JPH0570381A - Method for purifying 1,1-dichloro-1-fluoroethane - Google Patents

Abstract

PURPOSE:To purify the title compound useful as a blowing agent for urethane foam in production of dichlorofluoroethane by adsorbing and removing the by-product on a synthetic zeolite which is not specifically treated but dried and burnt. CONSTITUTION:In producing 1,1-dichloro-1-fluoroethane, C4H5ClxF5-x and/or C4H5ClyF5-y (x is 0.5; y is 0-4) contained as a by-product is adsorbed and removed with synthetic zeolite 13X which is not specifically treated, but immersed in an aqueous solution of an alkyline (earth) metal hydroxide or an alkyli metal carbonate, and dried and burnt, to purify 1,1-dichloro-1-fluoroethane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying 1,1-dichloro-1-fluoroethane which is useful as a foaming agent for urethane foam, a cleaning agent for removing oils and fats, a solvent for dry cleaning and the like.

[0002]

2. Description of the Related Art 1,1-Dichloro-1-fluoroethane (hereinafter referred to as HCFC-141b)
Is written. Conventionally, various methods have been proposed for the manufacturing method (1). For example, according to the specification of Japanese Examined Patent Publication (Kokoku) No. 50-5681, 1,1,1-trichloroethane and hydrogen fluoride are reacted under high pressure without using a catalyst to give 1-chloro-1 , 1-difluoroethane together with HCFC-141b. However, in the HCFC-141b synthesized by such a method, 1,1,1-trichloroethane as a raw material as a by-product or 4 carbon atoms or 6 carbon atoms in which an intermediate product is polymerized is used.
Often, individual C4 or C6 compounds are included. C4 occupies the majority of such polymerization products
The compound is C ₄ H ₅ Cl _X F _5-X or C ₄ H ₄ Cl _Y
F _4-Y (X is 0 to 5, Y is a positive integer of 0 to 4, hereinafter, C
4 by-product), but the molecular formula of the main by-product is CH ₃ CX ₂ CH ₂ CX ₃ (X is F or Cl) or CH ₃ CX ₂ CH═CX ₂ (X is F or Cl). expressed. Most of these components can be separated and purified by a distillation operation usually applied to such a reaction product. However, one of these components, 1,1,1,3,3-pentafluorobutane (CH ₃ C
F ₂ CH ₂ CF ₃ , hereinafter referred to as HFC-365. ) Has a boiling point of 40 to 41 ° C. and HCFC-141b (boiling point, 3
Despite the large difference in boiling point from
Separation is difficult due to the azeotropic phenomenon between -141b and HFC-365. Therefore, in order to improve the purity of HCFC-141b, the yield of HCFC-141b must be reduced. From the molecular structure of HFC-365, it is presumed that HFC-365 is chemically more stable than HCFC-141b. Therefore, the method of decomposing and removing HFC-365 cannot be adopted.

According to the method disclosed in JP-A-2-295937 disclosed for the purpose of solving the above problems,
A liquid mixture of HCFC-141b and HFC-365 is separated by distillation by adding to the mixture a liquid containing at least 3 moles of hydrogen fluoride per mole of HCFC-141b in the mixture to give HFC-36.
HCFC-141 containing no HFC-365 after obtaining a product consisting of HCFC-141b containing 5 and hydrogen fluoride as a top product and further separating hydrogen fluoride and the like.
141b is manufactured. However, adding such a method to the manufacturing process of HCFC-141b not only complicates the process but also complicates the manufacturing operation, which is not desirable.

Although the toxicity and toxicity of HFC-365 are not clear, considering that the product, HCFC-141b, is intended to be used for a wide range of general purposes, its safety is questionable. It is not preferable to mix such impurities, and it is needless to mention again the importance of reducing the content thereof as much as possible.

Therefore, the HFC-365 contained in the HCFC-141b can be easily operated and the HCFC-1
There is a demand for a method of efficiently removing 41b without lowering the yield.

[0006]

[Means for Solving the Problems] In view of the problems of the prior art, the inventors of the present invention have taken advantage of the solid state HCFC
As a result of intensive studies on selective adsorption properties of -141b and C4 by-products, the inventors have found that the synthetic zeolite 13X selectively adsorbs C4 by-products among these substances, and arrived at the present invention. That is, the present invention relates to a method for obtaining HCFC-141b substantially free of C4 by-product by bringing HCFC-141b containing C4 by-product into contact with synthetic zeolite 13X in a liquid phase.

More specifically, 1,1-dichloro-1-
C ₄ H ₅ Cl _X F _5-X and / or C ₄ H ₄ Cl _Y F contained as by-products in the production of fluoroethane
_4-Y (X is a positive integer of 0 to 5 and Y is a positive integer of 0 to 4) is not subjected to any special treatment, or is immersed in an aqueous solution of an alkali metal or alkaline earth metal hydroxide or alkali metal carbonate. And then dried and calcined synthetic zeolite 1
The present invention relates to a method for purifying 1,1-dichloro-1-fluoroethane, which comprises adsorbing and removing by 3X.

The synthetic zeolite 13X used in the present invention is
Commercially available molecular sieves (made by Union Carbide) 13X, Zeolum F-9 (made by Tosoh Corp.) and the like can be used without any treatment, but these synthetic zeolites 13X can be used as alkali metal or alkaline earth. It is more effective to use a pre-treated metal hydroxide or carbonate. The alkali metal hydroxides used in this treatment include lithium hydroxide, sodium hydroxide, potassium hydroxide, etc., and the alkaline earth metal hydroxides include calcium hydroxide, barium hydroxide, etc. , These carbonates include sodium carbonate and the like. This treatment method comprises immersing the synthetic zeolite 13X in an aqueous solution of a hydroxide or carbonate of an alkali metal or an alkaline earth metal for a predetermined time, taking it out from the solution, drying it, and then firing it in an electric furnace. ing.

The concentration of the aqueous solution used for treating the synthetic zeolite is 0.1 to 30% by weight. For example,
It is preferably 5 to 30% by weight for sodium hydroxide and 0.1 to 0.8% by weight for calcium hydroxide. The treatment temperature is not particularly limited, but it is usually convenient to perform it at room temperature. Drying is performed at 80 to 100 ° C., but it is not particularly limited thereto, and it is sufficient that the adhering water of the synthetic zeolite is substantially removed. The firing temperature is 25
0 to 400 ° C is preferable, and below 250 ° C, HCFC-
Decomposition of 141b occurs, and when it exceeds 400 ° C, the adsorption capacity is lost.

The temperature at which the present invention is carried out is -80 ° C to 30 ° C.
C is preferable, and -30 to 30 C is more preferable. -80
When the temperature is lower than ℃, the adsorption rate becomes slower, and a special device is required, which causes a problem that the operation becomes difficult. On the other hand, when the temperature exceeds 30 ℃, HCFC-1
The problem occurs that the decomposition of 41b occurs. The treatment pressure does not need to be particularly limited, but at that temperature the HCFC
It is necessary that -141b is a liquid, and it is usually carried out at a gauge pressure of 0 to 1 kg / cm ² .

Crude HCFC-141b to which the present invention is applied
May be a crude HCFC-141b obtained by removing an acidic gas such as hydrogen fluoride or hydrogen chloride from a reaction product, but more preferably it is a crude HCFC-141b consisting essentially of HCFC-141b and HFC-365. .. This rough HCF
The concentration of HCFC-365 contained in C-141b varies over a wide range depending on the reaction method, reaction conditions and pretreatment, but is generally 0.02 to 5% by weight.

In the embodiment of the present invention, a batch type method is naturally possible, but a flow type method is more preferable. For example, the objective can be achieved by circulating the crude HCFC-141b in a tubular container filled with the synthetic zeolite 13X, but it is also possible to take the usual application form applied to such an adsorption device. Needless to say. ..

[0013]

The present invention will be described below with reference to examples.
The embodiment is not limited to this. All analyzes were carried out by gas chromatography.

Example 1 Crude HCFC-141b60 synthesized by fluorinating 1,1,1-trichloroethane with hydrogen fluoride without a catalyst
After being charged in a 100 cc glass flask and adjusted to 0 ° C., 13 × 20 g of molecular sieves was added. The composition of this crude HCFC-141b changed with time as shown in Table 1. In Table 1, HCFC-142
b is 1-chloro-1,1-difluoroethane, HCFC
-364 is C ₄ H ₅ ClF ₄ , HCFC-1353 is C
₄ H ₄ ClF ₃ , 1,1,1-TCE is 1,1,1-trichloroethane, HCFC-363 is C ₄ H ₅ Cl ₂ F
_3, HCFC-362 represents _{C 4 H 5 Cl 3 F 2} .

[0015]

[Table 1]

Example 2 The same experiment as in Example 1 was conducted at -20 ° C and -76 ° C, and the composition of crude HCFC-141b was analyzed 2 hours after the addition. The analytical values are shown in Table 2.

[0017]

[Table 2]

Example 3 100 g of molecular sieve 13X was dipped in 200 cc of 20% by weight sodium hydroxide aqueous solution for 2 hours to remove excess aqueous solution, and dried overnight with a warm air circulation dryer kept at 100 ° C. It was fired at 300 ° C. in an electric furnace. Using 60 g of this treated molecular sieve 13X, the same experiment as in Example 1 was carried out at 25 ° C.
The results are shown in Table 3.

Example 4 The same experiment as in Example 3 was conducted except that potassium hydroxide was used instead of sodium hydroxide. The results are shown in Table 3.

Example 5 The same experiment as in Example 3 was conducted except that a 0.5 wt% calcium hydroxide aqueous solution was used instead of the 20 wt% sodium hydroxide aqueous solution. The results are shown in Table 3.

[0021]

[Table 3]

Comparative Example 3 g of the crude HCFC-141b used in Example 1 was placed in a 10 cc glass bottle, 1 g of molecular sieve 3A was added, and the mixture was kept at 25 ° C. for 2 hours. After that, when the composition of the liquid phase part was analyzed, a decrease in C4 by-product was not recognized. The same experiment was performed using molecular sieve 4A, molecular sieve 5A, activated alumina, silica alumina,
When carried out on silica gel, no reduction of C4 by-product was observed.

[0023]

According to the method of the present invention, by-products which are difficult to remove by distillation during the production of 1,1-dichloro-1-fluoroethane can be easily removed at room temperature and atmospheric pressure. Play.

Claims (1)

[Claims] 1. C ₄ H ₅ Cl _X F _5-X and / or C
₄ H ₄ Cl _Y F _4-Y (X is a positive integer of 0 to 5 and Y is 0 to 4) is not subjected to any special treatment, or is a hydroxide or alkali metal of an alkali metal or alkaline earth metal. A method for purifying 1,1-dichloro-1-fluoroethane, which comprises immersing it in an aqueous solution of a carbonate, and then adsorbing and removing it by using synthetic zeolite 13X which is dried and calcined.