Preparation method of oxalic acid ligand binary quaternary ammonium salt

Abstract

The invention provides a preparation method of oxalic acid ligand binary quaternary ammonium salt, and relates to the technical field of organic synthesis. The method comprises the following steps: mixing halogenated quaternary ammonium salt and a sodium hydroxide solution, heating and reacting in a reaction kettle, cooling and splitting phases to obtain trioctyl methyl ammonium hydroxide, mixing the obtained trioctyl methyl ammonium hydroxide and an oxalic acid solution, heating and reacting in the reaction kettle again, cooling and splitting phases to obtain a binary quaternary ammonium salt crude product, and separating phases to obtain the binary quaternary ammonium salt. And washing and drying the obtained binary quaternary ammonium salt crude product to obtain the oxalic acid ligand binary quaternary ammonium salt. The method is simple to operate, short in reaction time, easy in product separation and high in yield, and the obtained quaternary ammonium salt product can be used for green and environment-friendly extraction.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and in particular to a method for preparing a binary quaternary ammonium salt of oxalic acid ligand. Background Technology

[0002] Quaternary ammonium salts are a class of cationic surfactants and commonly used extractants in hydrometallurgy. They include halogenated ammonium salts and acid radical quaternary ammonium salts, playing a major role in various fields such as daily chemical industry, textiles, mining, asphalt, construction, plastics processing, oil extraction, and petrochemicals.

[0003] Commonly used quaternary ammonium salts are mainly trioctylmethylammonium chloride, followed by trioctylmethylammonium nitrate and trioctylmethylammonium bromide, all of which utilize anion exchange as their extraction mechanism. Currently synthesized quaternary ammonium salts for extraction are all inorganic ligand-based. When these quaternary ammonium salts are used as extractants, they will generate a large amount of Cl-containing compounds. - NO3 - and Br - Difficult-to-treat extraction waste liquids result in high wastewater treatment costs and environmental pollution.

[0004] Patent application ZL200510061094.4 discloses a method for synthesizing quaternary ammonium salts from carbonate diesters and ammonium salts under catalysis. This method uses ammonium salts instead of amines or amides as starting reactants and carbonate diesters instead of haloalkanes or sulfates as quaternizing reagents. Compared to traditional processes, this method offers significant advantages. Firstly, the anion of the target product can be artificially selected; synthesizing quaternary ammonium salts with anions of fluoride, sulfate, acetate, oxalate, nitrate, or phosphate requires only a single reaction step, eliminating the need for ion exchange. Secondly, phosphate diesters are non-toxic and exist as alcohols and carbon dioxide after the reaction, making them easy to separate from the product. However, according to this patent application, this preparation method requires a suitable catalyst. The ionic liquid 1-methyl-3-ethylimidazole and the product both belong to the quaternary ammonium salt family, making separation a challenge. Furthermore, anion exchange occurs between the catalyst and the product, causing anions from the catalyst to contaminate the product, resulting in impurities.

[0005] ZL 200910131461.1 describes a process that directly produces trioctylmethylammonium chloride by reacting trioctylammonium and chloromethane in the presence of a catalyst. The reaction temperature is 75–95°C, the reaction pressure is less than 0.2 MPa, and the reaction time is 10–15 h. After the reaction, the mixture is kept at 84–95°C for 2–3 h. This process synthesizes trioctylmethylammonium chloride with high purity under high temperature and pressure, but the high temperature and pressure require sophisticated equipment, result in a long reaction time, and lead to high production costs. When trioctylmethylammonium chloride is used for extraction, according to the anion exchange mechanism, chloride ions from the extractant enter the raffinate, generating a large amount of difficult-to-treat chlorine-containing wastewater, which pollutes the environment.

[0006] In summary, existing processes for synthesizing quaternary ammonium salts are complex and cumbersome, suffering from long reaction times, difficulties in product separation, low yields, and typically requiring high temperature and high pressure conditions. Therefore, a simple and easy-to-operate method for preparing quaternary ammonium salts is urgently needed. Summary of the Invention

[0007] To address the aforementioned technical problems in the existing technology, this invention provides a method for preparing a binary quaternary ammonium salt of oxalic acid ligand. The technical solution is as follows: A method for preparing a binary quaternary ammonium salt of oxalic acid ligand, the method comprising: S1. After mixing the quaternary ammonium halide with sodium hydroxide solution, the mixture is heated in a reaction vessel and then cooled and separated to obtain trioctylmethylammonium hydroxide. S2. The trioctylmethylammonium hydroxide obtained in S1 is mixed with oxalic acid solution and heated in a reaction vessel. After cooling, the phases are separated to obtain the crude product of binary quaternary ammonium salt. S3. Wash and dry the crude diquaternary ammonium salt obtained in S2 to obtain the oxalic acid ligand diquaternary ammonium salt.

[0008] The quaternary ammonium halide in S1 is one of trioctylmethylammonium chloride, trioctylmethylammonium iodide, and trioctylmethylammonium bromide.

[0009] The molar ratio of the quaternary ammonium halide salt to the sodium hydroxide solution in S1 is 1:1 to 1:4.

[0010] The heating temperature in the reactor in S1 is 50~70℃, and the reaction time is 10~20min.

[0011] The molar ratio of trioctylmethylammonium hydroxide to oxalic acid solution in S2 is 1:1 to 1:3.

[0012] The heating temperature in the reactor in S2 is 30~50℃, and the reaction time is 10~20min.

[0013] The crude binary quaternary ammonium salt product in S3 is washed with deionized water at least three times.

[0014] The crude diquaternary ammonium salt in S3 is washed and then vacuum dried at 30-50°C for no less than 24 hours to obtain the oxalic acid ligand diquaternary ammonium salt.

[0015] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following: Compared with traditional quaternary ammonium salt synthesis techniques, the above-described method eliminates the need for synthesis in organic solvents, requiring only atmospheric pressure and low temperature, with a reaction time of only 10-20 minutes. It offers advantages such as simple operation and short reaction time. The oxalic acid ligand binary quaternary ammonium salt synthesized in this invention contains oxalic acid functional groups. When used as an extractant, the exchanged oxalic acid functional groups enter the raffinate. Based on the principle of strong acid displacing weak acid, sulfuric acid can be added to the raffinate to recover the organic acid, thus avoiding the generation of difficult-to-treat and polluting waste liquid. It is a green and environmentally friendly extractant. Furthermore, the reagents used in the synthesis process are all water-soluble inorganic substances and oxalic acid solutions, which are easily separated from the oily quaternary ammonium salt. The yield of the quaternary ammonium salt product reaches over 95%, and the purity reaches over 98%.

[0016] Therefore, this invention has the advantages of simple operation, short reaction time, easy product separation, high yield, and applicability to green and environmentally friendly extraction. Detailed Implementation

[0017] The technical solutions of the present invention will be described below with reference to the embodiments.

[0018] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0019] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0020] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with specific embodiments.

[0021] This invention provides a method for preparing a binary quaternary ammonium salt of oxalic acid ligand. The method may include the following steps: S1. After mixing the quaternary ammonium halide with sodium hydroxide solution, the mixture is heated in a reaction vessel and then cooled and separated to obtain trioctylmethylammonium hydroxide. S2. The trioctylmethylammonium hydroxide obtained in S1 is mixed with oxalic acid solution and heated in a reaction vessel. After cooling, the phases are separated to obtain the crude product of binary quaternary ammonium salt. S3. Wash and dry the crude diquaternary ammonium salt obtained in S2 to obtain the oxalic acid ligand diquaternary ammonium salt.

[0022] The following description, in conjunction with specific embodiments, illustrates this point.

[0023] Organic quaternary ammonium salts have the general formula [R4N]. x • [ORG], where the chemical formula for ORG is: [C2O4] 2- [C6H5O7] 3- [C4H4O5] 2- [C4H4O6] 2- [C4H4O4] 2- [C6H6O6] 2- and [NH2SO3] - The simplified structure is as follows:

[0024] The oxalic acid ligand binary quaternary ammonium salt prepared in this invention is trioctylmethylammonium oxalate, with the chemical formula: [R4N]2·[C2O4].

[0025] Example 1

[0026] A method for preparing a binary quaternary ammonium salt of oxalic acid ligand is as follows: S1. Trioctylmethylammonium chloride and sodium hydroxide solution were mixed in a molar ratio of 1:1 and heated in a reaction vessel at 50°C for 15 min with continuous stirring during the reaction. After cooling, the phases were separated to obtain trioctylmethylammonium hydroxide. S2. The trioctylmethylammonium hydroxide obtained in S1 is mixed with oxalic acid solution at a molar ratio of 1:1 and then heated in a reactor at 30°C for 15 min. After cooling, the phases are separated to obtain the crude product of the binary quaternary ammonium salt. S3. The crude diquaternary ammonium salt obtained in S2 is washed three times with deionized water and then vacuum dried at 30°C for 30 hours to obtain trioctylmethyl oxalate ammonium, i.e., oxalate ligand diquaternary ammonium salt.

[0027] The yield of the trioctylmethyl oxalate ammonium product obtained in this embodiment is greater than 95.3%, and the purity is greater than 98.5%.

[0028] Taking the oxalic acid solution for vanadium extraction (vanadium concentration of 1.5 g / L, oxalate concentration of 150 g / L, initial pH=0.7) as an example, under the conditions of extractant concentration of 20%, relative O / A=1∶2 and extraction time of 5 min, the single-stage vanadium extraction rate obtained by trioctylmethyl oxalate ammonium was 82%, which is better than the effect achieved by other extractants. The results are shown in the table below.

[0029] Table of extraction rates for different extractants

[0030] Example 2

[0031] A method for preparing a binary quaternary ammonium salt of oxalic acid ligand is as follows: S1. Trioctylmethylammonium iodide and sodium hydroxide solution were mixed in a molar ratio of 1:3 and heated in a reactor at 60°C for 10 min with continuous stirring during the reaction. After cooling, the phases were separated to obtain trioctylmethylammonium hydroxide. S2. The trioctylmethylammonium hydroxide obtained in S1 is mixed with oxalic acid solution at a molar ratio of 1:2. The mixture is heated in a reactor at 40°C for 12 min. After cooling, the phases are separated to obtain the crude product of the binary quaternary ammonium salt. S3. The crude diquaternary ammonium salt obtained in S2 is washed four times with deionized water and then vacuum dried at 40°C for 25 hours to obtain trioctylmethyl oxalate ammonium, i.e., oxalate ligand diquaternary ammonium salt.

[0032] The yield of the trioctylmethyl oxalate ammonium product obtained in this embodiment is greater than 95.5%, and the purity is greater than 98.8%.

[0033] Example 3

[0034] A method for preparing a binary quaternary ammonium salt of oxalic acid ligand is as follows: S1. Trioctylmethylammonium bromide was mixed with sodium hydroxide solution at a molar ratio of 1:4 and heated at 70°C for 10 min in a reaction vessel with continuous stirring during the reaction. After cooling, the phases were separated to obtain trioctylmethylammonium hydroxide. S2. The trioctylmethylammonium hydroxide obtained in S1 is mixed with oxalic acid solution at a molar ratio of 1:3. The mixture is heated in a reactor at 50°C for 10 min. After cooling, the phases are separated to obtain the crude product of the binary quaternary ammonium salt. S3. The crude diquaternary ammonium salt obtained in S2 is washed four times with deionized water and then vacuum dried at 50°C for 24 hours to obtain trioctylmethyl oxalate ammonium, i.e., oxalate ligand diquaternary ammonium salt.

[0035] The yield of the trioctylmethyl oxalate ammonium product obtained in this embodiment is greater than 96.1%, and the purity is greater than 98.9%.

[0036] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a binary quaternary ammonium salt of oxalic acid ligand, characterized in that, The method includes: S1. After mixing the quaternary ammonium halide with sodium hydroxide solution, the mixture is heated in a reaction vessel and then cooled and separated to obtain trioctylmethylammonium hydroxide. S2. The trioctylmethylammonium hydroxide obtained in S1 is mixed with oxalic acid solution and heated in a reaction vessel. After cooling, the phases are separated to obtain the crude product of binary quaternary ammonium salt. S3. Wash and dry the crude diquaternary ammonium salt obtained in S2 to obtain the oxalic acid ligand diquaternary ammonium salt.

2. The method for preparing the oxalic acid ligand binary quaternary ammonium salt according to claim 1, characterized in that, The quaternary ammonium halide in S1 is one of trioctylmethylammonium chloride, trioctylmethylammonium iodide, and trioctylmethylammonium bromide.

3. The method for preparing the oxalic acid ligand binary quaternary ammonium salt according to claim 1, characterized in that, The molar ratio of the quaternary ammonium halide salt to the sodium hydroxide solution in S1 is 1:1 to 1:

4.

4. The method for preparing the oxalic acid ligand binary quaternary ammonium salt according to claim 1, characterized in that, The heating temperature in the reactor in S1 is 50~70℃, and the reaction time is 10~20min.

5. The method for preparing the oxalic acid ligand binary quaternary ammonium salt according to claim 1, characterized in that, The molar ratio of trioctylmethylammonium hydroxide to oxalic acid solution in S2 is 1:1 to 1:

3.

6. The method for preparing the oxalic acid ligand binary quaternary ammonium salt according to claim 1, characterized in that, The heating temperature in the reactor in S2 is 30~50℃, and the reaction time is 10~20min.

7. The method for preparing the oxalic acid ligand binary quaternary ammonium salt according to claim 1, characterized in that, The crude binary quaternary ammonium salt product in S3 is washed with deionized water at least three times.

8. The method for preparing the oxalic acid ligand binary quaternary ammonium salt according to claim 1, characterized in that, The crude diquaternary ammonium salt in S3 is washed and then vacuum dried at 30-50°C for no less than 24 hours to obtain the oxalic acid ligand diquaternary ammonium salt.

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