A deformation-resistant, cracking-resistant honeycomb activated carbon and a method for making the same

Abstract

The application provides anti-deformation and anti-cracking honeycomb activated carbon and a preparation method thereof. The anti-deformation and anti-cracking honeycomb activated carbon comprises the following raw materials: powdered activated carbon powder, hydrophilic fumed silica, aqueous blocked isocyanate emulsion, polydextrose, water-soluble polyether glycol and water. The application replaces water-soluble hydroxyl cellulose compounds with polydextrose and water-soluble polyether glycol, which can not only meet the requirement that the polydextrose and water-soluble polyether glycol do not degrade or become brittle to cause distortion and deformation in the unblocking and preliminary shaping stage, but also can react with the unblocked isocyanate group. The honeycomb activated carbon with a urea group cross-linked three-dimensional network structure gradually formed in the unblocking and hot air drying process can resist the capillary pressure generated by water evaporation in the hot air drying process, reduce the generation of cracks and improve the yield.

Description

Technical Field

[0001] This invention belongs to the field of honeycomb activated carbon technology, specifically relating to a deformation-resistant and crack-resistant honeycomb activated carbon and its preparation method. Background Technology

[0002] Honeycomb activated carbon refers to a new type of integrally structured activated carbon with many narrow, straight (or curved) parallel channels. Honeycomb activated carbon retains the advantages of traditional activated carbon, such as large specific surface area, stable surface chemical functional groups, resistance to acid and alkali corrosion, and hydrophobicity. Furthermore, its unique honeycomb structure gives it new advantages such as high porosity, uniform gas distribution, larger geometric surface area, shorter diffusion path, and strong resistance to dust pollution. Compared with other types of activated carbon, the biggest advantage of honeycomb activated carbon is its low pressure loss during fluid treatment. Under the same conditions, its resistance is only about 1 / 10 of that of granular activated carbon.

[0003] Based on the above advantages, honeycomb activated carbon is widely used in gas purification and gas storage. There are three main methods for preparing honeycomb activated carbon: integral extrusion molding, carbon coating, and sol-gel method. Among these, integral extrusion molding, with its simple operation and excellent performance, is the most widely used. In integral extrusion molding, activated carbon is mixed with a binder to obtain a plastic slurry, which is then extruded to form a honeycomb preform. This preform is then dried to obtain the honeycomb activated carbon. For example, patent CN113912058B discloses a method for preparing honeycomb activated carbon, in which the extruded preform is dried in a forced-air oven at an initial temperature of 60℃, increasing by 5-10℃ every 10-24 hours until reaching 150℃, and then continuing to dry at 150℃ for 24 hours. Patent CN101214955B discloses a hydrophobic honeycomb activated carbon and its preparation method, in which the honeycomb preform is dried at 100-200℃ for 3-12 hours.

[0004] The above techniques are all common integral extrusion methods for preparing honeycomb activated carbon. The honeycomb activated carbon is then produced by hot air drying. The preparation process is simple and suitable for industrial production. However, due to the strong capillary tension generated on the outer surface and at both ends during the hot air drying process, cracks on the outer wall and at the opening are prone to occur, resulting in a relatively low yield.

[0005] To address this issue, the applicant's prior patent CN2023111947146 discloses a crack-resistant honeycomb activated carbon and its preparation method. This method utilizes polyisocyanate, polydiol monoether, and a blocking agent to prepare an aqueous blocked isocyanate, which is stable in water at room temperature and can be deblocked at high temperatures to obtain active isocyanate. The wet preform of the honeycomb activated carbon containing this aqueous blocked isocyanate needs to be deblocked and preliminarily dried and shaped at a high temperature of 120-150℃, and then further crosslinked and dried in hot air at 60-80℃. During this process, the deblocked isocyanate reacts with surrounding water-soluble hydroxycellulose compounds, hydroxyl groups on hydrophilic fumed silica, and water to form a urea-based crosslinked three-dimensional network structure that can resist the capillary pressure of water evaporation, preventing deformation and cracking during hot air drying and improving the yield.

[0006] Water-soluble hydroxycellulose compounds are compounds that can dissolve in water and form pseudo-plastic solutions. Although they can dissolve in water over a wide temperature range, they will gradually decompose into small molecular segments above 100°C, resulting in unsuccessful shaping or damage to the network structure. As a result, the yield of the final hot-air dried product is still low and needs to be improved.

[0007] Using polyvinyl alcohol (PVA), an organic binder, to conventionally replace water-soluble hydroxycellulose compounds also presents certain problems: Due to the temperatures exceeding 100℃ during the initial unsealing and preliminary shaping stages, PVA is prone to embrittlement in air at around 100℃, easily losing its activity and becoming rigid and fixed, thus reducing its plasticity. Furthermore, the high water content inside the honeycomb activated carbon in the early stages causes the PVA molecular chains to break under gravity, leading to twisting and deformation of the honeycomb activated carbon and the generation of localized internal stress. This can still cause cracks in the honeycomb activated carbon during hot air drying.

[0008] Therefore, it is necessary to improve the prior patented technologies of water-containing blocked isocyanates and water-soluble hydroxycellulose compounds to further improve the yield of honeycomb activated carbon. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides a deformation-resistant and crack-resistant honeycomb activated carbon and its preparation method. Polydextrose and water-soluble polyether diols are used to replace water-soluble hydroxycellulose compounds. This ensures that polydextrose and water-soluble polyether diols do not degrade or become brittle during the unsealing and initial shaping stages, preventing distortion and deformation. Furthermore, they can react with the unsealed isocyanate groups. The honeycomb activated carbon, which gradually forms a urea-containing cross-linked three-dimensional network structure during unsealing and hot air drying, can resist the capillary pressure generated by water evaporation during the hot air drying process, reducing crack formation and improving yield.

[0010] A type of deformation-resistant and crack-resistant honeycomb activated carbon comprises the following raw materials: powdered activated carbon powder, hydrophilic fumed silica, water-based blocked isocyanate emulsion, polydextrose, water-soluble polyether diol, and water.

[0011] Furthermore, the deformation-resistant and crack-resistant honeycomb activated carbon comprises the following raw materials in parts by weight: 100 parts powdered activated carbon powder, 5-8 parts hydrophilic fumed silica, 18-20 parts aqueous blocked isocyanate emulsion, 1-3 parts polydextrose, 3-5 parts water-soluble polyether diol, and 40-60 parts water, wherein the total weight of the polydextrose and water-soluble polyether diol is 6-8 parts.

[0012] The number-average molecular weight of the polydextrose is 3000-5000 g / mol.

[0013] The water-soluble polyether diol has a number-average molecular weight of 300-800 g / mol and is selected from one or a combination of two of polyethylene glycol and polypropylene glycol.

[0014] The aqueous blocked isocyanate emulsion is prepared by a method comprising the following steps:

[0015] Polydiol monoethers and polyisocyanates are added to a reaction vessel, heated and kept at a constant temperature for reaction, a sealing agent is added to continue the reaction, and water is added after the reaction is completed. The mixture is stirred and dispersed into a uniform emulsion to obtain the final product.

[0016] The temperature is raised to 60-100℃, and the reaction time is 1-3 hours; after adding the blocking agent, the reaction time continues for 5-10 hours, and the solid content of the emulsion is 30-40 wt%.

[0017] The molar ratio of the polydiol monoether, polyisocyanate, and sealing agent is 1:1.08-1.1:2.0-2.1.

[0018] The polydiol monoether has a number-average molecular weight of 1000-2000 g / mol and is selected from at least one of polyethylene glycol monomethyl ether, polypropylene glycol monomethyl ether, polyethylene glycol monoethyl ether, and polypropylene glycol monoethyl ether.

[0019] The polyisocyanate is selected from one or a combination of two or more of HDI trimer, IPDI trimer, and MDI trimer.

[0020] The blocking agent is selected from one or a combination of two or more of methyl ethyl ketone oxime, 3,5-dimethylpyridine, and 2-ethylhexanol.

[0021] The specific surface area of ​​the powdered activated carbon is 1500-2000 m². 2 / g, with an average particle size of 300-500 mesh, selected from one or a combination of two or more of coal-based activated carbon, wood-based activated carbon, and fruit shell activated carbon.

[0022] The hydrophilic fumed silica has an average particle size of 5-25 nm and a specific surface area of ​​200-400 m². 2 / g.

[0023] This invention also provides a method for preparing the above-mentioned deformation-resistant and crack-resistant honeycomb activated carbon, comprising the following steps:

[0024] S1. Mix hydrophilic fumed silica, water-based blocked isocyanate emulsion, polydextrose, and water-soluble polyether diol evenly, add powdered activated carbon powder and water and mix evenly to obtain plastic mud.

[0025] S2. Add the plastic clay to the clay mixer for clay mixing, seal the clay with a film, let it stand and age, and then put it back into the clay mixer for vacuum clay mixing to obtain the clay.

[0026] S3. The clay material obtained in step S2 is extruded and molded using an extruder equipped with a honeycomb mold to obtain a honeycomb preform;

[0027] S4. The honeycomb preform is first heated to a constant temperature for reaction, and then dried in hot air to obtain honeycomb activated carbon.

[0028] The aging time in step S2 is 3-5 hours; the mud is kneaded 1-3 times before aging and 1-3 times after aging; the vacuum degree is 0.08-0.1 MPa.

[0029] In step S4, the temperature is raised to 120-150℃, the reaction time is 10-30 min, the hot air temperature is 60-80℃, and the drying time is 12-24 h.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] This invention uses polydextrose and water-soluble polyether diol to replace water-soluble hydroxycellulose compounds. This satisfies the requirement that polydextrose and water-soluble polyether diol do not degrade or become brittle during the unsealing and initial shaping stages, thus preventing distortion and deformation. At the same time, they can react with the unsealed isocyanate groups. The honeycomb activated carbon with a urea-containing cross-linked three-dimensional network structure gradually formed during the unsealing and hot air drying process can resist the capillary pressure generated by water evaporation in the hot air drying process, reduce the formation of cracks, and improve the yield. Attached Figure Description

[0032] Figure 1 The honeycomb activated carbon used in Example 1 is a qualified product.

[0033] Figure 2 The honeycomb activated carbon that fractured in Comparative Example 3 is shown. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments, but is not limited to the contents of the specification. Unless otherwise specified, all "parts" mentioned in the embodiments of the present invention are parts by weight. All reagents used are commercially available in the art.

[0035] Coal-based powdered activated carbon was purchased from Fujian Xinsen Carbon Industry Co., Ltd., with an average particle size of 500 mesh and a specific surface area of ​​1760 m². 2 / g.

[0036] Polyethylene glycol monomethyl ether was purchased from Jiangsu Dena Chemical Co., Ltd., with a number average molecular weight of 1500 g / mol.

[0037] Polydextrose was purchased from Henan Tailijie Biotechnology Co., Ltd., with a number-average molecular weight of 4600 g / mol.

[0038] Polyethylene glycol was purchased from Nantong Yuyuan New Material Technology Co., Ltd., with a number average molecular weight of 800 g / mol.

[0039] Hydroxyethyl cellulose was purchased from Hubei Zhongxiang Cellulose Co., Ltd., with a number average molecular weight of 160,000 g / mol and a molar degree of substitution of 1.6.

[0040] Preparation of aqueous blocked isocyanate emulsion

[0041] Preparation Example

[0042] 1.1 mol of dried polyethylene glycol monomethyl ether and 1 mol of HDI trimer were added to a reaction vessel, heated to 90°C and kept at a constant temperature for 2 hours. Then, 2.1 mol of the blocking agent methyl ethyl ketone oxime was added and the reaction continued for 8 hours. After the reaction was completed, water was added and stirred to disperse into a uniform emulsion with a solid content of 40 wt%.

[0043] Preparation of honeycomb activated carbon

[0044] Example 1

[0045] S1 mixes 8 parts of Degussa AEROSIL200 hydrophilic fumed silica, 20 parts of the aqueous blocked isocyanate emulsion prepared in the preparation example, 3 parts of polydextrose, and 5 parts of polyethylene glycol evenly, then adds 100 parts of coal-based powdered activated carbon and water and mixes evenly to obtain plastic slurry.

[0046] S2 adds plastic clay to a clay mixer for two clay mixing cycles. After sealing the clay with a film, it is left to stand and age. Then it is put back into the clay mixer for three vacuum clay mixing cycles at a vacuum degree of 0.1MPa.

[0047] S3 uses an extruder equipped with a honeycomb mold to extrude the mud material finally obtained in step S2 at 15MPa to obtain a honeycomb preform;

[0048] S4 first heats the honeycomb preform to 130℃ and reacts at a constant temperature for 30 minutes, then dries it in hot air at 80℃ for 24 hours to obtain a dried honeycomb preform with 200 pores, an outer wall thickness of 0.8 mm, an inner wall thickness of 0.5 mm, a diameter of 29 mm, and a length of 100 mm.

[0049] Example 2

[0050] The rest is the same as in Example 1, except that the amount of polyethylene glycol used is 3 parts.

[0051] Example 3

[0052] The rest is the same as in Example 1, except that the amount of polydextrose used is 1 part.

[0053] Example 4

[0054] The rest is the same as in Example 1, except that the amount of the aqueous blocked isocyanate emulsion prepared in the preparation example is 18 parts.

[0055] Comparative Example 1

[0056] The rest is the same as in Example 1, except that polydextrose is not added and the amount of water-soluble polyether diol is 8 parts.

[0057] Comparative Example 2

[0058] The rest is the same as in Example 1, except that no water-soluble polyether diol is added, and the amount of polydextrose is 8 parts.

[0059] Comparative Example 3

[0060] The rest is the same as in Example 1, except that water-soluble polyether diol and polydextrose are not added, and 8 parts of hydroxyethyl cellulose are added.

[0061] The honeycomb activated carbon prepared in the above examples and comparative examples was subjected to the following performance tests:

[0062] 1. Yield: 100 samples were prepared for each example. The final honeycomb activated carbon was visually inspected for cracks on the wall and end face. Those without cracks were considered qualified products. The yield was calculated as the proportion of qualified products to the total number of samples.

[0063] 2. Compressive strength: Tested in accordance with standard GB / T 5072-2008.

[0064] 3. Activated carbon butane working performance: The test was conducted according to the standard test method for determining the working capacity of activated carbon butane, ASTM D5228-2016.

[0065] 4. Iodine adsorption performance: The iodine adsorption value was determined according to the standard GB / T 12496.8-2015 Test Method for Wood-based Activated Carbon. The iodine adsorption value reflects the degree of micropore development and is a measure of the activated carbon's ability to adsorb small molecule impurities.

[0066] Table 1

[0067] project Finished Product Rate % compressive strength (MPa) Butane working capacity g / 100mL Iodine value (mg / g) Example 1 95 4.1 13.5 625 Example 2 92 4.0 13.4 630 Example 3 88 3.6 13.8 641 Example 4 90 3.8 13.7 626 Comparative Example 1 66 1.9 12.8 633 Comparative Example 2 73 2.4 13.3 629 Comparative Example 3 83 3.6 14.1 707

[0068] As shown in Table 1, replacing water-soluble hydroxycellulose compounds with polydextrose and water-soluble polyether diols not only prevents degradation or embrittlement leading to distortion and deformation during the unsealing and initial shaping stages, but also allows them to react with the unsealed isocyanate groups. The honeycomb activated carbon with a urea-containing cross-linked three-dimensional network structure gradually formed during unsealing and hot air drying can resist the capillary pressure generated by water evaporation in the hot air drying process, reducing crack formation and improving yield. Furthermore, the iodine value test results show that using polydextrose and water-soluble polyether diols causes a decrease in iodine value, presumably because polydextrose and water-soluble polyether diols are more likely to clog micropores, resulting in a decrease in the number of micropores.

[0069] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

Claims

1. A type of honeycomb activated carbon that is resistant to deformation and cracking, characterized in that, The raw materials include the following parts by weight: 100 parts powdered activated carbon powder, 5-8 parts hydrophilic fumed silica, 18-20 parts aqueous blocked isocyanate emulsion, 1-3 parts polydextrose, 3-5 parts water-soluble polyether diol, and 40-60 parts water, wherein the total weight of the polydextrose and water-soluble polyether diol is 6-8 parts; the aqueous blocked isocyanate emulsion is prepared by a method including the following steps: adding polydiol monoether and polyisocyanate to a reaction vessel, heating and maintaining the temperature for reaction, adding a blocking agent to continue the reaction, and adding water after the reaction is completed. The method for preparing the deformation-resistant and crack-resistant honeycomb activated carbon includes the following steps: S1. Mixing hydrophilic fumed silica, water-based blocked isocyanate emulsion, polydextrose, and water-soluble polyether diol evenly, then adding powdered activated carbon powder and water and mixing evenly to obtain plastic clay; S2. Adding the plastic clay to a clay mixer for clay mixing, sealing the clay and allowing it to stand and age, then putting it back into the clay mixer for vacuum clay mixing to obtain clay; S3. Extruding the clay into shape using an extruder equipped with a honeycomb mold to obtain a honeycomb preform; S4. The honeycomb preform is first heated to a constant temperature for reaction, and then dried in hot air to obtain honeycomb activated carbon.

2. The deformation-resistant and crack-resistant honeycomb activated carbon according to claim 1, characterized in that, The number-average molecular weight of the polydextrose is 3000-5000 g / mol.

3. The deformation-resistant and crack-resistant honeycomb activated carbon according to claim 1, characterized in that, The water-soluble polyether diol has a number-average molecular weight of 300-800 g / mol and is selected from one or a combination of two of polyethylene glycol and polypropylene glycol.

4. The deformation-resistant and crack-resistant honeycomb activated carbon according to claim 1, characterized in that, In the preparation of the aqueous blocked isocyanate emulsion, the temperature is raised to 60-100℃ and the reaction time is 1-3h; after adding the blocking agent, the reaction time continues for 5-10h, and the solid content of the emulsion is 30-40wt%; the molar ratio of the polydiol monoether, polyisocyanate, and blocking agent is 1:1.08-1.1:2.0-2.

1.

5. The deformation-resistant and crack-resistant honeycomb activated carbon according to claim 1, characterized in that, The polydiol monoether has a number-average molecular weight of 1000-2000 g / mol and is selected from at least one of polyethylene glycol monomethyl ether, polypropylene glycol monomethyl ether, polyethylene glycol monoethyl ether, and polypropylene glycol monoethyl ether; the polyisocyanate is selected from one or a combination of two or more of HDI trimer, IPDI trimer, and MDI trimer; the blocking agent is selected from one or a combination of two of methyl ethyl ketone oxime and 2-ethylhexanol.

6. The deformation-resistant and crack-resistant honeycomb activated carbon according to claim 1, characterized in that, The specific surface area of ​​the powdered activated carbon is 1500-2000 m². 2 / g, with an average particle size of 300-500 mesh, selected from one or more combinations of coal-based activated carbon, wood-based activated carbon, and fruit shell activated carbon; the hydrophilic fumed silica has an average particle size of 5-25 nm and a specific surface area of ​​200-400 m². 2 / g.

7. A method for preparing the deformation-resistant and crack-resistant honeycomb activated carbon as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Mix hydrophilic fumed silica, water-based blocked isocyanate emulsion, polydextrose, and water-soluble polyether diol evenly, add powdered activated carbon powder and water and mix evenly to obtain plastic mud. S2. Add the plastic clay to the clay mixer for clay mixing, seal the clay with a film, let it stand and age, and then put it back into the clay mixer for vacuum clay mixing to obtain the clay. S3. The clay material obtained in step S2 is extruded and molded using an extruder equipped with a honeycomb mold to obtain a honeycomb preform; S4. The honeycomb preform is first heated to a constant temperature for reaction, and then dried in hot air to obtain honeycomb activated carbon.

8. The method for preparing deformation-resistant and crack-resistant honeycomb activated carbon according to claim 7, characterized in that, In step S4, the temperature is raised to 120-150℃, the reaction time is 10-30 min, the hot air temperature is 60-80℃, and the drying time is 12-24 h.

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