KR960001910B1 - Preparation of 1,1-dichloro-1-fluoroethane - Google Patents

Abstract

1,1-Dichloro-1-fluoroethane is continuously prepared by : feeding and reacting the raw mixture contg. 1.1-1.5/1 mole of fluoric acid anhydride (HF) with 1,1,1-trichloroethane (1,1,1-TCE) then make to 5-10/1 mole of HF/1,1,1-TCE, at 80-100 deg.C under 10.5-12 Kg/cm2G; then recovering the obtd. products from a top of the reactor. The obtd. compsn. is useful as a substitute to chlorofluorocarbon(CFC)

Description

Method for producing 1,1-dichloro-1-fluoro ethane

1 shows a manufacturing process of HCFC-141b according to the present invention.

* Explanation of symbols for main parts of the drawings

R-1: Reactor V-1: Hydrogen Chloride Storage Tank

P-1: Pump R-2,3,4: Reboiler

E-1,2,3,4: condenser C-1,2,3,4,5: packed column

In the present invention, 1,1,1-trichloroethane (1,1,1-trichloroethane-hereinafter referred to as 1,1,1-TCE) and hydrofluoric anhydride (hereinafter referred to as HF) are reacted with 1,1-dichloro An improved method for preparing ro-1-poloroethane.

1,1-Dichloro-1-fluoroethane is a terminology well known in the field of halocarbons as HCFC-141b. The boiling point of this substance is 32 ℃, and it is a liquid at room temperature. The ozone depletion index is estimated to be a replacement for CFCs because it is about 10 minutes 1 compared to conventional chlorofluorocarbons (CFCs).

Due to the properties of HCFC-141b, it can be used as a cleaning agent for rigid electronic foam blowing agent, which is an alternative to trichlorofluoromethane (CFC-11), and an alternative electronic component of trichlorotrifluoroethane (CFC-113). It is a prospect.

HCFC-141b may be prepared by reacting a starting material of vinylidene chloride (Vinylidene Chloride) or 1,1,1, -trichloroethane (1,1,1-TCE) with HF, which are halogens. The method can be divided into a method using a catalyst and a method using no catalyst, that is, a method using no catalyst.

The reaction scheme of these production methods is as follows.

… … … … … … … … … … (I)

CH ₃ CCl ₃ + HF CH ₃ CFCl ₂ + HCL... … … … … … … … … … … … (II)

The method (I) has the advantage that 141b can be obtained without the production of hydrogen chloride as a by-product by the addition reaction of vinylidene chloride and HF, but there is a problem of maintaining a high conversion rate of vinylidene chloride.

In addition, when unreacted vinylidene chloride and 141b are mixed, their boiling points are around 32 ° C., which makes it difficult to separate them.

Korean Unexamined Patent Publication No. 90-17969 has proposed a method of preparing 141b by reacting HF with vinylidene chloride using an aluminum fluoride catalyst (AlF ₃ ).

However, in this method, the reaction is carried out in a three step process to increase the conversion rate of vinylidene chloride.

In the first step, vinylidene chloride and HF are reacted in the gas phase at a temperature of 25 to 150 ° C. and a pressure of atmospheric pressure to 160 psig.

In the two-stage process, HF is supplied and reacted again at a temperature of 5 to 75 ° C. and a pressure of atmospheric pressure to 80 psig in order to reduce unreacted vinylidene chloride contained in the product produced in the first step.

In a three-step process, an aqueous permanganate solution is added to oxidize or bromine with bromine to remove the remaining traces of vinylidene chloride.

Through this operation, the conversion rate of the raw material vinylidene chloride can be somewhat increased, but it is not suitable for industrialization because the operation is complicated and the operation cost is high and the equipment cost is high.

Korean Patent Publication No. 90-1629 discloses a method for producing HCFC-141b by gas phase reaction by adding HF to vinylidene chloride using an aluminum fluoride catalyst (AlF ₃ ).

In terms of the reaction conditions, the temperature is 120 DEG C or less, the reaction molar ratio is supplied to 1 mole of vinylidene chloride, HF is 1.5 to 10 mole, and the pressure is carried out at atmospheric pressure.

However, this method generates a lot of unreacted HF as a large amount of HF is added, but it is washed with 5% potassium hydroxide (KOH) solution.

Therefore, since the recovery reuse of HF is not possible, not only the conversion rate of the raw material HF is low but also the yield of HCFC-141b is low as 89.6%.

In the above method (II), HFC is reacted with 1,1,1-trichloroethane to produce HCFC-141b. When a catalyst is used, the reaction rate is influenced to produce HCFC-142b and HCFC-143a. Because of the use of catalysts (Tar) and high-boiling materials can be produced, there is a difficulty in their stagnation, separation.

On the other hand, in the non-catalytic reaction, there are problems such as the generation of by-products but a low conversion rate of 1,1,1-TCE.

US Pat. No. 2,894,044 describes the preparation of HCFC-141b by fluorination of 1,1,1-TCE in the gas phase using aluminum fluoride (AlF ₃ ) and tin fluoride (SnF ₄ ) as catalysts. have.

This method is characterized by preheating HF and 1,1,1-TCE to make it vapor phase and sending it to the reactor containing the catalyst for reaction.

In the reaction conditions, the preheating temperature of the preheater is 115-170 ° C, the reactor temperature is 60-125 ° C, more preferably 90-125 ° C, and the molar ratio of the feedstock is 1-2 moles per 1 mole of 1,1,1-TCE. Supply HF.

However, this method is difficult to control the reaction conditions than the liquid phase reaction as the reaction in the gas phase, and has the disadvantage that the yield of HCFC-141b is 11.2-80.4%.

Japanese Patent Publication No. 50-5681 describes a method for producing HCFC-141b and HCFC-142b by reacting HF with 1,1,1-TCE in the absence of a catalyst.

In terms of the reaction conditions, the reaction temperature is 70 to 140 ° C., and the molar ratio of the feedstock is 4 to 30 mol of HF per 1 mol of 1,1,1-TCE.

However, this method is not suitable for the manufacturing method of 141b because the conversion rate is low (72%) and the production ratio of 141b / 142b is 68.06 / 31.94 to 2.35 / 97.64 (mole%) despite the excessive supply of HF, and the selectivity of 142b is high. Do.

In Japanese Patent Laid-Open No. 2-152935, liquid phase reaction of 1 mole of HF with 1 mole of 1,1,1-TCE at 1 mole of 1,1,1-TCE at a reaction temperature of 40 to 110 ° C. and a reaction pressure of 8 to 10 Kg / cm 2 · G is carried out in the absence of a catalyst. The method is described.

However, this method uses a liquid phase effluent method for recovering the reaction product from the bottom of the reactor to the liquid phase, and a lot of unreacted 1,1,1-TCE is generated so that the conversion rate of raw material 1,1,1-TCE is about 72 to 79%. low. Therefore, the reaction time is long (2 to 20 hours) in order to increase the reactivity, but as the reaction time increases, the reactor capacity needs to be increased to obtain a certain amount of product, and as the contact time increases, side reaction materials are easily generated and energy consumption is increased. This is increased and economically disadvantageous.

In the patent, it was shown that the reaction experiment was conducted experimentally by batch rather than continuous, and the conversion rate of raw materials and the selectivity of 141b are low, making it difficult to apply to industrialization.

The present invention is a reactor in a non-catalytic state through a number of repeated experiments while changing the contact method of the feed molar ratio of the raw material and the reaction solution of the raw material in a pilot plant to improve the problems listed in the patent The gas phase effluent, which flows the reaction product from the top to the gaseous phase, provides the most economically advantageous method of producing 141b in a selective high yield while minimizing the production of by-products such as 142b and 143a.

Detailed reaction conditions in the present invention are as follows.

1) Using gaseous effluent method to recover product from the top of reactor by liquid phase reaction of HF and 1,1,1-TCE under no catalyst

2) The pressure of the reaction system is selected from 10.5 to 12 Kg / cm 2 · G.

3) The reaction temperature is selected at 80 to 100 ° C.

4) The feed ratio of HF / 1,1,1-TCE is controlled to 1,1 to 1.5 / 1 mol while maintaining HF / 1,1,1-TCE in the reactor to be 5-10 mole.

5) In the raw material input method, 1,1,1-TCE is supplied to the top of the reactor, and HF is supplied into the reactor liquid.

6) Recover the product from the top of the reactor, and recover the unreacted HF and 1,1,1-TCE from the HF separation tower and the high boiling point separation tower and return them to the reactor.

7) The manufacturing method is carried out continuously.

Under the above conditions, the feature is that it uses a gas phase outflow method to discharge the generated product from the top of the reactor to the gas phase while maintaining the HF / 1,1,1-TCE in the reactor to 5-10mole. The reaction time is considerably faster than the liquid phase outflow method in which the product produced as in the arc flows out from the bottom of the reactor to the liquid phase, so that the reaction time is 0.5 to 1 hour.

Therefore, less unreacted 1,1,1-TCE can be minimized and by-products such as 142b and 143a can be minimized. In addition, since the method of the present invention is a continuous process, the unreacted HF and 1,1,1-TCE can be separated and recovered in a separation column and recycled to the reactor, so that the high conversion rate of the raw material (HF: 90% or more, 1, 1,1-TCE 92% or more) to provide a manufacturing method capable of manufacturing 141b with a high selectivity (97.7% or more).

The invention is accomplished using conventional equipment as shown in the figures.

The raw material (HF, 1,1,1-TCE) is supplied to the reactor (R-1) which can adjust the temperature. The reactor is equipped with a reflux column and a reflux condenser to reflux unreacted raw materials (HF and 1,1,1-TCE) in the air stream from the reactor to increase the conversion of the raw materials. The reaction product is introduced into the hydrogen chloride separation column (C-2) in a gaseous state through the condenser (E-1). The gas introduced into the separation column is refluxed in the column and rectified with the liquid to liquefy the rest of the material except hydrogen chloride. The non-condensed hydrogen chloride gas is introduced into the lower portion of the hydrogen chloride absorption tower (C-3) through the condenser (E-2), is absorbed by the water to form a 35% aqueous hydrogen chloride solution and stored in the hydrogen chloride storage tank (V-1).

At this time, the organic matter flowing out of the reboiler (R-2) is transferred to the hydrogen fluoride separation tower (C-4) to recover the unreacted HF from the top of the column and re-reacted in the reactor (R-1) to increase the conversion rate of the raw material. . The crude product leaked from the reboiler (R-3) is transferred to the fertilizer separation tower (C-5) and the unreacted 1,1,1-TCE is discharged from the reboiler (R-4) to the reactor (R). The organic matter recycled to -1) and discharged from the top of the tower are sent to the product storage tank through the product separation tower, alkali washing and drying process.

At this time, the refrigeration condenser (E-1) is maintained at a cooling water temperature of 60 ℃, hydrogen chloride condenser (E-2) is a low-temperature refrigerant of -30 ~ -32 ℃, and the heavy water condenser (E-3) -15 ~- Pass the refrigerant at 20 ℃.

Hereinafter, the content of the present invention will be described with reference to specific examples.

And the content of the present invention is not limited only to the Examples.

Example 1

The reactor R-1 is initially fed with 7.5 Kg of HF and 10 Kg of 1,1,1-TCE. Heat was gradually added thereto, and HF and 1,1,1, -TCE were continuously supplied simultaneously while maintaining the reactor temperature at 80 ° C. and the reaction pressure at about 10.5 Kg / cm 2 · G.

At this time, the feed molar ratio of HF / 1,1,1-TCE is adjusted to maintain 5 / 1mole of HF / 1,1,1-TCE present in the reactor. The internal temperature of the reactor (R-1) was maintained at 80 ° C and the top temperature of the reflux column (C-1) at 60 ° C. The produced gas is introduced into the hydrogen chloride separation tower C-2 while maintaining the pressure in the system from the top of the reflux condenser E-1.

At this time, the lower temperature of the hydrogen chloride separation tower is maintained at 75 ~ 80 ℃, the upper temperature -15 ~ -30 ℃. Hydrogen chloride gas is introduced into the hydrogen chloride absorption tower (C-3) through the condenser (C-2) to be absorbed and stored in 35% aqueous hydrogen chloride solution.

In addition, the organics leaked from the reboiler (R-2) are recovered through the hydrofluoric acid separation tower (C-4) and the high-fertilizer separation tower (C-5), and unreacted HF and 1,1,1-TCE are recovered and the reactor ( Re-react to R-1) to increase the conversion of raw materials.

The crude product that is leaked is sent to the product storage tank through the product separation tower, alkali cleaning process and drying process. The results under the above conditions are as follows.

Example 2

It is carried out in the same apparatus as in Example 1 and the reaction conditions except for the reaction temperature, the reaction pressure, the molar ratio in the reactor is the same as in Example 1. Here, the reaction temperature is 100 ° C., the reaction pressure is 12 Kg / cm 2 · G, and the molar ratio in the reactor is maintained at HF / 1,1,1-TCE = 7/1 mol.

The results under the above conditions are as follows.

Example 3

The same apparatus as in Example 1 was carried out under the same conditions, and the molar ratio in the reactor was adjusted to be HF / 1,1,1-TCE = 10/1 mol.

The results under the above conditions are as follows.

Claims (1)

In the method for continuously producing 1,1-dichloro-1-fluoroethane by liquid-reacting 1,1,1-trichloroethane and hydrofluoric anhydride in the absence of a catalyst, the feed ratio of the raw materials into the reactor (HF / 1, Molar ratio of 1,1-TCE) is maintained at 1,1 to 1.5 / 1 mole so that the molar ratio of hydrofluoric anhydride / 1,1,1-trichloroethane in the reaction is 5 to 10/1, and 10.5 to 12 Kg / A process for producing 1,1-dichloro-1-fluoroethane by a continuous process of reacting at a pressure of cm 2 · G at a temperature of 80 to 100 ° C. and recovering the reaction product from the top of the reactor.