The way to select hexaferrite

 

(57) Abstract:

The invention relates to method selection hexaferrite gases from pyrolysis of diperchlorate production of tetrafluoroethylene. The process enables the selection of high-boiling products, tetrafluoroethylene and concomitant impurities from the original pyrolysis gases, extractive distillation fraction containing diperchlorate and hexaferrites, using a separating agent on the basis of lower aliphatic halogen carbon. These products share with obtaining the target components. The fraction containing diperchlorate, hexaferrites, fluorocarbons, tryptophanate, impose additional separating agent of diperchlorate in number, in which the ratio of the molar concentrations of diperchlorate and hexaferrite achieved at least 95: 5. The resulting mixture is subjected to azeotropic distillation under a pressure of more than 1.6 MPa with the Department of difenilamina and triptoreline as VAT residue. Obtained as distillate mixture of diperchlorate and hexaferrite share in the presence of a separating agent perftorsilanami or 1,1,2,2-tetrafluorodichloroethane with the subsequent removal it is relates to the field of industrial synthesis of organofluorine, in particular to method selection hexaferrite of the gases from the synthesis of tetrafluoroethylene.

Industrial method for the synthesis of tetrafluoroethylene is the pyrolysis of diperchlorate. In the pyrolysis process produces a complex reaction mixture containing in addition to the target product tetrafluoroethylene and not fully reacted with diperchlorate well as hydrogen chloride, small amounts of hydrogen fluoride, triptorelin, deformity, triptorelin, hexaferrites, tryptophanate, fluorocarbons, 1,1,2,2-tetrafluorochloroethane, 1,1,1,2-tetrafluorochloroethane, perftorsilanami, fertiliser and a number of volatile ingredients of the products.

Among these components, hexaferrite is one of the most valuable and therefore it must be allocated as a commercial product.

Adding even small amounts of hexaferrite upon receipt of a number of grades of fluoropolymers significantly improves their quality; hexaferrite - feedstock in the synthesis of fluorine-containing oxides, alcohols, ethers, etc. But to use hexaferrite for these purposes the deep treatment of this product.

In addition, in some cases, for example, when applying hexaflurophosphate very high purity. Thus, the content of triptoreline in this case should not exceed 1 ppm, which is difficult to achieve when using the absorption method of purification of hexaferrite.

The known method (U.S. Pat. RF 2063952, class C 07 C 17/386, 19/08, 19/10, publ. 20.07.1996, prototype) joint selection recoil diperchlorate and hexaferrite products from pyrolysis of diperchlorate based on allocation of diperchlorate by means of extractive distillation and purification of hexaferrite from accompanying impurities by selective absorption solvent.

In this way the mixture of diperchlorate, hexaferrite, difenilamina and triptoreline is subjected to extractive distillation using perftorsilanami, 1,1,2,2-tetrafluorodichloroethane or 1,1,2,2-TETRAFLUOROMETHANE as a separating agent. In the process, purified from the other three components of the mixture, diperchlorate stands out as distillate extractive distillation column and then returns back to the process of obtaining tetrafluoroethylene, and other shared components of the mixture together with the separating agent is removed from the column as a cubic product. The village is smetana and triptoreline.

Subsequent purification hexaferrite by absorption with the use of one of the polar solvent, N-methylpyrrolidone, ethyl acetate or dimethylformamide. Because absorption is lost a significant part of hexaferrite, absorbed products are desorbed, and the mixture is again subjected to absorbance using the same solvents.

However, this method has disadvantages. Absorption cleanup hexaferrite accompanied by a significant loss of this product, and reduce losses by using a two-stage absorption, leads to considerable complication of the technological scheme.

As follows from the materials presented in U.S. Pat. RF 2063952, the greatest loss of target products occur at the stage of absorption cleanup hexaferrite, and it is the purity of hexaferrite in the conduct described in U.S. Pat. RF 2063952 process is insufficient. Therefore, the direction of process improvement is the replacement of the absorption stage cleaning hexaferrite on more technological.

Consequently, the object of the present invention is to develop a method that would allow implementing the losses of the latter without the use of complicated additional equipment.

In most separation technologies of pyrolysis products of diperchlorate after separation of tetrafluoroethylene and concomitant impurities (triptorelin, deformity, triptorelin), for further separation comes a mixture of diperchlorate, hexaferrite, triptoreline, difenilamina.

Among these products, diperchlorate and hexaferrite form an azeotropic mixture with positive deviations from ideality. In diperchlorate - fluorocarbons, there are significant positive deviations from ideality, leading to azeotrope at pressures below 1.6 MPa, but at higher pressures the azeotrope disappears (M Kriebel. Kaltetechnik-Klimatisierung, 1967, 19, l, 8-14). System diperchlorate - tryptophanate LEASEUROPE, despite the significant positive deviations from ideality.

The difference of the normal boiling points of difenilamina and hexaferrite is 0.6 To, hexaferrite and triptoreline - 1,3, system fluorocarbons hexaferrite and hexaferrite - tryptophanate are azeotropic, and these azeotropy have a minimum boiling point.

Thus, the mixture of the mi usual rectification to separate the impossible. Even after the extractive distillation and removal of a mixture of diperchlorate mixture of hexaferrite, triptoreline, difenilamina also impossible to separate by conventional method of rectification.

We established that hexaferrite can be separated from triptoreline and difenilamina using the method of azeotropic distillation. When this separating agent must form an azeotropic mixture having a minimum boiling point, with geksaftorpropena, and do not form azeotropic mixtures with diftorhinolonom and Cryptosporidium.

As it turned out, such a separating agent can serve as diperchlorate when carrying out the azeotropic distillation under a pressure of more than 1.6 MPa. During the process of rectification of mixtures containing hexaferrite, tryptophanate, fluorocarbons and adding this mixture of diperchlorate in such quantity that the concentration of this substance in the mixture exceeded the content of diperchlorate in the azeotropic mixture of diperchlorate - hexaferrite, that is at least 95% molar, at a pressure of more than 1.6 MPa, as volatile fraction is selected azeotropic mixture debtor is on.

It should be noted that among the pyrolysis products of diperchlorate sent for further separation after separation of tetrafluoroethylene and concomitant impurities already present diperchlorate. If the content of hexaferrite in the partial mixture exceeds the concentration of this substance in the azeotropic mixture of diperchlorate - hexaferrite, to the mixture directed to the division, must be added the necessary number of diperchlorate.

CBM product column azeotropic distillation, which is a mixture of difenilamina and triptoreline, can then be sent for recycling or destruction, and the azeotropic mixture of diperchlorate and hexaferrite transferred to the stage extractive distillation.

During extractive distillation a mixture of diperchlorate and hexaferrite served in the lower part of the distillation column, and in the upper part introduces a separating agent, which can be used perftorsilanami, or 1,1,2,2-tetrafluorodichloroethane.

Schematic diagram of the separation of the mixture shown in the drawing.

The mixture is directed to the separation (flow 1), in the mixer 1 smartrate of diperchlorate and hexaferrite becomes not less than 95/5, and then pump 2 is fed to the column azeotropic distillation 3, working pressure 1.6 MPa. As the cubic product from this column is disposed fluorocarbons, tryptophanate (stream 6), and as distillate mixture of diperchlorate and hexaferrite.

The distillate of the column 3 is fed into the lower part of the extractive distillation column 4. A separating agent (perftorsilanami, or 1,1,2,2-tetrafluorodichloroethane) is fed into the upper part of the column 4. In the process of extractive distillation is the separation of azeotropic mixtures of diperchlorate - hexaferrite.

Diperchlorate allocated in column 4 as distillate (stream 7) is returned to the production process of tetrafluoroethylene, and a mixture of hexaferrite and separating agent is sent to column 5, where as distillate allocated purified hexaferrite (stream 9), and a separating agent is derived from a cube column and returns to the supply tank 6. As required in the system is added the required amount of separating agent (stream 11).

Next, the cleaning method of hexaferrite illustrated by examples.

EXAMPLE 1.

10 kg of the mixture obtained in the volatile ingredients of the products, having the following composition (in mol. %):

Diperchlorate (R22) - 93,64

Fluorocarbons (R12) - 0,34

Hexaferrite (R1216) of 5.84

Tryptophanate (R1113) - 0,18

were mixed with 12 kg of diperchlorate, resulting in 22 kg of a mixture of the following composition:

Diperchlorate (R22) - 97,18%

Fluorocarbons (R12) - 0,15%

Hexaferrite (R1216) at 2.59%

Tryptophanate (R1113) to 0.08%

The mixture was loaded into a cube periodic distillation column with a diameter of 50 mm with the height of the Packed layer 8 m filled spiral prismatic nozzle 44 mm, made of nichrome wire, and subjected to fractional distillation. The process was performed under a pressure of 2.5 MPa, with a flow rate of distillate that got smaller during the experience of 3.5 kg/h 1 kg/h

In the result of the process was allocated 18 kg purified mixture. The composition of the mixture was determined by gas chromatography. The mixture had the following composition:

Diperchlorate (R22) - 97,161%

Fluorocarbons (R12) - 0,0033%

Hexaferrite (R1216) - 2,8256%

Tryptophanate (R1113) - 0,01%

The temperature of distillate 61,5oC.

This mixture was again subjected to rectification in the column described above. The process was carried out under a pressure of 2.5 MPa is the product of the following composition:

Diperchlorate (R22) - 96,7890%

Fluorocarbons (R12) - 0,0000%

Hexaferrite (R1216) - 3,2104%

Tryptophanate (R1113) - 0,0006%

The temperature of distillate 61,5oC.

In the case of distillation columns sufficient efficiency of the cleaning process can be carried out in one stage.

Further separation of diperchlorate and hexaferrite was conducted by means of extractive distillation using as the separating agent perftorsilanami (RC318).

The process was performed in a Packed column with inner diameter of 40 mm and a height of the Packed part of 2700 mm, collected from 9 bars 300 mm each. The column is made of stainless steel, cap - nichrome spiral prismatic 33 mm

The initial mixture was applied to the dispenser between 3 and 4 bars, a separating agent on the distributor between 6 and 7 bars. Submission partial mixture was 0,78 kg/h

The flow separating agent (perftorsilanami) was 5 kg/h

The experiment was carried out at a pressure of 0.6 MPa.

In the process, the compounds of distillate and cubic product was determined chromatographically. The compositions of distillate and cubic product and tnoi rectification (composition shown in table 1) was subjected to rectification to separate the separating agent and hexaferrite with the accompanying impurities. Separation was carried out in a distillation column continuous action described above. The pressure was maintained equal to 0.5 MPa. Food was administered between 4 and 5 bars with a flow rate of 3 kg/h

The compositions of distillate and cubic product, and the temperature of the top and bottom of the column are presented in table. 2.

Experience has shown that when using the process described in the invention, of the products of pyrolysis of diperchlorate can be obtained hexaferrite high purity at almost its full allocation of pyrolysis products.

The share allocated hexaferrite significantly higher than the share of this product that can be allocated by using the method described in (U.S. Pat. RF 2063952). Thus, according to example 1 of the patent when using single-stage absorption fraction selected hexaferrite amounted to about 70%, and the use of technologically complex process of two-stage absorption is about 90%.

EXAMPLE 2.

Analogously to example 1.

However, as a separating agent on the stage extractive distillation was used 1,1,2,2-tetrafluorodichloroethane (R114).

The flow separating agent was 5.5 kg/HR, and the pressure at the stage extractive re the temperature of the top and bottom of the column are presented in table. 3.

Department of hexaferrite from separating agent was carried out in a distillation column, working under the pressure of 0.5 MPa.

The compositions of distillate and cubic product, the temperature of the top and bottom of the column are presented in table. 4.

Experience has shown that the allocation of hexaferrite can be carried out using as a separating agent extractive distillation 1,1,2,2-tetrafluorodichloroethane. Experience has shown that the allocation of hexaferrite can be carried out using as a separating agent extractive distillation 1,1,2,2-tetraphenylmethane.

EXAMPLE 3.

In a periodic cube of the distillation column described in example 1, was loaded with 22 kg of a mixture of the same composition as in example 1:

Diperchlorate (R22) - 97,18%

Fluorocarbons (R12) - 0,15%

Hexaferrite (R1216) at 2.59%

Tryptophanate (R1113) to 0.08%

The mixture was subjected to fractional distillation. The process was performed under a pressure of 0.9 MPa with a flow rate of distillate 2 kg/h

As a result of experience were selected 18 kg of distillate of the following composition:

Diperchlorate (R22) - 97,0664%

Fluorocarbons (R12) - 0,0498%

Hexaferrite (R1216) - 2,8775%

Tryptophanate the Tana (R12) distillate, obtained in this experience, exceeds the contents of R12 in distillate obtained in example 1 in 15 times. This proves that when carrying out rectification at low pressures deep cleaning R22 and R1216 from R12 is impossible.

EXAMPLE 4.

In a periodic cube of the distillation column described in example 1, was loaded with 22 kg of a mixture of the following composition (hereinafter concentrations are in molar percent):

Diperchlorate (R22) - 78,8120%

Fluorocarbons (R12) - 1,1270%

Hexaferrite (R1216) - 19,5899%

Tryptophanate (R1113) - 0,6011%

The mixture was subjected to fractional distillation. The process was performed under a pressure of 2.5 MPa with a flow rate of distillate 2 kg/h

As a result of experience were selected 18 kg of distillate of the following composition:

Diperchlorate (R22) - 89,4971%

Fluorocarbons (R12) - 1,2778%

Hexaferrite (R1216) - 8,5611%

Tryptophanate (R1113) - 0,6639

The temperature of distillate 60oC.

It is easy to see that the removal of difenilamina and triptoreline not occurred. This proves that when carrying out rectification of mixtures with a low content of diperchlorate cleaning mixture from R12 and R1113 does not occur.

The way to select hexaferrite of gases pittarello and concomitant impurities from the original pyrolysis gases, extractive distillation fraction containing diperchlorate and hexaferrites, using a separating agent on the basis of lower aliphatic halogen carbon, separation of the products obtained with the obtaining of the target component, characterized in that the fraction containing diperchlorate, hexaferrites, fluorocarbons, tryptophanate, impose additional separating agent of diperchlorate in number, in which the ratio of the molar concentrations of diperchlorate and hexaferrite achieved at least 95: 5, the resulting mixture is subjected to azeotropic distillation under a pressure of more than 1.6 MPa with the Department of difenilamina and triptoreline as VAT residue, and obtained as distillate mixture of diperchlorate and hexaferrite share in the presence of a separating agent perftorsilanami or 1,1,2,2-tetrafluorodichloroethane with the subsequent destruction of its rectification.

 

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