Process for the production of electronic grade sulfuric acid

Abstract

The present application relates to the field of electronic chemicals, and discloses a preparation method of electronic-grade sulfuric acid, which comprises the following steps: (1) vaporizing crude sulfur trioxide to obtain gaseous sulfur trioxide raw material; (2) filtering and absorbing the gaseous sulfur trioxide raw material and ultrapure water through a fiber microporous membrane to obtain a semi-finished product sulfuric acid solution; (3) concentrating the semi-finished product sulfuric acid solution to obtain electronic-grade sulfuric acid crude product; (4) cooling and filtering the electronic-grade sulfuric acid crude product to obtain the electronic-grade sulfuric acid; wherein the fiber microporous membrane is prepared from a mixture comprising fluorine-containing polymer and polyethylene glycol through granulation, spinning, winding and stretching. The method uses a fiber microporous membrane which has the functions of filtering and removing particulate impurities and absorbing and removing sulfur dioxide, can effectively remove sulfur dioxide and particulate impurities in the raw material, and obtain electronic-grade sulfuric acid with stable product quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electronic chemicals, in particular to a preparation method of electronic-grade sulfuric acid. BACKGROUND

[0002] Electronic-grade sulfuric acid is an ultra-clean high-purity reagent, which is often used for cleaning, photoetching, etching and plating cleaning of silicon wafers and printed circuit boards in microelectronic technology. Impurities in electronic-grade chemicals can seriously affect the reliability and completion of semiconductor device manufacturing.

[0003] The gas absorption method is commonly used in industry, that is, ultra-pure water or ultra-pure sulfuric acid is used to absorb sulfur trioxide to prepare ultra-clean sulfuric acid, but industrial sulfur trioxide contains a certain amount of particulate matter and sulfur dioxide impurities. In the prior art, methods such as adding oxidizing agents, air stripping, evaporation purification, and multi-stage filtration are usually used for purification, which has a complex system, high raw material cost, and high energy consumption. The waste gas produced by stripping also increases the cost of three-waste treatment.

[0004] Therefore, there is an urgent need for a high-purity electronic-grade sulfuric acid refining production method that is simple in device, has no stripping waste gas, and can effectively remove impurities from raw materials. SUMMARY

[0005] The purpose of the present application is to overcome the problem of difficulty in removing particulate matter and sulfur dioxide impurities from industrial sulfur trioxide in the prior art, and to provide a preparation method of electronic-grade sulfuric acid. The method uses a fiber microporous membrane that has both the functions of removing particulate impurities and absorbing and removing sulfur dioxide, which can effectively remove sulfur dioxide and particulate impurities from the raw materials and obtain electronic-grade sulfuric acid with stable product quality.

[0006] In order to achieve the above-mentioned purpose, the present application provides a preparation method of electronic-grade sulfuric acid, which comprises the following steps:

[0007] (1) vaporizing crude sulfur trioxide to obtain gaseous sulfur trioxide raw material;

[0008] (2) filtering and absorbing the gaseous sulfur trioxide raw material with ultra-pure water through a fiber microporous membrane to obtain a semi-finished sulfuric acid solution;

[0009] (3) concentrating the semi-finished sulfuric acid solution to obtain electronic-grade sulfuric acid crude product;

[0010] (4) cooling and filtering the electronic-grade sulfuric acid crude product to obtain the electronic-grade sulfuric acid;

[0011] The fiber microporous membrane is prepared from a mixture comprising fluorine-containing polymer and polyethylene glycol by granulation, spinning, winding and stretching.

[0012] By the technical scheme, the application has the following beneficial effects:

[0013] The application uses industrial sulfur trioxide as raw material, which is filtered and absorbed by a fiber microporous membrane filter after vaporization. The polyethylene glycol (PEG) contained in the fiber microporous membrane has a selective adsorption effect on sulfur dioxide, and the addition of PEG causes dense pores on the outer surface and inside of the fiber, increases the specific surface area of the fiber microporous membrane, and guarantees the mechanical strength of the membrane. Therefore, the fiber microporous membrane can not only filter and remove particulate impurities, but also effectively absorb and remove sulfur dioxide due to the hollow structure of the fiber microporous membrane. Compared with the prior art, the method can simultaneously filter and remove particulate impurities and remove sulfur dioxide, does not need to use desulfurization liquid, and does not need to use hydrogen peroxide or ozone for gas stripping, is simple to operate, reduces the introduction of hazardous chemicals, can effectively reduce the consumption and energy consumption of the device, can effectively remove sulfur dioxide and particulate impurities in the raw material, and can be used to produce high-purity electronic-grade sulfuric acid with sulfur dioxide content less than 1000 ppb, particulate impurity content less than or equal to 50 / mL, and single metal cation content less than 100 ppt. DETAILED DESCRIPTION

[0014] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the application. Any numerical values need not be a precision value, provided that these values are treated as approximations. The endpoints of the ranges and any values are provided as a separate endpoint and include any numerical value reasonably falling within these ranges. For numeric values, the endpoints of each range, the endpoints of each range and individual point values, and individual point values can be combined with each other to obtain one or more new numeric ranges, which should be considered as specifically disclosed herein.

[0015] The application provides a preparation method of electronic-grade sulfuric acid, which comprises the following steps:

[0016] (1) vaporizing crude sulfur trioxide to obtain gaseous sulfur trioxide raw material;

[0017] (2) filtering and absorbing the gaseous sulfur trioxide raw material and ultrapure water through a fiber microporous membrane to obtain a semi-finished product sulfuric acid solution;

[0018] (3) concentrating the semi-finished product sulfuric acid solution to obtain electronic-grade sulfuric acid crude product;

[0019] (4) cooling and filtering the electronic-grade sulfuric acid crude product to obtain the electronic-grade sulfuric acid;

[0020] The fiber microporous membrane is prepared by granulation, spinning, winding and stretching of a mixture comprising a fluorine-containing polymer and polyethylene glycol.

[0021] In the present application, industrial sulfur trioxide can be used as raw material, vaporized and filtered and absorbed by a fiber microporous membrane filter. The fluorine-containing polymer in the fiber microporous membrane has excellent chemical corrosion resistance, high temperature resistance and oxidation resistance, and excellent flexibility, and has the characteristics of wear resistance and easy processing, and can withstand temperature changes or thermal shock conditions within the range of -29℃-260℃ for long-term normal use.

[0022] The fiber microporous membrane introduces hydrophilic groups by adding polyethylene glycol (PEG), which has excellent removal effect on sulfur dioxide. In addition, the addition of PEG causes dense pores on the outer surface and inside of the fiber, increasing the specific surface area and porosity of the fiber microporous membrane, increasing the mass transfer channel, so that the fiber microporous membrane can effectively filter and remove particulate impurities and sulfur dioxide, and has excellent separation efficiency. Therefore, the fiber microporous membrane is a dual functional membrane that has the functions of filtering and removing particulate impurities and absorbing and removing sulfur dioxide. After filtering and absorbing by the fiber microporous membrane filter, a semi-finished sulfuric acid solution is obtained after removing particulate impurities and sulfur dioxide, and then evaporation and concentration, cooling and filtration are carried out to obtain electronic grade sulfuric acid meeting the standard. The prior art needs to absorb and filter the sulfur trioxide raw material multiple times, obtain high-purity sulfur trioxide gas, and then react with pure water to prepare electronic grade sulfuric acid. Compared with the prior art, the method and device provided by the present application are simple and easy to operate, can effectively reduce the consumption of the device, and can effectively remove sulfur dioxide and particulate impurities in the industrial sulfur trioxide raw material through the fiber microporous membrane filter, so that electronic grade sulfuric acid with stable product quality is obtained.

[0023] According to the present application, in step (2), the gaseous sulfur trioxide raw material is absorbed by the ultra-pure water through the fiber microporous membrane, and the obtained acidic liquid is filtered through the fiber microporous membrane. The fiber microporous membrane can filter and remove particulate impurities in the raw material, and can adsorb and remove sulfur dioxide in the gaseous sulfur trioxide raw material. The acidic liquid after removing particulate impurities and sulfur dioxide is a semi-finished sulfuric acid solution.

[0024] According to the present application, preferably, the preparation method of the fiber microporous membrane comprises the following steps: mixing the fluorine-containing polymer and the polyethylene glycol, then granulating and spinning, and then winding and stretching.

[0025] According to the specific embodiment of the present application, the preparation method of the fiber microporous membrane comprises the following steps: mixing the fluorine-containing polymer and the polyethylene glycol, then granulating, passing nitrogen gas through the obtained granules, spinning, cooling and solidifying, winding into a membrane, and then washing, drying and stretching.

[0026] According to the present application, preferably, the amount of the polyethylene glycol in the mixture is 6-10 wt% based on the weight of the fluorine-containing polymer. When the amount of the polyethylene glycol satisfies the range, the porosity of the fiber microporous membrane can be sufficiently improved on the basis of guaranteeing the mechanical strength of the fiber microporous membrane.

[0027] According to the present application, preferably, the fluorine-containing polymer is at least one selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride, polyvinylidene difluoride, fluorinated ethylene-propylene copolymer, ethylene-tetrafluoroethylene copolymer (ETFE) and chlorotrifluoroethylene-ethylene copolymer, and is preferably polytetrafluoroethylene. The polytetrafluoroethylene has strong hydrophobicity, oxidation resistance, acid and alkali resistance and temperature resistance. After mixing the polytetrafluoroethylene with the polyethylene glycol, the fiber microporous membrane with a hollow structure is prepared, which not only can exert the super mechanical performance, but also has more excellent absorption and filtration capacity and a longer service life.

[0028] According to the present application, preferably, the weight average molecular weight of the fluorine-containing polymer is 300-4000 kg / mol. After the mixture of the fluorine-containing polymer and the polyethylene glycol is dispersed and stretched to form microfibers, the unexpanded part is connected in the form of nodes. The point line connection forms a microporous structure. The greater the weight average molecular weight of the fluorine-containing polymer, the shorter the membrane microfiber, the greater the node and the larger the pore. When the weight average molecular weight of the fluorine-containing polymer satisfies the range, the porosity of the membrane can be improved on the premise of guaranteeing the length of the membrane microfiber.

[0029] When the fluorine-containing polymer is polytetrafluoroethylene, the weight average molecular weight is preferably 3000-4000 kg / mol; when the fluorine-containing polymer is polyvinylidene fluoride, the weight average molecular weight is preferably 700-800 kg / mol.

[0030] According to the present application, preferably, the weight average molecular weight of the polyethylene glycol is 4000-5000 g / mol. When the weight average molecular weight of the polyethylene glycol satisfies the range, the finger-shaped pores penetrating the fiber are not easy to form, and a relatively uniform pore structure is obtained.

[0031] According to the present application, preferably, the fiber microporous membrane has pores with a pore size of 10-500 μm, and preferably 20-50 μm. When the pore size satisfies the range, the particulate impurities with a particle size greater than 10 μm can be effectively controlled.

[0032] According to the present application, preferably, the porosity of the fiber microporous membrane is 70-80%, and preferably 75-80%.

[0033] According to the present application, preferably, the specific surface area of the fiber microporous membrane is 300-1000 m 2 / g, and more preferably 900-1000 m 2 / g.

[0034] According to the present application, preferably, in step (1), the purity of the crude sulfur trioxide is greater than or equal to 99.5wt%, the content of particulate matter contained in the crude sulfur trioxide is less than or equal to 400ppm, the content of iron is less than or equal to 60ppm, and the content of sulfur dioxide is less than or equal to 4000ppm.

[0035] In the present application, ppm, ppb and ppt are unit symbols for indicating the concentration of a solution, wherein 1 ppm is 1 mg / L (milligram per liter), 1 ppb is 1 μg / L (microgram per liter), and 1 ppt is 1 ng / L (nanogram per liter).

[0036] According to the present application, preferably, the content of sulfur dioxide contained in the semi-finished sulfuric acid solution is less than or equal to 1000ppb. The content of sulfur dioxide contained in the semi-finished sulfuric acid solution is the same as the content of sulfur dioxide contained in the electronic-grade sulfuric acid prepared.

[0037] According to the present application, preferably, in step (3), the content of sulfuric acid contained in the electronic-grade sulfuric acid crude product is 96-98wt% based on the total weight of the electronic-grade sulfuric acid crude product.

[0038] According to the present application, the content of sulfuric acid contained in the electronic-grade sulfuric acid crude product can be controlled by the concentration of the semi-finished sulfuric acid solution and the concentration temperature, the concentration being evaporative concentration using a concentration column, and the concentration temperature being the bottom temperature of the concentration column.

[0039] According to the present application, preferably, the content of sulfuric acid contained in the semi-finished sulfuric acid solution is 60-80wt% based on the total weight of the semi-finished sulfuric acid solution.

[0040] According to the present application, preferably, the concentration temperature is 130-150°C.

[0041] By controlling the concentration of the semi-finished sulfuric acid solution and the concentration temperature, not only the mass fraction of sulfuric acid in the electronic-grade sulfuric acid crude product can be controlled, but also the purity of the electronic-grade sulfuric acid product prepared can be further improved.

[0042] Further, the concentration temperature is 130-140°C.

[0043] According to the present application, preferably, the cooling temperature is 30-50°C.

[0044] In the preferred embodiment of the present application, the content of sulfur dioxide contained in the electronic-grade sulfuric acid is less than or equal to 1000ppb, the content of particulate impurities contained in the electronic-grade sulfuric acid is less than or equal to 50 / mL, and the content of single metal cations contained in the electronic-grade sulfuric acid is less than or equal to 100ppt.

[0045] In a more preferred embodiment of the present application, the electronic grade sulfuric acid contains sulfur dioxide in an amount of less than or equal to 500 ppb, contains particulate impurities in an amount of less than or equal to 15 pieces / mL, and contains single metal cations in an amount of less than or equal to 10 ppt.

[0046] In the present application, ppb and ppt are both by mass.

[0047] The present application will be described in detail below by way of examples and comparative examples. In the following examples and comparative examples, conventional methods were used unless otherwise specified, and reagents and materials were obtained commercially unless otherwise specified.

[0048] The industrial sulfur trioxide used in the following examples and comparative examples was obtained from Nanhua Company, and had a purity of greater than or equal to 99.5 wt%, a particulate matter content of less than or equal to 400 ppm, an iron content of less than or equal to 60 ppm, and a sulfur dioxide content of less than or equal to 4000 ppm.

[0049] The sulfur dioxide content was determined by potassium permanganate titration;

[0050] The particulate impurity content was determined by a laser liquid particle counter;

[0051] The metal cation content was determined by inductively coupled plasma mass spectrometry;

[0052] The non-metal ion content was determined by turbidimetry and standard comparison.

[0053] The following preparation examples are used to illustrate the preparation of the fiber microporous membrane.

[0054] Preparation Example 1

[0055] The method for preparing the fiber microporous membrane is as follows:

[0056] Polytetrafluoroethylene (with a weight average molecular weight of 3 million g / mol) and polyethylene glycol (with a weight average molecular weight of 4000 g / mol) were thoroughly mixed and granulated, and the obtained granules were passed through a twin-screw spinning machine, and nitrogen was introduced, and the filaments were cooled and solidified, and then wound into a membrane, and then washed with water, dried, and stretched. The amount of polyethylene glycol was 8 wt% based on the weight of the polytetrafluoroethylene. A fiber microporous membrane S1 was obtained, which had a pore size of 28 μm, a porosity of 75%, and a specific surface area of 1000 m 2 / g.

[0057] Preparation Example 2

[0058] A fibrous microporous membrane was prepared according to the method of Preparation Example 1, except that polytetrafluoroethylene having a weight average molecular weight of 4 million g / mol was used, and the amount of polyethylene glycol having a weight average molecular weight of 400 g / mol was 6 wt% based on the weight of the polytetrafluoroethylene. A fibrous microporous membrane S2 having a pore diameter of 400 μm, a porosity of 70%, and a specific surface area of 400 m 2 / g was obtained.

[0059] Preparation Example 3

[0060] A fibrous microporous membrane was prepared according to the method of Preparation Example 1, except that polyvinylidene fluoride having a weight average molecular weight of 700,000 g / mol was used. A fibrous microporous membrane S3 having a pore diameter of 10 μm, a porosity of 70%, and a specific surface area of 600 m 2 / g was obtained.

[0061] Preparation Example 4

[0062] A fibrous microporous membrane was prepared according to the method of Preparation Example 1, except that polytetrafluoroethylene having a weight average molecular weight of 3 million g / mol was used. A fibrous microporous membrane S4 having a pore diameter of 5 μm, a porosity of 50%, and a specific surface area of 500 m 2 / g was obtained.

[0063] Preparation Example 5

[0064] A fibrous microporous membrane was prepared according to the method of Preparation Example 1, except that polyethylene glycol having a weight average molecular weight of 8,000 g / mol was used, and the amount of polyethylene glycol was 2 wt% based on the weight of the polytetrafluoroethylene. A fibrous microporous membrane S5 having a pore diameter of 40 μm, a porosity of 50%, and a specific surface area of 300 m 2 / g was obtained.

[0065] Preparation Example 6

[0066] A fibrous microporous membrane was prepared according to the method of Preparation Example 1, except that polysulfone having a weight average molecular weight of 700,000 g / mol was used. A fibrous microporous membrane S6 having a pore diameter of 70 μm, a porosity of 40%, and a specific surface area of 300 m 2 / g was obtained.

[0067] Preparation Example 7

[0068] A fibrous microporous membrane was prepared according to the method of Preparation Example 1, except that no polyethylene glycol was added. A fibrous microporous membrane S7 having a pore diameter of 30 μm, a porosity of 37%, and a specific surface area of 340 m 2 / g was obtained.

[0069] Preparation Example 8

[0070] The method for preparing a polytetrafluoroethylene fibrous membrane is as follows:

[0071] Polytetrafluoroethylene (weight average molecular weight 3 million g / mol) and polyethylene glycol (weight average molecular weight 4000 g / mol) were formulated into a solution of a blended polymer, fibers were made by electrospinning, and then water washing and drying were performed, thereby obtaining a polytetrafluoroethylene fiber membrane without hollow structures.

[0072] In the above formula, the amount of polyethylene glycol is 8 wt% based on the weight of polytetrafluoroethylene.

[0073] The following examples are used to illustrate the preparation of electronic grade sulfuric acid.

[0074] Example 1

[0075] In a super-clean production system, electronic grade sulfuric acid was prepared according to the following method:

[0076] (1) Vaporization: The industrial sulfur trioxide raw material was pumped into an evaporator after preheating from the raw material storage tank to obtain gaseous sulfur trioxide raw material. The flow rate of the industrial sulfur trioxide raw material into the evaporator was 40 L / h, and the temperature of the evaporator was controlled at 120°C.

[0077] (2) Filtration and absorption using a fiber microporous membrane S1: The evaporated gaseous sulfur trioxide raw material and ultrapure water were passed through a fiber microporous membrane filter with hollow structures, with a residence time of 0.5 h, to obtain a semi-finished sulfuric acid solution after removing particulate impurities and removing sulfur dioxide, so that the content of sulfuric acid in the semi-finished sulfuric acid solution was 80 wt% based on the total weight of the semi-finished sulfuric acid solution.

[0078] (3) Concentration: The semi-finished sulfuric acid solution obtained in step (2) was pumped into a concentration tower, and the tower bottom temperature was controlled at 135°C to obtain electronic grade sulfuric acid crude product, so that the content of sulfuric acid in the electronic grade sulfuric acid crude product was 96 wt% based on the total weight of the electronic grade sulfuric acid crude product.

[0079] (4) Cooling: The electronic grade sulfuric acid crude product obtained in step (3) was continuously cooled through two heat exchangers, with a temperature control of 40°C, and the steam by-product of the heat exchanger was used for preheating of the raw material.

[0080] (5) Filtration: The cooled electronic grade sulfuric acid crude product was filtered to obtain high-purity electronic grade sulfuric acid product meeting the standard, which was stored in a sulfuric acid storage tank.

[0081] Example 2

[0082] Electronic grade sulfuric acid was prepared according to the method of Example 1, except that in step (2), a fiber microporous membrane S2 was used for filtration and absorption. A semi-finished sulfuric acid solution with a sulfuric acid content of 80 wt% was obtained, and then electronic grade sulfuric acid crude product with a sulfuric acid content of 96 wt% was obtained, and then electronic grade sulfuric acid product was prepared.

[0083] Example 3

[0084] The electronic grade sulfuric acid was prepared according to the method of Example 1, except that the concentration of the semi-finished sulfuric acid solution and the concentration temperature were different. Specifically, in step (2), the content of sulfuric acid in the semi-finished sulfuric acid solution was 70 wt% based on the total weight of the semi-finished sulfuric acid solution; in step (3), the bottom temperature of the column was controlled at 150°C to obtain the electronic grade sulfuric acid crude product, so that the content of sulfuric acid in the electronic grade sulfuric acid crude product was 96 wt% based on the total weight of the electronic grade sulfuric acid crude product. The electronic grade sulfuric acid product was prepared.

[0085] Examples 4-6

[0086] The electronic grade sulfuric acid was prepared according to the method of Example 1, except that different fiber microporous membranes were selected. Specifically, in step (2), fiber microporous membranes S3-S5 were used for filtration and absorption, respectively. The semi-finished sulfuric acid solution with a sulfuric acid content of 80 wt% was obtained, and then the electronic grade sulfuric acid crude product with a sulfuric acid content of 96 wt% was obtained, and then the electronic grade sulfuric acid product was prepared.

[0087] Comparative Example 1

[0088] The electronic grade sulfuric acid was prepared according to the method of Example 1, except that in step (2), fiber microporous membrane S6 was used for filtration and absorption. The semi-finished sulfuric acid solution with a sulfuric acid content of 81 wt% was obtained, and then the electronic grade sulfuric acid crude product with a sulfuric acid content of 96 wt% was obtained, and then the electronic grade sulfuric acid product was prepared.

[0089] However, after running for 12 hours, the sulfur dioxide content at the outlet of the fiber microporous membrane filter was 335 ppm, and part of the filter membrane was broken under the long-term impact of the acid solution.

[0090] Comparative Example 2

[0091] The electronic grade sulfuric acid was prepared according to the method of Example 1, except that no fiber microporous membrane was used for filtration and absorption, and the gaseous sulfur trioxide raw material obtained in step (1) was directly reacted with ultrapure water for 0.5 h to obtain a semi-finished sulfuric acid solution with a sulfuric acid content of 80 wt%, and then an electronic grade sulfuric acid crude product with a sulfuric acid content of 96 wt% was obtained, and then an electronic grade sulfuric acid product was prepared.

[0092] Comparative Example 3

[0093] The electronic grade sulfuric acid was prepared according to the method of Example 1, except that fiber microporous membrane S7 containing no polyethylene glycol was used for filtration and absorption. The semi-finished sulfuric acid solution with a sulfuric acid content of 81 wt% was obtained, and then the electronic grade sulfuric acid crude product with a sulfuric acid content of 96 wt% was obtained, and then the electronic grade sulfuric acid product was prepared.

[0094] Comparative Example 4

[0095] The electronic grade sulfuric acid was prepared according to the method of Example 1, except that in step (2), the polytetrafluoroethylene fiber membrane prepared in Preparation Example 8 was used for filtering and absorbing. A semi-finished sulfuric acid solution with a content of 80 wt% of sulfuric acid was obtained, and then a crude electronic grade sulfuric acid product with a content of 96 wt% of sulfuric acid was obtained, and then the electronic grade sulfuric acid product was prepared.

[0096] The content of sulfur dioxide, the content of particulate impurities and the ion content of the electronic grade sulfuric acid products obtained in each example and comparative example were determined, and the determination results are shown in Table 1. Among them, Li to V represent the content of metal elements.

[0097] Table 1

[0098]

[0099]

[0100] Table 1 (continued)

[0101]

[0102]

[0103] As can be seen from the results in Table 1, the preparation method provided by the present application can be used to prepare high-purity electronic grade sulfuric acid. The electronic grade sulfuric acid prepared in Examples 1-6 has a content of sulfur dioxide less than or equal to 1000 ppb, a content of particulate impurities less than or equal to 50 pieces / mL, and a content of single metal cations less than or equal to 100 ppt. In Comparative Example 1, a polysulfone fiber microporous membrane was used for filtering and absorbing. Since the chemical corrosion resistance, high temperature resistance and oxidation resistance of the prepared fiber microporous membrane are poor, part of the filter membrane is broken after running for 12 hours under the long-term impact of the acid solution, resulting in a significant increase in the content of sulfur dioxide, the content of particulate impurities and the ion content of the electronic grade sulfuric acid product. In Comparative Example 3, a fiber microporous membrane without polyethylene glycol was used for filtering and absorbing. The porosity of the prepared fiber microporous membrane is significantly reduced, resulting in a significant increase in the content of sulfur dioxide, the content of particulate impurities and the ion content of the electronic grade sulfuric acid product. In Comparative Example 2, no fiber microporous membrane was used for filtering and absorbing, and in Comparative Example 4, a polytetrafluoroethylene fiber membrane without hollow structure was used for filtering and absorbing. Compared with Examples 1-6, the content of sulfur dioxide, the content of particulate impurities and the ion content of the electronic grade sulfuric acid product are significantly increased, and the purity is greatly reduced.

[0104] In addition, the fiber microporous membrane prepared in Example 2 has a larger pore size, a lower porosity and a lower specific surface area than that prepared in Example 1, resulting in an increase in the content of sulfur dioxide, the content of particulate impurities and the content of some ions in the electronic-grade sulfuric acid product; the concentration of the semi-finished sulfuric acid solution and the concentration temperature are changed in Example 3, and the content of sulfur dioxide, the content of particulate impurities and the content of some ions in the electronic-grade sulfuric acid product prepared in Example 3 are increased compared with those in Example 1, which indicates that the purity of the electronic-grade sulfuric acid product is greatly affected by the concentration of the semi-finished sulfuric acid solution and the concentration temperature; the fiber microporous membrane prepared in Example 4 is prepared from polyvinylidene fluoride, and the mechanical strength of the fiber microporous membrane is weakened, and the pore size, the porosity and the specific surface area of the fiber microporous membrane are reduced, resulting in an increase in the content of sulfur dioxide, the content of particulate impurities and the content of ions in the electronic-grade sulfuric acid product; the fiber microporous membrane prepared in Example 5 is prepared from polytetrafluoroethylene with a smaller weight average molecular weight, and the pore size, the porosity and the specific surface area of the fiber microporous membrane are reduced, resulting in an increase in the content of sulfur dioxide, the content of particulate impurities and the content of ions in the electronic-grade sulfuric acid product; the fiber microporous membrane prepared in Example 6 is prepared from polyethylene glycol with a larger weight average molecular weight and a smaller amount, and the porosity and the specific surface area of the fiber microporous membrane are reduced, resulting in an increase in the content of sulfur dioxide, the content of particulate impurities and the content of ions in the electronic-grade sulfuric acid product. Therefore, the selection of the type of fluorine-containing polymer, the weight average molecular weight of polyethylene glycol and polytetrafluoroethylene and the amount of polyethylene glycol can obtain a fiber microporous membrane with moderate pore size, porosity and specific surface area and high mechanical strength, thereby improving the purity of the electronic-grade sulfuric acid product. In addition, the purity of the electronic-grade sulfuric acid product can be further improved by selecting a suitable concentration of the semi-finished sulfuric acid solution and a suitable concentration temperature.

[0105] The above describes the preferred embodiments of the present application in detail, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as the disclosed content of the present application and fall within the protection scope of the present application.

Claims

1. A process for the production of electronic grade sulfuric acid, characterized in that, The preparation method comprises the following steps: (1) vaporizing crude sulfur trioxide to obtain gaseous sulfur trioxide raw material; (2) filtering and absorbing the gaseous sulfur trioxide raw material and ultrapure water through a fiber microporous membrane to obtain a semi-finished product sulfuric acid solution; (3) concentrating the semi-finished product sulfuric acid solution to obtain electronic-grade sulfuric acid crude product; (4) cooling and filtering the electronic-grade sulfuric acid crude product to obtain the electronic-grade sulfuric acid. The fiber microporous membrane is prepared from a mixture comprising a fluorine-containing polymer and polyethylene glycol through granulation, spinning, winding and stretching.

2. The production method according to claim 1, characterized by, The amount of the polyethylene glycol in the mixture is 6-10 wt% based on the weight of the fluorine-containing polymer.

3. The preparation method according to claim 1, characterized in that, The fluorine-containing polymer is at least one selected from polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene difluoride, fluorinated ethylene-propylene copolymer, ethylene-tetrafluoroethylene copolymer and chlorotrifluoroethylene-ethylene copolymer.

4. The production method according to claim 3, characterized by, The fluorine-containing polymer is polytetrafluoroethylene.

5. The method of claim 1, wherein, The weight average molecular weight of the fluorine-containing polymer is 300-4000 thousand g / mol.

6. The method of claim 1, wherein, The weight average molecular weight of the polyethylene glycol is 4000-5000 g / mol.

7. The preparation method according to claim 1, characterized in that, The fiber microporous membrane has pores with a pore size of 10-500 μm.

8. The preparation method according to claim 7, characterized in that, The fiber microporous membrane has pores with a pore size of 20-50 μm.

9. The method of claim 1, wherein, The porosity of the fiber microporous membrane is 70-80%.

10. The method of claim 9, wherein, The porosity of the fiber microporous membrane is 75-80%.

11. The method of claim 1, wherein, The specific surface area of the fibrous microporous membrane is 300-1000 m 2 / g.

12. The method of claim 11, wherein, The specific surface area of the fibrous microporous membrane is 900-1000 m 2 / g.

13. The method of claim 1, wherein, In step (1), the purity of the crude sulfur trioxide is greater than or equal to 99.5 wt%, the content of particulate matter contained in the crude sulfur trioxide is less than or equal to 400 ppm, the content of iron is less than or equal to 60 ppm, and the content of sulfur dioxide is less than or equal to 4000 ppm.

14. The method of claim 1, wherein, The content of sulfur dioxide contained in the semi-finished product sulfuric acid solution is less than or equal to 1000 ppb.

15. The method of claim 1, wherein, In step (3), the content of sulfuric acid contained in the electronic-grade sulfuric acid crude product is 96-98 wt% based on the total weight of the electronic-grade sulfuric acid crude product.

16. The method of claim 1, wherein, The content of sulfuric acid contained in the semi-finished product sulfuric acid solution is 60-80 wt% based on the total weight of the semi-finished product sulfuric acid solution.

17. The method of claim 1, wherein, The concentration temperature is 130-150℃.

18. The method of claim 17, wherein, The concentration temperature is 130-140℃.

19. The method of claim 1, wherein, The cooling temperature is 30-50℃.

20. The method of claim 1, wherein, The content of sulfur dioxide contained in the electronic-grade sulfuric acid is less than or equal to 1000 ppb, the content of particulate impurities contained in the electronic-grade sulfuric acid is less than or equal to 50 pieces / mL, and the content of single metal cations contained in the electronic-grade sulfuric acid is less than or equal to 100 ppt.

21. The method of claim 20, wherein, The content of sulfur dioxide contained in the electronic-grade sulfuric acid is less than or equal to 500 ppb, the content of particulate impurities contained in the electronic-grade sulfuric acid is less than or equal to 15 pieces / mL, and the content of single metal cations contained in the electronic-grade sulfuric acid is less than or equal to 10 ppt.

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