JPH0733695A - Method for removing water from 1,1-dichloro-1-fluoroethane - Google Patents

Abstract

PURPOSE:To prevent the decomposition of 1,1-dichloro-1-fluoroethane in the case of removing water from 1,1-dichloro-1-fluoroethane with zeolite. CONSTITUTION:This process is carried out by using a zeolite dried after adsorbing water or a zeolite treated by immersing in a basic aqueous solution of sodium hydroxide, potassium hydroxide, etc., and drying and baking the product.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing water from 1,1-dichloro-1-fluoroethane which is useful as a foaming agent for rigid urethane foam and the like.

[0002]

2. Description of the Related Art Conventionally, various methods have been proposed for producing 1,1-dichloro-1-fluoroethane (hereinafter referred to as HCFC141b). For example, according to the description in Japanese Patent Publication No. 50-5681, 1,1,1-trichloroethane and hydrogen fluoride are reacted under high pressure to give 1-
HCFC1 with chloro-1,1-difluoroethane
I got 41b. HCFC synthesized by this method
141b contains hydrogen chloride and hydrogen fluoride, and after removing these acids by washing with water, a dehydration step,
The product is made through a distillation process. Further, since the HCFC 141b is recognized to have ozone depletion ability, it is necessary to install a recovery device for adsorbing activated carbon upon use, and the recovered liquid is recycled through a water washing step, a dehydration step and a distillation step.

As a method of removing water contained in the HCFC 141b, there is a method of using zeolite as a dehydrating agent. This method has the advantages that it is simple and that the dehydrated dehydrated agent can be easily regenerated. However, if untreated zeolite is used as a dehydrating agent, the original purpose of dehydrating HCFC141b can be achieved, but at the same time, HCFC141b
141b or 1, contained in HCFC 141b
There is a problem that 1,1-trichloroethane is decomposed and vinylidene chloride (hereinafter referred to as VDC) is produced.

It is said that VDC itself is highly reactive and easily causes a polymerization reaction, an oxidation reaction by air and the like, and its toxicity has been pointed out. Therefore, HCFC14
Considering the wide use of 1b, the dehydration method using untreated zeolite is practically problematic.

[0005]

[Means for Solving the Problems] As a result of intensive studies made by the present inventors in view of such problems, the zeolite treated with water or a basic aqueous solution was used as a dehydrating agent and at least H 2
Dehydration of a composition containing CFC141b results in substantially VD
The present invention has been completed by finding that C can achieve the purpose without being generated.

That is, the present invention is a method for removing water in a liquid or gas containing at least HCFC141b, characterized in that zeolite treated with water or a basic aqueous solution is used as a dehydrating agent.

The zeolite used in the present invention may be natural or synthetic, but synthetic zeolites such as 3A type, 4A type, 5A type and 13X type are preferable in terms of stable quality and supply. Specific examples are commercially available molecular sieves 3A and molecular sieves 4.
A, molecular sieves 13X (manufactured by Union Carbide Co., Zeorum A-3, Zeorum A-4, Zeorum A-
5, Zeolum F-9 (manufactured by Tosoh Corporation) and the like,
4A such as molecular sieves 4A, Zeolum A-4
Type is recommended.

When these zeolites are used as an adsorbent without treatment, HCFC141b or 1,1,1-trichloroethane may be decomposed to produce VDC.
However, by treating with water or basic aqueous solution,
A more effective dehydrating agent that can suppress the generation of VDC.

The most convenient method of adsorbing water is to immerse the zeolite in water, or to circulate water vapor or a conditioned gas in a container filled with zeolite. Alternatively, ethanol, acetone, benzene or the like may be used to adsorb water in the gas phase or the liquid phase. Depending on the amount of adsorbed water, it may be possible to use it as a dehydrating agent while adsorbing the water, but in order to increase the treatment amount of HCFC141b, it is desirable to dry these zeolites at 50 ° C to 300 ° C. . The drying is more preferably 80 ° C to 250 ° C.
The drying method may be any method using hot air, vacuum drying, etc., but the drying temperature is preferably 50 ° C to 300 ° C. If the drying temperature is 300 ° C. or higher, the effect of the treatment is small, and if it is 50 ° C. or lower, it takes a long time to dry the zeolite, which is not preferable.

As a method of treating with a basic aqueous solution,
An example is a method of immersing zeolite in an aqueous solution of a hydroxide or carbonate of a 1a group or 2a group element, followed by drying and firing. Examples of hydroxides or carbonates of 1a group and 2a group include lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, sodium carbonate and the like. The concentration of the aqueous solution used for treating the zeolite is 0.1 to 30% by weight. For example, 0.1 to 25% by weight is preferable for sodium hydroxide. The treatment temperature is not particularly limited, but it is usually convenient to perform it at room temperature. Drying is 80-12
It is carried out at 0 ° C., but it is not particularly limited to this and it is sufficient that the water adhering to the zeolite is substantially removed. Firing temperature is 2
50 to 400 ° C. is preferable.

Although the method of the present invention can be carried out in a liquid phase or a gas phase, the liquid phase treatment is recommended considering the size, shape and throughput of the apparatus. When carrying out the invention in the liquid phase,
The temperature is preferably −80 ° C. to 30 ° C., more preferably −30 ° C. to 30 ° C. At -80 ° C or lower, a special device is required, and the boiling point of HCFC141b is 32.5.
Considering that the temperature is 0 ° C, it is not preferable to perform the treatment at 30 ° C or higher.

At least HCFC1 dried according to the invention
Examples of the liquid or gas containing 41b include those generated during the production of HCFC 141b, those recovered from used liquid by washing, etc., but there is no particular limitation.

The method of the present invention may be a batch type method, but is more preferably a flow type method. For example, although the object can be achieved by circulating a liquid or gas containing at least HCFC-141b in a tubular container filled with the zeolite that has been subjected to the above-mentioned treatment, it is a usual application form applied to such an adsorption device. It goes without saying that it is possible to take

[0014]

EXAMPLES The present invention will be described below with reference to examples, but the method of implementation is not limited thereto. [Preparation Example 1] 100 g of molecular sieves 4A
It was immersed in 1 g of ion-exchanged water for 1 hour, filtered, pre-dried at 120 ° C. for 1 hour, and further dried at 250 ° C. for 2 hours. After drying, it was cooled to room temperature in a desiccator dried over silica gel. This is sample A. [Preparation Example 2] The same procedure as in Preparation Example 1 was repeated except that ethanol containing 10% by weight of water was used instead of ion-exchanged water. This is sample B.

Preparation Example 3 Molecular Sieves 4A5
50 g was immersed in 1100 ml of 20 wt% sodium hydroxide aqueous solution for 1 hour, filtered, pre-dried at 120 ° C. for 1 hour, and then calcined at 300 ° C. for 2 hours. After firing, it was cooled to room temperature in a desiccator dried over silica gel.
This is sample C. [Preparation Example 4] The same procedure as in Preparation Example 3 was repeated except that a 20 wt% aqueous solution of sodium hydroxide was used instead of the 20 wt% aqueous solution of sodium hydroxide. This is sample D. [Preparation Example 5] The same procedure as in Preparation Example 3 was repeated except that a 0.5 wt% calcium hydroxide aqueous solution was used instead of the 20 wt% sodium hydroxide aqueous solution. This is sample E. [Example 1] 20 g of sample A was placed in a glass container having a volume of 100 ml capable of being tightly closed, and then VDC 71 ppm,
HCFC14 with a purity of 99.8% containing 240 ppm of water
50 g of 1b was charged and the bottle was tightly closed. After 1 hour, the water content was measured by the Karl Fischer method, and the HCFC purity and VDC concentration were measured by gas chromatography. As a result, the water content is 3.8.
ppm, HCFC141b purity 99.8%, VDC concentration 79 ppm.

[Example 2] 1,1,1-without catalyst
Crude HCFC141 from which VDC was removed after washing the product synthesized by reacting trichloroethane and hydrogen fluoride with water
b (purity 96.5%, VDC concentration 156 ppm, 1,
1,1-trichloroethane 2.0%, water 268pp
Example 1 was repeated except that the zeolite prepared in the same manner as in Preparation Example 1 was used except that m) was used. As a result, water content was 4.9 ppm, HCFC141b purity was 96.5%, VD
The C concentration was 163 ppm. [Example 3] The same operation as in Example 1 was carried out except that Sample B was used. As a result, the water content was 3.6 ppm and HCFC141
b Purity was 99.8% and VDC concentration was 74 ppm. [Example 4] The same procedure as in Example 1 was carried out except that Sample C was used. As a result, the water content was 3.6 ppm and HCFC141
b Purity was 99.8% and VDC concentration was 72 ppm. [Example 5] The same operation as in Example 1 was carried out except that Sample D was used. As a result, the water content was 3.7 ppm, HCFC141
b Purity was 99.8% and VDC concentration was 72 ppm.

[Example 6] The same operation as in Example 1 was carried out except that Sample E was used. As a result, moisture 4.0ppm, H
CFC141b Purity 99.8%, VDC concentration 78ppm
Met. Example 7 500 g of sample C was filled in an SUS adsorption column having an inner diameter of 2.8 cm and a length of 1 m. The same HCFC141b as in Example 1 was circulated at a linear velocity of 1 m / h. The HCFC 141b at the loading and unloading outlet was measured for purity by gas chromatography and water content by the Karl Fischer method. as a result,
The water content was 2.8 ppm, the HCFC purity was 99.8%, and the VDC concentration was 72 ppm. [Comparative Example 1] The same operation as in Example 1 was carried out except that untreated molecular sieves 4A was used. As a result, the water content 3.
The concentration was 5 ppm, the purity of HCFC141b was 99.5%, the VDC concentration was 2800 ppm, and an increase in the VDC concentration was observed. [Comparative Example 2] The same operation as in Example 2 was carried out except that untreated molecular sieves 4A was used. As a result, the water content is 5.
0 ppm, HCFC141b purity 94.9%, VDC concentration 7990 ppm, and an increase in VDC concentration was observed.

[0018]

According to the method of the present invention, as is clear from the results of Examples and Comparative Examples, HCFC141b, 1,
This has the effect of suppressing the decomposition of 1,1-trichloroethane and the like.

Claims (3)

[Claims] 1. At least 1,1-characterized by using a zeolite which has been preliminarily adsorbed with water and then dried.
Method for removing water in liquid or gas containing dichloro-1-fluoroethane 2. At least 1,1-dichloro-1-fluoroethane characterized by using zeolite which has been previously treated with a basic aqueous solution containing an element of group 1a or 2a in the periodic table, dried and calcined. Method for removing water in liquid or gas 3. The method for removing water according to claim 1, wherein the zeolite is synthetic zeolite 4A.