KR100285073B1 - Vapor Chlorination of Difluoromethyl Methyl Ether - Google Patents

Abstract

This invention is of the formula CF ₂ HOCCl _x F _y H _{3+ (x + y)} (x is 0, 1 or 3 and y is 1,2 or 3 and the sum of x + y is 1,2 or 3) It relates to the synthesis of fluorinated dimethyl ether. This preparation method produces a chlorinated reaction product of the formula CF ₂ HOCH _3-z Cl _z (z is 1 or 2) by chlorinating methyldifluoromethylether in the presence of oxygen, producing CF ₂ HOCCl ₃ . Suppressed. The resulting compound undergoes fluorination reaction with HF before and after separation to obtain a fluorination reaction product containing fluorinated dimethyl ether.

Description

Vapor Chlorination of Difluoromethyl Methyl Ether

This invention relates generally to methyl difluoromethyl ether as starting material for the synthesis of fluorinated dimethyl ether, more particularly fluorinated dimethyl ether.

Such fluorinated dimethyl ethers, including bis (difluoromethyl) ether (CF ₂ O CHF ₂ ), are suitable for use as CFC substitutes, especially refrigerants, blowing agents and the like.

Bis (difluoromethyl) ether was conventionally prepared by chlorinating dimethyl ether and then separating and fluorinating bis (dichloromethyl) ether.

The chlorination process yielded a complex mixture of chlorinated dimethyl ethers, some of which were unstable in distillation and separated bis (dichloromethyl) ether in this state.

Moreover, chloromethyl methyl ether and bis (chloromethyl) ether are produced by this reaction and are carcinogens.

Another approach to the synthesis of methyl difluoromethyl ethers is Hine and Porter, Difluoromethylene in the Reaction of Methylene Derivatives, Chlorodifluoromethane and Sodium methoxide as Intermediates in Polar Reaction VIII, Journal of the American chemical society 17, 5493-6, 1957. This reference describes a reaction mechanism for synthesizing a preferred difluoromethyl-methyl-ether with by-product trimethylorthoformate in a batch reaction while simultaneously refluxing the unreacted feedstock.

However, this reaction not only produces a large amount of trimethylorthoformate, but also the product itself is destroyed by trimethyl orthoformate to obtain the required difluoromethyl methyl ether in a preferable yield or less.

U. S. Patent No. 5,185, 474 describes a technique for eliminating and eliminating unstable compounds and the production of such carcinogens by using methyldifluoromethyl ether as starting material.

The methyldifluoromethylether is chlorinated to produce a reaction mixture comprising at least one compound of the general formula CF ₂ HOCH ₃ - _z Cl _z (Z is 1,2 or 3).

This mixture may then be fluorinated or separately fluorinated either by first separating the chlorine compound from the mixture.

However, when chlorinating CF ₂ HOCH ₃ , the dispersion of the product is difficult to control. The molar flow rates of Cl ₂ and CF ₂ HOCH ₃ can be manipulated to obtain some of the major compounds, CF ₂ HOCH ₂ Cl or CF ₂ HOCHCl ₂ , but a significant amount of CF ₂ HOCCl ₃ is produced. Subsequently, when the fluorinated preferred product is CF ₂ HOCH ₂ Cl or CF ₂ HOCHCl ₂ , the production efficiency of CF ₂ HOCCl ₃ decreases considerably in its treatment efficiency.

It is therefore an object of this invention to provide an improvement in the process for the preparation of bis (difluoromethyl) ether.

Another object of the present invention is to provide a technique for producing a bis (difluoromethyl) ether, which enables various necessary separations by distillation without risk of explosion and yield loss due to the significant instability of various intermediates.

Yet another object of the present invention is to provide a method for efficiently preparing difluoromethyl methyl ether.

The present invention can overcome the conventional technical problem, and the present invention provides a method for preparing difluoromethylmethyl ether. More specifically, the method of the present invention includes means for selectively inhibiting the production of CF ₂ HOCCl ₃ and does not produce carcinogens as intermediates.

Some of the complex mixtures of unstable chlorinated ethers of the prior art are removed by using methyldifluoromethylether as a carcinogen, and in this invention as a starting material.

The methyldifluoromethylether is chlorinated to obtain a chlorinated reaction mixture comprising at least one compound of the general formula CF ₂ HOCH ₃ - _z Cl _z (z is 1,2 or 3), the compound being chlorine It can be easily separated from the reaction mixture.

The chlorination of methyl difluoromethyl ether generally yields only three derivatives (ie z = 1, z = 2 and z = 3).

Dichloromethyl difluoromethyl ether (z = 2) is easily separated from the chlorination reaction mixture and then fluorinated (with or without such separation) to form bis (difluoromethyl) ether.

The production of CF ₂ HOCCl ₃ (z = 3) can be inhibited and any product can be separated from the chlorinated reaction product and fluorinated.

The chlorination product itself can also be fluorinated (without prior separation) as follows:

All of the above products are useful as refrigerants, in particular (I) monofluoromethyl difluoro-methylether and (II) bis (difluoromethyl) ether can be replaced with R-11 and R-114 refrigerants, respectively. .

Methyldifluoromethylethyl, the starting material of the process of the invention, is a known compound, which compounds can be prepared by the methods reported by Hine and porter in the above references. In particular, difluoromethyl methyl ether is produced by the reaction of sodium methoxide (NaOMe) with chlorodifluoromethane (CF ₂ HCl), the reaction being represented as follows:

In summary, this method produces a alcohol solution of sodium methoxide and slowly bubbles the chlorodifluoromethane into the reaction mixture to obtain methyldifluoromethyl ether as a residue in the reaction mixture. This is included.

Some products may be entrained with unreacted CF ₂ HCl and separated by distillation.

The starting ether, CHF ₂ OCH _3, may also be prepared by first reacting NaOH with CH ₃ OH to effectively produce CH ₃ ONa and then reacting with CF ₂ HCl.

The effect water then produces CHF ₂ OCH ₃ in the reaction to reduce the yield of CHF ₂ OCH ₃ .

The chlorination and fluorination processes of this invention are shown as follows:

The inventors of the present invention confirmed that the production of CF ₂ HOCH ₃ - _z Cl _z (z = 3) in the above scheme can be suppressed or eliminated when an oxygen source, preferably air, is added to the gas phase reaction medium.

Rather than the same inhibition of the three chlorinated products, oxygen addition selectively inhibits the production of CF ₂ HOCl ₃ beyond expectations.

This invention is not limited to any mechanism theory, but the inhibition of oxygen as it forms complexes with active chlorine molecules causes the kinetic energy of the reaction to selectively inhibit the trichloro derivative.

Any oxygen source that is not harmful to the production of the desired compound can be used, including oxygenated compounds that liberate oxygen from the original compound.

The oxygen must be present in an amount effective for its desired inhibition.

In the case of the air, it is preferable to add the air in an amount of about 1.5 to about 5.5% of the total gas amount.

The skilled person is preferred to add an oxygen source to the reaction medium when the chlorine gas flows when using pure oxygen, the amount being about 1/5 of the amount of air.

It was recognized that CHF ₂ OCH ₃ can be appropriately chlorinated by irradiating with a visible light source while liquefying CHF ₂ OCH ₃ and reacting with chlorine gas. In addition, other light sources such as ultraviolet light or heat, a catalyst or a free radical initiator may be used to assist in this reaction.

The chlorinated product of CHF ₂ OCH ₃ can be easily separated before fluorination, and the reaction mixture is fluorinated without separating to give CF ₂ HOCCl ₂ F, CF ₂ HOCF ₂ Cl, CF ₂ HOCH ₂ F, CF _A mixture of ₂ HOCFHCl and CF ₂ HOCF ₂ H can be obtained, and all separation can be carried out by separate distillation.

A preferred method of chlorin screen the CHF ₂ OCH ₃ is sikineunde a light source, preferably a chlorine reaction with visible light or ultraviolet light, while the reaction with chlorine gas to maintain the CHF ₂ OCH ₃ in the vapor phase (Vapor phase). Further, other reaction aids such as catalysts, heat or free radical initiators can be used in the chlorination reaction.

In the preferred fluorination plant, the chlorination product reacts with anhydrous hydrogen fluoride (HF), which can be represented by the following scheme:

By using the above reaction with hydrogen fluoride, the applicant obtained a high yield of a small amount of CF ₂ HOCFCl ₂ and 78% CF ₂ HOCF ₂ Cl.

This is more than expected. The reason is that HF itself can replace halogen such as chlorine by the continuous regeneration of fluorinating agents of SbCl _5-y F _y such as SbF ₃ or SbF ₃ Cl ₂ instead of fluorinate. Because there is not.

The difluoromethoxy group activates its chlorine on an alpha-carbon atom to facilitate reaction with HF.

In addition, the HF is distilled with an organic solvent, preferably a dipolar aprotic solvent such as methylpyrrolidone to reduce the cleavage of the fluorinated substance, thereby producing a high yield of the desired product with less by-products. Get

Other fluoro rinwon of hydrofluoric process, _{KHF 2, NaHF 2, LiHF 2} , NH 4 HF 2 , etc. HF ₂ There are metal fluorides which can form HF and pyridine salts of NaF and KF in salts of anions and suitable solvents.

The resulting fluorinated product can be separated by distillation or by the treatment described in US Pat. Nos. 4,025,567 or 3,887,439, which are hereby incorporated by reference.

Next, the present invention will be described in more detail with reference to the following examples.

Example 1

a) Preparation of CF ₂ HOCH ₃

A 25 wt% solution in which sodium methoxide was dissolved in 7.1 mol-containing methanol (1533.1 g) in sodium methoxide was placed in a 4 liter jacketed autoclave equipped with a temperature sensor, a pressure gauge and a diptag.

The vessel was cooled to 0-5 [deg.] C. and chlorodifluoromethane (318.2 g, 3.70 mol) was added over 2.5 hours with stirring.

When gas addition was complete, the gaseous product was vented into a collection trap cooled to about -7 ° C through a water-cooled condenser.

Upon recovery of all volatiles, unreacted CHF ₂ Cl was removed at −20 ° C. and residual CF ₂ HOCH ₃ was transferred to a metal cylinder. The recovered difluoromethyl methyl ether (150.0 g, 1.88 mol) gave a yield of 49.4% based on CF ₂ HCl.

b) Chlorination of CF ₂ HOCH ₃

Pass the gaseous chlorine and CF ₂ HOCH ₃ through a separate condenser cooled to 0 ° C, then combine the gas streams and pass them through one arm of the U-shaped reactor to the visible or UV Was investigated.

The head of the reactor was jacketed and cooled with water.

The bottom of the U-shaped reactor has an outlet and a product recovery flask is attached to the reactor.

Dewar type condenser cooled to -50 ℃ is attached to the second arm outlet of U-shaped tube, and it is continuous to cold trap and NaoH scrubber to recover unreacted chlorine. To remove Hcl.

This reaction is normally carried out at atmospheric pressure but higher or lower pressures may be used. The temperature should not rise above 50 ° C. in the reactor to avoid attack on the glass.

Indeed, the device was flushed with nitrogen and then fed chlorine and CHF ₂ OCH ₃ to the reactor at a rate such that the flow rate ratio of chlorine's U-ring ratio and ether was maintained at about 2.5: 1. Yield of ₂ HOCHCl ₂ is obtained.

The product of any one of the three products can be obtained by changing the ratio of the gas flow rate.

After passing 2.3 moles of chlorine and 0.9 moles of CHF ₂ OCH _3, 136.6 g of the product was recovered.

The mixture of products was GC analyzed to show CF ₂ HOCH ₂ Cl 10.0%, CF ₂ HOCHCl ₂ 62.4% and CF ₂ HOCCl ₃ 22.2%.

c) Fluorination of CHF ₂ OCHCl ₂ with HF

Chlorinated CHF ₂ OCH ₃ (40.0 g) containing 46.1% CF ₂ HOCHCl _{2 in a} stainless steel cylinder was ice cooled before addition of anhydrous HF (30.0 g). The cylinder was sealed with a valve and pressure gauge and then placed in a water bath at 60 ° C. for 3 hours.

The cylinder is then evacuated through a NaOH scrubber to remove the volatiles.

Recovered to trop cooled to -70 ℃.

The heavy ring of the product recovered from the trap was 16.8 g.

The product contained 71.8% CF ₂ HOCF ₂ F by GC analysis, corresponding to a yield of 83.8% CF ₂ HOCF ₂ H.

When carried out on a large scale (ie 5 gallons), the yield of CF ₂ HOCF ₂ H (based on CF ₂ HOCHCl ₂ ) was obtained almost quantitatively.

Example 2

A sample of a chlorinated difluoromethyl ether mixture (25 g) containing 50% CF ₂ HOCCl ₃ was prepared from another polyethylene containing an inlet tube of nitrogen as a carrier gas and a NaOH solution (10%). The flask was placed in a polyethylene flask equipped with an outlet tube leading to the flask, followed by a dry tube and a trap cooled in dry ice / MeoH.

Excess anhydrous hydrogen fluoride was added to the chlorinated ether and mixtures thereof with stirring with a magnetic stirrer.

The temperature was maintained at about 20 ° C. without heating.

More hydrogen fluoride was added to the mixture as needed until all organics reacted. The weight of the material recovered in the cold trip was 9.5 g.

The recovered product was shown to be composed of 84.3% CF ₂ HOCH ₂ Cl by GC analysis, yielding a yield of 78% based on the CF ₂ OCCl ₃ content of the chlorinated mixture. Small amounts of CF ₂ HOCFCl ₂ were also present.

Example 3

The chlorination unit consists of two vertical lengths of four-feed, 2-inch-diameter jacketed glass tubes connected to the lower end of the U-shaped tube by a short, non-jacketed inner-diameter 2-inch tube.

The exhaust tube was guided at the lowest point of the U-shaped tube array so that the product was continuously produced in the unit to be recovered when removed or alternately accumulated in the receiver.

Three 150-watt incandescent lamps were set according to the length of each tube.

The gas was supplied to the upper end of the one arm of the U-shaped tube array. The flow rate was measured by a graduated flow meter.

The cold capacitor on the other arm outlet of the U-shaped tube brought unreacted E-152a and chlorine back to the irradiation zone.

Hydrogen chloride by-product and air were passed through the condenser to enter a water scrubber to remove the hydrogen chloride.

The mixed liquid of methanol and water cooled to 0 ° C to 5 ° C was purified through the cooling jacket of the device.

In a typical operation, a coolant with a temperature of 0-5 ° C. was circulated through a cooling jacket, the incandescent lamp was turned on, and dry ice was placed in the low temperature capacitor.

Chlorine was first introduced into the device, followed by difluoromethyl ether and air at the desired ratio.

The product was removed at intervals from the receiver and washed with saturated NaHCO ₃ solution to remove HCl.

The reaction continued, so it was treated for the desired time.

It was to be discharged from the vertical reactor tube to the receiver.

As a result, the data shown in Table 1 were obtained.

Examples 6-29-1 to 6-29-7 show the distribution of products normally obtained without adding air to the gas stream.

Examples 7-7-3 to 7-8-6 show the effect of air addition while reducing the amount by this invention.

TABLE 1

Claims (11)

In the method for preparing fluorinated dimethyl ether of the following formula, CHF ₂ OCH ₃ is chlorinated by the reaction of CHF ₂ OCH ₃ with chlorine in the presence of oxygen, and at least one CF ₂ HOCH _3-z C1 _z (z is Generating a chlorinated mixture comprising the compound of 1 or 2) to inhibit the production of CF ₂ HOCCl ₃ ; Hydrogen fluoride, hydrogen fluoride anhydrous, HF ₂ , A fluorine source selected from the group of metal salts of NaF, KF and pyridine salts of HF and at least one compound of the formula CF ₂ HOCH _3-z Cl _z in the presence of a catalyst to fluorinate the formula CF ₂ HOCH Method for producing a fluorinated mixture comprising at least one compound of _3-z F _y Cl _zy . CF ₂ HOCCl _x FyH _{3- (x + y) In the above} equation, x is 0, 1 or 2, y is 1, 2 or 3, and the sum of x + y is 1,2 or 3. The method according to claim 1, wherein the chlorination process is performed by gas phase or liquid phase, and the chlorine is liquid or gas. The gastric preparation method according to claim 1, wherein the chlorination process is carried out in the gas phase and the chlorine is a gas. The method according to claim 1, wherein the hydrogen fluoride is selected from the group of anhydrous hydrogen fluoride and hydrogen fluoride in an organic solvent. The method of claim 1, wherein at least one compound of the formula CF ₂ HOCH _3-z Cl _z is CF ₂ HOCHCl ₂ , and the fluorination reaction product comprises CF ₂ HOCF ₂ H and CF ₂ HOCHFCl. Manufacturing method. The compound of claim 1, wherein at least one compound of the formula CF ₂ HOCH _3-z Cl _z is CF ₂ HOCHCl _2, and at least one compound of the formula CF ₂ HOCCl _x F _y H _{3- (x + y)} is CF ₂ HOCF ₂ H, characterized in that the separation and recovery of CF ₂ HOCF ₂ H in the fluorinated mixture. The method according to claim 1, wherein the chlorination reaction is carried out at a temperature and pressure sufficient to maintain CF ₂ HOCH ₃ in the gas phase. The method according to claim 1, wherein the alkali metal methoxide is reacted with CHF ₂ Cl in a solvent solution to produce CHF ₂ OCH ₃ . The method of claim 1, wherein the air is an oxygen source. At least one compound of the formula CF ₂ HOCH _3-z Cl _z (z is 1 or 2) by chlorination of CHF ₂ OCH ₃ by the reaction of CHF ₂ OCH ₃ with chlorine in the process for preparing fluorinated dimethyl ether To produce chlorinated contaminants, wherein at least one compound of the formula CF ₂ HOCH _3-z Cl _z is selected from the group consisting of hydrogen fluoride, anhydrous hydrogen fluoride, metal salts of HF ₂ ⁻ , NaF, KF and pyridine of HF. Fluorination without a catalyst with fluorine selected from the group of salts yields a fluorinated mixture containing at least one compound of the formula CF ₂ HOCH _3-z Fl _y Cl _zy , and the chlorination reaction is carried out in the presence of oxygen And a means for suppressing the production of CF ₂ HOCCl ₃ . CF ₂ HOCCl _x F _y H _{3- (x + y)} where x is 0,1 or 2, y is 1,2 or 3 and the sum of x + y is 1,2 or 3. 11. The method of claim 10 wherein the air is an oxygen source.