A catalyst for low-temperature catalytic decomposition of N 2 O, its preparation method, activation method and uses

Abstract

The present invention relates to a catalyst for low-temperature catalytic decomposition of nitrous oxide (N2O), a preparation method, an activation method and a use thereof. The catalyst of the present invention uses rare earth metal elements and alkaline earth metal elements as promoters to assist in dispersing the active components and optimizing their electronic structures. After being pretreated and activated by H2, the activity of N2O catalytic decomposition is stably promoted, and a low-temperature N2O decomposition catalyst with excellent catalytic performance is obtained. In the catalyst preparation method of the present invention, through the co-doping of rare earth elements and alkaline earth Ba elements, the electronic structure of the catalyst is optimized; then it is activated by H2 pretreatment to generate surface defects and adjust the interaction between the active components and the promoters, thereby significantly improving the catalyst activity on the premise of maintaining good catalyst life.

Description

Technical Field

[0001] The present invention belongs to the field of catalysts, and relates to a catalyst and its preparation method, activation method and use, and particularly relates to a catalyst for low-temperature catalytic decomposition of nitrous oxide (N 2 O) and its preparation method, activation method and use. Background Art

[0002] In recent years, nitrous oxide (N 2 O) has received extensive attention due to its dual environmental effects. At present, N 2 O is the third greenhouse gas with the greatest impact on global emissions after CO 2 and CH 4 . Its global warming potential is 265-310 times that of CO 2 , making a significant contribution to the greenhouse effect. At the same time, after 2010, N 2 O has also surpassed chlorofluorocarbons to become the substance with the most serious damage to the ozone layer, and the ozone depletion potential is increasing year by year. A report by the United Nations Environment Programme points out that if N 2 O emissions are not controlled, the concentration of N 2 O in the atmosphere will double by 2050.

[0003] Industrial flue gas is an important source of N 2 O emissions, especially the N 2 O emitted during the production processes of nitric acid and adipic acid, accounting for about 97% of the total industrial N 2 O emissions. In the "China Greenhouse Gas Emission Accounting Method and Reporting Guide for Chemical Production Enterprises", the N 2 O emitted during the production processes of nitric acid and adipic acid has been clearly accounted for separately as a greenhouse gas. The direct catalytic decomposition technology for tail gas has the advantages of low temperature and high efficiency, and is the current research focus.

[0004] N 2 The technical core of the direct catalytic decomposition of O is the catalyst. The properties of the catalyst, such as its composition, crystal structure, morphology, and surface / interface properties, are closely related to the catalytic purification ability of N 2 O. Existing research mainly focuses on three systems: noble metal catalysts, metal oxide catalysts, and molecular sieve catalysts.

[0005] Using elements such as Rh, Pd, Ir, Pt as active components, supported on MgO, SiO 2 , CeO 2 , Al 2 O 3 or TiO 2The noble metal catalysts obtained on carriers such as etc. have good activity for the direct catalytic decomposition of N 2 O. For example, Reference 1 discloses a dinitrogen monoxide (N 2 O) removal catalyst composite material, which uses the noble metal rhodium (Rh) element as the active component and loads the active component on a cerium dioxide-based carrier to obtain a noble metal catalyst. However, due to high prices and scarce resources, the large-scale application of noble metal catalysts in the catalytic decomposition of N 2 O is restricted.

[0006] Most molecular sieve catalysts select transition metals such as Fe, Co, Ni, Cu, Mn, etc. for ion exchange with molecular sieves. Among them, Fe-ZSM-5 and Cu-ZSM-5 have high catalytic reduction activity for N 2 O. For example, Reference 2 discloses a selective catalytic reduction molecular sieve catalyst for NO x which is prepared by ion exchange using soluble iron salt as the raw material to obtain Fe-ZSM-5. Molecular sieve catalysts have high catalytic reduction activity for N 2 O, but they require the consumption of reducing agents, and the preparation process is too complex. At the same time, there is a problem of high-temperature sintering.

[0007] In addition, in Reference 3, catalysts with transition metal oxides as the active component and rare earth elements as the promoter have been studied, but this catalyst contains alkali metal K, and the situation where there is no alkali metal and the transition metal oxides are nickel oxide (NiO) and copper oxide (CuO) has not been studied. Under actual flue gas conditions (such as adipic acid and nitric acid industrial tail gas), there may be a certain amount of acidic gas in the flue gas, and catalysts containing alkali metals will be more likely to deactivate due to 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.

[0008] Therefore, considering the industrial application cost and actual conditions comprehensively, the research and development and scale-up application of transition metal oxide catalysts with high decomposition activity and excellent anti-impurity gas performance are the research focuses.

[0009] References:

[0010] Reference 1: CN107223072A

[0011] Reference 2: CN102416343A

[0012] Reference 3: CN113996305A Summary of the Invention

[0013] Problems to be Solved by the Invention

[0014] To overcome the above-mentioned disadvantages 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 a relatively low cost, and is suitable for large-scale industrial production applications.

[0015] Solution for solving the problem

[0016] To solve the above problems, the present invention uses rare earth metal elements as promoters to assist in dispersing the active components and optimizing their electronic structures, promoting the activity of nitrous oxide catalytic decomposition, and obtaining a low-temperature N 2 O decomposition catalyst with excellent catalytic performance.

[0017] [1] Specifically, the present invention provides a catalyst for catalytically decomposing N 2 O, the catalyst comprising a transition metal oxide as the active component and an oxide of a rare earth metal element as the promoter,

[0018] wherein, the transition metal oxide is NiO and / or CuO,

[0019] and the rare earth metal element is one or more of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Dy, Tm, Yb.

[0020] [2] According to the catalyst described in [1] above, wherein the rare earth metal element is one or more of Gd, Pr, Yb; and the transition metal oxide is NiO.

[0021] [3] According to the catalyst described in [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.

[0022] [4] According to the catalyst described in any one of [1]-[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 can be 1:1.5 to 1:5, preferably 1:2 to 1:3.

[0023] [5] A preparation method of the catalyst according to any one of [1]-[4] above, characterized in that the preparation method comprises:

[0024] Step S1: Dissolve the rare earth element promoter precursor and the active component precursor in deionized water to obtain a mixed solution;

[0025] Step S2: Add a precipitating agent to the mixed solution to obtain a suspension, and subject the suspension to ultrasonic treatment and stirring;

[0026] Step S3: Age the suspension overnight, wash, filter by suction, and dry it to obtain a catalyst precursor;

[0027] Step S4: Calcinate the catalyst precursor to obtain a catalyst powder material.

[0028] [6] According to the preparation method described in [5] above, it is characterized in that, in step S1, it further includes dissolving a barium salt together with a rare earth element promoter precursor and an active ingredient precursor in deionized water; the active ingredient precursor is an acetate, nitrate, sulfate or oxalate of Ni and / or Cu; the rare earth element promoter precursor is 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, Lu; the precipitating agent is Na 2 CO 3 , K 2 CO 3 , (NH 4 ) 2 CO 3 or (NH 4 )HCO 3 , preferably (NH 4 ) 2 CO 3 ; the barium salt is barium acetate or barium nitrate.

[0029] [7] According to the preparation method described in [5] or [6] above, wherein, in step S2, the precipitating agent controls the pH value of the solution to 8 - 10, the ultrasonic treatment time is 0.5 - 1 h, and the stirring time is 2 - 4 h; and / or, in step S3, the aging time is 8 - 15 h, 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 - 6 h.

[0030] [8] According to the preparation method described in any one of [5] - [7] above, the preparation method further includes a post-treatment step S4.5 carried out after step S4:

[0031] Put the catalyst powder material into a 0.1 - 0.5 M HNO 3 solution, continuously stir for 3 - 6 h, wash until pH = 7, dry at 100 - 120 °C, and then calcine at 500 - 700 °C for 2 - 4 h.

[0032] [9] According to the preparation method described in any one of the above [5]-[8], wherein the preparation method further comprises step S5:

[0033] Adding deionized water, a binder, a pore-forming agent, and an organic auxiliary agent to the catalyst powder material to prepare a slurry, casting and molding the slurry on a casting machine, drying, and calcining to obtain a monolithic catalyst; or,

[0034] Adding deionized water, a binder, a pore-forming agent, and an organic auxiliary agent to the catalyst powder material to prepare a slurry, coating the slurry on the surface of a carrier, drying, and performing high-temperature calcination to obtain a supported catalyst,

[0035] wherein the binder is one or more of clay, ZrO 2 、Al 2 O 3 -based materials, silica 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 an associative thickener, a surfactant, polyacrylamide, glycerol, citric acid; the associative thickener is one or more of a 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 4-6 h; the shape of the catalyst obtained by casting and molding is one of a cuboid, a rod shape, a sphere, and an ellipsoid; the carrier includes one or more of cordierite, mullite, α-alumina, silicon carbide, aluminum titanate, silicon nitride, zircon mullite, zirconium silicate, magnesium silicate, aluminosilicate, metal / alloy.

[0036] [9] The activation treatment method of the catalyst described in any one of the above [1]-[4] or the catalyst obtained by the preparation method described in any one of the above [5]-[9], characterized in that the activation treatment atmosphere is 5-10% H 2 , the treatment temperature is 300-500 °C, and the treatment time is 0.5-1 h.

[0037]

[10] The use of the catalyst described in any one of the above [1]-[4] or the catalyst obtained by the preparation method described in any one of the above [5]-[9] in the catalytic decomposition of N 2 O, characterized in that it is used in the scenarios of adipic acid, nitric acid plant waste gas treatment, and solid waste combustion tail gas purification.

[0038] Effects of the invention

[0039] The technical solution of the present invention may have the following beneficial effects:

[0040] (1) By using rare earth metal elements as promoters to assist in dispersing the active components and optimizing their electronic structures, the activity of nitrous oxide catalytic decomposition is promoted, and a low-temperature N 2 O 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.

[0041] (2) By adding barium elements to the catalyst, the electron transfer performance of the catalyst is further improved.

[0042] (3) In the catalyst preparation method of the present invention, after being pretreated and activated by H 2 , the activity of the catalyst in an O 2 -containing atmosphere is stably improved.

[0043] (4) Existing examples of H 2 activation are mostly used to adjust the metal-support interaction of costly noble metal catalysts, and it is often impossible to obtain a stable improvement effect for mixed oxides. In the catalyst activation method of the present invention, by using 5-10% H 2 for short-time activation treatment at an appropriate temperature, the structure-activity relationship between catalyst elements can be optimized, and the catalytic activity can be significantly and stably improved. Description of the Drawings

[0044] Figure 1 It is a result graph of the catalytic performance test of the catalysts prepared in Examples 1-7 and 10 and the catalyst prepared in Comparative Example 1.

[0045] Figure 2 It is a result graph of the catalytic performance test of the catalysts prepared in Comparative Examples 1-9.

[0046] Figure 3 It is a result graph of the 3-cycle experiment of Example 10 and the single activity test of Examples 8-9 and 11-12 among the catalysts prepared in Examples 8-12. The number of cycles x is denoted as Cx.

[0047] Figure 4 It is for Figure 3 the result graph of the catalytic activity stability test of the used catalyst Example 10. Detailed Description of the Invention

[0048] The various exemplary embodiments, features, and aspects of the present invention will be described in detail below. The special word "exemplary" here means "serving as an example, embodiment, or illustration". Any embodiment described as "exemplary" here does not have to be construed as superior to or better than other embodiments.

[0049] In addition, to better illustrate the present invention, numerous specific details are given in the following specific embodiments. Those skilled in the art should understand that the present invention can be implemented without some specific details. In other instances, methods, means, equipment, and steps well-known to those skilled in the art are not described in detail in order to highlight the gist of the present invention.

[0050] Unless otherwise specified, 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 systematic errors inevitable in industrial production.

[0051] In this specification, the meaning expressed by "may" includes both the meaning of performing a certain process and the meaning of not performing a certain process.

[0052] In this specification, the "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc. mentioned refer to the specific elements (e.g., features, structures, properties, and / or characteristics) related to the embodiment, which are included in at least one of the embodiments described herein, and may or may not exist in other embodiments. Additionally, it should be understood that the elements can be combined in various embodiments in any suitable manner.

[0053] In this specification, the numerical range represented by "numerical value A to numerical value B" refers to the range including the endpoint numerical values A and B.

[0054] In this specification, when "normal temperature" or "room temperature" is used, the temperature can be about 10 to 40 °C.

[0055] <First aspect>

[0056] The first aspect of the present invention provides a catalyst for low-temperature catalytic decomposition of N 2 O. The catalyst of the present invention includes a transition metal oxide as an active ingredient and an oxide of a rare earth metal element as an auxiliary agent.

[0057] In the present invention, the transition metal oxide can be NiO and / or CuO, preferably NiO. The rare earth metal element in the rare earth metal oxide can be selected from one or more of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, preferably one or more of Gd, Pr, Yb.

[0058] 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 can be 0.01:1 to 0.1:1, preferably 0.03:1 to 0.08:1. For example, the molar ratio can 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.

[0059] In some preferred embodiments of the present invention, the catalyst further includes barium oxide. When the catalyst includes barium oxide, the molar ratio of barium element to transition metal element in the catalyst can be 0.05:1 to 0.2:1, preferably 0.1:1 to 0.15:1. For example, the molar ratio can be 0.05:1, 0.08:1, 0.1:1, 0.12:1, 0.15:1, 0.18:1, 0.2:1, etc. When the catalyst includes barium oxide, the molar ratio of the rare earth metal element to the barium element in the catalyst can be 1:1.5 to 1:5, preferably 1:2 to 1:3. For example, it can be 1:1.5, 1:2, 1:3, 1:4, 1:5, etc. The catalyst of the present invention preferably includes a combination of NiO, Yb 2 O 3 and BaO. For the combination of Yb 2 O 3 , BaO, and NiO, there is no relevant research at present.

[0060] 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, and the surface oxygen vacancies are increased (some studies believe that they can be used as N 2 O adsorption sites). At the same time, the electronic structure of nickel oxide and / or copper oxide as the active components is optimized, the average Ni valence is reduced, and the M-O bond (M = Ni, Cu, Co, etc.) is weakened to a certain extent, thereby promoting the activity of N 2 O catalytic decomposition; in addition, when the catalyst includes Ba element, the Ba element tends to aggregate on the surface of the catalyst, promotes electron transfer through alkalinity, and the generated BaCO 3 significantly hinders the growth of NiO crystals, reduces the NiO grain size, and further improves the catalytic activity.

[0061] <Second aspect>

[0062] The second aspect of the present invention provides a preparation method of the catalyst described in the present invention. The catalyst preparation method of the present invention includes:

[0063] Step S1: Dissolve the rare earth element promoter precursor and the active component precursor in deionized water to obtain a mixed solution;

[0064] Step S2: Dropwise add a precipitating agent into the mixed solution to obtain a suspension, and subject the suspension to ultrasonic treatment and stirring;

[0065] Step S3: Age the suspension overnight, wash, filter by suction, and dry it to obtain a catalyst precursor;

[0066] Step S4: Calcinate the catalyst precursor to obtain a catalyst powder material.

[0067] The following details each step.

[0068] Step S1

[0069] In step S1, dissolve the rare earth element promoter precursor and the active ingredient precursor in deionized water to obtain a transparent mixed metal salt solution.

[0070] In addition, in some preferred embodiments, dissolve the barium salt together with the rare earth element promoter precursor and the active ingredient precursor in deionized water in step S1. Among them, the barium salt can be barium acetate or barium nitrate.

[0071] In the present invention, the active ingredient precursor can be acetate, nitrate, sulfate or oxalate of Ni and / or Cu, and acetate and nitrate are preferred. Specifically, the active ingredient precursor can be one or more of nickel acetate, nickel nitrate, nickel sulfate, nickel oxalate, copper acetate, copper nitrate, copper sulfate, copper oxalate.

[0072] The rare earth element promoter precursor can be 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, and acetate and nitrate are preferred. Specifically, the rare earth element promoter precursor can be selected from one or more of 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, samarium oxalate, 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, thulium oxalate, ytterbium acetate, ytterbium nitrate, ytterbium sulfate, ytterbium oxalate, lutetium acetate, lutetium nitrate, lutetium sulfate, lutetium oxalate.

[0073] In the present invention, the molar ratio of the rare earth element promoter 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 with the molar ratio of the rare earth metal element to the transition metal element also within this range can be obtained.

[0074] Step S2

[0075] In step S2, at room temperature, a precipitant (or pH regulator) solution is slowly added dropwise to the mixed metal salt solution while stirring. During the addition, the pH value of the solution system is continuously detected. After controlling the pH value at 8 - 10, preferably 8.5 - 9.5, the addition is stopped. The resulting suspension is ultrasonically treated for 0.5 - 1 h and then stirred continuously for 1 - 2 h.

[0076] The precipitant used in the present invention can be Na 2 CO 3 , K 2 CO 3 , (NH 4 ) 2 CO 3 or (NH 4 )HCO 3 , and among them, (NH 4 ) 2 CO 3 is preferred.

[0077] By performing short - time ultrasonic treatment after coprecipitation, the dispersion of the catalyst precursor particles can be promoted, the dispersion state of the particles can be changed, thereby optimizing the catalyst morphology and improving the catalytic performance.

[0078] Steps S3 and S4

[0079] In step S3, the suspension obtained through the above steps is aged overnight, washed with deionized water until the pH = 7 and then filtered by suction, and then dried to obtain the catalyst precursor.

[0080] In the present invention, the aging time can be 8 - 15 h, preferably 10 - 12 h. The drying temperature can be 100 - 120 °C, and the drying time can be 10 - 15 h, 10 - 12 h.

[0081] In step S4, the obtained catalyst precursor is calcined to obtain the catalyst powder material. Among them, the calcination temperature can be 500 - 700 °C, and the calcination time can be 4 - 6 h.

[0082] In the catalyst preparation method of the present invention, according to the specific material types, it may further include step S4.5 of post - treating the catalyst powder material after step S4.

[0083] Step S4.5

[0084] In step S4.5, the catalyst powder material can be post-treated for surface modification. Specifically, the catalyst powder material is put into 0.1 - 0.5M HNO 3 solution, continuously stirred for 3 - 6 h, washed until the pH = 7, dried at 100 - 120 °C, and then calcined at 500 - 700 °C for 2 - 4 h.

[0085] In the catalyst preparation method of the present invention, according to needs, it may further include step S5 of integrally forming the catalyst powder material or loading it on a carrier. The following is a detailed description.

[0086] Step S5

[0087] In step S5, the obtained catalyst powder material can be integrally formed according to needs.

[0088] Specifically, deionized water, a binder, a pore-forming agent, and an organic auxiliary agent can be added to the catalyst powder material to prepare a slurry, which is cast and molded on a casting machine and then dried and calcined to obtain a monolithic catalyst.

[0089] In the present invention, there are no particular limitations on the binder, the pore-forming agent, and the organic auxiliary agent, and the commonly used binder, pore-forming agent, and organic auxiliary agent in the art can be used.

[0090] Specifically, the binder can be selected from one or more of clay, ZrO 2 , Al 2 O 3 -based materials (aluminum hydroxide, hydroxyaluminum oxide, γ-Al 2 O 3 etc.), silica / silicate, Ca(OH) 2 , MgO, preferably ZrO 2 and Al 2 O 3 . Among them, the clay may include bentonite, kaolin, montmorillonite, and other clay materials.

[0091] The pore-forming agent can be one or more of ammonium bicarbonate, cellulose, carboxymethyl cellulose, phenolic resin, starch, preferably starch and carboxymethyl cellulose.

[0092] 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, glycerin, and citric acid. Among them, examples of the associative thickener may include modified ethylene oxide polyurethane copolymers, polyacrylates, vinyl alcohol, etc. The surfactant may be a common cationic surfactant, anionic surfactant, amphoteric surfactant, medium carbon chain fatty alcohol, etc.

[0093] The temperature for calcination after casting may be 500 - 800 °C, and the calcination time may be 4 - 6 h. The shape of the catalyst after casting may be one of a cuboid, rod-shaped, spherical, and ellipsoidal. Moreover, the shape and size of the catalyst can be adjusted.

[0094] In addition, in step S5, if necessary, the catalyst powder material can also be loaded on the carrier.

[0095] 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.

[0096] The preparation of the slurry is the same as that in the above-mentioned integral forming, and will not be elaborated here.

[0097] In the present invention, the carrier is not particularly limited, and conventional carriers in the art can be used. Examples thereof may include one or more of cordierite, mullite, α-alumina, silicon carbide, aluminum titanate, silicon nitride, zircon mullite, zirconium silicate, magnesium silicate, aluminosilicate, metal / alloys, and 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 ability and loading performance.

[0098] There are no particular limitations on the temperature and time for drying after coating the slurry on the carrier, as long as the catalyst can be dried. For example, the drying temperature may be 60 - 100 °C, and the drying time may be 2 - 12 h. The temperature for calcination may be 500 - 800 °C, and the calcination time may be 4 - 6 h.

[0099] <Third aspect>

[0100] The present invention also provides an activation method for the above-mentioned catalyst or the catalyst obtained by the above-mentioned preparation method and its use in catalytic decomposition of N 2 O.

[0101] The activation method of the present invention is that the treatment atmosphere is 5 - 10% H 2 / Ar, the treatment temperature is 300 - 500 °C, and the treatment time is 0.5 - 1 h.

[0102] The catalyst of the present invention can be used for the efficient catalytic decomposition of N 2 O under low-temperature conditions of 200-500 °C. The decomposition conditions of N 2 O can be as follows:

[0103] It is carried out in a fixed-bed reactor. The decomposition conditions of N 2 O are: the reaction pressure is atmospheric pressure, the raw material gas enters from the top and exits from the bottom. The volume concentration of N 2 O in the raw material gas is 1000-1200 ppm, the volume concentration of O 2 is 0-5%, the volume concentration of NO x (NO or NO 2 ) is 0-120 ppm, the space velocity is 20000-40000 h -1 , and the operating temperature is 200-500 °C.

[0104] The raw material gas can be waste gas rich in N 2 O components such as adipic acid waste gas, nitric acid waste gas, and combustion tail gas of solid waste. The catalyst dosage is usually 0.2-0.5 g / (100 mL / min gas flow rate).

[0105] The catalyst of the present invention can reach 100% N 2 O conversion rate at about 380 °C when not activated, and even can reach 80% N 2 O conversion rate at about 350 °C, having relatively good catalytic activity; after activation, it can reach 100% conversion rate at about 300 °C and is hardly affected by low-concentration O 2 .

[0106] Examples

[0107] The following will describe the implementation scheme of the present invention in detail with reference to examples. However, those skilled in the art 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. For those not specified in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified in the manufacturer, they are all conventional products that can be obtained through commercial purchase. In the drawings, example x is denoted as S(x), and comparative example y is denoted as D(y).

[0108] Example 1

[0109] Catalyst preparation: According to the molar ratio of Gd and Ni of 0.05:1, gadolinium nitrate and nickel acetate are dissolved in 100 mL of deionized water to obtain a transparent metal salt mixed solution, and the concentration of Ni 2+ in the solution is controlled to be 0.24 mol / L. Under normal temperature conditions, 0.1 g / mL of (NH 4 ) 2 CO3 A solution was prepared. After the pH value was controlled to 9, the dropping was stopped. The resulting solution was ultrasonically treated for 0.5 h and then continuously stirred for 2 h. The obtained suspension was aged overnight at room temperature for 12 h, washed with deionized water and filtered by suction, dried at 110 °C for 12 h, and then calcined in a muffle furnace at 500 °C for 4 h to obtain a catalyst powder material, denoted as catalyst S(1).

[0110] Examples 2 - 3

[0111] Except that the rare earth promoter element used was Yb, catalyst S(2) was prepared in the same manner as in Example 1; except that the rare earth promoter element used was Pr and the Pr:Ni molar ratio was 0.053:1, catalyst S(3) was prepared in the same manner as in Example 1.

[0112] Example 4

[0113] Catalyst preparation: Praseodymium nitrate and nickel acetate were dissolved in 100 mL of deionized water according to the molar ratio of Pr to Ni of 0.1:1 to obtain a transparent mixed metal salt solution, and the Ni concentration in the solution was controlled to be 0.24 mol / L. At room temperature, a 0.1 g / mL Na 2+ solution was slowly added dropwise to the mixed solution. After the pH value was controlled to 9, the dropping was stopped. The resulting solution was ultrasonically treated for 0.5 h and then continuously stirred for 2 h. The obtained suspension was aged overnight at room temperature for 12 h, washed with deionized water and filtered by suction, dried at 110 °C for 12 h, and then calcined in a muffle furnace at 500 °C for 4 h to obtain a catalyst powder material, denoted as catalyst S(4). 2 CO 3 solution was slowly added dropwise to the mixed solution. After the pH value was controlled to 9, the dropping was stopped. The resulting solution was ultrasonically treated for 0.5 h and then continuously stirred for 2 h. The obtained suspension was aged overnight at room temperature for 12 h, washed with deionized water and filtered by suction, dried at 110 °C for 12 h, and then calcined in a muffle furnace at 500 °C for 4 h to obtain a catalyst powder material, denoted as catalyst S(4).

[0114] Example 5

[0115] According to the molar ratio of Yb:Ba:Ni 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 mixed metal salt solution, and the Ni concentration in the solution was controlled to be 0.24 mol / L. The remaining steps were carried out in the same manner as in Example 1 to obtain catalyst S(5). 2+ solution was slowly added dropwise to the mixed solution. After the pH value was controlled to 9, the dropping was stopped. The resulting solution was ultrasonically treated for 0.5 h and then continuously stirred for 2 h. The obtained suspension was aged overnight at room temperature for 12 h, washed with deionized water and filtered by suction, dried at 110 °C for 12 h, and then calcined in a muffle furnace at 500 °C for 4 h to obtain a catalyst powder material, denoted as catalyst S(5).

[0116] Examples 6 - 7

[0117] Except that the rare earth promoter element used was Gd and the calcination time was 6 h, catalyst S(6) was prepared in the same manner as in Example 5; except that the rare earth promoter element used was Pr and the Pr:Ba:Ni molar ratio was 0.053:0.158:1, catalyst S(7) was prepared in the same manner as in Example 5.

[0118] Examples 8 - 12

[0119] The catalyst was prepared in the same manner as in Examples 1, 2, 5, 6, and 7.

[0120] The prepared catalyst was pretreated at 300 °C for 0.5 h under 5% H 2 / Ar, and then cooled to room temperature for performance testing, named as Examples S(8), S(9), S(10), S(11), and S(12) respectively.

[0121] Comparative Example 1

[0122] Catalyst preparation: Nickel acetate was dissolved in 100 mL of deionized water to obtain a transparent metal salt solution with a Ni 2+ concentration of 0.2 mol / L in the solution. At room temperature, 0.1 g / mL of (NH 4 ) 2 CO 3 solution was slowly added dropwise to the mixed solution. The addition was stopped after controlling the pH value at 9, and stirring was continued for 2 h. The obtained suspension was aged overnight at room temperature for 12 h, washed with deionized water and filtered by suction, dried at 110 °C for 12 h, and then calcined in a muffle furnace at 500 °C for 4 h to obtain the catalyst powder material, denoted as D(1).

[0123] Comparative Examples 2 - 3

[0124] Respectively, 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 mixed metal salt solution, controlling the Ni 2+ concentration in the solution to be 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.

[0125] Comparative Examples 4 - 9

[0126] Except that the rare earth element promoters were respectively Sm, Ho, Er, Lu, Tb, Sn, and the molar ratio of rare earth element to Ni was 0.1:1, the catalysts were prepared in the same manner as in Comparative Example 1 to obtain catalysts D(4), D(5), D(6), D(7), D(8), and D(9) respectively.

[0127] <Catalytic performance test>

[0128] The decomposition conditions of N 2 O can be as follows:

[0129] It was carried out in a fixed-bed reactor. The decomposition conditions of N 2 O were: the reaction pressure was atmospheric pressure, the raw material gas flowed from top to bottom, and the volume concentration of N 2 O in the raw material gas was 1000 - 1200 ppm, and O2 The volume concentration is 0-3%, the NO volume concentration is 0-100ppm, and the 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).

[0130] The catalysts prepared in the above examples and comparative examples were tested for catalytic performance under the above conditions. The results are as follows: Figure 1 and Figure 2 As shown. Among them, Figure 1 The reaction conditions are: the gas composition is 1100ppm N 2 O / N 2 , gas flow rate 100mL / min, GHSV=40000h -1 . Figure 2 The reaction conditions are: the gas composition is 1100ppm N 2 O / N 2 , gas flow rate 100mL / min, GHSV=40000h -1 .

[0131] Depend on Figure 1 and Figure 2 It can be seen that 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 leads to lower catalytic performance 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 orbital of Gd, Pr, and Yb interacts with the 3d orbital of the active component Ni, thereby optimizing electron transfer, while the opposite is true for elements such as Tb and Lu. Figure 1 It can be seen that when the molar ratio of rare earth element (Pr) to transition metal element is 0.05:1, the catalytic effect is better than that when the molar ratio is 0.1:1; moreover, when Ba element is included in the catalyst, the catalytic activity is improved. 2 After pretreatment and activation, the catalytic activity was significantly improved. Figure 3 2 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. Figure 3 The reaction conditions are: the gas composition is 1100ppm N 2 O / N 2 , gas flow rate 100mL / min, GHSV=40000h -1 .from Figure 3It can be seen that the catalyst of Example 10 has good activity stability in the temperature range of 200-500 °C, and there is a slight increase in low-temperature activity with the increase of the number of cycles, indicating that the properties of the catalyst are stable after activation; the activities of Examples 8, 9, 11 and 12 have also been improved to varying degrees. In addition, Figure 4 shows the stability test results of the catalyst that has undergone 3 cycle experiments in Example 10 in the catalytic oxidation of N 2 O. Figure 4 The reaction conditions are: temperature 300 °C, gas composition 1100 ppm N 2 O / N 2 , 3% O 2 (when in use), 100 ppm NO (when in use), gas flow rate 100 mL / min, GHSV = 40000 h -1 . From Figure 4 it can be seen that the used catalyst that has undergone multiple cycle experiments after activation still maintains stable activity in a pure N 2 O atmosphere, and there is a slight increase in activity with time, which is consistent with the Figure 3 results; even when 3% O 2 is introduced, the catalytic activity is hardly affected, and the activity can be quickly restored when O 2 is turned off; however, the introduction of NO will cause a relatively obvious irreversible effect on the catalyst. Even so, a conversion rate of 80% can be achieved after running at 300 °C for 2 h, which is much higher than that of the unactivated catalyst. Therefore, it can be seen that the catalytic activity stability is good.

[0132] The embodiments of the present invention have been described above. The above description is exemplary and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for activating a catalyst for catalytic decomposition of nitrous oxide (N 2 O), It is characterized in that the catalyst comprises 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 Pr, Gd, and Yb, In the activation treatment method, the activation treatment atmosphere is 5-10% H 2 , the treatment temperature is 300-500 °C, and the treatment time is 0.5-1 h.

2. The activation treatment method according to claim 1, wherein the transition metal oxide is NiO.

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

1.

4. The activation treatment method according to claim 1 or 2, wherein in the catalyst, the molar ratio of the rare earth metal element to the transition metal element is 0.03:1 to 0.08:

1.

5. The activation treatment method according to claim 1 or 2, wherein the catalyst further comprises barium oxide or barium carbonate; and / or, in the catalyst, the molar ratio of barium element to transition metal element is 0.05:1 to 0.2:1; and / or, in the catalyst, the molar ratio of rare earth metal element to barium element can be 1:1.5 to 1:

5.

6. The activation treatment method according to claim 4, wherein in the catalyst, the molar ratio of barium element to transition metal element is 0.1:1 to 0.15:

1.

7. The activation treatment method according to claim 4, wherein in the catalyst, the molar ratio of rare earth metal element to barium element can be 1:2 to 1:

3.

8. The activation treatment method according to claim 1 or 2, wherein the catalyst is prepared by a preparation method comprising the following steps: Step S1: Dissolve the rare earth element auxiliary precursor and the active ingredient precursor in deionized water to obtain a mixed solution; Step S2: Dropwise add a precipitant to the mixed solution to obtain a suspension, and perform ultrasonic treatment and stirring on the suspension; Step S3: Age the suspension overnight, wash, filter by suction, and dry to obtain a catalyst precursor; Step S4: Calcinate the catalyst precursor to obtain a catalyst powder material.

9. The activation treatment method according to claim 8, wherein Step S1 further includes dissolving a barium salt together with a rare earth element promoter precursor and an active ingredient precursor in deionized water; the active ingredient precursor is an acetate, nitrate, sulfate or oxalate of Ni and / or Cu; the rare earth element promoter precursor is an acetate, nitrate, sulfate or oxalate of one or more of Pr, Gd, Yb; the precipitant is Na 2 CO 3 , K 2 CO 3 , (NH 4 ) 2 CO 3 or (NH 4 )HCO 3 ; the barium salt is barium acetate or barium nitrate.

10. The activation treatment method according to claim 8, wherein in Step S2, the precipitant controls the pH value of the solution to 8-10, the ultrasonic treatment time is 0.5-1 h, and the stirring time is 2-4 h; and / or, in Step S3, the aging time is 8-15 h, 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 4-6 h.

11. The activation treatment method according to claim 8, wherein the preparation method further comprises a post-treatment step S4.5 carried out after Step S4: Put the catalyst powder material into 0.1 - 0.5M HNO 3 solution, continuously stir for 3 - 6 h, wash until pH = 7, dry at 100 - 120 °C, and then calcine at 500 - 700 °C for 2 - 4 h.

12. The activation treatment method according to claim 8, wherein the preparation method further comprises Step S5: Add deionized water, a binder, a pore-forming agent, and an organic auxiliary agent to the catalyst powder material to prepare a slurry, cast and mold it on a casting machine, and dry and calcine it to obtain a monolithic catalyst; Alternatively, deionized water, a binder, a pore former, and an organic auxiliary agent 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. Among them, the binder is one or more of clay, ZrO 2 , Al 2 O 3 -series materials, silicon dioxide or silicate, Ca(OH) 2 , MgO; the pore former is one or more of ammonium bicarbonate, cellulose, carboxymethyl cellulose, phenolic resin, starch; the organic auxiliary 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 nonionic, anionic or cationic; the calcination temperature is 500-800 °C, and the calcination time is 4-6 h; the shape of the catalyst formed by casting is one of cuboid, rod-shaped, spherical, ellipsoidal; the carrier includes one or more of cordierite, mullite, α-alumina, silicon carbide, aluminum titanate, silicon nitride, zircon mullite, zirconium silicate, magnesium silicate, aluminosilicate, metal / alloy.

13. The activation treatment method according to claim 1 or 2, wherein the catalyst is used in the scenarios of adipic acid production, nitric acid plant waste gas treatment, and solid waste combustion tail gas purification to catalytically decompose N 2 O.

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