PL90772B1 - - Google Patents

Description

The invention relates to a recovery process The separation of E-caprolactam from the reaction mixture containing sulfuric acid.

One method of producing lactams is based on the so-called Beckmann rearrangement in which Lactam is obtained from the cyclic oxime v the presence of acid. This reaction is particularly convenient for large-scale production of E-caprolactam from cyclohexanone oxime using sulfuric acid oil, oleum or SOa, the resulting mixture being mixed The reaction mixture contains caprolactam and acid sulfuric.

Another method of producing E-caprolactam involves on the reaction of cyclohexanecarboxylic acid or of its derivative with a reagent introducing a coarse full nitrosation in the presence of sulfuric acid. IN in this case, the reaction mixture is composed also from lactam and sulfuric acid.

Known from the United States patent No. 2,993,889 to isolate the waxes tamu with post-reaction mixtures containing sulfuric acid is the neutralization of the mixture aqueous ammonia solution, solution rich in lactam, containing approximately e.g. 70% by weight of lactam dissolved in water, forms the top layer and a concentrated sulfate solution in water is the bottom layer. After When the layers are separated, the lactam is separated therefrom and solid ammonium sulfate which after evaporation water crystallizes from a concentrated solution of sulfur ammonium chloride.

In this case, neutralize the acid sulfur to ammonium sulfate is converted usually in a separate operation, independent of crystallization of ammonium sulfate from the obtained concentrated solution.

The method is known from the German patent specification No. 858701 lactam recovery involves carrying out neutralization and crystallization in one step. Have lactam shanine containing sulfuric acid are e.g. introduced into a concentrated sulfate solution ammonia and then neutralize it favorably gaseous ammonia. After crystallization and recovery splitting the solid ammonium sulfate residue separates into a lactam-rich upper layer and a bottom layer formed of a saturated solution ammonium sulphate, which can be recycled to circulation.

In such a procedure, neutralization takes place at a relatively low temperature because the heat the neutralization field is picked up by the direct cooling.

They do, however, have known procedures disadvantages that crystallize during After cooling, the ammonium sulphate is deposited on the surface cooling surfaces, resulting in effective The heat exchange capacity decreases rapidly.

In the manner known from the British patent specification No. 1123472 neutralization and crystallization of 90 7723 also carried out in one step Jacuzzi and ammonia by dilution ammonium sulphate formation. In this process, warmth neutralization is not received by cooling, but by by evaporating the water at a low temperature in to prevent hydrolysis.

However, this method has the disadvantage that it is inert cooling and crystallization at low temperature The magician applying a pressure of 0.055-0.095 atmospheres ruthless.

The method according to the invention in which it is not used no cooling surfaces on which crystals could be deposited in which redundant there is equipment for working under. reduced cis it does not consume any energy to support reduced pressure is not shown above the disadvantages.

It was found that no risk of lactam loss through hydrolysis can be carried out, neutralization, crystalline talizations and evaporation of water in one step under atmospheric pressure, with relatively high boiling point, around 108 ° C per month post-reaction shame. It seems acceptable there are also higher temperatures, such as row temperatures 140 ° C, corresponding to a pressure of approximately 4 atmospheres so you can also apply pressures above down 1 atmosphere and recover evaporation water in the form of a steam with a pressure of bp. 4 atmospheres Observed it was decided that up to a temperature corresponding to cis Loss of lactam resulting from about 5 atmospheres from hydrolysis are insignificant.

Method of recovering E-caprolactam with mixing reaction line containing lactam and sulfuric acid According to the invention, the solution consists of neutralization with sulfuric acid ammonia in the circulation circuit of the ammonium sulphate solution at one early formation of ammonium sulfate crystals it, separating the crystals from the liquid phase and separating them pouring the liquid phase onto a layer of oily lactam, which is discharged and the ammonium sulfate solution which is turned around, whereby it becomes desensitized is carried out under a pressure of 1-5 atmospheres, and heat the neutralization is removed by evaporation water from neutralized solution.

The neutralization is preferably carried out under pressure at 2 atmospheres, because in these conditions the work there is no loss of lactam.

Compared to the known one-step processes According to the invention, the method according to the invention has the following advantages: energy to keep the pressure low it is redundant, as is the vacuum equipment we, provided that if the above pressures apply 1 atmosphere can be simultaneously recovered steam, eg for 1 ton of lactam you can get 1 ton of steam 6 pressures of 2 atmospheres.

In the method according to the invention, heat is released the neutralization is discharged by evaporation solvent, i.e. water, but in the event of condensate is returned to the inert zone cutting. No equipment is needed behind this to keep the temperature of the slurry low, after because neutralization and crystallization take place at the volume of the circulating saturated solution of sulfur ammonium chloride. Water evaporated by the heat of rea the mixture can be condensed and recycled in liquid form 772 4 or move in pairs. In order to maintain bi¬ the loss of water in equilibrium is returned to the system in the neutralization operation, usually the amount of water what is removed from the top layer of the rich solution s in lactam or an amount equivalent to the amount produced couples.

The method according to the invention is particularly advantageous bright and illustrated in the attached drawings, in which fig. 1 shows a diagram of the apparatus, 1a and Fig. 2 shows the obtained results graphically.

In Figure 1, A shows the columns of connection pipe connected at the top with a pipe entering tangentially to the spherical chamber B above which condenser C is located. The lower part of chamber B is is connected to the clarifier D by the pipe 12, whereby The decanter is connected to the lower end of the column AND.

A reaction mixture during the operation of the device containing caprolactam and sulfuric acid introduced It goes to the tank A through the gas line 1 ammonia through line 2 and water through line 3.

A boiling mixture containing a suspended crystal ammonium sulphate in lactam solution with saturated ammonium sulphate flows from the back to the bottom of column A through the chamber B and decanter D. Krazac, a liquid mass, strongly diluted thin post-reaction mixture with high content acid, thereby avoiding the risk of association with a high concentration of acid and thus hydrolysis lactam.

In the device of Fig. 1, circulation is maintained by feeding into gaseous ammonia, 2 nitrogen water. The rising gas bubbles will stop ensure adequate circulation.

Circulation in devices on an industrial scale can be held by pump.

The water vapor * generated in boiler B condenses in the C reflux cooler, which is equipped with the cooling jacket 9 and the hoses 10 and 11 lead 40 running and draining cooling water.

In the decanter D, the space between the wall and the seam the inside of the tube 12 is used as the space in which the upper layer of the solution is water The lactam-rich bottoms are separated and removed via 45 conduit 4. Lower layer made of slurry the ammonium sulfate crystals are discharged via conduit 5 to centrifuge 6, the lugs being small the cuttings and loins are returned to tank A. via conduit 7. Washed crystalline sulfate 50 ammonium is removed through line 8. In the method according to the invention, the amount of water removed from the system and located mainly in the upper layer of the expansion a product rich in lactam, as well as an amount of water after required to wash the crystals is supplemented with 55 way continuously fresh water brought by line 3. Top up with water instead of fresh water the jaca can be supplied as a sulfate solution ammonia obtained by another process, e.g. created as a by-product of production 60 cyclohexanone oxime. This is how you get savings in evaporation costs.

If more water is introduced into the system than can be removed as the top layer of solution rich in lactam, additional water should be Remove 65 tears or as pairs for incomplete 90 772 6 condensation in the cooler C or in the form of a condensation satu by incomplete recycling from cooler C to boiler B.

If the heat of neutralization is not sufficient to evaporate consuming the total amount of water in one step, then multi-stage evaporation can be used.

The method according to the invention is illustrated as follows practical example: Example. To the camera shown in fig. I is fed through line 1 the mixture post-reaction containing E-caprolactam and acid sulfur at a rate of 730 g / hour, with The shale consists of: 43.2% by weight E-caprolac- tamu, 56.4 wt% sulfuric acid "and 0.43 wt.% By-products, tar.

The reaction mixture becomes neutralized with 143 g / hour. ammonia, the line 3 is fed simultaneously 357 g / hour. fresh water, and by line 7 of 110 g of post-wash water is as follows With this composition: 22.7% by weight of ammonium sulfate % by weight of water, and 2.7% by weight E-caprolactam.

Average residence time of liquids in apparatus is 3 / 4-1 hours, the temperature of the circulating crystalline the total mass which is built up at a rate of 500 g per the hour is 108.5 ° C, and it receives through conduit 4 August 445 g per hour of lactam-rich solution with the following composition: 71.9% by weight of lactam, 27.6 wt.% Water, 0.7 wt.% Sulfate ammonia and 0.7% by weight "tar."

After washing and filtering off the crystalline mass, the you get 82 g of water through the conduit 5 hour and you get 557 g per hour raw the crystalline ammonium sulfate it contains still 1-2% by weight of water, but free from lactam.

In an exemplary process conducted in the I am, according to the invention, the pH value of the mixture the circulator was set to 4.5 and another to 3.3.

At these pH values, the lactam hydrolysis, at given the time spent in the system it seems be insignificant, as can be seen in the graph in fig. 2, on which the amount of lactam that has been hydrolysed in percent by weight based on total od is located on the ordinates, and the time in hours (h) on the observed axis.

Claims (2)

Patent claims 1. The method of recovering E-caprolactam from the reaction mixture containing lactam and sulfuric acid, consisting in neutralizing sulfuric acid with ammonia in the circulating volume of ammonium sulphate solution with simultaneous formation of ammonium sulphate crystals, separation of crystals from the liquid phase and separation of crystals from the liquid phase the oily lactam layer which is withdrawn and the ammonium sulphate solution which is recycled, characterized in that the neutralization is carried out at a pressure of 1-5 atmospheres, and the heat of neutralization is removed by evaporating the water from the neutralized solution. 2. The method according to claim The process of claim 1, wherein a pressure of 1-2 atmospheres is used in the neutralization process. 90 77290 772 FIG. 2