A catalytic material for methanol-hydroform co-oxidation, its preparation method and application

Abstract

The application provides a catalytic material for methanol and formaldehyde co-oxidation, a preparation method and application thereof, the catalytic material comprises a carrier and an active component loaded on the carrier, the carrier comprises Ce x Zr y O2, y > x > 0, x + y = 1, and the active component comprises a noble metal. The catalytic material provided by the application exhibits excellent redox capacity, can effectively activate surface oxygen species at a lower temperature, and thus can achieve complete removal of methanol and formaldehyde at a low temperature when the loading amount of the noble metal is low. In addition, the catalyst exhibits good water resistance and high-temperature stability in a test simulating an actual exhaust gas environment, and has industrial application potential.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, and relates to a catalytic material for methanol-formaldehyde co-oxidation, its preparation method, and its application. Background Technology

[0002] Thanks to the industrialization of green methanol technology, methanol vehicles have become an important new energy solution for long-distance transportation. Under the active guidance of the state, domestic methanol engine technology has made significant progress, with clear limits on methanol and formaldehyde emissions of 20 mg / kWh. However, efficient after-treatment systems matched with methanol engines are still immature, and there is an urgent need to develop dedicated catalytic materials to control emissions, especially for unconventional pollutants such as methanol and formaldehyde emitted during the cold start phase of methanol engines, for which mature solutions are still lacking. Therefore, developing dedicated after-treatment catalytic materials that combine high efficiency, low-temperature activity, and durability has become a key link in helping the transportation sector achieve its pollution reduction and carbon reduction goals.

[0003] To address this need, the core of dedicated catalytic technology lies in designing high-performance catalytic materials for the methanol-formaldehyde co-oxidation reaction system. Unlike single-component oxidation, co-oxidation systems require the construction of active sites that can synergistically catalyze both pollutants to achieve simultaneous and efficient removal at low temperatures. For the actual operating conditions of methanol vehicles, the developed catalysts must simultaneously meet three core requirements: first, excellent low-temperature ignition activity to meet the challenges of cold starts; second, high efficiency in methanol-formaldehyde co-oxidation to ensure simultaneous purification; and third, good resistance to hydrothermal aging and long-term stability to guarantee reliable operation throughout its entire lifecycle.

[0004] However, existing catalysts still face challenges in simultaneously meeting the three core requirements of "low-temperature activity, co-oxidation efficiency, and long-term stability." For example, CN104607187A has advantages in macroscopic mass transfer and thermal stability, but the noble metal is incorporated into the cerium-zirconium solid solution lattice in the form of doping, which limits the accessibility of surface active sites and low-temperature reducibility, and it is not specifically designed for methanol / formaldehyde co-oxidation systems. The core of CN108212152A is NO. x The storage and reduction of NO involved the introduction of an alkaline BaO component, which, while beneficial for NO... x It can adsorb, but it may inhibit the oxidation of methanol and formaldehyde or trigger unnecessary side reactions.

[0005] Therefore, developing a dedicated catalyst for the cold start conditions of methanol vehicles, capable of achieving efficient and low-temperature synergistic oxidation of methanol and formaldehyde, is key to meeting stringent emission standards and promoting the industrialization of methanol vehicles. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a catalytic material for the co-oxidation of methanol and formaldehyde, its preparation method, and its applications. The catalyst provided by this invention exhibits excellent redox capabilities, effectively activating surface oxygen species at lower temperatures, thereby achieving complete removal of methanol and formaldehyde at low temperatures even with low noble metal loading. Furthermore, in tests simulating actual exhaust gas environments, the catalyst demonstrates good water resistance and high-temperature stability, possessing potential for industrial applications.

[0007] To achieve this objective, the present invention employs the following technical solution: In a first aspect, the present invention provides a catalytic material for the co-oxidation of methanol and formaldehyde, the catalytic material comprising a support and an active component loaded on the support, the support comprising Ce x Zr y O2, y>x>0, x+y=1, the active component includes noble metals.

[0008] In this invention, Ce x Zr y The O2 (y>x>0) support possesses excellent oxygen storage and release capabilities and abundant oxygen vacancies. Noble metals exhibit good low-temperature oxygen activation capabilities and highly efficient activation performance for CH and CO bonds, thus achieving low-temperature, efficient, and deep oxidation of methanol and formaldehyde. A higher zirconium content helps improve the thermal and structural stability of the support, effectively preventing sintering of the noble metal nanoparticles and the support itself during the reaction, thereby extending catalyst lifetime. Strong interactions exist between the noble metal and the support, forming highly active sites at the interface, optimizing the reaction pathway, and promoting the rapid conversion of methanol and formaldehyde into CO2 and H2O. The catalyst provided by this invention achieves a balance between high and low temperature activity and long-term stability, making it particularly suitable for purifying unconventional pollutants such as methanol and formaldehyde emitted during the cold start phase of methanol engines.

[0009] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0010] Preferably, the morphology of the catalytic material is nanoparticles.

[0011] Preferably, the average size of the carrier is 7 nm to 10 nm, for example, 7 nm, 8 nm, 9 nm or 10 nm.

[0012] Preferably, the average size of the noble metal is 1 nm to 2 nm, such as 1 nm, 1.2 nm, 1.4 nm, 1.6 nm, 1.8 nm or 2 nm.

[0013] In this invention, both the small-sized support and the noble metal are at the nanoscale, which greatly increases the active specific surface area and the number of surface active sites of the material, enhances the electron synergy and oxygen species transfer between the metal and the support, and promotes the low-temperature deep oxidation efficiency of methanol and formaldehyde. Furthermore, the support within this size range also possesses excellent thermal stability, effectively anchoring ultrafine noble metal particles and preventing their agglomeration and sintering, thus ensuring the long-term stability of the catalyst.

[0014] Preferably, the Ce x Zr y In O2, x:y = 1:(1.5~2.5), for example, 1:1.5, 1:1.8, 1:2, 1:2.2 or 1:2.5, etc.

[0015] Preferably, the Ce x Zr y The crystallinity of O2 is 85%~95%, such as 85%, 88%, 90%, 92% or 95%.

[0016] Preferably, the noble metal includes Pt.

[0017] It should be noted that in this invention, the precious metal exists primarily in a metallic state, with both oxidized and metallic states coexisting.

[0018] Preferably, the loading of the precious metal is 0.1 wt.% to 0.5 wt.%, for example, 0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.% or 0.5 wt.%.

[0019] In this invention, by controlling the loading of noble metals within the aforementioned preferred range, combined with an ultrafine particle size of 1 nm to 2 nm, the high dispersion of the noble metals can be ensured, which is beneficial for fully exposing active sites and maximizing their utilization. However, if the loading is too high, it may lead to the aggregation of noble metal nanoparticles, reducing the catalytic performance of the material, and it will also increase the preparation cost, limiting practical applications.

[0020] In a second aspect, the present invention provides a method for preparing a catalytic material as described in the first aspect, the method comprising: S1. Mix Ce salt, Zr salt, noble metal salt and solvent to obtain precursor solution; S2. The precursor solution, precipitant solution and water described in S1 are introduced into a supercritical hydrothermal reactor, and the precipitated product is obtained after the reaction. S3. First, the precipitated product described in S2 is calcined in an air atmosphere, and then calcined in a reducing atmosphere to obtain the catalyst material.

[0021] In this invention, the extremely low dielectric constant of supercritical water gives it properties similar to a nonpolar solvent, significantly increasing its solubility for inorganic gases such as oxygen and making it a strong oxidizing agent. Secondly, when water enters the supercritical state, its density and dielectric constant decrease rapidly, leading to a sharp drop in its solubility for metal salts, causing the solute to precipitate rapidly as metal oxides. For continuous-flow supercritical hydrothermal technology, the excellent diffusivity and fluidity of supercritical water allow the precipitated nanoparticles to quickly escape the reaction system, effectively inhibiting their growth and aggregation. This enables one-step crystallization, resulting in a catalyst with extremely small particle size and high crystallinity, uniform component distribution, and high dispersion of noble metals on the support.

[0022] Furthermore, the present invention forms a catalyst through a two-step calcination process. The first calcination is to stabilize the catalyst to adapt to automotive operating conditions, thereby improving the structural stability of the catalyst. The second calcination is to fully reduce the noble metal ions to the noble metal element, thereby giving the prepared catalyst high activity.

[0023] Preferably, the Ce salt, Zr salt and noble metal salt mentioned in S1 each independently include nitrates, for example, Ce salt is Ce(NO3)3·6H2O, Zr salt is Zr(NO3)4·5H2O and Pt salt is Pt(NO3)2.

[0024] In this invention, nitrate ions are converted into gas and removed during the subsequent calcination process, without introducing impurities; however, if sulfates or chlorides are used, sulfur or chloride elements will be introduced, leading to catalyst poisoning.

[0025] Preferably, the precipitant solution in S2 comprises an aqueous solution of sodium hydroxide.

[0026] In this invention, NaOH, a highly alkaline precipitant, is used, which is more conducive to the rapid and complete precipitation of various metal salts.

[0027] Preferably, the ratio of the total flow rate of the precursor solution and the precipitant solution to the flow rate of the water in S2 is 1:(0.8~1.2), for example, 1:0.8, 1:0.9, 1:1, 1:1.1 or 1:1.2, etc.

[0028] Preferably, in the supercritical hydrothermal synthesizer described in S2, the ratio of the total ion concentration of the precursor solution to the concentration of the precipitant solution is 1:(20~30), for example, 1:20, 1:22, 1:25, 1:27 or 1:30, etc.

[0029] It should be noted that the present invention does not limit the concentration of the precursor solution or the concentration of the precipitant solution, as long as their final concentration in the reactor is similar. Furthermore, when the flow rate of water is similar to the sum of the flow rates of the two substances mentioned above, it is more conducive to the full progress of the reaction.

[0030] Preferably, the reaction temperature in S2 is 370℃~380℃, for example 370℃, 372℃, 375℃, 378℃ or 380℃.

[0031] Preferably, the pressure of the reaction in S2 is 22 MPa to 23 MPa, such as 22 MPa, 22.2 MPa, 22.5 MPa, 22.8 MPa or 23 MPa.

[0032] In this invention, under conditions of 370℃~380℃ and 22 MPa~23 MPa, the solution is converted to a supercritical state, which can rapidly react to form a precipitate.

[0033] Preferably, after the reaction in S2 is completed, the reaction product is subjected to standing, solid-liquid separation, washing and drying in sequence to obtain the precipitated product.

[0034] Preferably, the washing method includes centrifugal washing.

[0035] Preferably, the washing continues until the washing solution is neutral.

[0036] Preferably, the drying method includes freeze-drying or oven drying.

[0037] Preferably, the cutoff temperature of the first calcination in S3 is 300℃~500℃, such as 300℃, 350℃, 400℃, 450℃ or 500℃, and the holding time is 0.5 h~4 h, such as 0.5 h, 1 h, 2 h, 3 h or 4 h.

[0038] Preferably, the reducing atmosphere in S3 includes H2, and more preferably a combination of H2 and N2.

[0039] Preferably, when the reducing atmosphere described in S3 is a combination of H2 and N2, the volume percentage of H2 is 10% to 30%, such as 10%, 15%, 20%, 25%, or 30%.

[0040] Preferably, the cutoff temperature of the second calcination in S3 is 250℃~350℃, such as 250℃, 275℃, 300℃, 325℃ or 350℃, and the holding time is 0.5 h~2 h, such as 0.5 h, 1 h, 1.5 h or 2 h.

[0041] Thirdly, the present invention provides an application of the catalytic material as described in the first aspect in the purification of methanol vehicle exhaust, wherein the methanol vehicle exhaust includes methanol and formaldehyde.

[0042] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0043] Compared with the prior art, the present invention has the following beneficial effects: (1) The catalyst prepared by the present invention exhibits excellent redox ability and can effectively activate surface oxygen species at low temperatures, thereby achieving complete removal of methanol and formaldehyde at low temperatures even when the noble metal loading is low. (2) The catalyst prepared by the present invention exhibits good water resistance and high temperature stability in the test simulating the actual exhaust gas environment, and has application potential; (3) The present invention prepares a methanol-formaldehyde co-oxidation catalyst for methanol fuel engine aftertreatment system. The preparation process is simple and easy to scale up. Attached Figure Description

[0044] Figure 1 This is the H2-TPR diagram of the catalyst provided in Example 1.

[0045] Figure 2 This is a graph showing the methanol removal rate of the catalyst provided in Example 1 under anhydrous conditions.

[0046] Figure 3 This is a graph showing the formaldehyde removal rate of the catalyst provided in Example 1 under anhydrous conditions.

[0047] Figure 4 This is a graph showing the CO2 yield of the catalyst provided in Example 1 under anhydrous conditions.

[0048] Figure 5 This is a graph showing the methanol removal rate of the catalyst provided in Example 1 under water flow conditions.

[0049] Figure 6 This is a graph showing the formaldehyde removal rate of the catalyst provided in Example 1 under water flow conditions.

[0050] Figure 7 This is a graph showing the CO2 yield of the catalyst provided in Example 1 under water flow conditions.

[0051] Figure 8 This is a graph showing the methanol removal rate of the catalyst provided in Example 1 before and after cycling under high temperature conditions.

[0052] Figure 9This is a graph showing the formaldehyde removal rate of the catalyst provided in Example 1 before and after cycling under high temperature conditions.

[0053] Figure 10 This is a graph showing the CO2 yield of the catalyst provided in Example 1 before and after cycling under high temperature conditions. Detailed Implementation

[0054] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0055] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0056] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0057] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0058] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0059] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0060] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0061] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0062] In this invention, "optional" means that something is optional, that is, it refers to either "with" or "without". If there are multiple "optional" options in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, then each "optional" option is independent.

[0063] In this invention, "room temperature" generally refers to 4℃~35℃, and can refer to 20℃±5℃. In some embodiments of this invention, room temperature refers to 20℃~30℃.

[0064] Example 1 This embodiment provides a catalytic material for the co-oxidation of methanol and formaldehyde, which is Pt / Ce. 0.33 Zr 0.67 O2; Pt loading was 0.2 wt.%, with an average size of 1.5 nm; Ce 0.33 Zr 0.67 The average size of O2 is 8 nm, and its crystallinity is 90%. The preparation method is as follows: S1. Mix Ce(NO3)3·6H2O, Zr(NO3)4·5H2O, Pt(NO3)2 and water in a certain proportion to obtain a precursor solution (total concentration of 1 mol / L, of which Ce(NO3)3·6H2O concentration is 0.33 mol / L, Zr(NO3)4·5H2O concentration is 0.67 mol / L, and Pt(NO3)2 concentration is 1.43 mmol / L). S2. The precursor solution obtained in S1, NaOH solution (concentration of 25 mol / L) and water were introduced into a supercritical hydrothermal reactor (flow rate ratio of 1:1:2) and reacted at 374℃ and 22.1 MPa for 25 min. After the reactants were allowed to stand overnight, the supernatant was removed and the mixture was centrifuged and washed multiple times to reach neutrality. The precipitate was then obtained by freeze drying. S3. The precipitate obtained in S2 is first calcined at 300°C in air for 0.5 h, and then reduced at 300°C for 1 h in an H2 / N2 atmosphere (H2 volume percentage 20%) to obtain Pt / Ce. 0.33 Zr 0.67 O2 catalyst.

[0065] Example 2 This embodiment provides a catalytic material for the co-oxidation of methanol and formaldehyde, which is Pt / Ce. 0.4 Zr 0.6 O2; Pt loading was 0.1 wt.%, with an average size of 1 nm; Ce 0.4 Zr 0.6 The average size of O2 is 7 nm, and its crystallinity is 90%. The preparation method is as follows: S1. Mix Ce(NO3)3·6H2O, Zr(NO3)4·5H2O, Pt(NO3)2 and water in a certain proportion to obtain a precursor solution (total concentration of 1 mol / L, of which Ce(NO3)3·6H2O concentration is 0.4 mol / L, Zr(NO3)4·5H2O concentration is 0.6 mol / L, and Pt(NO3)2 concentration is 0.733 mmol / L). S2. The precursor solution obtained in S1, NaOH solution (concentration of 25 mol / L) and water were introduced into a supercritical hydrothermal reactor (flow rate ratio of 1:0.8:1.8) and reacted at 374℃ and 22.1 MPa for 30 min. After the reactants were allowed to stand overnight, the supernatant was removed and the mixture was centrifuged and washed multiple times to reach neutrality. The precipitate was then obtained by freeze drying. S3. The precipitate obtained in S2 is first calcined at 400℃ in air for 4 h, and then reduced at 250℃ for 2 h in an H2 / N2 atmosphere (H2 volume percentage 20%) to obtain Pt / Ce. 0.4 Zr 0.6 O2 catalyst.

[0066] Example 3 This embodiment provides a catalytic material for the co-oxidation of methanol and formaldehyde, which is Pt / Ce. 0.29 Zr 0.71 O2; Pt loading was 0.5 wt.%, with an average size of 2 nm; Ce 0.29 Zr 0.71 The average size of O2 is 10 nm, and its crystallinity is 90%. The preparation method is as follows: S1. Mix Ce(NO3)3·6H2O, Zr(NO3)4·5H2O, Pt(NO3)2 and water in a certain proportion to obtain a precursor solution (total concentration of 1 mol / L, of which Ce(NO3)3·6H2O concentration is 0.29 mol / L, Zr(NO3)4·5H2O concentration is 0.71 mol / L, and Pt(NO3)2 concentration is 3.54 mmol / L). S2. The precursor solution obtained in S1, NaOH solution (concentration of 25 mol / L) and water were introduced into a supercritical hydrothermal reactor (flow rate ratio of 1:1.2:2.6) and reacted at 374℃ and 22.1 MPa for 20 min. After the reactants were allowed to stand overnight, the supernatant was removed and the mixture was centrifuged and washed multiple times to reach neutrality. The precipitate was then obtained by freeze drying. S3. The precipitate obtained in S2 is first calcined at 500℃ in air for 2 h, and then reduced at 350℃ for 0.5 h in an H2 / N2 atmosphere (H2 volume percentage 20%) to obtain Pt / Ce.0.29 Zr 0.71 O2 catalyst.

[0067] Example 4 The difference between this embodiment and Example 1 is that the Pt loading is 2 wt.%, and the Pt(NO3)2 concentration in S1 is 14.6 mmol / L; The remaining preparation methods and parameters remain unchanged.

[0068] Example 5 The difference between this embodiment and Embodiment 1 is that the flow rate ratio of the precursor solution, NaOH solution and water in S2 is 1:1:1. The remaining preparation methods and parameters remain unchanged.

[0069] Example 6 The difference between this embodiment and Embodiment 1 is that the flow rate ratio of the precursor solution, NaOH solution and water in S2 is 1:0.5:1.5; The remaining preparation methods and parameters remain unchanged.

[0070] Example 7 The difference between this embodiment and Embodiment 1 is that in S3, reduction is carried out at 200°C for 1 hour in an H2 / N2 atmosphere; The remaining preparation methods and parameters remain unchanged.

[0071] Comparative Example 1 The difference between this comparative example and Example 1 is that the catalyst is Pt / Ce. 0.67 Zr 0.33 O2; The concentration of Ce(NO3)3·6H2O in S1 is 0.67 mol / L, and the concentration of Zr(NO3)4·5H2O is 0.33 mol / L; The remaining preparation methods and parameters remain unchanged.

[0072] Comparative Example 2 This comparative example provides a catalytic material whose preparation method differs from that of Example 1 in that, in S2, the precursor solution, NaOH solution (concentration of 1 mol / L) and water are mixed at room temperature, and then transferred to a high-pressure reactor for hydrothermal reaction at 150°C for 3 h; after the reaction is completed, the reactants are cooled and washed with distilled water, and then dried to obtain the precipitate. The remaining preparation methods and parameters are consistent with those in Example 1.

[0073] Comparative Example 3 The difference between this comparative example and Example 1 is that calcination is not performed in an air atmosphere in S3; The remaining preparation methods and parameters remain unchanged.

[0074] Performance testing The catalyst prepared in Example 1 was subjected to H2-TPR (hydrogen temperature programmed reduction) testing, and the test results are as follows: Figure 1 As shown.

[0075] The catalysts prepared in Examples 1-7 and Comparative Examples 1-3 were used for methanol-formaldehyde co-oxidation tests. The test method was as follows: 50 mg of catalyst was placed in a fixed-bed reactor, the reaction temperature was 25℃~500℃, the mass hourly space velocity was 120,000 mL / (g·h), the initial concentration of methanol was 300 ppm, the initial concentration of formaldehyde was 100 ppm, the initial concentration of oxygen was 10%, and the water vapor concentration was 0 or 5%. The test results are shown in Table 1 and... Figures 2-10 As shown in Table 1, the relevant data of methanol removal rate, formaldehyde removal rate and CO2 yield of the catalyst at 50℃ under H2O conditions are presented.

[0076] Table 1 like Figure 1 As shown, the Pt / Ce prepared in Example 1... 0.33 Zr 0.67 The O2 catalyst exhibits excellent redox performance. H2-TPR testing shows that the H2 consumption peak temperature is low at 32℃, which is significantly better than the Pt-based catalysts reported to date.

[0077] Figures 2-4 The graph shows the methanol-formaldehyde co-oxidation performance of the catalyst prepared in Example 1 under H2O-free conditions. It can be seen that at 25°C, the catalyst achieves a methanol removal rate of 88%, a formaldehyde removal rate of 100%, and a CO2 yield of 59%; at 50°C, the methanol removal rate is 93%, the formaldehyde removal rate is 100%, and the CO2 yield is 99%; at 75°C, the methanol removal rate is 95%, the formaldehyde removal rate is 100%, and the CO2 yield is 100%; and at 100°C, the methanol removal rate is 96%, the formaldehyde removal rate is 100%, and the CO2 yield is 100%.

[0078] Figures 5-7 This is a graph showing the methanol-formaldehyde co-oxidation data of the catalyst prepared in Example 1 under water flow conditions. It can be seen that at 25°C, the catalyst achieves a methanol removal rate of 29%, a formaldehyde removal rate of 100%, and a CO2 yield of 35%; at 50°C, the methanol removal rate is 94%, the formaldehyde removal rate is 100%, and the CO2 yield is 100%; at 75°C, the methanol removal rate is 97%, the formaldehyde removal rate is 100%, and the CO2 yield is 100%; and at 100°C, the methanol removal rate is 97%, the formaldehyde removal rate is 100%, and the CO2 yield is 100%.

[0079] Figures 8-10 This diagram shows the methanol-formaldehyde co-oxidation performance and cyclic activity data of the catalyst prepared in Example 1 under high-temperature conditions. It can be seen that before cycling, the catalyst exhibits the following characteristics: at 25°C, methanol removal rate is 87%, formaldehyde removal rate is 100%, and CO2 yield is 52%; at 50°C, methanol removal rate is 96%, formaldehyde removal rate is 100%, and CO2 yield is 100%; at 75°C, methanol removal rate is 100%, formaldehyde removal rate is 100%, and CO2 yield is 100%; at 100°C, methanol removal rate is 100%, formaldehyde removal rate is 100%, and CO2 yield is 100%; and between 100°C and 500°C, both removal rate and yield are 100%. After one reaction cycle, the catalyst achieved the following results: at 25°C, methanol removal rate was 76%, formaldehyde removal rate was 100%, and CO2 yield was 22%; at 50°C, methanol removal rate was 88%, formaldehyde removal rate was 94%, and CO2 yield was 90%; at 75°C, methanol removal rate was 100%, formaldehyde removal rate was 100%, and CO2 yield was 100%; and at 100°C, methanol removal rate was 100%, formaldehyde removal rate was 100%, and CO2 yield was 100%.

[0080] Therefore, the catalyst provided by this invention can still achieve excellent oxidation-reduction capabilities for methanol and formaldehyde at low temperatures even with low precious metal loading. In tests simulating actual exhaust gas environments, it exhibits good water resistance and high-temperature stability, and has potential for industrial application.

[0081] Furthermore, a comparison of the data from Example 1 and Comparative Example 1 in Table 1 shows that the molar ratio of Ce to Zr in the support affects the performance of the catalyst. If the molar content of Zr is lower than that of Ce, the oxygen vacancy content of the catalyst will decrease, resulting in a decline in catalytic oxidation capacity. A comparison of the data from Example 1 and Comparative Example 2 shows that the supercritical hydrothermal synthesis method used in this invention, compared with the conventional hydrothermal method, can prepare catalysts with smaller particle size, higher noble metal dispersion, and higher support crystallinity, thereby significantly improving the catalytic performance of the catalyst. A comparison of the data from Example 1 and Comparative Example 3 shows that the stability of the catalyst can be improved by pre-calcining the catalytic material in an air atmosphere.

[0082] As can be seen from the comparison of the data of Example 1 and Examples 4-7 in Table 1, in this invention, the loading of precious metals, the flow ratio of the three solutions during the preparation process, the molar ratio of the precipitant solution to the precursor solution, and the reduction temperature and time all affect the performance of the catalyst. By controlling them within the preferred range of this invention, it is more conducive to improving its overall performance.

[0083] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A catalytic material for the co-oxidation of methanol and formaldehyde, characterized in that, The catalytic material includes a support and an active component loaded on the support, the support comprising Ce. x Zr y O2, y>x>0, x+y=1, the active component includes noble metals.

2. The catalytic material according to claim 1, characterized in that, The morphology of the catalytic material is nanoparticles; Preferably, the average size of the carrier is 7 nm to 10 nm; Preferably, the average size of the noble metal is 1 nm to 2 nm.

3. The catalytic material according to claim 1 or 2, characterized in that, The Ce x Zr y In O2, x:y=1:(1.5~2.5); Preferably, the Ce x Zr y The crystallinity of O2 is 85%~95%.

4. The catalytic material according to any one of claims 1-3, characterized in that, The precious metal includes Pt; Preferably, the loading of the precious metal is 0.1 wt.% to 0.5 wt.%.

5. A method for preparing a catalytic material as described in any one of claims 1-4, characterized in that, The preparation method includes: S1. Mix Ce salt, Zr salt, noble metal salt and solvent to obtain precursor solution; S2. The precursor solution, precipitant solution and water described in S1 are introduced into a supercritical hydrothermal reactor, and the precipitated product is obtained after the reaction. S3. First, the precipitated product described in S2 is calcined in an air atmosphere, and then calcined in a reducing atmosphere to obtain the catalyst material.

6. The preparation method according to claim 5, characterized in that, The Ce salts, Zr salts, and noble metal salts mentioned in S1 each independently include nitrates; Preferably, the precipitant solution in S2 comprises an aqueous solution of sodium hydroxide; Preferably, the ratio of the total flow rate of the precursor solution and the precipitant solution to the flow rate of the water in S2 is 1:(0.8~1.2); Preferably, in the supercritical hydrothermal synthesizer described in S2, the ratio of the total ion concentration of the precursor solution to the concentration of the precipitant solution is 1:(20~30).

7. The preparation method according to claim 5 or 6, characterized in that, The reaction temperature described in S2 is 370℃~380℃; Preferably, the pressure of the reaction in S2 is 22 MPa to 23 MPa.

8. The preparation method according to any one of claims 5-7, characterized in that, After the reaction described in S2 is completed, the reaction product is subjected to static standing, solid-liquid separation, washing and drying in sequence to obtain the precipitated product. Preferably, the washing method includes centrifugal washing; Preferably, the washing continues until the washing solution is neutral; Preferably, the drying method includes freeze-drying or oven drying.

9. The preparation method according to any one of claims 5-8, characterized in that, The cutoff temperature for the first calcination in S3 is 300℃~500℃, and the holding time is 0.5 h~4 h; Preferably, the reducing atmosphere in S3 includes H2, and more preferably a combination of H2 and N2; Preferably, when the reducing atmosphere in S3 is a combination of H2 and N2, the volume percentage of H2 is 10% to 30%. Preferably, the cutoff temperature of the second calcination in S3 is 250℃~350℃, and the holding time is 0.5 h~2 h.

10. The application of a catalytic material as described in any one of claims 1-4 in the purification of methanol vehicle exhaust, characterized in that, The exhaust gas from the methanol vehicle includes methanol and formaldehyde.

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