A monolithic honeycomb cordierite carrier and preparation method thereof

Abstract

The invention discloses a monolithic honeycomb cordierite carrier and a preparation method thereof, comprising a honeycomb cordierite and an alumina coating, wherein the cordierite content is 75wt%-95wt%, and the alumina coating content is 5wt%-25wt%; the alumina coating is a flaky particle, the flaky particle size is 100-300nm, the thickness is 30-100nm, and the flaky particles are stacked to form a 10-200nm pore. The preparation method of the monolithic honeycomb cordierite carrier of the present invention comprises: (1) impregnating the pretreated cordierite with an aluminum salt solution, and drying and calcining the impregnated cordierite to obtain an aluminum-loaded cordierite; (2) immersing the aluminum-loaded cordierite in step (1) in a propylene oxide solution for sealed hydrothermal treatment, and drying and calcining the material after the hydrothermal treatment to obtain a monolithic honeycomb cordierite carrier. The aluminum oxide particles on the surface of the monolithic honeycomb cordierite carrier of the present invention are in a flaky structure, which can effectively improve the permeability of the carrier pores. The coating is firmly bonded to the carrier surface and is suitable for use as a carrier for catalysts such as flue gas denitration and catalyst combustion.

Description

Technical Field

[0001] The invention relates to the field of inorganic material preparation, and in particular to an integral honeycomb cordierite carrier and a preparation method thereof. Background Art

[0002] NOx in flue gas is one of the main sources of atmospheric pollution, causing serious harm to the environment and human health. 3 Selective catalytic reduction (SCR) of NO is considered to be the most economical and effective method for flue gas denitrification. Cordierite honeycomb ceramics are widely used as catalyst carriers due to their unique properties, but because they are extruded and calcined at above 1300°C, their specific surface area is small. The specific surface area of ​​the carrier directly determines the number of active centers of the catalyst, thus affecting the catalytic activity of the catalyst. Therefore, the specific surface area of ​​cordierite honeycomb ceramics must be increased.

[0003] Hua Jinming et al. studied the effect of acid etching pretreatment on honeycomb cordierite and its alumina coating by different methods (Molecular Catalysis, 2006, 20 (6): 550-555).

[0004] Liu Qingya et al. studied the coating of Al 2 O 3 Selective catalytic reduction of NO with NH3 over honeycomb cordierite supported CuO catalyst (Chinese Journal of Catalysis, 2005, 26(1): 59-64)

[0005] Conventional alumina particles are spherical in shape. The pores formed by the accumulation of spherical particles are small, which seriously affects the diffusion of the reaction raw materials. At the same time, metal impurities and dust particles generated in the reaction are easily deposited on the coating surface, blocking the surface pores and thus affecting the operation cycle of the catalyst. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a monolithic honeycomb cordierite carrier and a preparation method thereof. The monolithic honeycomb cordierite carrier of the present invention has a flaky alumina particle on its surface, which can effectively improve the permeability of the carrier pores, and the coating is firmly bonded to the carrier surface, and is suitable for use as a carrier for catalysts such as flue gas denitration and catalyst combustion.

[0007] The monolithic honeycomb cordierite carrier of the present invention comprises honeycomb cordierite and an alumina coating. Based on the weight of the carrier, the cordierite content is 75wt%-95wt%, and the alumina coating content is 5wt%-25wt%; the alumina coating is a flaky particle, the flaky particle size is 100-300nm, the thickness is 30-100nm, and the flaky particles are accumulated to form 10-200nm pores.

[0008] The monolithic honeycomb cordierite carrier prepared by the method of the present invention has a specific surface area of ​​45-120m 2 / g, the pore volume is 0.2-0.7mL / g, and the pores of 50-150nm account for 30%-55% of the total pore volume.

[0009] The method for preparing the monolithic honeycomb cordierite carrier of the present invention comprises:

[0010] (1) impregnating the pretreated cordierite with an aluminum salt solution, and drying and calcining the impregnated cordierite to obtain aluminum-loaded cordierite;

[0011] (2) The aluminum-loaded cordierite prepared in step (1) is immersed in a propylene oxide solution for sealed hydrothermal treatment. After the hydrothermal treatment, the material is dried and calcined to obtain a monolithic honeycomb cordierite carrier.

[0012] In the method of the present invention, the aluminum salt solution in step (1) is an aqueous solution of aluminum nitrate, aluminum chloride, or aluminum sulfate, preferably an aluminum nitrate solution, and the mass concentration of aluminum salt in the solution is 20%-70%. The amount of solution used is to completely immerse the cordierite. The immersion time is 0.5-2 hours, and the immersion can be performed once or multiple times as needed, preferably multiple times, and the number of immersions is preferably 2 times or more. When multiple immersions are used, drying and roasting treatments are required after each immersion.

[0013] In the method of the present invention, the drying temperature in step (1) is 100-160° C., the drying time is 2-10 hours, the roasting temperature is 450-600° C., and the roasting time is 4-10 hours.

[0014] In the method of the present invention, the pre-treated cordierite in step (1) generally refers to the cordierite soaked in an acidic solution, wherein the acidic solution may be an organic acid such as oxalic acid, lemonade, or acetic acid, or an inorganic acid such as nitric acid, hydrochloric acid, or sulfuric acid, and the mass concentration of the acidic solution is 1%-10%, preferably nitric acid. The soaking time is 0.5-2 hours, and after soaking, the cordierite is washed and dried, the drying temperature is 60-160°C, and the drying time is 1-6 hours.

[0015] In the method of the present invention, the mass percentage concentration of the propylene oxide aqueous solution in step (2) is 2.5%-12%, preferably 4%-8%, and the mass ratio of the propylene oxide aqueous solution to the aluminum-loaded cordierite is 3:1-10:1, preferably 4:1-8:1. More preferably, polyethylene glycol 2000-20000 is added to the propylene oxide aqueous solution at the same time, and the mass ratio of the polyethylene glycol 2000-20000 to the aluminum-loaded cordierite is 0.01:1-0.05:1.

[0016] In the method of the present invention, the sealed hydrothermal treatment in step (2) is carried out in a sealed container, which is preferably an autoclave, with a treatment temperature of 110-180° C., preferably 120-160° C., and a treatment time of 4-8 hours. During the hydrothermal treatment, the pressure in the sealed container is autogenous pressure.

[0017] In the method of the present invention, the drying temperature in step (2) is 100-160° C., and the drying time is 2-10 hours; the roasting temperature is 450-650° C., and the roasting time is 4-10 hours.

[0018] The monolithic honeycomb cordierite carrier of the present invention is used in the field of flue gas denitration and catalytic combustion.

[0019] Compared with the prior art, the surface alumina of the integral honeycomb cordierite carrier prepared by the present invention is a flaky structure, which effectively increases the specific surface area of ​​the carrier while the flaky particles accumulate to form 10-200nm channels. The channel structure is beneficial to the diffusion of reactant molecules, increases the contact area between the reactant molecules and the carrier, and improves the anti-clogging ability of the channels. In addition, the flaky particles grow epitaxially on the cordierite surface, and compared with the coating method, the combination with the carrier is more firmly. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a scanning electron microscope image of the carrier S1 prepared in Example 1.

[0021] FIG2 is a scanning electron microscope image of carrier S2 prepared in Comparative Example 1. DETAILED DESCRIPTION

[0022] The technical scheme and technical effects of the present invention are further illustrated below in conjunction with embodiments, but are not limited to the following embodiments.

[0023] Application N 2 The physical adsorption-desorption method was used to characterize the pore structure of the samples of the embodiment and the comparative example. The specific operation was as follows: ASAP-2420 N 2 Physical adsorption-desorption instrument was used to characterize the pore structure of the sample. A small amount of sample was vacuum treated at 300℃ for 3-4 hours, and finally the product was placed in liquid nitrogen low temperature (-200℃) for nitrogen adsorption-desorption test. The specific surface area was obtained according to the BET equation, and the pore size distribution and pore volume were obtained according to the BJH model.

[0024] The microstructure of the sample was characterized by scanning electron microscopy. The specific operation was as follows: The microstructure of the sample was characterized by a JSM-7500F scanning electron microscope, with an accelerating voltage of 5KV, an accelerating current of 20µA, and a working distance of 8mm. The longest distance between the two ends of the alumina grain was measured as the size of the flake alumina grain.

[0025] Cordierite pretreatment: The cordierite honeycomb ceramic was completely immersed in a 4.5wt% nitric acid solution for 2 hours, and then taken out and rinsed with deionized water for 3 times, and placed in an oven at 130°C and dried for 10 hours to pretreat the cordierite.

[0026] Example 1

[0027] The pretreated cordierite was immersed in a 35% aluminum nitrate solution for 1 hour, the impregnated cordierite was drained of water, dried at 110°C for 4 hours, and calcined at 500°C for 5 hours. The calcined cordierite was cooled and immersed in a 40% aluminum nitrate solution for 1.2 hours, the impregnated cordierite was drained of water, dried at 110°C for 4 hours, and calcined at 500°C for 5 hours to obtain aluminum-loaded cordierite.

[0028] 100 g of the aluminum-loaded cordierite was weighed, 640 g of a 5.5% propylene oxide solution was added, the mixture was transferred into an autoclave and sealed, and heated at 130° C. for 6.5 hours. The treated material was filtered, dried at 110° C. for 5 hours, and calcined at 550° C. for 6 hours to obtain the monolithic honeycomb cordierite carrier S1 of the present invention. The scanning electron microscope image of the carrier surface is shown in FIG. Figure 1 The properties of the carrier are shown in Table 1.

[0029] Example 2

[0030] The same as Example 1, except that the concentration of aluminum nitrate was 45% during the first impregnation with aluminum salt solution, and the concentration of the solution was 30% during the second impregnation with aluminum salt solution. The amount of propylene oxide used during the sealed heat treatment was 510 g, and the mass concentration of the solution was 6.7%. The heat treatment temperature was 140° C., and the treatment time was 5 hours. The monolithic honeycomb cordierite carrier S2 of the present invention was obtained. The properties of the carrier are shown in Table 1.

[0031] Example 3

[0032] The same as Example 1, except that the aluminum salt was impregnated once, aluminum nitrate was replaced by aluminum chloride, and the mass concentration of the solution was 55%. The amount of propylene oxide used during the sealed heat treatment was 750 grams, and the mass concentration of the solution was 4.3%. The heat treatment temperature was 120°C, and the treatment time was 7 hours, to obtain the monolithic honeycomb cordierite carrier S3 of the present invention, and the properties of the carrier are shown in Table 1.

[0033] Example 4

[0034] The same as Example 1, except that the aluminum salt was impregnated once, and the mass concentration of the aluminum nitrate solution was 65%. The amount of propylene oxide used during the sealed heat treatment was 420 grams, the mass concentration of the solution was 7.2%, and 1.5 grams of polyethylene glycol-18000 was added to the solution at the same time. The heat treatment temperature was 155°C, and the treatment time was 4.5 hours. The monolithic honeycomb cordierite carrier S4 of the present invention was obtained. The properties of the carrier are shown in Table 1.

[0035] Comparative Example 1

[0036] The same as Example 1, except that the propylene oxide solution was replaced with distilled water, to obtain a comparative carrier S5. No flaky aluminum oxide grains were observed on the carrier surface. The scanning electron microscope image of the carrier surface is shown in FIG. Figure 2 The properties of the carrier are shown in Table 1.

[0037] Comparative Example 2

[0038] The same method as Example 1 was used, except that the propylene oxide solution was replaced with an ethylene oxide solution to prepare a comparative carrier S6. No flaky aluminum oxide grains were observed on the surface of the carrier. The properties of the carrier are shown in Table 1.

[0039] Comparative Example 3

[0040] The same method as Example 1 was used, except that the mass concentration of the propylene oxide solution was 1.5%. A comparative carrier S7 was prepared. No flaky aluminum oxide grains were observed on the surface of the carrier. The properties of the carrier are shown in Table 1.

[0041] Comparative Example 4

[0042] The same method as Example 1, except that the heat treatment temperature was 90°C, was used to prepare a comparative carrier S8. No flaky aluminum oxide grains were observed on the surface of the carrier. The properties of the carrier are shown in Table 1.

[0043] Table 1 Carrier properties

[0044]

[0045] It can be seen from Table 1 that the monolithic honeycomb cordierite carrier prepared by the method of the present invention has a high specific surface area and macropore content. Figure 1 and Figure 2 It is found through observation that the aluminum oxide grains on the surface of the carrier prepared by the method of the present invention are in a flaky structure, which enables the carrier to have a higher specific surface area and macropore content.

[0046] Example 5

[0047] This example investigates the bonding strength between the alumina coating and the cordierite support.

[0048] Coating bonding strength test: Take an appropriate amount of the carrier samples prepared in the embodiments and comparative examples and place them in a beaker filled with deionized water. The beaker is placed in an ultrasonic instrument (power 150 W, frequency 50 kHz) and oscillated for 30 minutes and then taken out. After shaking, the carrier is washed three times with deionized water and then dried at 120°C and 250°C for 2 hours respectively.

[0049] The shedding rate V=(m1-m2) / (m3-m4)×100%, where m1 is the mass of the sample before ultrasound, m2 is the mass of the sample after ultrasound, and (m3-m4) is the coating loading. The shedding rates of each coating are shown in Table 2.

[0050] Table 2 Coating shedding rate

[0051] Carrier S1 S2 S3 S4 S5 S6 S7 S8 Dropout rate, % 1.11 0.91 0.74 1.04 0.65 0.71 0.74 0.68

[0052] It can be seen from the surface data that the carrier alumina coating prepared by the method of the present invention is firmly bonded to the cordierite substrate and is suitable for use as a carrier material.

Claims

1. A monolithic honeycomb cordierite carrier, comprising honeycomb cordierite and an alumina coating, Features: Based on the weight of the carrier, the cordierite content is 75wt%-95wt%, and the alumina coating content is 5wt%-25wt%; the alumina coating is flaky particles, the flaky particles have a size of 100-300nm, a thickness of 30-100nm, and the flaky particles are accumulated to form 10-200nm pores; The preparation method of the monolithic honeycomb cordierite carrier comprises the following contents: (1) impregnating the pretreated cordierite with an aluminum salt solution, and drying and calcining the impregnated cordierite to obtain aluminum-loaded cordierite; (2) immersing the aluminum-loaded cordierite in step (1) in a propylene oxide solution for sealed hydrothermal treatment, and drying and calcining the hydrothermally treated material to obtain a monolithic honeycomb cordierite carrier; The aluminum salt mass concentration in the aluminum salt solution of step (1) is 20%-70%; the immersion time of step (1) is 0.5-2 hours; The mass percentage concentration of the propylene oxide solution in step (2) is 4%-8%; The sealed hydrothermal treatment in step (2) is carried out in a sealed container at a treatment temperature of 110-180° C. for a treatment time of 4-8 hours.

2. The monolithic honeycomb cordierite carrier according to claim 1, Features: Specific surface area is 45-120m 2 / g, the pore volume is 0.2-0.7mL / g, and the pores of 50-150nm account for 30%-55% of the total pore volume.

3. A method for preparing the monolithic honeycomb cordierite carrier according to claim 1 or 2, Features The method comprises the following steps: (1) impregnating pretreated cordierite with an aluminum salt solution, drying and calcining the impregnated cordierite to obtain aluminum-loaded cordierite; (2) immersing the aluminum-loaded cordierite in step (1) in a propylene oxide solution for sealed hydrothermal treatment, drying and calcining the hydrothermally treated material to obtain a monolithic honeycomb cordierite carrier; The aluminum salt mass concentration in the aluminum salt solution of step (1) is 20%-70%; the immersion time of step (1) is 0.5-2 hours; The mass percentage concentration of the propylene oxide solution in step (2) is 4%-8%; The sealed hydrothermal treatment in step (2) is carried out in a sealed container at a treatment temperature of 110-180° C. for a treatment time of 4-8 hours.

4. The method according to claim 3, Features: The aluminum salt solution in step (1) is an aqueous solution of aluminum nitrate, aluminum chloride or aluminum sulfate. The amount of solution used is such that the cordierite is completely immersed, and the immersion is performed once or multiple times.

5. The method according to claim 3, Features: The drying temperature in step (1) is 100-160°C, the drying time is 2-10 hours, the roasting temperature is 450-600°C, and the roasting time is 4-10 hours.

6. The method according to claim 3, Features: The pretreated cordierite in step (1) is cordierite soaked in an acidic solution, wherein the acidic solution is one or more of oxalic acid, lemonade, acetic acid, nitric acid, hydrochloric acid or sulfuric acid, and the mass concentration of the acid solution is 1%-10%; the soaking time is 0.5-2 hours.

7. The method according to claim 3, Features: The mass ratio of the propylene oxide solution used in step (2) to the aluminum-loaded cordierite is 3:1-10:

1.

8. The method according to claim 3, Features: Polyethylene glycol 2000-20000 is added to the propylene oxide solution, and the mass ratio of the added amount of polyethylene glycol 2000-20000 to the aluminum-loaded cordierite is 0.01:1-0.05:

1.

9. The method according to claim 3, Features: During the sealed hydrothermal treatment in step (2), the pressure inside the sealed container is the autogenous pressure.

10. The method according to claim 3, Features: The drying temperature in step (2) is 100-160°C, and the drying time is 2-10 hours; the roasting temperature is 450-650°C, and the roasting time is 4-10 hours.

11. Use of the monolithic honeycomb cordierite carrier according to claim 1 or 2 in flue gas denitrification and catalytic combustion reactions.

12. A flue gas denitrification or catalytic combustion catalyst, Features: The catalyst comprises the monolithic honeycomb cordierite carrier according to claim 1 or 2.

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