SU250764A1 - METHOD OF OBTAINING DIMERS - Google Patents

Description

This invention relates to a process for the preparation of dicarboxylates and dinitriles, in particular, to the hydrodimerization of acrylonitriles to adiponitrile.

From: Vbstbn method of hydrodimerization of acrylonitrile with alkaline or alkaline-earth metal amalgam, according to which the B are carried out with medium containing most of the polar aprotic solvent, for example acetonitrile or adiponitrile, together with the onium additive (quaternary ammonium salts). The amalgam phase and the monomer-containing phase are in turbulent motion, which can be represented as a "dense fluidized bed, consisting of 20-65 vol. % amalgam "30-80 vol. % other phase.

An apparatus for carrying out this process according to the dense fluidized bed method is also known, in which the amalgam e is crushed into individual droplets and remains in the form of a physically interconnected fluid with fast-changing other phase and passing through the amalgam.

When the reaction is carried out in glass or steel apparatus, very small particles of neutralizing alkaline products are formed.

or alkaline earth metals, especially sodium bicarbonate, which causes certain harder; NO; sediment is deposited on the walls of the reactor and transmission lines, which leads to blockage. At the same time, the salt particles are so small that the filtration is very slow, besides, large amounts of organic matter and mercury stick together with the precipitating salt.

Difficulties arising from the precipitation of alkali metal and alkaline earth metal salts In the presence of a large amount of organic medium, can be overcome if these metal salts or metal ions are quickly transferred. During the reaction, or better after the reaction, from the organic phase into a separate water phase.

A method is proposed for the reductive dimerization of olefinic compounds from the group a, (3-monoolefinic nitriles and esters of aliphatic a, p-monoolefinic carboxylic acids, according to which reductive dimerization takes place in an environment consisting mostly of polar aprotic solvent capable of producing reactive hydrogen when interacting with metallic amalgam, with the addition of quaternary ammonium salts or so-called "onium additives, the amalgam phase and the monomer containing phase are always Turbulently agitated, alkaline or alkaline earth, coming from the amalgam into the organic phase, then reacting with a weak acid, better than carbon dioxide. The improvement of this method is characterized by the fact that ions or salts of alkali or alkaline earth metals are rapidly removed from the organic phase into a separate "A single phase during or after the reaction, where they precipitate and then are removed. For simplicity, this method. We will call the" water freezing method, the transfer of alkaline or alkaline mines lla - "water freezing. The aqueous phase may come into contact with the organic phase before, during or after passing through the reactor; However, it is preferable to transfer the alkaline or alkaline-earth metal to the aqueous phase after the hydrodimerization reaction at a high mass transfer rate, by contacting the yield of the organic phase (reaction product) from the reactor with water after delamination with amalgam, while simultaneously adjusting the pH of the aqueous phase to 8 , 1-8.5 and the pH of the organic phase is less than 10.5, preferably less than 9.5, which facilitates the transfer of alkaline 30 or alkaline earth metals from the organic phase to the aqueous phase (up to 90-99%), after which the aqueous and organic phases are separated, and part of the organic phase is almost anhydrous. returns to the reactor. It is preferable to divide the stage of mixing the organic and aqueous phases from the stage of precipitation of alkali or alkaline earth metal salts. The precipitation of metal salts of the aqueous layer is achieved by cooling, by adding spruce-40 to the acid, in particular carbon dioxide, by evaporation or by a combination of these and other known methods. After transferring from the organic phase to the aqueous phase, large crystals 45 of alkali and alkaline earth metal salts can be obtained, especially sodium bicarbonate, if there are no solid crystals or alkali or alkaline earth metal salts in the organic phase fed to the reactor, if 50 the concentration of the alkali metal or alkaline earth metal salt is lower 0.5 mol / l. The appearance of the dissolved alkali metal or alkaline earth metal salt is not crucial, and the total salt content is easily determined by titration, flame photometry or atomic spectroscopy. It is recommended in the process to keep the concentration of alkaline and 60 alkaline earth metals in the organic phase entering the reactor, and better at all stages after water freezing, i.e. during the separation of the organic and aqueous phases and when the organic phase is returned to 65 5 reactor, below 0.5 mol / l. If this condition is met, and the period from the separation of the organic phase from the amalgam to the contact of the organic and aqueous phases is small (preferably 20 seconds), then during the short stage of transfer of the organic phase from the reactor to the water freezing stage, very high concentrations can be allowed in the extractor 0.95 mol / l of alkali or alkaline earth metals leaving the reactor without the formation of undesired crystal nuclei. When the concentration of these salts in the organic phase is less than 1 mol / l, the separation of the organic and aqueous phases after the extraction is slow, it is difficult to avoid the penetration of water into the organic. Thus, the proposed method is also characterized in that the concentration of alkali and alkaline earth metals in the organic phase after the aqueous extraction is more than 1 mol / L. The crystal separation of metal salts is carried out in the usual way, for example, in a suction pan, a centrifuge or in a precipitator. The water stream, together with the necessary amount of fresh water, is returned to the point of contact with the organic phase leaving the reactor. The polar aprotic solvent is a liquid with a HIGH dielectric constant, not a proton donor and not miscible under operating conditions with the aqueous phase, but partially but soluble in water and slightly dissolving water. The solvent should not participate in the reaction and react with the components in a mixture or with amalgam. Examples of solvents are acrylonitriles and alkylene nitriles, for example acetonitrile and adiponitrile, nitrobenzene, sulfonal and other sulfones, dimethyl sulphoxide, dimethyl form amide, dimethyl acetonamide, and mixtures thereof. Preferred solvents are dimethylformamide, acetonitrile, adinonitrile, and mixtures thereof. The polar aprotic solvent is the main component in the organic phase, and other components, such as water, are only reagents; Water serves as a source of protons. The polar aprotic solvent is more than 50 wt. % reaction medium, but the best results are obtained when 75 weight. % and more. To calculate the amount of the reaction medium, solvents, organic reagents and other additives are taken into account, but without amalgam. The typical reaction medium according to the invention includes acrylonitrile, a polar aprotic solvent, an onium additive, water, carbon dioxide as a weak acid (buffer) for regulating the RP of the medium, and small amounts of nocturnal products. A polar organic solvent may contain impurities that change its polarity, water solubility and solubility of onium additives that promote hydrodimerization.

Thus, if the organic medium consists of a base of acetonitrile — with a small amount of adi ponitrile, it is preferable to add from O to 10 hours of water-soluble nonpolar high-boiling hydrocarbon, such as xylene, to 70 parts of acetonitrile in order to reduce water solubility.

The onium additive is a salt capable of producing alkylated cations in the medium, for example organic ammonium, phosphonium and sulfonium salts. Quaternary ammonium salts are preferred. These include salts with at least three short organic groups with nitrogen, preferably with at least 3 alkyl groups, such as halides or sulphates, especially chlorides with alkyl groups of four carbon atoms B each. Symmetric salts such as tetraethylammonium salts are particularly preferred. Onium supplements are required only for the organic phase.

The amount of onium supplement in the organic phase can vary widely. The upper limit of the Concentration is not critical: it is established depending on the solubility, etc.

In tab. Figure 1 shows the effect of circulating aqueous phase supply and the size of the crystals, the filtration time and the contamination of sodium bicarbonate with mercury.

Devices for mixing the organic and aqueous phases are known - these are mixers consisting of one or more nozzles, sprayers, distribution pipes, provided with holes, or distribution plates, and towers with nozzles.

Carbon dioxide, phosphoric or acetic acid, preferably carbon dioxide, which can be fed into the reactor either in the gas phase or dissolved in the organic phase or in the presence of bicarbonate in the aqueous phase, is used as acids to adjust the pH to neutralize alkali or alkaline earth metals. or in combination of these methods. To increase the solubility of carbon dioxide in the medium, an increased pressure can be applied (1-10 atm.). The amount of reactive carbon dioxide "e" is decisive.

The carbon dioxide content in the reactor and in the transfer from the reactor to the extractor, where water freezing occurs, is maintained below the concentration required for the precipitation of carbonate salts of alkali and alkaline earth metals. Carbon dioxide, which regulates the pH after sodium enters the reactor, is introduced only during or after water freezing (extraction stage). Sodium carbonate salts should not be precipitated even during the water freezing step by using the aqueous phase, supplying carbon dioxide gas only during the subsequent individual crystallization of sodium bicarbonate. The improvement consists in closely displacing the organic phase with the reaction product after separating it from the amalgam with an aqueous solution of sodium bicarbonate to extract sodium from the organic phase,

without precipitating the sodium salt, while simultaneously adjusting the pH of the organic phase to below 10.5, followed by separation of the organic and aqueous phases until salt crystals have formed in them,

with precipitating sodium bicarbonate in a separate stage from the aqueous phase by adding carbon dioxide while simultaneously adjusting the pH of the aqueous phase to 8.1-8.5. The preferred pH limit of the aqueous phase is 8.3 + 0.2. The upper pH limit is determined by the permissible amount of undesirable by-products due to the cyanoethylation reaction. It should be noted that the undesirable cyanoethylation reaction proceeds more easily in the reactor, i.e. in the presence of amalgam; therefore, without amalgam, larger pH values can be allowed in both the organic and aqueous phases than in the reactor,

where it is better to keep the RP below 9.5, while without an amalgam in the organic phase a pH of 10.5 is permissible, and in an aqueous pH of 11.5 it is not possible to form oxide-propionitrile. It is established that the working relations

organic to aqueous phase costs are from 20: 1 to 1: 5; however, at a ratio of about 20: 1, the efficiency of extraction of sodium decreases, therefore, it is desirable to add germinal crystals to the mold, while at a ratio of about 1: 5, a large crystallizer, a large separator and a large pumping power are required. Hence, the best ratio ratio is from 5: 1 to 1: 1.

It was also found that in this particular case it is advisable to keep an aqueous solution (mother liquor) near the bulk with respect to carbon dioxide, that crystals of good size are formed at a rate of

the growth of 50 g of mansose hour / l on the area of crystals from 2000 to 4000. These numbers may vary depending on the plant design and operating conditions.

So, the ratio of the total weight of the aqueous phase to

the crystallizer to the weight of sodium bicarbonate crystals formed per hour should be from 5: 1 to 50: 1, preferably from 8: 1 to 20: 1. Salt falling out in the crystallizer is separated from the mother liquor by ordinary filtration. The advantages of the method include: precipitating sodium bicarbonate in the form of large crystals; the ease and speed of filtration of the slurry of sodium salt; a significant decrease in the amount of organic matter and mercury entrained in the sediment; preventing the buildup of crystals on the walls of the reactor and pipes and the deposition of salt crystals in the LINES to the apparatus, other than the crystallizer and the centrifuge. Other benefits include: reducing the amount of heat generated in the reactor, which allows the use of lower circulation rates; increased phase separation efficiency; ease of pH adjustment. The drawing shows the technological scheme of the method. A weighted amount of the circulating aqueous phase is fed into the flow of the reacting organic liquid either in the mixing chamber /, or at the point where it leaves the fluidized bed in reactor 2, or at both points. The amalgam prepared outside the circuit is fed to reactor 2 via line 3, and the used amalgam exits in stream 4. The temperature of the supplied aqueous phase is controlled by a heat exchanger 5. After passing through hydrocycloi 6, where entrained mercury separates, the mixture of aqueous and orthanic phases enters the mixing chamber /, which provides the mass transfer from the organic phase to the aqueous phase. The mixing chamber is equipped with a stirrer and spray nozzle through which carbon dioxide is fed from line 7. From the mixing chamber, the mixed stream 35 of the aqueous and organic phases enters the separator 5, aerated by elongated cylindrical upper and lower sections, where the separation takes place) less dense organic phase from water. A portion of the organic 40 phase containing the reaction product is withdrawn in stream 9. The aqueous phase is cooled in the separator to the desired crystallization temperature using a cooling jacket 10; the crystallization of sodium bicarbonate ends in a separator. The sodium bicarbonate slurry is precipitated at the bottom of the separator and enters the basket centrifuge 11, where the precipitate is centrifuged in the cup 12. The aqueous filtrate passes through a separating vessel 13 and is pumped to the pumps 14 into the nano tank 15; from here it is metered and injected at feed points. An adjustable amount of the clear aqueous phase or suspension can be fed into the aqueous stream to increase the ratio of the aqueous and organic phases or to facilitate the growth of larger crystals by centrifuge bypassing the flow stream 16. From the storage 17, a metered amount of acrylonitrile 60 is fed to the vessel 18 A fresh aqueous solution of quaternary ammonium salt to compensate for the amount of quaternary salt retained on the sediment in a centrifuge or carried with the Food Stream 19 is dosed into a vessel 65 5 15 18 from storage 20; fresh water replacing the water in the reaction and the water removed from the system with sediment in the centrifuge and product stream 19 is dosed into the vessel 18 in the effluent 21. To mix the circulating organic stream 9 with fresh streams and carbon dioxide supplied through the line, there is a mixer connected to the atmosphere. A pump 22 provided with a bypass with a suction line to control the flow circulates the metered organic phase 23 to the reactor 2; The temperature of the flow of phase 23 is controlled in a heat exchanger 24. The organic stream 9 containing the product adnonitrile, a polar organic solvent, for example a mixture of acetonitrile and xylene, or acetonitrile with some water, possibly some amount of acrylonitrile and a surfactant, is divided into components by conventional distillation, the product is separated, the reagents and auxiliaries are recycled to the process. Sodium bicarbonate, sorbed organic matter and mercury are separated and separated separately. Example 1. The adiponitrile organic phase is circulated through reactor 2, immediately above the dense phase of the amalgam a circulating aqueous phase is fed at a temperature of 35 ° C provided by the heat exchanger 5 at a rate of 150 ml / min. This injected stream is a filtrate circulating from a centrifuge 11 containing 15 wt. % tetraammanium chloride along with acrylonitrile, adiponitrite, propionitrile, a small amount of olitomeric impurities, sodium bicarbonate in water and carbon dioxide. The thoroughly mixed phases are fed to a mixer with a stirrer and saturated with carbon dioxide before being fed to the separator 8 at a temperature of 34 ° C. Here, sodium bicarbonate crystals are collected in the aqueous phase. The organic phase is retained in the separator for 3 minutes. An aqueous suspension of sodium bicarbonate is taken from the bottom of the separator at an IB point slightly higher than the bottom to avoid contamination with traces of entrained mercury at such a rate as to maintain the sodium bicarbonate concentration and about 5 wt. In suspension. % The installation works for four shifts of 8 hours without serious blocking, while the filtration rate is high, the filter cake is clean, each (shown in Table 1. Example 2. A mixture of adionitrile, acetonitrile, and xylene is used as the organic phase. in contact with the aqueous phase, the composition of the organic phase is indicated in Table 2. In this case, the installation works satisfactorily for 8 hours without clogging. At a good filtration rate, the filtration rate and purity of the filter cake are shown in IB Table 1.

Table 1

Example 3. The apparatus shown is used, but with the following modifications; the carbon dioxide (spray nozzles) is extended to the mixing chamber of the hydrocyclone and the circulation line from the pressure tank. the aqueous phase through the heat exchanger 5 iB reactor 2. The mixing device consists of a Shibel column without a nozzle, the separator 8 is replaced with two separator vessels phases and crystallizer.

The Schiebel column is a cylindrical column equipped at the bottom with an inlet for the aqueous and organic phases, and in the upper part with an outlet for the dispersion. The column has three compartments for mixing with partitions, each compartment has four partitions on the cylindrical wall, and along the axis of the column a turbine stirrer is installed, which removes (Maximum mixing of the aqueous and organic phases along the height of the column.

Both vessels have a common outlet, equipped with a condenser. The phase separator has three adjustable height stations that pass through the bottom of the vessel. The inlet for mixed phases and the outlet for the organic phase are located in the annular gap formed by the cylinders, the outlet for the aqueous phase is located along the axis of the inner cylinder. The inlet level for the organic phase is 0.5 higher than for the aqueous phase, and a 7 above the base of the separator. Cylindrical walls serve to smooth the turbulent flow during phase separation. The separator is also provided with an outer jacket for temperature control. The redistandator is a cylindrical vessel made of soft steel, equipped with an outer jacket for water cooling, with a wide concentric exit of 3 conical parts suitable for dispensing solid crystals, an inlet for liquid in the upper part, an agitator in the tantra of a vessel with two sets of blades . Concentric stirrer with a gap of about 0.25 with respect to the blade m stirrer set

the draft tube, which during the operation of the stirrer, causes the liquid to circulate from the space between the crystallizer and the draft tube. In addition, four small pipes are installed for feeding carbon dioxide to the bottom of the draft pipe. At this point carbon dioxide is supplied (in some experiments it is introduced through line 25.

During operation, the organic phase 23, which contains almost no water, is fed to the reactor 2; the temperature of the organic phase supplied to the peaiKTop is controlled by a heat exchanger 24. The organic phase reacts in the reactor; The mass, almost completely freed from the amalgam, leaving the reactor, is quickly transferred to the mixing point of the organic and aqueous phases in the bottom part of the column Sh. ibel, where (Close mixing of both phases occurs. From: the Shibel column disperses the two phases; to the separator, where the aqueous and organic phases are separated into a less dense organic phase, from which product stream 9 and the aqueous phase entering the crystallizer are taken. The temperature in the latter is adjusted to an accuracy of 4: 2 ° C; carbon dioxide is fed through a draft tube. pH sodium bicarbonate drops out and settles on the conical bottom of the crystallizer.A note is collected from the crystalline slurry, which is sent to a centrifuge // for separation, and the transparent filtrate is combined with the mother liquor from the top of the crystallizer and returned to the pressure tank 15 and mixing device. Carbonic acid is introduced only into the crystallizer. The pH above the reactor at the point of exit to the Shibel column, in the organic and aqueous phases in the separator and at the outlet of the crystallizer is determined.

The composition of the adiponitrile (acetonitrile) xylene organic phase in contact with the corresponding aqueous phase is given in table. 3

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. Table of Composition of Phases, in Component Organic Adiponitrile Acetonitrile Water Chloride tetraethyl ammo2, 0 Unity 0.7 Oligomeric impurities. . 7.0 Acrylonitrile 0.3 Propionitrile 3.0 Xylene Slightly sodium bicarbonate. , . True values are + 5% accuracy. At the beginning of each, seed crystals are used, which crystallize. Example 5 shows the introduction of carbon at two points, in the crystallizer, and the nical phase without precipitating the crystalline crystal (the pH of the organic is extremely low).

In Example 15, with a small ratio of organic phase iK to aqueous, sodium is removed below the level at which phase separation is facilitated. Slightly reducing the extraction efficiency, in Example 16 a good phase separation is restored. Similarly, in Example 17, the phase separation is satisfactory, but after an extreme increase in the supply of the circulating aqueous phase to 910 ml / min and the accompanying increase in sodium content in the organic phase leaving the Schiebel column, the phase separation again becomes slower.

In Example 18, an intermediate vessel is installed between the reactor and the Schibel zholonnaya so that the transfer time of the organic phase from the reactor to the Shibel column can be controlled. With a transfer time to the column of up to 20 seconds, no crystal formation was observed.

In Example 19, a full analysis and material balacon was performed to establish the outputs with great accuracy. The results are shown in Table. 5. In all experiments, the release of adiponitrile is identical to the release of substances in experiments conducted without water freezing.

The filtration rate is determined in Example 19 as follows.

Composition, weight

The sodium bicarbonate precipitate is stirred from the filter in an aqueous mother liquor. After the supersaturation of the latter with sodium bicarbonate is reduced to zero, the dispersion is passed into a filter with a diameter of 73 / s and a height of 14 (187X357 mm). The crystals are allowed to settle, and the mother liquor is passed through a layer of crystals on the filter and filter cloth to a constant flow rate of the filtrate.

These EXPERIENCES are carried out with 216, 432 and 648 g of dry sodium bicarbonate at a pressure of

Table 5 In Examples 6-14, the effect of increasing the ratio of the organic phase to the aqueous phase in the Extraction Stage (aqueous freezing) is shown. At very high ratios, the extraction efficiency decreases, the sodium concentration of the IB organic phase exceeds the preferred limit and crystallization proceeds outside the crystallizer, the pH becomes too high in both phases, at ratios above 20: I unregulated lamination and blockage occur. In Example 7, the amalgam feed rate to the reactor is temporarily increased to set a limit at which the precipitation of sodium salts from the organic phase can be prevented from being transferred from the reactor to the Shibel column, 2 wt. % sodium is obtained without the formation of crystals. In Example 11, some carbon dioxide is also added to improve pH control in the organic phase; no crystals form outside the crystallizer. The mercury which has been spotted on wet crystals is determined in parts by weight per milion. Ion parts of sodium bicarbonate. Table 4

15

0.0014, 0.35, 0.7, 1.4, and 2.8 kg / sr, respectively, on the sediment layer and filter cloth. In all experiments, the resistance of the filter cloth is negligible.

SoprotiBleep layer of sediment on the filter the following: a, cm / g

For the sample, g

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0.29 432

4.4 J about 0.31

216

9.8

JQ6 0.31 648

16,1

where r is din / cm, i.e., the resistance of the layer of filter cake is from 1.6-IQs to 1.6-109 g / cm-2 for the specified range of pressures.

The average mercury content for the results given in IB Examples 3-19 is 10 hours; mil} yun in unwashed sediment. The precipitate formed from crystals grown in the orgavicheskoy phase passing through the reactor contains about 1,000 to 10,000 hours / million of mercury.

Subject invention

1. The method of preparing dnmer nitriles of esters a ,, rm; non-unsaturated compounds, for example adiponitrile, by means of hydrodim im of a nitriles or esters of a, p-monounsaturated compounds, 16

An example is acre | ilonitrile, alkaline or alkaline earth metal amalgam in a polar aprotic solvent, such as acetonitrile, dimethylformamide, added with slogan mislota, for example, carbon dioxide, in the presence of anionic additives, such as quaternary ammonium salts, with turbulent1, for example. mass, followed by separation of the amalgam phase from the organic phase, characterized in that, in order to simplify the process, the organic phase is treated with water in a ratio of 1-5 volumes of the organic phase to 1 volume m 1VODY organic phase to a pH less than 10.5 and the content therein of an alkali or schelochnozemelnogometallabolee

1 mol / L, carbon dioxide is added to a pH of the aqueous phase of 8.1-8.5, followed by separation of the aqueous and organic phases

and the selection of the last target (product known methods.

2. A method according to claim 1, characterized in that an inert B1 insoluble high boiling hydrocarbon solvent, for example xylene, is added to the reaction medium.

3. Method but CPU. 1 and 2, characterized in that the ii-i3 of the aqueous phase is separated by a sol: spruce: solid or alkaline earth metal, for example sodium bicarbonate.