JPS6023334A - Production and purification of 3,3,3-trifluoro-2- trifluoromethylpropene - Google Patents

Abstract

PURPOSE:To produce the titled compound in high yield, with a simple process, by heating an easily handleable 1,1,1,3,3,3-hexafluoropropane-2,2-diol.dihydrate and a ketene-producing compound in a reaction tube heated at a specific temperature. CONSTITUTION:The titled compound useful as an intermediate of polymer or various fluorine-containing compounds, economically, by heating 1,1,1,3,3,3- hexafluoropropnae-2,2-diol.dihydrate and a ketene-producing compound in a reaction tube maintained at 450-650 deg.C, and washing the resultant reaction product gas with concentrated sulfuric acid to remove the organic by-products. The washing of the reaction gas with concentrated sulfuric acid results in the remarkable improvement in the purity of the titled compound without causing the loss of the compound, and exhibits remarkable effect to remove the water entrained in the reaction gas by the water-washing and/or alkali-washing treatment carried out prior to the sulfuric acid washing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing and purifying 5.3.3-trifluoro-2-trifluoromethylpropene (hereinafter abbreviated as HFIB).

If it is more useful than HF as a raw material for polymers or as an intermediate raw material for various fluorine-containing compounds, it can be produced by various methods. 142504
No.), ■Hydrolysis of octafluoroisobutyl lower alkyl ether.

Methods such as reduction and dehydration (Japanese Unexamined Patent Publication No. 56-90026) have been proposed, but method (2) has the disadvantage of having to handle hexafluoroacetone, which is a toxic gas, and method (2) requires the use of raw materials. However, these methods were not necessarily desirable, as they were difficult and required a long process.

The present invention is easy to handle.1. lj, 3.3-hexafluoropropane-2,2-diol dihydrate (boiling point +06°C.

(hereinafter abbreviated as HFW) and a ketene-generating compound from 450 to
The present invention provides a method for producing HF with high yield through a simple process of heating in a reaction tube maintained at 650°C.

The ketene-generating compound is at least one compound selected from acetic acid, acetic anhydride, acetone, and diketene, and this compound is expected to generate ketene by heating in a reaction tube maintained at 450 to 650°C. be. It is known that ketene generally reacts rapidly with water to produce acetic acid. In the present invention, water is brought in from the HFW, and although water coexists in the reaction system, ketene is constantly reacted with water. This was achieved by discovering the unique fact that the reaction can be carried out efficiently at high pressure.

Although details of the reaction mechanism remain unclear, the mechanism is presumed to be as follows (Formula 1).

!・0＼. From 10 F''・10 CO□+3H20 H2 HF (Formula I) In the present invention, the raw materials are introduced into the reaction tube through a vaporizer, if necessary.The vaporizer is heated at a temperature sufficient to vaporize the ketene-generating compound. That is, the temperature is maintained at 50 to 500° C. The following three methods can be used to mix HFW and the ketene-generating compound, but there is no difference in production compared to HF, and the method is not particularly limited to these.

(Method 1) HFW and a ketene-generating compound are mixed in advance in a liquid state, the mixture is introduced into a vaporizer, and the vaporized mixture is subsequently introduced into a reactor to obtain HF. This method has the advantage that the ratio of amounts of HFW and ketene generating compound can always be kept constant.

(Method 2) A method for obtaining 5HF by vaporizing HFW and a ketene-generating compound in separate vaporizers, and then mixing the vaporized solid compounds and introducing them into a reactor.

(Method 3) A ketene-generating compound is introduced into a reaction tube (l) maintained at a temperature sufficient for ketene generation, that is, 450 to 650°C, and at the outlet of the reaction tube, HF, which has been vaporized in advance with a vaporizer, is
By mixing with W and guiding the mixed gas to the reaction tube (2),
Q How to get more than HF.

The molar ratio of the ketene-generating compound to HFW used in the present invention is in the range of 1 to 5 times the mole of ketene, more preferably 2 to 4 times the mole.

The reaction gas (containing HFIB gas) that exited the reaction tube was passed through an air-cooled trap, water washing, and alkali washing before being transferred to a cooling trap (-78
℃). High-boiling substances such as water and acetic acid contained in the reaction gas are removed by air-cooled trap and water washing.
Carbon dioxide gas is removed by alkaline cleaning. Crude HFIB condenses and accumulates in the cooling trap, but Kigumi HF''IB contains several to several types of low boiling point, by-product impurities (e.g. 3,3
．． :5-trifluoropropene). In principle, these low-boiling impurities can be removed by low-temperature distillation or addition.
- It has been found that it is more separable than HF by pressure distillation. However, separating various impurities with various boiling points by distillation alone involves a loss of HFIB in the distillation purification process, and an increase in the amount of impurities may result in a loss of HFIB in the distillation purification process. leading to an increase in Therefore, there is a strong demand for a method that can significantly increase the purity compared to HF without causing any loss in purity before the distillation purification process. The present inventors investigated various methods for separating and removing such low-boiling point impurities from HFIB, and found that by washing the gas from crude HF with concentrated sulfuric acid, the pH was reduced.
It has been found that a significant increase in the purity of HFIB (HFIB) results without any loss from F. Even more advantageously, washing of the reactant gas with concentrated sulfuric acid can be replaced with water washing and /'!l+ Alkaline cleaning is also very effective in removing moisture entrained in p-reactant gases.Cleaning of reaction gases with concentrated sulfuric acid can be easily done by using normal gas cleaning methods such as packed column type or bubble column type. The temperature of the sulfuric acid is not particularly specified, but it is convenient to use it at room temperature.

The concentration of concentrated sulfuric acid gradually decreases from the initial concentration (industrial grade 98% by weight of sulfuric acid) due to the absorption of impurities and entrained water, but when it decreases to 70% by weight, the impurity removal ability begins to decrease slightly. was discovered.

HFIB produced and purified according to the present invention can be easily fractionated by low temperature distillation or pressure distillation to provide highly purified HFIB.

The reaction tube is required to maintain sufficient strength at 450 to 650°C, and materials that yield good results include glass, alumina, and porcelain.

Copper, brass, etc. It has been observed that iron, stainless steel, and nickel accelerate the decomposition of HFW and the undesirable decomposition reactions of ketene-generating compounds, resulting in a decrease in the yield of HFIB,
Both purity is reduced as much as possible.

EXAMPLES The present invention will be described in more detail below with reference to Examples.

Example 1.1.1.5j, 3-hexafluoropropane-2,
A mixture of 2-diol dihydrate (HFW) 22Of (1 mol) and acetic anhydride 224F (2 mol) was pumped using a metering pump at a rate of 135E per hour with an inner diameter of 31fi and a length of 450 mm.
It was introduced into a copper reaction tube (SV-180Hr').
). Front part of the reaction tube! 15 is 200 to 25 as the carburetor part
The temperature is maintained at 0℃, and the rear 2/3 is heated to 550℃ as a reactor section.
The temperature was maintained at 570°C. The inside of the reaction tube was filled with a 7-mesh porcelain Rahitsuri ring (porosity: 70 cm). The reaction gas discharged from the reactor was passed through an air-cooled trap, water washing, alkali washing, and sulfuric acid washing, and then led to a cooling trap (-78°C). 2
Through the reaction for 2 hours, 285 ff of the raw material mixture was fed, and a product 2BOf (recovery rate 98.9%) was obtained. Of these, organic matter (from crude HF: purity 98.
5%)95. zy was condensed (yield 27.8cm: feed H
FW i standard). Distillation of this yielded 75p IF (purity 99.998p).

Example 2 1.1.1,5,5.5-hexafluoropropane-2
, 2-diol dihydrate (HFW) and diketene were each introduced into respective glass vaporizers maintained at 170°C by metering pumps [: HFW, sy4. Samurai to diketene 7.5, diketene/H'FW (molar ratio) -5,
3]. Both HFW and diketene gases coming out of the vaporizer are 550
A glass reactor (inner diameter 21.5
m.

(length 500+u+) (at SV-500") The reaction gas coming out of the X reactor was passed through an empty trap, water washing, alkali washing, and then led to a cold trap (-78°C). After 15 hours of reaction, HFW 220y (1 mol) and diketene 2f (1.33 mol) were introduced to obtain the product 322f (97% recovery).

Of these, organic matter (crude HFIB: purity 8
172y was condensed (yield: 84y).

This crude HFIB was purified with sulfuric acid before distillation. That is, crude H'F I B is converted into gaseous state (2
When the mixture was passed through a gas washing bottle containing 5005E'i of concentrated sulfuric acid at 0°C), 15Tf of organic matter was recovered. The purity is 98.5 from HF in the recovered organic matter.
%, and there was virtually no loss of HF'IB in this sulfuric acid gas scrubbing operation.

This crude HFIB was distilled under pressure at 2ν/cm G (column top temperature 17°C, methyl temperature 1180°C) to 115F
(purity 99,9998%) was obtained from purified HF.

Example 3 Glacial acetic acid'i instead of acetic anhydride as a ketene-generating compound
Use 4 times the molar amount for HFW, EIV=100Hr
6.6 under exactly the same reaction conditions as in Example 1 except for
The reaction was carried out for several hours, and when all 36.99 y of the raw material mixture was fed, 55.2 y of product was obtained (recovery rate 95.
5%). Of these, 8.
7y organic matter is condensed, and this material has an HFIBN degree of 98.
It had a composition of 7% (yield: 65.6%).

Example 4 A7Tone'1 instead of acetic anhydride as a ketene-generating compound
Using 4 times the mole of HFW, eV-18010-Hr'' and Tomo et al.
The reaction was carried out for 3 hours, and all 25.1y of the raw material mixture was fed. 17.57% of product was obtained (69.8% recovery), and a significant amount of gas that did not condense in the cold trap (-78°C) was discharged from the system. Organic matter at 9.6F was condensed in the cold trap, and had a composition with a purity of 71.9F compared to Kononoke HP (yield 76%).

Patent applicant: Central Glass Co., Ltd. 11-

Claims (1)

[Claims] 3.3 The method is characterized in that heating is performed in a supported reaction tube.
．． 3-) Method for producing refluoro-2-trifluoromethylpropene. (2) 1.1. L3.13-hexafluoropropane-2,2-diol dihydrate and ketene-generating compound 4
3,3,5-trifluoro-2-, which is characterized in that organic by-products are removed by washing the reaction product gas obtained by heating in a reaction tube maintained at 50 to 650°C with concentrated sulfuric acid. A purification method involved in the production of trifluoromethylpropene.