阅读说明：本技术 一种三氟甲烷的制备方法 (Preparation method of trifluoromethane ) 是由 耿谦 马毅斌 李金龙 倪珊珊 张雷 王利粉 付志杰 林坤 于 2020-12-15 设计创作，主要内容包括：本发明涉及一种三氟甲烷的制备方法,属于精细氟化工技术领域；将反应物与碱金属氢氧化物溶解于溶剂中形成反应溶液,加热回流,反应至没有气体生成为止,使用冷阱收集反应生成的气相产物,气相产物的沸点为-84℃,得到液态的目标产物,其主要成分为三氟甲烷,体积分数占95％以上；所述方法操作简单,并且产物三氟甲烷与微量杂质易于分离,有利于后续的纯化过程。(The invention relates to a preparation method of trifluoromethane, belonging to the technical field of fine fluorine chemical industry; dissolving reactants and alkali metal hydroxide in a solvent to form a reaction solution, heating and refluxing the reaction solution until no gas is generated, collecting a gas-phase product generated by the reaction by using a cold trap, wherein the boiling point of the gas-phase product is-84 ℃ to obtain a liquid target product, the main component of the liquid target product is trifluoromethane, and the volume fraction of the liquid target product is more than 95%; the method is simple to operate, and the product trifluoromethane and trace impurities are easy to separate, thereby being beneficial to the subsequent purification process.)

1. A method for preparing trifluoromethane is characterized in that: the method comprises the following steps:

dissolving reactants and alkali metal hydroxide in a solvent to form a reaction solution, heating and refluxing the reaction solution, reacting until no gas is generated, and collecting a gas-phase product generated by the reaction by using a cold trap to obtain a liquid target product, wherein the main component of the liquid target product is trifluoromethane;

the reactant is more than one of trifluoromethyl sulfonic acid and alkaline earth metal salt of the trifluoromethyl sulfonic acid;

the solvent is water or an alcohol solvent with the boiling point of more than 100 ℃;

the concentration of the reactant in the reaction solution is 0.05 mol/L-0.5 mol/L;

the ratio of the amounts of the reactants to the amount of alkali metal hydroxide is 1 or less;

the cold trap collection temperature is less than or equal to-100 ℃.

2. The method for preparing trifluoromethane according to claim 1, wherein the method comprises the following steps: the reactant is more than one of barium trifluoromethanesulfonate and calcium trifluoromethanesulfonate.

3. The method for preparing trifluoromethane according to claim 1, wherein the method comprises the following steps: the alkali metal hydroxide is more than one of potassium hydroxide, sodium hydroxide and lithium hydroxide.

4. The method for preparing trifluoromethane according to claim 1, wherein the method comprises the following steps: the solvent is more than one of water, diethylene glycol, tetraethylene glycol and polyethylene glycol.

5. The method for preparing trifluoromethane according to claim 1, wherein the method comprises the following steps: the concentration of the reactant in the reaction solution was 0.1 mol/L.

6. The method for preparing trifluoromethane according to claim 1, wherein the method comprises the following steps: the ratio of the amounts of the reactants to the mass of alkali metal hydroxide is 1: 1.1.

7. The method for preparing trifluoromethane according to claim 1, wherein the method comprises the following steps: the cold medium adopted in the cold trap collection is liquid nitrogen or dry ice.

8. The method for preparing trifluoromethane according to claim 1, wherein the method comprises the following steps: the cold medium adopted in the cold trap collection is liquid nitrogen.

9. The method for preparing trifluoromethane according to claim 1, wherein the method comprises the following steps: the heating reflux reaction temperature is 120-150 ℃.

10. The method for preparing trifluoromethane according to claim 1, wherein the method comprises the following steps: the reactant is more than one of barium trifluoromethanesulfonate and calcium trifluoromethanesulfonate;

the alkali metal hydroxide is more than one of potassium hydroxide, sodium hydroxide and lithium hydroxide;

the solvent is more than one of water, diethylene glycol, tetraethylene glycol and polyethylene glycol;

the concentration of the reactant in the reaction solution is 0.1 mol/L;

the ratio of the amount of the reactants to the amount of the alkali metal hydroxide is 1: 1.1;

the cold medium adopted in the cold trap collection is liquid nitrogen or dry ice;

the heating reflux reaction temperature is 120-150 ℃.

Technical Field

The invention relates to a preparation method of trifluoromethane, belonging to the technical field of fine fluorine chemical industry.

Background

Electronic gas is an indispensable basic supporting source material in the process of developing integrated circuits, photoelectrons and microelectronics, particularly ultra-large scale integrated circuits, liquid crystal display devices, semiconductor light emitting devices and semiconductor materials, is called blood and grain in the electronic industry, and the purity and cleanliness of the electronic gas directly influence the quality, the integration level, specific technical indexes and the yield of photoelectrons and microelectronic components and parts, and fundamentally restrict the accuracy and the precision of the circuits and the devices. In a silicon wafer manufacturing plant, a silicon wafer requires two to three months of process flow to complete 450 or more process steps to obtain chips with various circuit patterns. The process comprises a plurality of procedures of epitaxy, film forming, doping, etching, cleaning, packaging and the like, and high-purity electronic chemical gas and electronic mixed gas are required to be more than 30. The fluorine-containing electronic gas is mainly used as a cleaning agent and an etchant.

With the development of advanced processes of integrated circuits, silicon nitride films in shallow trench processes are chemically inert and difficult to be etched accurately, and the process affects the yield of integrated circuit manufacturing. The trifluoromethane is used as a main etchant of SiO2 and Si3N4, and can also be used as a supplementary gas of CF4 etching gas for adjusting the C/F ratio in plasma, so as to adjust the total amount and the types of high molecular byproducts in the etching process, thereby achieving the purposes of different anisotropic etching characteristics and high-selectivity etching characteristics of different base materials.

Trifluoromethane, molecular formula: CHF3, CAS number: 75-46-7, colorless flammable gas under standard conditions, molecular weight: 70.01, boiling point: -84 ℃, melting point: -155 ℃, density: 1.52(-80 ℃); the relative density is 2.43 (air is 1), the gas is nontoxic, colorless and tasteless under normal pressure, and the gas is mainly used as a refrigerant and a fire extinguishing agent in the past and is used as a novel electronic gas in the chip etching process in the field of semiconductor manufacturing at present.

Trifluoromethane (CHF)₃) As a new type of electronic gas, it is used in the field of semiconductor manufacturing for chip etching process. Trifluoromethane is used in addition to Silica (SiO)₂) And silicon nitride (Si)₃N₄) The main etchant of (2) can also be used as carbon tetrafluoride (CF)₄) The supplementary gas of etching gas is used for adjusting the C/F ratio in plasma, thereby achieving the purposes of anisotropic etching characteristics and high-selectivity etching characteristics of different base materials.

At present, the preparation method of trifluoromethane mainly comprises the following 5 methods:

1. electrolysis, i.e. electrolysis of acetic acid, acetone or methylamine in anhydrous hydrofluoric acid; however, this method is too energy-consuming to produce CHF having a purity of 5N continuously and integrally₃；

2. The method has the defects that the reaction cannot be continuous, more chlorine-containing byproducts exist, and the separation is difficult;

3. reacting antimony trifluoride or hydrogen fluoride with chloroform at 125 deg.C under pressure, which may be in accordance with CHF₃CHF with different solubility from hydrogen chloride in different solvents by solvent absorption₃And the separation of hydrogen chloride, the reaction has the defects of toxic catalyst, environmental pollution, higher temperature and more chlorine-containing byproducts.

4. Chlorodifluoromethane (CHClF)₂) In aluminium chloride (AlCl)₃) Catalytic disproportionation under the action of the current process for producing CHF₃The main method of (1). Namely CHClF₂Under certain temperature and pressure, the reaction product is first condensated to eliminate CHF₃After that, unreacted CHClF₂Entering a second-stage disproportionation reactor for further reaction. Removing trichloromethane and difluorodichloromethane from the product in the second-stage disproportionation reactor by a second-stage condenser to obtain CHF with purity of over 99.5%₃(ii) a In the reaction productIn a small amount of chlorofluoromethane, it is difficult to purify to 5N by rectification and adsorption.

5. Recovery of CHClF using membrane separation technology₂CHF as a by-product of the production₃。

CHClF₂Is an important raw material for producing tetrafluoroethylene, fluororesin and fluororubber, and is used in CHClF₂In the production process of (2), CHF is a large amount of by-product₃. It has been reported in the literature that CHClF is produced from CHClF by a two-stage three-stage membrane using a silicone rubber membrane₂CHF as a by-product is separated₃CHF with a purity of 97% can be obtained₃Even after multi-stage membrane separation techniques, purification to 5N is difficult.

Disclosure of Invention

In view of the above, the present invention aims to provide a method for preparing trifluoromethane, which is simple to operate and easy to separate the product trifluoromethane from trace impurities.

In order to achieve the purpose of the invention, the following technical scheme is provided.

A method for preparing trifluoromethane comprises the following steps:

dissolving reactants and alkali metal hydroxide in a solvent to form a reaction solution, heating and refluxing the reaction solution until no gas is generated, collecting a gas-phase product generated by the reaction by using a cold trap, wherein the boiling point of the gas-phase product is-84 ℃, and obtaining a liquid target product, wherein the main component of the liquid target product is trifluoromethane, and the volume fraction of the liquid target product is more than 95%.

Wherein the reactant is more than one of trifluoromethanesulfonic acid and alkaline earth metal salt of trifluoromethanesulfonic acid; preferably, one or more of barium trifluoromethanesulfonate and calcium trifluoromethanesulfonate.

Preferably, the alkali metal hydroxide is one or more of potassium hydroxide, sodium hydroxide and lithium hydroxide.

Wherein the solvent is water or an alcohol solvent with a boiling point of more than 100 ℃; preferably more than one of water, diethylene glycol, tetraethylene glycol and polyethylene glycol; more preferably tetraethylene glycol.

Wherein the concentration of the reactant in the reaction solution is 0.05 mol/L-0.5 mol/L; preferably 0.1 mol/L.

Wherein the ratio of the amount of the reactant to the amount of the substance of the alkali metal hydroxide is 1 or less; preferably 1: 1.1.

Wherein the collection temperature of the cold trap is less than or equal to-100 ℃.

Preferably, the refrigerant adopted in the cold trap collection is liquid nitrogen or dry ice; more preferably liquid nitrogen.

Preferably, the heating reflux reaction temperature is 120-150 ℃.

Advantageous effects

(1) The invention provides a preparation method of trifluoromethane, which uses trifluoromethane sulfonic acid and salt thereof as raw materials and water or high boiling point alcohol solvent to prepare trifluoromethane by one step through chemical reaction; the production operation is simple.

(2) The impurities generated by the method are air, carbon dioxide and a small amount of solvent steam, and the impurities have large physical property difference with trifluoromethane, can be easily separated and are beneficial to the subsequent purification process.

(3) And the subsequent purification of the trifluoromethane to prepare the electronic grade gas is facilitated because the trifluoromethane is not contacted with chlorine-containing compounds.

Drawings

FIG. 1 is an infrared absorption spectrum of the product obtained in example 1;

FIG. 2 is a gas chromatogram of the product of example 1;

FIG. 3 is a gas chromatogram of the product of example 2;

FIG. 4 is a gas chromatogram of the product of example 3.

Detailed Description

The invention is described in detail below with reference to the drawings and specific examples, but the invention is not limited thereto.

In the following examples:

and (3) identifying the substance by adopting an IS-10 infrared spectrometer.

The purity was determined using an agilent 7820 gas chromatograph.

Example 1

Dissolving 150g of trifluoromethanesulfonic acid and 62g of potassium hydroxide in 500mL of water, heating to 100 ℃, and carrying out reflux reaction until no gas is generated; collecting a gas-phase product with a boiling point of-84 ℃ generated by the reaction by using a liquid nitrogen cold trap at the temperature of-196 ℃ to obtain a liquid target product; the infrared spectrum test of the product is carried out, the result is shown in figure 1, and the comparison with the infrared spectrum of a trifluoromethane standard sample shows that the trifluoromethane is prepared in the embodiment; the product obtained in this example was subjected to gas chromatography, and the results are shown in fig. 2, and the product obtained in this example had a trifluoromethane volume fraction of 95.7% or more.

Example 2

Dissolving 165g of calcium trifluoromethanesulfonate and 44g of sodium hydroxide in 500mL of polyethylene glycol, wherein the molecular weight of the polyethylene glycol is 2000, heating to 150 ℃ for reaction, and reacting until no gas is generated; collecting a gas-phase product with a boiling point of-84 ℃ generated by the reaction by using a dry ice cold trap at the temperature of-100 ℃ to obtain a liquid target product; the product obtained in this example was subjected to a gas chromatography test, and the result is shown in fig. 3, in which the product obtained in this example contained trifluoromethane in a volume fraction of 98.5% or more.

Example 3

Dissolving 210g of trifluoromethanesulfonic acid and 27g of lithium hydroxide in 500mL of tetraethylene glycol, heating to 120 ℃ for reaction, and reacting until no gas is generated; collecting a gas-phase product with a boiling point of-84 ℃ generated by the reaction by using a liquid nitrogen cold trap at the temperature of-150 ℃ to obtain a liquid target product; the product obtained in this example was subjected to a gas chromatography test, and as a result, as shown in fig. 4, the volume fraction of trifluoromethane in the product obtained in this example was 95.5% or more.

In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.