RU2213722C1 - Method for preparing 1,1,1,2,3,3,3-heptafluoro- propane - Google Patents

Abstract

FIELD: organic chemistry, chemical technology. SUBSTANCE: invention relates to preparing 1,1,1,2,3,3,3-heptafluoropropane that is used as component of mixing coolants, gaseous dielectrics, fire-extinguishing agents, foaming agents. Method is carried out by interaction of hexafluoropropylene with organic nitrogen- -containing bases hydrofluoride of the general formula [B*nHF] wherein B is an organic nitrogen-containing base; n is number of moles HF, not above 4, at temperature 20-150 C. Process is carried for a single stage in moisture content in reaction mass 0.3 wt.-%, not above. Preferably to use mixture of hexafluoropropylene with trifluorochloroethylene as the parent raw. Content of trifluorochloroethylene in mixture is 0.03-10 wt.-%. Invention provides reducing economic and ecological indices of process. EFFECT: improved preparing method. 2 cl

Description

 The invention relates to a method for producing 1,1,1,2,3,3,3-heptafluoropropane, which is an ozone-safe product and is widely used as a component of mixed refrigerants, gas dielectrics, fire extinguishers, blowing agents.

 A known method of producing heptafluoropropane by the interaction of hexafluoropropylene with potassium fluoride in the medium of formamide [IACS 82, 3091-3099 (1960)].

 The disadvantage of this method is that the formation of a hydrofluorinating agent (HF) requires the presence of a proton-forming solvent. This leads to the formation of undesirable by-products and reduces the yield of the target product. The conversion of hexafluoropropylene in this case is also low.

 A known method of direct exposure to hydrogen fluoride on hexafluoropropylene in the presence of a catalyst. [UK Patent Specification GB-PS 902590].

The disadvantage of this method is the high temperature of 250-450 ^o C, which complicates the work with gaseous products, namely it increases the danger of the process, reduces the corrosion resistance of the materials used, contributes to the thermal decomposition of the initial olefin and the resulting product, which significantly reduces the yield of heptafluoropropane.

According to the method claimed in German patent 4323054.7, 1993, heptafluoropropane is formed by reacting hexafluoropropylene with hydrogen fluoride in the presence of a catalyst, a weakly basic ion-exchange material, the reaction centers of which consist of tertiary amino groups. The temperature of the process is 20-120 ^o C.

 The disadvantage of this method is the difficulty of preparing a solid catalyst. The catalyst is introduced into the reactor in the form of a suspension in a high boiling liquid (paraffin oil). Previously, water should be removed from the catalyst by heating in vacuo. After bringing the catalyst to a constant weight, it should be pre-saturated with hydrogen fluoride in an amount of 8-25 g per 100 g of ion exchanger.

 The closest in technical essence and combination of essential features is a method for producing 1,1,1,2,3,3,3-heptafluoropropane by reacting hexafluoropropylene with hydrogen fluoride in the presence of liquid hydrofluoride of an organic base of the general formula [B • nHF], where B is organic nitrogen-containing base, n is the number of moles of HF, not more than 4.

The reaction mixture is passed through two separate successively located zones. The pressure in the first zone P ₁ = 1.0-5.0 kg / cm ² , the temperature is 40-100 ^o C, in the second zone the pressure P _{2 is} up to 2 kg / cm ² .

P ₂ must be less than P ₁ , and there must be P ₁ -P ₂ ≥03 kg / cm ² , P ₂ ≥1 kg / cm ² [German patent 19534917, 1997, C 07 C 19/08].

The disadvantages of this method are:
- the need to use two reaction zones arranged in series;
- obtaining the target product under elevated pressure and with the obligatory pressure difference in the reaction zones, which complicates the technological scheme and increases the danger of the process, and also leads to a rise in the cost of the process.

In the patent of Germany 19534917 (prototype) there is no information about the level of moisture in the reaction medium, although it is known that:
1. Water should be carefully removed from the reaction medium, since it hydrates hydrogen fluoride, reducing its activity [W. Sheppard, C. Charts. Organic chemistry of fluorine. M., 1972, p. 56].

 2. The presence of water stimulates undesirable side processes. In particular, hexafluoropropylene in the presence of triethylamine and water reacts with the formation of 2,3,3,3-tetrafluoropropionic acid [I. of Fluorine Cemistry, 8, 1976, 535-540].

 3. The presence of water in the presence of hydrogen fluoride causes corrosion of the equipment, leading to an increase in the danger of the process.

 The task of the invention is to remedy these disadvantages. In addition, one of the objectives of the proposed method is the possibility of using not pure hexafluoropropylene but hexafluoropropylene containing 0.03-10% trifluorochlorethylene as the starting material for producing 1,1,1,2,3,3,3, -heptafluoropropane. the product is formed as a by-product in the production of tetrafluoroethylene by the pyrolysis of freon-22. The separation of hexafluoropropylene from this mixture is difficult due to the fact that this mixture is similar to an azeotrope and its separation requires special separation methods, for example extractive distillation, absorption separation methods, which greatly complicates and increases the cost of the process. When hydrofluorinating a mixture of hexafluoropropylene with trifluorochlorethylene, tetrafluorochloroethane is formed, in addition to heptafluoropropylene, which is used as a refrigerant or raw material for producing ozone-safe refrigerants.

The tasks are solved by the interaction of hexafluoropropylene or a mixture of hexafluoropropylene with trichlorethylene with hydrofluorides of nitrogen-containing bases. The hydrofluorination process is carried out in one stage. The temperature of the process is 20-150 ^o C, the pressure is atmospheric. The process in one stage under atmospheric pressure, the exclusion of the control of the pressure difference in the two reaction zones leads to a simplification of the scheme, and therefore, to cheaper the process.

 A complex of triethylamine with three moles of hydrogen fluoride (triethylamine trihydrofluoride) is used as a nitrogen-containing hydrofluoride base.

 The moisture content in the reaction zone does not exceed 0.3 wt.%, Which does not lead to increased corrosion of the equipment and a decrease in the activity of nitrogen-containing base hydrofluoride.

 The absence of free hydrogen fluoride in the reaction zone also reduces the corrosion of the equipment, making the process safer.

 The proposed method for producing heptafluoropropane is illustrated by the following examples.

 Example 1

A 0.5 L glass flask equipped with a reflux condenser and stirrer was charged with 240 g of triethylamine trihydrofluoride (C ₂ H ₅ ) ₃ N • 3HF. The contents of the reactor were heated to 70 ^{° C.} and hexafluoropropylene was introduced with stirring at a rate of 5.0 l / h. The water content in the reaction zone was 0.3 wt.%.

The reaction products were condensed in a trap cooled to a temperature of minus 30 ^o C.

 The conversion of hexafluoropropylene was 99.5%, selectivity - 99.9%.

 Example 2

120 g of triethylamine trihydrofluoride were charged into a steel reactor equipped with a stirrer. The moisture content in the reaction mass of 0.05 wt.%. At a temperature of 80 ^{° C.,} hexafluoropropylene was introduced at a rate of 3 l / h. The reaction products were condensed in a trap, cooled to minus 30 ^o C.

 The conversion of hexafluoropropylene was 99.7%, selectivity - 99.9%.

 Example 3

Under the conditions of Example 1, 240 g of triethylamine trihydrofluoride was charged into a reaction flask. The moisture content in the reaction mass of 0.05 wt.%. The contents of the reactor were heated to 80 ^{° C.} and a mixture of hexafluoropropylene with trifluorochlorethylene was introduced with stirring at a rate of 5 l / h. The content of trifluorochlorethylene is 0.03 wt.%. The reaction products were condensed in a cooled trap.

 The conversion of hexafluoropropylene 99.9%. Selectivity 99.9%.

 Example 4

Under the conditions of Example 1, 240 g of triethylamine trihydrofluoride was charged into a reaction flask. The moisture content in the reaction mass is 0.5 wt.%. The contents of the reactor were heated to 65 ^{° C.} and hexafluoropropylene was introduced with stirring at a rate of 5 l / h.

 The conversion of hexafluoropropylene is 99.9%, the selectivity is 98.7%.

According to chromatographic analysis, the resulting heptafluoropropane contains tetrafluoropropionic acid
CF ₃ CFHCOOH is the product of the reaction of hexafluoropropylene with water in the presence of triethylamine. According to elemental analysis, the fluorine content of F 51.7% (calculated 52.0%). Boiling point - 40 ^o C / 6 mm

Claims (2)

1. The method of producing 1,1,1,2,3,3,3-heptafluoropropane by reacting hexafluoropropylene with hydrofluorides of organic nitrogen-containing bases of the general formula [B • nHF], where B is an organic nitrogen-containing base, n is the number of moles of HF, not more than 4 , at a temperature of 20-150 ^o C, characterized in that the process is carried out in one stage with a moisture content in the reaction mass of not more than 0.3 wt.%.  2. The method according to claim 1, characterized in that a mixture of hexafluoropropylene with trifluorochlorethylene is used as the starting material, the content of trifluorochlorethylene in the mixture is 0.03-10 wt.%.