CN118515286A - A method for co-producing silicon tetrafluoride with anhydrous hydrogen fluoride - Google Patents

Abstract

The present invention relates to the technical field of preparation of inorganic materials, and in particular to a method for co-producing silicon tetrafluoride with anhydrous hydrogen fluoride. The method comprises the following steps: (1) mixing a first fluorosilicic acid aqueous solution with a second concentrated sulfuric acid, heating and decomposing the mixture in a decomposition zone, and performing gas-liquid separation to obtain a gas phase and a liquid phase respectively; the gas phase is a crude silicon tetrafluoride product; (2) purifying the crude silicon tetrafluoride product to obtain silicon tetrafluoride; (3) heating a sulfuric acid solution containing hydrogen fluoride to obtain a gas-liquid mixture of hydrogen fluoride and a dilute sulfuric acid solution; (4) separating a crude hydrogen fluoride gas from the gas-liquid mixture of hydrogen fluoride and a dilute sulfuric acid solution in a crude distillation zone, and then dehydrating and drying the crude hydrogen fluoride gas using a first concentrated sulfuric acid to obtain hydrogen fluoride. Compared with the prior art which can only produce one product, the present invention can simultaneously produce two products, hydrogen fluoride and silicon tetrafluoride, using the same raw material, thereby improving the utilization rate of the raw materials.

Description

A method for co-producing silicon tetrafluoride with anhydrous hydrogen fluoride

Technical Field

The invention relates to the technical field of preparation of inorganic materials, and in particular to a method for co-producing silicon tetrafluoride with anhydrous hydrogen fluoride.

Background Art

Silicon tetrafluoride is the main raw material in the electronics and semiconductor industries. It is mainly used as a silicon source for chemical vapor deposition, a P-type dopant, and an etchant for silicon nitride and tantalum silicide. At the same time, silicon tetrafluoride can also be used to prepare aluminum fluoride, cryolite, and fumed silica. Low-cost silicon tetrafluoride production technology is of great significance for reducing the production cost of semiconductor materials such as polysilicon. At present, the main production method of silicon tetrafluoride is the sulfuric acid rotary kiln production technology using fluorite and quartz as raw materials. The production cost is high, the production process has high energy consumption, high reaction temperature (250℃～300℃), and low yield. In the technology of preparing silicon tetrafluoride using fluorosilicic acid as raw material, the by-product hydrogen fluoride is treated as an impurity and is not used, resulting in waste. Hydrogen fluoride (HF) is the basis of modern fluorine chemical industry and is the most basic raw material for the preparation of elemental fluorine, various fluorine refrigerants, new fluorine-containing materials, inorganic fluoride salts, organic fluorides, etc.

Chinese patent CN116409751 A proposes a "method and system for producing hydrogen fluoride", which includes the following steps: 1) hydrofluorosilicic acid and a first concentrated sulfuric acid react in a main reaction zone to generate silicon tetrafluoride gas and a sulfuric acid solution containing hydrogen fluoride; 2) the silicon tetrafluoride gas is introduced into a silicon tetrafluoride generation zone; the sulfuric acid solution containing hydrogen fluoride is split to form at least two paths for preparing hydrogen fluoride gas; wherein: the first part of the sulfuric acid solution containing hydrogen fluoride is introduced into a distillation zone for separation, the separated hydrogen fluoride gas is introduced into a hydrogen fluoride generation zone to remove moisture, and dry crude hydrogen fluoride gas is collected; the second part of the sulfuric acid solution containing hydrogen fluoride is heated and introduced into a mixing zone with a second concentrated sulfuric acid, and the diluted sulfuric acid solution after mixing is reused as a raw material in the main reaction zone;

Chinese patent CN101973553A "Method for producing high-purity silicon tetrafluoride using fluorosilicic acid" includes the following steps: 1) mixing fluorosilicic acid with concentrated sulfuric acid and heating to produce a gaseous mixture; 2) introducing the gaseous mixture into a reactor, adding concentrated sulfuric acid, and removing the water therein; 3) passing the dried gaseous mixture into concentrated sulfuric acid containing hydrogen fluoride to remove carbon dioxide and oxygen-containing fluorine silicon compounds therein; 4) passing the gaseous mixture into pure sulfuric acid to further remove water, hydrogen fluoride, etc. in the gas; 5) the gaseous mixture is filtered in turn by entering a filter containing pre-dried activated carbon and diatomaceous earth; 6) the filtered silicon tetrafluoride gas is separated in two stages at low temperature, and the gas pressure is adjusted to obtain liquid/solid high-purity silicon tetrafluoride; 7) the liquid/solid high-purity silicon tetrafluoride is placed at room temperature to obtain a silicon tetrafluoride gas product;

However, CN116409751 A only utilizes fluorosilicic acid to obtain anhydrous hydrogen fluoride, so silicon tetrafluoride produced by the reaction of fluorosilicic acid and sulfuric acid is further reacted with water to generate fluorosilicic acid, which is used to decompose and obtain hydrogen fluoride. On the one hand, the reaction of silicon tetrafluoride and water will release a large amount of heat, which needs to be taken away by circulating water, resulting in high energy consumption; on the other hand, the reaction by-product silicon dioxide is very likely to cause scaling and clogging of the equipment, and a large amount of fluorine will be entrained when separating the silicon slag, resulting in a waste of fluorine and increasing the difficulty of handling the fluorine-containing silicon slag; and CN101973553A only utilizes silicon tetrafluoride, a decomposition product of fluorosilicic acid in sulfuric acid, and removes hydrogen fluoride gas as an impurity, with a utilization rate of fluorine of only 67%, resulting in a waste of fluorine resources.

Summary of the invention

In order to solve the problems existing in the prior art, the present invention provides a method for co-producing silicon tetrafluoride with anhydrous hydrogen fluoride. The method provided by the present invention can simultaneously produce two products, hydrogen fluoride and silicon tetrafluoride, using the same raw materials, thereby improving the utilization rate of the raw materials.

In order to achieve the above objectives, the present invention provides the following technical solutions:

The present invention provides a method for co-producing silicon tetrafluoride with anhydrous hydrogen fluoride, comprising the following steps:

(1) mixing a first fluorosilicic acid aqueous solution with a second concentrated sulfuric acid, heating and decomposing the mixture in a decomposition zone, and performing gas-liquid separation to obtain a gas phase and a liquid phase, respectively; the gas phase is a crude silicon tetrafluoride product; and the liquid phase is a sulfuric acid solution containing hydrogen fluoride;

(2) purifying the crude silicon tetrafluoride to obtain silicon tetrafluoride;

(3) heating the sulfuric acid solution containing hydrogen fluoride to obtain a gas-liquid mixture of hydrogen fluoride and dilute sulfuric acid solution;

(4) After separating the crude hydrogen fluoride gas from the gas-liquid mixture of hydrogen fluoride and the dilute sulfuric acid solution in the crude distillation zone, the crude hydrogen fluoride gas is dehydrated and dried using a first concentrated sulfuric acid to obtain hydrogen fluoride.

Preferably, the mass concentration of the first fluorosilicic acid aqueous solution is 30% to 52%.

Preferably, the mass ratio of the first aqueous fluorosilicic acid solution to the second concentrated sulfuric acid is 1:(15-25).

Preferably, the temperature of the thermal decomposition is 35-130° C., and the insulation time is 0.2-0.25 h.

Preferably, the heating temperature is 160-165°C.

Preferably, the mass concentration of the first concentrated sulfuric acid is 95% to 98%; the mass concentration of the second concentrated sulfuric acid is 75% to 95%.

Preferably, step (2) is replaced by: purifying part of the crude silicon tetrafluoride to obtain silicon tetrafluoride; passing the remaining crude silicon tetrafluoride into a second fluorosilicic acid aqueous solution to concentrate the second fluorosilicic acid aqueous solution; the mass concentration of the second fluorosilicic acid aqueous solution is 18% to 30%.

Preferably, the mass ratio of the part of the crude silicon tetrafluoride product to the remaining crude silicon tetrafluoride product is (4-5):1.

Preferably, the crude hydrogen fluoride gas is dehydrated and dried by the first concentrated sulfuric acid, and then mixed with the dilute sulfuric acid solution from which the hydrogen fluoride is separated to obtain fluorine-containing sulfuric acid;

The fluorine-containing sulfuric acid is partially recycled to the decomposition zone, and the remaining part is stripped to remove residual hydrogen fluoride in the fluorine-containing sulfuric acid to obtain dilute sulfuric acid.

The present invention also provides an apparatus for co-producing silicon tetrafluoride with anhydrous hydrogen fluoride, comprising a crude distillation tower (1), a buffer tank (2), a decomposition reactor (3), a gas-liquid separator (4), a material transfer pump (5) and an evaporator (6) which are connected in sequence; the outlet of the evaporator (6) is connected to the crude distillation tower (1);

It also includes a purification system (7) connected to the gas-liquid separator (4).

The present invention provides a method for co-producing silicon tetrafluoride with anhydrous hydrogen fluoride, comprising the following steps: (1) mixing a first fluorosilicic acid aqueous solution with a second concentrated sulfuric acid, heating and decomposing the mixture in a decomposition zone, and performing gas-liquid separation to obtain a gas phase and a liquid phase respectively; the gas phase is a crude silicon tetrafluoride product; the liquid phase is a sulfuric acid solution containing hydrogen fluoride; (2) purifying the crude silicon tetrafluoride product to obtain silicon tetrafluoride; (3) heating the sulfuric acid solution containing hydrogen fluoride to obtain a gas-liquid mixture of hydrogen fluoride and a dilute sulfuric acid solution; (4) separating a crude hydrogen fluoride gas from the gas-liquid mixture of hydrogen fluoride and the dilute sulfuric acid solution in a crude distillation zone, and then dehydrating and drying the crude hydrogen fluoride gas using a first concentrated sulfuric acid to obtain hydrogen fluoride. Compared with the prior art which can only produce one product, the present invention can simultaneously produce two products, hydrogen fluoride and silicon tetrafluoride, using the same raw material, thereby improving the utilization rate of the raw materials. The present invention eliminates the process of reacting silicon tetrafluoride with water, eliminates a large amount of exothermic reaction, reduces the amount of circulating water used, and reduces energy consumption; and since no fluorine-containing silicon slag is produced, no solid-liquid separation equipment is required, which reduces equipment investment and energy consumption and avoids the trouble of solid waste treatment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flow chart of the co-production of silicon tetrafluoride with anhydrous hydrogen fluoride provided in Example 1 of the present invention.

DETAILED DESCRIPTION

The present invention provides a method for co-producing silicon tetrafluoride with anhydrous hydrogen fluoride, comprising the following steps:

(1) mixing a first fluorosilicic acid aqueous solution and a second concentrated sulfuric acid, heating and decomposing the mixture in a decomposition zone, and then performing gas-liquid separation to obtain a gas phase and a liquid phase, respectively;

The gas phase is crude silicon tetrafluoride; the liquid phase is a sulfuric acid solution containing hydrogen fluoride;

(2) purifying the crude silicon tetrafluoride to obtain silicon tetrafluoride;

(3) heating the sulfuric acid solution containing hydrogen fluoride to obtain a gas-liquid mixture of hydrogen fluoride and dilute sulfuric acid solution;

(4) After separating the crude hydrogen fluoride gas from the gas-liquid mixture of hydrogen fluoride and the dilute sulfuric acid solution in the crude distillation zone, the crude hydrogen fluoride gas is dehydrated and dried using a first concentrated sulfuric acid to obtain hydrogen fluoride.

The invention mixes a first fluorosilicic acid aqueous solution with a second concentrated sulfuric acid, heats and decomposes them in a decomposition zone, and separates the gas and liquid to obtain a gas phase and a liquid phase respectively; the gas phase is a crude silicon tetrafluoride product; and the liquid phase is a sulfuric acid solution containing hydrogen fluoride.

In the present invention, the mass concentration of the first fluorosilicic acid aqueous solution is preferably 30% to 52%, more preferably 40 to 50%. In the present invention, the mass ratio of the first fluorosilicic acid aqueous solution to the second concentrated sulfuric acid is preferably 1:(15 to 25), more preferably 1:20.

In the present invention, the mass concentration of the second concentrated sulfuric acid is preferably 75% to 95%, more preferably 80 to 90%.

In the present invention, the temperature of the thermal decomposition is preferably 35 to 130° C., more preferably 40 to 100° C., and the holding time is preferably 0.2 to 0.25 h. In the present invention, the thermal decomposition is preferably carried out in a decomposition reactor.

In the present invention, the gas-liquid separation is preferably performed in a gas-liquid separator.

After obtaining the crude silicon tetrafluoride, the present invention purifies the crude silicon tetrafluoride to obtain silicon tetrafluoride.

In the present invention, the purification conditions include drying, absorption, adsorption and distillation in sequence. The drying temperature is 60-90°C, the time is 3-5 min, the absorption reagent is 98wt% sulfuric acid, the adsorption reagent is activated carbon or diatomaceous earth, the distillation temperature is -80°C to -40°C, and the time is 2-4h. In the present invention, the purification is preferably carried out in a purification system. The purification system preferably includes a drying unit, an absorption unit, an adsorption unit, and a distillation unit connected in sequence.

In the present invention, step (2) may also be replaced by: purifying a portion of the crude silicon tetrafluoride to obtain silicon tetrafluoride; and passing the remaining crude silicon tetrafluoride into a second fluorosilicic acid aqueous solution to concentrate the second fluorosilicic acid aqueous solution.

In the present invention, the mass concentration of the second hydrofluorosilicic acid aqueous solution is preferably 18% to 30%, more preferably 20%. In the present invention, the mass ratio of the part of the crude silicon tetrafluoride to the remaining crude silicon tetrafluoride is preferably (4 to 5): 1, more preferably 4.5: 1. In the present invention, the enrichment is preferably carried out in an enrichment system.

In the present invention, before purifying part of the crude silicon tetrafluoride and concentrating the remaining crude silicon tetrafluoride (ie before the crude silicon tetrafluoride is split), the crude silicon tetrafluoride is preferably cooled to 60°C.

The invention heats a sulfuric acid solution containing hydrogen fluoride to obtain a gas-liquid mixture of hydrogen fluoride and a dilute sulfuric acid solution.

In the present invention, the heating is preferably performed in an evaporator. In the present invention, the heating temperature is preferably 160-165°C, more preferably 162°C.

The invention separates the crude hydrogen fluoride gas from the gas-liquid mixture of hydrogen fluoride and dilute sulfuric acid solution in the crude distillation zone, and then uses the first concentrated sulfuric acid to dehydrate and dry the crude hydrogen fluoride gas to obtain hydrogen fluoride.

In the present invention, the mass concentration of the first concentrated sulfuric acid is 95% to 98%. In the present invention, the dehydration and drying is preferably carried out in a crude distillation tower.

In the present invention, the crude hydrogen fluoride gas is dehydrated and dried by the first concentrated sulfuric acid, and then mixed with the dilute sulfuric acid solution from which hydrogen fluoride is separated to obtain fluorine-containing sulfuric acid. In the present invention, the fluorine-containing sulfuric acid is preferably partially recycled to the decomposition zone, and the remaining part is stripped to remove the residual hydrogen fluoride in the fluorine-containing sulfuric acid to obtain dilute sulfuric acid.

The present invention also provides an equipment for co-producing silicon tetrafluoride with anhydrous hydrogen fluoride, comprising a crude distillation tower 1, a buffer tank 2, a decomposition reactor 3, a gas-liquid separator 4, a material transfer pump 5 and an evaporator 6 which are sequentially connected;

It also includes a purification system 7 connected to the gas-liquid separator 4.

In the present invention, the equipment for co-producing silicon tetrafluoride with anhydrous hydrogen fluoride preferably further comprises a concentration system 8 connected to the gas-liquid separator.

The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

Example 1

FIG. 1 is a flow chart of anhydrous hydrogen fluoride co-production of silicon tetrafluoride provided in Example 1 of the present invention. Taking FIG. 1 as an example, the reaction flow chart of Example 1 is described as follows:

(1) 185 g of a first fluorosilicic acid aqueous solution with a mass concentration of 30% and 3900 g of a second concentrated sulfuric acid are introduced into a decomposition reactor and heated and decomposed at a temperature of 130° C. for 0.25 h, and then the material in the decomposition reactor is introduced into a silicon tetrafluoride separator for gas-liquid separation to obtain a gas phase and a liquid phase, respectively; wherein the gas phase is 95 wt.% silicon tetrafluoride gas, and the liquid phase is a sulfuric acid solution containing hydrogen fluoride;

(2) Introducing 95% silicon tetrafluoride gas into a purification system for purification, i.e., drying, absorption, adsorption, and distillation are performed in sequence, wherein the drying temperature is 80° C., the time is 3 min, the absorption reagent is 98 wt % sulfuric acid, the adsorption reagent is activated carbon, the distillation temperature is -80° C., and the time is 4 h.

(3) The sulfuric acid solution containing hydrogen fluoride is pumped into an evaporator through a transfer pump and heated to 163° C. to form a gas-liquid mixture of hydrogen fluoride and dilute sulfuric acid solution, and then enters a crude distillation tower to separate crude hydrogen fluoride gas. 98 wt.% concentrated sulfuric acid is added to the crude distillation tower to dehydrate and dry the crude hydrogen fluoride gas. The concentrated sulfuric acid that has undergone dehydration and drying is mixed with the dilute sulfuric acid at the bottom of the crude distillation tower after the hydrogen fluoride gas is removed. The obtained fluorine-containing sulfuric acid stays in a buffer tank for a short time, and then part of it (accounting for 22/25 of the mass of the mixed fluorine-containing sulfuric acid) enters a decomposition reactor to react with fluorosilicic acid, and the rest of it enters a stripping tower to recover part of the hydrogen fluoride, and then is cooled and stored for use.

Example 2

(1) 185 g of a first fluorosilicic acid aqueous solution with a mass concentration of 35% and 3900 g of a second concentrated sulfuric acid are introduced into a decomposition reactor and heated and decomposed at a temperature of 130° C. for 0.2 h, and then the material in the decomposition reactor is introduced into a silicon tetrafluoride separator for gas-liquid separation to obtain a gas phase and a liquid phase, respectively; wherein the gas phase is 95 wt.% silicon tetrafluoride gas, and the liquid phase is a sulfuric acid solution containing hydrogen fluoride;

(2) introducing a portion of 95 wt.% silicon tetrafluoride gas into a purification system for purification; that is, drying, absorption, adsorption, and distillation are performed in sequence, wherein the drying temperature is 80°C, the time is 3 minutes, the absorption reagent is 98 wt.% sulfuric acid, the adsorption reagent is activated carbon, the distillation temperature is -80°C, and the time is 4 hours; the remaining 95 wt.% silicon tetrafluoride gas enters a concentration system to concentrate a second fluorosilicic acid aqueous solution with a mass concentration of 30%; the mass ratio of the portion of 95 wt.% silicon tetrafluoride gas to the remaining 95 wt.% silicon tetrafluoride gas is 5:1.

(3) The sulfuric acid solution containing hydrogen fluoride is pumped into an evaporator through a transfer pump and heated to 163° C. to form a gas-liquid mixture of hydrogen fluoride and sulfuric acid solution, and then enters a crude distillation tower to separate crude hydrogen fluoride gas. 98 wt.% concentrated sulfuric acid is added to the crude distillation tower to dehydrate and dry the crude hydrogen fluoride gas. The concentrated sulfuric acid that has undergone dehydration and drying is mixed with the dilute sulfuric acid at the bottom of the crude distillation tower after the hydrogen fluoride gas is removed. After the mixed fluorine-containing sulfuric acid stays in a buffer tank for a short time, part of it (accounting for 43/50 of the mass of the mixed fluorine-containing sulfuric acid) enters a decomposition reactor to react with fluorosilicic acid, and the rest enters a stripping tower to recover part of the hydrogen fluoride, and then is cooled and stored for use.

Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims (10)

1. A method for co-producing silicon tetrafluoride with anhydrous hydrogen fluoride, characterized in that it comprises the following steps: (1) mixing a first fluorosilicic acid aqueous solution with a second concentrated sulfuric acid, heating and decomposing the mixture in a decomposition zone, and performing gas-liquid separation to obtain a gas phase and a liquid phase, respectively; the gas phase is a crude silicon tetrafluoride product; and the liquid phase is a sulfuric acid solution containing hydrogen fluoride; (2) purifying the crude silicon tetrafluoride to obtain silicon tetrafluoride; (3) heating the sulfuric acid solution containing hydrogen fluoride to obtain a gas-liquid mixture of hydrogen fluoride and dilute sulfuric acid solution; (4) After separating the crude hydrogen fluoride gas from the gas-liquid mixture of hydrogen fluoride and the dilute sulfuric acid solution in the crude distillation zone, the crude hydrogen fluoride gas is dehydrated and dried using a first concentrated sulfuric acid to obtain hydrogen fluoride. 2. The method according to claim 1, characterized in that the mass concentration of the first hydrofluorosilicic acid aqueous solution is 30% to 52%. 3. The method according to claim 1 or 2, characterized in that the mass ratio of the first hydrofluorosilicic acid aqueous solution to the second concentrated sulfuric acid is 1:(15-25). 4. The method according to claim 1, characterized in that the temperature of the thermal decomposition is 35-130°C and the insulation time is 0.2-0.25h. 5. The method according to claim 1, characterized in that the heating temperature is 160-165°C. 6. The method according to claim 1, characterized in that the mass concentration of the first concentrated sulfuric acid is 95% to 98%; the mass concentration of the second concentrated sulfuric acid is 75% to 95%. 7. The method according to claim 1, characterized in that step (2) is replaced by: purifying part of the crude silicon tetrafluoride to obtain silicon tetrafluoride; passing the remaining crude silicon tetrafluoride into a second fluorosilicic acid aqueous solution to concentrate the second fluorosilicic acid aqueous solution; the mass concentration of the second fluorosilicic acid aqueous solution is 18% to 30%. 8. The method according to claim 7, characterized in that the mass ratio of the part of the crude silicon tetrafluoride product to the remaining crude silicon tetrafluoride product is (4-5):1. 9. The method according to claim 1, characterized in that the crude hydrogen fluoride gas is dehydrated and dried by the first concentrated sulfuric acid, and then mixed with the dilute sulfuric acid solution from which the hydrogen fluoride is separated to obtain fluorine-containing sulfuric acid; The fluorine-containing sulfuric acid is partially recycled to the decomposition zone, and the remaining part is stripped to remove residual hydrogen fluoride in the fluorine-containing sulfuric acid to obtain dilute sulfuric acid. 10. An apparatus for co-producing silicon tetrafluoride with anhydrous hydrogen fluoride, characterized in that it comprises a crude distillation tower (1), a buffer tank (2), a decomposition reactor (3), a gas-liquid separator (4), a material transfer pump (5) and an evaporator (6) which are connected in sequence; the outlet of the evaporator (6) is connected to the crude distillation tower (1); and it also comprises a purification system (7) connected to the gas-liquid separator (4).