JPH0699357B2 - Method for producing oxalyl fluoride - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing oxalyl fluoride from oxalyl chloride in good yield and easily.

[Prior Art and its Problems] Oxalyl fluoride is a useful material as a raw material for producing various organic fluorine compounds such as perfluorodivinyl ether. As a method of producing oxalyl fluoride, a method of fluorinating oxalyl chloride is known.

As the fluorinating agent for fluorinating oxalyl chloride as described above, a fluoride of an alkali metal such as NaF or KF is usually used. In this case, the alkali metal fluoride is heterogeneously suspended in a suitable neutral solvent such as sulfolane, tetraglyme, or acetonitrile, and the temperature of the reaction system is generally higher than 130 ° C. Is adopted. However, in this method, since the reaction proceeds at the solid-liquid interface,
Even if an alkali metal fluoride having a sufficiently small particle size is used, the reaction is very slow. Further, although the alkali metal fluoride is an expensive reagent, it is an industrially serious problem because only a part of the amount used is effectively consumed. Further, not only the yield of the reaction is low, but also the reaction temperature is high, so that fluorinated phosgene is easily produced as a by-product. On the other hand, hydrogen fluoride as a fluorinating agent is extremely inexpensive, but since it does not mix uniformly with oxalyl chloride and separates into two phases, it shows no reactivity with oxalyl chloride, and oxalyl fluoride is substantially It cannot be manufactured.

Therefore, the inventors of the present invention can obtain the desired oxalyl fluoride by the method of reacting oxalyl chloride and hydrogen fluoride under stirring under conditions that are more vigorous than the reaction activity limit. Finding that you can get it efficiently,
It has already been proposed (JP-A-57-67533). Also, in the same manner, it was found that the target oxalyl fluoride can be obtained in good yield by a method of simply reacting oxalyl chloride and hydrogen fluoride in a gas phase, and has already proposed (Japanese Patent Application No. 58-244411). . However, each of these proposed methods not only complicates the device because the former requires special stirring conditions, but it is complicated to predetermine specific stirring conditions.
Further, the latter requires an extremely excess amount of hydrogen fluoride relative to the theoretical amount with respect to oxalyl chloride, so that separation of the hydrogen fluoride entrained in the produced gas is troublesome, and additional equipment such as a vaporizer is required. Have.

On the other hand, JP-A-54-158396 proposes a method for producing oxalyl fluoride by fluorinating oxalyl chloride with hydrogen fluoride in the presence of acetonitrile, but the yield is
70%, which is not yet satisfactory.

[Means for Solving the Problem] In view of the above, the present inventors have conducted further studies and studied hydrogen fluoride in the presence of various additives such as primary to tertiary amines and aprotic polar compounds. We systematically investigated the fluorination of oxalyl chloride. As a result, it was found that by reacting oxalyl chloride with hydrogen fluoride in the presence of an aliphatic tertiary amine, the reaction rate is high and oxalyl fluoride can be obtained in an extremely high yield. It has been completed. That is, the present invention is characterized in that when oxalyl chloride is fluorinated with hydrogen fluoride to produce oxalyl fluoride, the fluorination is carried out using hydrogen fluoride in the presence of an aliphatic tertiary amine. It is a method for producing oxalyl. According to the present invention, oxalyl fluoride can be obtained in a yield of 80% or more, and further 90% or more with respect to oxalyl chloride.

In order to obtain oxalyl fluoride, which is the object of the present invention, a stoichiometric amount of hydrogen fluoride of 2 moles to 1 mole of oxalyl chloride is required. Therefore, in general, hydrogen fluoride consumed as the reaction is continued may be replenished according to the theoretical amount, and hydrogen fluoride used in advance in excess may be recovered or used for the next reaction. it can. When hydrogen fluoride contains water, oxalic acid is produced as a by-product during the reaction with oxalyl chloride, resulting in a decrease in the yield of the desired oxalyl fluoride. Therefore, the water content of hydrogen fluoride is generally
It is desirable to keep it to 0.5% by weight or more.

In the present invention, the presence of an aliphatic tertiary amine is extremely important in order to obtain the desired oxalyl fluoride in a high yield by the reaction between oxalyl chloride and oxalyl fluoride. The aliphatic tertiary amine may have a linear or branched carbon chain, and is particularly a trialkylamine, preferably an alkyl group having 1 to 8 carbon atoms. Examples of such aliphatic tertiary amines are trimethylamine, triethylamine, tri-n-propylamine, tri-n-butylamine, triisobutylamine, tri-n-amylamine, triisoamylamine, tri-n-octylamine, Examples include N-methyl-di-n-octylamine and tri- (2-ethylhexyl) -amine. When the aliphatic tertiary amine contains water, it is necessary to suppress the water content to 5% by weight or less in order to reduce the yield of oxalyl fluoride as a target by-product of oxalic acid. It is preferable that the content is not more than wt%.

In the present invention, the aliphatic tertiary amine varies depending on its type, but generally the concentration is 0.2 to 40 mol%, preferably 0.5 to 30 mol% in hydrogen fluoride. The desired oxalyl fluoride can be obtained. Further, the hydrogen fluoride solution containing such an aliphatic tertiary amine has a very low vapor pressure as compared with hydrogen fluoride and is stable even at a relatively high temperature, so that the volatilization amount of the hydrogen fluoride can be reduced and the reaction product gas can be reduced. Handling is advantageous because the amount of hydrogen fluoride entrained therein is small. However, when the concentration of the aliphatic tertiary amine in hydrogen fluoride is lower than 0.2 mol%, the phase separation between the hydrogen fluoride and oxalyl salt becomes remarkable, and the reaction is slowed down, or even the reaction does not occur at all. Not only does it not occur, but hydrogen fluoride is entrained in the reaction product gas due to the increase in vapor pressure of hydrogen fluoride. Further, when the concentration of the aliphatic tertiary amine in hydrogen fluoride becomes higher than 40 mol%, the reaction rate becomes slow, which is industrially disadvantageous.

The method for adjusting the mixing order of the aliphatic tertiary amine and hydrogen fluoride in the hydrogen fluoride solution containing the above-mentioned aliphatic tertiary amine is not particularly limited. Generally, hydrogen fluoride or aliphatic tertiary amine may be added to and mixed with the aliphatic tertiary amine under cooling and stirring to adjust the concentration to a predetermined level.

Next, the method of reacting oxalyl chloride and hydrogen fluoride in the present invention is not particularly limited as long as it is in the presence of an aliphatic tertiary amine, and both may be mixed batchwise or continuously. Generally, a method of adding and mixing oxalyl chloride in a liquid or gas state to the above-described hydrogen fluoride solution containing an aliphatic tertiary amine is recommended. A particularly industrially advantageous method is a method in which oxalyl chloride is continuously or intermittently added in a liquid or gas state to a hydrogen fluoride solution containing an aliphatic tertiary amine, and the yield of oxalyl fluoride is Is also good. When oxalyl chloride is continuously or intermittently supplied to a hydrogen fluoride solution containing an aliphatic tertiary amine, and the reaction rate becomes slower as the concentration of the hydrogen fluoride decreases, fresh fluoryl chloride is newly added. The reaction rate can be restored by supplementing with hydrogen fluoride. The method of supplementing hydrogen fluoride is not particularly limited, and a method of continuously adding a small amount in accordance with the reaction rate at which oxalyl chloride is fluorinated during the reaction, or cooling the reaction system once if necessary and cooling it to a predetermined amount After the hydrogen fluoride is added, a method of restarting the reaction at a predetermined reaction temperature is adopted.

When the reaction temperature in the present invention is too high, by-products such as fluorinated phosgene are unavoidable, and when it is too low, the reaction rate becomes slow and the yield is lowered. Therefore, generally a reaction temperature of 0 to 100 ° C, preferably 10 to 60 ° C is adopted. Further, the reaction according to the present invention can be carried out under normal pressure, increased pressure or reduced pressure, but it is generally convenient to carry out the reaction near atmospheric pressure. According to the reaction conditions of the present invention, the reaction rate of fluorination is extremely high, and the reaction time is generally about 0.2 to 15 hours, although it varies depending on the reaction method, the reaction amount, the size of the reactor and the like.

Since oxalyl fluoride produced in the present invention has a considerably low boiling point, it can be easily taken out from the reaction system together with by-produced hydrogen chloride. When the reaction temperature is lowered, oxalyl fluoride remaining in the reaction solution can be taken out by heating after the reaction. The obtained oxalyl fluoride and hydrogen chloride can be easily separated by utilizing the difference in boiling points. In the present invention, since the amount of hydrogen fluoride entrained in oxalyl fluoride is extremely small, the oxalyl fluoride can be easily purified and can be concentrated in a cold trap by a simple separation operation such as low temperature distillation. .

[Examples] Examples will be shown below, but the present invention is not limited thereto.

Example 1 Approximately 1.5 polychlorotrifluoroethylene reactor (internal diameter 11 cm, height 15 cm) equipped with reflux condenser (cooled to 0 ° C., outlet is connected to dry ice-methanol cold lap) and stirrer. ) Was used. Tri-n in the reactor
-Add 80 g of butylamine and cool down with 400 g of anhydrous hydrogen fluoride.
Was slowly added to adjust the tri-n-butylamine-hydrogen fluoride solution.

Next, 480 g of oxalyl chloride was fed at a flow rate of 2.5 g / min into the solution of tri-n-butylamine-hydrogen fluoride with stirring while controlling the temperature at about 25 ° C. 30 after supply
The reaction was terminated by blowing nitrogen gas at a low flow rate for 15 minutes for the purpose of expelling the product remaining in the reaction solution.

What was obtained from the dry ice-methanol trap was analyzed and found to consist mostly of oxalyl fluoride and contain small amounts of hydrogen chloride and hydrogen fluoride. By rectifying this, 320.8 g (yield 90.3%) of oxalyl fluoride was obtained. The analysis was carried out by measuring the IR spectrum, ¹³ C-NMR spectrum and ¹⁹ F-NMR spectrum.

Example 2 The reaction was carried out in the same manner as in Example 1 except that the amount of oxalyl chloride supplied was 1100 g, and after the completion of the reaction, the reactor was cooled again and 300 g of anhydrous hydrogen fluoride was replenished. Using this solution of tri-n-butylamine-hydrogen fluoride, the reaction was carried out with 480 g of oxalyl chloride under the same conditions as in Example 1, and the separation operation was carried out. As a result, 321.5 g (yield 90.5%) was obtained. Oxalyl fluoride was obtained.

Example 3 480 g of a solution of tri-n-butylamine-hydrogen fluoride prepared using the same reaction vessel and method as in Example 1-20
After cooling to 0 ° C., 480 g of oxalyl chloride was added.
Then, the temperature was slowly raised to 25 ° C, and the mixture was stirred at 25 ° C for 5 hours. Then, nitrogen gas was blown at a low speed for 15 minutes to complete the reaction.

Example 1 was used to separate the product obtained by cold trap.
In the same manner as in the above, 290.3 g (yield 81.7%) of oxalyl fluoride was obtained.

Example 4 In Example 1, instead of tri-n-butylamine,
Oxalyl chloride was fluorinated using the same apparatus and following the same procedure, except that the type of aliphatic tertiary amine was triethylamine or tri-n-acylamine, and 43.5 g and 98 g were used, respectively. As a result, the yield of oxalyl fluoride was 321 g (90%) when triethylamine was used and 323 g (91%) when tri-n-acylamine was used.

Claims (1)

[Claims] 1. A process for producing oxalyl fluoride, which comprises fluorinating oxalyl chloride with hydrogen fluoride in the presence of an aliphatic tertiary amine.