Processing formaldehydefree mixtures

 

The invention relates to an improved method for the removal of formaldehyde or its adducts of organic liquid mixtures obtained in the production of methyl methacrylate containing at least a carboxylic acid or an ester of carboxylic acid and formaldehyde or its adducts, which forms a two-phase mixture of water, comprising at least one extraction liquid organic mixture in the system liquid-liquid using water as the extractant with getting the flow of the organic phase and flow of the aqueous phase, and the flow of the organic phase contains significantly reduced the concentration of formaldehyde or its adducts compared with the liquid organic mixture. The invention also relates to a method for production of methyl methacrylate with the removal of formaldehyde or its adducts obtained from liquid organic mixture. The method allows to reduce the formaldehyde content in the product stream of methyl methacrylate to less than 0.5. %. 2 C. and 12 C. p. F.-ly, 5 PL. , 1 Il.

This invention relates to a method of processing formaldehydefree mixtures, in particular to the processing of methyl methacrylate streams containing formaldehyde.

Usually Sa capital-intensive and produces methyl methacrylate with a relatively high cost.

Other methods of production of methyl methacrylate published in the US-3535371, US-4336403, GB-A-1107234, JP-A-63002951 that require condensation of propionic acid with formaldehyde or metallum in the presence of methanol. In these references, however, are not described as methylmethacrylate product can be separated and extracted from the residual formaldehyde and other components, which can be found in the reactor product stream.

Currently, it is found that the residual formaldehyde may be separated from a stream of methyl methacrylate in a way that allows you to return the formaldehyde initial condensation process. Although it is recognized that this invention is particularly useful for the separation of formaldehyde from a stream containing methyl methacrylate, it should be clear that the method can also be applied to remove varieties of formaldehyde from a large number of other organic compounds.

Therefore, this invention relates to a method of removing varieties of formaldehyde from a liquid organic mixture which contains at least a carboxylic acid or an ester of carboxylic acid and varieties of formaldehyde and which forms a two-phase mixture of water, which contains SST, where water is used as the extractant to obtain the flow of the organic phase and flow of the aqueous phase so that the flow of the organic phase contains varieties of formaldehyde in significantly reduced concentrations compared with the liquid organic mixture.

Under varieties of formaldehyde, meaning that the formaldehyde in the liquid stream is usually present in the form of adducts with water or polar organic compounds such as alcohols. Generally, the free formaldehyde is in the form of light gas, and thus probably does not form part of the liquid mixture. Therefore, it is assumed that references to formaldehyde include varieties of formaldehyde, which are adducts of formaldehyde with components of the liquid mixture or water.

For the extraction of formaldehyde from a liquid stream using water, but it is not necessary that the water was clean. Used water can contain small amounts of dissolved compounds that do not have a noticeable effect on the extraction of varieties of formaldehyde in the aqueous phase. During the production process, which includes a method of removing formaldehyde of this invention may be Adobe this way. The suitability of a particular water stream for use as an extractant can be easily determined by analysis or experiment. Preferably the content of such water flow is known and contains compounds that are present in the organic stream, or which can be easily removed from the organic stream. Thus, the water, as used in these specifications should be considered, including such water stream, which may contain small amounts of dissolved compounds, such as trace amounts of organic substances.

The concentration of formaldehyde in the flow of the organic phase, leaving the solvent extraction process is preferably <10%, more preferably <5% and especially <1% of the concentration of formaldehyde in the raw mixture containing formaldehyde. The concentration of formaldehyde in an organic product will largely be determined by the equipment and method, such as number of stages, attained the degree of mixing or separation, etc., According to the invention the flow of the organic phase contains less than 2.5% by weight of formaldehyde. The final concentration is much less than 1 wt.% about the kind of the organic mixture is subjected to at least one stage extraction system liquid-liquid. Preferably spend more than one stage extraction system liquid-liquid, for example can be drawn between one and twenty, preferably between one and ten stages of extraction in the system liquid-liquid, although the number of stages required will depend on the nature and relative amounts of the compounds in the mixture. By reference to the stage of separation refers to theoretical stage. Specific process equipment, such as contact column with rotating disks, represents the continuity of one phase, so that certain physical stage may not be obvious, although the existence of theoretical stages can be calculated.

Although the aqueous phase at least one phase extraction system liquid-liquid can be removed, preferably as aqueous phase is subjected to further, at least one stage extraction system liquid-liquid, where it is mixed with a suitable organic liquid to be extracted (removed) from the water stream organic compounds other than formaldehyde. Suitable fluids include non-polar organic solvents that do not mix with water, such as alkanes, such as benzene, hexane or heptane, is in the system liquid-liquid contains the process in a counter, when the organic stream is directed in counterflow with water, so that the extraction of formaldehyde in the aqueous phase and removal of organic substances from aqueous phase into an organic solvent can be performed in one operation. Using this procedure, containing formaldehyde mixture is served between water and an organic stream, preferably approximately in the center between the two feeds that contain a counter-current flow. The preferred countercurrent flow can be conveniently generated in a well-known apparatus for extraction in the system liquid-liquid, such as a contact apparatus with rotating disks or cascade mixer-settlers.

As discussed above, it was found that the processing method according to the invention is particularly useful for removing formaldehyde from the containing formaldehyde liquid organic mixture which is the product of the production process complicated Olkiluoto ester of acrylic acid (e.g. methyl methacrylate), where the complex alkilany ether alanovoy acid is subjected to reaction with methanol and formaldehyde in the presence of a catalyst. In particular, one useful application of the invention was found to remove formaldehyde from the containing of metal is ethacrylate by condensation reactions of methylpropionate with formaldehyde and methanol over a suitable catalyst.

While specified liquid flow carboxylic acid, or a complex ester of carboxylic acid contains at least 5% (wt./wt.) of methyl methacrylate and at least 20% of methylpropionate.

Therefore, according to further aspect of the invention, a method for production of methyl methacrylate containing stages: (i) interaction propionic acid or its complex ester with formaldehyde or its predecessor on the stage of the condensation reaction with the formation of a gaseous product stream containing methyl methacrylate, residual formaldehyde, residual propionic acid or its ester and by-products; (ii) liquefying at least part of the gaseous product stream to the formation of the liquid product stream containing essentially all of the methyl methacrylate, the residual formaldehyde by-products and the rest of the residual propionic acid or its ether complex; (iii) exposure to liquid product stream in at least one stage extraction system liquid-liquid where water is used as the extractant to obtain the flow of the organic phase, which essentially does not contain formaldehyde, and flow of the aqueous phase, which contains, in suspect with formaldehyde or its predecessor, for example metallum, and specifically by condensation of methylpropionate with formaldehyde. By-products of the reaction include water, diethylketone (DPC), propionic acid (PC), methacrylic acid (MAC) and methylisobutyl (IIB). The reaction is preferably carried out in the presence of methanol. Methanol can also be obtained in the reactor as a byproduct of adverse reactions, such as reactions of methyl esters of propionic acid and methacrylic acid with water in the feed material. Therefore, the gaseous product stream may also contain methanol.

The condensation reaction is preferably carried out in the presence of a catalyst. Suitable catalysts include alkali metals and alkaline earth metals, optionally deposited on a suitable carrier, for example cesium catalyst on the carrier of silicon dioxide.

Stage of the condensation reaction can be conducted at any suitable temperature and pressure. Usually the stage of the condensation reaction is carried out at a temperature of from 250 to 400oWith and preferably from 300 to 375oC. Usually the stage of the condensation reaction is carried out at a pressure from 104up to 106Nm-2and preferably from 105up to 106

Stage extraction system liquid-liquid preferably carried out in apparatus in which create a counter-current flow of water and organic liquid, so that ISBN organic liquid, as mentioned previously, the preferred organic liquid for this purpose is methylpropionate, which is already present in the process and which can be reused in the production process of methyl methacrylate.

Water will flow out of the extractor rich in organic matter and organic flow will come out saturated with water, so preferably both threads to distill to remove organic matter and water, respectively, which can be re-fed to the extractor. After distillation of the water stream may be removed as a waste stream, but it may contain a significant amount of adducts of formaldehyde and therefore it may be preferable to continue to recycle this thread and return to the cycle of formaldehyde on the stage of the condensation reaction.

Found that the distribution of formaldehyde between organic and aqueous phases is improved, if the concentration of methanol in the liquid stream that is subject to division, is relatively low. In other words, low methanol content in the liquid product stream favors the movement of formaldehyde in the aqueous phase, i.e., the distribution coefficient of formaldehyde (defined as the ratio of to is the super low. Preferably the concentration of methanol in the liquid product stream is less than 5 mass%, more preferably less than 2.5%, especially less than 1% by weight. Therefore, at least some excess methanol in the liquid product stream, if it exists, is preferably removed, for example by distillation or by changing the conditions under which the gaseous reactor product stream is liquefied, or by other means before processing extraction system liquid-liquid. The excess methanol is conveniently can be removed with some excess methylpropionate by azeotropic distillation of a mixture of methylpropionate and methanol and returning it to the reactor.

The invention is illustrated by a single example in the drawing, which shows a map of the stream for the Department of methyl methacrylate from formaldehyde and other compounds using the extraction system liquid-liquid.

In the drawing the gaseous stream from the reactor (not shown), which receive the methyl methacrylate (MMA) by the condensation reaction between methylpropionate (MEP), methanol and formaldehyde, sharply cooled to a liquid product stream (1) containing MMA, formaldehyde, methanol, MEP, water, methylisobutyl (IIB), p is neither liquid-liquid, and which also serves water flow (2) and the flow MEP (3). The extractor system liquid-liquid separates incoming flows to the organic stream (5) and water flow (10). Organic stream (5) contains most of the MEP, MMA, PC, IIB and DEK fed to the extractor, and contains the equilibrium amount of water. Water flow (10) contains most of the water and formaldehyde (in the form of adducts with water and methanol) and also contains the equilibrium quantity is less polar molecules, mainly MEP. In this system, the methanol is split between organic and water flow, and probably should be more soluble in the aqueous phase than in the organic phase.

Organic stream (5) is sent to the distillation column (6) to remove the water. The head product of (6) is condensed with the formation of two liquid phases which are separated in the decanter (21). The aqueous layer (8) recycle to the top of the extractor and the organic layer (9) is recycled back as the phlegm in (6). The residual stream from (6) is sent to a distillation column (16) where MEP selected as a head product (14). Part of this stream may be recycled back to the extractor and used as organic feed material (3) and the rest can be re-filed in re). Stream (17) is the main product of (19) and contains MMA and components that boil close to the MMA, such as decks and IIB. This product can be further purified, e.g. by distillation, to increase the purity of MMA. The residual product of (19) is a stream (18), which contains molecules heavier than MMA, such as PCs and MACS. They can be re-submitted to the condensation reactor.

Water stream (10) is served on the top of the distillation column (12), and it acts as irrigation phlegm columns. Stream (11) is condensed head product from (12), and serves on the bottom of the extractor (4). The residual product from (12) contains water and adducts of formaldehyde, and can be either eliminated or further processed to remove the water, so that the adducts of formaldehyde could be recycled to the condensation reactor.

The invention is further illustrated by the following examples.

Example 1 Prepare the source solution containing the following components: formaldehyde of 13.4 wt. % methanol 19,56 wt. % methylpropionate 28,42 wt. % methyl methacrylate 18,33 wt. % water 20,29 wt. %. 100 ml of the original solution is mixed with 100 ml of demineralized water. Then the resulting mixture was subjected to phase separation of the first organic and the first aqueous phase. H, the button to get a second organic and the second aqueous phase. In this way a portion of the first aqueous phase is recovered and then carry out the extraction of the initial solution to produce a third organic and a third aqueous phase. The composition of the organic and aqueous phases are shown in table 1.

Example 2 Three initial solution of methyl methacrylate containing formaldehyde, methanol, methylpropionate, water and other impurities, cook until compounds containing approximately 15, 7.5 and 2% (wt./wt.) of methanol. The compositions are given in table 2. The content of methylpropionate lead in accordance with the change in the content of methanol in order to simulate the removal of methylpropionate with methanol as an azeotropic mixture.

Supplied to the mixture washed in water using single-stage installation of the mixer-settler at three different relations of the supplied material : wash water. The results are presented in table 3. The results show that when the percentage of methanol in the feed mixture is reduced, the distribution coefficient of formaldehyde between organic and aqueous phases (defined as the ratio of the formaldehyde concentration in the organic phase to the concentration of formaldehyde in the aqueous phase) is reduced, so that more formaldehyde p. the organic phase is increased at low concentrations of methanol, therefore, the Department of methyl methacrylate from formaldehyde significantly better at relatively low concentrations of methanol.

Example 3 Setting for solvent extraction type five-stage mixer-settler is prepared for operation by filling half of the cells of the heavy phase and subsequent refilling easy phase just prior to the flow cell through the top. Include pumps for light and heavy phases, followed by agitator/impeller mixer-settler. Flow rate of each phase level and establish in order to achieve the 60-minute time across the entire width of the mixer-settler. In this experiment, the heavy phase is water supplied to the cell 1 and the light phase is methylpropionate supplied to the cell 5. The mixer-settler reaches equilibrium within approximately 60 minutes.

An aqueous solution of 4.4 wt.% propionic acid is prepared from propionic acid and water, and the exact concentration is determined by titration 0,0095 N. NaOH (aq. ). A solution of 4% (wt./wt.) formaldehyde in methylpropionate prepared by extraction 35 wt. % solution of formalin in methylpropionate. When the mixer-settler is stabilized, distilled water, applied EUNIC, replace methylpropionate containing formaldehyde. The final sample obtained water from wells 5 and received methylpropionate from cell 1 analyzed for formaldehyde by titration using sodium sulfite as described by J. F. Walker, "Formaldehyde" (Reinhold/Chapman & Hall 1964-ACS monograph series 159), and propionic acid by titration with NaOH. The results in wt % are given in table 4.

Results marked with * indicate that the limit of detection of formaldehyde used titration method is 0.01%. The results show that formaldehyde can be extracted from the organic flow of water without loss of organic acid in the aqueous phase.

Example 4 Installation for the extraction of the type of mixer-settler used in example 3, provided with a backflow of methylpropionate and water as described in example 3, each served at a rate of 3 ml/min and allow to settle to steady state. Prepare a mixture of organic substances containing the components listed in table 5, and serves on stage 3 of the mixer-settler at a speed of 6 ml/min Sample taken from cells 1 and 5 and analyzed by gas chromatography. The concentration of formaldehyde determined by titration sulfite as described in example 3. Results Yes what you show, the formaldehyde from the stream of mixed organic substances can be extracted in the water flow without appreciable loss of other organic components of the organic mixture.

Claims

1. Method of removing formaldehyde or its adducts of organic liquid mixtures obtained in the production of methyl methacrylate containing at least a carboxylic acid or an ester of carboxylic acid and formaldehyde or its adducts, and which forms a two-phase mixture of water, comprising at least one extraction liquid organic mixture in the system liquid - liquid using water as the extractant with getting the flow of the organic phase and flow of the aqueous phase, and the flow of the organic phase contains significantly reduced the concentration of formaldehyde or its adducts compared with the liquid organic mixture.

2. The method according to p. 1, where the specified stream organic phase contains less than 2.5% by weight of formaldehyde.

3. The method according to p. 2, where the concentration of formaldehyde in the specified thread the organic phase is less than 10% of the concentration of formaldehyde in the specified liquid organic mixture.

4. The method according to p. 3, where the specified stream org is ne up to twenty consecutive stages of extraction in the system fluid the fluid.

6. The method according to any of paragraphs.1-5, optionally containing the stage at which the specified stream of the aqueous phase is brought into contact with an organic solvent, which forms a separate phase in the adulteration of the water.

7. The method according to p. 6, where stage extraction system liquid-liquid contains a counter-current process, where the thread of the specified organic solvent is passed as a counterflow to the water and the liquid flow carboxylic acid, or a complex ester of carboxylic acid is fed into the process at the stage between the flow of organic solvent and the feed water flow.

8. The method according to p. 6 or 7, where the specified organic solvent contains methylpropionate.

9. The method according to any of paragraphs.1-8, where a specified liquid flow carboxylic acid, or a complex ester of carboxylic acid contains methanol and at least some amount of methanol is removed from the liquid product stream before it is subjected to extraction in the system liquid - liquid.

10. The method according to any of paragraphs.1-9, where a specified liquid flow carboxylic acid, or a complex ester of carboxylic acid contains at least 5% wt./wt. of methyl methacrylate.

11. The method according to any of paragraphs.1-10, where a specified liquid flow CT the property according to any one of paragraphs.1-11, where specified containing formaldehyde liquid flow carboxylic acid, or a complex ester of carboxylic acid is a by product of the production process complicated Olkiluoto ester of acrylic acid, in which complex alkilany ether alanovoy acid is subjected to reaction with methanol and formaldehyde in the presence of a catalyst.

13. The method according to p. 12, where the specified containing formaldehyde liquid flow carboxylic acid, or a complex ester of carboxylic acid is a product of the process of production of methyl methacrylate by the interaction of methylpropionate with formaldehyde and methanol in the presence of a catalyst.

14. Method for the production of methyl methacrylate, providing for stage (i) interaction propionic acid or its complex ester with formaldehyde or its predecessor with the formation of a gaseous product stream containing methyl methacrylate, residual formaldehyde, residual propionic acid or its ester and by-products; (ii) liquefying at least part of the gaseous product stream to the formation of the liquid product stream containing essentially all of the methyl methacrylate, the residual formaldehyde by-products and residual propional system fluid the liquid using water as a solvent, to obtain a flow of the organic phase, which essentially does not contain formaldehyde, and flow of the aqueous phase, which contains essentially all of the residual formaldehyde.

 

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