or unsaturated, aliphatic or aromatic, cyclic or linear hydrocarbon, and linear or branched, saturated or unsaturated Aliphatic, aromatic, cyclic or linear heteroatom-containing hydrocarbons such as alkyl, hydroxyalkyl, aminoalkyl, other nitrogen and / or oxygen containing groups, glycols, diols, triols, bisphenols Selected from the group consisting of diols, fatty acid groups, wherein R is preferably methyl, ethyl, propyl, iso-propyl, butyl, in particular n-butyl, iso-butyl, hydroxyethyl, preferably 2-hydroxyethyl, and hydroxy Propyl, preferably 2-hydroxypropyl or 3-hydroxypropyl, 2-ethylhexyl, isodecyl, cyclohexyl, isobornyl, benzyl, 3,3,5-trimethylcyclohexyl, stearyl, dimethylaminoethyl, dimethylaminopropyl, 2-tert-butyl Aminoethyl, ethyl triglycol, tetrahydrofurfuryl, butyl diglycol, methoxypolyethylene glycol-350, methoxypolyethylene glycol 500, methoxypolyethylene glycol 750, metho Xypolyethylene glycol 1000, methoxypolyethylene glycol 2000, methoxypolyethylene glycol 5000, allyl, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol 200, polyethylene glycol 400, 1,3-butanediol, 1,4-butanediol, 1, 6-hexanediol, glycerol, diurethane, ethoxylated bisphenol A, ethoxylated bisphenol A having 10 ethylene oxide units; trimethylolpropane, for example ethoxylated C ₁₆ -C ₁₈ -fatty alcohol having 25 ethylene oxide units, 2 -Represents trimethylammonium ethyl.

  Methacrylic acid esters can also be prepared from methyl methacrylate by other methods known to those skilled in the art, for example by transesterification. In a further possible preparation of hydroxyester derivatives, methacrylic acid according to the invention can be reacted in a ring-opening reaction with a corresponding oxygen-containing ring, for example epoxides, in particular ethylene oxide or propylene oxide.

Preferred methacrylic esters are alkyl methacrylates, in particular methyl, ethyl, propyl, iso-propyl, butyl, methacrylate, in particular methyl, n-butyl, iso-butyl, sec-butyl methacrylate, in particular methyl methacrylate, n-butyl methacrylate, isobutyl. Methacrylate, hydroxyester methacrylate derivatives such as hydroxyethyl methacrylate, preferably 2-hydroxyethyl methacrylate, and hydroxypropyl methacrylate, preferably 2-hydroxypropyl methacrylate or 3-hydroxypropyl methacrylate, and other methacrylate esters such as ethyl methacrylate, 2 -Ethylhexyl methacrylate, isodecyl methacrylate, cyclohexyl meta Relate, isobornyl methacrylate, benzyl methacrylate, 3,3,5-trimethylcyclohexyl methacrylate, stearyl methacrylate, dimethylaminoethyl methacrylate, dimethylaminopropyl methacrylate, 2-tert-butylaminoethyl methacrylate, ethyltriglycol methacrylate, tetrahydrofurfuryl Methacrylate, butyl diglycol methacrylate, methoxy polyethylene glycol-350 methacrylate, methoxy polyethylene glycol 500 methacrylate, methoxy polyethylene glycol 750 methacrylate, methoxy polyethylene glycol 1000 methacrylate, methoxy polyethylene glycol 2000 methacrylate, methoxy polyethylene glycol 5000 methacrylate, allyl methacrylate, ethoxylated (optionally with, for example, 25 moles of EO) C ₁₆ ~C ₁₈ - methacrylic acid esters of fatty alcohols, 2-trimethyl ammonium ethyl methacrylate chloride, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate , Triethylene glycol dimethacrylate, polyethylene glycol 200 dimethacrylate, polyethylene glycol 400 dimethacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, glycerol dimethacrylate, Diurethane dimethacrylate, ethoxylated bisphenol A dimethacrylate, ethoxylated (optionally eg Bisphenol A dimethacrylate (with 10 EO); trimethylolpropane trimethacrylate, with methyl methacrylate, butyl methacrylate and hydroxyester methacrylate derivatives being particularly preferred.

In process step b) of the process according to the invention, at least part, preferably all, of the first aqueous phase comprising components i and ii is extracted with an extractant to obtain an extracted phase and a second aqueous phase, Form. According to the present invention, by extracting at least a portion of at least one component ii into the extraction phase, the second aqueous phase reduces at least one component ii compared to the first aqueous phase. It is preferable. Preferably, the extraction is performed at ambient or elevated temperature, preferably in the range of about 15 ° C to about 70 ° C, preferably in the range of about 20 ° C to about 65 ° C, more preferably about 30 ° C to It is carried out at a temperature in the range of about 60 ° C, even more preferably at a temperature in the range of about 40 ° C to about 55 ° C. The extraction is preferably liquid-liquid extraction. The extraction is known by those skilled in the art and considered to be suitable, for example by an extraction column, washing tower, phase separator or known to the person skilled in the art and suitable for liquid-liquid extraction. This can be done using other possible devices. Extractants that have been found suitable for process step b) of the process according to the invention are organic solvents, ionic liquids and organic or inorganic oils. Suitable extractants, in particular organic solvents, for use in process step b) of the process according to the invention are preferably at least 1, preferably at least 2, more preferably at least 3, of i) to iv) below: More preferably it is characterized by all properties:
i) Average k value measured for acetic acid in the extractant-water system at 25 ° C. by the method described within this application is in the range of 0.1-100, preferably in the range of 0.2-90, More preferably in the range of 0.3-80, even more preferably in the range of 0.3-70, more preferably in the range of 0.4-60;
ii) The evaporation enthalpy is 2260 kJ / kg or less, preferably 2000 kJ / kg or less, preferably 1500 kJ / kg or less, more preferably 1000 kJ / kg or less, even more preferably 800 kJ / kg or less;
iii) The boiling point is in the range of 35-140 ° C, preferably in the range of 35-125 ° C, more preferably in the range of 40-120 ° C, even more preferably in the range of 40-110 ° C;
iv) Solubility in water at a temperature of 25 ° C., preferably at a temperature of 35 ° C., more preferably at a temperature of 45 ° C., even more preferably at a temperature of 50 ° C., 150 g / l or less, preferably 130 g / l or less, more preferably 110 g / L or less, even more preferably 100 g / l or less, and even more preferably 90 g / l or less.

  Unless otherwise stated, the above properties are measured at about 50 ° C. and atmospheric pressure. The term “k value” relates to the partition coefficient, ie the distribution ratio of the respective organic compounds of component ii of the invention in the equilibrium state between the organic (extracted) phase and the aqueous phase. A k value greater than 1 means that each organic compound is present in the organic (extracted) phase more than in the aqueous phase. While extractants having a k value of less than 1 can be used for the good effect I of the method according to the invention, higher k values, for example k values greater than 1, are preferred because they are the first water This is because it shows a more complete extraction of the organic compound from the phase to the extraction phase. While k values up to 100 are possible, extractants having k values up to about 5, 10, 20, 30, 40, 50, 60, 70, 80 or 90 are also preferred according to the invention. is there. Lower k values, especially less than 5, and k values within the above ranges are also acceptable, for example, especially if the extractant also has one or more other favorable properties in an advantageous range. When the extractant is an organic solvent, its evaporation enthalpy and boiling point are preferably as low as possible within the practical limits that the extractant is preferably liquid, especially at the temperature at which the extraction is carried out. The evaporation enthalpy is preferably not below about 22 kJ / mol and the boiling point is preferably above 0 ° C. and more preferably below the operating temperature at which the extraction is carried out. The evaporation enthalpy is necessary for the thermal separation of any residual extractant remaining in the second aqueous phase after separation of the second aqueous phase from the extracted phase in step c) of the process according to the invention. In order to reduce the energy input as much as possible, the evaporation enthalpy of water is preferably not more than 2260 kJ / kg or 40.65 kJ / mol. The enthalpy of evaporation is preferably at least one of the organic compounds of component ii in order to reduce as much as possible the energy input required to thermally separate the extractant from one or more organic compounds of component ii. No more than two evaporation enthalpies. It is particularly preferred that the evaporation enthalpy does not exceed at least one evaporation enthalpy of methacrylic acid, acrylic acid and acetic acid. For the same reason and to facilitate separation of the extractant, the boiling point of the extractant is preferably lower than at least one boiling point of the organic compound of component ii, preferably at least one of methacrylic acid, acrylic acid and acetic acid Below the boiling point, preferably as low as possible in the preferred range. When ionic liquids or organic or inorganic oils are used as extractants, their enthalpies and boiling points for their evaporation are preferably as high as possible, preferably water and at least one of at least one organic compound of component ii. Higher than. The extractant preferably has a low solubility in water, and preferably, especially at the extraction temperature, in order to be able to make the separation of the extraction phase and the second aqueous phase as complete as possible. Are essentially or completely insoluble in water, and preferably essentially or completely immiscible with them.

  In step c) of the process according to the invention, the second aqueous phase is at least partly separated from the extraction phase. The extraction of step b) and the separation of process step c) of the process according to the invention can be carried out by any means known to the person skilled in the art and considered suitable, preferably by countercurrent extraction, Stages b) and c) are preferably carried out in the same apparatus, for example an extraction column, a pulse packed column or packed column, a rotary extractor, in particular those using centrifugal force for separation, a washing column, a phase separator, Alternatively, it is carried out using other equipment suitable for the separation of the organic phase or ionic liquid from the aqueous phase. If an organic solvent is used as the extractant in process step b), it is possible to incinerate the extract phase obtained after the separation in process step c). Such incineration has the advantage that the organic extraction phase essentially acts as a combustion, thus reducing the need to purchase fuel. This option can be used, for example, where the cost of fuel or related requirements, such as ease of transport and / or cost, is disadvantageous, and / or where one or more market values of the organic compound of component ii are particularly those It may be preferred if it is low compared to the overall effort and cost required for the separation and / or purification of.

The second aqueous phase is preferably 5.0% by weight or less, preferably 4.5% by weight, of organic compounds other than the extractant used in process step b), based on the total weight of the second aqueous phase. Hereinafter, more preferably 4.0% by mass or less, more preferably 3.5% by mass or less, more preferably 3.0% by mass or less, and still more preferably 2.5% by mass or less. The amount of organic compound other than the extractant in the second aqueous phase is preferably as small as possible and preferably 0% by weight, but 0.5% by weight, 0.8% by weight, 1.0% by weight. A lower limit of% or 1.2% by weight is also acceptable. The total amount of organic compounds (generally formaldehyde) in the second aqueous phase free of any residual extractant from process step b) is up to about 1.5% by weight, based on the total weight of the second aqueous phase. And the remainder is composed of C ₂ or more C-chain organic compounds, in particular C ₂ -C ₆ -or C ₂ -C ₄ -compounds. The total amount of such organic compounds depends on the number of extraction stages or extraction cycles involved in the extraction of process step b) and the amount of extractant used in this extraction. The higher the number of extraction stages, the lower the organic compound content of the second aqueous phase, but generally longer and / or multi-stage extraction and / or higher amounts of extractant are required. That can lead to a larger extraction phase that must be further processed or incinerated.

  The process according to the invention can also comprise an intermediate stage, for example stripping to remove low boilers or distillation to remove low boilers or high boilers.

In an optional step d) of the process according to the invention, the at least one organic compound is at least partly separated from the second aqueous phase and the at least one organic compound is reduced compared to the second aqueous phase. Get a third aqueous phase. Preferably, the third aqueous phase contains less than 3.0% by weight of organic compounds other than the extractant used in process step b), preferably 2.8% by weight, based on the total weight of the third aqueous phase. % Or less, more preferably 2.5% by mass or less, more preferably 2.2% by mass or less, more preferably 2.0% by mass or less. The amount of organic compound in the third aqueous phase is preferably as low as possible and is preferably 0% by weight. If the organic compound is present in the third aqueous phase, up to about 1.5% by weight may be in the form of formaldehyde, the remainder being C ₂ other than the extractant used in process step b) or more compounds more C chain, in particular C ₂ -C ₆ - containing compound - or C ₂ -C _4. Therefore, preferably the third aqueous phase contains less than 5000 ppm of organic compounds other than the C ₁ compound (formaldehyde) and other than the extractant used in process step b), based on the total mass of the third aqueous phase, Preferably less than 4000 ppm, more preferably less than 3000 ppm, preferably in the range of 0 to 3000 ppm, more preferably in the range of 0 to 2500, more preferably in the range of 0 to 2200 ppm, most preferably 2000 ppm or less, wherein the third Depending on the intended further use and / or treatment of the aqueous phase, a lower limit of 500 ppm, or 1000 ppm, or 1500 ppm, or 1800 ppm is acceptable. The separation in process step d) is preferably thermal separation, for example preferably distillation at atmospheric pressure or azeotropic distillation. In process step d), it is preferable to separate the residual extractant from process step b) remaining in the second aqueous phase to the maximum extent possible. If the extractant used in process step b) forms an azeotrope with water, the separation can comprise azeotropic distillation, for example azeotropic distillation using an entrainer. In a preferred embodiment of step d) of the process according to the invention, if separation by distillation, in particular by fractionation or rectification, is used in process step d), low-boiling components, in particular components having a lower boiling point than the extractant, Separated at the top of the column, extractant is withdrawn at the side outlet of the column, and optional component ii is with the extractant or at a further side outlet of the column, preferably from the side outlet from which the extractant is withdrawn. Preferably, it is pulled out at the lower side outlet. Any extractant so separated can then be recycled to the extraction in step b) of the process according to the invention, which corresponds to step h) of the process according to the invention. If one or more organic compounds of component ii are separated in the same phase as any extractant separated in this stage, this phase is added to the extracted phase separated in process stage c) be able to. If one or more organic compounds of component ii are separated in a different phase from the extractant, this different phase can be identified in step f) or step j) of the process according to the invention. Stage d) of the process according to the invention is preferably carried out when an organic solvent is used as the extractant in process stage b) of the process of the invention, but ionic liquid or oil extraction is performed in process stage b ) May also be implemented when used in

  In step e) of the process according to the invention, the extractant used in process step b) is at least partly separated from the extraction phase to obtain an extract comprising at least one component ii. If an organic solvent is used as the extractant, the separation in process step e) is preferably carried out by a thermal separation method. Suitable thermal separation methods are known to those skilled in the art, in which case distillation, fractional distillation, rectification and the like are preferred according to the invention, vacuum distillation being preferred. One or more separation methods can be included in process step e) according to the invention. In a preferred thermal separation process in which the organic solvent used as extractant in process step b) has a lower boiling point than the one or more components ii to be separated, the extractant is at the top of the distillation column or An extract taken at the higher level or fractions of the fractionation column or rectification column, preferably in the upper half of the column, and comprising one or more components ii or at least one component ii The extractant is removed at a level or levels that are lower than the level at which the extractant is removed, or is removed at the bottom of the column. The advantage of using an organic solvent having a boiling point lower than that of at least one component ii as extractant in process step b) is that some or all of component ii, in particular methacrylic acid and acrylic acid, are sensitive to heat. In addition, the tendency of dimerization, oligomerization, and polymerization increases when the temperature rises. Accordingly, heat treatment of these compounds at elevated temperatures generally requires the addition of a polymerization inhibitor. If a lower boiling extractant is to be separated and / or if the separation is a vacuum distillation, this separation is performed at a lower temperature below the boiling point of the respective component ii to reduce the tendency to polymerize Thus, the need for polymerization inhibitors can be reduced.

  If an ionic liquid or an organic or inorganic oil is used as extractant in process step b), the separation in process step e) is preferably by phase separation or evaporation, preferably the evaporation of one or more volatile components. Is done by.

  The process according to the invention removes one or more intermediate stages, for example stripping to remove low boilers, or low boilers or high boilers, during any or all of the process stages. Can also be included for distillation.

In a preferred embodiment of the method according to the invention, the method further comprises the following process steps:
f) separating at least a portion of at least one component ii from the extract.

  The separation in process step f) is preferably a thermal separation process, preferably distillation, fractionation or rectification, preferably vacuum distillation, in which at least a part of at least one component ii is separated from the extract. . The extract can contain, for example, an extractant or other component ii in addition to at least one component ii to be separated. If the extract contains more than one component ii, for example two or more components ii, either only one component ii is separated in process step f) or two or more Of component ii can be separated. The choice of distillation, fractionation or rectification as separation means can be easily determined by a person skilled in the art and depends mainly on the number and amount of other compounds in the extract from which at least one component ii is to be separated. And the separation of the boiling point of each of the one or more components ii to be separated and the boiling points of the components of the extract not intended to be separated, in particular the boiling points of the other components of the extract Depending on the proximity of the boiling point of at least one component ii to be done and, if more than one component ii is to be separated, depends on the proximity of the boiling points of the components ii to be separated from each other. Another factor to consider is the desired purity of at least one component to be separated. Subsequent to the separation in step f) of the process according to the invention, further purification of at least one component ii may be desirable or even necessary.

In the process according to the invention, in a further process step,
g) The third aqueous phase can be subjected to at least one biological purification process.

  In the context of the present invention, the term “biological purification treatment” means, for example, contaminants or impurities, preferably one or more biological organisms and / or microorganisms, or biologically or biochemically. It is intended to mean any treatment that increases the purity of water by removing organic contaminants from active substances, such as those derived from such organisms or microorganisms. The contaminants and impurities to be removed in this way are generally organic compounds remaining in the third aqueous phase. Removal takes place by digestion or destruction of some or all of the organic compounds. The increase in the purity of the water preferably depends on the purity achieved, preferably the wastewater as industrial process water or in the process according to the invention, in particular in one or both of the process steps a1) or a2). For example, to reduce pollutants and / or impurities and / or water biochemical oxygen demand (BOD) or chemical oxygen demand to a level that means it can be reused or released to the environment or water supply system Measured by the decrease in (COD). Biological purification processes are known to those skilled in the art and may be, for example, one or more so-called activated sludge processes. Such processing is conventional and well known to those skilled in the art. The biological purification process can be performed in one or more stages and it can be continuous or intermittent.

  If the third aqueous phase is subjected to at least one biological purification treatment in process step g), this treatment is preferably at least one of an aerobic treatment and an anaerobic treatment. In one embodiment of the treatment having two or more stages, for example, the aerobic treatment may be performed after the first anaerobic treatment, or the anaerobic treatment may be performed after the first aerobic treatment. Alternatively, a series of anaerobic and / or aerobic treatments may be used, for example in a continuous batch reactor.

In one embodiment of the method according to the invention, in a further process step,
h) Recycle at least a portion of the extractant separated in at least one of process steps d) and e) to process step b).

  Process step d, optionally using one or more intermediate steps to remove more volatile components such as cooling, purification, eg by distillation, washing or the like, or stripping. ) And e) part or substantially all of the extractant separated in one or both can be returned to process step b). Such recycling of the extractant has the advantage that the total amount of extractant in the process is reduced, in particular the amount of waste extractant that has to be discarded is reduced.

  If the separation in process step f) of the process according to the invention is a thermal separation, it is not always possible, or the components are separated from one another, for example if two or more components have very similar boiling points. For example, it may not be economically or technically practical. This is particularly the case when the extract subjected to process step f) contains a relatively large number of components, in particular at least one component ii to which one or more components ii are to be separated in process step f). And a case where the fine control of the separation of only one component ii in process step f) becomes more difficult. In doing so, it may be more appropriate or more practical to separate two or more components ii in a further process step j), which for specific separation requirements of each component ii Such adaptation can be achieved more easily. Thus, in one embodiment of the method according to the invention, the at least one component ii obtained in step f) is a mixture of at least two components ii and in a further process step j) at least one component ii Is at least partially separated from the mixture.

  The separation in process step j) of the process according to the invention can be carried out in one or more separation stages, for example thermal separation as already discussed above for other separation stages in the process according to the invention, chromatographic separation, For example, by preferentially reacting one component ii to form a reaction product that is more easily separable from one or more other components ii, or two or more components ii Chemical separations by reacting to form reaction products that are more easily separated from each other, or other separation means known and considered suitable by those skilled in the art.

  In a preferred embodiment of the process according to the invention, at least one organic compound of component ii, preferably at least one component ii separated at least partly in process step j) is selected from carboxylic acids, aldehydes and ketones. At least one organic compound. Among them, according to the invention, at least one component ii, preferably at least one component ii at least partially separated in process step j) is at least one of acetic acid, acrylic acid, propionic acid and methacrylic acid. One is preferred.

  When at least one component ii separated in at least one of process steps e), f) and j) is methacrylic acid or contains methacrylic acid, in a preferred embodiment of the process according to the invention, the methacrylic acid At least part of the phase is added to the crude aqueous phase obtained in process step a2) and / or to the crude organic phase obtained in process step a3). This embodiment may be preferred when, for example, methacrylic acid separated in one or more of process steps e), f) and j) is not of the desired purity for its final use. Addition to the crude aqueous phase may be preferred, for example, when the separated methacrylic acid is separated with one or more components having a lower boiling point than methacrylic acid. Addition to the crude organic phase may be preferred, for example, when components other than methacrylic acid have a higher boiling point than methacrylic acid, since such higher boiling point can be separated in process step a4) Because. In determining to which phase this methacrylic acid-containing phase separated in at least one of process steps e), f) and j) is added, to other components of methacrylic acid, in particular to other components ii While the relative ratio may also play a role, the nature of the other components in the at least one component ii separated in at least one of the process steps e), f) and j) occupies a greater weight. For example, the methacrylic acid separated in at least one of process steps e), f) and j) is relatively pure, for example about 5% by weight or less, preferably about 4% by weight or less, preferably about 3% by weight. This methacrylic acid is introduced into the optional purification step of process step a4) below, preferably if it contains impurities or other components ii in the range of about 2% by weight or less, preferably about 1% to about 2% by weight. It may be preferable.

In another embodiment of the process according to the invention, at least a part of at least one component ii separated in at least one of process steps e), f) and j), or the first obtained in process step a3) At least part of the aqueous phase, process steps:
k) subjecting to esterification to obtain an ester phase comprising at least one ester.

  This stage may be preferred when each at least one component ii is a carboxylic acid. The details of the esterification step are the same as those described above for process step a5) of the process according to the invention. For example, depending on the resulting purity of each separated component ii, for each component ii the market or further application compared to its ester, it was separated in at least one of process steps e), f) and j) It may be preferred to esterify at least one component ii rather than or in addition to obtaining at least one component ii itself. For example, the first aqueous phase has only a small proportion of impurities and / or component ii that is not intended to be separated, eg the total amount of impurities is less than about 6% by weight relative to the total weight of the first aqueous phase Preferably less than about 5% by weight, preferably less than about 4% by weight, more preferably less than about 3% by weight of impurities and / or components ii that are not intended to be separated, especially from eg component ii itself May also be preferred if at least one component ii contained in the first aqueous phase obtained in process step a3) is preferred if it contains impurities that are more easily separable from the respective component ii esters. .

Particularly preferred esters contained in the ester phase according to the invention are based on C ₁ -C ₄ -carboxylic acids and C ₁ -C ₄ -alcohols, with esters based on C ₂ -C ₄ -carboxylic acids being preferred. In addition to the methacrylate esters mentioned in connection with process step a5), particularly preferred esters are methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, sec-butyl acetate, methyl acrylate. , Ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, n-butyl Propionate, isobutyl propionate, sec-butyl propionate, among which acetate and acrylate are preferred.

  According to the invention, the ester phase can comprise at least two esters. This is because at least one component ii separated in at least one of process steps e), f) and j) or at least part of the first aqueous phase obtained in process step a3) has reacted. It may be the case when it contains at least two components ii, in particular at least two carboxylic acids, capable of forming esters. In this embodiment, the at least two components ii that can react to form an ester are, for example, very close in their properties, such as boiling point, solubility in certain solvents and volatility, especially by heat or other means. While difficult to separate, the esters may be preferred if they can be separated from each other with less difficulty.

The process according to the invention further comprises process step m) at least partially separating at least one ester from the ester phase;
n) It may optionally comprise a step of purifying at least one ester separated in process step m).

  In general, the ester phase comprises, in addition to at least one ester, a solvent, for example water, or at least one organic solvent suitable for esterification reactions or mixtures thereof, and unreacted components ii and optionally singular or Multiple additional esters may be included. The separation in process step m) may be by any separation means known to those skilled in the art and considered suitable for separating the respective ester from the ester phase. Examples of suitable separation means are, for example, thermal separation, such as distillation, fractionation or rectification, separation means based on different solubility of at least one ester compared to other components of the ester phase, solid-liquid separation means, such as in particular Filtration. If necessary or desirable, purification of at least one ester separated in process step m) can also be carried out. The purification means depends on the ester, and for example, purification by thermal means, purification by chromatography means, purification by washing, or purification by crystallization can be considered.

  In a preferred embodiment of the process according to the invention, at least a part of at least one ester obtained in at least one of process steps k), m) and n) is used as extractant in process step b).

In one embodiment of the method according to the invention, the method further comprises:
aa1) dissociating methyl tert-butyl ether (MTBE) to obtain at least one C ₄ compound and methanol, wherein at least one of process steps a1) using at least a portion of at least one C ₄ compound as a raw material Feed one gas phase oxidation. MTBE is widely used as a feedstock for isobutylene and the dissociation of MTBE is well known in the art. The dissociation of MTBE can be performed by any suitable means known to those skilled in the art. Suitable catalysts and reaction conditions are described, for example, in EP 1149814, WO 04/018393, WO 04/052809; Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, Vol. A4, 488 pages; Fattore, M.M. Massi Mauri, G.M. Oriani, G.M. Paret, Hydrocarbon Processing, August 1981, pp. 101-106; Ullmann's Encyclopedia of Industrial Chemistry, Fifth Edition, Vol. A16, pages 543-550; Chauvel, G.C. Lefbvre, “Petrochemical Processes, Technical and Economic Characteristics”, Vol. 1, Editions Technip, Paris, 1989, p. 213 et seq. U.S. Pat. No. 5,368,841, U.S. Pat. No. 4,957,0026 and references cited therein. The disclosures of these references are included herein by reference and form part of the disclosure of the present invention.

The two main products of MTBE dissociation are the C ₄ compounds isobutylene and methanol. Additional C ₄ compound tert-butanol may also be included in the dissociation reaction product phase. Either or both isobutylene and tert-butanol are fed as raw materials to process step a1) to constitute the total content of raw C ₄ compounds for this process step, or additional C ₄ from other sources. Can be added to the content. For example, to separate at least one C ₄ compound and methanol from each other as much as possible and to remove any by-products from dissociation that could adversely affect gas phase oxidation, There are one or more intermediate separation steps and / or purification steps between dissociation and feeding at least one C ₄ compound so obtained to gas phase oxidation in process step a1) Is possible. Separation and / or purification may be by any means known to those skilled in the art and deemed suitable. Suitable purification and separation methods are described, for example, in EP 1149814, WO 04/018393 and WO 04/052809. After the separation of methanol, the dissociated phase containing the C ₄ compound isobutylene as the main component can then be optionally purified and fed as raw material to process step a1). Suitable purification methods are known to the person skilled in the art and are preferably at least one of distillation, extraction, adsorption, absorption, chromatography or washing, preferably at least one of distillation and extraction, preferably at least one distillation. , And at least one extraction. Unreacted MTBE can be at least partially separated from the C ₄ compound phase at this stage. The separated MTBE can optionally be purified and at least partially recycled to the dissociation reaction.

  In a preferred embodiment of the process according to the invention, the methanol obtained in process step aa1) is fed to process step k). In another embodiment of the process according to the invention, the methanol obtained in process step aa1) can be fed to process step a5). Methanol can optionally be purified, preferably by thermal purification, such as distillation, fractionation or rectification, crystallization, extraction, column or washing, more preferably by at least one distillation. An example of the purification of methanol is described in EP1254887.

The present invention is an apparatus for producing at least one of methacrylic acid and methacrylic acid esters, wherein at least the following elements are fluidly connected to each other:
A1) Gas phase oxidation unit,
A2) Rapid cooling unit,
A3) First extraction unit,
A4) First separation unit,
A5) Optionally, a first esterification unit,
B) also relates to said device comprising a second extraction unit.

  The term “fluidically connected” means that in this application the unit is a fluid (which may be at least one of liquid, gas, vapor, supercritical fluid or any other fluid) from one unit. It is understood to mean connected so that it can be pulled into at least one other unit. For example, this may be direct via a tube or pipe made of a material that is resistant to reactants and prevailing conditions, such as stainless steel or glass, or any other suitable material known to those skilled in the art. This can be accomplished by simple connections or indirectly using tank transport means or tanks or reservoirs located between units. If the gas is introduced in a gaseous form and should remain in the gaseous form, the means for deriving the gas is preferably maintained at a temperature above the dew point of the gas. If the liquid is to be squeezed, the means for squeezing the liquid is preferably maintained at a temperature above the freezing and / or precipitation point of the liquid and / or components present in the liquid. This can be achieved by means of thermal insulation and / or heating of the means for the respective gas or liquid. All reactors, columns, and other equipment elements are preferably made from reactants and materials that are particularly resistant to the conditions in which they are subjected, such as temperature and pressure conditions.

  The gas phase oxidation unit A1) is preferably at least one reactor suitable for conducting a gas phase reaction, in particular a pressure reactor, preferably at least one formed as a tubular and / or shell reactor, for example. Including one multitubular reactor, and / or at least one plate reactor and / or at least one fluidized bed reactor, where a multitubular reactor is preferred. Particular preference is given to at least one multitubular reactor in which an oxidation catalyst is arranged in at least one tube, preferably in which case the tube is filled or coated with an oxidation catalyst, preferably filled. Preferred oxidation catalysts according to the present invention are those described above in connection with the process of the present invention. The reactor material should be resistant and preferably inert to the reactants and the prevailing conditions inside the reactor. Suitable reactors are commercially available, for example from MAN DWE GmbH (Deggendorferft, Germany) or from IHI (Japan) and are within the general knowledge of the person skilled in the art.

In a two-stage gas phase oxidation, the gas phase oxidation unit can include at least two reaction zones each containing an oxidation catalyst. The at least two reaction zones may be at least two reaction zones in a single reactor, or at least two reactors. The oxidation catalyst in the first reaction zone is preferably an oxidation catalyst for oxidizing at least one C ₄ compound, preferably isobutylene and / or tert-butanol to methacrolein, and the second reaction zone The oxidation catalyst is preferably suitable for the oxidation of methacrolein to methacrylic acid. Suitable catalysts are those mentioned above in connection with the process according to the invention.

In a preferred embodiment of the device according to the invention, the at least one oxidant source, preferably oxygen, preferably at least one supply means for air, and at least one supply means for water and / or steam are in the gas phase Fluidly connected to the oxidation unit. If the gas phase oxidation unit comprises at least a first oxidation region and a further oxidation region, the device for each oxidation region, at least one supply means for at least one oxidant source, and water and / or steam There may be included at least one supply means for. The apparatus further comprises a diluent, for example nitrogen, argon, and / or carbon dioxide, preferably nitrogen or carbon dioxide, for example carbon dioxide-containing recycle gas from a catalytic combustion unit (CCU) or a thermal combustion unit (TCU). Supply means may be included, preferably the CCU or TCU is downstream of the device according to the invention. Each supply means should be made of a material that is resistant to the reactants and the dominant conditions, such as stainless steel or glass. In a preferred design, oxygen, diluent and water are supplied to the C ₄ stream before entering the respective reactor, a mixture previously formed enters the reactor.

  Stage a1) of the process according to the invention is preferably carried out in a gas phase oxidation unit.

  In a preferred embodiment of the device according to the invention, the quench unit A2) is an absorption unit in which the gaseous oxidation phase is condensed and / or absorbed to form a liquid phase. It is preferred that the methacrylic acid leaving the catalytic reaction zone and present in the oxidation phase is condensed in the absorption unit to form a solution containing methacrylic acid as the main oxidation product, preferably an aqueous solution. Within the absorption unit, unreacted methacrolein can also be separated and, if desired, returned to the gas phase oxidation zone for further reaction. Quench units suitable for use in the apparatus according to the invention are known to those skilled in the art. Stage a2) of the process according to the invention is preferably carried out in the absorption unit.

  In a preferred embodiment of the device according to the invention, the quenching unit A2) is followed by a first extraction unit A3). The aqueous solution containing methacrylic acid formed in the quenching unit A2) is fed to a first extraction unit A3) where an organic solvent is fed into which methacrylic acid is preferably extracted essentially. The organic solvent is preferably essentially immiscible with water, thus forming an aqueous phase at least partially reduced in methacrylic acid and an organic phase containing methacrylic acid. Details regarding preferred organic solvents are given above in the description of process step a3). Process step a3) is preferably carried out in the first extraction unit A3). For use as the first extraction unit A3), any extraction unit known to those skilled in the art and considered suitable for such extraction of methacrylic acid is taken into account.

  The device according to the invention comprises a first separation unit A4) downstream of the first extraction unit A3). When the apparatus according to the invention is for the production of methyl methacrylate, the first separation unit A4) is upstream of the first esterification unit A5), preferably the first extraction unit A3) and the first esterification unit. And in fluid connection. The first separation unit A4) is preferably suitable for separating and preferably purifying methacrylic acid, in particular for separating methacrylic acid from the extractant used in the first extraction unit A3), And preferably, the methacrylic acid from the other components present in the crude organic phase exiting from the first extraction unit A3) of the device according to the invention and corresponding to the crude organic phase of process step a3) of the process according to the invention. Allows acid separation. Preferably, the first separation unit A4) is preferably suitable for the separation of distillation columns, fractionation columns, rectification columns and process steps a3) of the method known to the person skilled in the art and according to the invention. A thermal separation unit comprising at least one of any other thermal separation means considered. It is possible that the first separation unit A4) comprises one or more separation stages.

  An optional first purification unit for the purification of methacrylic acid separated in the first separation unit may also be arranged downstream of the first separation unit. An optional first purification unit is, for example, a thermal purification unit, such as a distillation column, fractionation column, rectification column or the like, a crystallization unit, or known to those skilled in the art and for the purification of methacrylic acid It can be any other device that is considered suitable.

  The apparatus according to the present invention provides a thermal means or storage for separating one or more further elements, for example high-boiling components and / or low-boiling components, between any or all of the above-mentioned units or elements. It may further comprise ripping means, means for solid / liquid separation, such as at least one filter and / or centrifuge, and / or a cooling and / or heating unit. In a preferred design, for example, a distillation column for low boilers and optionally a filter are placed downstream of the quench unit and upstream of the extraction unit. In a further preferred embodiment of the two-stage gas phase oxidation unit, a quench unit is arranged between the two stages.

  Unreacted methacrolein can be separated either in the quench unit, the first extraction unit, the first separation unit, the first purification unit, or any of the elements of the further apparatus described above, and further reaction Can be returned to the gas phase oxidation unit.

The first esterification unit A5) can be arranged downstream of the first separation unit A4) or optionally the first purification unit. The first esterification unit A5) is not particularly limited and may be any unit suitable for esterification to form a methacrylate ester, preferably methyl methacrylate, from methacrylic acid. It is preferably suitable for liquid phase esterification. The first esterification unit A5) preferably comprises an esterification catalyst, which may be a heterogeneous catalyst or a homogeneous catalyst, such as a solid catalyst or a liquid catalyst, and is preferably an acidic ion exchange resin, such as US Pat. No. 6,469,292. No., JP1249743, EP1254887, or trade name Amberlyst (registered trademark) (Rohm and Haas Corp.), Dowex (registered trademark) (Dow Corp.) or Lewerit (registered trademark) (Lancess AG) Or an acid that can catalyze esterification, such as sulfuric acid, H ₂ SO ₄ .

  A second purification unit can be arranged downstream of the first esterification unit A5) for purification of the methacrylate ester produced therein. An optional second purification unit is, for example, a thermal purification unit, such as a distillation column, a fractionation column, a rectification column or the like, a crystallization unit, or a methacrylic acid ester, in particular methyl methacrylate, known to those skilled in the art Any other device considered suitable for the purification of

  The device according to the invention further comprises a second extraction unit B). The second extraction unit B) converts at least a portion of the water contained in the first aqueous phase obtained in the first extraction unit A3) to at least one organic compound, in particular at least one component ii mentioned above. To obtain a second aqueous and organic phase, separated from at least a portion of Process step b) of the process according to the invention is preferably carried out in the second extraction unit B).

  In the second extraction unit B), at least a part of the first aqueous phase is extracted with an extractant to form a second aqueous phase and an extracted phase, and preferably the second water phase The phase is also separated from the extracted phase to the maximum extent possible within technical limits. Accordingly, at least process step b) and preferably process step c) of the process according to the invention are also preferably carried out continuously, preferably in the second extraction unit B). The second extraction unit B) is preferably at least one extraction column, wash column, phase separator or known to the person skilled in the art and suitable for liquid-liquid extraction and preferably an organic or ionic liquid phase Other devices considered to be suitable for extraction and separation, more preferably in a continuous process, such as at least one distillation column, at least one pulse packed column and / or packed column, At least one rotary extractor, in particular at least one rotary extractor that uses centrifugal force for separation, at least one wash tower, and / or at least one phase separator. The second extraction unit B) can preferably withstand the ambient temperature as well as temperatures other than ambient temperature, in particular elevated temperatures, in particular the temperatures mentioned above in connection with process steps b) and c), and Can operate.

  For example, at least one incinerator or combustion unit may be included in the apparatus according to the invention in order to incinerate the extracted phase obtained in the second extraction unit.

  The device according to the invention can further comprise a third separation unit D). The third separation unit D) preferably serves to separate any residual extractant used in process step b) from the second aqueous phase. Process step d) of the process according to the invention is preferably carried out in a third separation unit D). The third separation unit D) may further be an extraction unit, but is preferably a thermal separation unit, such as a distillation column, fractionation column, rectification column, or the like, in which case those skilled in the art Any means known and suitable for such separations are taken into account in the device according to the invention.

  The device according to the invention can further comprise a fourth separation unit E). A fourth separation unit E), corresponding to process step e) of the process of the present invention, separates at least part of the extractant from the extracted phase to obtain an extracted phase comprising at least one component ii according to the present invention. Preferably, it includes at least one heat separation device for. Corresponding to process step f) of the process according to the invention, at least one further thermal separation device may be included for separating at least part of the at least one component ii according to the invention from the extract. For use in the apparatus according to the invention, a thermal separation apparatus known to the person skilled in the art and considered suitable for carrying out the separation of process steps e) and f), such as a distillation, fractionation or rectification column. At least one or the like can be taken into account.

  Additional separation units may be included in the device according to the invention. One example of a preferred further separation unit corresponds to step j) of the process according to the invention, at least one component ii, a mixture comprising at least two components ii according to the invention, for example step f of the process according to the invention Is a separation unit suitable for separation from the mixture obtained in (1). Preferably, such further separation unit is a thermal separation unit, preferably comprising at least one distillation column, fractionation column, rectification column or the like.

  The apparatus according to the invention preferably has methacrylic acid between the fourth separation unit E) and / or at least one further separation unit and the first extraction unit A3) and / or the first separation unit A4). And at least one conduit for returning at least one of the methacrylic acid-containing phases to at least one of the first extraction unit A3) and the first separation unit A4).

  The apparatus according to the invention optionally comprises at least one second esterification unit K), preferably a second extraction unit B), a third separation for esterifying at least one component ii to obtain an ester phase. Unit D) and at least one downstream of the fourth separation unit E). Process step k) is preferably carried out in the second esterification unit. Details regarding the second esterification unit are the same as those described above for the first esterification unit A5).

  The device according to the invention corresponds to process step m) of the process according to the invention for at least partially separating one or more esters from one another, in particular at least one ester with at least one first step. It can also comprise at least one ester separation unit M) for at least partial separation from the ester phase obtained in the two esterification units. Any apparatus known to the person skilled in the art and considered suitable for the separation of esters can be used as the ester separation unit M). Thermal separators of the type already described, as well as crystallization devices, extraction devices, phase separation devices are preferred as ester separation units M) in the device according to the invention.

  In order to purify the ester and / or the esters obtained in the second esterification unit or separated in at least one ester separation unit, at least one further purification unit N) is used according to the invention. May be provided in the apparatus. Process step n) of the process according to the invention is preferably carried out in a further purification unit N). The details of this further purification unit correspond to those for the purification unit described above in connection with the first esterification unit A5).

  The apparatus according to the invention is between a second extraction unit B) and at least one of a second esterification unit K), an ester separation unit M) and a further purification unit N) for purifying at least one ester. May also include at least one ester conduit. The at least one ester conduit comprises at least one ester from at least one of the second esterification unit K), the ester separation unit M) and the further purification unit N) for purifying the at least one ester. In the extraction unit B), wherein at least one ester can optionally be used as an extractant.

  In a preferred embodiment of the device according to the invention, the device further comprises an MTBE dissociation unit AA1) upstream of the gas phase oxidation unit A1). Dissociation units and suitable catalysts for MTBT dissociation are well known in the art and are within the general knowledge of those skilled in the art, for example, Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, Vol. A4, 488 pages; Fattore, M.M. Massi Mauri, G.M. Oriani, G.M. Paret, Hydrocarbon Processing, August 1981, pp. 101-106; Ullmann's Encyclopedia of Industrial Chemistry, Fifth Edition, Vol. A16, pages 543-550; Chauvel, G.C. Lefbvre, “Petrochemical Processes, Technical and Economic Characteristics”, Vol. 1, Editions Technology, Paris, 1989, p. 213 et seq. U.S. Pat. No. 5,368,841, U.S. Pat. No. 4,957,0026 and references cited therein.

  The isobutylene separation unit S1) is preferably arranged between the MTBE dissociation unit AA1) and the gas phase oxidation unit A1) and is fluidly connected to each other. The isobutylene separation unit S1) serves to separate also the isobutylene phase and preferably the methanol phase from the effluent of the second catalytically active zone, said effluent comprising isobutylene and methanol as main components. The isobutylene separation unit S1) may be at least one of an extractor, a crystallization device, a column, a distillation device, a rectification device, a membrane, a dialysis evaporation device, a phase separator, and a washing device. The isobutylene separation unit S1) preferably comprises an outlet for the isobutylene phase and an outlet for the methanol phase. The outlet for the isobutylene phase is preferably connected to the gas phase oxidation unit, optionally via an intermediate unit, for example a purification unit, a heat exchanger and / or a pressurizer. The outlet for the methanol phase is preferably connected to at least one of the first esterification unit and the second esterification unit, optionally via an intermediate methanol purification unit. Any apparatus known to those skilled in the art and considered suitable for purifying methanol can be included as a methanol purification unit. Examples of suitable purification units preferably include at least one distillation apparatus, crystallization apparatus, extractor, column or washing apparatus, more preferably at least one distillation apparatus. An example of a purification unit for methanol is described in EP1254887.

  The invention also relates to a method according to the invention carried out in an apparatus according to the invention.

  The invention will be explained more precisely by the following figures and non-limiting examples.

FIG. 1 schematically shows a preferred embodiment of the method according to the invention in the form of a flowchart. FIG. 2 schematically shows an embodiment of the device according to the invention. FIG. 3 shows a pilot plant of the embodiment.

According to the embodiment of FIG. 2, a C ₄ compound is introduced into the gas phase oxidation unit A1, where it is oxidized to methacrylic acid in a one-stage or two-stage catalytic gas phase oxidation. The inlet to the gas phase oxidation unit A1 for C ₄ compounds, oxygen, steam, and inert diluent gas is not shown. The C ₄ compound can be supplied from the MTBT dissociation unit AA1 (not shown) via an isobutylene separation unit S1 (not shown). The gaseous methacrylic acid phase obtained in the gas phase oxidation unit A1 is led via line 1 to the quenching unit A2, where it is cooled and absorbed in water or in the aqueous phase, A containing aqueous phase is formed. The inlet for the quench liquid to the quench unit A2 is not shown. The aqueous phase of methacrylic acid is extracted via line 2 to the first extraction unit A3, where it is extracted with an organic solvent as the extractant and the organic and aqueous phases (method according to the invention). First aqueous phase) is formed. The two phases are separated in the first extraction unit A3.

  The organic phase from the first extraction unit A3 is routed via line 3 to the first separation unit A4, where it is distilled and separated into methacrylic acid and extractant. The extractant can be recycled via line 6 to the first extraction unit A3. Methacrylic acid can be recovered via line 5 and optionally purified in one or more purification units (not shown) downstream, or optionally purified via line 4 (Figure (Not shown) to the first esterification unit A5. In the first esterification unit A5, methacrylic acid can be esterified in the separation unit S1 (not shown), for example using methanol, for example methanol separated from the MTBE dissociation phase, to form methyl methacrylate. Methacrylic acid can also be esterified with alcohols other than those mentioned above in the first esterification unit A5. The ester produced in the first esterification unit A5 can be recovered via line 7 and optionally polymerized in the polymerization unit A6 (not shown), optionally in the middle and / or downstream. With purification.

  The aqueous phase separated in the first extraction unit A3 is extracted to the second extraction unit B via line 8, where it is extracted using an organic solvent as the second extractant, A phase (corresponding to the second aqueous phase of the process according to the invention) and an organic phase are formed. The aqueous phase is diverted via line 9 to a third separation unit D where residual extractant from the second extraction stage is at least partially separated and optionally via line 25. Can be recycled to a second separation unit B. The residual aqueous phase (corresponding to the third aqueous phase of the process according to the invention) can be recycled, for example, to the gas phase oxidation unit A1 (conduit not shown), can be used as process water, or a biological purification unit (figure (Not shown) or can be discharged via line 20. The organic phase separated in the second extraction unit B can be routed via line 10 to a fourth separation unit E, where at least one component ii can be separated. At least a portion of at least one component ii separated in the fourth separation unit E can be recovered via line 11 and optionally purified (not shown). If the mixture of components ii is separated in the fourth separation unit E, this mixture can be separated into further separation units for separating components ii from each other (not shown). If the methacrylic acid or methacrylic acid-containing phase is separated in the fourth separation unit E, this methacrylic acid or methacrylic acid-containing phase is fed to the first extraction unit A3 via line 15 or via line 16 The first separation unit A4 can be selected. It is also possible to find at least a part of the at least one component ii separated in the fourth separation unit E to the second esterification unit K via line 14. Either the organic phase and the aqueous phase separated in the second extraction unit B or the third separation unit D can be separated into the second esterification unit K. Within the second esterification unit K, at least one component ii is esterified with an alcohol to form the corresponding ester. If the alcohol is methanol, this methanol may be introduced, for example from the MTBE dissociator AA1, via the separation unit S1, optionally with intermediate purification (not shown). If the ester phase obtained in the second esterification unit K contains more than one ester, at least one ester can be separated in the ester separation unit M. At least one ester can be purified in a downstream ester purification unit N (not shown). At least one ester obtained in one or more of the second esterification unit K, the ester separation unit M and the ester purification unit N is selected in the second extraction unit B for use as an extractant. be able to.

Test method
Measurement of partition coefficient (k value) An aqueous phase containing a predefined amount of acetic acid is mixed with the same volume of organic solvent (extractant). The two phases are shaken and / or stirred at 50 ° C. for 15-30 minutes to ensure that an equilibrium distribution of acetic acid across the aqueous and organic phases is achieved. The mixture is then split back into an organic phase and an inorganic phase at 50 ° C., and the two phases are separated from each other. The amount of acetic acid present in the separated organic phase is measured by gas chromatography (GC) or high pressure liquid chromatography (HPLC).

・ 実行時間： １８．３分
・ 検出器 ＦＩＤ
・ 設定値 ２６０℃ HPLC: Agilent 1200
・ Pump: Quaternary pump ・ Eluent: Acetonitrile KH ₂ PO ₄ (0.02 mol / L) pH 2
・ Gradient 3 minutes 0% 100%
・ 15 minutes 50% 50%
・ 30 minutes 70% 30%
・ Flow rate: 1.0 ml / min ・ Stop time: 30 minutes ・ Post time: 5 minutes ・ Control pressure: 190 bar, maximum 250 bar
・ Autosampler: Autosampler ・ Injection volume: 20μL
・ Column oven: Including column switching control ・ Temperature: 30 ℃
-Column: Agilent SB-Aq
· Dimensions Length 150mm, d _i 4.6mm, 3.5μm materials Detector MWD or DAD
UV 210nm, 241nm, 254nm, 265nm (DAD is preferred)
-GC: Perkin Elmer Autosystem
・ Autosampler: Perkin Elmer
・ Cleaning solvent THF
・ Injection volume: 1.0 μL
・ Extractor ・ Split Split ratio 100
・ Temperature program 200 ℃
・ Flow rate Constant pressure 12.0
・ Column oven:
・ Column J & W Scientific DB 225
・ Dimensions Length 30m, d _i 0.25mm, 0.25μm Material ・ Temperature program

・ Execution time: 18.3 minutes ・ Detector FID
・ Set value 260 ℃

Example 1:
This example was carried out in a pilot plant according to FIG. The artificial first aqueous phase was mixed and stored in B-100. The first aqueous phase is filtered, preheated and pumped to the top of the liquid-liquid extraction column K-100. K-100 is a glass packed and jacketed extraction tower, which is temperature controlled at 50 ° C. via a heat exchange fluid in a double jacket. While the fluid-fluid extraction was carried out in countercurrent mode of operation, the raw material was pulled to the top of the column and the extractant was pulled to the bottom of the column. The extractant ethyl acetate was used at an extractant / raw material ratio of 2.5. K-100 was filled with irregular fillers and operated with continuous phase pulsations (stroke 10 mm, frequency 56 min ^-1 ). The extractant used was continuously regenerated and thus operated in a continuous recycling loop. The extraction phase was preheated and fed to an extractant regenerated glass distillation column K-200. The distillation column K-200 had a structured packing and was operated with a steam heated evaporator and a condenser with cooling water. The distillate showed regenerated extractant and was collected in a storage container. The bottom effluent was the final extract, which was pulled into the separation unit. The second aqueous phase was drawn from the bottom of K-100, preheated to 90 ° C. and fed to the second extractant regenerated glass distillation column K-300. The distillation column K-300 was continuously operated with a structured filler and a steam heated evaporator and a condenser operated with cooling water. The third aqueous phase was withdrawn from the K-300 tower bottom and fed to the final tank for the third aqueous phase. At the top of the K-300, the regenerated extractant was withdrawn and fed to the storage vessel along with the regenerated extractant from K-200.

ACA = acetic acid AA = acrylic acid MAA = methacrylic acid PRA = propionic acid EtAC = ethyl acetate EtOH = ethanol ACK = acetone FOL = formaldehyde

Claims (19)

At least one method for producing methacrylic acid and methacrylic acid ester ,
a1) gas phase oxidation of at least one C ₄ compound to obtain a reaction phase containing methacrylic acid;
a2) quenching the reaction phase to obtain a crude aqueous phase containing methacrylic acid;
a3) Step of extracting at least a part of methacrylic acid from a crude aqueous phase containing methacrylic acid into an organic solvent to obtain a crude organic phase containing methacrylic acid and a first aqueous phase. The aqueous phase contains the following components:
i. At least 65% by weight of water, based on the total weight of the first aqueous phase, and ii. At least one organic compound other than the organic solvent used as extractant in process step a3), not more than 35% by weight, based on the total weight of the first aqueous phase,
Here, the sum of the masses of i and ii is 100% by mass;
a4) separating and optionally purifying at least part of the methacrylic acid from the crude organic phase obtained in process step a3);
a5) optionally esterifying at least a portion of the methacrylic acid obtained in step a4);
b) extracting at least a portion of the first aqueous phase obtained in step a3) with an extractant to form an extracted phase comprising component ii and a second aqueous phase, wherein The second aqueous phase has a reduced component ii compared to the first aqueous phase;
c) at least partially separating the second aqueous phase obtained in step b) from the extracted phase obtained in step b);
d) Optionally, at least one organic compound is at least partially separated from the second aqueous phase obtained in step c) to reduce at least one organic compound compared to the second aqueous phase. Obtaining a third aqueous phase that is being treated;
e) optionally separating at least a portion of the extractant from the extraction phase to obtain an extract comprising at least one component ii.
And using the ester obtained by esterifying at least part of the first aqueous phase obtained in process step a3) as the extractant in process step b) . The process according to claim 1, further comprising the process step f) separating at least part of the at least one component ii from the extract.   The second aqueous phase contains not more than 5.0% by weight of organic compounds other than the extractant used in process step b), based on the total weight of the second aqueous phase. Method.   4. The method according to claim 1, wherein the third aqueous phase contains not more than 3% by weight of organic compounds other than the extractant used in process step b) with respect to the total weight of the third aqueous phase. The method according to item.   The process according to any one of claims 1 to 4, wherein in a further process step g) the third aqueous phase is subjected to at least one biological purification treatment.   6. The method according to claim 5, wherein the at least one biological purification treatment is at least one of an aerobic treatment and an anaerobic treatment.   7. In further process step h), at least a part of the extractant separated in at least one of process steps d) and e) is recycled to process step b). The method described.   At least one component ii obtained in step f) is a mixture of at least two components ii, and in a further process step j) at least one component ii is at least partly separated from this mixture. The method according to any one of claims 2 to 7.   9. A process according to any one of claims 1 to 8, wherein the at least one organic compound of component ii is at least one organic compound selected from carboxylic acids, aldehydes and ketones. 10. Process according to any one of claims 1 to 9, wherein the extractant used in process step b) is characterized by at least one of the following characteristics i) to iv):
i) The average k value measured for acetic acid in the extractant-water system at 25 ° C. by the methods described within this application is in the range of 0.1-100;
ii) the evaporation enthalpy is 2260 kJ / kg or less;
iii) the boiling point is in the range of 35-140 ° C;
iv) The solubility in water is 150 g / l or less at a temperature of 25 ° C.   The method according to any one of claims 1 to 10, wherein the at least one component ii is at least one of acetic acid, acrylic acid, propionic acid, and methacrylic acid.   At least one component ii separated in at least one of process steps e), f) and j) is methacrylic acid or contains methacrylic acid, and at least a part of this methacrylic acid is a process step a2 12. The process according to claim 11, wherein the process is added to the crude aqueous phase obtained in step a) or to the crude organic phase obtained in process step a3). Process step e), f) and j) of at least part of at least one component ii separated in at least one, process steps:
The process according to claim 1, wherein k) is subjected to esterification to obtain an ester phase comprising at least one ester.   14. A method according to claim 13, wherein the ester phase comprises at least two esters. Further, process step m) at least partially separating at least one ester from the ester phase;
n) Process according to claim 13 or 14, comprising the step of optionally purifying at least one ester separated in process step m).   16. At least one part of at least one ester obtained in at least one of steps k), m) and n) is used as an extractant in process step b) according to any one of claims 13-15. The method described. Wherein the at least one ester, C ₁ -C ₄ - carboxylic acid and C ₁ -C ₄ - based on alcohol, A method according to any one of claims 13 to 16. further,
aa1) dissociating methyl tert-butyl ether to obtain at least one C ₄ compound and methanol, and using at least a part of at least one C ₄ compound as a raw material, at least one gas phase oxidation of process step a1) 18. A method according to any one of claims 1 to 17, wherein the method is provided in   The process according to claim 18, wherein the methanol obtained in process step aa1) is fed to process step k).

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