Wide-temperature-window SAPO-18 molecular sieve denitration catalyst as well as preparation method and application thereof

Abstract

The invention relates to a wide-temperature-window SAPO-18 molecular sieve denitration catalyst as well as a preparation method and application thereof, and belongs to the technical field of porous inorganic materials and air pollution control. According to the SAPO-18 denitration catalyst, various organic matters, active metal ions and rare earth ions are added into a system, a metal element doped molecular sieve is synthesized through a one-pot hydrothermal method, and the synthesized metal doped molecular sieve is subjected to high-temperature roasting to prepare the molecular sieve denitration catalyst. The SAPO-18 molecular sieve denitration catalyst prepared by the method presents a microflower morphology compounded by a layered structure. Meanwhile, the catalyst has proper acidity and moderate oxidation-reduction capacity, so that the catalyst shows a wider denitration activity temperature window and higher hydrothermal stability. The method has the advantages of simple preparation process flow, low cost, high yield and suitability for large-scale production, and has wide application prospects in the fields of air pollution control and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of porous inorganic materials and air pollution control, and specifically relates to a wide temperature window SAPO-18 molecular sieve denitration catalyst and a preparation method and application thereof. Background Art

[0002] Diesel exhaust contains nitrogen oxides (N x O) Important emission source. NO x It is an important component of smog and acid rain. Its large-scale emission poses a serious threat to human health. 3 -SCR) technology is considered to solve the problem of NO in oxygen-rich diesel engine exhaust x An effective way to remove NO, the key lies in the research of SCR denitrification catalysts. Small-pore zeolites with special pore structures are an important type of industrial catalyst developed in recent years. They are widely used in petroleum catalytic cracking, methanol to olefins, gas separation, etc. In recent years, molecular sieve materials have been used in diesel engine exhaust purification. Among them, the copper ion exchanged CHA-type small-pore molecular sieve Cu-SSZ-13 catalyst exhibits efficient SCR denitrification effect. Compared with commercial denitrification catalysts, its active temperature window (NO conversion rate > 90%) is wider. Due to the NO x In the presence of high-temperature (>400°C) steam in the SCR reaction, CHA-type molecular sieve SCR catalysts face more severe hydrothermal aging problems, and improving the hydrothermal stability of Cu-based molecular sieve catalysts has become a key and difficult point in research. Studies have found that molecular sieve catalysts with AEI structure (such as SAPO-18) have higher hydrothermal stability. Therefore, the development of efficient SAPO-18 denitrification catalysts has become a solution to the problem of NO in oxygen-rich diesel exhaust. x However, the harsh and complex synthesis conditions, long synthesis cycle and high preparation cost of SAPO-18 limit its industrial application. Summary of the invention

[0003] In view of the deficiencies in the existing preparation technology, the present invention provides a wide-window SAPO-18 molecular sieve denitration catalyst and a preparation method thereof, and optimizes the synthesis steps and component combinations. The SAPO-18 molecular sieve synthesis method provided by the present invention adds active metal ions, organic directing agents and organic ligands to the synthesis system. During the hydrothermal reaction, the active metal ions, rare earth co-catalyst ions and organic ligands are coordinated to form metal organic complexes. The presence of organic ligands plays a role in shielding metal ions, avoiding the influence of active metal ions and rare earth co-catalyst ions on the crystallization growth of SAPO-18 molecular sieves. At the same time, under the action of the dual organic structure directing agent, the SAPO-18 molecular sieve is in situ grown on the surface of the metal organic complex, and it is coated to form a metal organic complex embedded SAPO-18 molecular sieve composite raw powder, and various parameters in the synthesis process are optimized to regulate the components and distribution of silicon, phosphorus and aluminum in the molecular sieve and the active metal content, and adjust the surface acidity and redox properties, thereby improving the denitration catalytic performance and hydrothermal stability of the catalyst.

[0004] To achieve this purpose, the technical solution adopted by the present invention is:

[0005] A method for preparing a wide temperature window SAPO-18 molecular sieve denitration catalyst, the preparation method comprising the following contents:

[0006] (1) adding an aluminum source, a phosphorus source, a silicon source, and a dual organic structure directing agent into a solvent and mixing them evenly;

[0007] (2) adding active metal salt, rare earth salt and organic ligand in the form of solution to the mixture obtained in step (1) and mixing them evenly to obtain a precursor mixture;

[0008] (3) transferring the precursor mixture obtained in step (2) into a hydrothermal reactor and performing crystallization;

[0009] (4) The product obtained in step (3) is centrifuged, washed, dried, and then calcined at high temperature to obtain a molecular sieve denitration catalyst.

[0010] In the technical solution of the present invention: the aluminum source in step (1) is at least one of aluminum chloride, pseudo-boehmite and aluminum oxide;

[0011] The silicon source is at least one of tetraethyl orthosilicate, silica sol and fumed silica, and the mass concentration of silica sol is 10-30%;

[0012] The phosphorus source is at least one of concentrated phosphoric acid and triethyl phosphate, and the mass concentration of the concentrated phosphoric acid is 80-90%;

[0013] The dual organic structure directing agent is tetraethylammonium hydroxide (TEAOH) and NN diisopropylethylamine (DIEA) in a molar ratio of 1-5:1-3;

[0014] The solvent is 10-30wt% ethanol aqueous solution.

[0015] In the technical solution of the present invention: the active metal salt described in step (2) is at least one of copper nitrate, copper sulfate and copper acetate;

[0016] The rare earth salt (RM) is at least one of lanthanum nitrate and cerium nitrate;

[0017] The organic ligand (OL) is at least one of 2-aminopyridine, hexamethylenetetramine and tetraethylenepentamine.

[0018] In the technical solution of the present invention: in step (1), the molar ratio of aluminum in the aluminum source, phosphorus in the phosphorus source, silicon in the silicon source and the dual organic structure directing agent is 1:0.1-1.5:0.1-1:0.1-3;

[0019] In step (2), the molar ratio of active metal salt, rare earth salt and organic ligand is 0.001-0.1:0.001-0.1:0.01-1;

[0020] The molar ratio of aluminum in the aluminum source to the active metal salt in the precursor mixture is 1:0.001-0.1.

[0021] In some preferred technical solutions: in step (1), the molar ratio of aluminum in the aluminum source, phosphorus in the phosphorus source, silicon in the silicon source and the dual organic structure directing agent is 1:0.6-1:0.1-0.5:0.4-2;

[0022] In step (2), the molar ratio of active metal salt, rare earth salt and organic ligand is 0.005-0.02:0.005-0.02:0.02-0.1;

[0023] The molar ratio of aluminum in the aluminum source to the active metal salt in the precursor mixture is 1:0.005-0.02.

[0024] In the technical solution of the present invention: the crystallization temperature of step (3) is 150-200° C., and the crystallization time is 50 to 100 hours.

[0025] In the technical solution of the present invention: the roasting temperature in step (4) is 500-700°C, and the roasting time is 3-6h.

[0026] A wide temperature window SAPO-18 molecular sieve denitration catalyst is prepared by the method.

[0027] In the technical solution of the present invention, the wide temperature window SAPO-18 molecular sieve denitration catalyst prepared by the method is used in treating nitrogen oxides in flue gas / tail gas.

[0028] Beneficial effects:

[0029] The present invention adopts a one-pot hydrothermal method, adds active metal ions, dual organic directing agents and organic ligands into the system, and synthesizes active metal Cu-doped SAPO-18 molecular sieves with a micro-nano multi-level structure by adjusting the synthesis conditions. The method has a simple process flow, low cost and high yield, and the catalyst exhibits high hydrothermal stability and a wide active temperature window. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a graph of the denitration efficiency of the molecular sieve denitration catalyst prepared in Examples 1-4.

[0031] Figure 2 This is the XRD diagram of the molecular sieve denitration catalyst prepared in Example 1-4.

[0032] Figure 3 This is the SEM image of the molecular sieve denitration catalyst prepared in Example 1. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with embodiments, but the protection scope of the present invention is not limited thereto:

[0034] The following non-limiting embodiments may enable a person skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0035] The test methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0036] Example 1

[0037] (1) Select 1.33 g aluminum chloride and 1.04 g concentrated phosphoric acid (85% H 3 PO 4 ), 0.42 g tetraethyl orthosilicate, 1.77 g tetraethylammonium hydroxide aqueous solution (25% TEAOH) and 1.16 g N-N-diisopropylethylamine (DIEA)

[0038] Add to 5 ml of ethanol aqueous solution (20 wt % ethanol) and mix well;

[0039] (2) Add 0.01 g copper nitrate, 0.02 g lanthanum nitrate and 0.03 g 2-aminopyridine to 5 ml water, stir evenly, add to the mixture obtained in step (1) and mix evenly to obtain a precursor mixture; wherein the molar ratio of each raw material is 1Al: 0.9P: 0.2Si: 0.3TEAOH: 0.9DIEA: 0.006Cu: 0.006La:

[0040] 0.03OL.

[0041] (3) The precursor mixture obtained in step (2) was transferred into a hydrothermal reactor, crystallized at 180°C for 56 hours, then centrifuged, washed, and dried to obtain molecular sieve raw powder A, and finally calcined at 550°C for 5 hours to obtain molecular sieve denitration catalyst A. The BET specific surface area was measured to be 742 m 2 / g, pore volume 0.32cm 3 / g.

[0042] (4) Test the denitrification performance of molecular sieve denitrification catalyst A, simulating NO in flue gas x (1000ppm), NH 3

[0043] (1000ppm), O 2 (10%); airspeed is 50000h -1 The particle size is 20-40 mesh, the catalyst activity temperature window is 190-550°C, and its denitration performance is shown in the figure Figure 1 shown.

[0044] Example 2

[0045] (1) 0.74 g pseudo-boehmite (69% Al 2 O 3 )、1.46g triethyl phosphate, 0.90g silica sol (20% SiO 2 ), 2.95 g of tetraethylammonium hydroxide aqueous solution (25% TEAOH) and 0.90 g of N-N-diisopropylethylamine (DIEA) were added to 5 ml of ethanol aqueous solution (20 wt% ethanol) and mixed evenly;

[0046] (2) Add 0.02 g of copper sulfate pentahydrate, 0.03 g of cerium nitrate, and 0.08 g of hexamethylenetetramine to 5 ml of water, stir evenly, and add to the mixture obtained in step (1) and mix evenly to obtain a precursor mixture; wherein the ratio of each raw material is 1Al: 0.8P: 0.3Si: 0.5TEAOH: 0.7DIEA: 0.01Cu: 0.01La:

[0047] 0.06OL.

[0048] (3) The precursor mixture obtained in step (2) was transferred into a hydrothermal reactor, crystallized at 170°C for 64 hours, then centrifuged, washed, and dried to obtain molecular sieve powder B, and finally calcined at 600°C for 4 hours to obtain molecular sieve denitration catalyst B. The BET specific surface area was measured to be 751 m 2 / g, pore volume 0.35cm 3 / g.

[0049] (4) Test the denitrification performance of molecular sieve denitrification catalyst B, simulating NO in flue gas x (1000ppm), NH 3

[0050] (1000ppm), O 2 (10%); airspeed is 50000h -1 The particle size is 20-40 mesh, the catalyst activity temperature window is 210-570℃, and its denitrification performance is shown in the figure Figure 1 shown.

[0051] Example 3

[0052] (1) Select 0.51g γ-Al 2 O 3 , 1.46 g triethyl phosphate, 0.24 g fumed silica, 4.12 g tetraethylammonium hydroxide aqueous solution (25% TEAOH) and 0.65 g NN diisopropylethylamine (DIEA) were added to 5 ml ethanol aqueous solution (20 wt% ethanol) and mixed evenly;

[0053] (2) Add 0.03 g of copper acetate, 0.05 g of lanthanum nitrate, and 0.15 g of tetraethylenepentamine to 5 ml of water, stir evenly, and add to the mixture obtained in step (1) and mix evenly to obtain a precursor mixture; wherein the ratio of each raw material is 1Al: 0.7P: 0.4Si: 0.7TEAOH: 0.5DIEA: 0.015Cu: 0.016La:

[0054] 0.08OL.

[0055] (3) The precursor mixture obtained in step (2) was transferred into a hydrothermal reactor, crystallized at 160°C for 84 hours, then centrifuged, washed, and dried to obtain molecular sieve raw powder C, and finally calcined at 650°C for 3 hours to obtain molecular sieve denitration catalyst C. The BET specific surface area was measured to be 747 m 2 / g, pore volume 0.33cm 3 / g.

[0056] (4) Test the denitrification performance of molecular sieve denitrification catalyst C, simulating NO in flue gas x (1000ppm), NH3

[0057] (1000ppm), O 2 (10%); airspeed is 50000h -1 The particle size is 20-40 mesh, the catalyst activity temperature window is 220-580℃, and its denitrification performance is shown in the figure Figure 1 shown.

[0058] Example 4

[0059] (1) 1.33 g aluminum chloride, 1.28 g triethyl phosphate, 0.24 g fumed silica, 5.30 g tetraethylammonium hydroxide aqueous solution (25% TEAOH) and 0.39 g NN diisopropylethylamine (DIEA) were added to 5 ml ethanol aqueous solution (20% wt ethanol) and mixed evenly;

[0060] (2) Add 0.03 g copper nitrate, 0.06 g cerium nitrate and 0.08 g 2-aminopyridine to 5 ml water, stir evenly, add to the mixture obtained in step (1) and mix evenly to obtain a precursor mixture; wherein the ratio of each raw material is 1Al: 0.7P: 0.4Si: 0.9TEAOH: 0.3DIEA: 0.018Cu: 0.018La:

[0061] 0.09OL.

[0062] (3) The precursor mixture obtained in step (2) was transferred into a hydrothermal reactor, crystallized at 150°C for 96 hours, then centrifuged, washed, and dried to obtain molecular sieve powder D, and finally calcined at 600°C for 4 hours to obtain molecular sieve denitration catalyst D. The BET specific surface area was measured to be 754 m 2 / g, pore volume 0.34cm 3 / g. (4) Test the denitrification performance of molecular sieve denitrification catalyst D, simulating NO in flue gas x (1000ppm), NH 3

[0063] (1000ppm), O 2 (10%); airspeed is 50000h -1 The particle size is 20-40 mesh, the catalyst activity temperature window is 230-600℃, and its denitrification performance is shown in the figure Figure 1 shown.

[0064] Comparative Example 1

[0065] (1) Select 1.33 g aluminum chloride and 1.04 g concentrated phosphoric acid (85% H 3 PO 4), 0.42 g tetraethyl orthosilicate, 1.77 g tetraethylammonium hydroxide aqueous solution (25% TEAOH) and 1.16 g N-N-diisopropylethylamine (DIEA)

[0066] Add to 5 ml of ethanol aqueous solution (20 wt % ethanol) and mix well;

[0067] (2) Add 0.01 g of copper nitrate to 5 ml of water, stir evenly, and add to the mixture obtained in step (1) and mix evenly to obtain a precursor mixture; wherein the molar ratio of each raw material is 1Al: 0.9P: 0.2Si:

[0068] 0.3TEAOH: 0.9DIEA: 0.006Cu.

[0069] (3) The precursor mixture obtained in step (2) was transferred into a hydrothermal reactor, crystallized at 180°C for 56 hours, then centrifuged, washed, and dried to obtain raw powder E, and finally calcined at 550°C for 5 hours to obtain denitration catalyst E. The BET specific surface area was measured to be 632 m 2 / g, pore volume 0.27cm 3 / g.

[0070] (4) Test the denitrification performance of denitrification catalyst E, simulating NO in flue gas x (1000ppm), NH 3 (1000ppm), O 2 (10%); airspeed is 50000h -1 The particle size is 20-40 mesh, the catalyst activity temperature window is 290-430°C, and its denitration performance is shown in the figure Figure 1 shown.

[0071] Comparative Example 2

[0072] (1) Select 1.33 g aluminum chloride and 1.04 g concentrated phosphoric acid (85% H 3 PO 4 ), 0.42 g tetraethyl orthosilicate, 1.77 g tetraethylammonium hydroxide aqueous solution (25% TEAOH) and 1.16 g N-N-diisopropylethylamine (DIEA)

[0073] Add to 5 ml of ethanol aqueous solution (20 wt % ethanol) and mix well;

[0074] (2) Add 0.01 g of copper nitrate and 0.03 g of 2-aminopyridine to 5 ml of water, stir evenly, and add to the mixture obtained in step (1) and mix evenly to obtain a precursor mixture; wherein the molar ratio of each raw material is 1Al:0.9P:0.2Si:0.3TEAOH:0.9DIEA:0.006Cu:0.03OL.

[0075] (3) The precursor mixture obtained in step (2) was transferred into a hydrothermal reactor, crystallized at 180°C for 56 hours, then centrifuged, washed, and dried to obtain molecular sieve powder F, and finally calcined at 550°C for 5 hours to obtain denitration catalyst F. The BET specific surface area was measured to be 641 m 2 / g, pore volume 0.25cm 3 / g.

[0076] (4) Test the denitrification performance of denitrification catalyst F, simulating NO in flue gas x (1000ppm), NH 3 (1000ppm), O 2 (10%); airspeed is 50000h -1 The particle size is 20-40 mesh, the catalyst activity temperature window is 270-430°C, and its denitrification performance is shown in the figure Figure 1 shown.

[0077] Comparative Example 3

[0078] (1) Select 1.33 g aluminum chloride and 1.04 g concentrated phosphoric acid (85% H 3 PO 4 ), 0.42 g tetraethyl orthosilicate, 1.77 g tetraethylammonium hydroxide aqueous solution (25% TEAOH) and 1.16 g N-N-diisopropylethylamine (DIEA)

[0079] Add to 5 ml of ethanol aqueous solution (20 wt % ethanol) and mix well;

[0080] (2) Add 0.02 g of lanthanum nitrate and 0.03 g of 2-aminopyridine to 5 ml of water, stir evenly, add to the mixture obtained in step (1) and mix evenly to obtain a precursor mixture; wherein the molar ratio of each raw material is 1Al:0.9P:0.2Si:0.3TEAOH:0.9DIEA:0.006La:0.03OL.

[0081] (3) The precursor mixture obtained in step (2) was transferred into a hydrothermal reactor, crystallized at 180°C for 56 hours, then centrifuged, washed, and dried to obtain molecular sieve raw powder G, and finally calcined at 550°C for 5 hours to obtain molecular sieve denitration catalyst G. The BET specific surface area was measured to be 587 m 2 / g, pore volume 0.26cm 3 / g.

[0082] (4) Test the denitrification performance of molecular sieve denitrification catalyst G, simulating NO in flue gas x (1000ppm), NH 3

[0083] (1000ppm), O 2 (10%); airspeed is 50000h -1 The particle size is 20-40 mesh, the catalyst activity temperature window is 0°C, and its denitration performance is shown in the figure Figure 1 shown.

[0084] Comparative Example 4

[0085] (1) Select 1.33 g aluminum chloride and 1.04 g concentrated phosphoric acid (85% H 3 PO 4 ), 0.42g tetraethyl orthosilicate, 1.77g tetraethylammonium hydroxide aqueous solution (25% TEAOH) were added to 5ml ethanol aqueous solution (20wt% ethanol)

[0086] Mix well;

[0087] (2) Add 0.01g copper nitrate, 0.02g lanthanum nitrate and 0.03g 2-aminopyridine to 5ml water, stir evenly, add to the mixture obtained in step (1) and mix evenly to obtain a precursor mixture; wherein the molar ratio of each raw material is 1Al: 0.9P: 0.2Si: 0.3TEAOH: 0.006Cu: 0.006La: 0.03OL. (3) Transfer the precursor mixture obtained in step (2) to a hydrothermal reactor, crystallize at 180°C for 56h, then centrifuge, wash and dry to obtain raw powder H, and finally calcine at 550°C for 5h to obtain denitration catalyst H. The BET specific surface area is measured to be 241m 2 / g, pore volume 0.11cm 3 / g.

[0088] (4) Test the denitrification performance of denitrification catalyst H, simulating NO in flue gas x (1000ppm), NH 3 (1000ppm), O 2 (10%); airspeed is 50000h -1 The particle size is 20-40 mesh, the catalyst activity temperature window is 330-390 ° C, and its denitrification performance is shown in the figure Figure 1 shown.

Claims

1. A method for preparing a wide temperature window SAPO-18 molecular sieve denitration catalyst, characterized in that: The preparation method comprises the following contents: (1) adding an aluminum source, a phosphorus source, a silicon source, and a dual organic structure directing agent into a solvent and mixing them evenly; (2) adding active metal salt, rare earth salt and organic ligand in the form of solution to the mixture obtained in step (1) and mixing them evenly to obtain a precursor mixture; (3) transferring the precursor mixture obtained in step (2) into a hydrothermal reactor and performing crystallization; (4) The product obtained in step (3) is centrifuged, washed, dried, and then calcined at high temperature to obtain a molecular sieve denitration catalyst.

2. The method for preparing a wide temperature window SAPO-18 molecular sieve denitration catalyst according to claim 1, characterized in that: The aluminum source in step (1) is at least one of aluminum chloride, pseudo-boehmite and aluminum oxide; The silicon source is at least one of tetraethyl orthosilicate, silica sol and fumed silica, and the mass concentration of silica sol is 10-30%; The phosphorus source is at least one of concentrated phosphoric acid and triethyl phosphate, and the mass concentration of the concentrated phosphoric acid is 80-90%; The dual organic structure directing agent is tetraethylammonium hydroxide (TEAOH) and NN diisopropylethylamine (DIEA) in a molar ratio of 1-5:1-3; The solvent is 10-30wt% ethanol aqueous solution.

3. The method for preparing a wide temperature window SAPO-18 molecular sieve denitration catalyst according to claim 1, characterized in that: The active metal salt in step (2) is at least one of copper nitrate, copper sulfate and copper acetate; The rare earth salt (RM) is at least one of lanthanum nitrate and cerium nitrate; The organic ligand (OL) is at least one of 2-aminopyridine, hexamethylenetetramine and tetraethylenepentamine.

4. The method for preparing a wide temperature SAPO-18 window molecular sieve denitration catalyst according to claim 1, characterized in that: In step (1), the molar ratio of aluminum in the aluminum source, phosphorus in the phosphorus source, silicon in the silicon source and the dual organic structure directing agent is 1:0.1-1.5:0.1-1:0.1-3; In step (2), the molar ratio of active metal salt, rare earth salt and organic ligand is 0.001-0.1:0.001-0.1:0.01-1; The molar ratio of aluminum in the aluminum source to the active metal salt in the precursor mixture is 1:0.001-0.

1.

5. The method for preparing a wide temperature SAPO-18 window molecular sieve denitration catalyst according to claim 4, characterized in that: In step (1), the molar ratio of aluminum in the aluminum source, phosphorus in the phosphorus source, silicon in the silicon source and the dual organic structure directing agent is 1:0.6-1:0.1-0.5:0.4-2; In step (2), the molar ratio of active metal salt, rare earth salt and organic ligand is 0.005-0.02:0.005-0.02:0.02-0.1; The molar ratio of aluminum in the aluminum source to the active metal salt in the precursor mixture is 1:0.005-0.

02.

6. The method for preparing a wide temperature window SAPO-18 molecular sieve denitration catalyst according to claim 1, characterized in that: The crystallization temperature of step (3) is 150-200° C., and the crystallization time is 50-100 h.

7. The method for preparing a wide temperature window SAPO-18 molecular sieve denitration catalyst according to claim 1, characterized in that: The calcination temperature in step (4) is 500-700° C. and the calcination time is 3-6 hours.

8. A wide temperature window SAPO-18 molecular sieve denitration catalyst, characterized in that: The method is prepared by any one of claims 1 to 7.

9. Application of the wide temperature window SAPO-18 molecular sieve denitration catalyst prepared by the method of claim 1 in treating nitrogen oxides in flue gas / exhaust gas.

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