Special extracting agent for preparing monopotassium phosphate by solvent extraction method

Abstract

The invention provides a special extracting agent for preparing monopotassium phosphate by a solvent extraction method, the extracting agent is composed of a main agent and an auxiliary agent, the main agent is N, N-diisooctyl ethanolamine and trioctyl methyl ammonium chloride, the auxiliary agent is xylene and C8-C16 alkane, the C8-C16 alkane is at least one of C8-C16 alkanes, and the volume ratio of the main agent to the auxiliary agent is (0.2-0.6): 1. The special extraction agent provided by the invention can improve the separation selectivity of hydrochloric acid and phosphoric acid while enhancing the extraction performance of hydrochloric acid, improves the separation performance of oil and water phases after extraction, avoids entrainment and shortens the phase separation time.

Description

Technical Field

[0001] The invention belongs to the field of extraction separation and inorganic chemistry, and relates to a special extractant for preparing potassium dihydrogen phosphate by a solvent extraction method. Background Art

[0002] Potassium dihydrogen phosphate (KH 2 PO 4 ) is an important inorganic salt, which is widely used in the fields of high-efficiency phosphorus-potassium compound fertilizers, food additives and pharmaceutical preparations in agriculture. At present, the main methods for preparing potassium dihydrogen phosphate include neutralization method, electrochemical method, double decomposition method and solvent extraction method. Among them, solvent extraction method has gradually received attention in recent years due to its advantages in production efficiency and cost control. Compared with other methods for preparing potassium dihydrogen phosphate, solvent extraction method has the characteristics of low energy consumption, mild operating conditions and low raw material prices, which can effectively reduce energy consumption and production and operation costs. In addition, solvent extraction method is also more superior in purity control and selectivity, which can improve the yield and purity of potassium dihydrogen phosphate. Therefore, solvent extraction method has gradually become the mainstream technology for preparing potassium dihydrogen phosphate.

[0003] In the solvent extraction method, the selection of the extractant is crucial and has a significant impact on the efficiency, cost and quality of the entire production process. At present, the extractants widely used in industry are mainly symmetrical or asymmetrical tertiary amine organic solvents. For example, Chen Ruoyu et al. reported a process for preparing potassium dihydrogen phosphate using a mixed extractant consisting of cyclohexane, symmetrical tertiary amine organic solvent trioctylamine and isopentanol (volume ratio 4:2:1). The extraction rates of hydrochloric acid and phosphoric acid were 95.7% and 4.5% respectively, and the phase separation time was 6 minutes (see Chen Ruoyu et al., Research on a New Process for Preparing Potassium Dihydrogen Phosphate by Extraction, "Chemical Minerals and Processing", Issue 11, 2001, Pages 5-7). For another example, CN 114191847 A discloses a method for producing potassium dihydrogen phosphate by solvent extraction. The extractant used in the method includes a main extractant and a diluent. The main extractant is an asymmetric tertiary amine organic solvent acetophenone-formaldehyde-di-n-butylamine, and the diluent is kerosene and octanol. The volume percentages of the main extractant, kerosene and octanol are 20% to 70%, 5% to 20% and 15% to 75%, respectively. The extraction rates of hydrochloric acid and phosphoric acid by the method are 99.7% and 3.5%, respectively, and the phase separation time is 3 minutes.

[0004] It can be found from the currently publicly reported literature that when using existing tertiary amine extractants to prepare potassium dihydrogen phosphate, the tertiary amine extractants will extract a certain amount of phosphoric acid while extracting hydrochloric acid, resulting in phosphorus loss. At the same time, when using existing tertiary amine extractants to prepare potassium dihydrogen phosphate, there is also an emulsification phenomenon. On the one hand, the emulsification phenomenon will cause a long separation time of the oil-water phase after extraction, resulting in a large equipment volume and increased operation difficulty, which is not conducive to improving production efficiency. On the other hand, the emulsification phenomenon will also cause the problem of entrainment of the extractant and phosphoric acid, thereby reducing the phosphorus utilization rate, which is not conducive to improving the quality of potassium dihydrogen phosphate products. Summary of the invention

[0005] In view of the fact that the tertiary amine extractants used in the prior art for preparing potassium dihydrogen phosphate by solvent extraction will extract phosphoric acid when extracting hydrochloric acid, and the selective separation ability of hydrochloric acid and phosphoric acid is poor, and the existence of emulsification will increase the difficulty of phase separation after extraction, resulting in a long phase separation time and entrainment problems, the present invention provides a special extractant for preparing potassium dihydrogen phosphate by solvent extraction, so as to enhance the extraction performance of hydrochloric acid while improving the separation selectivity of hydrochloric acid and phosphoric acid, and improve the separation performance of oil-water two phases after extraction, avoid entrainment and shorten the phase separation time.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0007] A special extractant for preparing potassium dihydrogen phosphate by solvent extraction, the extractant is composed of a main agent and an auxiliary agent, the main agent is N,N-diisooctylethanolamine and trioctylmethylammonium chloride, the auxiliary agent is xylene and C 8 ~C 16 Alkanes, the C 8 ~C 16 The alkane is at least one of alkanes with carbon atoms of 8 to 16, and the volume ratio of the main agent to the auxiliary agent is (0.2 to 0.6):1.

[0008] In the technical scheme of the special extractant for preparing potassium dihydrogen phosphate by solvent extraction, the volume ratio of N,N-diisooctylethanolamine to trioctylmethylammonium chloride in the main agent is preferably (0.5-1.2):1.

[0009] In the technical solution of the special extractant for preparing potassium dihydrogen phosphate by solvent extraction, the auxiliary agent is xylene and C 8 ~C 16 The volume ratio of alkanes is preferably (0.8-2):1.

[0010] In the technical solution of the special extractant for preparing potassium dihydrogen phosphate by the solvent extraction method, the volume ratio of the main agent to the auxiliary agent is preferably (0.4-0.6):1.

[0011] The special extractant for preparing potassium dihydrogen phosphate by the solvent extraction method can be used in conjunction with the existing solvent extraction method. For example, a feasible method for preparing potassium dihydrogen phosphate by solvent extraction using the special extractant of the present invention is as follows:

[0012] (1) preparing an aqueous solution by mixing phosphoric acid and potassium chloride in a molar ratio of (1-1.1):1;

[0013] (2) using the extractant of the present invention as an organic phase, mixing the organic phase with an aqueous phase solution in a volume ratio of (1-2):1 to perform an extraction reaction;

[0014] (3) After the extraction reaction is completed, the phases are separated by standing, and the residual water phase is concentrated and crystallized to obtain potassium dihydrogen phosphate; aqueous ammonia is added to the extracted water phase for neutralization reaction. After the neutralization reaction is completed, the phases are separated by standing, and the obtained organic phase is the regenerated extractant, which can be recycled. The obtained water phase is concentrated, cooled and crystallized to obtain ammonium chloride as a by-product.

[0015] When the extractant of the present invention is used to prepare potassium dihydrogen phosphate by the existing solvent extraction method, the extraction selectivity of hydrochloric acid and phosphoric acid can be improved while ensuring a high extraction rate for hydrochloric acid, and the phase separation time after extraction can be significantly shortened; at the same time, the extractant of the present invention also has excellent cyclic stability. For example: the present invention has confirmed through experiments that when the extractant of the present invention is used to prepare potassium dihydrogen phosphate by solvent extraction, the extraction rate of hydrochloric acid is between 99.3% and 99.6%, and the extraction rate of phosphoric acid is between 1.0% and 1.4%, and the phase separation time after extraction is between 9 and 35 seconds; the present invention has also confirmed through experiments that after the extractant of the present invention is recycled for 20 times, the extraction rate of hydrochloric acid and phosphoric acid is basically unchanged compared with the first use of the extractant.

[0016] The technical concept of the present invention is mainly as follows:

[0017] The special extractant for preparing potassium dihydrogen phosphate by solvent extraction method of the present invention is prepared by compounding a main agent and an auxiliary agent, wherein the main agent is compounded by two components of N, N-diisooctylethanolamine and trioctylmethylammonium chloride according to an appropriate ratio, and the auxiliary agent is compounded by xylene and C 8 ~C 16 Compounded with alkanes.

[0018] Due to the positively charged nitrogen atom (cation) contained in trioctylmethylammonium chloride, the polarity of trioctylmethylammonium chloride molecule is relatively strong, which makes it have a higher affinity for strong acid substances (such as hydrochloric acid), but a lower affinity for weak acids (such as phosphoric acid), so that it will show better separation selectivity for hydrochloric acid and phosphoric acid. N, N-diisooctylethanolamine has a highly polar ethanolamine group (the ethanolamine group contains -OH and -NH groups). When N, N-diisooctylethanolamine comes into contact with hydrochloric acid, the -NH group in N, N-diisooctylethanolamine will be protonated to form R 2 NH 2 + The positively charged amine salt can react with the negatively charged Cl - Combined, a charged ion pair is generated, and hydrochloric acid is extracted from the aqueous phase into the organic phase, but the acidity of phosphoric acid is weak, which is insufficient to form a stable amine salt with N, N-diisooctylethanolamine, thereby making N, N-diisooctylethanolamine show good separation selectivity for hydrochloric acid and phosphoric acid. In addition, trioctylmethylammonium chloride has a strong polarity, which is also conducive to enhancing its affinity for hydrochloric acid and improving the separation selectivity of hydrochloric acid and phosphoric acid. The present invention compounded N, N-diisooctylethanolamine and trioctylmethylammonium chloride in an appropriate ratio, rationally utilized the ability of trioctylmethylammonium chloride to extract hydrochloric acid and the combination ability of N, N-diisooctylethanolamine with hydrochloric acid, so that the two can effectively exert a synergistic effect, produce a better extraction effect than when the two are used alone, and effectively improve the separation selectivity of hydrochloric acid and phosphoric acid. At the same time, the compounding of the two can also improve the separation performance of the oil-water two phases after extraction to a certain extent.

[0019] On the basis of the above, the present invention combines low viscosity xylene (viscosity of 0.6-0.7 mPa·s at room temperature) and C 8 ~C 16 After the alkanes are compounded in appropriate proportions and then used in combination with the main agent in appropriate proportions, the viscosity and density of the extractant can be adjusted to appropriate levels, which is beneficial to further improve the separation performance of the oil and water phases after extraction, reduce emulsification and entrainment, and further shorten the phase separation time.

[0020] Compared with the prior art, the technical solution provided by the present invention produces the following beneficial technical effects:

[0021] 1. The present invention provides a special extractant for preparing potassium dihydrogen phosphate by solvent extraction, the extractant is composed of a main agent and an auxiliary agent, the main agent is N, N-diisooctylethanolamine and trioctylmethylammonium chloride, the auxiliary agent is xylene and C 8 ~C 16The volume ratio of the main agent to the auxiliary agent is (0.2-0.6):1. In the present invention, N,N-diisooctylethanolamine and trioctylmethylammonium chloride are compounded as the main agent of the extractant, and the ion exchange effect of trioctylmethylammonium chloride is used to extract hydrochloric acid, and N,N-diisooctylethanolamine is used to bind Cl after protonation. - By controlling the ratio of the two, the above two mechanisms can exert a synergistic effect, produce a better selective separation effect than when the two are used alone, and improve the phase separation effect of the oil-water phase after extraction to a certain extent. On this basis, the present invention combines low-viscosity xylene and C 8 ~C 16 After the alkanes are compounded in an appropriate ratio, they are used in combination with the main agent in an appropriate ratio, and the viscosity and density of the extractant are adjusted to an appropriate level by using an auxiliary agent, so as to further improve the phase separation effect of the oil-water two phases after extraction. That is, the present invention effectively enhances the selective separation effect of the extractant on hydrochloric acid and phosphoric acid and the phase separation effect of the oil-water two phases after extraction through multiple synergistic coordination between the main agent, between the auxiliary agents, and between the main agent and the auxiliary agent. When potassium dihydrogen phosphate is prepared by the extraction method, a better extraction and separation effect can be produced than when the main agent of the prior art uses a single component of tert-butylamine as the extractant in combination with an auxiliary agent with a relatively high viscosity.

[0022] 2. The present invention has been verified through experiments that when the extractant of the present invention is used to prepare potassium dihydrogen phosphate by solvent extraction, the extraction rate of hydrochloric acid is as high as 99.3% to 99.6%, and the extraction rate of phosphoric acid is as low as 1.0% to 1.4%. At the same time, the phase separation time after extraction is only 9 to 35 seconds. The present invention has also been verified through experiments that when the extractant of the present invention is recycled for 20 times, the extraction rates of hydrochloric acid and phosphoric acid are basically unchanged compared with the first use of the extractant. That is, when the extractant of the present invention is used in conjunction with the solvent extraction method to prepare potassium dihydrogen phosphate, the extraction selectivity of hydrochloric acid and phosphoric acid can be improved while ensuring a high extraction rate for hydrochloric acid and phosphoric acid and the phase separation time after extraction can be significantly shortened. At the same time, the extractant of the present invention also has excellent cyclic stability. These characteristics are conducive to the promotion and application of the extractant of the present invention in the production of potassium dihydrogen phosphate. DETAILED DESCRIPTION

[0023] The following examples further illustrate the special extractant for preparing potassium dihydrogen phosphate by solvent extraction provided by the present invention. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention according to the above invention content and implement them specifically, which still belongs to the scope of protection of the present invention.

[0024] Example 1

[0025] In this embodiment, a special extractant for preparing potassium dihydrogen phosphate by solvent extraction is provided, and potassium dihydrogen phosphate is prepared by solvent extraction based on the special extractant.

[0026] The special extractant for preparing potassium dihydrogen phosphate by solvent extraction is prepared by fully mixing a main agent and an auxiliary agent in a volume ratio of 0.4:1, wherein the main agent is composed of N,N-diisooctylethanolamine and trioctylmethylammonium chloride in a volume ratio of 1:1, and the auxiliary agent is composed of xylene and dodecane in a volume ratio of 1:1.

[0027] Phosphoric acid and potassium chloride were dissolved in deionized water at a molar ratio of 1:1 to form an aqueous solution, in which the concentration of chloride ions was 2.29 mol / L. The above-mentioned extractant of this embodiment was used as the organic phase. The aqueous phase and the organic phase were added to a 500 mL separatory funnel at a volume ratio of 1:1, and the reaction was oscillated for 6 minutes at room temperature and normal pressure, and then allowed to stand and the timing was started. The timing was stopped when the extracted organic phase and the residual aqueous phase were completely clarified. It was found that the phase separation time was 30 seconds.

[0028] According to the sampling test and calculation, the extraction rate of hydrochloric acid in this embodiment is 99.5%, and the extraction rate of phosphoric acid is only 1.1%. The raffinate aqueous phase is evaporated, concentrated and crystallized to obtain a potassium dihydrogen phosphate product, and the yield of potassium dihydrogen phosphate is 98.3%. Sampling and testing show that the purity of potassium dihydrogen phosphate is 99.5%.

[0029] Comparative Example 1

[0030] In this comparative example, the optimal extractant formula in CN114191847 A was used, and the extraction experiment was carried out with reference to the operation in Example 1, as follows:

[0031] The extractant used in this comparative example is prepared by fully mixing acetophenone-formaldehyde-di-n-butylamine, octanol and kerosene in a volume ratio of 2:4:1.

[0032] Phosphoric acid and potassium chloride were dissolved in deionized water at a molar ratio of 1:1 to form an aqueous solution, in which the concentration of chloride ions was 2.29 mol / L. The above-mentioned extractant of this comparative example was used as the organic phase. The aqueous phase and the organic phase were added to a 500 mL separatory funnel at a volume ratio of 1:1, and the reaction was oscillated for 10 minutes at room temperature and normal pressure, and then allowed to stand and the timing was started. The timing was stopped when the extracted organic phase and the residual aqueous phase were completely clarified. It was found that the phase separation time was 2 min 5 s.

[0033] According to the sampling test and calculation, the extraction rate of hydrochloric acid in this comparative example is 99.3%, and the extraction rate of phosphoric acid is 3.6%. The raffinate water phase is evaporated, concentrated and crystallized to obtain a potassium dihydrogen phosphate product, and the yield of potassium dihydrogen phosphate is 96.3%. The purity of potassium dihydrogen phosphate is 98.2%.

[0034] Comparative Example 2

[0035] In this comparative example, the optimal extractant formula in the literature (Chen Ruoyu et al., Study on a New Process for Preparing Potassium Dihydrogen Phosphate by Extraction, Chemical Minerals and Processing, Issue 11, 2001, Pages 5-7) was used, and the extraction experiment was carried out with reference to the operation in Example 1, as follows:

[0036] The extractant used in this comparative example is prepared by fully mixing trioctylamine, cyclohexane and isoamyl alcohol in a volume ratio of 2:4:1.

[0037] Phosphoric acid and potassium chloride were dissolved in deionized water at a molar ratio of 1:1 to form an aqueous phase solution, in which the concentration of chloride ions was 2.29 mol / L. The above-mentioned extractant of this comparative example was used as the organic phase. The aqueous phase and the organic phase were added to a 500 mL separatory funnel at a volume ratio of 1:1, and the reaction was oscillated for 10 minutes at room temperature and normal pressure, and then allowed to stand and the timing was started. The timing was stopped when the extracted organic phase and the residual aqueous phase were completely clear. It was found that the phase separation time was 6 minutes.

[0038] After sampling and testing, the extraction rate of the above extractant for hydrochloric acid is 95.7%, and the extraction rate for phosphoric acid is 4.5%. The residual water phase is evaporated, concentrated and crystallized to obtain potassium dihydrogen phosphate product, and the yield of potassium dihydrogen phosphate is 91.3%. After sampling and testing, the purity of potassium dihydrogen phosphate is 97.2%.

[0039] Combining Example 1 and Comparative Examples 1 to 2, it can be seen that, compared with the current situation in which a single component of symmetrical or asymmetrical tertiary amine substances is used as the main agent of the extractant, the present invention uses N,N-diisooctylethanolamine and trioctylmethylammonium chloride as the main agent of the extractant and cooperates with xylene and dodecane as auxiliary agents of the extractant. When preparing potassium dihydrogen phosphate by solvent extraction, the separation selectivity of hydrochloric acid and phosphoric acid can be improved, and the extraction rate of phosphoric acid can be effectively reduced on the basis of ensuring a high extraction rate of hydrochloric acid, and the phase separation time of the oil-water two phases after extraction can also be significantly shortened.

[0040] Comparative Example 3

[0041] In this comparative example, the extractant for preparing potassium dihydrogen phosphate by solvent extraction is composed of a main agent and an auxiliary agent fully mixed in a volume ratio of 0.4:1, wherein the main agent is N,N-diisooctylethanolamine, and the auxiliary agent is composed of xylene and dodecane in a volume ratio of 1:1.

[0042] Phosphoric acid and potassium chloride were dissolved in deionized water at a molar ratio of 1:1 to form an aqueous solution, in which the concentration of chloride ions was 2.29 mol / L. The above-mentioned extractant of this embodiment was used as the organic phase. The aqueous phase and the organic phase were added to a 500 mL separatory funnel at a volume ratio of 1:1, and the reaction was oscillated for 6 minutes at room temperature and normal pressure, and then allowed to stand and the timing was started. The timing was stopped when the extracted organic phase and the residual aqueous phase were completely clarified. It was found that the phase separation time was 3 minutes.

[0043] According to the sampling test and calculation, the extraction rate of hydrochloric acid in this comparative example is 89.5%, and the extraction rate of phosphoric acid is 2.3%. The raffinate aqueous phase is evaporated, concentrated and crystallized to obtain a potassium dihydrogen phosphate product, and the yield of potassium dihydrogen phosphate is 96.3%. The purity of potassium dihydrogen phosphate is 97.5%.

[0044] Comparative Example 4

[0045] In this comparative example, the extractant for preparing potassium dihydrogen phosphate by solvent extraction is composed of a main agent and an auxiliary agent fully mixed in a volume ratio of 0.4:1, wherein the main agent is trioctylmethylammonium chloride, and the auxiliary agent is composed of xylene and dodecane in a volume ratio of 1:1.

[0046] Phosphoric acid and potassium chloride were dissolved in deionized water at a molar ratio of 1:1 to form an aqueous solution, in which the concentration of chloride ions was 2.29 mol / L. The above-mentioned extractant of this embodiment was used as the organic phase. The aqueous phase and the organic phase were added to a 500 mL separatory funnel at a volume ratio of 1:1, and the reaction was oscillated for 6 minutes at room temperature and normal pressure, and then allowed to stand and the timing was started. The timing was stopped when the extracted organic phase and the residual aqueous phase were completely clarified. It was found that the phase separation time was 2.5 minutes.

[0047] According to the sampling test and calculation, the extraction rate of hydrochloric acid in this comparative example is 93.5%, and the extraction rate of phosphoric acid is 1.6%. The raffinate water phase is evaporated, concentrated and crystallized to obtain a potassium dihydrogen phosphate product, and the yield of potassium dihydrogen phosphate is 97.7%. The purity of potassium dihydrogen phosphate is 98.1%.

[0048] Combining Example 1 and Comparative Examples 3 to 4, it can be seen that when a single N, N-diisooctylethanolamine or a single trioctylmethylammonium chloride is used as the main agent of the extractant, the extraction rate of hydrochloric acid is not good, and the phase separation time of the oil-water phase after extraction is also long. When N, N-diisooctylethanolamine and trioctylmethylammonium chloride are compounded as the main agent of the extractant, the extraction rate of hydrochloric acid is effectively improved, and the selective extraction performance of hydrochloric acid and phosphoric acid is also improved, and the phase separation time of the oil-water phase after extraction can be significantly shortened. This shows that the present invention uses N, N-diisooctylethanolamine and trioctylmethylammonium chloride in a limited ratio, which can more effectively play the role of the two in promoting hydrochloric acid extraction and improving the separation selectivity of hydrochloric acid and phosphoric acid, as well as improving the phase separation effect after extraction.

[0049] Comparative Example 5

[0050] In this comparative example, the extractant for preparing potassium dihydrogen phosphate by solvent extraction is composed of a main agent and an auxiliary agent fully mixed in a volume ratio of 0.4:1, wherein the main agent is composed of N,N-diisooctylethanolamine and hexadecyldimethylammonium chloride in a volume ratio of 1:1, and the auxiliary agent is composed of xylene and dodecane in a volume ratio of 1:1.

[0051] Phosphoric acid and potassium chloride were dissolved in deionized water at a molar ratio of 1:1 to form an aqueous solution, in which the concentration of chloride ions was 2.29 mol / L. The above-mentioned extractant of this embodiment was used as the organic phase. The aqueous phase and the organic phase were added to a 500 mL separatory funnel at a volume ratio of 1:1, and the reaction was oscillated for 6 minutes at room temperature and normal pressure, and then allowed to stand and the timing was started. The timing was stopped when the extracted organic phase and the residual aqueous phase were completely clarified. It was found that the phase separation time was 10 minutes.

[0052] According to the sampling test and calculation, the extraction rate of hydrochloric acid in this comparative example is 78.5%, and the extraction rate of phosphoric acid is 2.0%. The raffinate aqueous phase is evaporated, concentrated and crystallized to obtain a potassium dihydrogen phosphate product, and the yield of potassium dihydrogen phosphate is 95.4%. The purity of potassium dihydrogen phosphate is 97.5%.

[0053] Combining Example 1 and Comparative Example 5, it can be seen that when the trioctylmethylammonium chloride in the extractant formula of Example 1 is replaced with the same quaternary ammonium salt of hexadecyldimethylammonium chloride, although the phosphoric acid extraction rate is not significantly increased, the hydrochloric acid extraction rate is significantly decreased and the oil-water phase separation time after extraction is significantly increased. This shows that not all quaternary ammonium salts and N,N-diisooctylethanolamine are used as the main agent of the extractant to improve the selective separation performance of hydrochloric acid and phosphoric acid and shorten the oil-water phase separation time after extraction on the basis of ensuring a high hydrochloric acid extraction rate.

[0054] Comparative Example 6

[0055] In this comparative example, the extractant for preparing potassium dihydrogen phosphate by solvent extraction is composed of a main agent and an auxiliary agent fully mixed in a volume ratio of 0.4:1, wherein the main agent is composed of N,N-diisooctylethanolamine and trioctylmethylammonium chloride in a volume ratio of 1:1, and the auxiliary agent is xylene.

[0056] Phosphoric acid and potassium chloride were dissolved in deionized water at a molar ratio of 1:1 to form an aqueous solution, in which the concentration of chloride ions was 2.29 mol / L. The above-mentioned extractant of this embodiment was used as the organic phase. The aqueous phase and the organic phase were added to a 500 mL separatory funnel at a volume ratio of 1:1, and the reaction was oscillated at room temperature and normal pressure for 6 minutes, then allowed to stand and the timing was started. The timing was stopped when the extracted organic phase and the residual aqueous phase were completely clarified. It was found that the phase separation time was 1 minute.

[0057] According to the sampling test and calculation, the extraction rate of the above-mentioned extractant in this embodiment for hydrochloric acid is 98.5%, and the extraction rate for phosphoric acid is 1.5%. The raffinate water phase is evaporated, concentrated and crystallized to obtain a potassium dihydrogen phosphate product, and the yield of potassium dihydrogen phosphate is 96.3%. Sampling and testing show that the purity of potassium dihydrogen phosphate is 98.5%.

[0058] Comparative Example 7

[0059] In this comparative example, the extractant for preparing potassium dihydrogen phosphate by solvent extraction is composed of a main agent and an auxiliary agent fully mixed in a volume ratio of 0.4:1, wherein the main agent is composed of N,N-diisooctylethanolamine and trioctylmethylammonium chloride in a volume ratio of 1:1, and the auxiliary agent is dodecane.

[0060] Phosphoric acid and potassium chloride were dissolved in deionized water at a molar ratio of 1:1 to form an aqueous solution, in which the concentration of chloride ions was 2.29 mol / L. The above-mentioned extractant of this embodiment was used as the organic phase. The aqueous phase and the organic phase were added to a 500 mL separatory funnel at a volume ratio of 1:1, and the reaction was oscillated for 6 minutes at room temperature and normal pressure, and then allowed to stand and the timing was started. The timing was stopped when the extracted organic phase and the residual aqueous phase were completely clarified. It was found that the phase separation time was 2 minutes.

[0061] According to the sampling test and calculation, the extraction rate of hydrochloric acid in this comparative example is 98.2%, and the extraction rate of phosphoric acid is 1.3%. The raffinate aqueous phase is evaporated, concentrated and crystallized to obtain a potassium dihydrogen phosphate product, and the yield of potassium dihydrogen phosphate is 98.3%. The purity of potassium dihydrogen phosphate is 97.4%.

[0062] Combining Example 1 with Comparative Examples 1-2 and Comparative Examples 6-7, it can be seen that, for the auxiliary agent of the extractant, compared with octanol and kerosene, or cyclohexane and isopentanol used in the prior art, using a single xylene or a single dodecane can help shorten the oil-water phase separation time after extraction. However, the present invention finds that the auxiliary agent of the extractant is a mixture of xylene and C-2-containing dodecane. 8 ~C 16 Alkanes can be compounded in appropriate proportions as auxiliary agents for the extraction agent, which can further shorten the phase separation time of the oil-water phase after extraction.

[0063] Example 2

[0064] In this embodiment, a special extractant for preparing potassium dihydrogen phosphate by solvent extraction is provided, which is formed by fully mixing a main agent and an auxiliary agent in a volume ratio of 0.5:1, wherein the main agent is composed of N,N-diisooctylethanolamine and trioctylmethylammonium chloride in a volume ratio of 0.5:1, and the auxiliary agent is composed of xylene and dodecane in a volume ratio of 2:1.

[0065] Phosphoric acid and potassium chloride were dissolved in deionized water at a molar ratio of 1:1 to form an aqueous solution, in which the concentration of chloride ions was 2.29 mol / L. The above-mentioned extractant of this embodiment was used as the organic phase. The aqueous phase and the organic phase were added to a 500 mL separatory funnel at a volume ratio of 1:1, and the reaction was oscillated for 6 minutes at room temperature and normal pressure, and then allowed to stand and the timing was started. The timing was stopped when the extracted organic phase and the residual aqueous phase were completely clarified. It was found that the phase separation time was 10 s.

[0066] According to the calculation of sampling test, the extraction rate of hydrochloric acid in this embodiment is 99.5%, and the extraction rate of phosphoric acid is only 1.2%. The raffinate aqueous phase is evaporated, concentrated and crystallized to obtain a potassium dihydrogen phosphate product, and the yield of potassium dihydrogen phosphate is 98.4%. Sampling test shows that the purity of potassium dihydrogen phosphate is 99.5%.

[0067] Example 3

[0068] In this embodiment, a special extractant for preparing potassium dihydrogen phosphate by solvent extraction is prepared by fully mixing a main agent and an auxiliary agent in a volume ratio of 0.5:1, wherein the main agent is composed of N,N-diisooctylethanolamine and trioctylmethylammonium chloride in a volume ratio of 0.5:1, and the auxiliary agent is composed of xylene and octane in a volume ratio of 2:1.

[0069] Phosphoric acid and potassium chloride were dissolved in deionized water at a molar ratio of 1:1 to form an aqueous phase solution, in which the concentration of chloride ions was 2.29 mol / L. The above-mentioned extractant of this embodiment was used as the organic phase. The aqueous phase and the organic phase were added to a 500 mL separatory funnel at a volume ratio of 1:1, and the reaction was oscillated for 6 minutes at room temperature and normal pressure, and then allowed to stand and the timing was started. The timing was stopped when the extracted organic phase and the residual aqueous phase were completely clarified. It was found that the phase separation time was 9 seconds.

[0070] According to the sampling test and calculation, the extraction rate of hydrochloric acid in this embodiment is 99.6%, and the extraction rate of phosphoric acid is only 1.0%. The raffinate aqueous phase is evaporated, concentrated and crystallized to obtain a potassium dihydrogen phosphate product, and the yield of potassium dihydrogen phosphate is 98.2%. Sampling and testing show that the purity of potassium dihydrogen phosphate is 99.5%.

[0071] Example 4

[0072] In this embodiment, a special extractant for preparing potassium dihydrogen phosphate by solvent extraction is prepared by fully mixing a main agent and an auxiliary agent in a volume ratio of 0.5:1, wherein the main agent is composed of N,N-diisooctylethanolamine and trioctylmethylammonium chloride in a volume ratio of 0.5:1, and the auxiliary agent is composed of xylene and hexadecane in a volume ratio of 2:1.

[0073] Phosphoric acid and potassium chloride were dissolved in deionized water at a molar ratio of 1:1 to form an aqueous solution, in which the concentration of chloride ions was 2.29 mol / L. The above-mentioned extractant of this embodiment was used as the organic phase. The aqueous phase and the organic phase were added to a 500 mL separatory funnel at a volume ratio of 1:1, and the reaction was oscillated for 6 minutes at room temperature and normal pressure, and then allowed to stand and the timing was started. The timing was stopped when the extracted organic phase and the residual aqueous phase were completely clarified. It was found that the phase separation time was 20 seconds.

[0074] According to the sampling test and calculation, the extraction rate of hydrochloric acid in this embodiment is 99.5%, and the extraction rate of phosphoric acid is only 1.2%. The raffinate aqueous phase is evaporated, concentrated and crystallized to obtain a potassium dihydrogen phosphate product, and the yield of potassium dihydrogen phosphate is 98.3%. Sampling and testing show that the purity of potassium dihydrogen phosphate is 99.5%.

[0075] Example 5

[0076] In this embodiment, a special extractant for preparing potassium dihydrogen phosphate by solvent extraction is prepared by fully mixing a main agent and an auxiliary agent in a volume ratio of 0.6:1, wherein the main agent is composed of N,N-diisooctylethanolamine and trioctylmethylammonium chloride in a volume ratio of 1.2:1, and the auxiliary agent is composed of xylene, nonane and pentadecane in a volume ratio of 0.8:0.5:0.5.

[0077] Phosphoric acid and potassium chloride were dissolved in deionized water at a molar ratio of 1:1 to form an aqueous solution, in which the concentration of chloride ions was 2.29 mol / L. The above-mentioned extractant of this embodiment was used as the organic phase. The aqueous phase and the organic phase were added to a 500 mL separatory funnel at a volume ratio of 1:1, and the reaction was oscillated for 6 minutes at room temperature and normal pressure, and then allowed to stand and the timing was started. The timing was stopped when the extracted organic phase and the residual aqueous phase were completely clarified. It was found that the phase separation time was 35 s.

[0078] According to the sampling test and calculation, the extraction rate of hydrochloric acid in this embodiment is 99.4%, and the extraction rate of phosphoric acid is only 1.2%. The raffinate aqueous phase is evaporated, concentrated and crystallized to obtain a potassium dihydrogen phosphate product, and the yield of potassium dihydrogen phosphate is 98.2%. Sampling and testing show that the purity of potassium dihydrogen phosphate is 99.5%.

[0079] Example 6

[0080] In this embodiment, a special extractant for preparing potassium dihydrogen phosphate by solvent extraction is prepared by fully mixing a main agent and an auxiliary agent in a volume ratio of 0.2:1, wherein the main agent is composed of N,N-diisooctylethanolamine and trioctylmethylammonium chloride in a volume ratio of 1:1, and the auxiliary agent is composed of xylene, decane and tridecane in a volume ratio of 1:0.5:0.5.

[0081] Phosphoric acid and potassium chloride were dissolved in deionized water at a molar ratio of 1:1 to form an aqueous solution, in which the concentration of chloride ions was 2.29 mol / L. The above-mentioned extractant of this embodiment was used as the organic phase. The aqueous phase and the organic phase were added to a 500 mL separatory funnel at a volume ratio of 1:1, and the reaction was oscillated for 6 minutes at room temperature and normal pressure, and then allowed to stand and the timing was started. The timing was stopped when the extracted organic phase and the residual aqueous phase were completely clarified. It was found that the phase separation time was 26 seconds.

[0082] According to the sampling test and calculation, the extraction rate of hydrochloric acid in this embodiment is 99.3%, and the extraction rate of phosphoric acid is 1.4%. The raffinate aqueous phase is evaporated, concentrated, and crystallized to obtain a potassium dihydrogen phosphate product, and the yield of potassium dihydrogen phosphate is 98.3%. Sampling and testing show that the purity of potassium dihydrogen phosphate is 99.5%.

[0083] Example 7

[0084] In this embodiment, a special extractant for preparing potassium dihydrogen phosphate by solvent extraction is prepared by fully mixing a main agent and an auxiliary agent in a volume ratio of 0.4:1, wherein the main agent is composed of N,N-diisooctylethanolamine and trioctylmethylammonium chloride in a volume ratio of 1:1, and the auxiliary agent is composed of xylene and dodecane in a volume ratio of 1:1.

[0085] (1) Phosphoric acid and potassium chloride are dissolved in deionized water at a molar ratio of 1:1 to form an aqueous solution, wherein the concentration of chloride ions in the aqueous solution is 2.29 mol / L. The above-mentioned extractant of this embodiment is used as the organic phase. The aqueous phase and the organic phase are added to a 500 mL separatory funnel at a volume ratio of 1:1, and the reaction is oscillated at room temperature and normal pressure for 6 minutes, then allowed to stand and timing is started. The timing is stopped when the extracted organic phase and the residual aqueous phase are completely clarified. It is found that the phase separation time is 30 seconds.

[0086] (2) After the extractant in the extracted organic phase is regenerated, it is continuously recycled according to the operation of step (1), and recycled again after each recycling. The regeneration method of the extractant is as follows: adding ammonia water to the extracted organic phase for neutralization reaction, the amount of ammonia water added is such that the molar ratio of ammonia water to hydrochloric acid in the extracted organic phase is 1:1, the neutralization reaction temperature is controlled to be 60°C, the neutralization reaction time is controlled to be 60 minutes, and after the neutralization reaction is completed, the obtained reaction solution is allowed to stand for phase separation, and the organic phase obtained by phase separation is the extractant.

[0087] After the extractant was recycled for 20 times, the extraction rate of hydrochloric acid was 99.5%, and the extraction rate of phosphoric acid was 1.1% after sampling and testing. The residual water phase was evaporated, concentrated, and crystallized to obtain a potassium dihydrogen phosphate product. The yield of potassium dihydrogen phosphate was 98.3%, and the purity of potassium dihydrogen phosphate was 99.5%. Since the extractant formula of this embodiment is the same as that of Example 1, that is, after the extractant of Example 1 is recycled for 20 times, the extraction rate of hydrochloric acid and phosphoric acid is the same as that of the extractant when it is used for the first time, it shows that the extractant of the present invention has good stability and has no performance loss after multiple cycles.

Claims

1. A special extractant for preparing potassium dihydrogen phosphate by solvent extraction, characterized in that: The extractant is composed of a main agent and an auxiliary agent. The main agent is N, N-diisooctylethanolamine and trioctylmethylammonium chloride, and the auxiliary agent is xylene and C8~C 16 Alkanes, the C8~C 16 The alkane is at least one of alkanes with carbon atoms of 8 to 16, and the volume ratio of the main agent to the auxiliary agent is (0.2 to 0.6):

1.

2. The special extractant for preparing potassium dihydrogen phosphate by solvent extraction according to claim 1, characterized in that: In the main agent, the volume ratio of N,N-diisooctylethanolamine to trioctylmethylammonium chloride is (0.5-1.2):

1.

3. The special extractant for preparing potassium dihydrogen phosphate by solvent extraction according to claim 1, characterized in that: In the auxiliary agent, xylene and C8~C 16 The volume ratio of alkanes is (0.8~2):

1.

4. The special extractant for preparing potassium dihydrogen phosphate by solvent extraction according to any one of claims 1 to 3, characterized in that: The volume ratio of the main agent to the auxiliary agent is (0.4-0.6):1.