Ultra-clean high-purity hydrochloric acid and its production process

Abstract

The present application relates to the production process of super-clean high-purity hydrochloric acid, and belongs to the technical field of high-purity hydrochloric acid preparation, comprising the following steps: first, filtering industrial hydrochloric acid through a microfilter into a hydrochloric acid storage tank; second, according to the content of free chlorine in the hydrochloric acid storage tank, preparing a sodium sulfite solution, adding the sodium sulfite solution into the hydrochloric acid storage tank, then adding a barium chloride solution, after 2-3 hours of reaction, filtering, adding modified carbon fiber into the filtrate, after 4-6 hours of standing, filtering again, and flowing the filtrate into a resin tower for further impurity removal, closed tower operation, discharging the liquid with iron content below 0.1 mg to obtain purified hydrochloric acid; third, flowing the purified hydrochloric acid into a condenser for preheating, then into a distiller for distillation, condensing the gas-phase hydrochloric acid after distillation in the condenser, collecting the condensed hydrochloric acid and flowing it into a finished product receiving tank to obtain super-clean high-purity hydrochloric acid; the high-purity hydrochloric acid obtained by the production process has low free chlorine content and low metal ion content.

Description

Technical Field

[0001] This invention belongs to the field of high-purity hydrochloric acid preparation technology, specifically, it relates to an ultra-clean high-purity hydrochloric acid and its production process. Background Technology

[0002] Ultra-clean and high-purity reagents, internationally known as process chemicals, are one of the key basic chemical materials in the manufacturing process of integrated circuits (ICs) and very large-scale integrated circuits (VLSIs). They are mainly used for chip cleaning and etching. In addition, ultra-clean and high-purity reagents are also used for chip doping and deposition processes and for cleaning the surface of silicon wafers. The purity and cleanliness of ultra-clean and high-purity reagents have a very important impact on the yield, electrical performance and reliability of integrated circuits.

[0003] Ultra-pure hydrochloric acid is a high-purity aqueous solution of hydrogen chloride, colorless and transparent, and is an important industrial raw material. In the ion-exchange membrane alkali production technology, the quality of the brine entering the electrolyzer directly affects the membrane's lifespan, cell voltage, current efficiency, and product quality. When impurities such as calcium, magnesium, strontium, barium, and sulfate in the brine enter the membrane in ionic form, they will deposit on the membrane as metal hydroxides, sulfates, and silicates. If these ions coexist, it will cause a sharp drop in current efficiency. These effects will drastically shorten the lifespan of the ion exchange membrane, causing difficulties in the alkali production process. Furthermore, the presence of free chlorine in hydrochloric acid will cause the resin to oxidize when it enters the resin exchange tower, even causing it to lose its activity and become unregenerable. It can also lead to the breakage of the ion exchange resin, ultimately resulting in a decrease in the quality of the secondary brine and a shortened ion-exchange membrane lifespan. Therefore, providing a production process for high-purity hydrochloric acid with low free chlorine content and low metal ion content is a technical problem that needs to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide ultrapure high-purity hydrochloric acid and its production process to solve the technical problems mentioned in the background.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] Ultra-clean, high-purity hydrochloric acid and its production process include the following steps:

[0007] The first step is to filter industrial hydrochloric acid with a mass fraction of 36-38% into the hydrochloric acid storage tank through a 0.45μm microfilter;

[0008] The second step involves preparing a sodium sulfite solution of a certain concentration based on the free chlorine content in the hydrochloric acid storage tank. This solution is then added dropwise to the hydrochloric acid storage tank through a dropper to eliminate the free chlorine. Next, a barium chloride solution of a certain concentration is added dropwise. After reacting for 2-3 hours, the solution is filtered, the precipitate is discarded, and modified carbon fiber is added to the filtrate. After standing for 4-6 hours, the solution is filtered again. The filtrate is then metered by a flow meter and pumped from top to bottom into a resin tower for further impurity removal. Once the tower is filled with acid, the tower is shut down and operated until the iron content in the effluent is below 0.1 mg, thus obtaining purified hydrochloric acid.

[0009] The third step involves preheating the purified hydrochloric acid by passing it through pipes and valves into a condenser, then distilling it in a still. The circulating water valve of the condenser is opened, and the distilled gaseous hydrochloric acid is condensed in the condenser. The condensed hydrochloric acid is collected and flows into the finished product receiving tank to obtain ultra-clean high-purity hydrochloric acid.

[0010] Furthermore, the modified carbon fiber is made by the following steps:

[0011] Step A1: Impregnate the horned melon fiber in a sodium hydroxide solution with a mass fraction of 1.3-1.5 g / L, add the penetrant JFC, and shake at room temperature for 24 h. Then filter, wash the filter cake with deionized water until the washing liquid is neutral, and then impregnate it in a phosphoric acid solution with a volume fraction of 25-30% for activation treatment for 12 h. Then take it out and dry it at 60 °C to constant weight, then transfer it to a muffle furnace and pre-oxidize it at 200 °C for 2 h. Then vacuum it and heat it to 600 °C at a rate of 10 °C / min for 70 min to obtain hollow carbon fiber.

[0012] The ratio of the amounts of horned melon fiber, sodium hydroxide solution, penetrant JFC, and phosphoric acid solution is 20-25g: 500mL: 0.1mL: 400-500mL. Horned melon fiber is the seed fiber of the perennial shrub horned melon. Its main components are cellulose, lignin, and hemicellulose. It has a high hollow structure with a hollowness greater than 90%. Therefore, hollow carbon fibers prepared by using it as a precursor for carbon fiber materials contain two surfaces, an inner and an outer surface, and have a significantly increased specific surface area compared to solid carbon fibers.

[0013] Step A2: Immerse the hollow carbon fiber in the oxidation solution for 12 hours, then filter it. Wash the filter cake with deionized water 3-5 times, and then dry it at 40°C to constant weight to obtain oxidized carbon fiber.

[0014] The ratio of hollow carbon fiber to oxidation solution is 10g:150-200mL. The oxidation solution is prepared by mixing potassium permanganate, sodium hydroxide and deionized water in a ratio of 0.3mol:0.01mol:0.9-1.1L. The hollow carbon fiber is oxidized by the oxidation solution to increase the number of oxygen-containing groups (hydroxyl, carbonyl and carboxyl groups) on its surface, thus obtaining oxidized carbon fiber.

[0015] Step A3: Dissolve 4'-acetylbenzo-18-crown-6-ether in methanol, then add hydroxypropylamine and a 6 mol / L hydrochloric acid solution. Reflux the mixture for 4-6 hours at a speed of 60-100 r / min. After the reaction is complete, adjust the pH to 7-8 with a 25% ammonia solution. Remove the solvent methanol and water by rotary evaporation to obtain the terminal hydroxycrown ether compound.

[0016] The specific reaction process is as follows:

[0017]

[0018] The ratio of 4'-acetylbenzo-18-crown-6-ether, methanol, hydroxypropylamine, and hydrochloric acid solution was 0.05 mol: 130-150 mL: 0.05 mol: 1.1-1.3 mL. The hydroxypropylamine's amino group reacted with the ketone group of 4'-acetylbenzo-18-crown-6-ether to form a Schiff base reaction, yielding a terminal hydroxycrown ether compound.

[0019] Step A4: Add carbon dioxide, p-toluenesulfonic acid, terminal hydroxy crown ether compound, ethylenediaminetetraacetic acid and DMF to a three-necked flask, heat to 60-75℃, stir and react for 4-6 hours. After the reaction is complete, add deionized water for washing, centrifuge at 1000-1500 r / min for 15 min, wash the precipitate with deionized water 3-5 times, and dry at 60℃ to constant weight to obtain modified carbon dioxide.

[0020] The ratio of carbon dioxide, hydroxyl-terminated crown ether compound, ethylenediaminetetraacetic acid (EDTA), and DMF is 2.5-2.8 g: 1.3-1.5 g: 0.3-0.5 g: 38.7-42.1 mL. The amount of p-toluenesulfonic acid is 3-5% of the total mass of carbon dioxide, hydroxyl-terminated crown ether compound, and EDTA. Under the catalysis of p-toluenesulfonic acid, the carboxyl groups on the surface of carbon dioxide react with the hydroxyl groups of the hydroxyl-terminated crown ether compound, and the hydroxyl groups of the carboxyl groups on the surface of carbon dioxide react with the carboxyl groups of EDTA to obtain modified carbon dioxide.

[0021] Furthermore, the temperature inside the resin tower is 22-30℃, and the pressure is 0.03-0.05MPa.

[0022] Furthermore, the temperature in the still is 84-88℃ and the pressure is 0.1-0.25MPa.

[0023] Furthermore, the condensation temperature of the cooler is -80 to 30°C, and the pressure is 0.1 to 1.0 MPa.

[0024] Furthermore, the ultrapure high-purity hydrochloric acid is obtained by the above-mentioned production process.

[0025] The beneficial effects of this invention are:

[0026] This invention provides an ultra-pure hydrochloric acid and its production process. Using industrial hydrochloric acid as the starting material, insoluble impurities are first removed through a 0.45μm microfilter. Then, sodium sulfite solution is added to initially remove free chlorine, oxidizing the sodium sulfite to sodium sulfate. Next, the characteristic that barium sulfate precipitate is poorly soluble in hydrochloric acid is utilized to remove newly formed sulfate impurities. Then, carbon fiber is added to adsorb residual free chlorine and metal ions in the hydrochloric acid solution. The solution is then purified again through a resin tower to obtain purified hydrochloric acid. Finally, high-purity hydrochloric acid is obtained through distillation and condensation. Notably, this invention utilizes the high-hollow structure of hornwort fiber as a precursor to prepare hollow carbon fibers, which have a significantly increased specific surface area compared to solid carbon fibers. Furthermore, it is oxidized using an alkaline potassium permanganate solution to obtain oxidized carbon fibers with a surface rich in oxygen-containing groups. A Schiff base reaction is performed between the amino group of hydroxypropylamine and the ketone group of 4'-acetylbenzo-18-crown-6-ether to obtain a terminal hydroxy crown ether compound. Finally, under the catalysis of p-toluenesulfonic acid, the carboxyl groups on the surface of oxidized carbon fibers undergo esterification with the hydroxyl groups of the terminal hydroxy crown ether compound, and the hydroxyl groups of the carboxyl groups on the surface of the oxidized carbon fibers undergo esterification with the carboxyl groups of ethylenediaminetetraacetic acid (EDTA) to obtain modified carbon fibers. These modified carbon fibers contain EDTA structures, benzocrown ether structures, and oxygen-containing groups. They can not only capture free chlorine, but the EDTA structure also contains multiple coordinating atoms, which can share electrons with metal ions to form stable compounds with multiple ring structures. The benzocrown ether structure exhibits complexing and selectivity for alkali metals and alkaline earth metals, and has a good removal effect on magnesium and calcium ions in solution. Therefore, the high-purity hydrochloric acid prepared by this invention has high purity, and the production process is simple. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] This embodiment provides a modified carbon fiber, which is prepared by the following steps:

[0030] Step A1: Impregnate 20g of horned melon fiber in 500mL of sodium hydroxide solution with a mass fraction of 1.3g / L, add 0.1mL of penetrant JFC, shake at room temperature for 24h, then filter, wash the filter cake with deionized water until the washing liquid is neutral, then impregnate it in 400mL of phosphoric acid solution with a volume fraction of 25% for 12h, then take it out and dry it at 60℃ to constant weight, then transfer it to a muffle furnace, pre-oxidize it at 200℃ for 2h, then vacuum it, heat it to 600℃ at a rate of 10℃ / min, and carbonize it for 70min to obtain hollow carbon fiber;

[0031] Step A2: Immerse 10g of hollow carbon fiber in 150mL of oxidation solution for 12h, then filter, wash the filter cake three times with deionized water, and then dry it at 40℃ to constant weight to obtain oxidized carbon fiber. The oxidation solution is prepared by mixing potassium permanganate, sodium hydroxide and deionized water in the ratio of 0.3mol:0.01mol:0.9L.

[0032] Step A3: Dissolve 0.05 mol of 4'-acetylbenzo-18-crown-6-ether in 130 mL of methanol, then add 0.05 mol of hydroxypropylamine and 1.1 mL of 6 mol / L hydrochloric acid solution. Reflux the mixture for 4 h at 60 r / min. After the reaction is complete, adjust the pH to 7 with 25% ammonia solution. Remove the solvent methanol and water by rotary evaporation to obtain the terminal hydroxycrown ether compound.

[0033] Step A4: Add 2.5g of oxidized carbon fiber, p-toluenesulfonic acid, 1.3g of terminal hydroxyl crown ether compound, 0.3g of ethylenediaminetetraacetic acid, and 38.7mL of DMF to a three-necked flask, heat to 60℃, and stir for 4h. After the reaction is complete, add deionized water for washing, centrifuge at 1000r / min for 15min, wash the precipitate three times with deionized water, and dry at 60℃ to constant weight to obtain modified carbon fiber. The amount of p-toluenesulfonic acid used is 3% of the total mass of oxidized carbon fiber, terminal hydroxyl crown ether compound, and ethylenediaminetetraacetic acid.

[0034] Example 2

[0035] This embodiment provides a modified carbon fiber, which is prepared by the following steps:

[0036] Step A1: 22g of horned melon fiber was impregnated in 500mL of sodium hydroxide solution with a mass fraction of 1.4g / L, and 0.1mL of penetrant JFC was added dropwise. The mixture was shaken at room temperature for 24h, then filtered. The filter cake was washed with deionized water until the washing liquid was neutral. Then it was impregnated in 450mL of phosphoric acid solution with a volume fraction of 28% for 12h activation treatment. Then it was taken out and dried at 60℃ to constant weight. Then it was transferred to a muffle furnace and pre-oxidized at 200℃ for 2h. Then it was vacuumed and heated to 600℃ at a rate of 10℃ / min for 70min to obtain hollow carbon fiber.

[0037] Step A2: Immerse 10g of hollow carbon fiber in 180mL of oxidation solution for 12h, then filter, wash the filter cake 4 times with deionized water, and then dry it at 40℃ to constant weight to obtain oxidized carbon fiber. The oxidation solution is prepared by mixing potassium permanganate, sodium hydroxide and deionized water in the ratio of 0.3mol:0.01mol:1.0L.

[0038] Step A3: Dissolve 0.05 mol of 4'-acetylbenzo-18-crown-6-ether in 140 mL of methanol, then add 0.05 mol of hydroxypropylamine and 1.2 mL of 6 mol / L hydrochloric acid solution. Reflux the mixture for 5 h at 80 r / min. After the reaction is complete, adjust the pH to 7 with 25% ammonia solution. Remove the solvent methanol and water by rotary evaporation to obtain the terminal hydroxycrown ether compound.

[0039] Step A4: Add 2.7g of oxidized carbon fiber, p-toluenesulfonic acid, 1.4g of terminal hydroxyl crown ether compound, 0.4g of ethylenediaminetetraacetic acid, and 39.5mL of DMF to a three-necked flask, heat to 68℃, and stir for 5h. After the reaction is complete, add deionized water for washing, centrifuge at 1200r / min for 15min, wash the precipitate 4 times with deionized water, and dry at 60℃ to constant weight to obtain modified carbon fiber. The amount of p-toluenesulfonic acid used is 4% of the total mass of oxidized carbon fiber, terminal hydroxyl crown ether compound, and ethylenediaminetetraacetic acid.

[0040] Example 3

[0041] This embodiment provides a modified carbon fiber, which is prepared by the following steps:

[0042] Step A1: 25g of horned melon fiber was impregnated in 500mL of sodium hydroxide solution with a mass fraction of 1.5g / L, and 0.1mL of penetrant JFC was added dropwise. The mixture was shaken at room temperature for 24h, then filtered. The filter cake was washed with deionized water until the washing liquid was neutral. Then it was impregnated in 500mL of phosphoric acid solution with a volume fraction of 30% for 12h for activation treatment. Then it was taken out and dried at 60℃ to constant weight. Then it was transferred to a muffle furnace and pre-oxidized at 200℃ for 2h. Then it was vacuumed and heated to 600℃ at a rate of 10℃ / min for 70min to obtain hollow carbon fiber.

[0043] Step A2: Immerse 10g of hollow carbon fiber in 200mL of oxidation solution for 12h, then filter, wash the filter cake 5 times with deionized water, and then dry it at 40℃ to constant weight to obtain oxidized carbon fiber. The oxidation solution is prepared by mixing potassium permanganate, sodium hydroxide and deionized water in the ratio of 0.3mol:0.01mol:1.1L.

[0044] Step A3: Dissolve 0.05 mol of 4'-acetylbenzo-18-crown-6-ether in 150 mL of methanol, then add 0.05 mol of hydroxypropylamine and 1.3 mL of 6 mol / L hydrochloric acid solution. Reflux the mixture for 6 h at 100 r / min. After the reaction is complete, adjust the pH to 8 with 25% ammonia solution. Remove the solvent methanol and water by rotary evaporation to obtain the terminal hydroxycrown ether compound.

[0045] Step A4: Add 2.8g of oxidized carbon fiber, p-toluenesulfonic acid, 1.5g of terminal hydroxyl crown ether compound, 0.5g of ethylenediaminetetraacetic acid, and 42.1mL of DMF to a three-necked flask, heat to 75℃, and stir for 6 hours. After the reaction is complete, add deionized water for washing, centrifuge at 1500r / min for 15min, wash the precipitate 5 times with deionized water, and dry at 60℃ to constant weight to obtain modified carbon fiber. The amount of p-toluenesulfonic acid used is 5% of the total mass of oxidized carbon fiber, terminal hydroxyl crown ether compound, and ethylenediaminetetraacetic acid.

[0046] Comparative Example 1

[0047] This comparative example uses carbon fiber sold by Nantong Yongtong Environmental Protection Technology Co., Ltd.

[0048] Comparative Example 2

[0049] This comparative example is the product obtained in Example 1 of the invention patent with publication number CN108187618A.

[0050] Comparative Example 3

[0051] This comparative example uses carbon fiber sold by Nantong Lushen Environmental Protection and Purification Materials Co., Ltd.

[0052] The carbon fibers of Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests, and the test procedures are as follows:

[0053] Specific surface area, pore volume and pore size were tested using a TriStar3000 adsorption apparatus manufactured by Micron Instruments, Inc., USA.

[0054] Free chlorine adsorption test: Using a PCT chlorine-specific adsorption device, each group of carbon fiber materials was added at 25℃, and then chlorine gas was introduced into the container to 0.30 MPa. When adsorption reached saturation, i.e., when the pressure gauge reading no longer changed, the adsorbed mass fraction was measured.

[0055] Metal ion adsorption test: Six groups of 25% calcium chloride solutions and six groups of 25% magnesium chloride solutions were prepared. Equal amounts of each group of carbon fibers were added, and the solutions were shaken for 2 hours at 25°C. The adsorption capacity of each group of carbon fibers for calcium and magnesium ions was tested. The adsorption capacity Qe = (C1 - C2) × V / m, where C1 and C2 are the initial concentrations of the calcium chloride and magnesium chloride solutions, V is the volume of the calcium chloride and magnesium chloride solutions, and m is the mass of the carbon fibers. The test results are shown in Table 1.

[0056] Table 1

[0057]

[0058]

[0059] As shown in Table 1, the carbon fibers of Examples 1-3 have larger specific surface area, pore volume, and pore size than those of Comparative Examples 1-3, and their adsorption performance for chlorine and Ca is also better. 2+ Adsorption capacity, Mg 2+ The adsorption capacity of the modified carbon fibers prepared in this invention is better than that of comparative examples 1-3, indicating that the modified carbon fibers prepared in this invention have better adsorption performance for free chlorine and metal ions than existing carbon fibers.

[0060] Example 4

[0061] Ultra-clean, high-purity hydrochloric acid and its production process include the following steps:

[0062] The first step is to filter 36% industrial hydrochloric acid by mass through a 0.45μm microfilter into the hydrochloric acid storage tank;

[0063] Step 2: Based on the free chlorine content in the hydrochloric acid storage tank, prepare a 20% sodium sulfite solution. Add the sodium sulfite solution dropwise to the hydrochloric acid storage tank through a dropping tank to eliminate the free chlorine. Then, add a 15% barium chloride solution. After reacting for 2 hours, filter and discard the precipitate. Add the modified carbon fiber from Example 1 to the filtrate. After standing for 4 hours, filter again. After the filtrate is metered by a flow meter, it is pumped from top to bottom into a resin tower for further impurity removal. After the tower is filled with acid, shut down the tower and run it until the iron content in the effluent is below 0.1 mg to obtain purified hydrochloric acid.

[0064] The third step is to preheat the purified hydrochloric acid by passing it through pipes and valves into the condenser, and then distill it in the still. Open the circulating water valve of the condenser, and condense the distilled gaseous hydrochloric acid in the condenser. The condensed hydrochloric acid is collected and flows into the finished product receiving tank to obtain ultra-clean high-purity hydrochloric acid.

[0065] The resin tower has a temperature of 22℃ and a pressure of 0.03MPa, the distiller has a temperature of 84℃ and a pressure of 0.1MPa, and the cooler has a condensation temperature of -80℃ and a pressure of 0.1MPa.

[0066] Example 5

[0067] Ultra-clean, high-purity hydrochloric acid and its production process include the following steps:

[0068] The first step is to filter 37% industrial hydrochloric acid by mass through a 0.45μm microfilter into the hydrochloric acid storage tank;

[0069] Step 2: Based on the free chlorine content in the hydrochloric acid storage tank, prepare a 20% sodium sulfite solution. Add the sodium sulfite solution dropwise to the hydrochloric acid storage tank through a dropping tank to eliminate the free chlorine. Then, add a 10% barium chloride solution. After reacting for 2.5 hours, filter and discard the precipitate. Add the modified carbon fiber from Example 2 to the filtrate. After standing for 5 hours, filter again. After the filtrate is metered by a flow meter, it is pumped from top to bottom into a resin tower for further impurity removal. After the tower is filled with acid, shut down the tower and run it until the iron content in the effluent is below 0.1 mg to obtain purified hydrochloric acid.

[0070] The third step is to preheat the purified hydrochloric acid by passing it through pipes and valves into the condenser, and then distill it in the still. Open the circulating water valve of the condenser, and condense the distilled gaseous hydrochloric acid in the condenser. The condensed hydrochloric acid is collected and flows into the finished product receiving tank to obtain ultra-clean high-purity hydrochloric acid.

[0071] The resin tower has a temperature of 25℃ and a pressure of 0.04MPa, the distiller has a temperature of 86℃ and a pressure of 0.2MPa, and the cooler has a condensation temperature of -60℃ and a pressure of 0.5MPa.

[0072] Example 6

[0073] Ultra-clean, high-purity hydrochloric acid and its production process include the following steps:

[0074] The first step is to filter 38% industrial hydrochloric acid through a 0.45μm microfilter into the hydrochloric acid storage tank.

[0075] Step 2: Based on the free chlorine content in the hydrochloric acid storage tank, prepare a 20% sodium sulfite solution. Add the sodium sulfite solution dropwise to the hydrochloric acid storage tank through a dropping tank to eliminate the free chlorine. Then, add a 10% barium chloride solution. After reacting for 3 hours, filter and discard the precipitate. Add the modified carbon fiber from Example 3 to the filtrate. After standing for 6 hours, filter again. After the filtrate is measured by a flow meter, it is pumped from top to bottom into a resin tower for further impurity removal. After the tower is filled with acid, shut down the tower and run it until the iron content in the effluent is below 0.1 mg to obtain purified hydrochloric acid.

[0076] The third step is to preheat the purified hydrochloric acid by passing it through pipes and valves into the condenser, and then distill it in the still. Open the circulating water valve of the condenser, and condense the distilled gaseous hydrochloric acid in the condenser. The condensed hydrochloric acid is collected and flows into the finished product receiving tank to obtain ultra-clean high-purity hydrochloric acid.

[0077] The resin tower has a temperature of 30℃ and a pressure of 0.05MPa, the distiller has a temperature of 88℃ and a pressure of 0.25MPa, and the cooler has a condensation temperature of 30℃ and a pressure of 1.0MPa.

[0078] Comparative Example 4

[0079] The modified carbon fiber in Example 4 was replaced with the modified carbon fiber in Comparative Example 1, and the other steps remained unchanged.

[0080] Comparative Example 5

[0081] The modified carbon fiber in Example 5 was replaced with the modified carbon fiber in Comparative Example 2, while the other steps remained unchanged.

[0082] Comparative Example 6

[0083] This comparative example is the product obtained in Example 1 of the invention patent with publication number CN109678112A.

[0084] The high-purity hydrochloric acid obtained from the production processes of Examples 4-6 and Comparative Examples 4-6 was tested, and the test results are shown in Table 2.

[0085] Table 2

[0086]

[0087] As can be seen from Table 2, the high-purity hydrochloric acid obtained by the production methods of Examples 4-6 has higher acidity, lower metal ion content, and lower content of evaporation residue and free chlorine than that of Comparative Examples 4-6. This indicates that the high-purity hydrochloric acid prepared by the present invention has higher purity and the production process is simple.

[0088] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0089] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A production process for ultra-clean, high-purity hydrochloric acid, characterized in that, Includes the following steps: The first step is to filter industrial hydrochloric acid with a mass fraction of 36-38% through a microfilter into the hydrochloric acid storage tank; The second step involves preparing a sodium sulfite solution based on the free chlorine content in the hydrochloric acid storage tank. The sodium sulfite solution is then added dropwise to the hydrochloric acid storage tank, followed by a barium chloride solution. After reacting for 2-3 hours, the solution is filtered. Modified carbon fiber is added to the filtrate, and after standing for 4-6 hours, the solution is filtered again. The filtrate flows into a resin tower for further impurity removal. The tower is then operated in a closed-loop manner. The iron content in the effluent is below 0.1 mg, yielding purified hydrochloric acid. The third step is to preheat the purified hydrochloric acid in the condenser, and then distill it in the distiller. The distilled gaseous hydrochloric acid is condensed in the condenser and collected into the finished product receiving tank to obtain ultra-clean high-purity hydrochloric acid. Modified carbon fiber is made by the following steps: Oxidized carbon fiber, p-toluenesulfonic acid, terminal hydroxy crown ether compound, ethylenediaminetetraacetic acid and DMF are mixed, heated to 60-75℃, stirred and reacted for 4-6 hours, washed, centrifuged, precipitated, washed and dried to obtain modified carbon fiber. The amount of p-toluenesulfonic acid used is 3-5% of the total mass of oxidized carbon fiber, terminal hydroxyl crown ether compound, and ethylenediaminetetraacetic acid; Carbon oxide is produced by the following steps: Hollow carbon fibers were immersed in an oxidizing solution for 12 hours, then filtered, the filter cake was washed and dried to obtain oxidized carbon fibers. The oxidation solution was prepared by mixing potassium permanganate, sodium hydroxide, and deionized water in a ratio of 0.3 mol: 0.01 mol: 0.9-1.1 L. The terminal hydroxy crown ether compound is prepared by the following steps: 4'-acetylbenzo-18-crown-6-ether was dissolved in methanol, hydroxypropylamine and 6 mol / L hydrochloric acid solution were added, the mixture was refluxed for 4-6 h, the pH was adjusted to 7-8 with ammonia solution, and the mixture was rotary evaporated to obtain the terminal hydroxycrown ether compound. The volume ratio of 4'-acetylbenzo-18-crown-6-ether, methanol, hydroxypropylamine, and hydrochloric acid solution was 0.05 mol: 130-150 mL. 0.05mol: 1.1-1.3mL; Hollow fibers are made by the following steps: The horned melon fiber was impregnated in sodium hydroxide solution, and JFC penetrant was added dropwise. The mixture was shaken at room temperature for 24 hours, filtered, the filter cake was washed, and then impregnated in phosphoric acid solution for 12 hours for activation treatment. The fiber was then removed and dried at 60°C to constant weight. It was then transferred to a muffle furnace and pre-oxidized at 200°C for 2 hours. After vacuuming, the temperature was increased to 600°C at a rate of 10°C / min and carbonized for 70 minutes to obtain hollow carbon fiber. The ratio of the following components to be used is 20-25g: 500mL: 0.1mL: 400-500mL.

2. Ultra-clean, high-purity hydrochloric acid, characterized in that, It is obtained by the production process described in claim 1.

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