Preparation method of gasoline car honeycomb ceramic carrier with ultralow thermal expansion coefficient

Abstract

The invention discloses a preparation method of a gasoline car honeycomb ceramic carrier with an ultralow thermal expansion coefficient, and belongs to the technical field of honeycomb ceramic materials. The method comprises the following steps: selecting raw materials; performing pretreatment; mixing the materials; kneading mud; performing extrusion molding; and cutting and firing to obtain the cordierite honeycomb ceramic carrier. A magnesium source in talc and a part of an aluminum source in alpha-aluminum oxide are replaced by the monohydrate boehmite and the magnesium oxide which are higher in reaction activity, the sol is formed through a complexation reaction with citric acid, then the sol is mixed with silicon dioxide and aluminum oxide particles, the reaction activity of a solid-phase reaction is improved at the same firing temperature, and the solid-phase reaction time is shortened. The thermal expansion coefficient of the cordierite honeycomb ceramic carrier is effectively reduced, and the thermal shock resistance requirement of gasoline cars in the national sixth emission standard can be met.

Description

Technical Field

[0001] The invention belongs to the technical field of honeycomb ceramic materials, and in particular relates to a method for preparing a honeycomb ceramic carrier for a gasoline vehicle with an ultra-low thermal expansion coefficient. Background Art

[0002] Honeycomb ceramics are porous industrial ceramics with many interconnected honeycomb-shaped parallel channels. These honeycomb units are divided by thin lattice partitions. Compared with general block ceramics, honeycomb ceramics have large specific surface area, low pressure drop, low resistance, high temperature resistance, good chemical stability, low thermal expansion, good thermal insulation, light weight, and high strength. Therefore, they are particularly suitable for catalyst carriers for various purposes. At present, honeycomb ceramics are mainly made of ceramic materials with cordierite as the main crystal phase. In the existing technology, kaolin, alumina, talc and other ingredients are extruded into molds, so that the flaky raw materials such as kaolin and talc are oriented in the extrusion direction of the product, and finally only a thermal expansion coefficient of <0.8×10 -6 / ℃ cordierite honeycomb ceramic carrier; For example, in the prior art, by controlling the diameter-thickness ratio of raw kaolin crystals, it is finally possible to prepare a honeycomb ceramic carrier with an expansion coefficient of <0.5×10 -6 / ℃ cordierite honeycomb ceramic carrier.

[0003] With the development of modern automobile industry, honeycomb ceramic carriers need to have stronger thermal shock resistance. Although increasing the number of holes and reducing the thickness of the pore wall can improve the thermal shock resistance of some ceramic carriers to a certain extent, it is still not enough to meet the needs of modern automobile industry. Therefore, the key to improving the thermal shock resistance of honeycomb ceramic carriers is to reduce the thermal expansion coefficient of honeycomb ceramic carriers. Summary of the invention

[0004] The technical problem solved by the present invention is to provide a method for preparing a honeycomb ceramic carrier for gasoline vehicles with an ultra-low thermal expansion coefficient. The carrier prepared by the present invention has an ultra-low thermal expansion coefficient and can meet the thermal shock resistance requirements of the National VI emission standards for gasoline vehicles.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a honeycomb ceramic substrate for a gasoline vehicle with an ultra-low thermal expansion coefficient, characterized in that it comprises the following steps:

[0007] 1) First, diaspore, magnesium oxide and citric acid are added to water and mixed, nitric acid is added, heated and stirred, and then ethanol is added to prepare a sol;

[0008] 2) mixing the sol prepared in step 1) with alumina, silica, a lubricant, a binder and water;

[0009] 3) kneading, roughing and refining the clay in a clay kneading machine to obtain clay material;

[0010] 4) The clay material is extruded and formed in an extruder to obtain a honeycomb ceramic carrier clay blank;

[0011] 5) The honeycomb ceramic carrier clay blank is subjected to microwave drying and shaping;

[0012] 6) The dried carrier is cut and fired to obtain a cordierite honeycomb ceramic carrier.

[0013] In the step 1), the molar ratio of aluminum ions to magnesium ions is 1:1-3.

[0014] In the step 1), the pH of the solution is adjusted to 3-5.

[0015] The heating and stirring temperature in step 1) is 80-90°C.

[0016] In the step 2), the average particle size of alumina is 5±0.5 μm, the average particle size of silicon dioxide is 13±1 μm, the average particle size of gibbsite is 42±1 μm, and the average particle size of magnesium oxide is 21±2 μm.

[0017] The amount of each raw material used in the steps 1) and 2) is 8-23 parts of diaspore, 12-13 parts of magnesium oxide, 19-30 parts of aluminum oxide, and 46-49 parts of silicon dioxide. In every 100 parts of inorganic main materials, 68-124 parts of citric acid, 1.2-1.7 parts of lubricant, and 2.3 parts of binder are added.

[0018] The moisture content of the mud in step 3) is 18% to 20% by weight.

[0019] In the step 6), at 200-400°C, the corresponding heating rate is ≤5°C / h; at 800-1300°C, the corresponding heating rate is ≥80°C / h; and the temperature is kept at 1390°C for 10 hours.

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

[0021] (1) The present invention replaces the magnesium source in talc and part of the aluminum source in α-alumina with gibbsite and magnesium oxide with higher reaction activity, forms a sol by complexing with citric acid, and then mixes with silicon dioxide, alumina particles, lubricant, and binder, and then performs subsequent steps according to the existing cordierite honeycomb ceramic process. By increasing the reaction activity of the solid phase reaction, the generation of cordierite is increased at the same firing temperature, and the thermal expansion coefficient of the cordierite honeycomb ceramic carrier is reduced.

[0022] (2) The thermal expansion coefficient of the cordierite honeycomb ceramic carrier prepared by the present invention in the extrusion axial direction is ≤0.2×10 -6 / ℃, which is at the leading level among similar products on the market. At the same time, the citric acid precursor acts as a pore-forming agent in the preparation process, improving the porosity and water absorption rate. DETAILED DESCRIPTION

[0023] The present invention is further illustrated below in conjunction with specific examples. The examples are implemented based on the technical solutions of the present invention. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0024] The raw material requirements used in the following examples are shown in Table 1.

[0025] Table 1 Specific parameters of raw materials

[0026]

[0027] Example 1

[0028] A method for preparing a honeycomb ceramic substrate for a gasoline vehicle with an ultra-low thermal expansion coefficient comprises the following steps:

[0029] (1) Citric acid, diaspore and magnesium oxide are added to deionized water respectively, and a 65% nitric acid solution is added to adjust the pH to 3. The mixture is heated and stirred at 80 to 90° C., and ethanol is gradually added to prepare a sol.

[0030] (2) Mix the sol of aluminum citrate and magnesium citrate with silicon dioxide, aluminum oxide, lubricant, binder and water. The specific amount of each raw material is shown in Table 2.

[0031] (3) Kneading, rough refining and refining are performed in a kneading machine to obtain a mud material, the moisture content of which is 18% to 20%.

[0032] (4) The clay material is extruded and formed in an extruder, and the temperature of the extruded clay blank is controlled to be ≤28° C. to obtain a honeycomb ceramic carrier clay blank.

[0033] (5) The honeycomb ceramic carrier clay blank is subjected to microwave drying and shaping, and the weight ratio of the clay blank after drying to the weight ratio of the clay blank before drying is controlled to be 0.8:1.

[0034] (6) The dried carrier is cut and fired to obtain a cordierite honeycomb ceramic carrier. The firing temperature control program is as follows: at 200-400°C, the heating rate is ≤5°C / h; at 800-1300°C, the heating rate is ≥80°C / h; and the carrier is kept at 1390°C for 10 hours.

[0035] Table 2 Product components and dosage (in parts) and test results

[0036]

[0037]

[0038] In Table 2, the lubricant is a mixture of polyethylene glycol and oleic acid; and the binder is hydroxypropyl methylcellulose.

[0039] Example 2

[0040] A honeycomb ceramic carrier was prepared according to the method of product 2 in Example 1, except that the pH value was adjusted to 4 in step 1).

[0041] Example 3

[0042] A honeycomb ceramic carrier was prepared according to the method of product 2 in Example 1, except that the pH value was adjusted to 5 in step 1).

[0043] Comparative Example 1

[0044] The steps of preparing the honeycomb ceramic carrier according to the original process are as follows:

[0045] 1) 35 parts of talc, 32 parts of alumina, 10 parts of silicon dioxide and 23 parts of kaolin, plus 0.2 parts of a binder, are mixed and then mixed with water.

[0046] 2) Kneading, rough refining and refining are carried out in a mud kneading machine to obtain mud material.

[0047] 3) The clay material is extruded and formed in an extruder to obtain a honeycomb ceramic carrier green body, which is then dried.

[0048] 4) After the processing, the green body is fired according to the firing method of Example 1 to obtain a cordierite honeycomb ceramic carrier.

[0049] Table 3 Product test results

[0050]

[0051]

[0052] From Table 3, compared with the conventional cordierite honeycomb ceramic carrier manufacturing process, the present application can effectively reduce the thermal expansion coefficient of the cordierite honeycomb ceramic carrier under the same firing system by improving the raw material selection and adjusting the corresponding process. At the same time, the micropores formed by citric acid after combustion can increase the water absorption rate of the carrier, which helps to increase the coating amount of the catalyst.

[0053] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a honeycomb ceramic substrate for a gasoline vehicle with an ultra-low thermal expansion coefficient, characterized in that: The following steps are involved: 1) First, diaspore, magnesium oxide and citric acid are added to water and mixed, nitric acid is added, heated and stirred, and then ethanol is added to prepare a sol; 2) mixing the sol prepared in step 1) with alumina, silica, a lubricant, a binder and water; 3) kneading, roughing and refining the clay in a clay kneading machine to obtain clay material; 4) The clay material is extruded and formed in an extruder to obtain a honeycomb ceramic carrier clay blank; 5) The honeycomb ceramic carrier clay blank is subjected to microwave drying and shaping; 6) The dried carrier is cut and fired to obtain a cordierite honeycomb ceramic carrier.

2. The method for preparing the honeycomb ceramic substrate for gasoline vehicles with ultra-low thermal expansion coefficient according to claim 1, characterized in that: In the step 1), the molar ratio of aluminum ions to magnesium ions is 1:1-3.

3. The method for preparing the honeycomb ceramic substrate for gasoline vehicles with ultra-low thermal expansion coefficient according to claim 1, characterized in that: In the step 1), the pH of the solution is adjusted to 3-5.

4. The method for preparing the honeycomb ceramic substrate for gasoline vehicles with ultra-low thermal expansion coefficient according to claim 1, characterized in that: The heating and stirring temperature in step 1) is 80-90°C.

5. The method for preparing the honeycomb ceramic substrate for gasoline vehicles with ultra-low thermal expansion coefficient according to claim 1, characterized in that: In the step 2), the average particle size of alumina is 5±0.5 μm, the average particle size of silicon dioxide is 13±1 μm, the average particle size of gibbsite is 42±1 μm, and the average particle size of magnesium oxide is 21±2 μm.

6. The method for preparing the honeycomb ceramic substrate for gasoline vehicles with ultra-low thermal expansion coefficient according to claim 1, characterized in that: The amount of each raw material used in the steps 1) and 2) is 8-23 parts of diaspore, 12-13 parts of magnesium oxide, 19-30 parts of aluminum oxide, and 46-49 parts of silicon dioxide. In every 100 parts of inorganic main materials, 68-124 parts of citric acid, 1.2-1.7 parts of lubricant, and 2.3 parts of binder are added.

7. The method for preparing the honeycomb ceramic substrate for gasoline vehicles with ultra-low thermal expansion coefficient according to claim 1, characterized in that: The moisture content of the mud in step 3) is 18% to 20% by weight.

8. The method for preparing the honeycomb ceramic substrate for gasoline vehicles with ultra-low thermal expansion coefficient according to claim 1, characterized in that: In the step 6), at 200-400°C, the corresponding heating rate is ≤5°C / h; at 800-1300°C, the corresponding heating rate is ≥80°C / h; and the temperature is kept at 1390°C for 10 hours.

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