Catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of air pollution control, and discloses a catalyst and a preparation method and application thereof. The catalyst comprises a carrier, an active component and alkali metal, wherein the carrier is selected from a molecular sieve with a 12-membered ring straight pore channel structure; the weight ratio of the active component to the carrier is (0.001-0.1): 1, and the molar ratio of the alkali metal to the active component is (0.001-0.1): 1. According to the catalyst provided by the invention, the molecular sieve with the 12-membered ring straight pore channel structure is used as the carrier, and a coordination microenvironment can be changed, so that the setting and distribution of active components are regulated and controlled, and the activity, stability and mechanical strength of the catalyst are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of air pollution control, and particularly to a catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Nitrous oxide (N 2 O) is a greenhouse gas, and its global warming potential is 310 times that of CO 2 and 21 times that of CH 4 , and it is the third contributor to greenhouse gases. At the same time, N 2 O can damage the ozone layer through free radical reactions, causing ozone hole disasters. The N 2 O emitted in industrial processes mainly comes from the production of adipic acid, caprolactam, and nitric acid. China is the world's largest producer of adipic acid, caprolactam, and nitric acid, and the annual emission of N 2 O reaches 950,000 tons. Therefore, the development of efficient purification technologies for N 2 O waste gas is urgent. Currently, the treatment methods of N 2 O mainly include cyclohexanol absorption oxidation method, high-temperature thermal decomposition method, direct catalytic decomposition method, selective catalytic reduction method, and one-step benzene oxidation to phenol method. Among them, the direct catalytic decomposition method has the advantages of simple process route, low operating cost, low reaction temperature, and no secondary pollution, and is one of the most economical and effective purification means. The development of efficient catalysts is the key.

[0003] CN111974208A discloses a method for removing nitrous oxide from process waste gas, using transition metals and noble metal Pd as active components, and molecular sieves such as MFI, BEA, FER, MOR, etc. as carriers to prepare a catalyst. However, this process needs to use reducing agents such as ammonia to remove N 2 O through catalytic reduction, which belongs to the selective catalytic reduction technology. In addition to the additional use of reducing agents increasing the process cost, this process is also prone to ammonia breakthrough, causing secondary pollution.

[0004] CN114247473A discloses a metal forming catalyst for decomposing N 2 O and a preparation method thereof. The transition metal supported on RUB-50, SSZ-16, SSZ-39 molecular sieves catalyst has high catalytic activity, high mechanical strength, and high-temperature stability, but the temperature for its complete decomposition of N 2 O is as high as 800 °C, and NOx is easily formed under high-temperature conditions.

[0005] CN102921454A discloses a method for N 2Preparation method of monolithic BEA zeolite catalyst for direct catalytic decomposition of O, the catalyst uses cordierite as a carrier and BEA zeolite modified with Fe and Co metal ions as the active component, and the catalyst can achieve high-efficiency decomposition of N at a relatively low reaction temperature 2 O, has high catalytic activity and selectivity, but the temperature for the best catalyst to completely purify N 2 O still reaches 500 °C.

[0006] CN114618572A discloses a bimetallic catalyst for efficient decomposition of N 2 O, its preparation method and decomposition method, using any two of Fe, Ru or Rh as the active components and MCM-22 zeolite as the carrier. This catalyst can achieve 100% decomposition of N at 400 °C 2 O, but the loading of precious metals ruthenium and rhodium is as high as 1%, the catalyst is expensive, and the strong oxidizing property of precious metals has the risk of over-oxidizing N 2 O to form NOx.

[0007] Aiming at the problems and deficiencies of the existing N 2 O decomposition zeolite catalyst, it is urgent to develop a new catalyst. Summary of the Invention

[0008] The purpose of the present invention is to overcome the problems of high catalyst cost, low activity, low mechanical strength in the existing technology, and the need to decompose N at high temperature 2 O, and provide a catalyst, its preparation method and application.

[0009] To achieve the above purpose, the first aspect of the present invention provides a catalyst, wherein the catalyst includes: a carrier, an active component and an alkali metal;

[0010] Among them, the carrier is selected from zeolites with a 12-membered ring straight pore channel structure;

[0011] The mass ratio of the active component to the carrier is (0.001-0.1):1, and the molar ratio of the alkali metal to the active component is (0.001-0.1):1.

[0012] The second aspect of the present invention provides a preparation method of a catalyst, wherein the method includes the following steps:

[0013] Mix the carrier with a solution containing a precursor of the active component and an alkali metal compound to obtain a catalyst;

[0014] Among them, the carrier is selected from molecular sieves having a 12-membered ring straight pore channel structure; the amounts of the carrier, the active component precursor, and the alkali metal compound are such that in the obtained catalyst, the weight ratio of the active component to the carrier is (0.001 - 0.1):1, and the molar ratio of the alkali metal to the active component is (0.001 - 0.1):1.

[0015] The third aspect of the present invention provides a catalyst prepared by the above preparation method.

[0016] The fourth aspect of the present invention provides the application of the above catalyst in catalytic decomposition of N 2 O.

[0017] Through the above technical solutions, a catalyst, a preparation method thereof, and an application provided by the present invention achieve the following beneficial effects:

[0018] The catalyst provided by the present invention uses a molecular sieve with a 12-membered ring straight pore channel structure as the carrier, which can change the coordination microenvironment, thereby regulating the deposition and distribution of the active component, and improving the activity, stability, and mechanical strength of the catalyst. Description of the Drawings

[0019] Figure 1 is the SEM image of the catalyst prepared in Example 1 of the present invention. Detailed Embodiments

[0020] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0021] The first aspect of the present invention provides a catalyst, among which, the catalyst includes: a carrier, an active component, and an alkali metal;

[0022] Among them, the carrier is selected from molecular sieves having a 12-membered ring straight pore channel structure;

[0023] The mass ratio of the active component to the carrier is (0.001 - 0.1):1, and the molar ratio of the alkali metal to the active component is (0.001 - 0.1):1.

[0024] In the present invention, the carrier is selected from molecular sieves having a 12-membered ring straight pore channel structure, which can change the coordination microenvironment, thereby regulating the deposition and distribution of the active component, and improving the activity, stability, and mechanical strength of the catalyst.

[0025] According to the present invention, the active component is selected from at least one of Cu, Fe, Co, and Ni.

[0026] According to the present invention, the alkali metal is selected from at least one of Li, Na, K, Rb, and Cs.

[0027] According to the present invention, the molecular sieve is selected from at least one of BEA, MOR, EON, CON, MTW, MOZ, and MAZ.

[0028] According to the present invention, the silica-alumina ratio of the molecular sieve is (10 - 30):1.

[0029] In the present invention, when the silica-alumina ratio of the molecular sieve satisfies the above range, the activity of the catalyst is high.

[0030] According to the present invention, the specific surface area of the catalyst is 300 - 900 m 2 / g.

[0031] The second aspect of the present invention provides a method for preparing a catalyst, wherein the method includes the following steps:

[0032] Mix a carrier with a solution containing a precursor of the active component and an alkali metal compound to obtain a catalyst;

[0033] Wherein, the carrier is selected from molecular sieves having a 12-ring straight pore channel structure; the amounts of the carrier, the precursor of the active component, and the alkali metal compound are such that in the obtained catalyst, the weight ratio of the active component to the carrier is (0.001 - 0.1):1, and the molar ratio of the alkali metal to the active component is (0.001 - 0.1):1.

[0034] According to the present invention, the precursor of the active component is selected from nitrates and / or acetates of the active component; wherein, the active component is selected from at least one of Cu, Fe, Co, and Ni; preferably the precursor of the active component is selected from Cu(NO 3 ) 2 , Fe(NO 3 ) 3 , Co(NO 3 ) 2 and Ni(NO 3 ) 2 and at least one of their hydrates.

[0035] According to the present invention, the alkali metal compound is selected from at least one of carbonates, nitrates, and hydroxides of the alkali metal; wherein, the alkali metal is selected from at least one of Li, Na, K, Rb, and Cs; preferably the alkali metal compound is LiNO 3 , NaNO 3 , KNO3 、RbNO 3 and CsNO 3 at least one of them.

[0036] According to the present invention, the mixing process includes: the temperature is 50 - 90 °C and the time is 2 - 8 h. According to the present invention, the mixing further includes drying and calcination, wherein the drying conditions include: the temperature is 50 - 110 °C and the time is 0.5 - 24 h; the calcination conditions include: the heating rate is 1 - 20 °C / min, the temperature is 300 - 800 °C, and the time is 2 - 10 h.

[0037] The third aspect of the present invention provides a catalyst prepared by the above preparation method.

[0038] The fourth aspect of the present invention provides the application of the above catalyst in catalytic decomposition of N 2 O.

[0039] The present invention will be described in detail below through examples. In the following examples,

[0040] the raw materials used in the examples and comparative examples are all commercially available products.

[0041] Example 1

[0042] Mix a molecular sieve BEA support with a silica - alumina ratio of 20 with a mixed solution containing cobalt nitrate hexahydrate, KNO 3 and 1 L of deionized water at 70 °C for 5 h, dry at 80 °C for 12 h, heat up to 550 °C at a heating rate of 10 °C / min, and calcine for 6 h to obtain catalyst A1, where the dosages of the BEA support, cobalt nitrate hexahydrate, and KNO 3 are such that in the obtained catalyst, the weight ratio of cobalt nitrate hexahydrate to the BEA support is 0.05:1; the molar ratio of KNO 3 to cobalt nitrate hexahydrate is 0.03:1.

[0043] Figure 1 is the SEM image of the catalyst prepared in Example 1 of the present invention. It can be seen from Figure 1 that the nanoparticles are ellipsoidal, with irregular protrusions on their surfaces, being relatively rough, and at the same time, no obvious oxide cluster particles are found, indicating that the active components and alkali metals are highly dispersed in the molecular sieve support.

[0044] Example 2

[0045] Mix a molecular sieve MOR support with a silica - alumina ratio of 25 with a solution containing Cu(NO 3 ) 2 、LiNO 3A mixed solution of 1 L of deionized water was mixed at 80 °C for 4 h, dried at 100 °C for 6 h, heated to 700 °C at a heating rate of 15 °C / min, and calcined for 4 h to obtain catalyst A2, where the MOR support, Cu(NO 3 ) 2 , LiNO 3 were used such that in the resulting catalyst, the weight ratio of Cu(NO 3 ) 2 to the MOR support was 0.07:1; the molar ratio of LiNO 3 to Cu(NO 3 ) 2 was 0.01:1.

[0046] Example 3

[0047] A molecular sieve BEA support with a silica-alumina ratio of 15 was mixed with a mixed solution containing Fe(NO 3 ) 3 , NaNO 3 and 1 L of deionized water at 60 °C for 6 h, dried at 60 °C for 18 h, heated to 400 °C at a heating rate of 5 °C / min, and calcined for 8 h to obtain catalyst A3, where the BEA support, Fe(NO 3 ) 3 , NaNO 3 were used such that in the resulting catalyst, the weight ratio of Fe(NO 3 ) 3 to the BEA support was 0.03:1; the molar ratio of NaNO 3 to Fe(NO 3 ) 3 was 0.05:1.

[0048] Example 4

[0049] A molecular sieve MOR support with a silica-alumina ratio of 30 was mixed with a mixed solution containing Ni(NO 3 ) 2 , RbNO 3 and 1 L of deionized water at 90 °C for 2 h, dried at 110 °C for 0.5 h, heated to 800 °C at a heating rate of 20 °C / min, and calcined for 2 h to obtain catalyst A4, where the MOR support, Ni(NO 3 ) 2 , RbNO 3 were used such that in the resulting catalyst, the weight ratio of Ni(NO 3 ) 2 to the MOR support was 0.1:1; the molar ratio of RbNO 3 to Ni(NO 3 ) 2The molar ratio is 0.1:1.

[0050] Example 5

[0051] The molecular sieve BEA support with a silica-alumina ratio of 10 was mixed with a mixed solution containing cobalt nitrate hexahydrate, CsNO 3 and 1 L of deionized water at 50 °C for 8 h, dried at 50 °C for 24 h, heated to 300 °C at a heating rate of 1 °C / min, and calcined for 10 h to obtain catalyst A5, where the amounts of the BEA support, cobalt nitrate hexahydrate, and CsNO 3 were such that in the resulting catalyst, the weight ratio of cobalt nitrate hexahydrate to the BEA support was 0.001:1; the molar ratio of CsNO 3 to cobalt nitrate hexahydrate was 0.001:1.

[0052] Comparative Example 1

[0053] The catalyst was prepared according to the method of Example 1, except that: KNO 3 was not added, and catalyst D2 was prepared.

[0054] Test Example 1

[0055] The catalysts prepared in the above examples and comparative examples were tested for content and specific surface area.

[0056] The specific surface area was detected by BET;

[0057] The contents in the catalyst were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0058] The results are shown in Table 1.

[0059] Table 1

[0060]

[0061] Test Example 2

[0062] The application of the catalysts prepared in the examples and comparative examples in the catalytic decomposition of N 2 O.

[0063] The specific test method is as follows:

[0064] The prepared catalyst was ground into powder, then pelletized and sieved to 40-60 mesh, loaded into a micro fixed-bed quartz reactor, and simulated N 2 O tail gas (30 vol% N 2 O, balance gas is He) was introduced, the total flow rate was 80 mL / min, and the volume space velocity was 30000 h -1, the reaction temperature range is 300 - 600 °C. A gas chromatograph (GC4000A) equipped with TDX-1 and 5A molecular sieve columns was used to qualitatively and quantitatively analyze the gases before and after the reaction.

[0065] N 2 The N

[0066]

[0067] The results are shown in Table 2.

[0068] Table 2

[0069]

[0070] As can be seen from the above results, the catalyst prepared in the examples of the present invention has excellent catalytic performance when used for catalytic decomposition of N 2 O. The N 2 O conversion rate of the catalyst prepared in Example 1 at 400 °C is 100%, and the N 2 O conversion rate of the catalysts prepared in Examples 2 - 3 at 450 °C is 100%. The N 2 O conversion rate of the catalysts prepared in Examples 4 - 5 at 500 °C is 100%.

[0071] Compared with Comparative Example 1, in the process of preparing the catalyst in Example 1, an alkali metal compound was added, and the catalyst has excellent catalytic performance. The N 2 O conversion rate at 400 °C is 100%, while the N 2 O conversion rate of the catalyst prepared in Comparative Document 1 at 400 °C is 75%.

[0072] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A catalyst, characterized in that, the catalyst comprises: a carrier, an active component and an alkali metal; wherein, the carrier is selected from molecular sieves having a 12-membered ring straight pore channel structure; the weight ratio of the active component to the carrier is (0.001 - 0.1):1, and the molar ratio of the alkali metal to the active component is (0.001 - 0.1):

1.

2. The catalyst according to claim 1, wherein, the active component is selected from at least one of Cu, Fe, Co and Ni; preferably, the alkali metal is selected from at least one of Li, Na, K, Rb and Cs; preferably, the molecular sieve is selected from at least one of BEA, MOR, EON, CON, MTW, MOZ and MAZ; more preferably, the silica-alumina ratio of the molecular sieve is (10 - 30):

1.

3. The catalyst according to claim 1 or 2, wherein, The specific surface area of the catalyst is 300 - 900 m 2 / g.

4. A method for preparing a catalyst, characterized in that, the method comprises the following steps: mixing a carrier with a solution containing a precursor of an active component and an alkali metal compound to obtain a catalyst; wherein, the carrier is selected from molecular sieves having a 12-membered ring straight pore channel structure; the amounts of the carrier, the precursor of the active component and the alkali metal compound are such that in the obtained catalyst, the weight ratio of the active component to the carrier is (0.001 - 0.1):1, and the molar ratio of the alkali metal to the active component is (0.001 - 0.1):

1.

5. The preparation method according to claim 4, wherein, the molecular sieve is selected from at least one of BEA, MOR, EON, CON, MTW, MOZ and MAZ.

6. The preparation method according to claim 4 or 5, wherein, The active component precursor is selected from nitrates and / or acetates of the active component; wherein, the active component is selected from at least one of Cu, Fe, Co, and Ni; preferably, the active component precursor is selected from Cu(NO 3 ) 2 , Fe(NO 3 ) 3 , Co(NO 3 ) 2 and Ni(NO 3 ) 2 and at least one of their hydrates; Preferably, the alkali metal compound is selected from at least one of carbonates, nitrates and hydroxides of alkali metals; wherein, the alkali metal is selected from at least one of Li, Na, K, Rb and Cs; preferably the alkali metal compound is LiNO 3 , NaNO 3 , KNO 3 , RbNO 3 and CsNO 3 and at least one of them.

7. The preparation method according to any one of claims 4 - 6, wherein, the conditions for the mixing include: temperature is 50 - 90 °C, and time is 2 - 8 h.

8. The preparation method according to any one of claims 4 - 7, and the mixing process further includes drying and calcination, wherein, the conditions for the drying include: temperature is 50 - 110 °C, and time is 0.5 - 24 h; the conditions for the calcination include: heating rate is 1 - 20 °C / min, temperature is 300 - 800 °C, and time is 2 - 10 h.

9. A catalyst prepared by the preparation method according to any one of claims 4 - 8.

10. Use of the catalyst according to any one of claims 1-3 and 9 in catalytic decomposition of N 2 O.

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