Catalytic oxidation catalyst, method for producing the same, and use thereof

Abstract

The application relates to the field of catalytic treatment of industrial waste gas, and discloses a catalytic oxidation catalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: 1) carrying out crushing treatment on mixed powder containing an active component, a catalytic additive, a coating additive and a catalytic carrier to obtain coated powder; and 2) coating the coated powder on a conductive honeycomb carrier in a manner of electrostatic spraying and carrying out calcination treatment. The method provided by the application does not introduce any liquid in the preparation process, the coating is uniform, the prepared catalyst has low shedding rate, and the catalyst has excellent catalytic activity at low temperature.

Description

Technical Field

[0001] This invention relates to the field of catalytic treatment of industrial waste gas, specifically to a catalytic oxidation catalyst, its preparation method, and its application. Background Technology

[0002] With the rapid development of industry, the emission of industrial waste gases containing carbon monoxide (CO), volatile organic compounds (VOCs), and other pollutants is one of the important causes of air pollution.

[0003] CO is a flammable, explosive, and toxic gas. Large-scale emissions not only cause significant harm to the ecological environment but also seriously threaten human health. VOCs are easily volatilized at room temperature and are important precursors to secondary pollutants such as fine particulate matter and ozone, which in turn damage the ozone layer and cause atmospheric environmental problems such as haze and photochemical smog. Furthermore, they are themselves toxic and carcinogenic, harming not only crop growth but also human health. The emissions of CO and VOCs severely restrict the sustainable development of society and the economy.

[0004] Catalytic oxidation is an important method for effectively removing CO and VOCs. It converts CO and VOCs into harmless substances such as carbon dioxide and water, thus achieving effective purification. In the catalytic oxidation treatment technology for CO and VOCs, the catalytic oxidation catalyst plays a crucial role. Currently, most of these catalytic oxidation catalysts have a honeycomb structure and are generally prepared using a slurry coating method, where the prepared catalyst slurry is coated onto a structural support.

[0005] For example, CN116251586A discloses a sulfur-resistant CO oxidation catalyst and its preparation method. After preparing a coating slurry, the slurry is coated onto a honeycomb ceramic carrier and dried and calcined. Then, the calcined product is immersed in a pore-expanding solution containing organic solvent to expand the pores. Finally, it is impregnated with a Pt noble metal salt solution, dried, and calcined a second time to prepare the catalytic oxidation catalyst.

[0006] In the traditional preparation method described above, the coating components need to be prepared into a slurry for coating, the coating is then processed, and the active components are impregnated. The coating operation itself makes it difficult to ensure uniform coating of the slurry on the honeycomb carrier, and the active components are difficult to distribute evenly on each catalyst piece due to factors such as concentration changes during the impregnation process. As a result, the quality of the prepared catalyst is not stable enough, which in turn affects the catalytic performance.

[0007] Furthermore, existing coating processes often use organic substances as solvents or additives, and require the addition of additional substances such as nitric acid and ammonia to adjust the pH of the slurry or impregnation solution. These substances inevitably volatilize, decompose, and are emitted during subsequent drying and calcination, becoming new sources of air pollution. Moreover, in traditional preparation methods, the remaining slurry and impregnation solution are not easily stored stably and are difficult to recover, resulting in the loss of active components such as precious metals and leading to a significant increase in production costs.

[0008] On the other hand, existing catalytic oxidation catalysts for CO and VOCs have high activity windows and limited conversion rates for CO and VOCs at relatively low reaction temperatures. Furthermore, existing catalytic oxidation catalysts generally rely on noble metals such as Pt, Pd, and Ag to improve catalytic activity, resulting in problems such as high cost, high required catalytic reaction temperature, and insufficient catalytic activity.

[0009] Therefore, developing catalytic oxidation catalysts that do not require slurry coating and a new coating method are important issues that urgently need to be addressed in this field. Summary of the Invention

[0010] The purpose of this invention is to overcome the problems of complex liquid-phase coating processes and uneven coating in existing catalytic oxidation catalysts, and to provide a catalytic oxidation catalyst and its preparation method. The method provided by this invention uses electrostatic spraying to prepare the catalyst, without introducing any liquid during the preparation process, resulting in uniform coating and a low catalyst shedding rate. Furthermore, the catalyst provided by this invention exhibits excellent catalytic activity at low temperatures, enabling the catalytic oxidation of CO and VOCs.

[0011] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a catalytic oxidation catalyst, wherein the preparation method includes:

[0012] 1) The mixed powder containing active components, catalyst aids, coating aids and catalyst carriers is pulverized to obtain coated powder;

[0013] 2) The coating powder is coated onto a conductive honeycomb carrier by electrostatic spraying and then calcined.

[0014] Preferably, in step 1), the active component is selected from one or more of copper salts, cobalt salts, iron salts and manganese salts, and more preferably copper salts.

[0015] Preferably, the catalyst is selected from one or more of lanthanum salt, cerium salt, praseodymium salt, neodymium salt, samarium salt and zirconium salt, more preferably cerium salt and samarium salt.

[0016] Preferably, the coating aid is selected from one or more of salts, oxides and hydroxides containing potassium and / or sodium, more preferably potassium oxide and / or sodium oxide.

[0017] Preferably, the catalyst support is selected from SiO2 and / or Al2O3.

[0018] Preferably, in step 1), the amount of the active component is such that, relative to the total weight of the calcined coated powder, the content of the active component, calculated as oxide, is 5-20% by weight, more preferably 9-15% by weight.

[0019] Preferably, the amount of the catalyst is such that, relative to the total weight of the calcined coated powder, the content of the catalyst, calculated as oxide, is 5-12% by weight, more preferably 7-9% by weight.

[0020] Preferably, the amount of the coating aid is such that, relative to the total weight of the calcined coating powder, the content of the coating aid, calculated as oxides, is 2-10% by weight, more preferably 4-6% by weight.

[0021] Preferably, in step 1), the particle size of the coated powder is 0.2-10 μm, more preferably 0.5-5 μm.

[0022] Preferably, in step 1), the pulverization process is carried out by ball milling.

[0023] Preferably, the ball milling conditions include: a rotation speed of 400-1000 r / min and a time of 10-180 min; more preferably, the ball milling conditions include: a rotation speed of 400-1000 r / min, with the ball milling process involving 5-20 min of forward rotation, a 20-60 s pause, 5-20 min of reverse rotation, a 20-60 s pause, and repeated 1-4 times.

[0024] Preferably, in step 2), on the surface of the cellular carrier with distributed pores, the mesh count of the pores is 30-200 cpsi, more preferably 50-120 cpsi.

[0025] Preferably, the size of the pores in the honeycomb carrier is 1-5 mm, more preferably 2-3 mm.

[0026] Preferably, the honeycomb carrier is selected from one or more of conductive cordierite honeycomb ceramics, conductive silicon carbide honeycomb ceramics, and stainless steel honeycomb materials, and more preferably conductive cordierite honeycomb ceramics.

[0027] Preferably, the coating amount of the coating powder is 40-200g relative to 1L of the honeycomb carrier, more preferably 80-150g.

[0028] Preferably, in step 2), the electrostatic spraying conditions include: an electrostatic high voltage of 70-80kV, an electrostatic current of 10-20μA, a flow rate pressure of 0.4-0.5MPa, and a distance of 10-30cm between the spray gun nozzle and the honeycomb carrier.

[0029] Preferably, the carrier gas for electrostatic spraying is selected from one or more of compressed air, compressed nitrogen, and compressed argon, and more preferably compressed air.

[0030] Preferably, in step 2), the roasting conditions include: a temperature of 500-800℃ and a time of 2-8h; more preferably, the roasting conditions include: a temperature of 550-650℃ and a time of 3-6h.

[0031] The second aspect of the present invention provides a catalytic oxidation catalyst prepared by the method described in the first aspect of the present invention.

[0032] Preferably, the catalytic oxidation catalyst is a CO and / or VOCs catalytic oxidation catalyst.

[0033] The third aspect of the present invention provides the application of the catalytic oxidation catalyst described in the second aspect of the present invention in the removal of CO and / or VOCs.

[0034] Through the above technical solution, the present invention provides a new method for preparing catalytic oxidation catalysts in addition to existing slurry coating and impregnation methods. It creatively adopts electrostatic spraying to prepare catalytic oxidation catalysts, which can solve the problem of uneven coating in existing slurry coating methods, significantly improve the uniformity of coating, and the catalyst prepared by the present invention has excellent catalytic activity.

[0035] The method described in this invention avoids the use of organic solvents, organic additives, and acids / bases in existing preparation processes, thereby eliminating the generation of polluting gases such as volatile organic compounds during catalyst preparation and preventing environmental pollution caused by traditional preparation processes. Furthermore, the method provided by this invention avoids the use of water, further reducing the cost burden and environmental pollution associated with wastewater treatment and discharge, and meeting the requirements of sustainable production.

[0036] Furthermore, the powder coated using the method provided by this invention can be recycled and reused, avoiding the difficulties in treating coating slurry in existing technologies and greatly improving resource utilization. Moreover, the electrostatic powder coating provided by this invention has the significant advantage of one-time film formation, simplifying the preparation process, improving production efficiency, and shortening the production cycle. At the same time, each step is simple to operate, easy to control, and the prepared catalyst product is uniform, reliable, and has excellent performance.

[0037] On the other hand, the catalyst provided by this invention does not require the use of precious metals such as Pt, Pd, and Ag. At the same time, the catalyst prepared can achieve catalytic treatment of CO and VOCs, and can exert excellent catalytic activity at a relatively low temperature (150-300℃), which significantly reduces the catalyst preparation cost and energy consumption in the catalytic oxidation process. Attached Figure Description

[0038] Figure 1 This refers to the CO removal rates of catalysts C1, D1, and D2 at different temperatures during the CO removal test.

[0039] Figure 2 This refers to the toluene removal rate of catalysts C1, D1, and D2 at different temperatures in the VOCs removal test. Detailed Implementation

[0040] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0041] The first aspect of this invention provides a method for preparing a catalytic oxidation catalyst, wherein the preparation method includes:

[0042] 1) The mixed powder containing active components, catalyst aids, coating aids and catalyst carriers is pulverized to obtain coated powder;

[0043] 2) The coating powder is coated onto a conductive honeycomb carrier by electrostatic spraying and then calcined.

[0044] In this invention, unlike the slurry coating method of the prior art, an electrostatic spraying method is used to coat a mixed powder containing active components, catalyst aids, coating aids and catalyst carriers onto a conductive honeycomb carrier, and the catalyst product is obtained by calcination.

[0045] Therefore, this method not only solves the problem of uneven coating in existing slurry coating methods, but also eliminates the need to prepare liquid slurry, avoids the use of organic solvents and water, and directly achieves the spraying and preparation of catalysts in a dry powder state using mixed powders.

[0046] The preparation method described in the first aspect of the present invention will now be described in detail.

[0047] According to step 1), the mixed powder contains active components, catalytic aids, coating aids, and catalytic carriers.

[0048] In this invention, the active component can be any active component commonly used in the art for preparing catalytic oxidation catalysts, and this invention does not have any particular limitation on it.

[0049] In a preferred embodiment of the present invention, the catalytic oxidation catalyst can be used to treat CO and VOCs, and the active component can be selected from one or more of copper salts, cobalt salts, iron salts and manganese salts.

[0050] The copper salt can be selected from, for example, Cu(CH3COO)2, Cu(NO3)2, CuCl2 or their respective hydrates, preferably Cu(NO3)2·3H2O and / or CuCl2·2H2O.

[0051] The cobalt salt can be selected, for example, from Co(NO3)2, CoCl2, or their respective hydrates.

[0052] The iron salt can be selected, for example, from Fe(NO3)3, FeCl3, or their respective hydrates.

[0053] The manganese salt can be selected, for example, from Mn(NO3)2, MnCl2, or their respective hydrates.

[0054] In this invention, by selecting the above-mentioned active components, it is possible to ensure that the catalyst prepared by the method described in this invention has excellent catalytic activity at a lower temperature. Moreover, the above-mentioned components are inexpensive, avoiding the use of precious metals such as Pt and Pd in ​​the prior art, and significantly reducing the cost of the catalyst.

[0055] In a preferred embodiment of the present invention, the active component is selected from one or more copper salts.

[0056] In this invention, the catalyst promoter can be any promoter commonly used in the art for preparing catalytic oxidation catalysts, other than the active component, and this invention does not have any particular limitation. In a preferred embodiment of this invention, the catalytic oxidation catalyst is used to catalytically treat CO and VOCs, and the catalyst promoter can be selected from one or more of lanthanum salts, cerium salts, praseodymium salts, neodymium salts, samarium salts, and zirconium salts;

[0057] The lanthanum salt can be selected, for example, from La(NO3)3, LaCl3, or their respective hydrates.

[0058] The cerium salt can be selected from Ce(NO3)3, CeCl3 or their respective hydrates, preferably Ce(NO3)3·6H2O or CeCl3·7H2O.

[0059] The praseodymium salt can be selected, for example, from Pr(NO3)3, PrCl3, or their respective hydrates.

[0060] The neodymium salt can be selected, for example, from Nd(NO3)3, NdCl3, or their respective hydrates.

[0061] The samarium salt can be selected from, for example, Sm(NO3)3, SmCl3 or their respective hydrates, preferably Sm(NO3)3·6H2O.

[0062] The zirconium salt can be selected, for example, from Zr(NO3)4, ZrCl4, or their respective hydrates.

[0063] In a preferred embodiment of the present invention, the catalyst is selected from cerium salts and samarium salts.

[0064] During the research and development process, the inventors of this invention discovered that if the active catalyst component and catalyst aid are prepared into a mixed powder and then coated directly by electrostatic spraying and calcined, the resulting catalyst coating has a high peeling rate, making it difficult to obtain a well-coated catalyst product that meets the catalytic performance requirements. On the other hand, if conventional organic binders are mixed into the mixed powder to increase adhesion, it is easy to cause powder agglomeration and clumping, making it difficult to achieve dry electrostatic spraying and thus impossible to prepare a coated catalyst.

[0065] The inventors of this invention conducted extensive and in-depth research and ultimately discovered that by adding specific coating aids to the mixed powder, not only can the powder maintain a good flow state, allowing the entire catalyst powder to be effectively ejected by compressed gas for dry electrostatic spraying, but the coating aids also, during the subsequent calcination process, can generate binding forces on other components in the coating powder under the calcination environment, resulting in a stronger interfacial bond between the formed coating and the honeycomb carrier, ensuring the coating is firmly adhered to the honeycomb carrier. Furthermore, the addition of the coating aids can reduce defects such as bubbles and pores generated in the coating powder under high-temperature calcination conditions, avoiding the weakening effect of these defects on the strength and adhesion of the coating, thereby preventing a decrease in catalytic activity.

[0066] On the other hand, based on common experience, those skilled in the art know that adding other additives to a coated powder containing active components and catalytic promoters is essentially equivalent to reducing the concentration of the active components. Therefore, without increasing the amount of active components, the catalytic performance of the subsequently prepared catalyst is often reduced. However, in this invention, the inventors unexpectedly discovered that introducing the coating additive can actually further improve the catalytic activity. The reason for this may be that the additive elements, after calcination, can promote the adsorption and activation of oxygen in the catalyst coating, generating more active oxygen species on the catalyst surface, thereby promoting the oxidation of target molecules such as CO and VOCs, and thus improving the catalytic activity of the prepared catalytic oxidation catalyst.

[0067] In this invention, the coating aid described above is selected from one or more salts, oxides and hydroxides containing potassium and / or sodium.

[0068] For example, in this invention, the coating aid may be one or more of potassium chloride, potassium sulfate, potassium carbonate, potassium nitrate, potassium acetate, sodium chloride, sodium sulfate, sodium carbonate, sodium nitrate, sodium acetate, potassium oxide, sodium oxide, potassium hydroxide, and sodium hydroxide.

[0069] Preferably, the coating aid is potassium oxide and / or sodium oxide. This allows for a further significant improvement in the adhesion of the catalyst coating and the activity of the catalyst.

[0070] In this invention, the catalyst support can be any of the catalyst supports commonly used in the preparation of catalytic oxidation catalysts in the art. For example, the catalyst support can be an inorganic metal oxide, and this invention does not have any particular limitation on this.

[0071] In a preferred embodiment of the present invention, the catalyst support is SiO2 and / or Al2O3.

[0072] According to a first aspect of the present invention, the mixed powder contains an active component, a catalytic aid, a coating aid, and a catalytic support, and may also contain other conventional components that do not affect coating and catalytic activity, or unavoidably introduced impurities, etc., in which the present invention does not impose any particular limitation.

[0073] In a preferred embodiment of the present invention, in step 1), the active component, catalyst aid, coating aid, and catalyst support are mixed to obtain the mixed powder. The order in which the components are added is not particularly limited and can be carried out according to conventional methods for obtaining mixed powders in the art, as long as the mixing of the components is ensured.

[0074] According to a more preferred embodiment of the present invention, in preparing the mixed powder, the catalyst support is first added, followed by the active component, which is then added and thoroughly mixed with the catalyst support. Next, a catalyst promoter and a coating promoter are added, and the mixture is further homogenized by stirring. This ensures better uniformity between the active component and the catalyst support, thereby further improving the quality of the catalyst obtained subsequently.

[0075] More specifically, the preparation of the mixed powder may include the following steps:

[0076] S1. Place the catalyst support in a container;

[0077] S2. Add the active component to the above container and mix evenly, preferably stirring at a temperature of 20-40°C for 0.5-2 hours;

[0078] S3. Continue to add the catalyst and coating agent into the container and mix them evenly. More preferably, stir at a temperature of 20-40°C for 0.5-2 hours.

[0079] Thus, a well-mixed powder with all components can be obtained.

[0080] On the other hand, the present invention does not have any particular limitation on the amount of each component in the above-mentioned mixed powder, and can be a conventional choice for the preparation of catalytic oxidation catalysts in the art.

[0081] In this invention, the amounts of the active component, catalyst, and coating agent can be calculated based on the content of each component in the calcined coating powder.

[0082] For example, in a preferred embodiment of the invention, the amount of the active component is such that, relative to the total weight of the calcined coated powder, the content of the active component, calculated as oxide, is 1-20% by weight, more preferably 5-20% by weight, and even more preferably 9-15% by weight.

[0083] In a preferred embodiment of the invention, the amount of the catalyst is such that, relative to the total weight of the calcined coated powder, the content of the catalyst, calculated as oxide, is 1-15% by weight, more preferably 5-12% by weight, and even more preferably 7-9% by weight.

[0084] In a preferred embodiment of the invention, the amount of the coating aid is such that, relative to the total weight of the calcined coating powder, the content of the coating aid, calculated as oxide, is 2-10% by weight, more preferably 3-9% by weight, and even more preferably 4-6% by weight.

[0085] For example, the amount of the coating aid is such that, relative to the total weight of the calcined coating powder, the content of the coating aid, calculated as oxides, is 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, and any two of the above values.

[0086] In addition, in a particularly preferred embodiment of the present invention, the amounts of the active component, catalyst aid, and coating aid are such that, relative to the total weight of the calcined coated powder, the content of the active component, calculated as oxides, is 9-15% by weight, the content of the catalyst aid is 7-9% by weight, the content of the coating aid is 4-6% by weight, and the balance may be the catalyst carrier.

[0087] Next, in step 1), after obtaining the mixed powder, in order to coat it onto the honeycomb carrier described later by electrostatic spraying and prepare a catalyst with uniform coating and excellent performance, the obtained mixed powder is pulverized to obtain the coated powder.

[0088] According to the present invention, the purpose of the pulverization process is twofold: first, to reduce the particle size of the resulting mixed powder, pulverizing it to a suitable particle size so that the catalytic oxidation catalyst can be prepared by the electrostatic spraying method described in the present invention; second, to further improve the mixing uniformity of each group in the mixed powder during the pulverization process, thereby further improving the catalytic performance of the subsequently prepared catalytic oxidation catalyst.

[0089] During the research process, the inventors of this invention discovered that during electrostatic spraying, the composition and particle size of the coating powder have an impact on the final coating formation, as well as on the durability and adhesion of the subsequent coating.

[0090] In existing technologies, the particle size of the raw material powder during electrostatic spraying is generally controlled between 20-100 μm. However, the inventors of this invention have discovered that when preparing the catalytic oxidation catalyst of this invention using electrostatic spraying, the particle size of the coated powder is preferably controlled within a smaller range, for example, 0.2-10 μm. When the particle size of the coated powder is larger than the above range, it is not conducive to the uniform dispersion of the powder in space, and it will cause a certain degree of blockage in the pores of the honeycomb carrier, reducing the uniformity of the coating and resulting in insufficient mixing of the components. Conversely, when the particle size of the coated powder is smaller than the above range, the particle size is too small, resulting in less charge, which is not conducive to the adsorption of particles on the honeycomb carrier. The excessively small particle size also requires a longer grinding time, thereby increasing energy consumption.

[0091] In a particularly preferred embodiment of the present invention, the particle size of the coated powder is 0.5-5 μm.

[0092] On the other hand, in this invention, the method of pulverization is not particularly limited, and various pulverization devices and methods conventionally used in the art can be used. For example, ball milling and air jet milling can be used for the pulverization process.

[0093] In a preferred embodiment of the present invention, the pulverization process is carried out by ball milling. This not only allows for more efficient pulverization of the mixed powder, but also further improves the uniformity of mixing among the components of the mixed powder during the ball milling process.

[0094] In this invention, when ball milling is used for the pulverization process, the specific ball milling conditions are not limited, as long as the particle size of the mixed powder can be pulverized to the target particle size. For example, the ball milling conditions may include: a rotation speed of 400-1000 r / min and a time of 10-180 min.

[0095] In a particularly preferred embodiment of the present invention, the ball milling conditions include: a rotation speed of 400-1000 r / min, and during ball milling, rotating clockwise for 5-20 min, stopping for 20-60 s, rotating counterclockwise for 5-20 min, stopping for 20-60 s, and repeating the above process 1-4 times. This further improves the efficiency of ball milling and makes the mixing of various components in the resulting coated powder more uniform, thereby improving the quality of the prepared catalyst.

[0096] Next, in step 2), the coating powder is coated onto the conductive honeycomb carrier by electrostatic spraying and then calcined.

[0097] According to the present invention, the shape of the honeycomb carrier can be a honeycomb carrier shape commonly used in the art, such as a hexahedral block shape, wherein two opposite surfaces have channels extending inward and penetrating through them, and powder is sprayed into the channels, while the other four surfaces are closed. Alternatively, the honeycomb carrier can be cylindrical, wherein two circular surfaces have channels extending inward and penetrating through them, and powder is sprayed into the channels, while the cylindrical surface of the cylinder is closed.

[0098] Furthermore, in this invention, there are no particular limitations on the conductive honeycomb carrier. It can be any honeycomb structure carrier commonly used in the art to prepare catalytic oxidation catalysts, such as CO and / or VOCs catalytic oxidation catalysts, as long as it further possesses conductivity on the basis of the honeycomb carrier. This allows the coating powder to be better adsorbed onto the pore surface of the honeycomb carrier during the electrostatic spraying process.

[0099] In this invention, the conductive honeycomb carrier can be one or more of conductive cordierite honeycomb ceramics, conductive silicon carbide honeycomb ceramics, and stainless steel honeycomb materials.

[0100] In this invention, the conductive cellular carrier used can be any commercially available conductive cellular carrier, or it can be prepared by conventional methods known in the art. This invention does not have any particular limitation on this.

[0101] In a preferred embodiment of the present invention, conductive cordierite honeycomb ceramic is used as a conductive honeycomb carrier.

[0102] In addition, this invention provides a method for preparing the conductive cordierite honeycomb ceramic used in this invention:

[0103] A) Mix cordierite ceramic powder, kaolin, conductive metal powder, and carboxymethyl cellulose ammonium evenly to obtain a powder;

[0104] B) Add water to the powder and mix well to obtain mud;

[0105] C) The obtained mud is aged to obtain aged material;

[0106] D) The aged material is put into a molding machine for extrusion molding to obtain a honeycomb block wet blank, and then dried and calcined.

[0107] In step A), the conductive metal powder can be, for example, stainless steel powder; the particle size of the cordierite ceramic powder and the conductive metal powder is preferably below 5 μm; the weight ratio of cordierite ceramic powder, kaolin, conductive metal powder and carboxymethyl cellulose ammonium can be 15-20:0.5-2:1-5:0.5-2.

[0108] In step B), preferably, water is added to the powder until the moisture content is 25-35% by weight.

[0109] In step C), the aging time can be, for example, 60-90 hours.

[0110] In step D), the drying conditions may include, for example, a temperature of 80-120°C and a time of 15-30 hours; the calcination conditions may include, for example, a temperature of 1200-1400°C and a time of 20-30 hours.

[0111] In addition, the mesh size of the pores on the surface of the honeycomb carrier is not particularly limited, for example, it can be 30-200 cpsi, preferably 50-120 cpsi. By selecting a honeycomb carrier with the above mesh size, the catalytic performance of the prepared catalytic oxidation catalyst can be further improved.

[0112] Furthermore, according to the present invention, the size of the pores in the honeycomb carrier can be, for example, 1-5 mm, preferably 2-3 mm, but is not limited thereto.

[0113] Regarding the dimensions of the aforementioned holes, it should be understood that when the cross-sectional shape of the hole is square, the dimension may refer to the side length of the square; when the cross-sectional shape of the hole is circular, the dimension may refer to the diameter of the circle. Those skilled in the art can also appropriately select the corresponding hole size based on the shape of the hole; there are no particular limitations here.

[0114] According to the present invention, the coating powder obtained in step 1) is coated onto the honeycomb carrier by electrostatic spraying.

[0115] In this invention, there are no particular limitations on the equipment used for electrostatic spraying. Various types of powder electrostatic spraying equipment commonly used in the field can be used, which can be purchased directly or prepared in-house. As long as the electrostatic spraying function can be achieved, this invention does not limit the electrostatic spraying equipment.

[0116] When manufactured in-house, the electrostatic spraying device can be assembled from a high-voltage electrostatic generator, a powder supply tank, a spray gun, a guide needle, a positive grounding clamp, and an air compressor. When using commercially available products, such as the powder electrostatic spraying machine sold by Jinan Zuosheng Environmental Protection Technology Co., Ltd., it can be employed.

[0117] According to the present invention, the specific method of electrostatic spraying is not particularly limited, and can be carried out in accordance with the electrostatic spraying method commonly used in the art, as long as the coating powder of the present invention can be sprayed into the pores of the honeycomb carrier.

[0118] For example, the channels of the honeycomb carrier can be placed parallel to the horizontal direction, and the spray head can be aimed at the channels of the honeycomb carrier during spraying. During spraying, the honeycomb carrier is grounded, receiving a positive electrode, and a high-voltage negative electrode is connected to the metal guide needle at the spray gun head to form an electrostatic field. The coating powder is loaded into the powder supply tank of the electrostatic spraying device, and the coating powder is sent to the spray gun by a carrier gas. After passing through the guide needle, it forms negatively charged powder particles. Under the action of airflow and electrostatic force, the negatively charged powder particles enter the channels of the honeycomb ceramic and are adsorbed onto the pore walls. Those skilled in the art can perform this according to conventional electrostatic spraying methods. Since this invention does not aim to improve the electrostatic spraying process itself, and to avoid obscuring the main point of this invention, further details are omitted here.

[0119] Furthermore, in this invention, there is no particular limitation on the carrier gas for electrostatic spraying. For example, it can be selected from one or more of compressed air, compressed nitrogen and compressed argon, with compressed air being more preferred.

[0120] According to a preferred embodiment of the present invention, in step 2), the conditions for electrostatic spraying may include: electrostatic high voltage of 70-80kV, electrostatic current of 10-20μA, flow rate pressure of 0.4-0.5MPa, and distance between the spray gun nozzle and the honeycomb carrier of 10-30cm.

[0121] Furthermore, in the electrostatic spraying of the present invention, the coating amount of the coating powder relative to 1L of the honeycomb carrier can be 40-200g, preferably 80-150g. This ensures that the catalyst coating achieves appropriate thickness and strength, while also possessing good catalytic activity and durability and adhesion for long-term use.

[0122] Next, the resulting electrostatically sprayed honeycomb carrier with the coating powder is subjected to a calcination treatment.

[0123] In this invention, there are no particular limitations on the calcination conditions, which can be the conventional calcination conditions used in the preparation of catalytic oxidation catalysts. For example, the calcination conditions may include: a temperature of 500-800℃ and a time of 2-8 hours; preferably, the calcination conditions include: a temperature of 550-650℃ and a time of 3-6 hours.

[0124] In addition, to further improve the coating effect, preferably, the heating rate during calcination is 2-10℃ / min, more preferably 4-6℃ / min.

[0125] The catalytic oxidation catalyst was prepared through the above steps.

[0126] Compared to traditional slurry coating, the method described in this invention fundamentally avoids the problems of slurry inhomogeneity caused by sedimentation and uneven coating due to the limitations of liquid phase slurry coating operations. It uses a fully solid phase mixed powder and innovatively electrostatically coats it onto a honeycomb carrier through electrostatic spraying, thereby fundamentally eliminating the problems existing in traditional liquid phase coating methods and significantly improving the quality of the obtained catalyst.

[0127] Furthermore, the preparation method provided by this invention can avoid the preparation of coating slurry and the use of organic solvents, thus directly avoiding pollution in subsequent processes, making it more environmentally friendly and efficient.

[0128] The second aspect of the present invention provides a catalytic oxidation catalyst prepared by the preparation method described in the first aspect of the present invention.

[0129] According to a preferred embodiment of a second aspect of the present invention, the catalytic oxidation catalyst is a CO and / or VOCs catalytic oxidation catalyst.

[0130] Compared with the prior art, the catalyst described in the second aspect of the present invention has a lower CO and VOCs treatment temperature and higher reaction catalytic activity, which not only has high treatment efficiency, but is also more energy-saving and environmentally friendly.

[0131] The third aspect of the present invention provides the application of the catalytic oxidation catalyst described in the second aspect of the present invention in the removal of CO and / or VOCs.

[0132] As described above, by using the catalytic oxidation catalyst provided in the second aspect of the present invention, it can not only be used for the catalytic oxidation removal of CO, but also for the removal of VOCs, with a wider range of applications, lower required catalytic temperature, and excellent catalytic activity.

[0133] The present invention will be described in detail below through embodiments.

[0134] In the following examples and comparative examples, the equipment used for electrostatic spraying is the powder electrostatic spraying machine of Jinan Zuosheng Environmental Protection Technology Co., Ltd.

[0135] In the following examples and comparative examples, the cordierite honeycomb ceramics used were prepared according to the following method:

[0136] A) Mix cordierite ceramic powder (particle size less than 5μm), kaolin, stainless steel powder (particle size less than 5μm), and carboxymethyl cellulose ammonium in a mass ratio of 16:1:3:1 to obtain powder material;

[0137] B) Add deionized water to the powder until the water content is 30% by weight, mix evenly to obtain mud;

[0138] C) The obtained mud material is aged for 72 hours to obtain aged material;

[0139] D) The aged material is placed in a vacuum single-screw extruder to extrude a 40×40-hole honeycomb structure, which is then cut to obtain a wet honeycomb block. The wet block is then dried at 80°C for 10 hours, and then dried at 120°C for 10 hours. After that, it is placed in a high-temperature furnace and calcined at 1320°C for 24 hours to obtain conductive cordierite honeycomb ceramic (of which the stainless steel content is 15% by weight).

[0140] The resulting conductive cordierite honeycomb ceramic has dimensions of 10cm in length, 10cm in width, and 5cm in height. It has through-holes on two 10cm×10cm surfaces, specifically 40 holes×40 holes. On the 10cm×10cm surfaces, the mesh size of the holes is 103cpsi, and the cross-section of the holes is a square with a side length of 2mm.

[0141] In the following examples, unless otherwise specified, room temperature refers to 25°C.

[0142] Example 1

[0143] 1) Add 200g of Al2O3 powder to a container, then add 80g of Cu(NO3)2·3H2O and stir at room temperature for 1 hour; then add 30g of Ce(NO3)3·6H2O, 20g of Sm(NO3)3·6H2O and 12g of K2O and stir at room temperature for 1 hour to obtain a mixed powder;

[0144] 2) Add the mixed powder to a ball mill jar, and at a speed of 800 r / min, rotate clockwise for 20 min, stop for 30 s, rotate counterclockwise for 20 min, stop for 30 s, and repeat this cycle 3 times to obtain coated powder with a particle size of 1-4 μm;

[0145] 3) Position the cordierite honeycomb ceramic with the channels parallel to the horizontal direction, and ground the honeycomb ceramic to obtain the positive electrode. Connect the high voltage negative electrode to the metal guide rod of the spray gun head. Take 200g of the coating powder obtained in step 2) and put it into the powder supply bucket. Make the coating powder negatively charged through the guide needle. The spraying conditions are: electrostatic high voltage 80kV, electrostatic current 15μA, compressed air flow rate and pressure 0.4MPa, and distance between the spray gun nozzle and the honeycomb carrier 10cm. After spraying once from the side of the cordierite honeycomb ceramic with open channels at room temperature, spray again from the other side of the cordierite honeycomb ceramic with open channels according to the above method.

[0146] 4) Under air atmosphere, the temperature was increased to 600℃ at a heating rate of 5℃ / min, and calcined at 600℃ for 4h to prepare catalyst C1.

[0147] In catalyst C1, relative to the total weight of the calcined coated powder, the content of Cu is 10.2 wt%, Ce is 4.6 wt%, Sm is 3.0 wt%, and K is 4.6 wt%, based on oxides.

[0148] Example 2

[0149] 1) Add 200g of Al2O3 powder to a container, then add 80g of CuCl2·2H2O and stir at room temperature for 1h; then add 30g of CeCl3·7H2O, 20g of Sm(NO3)3·6H2O and 12g of K2O and stir at room temperature for 1h to obtain a mixed powder.

[0150] 2) Add the mixed powder to a ball mill jar, and at a speed of 800 r / min, rotate clockwise for 20 min, stop for 30 s, rotate counterclockwise for 20 min, stop for 30 s, and repeat this cycle 3 times to obtain coated powder with a particle size of 1-4 μm;

[0151] 3) Position the cordierite honeycomb ceramic with the channels parallel to the horizontal direction, and ground the honeycomb ceramic to obtain the positive electrode. Connect the high-voltage negative electrode to the metal guide rod of the spray gun head. Take 200g of the coating powder obtained in step 2) and put it into the powder supply bucket. Make the coating powder negatively charged through the guide needle. The spraying conditions are: electrostatic high voltage 80kV, electrostatic current 15μA, compressed air flow rate and pressure 0.4MPa, and distance between the spray gun nozzle and the honeycomb carrier 10cm. After spraying once from the side of the cordierite honeycomb ceramic with open channels at room temperature, spray again from the other side of the cordierite honeycomb ceramic with open channels according to the above method.

[0152] 4) Under air atmosphere, the temperature was increased to 600℃ at a heating rate of 5℃ / min, and calcined at 600℃ for 4h to prepare catalyst C2.

[0153] In catalyst C2, relative to the total weight of the calcined coated powder, the content of Cu, Ce, Sm, and K, based on oxides, is 13.8 wt%, 5.1 wt%, 2.9 wt%, and 4.4 wt%.

[0154] Example 3

[0155] The procedure is performed according to the method described in Example 1, except that...

[0156] In step 1), K2O is replaced with the same weight of Na2O.

[0157] Catalyst C3 was prepared.

[0158] In catalyst C3, relative to the total weight of the calcined coated powder, the content of Cu, Ce, Sm, and Na, based on oxides, is 10.2 wt%, 4.6 wt%, 3.0 wt%, and 4.6 wt%.

[0159] Example 4

[0160] The procedure is performed according to the method described in Example 1, except that...

[0161] In step 1), add 24g of K2O.

[0162] Catalyst C4 was prepared.

[0163] In catalyst C4, relative to the total weight of the calcined coated powder, the content of Cu (calculated as oxides) is 9.8 wt%, Ce (calculated as oxides) is 4.4 wt%, Sm (calculated as oxides) is 2.9 wt%, and K (calculated as oxides) is 8.9 wt%.

[0164] Example 5

[0165] The procedure is performed according to the method described in Example 1, except that...

[0166] In step 1), add 6g of K2O.

[0167] Catalyst C5 was prepared.

[0168] In catalyst C5, relative to the total weight of the calcined coated powder, the content of Cu, Ce, Sm, and K, based on oxides, is 10.4 wt%, 4.7 wt%, 3.1 wt%, and 2.4 wt%.

[0169] Example 6

[0170] The procedure is performed according to the method described in Example 1, except that...

[0171] In step 2), the mixed powder is added to a ball mill jar and rotated at 400 r / min for 20 min, stopped for 30 s, rotated in the reverse direction for 20 min, stopped for 30 s, and repeated twice to obtain coated powder with a particle size of 6-9 μm.

[0172] Catalyst C6 was prepared.

[0173] Example 7

[0174] The procedure is performed according to the method described in Example 1, except that...

[0175] In step 1), 200g of Al2O3 powder is added to a container, followed by 30g of Ce(NO3)3·6H2O, 20g of Sm(NO3)3·6H2O, and 12g of K2O. The mixture is stirred at room temperature for 1 hour. Then, 80g of Cu(NO3)2·3H2O is added and the mixture is stirred at room temperature for 1 hour to obtain a mixed powder.

[0176] Catalyst C7 was prepared.

[0177] Example 8

[0178] The procedure is performed according to the method described in Example 1, except that...

[0179] In step 1), 30g of Ce(NO3)3·6H2O, 20g of Sm(NO3)3·6H2O and 12g of K2O are added to a container and stirred at room temperature for 1 hour; then 200g of Al2O3 powder is added and stirred at room temperature for 1 hour; next, 80g of Cu(NO3)2·3H2O is added and stirred at room temperature for 1 hour to obtain a mixed powder.

[0180] Catalyst C8 was prepared.

[0181] Example 9

[0182] The procedure is performed according to the method described in Example 1, except that...

[0183] In step 1), add 18.8g of KCl.

[0184] Catalyst C9 was prepared.

[0185] In catalyst C9, relative to the total weight of the calcined coated powder, the content of Cu is 10.2 wt%, Ce is 4.6 wt%, Sm is 3.0 wt%, and K is 4.6 wt%, based on oxides.

[0186] Comparative Example 1

[0187] The procedure is carried out according to the method of Example 1, except that...

[0188] In step 1), K2O is not added when preparing the mixed powder.

[0189] Catalyst D1 was prepared.

[0190] In catalyst D1, relative to the total weight of the calcined coated powder, the content of Cu is 10.7 wt%, the content of Ce is 4.8 wt%, and the content of Sm is 3.2 wt%, based on oxides.

[0191] Comparative Example 2

[0192] The procedure is carried out according to the method of Example 1, except that...

[0193] In step 1), K2O is replaced with the same weight of MgO.

[0194] Catalyst D2 was prepared.

[0195] In catalyst D2, relative to the total weight of the calcined coated powder, the content of Cu (calculated as oxides) is 10.2 wt%, Ce (calculated as oxides) is 4.6 wt%, Sm (calculated as oxides) is 3.0 wt%, and Mg (calculated as oxides) is 4.6 wt%.

[0196] Test Example 1: Coating Amount and Peel-off Rate Test

[0197] Using compressed air at 0.2 MPa, the catalyst was purged at a distance of 5 cm from any end face of the open channel for 5 minutes. Powder that failed to adhere firmly to the cordierite honeycomb ceramic carrier was then blown out from the other side of the open channel.

[0198] Calculate the coating amount and peeling rate of each catalyst using the following formula:

[0199] Coating amount = (M1 - M0) / V

[0200]

[0201] Where M0 is the weight of the honeycomb carrier before coating, in g; M1 is the weight of the catalyst obtained after purging according to the above method, in g; M2 is the weight of the catalyst obtained after calcination, in g; and V is the volume of the honeycomb carrier, in L.

[0202] The coating amount and peeling rate of the catalysts prepared in the above embodiments and comparative examples are shown in Table 1.

[0203] Table 1

[0204] Catalyst number Coating amount (g / L) Shedding rate (%) C1 108 0.8 C2 106 1.0 C3 104 0.9 C4 120 0.5 C5 81 3.8 C6 87 3.2 C7 103 0.9 C8 102 0.9 C9 84 4.1 D1 35 61 D2 26 75

[0205] Test Example 2: CO Catalytic Oxidation Performance Test

[0206] The catalysts prepared using the above-described embodiments and comparative examples were subjected to CO removal tests.

[0207] The test conditions are as follows:

[0208] Each catalyst was cut into cylinders with a diameter of 5 cm and a height of 5 cm, and packed into a cylindrical quartz reaction tube. The gas to be treated was then introduced into the tube. The composition of the gas to be treated was: 500 ppm CO, 5% by volume O2, with the balance being N2, and the volume hourly space velocity was 10,000 h⁻¹. -1 The catalyst was heated using an electric furnace and held at each temperature for 30 minutes. After the reaction stabilized, the CO concentration at the inlet and outlet was measured using an infrared gas analyzer. The CO removal rate was calculated using the following formula:

[0209] CO removal rate = (C1 - C2) / C1 × 100%

[0210] Where C1 is the CO concentration at the inlet and C2 is the CO concentration at the outlet.

[0211] As temperature increases, the temperatures at which CO removal rates reach 90% and 100% are denoted as T, respectively. 90％ and T 100％ T for each catalyst 90％ and T 100％ The test results are shown in Table 2.

[0212] Table 2

[0213] Catalyst number <![CDATA[T 90％ (℃)]]> <![CDATA[T 100％ (℃)]]> C1 129 149 C2 130 151 C3 138 156 C4 150 173 C5 156 178 C6 153 174 C7 134 155 C8 132 153 C9 154 175 D1 198 220 D2 208 231

[0214] In addition, in the CO removal test, the CO removal rates of catalysts C1, D1, and D2 at different temperatures were as follows: Figure 1 As shown.

[0215] Test Example 3: VOCs Catalytic Oxidation Performance Test

[0216] The catalysts prepared using the above-described embodiments and comparative examples were tested for VOC removal.

[0217] Each catalyst was cut into cylinders with a diameter of 5 cm and a height of 5 cm, and packed into quartz reaction tubes. A gas to be treated was introduced into the tubes. The composition of the gas to be treated was: 500 ppm toluene, 5% by volume O2, and the balance being N2. The volume hourly space velocity (VHSV) of the catalyst was 10,000 h⁻¹. -1 The catalyst was heated using an electric furnace and held at each temperature for 30 minutes. After the reaction stabilized, the concentration of toluene at the inlet and outlet was measured using a gas chromatograph. The toluene removal rate was calculated using the following formula:

[0218] Toluene removal rate = (V1-V2) / V1×100%

[0219] Where V1 is the toluene concentration at the inlet and V2 is the toluene concentration at the outlet.

[0220] As the temperature increases, the temperatures at which toluene achieves 90% and 100% removal rates are denoted as T, respectively. 90％ and T 100％ T for each catalyst 90％ and T 100％ The test results are shown in Table 3.

[0221] Table 3

[0222] Catalyst number <![CDATA[T 90％ (℃)]]> <![CDATA[T 100％ (℃)]]> C1 274 289 C2 277 293 C3 283 295 C4 295 310 C5 301 316 C6 298 313 C7 284 299 C8 286 297 C9 299 315 D1 332 360 D2 349 369

[0223] In addition, in the VOCs removal test, the toluene removal rates of catalysts C1, D1, and D2 at different temperatures were as follows: Figure 2 As shown.

[0224] 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 inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a catalytic oxidation catalyst, characterized in that, The preparation method includes: 1) The mixed powder containing active components, catalyst aids, coating aids and catalyst carriers is pulverized to obtain coated powder; 2) The coating powder is coated onto a conductive honeycomb carrier by electrostatic spraying and then calcined.

2. The preparation method according to claim 1, wherein, In step 1), the active component is selected from one or more of copper salts, cobalt salts, iron salts and manganese salts, more preferably copper salts; Preferably, the catalyst is selected from one or more of lanthanum salt, cerium salt, praseodymium salt, neodymium salt, samarium salt and zirconium salt, more preferably cerium salt and samarium salt; Preferably, the coating aid is selected from one or more of salts, oxides and hydroxides containing potassium and / or sodium, more preferably potassium oxide and / or sodium oxide; Preferably, the catalyst support is selected from SiO2 and / or Al2O3.

3. The preparation method according to claim 1, wherein, In step 1), the amount of the active component is such that, relative to the total weight of the calcined coated powder, the content of the active component, calculated as oxide, is 5-20% by weight, more preferably 9-15% by weight. Preferably, the amount of the catalyst is such that, relative to the total weight of the calcined coated powder, the content of the catalyst, calculated as oxide, is 5-12% by weight, more preferably 7-9% by weight; Preferably, the amount of the coating aid is such that, relative to the total weight of the calcined coating powder, the content of the coating aid, calculated as oxides, is 2-10% by weight, more preferably 4-6% by weight.

4. The preparation method according to any one of claims 1-3, wherein, In step 1), the particle size of the coated powder is 0.2-10 μm, preferably 0.5-5 μm.

5. The preparation method according to any one of claims 1-3, wherein, In step 1), the pulverization process is carried out by ball milling; Preferably, the ball milling conditions include: a rotation speed of 400-1000 r / min and a time of 10-180 min; More preferably, the ball milling conditions include: a rotation speed of 400-1000 r / min, and the following cycle: 5-20 min forward rotation, 20-60 s pause, 5-20 min reverse rotation, 20-60 s pause, and 1-4 cycles.

6. The preparation method according to any one of claims 1-3, wherein, In step 2), on the surface of the cellular carrier with distributed pores, the mesh count of the pores is 30-200 cpsi, more preferably 50-120 cpsi; Preferably, the size of the pores in the honeycomb carrier is 1-5 mm, more preferably 2-3 mm; Preferably, the honeycomb carrier is selected from one or more of conductive cordierite honeycomb ceramics, conductive silicon carbide honeycomb ceramics, and stainless steel honeycomb materials, and more preferably conductive cordierite honeycomb ceramics; Preferably, the coating amount of the coating powder is 40-200g relative to 1L of the honeycomb carrier, more preferably 80-150g.

7. The preparation method according to any one of claims 1-3, wherein, In step 2), the conditions for electrostatic spraying include: electrostatic high voltage of 70-80kV, electrostatic current of 10-20μA, flow rate pressure of 0.4-0.5MPa, and distance between the spray gun nozzle and the honeycomb carrier of 10-30cm. Preferably, the carrier gas for electrostatic spraying is selected from one or more of compressed air, compressed nitrogen, and compressed argon, and more preferably compressed air.

8. The preparation method according to any one of claims 1-3, wherein, In step 2), the roasting conditions include: a temperature of 500-800℃ and a time of 2-8 hours; Preferably, the calcination conditions include: a temperature of 550-650℃ and a time of 3-6 hours.

9. The catalytic oxidation catalyst prepared by the method according to any one of claims 1-8; Preferably, the catalytic oxidation catalyst is a CO and / or VOCs catalytic oxidation catalyst.

10. The application of the catalytic oxidation catalyst according to claim 9 in CO removal and / or VOCs removal.

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