A method for preparing anhydrous aluminum chloride by dehydration of crystalline aluminum chloride

Abstract

This invention discloses a method for preparing anhydrous aluminum chloride from crystalline aluminum chloride by dehydration, comprising: (1) dispersing crystalline aluminum chloride in anhydrous toluene or xylene, and dehydrating it by azeotropic distillation under the condition of passing hydrogen chloride, removing approximately 60% to 80% of the water of crystallization; (2) then stopping the passage of hydrogen chloride and distilling off the solvent toluene or xylene; (3) adding anhydrous toluene or xylene again, and adding thionyl chloride from a balanced feeder for stirring reaction, further removing the remaining water of crystallization by chemical reaction; (4) after the dehydration reaction is completed, distilling off the solvent; (5) adding anhydrous methanol and anhydrous methyl tert-butyl ether mixed solvent to fully dissolve, filtering, concentrating, crystallizing, filtering and drying to obtain anhydrous aluminum chloride; during the process, hydrogen chloride gas can be recycled; the raw materials of this process are easy to obtain, the cost is low, the process flow is convenient to operate, it is easy to carry out large-scale industrial production, the energy consumption is low, and it does not pollute the environment.

Description

Technical Field

[0001] This invention relates to a method for preparing anhydrous aluminum chloride, specifically a method for producing anhydrous aluminum chloride by dehydrating crystalline aluminum chloride through physical and chemical methods, followed by refining and impurity removal. Background Technology

[0002] Aluminum trichloride, also known as aluminum chloride, has the molecular formula AlCl3. It is a white granule or powder with a strong hydrochloric acid odor; industrial grade is pale yellow. Anhydrous aluminum trichloride is an important inorganic chemical product, mainly used in the manufacture of alkylating agents for detergents, synthetic pharmaceuticals, synthetic dyes, synthetic rubber, detergents, plastics, and fragrances. Aluminum trichloride is also a very important catalyst, widely used in the chemical and petroleum industries.

[0003] Currently, the main process for preparing anhydrous aluminum chloride is the aluminum ingot method, also known as the metallic aluminum method. This involves directly passing chlorine gas through molten aluminum, causing a direct reaction to produce anhydrous aluminum trichloride. The reaction equation is 2Al + 3Cl₂ = AlCl₃, and the reaction temperature is generally controlled at around 800–900℃. The gaseous product, anhydrous aluminum trichloride, is produced...

[0004] At approximately 400℃, the gas enters the product collector through a sublimation tube, where it undergoes natural condensation and crystallization to obtain anhydrous aluminum trichloride. The tail gas is absorbed by alkaline water and then discharged into the atmosphere. The aluminum ingot method is characterized by its simple process flow, fewer equipment requirements, and low investment, but its cost is relatively high due to the use of metallic aluminum as raw material. Another method is the alumina powder method, which uses alumina, chlorine, and carbon as raw materials, reacting them together at a specific temperature to produce anhydrous aluminum chloride. The alumina powder method is characterized by the relatively low price of alumina as a raw material, but the process for obtaining anhydrous aluminum chloride is more complex.

[0005] Chinese patent literature discloses a method for preparing anhydrous aluminum chloride (CN103708518): Solid aluminum chloride hexahydrate and liquid thionyl chloride are added to a dehydration reactor. Under normal or slightly negative pressure and at a temperature <76℃, crystalline water reacts with thionyl chloride to generate sulfur dioxide gas and hydrogen chloride gas, converting the hexahydrate crystalline aluminum chloride into anhydrous aluminum chloride. The slurry is then filtered, and the filter cake is distilled to obtain pure anhydrous aluminum chloride. This method suffers from problems such as complex processes, high manufacturing costs, and environmental unfriendliness. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing anhydrous aluminum chloride by dehydration of crystalline aluminum chloride, which has wide availability of raw materials, simple process, low cost, no environmental pollution, and produces anhydrous aluminum chloride with high purity.

[0007] The technical solution of this invention is: a method for preparing anhydrous aluminum chloride by dehydrating aluminum chloride hexahydrate, comprising the following steps:

[0008] (1) Crystalline aluminum chloride is dispersed in anhydrous toluene or xylene and dehydrated by azeotropic distillation under the condition of passing hydrogen chloride, removing about 60% to 80% of the water of crystallization.

[0009] (2) Stop the flow of hydrogen chloride and distill off the solvent toluene or xylene;

[0010] (3) Add anhydrous toluene or xylene again, and add thionyl chloride from the balance feeder to stir and react, and further remove the remaining water of crystallization by chemical reaction.

[0011] (4) After the dehydration reaction is complete, evaporate the solvent;

[0012] (5) Add anhydrous methanol and anhydrous methyl tert-butyl ether mixed solvent to fully dissolve, filter, concentrate, crystallize, filter and dry to obtain anhydrous aluminum chloride.

[0013] In step (1), the reflux temperature of the crystalline aluminum chloride and toluene solution is 110°C, and the reflux temperature of the crystalline aluminum chloride and xylene solution is 140°C. The ratio of anhydrous toluene or xylene to crystalline aluminum chloride is 300 mL / mol.

[0014] In step (3), the thionyl chloride is added at a temperature in the range of 90 to 110°C, and the addition method is to add it slowly in 4 batches.

[0015] In step (5), the ratio of anhydrous methanol to anhydrous methyl tert-butyl ether solution is 1 / 1, and the vacuum rotary evaporation crystallization temperature is 80℃.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] The raw material for this invention, crystalline aluminum chloride, is widely available and inexpensive. Toluene and xylene are also inexpensive. The process is simple, the production cost is low, and it does not pollute the environment. The purified anhydrous aluminum chloride has high purity. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0019] A method for preparing anhydrous aluminum chloride from crystalline aluminum chloride (aluminum trichloride hexahydrate) by dehydration includes the following steps: dispersing crystalline aluminum chloride in anhydrous toluene at a ratio of 1 mol / 300 ml; dehydrating by azeotropic distillation under hydrogen chloride purging at a reflux temperature of 110 °C, removing approximately 60%–80% of the water of crystallization; stopping the hydrogen chloride purging and distilling off the solvent toluene; adding anhydrous toluene again; and adding thionyl chloride via a balanced feeder while stirring the reaction, with a molar ratio of crystalline aluminum chloride to thionyl chloride of 1:1. / 7.88 (thionyl chloride in excess 30%), the thionyl chloride was added at a temperature in the range of 90-110℃, and the addition method was to add it slowly in four batches, with the reflux temperature controlled at around 120℃. The remaining water of crystallization was further removed by chemical reaction. After the dehydration reaction was completed, the solvent was evaporated. Anhydrous methanol and anhydrous methyl tert-butyl ether were added to dissolve the solution completely. The solution was then filtered, concentrated, crystallized, filtered, and dried to obtain anhydrous aluminum chloride. The ratio of anhydrous methanol to anhydrous methyl tert-butyl ether solution was 1:1, and the vacuum rotary evaporation crystallization temperature was 80℃.

[0020] A method for preparing anhydrous aluminum chloride from crystalline aluminum chloride by dehydration includes the following steps: dispersing crystalline aluminum chloride in anhydrous xylene at a ratio of 1 mol / 300 ml; dehydrating by azeotropic distillation while introducing hydrogen chloride, with the xylene reflux temperature at 140°C, removing approximately 60%–80% of the water of crystallization; stopping the introduction of hydrogen chloride and distilling off the solvent xylene; adding anhydrous xylene again, and adding thionyl chloride through a balanced feeder while stirring the reaction, with the molar ratio of crystalline aluminum chloride to thionyl chloride being 1 / 7. 0.88 (thionyl chloride in excess 30%), the thionyl chloride was added in the range of 90-110℃, and the method of addition was to add it slowly in four batches, with the reflux temperature controlled at about 120℃, and the remaining water of crystallization was further removed by chemical reaction; after the dehydration reaction was completed, the solvent was evaporated; anhydrous methanol and anhydrous methyl tert-butyl ether mixed solvent were added to fully dissolve it, and the solution was filtered, concentrated, crystallized, filtered and dried to obtain anhydrous aluminum chloride, wherein the ratio of anhydrous methanol to anhydrous methyl tert-butyl ether solution was 1:1, and the vacuum rotary evaporation crystallization temperature was 80℃.

[0021] Example 1

[0022] Take 0.5 mol of crystalline aluminum chloride (120.72 g) and 150 ml of xylene in a four-necked flask, pass hydrogen chloride through it, and perform azeotropic distillation at 135 °C. Theoretically, 54 g of water was removed, and the actual amount of water removed was 37 g, with a dehydration rate of 68.5%.

[0023] Take 0.5 mol of pre-dehydrated crystalline aluminum chloride and 150 ml of xylene in a four-necked flask. Add 3.94 mol of thionyl chloride to a balanced feeder at a dropping temperature of 90°C in four slow batches. The reflux temperature is around 120°C. Theoretically, 17 g of water was dehydrated, and 13 g of water was actually dehydrated, with a dehydration rate of 76.5% and a total dehydration rate of 92.6%.

[0024] After dehydration, aluminum chloride was added to a mixed solvent consisting of 150 ml of anhydrous methanol and 150 ml of anhydrous methyl tert-butyl ether. The mixture was refluxed at about 60°C for 5 hours. After filtration, the filter cake was dried by vacuum rotary evaporation at 80°C, yielding 57.4 g of anhydrous aluminum chloride, with a yield of 86.1%.

[0025] Example 2

[0026] Take 0.5 mol of crystalline aluminum chloride (120.72 g) and 150 ml of toluene in a four-necked flask, pass hydrogen chloride through it, and perform azeotropic distillation at 110 °C. Theoretically, 54 g of water was removed, and the actual amount of water removed was 39 g, with a dehydration rate of 72.2%.

[0027] Take 0.5 mol of pre-dehydrated crystalline aluminum chloride and 150 ml of toluene into a four-necked flask. Add 3.94 mol of thionyl chloride to the equilibrium feeder at a dropping temperature of 90°C in four slow batches. The reflux temperature is around 120°C. Theoretically, 15 g of water is dehydrated, and the actual dehydration is 11.5 g, with a dehydration rate of 76.7% and a total dehydration rate of 93.5%.

[0028] After dehydration, aluminum chloride was added to a mixed solvent consisting of 150 ml of anhydrous methanol and 150 ml of anhydrous methyl tert-butyl ether. The mixture was refluxed at about 60°C for 5 hours. After filtration, the filter cake was dried by vacuum rotary evaporation at 80°C, yielding 56.6 g of anhydrous aluminum chloride, with a yield of 84.9%.

Claims

1. A method for preparing anhydrous aluminum chloride by dehydrating crystalline aluminum chloride, characterized in that: Includes the following steps: (1) Crystalline aluminum chloride is dispersed in anhydrous toluene or anhydrous xylene and dehydrated by azeotropic distillation under the condition of passing hydrogen chloride, removing 60% to 80% of the water of crystallization. The reflux temperature of crystalline aluminum chloride and anhydrous toluene is 110℃, and the reflux temperature of crystalline aluminum chloride and anhydrous xylene is 140℃; the ratio of anhydrous toluene or anhydrous xylene to crystalline aluminum chloride is 300 mL / 1 mol. (2) Stop the flow of hydrogen chloride and distill off the solvent toluene or xylene; (3) Add anhydrous toluene or anhydrous xylene again, and add thionyl chloride from the balance feeder to stir and react, and further remove the remaining water of crystallization by chemical reaction. The molar ratio of crystalline aluminum chloride to thionyl chloride is 1 / 7.

88. The thionyl chloride is added at a temperature ranging from 90 to 110°C, and the addition method is to add it slowly in four batches. (4) After the dehydration reaction is complete, evaporate the solvent; (5) Add anhydrous methanol and anhydrous methyl tert-butyl ether mixed solvent to dissolve completely, reflux at 60°C for 5 hours, filter the filter cake and dry it under vacuum rotary evaporation at 80°C to obtain anhydrous aluminum chloride. The ratio of anhydrous methanol to anhydrous methyl tert-butyl ether solution is 1:1.

Images