Honeycomb ceramic monolith and honeycomb ceramic carrier, and preparation methods therefor, and exhaust gas catalytic core

Abstract

A honeycomb ceramic monolith and a honeycomb ceramic carrier, and preparation methods therefor, and an exhaust gas catalytic core. The honeycomb ceramic monolith has a porosity of 55-65%, a thermal diffusivity greater than or equal to 6 mm2 / s, and a shrinkage less than 5%. The present invention provides a honeycomb ceramic monolith having a suitable porosity, a sufficiently high thermal diffusivity, and a small shrinkage, a honeycomb ceramic carrier formed by the monolith, and an exhaust gas catalytic core formed by the honeycomb ceramic carrier.

Description

Honeycomb ceramic unit, honeycomb ceramic carrier and preparation method thereof, and tail gas catalytic core TECHNICAL FIELD

[0001] The present application relates to the field of honeycomb ceramic carrier, in particular to a honeycomb ceramic unit, a honeycomb ceramic carrier and a preparation method thereof, and a tail gas catalytic core. BACKGROUND

[0002] At present, the main filter materials on the market are cordierite, aluminum titanate, mullite, silicon carbide, etc. The cordierite material generally has a maximum temperature resistance of not more than 1300 DEG C, and the use temperature is relatively low. The filter made of aluminum titanate has the disadvantages of low mechanical strength, easy to break during packaging, and easy to decompose into titanium dioxide, which causes the thermal expansion coefficient of the product to rapidly increase and cracking. The mullite material also has the characteristics of high CTE, easy to produce chlorinated salt and fluorinated pollutants, etc. The porous ceramic made of silicon carbide material can maintain high temperature strength up to 1600 DEG C or above, completely avoiding the potential risks of other material filters, and can better adapt to the harsh working conditions during the use of diesel vehicles. Silicon bonding is a mainstream method for preparing silicon carbide honeycomb ceramics. However, the product prepared by silicon bonding has the problems of large shrinkage, difficult to maintain the shape of the finished product, low thermal diffusivity, and easy to cause uneven temperature distribution, etc. Especially when the porosity is increased to more than 60%, the shrinkage is often greater than 5%, and the thermal diffusivity is often less than 6 mm 2 / s.

[0003] Therefore, there is an urgent need for a honeycomb ceramic carrier with appropriate porosity, and at the same time, a large enough thermal diffusivity and a relatively small shrinkage, to meet the needs of tail gas catalytic filtration. SUMMARY

[0004] The purpose of the present application is to provide a honeycomb ceramic unit, a honeycomb ceramic carrier and a preparation method thereof, and a tail gas catalytic core, so as to obtain a honeycomb ceramic unit with appropriate porosity and large enough thermal diffusivity and relatively small shrinkage, a honeycomb ceramic carrier composed of the unit, and a tail gas catalytic core composed of the honeycomb ceramic carrier.

[0005] To achieve the above purpose, the present application provides the following technical solutions:

[0006] A honeycomb ceramic unit, the porosity of the honeycomb ceramic unit is 55-65%, the thermal diffusivity is greater than or equal to 6 mm 2 / s, and the shrinkage in each direction is less than or equal to 4%.

[0007] In some embodiments of the present application, the porosity of the honeycomb ceramic unit is 57-63%, the thermal diffusivity is greater than or equal to 7 mm 2 / s, and the shrinkage in each direction is less than 3.5%.

[0008] In some embodiments of the present application, the honeycomb ceramic unit has a shrinkage rate of 0.5-4% in the height direction, 1-4% in the length direction, and 1-4% in the width direction, and a compressive strength of 2-8 MPa in the longitudinal axis.

[0009] Preferably, the honeycomb ceramic unit has a shrinkage rate of 0.5-2% in the height direction, 1-3.5% in the length direction, and 1-3% in the width direction, and a compressive strength of 3-7.5 MPa in the longitudinal axis.

[0010] In some embodiments of the present application, the raw material of the honeycomb ceramic unit comprises silicon carbide powder, silicon powder, alkaline earth metal oxide, clay, binder, pore-forming agent, and lubricant.

[0011] In some embodiments of the present application, the raw material of the honeycomb ceramic unit comprises 75-85 parts by weight of silicon carbide powder, 15-25 parts by weight of silicon powder, 0.2-2 parts by weight of alkaline earth metal oxide, 0.5-1.5 parts by weight of clay, 15-25 parts by weight of binder, 25-35 parts by weight of pore-forming agent, 20-70 parts by weight of water, and 2-15 parts by weight of lubricant.

[0012] Preferably, the raw material of the honeycomb ceramic unit comprises 75-85 parts by weight of silicon carbide powder, 15-25 parts by weight of silicon powder, 1.2-2 parts by weight of alkaline earth metal oxide, 0.5-1.5 parts by weight of clay, 15-25 parts by weight of binder, 25-35 parts by weight of pore-forming agent, 30-60 parts by weight of water, and 3-10 parts by weight of lubricant.

[0013] In some embodiments of the present application, the silicon carbide powder comprises primary silicon carbide powder with a D50 of 15-50 μm and secondary silicon carbide powder with a D50 of 1-12 μm.

[0014] Preferably, the primary silicon carbide powder has a D50 of 20-45 μm, and the secondary silicon carbide powder has a D50 of 2-10 μm.

[0015] In some embodiments of the present application, the mass ratio of the primary silicon carbide powder to the secondary silicon carbide powder is (65-80):(2-15).

[0016] Preferably, the mass ratio of the primary silicon carbide powder to the secondary silicon carbide powder is (65-80):(5-15).

[0017] In some embodiments of the present application, the alkaline earth metal oxide is selected from at least one of magnesium oxide, beryllium oxide, strontium oxide, calcium oxide, and barium oxide.

[0018] In some embodiments of the present application, the binder is selected from at least one of polyvinyl alcohol, glycerol, ethyl cellulose, polyethylene glycol, methyl cellulose, potassium laurate and carboxymethyl cellulose.

[0019] In some embodiments of the present application, the clay is selected from at least one of kaolin, bentonite, montmorillonite, diatomite, perlite, illite and ozokerite.

[0020] In some embodiments of the present application, the mass fraction of the oxide in the raw material of the honeycomb ceramic unit body is less than 3%, preferably less than 2.6%, wherein the mass fraction of the oxide is the sum of the mass fraction of the alkaline earth metal oxide and the oxide in the clay.

[0021] In some embodiments of the present application, the pore-forming agent is selected from at least one of walnut powder, graphite, benzoic acid, starch, ammonium bicarbonate, ammonium chloride, polymethyl methacrylate and expanded microspheres.

[0022] And / or, the lubricant is glycerol.

[0023] In some embodiments of the present application, the particle size D50 of the pore-forming agent is 5-40 μm, preferably 10-30 μm.

[0024] To achieve the above-mentioned purposes, the present application further provides the following technical solutions:

[0025] A method for preparing the honeycomb ceramic unit body described above, the method comprising the following steps:

[0026] S11, dry mixing silicon carbide powder, pure silicon powder, alkaline earth metal oxide, clay, binder and pore-forming agent;

[0027] S12, adding water and lubricant to the mixture obtained in step S11 and wet mixing;

[0028] S13, kneading the mixture obtained in step S12;

[0029] S14, extrusion molding the mixture obtained in step S13;

[0030] S15, microwave drying and sintering the mixture obtained in step S14 to obtain the honeycomb ceramic unit body.

[0031] In some embodiments of the present application, the method has one or more of the following features:

[0032] In the step S11, a high-speed mixer is used for dry mixing, the dry mixing speed is 60-90 rpm, and the dry mixing time is 10-30 min, preferably, the dry mixing speed is 80 rpm, and the dry mixing time is 15 min;

[0033] In the step S12, the wet mixing rotation speed is 60-90 rpm, and the wet mixing time is 2-30 min, preferably, the wet mixing rotation speed is 80 rpm, and the wet mixing time is 5 min;

[0034] In the step S13, the kneading is performed by a double shaft kneader, and the kneading time is 10-20 min, preferably, the kneading time is 10-20 min, preferably 15 min;

[0035] In the step S14, the extrusion molding is performed by an extruder, and the extrusion pressure is 5-12 MPa, preferably, the extrusion pressure is 6-10 MPa;

[0036] In the step S15, the microwave drying time is 20-40 min, preferably 30 min.

[0037] To achieve the above object, the present application further provides the following technical solutions.

[0038] A honeycomb ceramic carrier composed of the honeycomb ceramic unit body or the honeycomb ceramic unit body obtained by the method.

[0039] To achieve the above object, the present application further provides the following technical solutions.

[0040] A method for preparing the honeycomb ceramic carrier, comprising the following steps:

[0041] S1, preparing the honeycomb ceramic unit body;

[0042] S2, splicing the honeycomb ceramic unit bodies to obtain a rough blank;

[0043] S3, adding splicing material to the splicing joint of the rough blank obtained in the step S2 to obtain a green body;

[0044] S4, polishing the periphery and end face of the green body obtained in the step S3 to obtain a green blank;

[0045] S5, skinning the green blank obtained in the step S4 and drying to obtain the honeycomb ceramic carrier.

[0046] To achieve the above object, the present application further provides the following technical solutions.

[0047] A tail gas catalytic core body, comprising:

[0048] The honeycomb ceramic unit body, or the honeycomb ceramic unit body prepared by the method, or the honeycomb ceramic carrier, or the honeycomb ceramic carrier obtained by the method; and

[0049] A catalyst coated on the partition wall of the internal partition of the honeycomb ceramic unit body.

[0050] Other suitable fields will become apparent from the description provided in this disclosure.

[0051] The description in the summary and the specific examples are only intended to be illustrative and not intended to limit the scope of the present disclosure.

[0052] Compared with the prior art, the technical solution provided by the present application has the following beneficial effects:

[0053] The present application provides a honeycomb ceramic unit body, a honeycomb ceramic carrier and a preparation method thereof, and a tail gas catalytic core body, and obtains a honeycomb ceramic unit body with a suitable porosity and a large enough thermal diffusion coefficient, a honeycomb ceramic carrier composed of the unit body, and a tail gas catalytic core body composed of the honeycomb ceramic carrier; specifically, the honeycomb ceramic carrier provided by the present application has a porosity of 55-65%, a thermal diffusion coefficient greater than or equal to 6 mm 2 / s, and an anisotropic shrinkage rate less than or equal to 4%, which can meet the needs of tail gas catalytic filtration. BRIEF DESCRIPTION OF DRAWINGS

[0054] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0055] Fig. 1 is a flow block diagram of a preparation method of a honeycomb ceramic carrier provided by an embodiment of the present application.

[0056] Fig. 2 is a structural schematic diagram of a honeycomb ceramic unit body provided by another embodiment of the present application. DETAILED DESCRIPTION

[0057] The technical solutions in the embodiments of the present application will be described clearly and completely as follows. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not intended to limit the present application.

[0058] Any specific numerical values (including any numerical range limits) disclosed herein are not intended to be exact, but rather are intended to be approximate, unless otherwise indicated. Moreover, any numerical value disclosed herein is intended to include all values reasonably falling within the range, unless otherwise indicated. Additionally, any numerical value disclosed herein is intended to include all reasonable approximations of the numerical value, unless otherwise indicated.

[0059] The terminology used in the present disclosure is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used in this disclosure, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," "includes," "including," "contains," and "containing," are inclusive and therefore specify the presence of stated features, integers, compositions, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Although the open-ended term "comprising," when used in the description and the claims, is intended to be understood as a non-limiting term used to describe and claim various embodiments of the disclosure, in some aspects, the term is instead alternatively understood as a more limiting and specific term, such as "consisting of or "consisting essentially of. Thus, in any given embodiment reciting a composition, material, component, element, feature, integer, operation, and / or process step, the disclosure also specifically includes embodiments that consist of or consist essentially of such recited composition, material, component, element, feature, integer, operation, and / or process step. In the case of a "consisting" embodiment, additional compositions, materials, components, elements, features, integers, operations, and / or process steps are not present, whereas in the case of a "consisting essentially of embodiment, any additional compositions, materials, components, elements, features, integers, operations, and / or process steps do not materially affect the basic and novel characteristics of the claimed embodiments.

[0060] Any method steps, processes, and operations described in the present disclosure are not to be construed as necessarily requiring their performance in the particular order in which they are discussed. It is also to be understood that additional or alternative steps can be employed, unless otherwise indicated.

[0061] In the present application, except for the explicitly stated content, any matter or item not mentioned is directly applicable to those known in the art without any change. Moreover, any embodiment described in the present disclosure can be freely combined with one or more other embodiments described in the present disclosure, and the technical solution or technical idea formed thereby is considered as part of the original disclosure or original description of the present application, and should not be considered as new content that has not been disclosed or anticipated by the present disclosure, unless the combination is considered to be obviously unreasonable by those skilled in the art.

[0062] Unless otherwise specified, the terms used herein have the same meaning as generally understood by those skilled in the art. If the term is defined herein and its definition is different from the general understanding in the art, the definition herein shall prevail.

[0063] Unless otherwise specified, the % mentioned herein refers to wt.%.

[0064] First aspect

[0065] Referring to FIG. 2, a honeycomb ceramic unit body has a porosity of 55-65%, a thermal diffusivity greater than or equal to 6 mm 2 / s, and an anisotropic shrinkage rate less than or equal to 4%.

[0066] It is worth noting that there is no mention in the current technology of a silicon carbide unit body that has both a shrinkage rate less than 4% and a thermal diffusivity higher than 6 mm 2 / s, the present application proposes a silicon carbide unit body that can have both high thermal diffusivity and low shrinkage, and a method for preparing the same.

[0067] In some embodiments of the present application, the honeycomb ceramic unit body has a porosity of 57-63%, a thermal diffusivity greater than or equal to 7 mm 2 / s, and an anisotropic shrinkage rate less than 3.5%.

[0068] In the context of the present application, porosity refers to the percentage of the volume of pores contained in the product to the total volume of the product.

[0069] In the context of the present application, thermal diffusivity is the ratio of thermal conductivity to volumetric heat capacity. The volumetric heat capacity is the product of density and specific heat capacity.

[0070] In the context of the present application, the anisotropic shrinkage rate includes the height direction shrinkage rate, the length direction shrinkage rate and the width direction shrinkage rate of the honeycomb ceramic unit body.

[0071] Referring to FIG. 2, L1 in the figure is the height direction of the honeycomb ceramic unit body, L2 is the length direction of the honeycomb ceramic unit body, and L3 is the width direction of the honeycomb ceramic unit body.

[0072] In some embodiments of the present application, the honeycomb ceramic unit body has a height direction shrinkage rate of 0.5-4%, a length direction shrinkage rate of 1-4%, a width direction shrinkage rate of 1-4%, and a longitudinal axis compressive strength of 2-8 MPa.

[0073] In some embodiments of the present application, the honeycomb ceramic unit body has a height direction shrinkage rate of 0.5-2%, a length direction shrinkage rate of 1-3.5%, a width direction shrinkage rate of 1-3%, and a longitudinal axis compressive strength of 3-7.5 MPa.

[0074] In some embodiments of the present application, the raw material of the honeycomb ceramic unit body comprises silicon carbide powder, silicon powder, alkaline earth metal oxide, clay, binder, pore-forming agent and lubricant. It is worth noting that the addition of part of silicon powder to the improved raw material ratio can improve the thermal diffusivity and mechanical strength of the product, and the proportion of silicon is controlled at 17%-34% of the silicon carbide powder, which can ensure that the shrinkage rate in each direction is less than 4%; at the same time, the product is prepared by using a silicon bonding method matched with the raw material, which has a sintering temperature about 1000℃ lower than the recrystallization method, lower energy consumption, and better thermal diffusivity and shrinkage rate than the product prepared by the conventional silicon bonding method.

[0075] In some embodiments of the present application, the raw material of the honeycomb ceramic unit body comprises 75-85 parts by weight of silicon carbide powder, 15-25 parts by weight of silicon powder, 0.2-2 parts by weight of alkaline earth metal oxide, 0.5-1.5 parts by weight of clay, 15-25 parts by weight of binder, 25-35 parts by weight of pore-forming agent, 20-70 parts by weight of water and 2-15 parts by weight of lubricant.

[0076] In some embodiments of the present application, the raw material of the honeycomb ceramic unit body comprises 75-85 parts by weight of silicon carbide powder, 15-25 parts by weight of silicon powder, 1.2-2 parts by weight of alkaline earth metal oxide, 0.5-1.5 parts by weight of clay, 15-25 parts by weight of binder, 25-35 parts by weight of pore-forming agent, 30-60 parts by weight of water and 3-10 parts by weight of lubricant.

[0077] In some embodiments of the present application, the silicon carbide powder comprises first-grade silicon carbide powder with a D50 of 15-50 μm and second-grade silicon carbide powder with a D50 of 1-12 μm.

[0078] In some embodiments of the present application, the D50 of the first-grade silicon carbide powder is 20-45 μm, and the D50 of the second-grade silicon carbide powder is 2-10 μm. It is worth noting that the raw material is selected as more common small particle size powder for particle grading to prepare a honeycomb ceramic unit body with lower shrinkage rate, and the ultra-fine silicon carbide powder with a particle size lower than 1 μm is not used to fill the large particle gap, which has lower preparation cost and is more suitable for industrial production.

[0079] In some embodiments of the present application, the mass ratio of the primary silicon carbide powder and the secondary silicon carbide powder is (65-80):(2-15).

[0080] In some embodiments of the present application, the mass ratio of the primary silicon carbide powder and the secondary silicon carbide powder is (65-80):(5-15).

[0081] In some embodiments of the present application, the alkaline earth metal oxide is selected from at least one of magnesium oxide, beryllium oxide, strontium oxide, calcium oxide, and barium oxide.

[0082] In some embodiments of the present application, the binder is selected from at least one of polyvinyl alcohol, ethyl cellulose, polyethylene glycol, methyl cellulose, potassium laurate, and carboxymethyl cellulose.

[0083] In some embodiments of the present application, the clay is selected from at least one of kaolin, bentonite, montmorillonite, diatomite, perlite, illite, and ozokerite.

[0084] In some embodiments of the present application, the mass fraction of the oxides in the raw material of the honeycomb ceramic unit body is less than 3%, preferably less than 2.6%, wherein the mass fraction of the oxides is the sum of the mass fraction of the alkaline earth metal oxides and the oxides in the clay. It is worth noting that the oxides used in the present application only include alkaline metal oxides and clay, and the content of the oxides in the raw material is controlled at a low level, so as to control the generation of oxides other than silicon oxide during the preparation and sintering process. A higher content of oxides will lead to a higher thermal expansion coefficient, and the thermal diffusion coefficient of the oxides is much lower than that of the silicon carbide crystal, and effectively controlling the content of the oxides can improve the thermal diffusion coefficient of the unit body.

[0085] In some embodiments of the present application, the pore-forming agent is selected from at least one of walnut powder, graphite, benzoic acid, starch, ammonium bicarbonate, ammonium chloride, polymethyl methacrylate, and expanded microspheres.

[0086] In some embodiments of the present application, the lubricant is glycerol.

[0087] In some embodiments of the present application, the particle size D50 of the pore-forming agent is 5-40 μm, preferably 10-30 μm.

[0088] It is worth noting that in some embodiments of the present application, the honeycomb ceramic unit body is used for tail gas purification treatment, and specifically can be used for purifying the gas generated after the combustion or incomplete combustion of diesel and the like.

[0089] Second aspect

[0090] The application provides a method for preparing the honeycomb ceramic unit body, and the method comprises the following steps: S11, dry mixing silicon carbide powder, pure silicon powder, alkaline earth metal oxide, clay, a binder and a pore-forming agent; S12, wet mixing the mixture obtained in the step S11 by adding water and a lubricant; S13, kneading the mixture obtained in the step S12; S14, extruding the mixture obtained in the step S13; and S15, microwave drying and sintering the mixture obtained in the step S14 to obtain the honeycomb ceramic unit body.

[0091] In some embodiments of the application, the step S11 is dry mixing by using a high-speed mixer, the dry mixing speed is 60-90 rpm, and the dry mixing time is 10-30 min, preferably, the dry mixing speed is 80 rpm, and the dry mixing time is 15 min.

[0092] In some embodiments of the application, the step S12 is wet mixing at a speed of 60-90 rpm for 2-30 min, preferably, the wet mixing speed is 80 rpm, and the wet mixing time is 5 min.

[0093] In some embodiments of the application, the step S13 is kneading by using a double-shaft kneader for 10-20 min, preferably, the kneading time is 10-20 min, preferably 15 min.

[0094] In some embodiments of the application, the step S14 is extruding by using an extruder at an extrusion pressure of 5-12 MPa, preferably, the extrusion pressure is 6-10 MPa.

[0095] In some embodiments of the application, the step S15 is microwave drying for 20-40 min, preferably 30 min.

[0096] The third aspect

[0097] The application provides a honeycomb ceramic carrier which is composed of a plurality of the honeycomb ceramic unit bodies or the honeycomb ceramic unit bodies obtained by the method.

[0098] The fourth aspect

[0099] Referring to FIG. 1, the application provides a method for preparing the honeycomb ceramic carrier, and the method comprises the following steps: S1, preparing a unit body; S2, splicing the unit bodies to obtain a rough blank; S3, adding splicing material to the splicing joints of the rough blank obtained in the step S2 to obtain a blank body; S4, polishing the periphery and end face of the blank body obtained in the step S3 to obtain a green body; and S5, skinning the green body obtained in the step S4 and drying to obtain the honeycomb ceramic carrier.

[0100] In some embodiments of the present application, the thickness of the joint is 1-5 mm in step S3.

[0101] In some embodiments of the present application, the thickness of the skin layer is 1-5 mm in step S5.

[0102] Fifth aspect

[0103] The present application also provides a tail gas catalytic core, which comprises the honeycomb ceramic unit body as described above, or the honeycomb ceramic unit body prepared by the method as described above, or the honeycomb ceramic carrier as described above, or the honeycomb ceramic carrier prepared by the method as described above; and a catalyst coated on the partition wall of the internal compartment of the honeycomb ceramic unit body.

[0104] It can be understood that the tail gas catalytic core provided by the present application can be used in the field of tail gas or exhaust gas purification catalytic treatment, and more specifically, can be used for purifying and catalytically treating the exhaust gas generated after incomplete combustion of diesel.

[0105] Embodiment 1

[0106] The embodiment provides a honeycomb ceramic unit body with high porosity, high thermal conductivity and low shrinkage, which is in the shape of a cuboid, and a plurality of honeycomb ceramic unit bodies are spliced together to form a honeycomb ceramic carrier with a substantially circular cross section; the raw material of the honeycomb ceramic unit body comprises, in parts by weight, 80 parts of silicon carbide powder, 20 parts of elemental silicon powder, 1.5 parts of alkaline earth metal oxide, 0.8 parts of clay, 20.5 parts of a binder and 30 parts of a pore-forming agent; the alkaline earth metal oxide in the honeycomb ceramic unit body comprises 0.5 parts of calcium oxide and 1 part of beryllium oxide; the clay in the honeycomb ceramic unit body comprises 0.8 parts of kaolin; the binder in the honeycomb ceramic unit body comprises 10 parts of hydroxymethyl cellulose, 5 parts of polyvinyl alcohol, 3 parts of glycerol and 2.5 parts of potassium laurate; the pore-forming agent in the honeycomb ceramic unit body comprises 14 parts of starch and 16 parts of walnut powder; and the silicon carbide powder in the honeycomb ceramic unit body comprises 78 parts of silicon carbide powder with a D50 of 20 μm and 2 parts of silicon carbide powder with a D50 of 7 μm.

[0107] The preparation method is as follows: 1) preparing the above-mentioned honeycomb ceramic unit: a) adding alkaline earth metal oxide, clay, silicon carbide powder, silicon powder, pore-forming agent and binder into a high-speed mixer and mixing at high speed for 15 minutes; b) adding water and lubricant and continuing to mix at high speed for 5 minutes; c) adding the raw material mixture obtained in step b) into a double-shaft kneader and kneading for 10 minutes; d) adding the raw material mixture obtained in step c) into an extruder and extruding; e) drying and sintering to obtain the unit; 2) splicing the unit, splicing the above-mentioned honeycomb ceramic unit into a green body with appropriate size according to the carrier specifications; 3) adding splicing material into the splicing joint of the green body to obtain the unit spliced into a whole; 4) polishing the periphery and end face of the spliced honeycomb ceramic unit to obtain a honeycomb ceramic blank with appropriate size and shape; 5) skinning the silicon carbide honeycomb ceramic blank and drying to obtain the above-mentioned honeycomb ceramic carrier.

[0108] Example 2

[0109] The embodiment provides a honeycomb ceramic unit with high porosity, high thermal conductivity and low shrinkage, which is in the shape of a cuboid, and a plurality of honeycomb ceramic units are spliced to form a honeycomb ceramic carrier with a substantially circular cross section; the raw material of the honeycomb ceramic unit comprises, in terms of weight fraction, 85 parts of silicon carbide powder, 15 parts of elemental silicon powder, 1.2 parts of alkaline earth metal oxide, 0.7 parts of clay, 18 parts of binder and 25 parts of pore-forming agent; the alkaline earth metal oxide in the honeycomb ceramic unit is 1.2 parts of magnesium oxide; the clay in the honeycomb ceramic unit is 0.2 parts of bentonite, 0.4 parts of montmorillonite and 0.1 parts of ozokerite; the binder in the honeycomb ceramic unit is 9 parts of hydroxymethyl cellulose and 9 parts of ethyl cellulose; the pore-forming agent in the honeycomb ceramic unit is 12 parts of starch, 10 parts of walnut powder and 3 parts of benzoic acid; and the silicon carbide powder in the honeycomb ceramic unit is 80 parts of silicon carbide powder with D50=25 μm and 5 parts of silicon carbide powder with D50=4 μm.

[0110] The preparation method is the same as that in example 1.

[0111] Example 3

[0112] The embodiment provides a high-porosity, high-thermal-conductivity and low-shrinkage honeycomb ceramic unit body which is cuboid and is used to form a honeycomb ceramic carrier with a substantially circular cross section by splicing a plurality of the honeycomb ceramic unit bodies adjacently; raw materials of the honeycomb ceramic unit body include, in terms of weight fractions, 81 parts of silicon carbide powder, 19 parts of elemental silicon powder, 1.4 parts of alkaline earth metal oxide, 0.8 parts of clay, 22 parts of binder and 27.5 parts of pore-forming agent; the alkaline earth metal oxide in the honeycomb ceramic unit body is 0.5 part of strontium oxide, 0.5 part of beryllium oxide and 0.4 part of barium oxide; the clay in the honeycomb ceramic unit body is 0.8 part of illite; the binder in the honeycomb ceramic unit body is 11 parts of hydroxymethyl cellulose, 3 parts of methyl cellulose and 7 parts of potassium laurate; the pore-forming agent in the honeycomb ceramic unit body is 13 parts of benzoic acid, 11 parts of graphite and 3.5 parts of ammonium chloride; and the honeycomb ceramic unit body uses 66 parts of silicon carbide powder with D50=45 μm and 15 parts of silicon carbide powder with D50=10 μm.

[0113] The preparation method is the same as that in Embodiment 1.

[0114] Embodiment 4

[0115] The embodiment provides a high-porosity, high-thermal-conductivity and low-shrinkage honeycomb ceramic unit body which is cuboid and is used to form a honeycomb ceramic carrier with a substantially circular cross section by splicing a plurality of the honeycomb ceramic unit bodies adjacently; raw materials of the honeycomb ceramic unit body include, in terms of weight fractions, 78 parts of silicon carbide powder, 22 parts of silicon powder, 1.2 parts of alkaline earth metal oxide, 1.5 parts of clay, 18 parts of binder and 25 parts of pore-forming agent; the alkaline earth metal oxide in the honeycomb ceramic unit body is 0.5 part of barium oxide, 0.5 part of magnesium oxide and 0.2 part of beryllium oxide; the clay in the honeycomb ceramic unit body is 0.5 part of perlite and 1 part of diatomite; the binder in the honeycomb ceramic unit body is 9 parts of glycerol, 4 parts of polyethylene glycol and 5 parts of potassium laurate; the pore-forming agent in the honeycomb ceramic unit body is 25 parts of expanded microspheres; and the honeycomb ceramic unit body uses 65 parts of silicon carbide powder with D50=30 μm and 13 parts of silicon carbide powder with D50=2 μm.

[0116] The preparation method is the same as that in Embodiment 1.

[0117] Embodiment 5

[0118] The embodiment provides a high-porosity, high-thermal-conductivity and low-shrinkage honeycomb ceramic unit body which is in the shape of a cuboid and is formed by adjacently splicing a plurality of honeycomb ceramic unit bodies to form a honeycomb ceramic carrier with a substantially circular cross section; raw materials of the honeycomb ceramic unit body include, in terms of weight fractions, 75 parts of silicon carbide powder, 25 parts of silicon powder, 1.1 parts of alkaline earth metal oxide, 0.8 parts of clay, 18 parts of a binder and 26 parts of a pore-forming agent; in the honeycomb ceramic unit body, the alkaline earth metal oxide is 0.5 part of magnesium oxide and 0.6 part of calcium oxide; in the honeycomb ceramic unit body, the clay is 0.3 part of perlite and 0.5 part of illite; in the honeycomb ceramic unit body, the binder is 9 parts of methyl cellulose and 9 parts of ethyl cellulose; in the honeycomb ceramic unit body, the pore-forming agent is 12 parts of graphite, 10 parts of walnut powder and 4 parts of polymethyl methacrylate; and in the honeycomb ceramic unit body, 70 parts of silicon carbide powder with D50=32 μm and 5 parts of silicon carbide powder with D50=6 μm are used.

[0119] The preparation method is the same as that in Embodiment 1.

[0120] Embodiment 6

[0121] The embodiment provides a high-porosity, high-thermal-conductivity and low-shrinkage honeycomb ceramic unit body which is in the shape of a cuboid and is formed by adjacently splicing a plurality of honeycomb ceramic unit bodies to form a honeycomb ceramic carrier with a substantially circular cross section; raw materials of the honeycomb ceramic unit body include, in terms of weight fractions, 79 parts of silicon carbide powder, 21 parts of silicon powder, 1.5 parts of alkaline earth metal oxide, 0.5 parts of clay, 18 parts of a binder and 25 parts of a pore-forming agent; in the honeycomb ceramic unit body, the alkaline earth metal oxide is 1.5 parts of barium oxide; in the honeycomb ceramic unit body, the clay is 0.2 part of ozocerite and 0.3 part of montmorillonite; in the honeycomb ceramic unit body, the binder is 13 parts of ethyl cellulose, 3 parts of glycerol and 2 parts of potassium laurate; in the honeycomb ceramic unit body, the pore-forming agent is 12 parts of benzoic acid, 10 parts of graphite and 3 parts of ammonium bicarbonate; and in the honeycomb ceramic unit body, 70 parts of silicon carbide powder with D50=28 μm and 9 parts of silicon carbide powder with D50=5 μm are used.

[0122] The preparation method is the same as that in Embodiment 1.

[0123] Embodiment 7

[0124] The embodiment provides a high-porosity, high-thermal-conductivity and low-shrinkage honeycomb ceramic unit body which is in the shape of a cuboid and is used to form a honeycomb ceramic carrier with a substantially circular cross section by splicing a plurality of the honeycomb ceramic unit bodies adjacently; raw materials of the honeycomb ceramic unit body include, in terms of weight fractions, 78 parts of silicon carbide powder, 22 parts of silicon powder, 1.5 parts of alkaline earth metal oxide, 0.5 part of clay, 15 parts of binder and 25 parts of pore-forming agent; the alkaline earth metal oxide in the honeycomb ceramic unit body is 1.5 parts of barium oxide; the clay in the honeycomb ceramic unit body is 0.2 part of kaolin and 0.3 part of montmorillonite; the binder in the honeycomb ceramic unit body is 10 parts of ethyl cellulose, 3 parts of glycerol and 2 parts of potassium laurate; the pore-forming agent in the honeycomb ceramic unit body is 12 parts of walnut powder, 10 parts of graphite and 3 parts of ammonium bicarbonate; and the honeycomb ceramic unit body uses 70 parts of silicon carbide powder with D50=29μm and 8 parts of silicon carbide powder with D50=5μm.

[0125] The preparation method is the same as that in Embodiment 1.

[0126] Embodiment 8

[0127] The embodiment provides a high-porosity, high-thermal-conductivity and low-shrinkage honeycomb ceramic unit body which is in the shape of a cuboid and is used to form a honeycomb ceramic carrier with a substantially circular cross section by splicing a plurality of the honeycomb ceramic unit bodies adjacently; raw materials of the honeycomb ceramic unit body include, in terms of weight fractions, 76 parts of silicon carbide powder, 24 parts of silicon powder, 2 parts of alkaline earth metal oxide, 1.1 part of clay, 25 parts of binder and 35 parts of pore-forming agent; the alkaline earth metal oxide in the honeycomb ceramic unit body is 0.5 part of strontium oxide, 1 part of calcium oxide and 0.5 part of magnesium oxide; the clay in the honeycomb ceramic unit body is 0.8 part of diatomite and 0.3 part of kaolin; the binder in the honeycomb ceramic unit body is 15 parts of hydroxymethyl cellulose, 2 parts of ethyl cellulose, 4 parts of glycerol and 4 parts of potassium laurate; the pore-forming agent in the honeycomb ceramic unit body is 20 parts of ammonium chloride, 10 parts of benzoic acid and 5 parts of polymethyl methacrylate; and the honeycomb ceramic unit body uses 70 parts of silicon carbide powder with D50=31μm and 6 parts of silicon carbide powder with D50=8μm.

[0128] The preparation method is the same as that in Embodiment 1.

[0129] Embodiment 9

[0130] The embodiment provides a high-porosity, high-thermal-conductivity and low-shrinkage honeycomb ceramic unit body which is in the shape of a cuboid and is formed by adjacently splicing a plurality of honeycomb ceramic unit bodies to form a honeycomb ceramic carrier with a substantially circular cross section; raw materials of the honeycomb ceramic unit body include, in terms of weight fractions, 75 parts of silicon carbide powder, 25 parts of silicon powder, 2 parts of alkaline earth metal oxide, 1.1 parts of clay, 18 parts of a binder and 25 parts of a pore-forming agent; the alkaline earth metal oxide in the honeycomb ceramic unit body is 0.5 parts of strontium oxide, 1 part of calcium oxide and 0.5 part of magnesium oxide; the clay in the honeycomb ceramic unit body is 0.8 part of montmorillonite and 0.3 part of kaolin; the binder in the honeycomb ceramic unit body is 15 parts of hydroxymethyl cellulose and 3 parts of ethyl cellulose; the pore-forming agent in the honeycomb ceramic unit body is 20 parts of graphite and 5 parts of walnut powder; and the silicon carbide powder in the honeycomb ceramic unit body is 70 parts of silicon carbide powder with D50=33 μm and 5 parts of silicon carbide powder with D50=7 μm.

[0131] The preparation method is the same as that in Embodiment 1.

[0132] Comparative Example 1

[0133] In the embodiment, no particle grading is used, and all the silicon carbide powder used is D50=25 μm, and the weight fractions of the remaining raw materials are the same as those in Embodiment 1; in addition, the raw materials of the honeycomb ceramic unit body include, in terms of weight fractions, 80 parts of silicon carbide powder, 20 parts of silicon powder, 1.5 parts of alkaline earth metal oxide, 0.8 parts of clay, 20.5 parts of a binder and 30 parts of a pore-forming agent; the alkaline earth metal oxide in the honeycomb ceramic unit body is 0.5 part of calcium oxide and 1 part of beryllium oxide; the clay in the honeycomb ceramic unit body is 0.8 part of kaolin; the binder in the honeycomb ceramic unit body is 10 parts of hydroxymethyl cellulose, 5 parts of polyvinyl alcohol, 3 parts of glycerol and 2.5 parts of potassium laurate; and the pore-forming agent in the honeycomb ceramic unit body is 14 parts of starch and 16 parts of walnut powder.

[0134] The preparation method is the same as that in Embodiment 1.

[0135] Comparative Example 2

[0136] The particle size grading was used, but the two particle size specifications of the silicon carbide powder used were a silicon carbide powder with a D50 = 19 μm and a silicon carbide powder with a D50 = 15 μm, and the weight fractions of the remaining raw materials were the same as in Example 1; the raw materials of the honeycomb ceramic unit body included, in terms of weight fractions: 80 parts of silicon carbide powder, 20 parts of silicon powder, 1.5 parts of alkaline earth metal oxide, 0.8 parts of clay, 20.5 parts of binder, and 30 parts of pore-forming agent; in the honeycomb ceramic unit body, the alkaline earth metal oxide was 0.5 parts of calcium oxide and 1 part of beryllium oxide; in the honeycomb ceramic unit body, the clay was 0.8 parts of kaolin; in the honeycomb ceramic unit body, the binder was 10 parts of hydroxymethyl cellulose, 5 parts of polyvinyl alcohol, 3 parts of glycerol, and 2.5 parts of potassium laurate; in the honeycomb ceramic unit body, the pore-forming agent was 14 parts of starch and 16 parts of walnut powder; in the honeycomb ceramic unit body, 78 parts of silicon carbide powder with a D50 = 19 μm and 2 parts of silicon carbide powder with a D50 = 15 μm were used.

[0137] The preparation method was the same as in Example 1.

[0138] Comparative Example 3

[0139] The particle size grading was used, but the silicon powder content used was not within the given range, and the weight fractions of the remaining raw materials were the same as in Example 1; in addition, the honeycomb ceramic unit body included, in terms of weight fractions: 80 parts of silicon carbide powder, 10 parts of silicon powder, 1.5 parts of alkaline earth metal oxide, 0.8 parts of clay, 20.5 parts of binder, and 30 parts of pore-forming agent; in the honeycomb ceramic unit body, the alkaline earth metal oxide was 0.5 parts of calcium oxide and 1 part of beryllium oxide; in the honeycomb ceramic unit body, the clay was 0.8 parts of kaolin; in the honeycomb ceramic unit body, the binder was 10 parts of hydroxymethyl cellulose, 5 parts of polyvinyl alcohol, 3 parts of glycerol, and 2.5 parts of potassium laurate. In the honeycomb ceramic unit body, the pore-forming agent was 14 parts of starch and 16 parts of walnut powder; in the honeycomb ceramic unit body, 78 parts of silicon carbide powder with a D50 = 20 μm and 2 parts of silicon carbide powder with a D50 = 7 μm were used.

[0140] The preparation method was the same as in Example 1.

[0141] The honeycomb ceramic carriers obtained in each of the above examples and comparative examples were subjected to performance testing:

[0142] 1. The porosity testing method was the mercury intrusion method, which was measured by using a mercury porosimeter (MicroActive AutoPore V9600 Version 2.03.00) of the United States Mac Company to prepare a sample block with a length, width, and height of 10 mm*10 mm*15 mm. The testing method was the national standard: GB / T21650.1-2008;

[0143] 2. The shrinkage rate is measured by using a vernier caliper to measure the length, width and height of the honeycomb ceramic unit before and after firing, and the shrinkage rate data is calculated;

[0144] 3. The thermal diffusivity is measured by cutting a sample with a length of 10 mm, a width of 10 mm and a thickness of 1 mm from the surface of the unit, using a German NIST laser thermal conductivity instrument (LFA467) under a temperature rise interval of 50 K / min, and the test method is the national standard GB / T22588-2008;

[0145] 4. The compressive strength is measured by preparing a sample block with a length, width and height of 25 mm*25 mm*25 mm, using a Suzhou Toba universal material testing machine, and the test method is the national standard GB / T4740-1999; the A-axis compressive strength refers to the compressive strength of the honeycomb ceramic carrier along its longitudinal direction.

[0146] The above performance parameters are listed in Table 1 below.

[0147] Table 1 Performance parameters of honeycomb ceramic carriers obtained from various examples and comparative examples

[0148] As can be seen from Table 1, as the content of the pore-forming agent increases, the porosity tends to increase, and as the content of Si increases, the thermal diffusivity and mechanical strength gradually increase, but the shrinkage rate also increases. Comparative Example 1 compared with Example 1, without using particle grading, the shrinkage rate is significantly increased, and the increase in shrinkage rate also leads to a decrease in porosity. Comparative Example 2 compared with Example 1, when the particle size of SiC used is not within the given range, the shrinkage rate of the product will also increase significantly. Comparative Example 3 compared with Example 1, when the content of Si used is low, although the shrinkage will decrease, but the thermal diffusivity and mechanical strength will be greatly reduced. Therefore, using particle grading can greatly reduce the shrinkage while ensuring high porosity (≥57%), and when the mass fraction of silicon powder is controlled at 15-25 parts, the thermal diffusivity > 6 mm 2 / s, the A-axis compressive strength > 3 MPa, and the overall shrinkage rate of the product < 3%.

[0149] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any skilled person in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims. In addition, specific examples are applied in the specification to describe the principles and embodiments of the present application, and the above examples are only used to help understand the method and core idea of the present application, and the content of the specification should not be understood as a limitation of the present application.

Claims

1. A honeycomb ceramic unit body characterized by, The honeycomb ceramic unit has a porosity of 55-65%, a thermal diffusivity greater than or equal to 6 mm 2 / s, and an isotropic shrinkage of less than or equal to 4%.

2. The honeycomb ceramic unit body of claim 1, wherein, The porosity of the honeycomb ceramic unit is 57-63%, the thermal diffusion coefficient is greater than or equal to 7mm 2 / s, and the anisotropic shrinkage is less than 3.5%.

3. The honeycomb ceramic unit body of claim 1 or 2, wherein, The honeycomb ceramic unit has a height direction shrinkage of 0.5-4%, a length direction shrinkage of 1-4%, a width direction shrinkage of 1-4%, and a longitudinal axis compressive strength of 2-8 MPa. Preferably, the honeycomb ceramic unit has a height direction shrinkage of 0.5-2%, a length direction shrinkage of 1-3.5%, a width direction shrinkage of 1-3%, and a longitudinal axis compressive strength of 3-7.5 MPa.

4. The honeycomb ceramic unit body of any of claims 1-3, wherein, The raw material of the honeycomb ceramic unit comprises silicon carbide powder, silicon powder, alkaline earth metal oxide, clay, binder, pore-forming agent and lubricant.

5. The honeycomb ceramic unit body of any of claims 1-4, wherein, The raw material of the honeycomb ceramic unit comprises 75-85 parts by weight of silicon carbide powder, 15-25 parts by weight of silicon powder, 0.2-2 parts by weight of alkaline earth metal oxide, 0.5-1.5 parts by weight of clay, 15-25 parts by weight of binder, 25-35 parts by weight of pore-forming agent, 20-70 parts by weight of water and 2-15 parts by weight of lubricant. Preferably, the raw material of the honeycomb ceramic unit comprises 75-85 parts by weight of silicon carbide powder, 15-25 parts by weight of silicon powder, 1.2-2 parts by weight of alkaline earth metal oxide, 0.5-1.5 parts by weight of clay, 15-25 parts by weight of binder, 25-35 parts by weight of pore-forming agent, 30-60 parts by weight of water and 3-10 parts by weight of lubricant.

6. The honeycomb ceramic unit body of any of claims 1-5, wherein, The silicon carbide powder comprises primary silicon carbide powder with a D50 of 15-50 μm and secondary silicon carbide powder with a D50 of 1-12 μm. Preferably, the primary silicon carbide powder has a D50 of 20-45 μm, and the secondary silicon carbide powder has a D50 of 2-10 μm.

7. The honeycomb ceramic unit body of any of claims 1-6, wherein The mass ratio of the primary silicon carbide powder to the secondary silicon carbide powder is (65-80):(2-15). Preferably, the mass ratio of the primary silicon carbide powder to the secondary silicon carbide powder is (65-80):(5-15).

8. The honeycomb ceramic unit body of any of claims 1-7, wherein, The alkaline earth metal oxide is selected from at least one of magnesium oxide, beryllium oxide, strontium oxide, calcium oxide and barium oxide.

9. The honeycomb ceramic unit body of any of claims 1-8, wherein, The binder is selected from at least one of polyvinyl alcohol, glycerol, ethyl cellulose, polyethylene glycol, methyl cellulose, potassium laurate and carboxymethyl cellulose.

10. The honeycomb ceramic unit of any of claims 1 to 9, wherein, The clay is selected from at least one of kaolin, bentonite, montmorillonite, diatomite, perlite, illite and ozokerite.

11. The honeycomb ceramic unit body of any of claims 1 to 10, wherein, The mass fraction of oxides in the raw material of the honeycomb ceramic unit is less than 3%, preferably less than 2.6%, wherein the mass fraction of oxides is the sum of the mass fraction of alkaline earth metal oxides and the mass fraction of oxides in clay.

12. The honeycomb ceramic unit body of any of claims 1-11, wherein, The pore-forming agent is selected from at least one of walnut powder, graphite, benzoic acid, starch, ammonium bicarbonate, ammonium chloride, polymethyl methacrylate and expanded microspheres. And / or, the lubricant is glycerol.

13. The honeycomb ceramic unit body of any of claims 1 to 12, wherein, The particle size D50 of the pore-forming agent is 5-40 μm, preferably 10-30 μm.

14. A method of manufacturing a honeycomb ceramic unit body as defined in any one of claims 1 to 13, characterized in that, The method comprises the following steps: S11, dry mixing silicon carbide powder, pure silicon powder, alkaline earth metal oxide, clay, binder and pore-forming agent; S12, adding water and lubricant to the mixture obtained in step S11, and wet mixing; S13, kneading the mixture obtained in step S12; and S14, drying the mixture obtained in step S13. S14, extruding the mixture obtained in step S13; S15, microwave drying and sintering the mixture obtained in step S14 to obtain the honeycomb ceramic unit body.

15. The method of claim 14, wherein, The method has one or more of the following features: In step S11, the dry mixing is performed by a high-speed mixer, the dry mixing speed is 60-90 rpm, and the dry mixing time is 10-30 min. Preferably, the dry mixing speed is 80 rpm, and the dry mixing time is 15 min. In step S12, the wet mixing speed is 60-90 rpm, and the wet mixing time is 2-30 min. Preferably, the wet mixing speed is 80 rpm, and the wet mixing time is 5 min. In step S13, the kneading is performed by a double-shaft kneader, and the kneading time is 10-20 min. Preferably, the kneading time is 10-20 min, and more preferably 15 min. In step S14, the extrusion molding is performed by an extruder, and the extrusion pressure is 5-12 MPa. Preferably, the extrusion pressure is 6-10 MPa. In step S15, the microwave drying time is 20-40 min, and more preferably 30 min.

16. A honeycomb ceramic structure, characterized by, The honeycomb ceramic carrier is composed of a plurality of honeycomb ceramic unit bodies according to any one of claims 1-13, or honeycomb ceramic unit bodies obtained by the method of claim 14 or 15.

17. A method of making the honeycomb ceramic carrier of claim 16, characterized in that, The method comprises the following steps: S1, preparing a honeycomb ceramic unit body according to any one of claims 1-13; S2, splicing the honeycomb ceramic unit bodies to obtain a rough blank; S3, adding splicing material to the splicing joint of the rough blank obtained in step S2 to obtain a green body; S4, polishing the periphery and end face of the green body obtained in step S3 to obtain a blank; S5, skinning the blank obtained in step S4, drying to obtain the honeycomb ceramic carrier.

18. An exhaust gas catalytic core body, characterized by The tail gas catalytic core comprises: The honeycomb ceramic unit body according to any one of claims 1-13, or the honeycomb ceramic unit body obtained by the method of claim 14 or 15, or the honeycomb ceramic carrier of claim 16, or the honeycomb ceramic carrier obtained by the method of claim 17; and A catalyst coated on the partition wall of the internal compartment of the honeycomb ceramic unit body.

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