Preparation method, product and application of an M / PNC catalyst

Abstract

The present invention discloses a preparation method, product and application of an M / PNC catalyst, belonging to the technical field of synthesis of toluene catalytic oxidation catalysts. The method comprises the following steps: First, prepare ZIF powder using 2-methylimidazole, zinc nitrate hexahydrate and cetyltrimethylammonium bromide as raw materials; then calcine the ZIF powder and dissolve it with a metal source and a phosphorus source in an organic solvent to obtain a phosphorus-doped transition metal catalyst precursor powder; and then calcine the precursor to obtain the M / PNC catalyst. This catalyst has high catalytic activity and stability, while reducing the catalyst preparation cost, improving the economy and sustainability of toluene catalytic oxidation, and having a broader application prospect in practical applications.

Description

Technical Field

[0001] The invention belongs to the technical field of synthesis of toluene catalytic oxidation catalysts, and in particular relates to a preparation method of an M / PNC catalyst and a product and application thereof. Background Art

[0002] Toluene is a volatile organic pollutant widely present in human production and life. It participates in a series of chemical reactions in the atmosphere to produce O 3 Secondary pollution such as PM2.5, photochemical smog, etc. seriously affects the air quality. At the same time, long-term exposure to toluene-contaminated environment will cause damage to multiple organs such as the human nervous system, liver, and respiratory system. Therefore, taking effective measures to reduce toluene emissions and pollution is crucial to protecting the ecological environment and human health. Catalytic oxidation is an effective technology for removing toluene. 2 Toluene is oxidized to harmless CO by a catalyst in the presence of 2 and H 2 O, but its reaction temperature is relatively high. Room temperature catalytic oxidation technology can effectively avoid a series of problems existing in high temperature catalytic oxidation technology, such as high energy consumption and easy sintering and deactivation of catalysts. It has the advantages of energy saving and environmental protection, safety and reliability, and long catalyst service life.

[0003] At present, most of the research on room-temperature catalytic oxidation of toluene is in the fields of photocatalysis, non-thermal plasma catalysis and ozone-assisted catalytic oxidation technology, which usually requires high temperature, high voltage discharge, light and O 3 Assist in reducing the activation energy of the reaction and promoting the oxidation reaction of toluene. However, the above-mentioned catalytic technology still needs to consume a large amount of external energy during the oxidation reaction, resulting in waste of energy and resources, and poor economy and safety. At present, there are few studies that can realize the catalytic oxidation of volatile organic compounds under normal temperature and normal pressure without the help of external energy. Most of the studies are focused on the development of catalysts for small molecular organics such as formaldehyde and methanol that are easily degraded. Due to the presence of the π bond of the six-membered ring, the toluene molecule has a stable structure and is not easy to be degraded by ring opening. It is difficult to realize the catalytic oxidation of toluene under environmental conditions. There are few studies on the catalytic oxidation of toluene at room temperature in the prior art. Studies have shown that improving the electron transfer ability of metal active sites is one of the key factors to improve the catalytic activity of catalysts and reduce the reaction temperature. Therefore, it is of great research significance and application value to develop a catalyst that can significantly improve the catalytic efficiency and performance and promote the catalytic oxidation reaction of toluene at room temperature by optimizing the catalyst structure and properties. Summary of the invention

[0004] The purpose of the present invention is to provide a highly efficient, stable and low-cost method for preparing an atomic-level active site M / PNC catalyst for catalytic oxidation of toluene at room temperature, by doping P atoms into the coordination configuration of transition metal active sites, thereby improving the catalytic oxidation efficiency of toluene and the stability of the catalyst, providing a feasible solution for effectively solving the problem of catalytic oxidation of toluene at room temperature, and providing new ideas for studying the catalytic oxidation of volatile organic compounds.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing an M / PNC catalyst comprises the following steps:

[0007] (1) dissolving 2-methylimidazole in deionized water to obtain solution A, dissolving zinc nitrate hexahydrate and hexadecyltrimethylammonium bromide in deionized water to obtain solution B, mixing solution A and solution B, stirring at room temperature for 4-10 hours, and centrifuging, washing, drying and grinding the obtained suspension to obtain ZIF powder;

[0008] (2) calcining the ZIF powder under an inert atmosphere to obtain a ZIF-derived carbon-nitrogen carrier;

[0009] (3) weighing the ZIF-derived carbon-nitrogen carrier, the metal source and the phosphorus source, dissolving them in methanol, mixing them evenly by ultrasonication for 0.5-1 h, stirring them at a temperature of 60-70° C. for 4-8 h, and centrifuging, washing and drying the obtained liquid to obtain a phosphorus-doped transition metal catalyst precursor powder;

[0010] (4) calcining the phosphorus-doped transition metal catalyst precursor powder under an inert atmosphere to obtain an M / PNC catalyst.

[0011] Furthermore, in step (1), the molar ratio of the 2-methylimidazole to the zinc nitrate hexahydrate is (8-20):1, and the amount of the hexadecyltrimethylammonium bromide added is 0.1-0.5 mmol.

[0012] Furthermore, in step (2), the calcination parameters are: temperature 900-1000°C, time 1-4h, heating rate 5-15°C / min. The inert atmosphere is nitrogen. The calcination temperature above 900°C can evaporate the Zn atoms in the carbon framework, which can provide abundant anchoring sites for the subsequent loading of transition metals.

[0013] Furthermore, in step (3), the ratio of transition metal atoms in the metal source to P atoms in the phosphorus source is (2-10):1.

[0014] Furthermore, the metal source is any one of transition metals Fe, Co and Ni, and the loading amount of the metal source on the ZIF-derived carbon-nitrogen carrier is 0.5-1.5 wt%.

[0015] Furthermore, the phosphorus source is any one of phytic acid, triphenylphosphine and sodium hypophosphite.

[0016] Furthermore, in step (4), the calcination parameters are: temperature 700-1000°C, time 1-4h, heating rate 5-15°C / min. The inert atmosphere is nitrogen. During the calcination process, the phosphorus source is carbonized, and the P atoms are doped into the carbon framework or form metal-P bonds with metal atoms, thereby generating a new transition metal active site coordination configuration.

[0017] The present invention also provides an M / PNC catalyst prepared by the above preparation method.

[0018] The present invention also provides an application of the M / PNC catalyst in catalytic oxidation of toluene at room temperature, wherein the room temperature is 30°C.

[0019] The present invention loads transition metals on ZIFs-derived carbon materials and introduces P atoms at the same time. The incorporation of P atoms can change the microscopic morphology of the catalyst surface and construct a rich pore structure, which is conducive to the adsorption and enrichment of toluene molecules on the catalyst surface. At the same time, doping with P atoms will cause the charge density of the metal active site to rearrange, changing the MN x -C y Configuration, enhance the metal-support interaction, thereby improving the adsorption and activation behavior of toluene molecules and key intermediates, and promoting the oxidation reaction. There are two forms of doping of P atoms in the catalyst. One is to directly form a metal-P coordination bond with the transition metal, adjust the electron cloud density of the transition metal, and thus improve the catalytic activity. The other is that the P atom is incorporated into the neighboring carbon framework of the metal center, and interacts with the C or N atoms of the first coordination shell of the metal, thereby playing a role in regulating the catalytic activity of the central metal. The P atom-doped atomic-level transition metal active site catalyst provided by the present invention effectively realizes the room-temperature catalytic oxidation of toluene, and provides strong support for the design of efficient new atomic-level active site catalysts for the catalytic oxidation of VOCs.

[0020] Compared with the prior art, the present invention has the following advantages and technical effects:

[0021] (1) The present invention reduces the catalytic oxidation temperature of toluene by constructing an atomic-level M / PNC catalyst loaded with transition metal active sites, thereby achieving catalytic oxidation of toluene at room temperature (30°C) without the need for external energy assistance, reducing the energy consumption of the reaction process, avoiding problems such as high-temperature agglomeration and deactivation of the catalyst, extending the service life of the catalyst, and achieving energy-saving and low-carbon treatment of toluene.

[0022] (2) The present invention discloses a method for preparing a catalyst for catalytic oxidation of toluene at room temperature, wherein a transition metal is loaded on a carbon-nitrogen carrier derived from ZIFs, the metal is dispersed at the atomic level, and the electron density and coordination structure of the active site are changed by doping atom P, thereby adjusting the electron transfer ability, reducing the activation energy of the oxidation reaction, and improving the catalytic efficiency. At the same time, the change in the structure of the active site of the catalyst enhances the ability of the transition metal center to adsorb and activate toluene molecules and O 2 ability to promote the deep catalysis of toluene.

[0023] (3) Compared with the scarcity and high price of precious metal catalysts, the P-doped transition metal atomic-level active site catalyst provided by the present invention has high catalytic activity and stability while reducing the catalyst preparation cost, thereby improving the economy and sustainability of toluene catalytic oxidation and having a broader application prospect in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0025] Figure 1 It is the X-ray diffraction spectrum diagram of the catalyst in Example 2, Example 4 and Example 5. DETAILED DESCRIPTION

[0026] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0027] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0028] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0029] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0030] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0031] The "room temperature" and "normal temperature" mentioned in the present invention are all 30°C unless otherwise specified.

[0032] The raw materials used in the following examples of the present invention are all commercially available.

[0033] The present invention loads transition metals on ZIFs-derived carbon materials and introduces P atoms at the same time. The incorporation of P atoms can change the microscopic morphology of the catalyst surface and construct a rich pore structure, which is conducive to the adsorption and enrichment of toluene molecules on the catalyst surface. At the same time, doping with P atoms will cause the charge density of the metal active site to rearrange, changing the MN x -C y Configuration, enhance the metal-support interaction, thereby improving the adsorption and activation behavior of toluene molecules and key intermediates, and promoting the oxidation reaction. There are two forms of doping of P atoms in the catalyst. One is to directly form a metal-P coordination bond with the transition metal, adjust the electron cloud density of the transition metal, and thus improve the catalytic activity. The other is that the P atom is incorporated into the neighboring carbon framework of the metal center, and interacts with the C or N atoms of the first coordination shell of the metal, thereby playing a role in regulating the catalytic activity of the central metal. The P atom-doped atomic-level transition metal active site catalyst provided by the present invention effectively realizes the room-temperature catalytic oxidation of toluene, and provides strong support for the design of efficient new atomic-level active site catalysts for catalytic oxidation of VOCs. The specific technical scheme is as follows:

[0034] The present invention provides a method for preparing an M / PNC catalyst, comprising the following steps:

[0035] (1) dissolving 2-methylimidazole in deionized water to obtain solution A, dissolving zinc nitrate hexahydrate and hexadecyltrimethylammonium bromide in deionized water to obtain solution B, mixing solution A and solution B, stirring at room temperature for 4-10 hours, and centrifuging, washing, drying (preferably at 60-80° C.) and grinding the obtained suspension to obtain ZIF powder;

[0036] (2) calcining the ZIF powder under an inert atmosphere to obtain a ZIF-derived carbon-nitrogen carrier;

[0037] (3) weighing the ZIF-derived carbon-nitrogen carrier, the metal source and the phosphorus source, dissolving them in methanol, mixing them evenly by ultrasonication for 0.5-1 h, stirring them at a temperature of 60-70° C. for 4-8 h, and centrifuging, washing and drying the obtained liquid to obtain a phosphorus-doped transition metal catalyst precursor powder;

[0038] (4) calcining the phosphorus-doped transition metal catalyst precursor powder under an inert atmosphere to obtain an M / PNC catalyst.

[0039] In some preferred embodiments of the present invention, in step (1), the molar ratio of 2-methylimidazole to zinc nitrate hexahydrate is (8-20):1, and the amount of hexadecyltrimethylammonium bromide added is 0.1-0.5 mmol.

[0040] In some preferred embodiments of the present invention, in step (2), the calcination parameters are: temperature 900-1000°C, preferably 900°C, 920°C, 950°C, 1000°C; time 1-4h, preferably 1h, 2h, 3h, 4h; heating rate 5-15°C / min, preferably 5°C / min, 10°C / min, 15°C / min. The inert atmosphere is nitrogen. The calcination temperature above 900°C can evaporate the Zn atoms in the carbon framework, which can provide abundant anchoring points for the subsequent loading of transition metals.

[0041] In some preferred embodiments of the present invention, in step (3), the ratio of transition metal atoms in the metal source to P atoms in the phosphorus source is (2-10): 1. The metal source is any one of transition metals Fe, Co and Ni, and the loading amount of the metal source on the ZIF-derived carbon-nitrogen carrier is 0.5-1.5wt%. The phosphorus source is any one of phytic acid, triphenylphosphine and sodium hypophosphite. The dosage ratio of the ZIF-derived carbon-nitrogen carrier, the metal source and the phosphorus source is preferably 0.5g: 40mg: 0.3mL, and can also be preferably 0.5g: (20-60mg): (36mg-0.27g).

[0042] In some preferred embodiments of the present invention, in step (4), the calcination parameters are: temperature 700-1000°C, preferably 700°C, 800°C, 900°C, 950°C, 1000°C; time 1-4h, preferably 1h, 2h, 3h, 4h; heating rate 5-15°C / min, preferably 5°C / min, 10°C / min, 15°C / min. The inert atmosphere is nitrogen. During the calcination process, the phosphorus source is carbonized, and the P atoms are doped into the carbon framework or form metal-P bonds with metal atoms, thereby generating a new transition metal active site coordination configuration. Below this temperature, the metal active atoms will agglomerate, affecting the existence form of the P element in the catalyst, and it is not easy to form a highly active MN x-C / P configuration; above this temperature, the pore structure of the material collapses, affecting the accessibility of the active sites. At the same time, the N and P elements in the catalyst evaporate severely at high temperatures, which can reduce the anchoring environment for the active metal and the active sites, resulting in a significant reduction in the catalytic performance.

[0043] The present invention also provides an M / PNC catalyst prepared by the above preparation method.

[0044] The present invention also provides an application of the M / PNC catalyst in catalytic oxidation of toluene at room temperature, wherein the room temperature is 30°C.

[0045] The following examples serve as further illustrations of the technical solutions of the present invention.

[0046] Example 1

[0047] A method for preparing an M / PNC catalyst comprises the following steps:

[0048] (1) 8.2 g of 2-methylimidazole was dissolved in deionized water to obtain solution 1, and 3.7 g of zinc nitrate hexahydrate and 182 mg of hexadecyltrimethylammonium bromide were dissolved in deionized water to obtain solution 2; solutions 1 and 2 were mixed and stirred at room temperature for 10 h to obtain a suspension; the suspension was centrifuged, and the obtained precipitate was washed three times with deionized water, dried in a vacuum drying oven at 60° C., and the obtained solid was ground in a mortar to obtain ZIF powder;

[0049] (2) Place the ZIF powder in a tube furnace under N 2 The temperature was raised to 920°C at a heating rate of 5°C / min under an atmosphere and calcined for 2 h, and then naturally cooled to room temperature to obtain a ZIF-derived carbon-nitrogen carrier;

[0050] (3) 40 mg of nickel nitrate hexahydrate, 0.3 mL of phytic acid (50% aqueous solution) and 0.5 g of ZIF-derived carbon nitrogen carrier were weighed and dissolved in methanol, ultrasonicated for 0.5 h, and then stirred at 70 ° C for 6 h. The precipitate obtained after liquid centrifugation was washed with methanol three times and dried in a vacuum drying oven at 60 ° C to obtain a phosphorus-doped transition metal catalyst precursor powder;

[0051] (4) Phosphorus-doped transition metal catalyst precursor powder is heated in N 2 The temperature was raised to 800°C at a heating rate of 10°C / min under an atmosphere and calcined for 3 h. After it was naturally cooled to room temperature, a Ni / PNC catalyst was obtained, which was recorded as A.

[0052] Example 2

[0053] A method for preparing an M / PNC catalyst comprises the following steps:

[0054] (1) 8.2 g of 2-methylimidazole was dissolved in deionized water to obtain solution 1, and 2.5 g of zinc nitrate hexahydrate and 109 mg of hexadecyltrimethylammonium bromide were dissolved in deionized water to obtain solution 2; solutions 1 and 2 were mixed and stirred at room temperature for 6 h to obtain a suspension; the suspension was centrifuged, and the obtained precipitate was washed three times with deionized water, dried in a vacuum drying oven at 80° C., and the obtained solid was ground in a mortar to obtain ZIF powder;

[0055] (2) Place the ZIF powder in a tube furnace under N 2 The temperature was raised to 950°C at a heating rate of 10°C / min under an atmosphere and calcined for 3 h, and then naturally cooled to room temperature to obtain a ZIF-derived carbon-nitrogen carrier;

[0056] (3) 60 mg of nickel nitrate hexahydrate, 0.27 g of triphenylphosphine and 0.5 g of ZIF-derived carbon nitrogen carrier were weighed and dissolved in methanol, ultrasonicated for 1 h, and then stirred at 70° C. for 4 h. The precipitate obtained after liquid centrifugation was washed with methanol three times and dried in a vacuum drying oven at 80° C. to obtain a phosphorus-doped transition metal catalyst precursor powder;

[0057] (4) Phosphorus-doped transition metal catalyst precursor powder is heated in N 2 The temperature was raised to 950°C at a heating rate of 5°C / min under atmosphere and calcined for 2 h. After it was naturally cooled to room temperature, a Ni / PNC catalyst was obtained, which was marked as B.

[0058] Example 3

[0059] A method for preparing an M / PNC catalyst comprises the following steps:

[0060] (1) 8.2 g of 2-methylimidazole was dissolved in deionized water to obtain solution 1, and 1.5 g of zinc nitrate hexahydrate and 36 mg of hexadecyltrimethylammonium bromide were dissolved in deionized water to obtain solution 2; solutions 1 and 2 were mixed and stirred at room temperature for 4 h to obtain a suspension; the suspension was centrifuged, and the obtained precipitate was washed three times with deionized water, dried in a vacuum drying oven at 70° C., and the obtained solid was ground in a mortar to obtain ZIF powder;

[0061] (2) Place the ZIF powder in a tube furnace under N 2 The mixture was heated to 1000°C at a heating rate of 15°C / min and calcined for 1 h under an atmosphere, and then naturally cooled to room temperature to obtain a ZIF-derived carbon-nitrogen carrier;

[0062] (3) 32 mg of nickel nitrate hexahydrate, 78 mg of sodium hypophosphite and 0.5 g of ZIF-derived carbon nitrogen carrier were weighed and dissolved in methanol, ultrasonicated for 0.75 h, and then stirred at 60° C. for 5 h. The precipitate obtained after liquid centrifugation was washed three times with methanol and dried in a vacuum drying oven at 70° C. to obtain a phosphorus-doped transition metal catalyst precursor powder;

[0063] (4) Phosphorus-doped transition metal catalyst precursor powder is heated in N 2 The temperature was raised to 700°C at a heating rate of 15°C / min under an atmosphere and calcined for 4 h. After it was naturally cooled to room temperature, a Ni / PNC catalyst was obtained, which was recorded as C.

[0064] Example 4

[0065] A method for preparing an M / PNC catalyst comprises the following steps:

[0066] (1) 8.2 g of 2-methylimidazole was dissolved in deionized water to obtain solution 1, and 3.0 g of zinc nitrate hexahydrate and 146 mg of hexadecyltrimethylammonium bromide were dissolved in deionized water to obtain solution 2; solutions 1 and 2 were mixed and stirred at room temperature for 8 h to obtain a suspension; the suspension was centrifuged, and the obtained precipitate was washed three times with deionized water, dried in a vacuum drying oven at 80° C., and the obtained solid was ground in a mortar to obtain ZIF powder;

[0067] (2) Place the ZIF powder in a tube furnace under N 2 The mixture was heated to 900°C at a heating rate of 5°C / min and calcined for 4 h under an atmosphere, and then naturally cooled to room temperature to obtain a ZIF-derived carbon-nitrogen carrier.

[0068] (3) Weighing 20 mg of cobalt nitrate hexahydrate, 36 mg of triphenylphosphine and 0.5 g of ZIF-derived carbon nitrogen carrier, dissolving them in methanol, ultrasonicating for 0.5 h, and then stirring at 70 ° C for 8 h. The obtained liquid was centrifuged and the precipitate was washed with methanol three times and dried in a vacuum drying oven at 80 ° C to obtain a phosphorus-doped transition metal catalyst precursor powder;

[0069] (4) Phosphorus-doped transition metal catalyst precursor powder is heated in N 2 The temperature was raised to 1000°C at a heating rate of 5°C / min under an atmosphere and calcined for 1 h. After it was naturally cooled to room temperature, a Co / PNC catalyst was obtained, which was recorded as D.

[0070] Example 5

[0071] A method for preparing an M / PNC catalyst comprises the following steps:

[0072] (1) 8.2 g of 2-methylimidazole was dissolved in deionized water to obtain solution 1, and 1.9 g of zinc nitrate hexahydrate and 73 mg of hexadecyltrimethylammonium bromide were dissolved in deionized water to obtain solution 2; solutions 1 and 2 were mixed and stirred at room temperature for 5 h to obtain a suspension; the suspension was centrifuged, and the obtained precipitate was washed three times with deionized water, dried in a vacuum drying oven at 60° C., and the obtained solid was ground in a mortar to obtain ZIF powder;

[0073] (2) Place the ZIF powder in a tube furnace under N 2 The mixture was heated to 900°C at a heating rate of 5°C / min and calcined for 4 h under an atmosphere, and then naturally cooled to room temperature to obtain a ZIF-derived carbon-nitrogen carrier.

[0074] (3) 30 mg of ferrous nitrate, 44 mg of triphenylphosphine and 0.5 g of ZIF-derived carbon nitrogen carrier were weighed and dissolved in methanol, ultrasonicated for 0.75 h, and then stirred at 60 ° C for 8 h. The precipitate obtained after liquid centrifugation was washed with methanol three times and dried in a vacuum drying oven at 60 ° C to obtain a phosphorus-doped transition metal catalyst precursor powder;

[0075] (4) Phosphorus-doped transition metal catalyst precursor powder is heated in N 2 The temperature was raised to 900°C at a heating rate of 10°C / min under an atmosphere and calcined for 3 h. After it was naturally cooled to room temperature, a Fe / PNC catalyst was obtained, which was recorded as E.

[0076] Comparative Example 1

[0077] Same as Example 2, except that no transition metal is added. The specific steps are:

[0078] (1) 8.2 g of 2-methylimidazole was dissolved in deionized water to obtain solution 1, and 2.5 g of zinc nitrate hexahydrate and 109 mg of hexadecyltrimethylammonium bromide were dissolved in deionized water to obtain solution 2; solutions 1 and 2 were mixed and stirred at room temperature for 6 h to obtain a suspension; the suspension was centrifuged, and the obtained precipitate was washed three times with deionized water, dried in a vacuum drying oven at 80° C., and the obtained solid was ground in a mortar to obtain ZIF powder;

[0079] (2) Place the ZIF powder in a tube furnace under N 2 The temperature was raised to 950°C at a heating rate of 10°C / min under an atmosphere and calcined for 3 h, and then naturally cooled to room temperature to obtain a ZIF-derived carbon-nitrogen carrier;

[0080] (3) Weighing 0.27 g of triphenylphosphine and 0.5 g of ZIF-derived carbon nitrogen carrier, dissolving them in methanol, ultrasonicating for 1 h, and then stirring at 70 ° C for 4 h. The obtained liquid was centrifuged and the precipitate was washed with methanol three times and dried in a vacuum drying oven at 80 ° C to obtain a phosphorus-doped catalyst precursor powder;

[0081] (4) Phosphorus-doped catalyst precursor powder is heated in N 2 The temperature was raised to 950°C at a heating rate of 5°C / min under an atmosphere and calcined for 2 h. After it was naturally cooled to room temperature, a PNC material was obtained, which was recorded as F.

[0082] Comparative Example 2

[0083] Same as Example 2, except that no phosphorus source is added. The specific steps are:

[0084] (1) 8.2 g of 2-methylimidazole was dissolved in deionized water to obtain solution 1, and 2.5 g of zinc nitrate hexahydrate and 109 mg of hexadecyltrimethylammonium bromide were dissolved in deionized water to obtain solution 2; solutions 1 and 2 were mixed and stirred at room temperature for 6 h to obtain a suspension; the suspension was centrifuged, and the obtained precipitate was washed three times with deionized water, dried in a vacuum drying oven at 80° C., and the obtained solid was ground in a mortar to obtain ZIF powder;

[0085] (2) Place the ZIF powder in a tube furnace under N 2 The temperature was raised to 950°C at a heating rate of 10°C / min under an atmosphere and calcined for 3 h, and then naturally cooled to room temperature to obtain a ZIF-derived carbon-nitrogen carrier;

[0086] (3) 60 mg of nickel nitrate hexahydrate and 0.5 g of a ZIF-derived carbon-nitrogen carrier were weighed and dissolved in methanol, ultrasonicated for 1 h, and then stirred at 70° C. for 4 h. The obtained liquid was centrifuged and the precipitate was washed three times with methanol and dried in a vacuum drying oven at 80° C. to obtain a transition metal catalyst precursor powder;

[0087] (4) The transition metal catalyst precursor powder is heated in N 2 The temperature was raised to 950°C at a heating rate of 5°C / min under atmosphere and calcined for 2 h. After it was naturally cooled to room temperature, a Ni / NC catalyst was obtained, which was marked as G.

[0088] Comparative Example 3

[0089] The same as Example 2, except that transition metal Cu, i.e., copper nitrate hexahydrate, is used. The obtained catalyst is denoted as H.

[0090] Performance Test:

[0091] The catalysts of Examples 1-5 and Comparative Examples 1-3 were loaded into a fixed bed reactor with an inner diameter of 10 mm, and the initial toluene concentration was controlled to be 800 mg / m 3 , reaction space velocity of 50000 mL / (g·h), reaction temperature of 30°C, relative humidity of 15%, catalyst evaluation conditions of air as oxidant, toluene concentration in tail gas monitored by gas chromatography FID detector, toluene removal rate calculated. The results are shown in Table 1.

[0092] Table 1

[0093]

[0094]

[0095] It can be seen from Table 1 that the P-doped atomic-level active site M / PNC catalysts prepared in Examples 1-5 have a good removal effect on toluene. Under normal temperature and pressure air conditions, the toluene removal rate is above 90%. Among them, the Ni / PNC catalyst prepared in Example 2 can achieve a toluene removal rate of 98.5% compared with other catalysts. The X-ray diffraction spectra of the catalysts in Examples 2, 4 and 5 are shown in Figure 1. Figure 1 , Catalysts B, D and E only have two broad peaks belonging to the (002) and (101) crystal planes of graphite carbon, and no diffraction peaks related to Ni, Co and Fe species appear, indicating that the transition metals in the catalyst are uniformly dispersed on the catalyst surface in the form of atomic-level active sites. Compared with Example 2, Comparative Example 1 does not add transition metals and is a PNC carrier material, and its toluene removal rate is only 40.1%, which can fully illustrate that the loaded atomic-level Ni active sites can effectively catalyze and oxidize toluene molecules at room temperature, and the removal effect is significant. Compared with Example 2, the performance of the Ni / NC catalyst in Comparative Example 2 without P element doping is lower, indicating that the doping of P element effectively regulates the Ni active sites, greatly improves the catalytic activity, and promotes the efficient degradation of toluene under room temperature conditions.

[0096] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. Application of an M / PNC catalyst in the catalytic oxidation of toluene at room temperature, characterized in that, the preparation method of the M / PNC catalyst comprises the following steps: Dissolve 2-methylimidazole in deionized water to obtain solution A, dissolve zinc nitrate hexahydrate and cetyltrimethylammonium bromide in deionized water to obtain solution B, mix solution A and solution B, stir at room temperature, and the obtained suspension is centrifuged, washed, dried and ground to obtain ZIF powder; Calcine the ZIF powder in an inert atmosphere to obtain a ZIF-derived carbon nitride support; Weigh the ZIF-derived carbon nitride support, metal source and phosphorus source, dissolve them in an organic solvent, mix well by ultrasonic, stir, and the obtained liquid is centrifuged, washed and dried to obtain a phosphorus-doped transition metal catalyst precursor powder; Calcine the phosphorus-doped transition metal catalyst precursor powder in an inert atmosphere to obtain an M / PNC catalyst.

2. The application according to claim 1, characterized in that, in step (1), the molar ratio of 2-methylimidazole to zinc nitrate hexahydrate is (8-20):

1.

3. The application according to claim 1, characterized in that, in step (2), the calcination parameters are: temperature 900-1000 °C, time 1-4 h, heating rate 5-15 °C / min.

4. The application according to claim 1, characterized in that, in step (3), the ratio of transition metal atoms in the metal source to P atoms in the phosphorus source is (2-10):

1.

5. The application according to claim 4, characterized in that, the metal source is any one of transition metals Fe, Co and Ni, and the loading amount of the metal source on the ZIF-derived carbon nitride support is 0.5-1.5 wt%.

6. The application according to claim 4, characterized in that, the phosphorus source is any one of phytic acid, triphenylphosphine and sodium hypophosphite.

7. The application according to claim 1, characterized in that, in step (4), the calcination parameters are: temperature 700-1000 °C, time 1-4 h, heating rate 5-15 °C / min.

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