Process for purifying high-purity sulfuric acid and device thereof

Abstract

The application provides a high-purity sulfuric acid purification process and device. By using specific adsorption, evaporation, filtration, distillation and other process flows, metal ions, sulfur dioxide, particles and other impurities are efficiently removed, and electronic-grade sulfuric acid with high purity is prepared, which meets the needs of microelectronic industry applications. The process flow and device of the application have high production yield of electronic-grade sulfuric acid, stable product quality and strong practicability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electronic-grade chemical preparation, and particularly relates to a purification process and device of high-purity sulfuric acid BACKGROUND

[0002] Electronic-grade sulfuric acid, also known as ultra-pure sulfuric acid or high-purity sulfuric acid, is one of the wet electronic chemicals used in the microelectronics industry. It can clean and etch silicon wafers, effectively removing impurity particles, inorganic residues and carbon deposits on the wafers, and is widely used in the production of electronic components such as photovoltaic solar cells, flat panel displays and integrated circuits.

[0003] With the increasing requirements of electronic component manufacturing, the purity of chemical reagents used in related industries is also increasing. In order to standardize the world's ultra-clean high-purity reagents and adapt to the trend of continuous improvement of the process technology level of the electronic information industry, the International Semiconductor Equipment and Materials Organization (SEMI) has developed an international classification standard for wet electronic chemicals based on metal impurities, particle size control, particle count and application range, which is divided into G1-G5. The domestic standard is divided into E1-E5. Among them, integrated circuits require the highest quality of wet electronic chemicals, and as the line width of integrated circuits decreases, the purity of wet electronic chemicals is constantly improving. From a technical trend, meeting the processing needs of nanoscale integrated circuits is one of the future directions of ultra-clean high-purity reagents.

[0004] Internationally, companies such as BASF, Evonik, Mitsubishi Corporation and Kanto Chemical Industry Corporation can produce electronic-grade sulfuric acid on a large scale, but there are few reports on the key technologies they use. In recent years, the expansion of domestic electronic-grade sulfuric acid production capacity has been rapid, but the output is still small, and most of the products are G1-G2, with few G3 products and unstable quality.

[0005] Patent CN110155955A discloses a production method for producing electronic-grade sulfuric acid from non-ferrous smelting flue gas, which uses oleum to absorb sulfur trioxide and performs two evaporation steps and high-temperature filtration. This method not only obtains high-purity SO3 from non-ferrous smelting flue gas, but also produces high-purity electronic-grade sulfuric acid. However, the absorption and evaporation process of this method has low removal efficiency for metal impurities, the smelting flue gas has a large variation range of flue gas volume and unstable SO2 concentration, which affects the product quality and requires further improvement of the product grade. In addition, the high-temperature filtration consumes a lot of energy.

[0006] Patent CN112320768A proposes a production method of electronic grade sulfuric acid, which uses concentrated sulfuric acid to absorb gaseous SO3 to generate oleum, then uses hydrogen peroxide to oxidize SO2 in the oleum to SO3, and then distills SO3 gas. This process needs to consume high-purity reagents, and O2 is generated during the hydrogen peroxide oxidation process, which enters the next process together with gaseous SO3 and is dissolved in the product. Simple degassing methods cannot completely remove O2, affecting the final product grade.

[0007] The existing disclosed preparation process has low removal efficiency for impurity metals, particles and non-target gases, and the process is complex, which cannot meet the needs of high-grade electronic grade sulfuric acid production and large-scale production. SUMMARY

[0008] The present application provides a purification process and device for high-purity sulfuric acid, aiming to provide a simple and efficient method to reduce the content of metal, particle and other impurities in electronic grade sulfuric acid and improve the quality of electronic grade sulfuric acid.

[0009] The purpose of the present application is to overcome the deficiencies in the prior art and provide a method for producing electronic grade sulfuric acid. To achieve the above technical purpose, the technical solution adopted by the present application is:

[0010] A method for producing high-purity sulfuric acid, comprising the following steps:

[0011] (1) Dilute industrial concentrated sulfuric acid, adsorb and filter to remove metal ions;

[0012] (2) Evaporate liquid sulfur trioxide as raw material to obtain sulfur trioxide gas;

[0013] (3) Use the product of step (1) as an absorption liquid to absorb the sulfur trioxide gas prepared in step (2) to prepare oleum;

[0014] (4) Evaporate the oleum, condense SO3 and then evaporate again into a first filter to remove sulfur dioxide and particles, and return the remaining sulfuric acid to step (3);

[0015] (5) Use electronic grade ultra-pure water to absorb sulfur trioxide to obtain electronic grade sulfuric acid;

[0016] (6) Perform rectification and heavy treatment on the electronic grade ultra-pure sulfuric acid in step (5), and then use a second filter to remove particulate matter to obtain high-purity electronic grade sulfuric acid.

[0017] Surprisingly, the adsorption efficiency of metal ions and particles can be significantly improved by diluting the industrial concentrated sulfuric acid to a specific concentration and then using activated carbon adsorption, thereby improving the quality of the final electronic-grade sulfuric acid. This may be because the concentration of sulfuric acid significantly affects the viscosity of the solution. If the concentration of sulfuric acid is too high, the viscosity is large, which affects the adsorption between metal ions, particles and activated carbon.

[0018] The filter in step (4) is a silicon carbide porous ceramic with a surface-loaded V2O5 catalyst. The ceramic matrix has a porous structure with pores having a diameter of 1-200 microns. The ceramic matrix is immersed in an emulsion, dried, oxidized, and pyrolyzed to obtain the filter. The emulsion includes a silicon source, a carbon source, halloysite nanotubes, a V2O5 catalyst precursor, and an emulsifier.

[0019] Optionally, the precursor of the V2O5 catalyst is one or more of ammonium metavanadate, vanadyl oxalate, and vanadyl sulfate.

[0020] Optionally, in step (1), the industrial concentrated sulfuric acid is diluted to 65-75% with 95-98% industrial concentrated sulfuric acid as the raw material.

[0021] Optionally, in step (2), the SO3 content in the fuming sulfuric acid is 20-45%.

[0022] Optionally, in step (4), the filter is heated to 400-450°C.

[0023] In addition, the present application also provides a device for producing electronic-grade sulfuric acid, which can produce electronic-grade sulfuric acid with excellent performance in cooperation with the preparation method of the present application.

[0024] A device for producing electronic-grade sulfuric acid, comprising a mixed acid device, an adsorption device, a first absorption tower, a second evaporator, a condenser, a third evaporator, a first filtration device, a second absorption tower, a rectification and heavy removal device, and a second filtration device connected in sequence. The first absorption tower and the second absorption tower each include an absorption tower body and an acid tank, the acid tank is connected to a cooler through a circulating pump, and the cooled acid is partially introduced into the absorption tower body or the acid tank, and the other part is introduced into the connected second evaporator or rectification and heavy removal device. The first evaporator is connected to the first absorption tower, and the liquid sulfur trioxide in the first evaporator is evaporated into the first absorption tower. The adsorption device is filled with coconut shell activated carbon modified by methylethylamine and carbon disulfide.

[0025] Optionally, the first filtration device is a silicon carbide porous ceramic with a surface-loaded V2O5 catalyst. The ceramic matrix has a porous structure with pores having a diameter of 1-200 microns. The ceramic matrix is immersed in an emulsion, dried, oxidized, and pyrolyzed to obtain the filter. The emulsion includes a silicon source, a carbon source, halloysite nanotubes, a V2O5 catalyst precursor, and an emulsifier.

[0026] Optionally, the second filtering device can be an electronic grade sulfuric acid filter, and the filter is connected with an electronic grade sulfuric acid storage tank.

[0027] Optionally, a diluter is arranged before the second filtering device, receives electronic grade pure water, and dilutes to a required concentration.

[0028] Compared with the prior art, the present application has the following advantages and beneficial effects.

[0029] (1) The industrial concentrated sulfuric acid is diluted to a certain concentration before being adsorbed by the activated carbon, which can significantly improve the adsorption efficiency of metal ions and particles, and further improve the quality of the final electronic grade sulfuric acid.

[0030] (2) The activated carbon modified by the specific reagent has good adsorption effect on metal ions, especially iron ions, copper ions, aluminum ions, cadmium ions and calcium ions. Compared with other adsorbents, the concentration of metal ions in the concentrated sulfuric acid can be significantly reduced, and the content of sulfur trioxide entraining metal ions in the subsequent fuming sulfuric acid evaporation process can be reduced.

[0031] (3) The present application uses silicon carbide porous ceramics loaded with V2O5 catalyst, which can effectively improve the efficiency of V2O5 catalytic removal of sulfur dioxide, and the porous ceramics can also block some particles.

[0032] (4) The process flow and equipment used in the present application have high production efficiency of electronic grade sulfuric acid, stable product quality, can meet the needs of customers, and have strong practicability. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is an electronic grade sulfuric acid production device, wherein: 110 - acid mixer; 120 - adsorption device; 130 - first absorption tower; 140 - second evaporator; 150 - condenser; 160 - third evaporator; 170 - first filtering device; 180 - second absorption tower; 190 - rectification and heavy component removal device; 200 - second filtering device; 210 - first evaporator; DETAILED DESCRIPTION

[0034] The following examples are only examples covered by the present application, and do not constitute any limitation on the scope of implementation.

[0035] Example 1

[0036] A method for producing electronic grade sulfuric acid is realized by using the device shown in the figure. Figure 1

[0037] ​Specifically, the industrial concentrated sulfuric acid is diluted in the mixing acid device 110, and the concentration of the sulfuric acid is reduced to 65%. The diluted sulfuric acid enters the adsorption device 120, which is filled with the coconut shell activated carbon modified by methyl ethyl amine and carbon disulfide. The sulfuric acid purified by adsorption is transferred to the first absorption tower 130. Liquid sulfur trioxide is added to the first evaporator 210, and evaporation is carried out at 55°C. The purified sulfur trioxide gas is introduced into the first absorption tower 130, and the sulfuric acid absorbs the sulfur trioxide to prepare fuming sulfuric acid with a sulfur trioxide concentration of 20%. The fuming sulfuric acid is evaporated in the second evaporator 140, and the evaporated sulfur trioxide gas enters the third evaporator 160 after passing through the condenser 150. The sulfur trioxide gas is evaporated again in the third evaporator 160 and then enters the first filter device 170 for filtration. The temperature of the filter device is controlled at 420°C. Subsequently, the electronic grade concentrated sulfuric acid is obtained by entering the second absorption tower 180. The remaining sulfuric acid in the second evaporator 140 can be transferred to the first absorption tower 130. The electronic grade concentrated sulfuric acid is preheated and sent to the rectification and heavy component removal device 190. The conditions of the removal tower are as follows: the top temperature is 180°C, the bottom temperature is 212°C, the number of plates is 25, the reflux ratio is 1:10, and the concentration of the electronic grade concentrated sulfuric acid collected at the top is 96.9%. The electronic grade concentrated sulfuric acid passes through the electronic grade sulfuric acid filter device 200 to obtain high-purity electronic grade sulfuric acid.

[0038] The first absorption tower 130 and the second absorption tower 180 each include an absorption tower body and an acid tank. The acid tank is connected to a cooler by a circulating pump. Part of the cooled acid enters the absorption tower body or the acid tank, and the other part enters the connected evaporator or rectification and heavy component removal device. The first evaporator 210 is connected to the first absorption tower 130, and the liquid sulfur trioxide in the first evaporator 210 is evaporated into the first absorption tower 130.

[0039] The connection order of the aforementioned devices mainly represents the flow direction of the gas or liquid. The absorption tower, evaporator, condenser, rectification device, and filter are all devices commonly used in the field of sulfuric acid purification. The connection of the devices can be made in a manner known in the art. In addition, the absorption tower, evaporator, and rectification device can be connected to a cooler, acid mist removal device, etc. according to specific application needs.

[0040] The first filter device includes a silicon carbide porous ceramic with a surface-loaded V2O5 catalyst. The ceramic matrix has a porous structure with a pore diameter of 30 microns. After being immersed in an emulsion, dried, oxidized, and cracked, the ceramic matrix becomes a filter material. The emulsion includes a silicon source, a carbon source, halloysite nanotubes, a V2O5 catalyst precursor, and an emulsifying agent.

[0041] The modification method of the coconut shell type activated carbon is: 180g of coconut shell activated carbon, 20g of carbon disulfide, 40g of methyl ethylamine are mixed and uniformly dispersed in deionized water. After 1 hour, the temperature of the solution is increased from room temperature to 45℃, and the reaction is carried out at this temperature for 2 hours, and then the temperature is increased to 95℃ and the reaction is carried out for 3 hours. Stop heating and let the solution stand for 10 hours, then wash with deionized water several times.

[0042] The adsorption efficiency of metal ions is different for different activated carbon modifiers. Among them, the adsorbent modified by carbon disulfide and methyl ethylamine has strong adsorption effect on iron ions, copper ions, aluminum ions, cadmium ions and calcium ions, which is beneficial to the removal of metal ions in the sulfuric acid purification process.

[0043] The preparation method of the silicon carbide porous ceramic loaded with V2O5 catalyst is: porous silicon carbide with a pore size of about 30 microns is used as a substrate, dimethylbenzene 150g, epoxy resin 10g, polycarbosilane 16g, span80 2g, ammonium metavanadate 5g, halloysite nanotube 2g, water 10g are mixed, stirred, fully dissolved and emulsified to obtain an emulsion, the porous silicon carbide substrate is immersed for 30min, then taken out, dried at 30℃ for 8 hours, pre-oxidized at 250℃ for 120min, and then cracked at 600℃ under argon atmosphere to obtain the porous ceramic.

[0044] Example 2

[0045] The conditions for controlling the rectification and heavy removal device are: the top temperature is 186℃, the bottom temperature is 218℃, the plate number is 28, and the reflux ratio is 1:9 (the other steps and conditions are the same as in Example 1), the concentration of the electronic grade concentrated sulfuric acid collected at the top is 96.8%, and the high-purity electronic grade concentrated sulfuric acid is obtained after passing through the electronic grade filter device 200.

[0046] Comparative Example 1

[0047] Except that the adsorbent is coconut shell type activated carbon modified by hydrazine and carbon disulfide, the other conditions are the same as in Example 1.

[0048] Comparative Example 2

[0049] Except that the adsorbent is coconut shell type activated carbon without modification, the other conditions are the same as in Example 1.

[0050] Comparative Example 3

[0051] Without passing through the first filter device, the other conditions are the same as in Example 1.

[0052] Comparative Example 4

[0053] The preparation method of the first filtering device: the first filtering device is a silicon carbide porous ceramic with a surface-loaded V2O5 catalyst, the ceramic matrix has a porous structure with a pore diameter of 1-200 microns, and the ceramic matrix is immersed in an emulsion, dried, oxidized, and pyrolyzed to obtain the filter. The emulsion includes a silicon source, a carbon source, a V2O5 catalyst precursor, and an emulsifier. The other conditions are the same as in Example 1.

[0054] Sulfuric acid mass fraction determination method: using methyl red-methylene blue mixed indicator solution as indicator, titrated with sodium hydroxide standard titration solution, the mass fraction of sulfuric acid was measured.

[0055] Colorimetric determination method: using APHA colorimeter for determination.

[0056] Potassium permanganate mass fraction test: 64g of sample was weighed to 0.1g, slowly put into 90mL of water, cooled to 25℃, 0.2mL, 0.4mL, 0.6mL, 0.8mL of potassium permanganate standard solution (0.01mol / L) titration solution was added, and the pink color should not disappear within 5min.

[0057] Metal ion mass fraction determination: using inductively coupled plasma mass spectrometer (ICP-MS) for determination. 5g of sample was weighed to 0.01g, slowly put into a 50mL volumetric flask containing a small amount of ultrapure water, cooled to room temperature, diluted to the mark with water, and shaken well. Under the same analysis conditions as the standard solution series, the signal intensity of each element in the sample was determined, and a blank test was performed. For specific instrument preparation, working curve drawing, test processing, etc., see GB / T 41881-2022.

[0058] Particle determination: using a laser liquid particle counter for determination.

[0059] The specific test data is shown in Table 1:

[0060]

[0061]

[0062] Comparative Example 3 did not use a second filtering device, and the mass of reduced potassium permanganate was greater than 4mg / kg. Comparative Example 4 used a second filtering device for filtration, and the mass of reduced potassium permanganate was greater than 2mg / kg but less than 3mg / kg.

[0063] The above examples and test data are only some applications and embodiments of the present application, and cannot limit the protection scope of the present application. From the above description, any person skilled in the art can see that the present application is innovated by using novel ideas and means, and has obvious practicality and creativity.

Claims

1. A method for purifying high-purity sulfuric acid, comprising the following steps: (1) diluting industrial concentrated sulfuric acid, removing metal ions by adsorption and filtration, and using coconut shell activated carbon modified by methylethylamine and carbon disulfide as the adsorbent; the modification method of the coconut shell activated carbon is as follows: 180 g of coconut shell activated carbon, 20 g of carbon disulfide, and 40 g of methylethylamine are mixed and uniformly dispersed in deionized water by stirring; after 1 hour, the temperature of the solution is increased from room temperature to 45°C, and the reaction is carried out at this temperature for 2 hours, and then the temperature is increased to 95°C and the reaction is carried out for 3 hours; the heating is stopped and the solution is allowed to stand for 10 hours, after which it is washed several times with deionized water; (2) evaporating liquid sulfur trioxide as raw material to obtain sulfur trioxide gas; (3) using the product of step (1) as an absorption liquid to absorb the sulfur trioxide gas prepared in step (2) to prepare oleum; (4) evaporating the oleum, condensing SO3, and then evaporating again into a first filter to remove sulfur dioxide and particles in it, and returning the remaining sulfuric acid to step (3); (5) using electronic-grade ultra-pure water to absorb sulfur trioxide to obtain electronic-grade sulfuric acid; (6) performing rectification and heavy-removal treatment on the electronic-grade ultra-pure sulfuric acid in step (5), and then using a second filter to remove particulate matter to obtain high-purity electronic-grade sulfuric acid; in step (1), 95-98% industrial concentrated sulfuric acid is used as raw material and diluted to 65-75%; in step (4), the first filter is a silicon carbide porous ceramic with a surface-loaded V2O5 catalyst, the ceramic matrix has a porous structure with a pore diameter of 1-200 microns, and the filter is obtained after the ceramic matrix is immersed in an emulsion, dried, oxidized, and pyrolyzed, the emulsion including a silicon source, a carbon source, halloysite nanotubes, a V2O5 catalyst precursor, and an emulsifier, the filter in step (4) is heated to 400-450°C, and the SO3 content in the oleum in step (3) is 20-45%.

2. The method of claim 1, wherein: the V2O5 catalyst precursor is one or more of ammonium metavanadate, vanadyl oxalate, and vanadyl sulfate.

3. An apparatus for producing electronic-grade sulfuric acid by the method of claim 1, comprising, in sequence, a mixed acid device (110), an adsorption device (120), a first absorption tower (130), a second evaporator (140), a condenser (150), a third evaporator (160), a first filter device (170), a second absorption tower (180), a rectification and heavy-removal device (190), and a second filter device (200); the first absorption tower (130) and the second absorption tower (180) each include an absorption tower body and an acid tank, the acid tank is connected to a cooler through a circulating pump, and part of the cooled acid enters the absorption tower body or the acid tank, and the other part enters the second evaporator (140) or the rectification and heavy-removal device (190) connected thereto; the first evaporator (210) is connected to the first absorption tower (130), and liquid sulfur trioxide in the first evaporator (210) is evaporated into the first absorption tower (130); the adsorption device (120) is filled with coconut shell activated carbon modified by methylethylamine and carbon disulfide. The first filtering device (170) is a surface load V2O5 catalyst silicon carbide porous ceramic, the ceramic matrix is a porous structure, the diameter of the pores is 1-200 microns, the ceramic matrix is immersed, dried, oxidized and cracked in an emulsion to obtain a filter material, the emulsion includes a silicon source, a carbon source, halloysite nanotubes, a V2O5 catalyst precursor and an emulsifier.

4. The apparatus of claim 3, wherein: A diluter is arranged before the second filtering device (200) to receive electronic grade pure water and dilute to a required concentration.

Images