Catalyst for low-temperature catalytic decomposition of n 2o, and preparation method therefor, activation method therefor and use thereof

Abstract

The present invention relates to a catalyst for low-temperature catalytic decomposition of nitrous oxide (N2O), and a preparation method therefor, an activation method therefor and the use thereof. In the catalyst of the present invention, a rare earth metal element and an alkaline earth metal element are used as auxiliary agents to assist in dispersing active components and optimizing the electronic structure of the catalyst, and after activation by means of H2 pretreatment, the activity of catalytic decomposition of N2O is stably promoted, and a low-temperature N2O decomposition catalyst having good catalytic performance is obtained. In the preparation method for the catalyst of the present invention, the electronic structure of the catalyst is optimized by means of the co-doping of a rare earth element and the alkaline earth element Ba; subsequently, activation is carried out by means of H2 pretreatment, surface defects are generated, and the interaction between the active components and the auxiliary agents is adjusted, thereby significantly improving the activity of the catalyst on the premise that a good service life of the catalyst is maintained.

Description

A catalyst for low-temperature catalytic decomposition of N2O and its preparation method, activation method and use Technical Field The invention belongs to the field of catalysts and relates to a catalyst and a preparation method, an activation method and use thereof, and in particular to a catalyst for low-temperature catalytic decomposition of nitrous oxide / nitrous oxide (N2O) and a preparation method, an activation method and use thereof. Background Art In recent years, nitrous oxide (N2O) has received widespread attention due to its dual environmental effects. At present, N2O is the third most important greenhouse gas in global emissions after CO2 and CH4. Its global warming potential is 265 to 310 times that of CO2, and its contribution to the greenhouse effect is significant. At the same time, after 2010, N2O also surpassed chlorofluorocarbons to become the substance that most seriously damages the ozone layer, and its potential for ozone depletion is increasing year by year. The United Nations Environment Programme report pointed out that if N2O emissions are not controlled, the concentration of N2O in the atmosphere will double by 2050. Industrial flue gas is an important source of N2O emissions, especially N2O emitted from the production process of nitric acid and adipic acid, which accounts for about 97% of the total industrial N2O emissions. The "Guidelines for the Calculation and Reporting of Greenhouse Gas Emissions from Chemical Production Enterprises in China" has clearly stated that N2O emitted from the production process of nitric acid and adipic acid shall be separately accounted as a greenhouse gas. The direct catalytic decomposition technology for tail gas has the advantages of low temperature and high efficiency, and is the focus of research at this stage. The core technology of direct catalytic decomposition of N2O is the catalyst. The composition, crystal structure, morphology and surface / interface properties of the catalyst are closely related to the catalytic purification ability of N2O. Existing research has mainly focused on three systems: precious metal catalysts, metal oxide catalysts and molecular sieve catalysts. Precious metal catalysts obtained by using Rh, Pd, Ir, Pt and other elements as active components and loaded on carriers such as MgO, SiO2, CeO2, Al2O3 or TiO2 have good activity for direct catalytic decomposition of N2O. For example, Reference 1 discloses a nitrous oxide (N2O) removal catalyst composite material, which uses precious metal rhodium (Rh) as an active component and loads the active component on a ceria-based carrier to obtain a precious metal catalyst. However, due to the high price and scarce resources, precious metal catalysts are not widely used in the market. Large-scale applications in catalytic decomposition of N2O are limited. Most molecular sieve catalysts use transition metals such as Fe, Co, Ni, Cu, Mn, etc. to exchange ions with molecular sieves, among which Fe-ZSM-5 and Cu-ZSM-5 have higher catalytic reduction activity for N2O. For example, Reference 2 discloses a NOx Selective catalytic reduction molecular sieve catalyst, which uses soluble iron salt as raw material and is prepared by ion exchange to obtain Fe-ZSM-5. Molecular sieve catalyst has high catalytic reduction activity for N2O, but it needs to consume reducing agent, and the preparation process is too complicated, and there is also the problem of high-temperature sintering. In addition, reference 3 has studied the catalyst with transition metal oxide as active component and rare earth element as auxiliary agent, but the catalyst contains alkali metal K, and no research has been conducted on the case where there is no alkali metal and the transition metal oxide is nickel oxide (NiO) and copper oxide (CuO). Under actual flue gas conditions (such as industrial tail gas of adipic acid and nitric acid), there may be a certain amount of acidic gas in the flue gas, and the catalyst containing alkali metal will be more easily deactivated by acid poisoning; at the same time, the cost of alkali metal reagents is also higher than that of alkaline earth metals, and it is more economically feasible to use alkaline earth metals under similar effects. Therefore, taking into account the industrial application cost and actual conditions, the development and scale-up of transition metal oxide catalysts with high decomposition activity and excellent resistance to impurity gases are the research focuses. References: Reference 1: CN107223072A Reference 2: CN102416343A Reference 3: CN113996305A Summary of the invention Problem that the invention aims to solve In order to overcome the above-mentioned shortcomings of the prior art, it is necessary to provide a catalyst that can maintain high decomposition activity at low temperatures, has excellent resistance to impurity gases, has low cost and is suitable for large-scale industrial production applications. Solutions for solving problems In order to solve the above problems, the present invention adopts rare earth metal elements as additives to assist in dispersing the active The active components were added and their electronic structure was optimized, which promoted the activity of catalytic decomposition of nitrous oxide and obtained a low-temperature N2O decomposition catalyst with excellent catalytic performance. [1] Specifically, the present invention provides a catalyst for catalytically decomposing N2O, the catalyst comprising a transition metal oxide as an active ingredient and an oxide of a rare earth metal element as an auxiliary agent, Wherein, the transition metal oxide is NiO and / or CuO, The rare earth metal element is one or more of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Dy, Tm, and Yb. [2] The catalyst according to [1] above, wherein the rare earth metal element is one or more of Gd, Pr, and Yb; and the transition metal oxide is NiO. [3] The catalyst according to [1] or [2] above, wherein the molar ratio of the rare earth metal element to the transition metal element in the catalyst is 0.01:1 to 0.1:1, preferably 0.03:1 to 0.08:1. [4] The catalyst according to any one of [1] to [3] above, wherein the catalyst further comprises barium oxide or barium carbonate; and / or the molar ratio of barium element to transition metal element in the catalyst is 0.05:1 to 0.2:1, preferably 0.1:1 to 0.15:1; and / or the molar ratio of rare earth metal element to barium element in the catalyst may be 1:1.5 to 1:5, preferably 1:2 to 1:3. [5] A method for preparing a catalyst according to any one of [1] to [4], characterized in that the method comprises: Step S1: dissolving a rare earth element auxiliary agent precursor and an active ingredient precursor in deionized water to obtain a mixed solution; Step S2: adding a precipitant dropwise to the mixed solution to obtain a suspension, and subjecting the suspension to ultrasonic treatment and stirring; Step S3: aging the suspension overnight, washing, filtering, and drying to obtain a catalyst precursor; Step S4: calcining the catalyst precursor to obtain a catalyst powder material. [6] The preparation method according to [5] above is characterized in that step S1 further comprises dissolving the barium salt together with the rare earth element auxiliary agent precursor and the active ingredient precursor in deionized water; the active ingredient precursor is acetate, nitrate, sulfate or oxalate of Ni and / or Cu; the rare earth element The auxiliary agent precursor is one or more acetates, nitrates, sulfates or oxalates of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; the precipitant is Na2CO3, K2CO3, (NH4)2CO3 or (NH4)HCO3, preferably (NH4)2CO3; the barium salt is barium acetate or barium nitrate. [7] The preparation method according to [5] or [6] above, wherein, in step S2, the precipitant controls the pH value of the solution to 8 to 10, the ultrasonic treatment time is 0.5 to 1 h, and the stirring time is 2 to 4 h; and / or, in step S3, the aging time is 8 to 15 h, and the drying temperature is 100 to 120°C; and / or, in step S4, the calcination temperature is 500 to 700°C, and the calcination time is 4 to 6 h. [8] The preparation method according to any one of [5] to [7] above, further comprising a post-processing step S4.5 performed after step S4: The catalyst powder material is placed in a 0.1-0.5M HNO3 solution, continuously stirred for 3-6 hours, washed until pH = 7, dried at 100-120°C, and then calcined at 500-700°C for 2-4 hours. [9] The preparation method according to any one of [5] to [8] above, wherein the preparation method further comprises step S5: Deionized water, a binder, a pore-forming agent and an organic additive are added to the catalyst powder material to prepare a slurry, which is then cast on a casting machine, dried and calcined to obtain a monolithic catalyst; or, Deionized water, a binder, a pore-forming agent and an organic additive are added to the catalyst powder material to prepare a slurry, the slurry is coated on the surface of the carrier and dried and calcined at high temperature to obtain a supported catalyst. Wherein, the binder is one or more of clay, ZrO2, Al2O3 series materials, silicon dioxide or silicate, Ca(OH)2, MgO; the pore-forming agent is one or more of ammonium bicarbonate, cellulose, carboxymethyl cellulose, phenolic resin, starch; the organic auxiliary agent is one or more of associative thickener, surfactant, polyacrylamide, glycerol, citric acid; the associative thickener is one or more of modified ethylene oxide polyurethane copolymer, polyacrylate, vinyl alcohol, and the surfactant is non-ionic, anionic or cationic; the calcination temperature is 500-800°C, and the calcination time is 4-6h; the shape of the cast catalyst is rectangular, stick-shaped, spherical, One of the ellipsoidal shapes; the carrier includes one or more of cordierite, mullite, α-alumina, silicon carbide, aluminum titanate, silicon nitride, zirconium mullite, zirconium silicate, magnesium silicate, aluminosilicate, and metal / alloy. [9] A method for activating a catalyst according to any one of [1] to [4] above or a catalyst obtained by the preparation method according to any one of [5] to [9] above, characterized in that the activation atmosphere is 5 to 10% H2, the treatment temperature is 300 to 500°C, and the treatment time is 0.5 to 1 h.

[0010] The use of the catalyst described in any one of [1]-[4] above or the catalyst obtained by the preparation method described in any one of [5]-[9] above in catalytic decomposition of N2O, characterized in that it is used in the scenarios of waste gas treatment of adipic acid and nitric acid plants and purification of tail gas from solid waste combustion. Effects of the Invention The technical solution of the present invention can have the following beneficial effects: (1) By using rare earth metal elements as additives to assist in dispersing active ingredients and optimizing their electronic structure, the activity of catalytic decomposition of nitrous oxide is promoted, and a low-temperature N2O decomposition catalyst with excellent catalytic performance is obtained. Compared with catalysts with the same effect, the catalyst of the present invention has a lower cost. (2) By adding barium to the catalyst, the electron transfer performance of the catalyst can be further improved. (3) In the catalyst preparation method of the present invention, the catalyst is activated by H2 pretreatment, which stably improves the activity of the catalyst in an O2-containing atmosphere. (4) Existing examples of H2 activation are mostly used to adjust the metal-support interaction of expensive precious metal catalysts, but a stable enhancement effect is often not achieved for mixed oxides. In the catalyst activation method of the present invention, by using 5-10% H2 for a short-term activation treatment at an appropriate temperature, the structure-activity relationship between the catalyst elements can be optimized, and the catalytic activity can be significantly and stably improved. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing the results of catalytic performance tests of the catalysts prepared in Examples 1-7 and 10 and the catalyst prepared in Comparative Example 1. FIG. 2 is a graph showing the results of catalytic performance tests of the catalysts prepared in Comparative Examples 1-9. FIG3 is a graph showing the results of three cycle experiments of Example 10 and single activity tests of Examples 8-9, 11-12 among the catalysts prepared in Examples 8 to 12, where the cycle number x is denoted as Cx. FIG. 4 is a graph showing the result of a catalytic activity stability test of the catalyst example 10 used in FIG. 3 . DETAILED DESCRIPTION Various exemplary embodiments, features and aspects of the present invention will be described in detail below. The word "exemplary" used here means "used as an example, embodiment or illustrative". Any embodiment described here as "exemplary" is not necessarily interpreted as being superior or better than other embodiments. In addition, in order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. It should be understood by those skilled in the art that the present invention can be implemented without certain specific details. In other examples, methods, means, equipment and steps well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present invention. Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values ​​and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production. In this specification, the word "may" means both performing a certain process and not performing a certain process. In this specification, the references to "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc., mean that the specific elements (e.g., features, structures, properties and / or characteristics) described in connection with the embodiments are included in at least one embodiment described herein, and may or may not exist in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner. In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints numerical values ​​A and B. In this specification, when "normal temperature" or "room temperature" is used, the temperature may be about 10 to 40°C. <First aspect> The first aspect of the present invention provides a catalyst for low-temperature catalytic decomposition of N2O. The catalyst of the present invention comprises a transition metal oxide as an active component and an oxide of a rare earth metal element as an auxiliary agent. In the present invention, the transition metal oxide may be NiO and / or CuO, wherein NiO is preferred. The rare earth metal element in the rare earth metal oxide may be selected from one or more of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, wherein one or more of Gd, Pr, and Yb are preferred. In the catalyst of the present invention, the molar ratio of the rare earth metal element to the transition metal element in the transition metal oxide may be 0.01:1 to 0.1:1, preferably 0.03:1 to 0.08:1. For example, the molar ratio may be 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.08:1, 0.1:1, etc. In some preferred embodiments of the present invention, the catalyst further comprises barium oxide. In the case where the catalyst comprises barium oxide, the molar ratio of the barium element to the transition metal element in the catalyst may be 0.05:1 to 0.2:1, preferably 0.1:1 to 0.15:1. For example, the molar ratio may be 0.05:1, 0.08:1, 0.1:1, 0.12:1, 0.15:1, 0.18:1, 0.2:1, etc. In the case where the catalyst comprises barium oxide, the molar ratio of the rare earth metal element to the barium element in the catalyst may be 1:1.5 to 1:5, preferably 1:2 to 1:3, for example, 1:1.5, 1:2, 1:3, 1:4, 1:5, etc. The catalyst of the present invention preferably comprises a combination of NiO, Yb2O3 and BaO. There is currently no relevant research on the combination of Yb2O3, BaO, and NiO. In the catalyst of the present invention, the specific surface area of ​​the catalyst is increased by the oxide solid solution doped with rare earth elements, the surface oxygen vacancies are increased (some studies believe that they can be used as N2O adsorption sites), and the electronic structure of nickel oxide and / or copper oxide as active ingredients is optimized, the average valence of Ni is reduced and the MO bond (M = Ni, Cu, Co, etc.) is weakened to a certain extent, thereby promoting the activity of catalytic decomposition of N2O; in addition, when the catalyst includes Ba element, Ba element tends to aggregate on the catalyst surface, promotes electron transfer through alkalinity, and the generated BaCO3 significantly hinders the growth of NiO crystals, reduces the NiO grain size, and further improves the catalytic activity. <Second Aspect> The second aspect of the present invention provides a method for preparing the catalyst of the present invention. The preparation method of the agent comprises: Step S1: dissolving a rare earth element auxiliary agent precursor and an active ingredient precursor in deionized water to obtain a mixed solution; Step S2: adding a precipitant dropwise to the mixed solution to obtain a suspension, and subjecting the suspension to ultrasonic treatment and stirring; Step S3: aging the suspension overnight, washing, filtering, and drying to obtain a catalyst precursor; Step S4: calcining the catalyst precursor to obtain a catalyst powder material. Each step is described in detail below. Step S1 In step S1, a rare earth element auxiliary agent precursor and an active ingredient precursor are dissolved in deionized water to obtain a transparent metal salt mixed solution. In addition, in some preferred embodiments, in step S1, the barium salt is dissolved in deionized water together with the rare earth element auxiliary agent precursor and the active ingredient precursor. The barium salt may be barium acetate or barium nitrate. In the present invention, the active ingredient precursor may be an acetate, nitrate, sulfate or oxalate of Ni and / or Cu, wherein acetate and nitrate are preferred. Specifically, the active ingredient precursor may be one or more of nickel acetate, nickel nitrate, nickel sulfate, nickel oxalate, copper acetate, copper nitrate, copper sulfate and copper oxalate. The rare earth element auxiliary agent precursor can be an acetate, nitrate, sulfate or oxalate of one or more of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, wherein acetate and nitrate are preferred. Specifically, the rare earth element auxiliary agent precursor can be selected from lanthanum acetate, lanthanum nitrate, lanthanum sulfate, lanthanum oxalate, cerium acetate, cerium nitrate, cerium sulfate, cerium oxalate, praseodymium acetate, praseodymium nitrate, praseodymium sulfate, praseodymium oxalate, neodymium acetate, neodymium nitrate, neodymium sulfate, neodymium oxalate, promethium acetate, promethium nitrate, promethium sulfate, promethium oxalate, samarium acetate, samarium nitrate, samarium sulfate, and oxalate. Europium acid, europium acetate, europium nitrate, europium sulfate, europium oxalate, gadolinium acetate, gadolinium nitrate, gadolinium sulfate, gadolinium oxalate, terbium acetate, terbium nitrate, terbium sulfate, terbium oxalate, dysprosium acetate, dysprosium nitrate, dysprosium sulfate, dysprosium oxalate, holmium acetate, holmium nitrate, holmium sulfate, holmium oxalate, erbium acetate, erbium nitrate, erbium sulfate, erbium oxalate, thulium acetate, thulium nitrate, thulium sulfate One or more of thulium, thulium oxalate, ytterbium acetate, ytterbium nitrate, ytterbium sulfate, ytterbium oxalate, lutetium acetate, lutetium nitrate, lutetium sulfate, and lutetium oxalate. In the present invention, the molar ratio of the rare earth element auxiliary agent precursor to the active ingredient precursor can be 0.01:1 to 0.2:1, preferably 0.05:1 to 0.1:1, so that a catalyst having a molar ratio of rare earth metal elements to transition metal elements within this range can be obtained. Step S2 In step S2, under normal temperature conditions, a precipitant (or pH regulator) solution is slowly added dropwise to the metal salt mixed solution while stirring. The pH value of the solution system is continuously detected during the addition process, and the addition is stopped after the pH value is controlled at 8 to 10, preferably 8.5 to 9.5. The suspension solution after the reaction is ultrasonically treated for 0.5 to 1 h, and stirring is continued for 1 to 2 h. The precipitant used in the present invention may be Na2CO3, K2CO3, (NH4)2CO3 or (NH4)HCO3, among which (NH4)2CO3 is preferred. By performing a short-time ultrasonic treatment after coprecipitation, the dispersion of catalyst precursor particles can be promoted and the dispersion of particles can be changed, thereby optimizing the catalyst morphology and improving the catalytic performance. Steps S3 and S4 In step S3, the suspension obtained in the above steps is aged overnight, washed with deionized water until pH=7, filtered, and then dried to obtain a catalyst precursor. In the present invention, the aging time can be 8 to 15 hours, preferably 10 to 12 hours. The drying temperature can be 100 to 120° C., and the drying time can be 10 to 15 hours, 10 to 12 hours. In step S4, the obtained catalyst precursor is calcined to obtain a catalyst powder material, wherein the calcination temperature may be 500 to 700° C. and the calcination time may be 4 to 6 hours. The catalyst preparation method of the present invention may further include step S4.5 of post-treating the catalyst powder material after step S4, depending on the specific material type. Step S4.5 In step S4.5, the catalyst powder material may be post-treated for surface modification. Specifically, the catalyst powder material is placed in a 0.1-0.5M HNO3 solution, continuously stirred for 3-6 hours, washed to pH = 7, dried at 100-120°C, and then calcined at 500-700°C for 2-4 hours. The catalyst preparation method of the present invention may further include step S5 of integrally molding the catalyst powder material or loading it on a carrier as required, which is described in detail below. Step S5 In step S5, the chemical agent powder material obtained above can be integrally formed as needed. Specifically, deionized water, a binder, a pore-forming agent and an organic additive can be added to the catalyst powder material to prepare a slurry, which is then cast on a casting machine and dried and calcined to obtain a monolithic catalyst. In the present invention, there is no particular limitation on the binder, pore former and organic auxiliary agent, and the binders, pore formers and organic auxiliary agents commonly used in the art can be used. Specifically, the binder can be selected from one or more of clay, ZrO2, Al2O3-based materials (aluminum hydroxide, aluminum oxyhydroxide, γ-Al2O3, etc.), silica / silicate, Ca(OH)2, and MgO, preferably ZrO2 and Al2O3. Among them, the clay can include bentonite, kaolin, montmorillonite and other clay-based materials. The pore former may be one or more of ammonium bicarbonate, cellulose, carboxymethyl cellulose, phenolic resin, and starch, preferably starch and carboxymethyl cellulose. Organic additives are used to adjust the properties and pH of the slurry, and examples thereof may include one or more of associative thickeners, surfactants, polyacrylamide, glycerol, and citric acid. Examples of associative thickeners may include modified ethylene oxide polyurethane copolymers, polyacrylates, vinyl alcohol, and the like. Surfactants may be commonly used cationic surfactants, anionic surfactants, amphoteric surfactants, medium-chain fatty alcohols, and the like. The temperature for calcination after casting can be 500-800°C, and the calcination time can be 4-6 hours. The shape of the catalyst formed by casting can be one of a cuboid, a stick, a sphere, and an ellipsoid. Moreover, the shape and size of the catalyst can be adjusted. In addition, in step S5, the catalyst powder material may be loaded on a carrier as required. Specifically, deionized water, a binder, a pore-forming agent and an organic additive are added to the catalyst powder material to prepare a slurry, and the slurry is coated on the surface of the carrier and dried and calcined to obtain a supported catalyst. The preparation of the slurry is the same as that in the above-mentioned integral forming, and will not be repeated here. In the present invention, the carrier is not particularly limited, and conventional carriers in the art can be used, and examples thereof can include one or more of cordierite, mullite, α-alumina, silicon carbide, aluminum titanate, silicon nitride, zirconium mullite, zirconium silicate, magnesium silicate, aluminosilicate, and metal / alloy, preferably one or more of cordierite, alumina, and silicon carbide. In the present invention, the carrier can be pretreated with nitric acid or sulfuric acid to improve its binding capacity and loading performance. The temperature and time for drying after applying the slurry to the support are not particularly limited, as long as the catalyst can be dried. For example, the drying temperature may be 60 to 100°C and the drying time may be 2 to 12 hours. The calcination temperature may be 500 to 800°C and the calcination time may be 4 to 6 hours. <Third Aspect> The present invention also provides the above catalyst or an activation method for the catalyst obtained by the above preparation method and use of the catalyst in catalytic decomposition of N2O. The activation method of the present invention is that the treatment atmosphere is 5-10% H2 / Ar, the treatment temperature is 300-500°C, and the treatment time is 0.5-1h. The catalyst of the present invention can be used for high-efficiency catalytic decomposition of N2O at low temperatures of 200 to 500°C. The N2O decomposition conditions can be as follows: The N2O decomposition conditions are as follows: the reaction pressure is normal pressure, the raw gas enters from the top and exits from the bottom, the N2O volume concentration in the raw gas is 1000-1200ppm, the O2 volume concentration is 0-5%, and the NO x (NO or NO2) volume concentration 0~120ppm, air velocity 20000~40000h -1 , operating temperature 200 ~ 500 ℃. The raw gas may be waste gas rich in N2O, such as adipic acid waste gas, nitric acid waste gas, solid waste combustion tail gas, etc. The amount of catalyst used is usually 0.2-0.5 g / (100 mL / min gas flow rate). The catalyst of the present invention can achieve a N2O conversion rate of 100% at about 380°C when not activated, and can even achieve a N2O conversion rate of 80% at about 350°C, and has relatively good catalytic activity; after activation, it can reach a conversion rate of 100% at about 300°C and is almost unaffected by low concentration O2. Example The embodiments of the present invention will be described in detail below with reference to the examples, but those skilled in the art will Personnel will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. If specific conditions are not specified in the examples, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be obtained commercially. In the accompanying drawings, Example x is recorded as S(x) and Comparative Example y is recorded as D(y). Example 1 Catalyst preparation: According to the molar ratio of Gd to Ni of 0.05:1, gadolinium nitrate and nickel acetate were dissolved in 100 mL of deionized water to obtain a transparent metal salt mixed solution. 2+ The concentration is 0.24 mol / L. Under normal temperature conditions, 0.1 g / mL (NH4)2CO3 solution was slowly added to the mixed solution, and the pH value was controlled to 9 before the addition was stopped. The solution after the reaction was ultrasonically treated for 0.5 h and stirred for 2 h. The obtained suspension was aged overnight at room temperature for 12 h, washed with deionized water and filtered, dried at 110 ° C for 12 h, and placed in a muffle furnace for calcination at 500 ° C for 4 h to obtain a catalyst powder material, which was recorded as catalyst S (1). Embodiment 2-3 Catalyst S(2) was prepared in the same manner as in Example 1 except that Yb was used as the rare earth promoter element; Catalyst S(3) was prepared in the same manner as in Example 1 except that Pr was used as the rare earth promoter element and the Pr:Ni molar ratio was 0.053:1. Example 4 Catalyst preparation: According to the molar ratio of Pr to Ni of 0.1:1, praseodymium nitrate and nickel acetate were dissolved in 100 mL of deionized water to obtain a transparent mixed solution of metal salts. 2+ The concentration is 0.24 mol / L. Under normal temperature conditions, 0.1 g / mL Na2CO3 solution was slowly added to the mixed solution, and the addition was stopped after the pH value was controlled at 9. The solution after the reaction was ultrasonically treated for 0.5 h and continued to be stirred for 2 h. The obtained suspension was aged overnight at room temperature for 12 h, washed with deionized water and filtered, dried at 110 ° C for 12 h, and placed in a muffle furnace for calcination at 500 ° C for 4 h to obtain a catalyst powder material, which was recorded as catalyst S (4). Example 5 According to the Yb:Ba:Ni molar ratio of 0.05:0.1:1, ytterbium nitrate, barium nitrate and nickel acetate were dissolved in 100 mL of deionized water to obtain a transparent metal salt mixed solution. 2+ The concentration was 0.24 mol / L. The remaining steps were carried out in the same manner as in Example 1 to obtain catalyst S (5). Embodiment 6-7 Catalyst Example S(6) was prepared in the same manner as in Example 5, except that Gd was used as the rare earth auxiliary element and the calcination time was 6 h. Catalyst Example S(7) was prepared in the same manner as in Example 5, except that Pr was used as the rare earth auxiliary element and the Pr:Ba:Ni molar ratio was 0.053:0.158:1. Embodiments 8 to 12 The catalyst was prepared in the same manner as in Examples 1, 2, 5, 6 and 7. The prepared catalysts were pretreated under 5% H2 / Ar, 300°C for 0.5 h, cooled to room temperature, and set aside for performance testing. They were named Examples S(8), S(9), S(10), S(11), and S(12), respectively. Comparative Example 1 Catalyst preparation: Dissolve nickel acetate in 100 mL of deionized water to obtain a transparent metal salt solution. 2+ The concentration is 0.2 mol / L. At room temperature, slowly add 0.1 g / mL (NH4)2CO3 solution to the mixed solution, stop adding after controlling the pH value to 9, and continue stirring for 2 hours. The obtained suspension is aged overnight at room temperature for 12 hours, washed with deionized water and filtered, dried at 110°C for 12 hours, and calcined at 500°C in a muffle furnace for 4 hours to obtain a catalyst powder material, which is recorded as D(1). Comparative Examples 2-3 According to the molar ratio of Ga or In to Ni of 0.05:1, gadolinium nitrate or indium nitrate and nickel acetate were dissolved in 100 mL of deionized water to obtain a transparent metal salt mixed solution. 2+ The concentration was 0.24 mol / L. The remaining steps were carried out in the same manner as in Comparative Example 1 to obtain catalysts D(2) and D(3), respectively. Comparative Examples 4 to 9 The catalysts were prepared in the same manner as in Comparative Example 1, except that the rare earth element additives were Sm, Ho, Er, Lu, Tb, Sn, and the molar ratio of rare earth element to Ni was 0.1:1, to obtain catalysts D(4), D(5), D(6), D(7), D(8), and D(9), respectively. <Catalytic performance test> The N2O decomposition conditions can be as follows: The N2O decomposition conditions are as follows: the reaction pressure is normal pressure, the raw gas enters from the top and exits from the bottom, the N2O volume concentration in the raw gas is 1000-1200ppm, the O2 volume concentration is 0-3%, and the NO Volume concentration is 0~100ppm, air velocity is 30000~40000h -1 , operating temperature 200~500℃. The raw material gas is the above mixed gas with a flow rate of 0.1~1L / min, and the corresponding amount of powder catalyst is 0.3g / (100mL / min gas flow rate). The catalysts prepared in the above examples and comparative examples were tested for catalytic performance under the above conditions, and the results are shown in Figures 1 and 2. The reaction conditions in Figure 1 are: gas composition 1100 ppm N2O / N2, gas flow rate 100 mL / min, GHSV = 40000 h -1 The reaction conditions in Figure 2 are: gas composition 1100ppm N2O / N2, gas flow rate 100mL / min, GHSV=40000h -1 . As can be seen from Figures 1 and 2, compared with SnNi, InNi, and Ni catalysts, the doping of some rare earth elements improves the catalytic activity of the catalyst, such as rare earth elements Yb, Gd, and Pr; however, the doping of some rare earth elements instead leads to catalytic performance lower than Ni, such as Tb, Lu, Er, and Ho. This may be due to the difference in the electronic structure of different rare earth elements. The 4f orbits of Gd, Pr, Yb, etc. interact with the 3d orbits of the active component Ni, thereby optimizing electron transfer, while elements such as Tb and Lu are the opposite. As can be seen from Figure 1, when the molar ratio of rare earth elements (Pr) to transition metal elements is 0.05:1, the catalytic effect is better than the effect when the molar ratio is 0.1:1; and when the Ba element is included in the catalyst, the catalytic activity is improved. After further activation using H2 pretreatment, the catalytic activity is significantly improved. Figure 3 shows the results of three consecutive cycle experiments of the catalyst after hydrogen pretreatment in Example 10 and the results of single activity tests of Examples 8-9 and 11-12. The reaction conditions in FIG3 are: gas composition 1100 ppm N2O / N2, gas flow rate 100 mL / min, GHSV = 40000 h -1. As can be seen from Figure 3, the catalyst of Example 10 has good activity stability in the temperature range of 200-500°C, and the low-temperature activity increases slightly with the increase in the number of cycles, indicating that the catalyst is stable after activation; the activities of Example 8, Example 9, Example 11 and Example 12 are also improved to varying degrees. In addition, Figure 4 shows the stability test results of the catalyst in Example 10 that has been subjected to three cycle experiments in catalytic N2O oxidation. The reaction conditions of Figure 4 are: temperature 300°C, gas composition 1100ppm N2O / N2, 3% O2 ​​(when used), 100ppm NO (when used), gas flow rate 100mL / min, GHSV=40000h -1 As shown in Figure 4, the activity of the used catalyst after multiple cycles of activation remains stable in pure N2O atmosphere, and the activity increases slightly with time, which is consistent with the results in Figure 3. Even after 3% O2 ​​is introduced, the catalytic activity is almost unaffected. However, the introduction of NO has an obvious irreversible effect on the catalyst. Even so, the conversion rate can reach 80% after running at 300 °C for 2 h, which is much higher than that of the inactivated catalyst. Therefore, it can be seen that the catalytic activity has good stability. The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A catalyst for catalytically decomposing nitrous oxide (N2O), characterized in that: The catalyst comprises a transition metal oxide as an active component and an oxide of a rare earth metal element as an auxiliary agent. Wherein, the transition metal oxide is NiO and / or CuO, The rare earth metal element is one or more of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Dy, Tm, and Yb.

2. The catalyst according to claim 1, wherein The rare earth metal element is one or more of Gd, Pr and Yb; and the transition metal oxide is NiO.

3. The catalyst according to claim 1 or 2, wherein The molar ratio of the rare earth metal element to the transition metal element in the catalyst is 0.01:1 to 0.1:1, preferably 0.03:1 to 0.08:

1.

4. The catalyst according to any one of claims 1 to 3, wherein The catalyst further comprises barium oxide or barium carbonate; and / or, the molar ratio of barium element to transition metal element in the catalyst is 0.05:1 to 0.2:1, preferably 0.1:1 to 0.15:1; and / or, the molar ratio of rare earth metal element to barium element in the catalyst may be 1:1.5 to 1:5, preferably 1:2 to 1:

3.

5. A method for preparing the catalyst according to any one of claims 1 to 4, characterized in that: The preparation method comprises: Step S1: dissolving a rare earth element auxiliary agent precursor and an active ingredient precursor in deionized water to obtain a mixed solution; Step S2: adding a precipitant dropwise to the mixed solution to obtain a suspension, and subjecting the suspension to ultrasonic treatment and stirring; Step S3: aging the suspension overnight, washing, filtering, and drying to obtain a catalyst precursor; Step S4: calcining the catalyst precursor to obtain a catalyst powder material.

6. The preparation method according to claim 5, characterized in that: Step S1 also includes dissolving the barium salt together with the rare earth element auxiliary agent precursor and the active ingredient precursor in deionized water; the active ingredient precursor is the acetate, nitrate, sulfate or oxalate of Ni and / or Cu; the rare earth element auxiliary agent precursor is the acetate, nitrate, sulfate or oxalate of one or more of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; the precipitant is Na2CO3, K2CO3, (NH4)2CO3 or (NH4)HCO3, preferably (NH4)2CO3; the barium salt is barium acetate or barium nitrate.

7. The preparation method according to claim 5 or 6, wherein: In step S2, the precipitant controls the pH value of the solution to 8-10, the ultrasonic treatment time is 0.5-1h, and the stirring time is 2-4h; and / or, in step S3, the aging time is 8-15h, and the drying temperature is 100-120°C; and / or, in step S4, the calcination temperature is 500-700°C, and the calcination time is 4-6h.

8. The preparation method according to claim 5-7, wherein the preparation method further comprises a post-processing step S4.5 performed after step S4: The catalyst powder material is placed in a 0.1-0.5M HNO3 solution, continuously stirred for 3-6 hours, washed until pH = 7, dried at 100-120°C, and then calcined at 500-700°C for 2-4 hours.

9. The preparation method according to any one of claims 5 to 8, wherein: The preparation method further comprises step S5: Deionized water, a binder, a pore-forming agent and an organic additive are added to the catalyst powder material to prepare a slurry, which is then cast on a casting machine, dried and calcined to obtain a monolithic catalyst; or, Deionized water, a binder, a pore-forming agent and an organic additive are added to the catalyst powder material to prepare a slurry, and the slurry is coated on the surface of the carrier and dried and calcined to obtain a supported catalyst. The binder is one or more of clay, ZrO2, Al2O3 materials, silicon dioxide or silicate, Ca(OH)2, and MgO; the pore-forming agent is one or more of ammonium bicarbonate, cellulose, carboxymethyl cellulose, phenolic resin, and starch; the organic auxiliary agent is one or more of an associative thickener, a surfactant, polyacrylamide, glycerol, and citric acid; the associative thickener is one or more of a modified ethylene oxide polyurethane copolymer, polyacrylates, and vinyl alcohol, and the surfactant is nonionic, anionic, or cationic; the calcination temperature is 500 to 800°C, and the calcination time is 4 to 6 hours; the shape of the cast catalyst is one of a rectangular parallelepiped, a stick, a sphere, and an ellipsoid; the carrier includes cordierite, mullite, α-alumina, silicon carbide, titanate One or more of aluminum, silicon nitride, zirconium mullite, zirconium silicate, magnesium silicate, aluminosilicate, metal / alloy.

10. A method for activating a catalyst according to any one of claims 1 to 4 or a catalyst obtained by the preparation method according to any one of claims 5 to 9, characterized in that: The activation treatment atmosphere is 5-10% H2, the treatment temperature is 300-500°C, and the treatment time is 0.5-1h.

11. Use of the catalyst according to any one of claims 1 to 4 or the catalyst obtained by the preparation method according to any one of claims 5 to 9 in catalytic decomposition of N2O, characterized in that: Used in waste gas treatment of adipic acid and nitric acid plants, and purification of tail gas from solid waste combustion.

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