CN118929691A

CN118929691A - A method for purifying electronic grade ammonium salt

Info

Publication number: CN118929691A
Application number: CN202410863763.2A
Authority: CN
Inventors: 李少平; 彭秋桂; 贺兆波; 王亮; 吴昊; 叶瑞; 谢建; 吴政; 汪凡杰; 孟牧麟; 彭俊杰
Original assignee: Hubei Xingfu Electronic Materials Co ltd
Current assignee: Hubei Xingfu Electronic Materials Co ltd
Priority date: 2024-06-29
Filing date: 2024-06-29
Publication date: 2024-11-12

Abstract

The present invention relates to a method for purifying an electronic-grade ammonium salt, comprising the following steps. First, an industrial-grade ammonium salt is used for crystallization, and then the industrial-grade ammonium salt is used to make crystal seeds distributed in a liquid state with high uniformity. Then, the industrial-grade ammonium salt is prepared into a concentrated solution, and after cooling to a certain degree, crystal seeds are added, and the temperature is further cooled to a target temperature to precipitate crystals, and then the temperature is raised to 10°C at 2min/°C. Finally, a dehydrating agent is added to the crystals in a tumbling state, the temperature is raised to 15°C, and the target product is obtained after being spun and dried. The method of adding crystal seeds and the subsequent steps of cooling and heating in the method are greatly different from the traditional process, and the steps of solution crystallization and two-step melt crystallization are coupled. Different industrial-grade ammonium salts are used as raw materials, and finally electronic-grade ammonium salts with a metal content of <1 ppb and an ammonium salt purity of >99% are obtained, which can be applied to various demanding high-end fields.

Description

Purification method of electronic grade ammonium salt

Technical Field

The invention belongs to the technical field of ammonium salt purification, and particularly relates to a purification method of electronic grade ammonium salt.

Background

Ammonium salts refer to salt compounds containing ammonium ions (nh4+), and common ammonium salts include ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium acetate, and the like. The ammonium salt has multiple uses and can be widely applied in the fields of chemical industry, pharmacy, food and the like.

Ammonium salts have found wide application in the chemical industry. Ammonium chloride is an important chemical raw material and is often used for preparing other ammonium salts and organic compounds. For example, ammonium chloride may be prepared by reacting with sulfuric acid to prepare ammonium sulfate, and ammonium nitrate may also be prepared by reacting ammonium chloride with nitric acid. In addition, ammonium salts can also be used in the manufacture of batteries, metal corrosion inhibitors, leather degreasing agents, and the like. Ammonium salts have also some important applications in the pharmaceutical field. Ammonium sulfate can be used as an auxiliary agent to improve the solubility and stability of the drug. Ammonium chloride can be used to prepare ammonia, an important solvent and pharmaceutical ingredient in the pharmaceutical industry, as a precursor for ammonia. In addition, ammonium salts can also be used as auxiliary materials for cremation and vacuum casting, for controlling flame temperature and reducing metal oxidation, as well as solvents and solvent powders for aluminum alloys, and for the preparation of smoke screens and smoke protection devices, etc.

Industrial grade ammonium salts contain large amounts of Fe, ca, na (> 500 ppb) and can greatly limit their range of use in some precision applications. At present, common purification technologies for preparing electronic grade products at home and abroad mainly comprise technologies of rectification, distillation, sublimation, resin exchange, membrane treatment, crystallization and the like, and different purification technologies are suitable for purification technologies of different products. For the technologies of nanofiltration, resin exchange, membrane treatment and the like, the purification effect and the service life of equipment often have certain requirements on the viscosity of the required purified product, and the ammonium salt is required to be configured into a dilute solution for use. However, the purified solution is not suitable for many fields due to the high content of water, and the concentration of the purified solution increases energy consumption and production cost.

The growth rate of spontaneous nucleation crystallization is slow, and the solution is easily prevented from precipitating even in a saturated state, and the yield is low. The added seed crystal is also often put into a solid form, and because of the extremely uneven dispersion of the seed crystal in the solution, the time difference of crystal growth and precipitation also easily causes the occlusion of the metal impurities by the crystal, and the metal content in the product is too high. In addition, the ammonium acetate crystal itself may also have a part of crystal water, and is extremely vulnerable to moisture, and conventional dehydrating agents tend to cause residues on the surface thereof.

Disclosure of Invention

The invention aims to provide a purification method of electronic grade ammonium salt, which comprises the steps of crystallizing through a concentrated solution, dissolving again to obtain seed crystals with high uniformity, and adding the seed crystals into a new concentrated solution to obtain pure crystals. And then dehydrating the crystal by using a dehydrating agent, heating to sweat the crystal, and spin-drying to obtain the electronic grade ammonium salt with the metal content reduced to below 1 ppb and the ammonium salt purity higher than 99%.

In order to achieve the aim of the invention, the invention adopts the following technical scheme:

the invention provides a purification method of electronic grade ammonium salt, which comprises the following steps:

Step one: dissolving industrial ammonium salt with ultrapure water, heating and stirring to prepare supersaturated ammonium salt solution;

step two: cooling the solution in the first step to obtain ammonium salt crystals;

step three: repeatedly washing and filtering the crystals in the second step by using a coarse filter bag and ultra-pure water mist to obtain pure ammonium salt crystals, and adding ultra-pure water to ensure that the pure ammonium salt crystals are not completely dissolved;

Step four: centrifuging after uniformly mixing, taking the centrifugate as seed crystal, and preserving heat;

Step five: preparing industrial ammonium salt into saturated solution by using ultrapure water, heating and stirring until the industrial ammonium salt is completely dissolved, and cooling;

step six: adding the liquid seed crystal obtained in the step four into the solution obtained in the step six;

step seven: continuously cooling to the target temperature, and then heating;

Step eight: adding a dehydrating agent into the crystal obtained in the step seven in a turning state, heating and spin-drying;

step nine: and (5) placing the spin-dried crystals in a vacuum rotary drying oven for drying.

In the first step, the mass solubility of the ammonium salt solution is 45-85%, and the temperature is increased to 25-70 ℃ at 2-5 ℃/min, preferably 60, 70, 80 and 90 ℃ until the ammonium salt solution is dissolved. Refers to no large-particle crystal bottom, but the solution still contains a large number of microcrystals, and the solution can be spontaneously crystallized and separated out after cooling and can be obtained through monitoring of a PCM system.

And in the second step, the solution is cooled to 22-27 ℃ at a rate of 15-25 min/DEG C to obtain ammonium salt crystals, and preferably cooled to 25 ℃ at a rate of 20-min/DEG C to obtain ammonium salt crystals. The slow cooling rate and small temperature difference in the second step reduce the yield, but the purpose of the process is to spontaneously grow high-purity seed crystals.

The crystal purity after repeated washing in the third step is high, and the mass of the added ultrapure water is 25% -40% of the mass of the crystal, preferably 25%, 30%, 35% and 40%. The purpose of failing to dissolve the crystals completely is to allow the liquid to contain ammonium salt as seed crystals.

In the fourth step, the mixture is centrifuged, and the centrifugal liquid is taken as seed crystal, so that the grain growth is more uniform, and the seed crystal is too large to cause uneven dispersion, the purpose of centrifugation is to settle large particles, and the centrifugal speed is 100-500 r/min, preferably 100, 200 and 300 r/min. The temperature of the heat preservation is 25-40 ℃. The seed crystal with high uniformity and distributed in liquid state can be obtained by centrifugation, and the seed crystal has extremely high purity at the moment because of repeated washing, and can be used as seed crystal to make grain growth more uniform. The purpose of the heat preservation is to ensure that the seed crystal is not dissolved and is not spontaneously crystallized and separated out. Experiments prove that the precipitation of the seed crystal is accelerated by high-energy metal content, the ultra-pure ammonium salt is used for dissolving and then cooling, supersaturated solution is formed, and no crystal is precipitated after cooling.

In the fifth step, the mass concentration of the saturated ammonium salt solution is 40-80%, the temperature rising end point is 50-100 ℃, the temperature reducing rate is 5-10 min/DEG C, and the temperature reducing end point is 20-40 ℃.

In terms of mechanism, the slower the cooling rate, the better the morphology and purity of the crystal, but the too slow cooling rate can reduce the production efficiency and increase the cost. It is important to choose a moderate cooling rate.

In the sixth step, the liquid seed crystal is added in an amount of 0.5 to 2.8% by mass, preferably 0.7%, 1.4%, 2.1% and 2.8% by mass of the solute.

The reason for adding seed crystals is that the growth induces and balances the supersaturation of the solution system. When the crystal addition amount is too small, the supersaturation degree in the solution is insufficient, and after the crystal addition amount reaches a certain proportion, the state is basically stable, and the continuous addition of the seed crystal can cause waste. When the size of the added seed crystal is too large, the seed crystal is easy to sink, so that the uniformity of the surface morphology is poor, too small a seed size is not likely to continue growing on its surface.

In the seventh step, the cooling rate is 10-30 min/DEG C, the cooling end point is 5 ℃, and then the temperature is increased to 10 ℃ at the rate of 2 min/DEG C.

The establishment of the temperature rise and fall end points is determined by the characteristic of the maximum ratio of concentration difference to temperature difference and high yield in the ammonium salt solubility curve. The subsequent heating process is to sweat the crystals, dissolve away the crystals which are secondarily nucleated and not grown up, melt and separate the partially adhered crystals, and remove the occluded mother solution.

The dehydrating agent in the eighth step is one or more of acetone, N-methylpyrrolidone, furaltadone, N-butanol, tert-butanol, 1,4 dioxane and glycerol, preferably acetone, N-methylpyrrolidone, N-butanol, tert-butanol and 1,4 dioxane.

The addition of the dehydrating agent can well combine the adsorption of the surface of the crystal and the water combination, and the crystal sweats by heating again, so that deep impurity removal is realized on the crystal, the residue of the dehydrating agent is also removed, and then the water and the impurities are removed by spin-drying.

In the eighth step, the temperature is raised to 13-17 ℃ at 0.5-1.5 min/DEGC;

Preferably, in step eight, the temperature is raised to 15℃at 1 min/DEG C.

Compared with the prior art, the invention has the following beneficial effects:

1) The method directly configures the product into a saturated solution with higher concentration, and can enrich metal impurities more quickly;

2) The seed crystal is generated by self crystallization of the stock solution and is put into the liquid state, so that the cost and the uniformity of subsequent product crystallization are greatly reduced, and the yield and purity of the product are greatly improved;

3) The coupling of solution crystallization and melt crystallization greatly reduces the content of metal ions in the product;

4) The dehydrating agent removes the water content of the product, so that the dehydrating agent is suitable for various precision fields;

5) The operation flow is simple and convenient, and the required equipment is easy to operate.

Drawings

FIG. 1 is a product diagram of example 1 electronic grade ammonium salt;

FIG. 2 is a diagram of the product of comparative example 1.

Detailed Description

The following description of the embodiments of the present invention will clearly and fully describe the technical solutions of the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

The concentrations of metal ions in the ammonium salt raw materials used in examples 1 to 13 of the present invention are shown in Table I, and the concentrations of metal ions in the ammonium salt raw materials were measured in ppb by ICP-MS spectrometer.

TABLE 1 concentration of metal ions in commercial grade ammonium salt raw materials

Examples 1 to 13

The invention relates to a method for purifying ammonium salt, which comprises the following steps:

Step one: preparing the ammonium salt raw material into a saturated ammonium salt solution with the concentration of 45-85%, and heating to 60, 70, 80 and 90 ℃ at 2-5 ℃/min until the saturated ammonium salt solution is dissolved.

Step two: cooling the solution in the first step to 25 ℃ at a rate of 20 min/DEG C to obtain ammonium salt crystals;

Step three: repeatedly washing the crystal in the second filtering step, and adding ultrapure water with the mass of 25, 30, 35 and 40% of the mass of the crystal again, wherein the ultrapure water is not completely dissolved;

Step four: mixing, centrifuging at a centrifugal speed of 100, 200, 300 r/min, collecting the clear liquid, and keeping the temperature at 25-40deg.C;

step five: preparing an ammonium salt raw material into a saturated ammonium salt solution, wherein the temperature rising end point is 50-100 ℃, the cooling rate is 5-10 min/DEG C, and the cooling end point is 20-40 ℃;

step six: adding liquid seed crystals with the mass of 0.7, 1.4, 2.1 and 2.8 percent of the solute into the solution in the step five;

step seven: continuously cooling at a cooling rate of 10-30 min/DEG C, wherein the cooling end point is 5 ℃, then heating to 10 ℃ at a rate of 2 min/DEG C, washing and filtering to obtain crystals;

step eight: spraying and adding one or more of acetone, N-methylpyrrolidone, N-butanol, tertiary butanol and 1,4 dioxane into the crystal obtained in the step seven under the stirring state, heating to 15 ℃ at the rate of 1 min/DEG C, and spin-drying;

step nine: and (3) drying the spin-dried crystals in a vacuum rotary drying oven at 15-30 ℃ for 1-4h.

Table 2 shows the ammonium salt concentration, the temperature raising conditions, the pure water addition amount, the rotation speed and the heat preservation temperature, which are different from each other, in examples 1 to 13; and step five to step nine, heating and cooling conditions, seed crystal adding amount, continuously cooling conditions, dehydrating agent types and vacuum drying conditions are implemented.

TABLE 2 Process conditions

The content of each metal of the electronic grade ammonium salt prepared under the above conditions is reduced to less than 1ppb, the purity is more than 99%, and the specific data are shown in Table 3.

Comparative example 1: the seed crystal preparation step from step one to step four and the seed crystal addition step six in example 1 are omitted, and the product is directly crystallized by using saturated ammonium salt solution, wherein the metal ion content of the product is more than 1ppb, and the product does not meet the requirements of electronic grade ammonium salt, and the specific data are shown in Table 3. The finished product was greyish in color and less uniform than comparative example 1, as shown in fig. 2.

Comparative example 2: the seed crystal making steps from the first step to the fourth step in the embodiment 1 are omitted, the liquid seed crystal adding in the step six is changed to the solid electronic grade ammonium salt adding, and other conditions are unchanged, so that the metal ion content of the product is qualified, but the final product yield is 90% of that of the embodiment one.

Comparative example 3: based on the example 1, the pure water addition amount was replaced by 60%, and other conditions were unchanged, wherein the metal ion content of the product was more than 1ppb, which did not meet the requirements of electronic grade ammonium salt, and the specific data are shown in Table 3.

Comparative example 4: based on the example 1, the rotating speed is replaced by 1000 r/min, other conditions are unchanged, the metal ion content of the product is more than 1ppb, the requirement of electronic grade ammonium salt is not met, and specific data are shown in Table 3.

Comparative example 5: based on the embodiment 1, the heat preservation temperature is replaced by 60 ℃, other conditions are unchanged, the metal ion content of the product is more than 1ppb, the requirement of electronic grade ammonium salt is not met, and specific data are shown in Table 3.

Comparative example 6: based on the example 1, the temperature rising end point of the saturated solution is replaced by 60 ℃, the metal ion content of the product is more than 1ppb, the requirement of the electronic grade ammonium salt is not met, and the specific data are shown in Table 3.

Comparative example 7: based on the embodiment 1, the saturated solution cooling rate is replaced by 5 ℃/min, the metal ion content of the product is more than 1ppb, the requirement of the electronic grade ammonium salt is not met, and the specific data are shown in Table 3.

Comparative example 8: based on the example 1, no dehydrating agent was added, the purity of the product was <96% at this time, and the product did not meet the requirements of electronic grade ammonium salt, and the specific data are shown in Table 3.

As is evident from example 1 and comparative example 1, the crystal growth after pre-seeding was more uniform, the dispersibility was better and the metal impurity content was low. This is probably because the added seed crystal passes over an energy barrier to form a crystal nucleus, which promotes rapid and orderly growth of crystals and reduces the generation of fine crystals, so that the occurrence probability of inter-crystalline occlusion of metal impurities is greatly reduced.

As is evident from example 1 and comparative example 2, the liquid seed crystals used in the same crystallization process are less costly and increase the yield of the final product compared to the lower metal content electronic grade solid ammonium salt. This is probably because the crystal growth process is greatly affected by hydrodynamic conditions and mass transfer processes, the position of the seed crystal adding point should be selected in the area with the best fluid mixing effect, and direct addition of solid seed crystals may lead to inconsistent saturation of the local area, and the generated fine crystals penetrate the filter bag during the washing process, so that the yield is reduced. In addition, direct solid input has the possibility of decrepitation. In addition, the metal impurities in the solution can promote the further growth of crystals and the surface area of the crystals is small, so that the crystals are more stable in the washing process, and the impurity metal and ammonium salt are free from eutectic phenomenon, so that the impurities can be removed in the subsequent temperature rising process.

As is evident from examples 1 and 3, too high a rotational speed may result in unacceptable metal content of the product, possibly due to seed crystals. The particle size distribution of the seed directly affects the particle size distribution of the final product. It is generally believed that the seed should have a narrower particle size distribution. That is, the seed crystal particle size is relatively uniform. Too fast a rotation speed will result in too fast a sedimentation rate of crystals in the suspension, too low a saturation of the seed crystals obtained, too slow a too large particle size, uneven particle size, and the seed crystals obtained at the rotation speed of example 1 are better in both saturation and particle size.

The temperature difference is provided between the temperature of the seed crystal for heat preservation and the temperature of the temperature rising end point of the solution, so that a part of the surface of the seed crystal is slightly dissolved, the inter-crystal-coated metal can be effectively removed, and the eutectic of the seed crystal serving as a crystal nucleus and ammonium salt in the solution is avoided. The temperature rise is insufficient to cause that part of crystals cannot be dissolved, bad crystallization centers are formed in the subsequent cooling process, and the risk of explosion exists, so that the metal impurities of the product are unqualified. In theory, the slower the cooling rate, the higher the purity of the obtained product crystals, but the time cost will be increased certainly, the cooling rate and the cooling end point selected in the embodiment 1 are all based on the premise that the metal content reaches the standard, and the process route is selected to have the lowest energy consumption, and the theoretical yield and the actual yield are better according to the saturation curve and the actual operation.

TABLE 3 Table 3

The technical solution of the present invention is explained by the above embodiments, but the present invention is not limited to the above embodiments, i.e. it does not mean that the present invention must be implemented depending on the above specific embodiments. Any modifications, or equivalent substitutions of materials for the invention, which are made by those skilled in the art based on the present invention, fall within the scope of protection of the patent.

Claims

1. The purification method of the electronic grade ammonium salt is characterized in that the etching solution comprises the following components in percentage by mass: the preparation method comprises the following steps:

Step three: repeatedly washing and filtering the crystals in the second step by using a coarse filter bag and ultra-pure water mist to obtain pure ammonium salt crystals, and adding ultra-pure water to dissolve the pure ammonium salt crystals;

step four: centrifuging after mixing uniformly, taking the centrifugate as seed crystal, and preserving heat;

step seven: continuously cooling to the target temperature, and then heating;

2. The method for purifying an electronic grade ammonium salt according to claim 1, wherein in the first step, the mass concentration of the supersaturated ammonium salt solution is 45-85%, and the temperature is raised to 60-110 ℃ at 2-5 ℃/min, preferably 60, 70, 80, 90 ℃ to dissolve;

and in the second step, the solution is cooled to 22-27 ℃ at a rate of 15-25 min/DEG C to obtain ammonium salt crystals, and preferably cooled to 25 ℃ at a rate of 20-min/DEG C to obtain ammonium salt crystals.

3. The method for purifying an electronic grade ammonium salt according to claim 1, wherein the ultrapure water is added in an amount of 25 to 40% by mass, preferably 25%, 30%, 35%, 40% by mass of the crystal in the third step.

4. The method for purifying an electronic grade ammonium salt according to claim 1, wherein in the fourth step, the centrifugal speed is 100-500 r/min, preferably 100, 200, 300r/min, and the heat preservation temperature is 25-40 ℃.

5. The method for purifying an electronic grade ammonium salt according to claim 1, wherein in the fifth step, the mass concentration of the saturated solution of the ammonium salt is 40-80%, the temperature rising end point is 50-100 ℃, the temperature lowering rate is 5-10min/°c, and the temperature lowering end point is 20-40 ℃.

6. The method for purifying an electronic grade ammonium salt according to claim 1, wherein in the step six, the liquid seed crystal is added in an amount of 0.5 to 2.8%, preferably 0.7%, 1.4%, 2.1%, 2.8% of the solid content.

7. The method for purifying an electronic grade ammonium salt according to claim 1, wherein in the seventh step, the cooling rate is 10 to 30 min/°c, the cooling target temperature is 3 to 7 ℃, and then the temperature is raised to 8 to 12 ℃ at a rate of 1.5 to 2.5 min/°c;

preferably, the reduced target temperature is 5℃followed by a temperature increase to 10℃at a rate of 2 min/. Degree..

8. The method for purifying electronic grade ammonium salt according to claim 1, wherein the dehydrating agent in the eighth step is one or more of acetone, N-methylpyrrolidone, furaltadone, N-butanol, tert-butanol, 1,4 dioxane, and glycerol, preferably acetone, N-methylpyrrolidone, N-butanol, tert-butanol, and 1,4 dioxane;

in the eighth step, the temperature is raised to 13-17 ℃ at 0.5-1.5 min/DEGC;

preferably, the temperature is raised to 15℃at 1 min/. Degree.C.

9. The process for purifying an electronic grade ammonium salt according to claim 1, wherein the vacuum spin-drying temperature in step nine is 15-30 ℃ for a period of time of 1-4 h.

10. The electronic grade ammonium salt purified by the method according to any one of claims 1 to 9, wherein the content of each metal in the electronic grade ammonium salt is reduced to less than 1 ppb, and the purity of the ammonium salt is >99%.