Method for preparing particle trap by coating wide-granularity-distribution slurry

Abstract

The invention belongs to the technical field of tail gas treatment, and provides a method for preparing a particle trap by coating wide-granularity-distribution slurry, the slurry with wide granularity distribution is used for coating GPF, and the prepared particle trap has the advantages that the back pressure is obviously reduced, the service life is prolonged and the service life is prolonged while the high trapping efficiency is maintained. The device is suitable for a gasoline engine tail gas after-treatment system, particulate matter emission is effectively reduced, and increasingly strict emission regulation requirements are met.

Description

Technical Field

[0001] This invention relates to the field of exhaust gas purification technology, and in particular to a method for preparing a particulate trap by coating a slurry with a wide particle size distribution. Background Technology

[0002] With the development of the automotive industry and increasingly stringent environmental protection requirements, the gasoline particulate filter (GPF), as a key aftertreatment device for controlling particulate emissions from gasoline engines, has become an essential component for meeting China VI and higher emission standards. The GPF not only needs to efficiently capture particulate matter but also needs to maintain low back pressure to avoid negatively impacting engine performance and fuel economy. In GPF technology, the particle size distribution of the coating has a decisive influence on filtration efficiency and back pressure.

[0003] Currently, GPF coating technology faces two main challenges: ensuring sufficiently high particulate matter capture efficiency while minimizing its impact on engine back pressure. Traditional GPF coating technology typically uses a slurry with a single particle size distribution for coating. While this method is simple, it struggles to simultaneously achieve both filtration efficiency and back pressure performance.

[0004] In existing technologies, catalyst coating is commonly used to improve the filtration efficiency of GPFs. CN119430997A discloses a gasoline engine particulate filter with low back pressure increase and narrow pore size distribution, and its preparation method. This method controls the median particle size D50 of the mixture of inorganic raw materials, pore-forming agent, and binder within the range of 20–26 μm, and the span (D90-D10) / D50 < 1.4, resulting in a gasoline engine particulate filter with a back pressure increase of 13–56%. Although this technology can ensure the consistency of pore size in mass-produced gasoline engine particulate filters, the problem of a large back pressure increase still exists.

[0005] CN114653396A proposes a DPF catalyst coating method that balances low exhaust back pressure and high catalytic efficiency. This method involves coating the catalyst wall surface with a slurry containing a non-precious metal catalyst at the front of the support and coating the catalyst inside the support at the rear. While this differentiated coating strategy reduces back pressure to some extent, the coating process is complex and does not adequately consider the particle distribution characteristics of the slurry.

[0006] CN117404157A discloses a particulate filter and its preparation method. This method increases the particle size of the catalyst slurry in the particulate filter, achieving a particle size D90 of 4.5–6 μm, which reduces the coefficient of thermal expansion of the particulate filter and thus improves its temperature tolerance. However, this technology primarily focuses on the thermal stability of the particulate filter, and its research on how to simultaneously reduce back pressure and improve filtration efficiency through slurry particle distribution optimization is insufficient.

[0007] CN109647088A proposes a method for preparing a diesel particulate filter (DPF) with low back pressure and high carbon soot filtration efficiency. This method employs a double-layer coating structure, optimizing the porosity and pore size of the bottom coating, as well as the catalytic material and coating loading of the top catalytic layer, to improve the filtration efficiency of the coating for carbon soot particles while reducing the DPF back pressure. However, this technology is primarily aimed at diesel particulate filters, and its coating structure design is not entirely suitable for the specific requirements of gas permeable filters (GPFs).

[0008] CN108561211A describes a DPF with a low back pressure and low ignition temperature catalytic layer and its preparation process. This process achieves low-temperature catalytic oxidation of PM and PN through a special slurry preparation and coating method, and has low back pressure characteristics. However, this technology does not have precise control over the slurry particle distribution, making it difficult to achieve optimal pore filling effect.

[0009] In summary, the existing GPF coating process has the following problems:

[0010] 1. Existing slurry formulations and coating processes are difficult to simultaneously meet the requirements of low back pressure and high filtration efficiency. They often significantly increase back pressure while improving filtration efficiency, which affects engine performance and fuel economy.

[0011] 2. Existing technologies do not provide precise control over the particle distribution of slurries, especially lacking research on the application of slurries with wide particle size distribution in GPF coating, which makes it impossible to achieve optimal filling of carrier pores.

[0012] 3. Existing coating methods fail to fully consider the matching relationship between slurry particle distribution and carrier pore structure, resulting in uneven coating distribution and affecting filtration efficiency and back pressure performance.

[0013] Therefore, there is an urgent need to develop a GPF coating method based on a slurry with a wide particle size distribution to achieve a particulate trap with low back pressure and high filtration efficiency, in order to meet increasingly stringent emission regulations and engine performance optimization requirements. Summary of the Invention

[0014] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for preparing a particle trap by coating a slurry with a wide particle size distribution, so as to solve the problems in the prior art.

[0015] To achieve the above and other related objectives, the present invention provides a method for preparing a particle trap by coating a slurry with a wide particle size distribution, comprising the following steps:

[0016] S1. Prepare a slurry containing catalytic materials with different particle size distributions;

[0017] S2. Adjust the pH value of the slurry to near the isoelectric point;

[0018] S3. Pretreatment of the particle trap substrate;

[0019] S4. Immerse the pretreated particle trap substrate into the slurry after pH adjustment in step S2, so that the slurry is adsorbed onto the pore walls of the particle trap substrate.

[0020] S5. Dry and calcine the particle trap obtained in step S4 to obtain a particle trap coated with catalytic material.

[0021] In this invention, in step S1, the particle size range is D90 3.5μm to 25.0μm. For example, it is 3.5μm to 5.0μm, 5.0μm to 10.0μm, 10.0μm to 15.0μm, 15.0μm to 20.0μm, or 20.0μm to 25.0μm.

[0022] In this invention, in step S1, the particle size of the slurry, D90 / D10, is 4.0–50.0. For example, it can be 4.0–5.0, 5.0–10.0, 10.0–15.0, 15.0–20.0, 20.0–25.0, 25.0–30.0, 30.0–35.0, 35.0–40.0, 40.0–45.0, or 45.0–50.0. This invention forms a porous filter layer by controlling the ratio of large to small particles in the slurry. Large particles form the main skeletal structure in the coating, providing larger pores and reducing gas flow resistance; small particles fill the gaps between the large particles, improving collection efficiency.

[0023] In this invention, in step S1, the different particle size distributions include 3 to 5 particle size distributions. For example, slurries with 3, 4, or 5 particle size distributions.

[0024] In this invention, in step S1, the catalytic material is one or more of the following: cerium-zirconium solid solution composite oxide powder, cerium-zirconium-lanthanum solid solution composite oxide powder, cerium-zirconium-lanthanum-yttrium solid solution composite oxide powder, cerium-zirconium-lanthanum-neodymium solid solution composite oxide powder, cerium-zirconium-lanthanum-praseodymium solid solution composite oxide powder, cerium-zirconium-lanthanum-yttrium-neodymium solid solution composite oxide powder, cerium-zirconium-lanthanum-titanium solid solution composite oxide powder, and cerium-zirconium-lanthanum-aluminum solid solution composite oxide powder, mixed with alumina powder.

[0025] In a preferred embodiment of the present invention, step S1, the preparation of a slurry containing catalytic materials with different particle size distributions specifically includes: mixing the catalytic materials with a solvent, performing a ball milling process to obtain an initial slurry, dividing the initial slurry into 2-5 parts, 2-3 parts, 3-4 parts, or 4-5 parts, and performing a second ball milling process and / or high shear treatment and / or ultrasonic treatment for different times to obtain slurries with different particle size distributions, and then mixing the slurries with different particle size distributions in a certain proportion.

[0026] The solvent is water, a mixture of water and ethanol, or a mixture of water and isopropanol.

[0027] The ball milling process is performed at a speed of 180–250 rpm. For example, it can be 180–200 rpm, 200–220 rpm, 220–240 rpm, or 240–250 rpm.

[0028] The time for one ball milling process is 4 to 10 hours. For example, it is 4 to 5 hours, 5 to 6 hours, 6 to 8 hours, or 8 to 10 hours.

[0029] The secondary ball milling process takes 5 to 35 minutes. For example, it can take 5 to 10 minutes, 10 to 15 minutes, 15 to 20 minutes, 20 to 25 minutes, 25 to 30 minutes, or 30 to 35 minutes.

[0030] The high-shear processing speed is 4000–10000 rpm. For example, it is 4000–5000 rpm, 5000–6000 rpm, 6000–7000 rpm, 7000–8000 rpm, 8000–9000 rpm, or 9000–10000 rpm.

[0031] The high-shear treatment time is 0–5 min. For example, it can be 0–1 min, 1–2 min, 2–3 min, 3–4 min, or 4–5 min.

[0032] The duration of the ultrasonic treatment is 0–30 min. For example, it can be 0–5 min, 5–10 min, 10–15 min, 15–20 min, 20–25 min, or 25–30 min.

[0033] Specifically, the catalyst material can be mixed with a solvent and ball-milled for 4 hours to obtain an initial slurry. The initial slurry is divided into three parts. The first part is ball-milled for 10 minutes, the second part for 20 minutes, and the third part for 30 minutes to obtain three slurries with different particle size distributions. The three slurries are then mixed evenly in a volume ratio of 1:1:1 to obtain a slurry containing catalyst materials with different particle size distributions.

[0034] Specifically, the catalytic material can be mixed with a solvent and ball-milled for 5 hours to obtain an initial slurry. The initial slurry is then divided into four portions. The first portion is ball-milled for 5 minutes, the second portion for 15 minutes, the third portion for 25 minutes, and the fourth portion for 35 minutes to obtain four slurries with different particle size distributions. The four slurries are then mixed evenly in a volume ratio of 1:1:1:1 to obtain a slurry containing catalytic materials with different particle size distributions.

[0035] Specifically, the catalytic material can be mixed with a solvent and ball-milled for 6 hours to obtain an initial slurry. The initial slurry is divided into five portions, each subjected to ball milling for different times and high-shear treatment at different speeds: the first portion is ball-milled for 5 minutes, then subjected to high-shear treatment at 5000 rpm for 3 minutes; the second portion is ball-milled for 10 minutes, then subjected to high-shear treatment at 6000 rpm for 3 minutes; the third portion is ball-milled for 15 minutes, then subjected to high-shear treatment at 7000 rpm for 3 minutes; the fourth portion is ball-milled for 20 minutes, then subjected to high-shear treatment at 8000 rpm for 3 minutes; and the fifth portion is ball-milled for 25 minutes, then subjected to high-shear treatment at 9000 rpm for 3 minutes, resulting in five slurries with different particle size distributions. The five slurries are then mixed uniformly in a volume ratio of 1:1:1:1:1 to obtain a slurry containing catalytic materials with different particle size distributions.

[0036] Specifically, the catalyst material can be mixed with a solvent and ball-milled for 8 hours to obtain an initial slurry. The initial slurry is divided into two parts. The first part (accounting for 70% of the total amount) is ball-milled for 10 minutes, and the second part is ball-milled (250 rpm) for 30 minutes. The two slurries are mixed and then divided into three parts. The first part is not ultrasonically treated, the second part is ultrasonically treated for 15 minutes, and the third part is ultrasonically treated for 30 minutes to obtain three slurries with different particle size distributions. The three slurries are mixed evenly in a volume ratio of 2:2:1 to obtain a slurry containing catalyst materials with different particle size distributions.

[0037] In a preferred embodiment of the present invention, the mass ratio of cerium oxide to zirconium oxide in the cerium-zirconium solid solution composite oxide powder is 10–50:50–90. For example, it is 10–20:50–90, 20–30:50–90, 30–40:50–90, 40–50:50–90, 10–50:50–60, 10–50:60–70, 10–50:70–80, or 10–50:80–90.

[0038] In a preferred embodiment of the present invention, the mass ratio of cerium oxide, zirconium oxide, and lanthanum oxide in the cerium-zirconium-lanthanum solid solution composite oxide powder is 10–50:50–90:3–7. For example, it can be 10–20:50–90:3–7, 20–30:50–90:3–7, 30–40:50–90:3–7, 40–50:50–90:3–7, 10–50:50–60:3–7, 10–50:60–70:3–7, 10–50:70–80:3–7, 10–50:80–90:3–7, 10–50:50–90:3–4, 10–50:50–90:4–5, 10–50:50–90:5–6, or 10–50:50–90:6–7.

[0039] In a preferred embodiment of the present invention, the mass ratio of cerium oxide, zirconium oxide, lanthanum oxide, and yttrium oxide in the cerium-zirconium-lanthanum yttrium solid solution composite oxide powder is 10–50:50–90:3–7:1–4. Examples include 10–20:50–90:3–7:1–4, 20–30:50–90:3–7:1–4, 30–40:50–90:3–7:1–4, 40–50:50–90:3–7:1–4, 10–50:50–60:3–7:1–4, 10–50:60–70:3–7:1–4, 10–50:70–80:3–7:1–4, and 10–50:80. ~90:3~7:1~4, 10~50:50~90:3~4:1~4, 10~50:50~90:4~5:1~4, 10~50:50~90:5~6:1~4, 10~50:50~90:6~7:1~4, 10~50:50~90:3~7:1~2, 10~50:50~90:3~7:2~3 or 10~50:50~90:3~7:3~4.

[0040] In a preferred embodiment of the present invention, the mass ratio of cerium oxide, zirconium oxide, lanthanum oxide, and neodymium oxide in the cerium-zirconium-lanthanum-neodymium solid solution composite oxide powder is 10–50:50–90:3–7:1–4. Examples include 10–20:50–90:3–7:1–4, 20–30:50–90:3–7:1–4, 30–40:50–90:3–7:1–4, 40–50:50–90:3–7:1–4, 10–50:50–60:3–7:1–4, 10–50:60–70:3–7:1–4, 10–50:70–80:3–7:1–4, and 10–50:80. ~90:3~7:1~4, 10~50:50~90:3~4:1~4, 10~50:50~90:4~5:1~4, 10~50:50~90:5~6:1~4, 10~50:50~90:6~7:1~4, 10~50:50~90:3~7:1~2, 10~50:50~90:3~7:2~3 or 10~50:50~90:3~7:3~4.

[0041] In a preferred embodiment of the present invention, the mass ratio of cerium oxide, zirconium oxide, lanthanum oxide, yttrium oxide and neodymium oxide in the cerium-zirconium-lanthanum-yttrium-neodymium solid solution composite oxide powder is 10-50:50-90:3-7:1-4:1-4. For example, 10~20:50~90:3~7:1~4:1~4, 20~30:50~90:3~7:1~4:1~4, 30~40:50~90:3~7:1~4:1~4, 40~50:50~90:3~7:1~4:1~4, 10~50:50~60:3~7:1~4:1~4, 10~50:60~70:3~7:1~4:1~4, 10~50:70~80:3~7:1~4:1~4, 10~50:80~90:3~7:1~4:1~4, 10~50:50~90:3~4:1~4:1~4 4. 10~50:50~90:4~5:1~4:1~4, 10~50:50~90:5~6:1~4:1~4, 10~50:50~90:6~7:1~4:1~4, 10~50:50~90:3~7:1~2:1~4, 10~50:50~90:3~7:2~3:1~4, 10~50:50~90:3~7:3~4:1~4, 10~50:50~90:3~7:1~4:1~2, 10~50:50~90:3~7:1~4:2~3 or 10~50:50~90:3~7:1~4:3~4.

[0042] In a preferred embodiment of the present invention, the mass ratio of cerium oxide, zirconium oxide, lanthanum oxide, and praseodymium oxide in the cerium-zirconium-lanthanum-praseodymium solid solution composite oxide powder is 10–50:50–90:3–7:1–4. Examples include 10–20:50–90:3–7:1–4, 20–30:50–90:3–7:1–4, 30–40:50–90:3–7:1–4, 40–50:50–90:3–7:1–4, 10–50:50–60:3–7:1–4, 10–50:60–70:3–7:1–4, 10–50:70–80:3–7:1–4, and 10–50:80. ~90:3~7:1~4, 10~50:50~90:3~4:1~4, 10~50:50~90:4~5:1~4, 10~50:50~90:5~6:1~4, 10~50:50~90:6~7:1~4, 10~50:50~90:3~7:1~2, 10~50:50~90:3~7:2~3 or 10~50:50~90:3~7:3~4.

[0043] In a preferred embodiment of the present invention, the mass ratio of cerium oxide, zirconium oxide, lanthanum oxide, and titanium oxide in the cerium-zirconium-lanthanum-titanium solid solution composite oxide powder is 10-50:50-90%:3-7:1-4. For example, it can be 10-20:50-90:3-7:1-4, 20-30:50-90:3-7:1-4, 30-40:50-90:3-7:1-4, 40-50:50-90:3-7:1-4, 10-50:50-60:3-7:1-4, 10-50:60-70:3-7:1-4, 10-50:70-80:3-7:1-4, or 10-50:80%. ~90:3~7:1~4, 10~50:50~90:3~4:1~4, 10~50:50~90:4~5:1~4, 10~50:50~90:5~6:1~4, 10~50:50~90:6~7:1~4, 10~50:50~90:3~7:1~2, 10~50:50~90:3~7:2~3 or 10~50:50~90:3~7:3~4.

[0044] In a preferred embodiment of the present invention, the mass ratio of cerium oxide, zirconium oxide, lanthanum oxide, and aluminum oxide in the cerium-zirconium-lanthanum-aluminum solid solution composite oxide powder is 10-50:10-50:3-7:50-80. For example, ratios include 10-20:10-50:3-7:50-80, 20-30:10-50:3-7:30-40, 10-50:10-50:3-7:50-80, 40-50:10-50:3-7:50-80, 10-50:10-20:3-7:50-80, 10-50:20-30:3-7:50-80, 10-50:30-40:3-7:50-80, and 10-50:40-50:40-50:3-7:50-80. 50:3~7:50~80, 10~50:10~50:3~4:50~80, 10~50:10~50:4~5:50~80, 10~50:10~50:5~6:50~80, 10~50:10~50:6~7:50~80, 10~50:10~50:3~7:50~60, 10~50:10~50:3~7:60~70 or 10~50:10~50:3~7:70~80.

[0045] In this invention, in step S1, the slurry further contains a dispersant, and the amount of the dispersant added is 1-5 wt% of the total mass of the catalytic material. For example, it is 1-2 wt%, 2-3 wt%, 3-4 wt%, or 4-5 wt%.

[0046] In a preferred embodiment of the present invention, the dispersant is selected from one or more of polyvinyl alcohol, ammonium polyacrylate, acrylate copolymers, polyacrylate copolymers, and carboxylated copolymers.

[0047] In this invention, in step S1, the slurry further contains a binder, and the amount of binder added is 1-5 wt% of the total mass of the catalytic material. For example, it is 1-2 wt%, 2-3 wt%, 3-4 wt%, or 4-5 wt%.

[0048] In a preferred embodiment of the present invention, the adhesive is selected from one or more of polyvinyl alcohol, polyacrylamide, hydroxypropyl methylcellulose, carboxymethyl cellulose, aluminum sol, and silica sol.

[0049] In this invention, in step S1, the solid content of the slurry is 35-45%. For example, it is 35-38%, 38-40%, 40-42%, or 42-45%.

[0050] In this invention, in step S2, the pH value is adjusted within the range of 6–8, 6–7, or 7–8. Adjusting the pH of the slurry can enhance the adhesion between the slurry and the carrier surface, thereby improving the coating quality.

[0051] In this invention, in step S2, the pH adjuster used to adjust the pH value of the slurry is tetramethylammonium or dilute nitric acid or dilute acetic acid.

[0052] In this invention, in step 2, the viscosity of the slurry after pH adjustment is 10–100 cP. For example, it is 10–20 cP, 20–40 cP, 40–60 cP, 60–80 cP, or 80–100 cP.

[0053] In this invention, in step S3, the particle trap substrate is made of cordierite with a pore density of 200-300 cpsi, 200-220 cpsi, 220-240 cpsi, 240-260 cpsi, 260-280 cpsi, or 280-300 cpsi and a wall thickness of 8-14 mil, 8-10 mil, 10-12 mil, or 12-14 mil.

[0054] In this invention, in step S3, the diameter of the particle trap substrate (GPF substrate) is 100-300mm, 100-130mm, 130-150mm, 150-180mm, 180-200mm, 200-250mm or 250-300mm, and the length is 50-300mm, 50-100mm, 100-150mm, 150-200mm, 200-250mm or 250-300mm.

[0055] In this invention, step S3, the pretreatment includes the step of: compressed air alternately blowing from both ends of the particle collector substrate at pressures of 0.5-0.8 MPa, 0.5-0.6 MPa, 0.6-0.7 MPa or 0.7-0.8 MPa to remove dust and impurities in the channel.

[0056] In this invention, the adsorption in step S4 is performed using a vacuum-assisted impregnation method, a pulse pressure-assisted coating method, or a multiple immersion method.

[0057] In a preferred embodiment of the present invention, the vacuum-assisted impregnation method includes the following steps: placing the GPF substrate horizontally in a coating container, first evacuating to -0.08 MPa and maintaining it for 5 minutes, then injecting slurry to completely cover the GPF substrate, releasing the vacuum, and immersing at normal pressure for 2 minutes; removing the GPF substrate from the slurry, placing it vertically, and letting it stand for 10 minutes to allow excess slurry to flow off naturally; and using compressed air at a pressure of 0.5 MPa to alternately blow from both ends of the GPF substrate to ensure that the channels are not blocked.

[0058] In a preferred embodiment of the present invention, the pulse pressure assisted coating method includes the following steps: placing the pretreated GPF substrate vertically in a coating container with its bottom immersed in the slurry; alternately applying a positive pressure of 0.1 MPa and a negative pressure of 0.1 MPa, each cycle lasting 10 seconds, for a total of 5 cycles; removing the GPF substrate from the slurry and rotating it on a rotating platform at a speed of 10 rpm, while simultaneously blowing hot air at a temperature of 40°C from above for 15 minutes to allow excess slurry to flow down evenly; and alternately blowing compressed air from both ends of the GPF substrate at a pressure of 0.25 MPa to ensure that the channels are not blocked.

[0059] In a preferred embodiment of the present invention, the multiple immersion method includes the following steps: placing the pretreated GPF substrate vertically in a coating container, immersing the bottom in the slurry for 20 seconds; applying a negative pressure of 0.06 MPa for 10 seconds to allow the slurry to be uniformly adsorbed onto the pore walls of the GPF substrate; removing the GPF substrate from the slurry, placing it vertically, and letting it stand for 3 minutes to allow excess slurry to flow off naturally; using compressed air at a pressure of 0.15 MPa to alternately blow air from both ends of the GPF substrate to ensure that the channels are not blocked; drying the GPF substrate at 80°C for 30 minutes; repeating the above immersion-blowing-drying process twice, for a total of three coatings.

[0060] In this invention, in step S5, the drying is natural drying at room temperature for 2-7 hours, 2-3 hours, 3-4 hours, 4-5 hours, 5-6 hours, or 6-7 hours, or natural drying in an environment with a relative humidity of 40-60%, 40-45%, 45-50%, 50-55%, or 55-60% for 1-4 hours, 1-2 hours, 2-3 hours, or 3-4 hours.

[0061] In this invention, in step S5, the roasting is first carried out at 80-180℃, 80-100℃, 100-120℃, 120-140℃, 140-160℃ or 160-180℃ for 1-5h, 1-2h, 2-4h or 4-5h, and then at 300-650℃, 300-350℃, 350-400℃, 400-450℃, 450-500℃, 500-550℃, 550-600℃ or 600-650℃ for 2-8h, 2-4h, 4-6h or 6-8h.

[0062] In this invention, in step S5, the amount of slurry coating on the particle collector after calcination is measured to be 60–150 g / L. For example, it is 60–150 g / L, 60–80 g / L, 80–100 g / L, 100–110 g / L, 110–130 g / L, or 130–150 g / L.

[0063] As described above, the method for preparing a particle trap by coating a slurry with a wide particle size distribution according to the present invention has the following beneficial effects:

[0064] The method for preparing a particulate filter (GPF) by coating a slurry with a wide particle size distribution according to the present invention significantly reduces the back pressure of the GPF and improves engine performance and fuel economy by using an optimized slurry particle size distribution and a slurry with a wide particle size distribution for GPF coating. Attached Figure Description

[0065] Figure 1 The image shows the morphology of the GPF coating with catalytic material prepared in Example 1.

[0066] Figure 2 The image shows the morphology of the GPF coating with catalytic material prepared in Example 2.

[0067] Figure 3 The image shows the morphology of the GPF coating with catalytic material prepared in Example 3.

[0068] Figure 4 The image shows the morphology of the GPF coating with catalytic material prepared in Example 4.

[0069] Figure 5 The image shows the morphology of the GPF coating with the catalyst material prepared for Comparative Example 1.

[0070] Figure 6 The image shows the morphology of the GPF coating with catalytic material prepared for Comparative Example 3.

[0071] Figure 7 The image shows the morphology of the GPF coating with catalytic material prepared in Example 5. Detailed Implementation

[0072] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0073] In the description of this invention, "a number" means two or more, unless otherwise explicitly specified.

[0074] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included. For example, a specified range from “1 to 10” should be considered to include any and all subranges between the minimum value 1 and the maximum value 10. Exemplary subranges of the range 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0075] Furthermore, it should be understood that the one or more method steps mentioned in this invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated; moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered as within the scope of the invention.

[0076] The reagents and raw materials used in the following embodiments of the present invention are all commercially available.

[0077] Example 1

[0078] A method for preparing a particle trap by coating a slurry with a wide particle size distribution:

[0079] S1. Preparation of slurry with a wide particle size distribution:

[0080] Alumina powder and cerium-zirconium solid solution composite oxide powder were mixed in a mass ratio of 60:40, and the mass ratio of cerium oxide to zirconium oxide in the cerium-zirconium solid solution composite oxide was 20:20. Deionized water was added to make the solid content reach 40wt%.

[0081] The mixture was ball-milled at 200 rpm for 4 hours to obtain the initial slurry.

[0082] The initial slurry was divided into three portions and ball-milled for different times (200 rpm): the first portion was ball-milled for 10 minutes, the second portion for 20 minutes, and the third portion for 30 minutes, resulting in three slurries with different particle size distributions.

[0083] The three slurries were mixed in a volume ratio of 1:1:1 and stirred evenly to obtain a slurry with a wide particle size distribution. The slurry had a D10 of 0.851 μm, a D50 of 2.038 μm, and a D90 of 6.638 μm, with a D90 / D10 ratio of 7.8, indicating a wide particle size distribution range.

[0084] Then polyvinyl alcohol is added as a dispersant and binder, at a rate of 4 wt% of the total mass of the solid powder.

[0085] S2. Adjust the pH value of the slurry to near its isoelectric point to ensure slurry stability:

[0086] The pH of the slurry was adjusted to 7.1 using a pH adjuster. This pH value is close to the isoelectric point of the slurry, which helps maintain its stability. In this embodiment, tetramethylammonium and / or dilute nitric acid were used as the pH adjuster, which was slowly added dropwise to the slurry while the pH value was monitored in real time using a pH meter until the target value of 7.1 was reached. At this point, the viscosity of the slurry was 82 cP. During the adjustment process, the slurry was kept under low-speed stirring to ensure that the pH adjuster was evenly dispersed.

[0087] S3, Pretreatment of GPF matrix:

[0088] A cordierite GPF matrix with a pore density of 300 cpsi (pores per square inch) and a wall thickness of 8 mil was selected, with dimensions of 132.1 mm in diameter and 101.6 mm in length. Compressed air was used to alternately blow from both ends of the GPF matrix at a pressure of 0.5 MPa to remove dust and impurities from the channels.

[0089] S4, Slurry Coating:

[0090] Pour the slurry with a wide particle size distribution prepared in step S1 into a coating container and stir evenly; place the pretreated GPF substrate vertically with its bottom immersed in the slurry for 30 seconds; apply a negative pressure of 0.05 MPa to make the slurry evenly adsorbed on the pore walls of the GPF substrate; remove the GPF substrate from the slurry and let it stand for 5 minutes to allow excess slurry to flow off naturally; use compressed air at a pressure of 0.2 MPa to alternately blow from both ends of the GPF substrate to ensure that the channels are not blocked.

[0091] S5. Drying and roasting:

[0092] The GPF substrate coated in step S4 was naturally dried at room temperature for 4 hours; the dried GPF substrate was placed in a programmed oven and heated to 120°C at a heating rate of 2°C / min and held for 2 hours; the GPF substrate was transferred to a high-temperature furnace and heated to 550°C at a heating rate of 5°C / min and held for 4 hours to complete the calcination process; it was then naturally cooled to room temperature to obtain GPF coated with catalytic material.

[0093] Quality control and performance testing:

[0094] The mass of the GPF substrate before and after coating was measured, and the coating load was calculated and controlled within the range of 80 to 100 g / L. In this embodiment, the coating load was 90.3 g / L.

[0095] The coating morphology was observed using a USB industrial camera, as shown in the attached image. Figure 1 The coating was confirmed to be evenly distributed on the hole wall, with no obvious cracks or peeling.

[0096] Using the SF-1020 back pressure tester from SuperFlow Technologies Group (USA), and in accordance with GB / T 18881-2017 "Exhaust Gas Purification Catalysts for Light-Duty Gasoline Vehicles", the test was conducted at a temperature of 37°C and an airflow of 600 m³ / h. 3 The back pressure of the GPF was measured under the condition of / h, and the back pressure value was 3.62kPa.

[0097] Using a standard particulate matter testing system, and in accordance with the "T / CAEPI 36—2021 Technical Requirements for Pollution Control Devices for Gasoline Vehicles Part 2: Gasoline Vehicle Particulate Filters", the filtration efficiency of the GPF for PM2.5 was measured to be 92.3%, and the filtration efficiency for PM10 was 98.1%.

[0098] Example 2

[0099] A method for preparing a particle trap by coating a slurry with a wide particle size distribution:

[0100] S1. Preparation of slurry with a wide particle size distribution:

[0101] Alumina powder and cerium-zirconium solid solution composite oxide powder were mixed in a mass ratio of 55:45, with the mass ratio of cerium oxide to zirconium oxide in the cerium-zirconium solid solution composite oxide being 20:25. Deionized water was added to bring the solid content to 35 wt%. Then, ammonium polyacrylate dispersant was added, with the amount of dispersant added being 2.0 wt% of the total mass of the solid powder.

[0102] The mixture was ball-milled at 180 rpm for 5 hours to obtain the initial slurry.

[0103] The initial slurry was divided into four portions and ball-milled for different times (180 rpm): the first portion was ball-milled for 5 minutes, the second portion for 15 minutes, the third portion for 25 minutes, and the fourth portion for 35 minutes, resulting in four slurries with different particle size distributions.

[0104] The four slurries were mixed in a volume ratio of 1:1:1:1 and stirred evenly to obtain a slurry with a wide particle size distribution. The slurry had a D10 of 0.638 μm, a D50 of 2.043 μm, and a D90 of 6.826 μm, with a D90 / D10 ratio of 10.7, indicating a wider particle size distribution range.

[0105] Then ammonium polyacrylate is added as a dispersant and binder, at a rate of 2.5 wt% of the total mass of the solid powder.

[0106] S2. Adjust the pH value of the slurry to near its isoelectric point to ensure slurry stability:

[0107] The pH of the slurry was adjusted to 6.8 using a pH adjuster. This pH value is close to the isoelectric point of the slurry, which helps maintain its stability. In this embodiment, tetramethylammonium and / or dilute acetic acid were used as the pH adjuster, which was slowly added dropwise to the slurry while the pH value was monitored in real time using a pH meter until the target value of 6.8 was reached, at which point the viscosity of the slurry was 77 cP. During the adjustment process, the slurry was kept under low-speed stirring to ensure that the pH adjuster was evenly dispersed.

[0108] S3, Pretreatment of GPF matrix:

[0109] A cordierite GPF matrix with a pore density of 300 cpsi (pores per square inch) and a wall thickness of 8 mil was selected, with dimensions of 132.1 mm in diameter and 101.6 mm in length. Compressed air was used to alternately blow from both ends of the GPF matrix at a pressure of 0.6 MPa to remove dust and impurities from the channels.

[0110] S4, Slurry Coating:

[0111] Pour the slurry with a wide particle size distribution prepared in step S1 into a coating container and stir evenly. Place the pretreated GPF substrate horizontally and coat it using a vacuum-assisted impregnation method. The specific process is as follows: first, evacuate to -0.08 MPa and maintain for 5 minutes, then inject the slurry to completely cover the GPF substrate; release the vacuum and soak at normal pressure for 2 minutes; remove the GPF substrate from the slurry, place it vertically, and let it stand for 10 minutes to allow excess slurry to flow off naturally; use compressed air at a pressure of 0.3 MPa to alternately blow from both ends of the GPF substrate to ensure that the channels are not blocked.

[0112] S5. Drying and roasting:

[0113] The GPF substrate coated in step S4 was naturally dried at room temperature for 6 hours; the dried GPF substrate was placed in a programmed oven and heated to 100°C at a heating rate of 1°C / min, held for 1 hour, and then heated to 150°C at a heating rate of 1°C / min, held for 2 hours; the GPF substrate was transferred to a high-temperature furnace and heated to 600°C at a heating rate of 3°C / min, held for 5 hours to complete the calcination process; the substrate was cooled to room temperature at a cooling rate of 2°C / min to obtain the GPF coated with the catalytic material.

[0114] Quality control and performance testing:

[0115] The mass of the GPF substrate before and after coating was measured, and the coating load was calculated and controlled within the range of 90 to 110 g / L. In this embodiment, the coating amount was 100.5 g / L.

[0116] The coating morphology was observed using a USB industrial camera, as shown in the attached image. Figure 2 The coating was confirmed to be evenly distributed on the hole wall, with no obvious cracks or peeling.

[0117] Using the same back pressure testing device as in Example 1, at a test temperature of 37°C and an air flow rate of 600 m³ / h... 3 The back pressure of GPF was measured under the condition of / h, and the back pressure value was 3.53kPa.

[0118] Using a standard particulate matter testing system, as in Example 1, the filtration efficiency of the GPF for PM2.5 was measured to be 94.5%, and the filtration efficiency for PM10 was measured to be 99.2%.

[0119] Example 3

[0120] A method for preparing a particle trap by coating a slurry with a wide particle size distribution:

[0121] S1. Preparation of slurry with a wide particle size distribution:

[0122] Alumina powder and cerium-zirconium-yttrium solid solution composite oxide powder were mixed in a mass ratio of 50:50. The mass ratio of cerium oxide, zirconium oxide and yttrium oxide in the cerium-zirconium-yttrium solid solution composite oxide was 20:25:5. A mixed solution of deionized water and ethanol (volume ratio of 10:1) was added to make the solid content reach 45wt%.

[0123] The mixture was ball-milled at 220 rpm for 6 hours to obtain the initial slurry.

[0124] The initial slurry was divided into five portions, each subjected to ball milling (220 rpm) for different durations and high-shear treatment at different speeds: the first portion was ball milled for 5 minutes, then subjected to high-shear treatment at 5000 rpm for 3 minutes; the second portion was ball milled for 10 minutes, then subjected to high-shear treatment at 6000 rpm for 3 minutes; the third portion was ball milled for 15 minutes, then subjected to high-shear treatment at 7000 rpm for 3 minutes; the fourth portion was ball milled for 20 minutes, then subjected to high-shear treatment at 8000 rpm for 3 minutes; and the fifth portion was ball milled for 25 minutes, then subjected to high-shear treatment at 9000 rpm for 3 minutes, resulting in five slurries with different particle size distributions.

[0125] The five slurries were mixed in a volume ratio of 1:1:1:1:1 and stirred evenly to obtain a slurry with a wide particle size distribution. The slurry had a D10 of 0.465 μm, a D50 of 2.044 μm, and a D90 of 18.604 μm, where D90 / D10 = 40, indicating an extremely wide particle size distribution range.

[0126] Then, add the high molecular weight block copolymer dispersant BYK190 containing affinity groups and the binder hydroxypropyl methylcellulose. The amount of dispersant added is 1.8 wt% of the total mass of the solid powder, and the amount of binder added is 1.0 wt% of the total mass of the solid powder.

[0127] S2. Adjust the pH value of the slurry to near its isoelectric point to ensure slurry stability:

[0128] The pH of the slurry was adjusted to 6.7 using a pH adjuster. This pH value is close to the isoelectric point of the slurry, which helps maintain its stability. In this embodiment, tetramethylammonium and / or dilute nitric acid were used as the pH adjuster, which was slowly added dropwise to the slurry while the pH value was monitored in real time using a pH meter until the target value of 6.7 was reached, at which point the viscosity of the slurry was 75 cP. During the adjustment process, the slurry was kept under low-speed stirring to ensure that the pH adjuster was evenly dispersed.

[0129] S3, Pretreatment of GPF matrix:

[0130] A cordierite GPF matrix with a pore density of 300 cpsi (pores per square inch) and a wall thickness of 8 mil was selected, with dimensions of 132.1 mm in diameter and 101.6 mm in length. Compressed air was alternately blown from both ends of the GPF matrix at a pressure of 0.7 MPa to remove dust and impurities from the channels. The GPF matrix was then surface-activated using a 5 wt% nitric acid solution, soaked for 10 minutes, rinsed with deionized water until neutral, and dried at 120°C for 2 hours.

[0131] S4, Slurry Coating:

[0132] Pour the slurry with a wide particle size distribution prepared in step S1 into a coating container and stir evenly. Use pulse pressure assisted coating method: place the pretreated GPF substrate vertically in a sealed container with the bottom immersed in the slurry; alternately apply a positive pressure of 0.1 MPa and a negative pressure of 0.1 MPa, each cycle lasting 10 seconds, for a total of 5 cycles; remove the GPF substrate from the slurry and rotate it on a rotating platform at a speed of 10 rpm, while using hot air at a temperature of 40°C to blow it from above for 15 minutes to make the excess slurry flow down evenly; use compressed air at a pressure of 0.25 MPa to alternately blow from both ends of the GPF substrate to ensure that the channels are not blocked.

[0133] S5. Drying and roasting:

[0134] The GPF substrate coated in step S4 was naturally dried for 8 hours in an environment with a relative humidity of 60%. The dried GPF substrate was then placed in a temperature-controlled oven and heated to 80°C at a rate of 1°C / min, held for 1 hour, then heated to 120°C at a rate of 1°C / min, held for 2 hours, and finally heated to 180°C at a rate of 1°C / min, held for 1 hour. The GPF substrate was then transferred to a high-temperature furnace and heated to 300°C at a rate of 2°C / min, held for 2 hours, then heated to 650°C at a rate of 2°C / min, held for 6 hours to complete the calcination process. The substrate was then cooled to room temperature at a rate of 1°C / min to obtain the GPF coated with the catalytic material.

[0135] Quality control and performance testing:

[0136] The mass of the GPF substrate before and after coating was measured, and the coating load was calculated and controlled within the range of 100-120 g / L. In this embodiment, the coating load was 110.3 g / L.

[0137] The coating morphology was observed using a USB industrial camera, as shown in the attached image. Figure 3 The coating was confirmed to be evenly distributed on the hole wall, with no obvious cracks or peeling.

[0138] Using the same back pressure testing device as in Example 1, at a test temperature of 37°C and an air flow rate of 600 m³ / h... 3 The back pressure of the GPF was measured under the condition of / h, and the back pressure value was 3.49kPa.

[0139] Using a standard particulate matter testing system, as in Example 1, the filtration efficiency of the GPF for PM2.5 was measured to be 95.2%, and the filtration efficiency for PM10 was measured to be 99.5%.

[0140] Thermal stability tests were conducted. After hydrothermal aging at 1050℃ for 10 hours, the back pressure of the GPF was 3.79 kPa, an increase of 8.6%; the filtration efficiency of the GPF for PM2.5 was 92.8%, a decrease of 2.5%; and the filtration efficiency for PM10 was 97.7%, a decrease of 1.8%.

[0141] Example 4

[0142] A method for preparing a particle trap by coating a slurry with a wide particle size distribution:

[0143] S1. Preparation of slurry with a wide particle size distribution:

[0144] Alumina powder and cerium-zirconium-titanium solid solution composite oxide powder were mixed in a mass ratio of 45:55. The mass ratio of cerium oxide, zirconium oxide and titanium oxide in the cerium-zirconium-titanium solid solution composite oxide was 25:25:5. A mixed solution of deionized water and isopropanol (volume ratio of 15:1) was added to make the solid content reach 38wt%.

[0145] The mixture was ball-milled at 250 rpm for 8 hours to obtain the initial slurry.

[0146] The initial slurry was divided into two parts: the first part (70% of the total) was ball-milled (250 rpm) for 10 minutes to obtain a slurry with a D50 of approximately 2.5 μm; the second part (30% of the total) was ball-milled (250 rpm) for 30 minutes to obtain a slurry with a D50 of approximately 0.5 μm. The two slurries were mixed and then divided into three portions, each subjected to different degrees of ultrasonic treatment: the first portion was not ultrasonicated, the second portion was ultrasonicated for 15 minutes, and the third portion was ultrasonicated for 30 minutes.

[0147] The three slurries were mixed in a volume ratio of 2:2:1 and stirred evenly to obtain a slurry with a wide particle size distribution. The slurry had a D10 of 0.463 μm, a D50 of 2.041 μm, and a D90 of 20.835 μm, with D90 / D10 = 45, indicating an extremely wide particle size distribution range.

[0148] Then, the dispersant Carbosperse K-XP228 and the binder aluminum sol were added. The amount of dispersant added was 1.5 wt% of the total mass of the solid powder, and the amount of binder added was 1.2 wt% of the total mass of the solid powder.

[0149] S2. Adjust the pH value of the slurry to near its isoelectric point to ensure slurry stability:

[0150] The pH of the slurry was adjusted to 6.6 using a pH adjuster. This pH value is close to the isoelectric point of the slurry, which helps maintain its stability. In this embodiment, tetramethylammonium and / or dilute nitric acid were used as the pH adjuster, which was slowly added dropwise to the slurry while the pH value was monitored in real time using a pH meter until the target value of 6.6 was reached. At this point, the viscosity of the slurry was 74 cP. During the adjustment process, the slurry was kept under low-speed stirring to ensure that the pH adjuster was evenly dispersed.

[0151] S3, Pretreatment of GPF matrix:

[0152] A cordierite GPF substrate with a pore density of 300 cpsi (pores per square inch) and a wall thickness of 8 mil was selected, with dimensions of 132.1 mm in diameter and 101.6 mm in length. The GPF substrate was dried in an oven at 150°C for 5 hours to remove moisture, which would facilitate the adsorption of the slurry and the adhesion of the coating during the coating process. Compressed air was alternately blown from both ends of the GPF substrate at a pressure of 0.8 MPa to remove dust and impurities from the channels. The GPF substrate was then subjected to surface alkaline activation treatment with a 3 wt% sodium hydroxide solution, soaked for 15 minutes, rinsed with deionized water until neutral, and dried at 130°C for 3 hours.

[0153] S4, Slurry Coating:

[0154] Pour the slurry with a wide particle size distribution prepared in step S1 into a coating container and stir evenly. Coat using a multiple immersion method: place the pretreated GPF substrate vertically and immerse the bottom in the slurry for 20 seconds; apply a negative pressure of 0.06 MPa for 10 seconds to allow the slurry to be evenly adsorbed onto the pore walls of the GPF substrate; remove the GPF substrate from the slurry, place it vertically, rotate it 90°, and let it stand for 3 minutes to allow excess slurry to flow off naturally; use compressed air at a pressure of 0.15 MPa to alternately blow from both ends of the GPF substrate to ensure that the channels are not blocked; dry the GPF substrate at 80°C for 30 minutes; repeat the above immersion-blowing-drying process twice, for a total of 3 coatings.

[0155] S5. Drying and roasting:

[0156] The GPF substrate coated in step S4 was naturally dried in an environment with a relative humidity of 50% for 12 hours. The dried GPF substrate was then placed in a temperature-controlled oven and heated to 100°C at a rate of 0.5°C / min, held for 2 hours, and then heated to 150°C at a rate of 0.5°C / min, held for 3 hours. The GPF substrate was then transferred to a high-temperature furnace and heated to 350°C at a rate of 1°C / min, held for 2 hours, and then heated to 550°C at a rate of 1°C / min, held for 8 hours to complete the calcination process. Finally, the substrate was cooled to room temperature at a rate of 0.5°C / min to obtain the GPF coated with the catalytic material.

[0157] Quality control and performance testing:

[0158] The mass of the GPF substrate before and after coating was measured, and the coating load was calculated and controlled within the range of 110 to 130 g / L. In this embodiment, the coating load was 119.9 g / L.

[0159] The coating morphology was observed using a USB industrial camera, as shown in the attached image. Figure 4 The coating was confirmed to be evenly distributed on the hole wall, with no obvious cracks or peeling.

[0160] Using the same back pressure testing device as in Example 1, at a test temperature of 37°C and an air flow rate of 600 m³ / h... 3 The back pressure of GPF was measured under the condition of / h, and the back pressure value was 3.46Pa.

[0161] Using a standard particulate matter testing system, as in Example 1, the filtration efficiency of the GPF for PM2.5 was measured to be 96.1%, and the filtration efficiency for PM10 was measured to be 99.8%.

[0162] Thermal stability tests were conducted. After hydrothermal aging at 1050℃ for 10 hours, the back pressure of the GPF was 3.68 kPa, an increase of 6.4%; the filtration efficiency of the GPF for PM2.5 was 93.9%, a decrease of 2.3%; and the filtration efficiency for PM10 was 98.5%, a decrease of 1.3%.

[0163] Comparative Example 1 (Single Particle Size Distribution)

[0164] A method for preparing a particle trap:

[0165] S1. Preparation of slurry:

[0166] Alumina powder and cerium-zirconium solid solution composite oxide powder were mixed in a mass ratio of 60:40, and the mass ratio of cerium oxide to zirconium oxide in the cerium-zirconium solid solution composite oxide was 20:20. Deionized water was added to make the solid content reach 40wt%.

[0167] The above mixture was ball-milled in a ball mill at 200 rpm for 4 hours to obtain a slurry; the slurry had a D10 of 0.952 μm, a D50 of 2.044 μm, and a D90 of 4.076 μm, where D90 / D10 = 4.3.

[0168] Then polyvinyl alcohol is added as a dispersant and binder, at a rate of 4 wt% of the total mass of the solid powder.

[0169] S2. Adjust the pH value of the slurry to near its isoelectric point to ensure slurry stability:

[0170] The pH of the slurry was adjusted to 7.1 using a pH adjuster. This pH value is close to the isoelectric point of the slurry, which helps maintain its stability. In this embodiment, tetramethylammonium and / or dilute nitric acid were used as the pH adjuster, which was slowly added dropwise to the slurry while the pH value was monitored in real time using a pH meter until the target value of 7.1 was reached, at which point the viscosity of the slurry was 80 cP. During the adjustment process, the slurry was kept under low-speed stirring to ensure that the pH adjuster was evenly dispersed.

[0171] S3, Pretreatment of GPF matrix:

[0172] A cordierite GPF matrix with a pore density of 300 cpsi (pores per square inch) and a wall thickness of 8 mil was selected, with dimensions of 132.1 mm in diameter and 101.6 mm in length. Compressed air was used to alternately blow from both ends of the GPF matrix at a pressure of 0.5 MPa to remove dust and impurities from the channels.

[0173] S4, Slurry Coating:

[0174] Pour the slurry with a wide particle size distribution prepared in step S1 into a coating container and stir evenly; place the pretreated GPF substrate vertically with its bottom immersed in the slurry for 30 seconds; apply a negative pressure of 0.05 MPa to make the slurry evenly adsorbed on the pore walls of the GPF substrate; remove the GPF substrate from the slurry and let it stand for 5 minutes to allow excess slurry to flow off naturally; use compressed air at a pressure of 0.2 MPa to alternately blow from both ends of the GPF substrate to ensure that the channels are not blocked.

[0175] S5. Drying and roasting:

[0176] The GPF substrate coated in step S4 was naturally dried at room temperature for 4 hours; the dried GPF substrate was placed in a programmed oven and heated to 120°C at a heating rate of 2°C / min and held for 2 hours; the GPF substrate was transferred to a high-temperature furnace and heated to 550°C at a heating rate of 5°C / min and held for 4 hours to complete the calcination process; it was then naturally cooled to room temperature to obtain GPF coated with catalytic material.

[0177] Quality control and performance testing:

[0178] The mass of the GPF substrate before and after coating was measured, and the coating load was calculated and controlled within the range of 80 to 100 g / L. In this comparative example, the coating load was 90.2 g / L.

[0179] The coating morphology was observed using a USB industrial camera, as shown in the attached image. Figure 5 The coating was confirmed to be evenly distributed on the hole wall, with no obvious cracks or peeling.

[0180] Using the same back pressure testing device as in Example 1, at a test temperature of 37°C and an air flow rate of 600 m³ / h... 3 The back pressure of GPF was measured under the condition of / h, and the back pressure value was 4.53kPa.

[0181] Using a standard particulate matter testing system, as in Example 1, the filtration efficiency of the GPF for PM2.5 was measured to be 84.1%, and the filtration efficiency for PM10 was measured to be 92.2%.

[0182] Experimental data show that, compared with the normal particle size distribution of Comparative Example 1, the back pressure growth of the GPF prepared by the method of the present invention in Example 1 was reduced by 20.1%, while the PM2.5 filtration efficiency was increased by 9.8% and the PM10 filtration efficiency was increased by 6.4%. This indicates that the slurry with a wide particle size distribution can more effectively fill the carrier pores and form a more optimized filter layer structure.

[0183] Comparative Example 2 (without pH adjustment of the slurry)

[0184] A method for preparing a particle trap:

[0185] The steps are basically the same as those in Comparative Example 1. The difference is that in step S2, the pH of the slurry is not adjusted, and the pH value of the slurry is kept constant at 5.2, with a viscosity of 62 cP. The remaining steps are the same as those in Comparative Example 1. In this comparative example, the coating amount is 90.3 g / L.

[0186] Using a back pressure testing device, at a test temperature of 37℃ and an air flow rate of 600m³ / h... 3 The back pressure of the GPF was measured under the condition of / h, and the back pressure value was 4.82kPa.

[0187] Using a standard particulate matter testing system, the GPF's filtration efficiency for PM2.5 was measured to be 80.5%, and its filtration efficiency for PM10 was measured to be 90.2%.

[0188] Experimental data show that, compared with Comparative Example 2 without pH adjustment, adjusting the pH value to be close to the isoelectric point of the slurry is beneficial to maintaining the stability of the slurry. The back pressure of the GPF prepared in Comparative Example 1 was reduced by 6.0%, while the PM2.5 filtration efficiency was increased by 4.5% and the PM10 filtration efficiency was increased by 2.2%.

[0189] Comparative Example 3 (without adjusting the slurry viscosity)

[0190] A method for preparing a particle trap:

[0191] The steps are basically the same as those in Comparative Example 1. The differences are: in step S2, polyvinyl alcohol is not added to the slurry as a dispersant and binder; the viscosity of the slurry is 534 cP; in step S3, compressed air is used at a pressure of 0.9 MPa to alternately blow away dust and impurities from both ends of the GPF substrate; in step S4, compressed air is used at a pressure of 0.5 MPa to alternately blow away dust and impurities from both ends of the GPF substrate to ensure that the channels are not blocked. The remaining steps are the same as in Comparative Example 1. The coating amount in this comparative example is 90.1 g / L.

[0192] The coating morphology was observed using a USB industrial camera, as shown in the attached image. Figure 6 The high viscosity of the slurry means that the coating can only cover part of the carrier. The coating is too thick in the coated part, which increases the back pressure. Meanwhile, more particles pass through the uncoated part, resulting in a decrease in filtration efficiency.

[0193] Using a back pressure testing device, at a test temperature of 37℃ and an air flow rate of 600m³ / h... 3 The back pressure of GPF was measured under the condition of / h, and the back pressure value was 5.85kPa, which is significantly increased.

[0194] Using a standard particulate matter testing system, the GPF's filtration efficiency for PM2.5 was measured to be 75.4%, and its filtration efficiency for PM10 was measured to be 82.6%.

[0195] Experimental data show that, compared with Comparative Example 3 without pH adjustment, adjusting the slurry viscosity is beneficial to achieving uniform slurry coating, and the back pressure of the GPF prepared in Comparative Example 1 is significantly reduced.

[0196] Comparative Example 4 (High Solids Content Slurry)

[0197] A method for preparing a particle trap:

[0198] Compared with Comparative Example 1, the solid content of the slurry is 50%. In step S3, compressed air is used at a pressure of 0.9 MPa to alternately blow from both ends of the GPF substrate to remove dust and impurities in the channels. In step S4, compressed air is used at a pressure of 0.5 MPa to alternately blow from both ends of the GPF substrate to ensure that the channels are not blocked. The remaining steps are the same as those in Comparative Example 1. In this comparative example, the coating amount is 89.7 g / L.

[0199] Using a back pressure testing device, at a test temperature of 37℃ and an air flow rate of 600m³ / h... 3 The back pressure of the GPF was measured under the condition of / h, and the back pressure value was 8.64kPa.

[0200] The excessively high solid content of the slurry caused uneven coating, resulting in excessively high back pressure, rendering it unusable in practical applications.

[0201] Comparative Example 5 (without dispersant)

[0202] Compared to Comparative Example 1, step S1 did not involve the addition of dispersant and binder polyvinyl alcohol. The remaining steps were the same as in Comparative Example 1, and the coating amount in this comparative example was 90.1 g / L.

[0203] Using a back pressure testing device, at a test temperature of 37℃ and an air flow rate of 600m³ / h... 3 The back pressure of the GPF was measured under the condition of / h, and the back pressure value was 3.25kPa.

[0204] Using a standard particulate matter testing system, the GPF's filtration efficiency for PM2.5 was measured to be 69.5%, and its filtration efficiency for PM10 was measured to be 78.2%.

[0205] The coating morphology was observed using a USB industrial camera, as shown in the attached image. Figure 7 The coating cracks, and although the back pressure is low, the filtration efficiency drops significantly due to the cracking, making it unusable in practice.

[0206] Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0207] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a particle trap by coating a slurry with a wide particle size distribution, characterized in that, Includes the following steps: S1. Prepare a slurry containing catalytic materials with different particle size distributions; S2. Adjust the pH value of the slurry to near the isoelectric point; S3. Pretreatment of the particle trap substrate; S4. Immerse the pretreated particle trap substrate into the slurry after pH adjustment in step S2, so that the slurry is adsorbed onto the pore walls of the particle trap substrate. S5. Dry and calcine the particle trap obtained in step S4 to obtain a particle trap coated with catalytic material.

2. The method for preparing a particle trap by coating a slurry with a wide particle size distribution according to claim 1, characterized in that, In step S1, the particle size range of the slurry is D90 3.5μm~25.0μm; And / or, in step S1, the particle size of the slurry is D90 / D10 = 4.0~50.0; And / or, in step S1, the different particle size distributions include 3 to 5 particle size distributions.

3. The method for preparing a particle trap by coating a slurry with a wide particle size distribution according to claim 1, characterized in that, In step S1, the catalyst material is one or more of the following: cerium-zirconium solid solution composite oxide powder, cerium-zirconium-lanthanum solid solution composite oxide powder, cerium-zirconium-lanthanum-yttrium solid solution composite oxide powder, cerium-zirconium-lanthanum-neodymium solid solution composite oxide powder, cerium-zirconium-lanthanum-praseodymium solid solution composite oxide powder, cerium-zirconium-lanthanum-yttrium-neodymium solid solution composite oxide powder, cerium-zirconium-lanthanum-titanium solid solution composite oxide powder, and cerium-zirconium-lanthanum-aluminum solid solution composite oxide powder, mixed with alumina powder; And / or, in step S1, the preparation of a slurry containing catalytic materials with different particle size distributions specifically includes: mixing the catalytic materials with a solvent, performing a ball milling process to obtain an initial slurry, dividing the initial slurry into 2 to 5 portions and performing a second ball milling process and / or high shear treatment and / or ultrasonic treatment for different times to obtain slurries with different particle size distributions, and then mixing the slurries with different particle size distributions in proportion.

4. The method for preparing a particle trap by coating a slurry with a wide particle size distribution according to claim 3, characterized in that, The mass ratio of cerium oxide to zirconium oxide in the cerium-zirconium solid solution composite oxide powder is 10-50:50-90. And / or, the mass ratio of cerium oxide, zirconium oxide and lanthanum oxide in the cerium-zirconium-lanthanum solid solution composite oxide powder is 10-50:50-90:3-7; And / or, the mass ratio of cerium oxide, zirconium oxide, lanthanum oxide and yttrium oxide in the cerium-zirconium-lanthanum-yttrium solid solution composite oxide powder is 10-50:50-90:3-7:1-4; And / or, the mass ratio of cerium oxide, zirconium oxide, lanthanum oxide and neodymium oxide in the cerium-zirconium-lanthanum-neodymium solid solution composite oxide powder is 10-50:50-90:3-7:1-4; And / or, the mass ratio of cerium oxide, zirconium oxide, lanthanum oxide, yttrium oxide and neodymium oxide in the cerium-zirconium-lanthanum-yttrium-neodymium solid solution composite oxide powder is 10-50:50-90:3-7:1-4:1-4; And / or, the mass ratio of cerium oxide, zirconium oxide, lanthanum oxide and praseodymium oxide in the cerium-zirconium-lanthanum-praseodymium solid solution composite oxide powder is 10-50:50-90:3-7:1-4; And / or, the mass ratio of cerium oxide, zirconium oxide, lanthanum oxide and titanium oxide in the cerium-zirconium-lanthanum-titanium solid solution composite oxide powder is 10-50:50-90%:3-7:1-4; And / or, the mass ratio of cerium oxide, zirconium oxide, lanthanum oxide and aluminum oxide in the cerium-zirconium-lanthanum-aluminum solid solution composite oxide powder is 10-50:10-50:3-7:50-80.

5. The method for preparing a particle trap by coating a slurry with a wide particle size distribution according to claim 1, characterized in that, In step S1, the slurry also contains a dispersant, and the amount of the dispersant added is 1 to 5 wt% of the total mass of the catalytic material.

6. The method for preparing a particle trap by coating a slurry with a wide particle size distribution according to claim 5, characterized in that, In step S1, the slurry also contains a binder, and the amount of binder added is 1 to 5 wt% of the total mass of the catalyst material.

7. The method for preparing a particle trap by coating a slurry with a wide particle size distribution according to claim 1, characterized in that, In step S1, the solid content of the slurry is 35-45%.

8. The method for preparing a particle trap by coating a slurry with a wide particle size distribution according to claim 1, characterized in that, In step S2, the pH value is adjusted within the range of 6 to 8; And / or, in step S2, the pH adjuster used to adjust the pH value of the slurry is tetramethylammonium or dilute nitric acid or dilute acetic acid; And / or, in step S2, the viscosity of the slurry after pH adjustment is 10-100 cP.

9. The method for preparing a particle trap by coating a slurry with a wide particle size distribution according to claim 1, characterized in that, In step S3, the particle trap substrate is made of cordierite material with a pore density of 200-300 cpsi and a wall thickness of 8-14 mil. And / or, in step S3, the diameter of the particle trap substrate is 100-300 mm and the length is 50-300 mm; And / or, in step S3, the pretreatment includes the step of: compressed air alternately blowing from both ends of the particle trap substrate at a pressure of 0.5 to 0.8 MPa to remove dust and impurities in the channel.

10. The method for preparing a particle trap by coating a slurry with a wide particle size distribution according to claim 1, characterized in that, The adsorption described in step S4 is performed using a vacuum-assisted impregnation method, a pulse pressure-assisted coating method, or a multiple immersion method. And / or, in step S5, the drying is natural drying at room temperature for 2 to 7 hours, or natural drying in an environment with a relative humidity of 40 to 60% for 1 to 4 hours; And / or, in step S5, the calcination is first carried out at 80-180°C for 2-5 hours, and then at 300-650°C for 4-8 hours; And / or, in step S5, the amount of slurry coating on the particle trap is measured to be 60-150 g / L after calcination.

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