A process for the preparation of ammonia-free impregnated charcoal

Abstract

The application discloses a preparation method of ammonia-free impregnated carbon and relates to the technical field of adsorbing material preparation, and comprises the following steps: completely dissolving strong alkali in deionized water to obtain a strong alkali solution and heating; adding copper hydroxide solid into the strong alkali solution and continuously stirring to keep the temperature of the solution, so as to prepare an impregnation solution; adding active carbon to be impregnated into the impregnation solution while hot, stirring and then standing; and drying the impregnated active carbon to obtain ammonia-free impregnated carbon. The prepared active carbon is proved to have certain protective effect on HCN and CNCl, has no ammonia smell, is convenient to use, is safe and environment-friendly in the preparation process, is simple to operate and is convenient for industrialization.

Description

Technical Field

[0001] This invention relates to the field of adsorption material preparation technology, specifically a method for preparing ammonia-free impregnated carbon. Background Technology

[0002] With the increasing demand for a high quality of life among Chinese residents, protective equipment is widely used in military, firefighting, petroleum, chemical, mining, metallurgy, disaster relief, epidemic prevention, and environmental protection fields. It also plays a crucial role in protecting the personal respiratory system in cities with severe smog and photochemical smog. Impregnated carbon is a commonly used adsorbent material in protective equipment. Currently, widely used types include broad-spectrum military ASC-type impregnated carbon, ASZM-type impregnated carbon, and civil defense impregnated carbon (these types primarily protect against typical military agents such as HCN and CNCl), holding a significant position in national defense security.

[0003] Traditional impregnated charcoal preparation uses ammonia water as a solvent and a metal ammonia complex as a precursor, loading the ammonia onto the surface of activated carbon via impregnation, followed by calcination to form active metal oxides. This process has the advantage that the decomposition temperature of the loaded metal ammonia complex precursor is lower than the ignition point of activated carbon; however, because a large amount of ammonia water and ammonium salts are used as the main solvent components in the preparation process, the ammonia-containing components in the product decompose during use, leading to the release of an "ammonia odor," which is particularly pronounced under high temperature and high humidity conditions and is extremely irritating. Ammonia gas is a colorless gas with a strong, pungent odor. It can absorb moisture from skin tissue, denature tissue proteins, saponify tissue fats, and damage cell membrane structures, exhibiting corrosive and irritating effects on skin tissue. This results in a poor experience for users of protective equipment, compromising both comfort and safety, and making it unsuitable for use.

[0004] The mechanism of action of traditional impregnated charcoal against HCN is as follows:

[0005]

[0006]

[0007] or

[0008] Due to the action of oxygen in the air, HCN can also be oxidized into isocyanate:

[0009]

[0010] Isocyanate further hydrolyzes to ammonium formate:

[0011]

[0012] The products of the hydrocyanic acid reaction are fixed on the surface of the activated carbon pores.

[0013] The mechanism of action of CNCl is as follows:

[0014]

[0015]

[0016]

[0017] The ammonia and hydrochloric acid in the product can still react, for example:

[0018]

[0019] or

[0020] The products of the hydrolysis reaction catalyzed by cyanide chloride, hydrochloric acid and ammonia, can continue to react to form solid products that adhere to the surface of activated carbon.

[0021] From the reaction mechanism perspective, CuO plays a crucial role in protecting against HCN and CNCl. To completely eliminate ammonia odor, existing technologies employ ammonia-free formulation processes. Some studies have used nitrates or sulfates as impregnation precursors, demonstrating that the resulting impregnated carbon exhibits good protection against gases such as SO2, NO2, HCN, and (CN)2. However, the decomposition temperature of copper nitrate (Cu(NO3)2) is 190–220℃, while that of copper sulfate (CuSO4) requires approximately 350℃. This process for preparing ammonia-free activated carbon not only necessitates increasing the calcination temperature but also requires the use of inert gas or a closed calcination environment to prevent fire during preparation, posing a safety hazard. Furthermore, the reaction conditions are demanding. Additionally, additional treatment of SO2 or NO2 is required during the preparation process. x Purification measures for calcination exhaust gases, etc., all lead to increased production costs and increased preparation difficulty. Summary of the Invention

[0022] To address the problems of current impregnated charcoal preparation processes that use ammonia as a solvent, resulting in an ammonia odor in the finished product, high requirements for preparation conditions, need to treat calcination tail gas, and high production costs, this invention provides a method for preparing ammonia-free impregnated charcoal.

[0023] This invention is achieved using the following techniques:

[0024] This invention provides a method for preparing ammonia-free impregnated charcoal, comprising the following steps:

[0025] a. Preparation of strong alkaline solutions

[0026] First, the strong base is completely dissolved in deionized water to obtain a solution with pH > 14. The strong base solution is then heated to maintain the temperature at 50~100℃.

[0027] b. Preparation of impregnation solution

[0028] Prepare an impregnation solution using deionized water as the solvent, according to the water capacity of activated carbon 100%. Add solid copper hydroxide to the strong alkaline solution obtained in step a and stir continuously. The strong alkaline is sodium hydroxide or potassium hydroxide, with a mass fraction of 20% to 50% and a mass fraction of 2% to 20% for copper hydroxide. Maintain the solution temperature until a blue sodium tetrahydroxycubic acid solution is formed to obtain the impregnation solution.

[0029] c, immersion

[0030] Add the activated carbon to be impregnated to the impregnation solution obtained in step b while it is still hot. The activated carbon to be impregnated is coal-based activated carbon with a particle size of 0.9 mm. Activated carbon can be replaced by adsorbent materials such as zeolite or ceramics. Stir evenly and let stand for 2 to 4 hours to allow the activated carbon to fully and evenly absorb the impregnation solution.

[0031] d, drying

[0032] The activated carbon impregnated in step c is dried at 70~200℃ to obtain ammonia-free impregnated carbon.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The present invention provides an ammonia-free impregnated charcoal, which uses activated carbon as a carrier and does not use ammonia / amine-containing substances. Copper hydroxide is dissolved in a strong alkaline solution to generate sodium tetrahydroxycuprate, which is then dried at a certain temperature to obtain the ammonia-free impregnated charcoal. This eliminates the "ammonia smell" at the source and has a certain protective effect against HCN and CNCl. No irritating ammonia smell is generated during the preparation and use process. The impregnated carbon prepared by the method provided by this invention was tested and found to have a protection time of 32 min and 36 min against hydrogen cyanide vapor, and a protection time of 18 min and 21 min against hydrogen chloride vapor. The test standards refer to GJB6239.18-2008 "Test Method for Performance of Military Impregnated Activated Carbon Part 18: Protection Time against Hydrogen Cyanide Vapor" and GJB6239.19-2008 "Test Method for Performance of Military Impregnated Activated Carbon Part 19: Protection Time against Cyanide Vapor". This proves that its protection performance against HCN is comparable to that of traditional impregnated carbon, but its protection performance against CNCl is slightly worse, although it still has a certain protective effect. This completely solves the problem that traditional impregnated carbon for CNCl and HCl protection uses a large amount of solvent system with ammonia and ammonium salts as the main components and metal ammonia complexes as precursors in the preparation process, which may lead to incomplete decomposition and the ammonia odor in the finished impregnated carbon. From an industrial preparation perspective, this invention involves a simple range of chemicals, a simple process, and is safe and environmentally friendly. It can be completed under normal conditions, is easy to operate, and is suitable for industrialization, providing a new approach for the subsequent research and development of ammonia-free impregnated carbon. Implementation

[0035] The specific embodiments of the present invention will be described in detail below. Example 1

[0036] A method for preparing ammonia-free impregnated carbon, the specific steps of which are as follows:

[0037] a. Preparation of strong alkaline solutions

[0038] First, completely dissolve 20g of sodium hydroxide solid in deionized water to obtain 90ml of sodium hydroxide solution. Heat the sodium hydroxide solution on an electric heating plate to maintain the temperature at 70℃.

[0039] b. Preparation of impregnation solution

[0040] Add 2g of copper hydroxide solid to the strong alkaline solution obtained in step a and stir continuously, keeping the solution temperature at 70℃, until a blue sodium tetrahydroxycubic acid solution is formed to obtain the impregnation solution.

[0041] c, immersion

[0042] Add 100g of coal-based activated carbon with a particle size of 0.9mm to the impregnation solution obtained in step b while it is still hot, stir evenly, and let stand for 2 hours to allow the activated carbon to fully and evenly absorb the impregnation solution.

[0043] d, drying

[0044] The activated carbon impregnated in step c is dried at 100℃ for 24 hours to obtain ammonia-free impregnated carbon.

[0045] The samples obtained by the above steps were tested for various parameters.

[0046] 1. Hydrogen cyanide vapor protection time

[0047] The testing standard refers to GJB6239.18-2008 "Test Methods for Performance of Military Impregnated Activated Carbon - Part 18: Protection Time Against Hydrogen Cyanide Vapor". The test calculation shows that the protection time of impregnated coal-based activated carbon against hydrogen cyanide is 32 minutes.

[0048] 2. Protection time for cyanide vapor

[0049] The testing standard refers to GJB6239.19-2008 "Test Methods for Performance of Military Impregnated Activated Carbon - Part 19: Protection Time Against Cyanide Vapor". The test calculation shows that the protection time of impregnated coal-based activated carbon against cyanide vapor is 18 minutes. Example 2

[0050] A method for preparing ammonia-free impregnated carbon, the specific steps of which are as follows:

[0051] a. Preparation of strong alkaline solutions

[0052] First, completely dissolve 45g of potassium hydroxide solid in deionized water to obtain 90ml of potassium hydroxide solution. Heat the potassium hydroxide solution on an electric heating plate to maintain the temperature at 55℃.

[0053] b. Preparation of impregnation solution

[0054] Add 8g of copper hydroxide solid to the strong alkaline solution obtained in step a and stir continuously, keeping the solution temperature at 55℃, until a blue sodium tetrahydroxycubic acid solution is formed to obtain the impregnation solution.

[0055] c, immersion

[0056] Add 100g of coal-based activated carbon with a particle size of 0.9mm to the impregnation solution obtained in step b while it is still hot, stir evenly, and let stand for 2 hours to allow the activated carbon to fully and evenly absorb the impregnation solution.

[0057] d, drying

[0058] The activated carbon impregnated in step c is dried at 110°C to obtain ammonia-free impregnated carbon.

[0059] The samples obtained by the above steps were tested for various parameters.

[0060] 1. Hydrogen cyanide vapor protection time

[0061] The testing standard refers to GJB6239.18-2008 "Test Methods for Performance of Military Impregnated Activated Carbon - Part 18: Protection Time Against Hydrogen Cyanide Vapor". The test calculation shows that the protection time of impregnated coal-based activated carbon against hydrogen cyanide is 36 minutes.

[0062] 2. Protection time for cyanide vapor

[0063] The testing standard refers to GJB6239.19-2008 "Test Methods for Performance of Military Impregnated Activated Carbon - Part 19: Protection Time Against Cyanide Vapor". The test calculation shows that the protection time of impregnated coal-based activated carbon against cyanide vapor is 21 minutes.

[0064] Coal-based activated carbon was prepared using traditional methods, and various parameters of the obtained samples were tested.

[0065] 1. Hydrogen cyanide vapor protection time

[0066] The testing standard refers to GJB6239.18-2008 "Test Methods for Performance of Military Impregnated Activated Carbon - Part 18: Protection Time Against Hydrogen Cyanide Vapor". The test calculation shows that the protection time of traditional impregnated carbon against hydrogen cyanide is 36 minutes.

[0067] 2. Protection time for cyanide vapor

[0068] The testing standard refers to GJB6239.19-2008 "Test Methods for Performance of Military Impregnated Activated Carbon - Part 19: Protection Time Against Cyanide Vapor". The test calculation shows that the protection time of traditional impregnated carbon against cyanide vapor is 28 minutes.

[0069] The impregnated carbon prepared in Examples 1 and 2 had no ammonia odor, while the impregnated activated carbon prepared in Comparative Example 1 had an ammonia odor.

[0070] Compared with traditional impregnated carbon, the impregnated carbon provided in Examples 1 and 2 has comparable HCN protection performance to that of the traditional impregnated carbon prepared in Comparative Example 1, but slightly inferior CNCl protection performance.

[0071] Combining Examples 1 and 2 with Comparative Example 1, it can be concluded that Examples 1 and 2 both have a certain protective effect against HCN and CNCl.

[0072] The scope of protection claimed by this invention is not limited to the specific embodiments described above. Moreover, for those skilled in the art, this invention can have various modifications and alterations. Any modifications, improvements, and equivalent substitutions made within the concept and principles of this invention should be included within the scope of protection of this invention.

Claims

1. Use of ammonia-free impregnated carbon in protection against CNCl and HCN, characterized in that: Preparation method of ammonia-free impregnated carbon The preparation method comprises the following steps: a. preparing a strong alkali solution First, the strong alkali is completely dissolved in deionized water to obtain a solution with pH>14, and the strong alkali solution is heated to keep the temperature at 50-100℃, wherein the strong alkali is sodium hydroxide; b. preparing an impregnation solution 2g or 8g of copper hydroxide solid is added to the strong alkali solution prepared in step a. under continuous stirring, and the solution temperature is kept until a blue sodium tetraborate solution is formed to prepare the impregnation solution; c. impregnation The impregnation solution prepared in step b. is heated and added to the active carbon to be impregnated, and stirred uniformly, and then left to stand for 2-4h to make the active carbon fully and uniformly absorb the impregnation solution; d. drying The active carbon impregnated in step c. is dried at 70-200℃ to obtain ammonia-free impregnated carbon.

2. Use of an ammonia-free impregnated carbon according to claim 1 in the protection against CNCl and HCN, characterized in that: In step b., the mass fraction of the strong alkali is 20%-50%, and the mass fraction of the copper hydroxide is 2%-20%.

3. Use of an ammonia-free impregnated carbon according to claim 1 in the protection against CNCl and HCN, characterized in that: According to the water capacity of the active carbon, the impregnation solution is prepared with deionized water as the solvent.

4. Use of an ammonia-free impregnated carbon according to claim 1 in the protection against CNCl and HCN, characterized in that: In step c., the active carbon to be impregnated is coal-based active carbon with a particle size of 0.9mm.