Coating slurry and application thereof, monolithic catalyst and preparation method and application thereof

Abstract

The invention relates to the technical field of slurry preparation, and discloses coating slurry and application thereof, a monolithic catalyst and a preparation method and application thereof. The invention relates to coating slurry, which contains aluminum oxide, a solvent, a surfactant, an aluminum oxide precursor and an organic silicon source, and on the basis of the total amount of the coating slurry, the content of the solvent is 40-70 wt%, the content of the aluminum oxide is 15-45 wt%, the content of the surfactant is 1-6 wt%, the content of the aluminum oxide precursor is 1-6 wt%, and the content of the organic silicon source is 1-6 wt%. By modulating the formula of the coating slurry, the dispersity of the active components in the monolithic catalyst is improved, the utilization rate of the active components is improved, and the catalyst has wide application prospects in the field of catalytic combustion.

Description

Technical Field

[0001] The present invention relates to the technical field of slurry preparation, and particularly relates to a coating slurry and its application, an integral catalyst, and its preparation method and application. Background Art

[0002] Honeycomb catalysts are common catalysts used in gas-phase conversion reactions. They are generally used to handle high-space-velocity gases, especially automotive exhaust or industrial waste gases. Generally speaking, honeycomb catalysts are divided into two types. One is an integral catalyst, where the active components are directly formed by an extruder. The other is to make a honeycomb-shaped carrier, such as ceramics, and then coat it with a slurry containing powders with stronger loading capabilities. After drying and calcination, a coating with a higher specific surface area is left for loading the active components. For the latter, the formulation of the slurry plays a decisive role in the coating amount, coating shedding rate, and coating loading capacity of the coating. Generally speaking, in order to improve the utilization rate of the active ingredients, the formulation of the slurry is mainly focused on increasing the slurry amount and improving the pore structure of the powders. Ultimately, it is to increase the specific surface area of the coating to improve the dispersion degree of the active centers.

[0003] Chinese Patent Application No. 200910193316.6 discloses a method for preparing a coating on a honeycomb ceramic carrier. In this method, cordierite is used as the carrier, polyethylene glycol or polyvinyl alcohol or carboxymethyl cellulose is used as the pore-forming agent, and urea is used as the dispersant. Boehmite slurry is used as the raw material, nitric acid is added, and high-speed stirring is carried out to obtain alumina sol. Then, the pretreated honeycomb ceramic cordierite is impregnated in the alumina sol. The main purpose is to obtain a carrier with a high specific surface area, and then to obtain a subsequent uniform dispersion of active centers.

[0004] Chinese Patent Application No. 201310495782.6 discloses a honeycomb ceramic carrier and its preparation method. Using cordierite honeycomb ceramic as the substrate, the substrate surface has an alumina coating and a composite coating in sequence. The composite coating contains 40wt%-80wt% of titanium dioxide, 5wt%-35wt% of silicon dioxide, 1wt%-10wt% of alumina, and 10wt%-40wt% of additives. The main purpose of this composite coating is to obtain better mechanical strength and prevent shedding when the coating amount is large.

[0005] The honeycomb catalysts prepared by the above methods are limited by the properties of the coating. The research direction often lies in how to further increase the coating amount to achieve good dispersion of the active metal. Summary of the Invention

[0006] The object of the present invention is to overcome the technical problems existing in the prior art, and to provide a coating slurry and its application, a monolithic catalyst and its preparation method and application. The coating slurry introduces a silicone source to cooperate with other components. By adjusting the formulation of the coating slurry, the dispersion degree of the active components in the monolithic catalyst is improved, the utilization rate of the active components is increased, and it has broad application prospects in the field of catalytic combustion.

[0007] To achieve the above object, in the first aspect of the present invention, a coating slurry is provided, wherein the coating slurry contains alumina, a solvent, a surfactant, an alumina precursor, and a silicone source. Based on the total amount of the coating slurry, the content of the solvent is 40-70 wt%, the content of alumina is 15-45 wt%, the content of the surfactant is 1-6 wt%, the content of the alumina precursor is 1-6 wt%, and the content of the silicone source is 1-6 wt%.

[0008] In the second aspect of the present invention, an application of the coating slurry described in the first aspect in a monolithic catalyst is provided.

[0009] In the third aspect of the present invention, a preparation method of a monolithic catalyst is provided, wherein the method includes the following steps:

[0010] (1) Introduce the coating slurry onto a structured support, and then perform a first drying and optionally a first calcination to obtain a structured support carrier loaded with a coating;

[0011] (2) Immerse the structured support carrier in an impregnation solution containing a noble metal precursor, adjust the pH to alkaline, preferably adjust it to pH 8-9, let it stand and then heat, and then perform a second drying and a second calcination;

[0012] Wherein, the coating slurry in step (1) is the coating slurry described in the first aspect.

[0013] In the fourth aspect of the present invention, a monolithic catalyst prepared by the preparation method described in the third aspect is provided.

[0014] In the fifth aspect of the present invention, an application of the monolithic catalyst described in the fourth aspect in a catalytic oxidation reaction is provided.

[0015] The coating slurry provided by the present invention introduces a silicone source to cooperate with other components. By adjusting the formulation of the coating slurry, the components act synergistically, improving the dispersion degree of the active components in the monolithic catalyst and the utilization rate of the active components, and having broad application prospects in the field of catalytic combustion.

[0016] The preparation method of the monolithic catalyst provided by the present invention modifies the regular-structured support carrier by using the coating slurry described in the present invention. In the process of impregnating noble metals, the ammonium complexation method is adopted to make the noble metals form a positively charged group of ammonium complex. By utilizing the characteristic that silicon functional groups are prone to form Si-OH bonds in an aqueous environment, during the process of impregnating noble metals, the formed Si-OH is used to pair with the aforementioned positively charged group, promoting the dispersion of noble metals and being beneficial to improving the performance of catalytic oxidation reactions. Detailed implementation manners

[0017] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0018] In the present invention, it should be noted that the solvent includes all solvents in the coating slurry that can provide a mixing environment. For example, it can include the solvents in the transition metal salt solution and other solvents in the coating slurry other than the solvents in the transition metal salt solution.

[0019] The first aspect of the present invention provides a coating slurry, wherein the coating slurry contains alumina, a solvent, a surfactant, an alumina precursor, and an organosilicon source. Wherein, based on the total amount of the coating slurry, the content of the solvent is 40 - 70 wt%, the content of alumina is 15 - 45 wt%, the content of the surfactant is 1 - 6 wt%, the content of the alumina precursor is 1 - 6 wt%, and the content of the organosilicon source is 1 - 6 wt%.

[0020] The coating slurry provided by the present invention can change the properties of the coating slurry by introducing a silicon source and cooperating with other components synergistically, enabling the coating slurry to have broad application prospects in the field of catalytic combustion.

[0021] In the present invention, by regulating the content of each component in the coating slurry, the surface properties of the coating slurry are further optimized, and the viscosity of the coating slurry is increased. Preferably, based on the total amount of the coating slurry, the content of the solvent is 45 - 65 wt%, the content of alumina is 20 - 40 wt%, the content of the surfactant is 2 - 6 wt%, the content of the alumina precursor is 2 - 6 wt%, and the content of the organosilicon source is 2 - 6 wt%.

[0022] In the present invention, the content of each component in the coating slurry is calculated based on the feeding amount.

[0023] In the present invention, the types of solvents can be selected within a relatively wide range, as long as they can provide an environment for mixing other components in the slurry. Preferably, the solvent is water and / or alcohol, and more preferably water and alcohol.

[0024] In the present invention, the types of alcohols can be selected within a relatively wide range, and the low-carbon alcohols defined in the art can all be applicable to the present invention. Preferably, the alcohol is an alcohol with 1 to 5 carbon atoms, and more preferably at least one selected from ethanol, ethylene glycol, glycerol, and butanol.

[0025] In the present invention, the amounts of alcohol and water are not particularly limited, as long as they can meet the requirements for mixing other components in the slurry. Preferably, the mass ratio of the alcohol to the water is 1 - 2.5:20.

[0026] In the present invention, the properties of alumina are not particularly limited. Preferably, the specific surface area of the alumina is 100 - 1000 m 2 / g.

[0027] In the present invention, the source of alumina is not particularly limited. For example, commercially available products can be used or it can be prepared according to the prior art.

[0028] In the present invention, the types of alumina precursors can be selected within a relatively wide range. Preferably, the alumina precursor is at least one selected from pseudoboehmite, aluminum hydroxide, and aluminum sec-butoxide, and more preferably pseudoboehmite. Even more preferably, the specific surface area of the pseudoboehmite is 150 - 380 m 2 / g.

[0029] In the present invention, the source of the alumina precursor is not particularly limited. For example, commercially available products can be used or it can be prepared according to the prior art.

[0030] In the present invention, the types of surfactants can be selected within a relatively wide range, as long as they can achieve the purpose of uniformly dispersing each component in the slurry. Preferably, the surfactant is at least one selected from polyethylene glycol, urea, sodium dodecylbenzenesulfonate, and stearic acid.

[0031] In the present invention, by introducing an organosilicon source, it cooperates with other components in the coating slurry to control the viscosity of the coating slurry. Preferably, the organosilicon source is at least one selected from tetraethyl orthosilicate, tetramethyl orthosilicate, polysiloxane, and ethoxysiloxane, and even more preferably tetraethyl orthosilicate.

[0032] In the present invention, preferably, the coating slurry further contains a transition metal, and the transition metal is selected from at least one of the Group IIIB metal elements, Group IVB metal elements, and Group VB metal elements. The Group IIIB metal elements include, but are not limited to, Y and lanthanide metals. The Group IVB metal elements include, but are not limited to, Ti and Zr. The Group VB metal elements include, but are not limited to, V, Nb, and Ta.

[0033] In the present invention, preferably, the transition metal is selected from at least one of cerium, lanthanum, zirconium, titanium, and vanadium. Adding the transition metal within the above preferred range to the coating slurry can improve the stability of the coating slurry.

[0034] In the present invention, there is no particular limitation on the form of existence of the transition metal, as long as the transition metal can be introduced into the slurry coating. According to a preferred embodiment of the present invention, the transition metal exists in the coating slurry in the form of a transition metal salt. The advantage of adopting this preferred embodiment is that the feeding is simple.

[0035] In the present invention, there is no particular limitation on the content of the transition metal salt. Preferably, based on the total amount of the coating slurry, the content of the transition metal salt is 1-5 wt%.

[0036] According to another preferred embodiment of the present invention, the transition metal is loaded on alumina in the form of a transition metal salt or a transition metal oxide. The advantage of adopting this preferred embodiment is that local agglomeration is not likely to occur.

[0037] In the present invention, there is no particular limitation on the content of the transition metal salt or the transition metal oxide. Preferably, based on the total amount of the coating slurry, the content of the transition metal salt or the transition metal oxide is 1-5 wt%.

[0038] In the present invention, preferably, the pH value of the coating slurry is 3-4.

[0039] In the present invention, the pH value of the coating slurry can be adjusted by adding an acid or a base, and preferably an inorganic acid solution. For example, it can be at least one of nitric acid, sulfuric acid, and hydrochloric acid.

[0040] In the present invention, there is no particular limitation on the amount of the inorganic acid solution, as long as the pH value of the coating slurry is 3-4. Those skilled in the art can select according to actual needs. In the present invention, the total amount of the amount of the inorganic acid solution and the content of other components in the coating slurry satisfies 100%.

[0041] In the present invention, preferably, at 25 °C, the viscosity of the coating slurry is 10-100 mPa·s.

[0042] In the present invention, the viscosity of the coating slurry refers to the viscosity measured by a viscometer at 25°C.

[0043] In the present invention, there is no particular limitation on the preparation method of the coating slurry. Preferably, the preparation method of the coating slurry includes the following steps: under stirring conditions, alumina, an alumina precursor, a surfactant, a silicon source, and a solvent are mixed uniformly, and then the pH is adjusted to obtain the coating slurry.

[0044] The preparation method of the coating slurry provided by the present invention modifies the surface of alumina by introducing an organosilicon source, and a large number of silicon-containing functional groups are formed on the modified surface. In an aqueous environment, hydroxyl functional groups are more likely to be generated. The hydroxyl functional groups attract the complexed metal cations, uniformly dispersing the active centers on the surface of the coating carrier and promoting the dispersion of the active components. The method provided by the present invention modifies the coating slurry formulation by introducing an organosilicon source, improves the surface properties of the coating, further increases the dispersion degree of the active components in the monolithic catalyst, improves the utilization rate, and has broad application prospects in the field of catalytic combustion.

[0045] In the present invention, there is no particular limitation on the introduction order of each component in the coating slurry. For example, all components can be mixed and added together, or the transition metal, alumina, alumina precursor, and surfactant can be mixed first, and then the solvent and organosilicon source can be added. According to a specific embodiment of the present invention, the method includes the following steps: S1. Mix the transition metal, alumina, alumina precursor, and surfactant to obtain a first mixed slurry; S2. Add a solvent to the first mixed slurry obtained in step S1 to obtain a second mixed slurry; S3. Add an organosilicon source to the second mixed slurry obtained in step S2, and then add an acid-base regulator to adjust the pH to 3-4 to obtain the coating slurry. Steps S1-S3 are each independently carried out under stirring conditions. Preferably, the stirring conditions include: a rotation speed of 2000-12000 revolutions per minute and a time of 4-12 hours. Here, the stirring time is the total stirring time of steps S1-S3.

[0046] The second aspect of the present invention provides an application of the coating slurry described in the first aspect in a monolithic catalyst.

[0047] The third aspect of the present invention provides a preparation method of a monolithic catalyst, wherein the method includes the following steps:

[0048] (1) Introduce the coating slurry onto a structured support, and then perform a first drying and optionally a first calcination to obtain a structured support carrier loaded with a coating.

[0049] (2) Immerse the regular structure support carrier in an impregnation solution containing a noble metal precursor, adjust the pH to alkaline, preferably adjust it to pH 8-9, let it stand and then heat, and then perform second drying and second calcination;

[0050] Among them, the coating slurry in step (1) is the coating slurry described in the first aspect or the coating slurry prepared by the preparation method described in the second aspect.

[0051] The preparation method of the monolithic catalyst provided by the present invention modifies the carrier (the regular structure support carrier loaded with a coating) by using the coating slurry described in the present invention. In the process of impregnating the noble metal, the ammonium root complexation method is used to make the noble metal form a positively charged group of ammonium root complexation. Utilizing the characteristic that the silicon functional group is easy to form Si-OH bonds in an aqueous environment, during the process of impregnating the noble metal, the formed Si-OH is used to pair with the above-mentioned positively charged group to promote the dispersion of the noble metal and improve the catalytic oxidation performance of the monolithic catalyst.

[0052] In the present invention, the selection range of the matrix type is relatively wide. The regular structure support can be a whole carrier block with a hollow pore structure formed inside. A coating containing alumina can be distributed on the inner wall of the pore, and the pore can be used as a flow space for the fluid. The matrix is selected from the regular structure support selected from a monolithic carrier with a parallel pore structure having two open ends; the regular structure support can be a honeycomb-type regular carrier (referred to as honeycomb ceramics) with honeycomb-shaped openings in the cross-section.

[0053] In the present invention, preferably, the regular structure support is honeycomb ceramics.

[0054] In the present invention, preferably, the regular structure support is selected from at least one of cordierite honeycomb carriers, mullite honeycomb carriers, diamond honeycomb carriers, corundum honeycomb carriers, zircon corundum honeycomb carriers, quartz honeycomb carriers, nepheline honeycomb carriers, feldspar honeycomb carriers, alumina honeycomb carriers, and metal alloy honeycomb carriers.

[0055] In the present invention, preferably, before step (1), the regular structure support is pretreated to achieve the purpose of easier attachment of the slurry. The specific operations and conditions of the pretreatment can be carried out according to the conventional technical means in the art. Preferably, under ultrasonic conditions, an acid, particularly preferably nitric acid, is used for the pretreatment (the concentration of nitric acid is preferably 0.2-1 mol / L), and the ultrasonic oscillation treatment time is preferably 10-60 minutes. More preferably, washing and first drying are also included after the pretreatment. In the present invention, the washing can be carried out by conventional technical means in the art, and the present invention has no particular limitation on this. In the present invention, the selection range of the conditions for the first drying is relatively wide. Preferably, the conditions for the first drying include: the temperature is 100-150 °C, and the time is 12-24 hours.

[0056] In the present invention, there is no particular limitation on the specific manner of introducing the coating slurry onto the regular structure support. For example, it can be coating or impregnation, and impregnation is preferred. In the present invention, the coating can be carried out once or multiple times as long as a required amount of the alumina-containing coating can be obtained. In the present invention, preferably, in step (1), the impregnation time is 2 - 10 minutes.

[0057] In the present invention, the selection range of the conditions for the first calcination is relatively wide. Preferably, the conditions for the first calcination include: the temperature is 400 - 500 °C and the time is 2 - 4 hours.

[0058] In the present invention, the selection range of the types of noble metals is relatively wide. Preferably, in step (2), the noble metal is selected from at least one of platinum, palladium, rubidium, and rhodium. The present invention has a relatively wide selection range for the ratio of platinum to palladium, for example, it can be 1:0.1 - 10.

[0059] In the present invention, preferably, in step (2), the impregnation solution containing the noble metal precursor is provided by a salt solution of the noble metal, preferably provided by a nitrate solution and / or a chlorate solution.

[0060] In the present invention, there is no particular limitation on the concentration of the impregnation solution containing the noble metal precursor. Preferably, in step (2), the concentration of the impregnation solution containing the noble metal precursor is 0.1 - 5 g / L.

[0061] In the present invention, preferably, in step (2), the conditions for standing include: the time is 1 - 6 hours.

[0062] In the present invention, preferably, in step (2), the conditions for heating include: the temperature is 50 - 80 °C and the time is 1 - 6 hours.

[0063] In the present invention, ammonia water can be used to adjust the pH to alkaline, and preferably the pH is adjusted to 8 - 9. Preferably, the concentration of the ammonia water is 0.5 - 1 mol / L. Using ammonia water to adjust the pH value is beneficial to the dispersion of the noble metal and improves the catalytic performance of the catalyst.

[0064] In the present invention, the selection range of the conditions for the second drying is relatively wide. Preferably, the conditions for the first drying include: the temperature is 100 - 150 °C and the time is 12 - 24 hours.

[0065] In the present invention, the selection range of the conditions for the second calcination is relatively wide. Preferably, in step (2), the conditions for the second calcination include: the calcination temperature is 400 - 500 °C and the time is 2 - 4 hours.

[0066] In the present invention, preferably, the amounts of the regular structure support and the coating slurry are such that in the supported regular structure support carrier with a coating, based on the total amount of the supported regular structure support carrier, the content of the regular structure support is 88-95 wt%, for example, it can be 88 wt%, 89 wt%, 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt% and the values between any two groups, and the content of the coating is 5-12 wt%, for example, it can be 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt% and the values between any two groups.

[0067] In the present invention, in the supported regular structure support carrier with a coating, the content of the regular structure support and the content of the coating can be measured by conventional technical means in the art. For example, it can be obtained by weighing the materials before and after coating, or the weight can be determined according to the shape and manufacturer of the regular structure support, and then the percentage content of the regular structure support can be calculated.

[0068] In the present invention, preferably, the amount of the impregnating solution containing the noble metal precursor is such that in the monolithic catalyst prepared, based on the total volume of the monolithic catalyst, the content of the noble metal in terms of elements is 0.1-5 g / L, for example, it can be 0.1 g / L, 0.5 g / L, 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L, 5 g / L and the values between any two groups.

[0069] In the present invention, the noble metal content in the monolithic catalyst is measured by ICP.

[0070] The fourth aspect of the present invention provides a monolithic catalyst prepared by the preparation method described in the third aspect.

[0071] The fifth aspect of the present invention provides an application of the monolithic catalyst described in the fourth aspect in a catalytic oxidation reaction, preferably in a catalytic oxidation reaction of waste gas containing VOCs.

[0072] In the present invention, preferably, the conditions of the catalytic oxidation reaction include: the reaction pressure is normal pressure, the reaction temperature is 200-600 °C, and the volumetric space velocity of the waste gas containing VOCs is 5000-60000 h -1 .

[0073] In the present invention, preferably, in the waste gas containing VOCs, the concentration of VOCs is 500-10000 ppm.

[0074] The present invention has a wide selection range for the types of VOCs substances, which can be one or several substances among alkanes, alkenes, benzene series substances, oxygen-containing VOCs, chlorine-containing VOCs, etc.

[0075] The monolithic catalyst provided by the present invention is applicable to the treatment of various industrial waste gases, and is particularly applicable to the treatment of VOCs substances contained in the waste gases in the oil refining and chemical industries.

[0076] The present invention will be described in detail below through examples. Unless otherwise specified, the raw materials used in the following examples are all commercially available products.

[0077] The pseudoboehmite used in the following examples and comparative examples is SB powder, with a specific surface area of 350 m 2 / g. The alumina powder is obtained by calcining SB powder at 540 °C, and has a specific surface area of 300 m 2 / g. The honeycomb ceramic is a 400-mesh cordierite honeycomb ceramic.

[0078] The present invention measures the specific surface area of the sample through a physical adsorption instrument, using an AUTO-SORB-1-MP type analyzer from Quantachrome Corporation, USA. Operating conditions: Before testing, the sample is vacuum degassed at 300 °C on the external degassing station for 6 hours. Subsequently, nitrogen is used as the adsorbate, and the adsorption and desorption tests are carried out at the liquid ammonia temperature (77 K). The specific surface area of the sample is calculated by the Brunauer-Emmett-Teller (BET) method.

[0079] The noble metal content is measured by ICP testing.

[0080] The average particle diameter of the noble metal component is statistically analyzed by observing the sample morphology and particle size distribution through STEM to measure the particle size, using a JEM-F200 field emission transmission electron microscope from JEOL Ltd., Japan. Operating conditions: The acceleration voltage is 200 kV. Before testing, a small amount of powder sample is ultrasonically dispersed in anhydrous ethanol, and then dropped onto a copper mesh with a capillary and dried before testing.

[0081] Examples 1-6 and Comparative Examples 1-2 are used to illustrate the preparation of the coating slurry.

[0082] Example 1

[0083] (1) Dissolve 5 g of cerium nitrate in 165 g of water;

[0084] (2) Mix the nitrate solution obtained in step (1) with alumina powder, urea, and pseudoboehmite in a mass ratio of 170:90:10:10, and stir strongly at a rotation speed of 10,000 revolutions per minute for 6 hours to obtain a first mixed slurry;

[0085] (3) Add 18 g of butanol to the first mixed slurry obtained in step (2), and then stir at a rotation speed of 10,000 revolutions per minute for 1 hour to obtain a second mixed slurry;

[0086] (4) Add 10 g of tetraethyl orthosilicate to the second mixed slurry obtained in step (3), and then stir at a rotation speed of 10,000 revolutions per minute for 1 hour; add concentrated nitric acid to adjust the pH and continue stirring for 1 hour to obtain the coating slurry.

[0087] Example 2

[0088] (1) Dissolve 2.5 g of lanthanum nitrate and 2 g of cerium nitrate in 155.5 g of water;

[0089] (2) Mix the nitrate solution obtained in step (1) with alumina powder, urea, and pseudoboehmite in a mass ratio of 160:90:8:8 and stir vigorously at a rotation speed of 5,000 revolutions per minute for 8 hours to obtain a first mixed slurry;

[0090] (3) Add 15 g of isopropanol to the first mixed slurry obtained in step (2), and then stir at a rotation speed of 5,000 revolutions per minute for 1 hour to obtain a second mixed slurry;

[0091] (4) Add 8 g of tetraethyl orthosilicate to the second mixed slurry obtained in step (3), and then stir at a rotation speed of 5,000 revolutions per minute for 1 hour; add concentrated nitric acid to adjust the pH and continue stirring for 1 hour to obtain the coating slurry.

[0092] Example 3

[0093] (1) Dissolve 2.5 g of zirconium nitrate and 2.5 g of cerium nitrate in 175 g of water;

[0094] (2) Mix the nitrate solution obtained in step (1) with alumina powder, glycerol, and pseudoboehmite in a mass ratio of 180:90:12:12 and stir vigorously at a rotation speed of 5,000 revolutions per minute for 8 hours to obtain a first mixed slurry;

[0095] (3) Add 15 g of ethanol to the first mixed slurry obtained in step (2), and then stir at a rotation speed of 5,000 revolutions per minute for 1 hour to obtain a second mixed slurry;

[0096] (4) Add 12 g of tetraethyl orthosilicate to the second mixed slurry obtained in step (3), and then stir at a rotation speed of 5,000 revolutions per minute for 1 hour; add concentrated nitric acid to adjust the pH and continue stirring for 1 hour to obtain the coating slurry.

[0097] Example 4

[0098] According to the method of Example 1, the difference is that cerium nitrate is not introduced, and an equal mass of water is used to replace the cerium nitrate solution.

[0099] Example 5

[0100] (1) Dissolve 5 g of cerium nitrate in 75 g of water, and impregnate 90 g of alumina by the equal - volume impregnation method. Then dry it at 110 °C for 12 hours, and then calcine it at 500 °C for 4 hours to obtain modified alumina powder.

[0101] (2) Mix the modified alumina powder obtained in step (1) with water, urea, and pseudoboehmite in a mass ratio of 90:160:8:8, and stir vigorously at a rotation speed of 5000 revolutions per minute for 8 hours to obtain a first mixed slurry.

[0102] (3) Add 15 g of isopropanol to the first mixed slurry obtained in step (2), and then stir at a rotation speed of 5000 revolutions per minute for 1 hour to obtain a second mixed slurry.

[0103] (4) Add 8 g of tetraethyl orthosilicate to the second mixed slurry obtained in step (3), and then stir at a rotation speed of 5000 revolutions per minute for 1 hour; add concentrated nitric acid to adjust the pH, and continue to stir for 1 hour to obtain the coating slurry.

[0104] Comparative Example 1

[0105] According to the method of Example 1, the difference is that ethyl acetate is used to replace tetraethyl orthosilicate in step (4).

[0106] Comparative Example 2

[0107] According to the method of Example 1, the difference is that tetraethyl orthosilicate is not added in step (4).

[0108] Comparative Example 3

[0109] According to the method of Example 1, the difference is that tetraethyl orthosilicate is replaced with silica sol in terms of an equal mass of silicon dioxide.

[0110] The parameters of the coating slurries prepared in the above Examples 1 - 5 and Comparative Examples 1 - 3 are shown in Table 1.

[0111] Table 1

[0112]

[0113]

[0114] Examples 6 - 11 and Comparative Examples 4 - 6 are used to illustrate the preparation of the monolithic catalyst

[0115] Example 6

[0116] (1) Put 100 mL of honeycomb ceramics into 200 mL of 1 mol / L nitric acid solution, and shake in an ultrasonic oscillator for 1 hour; then rinse repeatedly with 500 mL of clear water, and then dry in an oven at 110 °C for 12 hours;

[0117] (2) Immerse the honeycomb ceramics in step (1) in the coating slurry of Example 1 for 5 minutes. After taking out, blow out the residual slurry in the pores. The honeycomb ceramics after loading are dried in an oven at 110 °C for 12 hours, and then calcined in a muffle furnace at 500 °C for 2 hours to obtain a honeycomb ceramic carrier loaded with a coating;

[0118] (3) Prepare 150 mL of nitrate solutions of palladium and platinum with a concentration of 1 g / L for palladium and 0.5 g / L for platinum;

[0119] (4) Immerse the honeycomb ceramic carrier loaded with a coating obtained in step (2) in the solution in step (3), add concentrated ammonia water to adjust the pH to 8 - 9, and then let it stand for 2 hours;

[0120] (5) Heat the solution after standing in step (4) to 60 °C and keep it for 1 hour;

[0121] (6) Take out the monolithic honeycomb ceramic catalytic oxidation catalyst carrier in step (5), rinse it 3 times with water, then dry it in an oven at 110 °C for 12 hours, and then calcine it in a muffle furnace at 450 °C for 4 hours to obtain the monolithic honeycomb ceramic catalytic oxidation catalyst SiM - 1;

[0122] Based on the total amount of the honeycomb ceramic carrier loaded with a coating, the content of the honeycomb ceramic is 88 wt%, and the content of the coating is 12 wt%.

[0123] Example 7

[0124] (1) Put 100 mL of honeycomb ceramics into 200 mL of 1 mol / L nitric acid solution, and shake in an ultrasonic oscillator for 1 hour; then rinse repeatedly with 500 mL of clear water, and then dry in an oven at 110 °C for 12 hours;

[0125] (2) Immerse the honeycomb ceramics in step (1) in the coating slurry of Example 2 for 5 minutes. After taking out, blow out the residual slurry in the pores. The honeycomb ceramics after loading are dried in an oven at 110 °C for 12 hours, and then calcined in a muffle furnace at 450 °C for 4 hours to obtain a honeycomb ceramic carrier loaded with a coating;

[0126] (3) Prepare 150 mL of nitrate solutions of palladium and platinum with a concentration of 0.5 g / L for palladium and 1 g / L for platinum;

[0127] (4) Immerse the honeycomb ceramic carrier loaded with the coating in the solution in step (3), add concentrated ammonia water to adjust the pH to 8 - 9, and then let it stand for 1 hour;

[0128] (5) Heat the solution after standing in step (4) to 60 °C and keep it for 1 hour;

[0129] (6) Take out the monolithic honeycomb ceramic catalytic oxidation catalyst carrier obtained in step (5), rinse it with water 3 times, then dry it in an oven at 110 °C for 12 hours, and then calcine it in a muffle furnace at 450 °C for 4 hours to obtain the monolithic honeycomb ceramic catalytic oxidation catalyst SiM - 2;

[0130] Based on the total amount of the honeycomb ceramic carrier loaded with the coating, the content of the honeycomb ceramic is 89 wt%, and the content of the coating is 11 wt%.

[0131] Example 8

[0132] (1) Put 100 mL of honeycomb ceramic into 200 mL of 1 mol / L nitric acid solution, and shake it in an ultrasonic oscillator for 1 hour; then rinse it repeatedly with 500 mL of clear water, and then dry it in an oven at 110 °C for 12 hours;

[0133] (2) Immerse the honeycomb ceramic in step (1) in the coating slurry of Example 3 for 5 minutes, take it out and blow out the residual slurry in the pores, and the supported honeycomb ceramic is dried in an oven at 110 °C for 18 hours, and then calcined in a muffle furnace at 450 °C for 4 hours to obtain a honeycomb ceramic carrier loaded with the coating;

[0134] (3) Prepare 150 mL of palladium nitrate solution with a concentration of 1.5 g / L of palladium;

[0135] (4) Immerse the honeycomb ceramic carrier loaded with the coating obtained in step (2) in the solution in step (3), add concentrated ammonia water to adjust the pH to 8 - 9, and then let it stand for 2 hours;

[0136] (5) Heat the solution after standing in step (4) to 60 °C and keep it for 1 hour;

[0137] (6) Take out the monolithic honeycomb ceramic catalytic oxidation catalyst carrier obtained in step (5), rinse it with water 3 times, then dry it in an oven at 110 °C for 12 hours, and then calcine it in a muffle furnace at 450 °C for 4 hours to obtain the monolithic honeycomb ceramic catalytic oxidation catalyst SiM - 3;

[0138] Based on the total amount of the honeycomb ceramic carrier loaded with the coating, the content of the honeycomb ceramic is 88 wt%, and the content of the coating is 12 wt%.

[0139] Example 9

[0140] According to the method of Example 6, except that in step (4), 1 mol / L NaOH solution was used to adjust the pH to 8 - 9, obtaining the monolithic honeycomb ceramic catalytic oxidation catalyst SiM-4.

[0141] Example 10

[0142] According to the method of Example 6, except that the coating slurry of Example 4 was selected, obtaining the monolithic honeycomb ceramic catalytic oxidation catalyst SiM-5.

[0143] Example 11

[0144] According to the method of Example 6, except that the coating slurry of Example 5 was selected, obtaining the monolithic honeycomb ceramic catalytic oxidation catalyst SiM-6.

[0145] Comparative Example 4

[0146] According to the method of Example 6, except that the coating slurry of Comparative Example 1 was selected, obtaining the monolithic honeycomb ceramic catalytic oxidation catalyst SiM-7.

[0147] Comparative Example 5

[0148] According to the method of Example 6, except that the coating slurry of Comparative Example 2 was selected, obtaining the monolithic honeycomb ceramic catalytic oxidation catalyst SiM-8.

[0149] Comparative Example 6

[0150] According to the method of Example 6, except that the coating slurry of Comparative Example 3 was selected, obtaining the monolithic honeycomb ceramic catalytic oxidation catalyst SiM-9.

[0151] The parameters of the catalysts prepared in the above Examples 6 - 11 and Comparative Examples 4 - 6 are shown in Table 2.

[0152] Table 2

[0153]

[0154] Note: In Table 2, the noble metal content is based on the total volume of the monolithic honeycomb ceramic catalytic oxidation catalyst.

[0155] Test Example

[0156] The monolithic honeycomb ceramic catalytic oxidation catalysts of Examples 6 - 11 and Comparative Examples 4 - 6 were applied to the ethane catalytic oxidation reaction, and the reaction was carried out in a fixed-bed reactor of a medium-scale reaction evaluation device. The filling amount of the monolithic honeycomb ceramic catalytic oxidation catalyst was 100 mL, the bed height was 10 cm, the initial concentration of ethane was 2000 ppm, the carrier gas was air, and the volume space velocity was 20000 h-1 The ethane concentration was measured by Agilent 7890A gas chromatography, and the test results are shown in Table 3. Under the same conditions, benzene was used as the reactant with an initial concentration of 3000 ppm, and the test results are shown in Table 4.

[0157] Table 3

[0158] Catalyst Temperature for 50% ethane conversion Temperature for 70% ethane conversion Temperature for 90% ethane conversion Example 6 SiM-1 382℃ 401℃ 420℃ Example 7 SiM-2 380℃ 399℃ 415℃ Example 8 SiM-3 375℃ 395℃ 411℃ Example 9 SiM-4 402℃ 411℃ 435℃ Example 10 SiM-5 388℃ 405℃ 425℃ Example 11 SiM-6 385℃ 403℃ 423℃ Comparative Example 4 SiM-7 428℃ 446℃ 472℃ Comparative Example 5 SiM-8 424℃ 443℃ 470℃ Comparative Example 6 SiM-9 420℃ 435℃ 460℃

[0159] Table 4

[0160] Catalyst Temperature for 50% benzene conversion Temperature for 70% benzene conversion Temperature for 90% benzene conversion Example 6 SiM-1 160℃ 177℃ 201℃ Example 7 SiM-2 159℃ 175℃ 198℃ Example 8 SiM-3 156℃ 172℃ 195℃ Example 9 SiM-4 169℃ 186℃ 211℃ Example 10 SiM-5 163℃ 180℃ 205℃ Example 11 SiM-6 163℃ 182℃ 205℃ Comparative Example 4 SiM-7 200℃ 220℃ 250℃ Comparative Example 5 SiM-8 197℃ 215℃ 245℃ Comparative Example 6 SiM-9 186℃ 206℃ 235℃

[0161] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A coating slurry, characterized in that, The coating slurry contains alumina, a solvent, a surfactant, an alumina precursor, and an organosilicon source. Among them, based on the total amount of the coating slurry, the content of the solvent is 40-70 wt%, the content of alumina is 15-45 wt%, the content of the surfactant is 1-6 wt%, the content of the alumina precursor is 1-6 wt%, and the content of the organosilicon source is 1-6 wt%.

2. The coating slurry according to claim 1, wherein, Based on the total amount of the coating slurry, the content of the solvent is 45-65 wt%, the content of alumina is 20-40 wt%, the content of the surfactant is 2-6 wt%, the content of the alumina precursor is 2-6 wt%, and the content of the organosilicon source is 2-6 wt%.

3. The coating slurry according to claim 1 or 2, wherein, The solvent is water and / or alcohol; Preferably, the alcohol is an alcohol with 1-5 carbon atoms, and more preferably, it is at least one selected from ethanol, ethylene glycol, glycerol, and butanol; Preferably, the mass ratio of the alcohol to the water is 1-2.5:

20.

4. The coating slurry according to claim 1 or 2, wherein, The specific surface area of the alumina is 100 - 1000 m 2 / g; And / or, the alumina precursor is selected from at least one of pseudoboehmite, aluminum hydroxide, and aluminum sec-butoxide, and preferably is pseudoboehmite; Preferably, the specific surface area of the pseudo-boehmite is 150-380 m 2 / g.

5. The coating slurry according to claim 1 or 2, wherein, The surfactant is selected from at least one of polyethylene glycol, urea, sodium dodecylbenzenesulfonate, and stearic acid; Preferably, the organosilicon source is selected from at least one of tetraethyl orthosilicate, tetramethyl orthosilicate, polysiloxane, and ethoxysiloxane.

6. The coating slurry according to claim 1 or 2, wherein, The coating slurry further contains a transition metal, and the transition metal is selected from at least one of group IIIB metal elements, group IVB metal elements, and group VB metal elements, and preferably is selected from at least one of cerium, lanthanum, zirconium, titanium, and vanadium; Preferably, the transition metal exists in the coating slurry in the form of a transition metal salt, and based on the total amount of the coating slurry, the content of the transition metal salt is 1-5 wt%; And / or, the transition metal is loaded on alumina in the form of a transition metal salt or a transition metal oxide, and based on the total amount of the coating slurry, the content of the transition metal salt or the transition metal oxide is 1-5 wt%.

7. The coating slurry according to claim 1 or 2, wherein, The pH value of the coating slurry is 3-4; And / or, at 25°C, the viscosity of the coating slurry is 10-100 mPa·s.

8. The application of the coating slurry according to any one of claims 1 - 7 in a monolithic catalyst.

9. A method for preparing a monolithic catalyst, wherein, The method includes the following steps: (1) Introduce the coating slurry onto a structured support, and then perform first drying and optionally first calcination to obtain a structured support carrier loaded with the coating; (2) Immerse the structured support carrier in an impregnating solution containing a noble metal precursor, adjust the pH to alkaline, preferably adjust it to pH 8-9, let it stand and then heat, and then perform second drying and second calcination; Among them, the coating slurry in step (1) is the coating slurry according to any one of claims 1-7.

10. The method according to claim 9, wherein, In step (1), the structured support is selected from a monolithic carrier having a parallel pore structure with both ends open; Preferably, the structured support is a honeycomb ceramic; Preferably, the regular structure support is selected from at least one of cordierite honeycomb carriers, mullite honeycomb carriers, diamond honeycomb carriers, corundum honeycomb carriers, zirconium corundum honeycomb carriers, quartz honeycomb carriers, nepheline honeycomb carriers, feldspar honeycomb carriers, alumina honeycomb carriers, and metal alloy honeycomb carriers.

11. The method according to claim 9 or 10, wherein, In step (2), the noble metal is selected from at least one of platinum, palladium, rubidium, and rhodium; Preferably, in step (2), the impregnating solution containing the noble metal precursor is provided by a salt solution of the noble metal; Preferably, in step (2), the concentration of the impregnating solution containing the noble metal precursor is 0.1 - 5 g / L; Preferably, in step (2), the conditions for standing include: the time is 1 - 6 hours; Preferably, in step (2), the conditions for heating include: the temperature is 50 - 80 °C, and the time is 1 - 6 hours; Preferably, in step (2), the conditions for the second calcination include: the calcination temperature is 400 - 500 °C, and the time is 2 - 4 hours.

12. The method according to any one of claims 9 - 11, wherein, The amounts of the regular structure support and the coating slurry are such that in the prepared regular structure support carrier loaded with the coating, based on the total amount of the regular structure support carrier loaded with the coating, the content of the regular structure support is 88 - 95 wt%, and the content of the coating is 5 - 12 wt%; Preferably, the amount of the impregnating solution containing the noble metal precursor is such that in the prepared monolithic catalyst, based on the total volume of the monolithic catalyst, the content of the noble metal in terms of elements is 0.1 - 5 g / L.

13. A monolithic catalyst prepared by the preparation method according to any one of claims 9 - 12.

14. Use of the monolithic catalyst according to claim 13 in a catalytic oxidation reaction.

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