KR950011101B1 - Contineous preparationg of 1,1-dichloro-1-fluoroethane - Google Patents

Abstract

The continuous production of 1,1-dichloro-1-fluoroethane(HCFC-1416) comprises (a) continuously liquid phase reacting 1,1,1- trichloroethane with an excessive amount of an anhydrous hydrofluoric acid in the reactor at 4-20 bar and 60-130 deg.C., (b) contacting and rectifying the produced gas and the anhydrous hydrofluoric acid to recycle a low volatile material of the anhydrous hydrofluoric acid to the reactor, and to condense an azeotropic mixture of an organic material and the hydrofluoric acid and high volatile material of a hydrochloric acid in the condenser, (c) separating an inorganic layer(HF), an organic layer and a gas layer(HCl) from the liquid-gas mixture in the layer separator, and (d) purifying the exhausted organic layer. The HCFC-1416 is a CFC substitute material

Description

Continuous production process of 1,1-dichloro-1-fluoroethane

1 is a process flowchart showing a method for preparing 1,1-dichloro-1-fluoroethane according to the present invention.

* Explanation of symbols for main parts of the drawings

1: reactor 6: distillation column

8, 14 condenser 10: separator

16: absorption tower

The present invention continuously reacts 1,1,1-trichloroethane (hereinafter referred to as T111) with an excess of anhydrous hydrofluoric acid in a liquid phase to continuously 1,1-dichloro-1-fluoroethane (hereinafter referred to as "HCFC-141b"). And abbreviated to " ".

HCFC-141b is a known substance used as a solvent, a blowing agent, etc., and is known as one of CFC substitutes because it has little effect on the destruction of the global ozone layer.

HCFC-141b is prepared according to the following reaction formula using T111 and anhydrous hydrofluoric acid as raw materials.

CH ₃ CCl ₃ + HF → CH ₃ CCl ₂ F + HCl

In practice, however, in addition to the above main reaction, HCFC-141b continuously reacts with anhydrous hydrofluoric acid, and 1-chloro-1,1-difluoroethane (hereinafter referred to as HCFC-142b) and 1, A side reaction proceeds to produce 1,1-trifluoroethane (hereinafter referred to as HFC-143a).

CH ₃ CCl ₂ F + HF → CH ₃ CClF ₂ + HCl

CH ₃ CClF ₂ + HF → CH ₃ CF ₃ + HCl

In addition, the decomposition reaction of T111 occurs to produce vinylidene chloride (hereinafter referred to as VDC), and a side reaction of polymerization of two molecules of VDC occurs to generate oligomers and tars as by-products. Therefore, the production of HCFC-141b should minimize the production of by-products such as HCFC-142b, HFC-143a, VDC, oligomer, tar. In particular, since VDC is similar to HCFC-141b in boiling point, it is difficult to remove by conventional separation methods such as distillation, so it is particularly important to minimize the VDC production rate.

Numerous known methods for preparing HCFC-141b are known in the art.

For example, US Pat. No. 3, 755, 477 describes a method for preparing HCFC-141b by reacting T111 with anhydrous hydrofluoric acid under a chromium catalyst. However, in this method, the performance of the catalyst deteriorates with time, and the product has a disadvantage in that a large amount of by-product HFC-143a is contained in 5% or more.

Japanese Patent No. 50-5681 describes a method for producing HCFC-141b without a catalyst by mixing at least 4 moles of hydrofluoric anhydride with respect to 1 mole of T111. However, this method is a batch production method of HCFC-141b, not continuously, the maximum yield of HCFC-141b is low as 58.2%, and a lot of by-products such as HCFC-142b and HFC-143a are produced.

Japanese Patent Laid-Open No. 2-152, 935 describes a method for producing HCFC-141b by reacting T111 with anhydrous hydrofluoric acid without a catalyst. According to this method, HCFC-141b is obtained at a selectivity of 97% by adding 1 to 4 moles of hydrofluoric anhydride to 1 mole of T111 in the reactor and reacting at 40 to 110 ° C. The disadvantage of this method is that the liquid separates into two layers in the reactor, so that the reaction mainly takes place at the interface between the two layers. That is, in the reactor, since the reactants are separated into the lower layer of the organic material containing a lot of T111 and HCFC-141b and the upper layer of anhydrous hydrogen fluoride, an apparatus for sufficiently mixing the two layers is required to promote the reaction. Moreover, since it is a batch apparatus, reaction requires a long time of 3 to 10 hours, and it is inferior to economy when operating in a continuous apparatus.

Therefore, an object of the present invention is to suppress the production of by-products such as HCFC-142b, HCFC-143a, oligomers when the reaction of T111 and hydrofluoric anhydride in the liquid phase to obtain HCFC-141b with high yield and high selectivity It is to provide.

Still another object of the present invention is to perform HCFC-141b by continuously reacting T111 with hydrofluoric anhydride to produce HCFC-141b, thereby degrading catalyst, entraining splash of catalyst and corrosion of the device. It is to provide a method for facilitating operation by preventing the problem of the source.

The object of the present invention is to continuously liquid-react 1,1,1-trichloroethane and hydrofluoric anhydride at a pressure of 4 to 20 bar and a temperature of 60 to 130 ° C. at a molar ratio of 1: 5 to 1: 200. It is to provide a method for producing 1,1-dichloro-1-fluoroethane.

The production process according to the invention is carried out by the following process:

a) Continuous liquid phase reaction of 1,1,1-trichloroethane with excess anhydrous hydrofluoric acid in a suitable reactor at a pressure of 4-20 bar and a temperature of 60-130 ° C.

b) introducing a reaction product gas into the bottom of the distillation column, contacting and rectifying with anhydrous hydrofluoric acid, which is the main from the top of the distillation column to recycle the low volatiles to the reactor and send the high volatiles to the condenser to condense.

c) The liquid-gas mixture passed through the condenser is introduced into a bed separator, separated into an inorganic bed (HF), an organic bed and a gas bed (HCl), after which the inorganic bed is recycled to the top of the distillation column, and the gas bed is Exhausting through the government, and the organic layer is discharged through the bottom of the bed separator, and

d) A step of separating and purifying the organic layer discharged from the layer separator by a conventional method to obtain 1,1-dichloro-1-fluoroethane.

The gas layer exhausted from the bed separator is mainly hydrogen chloride gas, which is passed through the condenser, introduced into the lower part of the absorption tower and brought into contact with the main water from the column top, and the resulting aqueous hydrogen chloride solution is discharged from the bottom of the absorption tower. Keep at.

The method of the present invention is described in detail below with reference to FIG.

In FIG. 1, the reaction raw material T111 and hydrofluoric anhydride are introduced into the reactor 1 through the tube 2 and the tube 3, respectively. The reaction is started by heating the reaction liquid introduced into the reactor 1 to the boiling point by the heater 20 attached to the outside of the reactor. The resulting HCFC-141b, HCFC-142b, hydrochloric acid, VDC, unreacted T111 and anhydrous hydrofluoric acid and trace impurities are vaporized, and this gas is introduced into the bottom of the distillation column 6 through the tube 4. . The gas introduced into the distillation column 6 is brought into contact with and rectified with anhydrous hydrofluoric acid, which is mainly used at the top of the distillation column. The low volatile substance whose main component is anhydrous hydrofluoric acid is recycled to the reactor (1) through a tube (5), and a highly volatile substance such as an azeotropic mixture of T111, HCFC-141b, HCFC-142b and anhydrous hydrofluoric acid, and hydrochloric acid. They are introduced into the condenser 8 through a tube 7 to liquefy most substances except hydrochloric acid. Mixed liquid and gas which have passed through the condenser 8 are introduced through the tube 9 into the separator 10. In this layer separator (10), the layer is separated into a heavy organic material layer whose main components are HCFC-141b and HCFC-142b, a light inorganic layer whose main component is hydrofluoric anhydride, and a gas layer whose main component is hydrochloric acid. This inorganic layer liquid and a portion of the organic layer liquid are recycled to the distillation column through the tube 11, and the remaining organic layer liquid is obtained as the final product of the reaction through the tube (12). As the gas layer passes through the condenser 14 maintained at -40 to -20 ° C through the tube 13, traces of organic matter and hydrofluoric anhydride having a higher boiling point than hydrochloric acid are condensed. The condensate is recycled to the bed separator and the non-condensable gas is depressurized by the pressure regulating valve 15 to be introduced into the bottom of the absorption tower 16. Water, which is mainly supplied to the absorption tower through the tube 19, absorbs hydrochloric acid and is introduced into the aqueous hydrogen chloride solution tank (not shown in FIG. 1) through the tube 17, and the unabsorbed gas is transferred to the tube 18. To the atmosphere.

In this reaction, the molar ratio of hydrofluoric anhydride is maintained in excess in comparison with T111 in the reactor. Preferably, the hydrofluoric anhydride is maintained at 5 mol to 200 mol with respect to 1 mol of T111 present in the reactor, and more preferably, the hydrofluoric anhydride is maintained at 20 mol to 100 mol with respect to 1 mol of T111. As such, when the hydrofluoric acid anhydride is kept in excess of the T111 in the reactor for reaction, the amount of the organic layer is reduced even if the reaction system is uniform or separated into two layers. Therefore, the reaction proceeds in an atmosphere mainly containing anhydrous hydrofluoric acid, and the amount of by-product oligomer and tar is reduced.

Reaction temperature is 60-130 degreeC, Preferably it is 70-120 degreeC. If the reaction temperature is lower than this temperature, the reaction conversion rate of T111 is lowered. On the contrary, when the reaction temperature is higher than this temperature, the selectivity of HCFC-142b is increased because the selectivity of HCFC-142b is increased. This preferred reaction temperature is determined as a temperature about 1 to 15 ° C. below the boiling point of anhydrous hydrofluoric acid at the pressure of the reactor.

The reaction pressure is 4 to 20 bar, preferably 6 to 15 bar. When reacting under this pressure, the produced hydrochloric acid can be easily removed from substances such as T111, HCFC-141b, HCFC-142b and hydrofluoric anhydride by distillation.

One advantage of the process of the invention is that it does not necessarily require a catalyst. Thus, the problems resulting from the degradation of the catalyst and the increase in the corrosion rate of the device, which may occur during the catalytic reaction, do not arise. In addition, there may be a loss of the catalyst in the presence of a catalyst when removing the tar generated during the reaction, a separate catalyst recovery device is required, but this process is not necessary in the reaction without the catalyst.

Another advantage of the inventive process is that the reaction is carried out continuously. More specifically, T111 and raw anhydrous hydrofluoric acid are continuously injected into the reactor, and reaction products such as HCFC-141b, HCFC-142b, and hydrochloric acid and unreacted raw materials are continuously discharged out of the reactor to achieve high reaction conversion rate. HCFC-141b can be obtained in excess yield.

Another advantage of the process of the present invention is that it allows the reaction to proceed in the distillation column as well as in the reactor, thereby increasing the reaction conversion. More specifically, the reaction product and the unreacted mixed gas discharged from the reactor are injected into the bottom of the distillation column so that the distillation column is contacted with anhydrous hydrofluoric acid refluxed in the column top to rectify the distillation column as well as the unreacted T111 and hydrofluoric anhydride. This reaction increases the reaction conversion rate of T111.

As the material of the reactor used in the present invention, metals such as carbon steel, stainless steel, nickel, monel, and Hastelloy which are corrosion resistant to hydrofluoric acid may be used. In addition, a reactor coated with fluorine resin may be used.

Although the present invention will be described in detail with reference to the following examples, it should be understood that the scope of the present invention is not limited to these examples.

Example 1

200 g (10 mol) of hydrofluoric anhydride was first added to a reactor (1) having a content of 250 ml and carbon steel, and heated to a boiling point at 9.4 bar. At this time, the refrigerant flowed through the condenser 8 and the condenser 14 to liquefy all of the anhydrous hydrofluoric acid passed through the distillation column 6 and refluxed through the layer separator 10 to the top of the distillation column (6). Subsequently, 111 g / hr (1.1 mol per hour) of T111 through the tube (2) and 35 g / hr (1.8 mol per hour) of anhydrous hydrofluoric acid were continuously injected through the tube (3). The internal temperature of the reactor 1 was maintained at 95 ° C, the top temperature of the distillation column 6 at 86 ° C, and the temperature of the bed separator 10 at 20 ° C. In addition, the liquid level in the reactor was maintained at 200 ml while the reaction was in progress, and the inorganic layer composed mainly of anhydrous hydrofluoric acid in the layer separator 10 was continuously refluxed to the distillation column 6, and the produced hydrochloric acid was a pressure regulating valve (15). ) Through the absorption tower (16). The organic layer of the layer separator 10 all flowed out into the product. The composition of this organic material was analyzed by gas chromatography using a column coated with DC-200. The organic composition (% by weight) obtained at this time was as follows.

These other components are mainly oligomers, and also contain very small amounts of HFC-143a. The tar remaining in the reactor 1 after the reaction was completed was about 0.05% by weight of the total organic matter produced.

Example 2

In the reactor of Example 1, the reaction pressure was 7.5 bar, the internal temperature of the reactor 1 was 86 ° C., and the top temperature of the distillation column 6 was about 79 ° C., except that the operating conditions were changed. Was performed. The composition (% by weight) of the organic material obtained under these conditions was as follows.

As a result of analyzing the liquid remaining in the reactor 1 after the reaction was completed, the resulting tar was about 0.05% by weight of the total organic matter produced.

Example 3

In the reactor of Example 1, the reaction pressure was 11.2 bar, the internal temperature of the reactor 1 was 103 ° C, and the top temperature of the distillation column 6 was about 92 ° C, except that the operating conditions were changed. Was performed. The composition (% by weight) of the organic material obtained under these conditions was as follows.

As a result of analyzing the liquid remaining in the reactor 1 after the reaction was completed, the resulting tar was about 0.05% by weight of the total organic matter produced.

Example 4

Into a reactor (1) having a volume of 8000 ml and a material of carbon steel, 2700 g (135 mol) of hydrofluoric anhydride were first added and heated to a boiling point at 8.1 bar. At this time, the refrigerant flows through the condenser 8 and the condenser 14 to liquefy all the hydrofluoric acid passed through the distillation column 6 to reflux to the top of the distillation column 6 through the layer separator 10. Subsequently, 1001 g / hr (7.5 mol per hour) of T111 was injected through the tube 2, and 210 g / hr (10.5 mol per hour) of anhydrous hydrofluoric acid was continuously injected through the tube 3. The internal temperature of the reactor 1 was 88 ° C, the tower temperature of the distillation column 6 was 83 ° C, and the temperature of the bed separator 10 was 20 ° C. In addition, the liquid level in the reactor was maintained at 2700ml during the reaction, and the rest was carried out in the same manner as in Example 1. The organic matter composition (wt%) obtained under these conditions is as follows.

As a result of analyzing the liquid remaining in the reactor 1 after the reaction was completed, the resulting tar was about 0.1% by weight of the total organic matter produced.

Example 5

In the reaction apparatus of Example 4, 5400 g (270 mol) of anhydrous hydrofluoric acid was added first, and the reaction pressure was maintained at 9.2 bar. Then, T111 was 3335 g / hr (25 mol per hour) through the tube (2), and the tube (3) was used. Hydrofluoric anhydride was injected continuously at 700 g / hr (35 moles per hour). In addition, the internal temperature of the reactor 1 was maintained at 86 ° C., the top temperature of the distillation column 6 was 79 ° C., and the reactor liquid level was 5400 ml, and the rest was carried out in the same manner as in Example 4. The composition (% by weight) of the organic material obtained under these conditions was as follows.

As a result of analyzing the liquid remaining in the reactor 1 after the reaction was completed, the resulting tar was about 0.1% by weight of the total organic matter produced.

Claims (5)

171-dichloro-1 comprising the continuous liquid phase reaction of 1,1,1-trichloroethane and anhydrous hydrofluoric acid at a pressure of 4 to 20 bar and a temperature of 60 to 130 ° C. in a molar ratio of 1: 5 to 1: 200. Process for the preparation of fluoroethane. The method according to claim 1, wherein the molar ratio of 1,1,1-trichloroethane and hydrofluoric anhydride is from 1:20 to 1: 100. The process according to claim 1, wherein the reaction temperature is 70 to 120 ° C. The method of claim 1 wherein the reaction pressure is 6-15 bar. (a) 1,1,1-trichloroethane and excess anhydrous hydrofluoric acid were introduced into the reactor (1) via tubes (2) and (3), respectively, at a pressure of 4 to 20 bar and a pressure of 60 to 130 ° C. (B) introducing a gas, which is a reaction product, into the lower part of the distillation column 6 through the tube 4, and contacting and rectifying the introduced gas with anhydrous hydrofluoric acid, which is mainly used in the column top of the distillation column. The low volatile substance whose main component is anhydrous hydrofluoric acid is recycled to the reactor (1), and the high volatile substance such as an azeotrope of organic matter and anhydrous hydrofluoric acid, and hydrochloric acid is sent to the condenser (8) through the tube (7) to condense. Process, (c) the liquid-gas mixture passed through the condenser is introduced into the layer separator 10 through the tube 9 and separated into an inorganic layer (HF), an organic layer and a gas layer (HCl), and then the inorganic layer is Recycle to the top of the distillation column via (11), and the gas layer And exhausting the organic layer through the pipe (12), and (d) separating and purifying the organic layer discharged from the layer separator in a conventional manner to obtain 1,1-dichloro-1-. A method for producing 1,1-dichloro-1-fluoroethane comprising the step of obtaining fluoroethane.