A gasoline engine particulate filter with low coefficient of expansion and a method for manufacturing the same

Abstract

The application discloses a gasoline engine particle trap with low expansion coefficient and a preparation method thereof, and belongs to the technical field of gasoline engine tail gas emission treatment. Inorganic raw materials, a pore forming agent, a binder and a powder electric neutral modifier are mixed, then water is added and stirred to form mud, and the mud is subjected to mud refining, extrusion molding, drying and sintering to obtain a ceramic matrix, and then the ceramic matrix is subjected to cross hole blocking at both ends to obtain the particle trap; wherein the inorganic raw materials are composed of talc, kaolin, fused quartz powder, alpha-alumina and magnesium-aluminum double hydroxide. The synthesized magnesium-aluminum double hydroxide used in the application completely or partially replaces active alumina, can directly and greatly reduce the thermal expansion coefficient of the ceramic matrix, and improves the thermal shock resistance of the particle trap.

Description

Technical Field

[0001] This invention belongs to the field of gasoline engine exhaust emission control technology, specifically relating to a gasoline engine particulate filter with a low expansion coefficient and its preparation method. Background Technology

[0002] With increasingly stringent global emission regulations, gasoline particulate filters (GPFs), as core components for controlling PM2.5 and other ultrafine particulate emissions from vehicle exhaust, face ever-increasing performance requirements. While existing technologies commonly use cordierite or silicon carbide substrates, which possess some filtration performance, they suffer from low thermal shock resistance and insufficient durability. With vehicle use, carbon and dust build-up occurs inside the particulate filter. Furthermore, frequent vehicle starts and stops, or regeneration processes, generate localized high temperatures within the filter. Excessive internal temperature differences, exceeding the ceramic matrix's tolerance, can lead to thermal stress cracking and even structural failure, severely impacting service life and potentially causing secondary pollution. Therefore, reducing the material's coefficient of thermal expansion and improving thermal shock resistance while maintaining porosity and filtration efficiency has become a pressing technical challenge for the industry.

[0003] Currently, most particulate filters used in gasoline engines are based on cordierite ceramics. Their preparation methods primarily utilize traditional honeycomb ceramic raw materials, such as talc, kaolin, quartz alumina, and aluminum hydroxide as inorganic raw materials. In existing formulations, aluminum hydroxide is often used to reduce the thermal expansion coefficient of the ceramic matrix; however, its reduction capability is limited (generally controllable to (0.7~1.0) × 10⁻⁶). -6 The particulate filter has a thermal shock resistance of 650℃ and requires relatively clean raw materials (the content of K, Na, and Ca in the raw materials needs to be strictly controlled). This places high demands on the raw materials used, with specific requirements on the mineral sources and processing techniques. Furthermore, because gasoline engine particulate filters require high porosity (generally greater than 60%), the industry often uses large amounts of pore-forming agents to create pores in the ceramic matrix to achieve high porosity. The use of large amounts of organic pore-forming agents brings significant difficulties to the particulate filter manufacturing process, especially the sintering process. More precise control of the discharge of organic matter during sintering is required; improper control can easily cause defects such as cracking of the ceramic matrix during firing. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a gasoline engine particulate filter with a low coefficient of thermal expansion; another technical problem to be solved by the present invention is to provide a method for preparing a gasoline engine particulate filter with a low coefficient of thermal expansion, wherein the method uses synthetic magnesium aluminum double hydroxide to completely or partially replace active oxidation, which can directly and significantly reduce the coefficient of thermal expansion of the ceramic matrix and improve the thermal shock resistance of the particulate filter.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a gasoline engine particulate filter with a low coefficient of expansion involves mixing inorganic raw materials, a pore-forming agent, a binder, and a powder-based neutral modifier, then adding water to form a slurry. The slurry is then kneaded, extruded, dried, and sintered to obtain a ceramic matrix. The particulate filter is then obtained by cross-plugging the two ends of the ceramic matrix. The inorganic raw materials consist of talc, kaolin, fused silica powder, α-alumina, and magnesium aluminum hydroxide.

[0007] Furthermore, the pore-forming agent is selected from one or more of starch, expanded plastic microspheres, graphite, and carbon powder.

[0008] Furthermore, the binder is selected from one or more of cellulose and PVA.

[0009] Furthermore, the powder electrically neutral modifier is selected from one or more of polyvinyl alcohol, lauric acid, and oleic acid.

[0010] Furthermore, the magnesium-aluminum double hydroxide comprises 8-25% of the inorganic raw material by weight; its D50 is 15.0-25.0 μm, and its specific surface area is 400 m². 2 / g~500m 2 / g.

[0011] Furthermore, the magnesium-aluminum double hydroxide is prepared by a hot water reaction of brucite and boehmite, with the hot water reaction conditions being a temperature of 180-200 °C, a pH of 9-10, and a reaction time of 15-25 h.

[0012] Furthermore, the particle size D50 of brucite is 5.0~10.0μm, and the particle size D50 of boehmite is 5.0~10.0μm.

[0013] Furthermore, the talc content is 5.0-29.5% by mass, the kaolin content is 10-15% by mass, the fused silica powder content is 24-33.5% by mass, and the α-alumina content is 21-28.5% by mass.

[0014] Furthermore, the coefficient of thermal expansion of the ceramic matrix is ​​0.1 × 10⁻⁶. -6 ~0.6×10 -6 / ℃, median pore size is 16~20μm, porosity is 60~70%, and thermal shock resistance is 650~900℃.

[0015] Furthermore, the gasoline engine particulate filter prepared from the low expansion coefficient gasoline engine particulate filter is a gasoline engine particulate filter.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) The present invention uses the above-mentioned synthetic magnesium-aluminum double hydroxides (Mg-Al LDHs) to completely or partially replace the active oxidation, which can directly and significantly reduce the thermal expansion coefficient of the ceramic matrix and improve the thermal shock resistance of the particle trap.

[0018] (2) In this invention, the amount of magnesium aluminum hydroxide (Mg-Al LDHs) used in the formula is 12-20%, and its particle size is 15-25μm. After synthesizing cordierite, it will leave pores and also have the function of pore formation. In the manufacturing process of particle trap, it can also act as a part of the pore-forming agent, which can reduce the amount of organic pore-forming agent, reduce the sintering difficulty of particle trap, reduce the proportion of its cracking defects, and also reduce the carbon emissions brought about by organic pore formation discharge.

[0019] (3) For particle traps or honeycomb ceramic carriers with low technical performance (thermal shock resistance) requirements, the present invention can improve the tolerance of impurity (K, Na, Ca elements) content and particle morphology of raw materials used in the production process, reduce the procurement cost of raw materials, and reduce dependence on international raw materials. Attached Figure Description

[0020] Figure 1 A schematic diagram of the particle trap obtained in this application;

[0021] Figure 2 A physical image of the particle trap prepared in this application;

[0022] Figure 3 The diagram shows the coefficient of thermal expansion of the ceramic matrix of the particle trap prepared in Examples 1-13 of this application;

[0023] Figure 4 The diagram shows the coefficient of thermal expansion of the ceramic matrix of the particle trap prepared in Comparative Examples 1 to 9 of this application. Detailed Implementation

[0024] The present invention will be further illustrated below with reference to specific embodiments. These embodiments are implemented based on the technical solutions of the present invention, and it should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0025] The plastic expandable microspheres in the following examples were purchased from Norio Japan, model 461WU40.

[0026] The specific preparation method of magnesium-aluminum double hydroxides in the following examples includes: using brucite (D50 of 5.0~10.0 μm) and boehmite (D50 of 5.0~10.0 μm) as raw materials, a hydrothermal co-treatment method is adopted. The hydrothermal co-treatment conditions are: temperature 180~200 °C, pressure 1.2~1.5 MPa, pH value of the mixed solution of ammonia water 9~10, reaction time 15~25 h. After washing, spray drying and granulation are performed to obtain magnesium-aluminum double hydroxides (Mg-Al LDHs). The obtained magnesium-aluminum double hydroxides have a specific surface area of ​​400 m². 2 / g~500m 2 / g.

[0027] The raw material parameters used in the examples are shown in Table 1.

[0028] Table 1. Specific parameters of raw materials

[0029]

[0030] Example 1

[0031] A method for preparing a gasoline engine particulate filter with a low coefficient of expansion includes the following steps:

[0032] 1) Mix 29.5% talc-A, 10.0% kaolin, 24.0% fused silica powder, 28.5% α-alumina-A, and 8.0% magnesium aluminum hydroxide by mass using a mixer to form inorganic raw materials; add 18% starch and 3.0% expanded plastic microspheres by mass to the inorganic raw materials and mix; add 6.5% cellulose ether by mass to the total dry powder; add 4.0% lauric acid by mass to the total dry powder; and add 25% RO water by mass to the total dry powder to form mud.

[0033] 2) The obtained mud is vacuum-kneaded to a vacuum degree of less than -95 kPa; the mud is extruded and shaped in an extruder at an extrusion pressure of 15~25 MPa, and then microwave-dried until the moisture content of the mud is less than 1%.

[0034] 3) After drying, the carrier is cut and sintered at high temperature of 1410℃ for 12 hours to obtain the ceramic matrix of the particle trap. The prepared matrix has a diameter of 132.1 mm, a length of 127 mm, a pore density of 300 mesh, and a wall thickness of 0.210 mm.

[0035] 4) The ceramic substrate of the obtained particulate filter is plugged. A plugging slurry is prepared using cordierite powder, quartz powder, and silica sol. The viscosity of the slurry is 80,000~100,000 mPa·s. The two ends of the ceramic substrate are cross-plugged to a depth of 5 mm to obtain a blank gasoline engine particulate filter. Figure 1-2 As shown.

[0036] Example 2

[0037] The difference from Example 1 is that in step 1), the amount of magnesium-aluminum double hydroxide (Mg-Al LDHs) added is 12.0%, and the detailed proportions of the remaining raw materials are shown in Table 2, thus obtaining a gasoline engine particulate filter.

[0038] Example 3

[0039] The difference from Example 1 is that in step 1), the amount of magnesium-aluminum double hydroxide (Mg-Al LDHs) added is 15.0%, and the detailed proportions of the remaining raw materials are shown in Table 2, thus obtaining a gasoline engine particulate filter.

[0040] Example 4

[0041] The difference from Example 1 is that in step 1), the amount of magnesium-aluminum double hydroxide (Mg-Al LDHs) added is 18.0%, and the detailed proportions of the remaining raw materials are shown in Table 2, thus obtaining a gasoline engine particulate filter.

[0042] Example 5

[0043] The difference from Example 1 is that in step 1), the amount of magnesium-aluminum double hydroxide (Mg-Al LDHs) added is 21.0%, and the detailed proportions of the remaining raw materials are shown in Table 2, thus obtaining a gasoline engine particulate filter.

[0044] Example 6

[0045] The difference from Example 1 is that in step 1), the amount of magnesium-aluminum double hydroxide (Mg-Al LDHs) added is 25.0%, and the detailed proportions of the remaining raw materials are shown in Table 2, thus obtaining a gasoline engine particulate filter.

[0046] Example 7

[0047] The difference from Example 1 is that in step 1), the amount of magnesium-aluminum double hydroxide (Mg-Al LDHs) added is 8.0%, and the detailed proportions of the remaining raw materials are shown in Table 2, thus obtaining a gasoline engine particulate filter.

[0048] Example 8

[0049] The difference from Example 1 is that in step 1), the amount of magnesium-aluminum double hydroxide (Mg-Al LDHs) added is 12.0%, and the detailed proportions of the remaining raw materials are shown in Table 2, thus obtaining a gasoline engine particulate filter.

[0050] Example 9

[0051] The difference from Example 1 is that in step 1), the amount of magnesium-aluminum double hydroxide (Mg-Al LDHs) added is 15.0%, and the detailed proportions of the remaining raw materials are shown in Table 2, thus obtaining a gasoline engine particulate filter.

[0052] Example 10

[0053] The difference from Example 1 is that in step 1), the amount of magnesium-aluminum double hydroxide (Mg-Al LDHs) added is 18.0%, and the detailed proportions of the remaining raw materials are shown in Table 2, thus obtaining a gasoline engine particulate filter.

[0054] Example 11

[0055] The difference from Example 1 is that in step 1), the amount of magnesium-aluminum double hydroxide (Mg-Al LDHs) added is 12.0%, and the detailed proportions of the remaining raw materials are shown in Table 2, thus obtaining a gasoline engine particulate filter.

[0056] Example 12

[0057] The difference from Example 1 is that in step 1), the amount of magnesium-aluminum double hydroxide (Mg-Al LDHs) added is 15.0%, and the detailed proportions of the remaining raw materials are shown in Table 2, thus obtaining a gasoline engine particulate filter.

[0058] Example 13

[0059] The difference from Example 1 is that in step 1), the amount of magnesium-aluminum double hydroxide (Mg-Al LDHs) added is 18.0%, and the detailed proportions of the remaining raw materials are shown in Table 2, thus obtaining a gasoline engine particulate filter.

[0060] Comparative Example 1

[0061] The difference from Example 1 is that in step 1), 10% highly active alumina is used, and the detailed proportions of the remaining raw materials are shown in Table 3, to prepare a gasoline engine particulate filter.

[0062] Comparative Example 2

[0063] The difference from Example 1 is that in step 1), 15% highly active alumina is used, and the detailed proportions of the remaining raw materials are shown in Table 3, to prepare a gasoline engine particulate filter.

[0064] Comparative Example 3

[0065] The difference from Example 1 is that in step 1), 12% gibbsite is used, and the detailed proportions of the remaining raw materials are shown in Table 3, to prepare a gasoline engine particulate filter.

[0066] Comparative Example 4

[0067] The difference from Example 1 is that in step 1), 12% gibbsite is used, and the detailed proportions of the remaining raw materials are shown in Table 3, to prepare the gasoline engine particulate filter.

[0068] Comparative Example 5

[0069] The difference from Example 1 is that in step 1), 10% highly active alumina and 10% boehmite are used, and the detailed proportions of the remaining raw materials are shown in Table 3, in order to prepare a gasoline engine particulate filter.

[0070] Comparative Example 6

[0071] The difference from Example 1 is that in step 1), 10% highly active alumina and 10% gibbsite are used, and the detailed proportions of the remaining raw materials are shown in Table 3, in order to prepare a gasoline engine particulate filter.

[0072] Comparative Example 7

[0073] The difference from Example 1 is that in step 1), 10% of gibbsite monohydrate and 10% of gibbsite trihydrate are used, and the detailed proportions of the remaining raw materials are shown in Table 3, in order to prepare a gasoline engine particulate filter.

[0074] Comparative Example 8

[0075] The difference from Example 1 is that in step 1), it is a blank example, and the detailed proportions of the remaining raw materials are shown in Table 3, and a gasoline engine particulate filter is prepared.

[0076] Comparative Example 9

[0077] The difference from Example 1 is that in step 1), it is a blank example, and the detailed proportions of the remaining raw materials are shown in Table 3, and a gasoline engine particulate filter is prepared.

[0078] Table 2 Specific product formulations for Examples 1-13

[0079]

[0080] Table 3. Specific product formulations for Comparative Examples 1-9

[0081]

[0082] The ceramic matrices for particle traps prepared in Examples 1-13 and Comparative Examples 1-9 were tested for their coefficient of thermal expansion, median pore size, porosity, and thermal shock resistance. The results are shown in Table 4 and 5. Figure 3-4 The testing methods include:

[0083] Coefficient of thermal expansion: GB / T 7320-2018;

[0084] Center aperture: GB / T 21650.1-2008;

[0085] Porosity: GB / T 21650.1-2008;

[0086] Thermal shock resistance: GB / T 25994-2010.

[0087] Table 4 Performance results of the ceramic substrates for the particle traps prepared in Examples 1-13 and Comparative Examples 1-9

[0088]

[0089] From Table 4 and Figure 3-4 It is evident that the introduction of magnesium-aluminum double hydroxides (Mg-Al LDHs) into the process formulation for preparing cordierite honeycomb ceramic particle traps can significantly reduce the thermal expansion coefficient of the ceramic matrix, thereby improving the thermal shock resistance of the cordierite honeycomb ceramic particle traps. In Examples 7, 8, 9, 10, 11, 12, and 13, the low-grade raw materials (high-calcium talc and high-sodium α-alumina) used can also meet the application requirements of cordierite honeycomb ceramic particle traps by using magnesium-aluminum double hydroxides (Mg-Al LDHs). At the same time, the use of magnesium-aluminum double hydroxides (Mg-Al LDHs) can reduce the amount of organic pore-forming agent used, while still meeting the requirements for pore size and porosity of the cordierite honeycomb ceramic particle traps, thus reducing the sintering difficulty of the cordierite honeycomb ceramic particle traps.

[0090] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing a gasoline particulate filter having a low coefficient of expansion, characterized by, The inorganic raw material, pore forming agent, binder and powder electric neutral modifier are mixed, then water is added and mixed into mud, and then the mud is refined, extruded, dried, sintered to obtain a ceramic matrix, and then the ceramic matrix is cross-plugged at both ends to obtain a particle trap; wherein the inorganic raw material is composed of talc, kaolin, fused quartz powder, alpha-alumina and magnesium-aluminum double hydroxide; the powder electric neutral modifier is selected from one or more of polyvinyl alcohol, lauric acid and oleic acid; the weight percentage of the magnesium-aluminum double hydroxide is 8-25% of the inorganic raw material; D50 is 15.0-25.0 microns, the specific surface area is 400 m 2 / g-500 m 2 / g; the mass percentage of the talc is 5.0-29.5%, the mass percentage of the kaolin is 10-15%, the mass percentage of the fused quartz powder is 24-33.5%, and the mass percentage of the alpha-alumina is 21-28.5%.

2. The method of claim 1, wherein: The pore-forming agent is selected from one or more of starch, plastic expansion microspheres, graphite, carbon powder.

3. The method of claim 1, wherein: The binder is selected from one or more of cellulose, PVA.

4. The method of claim 1, wherein: The magnesium-aluminum double hydroxide is obtained by a thermal hydration reaction of brucite and diaspore, the thermal hydration condition being a temperature of 180-200 DEG C and a pH value of 9-10, and the reaction time being 15-25 h.

5. The method of claim 4, wherein: The brucite has a particle size D50 of 5.0-10.0 mu m, and the diaspore has a particle size D50 of 5.0-10.0 mu m.

6. The method of claim 1, wherein: The coefficient of thermal expansion of the ceramic matrix is 0.1×10 -6 -0.6×10 -6 / ℃, the median pore size is 16-20 μm, the porosity is 60-70%, and the thermal shock resistance is 650-900℃.

7. The gasoline engine particulate filter prepared by the method according to any one of claims 1-6.

Images