KR20070038566A - Fluoromethane production process and product - Google Patents

Abstract

The present invention relates to the reaction of methyl chloride and hydrogen fluoride in the presence of a fluorination catalyst in a gas phase, and to injecting the resulting mixture containing fluoromethane and hydrogen chloride into a distillation column to separate and purify fluoromethane and hydrogen chloride as an upper layer. . In this way, HFC-41 of high purity suitable for use as a semiconductor etching gas can be effectively produced.

Description

Fluoromethane manufacturing method and product {FLUOROMETHANE PRODUCTION PROCESS AND PRODUCT}

(Cross-reference of related application)

This application claims 35 U.S.C. Under 35. U.S.C. 35 U.S.C. Claims Priority Benefits Under §119 (e) (1) An application filed under § 111 (a).

The present invention relates to a method for producing fluoromethane (CH ₃ F, hereinafter also referred to as HFC-41).

Hydrofluorocarbon (HFC) is characterized by having an ozone depletion coefficient of 0, in particular, HFC-41, difluoromethane (CH ₂ F ₂ ) and trifluoromethane (CHF ₃ ) are useful as semiconductor etching gases.

HFCs used as semiconductor etching gases should be of high purity, more specifically, the content of these acid components (hydrogen chloride, hydrogen fluoride, etc.) is preferably 1.0 mass ppm or less, and their water content is preferably 10 mass ppm or less. More preferably, it is 5 mass ppm or less.

Therefore, many methods for producing high purity HFCs have been proposed, but these are molecules having two or more carbon atoms, whereas fluorination of chloroform or fluorination of dichloromethane is related to methane having one carbon atom, and the method of preparing HFC-41 Almost not proposed. The main reason is that when the halogenated hydrocarbon is fluorinated, the larger the number of hydrogen atoms in the molecule, the lower the fluorinated reactivity and tend to promote decomposition or by-products.

Japanese Patent Application Laid-open No. Hei 4-7330 discloses a method for producing HFC-41 in which gaseous reaction of methyl alcohol and hydrogen fluoride (HF) is carried out at a temperature of 100 to 500 ° C. using a fluorination catalyst (chromium fluoride). However, the above method has a problem of deterioration of the fluorination catalyst with water as a by-product obtained as a result and corrosion of the reaction apparatus.

In addition, Japanese Patent Application Laid-open No. 60-13726 discloses a method for producing HFC-41 in which gaseous reaction of methyl chloride (CH ₃ Cl) and HF is carried out at a reaction temperature of 100 to 400 ° C. using a fluorination catalyst (chromium fluoride). It is. However, the method needs to improve the catalytic activity due to the equilibrium reaction shown in the following formula (1), HFC-41 (boiling point at atmospheric pressure: -78.5 ° C) and hydrogen chloride (boiling point at atmospheric pressure: -84.9 ° C Separation is difficult because it forms an azeotrope having a boiling point close to).

CH ₃ Cl + HF ⇔ CH ₃ F + HCl (1)

An object of the present invention is to provide a method for efficiently producing a high purity HFC-41 that can be used as a semiconductor etching gas, and a product thereof.

As a result of earnestly examining in order to solve the above-mentioned problem, the present inventors reacted methyl chloride and hydrogen fluoride in the presence of a fluorination catalyst in the gaseous phase, and injected a mixture containing fluoromethane and hydrogen chloride into a distillation column to produce fluoromethane and hydrogen chloride. It was found that HFC-41 (HCl concentration: 20 mass ppm or less) substantially free of hydrogen chloride (HCl) can be obtained by separating and purifying as an upper portion, thereby completing the present invention.

The present invention relates to a method for producing HFC-41 according to the following [1] to [11].

[1] (1) a step of bringing methyl chloride into contact with the zeolite in the liquid phase;

(2) a step of reacting methyl chloride and hydrogen fluoride obtained in step (1) in the gas phase in the presence of a fluorination catalyst to obtain mainly fluoromethane,

(3) A step of injecting the mixed gas containing fluoromethane obtained in step (2) into the distillation column, and separating the upper layer portion mainly containing fluoromethane and hydrogen chloride from the lower portion mainly containing methyl chloride and hydrogen fluoride. , And

(4) A process for producing fluoromethane, comprising a four-step process of separating and purifying fluoromethane from the upper layer portion obtained in step (3).

[2] The method for producing fluoromethane according to the above [1], further comprising the step of circulating the lower portion obtained in the step (3) to the step (2).

[3] The method for producing fluoromethane according to the above [1] or [2], wherein the zeolite used in the step (1) is molecular sieve 3A and / or molecular sieve 4A.

[4] The above-mentioned [1], wherein the fluorination catalyst used in the step (2) comprises at least one element mainly composed of trivalent chromium oxide and selected from the group consisting of In, Zn, Ni, Co, Mg and Al. A process for producing fluoromethane, which is a supported catalyst or a bulk catalyst.

[5] The above-mentioned [1] or [4], wherein the fluorinated catalyst used in the step (2) is a supported catalyst supported on activated alumina, wherein the activated alumina has a central pore size of 50 to 400 mm 3 and a ± ± center size. A method for producing fluoromethane, characterized in that the pore volume is made up of 70% or more with a distribution of 50%, the pore volume is in the range of 0.5 to 1.6 ml / g, the purity is 99.9% by mass or more, and the sodium content is 100 ppm or less. .

[6] The method for producing fluoromethane according to the above [1], [4] or [5], wherein the reaction temperature in the step (2) is 150 to 350 ° C.

[7] The method for producing fluoromethane according to the above [1], wherein the distillation in the step (3) is performed within a pressure range of 0.1 to 5 MPa.

[8] The above-mentioned [1], wherein the separation and purification step in the step (4) further includes the step of contacting the fluoromethane with a treatment agent containing water and / or an alkali to remove an acid component containing hydrogen chloride. Method for producing fluoromethane, characterized in that.

[9] The method for producing fluoromethane according to the above [8], further comprising contacting fluoromethane with zeolite after removing an acid component in fluoromethane.

[10] The method for producing fluoromethane according to the above [9], wherein the zeolite is molecular sieve 3A and / or molecular sieve 4A.

[11] A fluoromethane product obtained by the method according to any one of [1] to [10] and containing fluoromethane having a hydrogen chloride concentration of 1.0 mass ppm or less.

[12] A fluoromethane product obtained by the method according to any one of [1] to [10] and containing fluoromethane having a water concentration of 10 mass ppm or less.

According to the present invention, high purity HFC-41 can be obtained by efficiently separating HCl from a mixture of HFC-41 and HCl obtained by reacting methyl chloride and hydrogen fluoride in the presence of a fluorination catalyst in the gas phase.

In the method for producing HFC-41 according to the present invention, methyl chloride and hydrogen fluoride are used as raw materials, and these are reacted in the gas phase in the presence of a supported or bulk fluorination catalyst composed mainly of trivalent chromium oxide, and HFC-41 and HCl are reacted. The mixture containing the mixture is injected into a distillation column, and HFC-41 and HCl are distilled and purified from the top of the distillation column to obtain high purity HFC-41.

The raw material methyl chloride is preferably in contact with the zeolite in the liquid phase in a step before feeding into the reaction zone to minimize the moisture. If a stabilizer is included, this must also be removed to maintain catalyst life. Moisture incorporation into the reaction zone can adversely promote the generation of corrosion and decomposition byproducts of the device material. The zeolite is preferably molecular sieve 3A and / or molecular sieve 4A. Methyl chloride and hydrogen fluoride are mixed at the reactor inlet and introduced into the reactor. The molar ratio of hydrogen fluoride to methyl chloride (HF / CH ₃ Cl) is 5 to 30, and preferably, and more preferably 8-20. If the molar ratio is less than 5, the generation rate of impurities is increased, resulting in poor selectivity. If it exceeds 30, the yield decreases, the circulation of unreacted raw materials increases, and the size of the apparatus is required, which is not preferable.

The reactor is preferably a multi-pipe type in view of prevention of drift. The fluorinated catalyst charged in the reactor is preferably a bulk catalyst or a supported catalyst mainly composed of trivalent chromium oxide. The bulk catalyst is preferably composed of trivalent chromium oxide and preferably contains at least one element selected from the group consisting of In, Zn, Ni, Co, Mg and Al. The supported catalyst is a catalyst carrier with a pore size of 50 to 400Å, 70% or more of pores having a distribution of ± 50% of the center size, pore volume of 0.5 to 1.6ml / g, and purity of 99.9. At least one element selected from the group consisting of trivalent chromium oxide or trivalent chromium oxide, in which the active alumina is mass% or more and has a sodium content of 100 ppm or less and is selected from the group consisting of In, Zn, Ni, Co, and Mg. It is preferable to carry | support the material containing these, and 30 mass% or less of the support ratio is preferable. Prior to use in the reaction, at least part of the fluorination catalyst is preferably fluorinated (catalytically activated) by hydrogen fluoride or the like.

The reaction temperature range is preferably 150 to 350 ° C, more preferably 200 to 300 ° C. If it is less than 150 ° C, the reaction yield tends to decrease, and if it exceeds 350 ° C, impurities tend to increase. The reaction pressure range is preferably 0.05 to 1.0 MPa, more preferably 0.1 to 0.7 MPa. Below 0.05 MPa, operation is complicated, and above 1.0 MPa, the cost is increased because the device has to be designed with higher pressure resistance. The product (outlet) gas from the reaction in the reactor is, for example, cooled and introduced into the distillation column with a pump or introduced into the distillation column using a compressor. The operating pressure of the distillation column is preferably in the range of 0.1 to 5 MPa, more preferably 0.3 to 3 MPa from the viewpoint of economical efficiency and operability. The product gas introduced into the distillation column is mainly separated into HCl and HFC-41 at the top, and is mainly separated into hydrogen fluoride and methyl chloride, which are unreacted components, and at least part is circulated to the reaction process and reused.

The HFC-41 separated at the top of the distillation column contains HCl and, therefore, is contacted with a treatment agent containing water and / or alkali to remove the acid component containing HCl. The treating agent containing an alkali may be an aqueous alkali solution or a solid material containing an alkali (for example, soda lime or the like). Preferred treatment agents are water and aqueous alkali solution. Preferred aqueous alkali solutions are sodium hydroxide and potassium hydroxide, and the concentration of the aqueous alkali solution is in the range of 0.01 to 20%, particularly preferably in the range of 0.1 to 10%. Although contact time is not specifically limited, Since the solubility of HFC-41 in water is rather high, the low temperature range is preferable, and the range of 5-40 degreeC is specifically, preferable.

The HCl concentration of the acid component removed HFC-41 was 1.0 ppm by mass or less (measured by ion chromatography).

Since water is present in the HFC-41 from which the acid component has been removed, it is preferable to remove the water by contacting the zeolite. The zeolite is preferably a zeolite having a small pore size of the molecular sieve 3A and / or the molecular sieve 4A in consideration of the small molecular size of the HFC-41 and the heat generation and decomposition by the heat of adsorption. Is 10 mass ppm or less (measurement instrument: Carl Fisher).

Although an Example demonstrates this invention in detail, this invention is not limited to these Examples.

Example 1

Catalyst Preparation Example 1

In a 10 L vessel containing 0.6 L of pure water, a solution of 452 g of Cr (NO ₃ ) ₃ .9H ₂ O and 42 g of In (NO ₃ ) ₃ .nh ₂ O (n = about 5) in 1.2 L of pure water While stirring 0.3 L of 28% aqueous ammonia, the reaction solution was added dropwise for about 1 hour while adjusting the flow rates of the two aqueous solutions so that the pH of the reaction solution was within the range of 7.5 to 8.5. The obtained hydroxide slurry was filtered and thoroughly washed with pure water, and then dried at 120 ° C for 12 hours. The obtained solid was pulverized, mixed with graphite, and formed into pellets using a purifier. This pellet was ignited at 400 DEG C for 4 hours under a nitrogen stream to obtain a catalyst precursor. The catalyst was charged by charging the catalyst precursor to an Inconel reactor, followed by fluorination treatment (catalytic activation) under a nitrogen-dilute hydrogen fluoride stream at atmospheric pressure and 350 ° C., followed by a 100% hydrogen fluoride stream.

Example 2

Catalyst Preparation Example 2

The catalyst carrier has a central pore size of 50 to 400 microns, a pore volume of 70% or more with a distribution of ± 50% of the central size, a pore volume of 0.5 to 1.6 ml / g, and a purity of 99.9 mass% or more. Activated alumina (NTS-7, manufactured by Nikki Universal Co., Ltd.) having a sodium content of 100 ppm or less was used.

191.5 g of chromium chloride (CrCl ₃ · 6H ₂ O) was added to 132 ml of pure water, and the mixture was heated and dissolved in a hot water bath at 70 to 80 ° C. After cooling the solution to room temperature, 400 g of the activated alumina was immersed until the solution was all absorbed into the activated alumina. Next, the wet alumina was dried on a 90 ° C. hot water bath and cured. The cured catalyst was dried for 3 hours in an air circulating hot air dryer. The catalyst was then charged to an Inconel reactor and subjected to fluorination (catalytic activation) under a nitrogen fluoride stream of hydrogen fluoride at atmospheric pressure, 330 ° C. and then under a 100% hydrogen fluoride stream.

Example 3

Catalyst Preparation Example 3

A catalyst was obtained in the same manner as in Catalyst Preparation Example 2, except that 16.57 g of zinc chloride (ZnCl ₂ ) was added as a second component to Preparation Example 2 of Example 2.

Example 4

Commercially available methyl chloride (purity 99.9 vol%, water content 48 mass ppm) was contacted in liquid phase with zeolite (molecular sieve 3A (manufactured by Union Showa Co., Ltd., average pore size: 3 kPa)) before feeding to the reaction system. It was analyzed by a water meter (Carl Fisher) that the water in the methyl chloride is 6 ppm by mass.

80 ml of the catalyst prepared in Preparation Example 1 of the catalyst was charged to an Inconel 600 reactor having an internal diameter of 1 inch and a length of 1 m, and then maintained at a temperature of 300 ° C. and a pressure of 0.25 MPa while circulating nitrogen gas. The reaction was started by supplying 73.85 NL / hr and terminating the supply of nitrogen gas, and then supplying the zeolite treated methyl chloride at 6.15 NL / hr. After about 3 hours, the acid component in the reactor outlet gas was removed with an aqueous alkali solution and analyzed by gas chromatography. The results are as follows.

CH ₃ F 18.9470 CH ₃ Cl 80.9100

Others 0.1431 (Unit: vol%)

The methyl chloride conversion was about 19.1% and the fluoromethane selectivity was about 99.2%.

Example 5

The reaction and analysis were carried out under the same conditions and procedures as in Example 4, except that 80 ml of the catalyst prepared in Preparation Example 2 of Example 2 was charged. The results are as follows.

CH ₃ F 19.7816 CH ₃ Cl 80.0976

Others 0.1208 (Unit: vol%)

The fluoromethane selectivity was about 99.4%, yielding satisfactory results.

Next, pure water was added to the commercially available methyl chloride (water content: 48 mass ppm) to prepare a methyl chloride raw material having a water concentration of 208 mass ppm in methyl chloride. Supply of the said zeolite-treated methyl chloride was complete | finished, and the reaction was restarted by supplying the said methyl chloride of 208 mass ppm of water concentrations. After about 8 hours, the acid component in the reactor outlet gas was removed with an aqueous alkali solution and analyzed by gas chromatography. The results are as follows.

CH ₃ F 17.4412 CH ₃ Cl 82.1959

Others 0.3629 (Unit: vol%)

As can be seen from the above results, moisture in the raw material methyl chloride is not preferable because it adversely affects the reaction and lowers the conversion and selectivity.

Example 6

Reaction and analysis were carried out in the same conditions and procedures as in Example 4, except that 80 ml of the catalyst prepared in Preparation Example 3 of Example 3 was charged and the reaction temperature was 250 ° C. The results are as follows.

CH ₃ F 15.2266 CH ₃ Cl 84.7576

Others 0.0158 (Unit: vol%)

A fluoromethane selectivity of about 99.9% yielded satisfactory results.

Then, the reactor outlet gas was collected in a vessel equipped with a cooler, and the recovered mixture was distilled off. The recovered mixture was introduced into a distillation column. The distillation column has a condenser and has 20 theoretical stages (36 in fact); At the top of the tower, HCl and CH ₃ F of low boiling point components were separated and CH ₃ Cl and HF of high boiling point components were separated from the bottom of the tower. When HCl and CH ₃ F separated at the top were contacted with a 2% aqueous potassium hydroxide solution at a temperature of about 5 ° C., the HCl concentration in HFC-41 was analyzed by ion chromatography, and the HCl concentration was 0.5 ppm by mass.

After contacting the aqueous alkali solution, HFC-41 was contacted with zeolite (molecular sieve 3A (manufactured by Union Showa Ci., Ltd.), and the water content in HFC-41 was 4 mass ppm or less using a water meter (Carl Fisher). It was found that HFC-41 of high purity was obtained.

According to the present invention, since HCl can be efficiently separated from a mixture containing HFC-41 and HCl, high purity HFC-41 can be obtained, which is industrially useful.

Claims (12)

(1) contacting methyl chloride with a zeolite in a liquid phase, (2) a step of reacting methyl chloride and hydrogen fluoride obtained in step (1) in the gas phase in the presence of a fluorination catalyst to obtain mainly fluoromethane, (3) A step of injecting the mixed gas containing fluoromethane obtained in step (2) into the distillation column, and separating the upper layer portion mainly containing fluoromethane and hydrogen chloride from the lower portion mainly containing methyl chloride and hydrogen fluoride. , And (4) A process for producing fluoromethane, comprising a four-step process of separating and purifying fluoromethane from the upper layer portion obtained in step (3). The method for producing fluoromethane according to claim 1, further comprising the step of circulating the lower portion obtained in step (3) to step (2). The method for producing fluoromethane according to claim 1 or 2, wherein the zeolite used in step (1) is molecular sieve 3A and / or molecular sieve 4A. The supported catalyst according to claim 1, wherein the fluorination catalyst used in the step (2) is mainly composed of trivalent chromium oxide and contains at least one element selected from the group consisting of In, Zn, Ni, Co, Mg and Al. Or a bulk catalyst. 5. The fluorinated catalyst used in the process (2) is a supported catalyst supported on activated alumina, wherein the activated alumina has a central pore size of 50 to 400 mm 3 and a distribution of ± 50% of the central size. A method for producing fluoromethane, comprising a pore volume of 70% or more, a pore volume in the range of 0.5 to 1.6 ml / g, a purity of 99.9% by mass or more, and a sodium content of 100 ppm or less. The method for producing fluoromethane according to claim 1, 4 or 5, wherein the reaction temperature in the step (2) is 150 to 350 ° C. The method for producing fluoromethane according to claim 1, wherein the distillation in step (3) is performed within a pressure range of 0.1 to 5 MPa. The process of claim 1, wherein the separation and purification step in step (4) further comprises the step of contacting the fluoromethane with a treatment agent containing water and / or alkali to remove the acid component containing hydrogen chloride. Method for producing fluoromethane. The method for producing fluoromethane according to claim 8, further comprising contacting fluoromethane with zeolite after removing an acid component in fluoromethane. 10. The method of claim 9, wherein the zeolite is molecular sieve 3A and / or molecular sieve 4A. A fluoromethane product obtained by the method according to any one of claims 1 to 10 and containing fluoromethane having a hydrogen chloride concentration of 1.0 mass ppm or less. A fluoromethane product obtained by the method according to any one of claims 1 to 10 and containing fluoromethane having a water concentration of 10 mass ppm or less.