A low-cost and high-performance honeycomb ceramic and its preparation method and application

Abstract

The present invention discloses a low-cost and high-performance honeycomb ceramic, its preparation method and application. Silica fume is added to the inorganic raw materials of the low-cost and high-performance honeycomb ceramic to completely or partially replace the quartz powder commonly used in the traditional synthesis of cordierite. Since the price of silica fume is much lower than that of fused quartz powder, but its influence on the performance of the honeycomb ceramic is small when partially replacing quartz powder, and it has an obvious effect on cost reduction.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramics, and particularly relates to a honeycomb ceramic with low cost and high performance, a preparation method thereof, and an application thereof. Background Art

[0002] Honeycomb ceramics are mainly applied to the post-treatment system of vehicle engines to treat and purify engine exhaust gas. The main functions are to reduce the emissions of harmful substances such as nitrogen oxides, hydrocarbons, nitric oxide, soot particles, and formaldehyde in vehicle exhaust gas, reduce the environmental pollution caused by vehicles during driving, and reduce the harm to human health. At the same time, the post-treatment system can improve the combustion efficiency and energy utilization rate of the engine. Since the implementation of the National IV emission standard, the post-treatment system has become an essential device for controlling vehicle exhaust pollutants. Honeycomb ceramics have become indispensable components of the post-treatment system due to their unique structure and are widely used in purifying vehicle exhaust gas. They can be used as carriers to provide reaction sites for catalysts for purifying exhaust gas, or as filters to remove particulate matter in the exhaust gas. However, as a means of transportation, the space left for the post-treatment system in vehicles is limited. During the development of the post-treatment system, not only the emission limit requirements need to be considered, but also the reasonable layout of the configuration needs to be considered. At the same time, the market's acceptance of prices needs to be concerned. Therefore, the development of the post-treatment system needs to meet the design goal of low cost, and the development of low-cost honeycomb ceramics has also become part of reducing the cost of the post-treatment system.

[0003] Currently, the wall thickness of honeycomb ceramic catalyst carriers that meet the market regulatory limit standards of Euro VI, National VI and later and are widely used is generally 3 - 6 mil, and the porosity is 30 - 40%. The wall thickness of honeycomb ceramic diesel particulate filters is generally 9 - 12 mil, and the porosity is 45% - 55%. The wall thickness of honeycomb ceramic gasoline particulate filters is generally 8 mil, and the porosity is 55% - 65%. The future market demand for Euro VII and National VII is for honeycomb ceramics with a wall thickness of 2 mil - 9 mil and a porosity of 45 - 65%. Compared with the National IV and National V stages, whether it is the regulations in the National VI stage or the National VII stage, higher requirements are put forward for the post-treatment system. The upgrade of technology will definitely bring an increase in cost. In order to better meet the needs of users, reducing costs has become the focus of market attention. However, low cost and high performance of honeycomb ceramics are a pair of contradictory points and also difficult technical problems to overcome. Summary of the Invention

[0004] In order to solve the above technical problems, one of the purposes of the present invention is to provide a honeycomb ceramic that can reduce costs and has good performance.

[0005] In order to achieve the above purpose, the technical solution of the present invention is as follows: A low-cost and high-performance honeycomb ceramic, in which silica fume is added to the inorganic raw materials to completely or partially replace quartz powder.

[0006] Preferably, the inorganic raw materials include talc, alumina, quartz powder and silica fume.

[0007] Preferably, the inorganic raw materials further include at least one of kaolin, boehmite and aluminum hydroxide.

[0008] Preferably, the mass fractions of the raw materials in the inorganic raw materials are as follows: talc 38 - 40 wt%, kaolin 0 - 7 wt%, boehmite 0 - 2%, aluminum hydroxide 0 - 10 wt%, alumina 22 - 32 wt%, quartz powder 4 - 16 wt%, silica fume 6 - 18 wt%.

[0009] Preferably, the specifications of the raw materials in the inorganic raw materials are as follows:

[0010] Talc: D50 is 31 - 50 μm, D97 ≤ 95 μm;

[0011] Kaolin: D50 is 2 - 20 μm, D97 ≤ 60 μm;

[0012] Boehmite: D50 is 0.5 - 6 μm, D97 ≤ 6 μm;

[0013] Aluminum hydroxide: D50 is 1 - 10 μm, D97 ≤ 20 μm;

[0014] Alumina: D50 is 1 - 7 μm, D97 ≤ 25 μm;

[0015] The particle size D50 of quartz powder is 30 - 40 μm, D97 ≤ 90 μm;

[0016] The purity of silica fume ≥ 95%, the particle size D50 is 0.5 - 15 μm, D97 ≤ 40 μm.

[0017] The second object of the present invention is to provide a preparation method of a honeycomb ceramic with low cost and high performance.

[0018] In order to achieve the above object, another technical solution of the present invention is as follows: A preparation method of a honeycomb ceramic with low cost and high performance as described above, characterized by comprising the following steps:

[0019] Step 1: Mix the inorganic raw materials, pore-forming agent and binder to obtain a powder material;

[0020] Step 2: Add water and lubricant to the powder material, and knead and refine it into a plastic clay segment;

[0021] Step 3: Extrude the clay segment into a green body with a honeycomb structure and dry and shape it;

[0022] Step 4: Fire the green body to obtain a cordierite honeycomb ceramic body.

[0023] Preferably, the addition amount of the pore former is 11-21% of the total weight of the inorganic raw materials, and the addition amount of the binder is 5-6% of the total weight of the inorganic raw materials.

[0024] Preferably, in step 2, the addition amounts of the lubricant and water are 1% and 30% of the total weight of the powder respectively.

[0025] Preferably, the pore former is at least one of starch, graphite, polymethyl methacrylate, polyethylene polymer, graphene precursor and fruit shell powder, and its particle size D50 is 30-40μm, D97≤90μm.

[0026] The third object of the present invention is to provide an application of a low-cost and high-performance honeycomb ceramic, which is used as a catalyst carrier or a filter.

[0027] The beneficial effects of the present invention are as follows: The present invention breaks through the technical difficulties in the development of low-cost and high-performance honeycomb ceramics, and develops honeycomb ceramics with a wall thickness of 2mil-12mil and a porosity of 45-65%, meeting the diversified needs of different regional markets and contributing to the control of air pollution. It can adopt single pore shapes such as triangular, quadrangular, hexagonal, etc., or multiple pore types such as quadrangular, hexagonal, asymmetric, etc. There is no need to adopt a single pore shape in the honeycomb structure, and preferably a quadrangular pore is adopted. The present invention has no particular limitation on the pore density of the honeycomb structure, and it can be any pore density that can be extruded into a honeycomb shape, such as 200cpsi, 300cpsi, 400cpsi, etc. Detailed Embodiments

[0028] Next, the technical solutions in the embodiments of the present invention will be described clearly and completely in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts belong to the scope of protection of the present invention.

[0029] On the one hand, this embodiment provides a honeycomb ceramic with low cost and high performance, in which silica fume is added to the inorganic raw materials to completely or partially replace quartz powder. Preferably, the inorganic raw materials include talc, alumina, quartz powder and silica fume. Further preferably, the inorganic raw materials further include at least one of kaolin, boehmite and aluminum hydroxide. Specifically, the mass fractions of the respective raw materials in the inorganic raw materials are as follows: talc 38-40 wt% (which can be any value from 38 wt%, 38.1 wt%, 38.2 wt%, 38.3 wt%, 38.4 wt%, 38.5 wt%, 38.6 wt%, 38.7 wt%, 38.8 wt%, 38.9 wt%, 39 wt%, 39.1 wt%, 39.2 wt%, 39.3 wt%, 39.4 wt%, 39.5 wt%, 39.6 wt%, 39.7 wt%, 39.8 wt%, 39.9 wt% and 40 wt% or the corresponding range between any two values), kaolin 0-7 wt% (which can be any value from 0, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt% and 7 wt% or the corresponding range between any two values), aluminum hydroxide 0-10 wt% (which can be any value from 0, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt% and 10 wt% or the corresponding range between any two values), boehmite 0-2 wt% (which can be any value from 0, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt% and 2 wt% or the corresponding range between any two values), alumina 24-30 wt% (which can be any value from 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt% and 30 wt% or the corresponding range between any two values), quartz powder 4-16 wt% (which can be any value from 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt% and 16 wt% or the corresponding range between any two values), silica fume 6-18 wt% (which can be any value from 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt% and 18 wt% or the corresponding range between any two values).

[0030] Preferably, the specifications of each raw material in the inorganic raw materials are as follows: talc: D50 is 31 - 50 μm, D97 ≤ 95 μm; kaolin: D50 is 2 - 20 μm, D97 ≤ 60 μm; boehmite: D50 is 0.5 - 6 μm, D97 ≤ 10 μm; aluminum hydroxide: D50 is 1 - 10 μm, D97 ≤ 20 μm; alumina: D50 is 1 - 7 μm, D97 ≤ 25 μm; quartz powder can be ordinary irregular-shaped quartz powder, or spherical quartz powder, hollow quartz powder, etc., and can be crystalline quartz powder or amorphous quartz powder, with a particle size D50 of 30 - 40 μm, D97 ≤ 90 μm; the purity of silica fume is ≥ 95%, preferably ≥ 96%, more preferably ≥ 97%, with a particle size D50 of 0.5 - 15 μm, D97 ≤ 40 μm.

[0031] On the other hand, this embodiment provides a method for preparing the low-cost and high-performance honeycomb ceramics as described above, comprising the following steps:

[0032] Step 1: Dry-mix the inorganic raw materials, pore-forming agent, and binder to obtain a powder material;

[0033] Step 2: Add water and a lubricant to the powder material, and knead and refine it into a plastic clay segment;

[0034] Step 3: Extrude the clay segment into a green body with a honeycomb structure and dry and shape it;

[0035] Step 4: Fire the green body to obtain a cordierite honeycomb ceramic body (heating at a rate of less than 20 °C / h between room temperature and 500 °C, heating at a rate of less than 30 °C / h between 500 - 1000 °C, heating at a rate of less than 50 °C / h between 1000 °C and the holding temperature, and the holding time is 10 - 16 hours).

[0036] Preferably, the addition amount of the pore-forming agent is 11 - 21% of the total weight of the inorganic raw materials, and the addition amount of the binder is 5 - 6% of the total weight of the inorganic raw materials.

[0037] Preferably, the addition amounts of the lubricant and water in Step 2 are 1% and 30% of the total weight of the powder material, respectively.

[0038] Preferably, the pore-forming agent is at least one of starch, graphite, polymethyl methacrylate, polyethylene polymer, graphene precursor, and fruit shell powder, and its particle size D50 is 30 - 40 μm, D97 ≤ 90 μm.

[0039] The third object of the present invention is to provide an application of the low-cost and high-performance honeycomb ceramics, used as a catalyst carrier (the honeycomb ceramics of the present invention can be used as a diesel particulate filter, can be used as a gasoline particulate filter, or can be used as a high-porosity catalyst carrier. Just as a filter, there is a difference in the preparation method from the catalyst carrier, with the addition of a pore plugging process).

[0040] Silica fume, also known as microsilica or silicon powder, is formed by collecting and processing the smoke and dust escaping with the waste gas during the high-temperature smelting of industrial silicon and ferrosilicon in industrial electric furnaces through special trapping devices. Among the main components of silica fume, the SiO2 content reaches over 80%, and most of it is amorphous SiO2. The contents of other components are relatively small. The contents of iron oxide, calcium oxide, and sulfur oxide vary slightly depending on the ore composition, generally not exceeding 1%, and the loss on ignition is about 1.5% - 3%. Due to the special formation conditions of silica fume, it has the characteristics of fine particles and a large specific surface area. At the same time, silicon powder also has extremely high pozzolanic activity. It should be noted that very small particles will necessarily exhibit a strong filling effect, and spherical particle shapes will necessarily exhibit a strong lubricating effect. Compared with the silica source quartz powder commonly used in the industrial synthesis of cordierite, silica fume is very cheap. The price of silica fume with a content of ≥95% is 200 - 3000 yuan / ton, the price of ordinary fused quartz powder is at least 7000 - 9000 yuan / ton, and the price of spherical fused quartz powder exceeds 12000 - 18000 yuan / ton. Therefore, the use of silica fume can reduce costs from both the aspects of raw material price and production efficiency, and can also maintain the high performance of cordierite.

[0041] Among them, the lubricant is base oil, tall oil, oleic acid, poly-α-olefin oil, stearate, hydrocarbon oil, etc.; the binder is methyl cellulose, hydroxypropyl methyl cellulose or carboxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose or polyvinyl alcohol, etc.

[0042] In the present invention, by using low-cost silica fume as the silica source for synthesizing cordierite, compared with quartz powder, silica fume has a lower price, achieving the purpose of cost reduction. And silica fume has a spherical particle shape and a large specific surface area, showing a strong lubricating effect, which can improve the lubricating performance of the mud, improve production efficiency, and reduce production costs. At the same time, some special requirements are made for silica fume. High-purity silica fume is selected and the formula ratio is adjusted to overcome the contradiction between low cost and high performance. Honeycomb ceramics with a wall thickness of 2mil - 12mil and a porosity of 45 - 65% are developed. At the same time, the developed honeycomb ceramics have a narrow micropore distribution with D10≥5μm and D90≤18μm, providing guarantee for the diversified needs of the market under the emission regulations of the sixth and seventh stages, and contributing to the treatment of air pollution.

[0043] Example 1

[0044] The inorganic raw materials are 40wt% talc, 7wt% kaolin, 2% diaspore, 30wt% alumina, 15wt% quartz powder, and 6wt% silica fume; the addition amount of the pore former is 11wt% of the total weight of the inorganic raw materials, and the addition amount of the binder is 5wt% of the total weight of the inorganic raw materials; the addition amount of the lubricant is 1wt% of the total weight of the powder, and the addition amount of water is 30wt% of the total weight of the powder.

[0045] Example 2

[0046] Same as Example 1, except that the content of quartz powder in the inorganic raw material is 12 wt%, and the content of silica fume is 9 wt%.

[0047] Example 3

[0048] Same as Example 1, except that the content of quartz powder in the inorganic raw material is 9 wt%, and the content of silica fume is 12 wt%.

[0049] Example 4

[0050] Same as Example 1, except that the content of quartz powder in the inorganic raw material is 6 wt%, and the content of silica fume is 15 wt%.

[0051] Example 5

[0052] Same as Example 1, except that the content of alumina in the inorganic raw material is 29 wt%, the content of quartz powder is 4 wt%, and the content of silica fume is 18 wt%.

[0053] Example 6

[0054] Same as Example 1, except that the inorganic raw material includes 40 wt% talc, 2 wt% boehmite, 33 wt% alumina, 16 wt% quartz powder, and 9 wt% silica fume.

[0055] Example 7

[0056] Same as Example 1, except that the inorganic raw material includes 38 wt% talc, 7 wt% kaolin, 2 wt% boehmite, 10 wt% aluminum hydroxide, 22 wt% alumina, 12 wt% quartz powder, and 9 wt% silica fume.

[0057] Example 8

[0058] Same as Example 1, except that the inorganic raw material includes 40 wt% talc, 7 wt% kaolin, 32 wt% alumina, 12 wt% quartz powder, and 9 wt% silica fume, the addition amount of the pore-forming agent is 21 wt% of the total weight of the inorganic raw material, and the addition amount of the binder is 5 wt% of the total weight of the inorganic raw material.

[0059] Comparative Example 1

[0060] Same as Example 1, except that the inorganic raw material includes 40 wt% talc, 7 wt% kaolin, 2 wt% boehmite, 30 wt% alumina, and 21 wt% quartz powder.

[0061] Comparative Example 2

[0062] Same as Example 1, except that the inorganic raw materials include 40 wt % talc, 7 wt % kaolin, 32 wt % alumina and 21 wt % quartz powder.

[0063] Comparative Example 3

[0064] Same as Example 1, except that the inorganic raw materials include 39wt% talc, 7wt% kaolin, 2wt% boehmite, 10wt% aluminum hydroxide, 22wt% aluminum oxide, and 20wt% quartz powder.

[0065] Comparative Example 4

[0066] Same as Example 1, except that the inorganic raw materials include 40wt% talc, 7wt% kaolin, 2wt% boehmite, 30wt% alumina, and 21wt% quartz powder.

[0067] The specific properties of honeycomb ceramics are shown in the following table:

[0068] Performance List

[0069]

[0070] In order to compare and analyze the advantages of each embodiment, the honeycomb ceramic is extruded into 7 mil wall thickness and 300 cpsi pore density for performance listing, and the test methods of the above indicators belong to the prior art in this field and are not described here in detail.

[0071] Examples 1 to 5 list the extrusion speed and performance of honeycomb ceramics with different silica fume additions, and the results are shown in the table above. Comparison with Comparative Example 1 shows that as the amount of silica fume added increases, the extrusion speed shows an increasing trend, and the thermal expansion coefficient, porosity, D10, D90, and micropore distribution show a decreasing trend as the amount of silica fume added increases. This is mainly because the impurity content of silica fume as a silicon source for synthesizing cordierite is higher than that of quartz powder. As the amount of silica fume added increases, the impurity content increases. When the impurity content increases to a certain extent, the thermal expansion coefficient will increase significantly. At the same time, the source of silica fume determines that the particle size is slightly fine, so the porosity, D10, and D90 all have a decreasing trend. However, when the amount of silica fume added is 9-12wt%, the extrusion speed of the carrier is faster, and the thermal expansion coefficient and other properties are not significantly different from those without adding silica fume. However, when the amount of silica fume added is 9wt%, the micropore distribution D90 / D10 is not significantly different from the comparative example, and the micropore distribution D90 / D10 is slightly wider when the amount of silica fume added is 12wt%. Compared with spherical quartz powder, silica fume can increase the extrusion speed because of its fine particles and large specific surface area. At the same time, silica fume also has extremely high volcanic ash activity. Very small particles will inevitably show a strong filling effect, and the spherical particle shape will inevitably show a strong lubricating effect.

[0072] Comparing Examples 6-8 with Comparative Examples 2-4, it can be seen that under the condition of the optimal addition amount of 9 wt% of selected-area silica fume, by adjusting the types and addition amounts of the raw materials for synthesizing cordierite, the extrusion speed using silica fume is faster than that using quartz powder, and at the same time, the performance has no significant difference from that using quartz powder. Therefore, from the perspective of the cost of silica fume raw materials and the extrusion speed, the production cost of the carrier is significantly reduced.

[0073] The embodiments of the present invention have been introduced in detail above. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those skilled in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A low-cost and high-performance honeycomb ceramic is used to prepare a cordierite honeycomb ceramic body with a coefficient of thermal expansion of 0.36×10 -6 ( / ℃), a wall thickness of 2 mil - 12 mil, a porosity of 54%, D10 = 6.3 μm and D90 = 17.5 μm, characterized in that The mass fractions of the raw materials in the inorganic raw materials are as follows: talc 40wt%, kaolin 7wt%, boehmite 2wt%, alumina 30wt%, quartz powder 15wt%, silica fume 6wt%; The specifications of the raw materials in the inorganic raw materials are as follows: Talc: D50 is 31 - 50μm, D97 ≤ 95μm; Kaolin: D50 is 2 - 20μm, D97 ≤ 60μm; Boehmite: D50 is 0.5 - 6μm, D97 ≤ 6μm; Alumina: D50 is 1 - 7μm, D97 ≤ 25μm; The particle size of the quartz powder D50 is 30 - 40μm, D97 ≤ 90μm; The purity of the silica fume ≥ 95%, the particle size D50 is 0.5 - 15μm, D97 ≤ 40μm.

2. A preparation method of the low-cost and high-performance honeycomb ceramics as described in claim 1, characterized in that, It includes the following steps: Step 1: Mix the inorganic raw materials, pore-forming agent and binder to obtain a powder; Step 2: Add water and lubricant to the powder, knead and refine it into a plastic clay segment; Step 3: Extrude the clay segment into a green body with a honeycomb structure and dry and shape it; Step 4: Fire the green body to obtain a cordierite honeycomb ceramic body.

3. The preparation method of the low-cost and high-performance honeycomb ceramics according to claim 2, characterized in that, The addition amount of the pore-forming agent is 11 - 21% of the total weight of the inorganic raw materials, and the addition amount of the binder is 5 - 6% of the total weight of the inorganic raw materials.

4. The preparation method of the low-cost and high-performance honeycomb ceramics according to claim 2, wherein In Step 2, the addition amounts of the lubricant and water are 1% and 30% of the total weight of the powder respectively.

5. The preparation method of the low-cost and high-performance honeycomb ceramics according to claim 2, wherein, The pore-forming agent is at least one of starch, graphite, polymethyl methacrylate, polyethylene polymer and fruit shell powder, and its particle size D50 is 30 - 40μm, D97 ≤ 90μm.

6. Application of a low-cost and high-performance honeycomb ceramic as described in claim 1, characterized in that, It is used as a catalyst carrier.

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