RU2160245C2 - Method of preparing 1-fluor-1,1-dichloroethane, 1,1-difluoro 1-chloroethane, 1,1,1-trifluoroethane and reaction unit device for carrying it through - Google Patents

Abstract

FIELD: chemical industry. SUBSTANCE: described is method preparing 1-fluoro-1,1- dichloroethane, 1,1-difluoro-1-chloroethane and 1,1,1-trifluoroethane. Organochlorine compound is reacted with hydrogen fluoride at elevated temperature and pressure followed by isolation of desired products, original organochlorine compound (1,1-dichloro ethylene or 1,1,1-trichloroethane) is introduced under layer of liquid hydrogen fluoride at original hydrogen fluoride to original organochlorine stock molar ratio of 1,0-1,1: 1,0. Reaction is carried out during continuous circulation of hydrogen fluoride along closed technological space at temperature and pressure which is equal to equilibrium pressure of hydrogen fluoride at temperature given as above. The resulting reaction mixture is distilled off together with circulating hydrogen fluoride and condensed, and hydrogen fluoride with reflux ratio of 2-5 is recycled for further reaction. Hydrogen fluoride is directed to produce hydrochloric acid, and condensed desired products are separated, purified and isolated. Device includes volume-type reactor, rectification column, and phase separator; reactor, column, capacitor and phase separator are interconnected to form closed space and hydrogen fluoride losses are thus reduced and formation of by-products is decreased. EFFECT: more efficient preparation method. 6 cl, 10 ex, 2 dwg, 1 tbl

Description

 The invention relates to the field of chemical technology, namely to the production of 1-fluoro-1,1-dichloroethane, 1,1-difluoro-1-chloroethane and 1,1,1-trifluoroethane.

 1-Fluoro-1,1-dichloroethane is a low-toxic solvent and can be used as a blowing agent, 1,1-difluoro-1-chloroethane and 1,1,1-trifluoroethane are refrigerants and feedstock for other fluorine-containing compounds.

 1-Fluoro-1,1-dichloroethane, 1,1-difluoro-1-chloroethane and 1,1,1-trifluoroethane are obtained by the liquid phase method from 1,1,1-trichloroethane (methyl chloroform) or 1,1-dichloroethylene (vinylidene chloride) and hydrogen fluoride in the presence of a catalyst or in a non-catalytic manner. As a catalyst for the hydrofluorination of 1,1-dichloroethylene, tin tetrachloride is used (UK Patent N 627773, class C 07 C 17/00, publ. 08.16.1949), antimony halides (US Patent N 2146354, class C 07 C, 19/08, publ. 1940), tantalum halides. Antimony halides (US Pat. No. 2,146,354, class C 07 C, 19/08, publ. 1940), tin tetrachloride (UK Patent 627773, class C 07) are used as catalysts for the exchange fluorination of 1,1,1-trichloroethane. C 17/00, published on 08.16.1949).

 Tin tetrachloride as a catalyst is used for the industrial production of 1,1-difluoro-1-chloroethane from 1,1-dichloroethylene.

 Known methods for liquid-phase non-catalytic production of 1-fluoro-1,1-dichloroethane, 1,1-difluoro-1-chloroethane and 1,1,1-trifluoroethane from 1,1,1-trichloroethane (US Patent N 3833676, CL C 07 C, 17/20, publ. 09/03/1974, European application N 0407689, class C 07 C 19/08, publ. 07/15/1989) and 1,1-dichloroethylene (Canadian Patent N 2004831, class. C 07 C 19/08, publ. 1991).

 All of the above processes are carried out by supplying hydrogen fluoride to a bulk reactor filled with a catalyst in a mixture with organochlorine feed (or one organochlorine feed in the case of a noncatalytic process) at elevated temperature and pressure. The desired level in the reactor is maintained by supplying the reactor with the starting organochlorine feed.

 In European application N 0402626 (class C 07 C, 19/08, published July 15, 1989), a non-catalytic synthesis unit (Fig. 1) for 1,1,1-trichloroethane fluorination is described, in which a volumetric type 10 reactor is connected with a distillation column 16. The selection of the synthesis products for subsequent separation is carried out in the gas phase after the reflux condenser 18 of the column 16 has been set. The molar ratio of the starting hydrogen fluoride to 1,1,1-trichloroethane fed to the reactor is 3.0 - 5.2; the reflux ratio of the condensate returned from the reflux condenser 18 to the condensate column 16 is close to 1. The synthesis products leaving the reflux condenser 18 contain 19.7 - 27.2 wt.% hydrogen fluoride, which is subsequently separately separated from the reaction mixture and returned to the synthesis . Such a solution of the reaction unit scheme does not allow the complete condensation of organic products and hydrogen fluoride, which complicates their further processing.

 The main disadvantage of these processes is the formation of significant quantities of resinous products due to the tendency of 1,1,1-trichloroethane and 1,1-dichloroethylene to spontaneously oxidize and polymerize in the presence of metal salts - Lewis acids, which are the used catalysts - tin, antimony, tantalum halides , or when the initial organochlorine material comes into contact with the material of the walls of the reactor and the corrosion products of the apparatus during the non-catalytic process. So, according to (Canadian Patent N 2004831, class C 07 C, 19/08, publ. 1991), the content of gummy substances in the synthesis products reaches 15%. All this leads to deactivation of the catalyst and the need for its frequent replacement in the case of a catalytic process or the accumulation of resins in the reactor volume during a non-catalytic process.

 All these processes are carried out with a significant contact time reaching several hours and with a large excess of hydrogen fluoride in relation to organochlorine raw materials compared with stoichiometry, which leads to the presence of a technological stage of the separation of unreacted hydrogen fluoride and an additional metering unit for returning hydrogen fluoride to the synthesis unit, which due to the inevitable loss of products at these stages.

Closest to the claimed method is a method (International application WO 091/18852, class C 07 C 19/08, publ. 12/12/1991) (prototype) for the preparation of 1-fluoro-1,1-dichloroethane from 1,1- dichloroethylene and hydrogen fluoride in a non-catalytic manner. The starting 1,1-dichloroethylene and hydrogen fluoride are loaded into the reactor, the process is carried out periodically at temperatures of 75 - 125 ^o C, with a double molar excess of hydrogen fluoride to 1,1-dichloroethylene compared to stoichiometry and a contact time of 2.5 - 5 hours. The reaction products are distilled off from the reactor, neutralized and analyzed.

With a total conversion of the starting 1,1-dichlorethylene ≈ 98.7 ÷ 99.3%, it forms: at 75 ^° C - 86.7%, at 100 ^° C - 83.2% and at 125 ^° C - 79% 1-fluorine -1,1-dichloroethane, up to 16% (at a temperature of 125 ^o C) 1,1-difluoro-1-chloroethane and up to 3-4% 1,1,1-trifluoroethane. At the same time, up to 1.3% of unreacted starting 1,1-dichloroethylene remains in the synthesis products and up to 4.7% of oligomers - polymerization products of starting 1,1-dichloroethylene are also contained.

With a continuous embodiment of this process, hydrogen fluoride and 1,1-dichloroethylene are fed into a bulk reactor at a temperature of 120 ^° C, a pressure of 18 bar (≈18 kgf / cm ² ) and a molar ratio of hydrogen fluoride to 1,1-dichloroethylene equal to 1 , 7. The content of the target product - 1-fluoro-1,1-dichloroethane is 91.2%.

The disadvantages of the prototype are:
- insufficient sensitivity of the process to an increase in reaction temperature; thus, with increasing temperature from 75 to 125 ^o C, the yield of one of the important synthesis products - 1,1-difluoro-1-chloroethane - increases from 4 to 16%, the yield of 1,1,1-trifluoroethane remains almost constant;
- the process is carried out with a significant excess of hydrogen fluoride, therefore, excess hydrogen fluoride must be isolated and dosed return hydrogen fluoride as a separate stage of the process, which complicates the process and increases the loss of hydrogen fluoride;
- the presence in the products of the synthesis of resins and oligomers, which leads to the emergence of an additional stage of separation of the products of synthesis, the loss of feedstock - 1,1-dichloroethylene and the appearance of unused waste products;
- incomplete conversion of 1,1-chloroethylene, which complicates the process of purification of 1-fluoro-1,1-dichloroethane due to the proximity of its boiling point (31.9 ^o C) and the boiling point of 1,1-dichloroethylene (31.7 ^o C );
- relatively high temperatures of the process (75 - 125 ^o C), which leads to excessive energy consumption.

The objective of the invention is:
- development of a technological process for the joint production of 1-fluoro-1,1-dichloroethane, 1,1-difluoro-1-chloroethane and 1,1,1-trifluoroethane with controlled production of these products, depending on the necessary need and the design of the reaction unit, which allows you to carry out this process;
- reducing losses of hydrogen fluoride by reducing the excess hydrogen fluoride supplied to the reactor with respect to the organochlorine feedstock and by eliminating a separate dosing step for the return of hydrogen fluoride;
- reducing the formation of oligomers and resins and thereby reducing the loss of the original 1,1-dichloroethylene or 1,1,1-trichloroethane and reducing the amount of unused production waste;
- reduction of energy consumption by reducing the temperature of the process;
- an increase in the conversion of 1,1-dichloroethylene or 1,1,1-trichloroethane, a decrease in the amount of unreacted 1,1-dichloroethylene in the synthesis products, and thereby a simplification of the method of purification of 1-fluoro-1,1-dichloroethane from 1,1-dichloroethylene impurities .

 This object is achieved in that the production of 1-fluoro-1,1-dichloroethane, 1,1-difluoro-1-chloroethane and 1,1,1-trifluoroethane is carried out in the reaction unit (figure 2), consisting of a volume type reactor with a distillation column, a condenser, a phase separator (a separator of two liquid immiscible phases) in which hydrogen fluoride is continuously circulated in a closed loop: reactor - column - condenser phase separator - column - reactor. Dosing of the starting organochlorine feedstock - 1,1-dichloroethylene or 1,1,1-trichloroethane, as well as hydrogen fluoride (when their ratio is close to stoichiometric) is carried out, unlike all previously known methods, into the volume under the layer of liquid hydrogen fluoride, located in the reactor at the appropriate temperature and pressure equilibrium with this temperature. Moreover, due to the large excess of hydrogen fluoride in comparison with stoichiometry, a very fast interaction of organochlorine feed with hydrogen fluoride occurs with the formation of target products and their distillation from the reactor together with circulating hydrogen fluoride, without the accumulation of organochlorine feed and liquid synthesis products in the reactor.

 In contrast to the circuit solution (European application N 0402626, class C 07 C 19/08, publ. 12/19/1990) (figure 1), in the proposed technological scheme of the reaction unit, the organic synthesis products and hydrogen fluoride are completely condensed in the condenser and enter the phase separator. Full condensation is achieved by the proposed device of the reaction unit (figure 2).

 The selection of a liquid mixture of 1-fluoro-1,1-dichloroethane, 1,1-difluoro-1-chloroethane and 1,1,1-trifluoroethane is carried out from the lower phase of the phase separator, followed by feeding at the stage of separation, purification and isolation of finished products. The proposed device of the reaction unit allows the upper layer of the phase separator - hydrogen fluoride - to continuously return to the distillation column in the form of reflux. Hydrogen chloride after the condenser enters the stage of obtaining hydrochloric acid.

 Compared with the prototype, the proposed method allows the simultaneous production of 1-fluoro-1,1-dichloroethane, 1,1-difluoro-1-chloroethane and 1,1,1-trifluoroethane in a given ratio with a high conversion of the starting organochlorine feed, with a decrease in the formation resins and oligomers, with a high yield at comparable temperatures of 1,1-difluoro-1-chloroethane and 1,1,1-trifluoroethane, reduce the required temperature of the reactor for the preferential production of 1-fluoro-1,1-dichloroethane, reduce the loss of hydrogen fluoride. Compared with the prototype, by controlling the temperature of hydrogen fluoride in the reactor and, accordingly, the equilibrium pressure in the system, it is possible to obtain the above products in a given ratio based on needs.

Only a simultaneous combination of all of the following distinguishing features in both the production method and the arrangement of the reaction unit allows achieving the above results; These signs are:
- the presence of a reaction unit, consisting of a volume type reactor, a column above the reactor, a condenser, a phase separator;
—continuous circulation of hydrogen fluoride in the reaction unit in a closed loop: reactor — column — condenser — phase separator column — reactor;
- maintaining the pressure in the reaction unit, corresponding to the equilibrium pressure of hydrogen fluoride at a given temperature of the process in the reactor;
- feeding into the reactor the starting organochlorine feed (1,1-dichloro-ethylene, 1,1,1-trichloroethane) and hydrogen fluoride in a ratio close to stoichiometric and under a layer of hydrogen fluoride filling the reactor volume;
- selection of organochlorine synthesis products in the liquid phase from the lower phase of the phase separator.

 The use of these signs is possible only in the aggregate, the use of each sign separately does not lead to the achievement of the goal. So, the continuous circulation of hydrogen fluoride is possible only in the reaction unit shown in figure 2 and characterized in that the stream of condensed products in the condenser enters the phase separator, from which the upper layer (hydrogen fluoride) returns to the column in the form of reflux, and the lower layer (organochlorine products) is selected for further processing. In the reaction unit, a pressure is maintained equal to the equilibrium pressure of hydrogen fluoride at a given temperature in the reactor.

Deviation of the pressure in the reaction unit from the equilibrium hydrogen fluoride in the reactor at a given temperature leads to the cessation of hydrogen fluoride circulation - an increase in pressure leads to a decrease in the flow of hydrogen fluoride driven off from the reactor, overflow of the reactor and the cessation of the discharge of hydrogen fluoride from the phase separator; a decrease in pressure leads to the rapid evaporation of hydrogen fluoride from the reactor, its emptying, filling the column and phase separator
With such a device and the principles of the reaction unit, the selection of synthesis products for further separation and isolation of the target products is possible only in the liquid phase from the lower phase of the phase separator.

 A change in the order in which the components are fed into the reactor, namely, the supply of hydrogen fluoride to the volume of organochlorine feed in the reactor, as is traditionally done, leads to a decrease in reactor productivity due to the impossibility or difficulty of creating a sufficient excess of hydrogen fluoride with respect to organochlorine raw materials, and also leads to rapid resinification of organochlorine feedstocks (1,1-dichloroethylene, 1,1,1-trichloroethane), the accumulation of gummy products in the reactor and, as a result, gradual attenuation NIJ chemical reaction in a reactor and the circulation of hydrogen fluoride due to clogging siphon feed.

 The feed of the organochlorine components and hydrogen fluoride to the reactor is carried out with a mandatory excess of the stoichiometric ratio of hydrogen fluoride to the organochlorine feedstock, but not more than 10 moles. % An increase in this ratio by more than 10% leads to an increase in the level in the reactor, i.e. leads to the accumulation of hydrogen fluoride in the reactor. A decrease in this ratio leads to a decrease in the level in the reactor, i.e. to exhaust hydrogen fluoride from the reactor.

 The authors found that the proposed device for the circulation of the reaction unit in combination with supplying the reactor with the starting organochlorine feed and hydrogen fluoride in a ratio close to stoichiometric and under a layer of hydrogen fluoride in the reactor, determined by the dependence of temperature and pressure in the reaction unit, selection of organochlorine synthesis products in the liquid phase from the phase separator allows you to create a highly efficient process for producing 1-fluoro-1,1-dichloroethane, 1,1-difluoro-1-chloroethane and 1,1,1-trifluoro tana in industrial production.

 According to the authors, a combination of such features as the arrangement of the reaction unit, the continuous circulation of hydrogen fluoride in it, the supply of raw materials in a ratio close to stoichiometric, and under the layer of hydrogen fluoride in the reactor, a certain dependence of the temperature in the reactor and the pressure in the synthesis unit and selection organochlorine synthesis products in liquid form from a phase separator in the proposed method meets the criterion of "significant differences".

 The specific implementation of the process.

 The process has been tested in a pilot installation, which has confirmed its reproducibility and performance for each individual product. The following is the methodology of the process.

 Specific process parameters and results are shown in the table.

The reactor 1 (figure 2) with a volume of 1 liter is filled with hydrogen fluoride. The reactor is heated to a predetermined temperature and at a pressure in the system equal to the equilibrium pressure of hydrogen fluoride at this temperature, circulation of hydrogen fluoride in a closed loop begins - reactor 1 - column 2 - condenser 3 - phase separator 4 - column 2 - reactor 1. After establishing a constant circulation the level of hydrogen fluoride in the reactor is brought to 600 cm ³ . The level control in the reactor is carried out on the sight glass with divisions. Then, into the reactor using siphons lowered to the bottom of the reactor, dosing of the starting organochlorine feedstock - 1,1-dichloroethylene or 1,1,1-trichloroethane at a speed of 100 cm ³ / h under a layer of hydrogen fluoride and hydrogen fluoride at a speed of 28 cm begins with pumps. ³ / h (in the case of supply of 1,1-dichloroethylene) or 21 cm ³ / h (in the case of supply of 1,1,1-trichloroethane), which is 10 mol. % exceeds the stoichiometric amount of hydrogen fluoride relative to the corresponding corresponding organochlorine feed. The duration of each experiment is 8 hours. In the process, the level in the reactor 1 remains constant - 600 cm ³ . After condensation, the resulting organochlorine reaction products are collected in phase separator 4 (bottom layer), from where they are taken for further processing and a sample is taken for analysis. Hydrogen fluoride from the phase separator in the form of reflux with a reflux ratio of 2 to 5 enters the top of the column.

 When the reactor was opened after the experiment was completed and the system was emptied, there was no resin build-up on its internal surface and on siphons.

 The process proceeds the same way when using both types of organochlorine raw materials - 1,1-dichloroethylene and 1,1,1-trichloroethane. The composition of the synthesis products with this method of carrying out the process depends on the temperature in the reactor and the corresponding equilibrium pressure of hydrogen fluoride.

 The results of the examples are shown in the table.

Claims (5)

 1. The method of producing 1-fluoro-1,1-dichloroethane, 1,1-difluoro-1-chloroethane and 1,1,1-trifluoroethane by reacting an organochlorine compound with hydrogen fluoride at elevated temperature and pressure, followed by isolation of the target products, characterized in that the starting organochlorine compound 1,1-dichloroethylene or 1,1,1-trichloroethane is fed under a layer of liquid hydrogen fluoride at a molar ratio of the starting hydrogen fluoride and the starting organochlorine feed of 1.0-1.1: 1.0 and the reaction is carried out under continuous water fluoride circulation of a kind in a closed process loop at a temperature and pressure equal to the equilibrium pressure of hydrogen fluoride at this temperature, the resulting reaction mixture is distilled off with circulating hydrogen fluoride, condensed, after which hydrogen fluoride in the form of reflux with a reflux number of 2 to 5 is returned to the reaction, hydrogen chloride is sent to obtain hydrochloric acid, and the condensed target products are separated, purified and isolated. 2. The method according to claim 1, characterized in that to obtain 1-fluoro-1,1-dichloroethane, the interaction is carried out at 63 - 83 ^o C and 4.0 - 7.0 at (0.4 - 0.7 MPa) . 3. The method according to p. 1, characterized in that to obtain 1,1-difluoro-1-chloroethane, the interaction is carried out at 120 - 130 ^o C and 16.6 - 20.2 ata (1.66 - 2.02 MPa) . 4. The method according to claim 1, characterized in that to obtain 1,1,1-trifluoroethane, the interaction is carried out at a temperature of more than 130 ^o C and a pressure of more than 20.2 ata (2.02 MPa).  5. The device of the reaction unit for producing 1-fluoro-1,1-dichloroethane, 1,1-difluoro-1-chloroethane and 1,1,1-trifluoroethane, including a volume reactor, distillation column, condenser, phase separator, characterized in that that the volumetric type reactor is connected in series with a distillation column located at a height above the reactor, which is connected to a condenser, the lower part of which is connected to the phase separator, the upper part of the phase separator connected to the upper part of the distillation column, the lower part of the distillation The column is connected to the reactor, forming a closed circulation loop, with the lower part of the phase separator connected to the separation and purification system of the target products, the upper part of the condenser connected to the system for purifying hydrogen chloride and producing hydrochloric acid.

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