High-strength flat-plate catalyst and preparation method therefor

Abstract

The present invention relates to the technical field of catalysts. Disclosed are a high-strength flat-plate catalyst and a preparation method therefor. The technical solution thereof is the catalyst comprising the following components in parts by mass: 50-80 parts of titanium dioxide, 2-15 parts of high-viscosity kaolin, 2-10 parts of glass fibers, 2-10 parts of carbon fibers, 2-15 parts of a plasticizer, 0.5-2 parts of ammonium heptamolybdate, 0.5-2 parts of ammonium metavanadate, and 10-30 parts of water. In the present invention, the high-viscosity kaolin is prepared, and in combination with the subsequent high-temperature coating process, the adhesive force between a catalyst slurry and a stainless steel screen plate is greatly improved, thereby enhancing the stability of the catalyst, prolonging the service life of the catalyst, and improving the reaction efficiency of the catalytic.

Description

High-strength planar catalysts and their preparation methods Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a high-strength planar catalyst and its preparation method. Background Technology

[0002] Flat-plate catalysts are widely used in denitrification processes. They are characterized by using a thin stainless steel screen as the substrate, with active ingredients pressure-coated onto the screen surface. The coated catalyst sheets are then folded, cut into individual plates as required, and assembled into catalyst units. These catalyst units are then calcined and assembled into catalyst modules. This preparation process gives flat-plate catalysts significant advantages in preventing fly ash blockage, resisting wear, and resisting poisoning, making them particularly suitable for environments with unstable coal types and high dust content in coal-fired flue gas.

[0003] However, current flat-plate catalysts suffer from the following problems: insufficient adhesion between the catalyst slurry and the stainless steel screen plate, leading to easy catalyst layer detachment; and the catalyst is susceptible to fluid erosion during operation, resulting in accelerated catalyst layer wear, which in turn affects the catalyst's stability and lifespan, reducing the efficiency of the catalytic reaction. Therefore, how to further improve the adhesion between the catalyst and the stainless steel screen plate is an urgent problem to be solved. Technical issues

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a high-strength flat plate catalyst and its preparation method. The catalyst produces high-viscosity kaolin, which, combined with the subsequent high-temperature coating process, greatly improves the adhesion between the catalyst sludge and the stainless steel screen plate, thereby enhancing the stability of the catalyst, extending the service life of the catalyst, and improving the catalytic reaction efficiency. Technical solutions

[0005] The technical solution of this invention is as follows:

[0006] On one hand, the present invention provides a high-strength flat-plate catalyst comprising the following components in parts by weight: 50-80 parts titanium dioxide, 2-15 parts high-viscosity kaolin, 2-10 parts glass fiber, 2-10 parts carbon fiber, 2-15 parts plasticizer, 0.5-2 parts ammonium heptamolybdate, 0.5-2 parts ammonium metavanadate, and 10-30 parts water.

[0007] Preferably, the high-viscosity kaolin is prepared by washing, filtering and drying the raw kaolin ore with water, then hydrothermally treating it with petroleum resin (such as C5 or C9 thermoplastic petroleum resin) at 150-450℃ for 0.5-4 hours, and then grinding it after drying to obtain high-viscosity kaolin.

[0008] Preferably, the silicon content in the raw kaolin ore is >50 wt.%.

[0009] Preferably, the mass ratio of kaolin ore to petroleum resin is 10:(0.5-1); the high-viscosity kaolin is ≥100 mesh.

[0010] Preferably, the carbon fiber is a mixture of two or three carbon fibers with different thicknesses and lengths, and the glass fiber is a mixture of two or three glass fibers with different thicknesses and lengths. The diameter of the carbon fiber and the glass fiber is 1.5-3 μm, and the length is 1-6 mm.

[0011] Preferably, the plasticizer is one or more of PVA, PEO, PEG, HPMC, CMC and HEMC.

[0012] On the other hand, the present invention provides a method for preparing the above-mentioned high-strength planar catalyst, comprising the following steps:

[0013] S1 involves dry mixing high-viscosity kaolin, plasticizer, and 30-70 parts of titanium dioxide for 1-15 minutes, followed by adding water for a first mixing at 20-70℃ for 5-30 minutes. After the first mixing, glass fiber, carbon fiber, and the remaining titanium dioxide are added for a second mixing at 40-80℃ for 5-20 minutes. After the second mixing, ammonium heptamolybdate and ammonium metavanadate are added for a third mixing at 40-80℃ for 3-15 minutes. At this point, the plasticity and moisture content of the clay meet the discharge standards (moisture 20-35 wt.%, plasticity 0.2-1). The material is then discharged after the third mixing.

[0014] S2 granulates the mud obtained in step S1 after ultrasonic treatment, and then extrudes it onto a stainless steel screen plate through a coating roller. After drying, cutting, pleating, unit assembly, and calcination, a flat catalyst is obtained.

[0015] Preferably, in step S1, during the three mixing processes, the pH of the mud is adjusted to 8-9 using lactic acid and ammonia.

[0016] Preferably, in step S2, the ultrasonic frequency is 20kHz-1MHz, and the ultrasonic time is 1-30min. The device used for ultrasonic treatment is a container with ultrasonic transmitters mounted around its perimeter.

[0017] Preferably, in step S2, the coating roller is equipped with an electromagnetic rotary heating device to bring its temperature to 60-200℃; the drying temperature is 100-200℃ and the drying time is 2-10 min; the calcination temperature is 450-650℃ and the calcination time is 2-12 h. Beneficial effects

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. This invention innovatively prepares high-viscosity kaolin by grafting resin onto kaolin through a hydrothermal reaction, resulting in a tight bond between the two. The increased temperature enhances the intermolecular interactions and reduces the intermolecular distance, thus decreasing the resin's fluidity and increasing its viscosity. Therefore, the resin-modified kaolin exhibits significantly improved viscosity in the mid-temperature range (100-200℃). Controlling the roller temperature within this mid-temperature range during coating significantly improves the cohesiveness of the slurry, resulting in a tighter and stronger bond between the slurry and the stainless steel screen plate. This greatly enhances the adhesion between the catalyst slurry and the stainless steel screen plate, thereby improving catalyst stability, extending catalyst lifespan, and increasing catalytic reaction efficiency.

[0020] 2. By combining glass fiber and carbon fiber of different specifications, this invention can increase the strength of the catalyst without affecting its toughness, thus solving the problem of inhibiting the bending performance of current flat-plate catalyst products when improving wear resistance. Embodiments of the present invention

[0021] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Example 1

[0022] The preparation method of the high-strength planar catalyst in this embodiment includes the following steps:

[0023] S1. After washing, filtering and drying 10 parts of raw kaolin ore, it is hydrothermally treated with 0.5 parts of C5 petroleum resin at 300℃ for 30 minutes. After cooling and drying, it is ground to obtain 100 mesh high-viscosity kaolin.

[0024] S2 mixes 50 parts titanium dioxide, 5 parts high-viscosity kaolin, and 5 parts PEO dry for 5 minutes, then adds 20 parts water for a first mixing at 40°C for 5 minutes. After the first mixing, adds 20 parts titanium dioxide, 2 parts glass fibers (3mm in length and 3μm in diameter), and 2 parts carbon fibers (3mm in length and 3μm in diameter) for a second mixing at 60°C for 15 minutes. After the second mixing, adds 0.5 parts ammonium heptamolybdate and 0.5 parts ammonium metavanadate for a third mixing at 70°C for 15 minutes. During this third mixing, lactic acid and ammonia are added to adjust the pH of the mud to 8.5. At this point, the mud has a plasticity of 0.8 and a moisture content of 25 wt.%, meeting the discharge standard. The mud is then discharged after mixing.

[0025] S3 involves ultrasonically treating the mud obtained in step S2 and then granulating it. The ultrasonic frequency is 80kHz, and the ultrasonic time is 20min. The coating roller is equipped with an electromagnetic rotary heating device (Shanghai Dunas electromagnetic heating calendering roller DNS-YY-F2). The temperature of the coating roller is adjusted to 200℃, and the coating speed is adjusted to 8m / min. The mud is squeezed onto a stainless steel screen plate through the heated coating roller. Then, after drying, cutting, pleating, assembly, and calcination, a flat catalyst is obtained. During drying, electric heating rods are arranged on the upper and lower ends of the drying channel. The flat catalyst passes horizontally through the middle. The current on the upper and lower ends of the drying channel is controlled by infrared thermometry and PLC controller to adjust the drying temperature of the flat catalyst to 150℃ and the drying time to 5min. The calcination temperature is 550℃ and the calcination time is 2h. Example 2

[0026] The difference from Example 1 is that in step S2, one part of glass fiber with a length of 3 mm and a diameter of 3 μm, one part of glass fiber with a length of 6 mm and a diameter of 3 μm, and two parts of carbon fiber with a length of 3 mm and a diameter of 3 μm are used instead of the glass fiber and carbon fiber in Example 1. Example 3

[0027] The difference from Example 1 is that in step S2, one part of glass fiber with a length of 3 mm and a diameter of 3 μm, one part of glass fiber with a length of 6 mm and a diameter of 1.5 μm, one part of carbon fiber with a length of 3 mm and a diameter of 3 μm, and one part of carbon fiber with a length of 6 mm and a diameter of 1.5 μm are used instead of the glass fiber and carbon fiber in Example 1. Example 4

[0028] The preparation method of the high-strength planar catalyst in this embodiment includes the following steps:

[0029] S1 After washing, filtering and drying 10 parts of raw kaolin ore, it is hydrothermally treated with 1 part of C5 petroleum resin at 150℃ for 4 hours, then cooled, dried and ground to obtain 120 mesh high-viscosity kaolin.

[0030] S2 involves dry mixing 70 parts titanium dioxide, 15 parts high-viscosity kaolin, and 15 parts PVA for 15 minutes, followed by adding 30 parts water for a first mixing at 20°C for 30 minutes. After the first mixing, 10 parts titanium dioxide, 5 parts glass fibers (3mm in length and 3μm in diameter), 5 parts glass fibers (6mm in length and 1.5μm in diameter), 5 parts carbon fibers (3mm in length and 3μm in diameter), and 5 parts carbon fibers (6mm in length and 1.5μm in diameter) are added for a second mixing at 40°C for 20 minutes. After the second mixing, 2 parts ammonium heptamolybdate and 2 parts ammonium metavanadate are added for a third mixing at 80°C for 3 minutes. During this third mixing, lactic acid and ammonia are added to adjust the pH of the mud to 9. At this point, the mud has a plasticity of 0.7 and a moisture content of 20 wt.%, meeting the discharge standard. The mud is then discharged after the mixing process is complete.

[0031] S3 involves ultrasonically treating the mud obtained in step S2 and then granulating it. The ultrasonic frequency is 1MHz and the ultrasonic time is 1min. The coating roller is equipped with an electromagnetic rotary heating device. The temperature of the coating roller is adjusted to 150℃ and the coating speed is adjusted to 8m / min. The mud is squeezed onto a stainless steel screen plate through the heated coating roller. Then, after drying, cutting, pleating, unit assembly, and calcination, a flat catalyst is obtained. During drying, electric heating rods are arranged on the upper and lower ends of the drying channel. The flat catalyst passes horizontally through the middle. The current on the upper and lower ends of the drying channel is controlled by infrared thermometry and PLC controller to adjust the drying temperature of the flat catalyst to 200℃ and the drying time to 2min. The calcination temperature is 450℃ and the calcination time is 12h. Example 5

[0032] The preparation method of the high-strength planar catalyst in this embodiment includes the following steps:

[0033] S1. After washing, filtering and drying 10 parts of raw kaolin ore, it is hydrothermally treated with 0.5 parts of C5 petroleum resin at 450℃ for 1 hour, then cooled, dried and ground to obtain 170 mesh high-viscosity kaolin.

[0034] S2 involves dry mixing 30 parts titanium dioxide, 2 parts high-viscosity kaolin, and 2 parts PEG for 1 minute, followed by adding 10 parts water for a first mixing at 70°C for 6 minutes. After the first mixing, 20 parts titanium dioxide, 2 parts glass fibers (3mm in length and 3μm in diameter), 2 parts glass fibers (6mm in length and 1.5μm in diameter), 2 parts carbon fibers (3mm in length and 3μm in diameter), and 2 parts carbon fibers (6mm in length and 1.5μm in diameter) are added for a second mixing at 80°C for 5 minutes. After the second mixing, 1 part ammonium heptamolybdate and 1 part ammonium metavanadate are added for a third mixing at 40°C for 10 minutes. During this third mixing, lactic acid and ammonia are added to adjust the pH of the mud to 8. At this point, the mud has a plasticity of 0.6 and a moisture content of 35 wt.%, meeting the discharge standard. The mud is then discharged after the mixing process is complete.

[0035] S3 involves ultrasonically treating the mud obtained in step S2 and then granulating it. The ultrasonic frequency is 20kHz, and the ultrasonic time is 30min. The coating roller is equipped with an electromagnetic rotary heating device. The temperature of the coating roller is adjusted to 60℃, and the coating speed is adjusted to 8m / min. The heated coating roller extrudes the mud onto a stainless steel screen plate. Then, after drying, cutting, pleating, unit assembly, and calcination, a flat-plate catalyst is obtained. During drying, electric heating rods are arranged on the upper and lower ends of the drying channel. The flat-plate catalyst passes horizontally through the middle. The current on the upper and lower ends of the drying channel is controlled by infrared thermometry and PLC controller to adjust the drying temperature of the flat-plate catalyst to 100℃ and the drying time to 10min. The calcination temperature is 650℃ and the calcination time is 3h.

[0036] Comparative Example 1

[0037] The difference from Example 1 is that the high-viscosity kaolin is replaced with an equal amount of kaolin ore that has been washed, filtered and dried.

[0038] Comparative Example 2

[0039] The difference from Example 1 is that in step S2, four pieces of glass fiber with a length of 3 mm and a diameter of 3 μm are used instead of the glass fiber and carbon fiber in Example 1.

[0040] Comparative Example 3

[0041] The difference from Example 1 is that in step S2, four carbon fibers with a length of 3 mm and a diameter of 3 μm are used instead of the glass fiber and carbon fiber in Example 1.

[0042] Comparative Example 4

[0043] The difference from Example 1 is that in step S3, the mud obtained in step S2 is not subjected to ultrasonic treatment, but is directly granulated.

[0044] Comparative Example 5

[0045] The difference from Example 1 is that in step S3, the coating roller is not electromagnetically heated, and the coating temperature is 25°C.

[0046] Comparative Example 6

[0047] The difference from Example 1 is that in step S2, lactic acid and ammonia water are not used to adjust the pH of the mud during the three mixing processes, and its pH is measured to be 7.5.

[0048] The performance of the plate-type catalysts prepared in Examples 1-5 and Comparative Examples 1-6 was tested. The wear resistance was tested according to GB / T31584-2015 Plate-type Flue Gas Denitrification Catalyst, and the adhesion strength was tested according to T / ZZB 0389-2018 Plate-type Flue Gas Denitrification Catalyst. The test results are shown in Tables 1-2.

[0049]

[0050]

[0051] As shown in Tables 1-2, compared to Example 1, the wear resistance and adhesion strength of the catalyst in Comparative Example 1 increased significantly, indicating a decrease in both wear resistance and adhesion. This suggests that the kaolin modification in Example 1 not only increased the viscosity of the slurry, significantly improving the adhesion between the slurry and the stainless steel screen plate, but also enhanced the wear resistance of the product. This is mainly because the increased adhesion after kaolin modification results in better slurry adhesion under the same coating conditions, leading to denser compaction and thus greater wear resistance of the catalyst.

[0052] Compared to Example 1, in Comparative Example 2, after removing carbon fibers, the abrasion resistance of the catalyst increased from 66.56 mg / 100r to 75.56 mg / 100r. Under the same conditions, the mass of catalyst worn away increased, and the abrasion resistance deteriorated significantly. The adhesion strength did not change much, indicating that Example 1 used carbon fibers to replace part of the glass fiber as the catalyst skeleton. Since the abrasion resistance of carbon fibers is higher than that of glass fibers, the addition of carbon fibers can significantly improve the abrasion resistance of the catalyst.

[0053] Compared to Example 1, in Comparative Example 3, replacing glass fiber with carbon fiber significantly improved the catalyst's wear resistance, but the adhesion strength increased from 1.67% to 1.97%, and the amount of catalyst detachment per unit mass increased by 0.3%, resulting in a decrease in adhesion performance. This is mainly because the excessive rigidity of carbon fiber caused inconsistent bending between the carbon fiber and the steel mesh during adhesion testing, leading to the separation of the carbon fiber from the steel mesh and the removal of a significant amount of mud. Therefore, the rigidity of carbon fiber and glass fiber of different diameters and lengths needs to be matched with the catalyst.

[0054] In Comparative Example 4, the clay was not subjected to ultrasonic treatment, which led to a decrease in the wear resistance and adhesion of the product. The reason for this is that ultrasound redistributes the free water in the clay through capillary action between particles, eliminating local high humidity areas and increasing the ductility and fluidity of the clay. Under the same coating pressure, the clay and the stainless steel screen plate are more tightly bonded, which is beneficial to improving the mechanical properties of the product. Therefore, the wear resistance and adhesion of the sample without ultrasonic treatment are reduced.

[0055] In Comparative Example 5, the coating temperature was too low, which led to a significant decrease in the wear resistance and adhesion of the product. The reason for this was that when the mud was coated at 200℃, the mud had better fluidity. Under the same coating pressure, the mud bonded more tightly to the stainless steel screen plate, and the mud itself was more compacted. Therefore, the mud coated at 200℃ had better mechanical properties than that coated at 25℃.

[0056] In Comparative Example 6, without adding lactic acid and ammonia to adjust the pH of the clay, the wear resistance and adhesion of the coated product significantly decreased. The reason for this is that when lactic acid and ammonia are added to the clay, the carboxyl groups in the lactic acid molecules can form hydrogen bonds or chemical adsorption with the surface of inorganic particles (such as TiO2) in the clay, reducing direct contact between particles and lowering internal friction. Ammonia adjusts the pH of the clay to 8-9, optimizing the Zeta potential (surface charge) of the clay particles, maximizing the electrostatic repulsion between particles, and reducing agglomeration. The synergistic effect of both increases the lactate group (CH3CH(OH)COO) - NH4 adsorbs onto the positively charged regions on the particle surface. + Adsorption in negatively charged regions forms an electric double layer, enhancing interparticle repulsion and improving the lubricity of the slurry. Simultaneously, the reaction of ammonia and lactic acid produces ammonium lactate, which, as a small-molecule electrolyte, reduces the viscosity of the slurry and improves shear thinning behavior (thixotropy), making it easier for the slurry to be evenly and tightly coated onto the stainless steel mesh. Under the same coating pressure, the slurry bonds more tightly to the stainless steel mesh, thereby improving the mechanical properties of the catalyst product.

Claims

1. A high-strength planar catalyst, characterized in that, The components include the following parts by weight: 50-80 parts titanium dioxide, 2-15 parts high-viscosity kaolin, 2-10 parts glass fiber, 2-10 parts carbon fiber, 2-15 parts plasticizer, 0.5-2 parts ammonium heptamolybdate, 0.5-2 parts ammonium metavanadate, and 10-30 parts water.

2. The high-strength planar catalyst as described in claim 1, characterized in that, The preparation method of the high-viscosity kaolin is as follows: after washing, filtering and drying the raw kaolin ore, it is subjected to hydrothermal treatment with petroleum resin at 150-450℃ for 0.5-4 hours, and after drying, it is ground to obtain the high-viscosity kaolin.

3. The high-strength planar catalyst as described in claim 2, characterized in that, The silicon content in raw kaolin ore is >50 wt.%.

4. The high-strength planar catalyst as described in claim 2, characterized in that, The mass ratio of raw kaolin ore to petroleum resin is 10:(0.5-1); high-viscosity kaolin ≥100 mesh.

5. The high-strength planar catalyst as described in claim 1, characterized in that, Carbon fiber is a mixture of two or three different thicknesses and lengths of carbon fiber, and glass fiber is a mixture of two or three different thicknesses and lengths of glass fiber. The diameter of carbon fiber and glass fiber is 1.5-3μm and the length is 1-6mm.

6. The high-strength planar catalyst as described in claim 1, characterized in that, The plasticizer is one or more of PVA, PEO, PEG, HPMC, CMC and HEMC.

7. The method for preparing the high-strength planar catalyst according to any one of claims 1-6, characterized in that, Includes the following steps: S1 involves dry mixing high-viscosity kaolin, plasticizer, and 30-70 parts of titanium dioxide for 1-15 minutes, followed by adding water for a first mixing at a temperature of 20-70℃ for 5-30 minutes. After the first mixing, glass fiber, carbon fiber, and the remaining titanium dioxide are added for a second mixing at a temperature of 40-80℃ for 5-20 minutes. After the second mixing, ammonium heptamolybdate and ammonium metavanadate are added for a third mixing at a temperature of 40-80℃ for 3-15 minutes. The material is then discharged after the third mixing. S2 granulates the mud obtained in step S1 after ultrasonic treatment, and then extrudes it onto a stainless steel screen plate through a coating roller. After drying, cutting, pleating, unit assembly, and calcination, a flat catalyst is obtained.

8. The method for preparing the high-strength planar catalyst as described in claim 7, characterized in that, In step S1, during the three mixing processes, the pH of the mud is adjusted to 8-9 using lactic acid and ammonia.

9. The method for preparing the high-strength planar catalyst as described in claim 7, characterized in that, In step S2, the ultrasonic frequency is 20kHz-1MHz and the ultrasonic time is 1-30min.

10. The method for preparing the high-strength planar catalyst as described in claim 7, characterized in that, In step S2, the coating roller is equipped with an electromagnetic rotary heating device to bring its temperature to 60-200℃; the drying temperature is 100-200℃ and the drying time is 2-10 min; the calcination temperature is 450-650℃ and the calcination time is 2-12 h.

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