Resource utilization method of potassium fluoride and potassium chloride mixed salt

Abstract

The invention discloses a resource utilization method of potassium fluoride and potassium chloride mixed salt, and belongs to the field of comprehensive utilization of resources. A resource utilization method of potassium fluoride and potassium chloride mixed salt comprises the following steps: S1, taking the mixed salt obtained by fluorination reaction in a certain fine chemical production process, adding water for dissolving, then adding activated carbon, stirring and filtering, then adding an Fe-g-C3N4 / MCM-41 catalyst and hydrogen peroxide, stirring for reaction, then filtering, and collecting filtrate for later use; s2, adding hydrochloric acid and boric acid into the filtrate obtained in the step S1, carrying out a heat preservation reaction, then adjusting the pH value to be neutral, cooling, filtering, and collecting the filtrate and a filter cake; the filter cake is potassium fluoborate; adding calcium chloride into the filtrate, stirring while keeping the temperature, filtering, adjusting the pH value of the filtrate to be neutral, and performing post-treatment to obtain potassium chloride. The method can realize effective utilization of potassium fluoride and potassium chloride mixed salt generated in the production process of the aromatic fluorine-containing fine chemicals, reduces the environmental protection pressure, and realizes resource utilization of wastes and sustainable development of the fluorine chemical industry.

Description

Technical Field

[0001] The invention relates to the field of comprehensive resource utilization, and more specifically to a resource utilization method of a mixed salt of potassium fluoride and potassium chloride. Background Art

[0002] In recent years, my country's fluorine chemical industry has developed rapidly, the scale of equipment has been continuously expanded, and the product grades have gradually increased. In particular, fluorine-containing intermediates and fine chemicals have become important components of the pharmaceutical, auxiliary, reagent and new material industries. Fluorine-containing intermediates can be divided into three categories: aromatic fluorides, aliphatic fluorides and heterocyclic fluorine-containing compounds. Aromatic fluorine-containing compounds are the most important fluorine-containing fine chemicals. In the production process of aromatic fluorine-containing fine chemicals, there are many types of reactions involved, among which fluorination reaction is a relatively important one. This type of reaction usually uses potassium fluoride as a fluorination reagent, and the fluorination of the benzene ring is completed by exchanging fluorine with chlorine on the benzene ring. In industrial production, generally speaking, the amount of potassium fluoride added during the fluorination reaction is more than 1.2 times the theoretical amount, which leads to a large amount of mixed salt of potassium fluoride and potassium chloride after the reaction is completed. At present, the main disposal method for mixed salt is still traditional landfill treatment, but such treatment has the disadvantages of easy pollution and occupying a large amount of landfill resources without effective utilization.

[0003] Potassium is an important resource with important and extensive applications in the field of agricultural fertilizers. my country's potash resources are scarce, accounting for only 6% of the world's total, and economically recoverable reserves are constantly decreasing. We need to import more than 50% from global oligopoly suppliers such as Canada, Russia, and Belarus every year to meet the huge domestic demand for potash fertilizers. In addition, the exploitable reserves of fluorite resources, the source of my country's fluorine resources, are about 50 million tons, and its output and consumption rank first in the world. In 2018, my country's fluorite imports exceeded exports for the first time. With the vigorous development of my country's fluorine chemical industry, my country's fluorite resource gap will continue to increase in the future, so fluorine resources will become increasingly scarce.

[0004] In order to solve the resource utilization problem of mixed salt of potassium fluoride and potassium chloride, it has been reported that fluoride ions can be separated by converting them into calcium fluoride precipitates. However, the calcium fluoride precipitates have finer particles, which leads to inconvenience in filtering operations of large amounts of precipitation, and the economic benefits of converting fluoride ions into calcium fluoride are not high. In addition, some organic solvents are used in some resource utilization processes, which is disadvantageous in terms of environmental protection. There are also some treatment methods that fail to thoroughly treat fluoride ions, which may affect the product quality of potassium chloride. In most treatment methods, the mixed salt needs to be calcined at high temperature in advance, which may produce new tail gas pollution.

[0005] Therefore, it is necessary to provide a new method for treating mixed salt of potassium fluoride and potassium chloride, which can reduce environmental pressure, realize waste resource utilization and sustainable development of the fluorine chemical industry. Summary of the invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for resource utilization of a mixed salt of potassium fluoride and potassium chloride, which can effectively utilize the mixed salt of potassium fluoride and potassium chloride produced in the production process of aromatic fluorine-containing fine chemicals, reduce environmental pressure, and achieve waste resource utilization and sustainable development of the fluorine chemical industry.

[0007] To solve the above problems, the present invention adopts the following technical solutions:

[0008] A method for resource utilization of potassium fluoride and potassium chloride mixed salt comprises the following steps:

[0009] S1: Take a mixed salt obtained by fluorination reaction in the production process of a certain fluorine-containing fine chemical, add water to dissolve it, add activated carbon, stir for 1 to 2 hours, and filter; then add Fe-g-C3N4 / MCM-41 catalyst and hydrogen peroxide to the filtrate, stir and react for 3 to 8 hours, then filter, collect the filtrate for standby use, and the filter cake is Fe-g-C3N4 / MCM-41 catalyst, which can be reused;

[0010] S2: Control the reaction temperature and add a mixed solution of hydrochloric acid and boric acid to the filtrate of step S1, keep the reaction warm for 3 to 6 hours, then add HCl and NaOH to adjust the pH to neutral, cool to 5 to 10°C and keep warm with stirring for 1 to 2 hours, filter and collect the filtrate and filter cake; wash the filter cake and dry it to obtain potassium fluoroborate, and the washing liquid is used in step S1; add calcium chloride to the filtrate, raise the temperature to 60 to 80°C, keep warm with stirring for 0.5 to 2 hours, filter, add HCl and NaOH to adjust the pH of the filtrate to neutral, then pass it through an adsorption column equipped with a boron removal resin to collect the effluent, distill it under reduced pressure, and dry it in vacuum to obtain potassium chloride.

[0011] Furthermore, in the mixed salt obtained by the fluorination reaction in the production process of the fine chemicals, the mass content of potassium fluoride is 12-22%, the mass content of potassium chloride is 75-85%, and the rest is tar and a small amount of organic components. The fine chemicals are aromatic fluorine-containing compounds, such as 3,4.5-trifluorobromobenzene and 2,4-dichloro-5-fluoroacetophenone.

[0012] Furthermore, in step S1, the mass of the activated carbon is 2-5% of the mass of the mixed salt.

[0013] Furthermore, in step S1, the mass amount of water used is 4 to 6 times the mass of the mixed salt.

[0014] Furthermore, in the step S1, the mass dosage of the Fe-g-C3N4 / MCM-41 catalyst is 3 to 8% of the mass of the mixed salt.

[0015] Furthermore, in the step S1, the concentration of hydrogen peroxide is 30%, and the mass amount of hydrogen peroxide is 10-20% of the mass of the mixed salt.

[0016] Furthermore, in the step S2, the reaction temperature of adding the mixed solution of hydrochloric acid and boric acid is 25 to 35°C.

[0017] Furthermore, in the step S2, the molar ratio of hydrochloric acid to KF in the mixed salt is 3:4.

[0018] Furthermore, in the step S2, the molar ratio of boric acid to KF in the mixed salt is 1:4.

[0019] Furthermore, in the step S2, the mass dosage of calcium chloride is 1-2% of the mass of the mixed salt.

[0020] Furthermore, in the step S2, clean water is used for rinsing, the mass of the clean water used is 1 to 3 times the mass of the filter cake, and the number of rinsing times is 3 to 5 times.

[0021] Furthermore, in the step S1, the Fe-g-C3N4 / MCM-41 catalyst is obtained by the following operations: adding melamine to a methanol solution, heating to reflux, then adding ferric chloride, keeping the temperature for reaction, adding MCM-41 mesoporous molecular sieve after the reaction, heating to reflux for 0.5 to 1 h, stirring, drying, and then calcining it in a nitrogen atmosphere at 500 to 700° C. for 3 to 7 h to obtain the Fe-g-C3N4 / MCM-41 catalyst.

[0022] Furthermore, the mass ratio of the added amount of ferric chloride to melamine is 0.4-0.7 mmol / g.

[0023] Furthermore, the mass ratio of the MCM-41 mesoporous molecular sieve to melamine is 4 to 8:1.

[0024] Furthermore, the preparation method of the Fe-g-C3N4 / MCM-41 catalyst is preferably as follows: adding melamine to a methanol solution and heating under reflux for 0.5 to 1 h; adding ferric chloride in an amount of 0.4 to 0.7 mmol / g relative to melamine and heating under reflux for 0.5 to 1 h; adding MCM-41 mesoporous molecular sieve in an amount of 4 to 8 times the mass of melamine and heating under reflux for 0.5 to 1 h; distilling out methanol under stirring, and then heating in a vacuum oven to completely remove methanol; placing the obtained powder in a tubular furnace and calcining at 500 to 700° C. for 3 to 7 h in a nitrogen atmosphere; cooling in a nitrogen atmosphere to obtain Fe-g-C3N4 / MCM-41.

[0025] Furthermore, the resource utilization method of the mixed salt of potassium fluoride and potassium chloride is specifically as follows: the mixed salt obtained by fluorination reaction in the production process of aromatic fluorine-containing fine chemicals is used as a raw material, the mass content of potassium fluoride in the mixed salt is 12-22%, the mass content of potassium chloride is 75-85%, and the rest is tar and a small amount of organic components; the steps are as follows:

[0026] (1) Take a certain amount of the above mixed salt, add 4 to 6 times the mass of water to dissolve the mixed salt, add activated carbon, the mass of which is 2 to 5% of the mass of the mixed salt, stir for 1 to 2 hours, filter and collect the filtrate;

[0027] (2) adding Fe-g-C3N4 / MCM-41 catalyst and a certain mass of 30% hydrogen peroxide to the filtrate of step (1), wherein the mass amount of the Fe-g-C3N4 / MCM-41 catalyst is 3-8% of the mass of the mixed salt, and the mass amount of the 30% hydrogen peroxide is 10-20% of the mass of the mixed salt, stirring for 3-8 hours, performing Fenton oxidation to degrade organic impurities, and then filtering to obtain a reusable Fe-g-C3N4 / MCM-41 catalyst and filtrate, and retaining the filtrate for standby use;

[0028] (3) Controlling the reaction temperature to 25-35° C., gradually adding a mixed solution of hydrochloric acid and boric acid to the filtrate obtained in step (2), wherein the molar ratio of the hydrochloric acid to the KF in the mixed salt is 3:4, and the molar ratio of the boric acid to the KF in the mixed salt is 1:4. After the addition is completed, continuing the reaction for 3-6 hours, and adjusting the reaction solution to neutrality with a small amount of HCl and KOH solution; cooling the reaction solution to 5-10° C., stirring for 1-2 hours, filtering, collecting the filtrate for standby use, rinsing the filter cake with clean water for 3-5 times, wherein the mass amount of clean water used for each rinsing is 1-3 times the mass of the filter cake, and obtaining pure potassium fluoroborate after vacuum drying, wherein the potassium fluoroborate content is greater than 99%; the rinsing solution can be used in step (1); the chemical reaction occurring in this step is:

[0029] 4KF+H3BO3+3HCl→KBF4+3KCl+3H2O;

[0030] (4) adding a small amount of calcium chloride to the filtrate obtained in step (3), wherein the mass amount of calcium chloride is 1 to 2% of the mass of the mixed salt, heating the solution to 60 to 80° C., stirring at this temperature for 0.5 to 2 h, completely hydrolyzing the remaining fluoroborate ions in the solution into fluoride ions and borate ions, cooling the temperature to room temperature, filtering out the small amount of calcium fluoride generated, and collecting the filtrate for later use;

[0031] (5) Add a small amount of HCl and KOH solution to the filtrate obtained in step (4) to adjust it to neutrality, then pass it through an adsorption column filled with a boron removal resin, collect the effluent, evaporate most of the water under reduced pressure, and then vacuum dry to obtain potassium chloride, wherein the potassium chloride content is greater than 98%.

[0032] Compared with the prior art, the advantages of the present invention are:

[0033] 1. This method uses potassium fluoride and potassium chloride mixed salt obtained in the production process of aromatic fluorine-containing fine chemicals as raw materials to prepare potassium fluoroborate and potassium chloride, which can reduce the disposal cost of solid waste and avoid solid waste pollution to the environment. In addition, this method can effectively utilize fluorine and potassium resources and avoid waste of resources.

[0034] 2. This method uses a solid catalyst Fe-g-C3N4 / MCM-41 to perform Fenton oxidation to degrade organic impurities in the mixed salt, so that the mixed salt does not need to be calcined at high temperature, and Fe-g-C3N4 / MCM-41 can be reused.

[0035] 3. The potassium fluoroborate and potassium chloride prepared by this scheme are of good quality and high content. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The present invention is a flow chart for resource utilization of potassium fluoride and potassium chloride mixed salt. DETAILED DESCRIPTION

[0037] Preparation of catalyst Fe-g-C3N4 / MCM-41:

[0038] Add 80 g of melamine to 800 mL of methanol, heat under reflux and stir for 0.5 h; add 40 mmol of FeCl3, reflux and stir for 0.5 h; add 400 g of MCM-41 mesoporous molecular sieve, reflux and stir for 0.5 h; evaporate the methanol under stirring, and then heat in a vacuum oven to completely remove the methanol; place the obtained powder in a tubular furnace and calcine at 600°C for 4 h in a nitrogen atmosphere; then cool in a nitrogen atmosphere to obtain Fe-g-C3N4 / MCM-41.

[0039] Embodiment 1:

[0040] (1) Take 100g of mixed salt obtained in the production process of aromatic fluorine-containing fine chemicals, in which the mass content of potassium fluoride is 17.4% and the mass content of potassium chloride is 79.7%. Add the mixed salt into 500g of water, stir to dissolve, then add 3g of activated carbon, stir for 1.5h, filter, and collect the filtrate for later use.

[0041] (2) Add 5 g of Fe-g-C3N4 / MCM-41 catalyst and 15 g of 30% hydrogen peroxide to the filtrate of step (1), stir for 6 h, perform Fenton oxidation to degrade organic impurities, and then filter to obtain a filter cake and a filtrate, the filtrate is set aside; the filter cake is the Fe-g-C3N4 / MCM-41 catalyst and can be reused.

[0042] (3) gradually adding a mixed solution of hydrochloric acid and boric acid (0.225 mol of hydrochloric acid and 0.075 mol of boric acid) to the filtrate obtained in step (2), controlling the reaction temperature to 30°C, and after the addition, continuing the reaction for 5 hours, adjusting the reaction solution to neutrality with a small amount of HCl and KOH solution; cooling the reaction solution to 10°C, stirring for crystallization for 2 hours, filtering to obtain a filtrate and a filter cake, and the filtrate is set aside; the filter cake is rinsed with clean water (washed 3 times with 20 ml of clean water), and after vacuum drying, 8.9 g of white solid is obtained as pure potassium fluoroborate, with a potassium fluoroborate content of 99.1%, and the rinsing liquid can be used in step (1).

[0043] (4) Add 1 g of calcium chloride to the filtrate obtained in step (3), heat the solution to 75° C., and stir for 1 h to completely hydrolyze the remaining fluoroborate ions in the solution into fluoride ions and borate ions. Cool the temperature to room temperature and filter out the generated calcium fluoride.

[0044] (5) The filtrate obtained in step (4) was adjusted to neutrality with a small amount of HCl and KOH solution, passed through an adsorption column filled with a boron removal resin, the effluent was collected, most of the water was evaporated under reduced pressure, and then vacuum dried to obtain 91.5 g of white solid potassium chloride with a potassium chloride content of 98.3%.

[0045] Embodiment 2:

[0046] The difference between this embodiment and embodiment 1 is that the dissolving water used in step (1) is the eluent in step (3) of embodiment 1 plus clean water, totaling 500 g; the Fe-g-C3N4 / MCM-41 catalyst used in step (2) is recovered in step (2) of embodiment 1; and finally 8.85 g of white solid potassium fluoroborate (content 99.1%) and 96.4 g of white solid potassium chloride (content 98.2%) are obtained.

[0047] Embodiment 3:

[0048] (1) Take 100g of mixed salt obtained in the production process of aromatic fluorine-containing fine chemicals, in which the mass content of potassium fluoride is 20.3% and the mass content of potassium chloride is 76.6%. Add the mixed salt to 450g of water, stir to dissolve, then add 4g of activated carbon, stir for 1h, filter; collect the filtrate for later use.

[0049] (2) Add 6 g of Fe-g-C3N4 / MCM-41 catalyst and 17 g of 30% hydrogen peroxide to the filtrate obtained in step (1), stir for 5 h, perform Fenton oxidation to degrade organic impurities, and then filter to obtain a filter cake and a filtrate, the filtrate is set aside; the filter cake is the Fe-g-C3N4 / MCM-41 catalyst and can be reused.

[0050] (3) gradually adding a mixed solution of hydrochloric acid and boric acid (0.263 mol of hydrochloric acid and 0.088 mol of boric acid) to the filtrate obtained in step (2), controlling the reaction temperature to 25°C, and after the addition, continuing the reaction for 6 hours, adjusting the reaction solution to neutrality with a small amount of HCl and KOH solution; cooling the reaction solution to 8°C, stirring for crystallization for 2 hours, filtering, rinsing the filter cake with clean water (washing with 20 ml of clean water 3 times), and vacuum drying to obtain 10.5 g of white solid as pure potassium fluoroborate with a potassium fluoroborate content of 99.1%. The rinsing solution can be used in step (1).

[0051] (4) Add 1.2 g of calcium chloride to the filtrate obtained in step (3), heat the solution to 80° C., and stir for 1.5 h to completely hydrolyze the remaining fluoroborate ions in the solution into fluoride ions and borate ions. Cool the temperature to room temperature and filter out the generated calcium fluoride.

[0052] (5) The filtrate obtained in step (4) was adjusted to neutrality with a small amount of HCl and KOH solution, passed through an adsorption column filled with a boron removal resin, the effluent was collected, most of the water was evaporated under reduced pressure, and then vacuum dried to obtain 92.8 g of white solid potassium chloride with a potassium chloride content of 98.2%.

Claims

1. A method for resource utilization of potassium fluoride and potassium chloride mixed salt, characterized in that: The following steps are involved: S1: Take a mixed salt obtained from the fluorination reaction in the production process of a certain fluorine-containing fine chemical, add water to dissolve it, add activated carbon, stir for 1-2 hours, and filter; then add Fe-g-C3N4 / MCM-41 catalyst and hydrogen peroxide to the filtrate, stir for 3-8 hours, filter, collect the filtrate for standby use, and the filter cake is Fe-g-C3N4 / MCM-41 catalyst, which can be reused; S2: Control the reaction temperature and add a mixed solution of hydrochloric acid and boric acid to the filtrate of step S1, keep the reaction warm for 3 to 6 hours, then add HCl and NaOH to adjust the pH to neutral, cool and keep warm with stirring for 1 to 2 hours, filter and collect the filtrate and filter cake; wash the filter cake and dry it to obtain potassium fluoroborate, and the washing liquid is used in step S1; add calcium chloride to the filtrate, heat it to 60 to 80 ° C, keep warm with stirring for 0.5 to 2 hours, filter, add HCl and NaOH to adjust the pH of the filtrate to neutral, then pass it into an adsorption column filled with boron removal resin and collect the effluent, distill it under reduced pressure, and dry it in vacuum to obtain potassium chloride.

2. The method for resource utilization of a mixed salt of potassium fluoride and potassium chloride according to claim 1, characterized in that: In step S1, the mass of the activated carbon is 2-5% of the mass of the mixed salt.

3. The method for resource utilization of a mixed salt of potassium fluoride and potassium chloride according to claim 1, characterized in that: In the step S1, the mass dosage of the Fe-g-C3N4 / MCM-41 catalyst is 3-8% of the mass of the mixed salt.

4. The method for resource utilization of a mixed salt of potassium fluoride and potassium chloride according to claim 1, characterized in that: In the step S1, the concentration of hydrogen peroxide is 30%, and the mass amount of hydrogen peroxide is 10-20% of the mass of the mixed salt.

5. The method for resource utilization of a mixed salt of potassium fluoride and potassium chloride according to claim 1, characterized in that: In the step S2, the molar ratio of hydrochloric acid to potassium fluoride in the mixed salt is 3:4, and the molar ratio of boric acid to potassium fluoride in the mixed salt is 1:

4.

6. The method for resource utilization of a mixed salt of potassium fluoride and potassium chloride according to claim 1, characterized in that: In the step S2, the reaction temperature of adding the mixed solution of hydrochloric acid and boric acid is 25-35°C.

7. The method for resource utilization of a mixed salt of potassium fluoride and potassium chloride according to claim 1, characterized in that: In the step S2, the mass dosage of calcium chloride is 1-2% of the mass of the mixed salt.

8. The method for resource utilization of a mixed salt of potassium fluoride and potassium chloride according to claim 1, characterized in that: In the step S1, the Fe-g-C3N4 / MCM-41 catalyst is obtained by the following operations: Melamine was added to a methanol solution, heated to reflux, and then ferric chloride was added and kept warm for reaction. After the reaction, MCM-41 mesoporous molecular sieve was added, heated to reflux for 0.5-1 h, stirred, dried, and then calcined in a nitrogen atmosphere at 500-700 °C for 3-7 h to obtain Fe-g-C3N4 / MCM-41 catalyst.

9. The method for resource utilization of a mixed salt of potassium fluoride and potassium chloride according to claim 8, characterized in that: The mass ratio of the added amount of ferric chloride to melamine is 0.4-0.7 mmol / g.

10. The method for resource utilization of a mixed salt of potassium fluoride and potassium chloride according to claim 8, characterized in that: The mass ratio of the MCM-41 mesoporous molecular sieve to melamine is 4-8:1.

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