Method of cleaning acrolein

FIELD: continuous cleaning of acrolein.

SUBSTANCE: proposed method consists in continuous cleaning of acrolein. Aqueous solution of acrolein free from difficult-to-condense gas is fed to distilling column equipped with at least one evaporator mounted in its base and at least one condenser mounted in its upper part. Mixture mainly containing water is discharged from distilling column base. Mixture mainly containing acrolein and water is discharged from upper part of distilling column. Mixture discharged from upper part of distilling column is cooled in condenser to temperature at which aqueous condensate may be obtained in addition to considerable amount of acrolein-rich gaseous mixture.

EFFECT: facilitated and safe procedure of cleaning acrolein; reduction of contaminating deposits in distilling column.

22 cl, 2 dwg, 2 ex

The scope of this invention is the production of acrolein as an intermediate product or finished product. It refers in particular to the cleaning of acrolein from the aqueous phase of acrolein. The invention also relates to the production of MTPA, that is, 3-(methylthio)propionovogo aldehyde.

Acrolein is a starting material, the main application of it on an industrial scale is the synthesis of MTPA by introducing acrolein reaction with the mercaptan.

The production methods of acrolein well known. These methods typically include the operation of the oxidation reaction of propylene and/or propane. Thus, it is possible to obtain the crude gaseous product based acrolein. This crude product is usually present in the form of a gas mixture comprising, firstly, acrolein in respect of typically more than 10 wt. -%, secondly, inert or non-condensable gases (also known as flue gases, such as nitrogen, oxygen, carbon monoxide, carbon dioxide, propylene or propane, third, water, and, fourthly, the reaction by-products such as acids, aldehydes, alcohols and other compounds. Thus, the subsequent processing required to remove certain compounds from the crude product and to highlight the pure acrolein.

The crude product is based acrolein usually subjected to the first processing, that allows you to remove acids such as acrylic acid and acetic acid. A second later processing makes it possible to absorb acrolein in water using an absorption column, in the lower part of which is collected aqueous solution of acrolein. This solution is subsequently subjected to cleaning operations using one or more distillation columns for separation of purified acrolein in gaseous form.

Cleaning acrolein often requires the use of two distillation columns. The first optional column allows you to deoxygenate solution and to remove minor impurities. The second column, for its part, is used for the upper part of the specified column and, in particular, at the outlet of the condenser liquid acrolein in the azeotropic concentration with water.

As in the case of a single column, and with a larger number of distillation columns, the contamination of these columns is a problem usually found when cleaning acrolein. This contamination is usually characterized by the deposition of the solid phase resulting from the polymerization residue of acrylic acid, even acrolein. In the special case of cleaning methods, which use two columns, these contaminating deposits typically occur in the second column, which, moreover, is often used in azeotropic conditions.

These deposits lead to a gradual decrease in the efficiency of distillation and lead to partial, sometimes even complete blockage of the distillation column. Thus, this issue requires frequent closures of facilities for the production of acrolein for maintenance and repair necessary to remove deposits in the distillation column or columns. These stops thus lead to higher costs and subsequent loss of power production installations.

This invention, therefore, aims at the purification method of acrolein simple, inexpensive and safer by minimizing polluting sediments used in the distillation column.

Thus, it was found that it is possible to overcome the disadvantages related to contamination by distillation of an aqueous solution of acrolein under certain operating modes.

The subject of this invention, therefore, is a continuous method of cleaning acrolein, in which

aqueous solution of acrolein devoid of gas, which is difficult to condense, served in a distillation column provided with at least one evaporator, at its base, and at least one of the capacitors in its upper part,

- liquid mixture essentially comprising water, extracted from the base of the distillation column,

- gas mixture essentially comprising acrolein and water are then removed from the upper part distillation the Oh column

- gas mixture extracted from the upper part of the distillation column is cooled in the condenser to a temperature at which it is possible to obtain, on the one hand, water condensate and, on the other hand, a significant quantity of the gas mixture rich in acrolein, and

- extract purified acrolein from the gas mixture rich in acrolein.

In particular, the invention relates to a continuous method of cleaning acrolein, in which

aqueous solution of acrolein is introduced into the distillation column equipped with at least one evaporator, at its base, and at least one of the capacitors in its upper part,

a liquid mixture comprising water, remove from the base of distillation columns,

- gas mixture comprising acrolein, is extracted from the upper part of the distillation column,

- gas mixture extracted from the upper part of the distillation column is cooled in the condenser to a temperature at which it is possible to obtain, on the one hand, water condensate and, on the other hand, a gas mixture rich in acrolein, and

- remove the specified gas mixture,

characterized in that the distillation is carried out by receiving from the base of the column non-azeotrope blends liquid mixture essentially comprising water and condensation is carried out with the receiving water condensate is depleted acrolein, and gas with the art, enriched with acrolein.

Preferably the gas mixture obtained from the upper part of the column, comprises from 30 to 70 vol.% water, preferably from 40 to 60 vol.% water.

Based on the above working example, the distillation is carried out at temperatures that are restricted, since, in particular, made the production of a gas mixture comprising a substantial fraction of water in the upper part of the column. The Department of water subsequently receive special conditions of cooling in the condenser, by compensation, as it was for a limited branch of acrolein in the distillation column.

Another object of this invention is a continuous method for the production of 3-(methylthio)propionic aldehyde (MTPA).

Known methods of production of MTPA usually include chemical reaction of liquid acrolein with methylmercaptan usually in the presence of a catalyst. These methods often require one or more intermediate storage of liquid acrolein. This can lead to a security problem related to the properties of acrolein, in particular its polymerization to its high toxicity and its ability to fire.

Have developed other ways to solve this security problem, such as the methods proposed in US 4225516, US 4319047 and US 5352837.

The documents described the partial purification of the crude gas mixture comprising acrolein, for example, by two sequential cooling to remove, in particular, acids. The gas stream, thus purified, involving only a limited number of acrolein, diluted exhaust gases of the reaction, is introduced into reaction with the mercaptan (MSH) in the reactor by gas-liquid contact.

In this case, the exhaust gases are removed after the reaction of acrolein with MSH; this leads to a significant loss of acrolein, MTPA due to distillation or elution. In addition, exhaust gases, including these fractions acrolein, MTPA, require special and expensive treatments to remove odors and to comply with the law relating to emissions.

To resolve, on one hand, security issues related to storage of liquid acrolein and, on the other hand, in order to avoid losses in yield due to distillation of MTPA and expensive treatment of gaseous effluents was found that it is advantageous to carry out the above-described cleaning method acrolein and producing MTPA by introducing gaseous acrolein, thus purified, obtained by a specified method, react directly with liquid or gaseous mercaptan. Thus, the reaction of the receipt of MTP can be performed directly on the basis of the purified gaseous acrolein free from non-condensable gases. This method dei is of textbooks allows therefore, to avoid any intermediate storage of liquid acrolein, thus solving the problem of security, above, and except for the loss of MTPA and acrolein.

Thus, the objective of the invention is a continuous method for the production of MTPA, including clearing operation acrolein according to the purification method of acrolein described above.

This invention relates, in particular, to a continuous production method of MTPA, namely, that

(a) carry out the oxidation of propylene in the vapor phase using a catalyst, to obtain the crude product is based acrolein,

(b) remove the acid present in the crude product obtained in the preceding operation,

(b) the product obtained in the previous operation, absorb water to obtain an aqueous solution of acrolein essentially free from acid,

(g) this solution is cleaned with obtaining a purified gaseous acrolein, and

(d) purified gaseous acrolein obtained in the previous operation, is introduced into reaction with the mercaptan (MSH) to obtain MTPA,

and non-condensable gases originally present in the crude product due to operation (a) oxidation is separated before the operation (d).

Preferably the separation of non-condensable gases conduct PE the units operation (g) cleaning, especially preferably during the operation (b) and/or operation (b), for example during surgery ().

Non-condensable gases or served by recycling to the operation (a) oxidation, or removed from the process and, for example, burn at a relatively low temperature (for example, 900° (C)as in the case of containing carbon emissions and contains no sulfur emissions.

The separation of non-condensable gases in a process line according to the thread above for the synthesis of MTPA contributes to the fact that these gases do not include any sulfur compounds generated by MSH and/or MTPA, and, thus, can be made by recycling to the oxidation of propylene in the form of a mixture with the latter without the risk of poisoning of the oxidation catalyst by sulfur compounds.

The separation of non-condensable gases in the technological line of flow above cleanup acrolein also allows you to remove the gas ballast usually in relatively large quantities by volume in the entire process leading to MTPA.

Because of this located upstream the separation of non-condensable gases there is no reason to hold it during or after synthesis of MTPA by introducing acrolein reaction with MSH, which prevents the need to remove sulfur compounds before emission by burning of exhaust gases at a relatively high temperature (for example, 1200°).

In the case of feed n is condensable gas recycle to the oxidation, the output MTPA expressed in relation to downloadable molar number of propylene, is significantly increased.

This invention also relates to a continuous production method of MTPA, namely, that

(a) carry out the oxidation of propylene in the vapor phase using a catalyst to obtain the crude product based acrolein,

(b) remove the acid present in the crude product obtained in the preceding operation,

(b) the product obtained in the previous operation, absorb water to obtain an aqueous solution of acrolein, separated from non-condensable gases

(g) this solution is cleaned with obtaining a purified gaseous acrolein, and

(d) purified gaseous acrolein obtained in the previous operation, is introduced into the reaction directly with liquid or gaseous mercaptan (MSH) to obtain MTPA.

The operation (d) is preferably carried out between a liquid mercaptan and purified acrolein supported in the gas phase.

Figures 1 and 2 without implied limitations shows a device for cleaning acrolein and installation for the production of MTPA using the method according to the invention.

Figure 1 schematically illustrates a device for cleaning acrolein according to the invention.

Figure 2 schematic the key illustrates the installation for the production of MCPA according to the invention.

The invention is described hereinafter in more detail with reference to Figure 1.

The method according to the invention performed by distillation of an aqueous solution of 2 acrolein free from non-condensable gases, i.e. the mixture in liquid form, essentially comprising acrolein and water.

The term "non-condensable" gases, or inert gases, or exhaust gas" means any gas that cannot adequately condense under the conditions of purification according to the method proposed in the invention. In General, these gases can condense only at temperatures well below 100°C. as examples of these "non-condensable" gases can be nitrogen, propylene, propane or oxygen, which are usually present in the gas stream, resulting in the synthesis of acrolein.

"Non-condensable" gases are removed in the method according to the invention during the preliminary operations of absorption of acrolein in the water.

An aqueous solution of 2 acrolein, i.e. boot the mixture to the distillation column may have a concentration of acrolein above 1%, but in any case, this concentration is less than or equal to the concentration corresponding to the limit of solubility of acrolein in the water.

An aqueous solution of 2 acrolein preferably has a concentration of acrolein which is less than or equal to the limit of solubility of acrolein in water, for example 5% of the mass.

Distill the operating column 1 also has at its base an evaporator (not shown), function of which is at least partial evaporation of the aqueous solution obtained at the bottom of the column. The operating modes of the evaporator standard. The temperature in the evaporator can be maintained, if the distillation column operates at atmospheric conditions is in the range of from 100 to 130°C, preferably from 100 to 120°S, especially preferably from 102 to 110°C. the Specialist knows how to regulate these temperature conditions in accordance with the fact, are working in a vacuum or under pressure.

In accordance with the invention, a mixture of 4, essentially comprising water, remove from the Foundation of the distillation column 1. This extract mixture may, however, have a concentration of acrolein less than 0.1 wt. -%, preferably less than 0.05 wt. -%, more preferably 0.01% by mass.

According to this invention an aqueous solution of 2 acrolein purified in the distillation column 1, from the upper part of which is extracted gas mixture 6, essentially comprising acrolein and water. This gas mixture 6 then the first operation is cooled by the means shown in the diagram link 204, with the aim of obtaining condensate 10 and a significant quantity of the gas mixture 11, rich acrolein. On the second operation purified acrolein 12 in gaseous form is extracted from the gas mixture 11, rich acrolein. The cooled mixture 6 was removed emnd from the upper part of the column, and removing the purified acrolein 12 comprises two essential operations of the method according to the invention, these operations can be performed simultaneously or sequentially.

In accordance with one of these essential aspects of a mixture of 6 extracted from the upper part of the distillation column, cooled, thus, in the capacitor 7 for receiving condensate 10 and a significant quantity of the gas mixture 11, rich acrolein.

The term "significant amount" means that acrolein is due to the chosen cooling conditions to a greater extent in the gas mixture 11 than in the condensate 10. It can be assumed that more than 50%, preferably more than 70%, especially preferably more than 90% of the mass. acrolein originally present in the gas mixture 6 extracted from the upper part of the column 1 is after cooling, 204 purified in gaseous form.

Such a gas mixture rich in acrolein, can be obtained by a reasonable choice of the temperature of the cooling 204 of the capacitor 7. The choice of this temperature should obviously be made based on the values of other physical parameters, such as, for example, pressure.

Thus, in accordance with a special case of this invention, if the distillation column 1 is supported at a pressure P, the temperature of the condenser 7 you need to maintain when the value of T according to the alignment T> 21,28·P+32,9, while P is expressed in atmospheres. For example, if P is 1 ATM, T>53°if P is equal to 2 ATM, T>75°C.

Column 1 is supported at atmospheric pressure, which requires maintaining the temperature of the condenser 7 to the value above 54°C, preferably in the range from 55 to 70°S, particularly preferably in the range from 60 to 65°C.

In accordance with another important aspect of the purified acrolein 12 is extracted from the gas mixture 11, rich acrolein, while the latter is obtained by cooling 204 of the gas mixture 6 extracted from the upper part of the distillation column 1.

The verb "remove" should be understood in a very broad sense. In accordance with the invention, the term "extract the product from a mixture" means fractionation or removing at least part of this mixture.

Preferably the purified acrolein 12 is obtained by removal of the entire gas mixture 11, rich acrolein. In this case, the purified acrolein can be distinguished, on the one hand, a simple separation of the gas mixture 11, rich acrolein, and on the other hand, from the condensate 10. Purified acrolein 12 can essentially be removed through the pipe led out through the top of the condenser 7, which includes the gas mixture 11, rich acrolein.

Purified acrolein 12 usually exists in the form of a gas mixture, with the society, including acrolein with low water content. Cleaning refers mainly to a significant reduction in water content.

Mainly, as an example, through regulation of the condensing temperature, the purified acrolein 12 may have a concentration of acrolein in the range from 86 to 95 wt. -%, preferably from 88 to 94 wt. -%, particularly preferably from 90 to 93% of the mass.

In accordance with the preferred form of this invention, the condensate 10 at least partially re-enter 13 in the distillation column. Preferably all of the condensate is re-injected into the upper part of the distillation column 1.

To further reduce polluting sediments solution 2 acrolein can be successfully subjected to a prior operation desoxyribose before feeding to the distillation column 1. This deoksigenirovanii can be performed by placing a solution of 2 acrolein in vacuum.

You can also include the use of distillation column 1 equipped with Nekunam plates with large holes and having heated walls, to avoid condensation of stagnant fluids that may trigger undesirable point of polymerization. However, this can be expensive and unnecessary in connection with the improvements introduced in the method according to this invention.

Advantages of the method of cleaning according to this invention is ozbolat:

to obtain acrolein in the gas phase 12 with a high degree of purity, without the need to shutdown for removal of contaminating deposits from the column 1 and the condenser 7, resulting from the polymerization of acrylic acid and/or acrolein,

to minimize cooling of the condenser 7,

to avoid the need for storage of liquid acrolein and, thus, make it possible to minimize the intermediate stocks of this highly toxic, combustible and hazardous product.

With reference to Figure 2, another object of this invention is the continuous production method of MTPA, that is, 3-(methylthio)propionovogo aldehyde. This method differs in that it includes an operation 114 cleaning acrolein according to the method specified above.

MTPA it is an intermediate product of methionine or HMBC, that is, 2-hydroxy-4-(methylthio) butane acid. Methionine is an important amino acid that helps to supply deficiencies in animal nutrition. GMC provides a source of methionine, which is usually used as methioninol additives to the formulation of animal feed. MTPA usually required in the production GMBC or methionine.

In accordance with the preferred form of the invention and with reference to Figure 2, a continuous production method of MTPA characterized in that

(a) oxidation of 10 propylene 104 in the vapor phase is carried out with the use of a catalyst, to get the crude gaseous product 105 on the basis of acrolein,

(b) remove 106 acids present in the crude product 105, obtained in the previous operation,

(b) the product obtained in the previous operation, absorb 110 water 111, to obtain an aqueous solution of 2 acrolein essentially free from acid and separated from the "non-condensable" gases 113,

(g) the specified solution 2 is cleaned by the above described method 114 cleaning acrolein to receive a stream 12 of purified gaseous acrolein, and

(d) purified gaseous acrolein 12 obtained in the previous operation, is introduced into reaction with gaseous or liquid MSH 116, that is, with a mercaptan in the presence of a catalyst to obtain MTPA 117.

The crude product 105 on the basis of acrolein obtained in the first stage (a) of the method of production of MTPA, usually exists in the form of a gas mixture comprising, firstly, acrolein in the proportion of more than 5%, preferably 10%, and secondly, recondenses gases, such as nitrogen, oxygen, carbon monoxide, carbon dioxide, propane or propylene, thirdly, water and, fourthly, the reaction by-products such as acids, aldehydes, alcohols and other compounds.

This crude product 105 is then treated in any way to the next operation (b) to remove KIS is on, such as, for example, acrylic acid and acetic acid.

The crude product is treated with 109 thus, it is possible in accordance with the operation () method to enter into contact with cooling water 111 in the absorption column 110 for collecting water solution of 2 acrolein in the basis of the specified column and get to the top of the thread 113 of the exhaust gases, containing only traces of acrolein. Non-condensable gases 113 can be completely removed through line 208, or can be partially served by recycling on the way 101 oxidation of propylene 104.

The fourth operation (g) of the production method of MTPA is the purification of an aqueous solution of 2 acrolein according to the above method 114 cleaning. In accordance with this cleaning process, the first operation in the distillation column 1 serves an aqueous solution of 2 acrolein, free from non-condensable gases or exhaust gases.

With regard to the fifth operation (d) of the method of production of MTPA, i.e. the reaction of purified acrolein 12 MSH 116, it is possible to envisage the use of acrolein in liquid or gaseous form in the presence of a catalyst.

In accordance with the preferred form of this invention, the synthesis of MTPA spend between liquid MSH 116 or gaseous MSH 116 and purified acrolein 12, supported in the gas phase. The advantage of this form is to simplify the act is both and, in particular, the elimination of intermediate storage of liquid acrolein, which is harmful from the point of view of security.

One advantage of this invention is the possibility of synthesis of MTPA using a source of purified acrolein supported in gaseous form.

Another advantage of this new method, which uses acrolein in gaseous form and free from non-condensable gases, is an exception ash after synthesis of MTPA containing sulfur compounds and acrolein, such as ablation requires expensive processing and leads to a significant loss in output.

Another object of this invention is a device for cleaning acrolein, including

- supply line to a water solution of 2 acrolein free from non-condensable gases

- the distillation column 1, fed through the feeding pipe,

- the discharge pipe 6 in the upper part of the distillation column 1,

capacitor 7, powered by a discharge line and provided with means 204 cooling to maintain the temperature at values that allow you to receive condensate 10 and a significant amount of rich acrolein gas mixture 11, and

pipe 12 for discharging the capacitor 7 to the second allows you to isolate the purified acrolein from the gas mixture rich in acrolein.

The capacitor 7 is preferably vertical to create a possible flow through flow along the inner walls. The capacitor 7, in particular, supplied

- hole 201 for discharging condensate 10 located below the level of 203 condensate accumulation in the base of the condenser 7,

- hole 202 for discharging purified acrolein in gaseous form, above the specified level 203 condensate, and

two pipes 13 and 12 unloading attached to each of these holes.

The invention also relates to an apparatus for the production of MTPA, including:

reactor 101, which allows to obtain the crude gaseous product 105 on the basis of acrolein,

device 106 to remove acids, fed through the feeding pipe 105 to the crude gaseous product based acrolein,

device 110 for absorption of acrolein water, fed through the inlet pipe 109 for crude gaseous product based acrolein devoid of acid,

device 114 for cleaning acrolein, powered with an aqueous solution of acrolein through the inlet pipe 2, and

the reactor 115 for the production of MTPA, fed through the inlet pipe 12 for the pure acrolein and inlet pipes the wire 116 to MSH,

characterized in that the device 114 for cleaning acrolein is described above with reference to Figure 1.

Preferably, the supply line 12 to the reactor 115 for the production of MTPA directly related to the discharge pipe of the condenser 7 of the cleaning method.

Figure 1 in the form of the scheme and without implicit constraints illustrated installation for cleaning acrolein in accordance with this invention.

This setting enables the distillation column 1, fed with an aqueous solution of acrolein by means of feed line 2. The distillation column 1 includes a base 3, equipped with an evaporator, not shown in the drawing. A mixture essentially comprising water, removed from the base 3 through the outlet pipe 4. The distillation column includes a top portion 5 connected to the discharge pipe 6.

The installation is presented in figure 1, also includes a capacitor 7, the latter zapityvat through outlet pipe 6 located in the upper part 5 of the distillation column 1. The capacitor 7 is presented in the form of a scheme by the camera 8 and the pipe 204 (represented by arrow), intended for the circulation of cooling fluid. The camera 8 in the condenser 7 includes in its lower part the condensate 10 and at its upper part razoobrazny the second mixture 11, rich acrolein. The capacitor 7 is also connected with the pipe 12 for discharging purified acrolein in gaseous form. The pipe 12 extends within the upper part of the chamber 8, which includes a gas mixture rich in acrolein.

Installation for cleaning, presented in figure 1, also includes a pipe 13 that enables the submission of the recycling in the distillation column condensate 10, which is accumulated in the bottom of the chamber 8 of the capacitor 7.

Figure 2 illustrates in schematic and without implied limitation for the production of MCPA in accordance with this invention.

The plant includes a reactor for the production of crude acrolein 101, powered by propylene or propane, air and water through pipelines, represented respectively by links 102, 103 and 104. The crude gaseous product based acrolein get in the reactor 101 by catalytic oxidation of propylene or propane air in the presence of water. The pipe 105 connected to the reactor 101 allows you to translate the specified crude product in the device 106 for removal of acid.

This unit 106 for removal of acid includes a column for absorption of water, powered, on the one hand, the crude gaseous product based acrolein through pipe 105 and, on the other hand, the water by pipeline is 107. Liquid discharge, including acid unload at the base of the column through the discharge pipe 108. In the upper part of the absorption column 106 gaseous discharge, including acrolein and free from acids, is transferred through pipe 109 to the device 110 for absorption of acrolein.

This device 110 for absorption of acrolein is also a column for absorption of water, given the crude gaseous product based acrolein, free from acid through pipe 109 and water through pipes 111 and 112. Gaseous discharges obtained in the upper part of the device 110 can be partially served by recycling to the reactor 104 to produce acrolein through pipe 113. The solution acrolein, essentially comprising acrolein and water are transferred from the base of the absorption column 110 through the inlet pipe 2 to the installation of 114 for cleaning acrolein in accordance with the order as listed and described according to the reference in figure 1.

The cleaning device 114, are presented in figure 2, therefore, includes, as described above:

- supply line 2 to an aqueous solution of acrolein,

- the distillation column 1, associated with the specified pipe 2,

capacitor 7 connected with the upper part of the distillation column 1 through the outlet pipe 6 and is equipped with the first cooling means (not shown) to maintain the temperature at values, which make it possible to obtain a condensate and a gas mixture rich in acrolein,

the pipeline 12 for unloading purified acrolein in gaseous form, separated from the gas mixture rich in acrolein present in the condenser 7, and

pipe 13, which allows you to submit recycling the condensate to the distillation column 1.

Installation for the production of MTPA presented in figure 2 also includes the reactor 115 for the production of MTPA, equipped with a supply line for the purified gaseous acrolein, while the pipeline corresponds to the pipeline 12 unloading. The reactor 115 is also supplied through the inlet pipeline for MSH 116. Get MTPA also relieve through the discharge pipe 117.

The following examples provide an opportunity to understand the advantage of the present invention.

Example 1

This example illustrates a known method of purification of acrolein, which uses one 40-disc distillation column. This column supported at atmospheric pressure, zapisyvali solution acrolein, comprising 6% of the mass. acrolein and 93.5% of the mass. water. The temperature at the base of the column was maintained at a value of 110°through the evaporator. Azeotropic mixture of acrolein and water extracted from the upper part of the column are condensed and fully what the exploits of the capacitor. The mixture has a concentration of acrolein 95 wt. -%, moreover, the inclusion of mainly consisted of water at the level of 3% and acetaldehyde at the level of 1.5%. Nominal output thus purified of acrolein was 70 tons per day.

Column worked with these two operational modes of approximately 3 to 4 weeks from its nominal output level. This column then had to close for cleaning plates and heat exchangers associated with this column.

Example 1A

To minimize pollution of sediments in the column used in example 1, the installation, including her, was modified by adding degassing in vacuum (20°C, 0.7 bar). This modification made it possible to significantly reduce the polluting sediments found above.

Example 2

This example illustrates the purification method of acrolein included in the unit experienced production MTPA according to this invention.

Synthesis of acrolein

The crude product 105 on the basis of acrolein obtained at the outlet of the reactor 101 oxidation of propylene to acrolein in the vapor phase. This crude product consisted of a gas mixture with a temperature of 180°including 63% of the mass. non-condensable gases (propane, nitrogen, oxygen, propylene, CO, CO₂), 21% of the mass. water, 12% of the mass. acrolein, 2% of the mass. acrylic acid and 2% other compounds.

Absorption of acids

This neocidin is the first product based acrolein in the vapor phase was injected 105 at a rate of 20 kg/h at the bottom of the cooling column 106, equipped with sieve plate, sieve plates)supported pressure 121000 PA. Liquid cooled 108, including acid and 1.3% of the mass. acrolein, extracted from the base of the column and maintained at a temperature 70,3°C. the Acid gas phase removed from the upper part of the column and then cooled to 4°C.

Absorption acrolein

Acid gas phase, thus obtained, was then introduced with a flow rate of 16.2 kg/h in the base of the pillar 110 to absorb water. The flow of water 111 entered at 4°circulate this absorption tower for absorption of acrolein. Non-condensable gases mentioned above, unloaded 113 from the top of the absorption column, and the aqueous solution 2 containing 6% wt. acrolein received at the bottom of the column.

Cleaning acrolein

An aqueous solution of acrolein was purified according to the purification method of the invention (cf. Figure 1) using a single distillation column 1, including disordered attachment. This column supported at atmospheric pressure, thus zapisyvali 2 aqueous solution comprising 6% of the mass. acrolein. The temperature at the base of the distillation column is then maintained at 105°through the evaporator. The upper part of the column was equipped with a condenser 7 for cooling to 60°With the mixture to be extracted from the upper part of the column. Condensate 9 and the gas mixture is 12, rich acrolein received at this temperature. The condensate as it is, was re-introduced 13 in the upper part of the column 1. Purified acrolein with a purity of 93% of the mass. (the remaining 7% was mainly water) was allocated 12 by removing the entire gas mixture 8, rich acrolein.

After working for five weeks was not found dirt in the nozzle distillation column 1.

The reaction MTPA

Purified acrolein 12 in gaseous form and liquid MSH in stoichiometric quantities introduced in the presence of a catalyst in a circulating reactor 115 with recirculation of MTPA.

Output watched virtually quantitative. The presence of a quantity of water introduced by thus purified of acrolein, does not cause any complications compared with acrolein, obtained by azeotropic distillation.

Obviously, the cleaning method according to this invention allows to significantly reduce pollutant deposition in the distillation column used for the purification of acrolein.

1. Continuous method for the production of 3-(methylthio)propionic aldehyde (MTPA), namely, that

(a) carry out the oxidation (101) of propylene in the vapor phase using a catalyst to obtain the crude product (105) on the basis of acrolein,

(b) remove (106) acid present in neocis nom product (105), obtained in the previous operation,

(b) the product obtained in the previous operation, absorb (110) water to obtain an aqueous solution(2) acrolein,

(g) the specified solution (2) is treated with obtaining a purified gaseous acrolein (12), and

(d) purified gaseous acrolein obtained in the previous operation, is introduced into the reaction (115) with a mercaptan (MSH) to obtain MTPA,

and non-condensable gases originally present in the crude product (105)resulting from operations (a) oxidation is separated before the operation (d).

2. The method according to claim 1, characterized in that the separation of non-condensable gases are conducted before the operation (g) cleanup.

3. The method according to claim 2, characterized in that the separation of non-condensable gases are conducted during the operation (b) and/or transaction ().

4. The method according to claim 3, characterized in that the separation of non-condensable gases are conducted during the operation (b).

5. The method according to claim 1, wherein the non-condensable gases are served by recycling to the operation (a) oxidation.

6. The method according to claim 1, wherein the non-condensable gases are removed and burned.

7. The method according to claim 1, wherein the operation (d) is carried out between the mercaptan and acrolein supported in the gas phase.

8. The method according to claim 1, characterized in that the cleaning water RA the creators of acrolein operations (g) is conducted according to the following method:

an aqueous solution of acrolein is introduced into the distillation column (1), provided with at least one evaporator, at its base, and at least one capacitor (7) in its upper part,

the liquid mixture essentially comprising water, remove the (4) from the base of the distillation column,

the gas mixture essentially comprising acrolein and water, remove the (6) from the upper part (5) distillation columns,

the gas mixture (6)extracted from the upper part of the distillation column is cooled in the condenser to a temperature at which it is possible to obtain, on the one hand, water condensate (13) and, on the other hand, the gas mixture (12), rich acrolein, and

extract (12) gas mixture rich in acrolein.

9. The method according to claim 8, characterized in that an aqueous solution (2) acrolein has a concentration of acrolein less than or equal to the limit of solubility of acrolein in the water.

10. The method according to claim 8, characterized in that the distillation column (1) support at pressure P and temperature T of the condenser (7) support according to the equation T>21,28·P+32,9.

11. The method according to claim 10, characterized in that the column (1) support at atmospheric pressure and the temperature of the condenser support at a value above 54°C, preferably in the range from 55 to 70°S, especially preferably online is rule from 60 to 65° C.

12. The method according to claim 1, characterized in that the gas mixture (2), rich acrolein has a concentration of acrolein in the range from 86 to 95 wt.%, preferably from 88 to 94 wt.%, particularly preferably from 90 to 93 wt.%.

13. The method according to claim 1, characterized in that the condensate (13) at least partially re-introduced into the distillation column (1).

14. The method according to item 13, wherein the entire condensate (13) is re-injected into the upper part of the distillation column (1).

15. Continuous method for the production of 3-(methylthio)propionic aldehyde (MTPA), namely, that

(a) carry out the oxidation (101) of propylene in the vapor phase using a catalyst to obtain the crude product (105) on the basis of acrolein,

(b) remove (106) acid present in the crude product (105)obtained in the previous operation,

(b) the product obtained in the previous operation, absorb (110) water to obtain an aqueous solution (2) acrolein, separated from non-condensable gases

(g) the specified solution (2) is treated with obtaining a purified gaseous acrolein(12), and

(d) purified gaseous acrolein obtained in the previous operation, is introduced into the reaction (115) directly with methylmercaptan (MSH) to obtain MTPA.

16. The method according to item 15, wherein the operation (d)is carried out between the mercaptan and acrolein, supported in the gas phase.

17. The method according to item 15, wherein the purification of an aqueous solution of acrolein operations (g) is conducted according to the following method:

an aqueous solution of acrolein is introduced into the distillation column (1), provided with at least one evaporator, at its base, and at least one capacitor (7) in its upper part,

the liquid mixture essentially comprising water, remove the (4) from the base of the distillation column,

the gas mixture essentially comprising acrolein and water, remove the (6) from the upper part (5) distillation columns,

the gas mixture (6)extracted from the upper part of the distillation column is cooled in the condenser to a temperature at which it is possible to obtain, on the one hand, water condensate (13) and, on the other hand, the gas mixture (12), rich acrolein, and

extract (12) gas mixture rich in acrolein.

18. The method according to 17, characterized in that an aqueous solution (2) acrolein has a concentration of acrolein less than or equal to the limit of solubility of acrolein in the water.

19. The method according to 17, characterized in that the distillation column (1) support at pressure P and temperature T of the condenser (7) support according to the equation T>21,28·P+32,9.

20. The method according to claim 19, characterized in that the column (1) support at atmospheric pressure, as the temperature of the condenser support at a value above 54°C, preferably in the range from 55 to 70°S, particularly preferably in the range from 60 to 65°C.

21. The way to clean acrolein, in which an aqueous solution of acrolein enter (2) to a distillation column (1), provided with at least one evaporator, at its base, and at least one capacitor (7) in its upper part, a liquid mixture comprising water, remove the (4) from the base of the distillation column, a gas mixture comprising acrolein, derive (6) from the upper part of the distillation column, the gas mixture (6)extracted from the upper part of the distillation column is cooled in the condenser to a temperature at which it is possible to obtain, on the one hand, water condensate (13) and, on the other hand, the gas mixture (12), rich acrolein, and extract the specified gas mixture, characterized in that the distillation (1) conduct with receiving from the base of the column (1) non-azeotrope blends liquid mixture mainly comprising water and condensation (7) is carried out with the receiving water condensate (13), depleted acrolein, and the gas mixture (12), enriched acrolein.

22. The method according to item 21, wherein the obtained from the upper part of the column comprises from 30 to 70 vol.% water, preferably from 40 to 60 vol.% water.