The method of producing tetrafluoroethylene

 

(57) Abstract:

The invention relates to the production of tetrafluoroethylene - raw material for a wide class of fluoropolymers. The method of diperchlorate(Halocarbon 22) is subjected to pyrolysis in the presence of water vapor and 1,1,2,2-tetrafluorochloroethane (halon 124A beaches). Then conduct a quenching of the pyrolysis products, separating hydrochloric acid, and then subjected to neutralization, compression, condensation. Next, by using a multistage rectification produce tetrafluoroethylene and the fraction with a boiling point at atmospheric pressure from -42 to 0oC, which contains mainly freon 22, S, 124A beaches and HEXAFLUOROPROPYLENE. The fraction divided by the absorption of water. The absorbed components (freon 22 and 124A beaches) is desorbed and returned to the pyrolysis, and unabsorbed gases by distillation produce halon S and HEXAFLUOROPROPYLENE. Absorption of water is conducted at 5 - 25oC and a pressure of 3 to 7 MPa in the machine column type in countercurrent with the flow of water from the top of the apparatus, and products of pyrolysis from the bottom, when the mass ratio of water:the products of pyrolysis of 50 to 150 : 1. The result is improved efficiency of the process and also get OCTAFLUOROCYCLOBUTANE (halon S) is a valuable refrigerant Il is receiving tetrafluoroethylene - raw materials for the production of a wide class of fluoropolymers.

A method of obtaining tetrafluoroethylene, including pyrolysis of diperchlorate, washing pyrolysis products from acidic impurities, compression and isolation of the target product by distillation [U.S. Pat. USA N 3459818, CL 260-653.3, publ. 05.08.69] . The method is characterized by the formation of large amounts of by-products and low yield of the target product.

Know of any other way to get tetrafluoroethylene, which avoids the disadvantages of the previous method and the set of essential characteristics most similar to that proposed. This method involves the pyrolysis of diperchlorate in the presence of water vapor and supplements 1,1,2,2-tetrafluorochloroethane and OCTAFLUOROCYCLOBUTANE in the form of an azeotropic mixture in an amount of 2-15 wt.% in relation to diperchlorate, quenching of the pyrolysis products, the side branch of hydrogen chloride with obtaining hydrochloric acid, neutralization, drying, compression, condensation products of pyrolysis and the two-stage rectification with the separation of the target product, as well as rectifying the allocation fractions of diperchlorate in the form azeotropic mixtures with HEXAFLUOROPROPYLENE, which is shared by absorb is chlorethane, you return to the stage pyrolysis of diperchlorate [U.S. Pat. RF N 2061672, class C 07 C 21/185, 17/00, publ. 10.06.96]. The method is characterized by a high yield of the target product, in addition, of the side products formed in the pyrolysis process, allocate valuable pterolepis - HEXAFLUOROPROPYLENE, which is a co monomer for a number of fluoropolymers and ftorkauchukov. Thanks to the return of the azeotropic mixture of OCTAFLUOROCYCLOBUTANE with tetrafluorochloroethane significantly reduced the number of unusable bottoms.

The disadvantage of this method is that this method does not allow you to select products from pyrolysis valuable, low-impact fluorocarbon - OCTAFLUOROCYCLOBUTANE used as a refrigerant, propellant, the working fluid in heat pumps and power plants.

The technical problem solved by the present invention, the efficiency of the way through the allocation of by-products formed during the pyrolysis, OCTAFLUOROCYCLOBUTANE.

The problem is solved in that in the method of producing tetrafluoroethylene, including pyrolysis of diperchlorate in the presence of water vapor and supplements 1,1,2,2-tetrafluorochloroethane, quenching of pyrolysis products, otdeleniye pyrolysis and multistage rectification emitting fraction of the target product and fractions includes diperchlorate and HEXAFLUOROPROPYLENE, which is shared by absorption of water, absorption of water serves a fraction of the pyrolysis products with a boiling point at atmospheric pressure of minus 42oC and 0oC, unabsorbed gases separated by distillation from the release of hexaferrite and OCTAFLUOROCYCLOBUTANE absorbed water components desorbed and returned to the pyrolysis.

In addition, the absorption of water is carried out in the device column type in counter-current mode when the supply of water from the top of the apparatus, and products of pyrolysis from the bottom at a temperature of 5 - 25oC, a pressure of 3 to 7 MPa, and a mass ratio of water: the products of pyrolysis of 50-150:1.

Example 1. Pyrolysis of diperchlorate carried out in a tube furnace pyrolysis in the presence of water vapor (670 kg per 1000 kg of diperchlorate) and additives 1,1,2,2-tetrafluorochloroethane (halon 124a) in an amount of 3.2% vol. from the original diperchlorate. The products of pyrolysis can be subjected to quenching, cooling and condensation of hydrochloric acid, the organic components are washed with sodium hydroxide solution, komprimiert, condense and rectificatum emitting fraction of tetrafluoroethylene and the fraction with a boiling point at atmospheric pressure of minus 42oF8OCTAFLUOROCYCLOBUTANE - 5,9

C2F3Cl, Tryptophanate - 0,5

CF2Cl2Fluorocarbons - 0,6

CF2HCl, Diperchlorate - 81,8

C2F4HCl 1,1,2,2-Tetrafluorochloroethane - 2,9

The last fraction is subjected to countercurrent water treatment on spetsstalej column with a diameter of 24 mm and a length of 950 mm, filled with a nozzle made of nichrome coils. Organofluorine products served at the column bottom, the water from above. The absorption process is carried out at 20oC and a gauge pressure of 5 MPa. Within 5 h filed with 400 g of pyrolysis products (fractions -42oC0oC) and 60 kg of water (mass ratio of water: the products of pyrolysis of 150:1). Rezorbirovanny water gases removed from the top of the column, condensed in cooled at -196oC the cylinder and subjected to low-temperature rectification in a rectification column efficiency 40 so so Of 112 g nenormirovannyj gases selected 48 g hexaferrite and 47 g of OCTAFLUOROCYCLOBUTANE. Sorbed water gases separated from the sorbate by desorption at low pressure to atmospheric and analyzed chromatographically. Received 84 l gaseous product composition,%:

CF2HCl, Diperchlorate - 96,4

C2F4HCl 1,1,2,2-Tetrathlon on pyrolysis.

Example 2. Pyrolysis of diperchlorate carried out as in example 1. As a result of processing and distillation of the pyrolysis products emit a fraction with so Kip. at atmospheric pressure -42 - 0oC composition, vol.%:

C3F6The HEXAFLUOROPROPYLENE - 6,7

C-C4F8OCTAFLUOROCYCLOBUTANE - 4,5

C2F3Cl, Tryptophanate - 0,3

CF2Cl2Fluorocarbons - 0,7

CF2HCl, Diperchlorate - 84,5

C2F4HCl 1,1,2,2-Tetrafluorochloroethane - 3,3

The specified fraction is subjected to countercurrent water treatment on the column described in example 1, 5oC and a gauge pressure of 3 MPa. For 5 h filed 400 g products specified fraction and 40 kg of water. Collected 85 g nenormirovannyj products, of which the rectification is allocated 41 g hexaferrite and 36 g of OCTAFLUOROCYCLOBUTANE. From the sorbate selected by desorption at atmospheric pressure 86 l gaseous products of composition, vol.%:

CF2HCl, Diperchlorate to 96.5

C2F4HCl 1,1,2,2-Tetrafluorochloroethane - 3,5

Example 3. The fraction of the pyrolysis products of diperchlorate with a boiling point at ATM. press. -42 - 0oC having the composition as in example 1, is subjected to countercurrent processing water at 25oC and 7 MPa. 5 hours is UP>o
C and subjected to low-temperature rectification. 103 g of the condensed products emit 47 g hexaferrite and 46 g of OCTAFLUOROCYCLOBUTANE. Of water sorbate by desorption at low pressure to atmospheric allocated 85 l gaseous products of composition, vol.%:

CF2HCl, Diperchlorate - 96,3

C3F6The HEXAFLUOROPROPYLENE - 0,1

C-C4F8OCTAFLUOROCYCLOBUTANE - 0,2

C2F4HCl 1,1,2,2-Tetrafluorochloroethane - 3,3

CF2Cl2Fluorocarbons - 0,1

Examples 4-8. Pyrolysis of diperchlorate, purification of the pyrolysis products from acidic impurities and their distillation separation is carried out as in example 1. Allocate a fraction with a boiling point at ATM.press. from minus 42oC and 0oC and divide it by the absorption of water with the setup described in example 1. The composition of this fraction is shown in example 1. The duration of the process of absorption and separation in each of the experiments 5 o'clock

The specific conditions and the results of the experiments for all given examples are presented in table. 1 and 2. The experiments in examples 1 to 4 were conducted under optimal conditions, experiments 5 - 8 - to justify the boundary conditions.

From table. 1 shows that the proposed method allows OCTAFLUOROCYCLOBUTANE, and in optimal conditions (examples 1 to 4) is most effective, namely high efficiency of extraction of pyrolysis products of hexaferrite and OCTAFLUOROCYCLOBUTANE.

From table. 2 shows that the adsorbed water gases are predominantly diperchlorate mixed with mainly 1,1,2,2-tetrafluorochloroethane. These gases are separated from the water by lowering the pressure to atmospheric and return on pyrolysis.

Reducing the mass of water relations: the products of pyrolysis below 50 (see example 8), the temperature increase over the 25oC (example 5), and the reduction of pressure below 3 MPa (example 7) leads to a reduction in the efficiency of extraction of hexaferrite and OCTAFLUOROCYCLOBUTANE, despite the increase in the number nenormirovannyj water gases. This result, apparently, is not enough to explain fully in these conditions, the absorption of diperchlorate and tetrafluorochloroethane, which form azeotropic mixtures, respectively, with HEXAFLUOROPROPYLENE and OCTAFLUOROCYCLOBUTANE, which reduces the weight of the last selection. Increasing the pressure up to 7 MPa (example 6) is also undesirable because of the sorbed in these conditions, the gas contains HEXAFLUOROPROPYLENE, and the way, the proposed method of producing tetrafluoroethylene efficient and environmentally preferable, because it allows along with tetrafluoroethylene to allocate and utilize large main by-products formed during the pyrolysis of diperchlorate, HEXAFLUOROPROPYLENE, OCTAFLUOROCYCLOBUTANE, tetrafluorochloroethane.

1. The method of producing tetrafluoroethylene, including pyrolysis of diperchlorate in the presence of water vapor and supplements 1,1,2,2-tetrafluorochloroethane, quenching of the pyrolysis products, the side branch of hydrogen chloride with obtaining hydrochloric acid, neutralizing, compression, condensation products of pyrolysis and multistage rectification emitting fraction of the target product and fractions, including diperchlorate and HEXAFLUOROPROPYLENE, which is shared by absorption of water, characterized in that the absorption of water serves a fraction of the pyrolysis products with a boiling point at atmospheric pressure of minus 42 to 0oWith, unabsorbed gases separated by distillation from the release of hexaferrite and OCTAFLUOROCYCLOBUTANE absorbed water components desorbed and returned to the pyrolysis.

2. The method according to p. 1, characterized in that the absorption of the pyrolysis bottom, at a temperature of 5oC 25oC, pressure 3oC 7 MPa and a mass ratio of water : the products of pyrolysis of 50 to 150 : 1.

 

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