The method of dehydration

 

The invention relates to an improved method of dewatering solution of formaldehyde containing formaldehyde, water and methanol, including the distillation of the specified solution of formaldehyde in the presence of exciting water connection with obtaining the formaldehyde-containing product that contains significantly less water than the original solution, and use a solution of formaldehyde containing methanol at a molar ratio of methanol to formaldehyde 0.3 to 1.5:1, obtaining the formaldehyde-containing product in the form of a complex with methanol. The invention relates also to a method of producing methyl methacrylate by reaction of formaldehyde with methylpropionate in the presence of methanol and a suitable catalyst, and the use of formaldehyde in the form of a formaldehyde-containing product with methanol, obtained by distillation of a solution of formaldehyde containing formaldehyde, water and methanol in a molar ratio of methanol to formaldehyde 0.3 to 1.5:1, in the presence of methylpropionate, and complex formaldehydefree product with methanol contains significantly less water than the specified solution of formaldehyde; and also refers to the containing formaldehyde product in the form of the complex is popular with respect methanol to formaldehyde 0.3 to 1.5:1, in the presence of exciting water connections, the original formaldehyde solution has a higher concentration of water than the specified containing formaldehyde product. The method allows to obtain formaldehyde raw materials, suitable for the production of methyl methacrylate containing less water compared to the original containing formaldehyde solution. 3 C. and 10 C.p. f-crystals, 1 Il.

This invention relates to a method of removing water from solutions containing formaldehyde, to obtain formaldehyde.

Formaldehyde is a commodity chemical, which is usually produced and transported in the form of solutions of formalin. Solutions of formalin usually contain between 30 and 60% formaldehyde, and the rest in a solution composed mainly of water, usually with a small presence of methanol. Formaldehyde is present mostly in the form of complexes with water or methanol in the form of glycols or semiformally. There is described in patent literature methods of dehydration of formaldehyde solutions with the aim of obtaining a dry stream of Monomeric formaldehyde. For example, U.S. patent 4962235 describes the purification of a mixture of formaldehyde, water and methanol by distillation in p is methanol away from the bottom of the column.

NL-A-6814946 describes the method of extraction of formaldehyde from aqueous streams formaldehyde by contacting the stream with an5-C10aliphatic alcohol which reacts with formaldehyde to form semiformal, which can be separated from the water and subsequently again subjected to dissociation to alcohol and formaldehyde components.

US-A-3174912 describes a method of removing water and colored organic impurities from dilute aqueous formaldehyde mixture by distillation in the presence of acetone. A mixed stream containing acetone and formaldehyde and a small amount of water, ush with the top of the column and divide by the partial condensation of the stream containing a relatively small quantity of formaldehyde in acetone, and a stream containing a greater quantity of formaldehyde in acetone.

However, it is desirable to avoid the introduction of additional chemical compounds in a process that requires purified formaldehyde, because additional connection may be required to remove from the process at a later stage.

One of the processes that use formaldehyde, is the production of methyl methacrylate by reaction of methylpropionate with formaldehyde in the in the reaction, which may have a harmful effect on the used catalyst and is suitable for promotion of the reaction of hydrolysis of the reagent methylpropionate and product of methyl methacrylate. Water is formed as a side product of the synthesis reaction of the methacrylate, and it is therefore desirable to minimize the amount of water that is injected into the reaction zone with the raw material, so that the water content in the reactor to ensure as low as possible. Methods of production of methyl methacrylate, in which propionic acid or its methyl ester is subjected to reaction with formaldehyde or metallum in the presence of methanol, are disclosed in US-3535371, US-4336403, GB-A-1107234, JP-A-63002951. However, these links have not been informed how to cook raw materials, especially formaldehyde, for the desired reaction.

U.S. patent 4040913 discloses the use of exciting water compounds, such as benzene, toluene or methylisobutyl-ketone, and FR-A-2409975 discloses the use of saturated C4-C6of hydrocarbons. GB-A-1301533 discloses the use of alkanols, which With3-C6connections, but alkanols not applied as exciting water connections.

Therefore, the purpose of the invention is to provide a method of obtaining formaldehide treatment contains formaldehyde solution, to obtain formaldehyde raw materials, suitable for use in the production of methyl methacrylate, which contains a reduced amount of water compared to the original containing formaldehyde solution.

According to the invention, the method branches containing formaldehyde product from formaldehyde solution containing formaldehyde, water and methanol, where the specified containing formaldehyde product contains significantly less water than the specified solution of formaldehyde, includes distillation of the specified solution of formaldehyde in the presence of exciting water connections.

Exciting water connection is chosen so that it is capable of dissolving water, formaldehyde, methanol and connecting semiformal formed by the reaction of formaldehyde with methanol. Breathtaking water connection preferably is a saturated or unsaturated carboxylic acid or ester or carbonyl compound, which is essentially directionspanel in relation to formaldehyde under the conditions of distillation, and is also able to capture the water, preferably by education minimum boiling azeotropic mixture with water. Preferably exciting water seediness4-C8alcamovia acids and their lower alkalemia C1-C6esters and ketones having at least 4 carbon atoms, such as diethylketone. Particularly preferred compounds are esters, and methylpropionate and methyl methacrylate was found particularly useful in some processes. Very preferable to use a compound that is intended for introduction into the process in which you intend to use dehydrated formaldehyde product.

One particularly preferred compound for use in the dehydration of formalin solution to obtain formaldehyde, suitable for use in the process for the implementation of the reaction of formaldehyde with methylpropionate in the presence of methanol, is methylpropionate. In one preferred form of the invention, a method for separation containing formaldehyde product from formaldehyde solution containing formaldehyde, water and optionally methanol, where the specified containing formaldehyde product contains significantly less water than specified formalin solution, which includes a distillation of the specified solution of formaldehyde in the presence of methylpropionate.

According to the second aspen in the presence of methanol and a suitable catalyst, where specified formaldehyde is obtained from solution of formaldehyde by distillation of the specified solution of formaldehyde in the presence of methylpropionate. Suitable catalysts are known in the art, and they include the catalysts of silicon dioxide having sites alkali metal.

The method of this aspect of the invention is advantageous because formaldehyde source material is extracted in the form of a complex with methanol in the stream enriched in methylpropionate, and water are removed from the process is essentially free from organic impurities. The Association method of producing formaldehyde present invention with the process of obtaining methyl methacrylate, as described, has the additional advantage that the total energy demand of the combined process can be reduced compared to other methods of dehydration of formaldehyde.

Although it was found that the method of the present invention is particularly suitable for providing formaldehyde starting material for the subsequent reaction of receipt of methyl methacrylate, the invention is not limited to the obtaining of formaldehyde for such a process and may be appropriate for obtaining anhydrous formaldehyde for other PR is it water and formaldehyde in approximately equal shares, usually with a small amount of methanol. At least some amount of formaldehyde is usually present in the form of various adducts water-formaldehyde or methanol-formaldehyde. Usually the term "formaldehyde" is used here to refer to the entire formaldehyde, if it is present as free formaldehyde or in the form of such adducts. The solutions of formalin may change, and the method of the invention can be implemented with different formulations of formalin.

Preferably, the formaldehyde solution was pre-mixed with methanol before the refining process. A mixture of methanol with formaldehyde preferably allow you to reach a state of equilibrium, so as to promote the formation of particles of the adduct of methanol-formaldehyde, for example by providing a mixture for sufficient time to achieve equilibrium or by mixing or adjusting the temperature of the mixture. Preferably use a suitable amount of methanol to provide a molar ratio of methanol to formaldehyde 0.3 to 1.5:1, more preferably 0.5 to 1.2:1, especially from 0.8 to 1.1:1. Methanol can be provided in the form of a mixture with methyl propionate, for example, to make suitable for use releasego water connection, introduced into the distillation exceeds the number required to form an azeotropic mixture with water and preferably also with some presence of methanol, so that the water in the mixture is more volatile than the adducts of formaldehyde. Methylpropionate forms an azeotropic mixture with water containing 92% of methylpropionate and 8% water. The azeotrope of methyl methacrylate/water contains about 14% water (by weight), and the azeotrope of diethylketone/water contains about 84% of diethylketone (by weight). Preferably the ratio of the exciting water connection to formaldehyde in the base of the column is in the range 5:1 to 20:1, for example about 10:1 by weight. However, when exciting the water connection is refluxed, the quantity supplied to the column can be increased as needed.

Most of the water is removed in the form of a mixture with spectacular water connection. A stream containing most of the water, can usually be removed from the distilling process as a liquid side stream, for example, via the idler plate or similar device in a suitable place columns. A suitable place for removal of a side stream may be determined by methods known in the art in light of the composition of the liquid phase passing through carobna the mixture can be separated in the apparatus for decanting and thus obtained organic phase, which mainly contains methylpropionate may be returned with phlegm in the process of distillation. The aqueous phase obtained from the apparatus for decanting, can be further processed in the second distillation installation, preferably at elevated temperature, to obtain a water stream, which is substantially freed from methanol, formaldehyde and methylpropionate. The upper shoulder straps from the second distillation units can be returned back to the main column or apparatus for decanting or pre-treatment solution of formaldehyde, if available.

A large part of formaldehyde selected as VAT product in the form of a mixture with spectacular water connection. This mixture can be used directly, if required, for further reactions, which use both connections together, for example in the synthesis of methyl methacrylate. Containing formaldehyde mixture contains significantly less water than formaldehyde solution supplied to the process. For example, in a typical process according to the invention, in which use methylpropionate as exciting water connection, a formalin solution containing formaldehyde and water at a mass ratio of approximately 1:1, you can get the IB of the present invention is preferably carried out so that cleared formaldehyde product can be used in the further process, for which it is needed. Preferably the method of the present invention together with such additional process, so that the purified formaldehyde product is fed directly to this additional process. When formaldehyde product of the method of the present invention is intended for use as source material together with spectacular water connection in the further process, for example for the production of methyl methacrylate from formaldehyde and methylpropionate when methylpropionate used as an exciting water connection, then the method of the present invention and obtaining methylpropionate can be advantageously carried out in close proximity to the further process or combined with it.

In the preferred device methylpropionate get through a process which provides a source of methylpropionate mixed with methanol and, optionally, water. This mixture may be fed to distillation of this invention to remove formaldehyde from the formalin solution. In this way you can avoid separation of methylpropionate from the process in which it is received. Knole, not formed complexes with formaldehyde, can be withdrawn from the top of the distillation column. This mixture can be recycled or allocated for storage, or sent to further the process.

When the formaldehyde of the method of the invention intend to make it reacted with methylpropionate and methanol to obtain methyl methacrylate, then the method of the present invention is particularly useful especially if it is used in combination with the process of obtaining methylpropionate, as described above. So, in the second preferred device anhydrous formaldehyde mixture with methylpropionate, directly or after intermediate processing use in this methylmethacrylate process. In this way the flow of methylpropionate and methanol, which can be obtained in the process of obtaining methylpropionate and used in this invention can also be used to produce methyl methacrylate in the combined process.

One embodiment of the invention will now be additionally described by way only of example with reference to the drawing which is a schematic diagram of the process.

The formalin solution is mixed with methanol and injected into the distillation column 10 as the source is STV or all of the liquid at a location above the filing of the original material 22. Above the idler plates admit additional source material 21, which contains methanol, water and methylpropionate, which can be obtained from the previous process. Side stream 40, which may constitute the entire liquid flow in the column and phase separated in the apparatus for decanting 12, remove the idler plate. The organic phase is returned to the column below the idler plates as stream 43, while the aqueous phase in the form of stream 41 is passed into column 11 for further processing. The column 10 is usually operated so that a large part of the formaldehyde released from the bottom of the column in the form of a complex with methanol as stream 31, the free methanol is taken from the top of the column in the form of its azeotrope with methylpropionate as stream 30, while water is removed via a side stream and decanting system.

Column 11 operate to apply selected from the top of formaldehyde, methanol and methylpropionate in stream 42 with a certain amount of water. The best way to reach at elevated pressures, typically between 3 and 20 bar. Kubovy product is a stream 32 of pure water, which can be either reused in the process or removed. Stream 42 is shown as returned to the apparatus for decantate column 10.

Example 1

Formalin, consisting of 28.5% formaldehyde, 30.7% of methanol and 40.8% water by weight, is mixed with methylpropionate, so methylpropionate represents 43.5% of the mass of the mixture. The mixture was incubated for several hours to come to equilibrium, and then fed at 150 ml/h on a plate 15 Oldershaw column of 40 plates, numbered from the bottom up. Column equipped with a water cooled condenser and a device for decanting. Net methylpropionate add in apparatus for decanting with a speed of 360 ml/h of Organic phase from the apparatus for decanting is used for irrigation of the column, while the aqueous phase is collected and analyzed.

90% of submitted formaldehyde extract in the stream taken from the bottom of the column, and 95% of water applied is extracted in the water flow, taken from the top. Taken from the bottom stream contains formaldehyde and water in the ratio 1:0,076, whereas the original formalin is the ratio of formaldehyde to water of 1:1,4.

Example 2

In the example of the method of the invention on a continuous basis formalin, consisting of 55% water, 35% formaldehyde and 10% of methanol, mixed with azeotropic mixture of methylpropionate and methanol, resulting in the blend containing by weight 20% METI is in, to allow adducts of formaldehyde to come to equilibrium. The mixture is then served with a speed of 18 ml per hour on level 30 (counting from the bottom level) Oldershaw column 100 steps. The second source material containing 86% of methylpropionate, 9% methanol, 3% water and 2% formaldehyde, served on a level 80 columns with the speed of 162 ml per hour. Side stream containing the entire liquid flow columns, select from one level 60 and served in a water-cooled apparatus for decanting, where the separation of the phases. The organic phase is returned to the column as irrigation and the aqueous phase is removed.

After continuous operation of the column within 12 hours all the products collected from the top and bottom threads of the column, analyze. The head product of the column is the azeotropic mixture of methanol and methylpropionate. CBM product from the column contains approximately 0.3% of water, 4,75% formaldehyde with the rest of the number of methylpropionate. Thus, the mass ratio of water to formaldehyde reduced from 1.57:1 in formalin solution to 0.06:1 in the product stream from the bottom of the column.

Claims

1. The method of dehydration of a solution of formaldehyde containing formaldehyde, water and methanol, including distillation ubergames product, contains significantly less water than the original solution, characterized in that use formaldehyde solution containing methanol at a molar ratio of methanol to formaldehyde 0.3 to 1.5:1, obtaining formaldehydefree product in the form of a complex with methanol.

2. The method according to p. 1, characterized in that the formaldehyde solution is pre-mixed with a certain amount of methanol before the distillation process so that the molar ratio of methanol to formaldehyde is in the range of 0.3 to 1.5:1.

3. The method according to any of the preceding paragraphs, characterized in that the exciting water connection selected from the group consisting of saturated or unsaturated carboxylic acid of ester or carbonyl compounds.

4. The method according to p. 3, characterized in that the exciting water connection is methylpropionate or methacrylate.

5. The method according to any of the preceding paragraphs, characterized in that the ratio of the exciting water connection to formaldehyde in the base of the column is in the range 5:1 to 20:1 by weight.

6. The method according to any of the preceding paragraphs, characterized in that the liquid side stream containing most of the water contained in the mswb, characterized in that formaldehydefree product used in the method of producing methyl methacrylate.

8. The method according to any of paragraphs.1-7, characterized in that methanol is used in the form of a mixture with methylpropionate.

9. The method of producing methyl methacrylate by reaction of formaldehyde with methylpropionate in the presence of methanol and a suitable catalyst, characterized in that the use of formaldehyde in the form of formaldehydefree product with methanol, obtained by distillation of a solution of formaldehyde containing formaldehyde, water and methanol in a molar ratio of methanol to formaldehyde 0.3 to 1.5:1, in the presence of methylpropionate, and complex formaldehydefree product with methanol contains significantly less water than the specified solution of formaldehyde.

10. The method according to p. 9, characterized in that methanol is used in the form of a mixture with methylpropionate.

11. Containing formaldehyde product in the form of a complex with methanol, obtained by distillation of a solution of formaldehyde containing formaldehyde, water and methanol in a molar ratio of methanol to formaldehyde 0.3 to 1.5:1, in the presence of exciting water connections, the original formaldehyde solution has a higher concentration is, the action scene, what an exciting water connection selected from the group consisting of saturated or unsaturated carboxylic acid of ester or carbonyl compounds.

13. Containing formaldehyde product under item 12, characterized in that the exciting water connection is methylpropionate or methyl methacrylate.

 

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