A preparation method of a carbon-coated catalyst and a method for removing free chlorine in hydrochloric acid

Abstract

The application discloses a preparation method of a carbon-coated catalyst, and a method for removing free chlorine in hydrochloric acid. The catalyst is prepared by taking sugar as a carbon source, adding an active metal core, and then performing a hydrothermal reaction, filtration and high-temperature calcination. The carbon-coated catalyst is mixed with ion exchange resin in a certain proportion, and then free chlorine in hydrochloric acid can be removed. The application can effectively decompose free chlorine in hydrochloric acid, remove metal ions in the hydrochloric acid, and greatly improve the quality of the hydrochloric acid.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of fine chemical industry and catalysis technology, and particularly relates to a preparation method of carbon-coated catalyst and a method for removing free chlorine in hydrochloric acid. BACKGROUND

[0002] In industry, hydrogen chloride gas is generally treated by water absorption to prepare hydrochloric acid, which is used as a raw material for the production of other products or is sold as by-product hydrochloric acid. However, because unreacted chlorine gas is mixed in the hydrogen chloride gas, the prepared hydrochloric acid contains a small amount of free chlorine. The free chlorine is very active and can participate in many chemical reactions, thereby limiting the application of the hydrochloric acid. At the same time, the free chlorine can also be emitted during use, causing serious pollution to the production environment and even endangering the health of workers.

[0003] At present, the methods for removing free chlorine in hydrochloric acid mainly include air (nitrogen) stripping and activated carbon adsorption. For example, in patent CN100361891C, most of the free chlorine in the hydrochloric acid is blown out by compressed air, and the blown-out chlorine gas is reacted with iron filings. After purification, the residual chlorine is removed by adding an organic acid. In patent CN101332977A, air is introduced to carry out the free chlorine in the form of chlorine gas, and then the residual chlorine is removed by passing through an activated carbon fixed bed. In these methods, the introduction of air (nitrogen) not only carries away part of the hydrogen chloride gas when stripping the free chlorine, but also increases the cost of tail gas treatment in the later stage and wastes a large amount of hydrogen chloride gas. In the activated carbon adsorption method, in actual application, special coal-based activated carbon with extremely low iron content or high-quality coconut shell activated carbon must be selected, which is expensive. Moreover, the above-mentioned methods are not sufficient for removing free chlorine, and a small amount of residual chlorine still remains. SUMMARY

[0004] The present application provides a preparation method of carbon-coated catalyst and a method for removing free chlorine in hydrochloric acid, which can decompose chlorine gas dissolved in hydrochloric acid at low temperature and catalyst conditions, thereby removing the free chlorine in the hydrochloric acid. The method is simple and has high removal efficiency.

[0005] To achieve the above-mentioned purposes and effects, the technical scheme of the present application is as follows:

[0006] A preparation method of carbon-coated catalyst, comprising the following steps:

[0007] (1) preparing an active metal core: uniformly mixing an active metal salt and a solvent, then crystallizing in a crystallization kettle, cooling after crystallization, separating the precipitate, washing, drying, and calcining to obtain an active metal core;

[0008] (2) Carbon coating: water is added to the carbon source and active metal core, and stirred and mixed uniformly, then crystallized, and after crystallization, cooled, then washed, dried, and calcined to obtain a carbon-coated catalyst.

[0009] In the present application, the active metal is one or more of Ni, Ti, and Sn.

[0010] In the present application, the solvent in step (1) is an alcohol solvent, preferably one or more of ethylene glycol, propylene glycol, glycerol, etc.

[0011] In the present application, the mass ratio of the active metal salt to the solvent is 1:10-100, preferably 1:20-60.

[0012] In the present application, the metal salt in step (1) is a soluble salt, which can be a nitrate, nitrite, or chloride, etc.

[0013] In the present application, step (1) is crystallized at 120-250°C, preferably 180-220°C, for 2-48h, preferably 5-18h.

[0014] In the present application, after step (1) is crystallized, the precipitate is separated by centrifugal separation.

[0015] In the present application, step (1) is washed with acetone for 3-5 times.

[0016] In the present application, step (1) is dried at 50-150°C after washing.

[0017] In the present application, step (1) is calcined at a temperature of 300-1000°C, preferably 400-800°C, for 1-10h, preferably 3-8h.

[0018] In the present application, the carbon source in step (2) is a monosaccharide or disaccharide such as glucose, fructose, sucrose, etc.

[0019] In the present application, the mass ratio of the active metal core to the carbon source is 1:0.1-20, preferably 1:0.5-10.

[0020] In the present application, the amount of water added to the carbon source and active metal core in step (2) is 1-20 times the total mass of the carbon source and active metal core.

[0021] In the present application, step (2) is crystallized at a temperature of 120-250°C, preferably 180-220°C, for 2-48h, preferably 5-18h.

[0022] In the present application, after step (2) is crystallized, it is cooled to room temperature, and then washed.

[0023] In the present application, step (2) is washed with water and ethanol alternately, each for 3-5 times.

[0024] In the present application, after step (2) is washed, drying is performed at 50-150℃.

[0025] In the present application, in step (2), under the protection of inert atmosphere, calcination is performed in a calcination furnace with a programmed temperature rising rate of 5-20℃ / min to a calcination temperature, the calcination temperature is 300-1000℃, preferably 400-800℃, and the calcination time is 1-10h, preferably 3-8h.

[0026] The present application also provides the use of the carbon-coated catalyst as described above, which can be used for removing free chlorine in hydrochloric acid. The present application also provides a method for removing free chlorine in hydrochloric acid, wherein crude hydrochloric acid containing chlorine gas is catalytically treated by a reactor containing the carbon-coated catalyst and ion exchange resin as described in the present application to obtain purified hydrochloric acid.

[0027] In the present application, the ion exchange resin includes one or more of acidic cation exchange resin, acidic anion exchange resin, basic cation resin, basic anion resin, chelating resin, etc., such as one or more of macroporous strong acid styrene cation resin D001, macroporous weak base styrene cation exchange resin D301, macroporous strong base styrene cation exchange resin D201, chelating resin D68, strong base styrene anion resin 201*7, and weak acid macroporous cation exchange resin D113.

[0028] In the present application, the mass ratio of the carbon-coated catalyst to the ion exchange resin is 1:0.1-10.

[0029] Preferably, the mass ratio of the carbon-coated catalyst to the ion exchange resin is 1:0.5-5.

[0030] The inlet volumetric space velocity of the crude hydrochloric acid into the reactor is 0.2-0.7h -1 , the reaction pressure is 0.2-4MPaG, and the reaction temperature is 20-70℃.

[0031] Further preferably, the inlet volumetric space velocity of the crude hydrochloric acid into the reactor is 0.3-0.5h -1 , the reaction pressure is 0.2-1MPaG, and the reaction temperature is 35-55℃.

[0032] Preferably, the reactor is a plug flow fixed bed reactor.

[0033] In the present application, under normal hydrochloric acid production conditions (normal pressure, 40℃), the solubility of chlorine gas in hydrochloric acid can be as high as 400mg / kg. It has been verified that the present application has good chlorine removal effect on hydrochloric acid streams with chlorine concentration less than 400mg / kg.

[0034] The catalyst prepared by the present application has excellent selectivity and stability, can decompose the chlorine dissolved in hydrochloric acid under low-temperature catalytic conditions to generate products HCl and O2, can effectively remove chlorine, and can remove metal impurities in hydrochloric acid, thereby achieving the purpose of purifying hydrochloric acid. DETAILED DESCRIPTION

[0035] In order to facilitate the understanding of the present application, the present application lists the following embodiments for example, but the embodiments are only used to help understand the present application, and should not be regarded as specific limitations of the present application.

[0036] The free chlorine in hydrochloric acid is titrated by iodimetry introduced in the national standard GBT320-2006. The metal content is measured by ICP, and the measuring instrument is Agilent 5900.

[0037] Example 1

[0038] S1: 5g of nickel nitrate was weighed in a 100ml beaker, 20ml of ethylene glycol solution was added, and it was stirred at room temperature to dissolve; it was transferred to a polytetrafluoroethylene-lined crystallization kettle, and was placed in a 120℃ oven for crystallization for 48h. The crystallization kettle was taken out, and was naturally cooled to room temperature. The precipitate was centrifugally separated, and was washed with acetone for 3 times. Then it was placed in a 50℃ oven to dry overnight. The dried solid was loaded into a crucible, and was calcined at 500℃ for 2h in a muffle furnace to obtain the sample, Nucleus-1.

[0039] S2: 20g of sucrose and 2g of Nucleus-1 were weighed in a beaker, 50ml of water was added, and it was stirred at room temperature for 1h. The uniformly stirred mixture was transferred to a crystallization kettle, and was placed in a 250℃ oven for crystallization for 2h. The crystallization kettle was taken out, and was naturally cooled to room temperature. The precipitate was washed with deionized water and anhydrous ethanol alternately for 3 times. The washed precipitate was placed in a 50℃ oven to dry overnight. The dried solid was loaded into a quartz boat, and was heated to 300℃ at a rate of 5℃ / min under N2 atmosphere in a tube furnace, and was calcined for 10h to obtain the carbon-coated catalyst, 1@C.

[0040] Example 2

[0041] S1: 4g of nickel nitrite and 2g of titanium chloride were weighed in a 500ml beaker, 300ml of ethylene glycol solution was added, and it was stirred at room temperature to dissolve; it was transferred to a polytetrafluoroethylene-lined crystallization kettle, and was placed in a 250℃ oven for crystallization for 2h. The crystallization kettle was taken out, and was naturally cooled to room temperature. The precipitate was centrifugally separated, and was washed with acetone for 3 times. Then it was placed in a 50℃ oven to dry overnight. The dried solid was loaded into a crucible, and was calcined at 1000℃ for 1h in a muffle furnace to obtain the sample, Nucleus-2.

[0042] S2: 12 g of fructose and 5 g of Nucleus-2 were weighed into a beaker, 50 ml of water was added, and stirred at room temperature for 1 h; the uniformly stirred mixture was transferred into a crystallization kettle, and placed into a 200 °C oven for crystallization for 48 h. The crystallization kettle was taken out, and naturally cooled to room temperature, washed with deionized water and anhydrous ethanol alternately for 3 times each, and the washed precipitate was placed into a 50 °C oven for drying overnight. The dried solid was placed into a quartz boat, and calcined in a tube furnace under the protection of N2 atmosphere at a programmed temperature increase rate of 5 °C / min to 700 °C for 5.5 h to obtain a carbon-coated catalyst, 2@C.

[0043] Example 3

[0044] S1: 9 g of titanium nitrate and 1.5 g of tin chloride were weighed into a 100 ml beaker, 210 ml of ethylene glycol solution was added, and stirred at room temperature until dissolved; transferred into a crystallization kettle lined with polytetrafluoroethylene, and placed into a 200 °C oven for crystallization for 4 h. The crystallization kettle was taken out, and naturally cooled to room temperature, the precipitate was separated by centrifugation, and washed with acetone for 3 times, and then placed into an 80 °C oven for drying overnight, the dried solid was loaded into a crucible, and calcined in a muffle furnace at 800 °C for 6 h to obtain a sample, Nucleus-3.

[0045] S2: 10 g of glucose and 10 g of Nucleus-3 were weighed into a beaker, 50 ml of water was added, and stirred at room temperature for 1 h; the uniformly stirred mixture was transferred into a crystallization kettle, and placed into a 250 °C oven for crystallization for 24 h. The crystallization kettle was taken out, and naturally cooled to room temperature, washed with deionized water and anhydrous ethanol alternately for 3 times each, and the washed precipitate was placed into a 60 °C oven for drying overnight. The dried solid was placed into a quartz boat, and calcined in a tube furnace under the protection of N2 atmosphere at a programmed temperature increase rate of 5 °C / min to 1000 °C for 10 h to obtain a carbon-coated catalyst, 3@C.

[0046] Example 4

[0047] S1: 0.5 g of nickel chloride, 2 g of titanium nitrate and 5 g of tin chloride were weighed into a 100 ml beaker, 150 ml of ethylene glycol solution was added, and stirred at room temperature until dissolved; transferred into a crystallization kettle lined with polytetrafluoroethylene, and placed into a 220 °C oven for crystallization for 24 h. The crystallization kettle was taken out, and naturally cooled to room temperature, the precipitate was separated by centrifugation, and washed with acetone for 3 times, and then placed into a 50 °C oven for drying overnight, the dried solid was loaded into a crucible, and calcined in a muffle furnace at 800 °C for 8 h to obtain a sample, Nucleus-4.

[0048] S2: Weigh 10 g of 1@C and 1 g of Nucleus-4 in a beaker, add 50 ml of water, and stir at room temperature for 1 h; transfer the uniformly stirred mixture to a crystallization kettle, and place it in a 120℃ oven for crystallization for 48 h. Take out the crystallization kettle, and cool it to room temperature naturally, and wash the precipitate with deionized water and anhydrous ethanol alternately for 3 times each, and place the washed precipitate in an 80℃ oven to dry overnight. Place the dried solid in a quartz boat, and in a tubular furnace under the protection of N2 atmosphere, program the temperature to rise to 500℃ at a rate of 5℃ / min, and calcine for 5 h to obtain the carbon-coated catalyst, 4@C.

[0049] Example 5-8 Catalyst Application

[0050] Example 5

[0051] S1: Weigh 10 g of 1@C and 10 g of macroporous strong-acid styrene cation resin D001, and mix thoroughly to obtain a de-Cl catalyst, CAT-1.

[0052] S2: Pass a crude hydrochloric acid stream containing 60 mg / kg of chlorine and 10 mg / kg of Fe through a plug flow reactor filled with 20 g of CAT-1; the crude hydrochloric acid enters the reactor at a volume space velocity of 0.3 h -1 After the reactor is continuously operated for 96 h, the free chlorine content in the purified hydrochloric acid is not detected (<2 mg / kg), and the Fe content is not detected (<0.1 mg / kg).

[0053] Example 6

[0054] S1: Weigh 15 g of 2@C and 5 g of macroporous strong-base styrene cation exchange resin D201, and mix thoroughly to obtain a de-Cl catalyst, CAT-2.

[0055] S2: Pass a crude hydrochloric acid stream containing 400 mg / L of chlorine, 10 mg / kg of Fe, and 0.5 mg / kg of Cu through a plug flow reactor filled with 20 g of CAT-2; the crude hydrochloric acid enters the reactor at a space velocity of 0.7 h -1 After the reactor is continuously operated for 24 h, the free chlorine content in the purified hydrochloric acid is not detected (<2 mg / kg), the Fe content is not detected (<0.1 mg / kg), and the Cu content is not detected (<0.1 mg / kg).

[0056] Example 7

[0057] S1: Weigh 12 g of 3@C and 120 g of strong-base styrene anion resin 201*7, and mix thoroughly to obtain a de-Cl catalyst, CAT-3.

[0058] S2: The crude hydrochloric acid stream containing 200 mg / L chlorine, containing 5 mg / kg Fe, 2 mg / kg Cr was passed through a plug flow reactor packed with 40 g CAT-3; the crude hydrochloric acid was passed at a space velocity of 0.5 h -1 into the reactor, and the reaction pressure was controlled at 0.6 MPaG, and the reaction temperature was 55°C. After the reactor was continuously operated for 24 h, the free chlorine content in the purified hydrochloric acid obtained was not detected (<2 mg / kg), the Fe content was not detected (<0.1 mg / kg), and the Cr content was not detected (<0.1 mg / kg)

[0059] Example 8

[0060] S1 : 5 g of 4@C and 25 g of macroreticular resin D68 were weighed, and after being thoroughly mixed, a de-free-chlorine catalyst, CAT-4, was obtained.

[0061] S2: The crude hydrochloric acid stream containing 150 mg / L chlorine, containing 50 mg / kg Fe, 1 mg / kg Cu was passed through a plug flow reactor packed with 30 g of CAT-2; the crude hydrochloric acid was passed at a space velocity of 0.7 h -1 into the reactor, and the reaction pressure was controlled at 0.2 MPaG, and the reaction temperature was 35°C. After the reactor was continuously operated for 48 h, the free chlorine content in the purified hydrochloric acid obtained was not detected (<2 mg / kg), the Fe content was not detected (<0.1 mg / kg), and the Cu content was not detected (<0.1 mg / kg)

[0062] Comparative Example 1

[0063] This comparative example mainly used commonly used coal-based activated carbon as the adsorbent, and the adsorption experiment was carried out according to Example 8.

[0064] The crude hydrochloric acid stream containing 150 mg / L chlorine, containing 50 mg / kg Fe, 1 mg / kg Cu was passed through a plug flow reactor packed with 30 g of coal-based activated carbon; the crude hydrochloric acid was passed at a space velocity of 0.7 h -1 into the reactor, and the reaction pressure was controlled at 0.2 MPaG, and the reaction temperature was 35°C. After the reactor was continuously operated for 48 h, the free chlorine content in the purified hydrochloric acid obtained was not detected (<2 mg / kg), the Fe content was not detected (<0.1 mg / kg), and the Cu content was not detected (<0.1 mg / kg)

Claims

1. Use of a carbon-coated catalyst, characterized in that, It is used for removing free chlorine in hydrochloric acid, The preparation method of the carbon-coated catalyst comprises the following steps: (1) preparing an active metal core: uniformly mixing an active metal salt and a solvent, then crystallizing in a crystallization kettle, taking out and cooling after crystallization, separating the precipitate, washing, drying, and calcining to obtain the active metal core; (2) carbon coating: adding water to the carbon source and the active metal core, uniformly mixing, then crystallizing, taking out and cooling after crystallization, then washing, drying, and calcining to obtain the carbon-coated catalyst; The active metal is one or more of Ni, Ti, and Sn. The carbon source in step (2) is glucose, fructose, or sucrose.

2. Use according to claim 1, characterized in that, The solvent in step (1) is an alcohol solvent.

3. Use according to claim 2, characterized in that, The solvent in step (1) is a mixture of one or more of ethylene glycol, propylene glycol, and glycerol.

4. Use according to claim 2, characterized in that, The mass ratio of the active metal salt to the solvent is 1:10-100.

5. Use according to claim 4, characterized in that, The mass ratio of the active metal salt to the solvent is 1:20-60.

6. Use according to claim 1, characterized in that, Step (1) is crystallized at 120-250 ℃ for 2-48 h.

7. Use according to claim 6, characterized in that, Step (1) is crystallized at 180-220 ℃ for 5-18 h.

8. The use according to claim 1, characterized in that, After crystallization in step (1), the precipitate is separated by centrifugal separation after cooling to room temperature.

9. The use according to claim 1, characterized in that, In step (1), the precipitate is washed with acetone for 3-5 times.

10. The use according to claim 1, characterized in that, After washing in step (1), the precipitate is dried at 50-150 ℃.

11. Use according to claim 1, characterized in that, The calcination temperature in step (1) is 300-1000 ℃, and the calcination time is 1-10 h.

12. Use according to claim 11, characterized in that, The calcination temperature in step (1) is 400-800 ℃, and the calcination time is 3-8 h.

13. The use according to claim 1, characterized in that, The mass ratio of the active metal core to the carbon source is 1:0.1-20.

14. Use according to claim 13, characterized in that, The mass ratio of the active metal core to the carbon source is 1:0.5-10.

15. The use according to claim 1, characterized in that, In step (2), the mass of water added to the carbon source and the active metal core is 1-20 times the total mass of the carbon source and the active metal core.

16. The use according to claim 1, characterized in that, The crystallization temperature in step (2) is 120-250 ℃, and the crystallization time is 2-48 h.

17. Use according to claim 16, characterized in that, The crystallization temperature in step (2) is 180-220 ℃, and the crystallization time is 5-18 h.

18. The use according to claim 1, characterized in that, After crystallization in step (2), the precipitate is washed.

19. The use according to claim 1, characterized in that, In step (2), the precipitate is washed with water and ethanol alternately for 3-5 times.

20. The use according to claim 1, characterized in that, After washing in step (2), the precipitate is dried at 50-150 ℃.

21. The use according to claim 1, characterized in that, In step (2), the precipitate is calcined in a calcination furnace under the protection of an inert atmosphere at a temperature rising rate of 5-20 ℃ / min to a calcination temperature, the calcination temperature is 300-1000 ℃, and the calcination time is 1-10 h.

22. The use according to claim 21, characterized in that, In step (2), the calcination temperature is 400-800 ℃, and the calcination time is 3-8 h.

23. A method for removing free chlorine in hydrochloric acid, wherein crude hydrochloric acid containing chlorine gas is catalytically treated by a reactor loaded with the carbon-coated catalyst according to any one of claims 1-22 and ion exchange resin to obtain purified hydrochloric acid.

24. The method of claim 23, wherein, The ion exchange resin comprises one or more of an acidic cation exchange resin, an acidic anion exchange resin, a basic cation resin, a basic anion resin, and a chelating resin.

25. The method of claim 24, wherein, The ion exchange resin is selected from one or more of macroporous strong acid styrene cation resin D001, macroporous weak base styrene cation exchange resin D301, macroporous strong base styrene cation exchange resin D201, chelating resin D68, strong base styrene anion resin 201*7, weak acid macroporous cation exchange resin D113.

26. The method of claim 23, wherein, The mass ratio of the carbon-coated catalyst to the ion exchange resin is 1:0.1-10.

27. The method of claim 24, wherein, The mass ratio of the carbon-coated catalyst to the ion exchange resin is 1:0.5-5.

28. The method of claim 23, wherein, The inlet volume space velocity of the crude hydrochloric acid into the reactor is 0.2-0.7h -1 The reaction pressure is 0.2-4 MPaG, and the reaction temperature is 20-70℃.

29. The method of claim 23, wherein, The inlet volume space velocity of the crude hydrochloric acid into the reactor was 0.3-0.5 h -1 The reaction pressure was 0.2-1 MPaG, and the reaction temperature was 35-55℃.

30. The method of claim 23, wherein, The reactor is a plug flow fixed bed reactor.