A low-temperature high-efficiency catalytic oxidation low-carbon alkane catalyst and a preparation method thereof

Abstract

The application belongs to the technical field of catalyst preparation, and specifically discloses a low-temperature high-efficiency catalytic oxidation low-carbon alkane catalyst and a preparation method. x Co 3‑x O4 spinel nanoclusters, x is 0.4-0.99, the active component is a composite metal oxide composed of noble metals and transition metals, the catalyst is combined with the active component and the catalytic material first, and then combined with non-metering ratio Ni x Co 3‑x O4 spinel nanoclusters; in the catalyst, the content of Ni x Co 3‑x O4 spinel nanoclusters accounts for 1.0-20.0wt%; the content of noble metals accounts for 0.1-2.0wt%, and the content of transition metals accounts for 1.0-20.0wt%. The catalyst has good low-temperature catalytic purification performance on low-carbon alkane, has good stability, can be widely applied to the industrial waste gas purification industry such as petroleum, chemical industry and refining, can realize low-temperature high-efficiency catalytic combustion purification on various low-carbon alkane and other toxic and harmful waste gas, has simple preparation process and is suitable for large-scale production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalyst preparation, in particular to a low-temperature high-efficiency catalytic oxidation low-carbon alkane catalyst and a preparation method thereof. BACKGROUND

[0002] Volatile organic compounds (VOCs) are a kind of toxic and harmful pollutants, which form ozone or haze with NO x , PM 2.5 and other pollutants, seriously threatening human health. VOCs include alkanes, alkenes, aromatic hydrocarbons, aldehydes, ketones and several other categories. Under the increasingly stringent emission standard requirements and the strong promotion of national and local policies, industrial source VOCs emission control has received widespread attention, especially in the fields of petroleum and petrochemical industry. VOCs pollution control can be divided into adsorption method, incineration method, catalytic oxidation, biological method and membrane separation method, etc. Among them, catalytic oxidation technology is one of the most promising technologies for removing VOCs because of its low energy consumption and no secondary pollution; and the development of high-performance catalytic oxidation catalyst is the key to realizing waste gas purification and green production.

[0003] VOCs catalytic oxidation catalysts usually use platinum, palladium and other noble metals as active components. These noble metals can activate hydrocarbons and oxygen at low temperatures, so that the two can activate C-H or strengthen the adsorption of low-carbon molecules through L-H or MvK mechanism, and catalytic reaction occurs at the active sites of the catalyst, showing excellent low-temperature catalytic oxidation activity. However, low-carbon alkanes such as methane, ethane, propane or isobutane are difficult to break due to the strong carbon-hydrogen bond. The existing low-carbon alkane catalysts have high light-off temperature and low conversion efficiency when treating low-concentration low-carbon alkanes. In actual industrial applications, the T 50 of the general low-carbon alkane catalyst is greater than 340℃, and the T 99 reaches more than 450℃. The expensive price of noble metals determines that the noble metal loading in the oxidation catalyst is limited, and the performance of the catalyst is difficult to further improve.

[0004] In order to improve the low-temperature performance of low-carbon alkane catalysts, patent CN117563629A discloses a monolithic catalytic material for low-carbon alkane oxidation and its preparation method and application. A palladium source is dissolved in hydrochloric acid, then a Group VIII transition metal nitrate is added, after stirring and clarification, a cerium oxide carrier is added, the pH is adjusted to 9-9.5, after stirring, it is left to stand, and then calcination is performed to obtain a catalyst powder. The catalyst powder is loaded on the surface of a metal aluminum fiber carrier by a wet impregnation method to obtain a monolithic catalytic material. The mass percentage of palladium in the monolithic catalyst is 0.5-1.0%. The material has abundant oxygen vacancies and high palladium dispersion. Compared with unmodified pure palladium supported catalysts, the monolithic catalyst modified by strong electron-donating transition metals has better low-carbon alkane oxidation performance, excellent water resistance, CO resistance and stability, and is renewable. Although the above method adds transition metals to noble metals to provide oxygen vacancies, the number of oxygen vacancies provided is limited, and the low-temperature performance of low-carbon alkane catalysts cannot be effectively improved.

[0005] Therefore, it is an urgent problem in the art to provide a low-carbon alkane catalyst that can fully exhibit catalytic performance at low temperatures. SUMMARY

[0006] The present application aims to solve the problems of high catalyst light-off temperature and low catalyst conversion efficiency when existing low-carbon alkane catalysts purify low-carbon alkanes, and to provide a low-temperature and high-efficiency catalytic oxidation low-carbon alkane catalyst and a preparation method. The catalyst has outstanding low-temperature and high-efficiency performance when purifying low-concentration low-carbon alkanes.

[0007] To achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0008] A low-temperature and high-efficiency catalytic oxidation low-carbon alkane catalyst, the catalyst comprising a catalytic material and an active component loaded on the catalytic material, Ni x Co 3-x O4 spinel nanoclusters, x is 0.4-0.99, the active component is a composite metal oxide composed of a noble metal and a transition metal, and the catalyst is combined with the active component and the Ni x Co 3-x O4 spinel nanoclusters first, and then combined with the Ni x Co 3-x O4 spinel nanoclusters; the content of the Ni

[0009] In the above technical solution, the catalyst is a combination of noble metals (PGM), transition metals (TM), and catalytic materials (MO) as active components. y Combined with, and then with, non-stoichiometric Ni x Co 3-x The desired catalyst Ni was finally prepared by combining O4 spinel nanoclusters. x Co 3-x O4-PGM-TM / MO y Abbreviated as N x C 3-x -PT / M, where the composite metal oxide composed of noble metals and transition metals is a bimetallic oxide or a trimetallic oxide, N x C 3-x In the -PT / M catalyst, the non-stoichiometric Ni x Co 3-x The content of O4 spinel is 1.0 wt% to 20.0 wt%, the content of precious metals is 0.1 wt% to 2.0 wt%, and the content of transition metals is 1.0 wt% to 20.0 wt%.

[0010] The catalyst of this invention is designed with non-stoichiometric Ni x Co 3-x O4 spinel nanoclusters, with composite active sites of noble and transition metals, synergistically integrate spinel nanoclusters, noble metals, transition metals, and catalytic materials, because Ni x Co 3-x O4 spinel nanoclusters possess excellent redox properties. When prepared in catalysts, they acquire more defect sites, resulting in better dispersion of noble metals in the catalytic material. Simultaneously, the transition metals promote the noble metal active sites to exhibit more metallic valence active sites, enhancing the stability and redox characteristics of active species and enriching the active oxygen species on the catalyst surface. This further synergistically improves the low-temperature adsorption capacity for low-carbon alkanes, achieving high-efficiency low-temperature catalytic oxidation of low-carbon alkanes and laying the foundation for long-term achievement of 99% good ignition performance.

[0011] In a preferred embodiment of the present invention, the noble metal is at least one of Pt and Pd.

[0012] As a more preferred embodiment of the present invention, the content of the precious metal is 0.5 to 1 wt%.

[0013] As a more preferred embodiment of the present invention, the non-stoichiometric Ni x Co 3-x The content of O4 spinel nanoclusters is 5-15 wt%.

[0014] As a preferred scheme of the present application, the transition metal is at least one of tungsten (W), cobalt (Co), molybdenum (Mo), niobium (Nb), nickel (Ni), zirconium (Zr), titanium (Ti), vanadium (V), and manganese (Mn).

[0015] As a more preferred scheme of the present application, the content of the transition metal is 3.0-15.0wt%.

[0016] As a preferred scheme of the present application, the catalytic material is at least one of aluminum oxide, silicon oxide, titanium oxide, cerium oxide, and zirconium oxide.

[0017] Another aspect of the present application provides a preparation method of a low-temperature high-efficiency catalytic oxidation low-carbon alkane catalyst, comprising the following steps:

[0018] S1, dissolving the soluble precursor salts of noble metals and transition metals to form a mixed solution, adding a first additive to form solution A, stirring solution A at a temperature of 40-90℃ for 1h-4h, then adding a catalytic material to solution A, the mass ratio of the catalytic material to solution A being 0.8-1.2, and continuing to stir at a temperature of 40-90℃ for 3h-10h, and then drying and calcining to obtain a PT / M catalyst;

[0019] A sodium hydroxide-ammonia solution with a pH of 8.5-11 is prepared to obtain solution C, and the PT / M catalyst is added to solution C to obtain a suspension containing the PT / M catalyst after stirring, and the suspension is incubated at a temperature of 40-90℃ for 1h-6h;

[0020] A mixed solution of nickel soluble precursor salt and cobalt soluble precursor salt is prepared to obtain solution B, wherein the molar ratio of Ni to Co is x:(3-x), and x is 0.4-0.99;

[0021] S2, the solution B is added dropwise to the suspension under stirring at a stirring rate of 100-300r / min for 1h-3h, and then aging, filtering, and washing are sequentially performed, and then drying and calcining are performed to obtain a catalytic oxidation low-carbon alkane catalyst.

[0022] In the above technical solution, the active components, noble metals (PGM) and transition metals (TM), are combined with the catalytic material (MO y ) to prepare a PT / M catalyst; then the PT / M catalyst is suspended in a sodium hydroxide-ammonia solution, and the pH of the solution is controlled to be 8.5-11 to create an alkaline environment for the subsequent Ni x Co 3-xThe formation and combination of O4 spinel nanoclusters are provided; then a mixed solution of nickel and cobalt in a designed non-stoichiometric ratio is configured, the solution B is added to the suspension by dropwise method, the size of the formed spinel nanoclusters is controlled by controlling the feeding ratio, temperature and concentration, the in-situ synthesized crystallization is fully combined, and finally the catalyst for catalytic oxidation of low-carbon alkanes is obtained.

[0023] As a preferred scheme of the present application, the soluble precursor salt of the noble metal is at least one of nitrate, acetate and oxalate, and the soluble precursor salt of the transition metal is at least one of nitrate, acetate and oxalate.

[0024] As a preferred scheme of the present application, the first additive is at least one of citric acid and oxalic acid, and the first additive is fed in a molar ratio of 1.5-5:1 to the noble metal; more preferably, the first additive is fed in a molar ratio of 3:1 to the noble metal.

[0025] As a preferred scheme of the present application, the aging process is performed at room temperature for 10-24 hours.

[0026] As a preferred scheme of the present application, the washing process is performed by using deionized water for 1-3 times.

[0027] As a preferred scheme of the present application, the drying process is performed at 90-120℃ for 5-10 hours.

[0028] As a preferred scheme of the present application, the calcination is performed by using a continuous calcination process, and is divided into two times of calcination, the first time of calcination is performed at 300-450℃ for 3-5 hours, and the second time of calcination is performed at 650-900℃ for 3-7 hours.

[0029] The present application also provides a monolithic catalyst, which comprises a carrier and a catalytic coating, and the catalytic coating comprises the above low-temperature high-efficiency catalyst for catalytic oxidation of low-carbon alkanes.

[0030] As a preferred scheme of the present application, the carrier comprises a porous metal honeycomb carrier or a porous ceramic honeycomb carrier, and a catalyst coating with a certain thickness is coated on the carrier by single or multiple coating.

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] 1. The catalyst of the present application is designed to have a non-stoichiometric ratio of Ni x Co 3-x O4 spinel nanoclusters, noble metal and transition metal complex active sites, which are combined with catalytic materials, because Ni x Co 3-xThe spinel nanoclusters O4 have good redox performance, and the preparation makes the catalyst have more defect sites, the noble metal has better dispersibility on the catalytic material, and the transition metal promotes the noble metal active site to be more metal valence active site, enhances the stability of active species and the redox characteristics, enriches the active oxygen species on the surface of the catalyst, thereby further synergistically improving the low-temperature adsorption capacity of low-carbon alkanes, and realizing the low-temperature and efficient catalytic oxidation of low-carbon alkanes.

[0033] 2、The catalyst prepared by the application has good low-temperature light-off performance for low-concentration low-carbon alkanes, and the conversion rate of low-carbon alkanes is more than 95% at a space velocity of 25000h-1 and a temperature of 350℃. -1 50 99 The temperature range is 350-365℃, the stability test is carried out at 350℃, the catalytic efficiency of the catalyst prepared by the application can reach more than 93%, and the catalyst efficiency fluctuation range is less than 1.0% in the test time of 200h, and the catalyst still has good stability at high conversion rate.

[0034] 3、The catalyst provided by the application has good low-temperature light-off performance for low-carbon alkanes such as methane, ethane and propane, and is suitable for scenes such as acrylic acid, propylene, acrylonitrile, phenol acetone and other petroleum refining and chemical device, realizes low-temperature and efficient catalytic purification of low-carbon alkanes in waste gas, has large treatment capacity, wide application range, simple process, easy industrialization, high catalyst activity, good use effect, and good industrial application potential. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The preparation method flow chart of the low-temperature and efficient catalytic oxidation low-carbon alkane catalyst of the application is shown in the figure. DETAILED DESCRIPTION

[0036] In order to more clearly describe the purposes, technical solutions and technical effect advantages of the specific implementation cases of the application, the solutions in the specific embodiments will be described in detail in combination with the drawings of the specification. The specific technical solutions involved in the following specific embodiments are only for clearly and completely describing the innovative technical solutions of the application, and are only a part of the specific implementation schemes of the application, not all embodiments, and should not be understood as a limitation of the innovative solutions of the application. Any solution adopting the same inventive concept of the application should be included in the protection scope of the application.

[0037] ​​Secondly, the related description of the drawings in the specific embodiments of the present application is only for the convenience of the technicians to understand the present application scheme, and part of the details in the drawings is exhibited for the convenience of clear presentation of the technical scheme, and it should not be considered that all the technical features in the drawings must be included in the specific implementation cases, and more, the details in the drawings cannot be identified as additional limitations on the innovative technical scheme of the present application. The components in each embodiment described and exhibited in the drawings can be combined and arranged in different configurations, and these combinations and arrangements should be considered as part of all embodiments of the present application and included in the scope of the present application.

[0038] Embodiment 1

[0039] The present embodiment provides a low-temperature and high-efficiency catalytic oxidation low-carbon alkane catalyst, the active component is a bimetallic oxide or a trimetallic oxide composed of noble metal and transition metal, Ni x Co 3-x In the Co4 spinel nanocluster, x is 0.5, N 0.5 C 2.5 In the 4Pt1PdW / Al2O3 catalyst, the non-stoichiometric ratio of Ni 0.5 Co 2.5 The content of the Co4 spinel accounts for 5.0wt%, the content of the noble metal platinum palladium accounts for 1.0wt%, the mass ratio of platinum to palladium is 4:1, the content of the transition metal WO3 accounts for 5.0wt%, and the catalyst is prepared by the following method:

[0040] 1) According to the content design, the noble metal platinum nitrate, the platinum nitrate and the ammonium metatungstate salt are prepared into a mixed solution, oxalic acid is added, a solution A is formed, and the oxalic acid content and the noble metal content are added according to the molar ratio of 3:1;

[0041] 2) Put the solution A in the water bath and continuously stir, the water bath temperature is 60℃, and the time is 2h. Add the catalytic material alumina to the solution A, the addition amount and the mass ratio of the solution A is 0.9; and continue to stir, the water bath temperature is 60℃, and the time is 5h; then go through the drying and calcination process, the drying process is 110℃@4h, the calcination process is temperature: 400℃, time: 3h; and the 4Pt1PdW / Al2O3 catalyst is obtained.

[0042] 3) Prepare a sodium hydroxide-ammonia solution, control the solution pH in the range of 10.5, obtain a solution C, then add the 4Pt1PdW / Al2O3 catalyst obtained in 2) to the solution C, continuously stir to obtain a suspension containing the 4Pt1PdW / Al2O3 catalyst, and perform water bath, temperature: 90℃, holding time: 3h.

[0043] 4) According to the molar ratio of Ni 0.5 Co2.5 O4 accounts for 5wt% of the total mass of the catalyst, and the corresponding precursor salt nickel nitrate and cobalt nitrate are mixed to obtain solution B; the molar concentration of 4Pt1PdW / Al2O3 catalyst in the suspension is required to be at least 2 times that of solution B, and the excess can ensure as much deposition as possible during subsequent dropwise addition,

[0044] 5) Add solution B to the suspension, stirring while adding, stirring rate 200r / min; time: 1h; then sequentially perform aging, filtering, washing, drying, calcination and other processes to obtain N 0.5 C 2.5 -4Pt1PdW / Al2O3 catalyst; wherein the aging process is 15h at room temperature; the washing is 3 times with deionized water; the drying process is at 110℃ for 5h; the continuous calcination process is used, the first calcination temperature is 400℃, the time is 3h; the second calcination temperature is 750℃, the time is 5h.

[0045] Example 2

[0046] This example is similar to Example 1, the difference is that the transition metal in this example is niobium, and the molar ratio of Ni to Co is 0.7:2.3, so the catalyst is N 0.7 C 2.3 -4Pt1PdNb / Al2O3, the non-stoichiometric ratio of Ni 0.7 Co 2.3 O4 spinel content accounts for 5.0wt%, noble metal platinum palladium content accounts for 1.0wt%, platinum palladium mass ratio is 4:1, transition metal NbO3 content accounts for 5.0wt%, the preparation method is the same as Example 1, and the catalyst of this example is prepared.

[0047] Example 3

[0048] This example is similar to Example 2, the difference is that the transition metal in this example is zirconium, and the molar ratio of Ni 0.7 Co 2.3 O4 accounts for 10wt% of the total mass of the catalyst. Thus, the catalyst is N 0.7 C 2.3 -4Pt1PdZr / Al2O3, the non-stoichiometric ratio of Ni 0.7 Co 2.3 O4 spinel content accounts for 10wt%, noble metal platinum palladium content accounts for 1.0wt%, platinum palladium mass ratio is 4:1, transition metal ZrO2 content accounts for 5.0wt%, the preparation method is the same as Example 1, and the catalyst of this example is prepared.

[0049] Example 4

[0050] This example is similar to example 3, the difference is that the transition metal in this example is molybdenum. Thus the catalyst is N 0.7 C 2.3 -4Pt1PdMo / Al2O3, non-stoichiometric Ni 0.7 Co 2.3 O4 spinel content accounts for 10wt%, noble metal platinum palladium content accounts for 1.0wt%, platinum palladium mass ratio is 4:1, transition metal MoO3 content accounts for 5.0wt%, the preparation method is the same as example 1, and the catalyst of this example is prepared.

[0051] Example 5

[0052] This example is similar to example 1, the difference is that the noble metal in this example is platinum, the transition metal is cobalt, the molar ratio of Ni and Co is 0.9:2.1, N 0.9 C 2.1 -4Pt1PdMo / Al2O3, non-stoichiometric Ni 0.9 Co 2.1 O4 spinel content accounts for 15.0wt%, noble metal platinum content accounts for 1.0wt%, Co3O4 content accounts for 5.0wt%. The preparation steps are as follows:

[0053] 1) according to the content design, the noble metal platinum nitrate and cobalt nitrate are prepared into a mixed solution, citric acid is added to form solution A, and the molar ratio of citric acid content to noble metal content is 3:1;

[0054] 2) solution A is placed in a water bath and continuously stirred, the water bath temperature is 60℃, and the time is 2h. Alumina catalyst material is added to solution A, the amount is 0.9 times the mass of solution A; and continue to stir, the water bath temperature is 60℃, and the time is 5h; then go through the drying and calcination process, drying process: 110℃@4h, calcination process: temperature: 400℃, time: 3h; to get PtCo / Al2O3 catalyst.

[0055] 3) prepare sodium hydroxide-ammonia solution, pH control range 10.5, get solution C, then add PtCo / Al2O3 catalyst obtained in 2) to the prepared sodium hydroxide-ammonia solution C, continuously stir to get PtCo / Al2O3 catalyst containing suspension C, and carry out water bath, temperature: 90℃, holding time: 3h.

[0056] 4) according to the molar ratio of Ni 0.9 Co 2.1 O4 accounts for 15.0wt% of the total mass, and the corresponding precursor salt is nickel nitrate and cobalt nitrate; and mix them to get solution B;

[0057] 5) Add solution B to suspension C, stirring at 200 r / min while adding; time: 1 h;

[0058] Then, aging, filtering, washing, drying, and calcining processes are sequentially performed. Ni 0.9 Co 2.1 O 4- PtCo / Al2O3 catalyst; aging process: room temperature: 15 h. Washing: deionized water is used, and washing is performed 3 times; drying process: 110°C @ 5 h; a continuous calcining process is used, first calcining temperature: 400°C, time: 3 h; second calcining temperature: 750°C, time: 5 h.

[0059] Example 6

[0060] This example is similar to Example 1, except that in this example, the non-stoichiometric Ni 0.5 Co 2.5 O4 spinel accounts for 10.0 wt%, and the transition metal WO3 accounts for 5.0 wt%. 0.5 C 2.5 The noble metal platinum-palladium content accounts for 1.0 wt% in the 4Pt1PdW / Al2O3 catalyst, the mass ratio of platinum-palladium is 4:1, and the transition metal WO3 content accounts for 5.0 wt%. The preparation method is the same as that of Example 1, and the catalyst of this example is prepared.

[0061] Comparative Example 1

[0062] In this comparative example, the catalytic material of the catalyst does not load the transition metal W and the non-stoichiometric Ni 0.5 Co 2.5 O4 spinel, and the active component of the catalyst is platinum-palladium, with a mass ratio of 4:1, and the noble metal platinum-palladium content accounts for 1.0 wt%. The preparation method includes the following steps:

[0063] 1) According to the content design, noble metal platinum nitrate and palladium nitrate are prepared into a mixed solution, oxalic acid is added, and solution A is formed. The molar ratio of oxalic acid content to noble metal content is 3:1.

[0064] 2) Place solution A in a water bath and continuously stir. The water bath temperature is 60°C, and the time is 2 h. Add alumina, the catalyst material, to solution A, with a mass ratio of 0.9 to solution A, and continue to stir. The water bath temperature is 60°C, and the time is 5 h. Then, dry and calcine in a muffle furnace. The drying process is 110°C @ 4 h, and the calcining process is temperature: 400°C, time: 3 h. The 4Pt1Pd / Al2O3 catalyst is obtained.

[0065] Comparative Example 2

[0066] The comparative example is similar to example 1, except that the catalytic material in the comparative example does not have a transition metal W loaded thereon, and the active component is a noble metal platinum palladium, with a mass ratio of 4:1, and the noble metal platinum palladium content is 1.0wt%, Ni x Co 3-x x is 0.5 in the non-stoichiometric Ni 0.5 Co 2.5 O4 spinel content is 5.0wt%, and the preparation method comprises the following steps:

[0067] 1) According to the content design, the noble metal platinum nitrate and platinum nitrate are prepared into a mixed solution, oxalic acid is added to form solution A, and the molar ratio of the content of oxalic acid to the content of noble metal is 3:1;

[0068] Steps 2)-5) are the same as in example 1, and the catalyst of the comparative example is prepared.

[0069] Comparative example 3

[0070] The comparative example is similar to example 1, except that the catalytic material in the comparative example does not have a transition metal W loaded thereon, and the active component is a noble metal platinum palladium, with a mass ratio of 4:1, and the noble metal platinum palladium content is 1.0wt%, Ni 0.5 Co 2.5 O4 spinel, the noble metal platinum palladium content is 1.0wt%, the mass ratio of platinum to palladium is 4:1, and the transition metal WO3 content is 5.0wt%. The preparation method is the same as steps 1)-3) in example 1, and the catalyst of the comparative example is prepared.

[0071] Comparative example 4

[0072] The comparative example is similar to example 1, except that the catalytic material in the comparative example does not have a transition metal W loaded thereon, and the active component is a noble metal platinum palladium, with a mass ratio of 4:1, and the noble metal platinum palladium content is 1.0wt%, Ni x Co 3-x x is 0.5 in the non-stoichiometric Ni 0.5 Co 2.5 O4 spinel content is 5.0wt%, and the preparation method comprises the following steps:

[0073] 1) According to the content design, the noble metal platinum nitrate and platinum nitrate are prepared into a mixed solution, oxalic acid is added to form solution A, and the molar ratio of the content of oxalic acid to the content of noble metal is 3:1;

[0074] Steps 2)-5) are the same as in example 1, and the catalyst of the comparative example is prepared.

[0075] Comparative example 5

[0076] The comparative example is similar to example 1, except that step 5) in the preparation method of the comparative example is different, specifically: 5) add solution B into the suspension, stirring while dropping, stirring rate 200 r / min; time: 1 h; then sequentially perform aging, filtering, washing, drying, and calcining processes to obtain the catalyst of the comparative example; wherein the aging process is 15 h at room temperature; the washing is deionized water washing 3 times; the drying process is at 110°C for 5 h; the calcining is a one-time calcining process, calcining temperature: 750°C, time 5 h.

[0077] Comparative example 6

[0078] The comparative example is similar to example 1, except that the catalyst of the comparative example uses stoichiometric NiCo2O4, the molar ratio of Ni and Co is 1:2, and in the catalyst, the content of stoichiometric NiCo2O4 spinel is 5wt%, the content of noble metal platinum palladium is 1.0wt%, the mass ratio of platinum and palladium is 4:1, and the content of transition metal WO3 is 5.0wt%, and the catalyst is prepared by the following method:

[0079] Steps 1)-3) are the same as example 1;

[0080] 4) With the molar ratio of Ni and Co being 1:2, the total mass of the catalyst is 5wt%, the corresponding precursor salt nickel nitrate and cobalt nitrate are mixed to obtain solution B;

[0081] Step 5) is the same as example 1, and the catalyst of the comparative example is prepared.

[0082] Comparative example 7

[0083] The comparative example is similar to example 1, except that in the catalyst of the comparative example, the molar ratio of Ni and Co is 0.3:2.7, and in the catalyst, the content of stoichiometric NiCo2O4 spinel is 5wt%, the content of noble metal platinum palladium is 1.0wt%, the mass ratio of platinum and palladium is 4:1, and the content of transition metal WO3 is 5.0wt%, and the catalyst is prepared by the following method: 0.3 Co 2.7 O4 spinel is 5wt%, the content of noble metal platinum palladium is 1.0wt%, the mass ratio of platinum and palladium is 4:1, and the content of transition metal WO3 is 5.0wt%, and the catalyst is prepared by the following method:

[0084] Steps 1)-3) are the same as example 1;

[0085] 4) With the molar ratio of Ni and Co being 0.3:2.7, the total mass of the catalyst is 5wt%, the corresponding precursor salt nickel nitrate and cobalt nitrate are mixed to obtain solution B;

[0086] Step 5) is the same as example 1, and the catalyst of the comparative example is prepared.

[0087] Comparative example 8

[0088] The comparative example is similar to example 1, except that in the preparation method of the comparative example, solution B is not added by dropwise method in step 5), specifically:

[0089] Steps 1)-4) are the same as example 1;

[0090] 5) Solution B is directly added to the suspension, and stirred for 1h; then the processes of aging, filtering, washing, drying, and calcining are sequentially performed to obtain the catalyst of the comparative example; the aging process is 15h at room temperature; the washing is performed with deionized water for 3 times; the drying process is performed at 110℃ for 5h; the continuous calcining process is used, the first calcining temperature is 400℃, and the time is 3h; the second calcining temperature is 750℃, and the time is 5h.

[0091] Comparative example 9

[0092] The comparative example provides a catalyst, the content of Ni x Co 3-x x in the Ni 0.5 Co 2.5 O4 spinel is 0.5, the content of Ni 0.5 Co 2.5 O4 spinel accounts for 5.0wt% of the total mass of the catalyst, the content of noble metal platinum palladium accounts for 1.0wt%, the mass ratio of platinum palladium is 4:1, and the content of transition metal WO3 accounts for 5.0wt%, and the preparation method is as follows:

[0093] 1) According to the content design, the noble metal platinum nitrate, platinum nitrate, and tungsten acid ammonium salt are prepared into a mixed solution, oxalic acid is added, and solution A is formed, and the molar ratio of the content of oxalic acid to the content of noble metal is 3:1;

[0094] 2) Place solution A in a water bath and continuously stir, the water bath temperature is 60℃, and the time is 2h. Add the catalytic material alumina to solution A, and the mass ratio of the addition amount to solution A is 0.9; and continue to stir, the water bath temperature is 60℃, and the time is 5h;

[0095] 3) Prepare a sodium hydroxide-ammonia solution, add the sodium hydroxide-ammonia solution to solution A, adjust the pH control range to 10-10.5, continuously stir, and perform water bath, the temperature is 90℃, and the holding time is 3h, to obtain mixed solution A;

[0096] 4) The molar ratio of Ni to Co is 0.5:2.5, and the content of Ni 0.5 Co 2.5 O4 accounts for 5wt% of the total mass of the catalyst, and the corresponding precursor salt nickel nitrate and cobalt nitrate are mixed to obtain solution B;

[0097] 5) Add solution B to mixture A while stirring dropwise at a rate of 200 r / min for 1 hour. Then, perform aging, filtration, washing, drying, and calcination processes sequentially to obtain the comparative catalyst. The aging process is carried out at room temperature for 15 hours. The washing process involves washing three times with deionized water. The drying process is carried out at 110℃ for 5 hours. A continuous calcination process is used, with the first calcination temperature at 400℃ for 3 hours and the second calcination temperature at 750℃ for 5 hours.

[0098] Test Example 1

[0099] The catalysts of Examples 1-6 and Comparative Examples 1-9 were prepared into monolithic catalysts. Specifically, the catalyst, water, and binder were mixed and ball-milled in a mass ratio of 40:100:4. The binder was boehmite. The particle size after ball milling was controlled to be 3-10 μm to prepare a catalyst slurry. The catalyst slurry was then coated onto a porous ceramic honeycomb carrier, with the catalyst mass ratio required to be 25%. After hot air drying at 60-90°C for 2-5 hours, and then calcined at 400-650°C for 3-5 hours, the monolithic catalyst was obtained.

[0100] The prepared catalyst was used to test the low-temperature ignition performance and stability of propane. The concentrations of exhaust gas before and after passing through the catalyst were measured using a chromatograph. In the low-temperature ignition performance test, propane (C3H8) was used, and the test atmosphere was O2: 2%, C3H8: 100ppm, H2O: 10vol%, and balance gas: N2; the test space velocity was 25000 h⁻¹. -1 The test temperature ranged from 250 to 450℃, with a temperature gradient of 5℃, and the test conditions were steady-state. The test atmosphere for the stability test was O2: 2%, C3H8: 100ppm, H2O: 10vol%, and the balance gas was N2; the test space velocity was 25000 h⁻¹. -1 The test temperature was 350℃ for 200 hours. The test results are shown in Tables 1 and 2 below. The difference between the comparative example and the embodiment is calculated by comparing the comparative example with embodiment 1, and the fluctuation rate is the ratio of the difference between the catalytic efficiency at the Xth hour and the catalytic efficiency at the 10th hour to the catalytic efficiency at the corresponding time.

[0101] Table 1 Ignition temperature T of Examples 1-6 and Comparative Examples 1-9 50 and T 99 Test Results

[0102]

[0103] Table 2. Catalyst stability test results for Examples 1-6 and Comparative Examples 1-9

[0104]

[0105] Note: Since the performance of Comparative Example 4 is too poor, no stability test is performed.

[0106] According to the data in the above table, the T 50 The temperature range is 290-315℃, and the T 99 The temperature range is 350-365℃, and the T 50 The temperature range is 340-425℃, and the T 99 All are greater than 380℃, and it can be seen that the T 50 and T 99 The light-off performance is significantly better than that of the comparative examples. By comparing Examples 1-6 and Comparative Examples 1-3, it can be seen that the Ni x Co 3-x O4 spinel nanoclusters and the transition metal and noble metal are mutually synergistic, which can significantly reduce the T 50 and T 99 , and further illustrate that the light-off performance of the prepared catalyst is excellent, which is mainly because the non-metering ratio of Ni x Co 3-x O4 spinel nanoclusters exhibits good redox performance and has more defect sites, and at the same time, the transition metal promotes the noble metal active site to be more metal valence active site, thereby further synergistically improving the adsorption and cracking of propane, and realizing better low-temperature light-off. When only containing Ni x Co 3-x O4 spinel nanoclusters or transition metals, significant benefits cannot be well achieved, and by combining Comparative Example 4, it is further illustrated that the Ni X Co 3-x O4 spinel nanoclusters, transition metals and noble metals are combined to achieve the beneficial effects of the present patent. By comparing Example 1 and Comparative Example 5, it is illustrated that the performance of two calcinations is better than that of one calcination, which is mainly to ensure that the Ni X Co 3- x O4 spinel nanoclusters have better particle size distribution and stability, and at the same time, the interaction force with the catalytic material is enhanced, which is more conducive to the synergistic low-temperature light-off performance of the transition metal and noble metal and ensures the stability of the catalyst. The catalyst of Comparative Example 4 has poor catalytic performance because it does not contain noble metal active sites, and the conversion efficiency of propane is only 6.2% at 450℃, which cannot be compared with the performance of the catalyst containing noble metal active sites, which is mainly because the noble metal active site is the main contributor to the catalytic oxidation of propane.

[0107] The present application can adjust the ratio of Ni X Co 3-x O4 spinel nanoclusters, the Ni X Co 3-xThe catalyst for the catalytic oxidation of low-carbon alkanes was prepared by adjusting the content of O4 spinel nanoclusters and the types of transition metals. Simultaneously, the preparation method of this invention was used to achieve excellent low-temperature ignition performance and significantly reduce To. 50 and T 99 Comparative examples 6-9 illustrate the use of non-chemical Ni... X Co 3-x The importance of controlling the content and particle size of O4 spinel nanoclusters, especially in comparative examples 8 and 9, further illustrates the significance of Ni. X Co 3-x The excessively large size of O4 spinel nanoclusters and the lack of stepwise calcination will both lead to severely insufficient catalyst performance, failing to achieve the significant benefits of this patented invention.

[0108] Stability tests were conducted at 350°C. The catalysts prepared using the method of this invention in Examples 1-6 all achieved catalytic efficiencies exceeding 93% and maintained good stability for 200 hours, with efficiency fluctuations less than 1.0%, demonstrating good stability even at high conversion rates. Regarding the comparative examples, the catalytic efficiencies of Comparative Examples 1-9 were lower at 350°C. Except for Comparative Example 4, Comparative Examples 1-7 showed relatively good stability, with efficiency fluctuations less than 6.3% within 200 hours. Comparative Examples 8-9 exhibited poor stability, with efficiency fluctuations greater than 10% within 50-200 hours. This is mainly due to the non-stoichiometric Ni content. X Co 3-x The O4 particles are large in size, unevenly distributed, and cannot form good synergy with the noble metal active components, which leads to the problem.

[0109] For those skilled in the art, when understanding the solutions described in the specific embodiments of the present invention, conventional technical manuals in the field can be consulted. At the same time, appropriate understandings or adjustments can be made to the places where the above terms appear, so as to deduce the same or similar technical solutions without creative effort.

[0110] The above embodiments describe only the basic principles, main features and / or advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and the description of the invention content in the specification are only the principles or specific cases of the present invention. Without departing from the essence of the innovative idea of ​​the present invention, there are various changes and improvements to the innovative solution of the present invention, and all such changes and improvements fall within the scope of protection claimed by the present invention.

Claims

1. A low-temperature, high-efficiency catalyst for the catalytic oxidation of low-carbon alkanes, characterized in that, The catalyst comprises a catalytic material and an active component supported on the catalytic material, Ni x Co 3-x O4 spinel nanoclusters, x is 0.4-0.99, the active component is a composite metal oxide composed of noble metal and transition metal, and the catalyst is prepared by combining the active component with the catalytic material first and then combining with the Ni x Co 3-x O4 spinel nanoclusters; in the catalyst, the content of the Ni x Co 3-x O4 spinel nanoclusters is 1.0-20.0 wt%, the content of the noble metal is 0.1-2.0 wt%, and the content of the transition metal is 1.0-20.0 wt%.

2. The catalyst according to claim 1, wherein the catalyst is characterized by, The noble metal is at least one of Pt and Pd, and the noble metal content is 0.5-1wt%.

3. The catalyst according to claim 1, wherein the catalyst is characterized by, The Ni x Co 3-x The content of the O4 spinel nanoclusters is 5-15.0 wt%.

4. The catalyst according to claim 1, wherein the catalyst is characterized by, The transition metal is at least one of tungsten, cobalt, molybdenum, niobium, nickel, zirconium, titanium, vanadium, and manganese, and the transition metal content is 3.0-15.0wt%.

5. The catalyst according to claim 1, wherein the catalyst is characterized by, The catalytic material is at least one of aluminum oxide, silicon oxide, titanium oxide, cerium oxide, and zirconium oxide.

6. The method for preparing a low-temperature high-efficiency catalytic oxidation catalyst for low-carbon alkanes according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: S1, soluble precursor salts of noble metals and transition metals are prepared into a mixed solution, a first additive is added to form solution A, solution A is stirred at a temperature of 40-90℃ for 1-4h, then a catalytic material is added to solution A, the mass ratio of the catalytic material to solution A is 0.8-1.2, and the stirring is continued at a temperature of 40-90℃ for 3-10h, after which drying and calcination are performed to obtain a PT / M catalyst; A sodium hydroxide-ammonia solution with a pH of 8.5-11 is prepared to obtain solution C, the PT / M catalyst is added to solution C, and after stirring, a suspension containing the PT / M catalyst is obtained, and the suspension is incubated at a temperature of 40-90℃ for 1-6h; A mixed solution of soluble precursor salts of nickel and cobalt is prepared to obtain solution B, wherein the molar ratio of Ni to Co is x:(3-x), and x is 0.4-0.99; S2, the solution B is added dropwise to the suspension under stirring at a stirring rate of 100-300r / min, and the dropwise duration is 1h-3h; then aging, filtration, and washing are sequentially performed, and drying and calcination are performed to obtain a catalytic oxidation low-carbon alkane catalyst.

7. The method for preparing a low-temperature, high-efficiency catalytic oxidation catalyst for low-carbon alkanes according to claim 6, characterized in that, The first additive is at least one of citric acid and oxalic acid, and the first additive content and the noble metal content are added in a molar ratio of 1.5-5:

1.

8. The method for preparing a low-temperature high-efficiency catalytic oxidation catalyst for low-carbon alkanes according to claim 6, characterized in that, The aging process is performed at room temperature for 10-24h; The washing process is performed using deionized water for 1-3 times; The drying process is performed at 90-120℃ for 5-10h.

9. The method for preparing a low-temperature high-efficiency catalytic oxidation catalyst for low-carbon alkanes according to any one of claims 6-8, characterized in that, The calcination is performed using a continuous calcination process, which is divided into two times of calcination, the first calcination is performed at 300-450℃ for 3-5h, and the second calcination is performed at 650-900℃ for 3-7h.

10. A monolithic catalyst comprising a carrier and a catalytic coating, characterized in that, The catalytic coating comprises a low-temperature high-efficiency catalytic oxidation low-carbon alkane catalyst according to any one of claims 1-5.

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