Soxhlet purification device and purification method of crude crystalline aluminum chloride

Abstract

The present invention relates to the technical field of crude crystalline aluminum chloride purification, and discloses a Soxhlet purification device and a method for purifying crude crystalline aluminum chloride. The Soxhlet purification device comprises a distillation kettle (1), a purification tank (2) and an elastic air bag (3) connected in sequence, and a hydrochloric acid online concentration meter (4) connected to the purification tank (2); wherein the purification tank (2) has an air guide tube (21) and a siphon tube (22), and the air guide tube (21) is in an inverted U shape and is arranged inside the purification tank (2). The method for purifying crude crystalline aluminum chloride provided by the present invention has a high degree of automation, simple operation, high purification efficiency, and can obtain aluminum chloride products with a higher purity level, and is suitable for industrial promotion.

Description

Technical Field

[0001] The invention relates to the technical field of crude crystalline aluminum chloride purification, and in particular to a Soxhlet purification device and a method for purifying crude crystalline aluminum chloride. Background Art

[0002] When using the hydrochloric acid method to produce alumina, the removal efficiency of metal cations such as Fe, Ca, Na, K, and Mg directly affects the purity of the intermediate product crude crystalline aluminum chloride, which in turn determines the purity index of the final alumina product. Studies have shown that in a concentrated hydrochloric acid solution with HCl>33% (mass fraction), the solubility of aluminum chloride will drop sharply and precipitate in the form of hydrated aluminum chloride hexahydrate crystals, while impurities such as ferric chloride, calcium chloride, and potassium chloride in crude crystalline aluminum chloride still maintain a high solubility and are therefore retained in the liquid phase. This principle can be used to separate and purify aluminum chloride. The process of separation and purification using this principle is also called salting-out crystallization process. The purified aluminum chloride crystals are then calcined and decomposed to remove the Cl element and crystal water to obtain a high-purity alumina powder product.

[0003] When using high-concentration hydrochloric acid to purify crude crystalline aluminum chloride, it often involves the purification and recycling of hydrochloric acid. Among them, the purification and recycling of hydrochloric acid and HCl are the key to reducing the cost of salting-out crystallization and purification of aluminum chloride and improving the economic efficiency of the process technology.

[0004] CN103738990B discloses a method for preparing aluminum oxide using crystalline aluminum chloride. The principle of the method is to dissolve aluminum chloride crystals in a hydrochloric acid solution with a concentration of 14%-28% to prepare a saturated aluminum chloride solution, then add some aluminum chloride crystals to induce aluminum chloride to recrystallize and precipitate, and then wash the obtained primary purified aluminum chloride crystals with concentrated hydrochloric acid with a concentration of not less than 30% to obtain secondary purified aluminum chloride crystals, and then calcine at 1000℃-1200℃ to obtain an aluminum oxide product with a purity greater than 99.9%. The subsequent treatment method of the waste acid obtained by the method after two purifications is not disclosed. If it continues to be directly recycled, it will inevitably cause the accumulation of metal cation impurities, and an additional impurity removal system (such as iron removal by resin adsorption method) needs to be added. Moreover, the crystallization separation and purification of aluminum chloride in the method are implemented in two steps, and the operation process is long and the comprehensive cost is high.

[0005] CN107285351A discloses a method for extracting aluminum oxide from fly ash by hydrochloric acid leaching. The method introduces HCl dry gas with a purity higher than 85% into the fly ash hydrochloric acid leaching solution (the main component is aluminum chloride) to obtain crude aluminum chloride crystals, and the obtained crude aluminum chloride is then washed and purified with 27%-31% hydrochloric acid to obtain high-purity crystalline aluminum chloride, and then calcined to obtain aluminum oxide. The method focuses on the recycling of waste acid and waste HCl gas generated in the crystallization, washing and calcination stages, but the heating and concentration process to obtain HCl gas involves collection, purification and drying processes, which are complex and costly in actual industrial production operations; the waste acid is directly reused in the fly ash leaching and crude aluminum chloride washing stages, which will inevitably lead to the accumulation of impurity elements and affect the purity of the product after multiple cycles, and an impurity separation process must still be added.

[0006] Therefore, it is urgent to provide a method for purifying crude crystalline aluminum chloride which is simple to operate, has a high recycling rate of hydrochloric acid and a good purification effect. Summary of the invention

[0007] The purpose of the present invention is to overcome the problems of complex hydrochloric acid / HCl purification and recycling process, high cost, complicated aluminum chloride purification procedure and low efficiency in the existing salting-out crystallization aluminum chloride purification technology, and provide a Soxhlet purification device and a purification method for crude crystalline aluminum chloride. The initial material used in the method can be industrial-grade hydrochloric acid with a mass concentration of 31%-38%, and the raw material cost advantage is significant. The purification and circulation of HCl / hydrochloric acid are carried out simultaneously with the crystallization and purification of aluminum chloride, and the system has high integration, simple operation, low cost and good purification effect.

[0008] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a Soxhlet aluminum chloride purification device, which includes a distillation kettle 1, a purification tank 2, an elastic airbag 3, and a hydrochloric acid online concentration meter 4 connected to the purification tank 2 in sequence; wherein the purification tank 2 has an air duct 21 and a siphon 22, and the air duct 21 is an inverted U-shape and is arranged inside the purification tank 2.

[0009] The second aspect of the present invention provides a method for purifying crude crystalline aluminum chloride using the device described in the first aspect of the present invention, the method comprising the following steps:

[0010] (1) Feeding: adding hydrochloric acid solution I to a distillation kettle, and adding crude crystalline aluminum chloride and hydrochloric acid solution II to a purification tank; the liquid level of the mixture containing crude crystalline aluminum chloride and hydrochloric acid solution II in the purification tank is located between the gas outlet of the air guide pipe and the liquid inlet of the siphon pipe; wherein the initial concentration of hydrochloric acid solution I is greater than 20.2wt% and less than 40wt%; and the initial concentration of hydrochloric acid solution II is less than 40wt%;

[0011] (2) Purification: The distillation kettle is heated, and the acidic steam in the distillation kettle enters the purification tank through the air duct; when the concentration of the hydrochloric acid II in the purification tank drops from the maximum value to 38-33wt%, the liquid phase in the mixture returns to the distillation kettle, completing a purification operation; wherein the maximum concentration of the hydrochloric acid II is ≤40wt%;

[0012] (3) Separation: Repeat the purification in step (2) multiple times; then stop heating, remove the mixture and filter it to obtain purified crystalline aluminum chloride.

[0013] The third aspect of the present invention provides a method for purifying crude crystalline aluminum chloride, the method comprising the following steps:

[0014] (i) heating the hydrochloric acid solution I to obtain acidic steam;

[0015] (ii) introducing the acidic steam into a solid-liquid mixture containing crude crystalline aluminum chloride and hydrochloric acid solution II, controlling the maximum concentration of hydrochloric acid solution II in the solid-liquid mixture to be ≤40wt%, and when the concentration of hydrochloric acid solution II in the solid-liquid mixture decreases from the maximum concentration to 33-38wt%, drawing out the solution in the solid-liquid mixture and returning it to hydrochloric acid solution I, thereby completing a purification operation;

[0016] (iii) repeating the purification operation of step (2) multiple times, then stopping the heating, filtering the solid-liquid mixture to obtain purified crystalline aluminum chloride.

[0017] Through the above technical solution, the beneficial technical effects of the present invention are as follows:

[0018] 1) The Soxhlet purification device provided by the present invention can be used to purify crude crystalline aluminum chloride. During the purification process, the acid vapor is introduced into the purification tank by using an air guide pipe, and the hydrochloric acid circulation is realized by using a siphon. The two processes of HCl gas recovery and aluminum chloride purification can be combined into one, with a high degree of automation, which can effectively simplify the operation process and improve the recycling rate of hydrochloric acid / HCl;

[0019] 2) The Soxhlet purification device provided by the present invention uses an elastic airbag to seal the device, which can avoid loss and pollution caused by HCl escape; at the same time, the elastic airbag can also keep the system at normal pressure or slightly positive pressure, and has the functions of partial water vapor condensation and reflux, which can further simplify the operation process;

[0020] 3) The Soxhlet apparatus provided by the present invention is used to purify crude crystalline aluminum chloride, which has higher overall purification efficiency and convenient operation, and can obtain aluminum chloride products with higher purity levels. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1It is a schematic structural diagram of a Soxhlet purification device in a preferred embodiment of the present invention.

[0022] Description of Reference Numerals

[0023] 1. Distillation kettle 2. Purification tank 3. Elastic airbag

[0024] 21. Air guide tube 22. Siphon 23. Partition

[0025] 4. Hydrochloric acid online concentration meter DETAILED DESCRIPTION

[0026] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0027] The first aspect of the present invention provides a Soxhlet purification device, wherein the device comprises a distillation kettle 1, a purification tank 2, an elastic air bag 3, and a hydrochloric acid online concentration meter 4 connected to the purification tank 2 in sequence; wherein the purification tank 2 has an air guide tube 21 and a siphon tube 22, wherein the air guide tube 21 is inverted U-shaped and is arranged inside the purification tank 2. Specifically, Figure 1 shown.

[0028] In a preferred embodiment, a partition 23 is provided in the lower part of the purification tank 2, the air inlet of the air duct 21 is provided on the partition 23, and the air outlet of the air duct 21 is not connected to the partition 23, which is used to introduce the steam in the distillation kettle 1 into the purification tank 2.

[0029] In a preferred embodiment, the air inlet of the air guide tube 21 is in an inverted funnel shape, and the air outlet of the air guide tube 21 is provided with small holes that are beneficial to steam dispersion.

[0030] In a preferred embodiment, the siphon tube 22 is configured as a hose connecting the purification tank 2 and the distillation kettle 1 through the outside of the purification tank 2 .

[0031] In a preferred embodiment, the liquid inlet and liquid outlet of the siphon tube 22 are respectively located above and below the partition 23. In the present invention, the liquid inlet of the siphon tube is located above the partition, and the liquid outlet of the siphon tube is located below the partition.

[0032] In a preferred embodiment, the liquid inlet of the siphon tube 22 is higher than the air outlet of the air guide tube 21 .

[0033] In a preferred embodiment, the liquid inlet of the siphon tube 22 is provided with an enlarged neck.

[0034] In the present invention, when the liquid inlet of the siphon tube is a straight tube, in actual use, siphoning will occur before the liquid level in the purification tank reaches the highest point of the siphon tube. To avoid siphoning in advance, it is preferred to provide an enlarged neck at the liquid inlet of the siphon tube.

[0035] In a preferred embodiment, the Soxhlet purification apparatus further comprises a fixing component, wherein the fixing component is used to adjust the height of the siphon tube 22 .

[0036] The present invention does not specifically limit the fixing parts, and the fixing parts may be an iron frame and a self-locking nylon cable tie or a test tube clamp. In the present invention, the concentration of the hydrochloric acid solution in the purification tank increases first and then decreases due to the absorption of the acidic steam from the distillation kettle. The siphon tube is set as a hose, and the conditions for the occurrence of the siphon phenomenon can be regulated so as to return the hydrochloric acid in the purification tank to the distillation kettle in time, thereby controlling the concentration of the hydrochloric acid solution in the purification tank, ensuring that the hydrochloric acid in the purification tank can dissolve metal chloride impurities but basically does not dissolve aluminum chloride, and utilizing the difference in solubility of metal chloride impurities and aluminum chloride in the hydrochloric acid solution to achieve efficient purification of crude crystalline aluminum chloride.

[0037] In a preferred embodiment, the connection method between the distillation kettle 1 and the purification tank 2 is selected from ground connection and / or flange connection; the connection method between the elastic airbag 3 and the purification tank 2 is selected from socket connection and / or flange connection.

[0038] In the present invention, when the volume of the distillation kettle is relatively small and belongs to the laboratory scale, for example, the volume of the distillation kettle is less than 5L, the distillation kettle and the purification tank can be glass products, and the two are connected by a glass ground connection method. At the same time, the elastic airbag can be directly mounted on the upper end of the purification tank; when the volume of the distillation kettle is relatively large and belongs to the factory production scale, for example, the volume of the distillation kettle is greater than 5L, the distillation kettle, the purification tank and the elastic airbag can be connected by a flange.

[0039] In a preferred embodiment, a safety pressure relief valve is provided on the elastic airbag 3. The safety valve provided on the elastic airbag can be used for emergency pressure relief to avoid safety accidents.

[0040] In the present invention, the still is used to place hydrochloric acid solution I, and the purification tank is used to place crude crystalline aluminum chloride and hydrochloric acid solution II, wherein the addition amount of crude crystalline aluminum chloride and hydrochloric acid solution II makes the liquid level in the purification tank located between the gas outlet of the air guide pipe and the liquid inlet of the siphon pipe. When the still is heated, the acidic vapor evaporated from the still enters the purification tank through the air guide pipe and is absorbed by the hydrochloric acid solution II in the purification tank, thereby causing the concentration of the hydrochloric acid solution II in the purification tank to change. With the change of the concentration of the hydrochloric acid solution II in the purification tank, the metal cation impurities such as Ca, Fe, and K contained in the crude crystalline aluminum chloride are dissolved into the solution due to their high solubility, while the solubility of aluminum chloride in the hydrochloric acid concentration range is relatively low and still maintains a crystalline state. Among them, in the present invention, the hydrochloric acid concentration interval that can dissolve impurities but basically does not dissolve aluminum chloride is called the purification concentration interval of hydrochloric acid. While the solution in the purification tank absorbs the acidic vapor evaporated from the still, the liquid level in the purification tank will continue to rise. In this process, the concentration of the hydrochloric acid solution in the purification tank is monitored in real time by a hydrochloric acid online concentration meter. When the concentration of the hydrochloric acid solution in the purification tank drops to the purification concentration range of hydrochloric acid, the siphon tube is siphoned, and the liquid in the purification tank automatically flows out of the siphon tube and returns to the distillation kettle, thereby enriching the metal chloride impurities in the crude crystalline aluminum chloride in the distillation kettle, completing a round of purification operation. By continuing to heat the distillation kettle, the crude crystalline aluminum chloride in the purification tank can be repeatedly purified to finally obtain a high-purity aluminum chloride product.

[0041] In the present invention, when the siphon tube is a hose, the height of the siphon tube can be adjusted according to the concentration of hydrochloric acid, so that siphoning occurs when the concentration of the hydrochloric acid solution in the purification tank drops to the purification concentration range of hydrochloric acid. When the siphon tube is a fixed tube, a blank test without adding crude crystalline aluminum chloride can be used to test the concentration of hydrochloric acid when siphoning occurs with the help of a hydrochloric acid online concentration meter, and the amount of hydrochloric acid added can be adjusted according to the test result, so that siphoning occurs when the concentration of the hydrochloric acid solution in the purification tank drops to the purification concentration range of hydrochloric acid.

[0042] The second aspect of the present invention provides a method for purifying crude crystalline aluminum chloride using the device described in the first aspect of the present invention, wherein the method comprises the following steps:

[0043] (1) Feeding: adding hydrochloric acid solution I to a distillation kettle, and adding crude crystalline aluminum chloride and hydrochloric acid solution II to a purification tank; the liquid level of the mixture containing crude crystalline aluminum chloride and hydrochloric acid solution II in the purification tank is located between the gas outlet of the air guide pipe and the liquid inlet of the siphon pipe; wherein the initial concentration of hydrochloric acid solution I is greater than 20.2wt% and less than 40wt%; and the initial concentration of hydrochloric acid solution II is less than 40wt%;

[0044] (2) Purification: The distillation kettle is heated, and the acidic steam in the distillation kettle enters the purification tank through the air duct; when the concentration of the hydrochloric acid II in the purification tank drops from the maximum value to 33-38wt%, the liquid phase in the mixture returns to the distillation kettle, completing a purification operation; wherein the maximum concentration of the hydrochloric acid II is ≤40wt%;

[0045] (3) Separation: Repeat the purification in step (2) multiple times; then stop heating, remove the mixture and filter it to obtain a solid which is purified crystalline aluminum chloride.

[0046] Among them, in the present invention, the specific process of purifying crude crystalline aluminum chloride using a Soxhlet purification device is as follows: in the initial stage of heating the distillation kettle, since the volatilization rate of HCl is greater than that of H2O, at this time, the concentration of hydrochloric acid solution I in the distillation kettle gradually decreases, and the acidic steam entering the purification tank causes the concentration of hydrochloric acid solution II in the purification tank to gradually increase, and the liquid level in the purification tank also gradually increases.

[0047] When the concentration of hydrochloric acid solution I in the still kettle drops to 20.2wt%, the concentration of hydrochloric acid solution II in the purification tank reaches the maximum. The still kettle is heated continuously. Since hydrochloric acid solution I in the still kettle is in a constant boiling stage, the HCl content in the acidic steam is stabilized at 20.2wt%. The acidic steam entering the purification tank causes the concentration of hydrochloric acid solution II in the purification tank to begin to decrease, and the liquid level in the purification tank continues to rise.

[0048] In the process of heating the still, the concentration of the hydrochloric acid solution II in the purification tank first increases and then decreases. As the concentration of the hydrochloric acid solution II changes, the metal chloride impurities and other soluble impurities in the crude crystalline aluminum chloride are gradually dissolved, but the aluminum chloride crystals are basically insoluble. When the liquid level of the mixture in the purification tank rises to the highest point of the siphon, the liquid in the mixture in the purification tank will automatically flow out of the siphon and return to the still. The process from starting heating to completing a siphon is considered a purification operation. During the siphon process, the metal chloride impurities dissolved in the hydrochloric acid solution also enter the still, thereby achieving the purification of aluminum chloride.

[0049] After completing a siphon purification operation, continue to heat the distillation kettle, and the crude crystalline aluminum chloride in the purification tank can be repeatedly purified to further obtain high-purity purified crystalline aluminum chloride. After multiple rounds of siphon purification operations, the metal chloride impurities in the crude crystalline aluminum chloride are continuously dissolved and eventually enter the distillation kettle. When the circulation accumulates to a certain amount, it can be cleared out without affecting the entire purification process. The aluminum chloride remains in the purification tank in a crystalline state, and the purification of the crude crystalline aluminum chloride is finally completed.

[0050] During the purification process, in order to ensure that the hydrochloric acid solution II in the purification tank can dissolve metal chloride impurities but basically does not dissolve aluminum chloride, the maximum concentration of the hydrochloric acid solution II in the purification tank is controlled to be ≤40wt%, and the concentration of the hydrochloric acid solution II in the purification tank is ≥33wt% when siphoning occurs.

[0051] In a preferred embodiment, the initial concentration of the hydrochloric acid solution I is 30-38wt%, preferably 31-35wt%; the initial concentration of the hydrochloric acid solution II is 30-38wt%, preferably 31-35wt%; further preferably, the initial concentrations of the hydrochloric acid solution I and the hydrochloric acid solution II are the same.

[0052] The hydrochloric acid solution I and the hydrochloric acid solution II in the present invention can be commercially available industrial grade crude hydrochloric acid or chemical reagent hydrochloric acid of analytical grade. The initial concentration of the hydrochloric acid solution I and the hydrochloric acid solution II refers to the concentration at the time of feeding.

[0053] In a preferred embodiment, the mass ratio of the hydrochloric acid solution I, the crude crystalline aluminum chloride and the hydrochloric acid solution II is 0.18-1.15:0.2-1:1, preferably 0.2-1.1:0.4-0.7:1.

[0054] In a preferred embodiment, the maximum concentration of the hydrochloric acid solution II in the purification tank is 36-40 wt %, and the concentration of the hydrochloric acid solution II in the purification tank when siphoning occurs is preferably 33-35 wt %.

[0055] In a preferred embodiment, the heating temperature is 105-110°C, preferably 107-109°C.

[0056] In a preferred embodiment, the present invention does not specifically limit the number of repetitions, and can be specifically selected according to actual conditions. Preferably, the purification operation is repeated 2-10 times, and more preferably, the purification operation is repeated 3-5 times.

[0057] In a preferred embodiment, the method further comprises (4): distilling the liquid in the distillation kettle to obtain pure hydrochloric acid.

[0058] After purification, the distillation kettle mainly contains hydrochloric acid solution, metal chloride impurities and other soluble impurities. By distilling them, pure hydrochloric acid can be recovered, thereby achieving efficient reuse of hydrochloric acid.

[0059] The third aspect of the present invention provides a method for purifying crude crystalline aluminum chloride, the method comprising the following steps:

[0060] (1) heating a hydrochloric acid solution I to obtain acidic steam;

[0061] (2) introducing the acidic steam into a solid-liquid mixture containing crude crystalline aluminum chloride and hydrochloric acid solution II, controlling the maximum concentration of hydrochloric acid solution II in the solid-liquid mixture to be ≤40wt%, and when the concentration of hydrochloric acid solution II in the solid-liquid mixture decreases from the maximum concentration to 33-38wt%, drawing out the solution in the solid-liquid mixture and returning it to hydrochloric acid solution I, thereby completing one round of purification operation;

[0062] (3) Repeat the purification operation of step (2) multiple times, then stop heating, filter the solid-liquid mixture, and obtain purified crystalline aluminum chloride.

[0063] In a preferred embodiment, the initial concentration of the hydrochloric acid solution I is 30-38wt%, preferably 31-35wt%; the initial concentration of the hydrochloric acid solution II is 30-38wt%, preferably 31-35wt%; further preferably, the initial concentrations of the hydrochloric acid solution I and the hydrochloric acid solution II are the same.

[0064] In a preferred embodiment, the mass ratio of the hydrochloric acid solution I, the crude crystalline aluminum chloride and the hydrochloric acid solution II is 0.18-1.15:0.2-1:1, preferably 0.2-1.1:0.4-0.7:1.

[0065] In a preferred embodiment, the maximum concentration of hydrochloric acid in the solid-liquid mixture is controlled to be 36-40wt%, and when the concentration of hydrochloric acid solution II in the solid-liquid mixture drops from the maximum concentration to 33-35wt%, the solution in the solid-liquid mixture is drawn out.

[0066] The present invention will be described in detail below through examples.

[0067] The Soxhlet purification apparatus used in the embodiments and comparative examples is as follows: Figure 1 As shown: the Soxhlet purification device comprises a distillation kettle 1, a purification tank 2, an elastic airbag 3 and a hydrochloric acid online concentration meter 4; wherein the distillation kettle 1 and the purification tank 2 are made of glass and connected by a ground joint; a partition 23 is provided at the lower part of the purification tank 2, an inverted U-shaped air guide tube 21 is provided on the partition 23, and the air inlet of the air guide tube 21 is provided on the partition 23, which is in an inverted funnel shape; the air outlet of the air guide tube 21 is not connected to the partition 23, and a small hole is provided at the air outlet; the outside of the purification tank 2 is provided with a connecting A hose siphon tube 22 is provided between the purification tank 2 and the distillation kettle 1, wherein the liquid inlet of the siphon tube 22 is located above the partition 23, and the liquid outlet is located below the partition 23, and the liquid inlet of the siphon tube 22 is higher than the air outlet of the air guide tube 21; an enlarged neck is provided at the liquid inlet of the siphon tube 22, and the siphon tube is fixed by an iron frame and a self-locking nylon tie; a safety pressure relief valve is provided on the elastic airbag 3, and the elastic airbag 3 is mounted on the purification tank 2, and the hydrochloric acid online concentration meter is connected to the purification tank 2.

[0068] The purity of the crude crystalline aluminum chloride used in the examples and comparative examples is 97wt%, and the impurity elements and the mass contents of the impurity elements contained in the crude crystalline aluminum chloride are: S: 161ppm, Na: 112ppm, Mg: 66.2ppm, K: 62.4ppm, P: 28.4ppm, Fe: 16.0ppm, Ca: 8.9ppm.

[0069] Example 1

[0070] (1) Adding materials: 180 g of hydrochloric acid solution I with an initial concentration of 31 wt% is added to a distillation kettle, and 100 g of crude crystalline aluminum chloride and 200 g of hydrochloric acid solution II with an initial concentration of 31 wt% is added to a purification tank, wherein the liquid level in the purification tank is located between the gas outlet of the air guide pipe and the liquid inlet of the siphon pipe;

[0071] (2) Purification: The distillation kettle is heated to a temperature of 108° C. The acidic steam in the distillation kettle enters the purification tank through the air duct. The concentration of the hydrochloric acid solution in the purification tank is detected by a hydrochloric acid online concentration meter. When the hydrochloric acid solution II in the purification tank increases from an initial concentration of 31 wt % to a maximum concentration of 38 wt % and then decreases from the maximum concentration of 38 wt % to 35 wt %, the height of the siphon pipe is adjusted to cause siphoning, and the hydrochloric acid solution in the purification tank is returned to the distillation kettle, thereby completing a purification operation;

[0072] (3) Separation: Continue heating, repeat the purification operation 4 times in total, then stop heating, cool to room temperature, and then remove the solid-liquid mixture in the purification tank for filtration to obtain purified crystalline aluminum chloride. The specific operating conditions and experimental results of Example 1 are shown in Table 1.

[0073] Embodiment 2-7

[0074] The same as Example 1, except that the operating conditions are changed. The specific operating conditions and experimental results are shown in Table 1.

[0075] Comparative Examples 1-5

[0076] The same as Example 1, except that the operating conditions are changed. The specific operating conditions and experimental results are shown in Table 1.

[0077] Table 1

[0078]

[0079]

[0080] It can be seen from Examples 1-5 that when the crude crystalline aluminum chloride is purified by the Soxhlet purification device provided by the present invention, the purified crystalline aluminum chloride obtained has high purity and high yield, and is suitable for industrial production.

[0081] Compared with Examples 1-4, the dosage of hydrochloric acid solution I in Comparative Example 1 is low. After 5 siphon purification operations, the loss of aluminum chloride is large, resulting in a low recovery rate of aluminum chloride and a decrease in the purity of aluminum chloride.

[0082] Compared with Examples 1-4, the amount of hydrochloric acid solution I in Comparative Example 2 is too large, the maximum concentration of hydrochloric acid solution II in the purification tank exceeds 40wt%, and the purity of aluminum chloride is 98% after 4 purification operations. The purity of aluminum chloride is low, and the purification effect of aluminum chloride is not good.

[0083] By comparing Example 5 with Comparative Example 3, it can be seen that the dosage of hydrochloric acid solution I is too large. When the maximum concentration of hydrochloric acid exceeds 40wt%, the purity and recovery rate of aluminum chloride are still low after reducing the number of purification operations.

[0084] By comparing Example 7 and Comparative Example 4, it can be seen that when the amount of hydrochloric acid solution I is too large and the maximum concentration of hydrochloric acid solution II is far more than 40wt%, the acid steam in the purification tube will increase sharply, and the acid steam will overflow through the safety pressure relief valve, causing HCl gas loss, resulting in a significant decrease in the recovery rate of aluminum chloride.

[0085] By comparing Example 2 with Comparative Example 5, it can be seen that in Comparative Example 5, when the siphon tube height is adjusted, siphoning occurs when the hydrochloric acid concentration drops to 32wt%, and the aluminum chloride recovery rate is low (89.6%) after three purification operations. It can be seen that when the hydrochloric acid concentration during siphoning is lower than 33wt%, it is not conducive to the aluminum chloride recovery rate.

[0086] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A Soxhlet purification device, characterized in that: The device comprises a distillation kettle (1), a purification tank (2) and an elastic airbag (3) which are connected in sequence, and an online hydrochloric acid concentration meter (4) connected to the purification tank (2); wherein the purification tank (2) has an air guide tube (21) and a siphon tube (22); the air guide tube (21) is in an inverted U shape and is arranged inside the purification tank (2).

2. The purification device according to claim 1, wherein: A partition (23) is arranged at the lower part of the purification tank (2), the air inlet of the air guide pipe (21) is arranged on the partition (23), and the air outlet of the air guide pipe (21) is not connected to the partition (23), and is used to introduce the steam in the distillation kettle (1) into the purification tank (2).

3. The purification device according to claim 2, wherein: The siphon tube (22) is configured as a hose that connects the purification tank (2) and the distillation kettle (1) through the outside of the purification tank (2).

4. The purification device according to claim 2, wherein: The liquid inlet and the liquid outlet of the siphon tube (22) are located above and below the partition plate (23) respectively.

5. The purification device according to claim 2, wherein: The liquid inlet of the siphon tube (22) is higher than the air outlet of the air guide tube (21).

6. The purification device according to claim 2, wherein: The liquid inlet of the siphon tube (22) is provided with an enlarged neck.

7. The purification device according to claim 2 or 3, wherein: The Soxhlet purification device further comprises a fixing component, wherein the fixing component is used to adjust the height of the siphon tube (22).

8. The purification device according to claim 2 or 3, wherein: The elastic airbag (3) is provided with a safety pressure relief valve.

9. A method for purifying crude crystalline aluminum chloride using the device described in any one of claims 1 to 8, characterized in that: The method comprises the following steps: (1) Feeding: adding hydrochloric acid solution I to a distillation kettle, and adding crude crystalline aluminum chloride and hydrochloric acid solution II to a purification tank; the liquid level of the mixture containing crude crystalline aluminum chloride and hydrochloric acid solution II in the purification tank is located between the gas outlet of the air guide pipe and the liquid inlet of the siphon pipe; wherein the initial concentration of hydrochloric acid solution I is greater than 20.2wt% and less than 40wt%; and the initial concentration of hydrochloric acid solution II is less than 40wt%; (2) Purification: The distillation kettle is heated, and the acidic steam in the distillation kettle enters the purification tank through the air duct; when the concentration of the hydrochloric acid II in the purification tank drops from the maximum value to 33-38wt%, the liquid phase in the mixture returns to the distillation kettle, completing a purification operation; wherein the maximum concentration of the hydrochloric acid II is ≤40wt%; (3) Separation: Repeat the purification operation of step (2) multiple times; then stop heating, remove the mixture and filter it to obtain purified crystalline aluminum chloride.

10. The method according to claim 9, wherein: The initial concentration of the hydrochloric acid solution I is 30-38 wt %, and the initial concentration of the hydrochloric acid solution II is 30-38 wt %.

11. The method according to claim 10, wherein: The initial concentration of the hydrochloric acid solution I is 31-35 wt %, and the initial concentration of the hydrochloric acid solution II is 31-35 wt %.

12. The method according to claim 9 or 10, wherein: The mass ratio of the hydrochloric acid solution I, the crude crystalline aluminum chloride and the hydrochloric acid solution II is 0.18-1.15:0.2-1:

1.

13. The method according to claim 12, wherein: The mass ratio of the hydrochloric acid solution I, the crude crystalline aluminum chloride and the hydrochloric acid solution II is 0.2-1.1:0.4-0.7:

1.

14. The method according to claim 9, wherein: The heating temperature is 105-110°C.

15. The method according to claim 14, wherein: The heating temperature is 107-109°C.

16. The method according to claim 9, wherein: Repeat the purification operation 2-10 times.

17. The method according to claim 16, wherein: Repeat the purification operation 3-5 times.

18. The method according to claim 9, wherein: The method further comprises (4): distilling the liquid in the distillation kettle to obtain pure hydrochloric acid.

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