The way to obtain 1,1,1,2-tetrafluoroethane

 

(57) Abstract:

Usage: 1,1,1,2-Tetrafluoroethane is used as a solvent in refrigeration. The inventive obtain 1,1,1,2-Tetrafluoroethane (134a) of trichloroethylene lead in two stages. The method involves reacting trichloroethylene with hydrogen fluoride at a pressure above atmospheric in the first reaction zone with the formation of 1,1,1-Cryptor-2-chlorethane (a) and the interaction of 1,1,1,-Cryptor-2-chlorethane with hydrogen fluoride in the second reaction zone with the formation of 1,1,1,2-Tetrafluoroethane. The product stream from the reaction zone, where the education a, together with the necessary additional amount of HF is completely fed into the reaction zone education (134a). Two reaction zones can be formed in a single reactor. 9 C.p. f-crystals, 1 table.

The invention relates to methods for chemicals, particularly to a method of production of 1,1,1,2-Tetrafluoroethane, usually referred to as HFA 134a.

Proposed several ways to obtain 1,1,1,2-Tetrafluoroethane (HFA 134a), which is used as a substitute for CFCs in refrigeration and other areas. In the United Kingdom patent N 1589924 described receiving HFA vapor-phase fluorination 1,1,1-thrifts described in UK Patent N 1307224 way.

The formation of small amounts of HFA 134a when the fluorination of trichloroethylene described in UK patent N 819849, the main product of the process is HCFC a. Proposed in WO 90/08755 method of conversion of trichloroethylene in HFA 134a reaction of both stages occur in the same reaction zone with a partial return to the cycle of flow of the reaction products.

Carrying out the conversion in a single reaction zone, as described in WO 90/08755 differs serious drawback, namely the rapid inactivation of the catalyst fluorination, which is largely due to the deposition of carbon, and, as a consequence of very low life. We found, for example, that less than 24 hours of operation of the process with one reaction zone under the following conditions: catalyst of chromium oxide, the temperature of 340aboutWith the content of trichloroethylene in the feedstock 10 mol.%, the contact time 20 - conversion of organic matter contained in the flow of raw materials, in HFA 134a fell to below 10%, and after period 4 days to maintain a conversion rate of 10% had to increase the temperature of the catalyst 30 to 40about(C 340 to 370-380aboutC). The problem of short service life of the catalyst used prevents the th, conducted in separate reaction zones, as described below, provides a significant increase in the yield of the desired product in high selectivity of the catalyst and its performance and increase the life of the catalyst. For example, the operation of the process implemented in accordance with the claimed method, in the above-described conditions, but with the contact time of 10 s in each reaction zone, resulted in a slight aging of the catalyst after 4 days; to maintain a degree of conversion of organic matter above 10% was sufficient temperature increase of about 2aboutWith in 4 days.

Found that it is impractical to conduct a two-stage conversion of trichloroethylene in HFA 134a in separate reaction zones of the same size, if each reaction zone is supported by atmospheric pressure, as in the first reaction zone can be obtained only a low degree of conversion, for example, 20-30% . This invention allows to obtain a degree of conversion of trichloroethylene 90% and above.

According to the invention, it is proposed a method of obtaining 1,1,1,2-Tetrafluoroethane, comprising the stage of:

A) contacting a mixture of trichloroethylene and hydrogen fluoride with the aboutIn the first reaction zone to obtain a product containing 1,1,1-Cryptor-2-chlorate and hydrogen chloride, and unreacted starting materials;

B) the transition of the entire product obtained in stage A), the second reaction zone, in which the fluorination catalyst at a temperature approximately in the range of 280-450aboutWith, but higher than in stage A), resulting in a product containing 1,1,1,2-Tetrafluoroethane, 1,1,1-Cryptor-2-chlorate and hydrogen chloride;

C) treatment of the product obtained in stage (B), with the aim of separating 1,1,1,2-Tetra-floridana and hydrogen chloride from 1,1,1-tri-fluoro-2-chlorethane and unreacted hydrogen fluoride;

G) supply obtained in stage (C) mixtures containing 1,1,1-Cryptor-2-chlorate, together with trichloroethylene and hydrogen fluoride specified in the first reaction zone (stage (A), and

D) allocation of 1,1,1,2-Tetrafluoroethane from a mixture of 1,1,1,2-Tetrafluoroethane and hydrogen chloride separated at the stage Century.

The fluorination catalyst used in the stages a and B of the proposed method may be the same or different (although it is preferable that he was the same), to be used on the substrate or without him. May is some connection, for example, the oxides, halides and oxychloride metals such as aluminum, cobalt, manganese, iron and especially chrome. Suitable chromium catalysts include oxide, hydroxide, oxychloride, chromium halides, salts of mineral acids, basic chromium fluoride, as well as the catalysts described in UK patent N 1307224. The preferred catalysts are chromium oxide and chromium oxide, activated zinc or Nickel. Such catalysts may be subjected prior to use prior to fluorination by passing over the surface of the hydrogen fluoride catalyst, in a mixture with nitrogen or without nitrogen, at a temperature of about 250-450aboutC.

You can extrude catalysts in the form of granules and their use in a fixed bed or, on the contrary, to use catalysts, particles which have corresponding dimensions in the moving layer, for example in a fluidized bed.

The amount of hydrogen fluoride introduced at the stage B of the proposed method, can vary within wide limits: from values much smaller stoichiometric much to her in excess of. The typical amount includes a value from 1 to 10 moles, preferably from 2 to 6, fluoride water is the rule, in addition to 1,1,1,2-Tetrafluoroethane, hydrogen chloride and side reaction products, and unreacted hydrogen fluoride. Preferably the temperature of the reactions this stage of the process ranges from 285 to 385aboutWith, especially in the range from 300 to 385aboutS, even more preferably from 325 to 385aboutSince, at the time of contact is from 1 to 100, preferably 5 to 30 C and a pressure of 5-20 bar.

At stage (A) is introduced, usually 10-100, preferably from 16 to 60 moles of hydrogen fluoride per mole of trichloroethylene. Again, the reaction products of this stage usually contain unreacted hydrogen fluoride and possibly minor amounts of unreacted trichloroethylene. The contact time can be up to 100, preferably using from 5 to 30, usually at a temperature of 230-350aboutC and a pressure of from 5 to 20 bar.

Stage (A) of the process carried out at a pressure above atmospheric; the minimum pressure is preferably 2 bar, more preferably the pressure is at least 5 bar. Generally speaking, the pressure increase leads to an increase in productivity of the catalyst in stage A. In practice, the pressure usually does not exceed 30 bar. Stage B can be conducted at atmospheric or th, on stage (In) pressure, as a rule, corresponds to the value used in stages (a) and (B).

Stage of reaction and separation, which are the method according to this invention, can be carried out using traditional methods and equipment. For example, the allocation of 1,1,1,2-Tetrafluoroethane in stage (D) can be achieved by washing the gaseous Tetrafluoroethane water and aqueous solution of sodium hydroxide, followed by drying and or of Tetrafluoroethane.

It is preferable to implement the method according to the invention in a continuous process. In practice, however, is inaktivera catalyst requiring periodic interrupt process for catalyst regeneration or reactivation, which may be done by passing over the catalyst of air or mixture of air and inert gas, e.g. nitrogen, at 300-500aboutC. In a preferred embodiment, the process of reactivation of the catalyst is heated catalyst in a mixture of air and hydrogen fluoride, so that the resulting hot hydrogen fluoride can be used directly on the stage and/or stage B of the method according to this invention. The frequency of reg is

A particularly useful characteristic of the invention is that the exothermic conversion of trichloroethylene in 1,1,1-Cryptor-2 - chlorate on stage And you can make cheap adiabatic reactor that creates significant advantages in terms of cost compared to systems using cooled from the inside surface. If desired, stage B can also be carried out in an adiabatic reactor using to raise the temperature of the gas stream between the two reactors intermediate heater.

On stage And process use more low, than at the stage B, the temperature. May be necessary, in the cooling return in a cycle from stage B stream to a temperature equal to the temperature of stage a or lower; in this case, use the procedure, which consists in mixing trichloroethylene supplied to the stage And back into the cycle stream before entering the reactor stage; thus returning to the cycle stream is cooled due to the heat of trichloroethylene, while trichloroethylene is heated, reducing the need for external heating.

The separation of 1,1,1,2-Tetrafluoroethane and hydrogen chloride from the product stream of the reaction stage In the process mo is the process of obtaining 1,1,1,2-Tetrafluoroethane is carried out in two reaction zones, the temperature which is maintained at different levels. If desired, two reaction zones can be formed in different reactors, but preferred characteristic of the invention is that the process is carried out in one reactor, in which are placed the two reaction zones. For example, the reactor may be a number of pipes, which is a stream of reagents in each tube is placed in a fluorination catalyst and a certain part of each tube is maintained at a lower temperature (for phase A) and the other at higher (stage B). At the end of the tube, in which is supported a lower temperature, served trichloroethylene and hydrogen fluoride together with returning to the loop flow (stage D), and from the hot end of the tube shows the flow of the reaction products, containing 1,1,1,2-Tetrafluoroethane. The reaction vessel can be an adiabatic reactor.

Obtained in accordance with the inventive method HFA 134a contains a small amount, for example, from 200 to 1000 ppm, toxic impurities 1-chloro-2,2-diftoretilena, commonly called 1122. A method for processing stream products obtained in stage B) including the separation stage B), includes, as the government is nciu to stay with him during the processing operations.

At least a portion 1122 may be removed from the product stream to separate it at the stage In at the expense of shielding the flow of the products of the reaction stage B with hydrogen fluoride (which is already present in the product stream) over a fluorination catalyst, for example, chromium oxide, at a temperature approximately in the range of from 150 to 250aboutC.

In a preferred execution of the invention, according to which stage a and B occur in different reaction zones in a single reactor can produce a third reaction zone, in which the flow of products containing HFA 134a HF at low temperature, resulting removes at least a portion 1122 contained in this product stream. So, for example, described a tubular reactor, each tube containing a fluorination catalyst, such as chromium oxide, may include a first zone in which the temperature is maintained at a certain level, necessary for the occurrence of stage a of the process, a second zone in which is supported a higher temperature for stage B, and a third zone in which at lower temperatures is removed 1122 from the stream of products. At the end of the tube is supplied with trichloroethylene is ion zones.

The whole 1122 present in HFA 134a after stage, you can remove the azeotropic distillation or extractive distillation and/or by contacting HFA 134a with zeolite molecular sieve.

P R I m e R 1. Got 1,1,1,2-Tetrafluoroethane in a twin system comprising a first reactor for the conversion of trichloroethylene in 1,1,1-Cryptor-2-chlorate (stage a) and the second reactor for the conversion of 1,1,1-Cryptor-2-chlorethane obtained at stage a, 1,1,1,2-Tetrafluoroethane (stage B). In the first, low-temperature reactor (273about(C) filed at a pressure of 13.5 bar trichloroethylene and hydrogen fluoride for selective transformation of trichloroethylene in 1,1,1-Cryptor-2-chlorate (a). Then the products obtained in the reactor 1, received in the second reactor, which was maintained higher temperature 366aboutC and a pressure of 13.5 bar and which is obtained in the first reactor a partially turned in HFA 134a. I served in the 1st reactor together with hydrogen fluoride and trichloroethylene to simulate a typical flow of reagents, which includes returning to the cycle a, HF and small amounts of trichloroethylene from the second reactor. The process was performed under the following conditions: molar ratio of HF : organics in the first stage of 3.5:1, with which Yunosti reactions to a twin system are presented in table 1.

For comparison repeated the procedure described above, using the same reactor, but carrying out the process in both reactors at atmospheric pressure (contact time of approximately 1 second). The efficiency of the reactions are given in table 1. The results in table 1 show that by carrying out the reaction in the first reactor at a pressure above atmospheric is possible to achieve significant improvement in the performance of the catalyst.

It is shown that the method according to the invention has considerable advantages with respect to performance of the catalyst, as well as the high selectivity of the reaction.

1. The WAY to OBTAIN 1,1,1,2-TETRAFLUOROETHANE by hydroperiodide trichloroethylene at 200 - 400oIn the presence of a catalyst of hydroperiodide, characterized in that exercise:

a) contacting a mixture of trichloroethylene and hydrogen fluoride with a catalyst hydroperiodide at a pressure not higher than 20 bar in the first reaction zone to form a product containing 1,1,1-Cryptor-2-chlorate and hydrogen chloride, and unreacted starting materials;

b) miss the entire product of stage a) with hydrogen fluoride in the second reaction zone, mperature stage (a), with the formation of a product containing 1,1,1,2-Tetrafluoroethane, 1,1,1-Cryptor-2-chlorate, hydrogen chloride and unreacted hydrogen fluoride;

in) handle of the product of stage (C) for separating 1,1,1,2-Tetrafluoroethane and hydrogen chloride from 1,1,1-Cryptor-2-chlorethane and unreacted hydrogen fluoride;

g) feed mixtures containing 1,1,1,-Cryptor-2-chlorate and obtained in stage (C), together with trichloroethylene and hydrogen fluoride specified in the first reaction zone (stage a).

2. The method according to p. 1, characterized in that in the first reaction zone at stage (a) being 15 to 60 mol of hydrogen fluoride per 1 mole of trichloroethylene.

3. The method according to p. 1 or 2, characterized in that the temperature in the first reaction zone at stage (a) support in the range of 220 - 350oC.

4. The method according to any of paragraphs.1 to 3, characterized in that the second reaction zone at stage (b) is administered 2 to 6 mol of hydrogen fluoride per 1 mol of 1,1,1-Cryptor-2-chlorethane.

5. The method according to any of paragraphs.1 to 4, characterized in that the temperature in the second reaction zone at stage (b) support in the range of 305 - 385oC.

6. The method according to any of paragraphs.1 to 5, characterized in that the contact time on the stage (who dealt with (a) and (b) is performed at a pressure of 5 20 bar.

8. The method according to any of paragraphs.1 to 7, characterized in that the process is conducted continuously.

9. The method according to any of paragraphs.1 to 8, characterized in that the contacts in the first and second reaction zones are in the adiabatic reactors.

10. The method according to any of paragraphs.1 to 9, characterized in that trichloroethylene supplied to the first reaction zone at stage (a) together with the product stream from step (b) add to the specified product stream from step (b) to heat trichloroethylene and cooling of the product stream prior to entry into the first reaction zone.

 

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