Method for in-situ preparation of anhydrous ferric trichloride and application

Abstract

The invention discloses a method for in-situ preparation of anhydrous ferric trichloride and application, and the method comprises the following steps: placing ferric trichloride hexahydrate in a reactor, introducing hydrogen chloride gas, and then heating and evaporating to remove crystal water in the ferric trichloride hydrate under the conditions that the reaction temperature is 70-100 DEG C and the vacuum degree is 0.01-0.03 MPa to obtain the anhydrous ferric trichloride. After the reaction is completed, the system is cooled, and NO introduced into the reactor and anhydrous ferric trichloride are subjected to a gas-solid adsorption chemical reaction so as to be absorbed and removed. In the process, hydrolysis of Fe < 3 + > is inhibited by the introduced hydrogen chloride gas, so that the obtained anhydrous ferric trichloride has higher activity and adsorption capacity. The problem of deliquescence of anhydrous ferric trichloride in the application process is solved, nitric oxide gas can be adsorbed in situ, and the purpose of flue gas purification is achieved.

Description

Technical Field

[0001] The invention relates to the field of preparation of anhydrous ferric chloride, and in particular to a method for in-situ preparation of anhydrous ferric chloride and application thereof. Background Art

[0002] Ferric chloride exists in two forms: aqueous solution and solid. Ferric chloride solution is reddish brown and has strong oxidizing properties. Solid ferric chloride is yellow-brown crystal or block solid. The main products are hexahydrate ferric chloride and anhydrous ferric chloride. Hexahydrate ferric chloride is a cheap and readily available inorganic substance. It can be used as an efficient and cheap flocculant in water treatment. Anhydrous ferric chloride is a dark hexagonal flaky structure. It is less corrosive and polluting than strong inorganic acids. It is often used as a catalyst in organic synthesis. At the same time, anhydrous ferric chloride can be used as an activator to participate in the preparation of activated carbon.

[0003] Nitrogen oxides (NO x ) mainly includes nitric oxide (NO) and nitrogen dioxide (NO2), of which NO accounts for more than 95% of the nitrogen oxides produced by fuel combustion. Other industrial processes such as nitric acid production, nitration reactions in chemical and pharmaceutical industries, metal surface treatment, and semiconductor production also produce and emit nitrogen oxide waste gas. NO x It is toxic, and large amounts of nitrogen oxide emissions are also one of the main causes of atmospheric photochemical smog and acid rain.

[0004] The conventional process route for producing anhydrous ferric chloride is to use scrap iron and chlorine as raw materials and react in a vertical reactor. The generated ferric chloride vapor and tail gas are discharged from the top of the furnace, enter the trap and condense into solid crystals, and the finished product of anhydrous ferric chloride can be obtained. In this process, the tail gas contains a small amount of unreacted free chlorine, and ferric chloride solution can be obtained as a by-product by absorbing chlorine with ferrous chloride solution. In production operations, ferric chloride vapor will produce a strong exothermic reaction after contacting with moisture in the air, releasing hydrochloric acid gas, so pipelines and equipment require good sealing. In addition, anhydrous ferric chloride has extremely strong hygroscopicity, and when exposed to air, it will quickly absorb moisture and be converted into hydrated ferric chloride, causing the physical properties of anhydrous ferric chloride to change. Summary of the invention

[0005] The purpose of the present invention is to provide an in-situ preparation method and application of anhydrous ferric chloride, which avoids the deliquescence problem of anhydrous ferric chloride during application and can adsorb nitric oxide gas in situ, thereby achieving the purpose of flue gas purification.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The method for in-situ preparation of anhydrous ferric chloride comprises the following steps: placing ferric chloride hexahydrate in a reactor, then heating and evaporating under vacuum to remove crystal water in the hydrated ferric chloride, while heating and evaporating, introducing HCl gas into the ferric chloride hexahydrate, and finally obtaining anhydrous ferric chloride.

[0008] Hydrated ferric chloride melts at 35-40°C and hydrolyzes to generate different types of iron oxides at temperatures above 100°C, so the heating temperature is preferably between 70 and 100°C. Possible reactions during the heating process:

[0009] FeCl3·xH2O(s)→FeCl3·2H2O(s)+(x-2)H2O(g).

[0010] The dehydration rate of ferric chloride hydrate depends on the partial pressure of water vapor in the medium surrounding the hydrate. At room temperature, the vapor pressure of the crystalline hydrate of ferric chloride hexahydrate is less than the partial pressure of water vapor in the air. Therefore, a vacuum pump can be used to create a reduced pressure environment to accelerate the evaporation of water. The vacuum degree is preferably 0.01 to 0.03 MPa.

[0011] Furthermore, the purity of the ferric chloride hexahydrate raw material of the present invention is above 99%.

[0012] Furthermore, the amount of hydrogen chloride gas introduced is adjusted so that the molar ratio of hydrogen chloride gas to anhydrous ferric chloride is 0.13 to 0.19.

[0013] Furthermore, the present invention also provides an application of the anhydrous ferric chloride, which is used to convert and absorb NO. The specific operation is: the anhydrous ferric chloride is heated to a temperature of 65°C to 75°C, NO gas is introduced, and NO and ferric chloride undergo a gas-solid adsorption chemical reaction to achieve the effect of purifying and removing NO. The concentration of the NO gas is 200 to 600 ppm.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1) The conventional anhydrous ferric chloride production process has potential safety hazards caused by high-temperature reactions. The present invention uses reduced-pressure heating and evaporation to remove water from hydrated ferric chloride, thereby avoiding the corresponding potential safety hazards. It has incomparable advantages in terms of both safe production and environmental protection.

[0016] 2) A certain amount of hydrogen chloride gas was introduced during the heating process to inhibit the Fe 3+ The hydrolysis of , which involves the following reactions: The in-situ preparation method of anhydrous ferric chloride of the present invention enables the obtained anhydrous ferric chloride to have higher activity and adsorption capacity.

[0017] 3) After the anhydrous ferric chloride is cooled, NO is introduced into the container, where it undergoes a gas-solid adsorption chemical reaction with the ferric chloride and is absorbed and removed. The intermediate product of the reaction is presumed to be a nitrosyl iron-based complex, which avoids the deliquescence problem of anhydrous ferric chloride during its use and can adsorb nitric oxide gas in situ to achieve the purpose of flue gas purification. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of the experimental device for in-situ preparation of anhydrous ferric chloride in the examples of the present application. DETAILED DESCRIPTION

[0019] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0020] The schematic diagram of the structure of the experimental device for in-situ preparation of anhydrous ferric chloride in the embodiment of the present invention is shown in FIG. Figure 1 The round-bottom flask 1 has three ports, the first port is connected to an inlet pipe for adding concentrated hydrochloric acid, the other end of the inlet pipe is connected to a concentrated hydrochloric acid inlet pump, the second port is connected to an air release valve, and the third port is connected to an outlet pipe, the other end of the outlet pipe extends into the bottom of the three-necked flask 2, the vacuum port of the three-necked flask 2 is connected to the exhaust pipe, the other end of the exhaust pipe is inserted into the water contained in the absorption bottle 4, and the vacuum port of the absorption bottle 4 is then connected to a water pump 5 through a pipe.

[0021] The round-bottom flask 1, the three-necked flask 2 and the absorption bottle 4 are all sealed.

[0022] Concentrated hydrochloric acid is added into the round-bottom flask 1, ferric chloride hexahydrate is put into the three-necked flask 2, and the three-necked flask 2 is placed on a constant temperature water bath 3 for heating.

[0023] The purity of anhydrous ferric chloride in the embodiment of the present invention is determined according to the content of crystal water in the product.

[0024] Example 1

[0025] 10 g of 99% pure ferric chloride hexahydrate was placed in a three-necked flask, and then the three-necked flask was placed in a constant temperature water bath at 85°C and heated to remove the crystal water in the hydrated ferric chloride by heating and evaporation. The evaporation was carried out for 1 hour to finally obtain 6.35 g of anhydrous ferric chloride.

[0026] When the temperature drops to about 75°C, a simulated flue gas flow is introduced, with nitrogen as the protective gas, a nitrogen flow rate of 500 ml / min, a nitric oxide concentration of about 200 ppm, and oxygen of about 2%. The gas contact time in the three-necked flask is about 3-5 seconds. The nitric oxide concentration at the outlet of the purified gas is 150 ppm, and the measured nitric oxide outlet concentration is the value at the maximum continuous removal rate. After a period of absorption, the adsorbed anhydrous ferric chloride is dissolved in 1 L of water, and NO is detected by ion chromatography. 3- and NO 2- The content indicates that the absorbed NO content is 24.8 mg, that is, the absorption and conversion capacity of anhydrous ferric chloride for NO is 3.91 mg / g.

[0027] Example 2

[0028] 10 g of ferric chloride hexahydrate with a purity of 99% was placed in a three-necked flask, and then concentrated hydrochloric acid was added to the round-bottomed flask, and the round-bottomed flask was heated (heated to between 40 and 60° C., and the volatilization rate of the concentrated hydrochloric acid was controlled by adjusting the heating temperature). By utilizing the strong volatility of the concentrated hydrochloric acid, hydrogen chloride gas was continuously introduced into the three-necked flask containing the ferric chloride hexahydrate, and the three-necked flask was placed in a constant temperature water bath at 85° C. and heated to remove the crystal water in the hydrated ferric chloride by heating and evaporation. The heating and evaporation was performed for 1 hour, during which time about 0.11 L (about 4.91 mmol) of HCL gas was continuously introduced, and 6.32 g of anhydrous ferric chloride was finally obtained with a purity of 92.2%.

[0029] When the temperature drops to about 75°C, a simulated flue gas flow is introduced, with nitrogen as the protective gas, a nitrogen flow rate of 500 ml / min, a nitric oxide concentration of about 200 ppm, and oxygen of about 2%. The gas contact time in the three-necked flask is about 3-5 seconds. The nitric oxide concentration at the outlet of the purified gas is 102 ppm, and the measured nitric oxide outlet concentration is the value at the maximum continuous removal rate. After a period of absorption, the adsorbed anhydrous ferric chloride is dissolved in 1 L of water, and NO is detected by ion chromatography. 3- and NO 2- The content indicates that the absorbed NO content is 44.8 mg, that is, the absorption and conversion capacity of anhydrous ferric chloride for NO is 7.09 mg / g.

[0030] Example 3

[0031] 10 g of 99% pure ferric chloride hexahydrate was placed in a three-necked flask, and then the three-necked flask was placed in a constant temperature water bath at 95°C and heated to remove the crystal water in the hydrated ferric chloride by heating and evaporation. The evaporation was carried out for 1 hour to finally obtain 6.28 g of anhydrous ferric chloride.

[0032] When the temperature drops to about 75°C, a simulated flue gas flow is introduced, with nitrogen as the protective gas, a nitrogen flow rate of 500 ml / min, a nitric oxide concentration of about 200 ppm, and oxygen of about 2%. The gas contact time in the three-necked flask is about 3-5 seconds. The nitric oxide concentration at the outlet of the purified gas is 140 ppm, and the measured nitric oxide outlet concentration is the value at the maximum continuous removal rate. After a period of absorption, the adsorbed anhydrous ferric chloride is dissolved in 1 L of water, and NO is detected by ion chromatography. 3- and NO 2- The content indicates that the absorbed NO content is 29.8 mg, that is, the absorption and conversion capacity of anhydrous ferric chloride for NO is 4.74 mg / g.

[0033] In the process of preparing anhydrous ferric chloride by heating in Example 1 and Example 3, a hydrolysis reaction occurs, and the final product has a certain adverse effect on the absorption and conversion performance of NO.

[0034] Example 4

[0035] 10 g of ferric chloride hexahydrate with a purity of 99% was placed in a three-necked flask, and then concentrated hydrochloric acid was added to the round-bottomed flask, and the round-bottomed flask was heated (heated to between 40 and 60° C., and the volatilization rate of the concentrated hydrochloric acid was controlled by adjusting the heating temperature). By utilizing the strong volatility of the concentrated hydrochloric acid, hydrogen chloride gas was continuously introduced into the three-necked flask containing the ferric chloride hexahydrate, and the three-necked flask was placed in a constant temperature water bath at 95° C. and heated to remove the crystal water in the hydrated ferric chloride by heating and evaporation. The heating and evaporation were performed for 1 hour, during which about 0.11 L (about 4.91 mmol) of HCL gas was continuously introduced, and 6.24 g of anhydrous ferric chloride was finally obtained with a purity of 94.2%.

[0036] When the temperature drops to about 75°C, a simulated flue gas flow is introduced, with nitrogen as the protective gas, a nitrogen flow rate of 500 ml / min, a nitric oxide concentration of about 200 ppm, and oxygen of about 2%. The gas contact time in the three-necked flask is about 3-5 seconds. The nitric oxide concentration at the outlet of the purified gas is 96 ppm, and the measured nitric oxide outlet concentration is the value at the maximum continuous removal rate. After a period of absorption, the adsorbed anhydrous ferric chloride is dissolved in 1 L of water, and NO is detected by ion chromatography. 3- and NO 2- The content indicates that the absorbed NO content is 45.7 mg, that is, the absorption and conversion capacity of anhydrous ferric chloride for NO is 7.32 mg / g.

[0037] Example 5

[0038] 10 g of ferric chloride hexahydrate with a purity of 99% was placed in a three-necked flask, and then concentrated hydrochloric acid was added to the round-bottomed flask, and the round-bottomed flask was heated (heated to between 40-60° C., and the volatilization rate of the concentrated hydrochloric acid was controlled by adjusting the heating temperature). By utilizing the strong volatility of concentrated hydrochloric acid, hydrogen chloride gas was continuously introduced into the three-necked flask containing the ferric chloride hexahydrate, and at the same time, the three-necked flask was placed in a constant temperature heating mantle at 105° C. and heated to remove the crystal water in the hydrated ferric chloride by heating and evaporation. The heating and evaporation were performed for 1 hour, during which the HCL gas continuously introduced accumulated to about 0.11 L (about 4.91 mmol HCL gas), and 6.047 g of anhydrous ferric chloride was finally obtained.

[0039] When the temperature drops to about 75°C, a simulated flue gas flow is introduced, with nitrogen as the protective gas, a nitrogen flow rate of 500 ml / min, a nitric oxide concentration of about 200 ppm, and oxygen of about 2%. The gas contact time in the three-necked flask is about 3-5 seconds. The nitric oxide concentration at the outlet of the purified gas is 120 ppm, and the measured nitric oxide outlet concentration is the value at the maximum continuous removal rate. After a period of absorption, the adsorbed anhydrous ferric chloride is dissolved in 1 L of water, and NO is detected by ion chromatography. 3- and NO 2- The content indicates that the absorbed NO content is 35.8 mg, that is, the absorption and conversion capacity of anhydrous ferric chloride for NO is 5.92 mg / g.

[0040] Example 6

[0041] 10 g of ferric chloride hexahydrate with a purity of 99% was placed in a three-necked flask, and then concentrated hydrochloric acid was added to the round-bottomed flask. The vacuum degree in the three-necked flask was reduced to 0.01 MPa by a vacuum pump. The three-necked flask was placed in a constant temperature water bath at 95° C. and heated. Meanwhile, during the vacuuming process, the hydrogen chloride gas volatilized by the concentrated hydrochloric acid (accumulated about 0.122 L of hydrogen chloride, i.e., about 4.9 mmol HCL gas) was introduced into the ferric chloride hexahydrate. The crystal water in the hydrated ferric chloride was removed by heating and evaporation. The heating and evaporation were performed for 1 hour, and finally 6.115 g of anhydrous ferric chloride was obtained with a purity of 97.3%.

[0042] When the temperature drops to about 75°C, a simulated flue gas flow is introduced, with nitrogen as the protective gas, a nitrogen flow rate of 500 ml / min, a nitric oxide concentration of about 200 ppm, and oxygen of about 2%. The gas contact time in the three-necked flask is about 3-5 seconds. The nitric oxide concentration at the outlet of the purified gas is 84 ppm, and the measured nitric oxide outlet concentration is the value at the maximum continuous removal rate. After a period of absorption, the adsorbed anhydrous ferric chloride is dissolved in 1 L of water, and NO is detected by ion chromatography. 3- and NO 2-The content indicates that the absorbed NO content is 47.4 mg, that is, the absorption and conversion capacity of anhydrous ferric chloride for NO is 7.75 mg / g.

[0043] Example 7

[0044] 10 g of ferric chloride hexahydrate with a purity of 99% was placed in a three-necked flask, and then concentrated hydrochloric acid was added to the round-bottomed flask. The vacuum degree in the three-necked flask was reduced to 0.02 MPa by a vacuum pump. The three-necked flask was placed in a constant temperature water bath at 95° C. and heated. Meanwhile, during the vacuuming process, the hydrogen chloride gas volatilized by the concentrated hydrochloric acid (accumulated about 0.137 L of hydrogen chloride, i.e., about 4.9 mmol HCL gas) was introduced into the ferric chloride hexahydrate. The crystal water in the hydrated ferric chloride was removed by heating and evaporation. The heating and evaporation were performed for 1 hour, and finally 6.071 g of anhydrous ferric chloride was obtained with a purity of 98.4%.

[0045] When the temperature drops to about 75°C, a simulated flue gas flow is introduced, with nitrogen as the protective gas, a nitrogen flow rate of 500 ml / min, a nitric oxide concentration of about 200 ppm, and oxygen of about 2%. The gas contact time in the three-necked flask is about 3-5 seconds. The nitric oxide concentration at the outlet of the purified gas is 75 ppm, and the measured nitric oxide outlet concentration is the value at the maximum continuous removal rate. After a period of absorption, the adsorbed anhydrous ferric chloride is dissolved in 1 L of water, and NO is detected by ion chromatography. 3- and NO 2- The content indicates that the absorbed NO content is 48.2 mg, that is, the absorption and conversion capacity of anhydrous ferric chloride for NO is 7.94 mg / g.

[0046] Example 8

[0047] 10 g of ferric chloride hexahydrate with a purity of 99% was placed in a three-necked flask, and then concentrated hydrochloric acid was added to the round-bottomed flask. The vacuum degree in the three-necked flask was reduced to 0.03 MPa by a vacuum pump, and the three-necked flask was placed in a constant temperature water bath at 95° C. for heating. Meanwhile, during the vacuuming process, the hydrogen chloride gas volatilized by the concentrated hydrochloric acid (accumulated about 0.157 L of hydrogen chloride, i.e., about 4.91 mmol HCL gas) was introduced into the ferric chloride hexahydrate, and the crystal water in the hydrated ferric chloride was removed by heating and evaporation. The heating and evaporation were performed for 1 hour, and finally 6.16 g of anhydrous ferric chloride was obtained with a purity of 96.2%.

[0048] When the temperature drops to about 75°C, a simulated flue gas flow is introduced, with nitrogen as the protective gas, a nitrogen flow rate of 500 ml / min, a nitric oxide concentration of about 200 ppm, and oxygen of about 2%. The gas contact time in the three-necked flask is about 3-5 seconds. The nitric oxide concentration at the outlet of the purified gas is 90 ppm, and the measured nitric oxide outlet concentration is the value at the maximum continuous removal rate. After a period of absorption, the adsorbed anhydrous ferric chloride is dissolved in 1 L of water, and NO is detected by ion chromatography. 3- and NO 2- The content indicates that the absorbed NO content is 46.7 mg, that is, the absorption and conversion capacity of anhydrous ferric chloride for NO is 7.58 mg / g.

[0049] Example 9

[0050] After the absorption and conversion of NO by anhydrous ferric chloride according to the method of Example 7, the anhydrous ferric chloride after use is regenerated, and the specific operation is as follows: at a temperature of 75 ° C, 120 mg of deionized water is added to the three-necked flask equipped with the anhydrous ferric chloride after use, and then heated at 95 ° C for about 30 min to release NO and remove the water in the ferric chloride. After the regeneration process is completed, when the temperature drops to about 75 ° C, a simulated flue gas flow is introduced thereto, and nitrogen in the airflow is used as a protective gas, the nitrogen flow rate is 500 ml / min, the concentration of nitric oxide is about 200ppm, and oxygen is about 2%, and the contact time of the gas in the three-necked flask is about 3-5s. After purification, the concentration of nitric oxide at the gas outlet is 115ppm, and the measured nitric oxide outlet concentration is the value at the maximum continuous removal rate. After absorbing for a period of time, the anhydrous ferric chloride solution water after adsorption is used, and NO is detected by ion chromatography 3- and NO 2- The content indicates that the absorbed NO content is 36.15 mg, that is, the absorption and conversion capacity of anhydrous ferric chloride for NO is 5.95 mg / g.

[0051] After absorbing NO, the anhydrous ferric chloride in the present invention can be regenerated by the following steps: adding 100-150 mg of deionized water to the anhydrous ferric chloride after absorbing and converting NO at a temperature of 55-75° C., and then heating at 95° C. for about 30 minutes, so that the complex releases NO and removes water in the ferric chloride, thereby achieving the purpose of regeneration.

[0052] When measuring the absorption content of NO by anhydrous ferric chloride, the absorbed ferric chloride is dissolved in 1L of water, and the NO in the solution is detected. 3- and NO 2- The content of NO is derived from the content of NO. During regeneration, a small amount of water is added and heated, and the gas released is NO.

[0053] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for in-situ preparation of anhydrous ferric chloride, characterized in that: The method comprises the following steps: placing ferric chloride hexahydrate in a reactor, then heating and evaporating under vacuum to remove crystal water in the hydrated ferric chloride, and introducing HCl gas into the ferric chloride hexahydrate during the heating and evaporation to finally obtain anhydrous ferric chloride.

2. A method for in-situ preparation of anhydrous ferric chloride as claimed in claim 1, characterized in that: The heating evaporation temperature is 70-100° C. and the vacuum degree is 0.01-0.03 MPa.

3. A method for in-situ preparation of anhydrous ferric chloride as claimed in claim 1, characterized in that: The purity of the ferric chloride hexahydrate raw material is above 99%.

4. A method for in-situ preparation of anhydrous ferric chloride as claimed in claim 1, characterized in that: The amount of hydrogen chloride gas introduced was adjusted so that the molar ratio of hydrogen chloride gas to anhydrous ferric chloride was 0.13 to 0.

19.

5. A method for in-situ preparation of anhydrous ferric chloride as claimed in claim 1, characterized in that: The heating evaporation time is 0.5-2h, preferably 1h.

6. Anhydrous ferric chloride prepared by the method as described in any one of claims 1 to 5.

7. The use of anhydrous ferric chloride as claimed in claim 6, characterized in that The anhydrous ferric chloride is used for converting and absorbing NO.

8. The use according to claim 7, characterized in that The anhydrous ferric chloride is heated to a temperature of 65°C to 75°C, NO gas is introduced, and NO and ferric chloride undergo a gas-solid adsorption chemical reaction to achieve the effect of purifying and removing NO.

9. The use according to claim 8, characterized in that The concentration of the NO gas is between 200 and 600 ppm.

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