阅读说明：本技术 一种一氟甲烷的制备方法 (Preparation method of monofluoromethane ) 是由 李金龙 耿谦 徐海云 林坤 张琴 郑秋艳 郑艺 闫云 于 2020-09-30 设计创作，主要内容包括：本发明涉及一种一氟甲烷的制备方法,属于精细氟化工技术领域。通过将碳酸二甲酯与碱金属氟化盐溶解于聚醚类溶剂中,加热至100℃～200℃回流反应,反应至没有气体生成；使用低温冷阱收集反应气相产物,气相产物的沸点为-78℃,得到一氟甲烷粗产物,其中主要成分为一氟甲烷,纯度为93％以上；所述粗产品经过纯化后,得到纯度大于99.5％的一氟甲烷。所述方法绕开具有高毒且潜在致癌的硫酸二甲酯生产工艺路线,通过一步化学反应制备一氟甲烷；具有生产方法简单、原料无毒性且副产物极少的特点,粗产物可以提纯至电子级。(The invention relates to a preparation method of fluoromethane, belonging to the technical field of fine fluorine chemical industry. Dissolving dimethyl carbonate and alkali metal fluoride in a polyether solvent, heating to 100-200 ℃ for reflux reaction, and reacting until no gas is generated; collecting a reaction gas-phase product by using a low-temperature cold trap, wherein the boiling point of the gas-phase product is-78 ℃ to obtain a crude monofluoromethane product, wherein the main component is monofluoromethane, and the purity of the monofluoromethane product is more than 93%; and purifying the crude product to obtain the monofluoromethane with the purity of more than 99.5 percent. The method bypasses the production process route of dimethyl sulfate which is highly toxic and potentially carcinogenic, and prepares monofluoromethane through one-step chemical reaction; the method has the characteristics of simple production method, no toxicity of raw materials and few byproducts, and the crude product can be purified to electronic grade.)

1. A method for preparing monofluoromethane, which is characterized in that: the method comprises the following steps:

(1) dissolving dimethyl carbonate and alkali metal fluoride in a polyether solvent, heating to 100-200 ℃ for reflux reaction, and reacting until no gas is generated;

(2) collecting a reaction gas-phase product by using a low-temperature cold trap, wherein the boiling point of the gas-phase product is-78 ℃ to obtain a crude monofluoromethane product, wherein the main component is monofluoromethane, and the purity of the monofluoromethane product is more than 93%;

the ratio of the amounts of dimethyl carbonate, alkali metal fluoride salt and polyether solvent is 1:2.2: 5-10.

2. The process according to claim 1, wherein: the alkali metal fluoride is at least one of potassium fluoride, cesium fluoride and sodium fluoride.

3. The process according to claim 1, wherein: the polyether solvent is at least one of diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether and methyl ether-terminated polyethylene glycol.

4. The process according to claim 1, wherein: the polyether solvent is tetraethylene glycol dimethyl ether.

5. The process according to claim 1, wherein: the low-temperature refrigerant is liquid ammonia or dry ice.

6. The process according to claim 1, wherein: the low-temperature refrigerant is liquid nitrogen.

7. The process according to claim 1, wherein: the alkali metal fluoride is at least one of potassium fluoride, cesium fluoride and sodium fluoride;

the polyether solvent is at least one of diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether and methyl ether-terminated polyethylene glycol;

the low-temperature refrigerant is liquid ammonia or dry ice.

8. The process according to claim 1, wherein: the alkali metal fluoride is at least one of potassium fluoride, cesium fluoride and sodium fluoride;

the polyether solvent is tetraethylene glycol dimethyl ether;

the low-temperature refrigerant is liquid nitrogen.

9. The method according to any one of claims 1 to 8, wherein: the crude product of the monofluoromethane is washed by potassium hydroxide aqueous solution, dried by a molecular sieve and removed with light components and heavy components by a continuous rectifying tower, and then the monofluoromethane with the purity of more than 99.5 percent is obtained.

Technical Field

The invention relates to a preparation method of fluoromethane, 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. In recent years, electron-grade monofluoromethanes have often been targeted to CH processes₂F₂Argon and oxygen mixture are widely used for etching silicon nitride films, have high selectivity ratio to SiO and Si, and CF₄Cannot be substituted by each other. The manufacturing process of Fin-FET, 3D-NAND and DRAM semiconductor devices is in great demand.

Monofluoromethane, formula: CH (CH)₃F, CAS number: 593-53-3, colorless flammable gas under standard condition, molecular weight: 34.0, boiling point: -78.2 ℃, melting point: -142 ℃, density: 0.88(-78 ℃); has a relative density of 1.20 (air is 1), and is nontoxic and non-toxic under normal pressureThe odorless gas has a Global Warming Potential (GWP) value of 7, is mainly used as a methylating agent in organic synthesis in the past, and is currently used as a novel electronic gas in a chip etching process in the field of semiconductor manufacturing.

At present, the preparation method of monofluoromethane mainly adopts the following three methods:

1. heating potassium fluoride and dimethyl sulfate in water or sulfone solvent, and collecting gas product, mainly comprising fluoromethane, possibly containing a small amount of methyl ether; the method involves the following chemical reaction formula:

the method has the advantages that the gas impurities are few, and the purification is easy; the disadvantage is that dimethyl sulfate is a highly toxic compound and has a carcinogenic potential (Daikin US2016168060/Central Glass JP 5716482).

2. Methane fluoride is prepared by using methane chloride as a raw material and reacting hydrogen fluoride with a catalyst (Cat), and the method relates to a chemical reaction formula as follows:

the method has low conversion rate and a plurality of gas phase byproducts (HCl, HF, CH)₃Cl、CH₂FCl、CH₄、C₂H₄) Has the disadvantage of being difficult to purify to the electronic grade standards of semiconductor manufacturers.

3. The method takes monofluorodichloromethane or monofluorochloromethane as raw material to perform hydrodechlorination reaction with hydrogen in the presence of a noble metal catalyst to prepare monofluoromethane, and the method relates to the following chemical reaction formula:

the method has the defects of short service life of the catalyst, large amount of corrosive gas and various halogen substituted products contained in the product, and difficulty in separation and purification.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention aims to provide the preparation method of the monofluoromethane, which has the characteristics of simple production process, low raw material toxicity and easy separation and purification of the monofluoromethane product, and the monofluoromethane prepared by the method has the purity of more than 5N after purification, thereby meeting the requirements of semiconductor manufacturing.

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

A method for preparing monofluoromethane, which comprises the following steps:

(1) dissolving dimethyl carbonate and alkali metal fluoride in a polyether solvent, heating to 100-200 ℃ for reflux reaction, and reacting until no gas is generated;

(2) collecting a reaction gas-phase product by using a low-temperature cold trap, wherein the boiling point of the gas-phase product is-78 ℃ to obtain a crude monofluoromethane product, wherein the main component is monofluoromethane, and the purity of the monofluoromethane product is more than 93%;

preferably, the alkali metal fluoride salt is at least one of potassium fluoride, cesium fluoride and sodium fluoride.

Preferably, the polyether solvent is at least one of diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether and methyl ether-terminated polyethylene glycol, and more preferably tetraethylene glycol dimethyl ether.

The ratio of the amounts of dimethyl carbonate, alkali metal fluoride salt and polyether solvent in the reaction system is 1:2.2: 5-10.

The crude product of the monofluoromethane is washed by a potassium hydroxide aqueous solution, dried by a molecular sieve and subjected to light components and heavy components removal by a continuous rectifying tower, and then the monofluoromethane with the purity of more than 99.5 percent can be obtained.

Preferably, the low-temperature refrigerant is liquid ammonia or dry ice, preferably liquid nitrogen.

Advantageous effects

The invention provides a preparation method of monofluoromethane, which takes dimethyl carbonate and alkali metal fluoride as raw materials, uses polyether solvent with high boiling point, bypasses the production process route of dimethyl sulfate with high toxicity and potential carcinogenicity, and prepares monofluoromethane through one-step chemical reaction; the method has the characteristics of simple production method, no toxicity of raw materials and few byproducts, and the crude product can be purified to electronic grade.

Drawings

FIG. 1 is an infrared absorption spectrum of monofluoromethane (135mmHg) prepared in example.

FIG. 2 is a gas chromatography spectrum of the gas phase product prepared in example 1.

FIG. 3 is a gas chromatogram of the final product prepared in example 1.

FIG. 4 is a gas chromatogram of the final product prepared in example 2.

FIG. 5 is a gas chromatogram of the final product prepared in 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.

Example 1

A process for the preparation of monofluoromethane, said process comprising the steps of:

(1) dissolving 90g of dimethyl carbonate and 330g of cesium fluoride in 500mL of tetraethylene glycol dimethyl ether, heating to 130 ℃, and carrying out reflux reaction until no gas is generated;

(2) collecting a gas-phase product with a boiling point of-78 ℃ by using a liquid nitrogen cold trap;

(3) and (3) washing the gas-phase product by using a potassium hydroxide aqueous solution, drying by using a molecular sieve, and removing light components and heavy components by using a continuous rectifying tower to obtain a final product.

The gas phase products and end products obtained in this example were tested as follows:

as shown in FIG. 1, gas samples were examined using the Saimerfin IS-10 infrared spectroscopy, demonstrating monofluoromethane.

As shown in fig. 2, agilent 7820 gas chromatography was used to test the gas phase product, helium was used as a carrier gas, the column temperature was maintained at 60 ℃, a TCD detector indicated that the main component in the gas phase product was monofluoromethane, and the purity of monofluoromethane was 93.7% using area normalization.

As shown in fig. 3, the end product was measured by agilent 7820 gas chromatography with helium as carrier gas, maintaining the column temperature at 60 ℃, using TCD detector, using area normalization, and the end product was monofluoromethane with a purity of 99.8%.

Example 2

A process for the preparation of monofluoromethane, said process comprising the steps of:

(1) dissolving 90g of dimethyl carbonate and 140g of potassium fluoride in 500mL of diethylene glycol dimethyl ether, heating to 120 ℃, and carrying out reflux reaction until no gas is generated;

(2) collecting a gas-phase product with a boiling point of-78 ℃ by using a dry ice cold trap;

(3) and (3) washing the gas-phase product by using a potassium hydroxide aqueous solution, drying by using a molecular sieve, and removing light components and heavy components by using a continuous rectifying tower to obtain a final product.

The gas phase products and end products obtained in this example were tested as follows:

as shown in FIG. 1, gas samples were examined using the Saimerfin IS-10 infrared spectroscopy, demonstrating monofluoromethane.

An Agilent 7820 gas chromatography is used for testing a gas phase product, helium is used as a carrier gas, the column temperature is kept at 60 ℃, a TCD detector can detect that the main component in the gas phase product is monofluoromethane, and the purity of the monofluoromethane is 95% by using an area normalization method.

As shown in fig. 4, the final product was measured by agilent 7820 gas chromatography with helium as carrier gas, maintaining the column temperature at 60 ℃, using TCD detector, using area normalization, and the final product was monofluoromethane with a purity of 99.8%.

Example 3

A process for the preparation of monofluoromethane, said process comprising the steps of:

(1) dissolving 90g of dimethyl carbonate and 90g of sodium fluoride in 500mL of methyl ether-terminated polyethylene glycol (molecular weight is 2000), heating to 150 ℃, and carrying out reflux reaction until no gas is generated;

(2) collecting a gas-phase product with a boiling point of-78 ℃ by using a dry ice cold trap;

(3) and (3) washing the gas-phase product by using a potassium hydroxide aqueous solution, drying by using a molecular sieve, and removing light components and heavy components by using a continuous rectifying tower to obtain a final product.

The gas phase products and end products obtained in this example were tested as follows:

as shown in FIG. 1, gas samples were examined using the Saimerfin IS-10 infrared spectroscopy, demonstrating monofluoromethane.

An Agilent 7820 gas chromatography is used for testing a gas phase product, helium is used as a carrier gas, the column temperature is kept at 60 ℃, a TCD detector is used, the main component in the gas phase product is monofluoromethane, and the purity of the monofluoromethane is 95.4% by using an area normalization method.

As shown in fig. 5, the gas product of the final product was tested by agilent 7820 gas chromatography with helium as carrier gas, column temperature maintained at 60 ℃, TCD detector, and area normalization method, and the final product was monofluoromethane with purity of 99.8%.

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.