JPH0410462B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for efficiently and simply producing oxalyl fluoride from oxalyl chloride.

Oxalyl fluoride is useful as a raw material for producing various organic fluorine compounds such as perfluorodivinyl ether. Furthermore, as a method for producing oxalyl fluoride, fluorination of oxalyl chloride is known. As the fluorinating agent for oxalyl chloride, alkali metal fluorides such as NaF and KF are usually used. In this case, the contact between the alkali metal fluoride and oxalyl chloride is carried out in a state in which the alkali metal fluoride is suspended uniformly in a suitable neutral medium such as sulfolane, tetraglyme, acetonitrile, etc., and the reaction system is A relatively high temperature of up to 130°C is usually used. however,
This method has the drawback that the reaction proceeds at the solid-liquid interface, so even if an alkali metal fluoride with a sufficiently small particle size is used, the reaction is very slow. Furthermore, although alkali metal fluorides are expensive reagents, it is a major industrial problem that only a portion of the amount used is consumed. Furthermore, not only is the reaction yield low, but also fluorinated phosgene is likely to be produced as a by-product due to the high reaction temperature.

On the other hand, although hydrogen fluoride is extremely inexpensive as a fluorination agent, it was thought to have almost no reactivity with oxalyl chloride. On the other hand, the present inventor has already proposed that oxalyl fluoride can be obtained in good yield by reacting oxalyl chloride with hydrogen fluoride in the liquid phase under vigorous stirring that exceeds the reaction activity limit (particularly Gansho 55-141985). however,
The above method also requires special stirring conditions, which makes the apparatus complicated, and requires preliminary experiments to determine the manufacturing conditions, which is cumbersome.

In view of the above, the present inventor conducted further research and found that by simply reacting oxalyl chloride and hydrogen fluoride in the gas phase, the reaction rate was surprisingly fast and the yield of oxalyl fluoride was also improved. The present invention was completed by discovering the fact that this is possible.
That is, the present invention is a method for producing oxalyl fluoride, which is characterized by reacting oxalyl chloride and hydrogen fluoride in a gas phase. Therefore, in the present invention, the raw materials oxalyl chloride and hydrogen fluoride are each converted into gases and subjected to the reaction. Generally, oxalyl chloride and hydrogen fluoride may be heated and vaporized, respectively, and then supplied in a gaseous state to a reactor and mixed. That is,
Since oxalyl chloride and hydrogen fluoride do not mix uniformly in a liquid state, it is difficult to uniformly vaporize and react the mixed liquid.

For the above raw materials, theoretically, 2 moles of hydrogen fluoride are required per 1 mole of oxalyl chloride. However, as is generally practiced industrially, it is preferred to carry out the reaction with an excess of hydrogen fluoride, for example 2.2 to 10 moles of hydrogen fluoride per mole of oxalyl chloride. In this case, excess hydrogen fluoride is recovered and reused after the reaction. It should be noted that if hydrogen fluoride contains water, oxalic acid will be produced as a by-product during the reaction with oxalyl chloride, which will reduce the yield of the target product, oxalyl fluoride, which is generally not preferred. Particularly when carrying out a reaction using a large excess of hydrogen fluoride relative to oxalyl chloride, the presence of water in hydrogen fluoride becomes a big problem, so the moisture content of hydrogen fluoride, which is generally used suitably, is is preferably 0.5% or less, more preferably 0.1% or less.

The reaction temperature of the present invention may be any temperature that allows at least oxalyl chloride to exist in a gaseous state. Therefore, even if the temperature is considerably lower than the boiling point of oxalyl chloride, the method may be carried out by supplying the oxalyl chloride to the reactor while being accompanied by an inert gas such as nitrogen or helium with a sufficient flow rate. I can do it. However, since lowering the reaction temperature slows down the reaction rate, it is generally preferable to carry out the reaction at a temperature of 40°C or higher. Furthermore, if the reaction temperature is increased, by-products such as phosgene fluoride are unavoidable, so it is generally preferred to maintain the temperature at 100°C or lower, particularly 80°C or lower.

Further, the pressure of the reaction in the present invention is not particularly limited and can be carried out at normal pressure, increased pressure, or reduced pressure.
It is generally convenient to carry out near normal pressure.

Furthermore, the reaction time of the present invention (the residence time of oxalyl chloride and hydrogen fluoride in the reactor) varies depending on the reaction temperature, the quantitative ratio of oxalyl chloride and hydrogen fluoride, the addition ratio of inert gas, etc., but generally
It is extremely advantageous industrially because the reaction takes a short time of 0.5 to 20 seconds, especially 1 to 10 seconds.

According to the present invention, the reaction yield of oxalyl fluoride from oxalyl chloride can be increased to 65% or more, and further to 80% or more. The oxalyl fluoride produced by the reaction is separated by low-temperature distillation or other means using the difference in boiling point, melting point, etc. with hydrogen fluoride, hydrogen chloride, oxalyl chloride, and other oxalyl fluorides contained in the reaction gas. can be concentrated in cold traps.

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

Example 1 Oxalyl chloride and anhydrous hydrogen fluoride are vaporized at a rate of 15.0 g and 21.0 g per hour, respectively, and the temperature is controlled at 60°C. Cross-sectional area 2 cm ² and length 39
cm stainless steel reactor (residence time 8.5 seconds). The pressure inside the reactor was approximately 1 atmosphere. The feed was continued for 2 hours, during which time components with relatively low boiling points in the gas exiting the reactor were trapped in a dry ice-methanol bath immediately after the reactor. By rectifying this, 20.1 g of oxalyl fluoride was obtained.

Claims (1)

[Claims] 1. A method for producing oxalyl fluoride, which comprises reacting oxalyl chloride and hydrogen fluoride in a gas phase.