A method for making a monolithic honeycomb cordierite support

Abstract

The application discloses a preparation method of a monolithic honeycomb cordierite carrier, and comprises the following steps: (1) a honeycomb cordierite base A is immersed into alumina sol containing a physical pore expander to perform first coating, then drying, and baking under an inert atmosphere to obtain a first-coated base B; (2) the base B is immersed into an aqueous propylene oxide solution, and then the reaction is performed in a sealed reaction kettle, and then drying treatment is performed to obtain a base C; and (3) the base C is immersed into alumina sol to perform second coating, then drying is performed, and baking treatment is performed in an oxygen-containing atmosphere to obtain the monolithic honeycomb cordierite carrier. The carrier coating has a stepped pore distribution, the coating firmness is high, the preparation process is simple, and the monolithic honeycomb cordierite carrier is beneficial to practical industrial application.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of a monolithic honeycomb cordierite carrier. BACKGROUND

[0002] Compared with general blocky ceramics, monolithic honeycomb cordierite is particularly suitable for catalyst carriers for various purposes due to its stable performance, low expansion coefficient, high void ratio, low pressure drop and high geometric surface area, and has a broad application prospect in the fields of chemical industry, environmental protection, metallurgy, electronics, automobiles and the like. 2 The surface of cordierite honeycomb ceramic carrier is relatively smooth, and the specific surface area is very small (<1 m

[0003] The catalyst prepared from monolithic cordierite material is widely used in the removal of nitrides, sulfides and organic volatile substances, and the main reason for catalyst deactivation is that a large number of submicron particles with different particle sizes in various pollutants, such as alkali metals, alkaline earth metals and heavy metals, are easily enriched on particles with a size of tens of nanometers to several microns, deposited on the surface of the catalyst, causing catalyst poisoning and catalyst channel blockage, which are the key factors affecting catalyst deactivation. Therefore, the coating generally needs to have micropores, mesopores and macropores at the same time to provide more effective dust holding space and prevent catalyst poisoning. In the existing monolithic cordierite loading coating process, multiple coating, drying and calcination processes are generally required, and then the next coating is performed, and finally calcination is performed, so that the gas phase in the carrier expands instantaneously and is discharged, thereby causing more cracks on the surface of the coating and reducing the firmness. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a preparation method of a monolithic honeycomb cordierite carrier. The carrier coating has a hierarchical pore distribution, high coating firmness, and a simple preparation process, which is beneficial to practical industrial application.

[0005] The preparation method of the monolithic honeycomb cordierite carrier of the present application comprises the following contents:

[0006] (1) The honeycomb cordierite base A is immersed in an alumina sol containing a physical hole expander for one-time coating, and then dried and calcined in an inert atmosphere to obtain a one-time coated base B;

[0007] (2) The base B is immersed in an epoxy propane aqueous solution, and reacted in a sealed reaction kettle, and then dried to obtain a base C;

[0008] (3) the substrate C is immersed into the alumina sol for secondary coating, then dried, and calcined in an oxygen-containing atmosphere to obtain the monolithic honeycomb cordierite carrier.

[0009] In the method, after the primary and secondary coating, the surface and the inside of the pores are blown by compressed air to remove the excess sol or slurry, and then dried and calcined after confirming that the inside of the pores is not blocked.

[0010] In the method, the solid content of the alumina sol in the alumina sol containing the physical pore-expanding agent in step (1) is 10wt%-20wt% in terms of alumina, the physical pore-expanding agent is spherical activated carbon with a diameter of 1-5μm, and the addition amount of the physical pore-expanding agent is 1wt%-5wt% based on the mass of the alumina sol.

[0011] In the method, the immersion time in step (1) is 3-30 minutes, and the addition amount of the alumina sol containing the physical pore-expanding agent needs to be able to immerse the honeycomb cordierite substrate A.

[0012] In the method, the drying temperature in step (1) is 100-160℃, the drying time is 2-10 hours, the calcination temperature is 450-650℃, and the calcination time is 4-10 hours; and the inert atmosphere is nitrogen and / or inert gas, preferably nitrogen.

[0013] In the method, the mass percentage concentration of the propylene oxide aqueous solution in step (2) is 2.5%-12%, preferably 4%-8%, the mass ratio of the propylene oxide aqueous solution to the substrate B is 3:1-10:1, preferably 4:1-8:1.

[0014] In the method, the reaction in step (2) is first carried out at 60-100℃ for 1-4 hours, then heated to 110-180℃, preferably 120-160℃, and the treatment time is 4-8 hours, and the reaction pressure is autogenous pressure.

[0015] In the method, the drying temperature in step (2) is 100-140℃, and the drying time is 4-10 hours.

[0016] In the method, the alumina sol in step (3) is the same as that in step (1), except that no physical pore-expanding agent is added.

[0017] In the method, the immersion time for the secondary coating in step (3) is 3-30 minutes, and the addition amount of the alumina sol needs to be able to immerse the substrate C.

[0018] In the method, the drying temperature in step (3) is 100-160℃, and the drying time is 4-20 hours. The calcination temperature is 400-750℃, and the calcination time is 4-10 hours. The calcination is carried out in an oxygen-containing atmosphere, preferably in an air atmosphere.

[0019] The integral honeycomb cordierite carrier of the application is applied in selective catalytic reduction, catalytic oxidation, hydrogenation reaction and dehydrogenation reaction.

[0020] Compared with the prior art, the application has the following advantages:

[0021] First, a layer of sol containing a physical pore-expanding agent (micron-sized spherical activated carbon) is coated on the honeycomb cordierite substrate, and the coating layer retains the pore-expanding agent after calcination in an inert atmosphere. Then, the coating layer is reacted in an aqueous propylene oxide solution, so that worm-like pseudo-boehmite grows on the surface of the coating layer, and the worm-like pseudo-boehmite accumulates to form pores of tens to hundreds of nanometers. The interaction between the coating layer and the worm-like pseudo-boehmite is further enhanced during the hydrothermal process, thereby improving the stability of the coating layer. After drying treatment, the coating layer is subjected to secondary coating, and the worm-like pseudo-boehmite is combined with the alumina sol tightly, thereby ensuring the amount and bonding degree of the secondary coating. Then, the pore-expanding agent is removed by calcination again, so that the coating layer has abundant nanometer- to micron-sized spherical cavity pores, and the honeycomb cordierite has excellent permeability and high impurity capacity. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A scanning electron microscope (SEM) photograph of the substrate C of Example 1.

[0023] Figure 2 A scanning electron microscope (SEM) photograph of the internal cross section of the carrier of Example 1. DETAILED DESCRIPTION

[0024] The application will be further described below with reference to the examples, but the application is not limited to the following examples. The concentration of the acid solution in the examples is a mass percentage concentration. In the examples, honeycomb cordierite is selected, cut into a cuboid of 30mm x 30mm x 45mm, and subjected to compressed air to remove the powder remaining during cutting for standby use.

[0025] The microstructure of the alumina carrier is characterized by a scanning electron microscope, and the specific operation is as follows: the microstructure of the carrier is characterized by a JSM-7500F scanning electron microscope, the acceleration voltage is 5KV, the acceleration current is 20µA, and the working distance is 8mm.

[0026] The preparation method of the alumina sol is known in the art, which generally comprises uniformly mixing pseudo-boehmite with a certain volume of distilled water, then adding a certain acid solution such as nitric acid solution under stirring, and continuing to stir for 1-5 hours to obtain an aluminum sol. Example 1

[0027] (1) The cut honeycomb cordierite matrix A cuboid is immersed in 3wt% activated carbon microspheres (1-5 microns) alumina sol (solid content 15wt%) for 10 minutes, the residual liquid is blown away with compressed air, then dried at 120℃ for 4 hours, calcined at 500℃ under nitrogen atmosphere for 8 hours, to obtain the first coated matrix B;

[0028] (2) The matrix B is immersed in a reaction kettle containing 5.5wt% propylene oxide aqueous solution, and the reaction is carried out after being sealed, the mass ratio of propylene oxide aqueous solution to matrix B is 5:1; first react at 85℃ for 1 hour, then heat to 160℃ for 5 hours, then take out after cooling, dry at 120℃ for 8 hours, to obtain matrix C;

[0029] (3) The matrix C is immersed in alumina sol (solid content 15wt%) for 8 minutes, taken out, the residual liquid is blown away with compressed air, then dried at 120℃ under air atmosphere for 10 hours, calcined at 600℃ for 5 hours, to obtain the whole honeycomb cordierite carrier. Example 2

[0030] (1) The cut honeycomb cordierite matrix A cuboid is immersed in 2wt% activated carbon microspheres (1-5 microns) alumina sol (solid content 12wt%) for 8 minutes, the residual liquid is blown away with compressed air, then dried at 120℃ for 4 hours, calcined at 500℃ under nitrogen atmosphere for 8 hours, to obtain the first coated matrix B;

[0031] (2) The matrix B is immersed in a reaction kettle containing 4.5wt% propylene oxide aqueous solution, and the reaction is carried out after being sealed, the mass ratio of propylene oxide aqueous solution to matrix B is 6:1; first react at 80℃ for 1 hour, then heat to 140℃ for 6 hours, then take out after cooling, dry at 120℃ for 8 hours, to obtain matrix C;

[0032] (3) The matrix C is immersed in alumina sol (solid content 12wt%) for 8 minutes, taken out, the residual liquid is blown away with compressed air, then dried at 120℃ under air atmosphere for 10 hours, calcined at 550℃ for 5 hours, to obtain the whole honeycomb cordierite carrier. Example 3

[0033] (1) The cut honeycomb cordierite matrix A cuboid is immersed in 4wt% activated carbon microspheres (1-5 microns) alumina sol (solid content 18wt%) for 10 minutes, the residual liquid is blown away with compressed air, then dried at 120℃ for 5 hours, calcined at 550℃ under nitrogen atmosphere for 6 hours, to obtain the first coated matrix B;

[0034] (2) The substrate B was immersed in a reactor containing 7 wt% propylene oxide aqueous solution and reacted after being sealed, the mass ratio of propylene oxide aqueous solution to substrate B was 8:1; first reacted at 100°C for 1 hour, then heated to 155°C for 5 hours, then cooled and taken out, the residual liquid was blown off with compressed air, and dried at 120°C for 8 hours to obtain substrate C;

[0035] (3) The substrate C was immersed in alumina sol (solid content 18 wt%) for 5 minutes, taken out, the residual liquid was blown off with compressed air, then dried at 120°C for 10 hours under air atmosphere, and calcined at 600°C for 5 hours to obtain the monolithic honeycomb cordierite carrier.

[0036] Comparative Example 1

[0037] The same as Example 1, except that the propylene oxide aqueous solution was replaced by an ethylene oxide aqueous solution with the same concentration, and the worm-like structure was not formed on the surface of the coating of substrate C.

[0038] Comparative Example 2

[0039] The same as Example 1, except that the reaction condition in step (2) was changed to 100°C for 6 hours, and the worm-like structure was not formed on the surface of the coating of substrate C.

[0040] Comparative Example 3

[0041] The same as Example 1, except that the substrate C obtained in step (2) was calcined at 550°C for 3 hours. Example 4

[0042] The loadings of the coatings and the binding strength between the coatings and the carriers were investigated. The coating firmness test: an appropriate amount of the coated honeycomb sample was placed in a beaker containing deionized water, the beaker was placed in an ultrasonic instrument (power 100W, frequency 40kHz) and oscillated for 20 minutes, then the sample was taken out, the water in the pores of the sample was blown out, and then dried at 120°C and 300°C for 2 hours respectively. The firmness calculation formula: the shedding rate V = (m3-m4) / (ml-m2) x 100%, wherein m3 is the mass of the sample before ultrasonic, m4 is the mass of the sample after ultrasonic, (ml-m2) is the loading of the coating, and the shedding rates of the coatings are shown in Table 1.

[0043] Table 1 Properties of the product coatings.

Claims

1. A method for making a monolithic honeycomb cordierite support body, characterized by The method comprises the following steps: (1) immersing the honeycomb cordierite matrix A into alumina sol containing a physical pore-expanding agent for primary coating, then drying, and calcining in an inert atmosphere to obtain a primary coated matrix B; (2) immersing the matrix B into an aqueous propylene oxide solution, and reacting in a sealed reactor, then drying to obtain a matrix C; (3) immersing the matrix C into alumina sol for secondary coating, then drying, and calcining in an oxygen-containing atmosphere to obtain a monolithic honeycomb cordierite carrier; in step (1), the solid content of the alumina sol in the alumina sol containing a physical pore-expanding agent is 10wt%-20wt% in terms of alumina, the physical pore-expanding agent is spherical activated carbon with a diameter of 1-5 μm, and the addition amount of the physical pore-expanding agent is 1wt%-5wt% based on the mass of the alumina sol; in step (2), the reaction is first carried out at 60-100 ℃ for 1-4 hours, then the temperature is raised to 110-180 ℃, and the reaction is carried out for 4-8 hours at the reaction pressure of autogenous pressure.

2. The method of claim 1, wherein: After the primary and secondary coating, compressed air is used to blow off the excess sol or slurry adsorbed on the surface and in the pores, and then drying and calcining are carried out after it is determined that the pores are not blocked.

3. The method of claim 1, wherein: In step (1), the drying temperature is 100-160 ℃, the drying time is 2-10 hours, the calcining temperature is 450-650 ℃, and the calcining time is 4-10 hours; the inert atmosphere is nitrogen and / or an inert gas.

4. The method of claim 1, wherein: In step (2), the mass percentage concentration of the aqueous propylene oxide solution is 2.5%-12%, and the mass ratio of the aqueous propylene oxide solution to the matrix B is 3:1-10:

1.

5. The method of claim 1, wherein: In step (2), the mass percentage concentration of the aqueous propylene oxide solution is 4%-8%.

6. The method of claim 1, wherein: In step (2), the mass ratio of the aqueous propylene oxide solution to the matrix B is 4:1-8:

1.

7. The method of claim 1, wherein: In step (2), the reaction is first carried out at 60-100 ℃ for 1-4 hours, then the temperature is raised to 120-160 ℃, and the reaction is carried out for 4-8 hours at the reaction pressure of autogenous pressure.

8. The method of claim 1, wherein: In step (2), the drying temperature is 100-140 ℃, and the drying time is 4-10 hours.

9. The method of claim 1, wherein: In step (3), the immersion time for the secondary coating is 3-30 minutes, and the addition amount of the alumina sol needs to be able to immerse the matrix C.

10. The method of claim 1, wherein: In step (3), the drying temperature is 100-160 ℃, the drying time is 4-20 hours, the calcining temperature is 400-750 ℃, and the calcining time is 4-10 hours.

11. The monolithic honeycomb cordierite carrier prepared by the method according to any one of claims 1-10 is used in selective catalytic reduction, catalytic oxidation, hydrogenation reaction, and dehydrogenation reaction.

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