Rare earth molecular sieve as well as preparation method and application thereof

Abstract

The invention discloses a rare earth molecular sieve and a preparation method and application thereof, and belongs to the technical field of NH3-SCR catalysis. A trivalent aluminum source, a tetravalent silicon source and a monovalent alkali source are used as reaction raw materials; a copper amine complex and a quaternary ammonium salt compound are used as a co-template agent; a rare earth source and a rare earth chelate are used as complexing agents; the rare earth molecular sieve is prepared by utilizing a hydrothermal reaction to cooperate with a microwave ultrasonic reaction. The preparation process is simple, and the rare earth molecular sieve with excellent catalytic purification of diesel vehicle tail gas NOx under hydrothermal aging can be prepared.

Description

Technical Field

[0001] The invention belongs to the technical field of NH3-SCR catalysis, and in particular relates to a rare earth molecular sieve and a preparation method and application thereof. Background Art

[0002] NH3 selective catalytic reduction of nitrogen oxides (NH3-SCR) is currently widely used in the elimination of nitrogen oxides in diesel vehicle exhaust aftertreatment systems. Cu-SSZ-13 molecular sieve has NH3-SCR catalytic performance and is therefore widely used in diesel vehicle exhaust NO x purification; however, as diesel vehicle exhaust emission regulations become increasingly stringent, the catalytic activity of this type of molecular sieve catalyst needs to be further improved; in addition, in the diesel vehicle exhaust aftertreatment NH3-SCR system, since the urea solution and the biodiesel additives in the engine lubricating oil contain alkali metals, these alkali metal oxides will react with the Cu-SSZ-13 molecular sieve catalyst, reducing the acid content and active site content of the Cu-SSZ-13 molecular sieve, resulting in a decrease in catalytic activity.

[0003] CN108128784A discloses a method for preparing a Cu-Ce-La-SSZ-13 molecular sieve catalyst. Preparation of liquid A: dissolve sodium aluminate in sodium hydroxide solution and stir until the solution is clear and transparent; preparation of liquid B: slowly drip tetraethylene pentamine in copper sulfate solution, carry out complexation reaction at 25-30°C, add cerium nitrate hexahydrate and lanthanum nitrate hexahydrate in sequence after the reaction, stir and react, and obtain liquid B after the reaction. Liquid B is slowly added to liquid A, mixed evenly, and then silica sol is slowly dripped, stirred and aged. The obtained sol-gel precursor is subjected to homogeneous hydrothermal reaction at 140-160°C for 72h-96h. After crystallization, it is centrifuged, washed with water to PH=7, dried, and then calcined at 500-550°C for 4-8h to obtain Cu-Ce-La-SSZ-13 molecular sieve. The molecular sieve is an aluminum-rich molecular sieve with a silicon-aluminum ratio of <10. The catalytic ability of the molecular sieve under hydrothermal aging is weak and the resistance to alkali metal poisoning is not mentioned.

[0004] CN111762795B discloses a molecular sieve containing rare earth elements and a production method thereof. A molecular sieve framework mixture including a silicon source, an aluminum source, a template, an organic base and water is subjected to a first hydrothermal reaction to obtain a first reaction product; the first reaction product, an ammonium source and a copper source are mixed, and then a second hydrothermal reaction is performed to obtain a second reaction product; the second reaction product is mixed with a rare earth source, and then a third hydrothermal reaction is performed to obtain a third reaction product; the third reaction product is separated to obtain a solid reaction product, and the solid reaction product is roasted to obtain a molecular sieve containing rare earth elements. The molecular sieve has a silicon-aluminum ratio of <20 and the steps of adding a copper source and a rare earth source are cumbersome.

[0005] Therefore, there is an urgent need to provide a molecular sieve with a simple preparation process, excellent catalytic ability in fresh state and hydrothermal aging state and resistance to alkali metal poisoning. Summary of the invention

[0006] In view of the above technical problems, the present invention proposes a rare earth molecular sieve and a preparation method and application thereof.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] One of the technical solutions of the present invention:

[0009] A method for preparing a rare earth molecular sieve comprises the following steps:

[0010] A trivalent aluminum source, a tetravalent silicon source and a monovalent alkali source are used as reaction raw materials, a copper amine complex and a quaternary ammonium salt compound are used as co-template agents, a rare earth source and a rare earth chelate are used as complexing agents, and a hydrothermal reaction is used in coordination with a microwave ultrasonic reaction to prepare a rare earth molecular sieve.

[0011] Preferably, the quaternary ammonium salt compound includes one or more of N,N,N-trimethyladamantanammonium, benzyltrimethylammonium, tetraethylammonium hydroxide or tetrapropylammonium hydroxide. More preferably, the quaternary ammonium salt compound is N,N,N-trimethyladamantanammonium.

[0012] Preferably, the rare earth source is selected from one or more of rare earth nitrate, rare earth acetate, rare earth chloride or rare earth oxide; wherein the rare earth element includes one or more of lanthanum, cerium, praseodymium, neodymium, samarium, europium, ytterbium or yttrium; more preferably lanthanum, cerium, praseodymium, europium and yttrium.

[0013] The trivalent aluminum source is selected from one or more of boehmite, aluminum hydroxide, aluminum sol or sodium aluminate; more preferably, sodium aluminate or aluminum sol.

[0014] The tetravalent silicon source is selected from one or more of silicate, fumed silica, and silica sol; more preferably, it is silica sol.

[0015] Preferably, the molar ratio of the trivalent aluminum source, the tetravalent silicon source and the monovalent alkali source is: 1:(10-50):(1-10).

[0016] Preferably, the preparation method comprises the following steps:

[0017] (1) preparing a copper amine complex solution;

[0018] (2) adding a quaternary ammonium salt compound, a monovalent alkali source, a trivalent aluminum source, a rare earth source, a rare earth chelating agent and a tetravalent silicon source to the copper amine complex solution in sequence and mixing them evenly;

[0019] (3) subjecting the mixed solution obtained in step (2) to a hydrothermal reaction and a microwave ultrasonic reaction in sequence, and drying and calcining the obtained product to prepare the rare earth molecular sieve.

[0020] Preferably, the specific conditions of the hydrothermal reaction in step (3) are:

[0021] At 120-200°C, the reaction time is 2-7 days.

[0022] Preferably, the specific conditions of the microwave ultrasonic reaction in step (3) are:

[0023] The product after the hydrothermal reaction is added to an ammonium source solution, and the reaction is carried out for 10 to 24 hours at a temperature of 40 to 90° C., a microwave power of 100 to 1500 W, and an ultrasonic power of 100 W to 1000 W.

[0024] Preferably, the calcination process is carried out at 450-800° C. for 3-8 hours.

[0025] The second technical solution of the present invention:

[0026] A rare earth molecular sieve is prepared by the above preparation method.

[0027] The specific surface area of ​​the molecular sieve is greater than 600m 2 / g; pore volume is 0.1-0.5mL / g, pore diameter is 1-2nm; hydrogen consumption of the molecular sieve is 1-2.5mmol / g; acid content of the molecular sieve is 1mmol / g-2mmol / g. More preferably, the specific surface area of ​​the molecular sieve is greater than 700m 2 / g, the pore volume is 0.3-0.5mL / g, and the pore diameter is 1-1.5nm; the hydrogen consumption of the molecular sieve is 1.5-2.5mmol / g, wherein the hydrogen consumption can measure the redox performance of the catalyst; the acid content of the molecular sieve is 1.3-2mmol / g, and the acid content can measure the ammonia storage performance of the catalyst.

[0028] The third technical solution of the present invention:

[0029] For example, the rare earth molecular sieve mentioned above can effectively reduce the NO x Purification applications.

[0030] Compared with the prior art, the present invention has the following advantages and technical effects:

[0031] The invention discloses a method for preparing a rare earth-based molecular sieve denitration catalyst, which has a simple and easy process, a wide range of applications, saves production costs, and is suitable for industrial production.

[0032] The rare earth molecular sieve prepared by the method of the present invention has a wider silicon-aluminum ratio range, which broadens its application in eliminating nitrogen oxides in diesel vehicle exhaust aftertreatment systems; further, the molecular sieves with a silicon-aluminum ratio of 20 or 25 prepared in Examples 1 and 2 of the present invention have also been proven to have excellent fresh catalytic performance and hydrothermal aging performance; in addition, the rare earth-based molecular sieve denitrification catalyst prepared by the present invention also has good resistance to alkali metal poisoning, that is, the catalyst can maintain high catalytic activity and stability in an environment containing alkali metal pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0034] Figure 1 This is a scanning electron microscope image of the rare earth molecular sieve prepared in Example 1 of the present invention;

[0035] Figure 2 This is a scanning electron microscope image of the rare earth molecular sieve prepared in Example 2 of the present invention;

[0036] Figure 3 This is a scanning electron microscope image of the molecular sieve prepared in Comparative Example 1 of the present invention;

[0037] Figure 4 This is a scanning electron microscope image of the molecular sieve prepared in Comparative Example 2 of the present invention;

[0038] Figure 5 This is a scanning electron microscope image of the molecular sieve prepared in Comparative Example 3 of the present invention;

[0039] Figure 6 XRD diagrams of the molecular sieves prepared in Examples 1-2 and Comparative Examples 1-3 of the present invention;

[0040] Figure 7 The molecular sieves prepared in Examples 1-2 and Comparative Examples 1-3 catalyze NO x Conversion rate graph;

[0041] Figure 8 The molecular sieves prepared in Examples 1-2 and Comparative Examples 1-3 were hydrothermally aged to catalyze NO x Conversion rate graph. DETAILED DESCRIPTION

[0042] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0043] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0044] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0045] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0046] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0047] The invention provides a method for preparing a rare earth molecular sieve. The method uses a trivalent aluminum source, a tetravalent silicon source, and a monovalent alkali source as main raw materials, uses a copper amine complex and a quaternary ammonium salt compound as co-template agents, and uses a rare earth source and a rare earth chelate as complexing agents to prepare the rare earth molecular sieve; wherein the copper amine complex is obtained by mixing a divalent copper source with a tetraethylenepentamine solution.

[0048] The skeleton of the molecular sieve prepared by the invention comprises aluminum and silicon elements, and the active components of the molecular sieve comprise rare earth elements and copper elements; and the molecular sieve is a CHA-configured molecular sieve, and its microscopic morphology is irregular block.

[0049] In some preferred embodiments, the rare earth element includes one or more of lanthanum, cerium, praseodymium, neodymium, samarium, europium, ytterbium, and yttrium.

[0050] In some preferred embodiments, the mass of rare earth elements is 0.1wt% to 3wt% of the molecular sieve framework, and the mass of rare earth elements is calculated as rare earth elements; the mass of copper elements is 2 to 6wt% of the molecular sieve framework, and the mass of copper elements is calculated as Cu.

[0051] In some preferred embodiments, the specific surface area of ​​the molecular sieve is greater than 700 m 2 / g, the pore volume is 0.3-0.5mL / g, the pore diameter is 1-1.5nm, the hydrogen consumption of the molecular sieve is 1.5-2.5mmol / g, and the acid content of the molecular sieve is 1.3-2mmol / g.

[0052] In some preferred embodiments, the rare earth chelating agent includes: diethylenetriamine pentaacetic acid calcium trisodium salt, ethylenediamine-N, N-disuccinic acid trisodium salt, diethyl oxaloacetate sodium salt, ethylenediaminetetraacetic acid disodium salt, diethylenetriamine pentaacetic acid pentasodium salt, ethylenediaminetetraacetic acid tetrasodium salt, nitrilotriacetic acid sodium salt, ethylenediaminetetraacetic acid calcium disodium salt, N-hydroxyethylethylenediaminetriacetic acid trisodium salt, ethylenediaminetetraacetic acid trisodium salt, triphenylphosphine trisulfonic acid sodium salt, N-(2-hydroxyethyl)ethylenediamine-N, N, N-triacetic acid trisodium salt, N-methyliminodiacetic acid disodium salt, 1,3-benzoxazol-2-acetic acid sodium salt, ethylenediaminetetraacetic acid disodium magnesium salt or 6-phosphogluconate trisodium salt, any one or more of them, and the addition of the rare earth chelating agent is beneficial to the interaction between the rare earth ions and the molecular sieve framework, and is beneficial to improving the hydrothermal stability and anti-alkali metal poisoning performance of the molecular sieve.

[0053] In some preferred embodiments, the molar ratio of the rare earth source to the chelating agent is 1:1-10; wherein the preferred molar ratio is 1:2-8.

[0054] In some preferred embodiments, the rare earth metal salt (rare earth source) is one or more of rare earth nitrate, rare earth acetate, rare earth chloride or rare earth oxide; more preferably, the rare earth source is rare earth nitrate or rare earth acetate.

[0055] The molar ratio of the rare earth source to the aluminum source can be 0.05 to 2.3:1, preferably 0.05 to 1.5:1. The aluminum source is calculated as alumina, and the rare earth source is calculated as a rare earth element. Within the limited molar ratio range, it is beneficial to improve the catalytic activity of the molecular sieve.

[0056] In some preferred embodiments, the trivalent aluminum source is selected from one or more of boehmite, aluminum hydroxide, aluminum sol or sodium aluminate. Preferably, the trivalent aluminum source is selected from sodium aluminate or aluminum sol. More preferably, the aluminum source is selected from sodium aluminate. The aluminum sol has a solid content of 8 to 20 wt%, a pH of 3 to 6, a viscosity of 35 to 50 Pa.s, and a particle size of 5 to 15 nm.

[0057] In some preferred embodiments, the tetravalent silicon source is selected from one or more of silicate, fumed silica, and silica sol. Preferably, the silicon source is selected from one or both of silica sol and fumed silica. More preferably, the silicon source is silica sol. The solid content of the silica sol is 15-30 wt%, the pH is 3-10, and the density is 1-2 g / cm 3, particle size is 5 to 15 nm.

[0058] The molar ratio of the tetravalent silicon source to the trivalent aluminum source is 10-50:1, preferably 10-40:1; the aluminum source is calculated as alumina, and the silicon source is calculated as silicon dioxide, so that the synthesized rare earth molecular sieve has a wide silicon-aluminum ratio.

[0059] In some preferred embodiments, the monovalent alkali source is selected from an inorganic base or an organic base; wherein the inorganic base is selected from sodium hydroxide and / or potassium hydroxide; the organic base is selected from one or more of sodium alcoholate, potassium alcoholate or tetraethylammonium hydroxide. Preferably, the inorganic base is selected from one or a mixture of sodium hydroxide and potassium hydroxide, which is conducive to improving the catalytic activity of the molecular sieve at high temperature; the molar ratio of the monovalent alkali source to the trivalent aluminum source is: 1 to 10:1, preferably: 2 to 7:1, the alkali source is calculated as sodium hydroxide, and the aluminum source is calculated as aluminum oxide, so that the molecular sieve formed has an irregular block morphology.

[0060] In some preferred embodiments, the co-template agent is a copper amine complex and a quaternary ammonium salt compound. The quaternary ammonium salt compound is selected from one or more of N,N,N-trimethylammonium adamantanium, benzyltrimethylammonium, tetraethylammonium hydroxide or tetrapropylammonium hydroxide. Preferably, N,N,N-trimethylammonium adamantanium and the copper amine complex are co-template agents. The molar ratio of the co-template agent to the aluminum source can be 1.3 to 10:1; preferably 1.3 to 7.5:1; the molar ratio of N,N,N-trimethylammonium adamantanium to the aluminum source is: 1 to 5:1, preferably: 1 to 4:1. The aluminum source is calculated as alumina. The use of the two as co-template agents can widen the synthesized silicon-aluminum ratio width, which can improve the catalytic activity of the molecular sieve.

[0061] In some preferred embodiments, the copper source is selected from one or more of copper nitrate, copper sulfate, copper chloride, copper gluconate, copper propionate, copper acetate, copper isopropionate and glutamic acid chelated copper. Preferably, the copper source is copper sulfate, which is conducive to forming a stable copper amine complex with tetraethylenepentamine. The generated copper amine complex can participate in the formation of the molecular sieve framework on the one hand, and on the other hand, it can allow copper to enter the ring of the molecular sieve in the form of more active copper, which is conducive to improving the utilization rate of Cu in the molecular sieve. The molar ratio of the copper source to the aluminum source is 0.3 to 5:1; preferably 0.3 to 3.5:1, and the copper source is calculated as divalent copper ions.

[0062] In some preferred embodiments, the tetravalent silicon source is calculated as silicon dioxide, the trivalent aluminum source is calculated as aluminum oxide, the alkali source is calculated as sodium hydroxide, and the rare earth source is calculated as a rare earth element. The molar ratio of silicon source: aluminum source: alkali: divalent copper ion: tetraethylenepentamine: adamantane: water: rare earth source is: (10-50): 1: (1-10): (0.3-5): (0.3-5): (1-5): (150-1000): (0.05-2.3).

[0063] The above raw materials can be used to prepare rare earth molecular sieves by hydrothermal reaction method, and the specific steps are as follows:

[0064] (1) adding a copper source containing divalent copper ions and tetraethylenepentamine to an aqueous solution in sequence to form a first mixture;

[0065] (2) mixing the quaternary ammonium salt compound with the first mixture to form a second mixture;

[0066] adding a monovalent alkali source, a trivalent aluminum source, a rare earth source, and a rare earth chelating agent to the second mixture to form a third mixture;

[0067] mixing a tetravalent silicon source with the third mixture to form a fourth mixture;

[0068] (3) Crystallizing the fourth mixture (hydrothermal reaction), and washing and drying the crystallized product.

[0069] In some preferred embodiments, tetraethylenepentamine and tetravalent silicon source are added to the system dropwise, so that a rare earth molecular sieve with high catalytic activity can be obtained.

[0070] In some preferred embodiments, the hydrothermal reaction temperature of step (3) is 120-200° C., and the reaction time is 2-7 days. Preferably, the hydrothermal reaction temperature is 140-180° C., and the reaction time is 3-5 days. This is beneficial to the synthesis of rare earth molecular sieves.

[0071] In some preferred embodiments, the drying method in step (3) is microwave drying, wherein the microwave drying temperature is 60-110° C., and the microwave drying time is 3-24 h. More preferably, the microwave drying is performed at 100° C. for 12 h.

[0072] In some preferred embodiments, the preparation method further comprises step (4) after step (3): adding the microwave-dried product to an ammonium source solution for treatment, performing microwave ultrasonic reaction, washing and filtering, and then performing a second microwave drying to obtain a second dried product, and roasting the second dried product.

[0073] In some preferred embodiments, the ammonium source is selected from one or both of ammonium nitrate and ammonium chloride. Preferably, the ammonium source is ammonium nitrate. The concentration of the ammonium source solution is: 1-2 mol / L, preferably 1.25-1.75 mol / L; the temperature of the microwave ultrasonic reaction is 40-90°C, and the reaction time is 10-24h. Preferably, the temperature of the microwave ultrasonic reaction is 70°C-90°C, and the reaction time is 12-20h; wherein the microwave power is 100-1500W, and its preferred power range is 700W-1000W, and the ultrasonic power is 100W-1000W, and its preferred power range is 500W-700W.

[0074] The secondary microwave drying time is 10 to 15 hours, preferably 10 to 12 hours, the secondary drying temperature is 60 to 110° C., preferably 80 to 100° C.; the microwave roasting temperature is 450 to 800° C., preferably 500 to 600° C. Preferably, the roasting time is 3 to 8 hours, preferably 4 to 7 hours. This is conducive to improving the hydrothermal aging performance of the rare earth molecular sieve.

[0075] The "room temperature" in the present invention refers to 20-30°C unless otherwise specified.

[0076] The raw materials used in the present invention are all purchased from the market.

[0077] The technical solution of the present invention is further illustrated by the following embodiments.

[0078] Example 1

[0079] (1) at room temperature, 0.0035 mol of copper sulfate is added to 2.23 mol of distilled water to form an aqueous solution, 0.0035 mol of tetraethylene pentamine is slowly added dropwise to the aqueous solution, and the mixture is stirred thoroughly to form a first mixture;

[0080] (2) 0.0105 mol of N,N,N-trimethylammonium adamantanium was mixed uniformly with the first mixture to form a second mixture; 0.0105 mol of sodium hydroxide, 0.007 mol of sodium aluminate, 0.33 mmol of cerium acetate, and 2 mmol of N-(2-hydroxyethyl)ethylenediamine-N,N,N-triacetic acid trisodium salt solution were added to the second mixture and stirred uniformly under heating reflux at a temperature of 40° C. to form a third mixture; 0.07 mol of silica sol (solid content: 30%, pH: 9.1, density: 1.2 g / cm 3 ) is mixed with the third mixture and stirred until a uniform gel is formed to form a fourth mixture;

[0081] (3) the fourth mixture was placed into a hydrothermal reactor lined with polytetrafluoroethylene, and crystallized at 160° C. for 4 days, the crystallized product was washed, and dried at 100° C. for 12 h in a microwave (microwave power of 2000 W);

[0082] (4) The dried product was added to 100 mL of ammonium nitrate solution with a concentration of 1.25 mol / L, treated for 12 h under the conditions of microwave power of 1000 W, ultrasonic power of constant 600 W, and temperature of 80°C, washed and filtered, and then microwave dried at 110°C for 12 h to obtain a secondary dried product; the secondary dried product was calcined at 600°C for 4 h in a microwave (microwave power of 1000 W) to obtain a rare earth molecular sieve.

[0083] Example 2

[0084] (1) at room temperature, 0.0072 mol of copper sulfate is added to 2.23 mol of distilled water to form an aqueous solution, 0.0072 mol of tetraethylene pentamine is slowly added dropwise to the aqueous solution, and the mixture is stirred thoroughly to form a first mixture;

[0085] (2) 0.010 mol of N,N,N-trimethylammonium adamantanium was mixed uniformly with the first mixture to form a second mixture; 0.011 mol of potassium hydroxide, 0.0048 mol of aluminum sol (solid content 10 wt%, pH 4, viscosity 43 mPa.s, particle size 10 nm), 1 mmol of europium nitrate, and 3 mmol of diethylenetriamine pentaacetic acid pentasodium salt were added to the second mixture and stirred uniformly under heating reflux at 30° C. to form a third mixture; 0.12 mol of silica sol (solid content 30%, pH: 9.1, density 1.2 g / cm 3 ) is mixed with the third mixture and stirred until a uniform gel is formed to form a fourth mixture;

[0086] (3) the fourth mixture was placed into a polytetrafluoroethylene-lined hydrothermal reactor, and crystallized at 170° C. for 4 days. The crystallized product was washed and dried at 100° C. in a microwave (microwave power of 2000 W) for 12 h.

[0087] (4) The dried product was added to 100 mL of 1.5 mol / L ammonium nitrate solution, treated for 12 h under the conditions of microwave power of 1000 W, ultrasonic power of 600 W, and temperature of 70 ° C, washed and filtered, and then microwave dried at 110 ° C for 12 h to obtain a secondary dried product; the secondary dried product was calcined at 600 ° C for 3 h in a microwave (microwave power of 1000 W) to obtain a rare earth molecular sieve.

[0088] Comparative Example 1

[0089] 0.0035 mol of copper sulfate, 0.0105 mol of N,N,N-trimethylammonium adamantanium, 0.0105 mol of sodium hydroxide, and 0.007 mol of sodium aluminate were added to 2.23 mol of distilled water and 0.073 mol of silica sol (solid content 30%, pH: 9.1, density 1.2 g / cm 3 ), stirred until a uniform gel is formed, the mixture is subjected to a hydrothermal reaction, crystallized at 160°C for 4 days, the crystallized product is washed, and dried at 100°C for 12 hours. The primary dried product obtained by drying is added to 100mL of 1.25mol / L ammonium nitrate solution, treated at room temperature for 12 hours, washed and filtered, and then dried at 110°C for 12 hours to obtain a secondary dried product; the secondary dried product is calcined at 600°C in air for 4 hours to obtain a copper-containing molecular sieve.

[0090] Comparative Example 2

[0091] 0.0072 mol of copper sulfate, 0.010 mol of N,N,N-trimethylammonium adamantanium, 0.011 mol of potassium hydroxide, 0.0048 mol of aluminum sol (solid content 10 wt%, pH 4, viscosity 43 mPa.s, particle size 10 nm) were added to 2.23 mol of distilled water and 0.12 mol of silica sol (solid content 30%, pH: 9.1, density 1.2 g / cm 3 ), stirred until a uniform gel is formed, crystallized at 170°C for 4 days, washed the crystallized product, dried at 100°C for 12h to obtain a primary dried product; 0.15 mol of ammonium nitrate is dissolved in 100 mL of aqueous solution, the primary dried product (i.e., copper CHA zeolite containing K ions) is added thereto, treated at room temperature for 12 hours, washed and filtered, and then dried at 110°C for 12h to obtain a secondary dried product. The product is calcined at 600°C in air for 4h to obtain a copper-containing zeolite molecular sieve.

[0092] Comparative Example 3

[0093] (1) at room temperature, 0.0035 mol of copper sulfate is added to 2.23 mol of distilled water to form an aqueous solution, 0.0035 mol of tetraethylene pentamine is slowly added dropwise to the aqueous solution, and the mixture is stirred thoroughly to form a first mixture;

[0094] (2) 0.01055 mol of sodium hydroxide, 0.007 mol of sodium aluminate and 0.07 mol of silica sol (solid content 30%, pH: 9.1, density 1.2 g / cm 3 ) is added to the above mixed solution, stirred to form a uniform gel, crystallized in a hydrothermal reactor at 160°C for 4 days, the crystallized product is washed, dried at 100°C for 12h, the primary dried product is added to 100mL of 1.5mol / L ammonium nitrate solution, treated at room temperature for 12h, washed and filtered, and then dried at 110°C for 12h to obtain a secondary dried product; the secondary dried product is calcined at 600°C in air for 4h.

[0095] The physical and chemical parameters of the catalysts prepared in the above Examples 1-2 and Comparative Examples 1-3 are shown in Table 1:

[0096] Table 1

[0097]

[0098] Figure 6The XRD diagrams of the molecular sieves prepared in Examples 1-2 of the present invention and Comparative Examples 1-3 show that Examples 1-2 have a typical CHA configuration structure, indicating that the SSZ-13 molecular sieve can be synthesized using a copper amine complex and N,N,N-trimethyladamantanium as co-templates, and no corresponding rare earth peaks and copper peaks are observed, indicating that the rare earth and copper mainly enter the rings in the molecular sieve; in Comparative Examples 1-2, CHA characteristic peaks and CuO characteristic peaks can be observed, indicating that the molecular sieve SSZ-13 can be synthesized using only N,N,N-trimethyladamantanium, but copper mainly exists in the form of CuO; in Comparative Example 3, it can be observed that the large package peak at 20-30o is a characteristic peak of SiO2, and no characteristic peak of CHA is observed, indicating that it is not feasible to synthesize a molecular sieve with a high silicon-to-aluminum ratio using only Cu-TEPA, and a CuO characteristic peak is observed, indicating that copper mainly exists in the form of CuO.

[0099] Effect verification

[0100] The molecular sieve catalysts prepared in Examples 1-2 and Comparative Examples 1-3 were tested for NH3-SCR activity:

[0101] (I) The results of nitrogen oxide conversion rate of fresh samples are shown in Figure 2 and Figure 7 The test conditions are: [NO] = 500ppm; [NH3] = 500ppm; [O2] = 10vol%; [C3H6] = 200ppm; [CO] = 8vol%; [H2O] = 5vol%; N2 as the balance gas; total flow rate is 750mL / min; space velocity = 150000h -1 .

[0102] Table 2

[0103]

[0104] (ii) The catalyst hydrothermal aging conditions are: aging at 800°C for 16 h, with the amount of water being 10 vol% of the total gas volume.

[0105] The catalysts in Examples 1-2 and Comparative Examples 1-3 were tested for NH3-SCR activity. The results of nitrogen oxide conversion rates of aged samples are shown in Figures 3 and Figure 8 shown.

[0106] Table 3

[0107]

[0108] Conclusion: As shown in Table 2-3 and Figure 7-8As shown, whether the silicon-aluminum ratio is 20 or 25, the catalytic activity of the rare earth molecular sieve synthesized by the dual template and rare earth chelating agent of the present invention is better than that of the molecular sieve with a single template. At the same time, under the condition of silicon-aluminum ratio>15, the molecular sieve cannot be synthesized by simply using the copper ammonium complex as a single template. Therefore, the use of dual templates can broaden the silicon-aluminum ratio range of the molecular sieve. At the same time, the rare earth and copper added in situ are easy to produce strong interactions, simplifying the production steps, and showing excellent fresh catalytic performance and hydrothermal aging performance.

[0109] (III) The catalysts in Examples 1 to 2 and Comparative Examples 1 to 3 were prepared as alkali-poisoned catalysts, and NH3-SCR activity tests were performed. The results of nitrogen oxide conversion rates are shown in Table 4. The alkali poisoning method is as follows:

[0110] Take 5g of the catalyst prepared in Examples 1-2 and Comparative Examples 1-3, dissolve 0.37g of NaNO3 in deionized water, and then add the NaNO3 aqueous solution drop by drop on the above molecular sieve by an equal volume impregnation method, impregnate at room temperature for 6h, microwave dry at 110°C (microwave power is 2000W) overnight, and microwave roast at 500°C for 2h (microwave power is 1000W) to obtain Na + Catalyst with 2% Na / gcat loading.

[0111] Test conditions: [NO] = 500ppm; [NH3] = 500ppm; [O2] = 10vol%; [C3H6] = 200ppm; [CO] = 8vol%; [H2O] = 5vol%; N2 as balance gas; total flow rate 750mL / min; space velocity = 150000h -1 .

[0112] Table 4

[0113]

[0114] Conclusion: As shown in Table 4, alkali metal Na poisoning will reduce the catalyst activity to a certain extent, but the activity of Examples 1 and 2 is much greater than that of Comparative Examples 1 to 3. This shows that the rare earth molecular sieve synthesized by using dual templates and rare earth chelating agents in the present invention has better alkali metal poisoning resistance than the molecular sieve with a single template.

[0115] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing a rare earth molecular sieve, characterized in that: The following steps are involved: Trivalent aluminum source, tetravalent silicon source and monovalent alkali source are used as reaction raw materials; copper amine complex and quaternary ammonium salt compounds are used as co-template agents; rare earth source and rare earth chelate are used as complexing agents; and rare earth molecular sieves are prepared by hydrothermal reaction in coordination with microwave ultrasonic reaction.

2. The method for preparing a rare earth molecular sieve according to claim 1, characterized in that: The quaternary ammonium salt compound includes one or more of N,N,N-trimethyladamantanammonium, benzyltrimethylammonium, tetraethylammonium hydroxide or tetrapropylammonium hydroxide.

3. The method for preparing a rare earth molecular sieve according to claim 1, characterized in that: The rare earth source is selected from one or more of rare earth nitrate, rare earth acetate, rare earth chloride, and rare earth oxide; the rare earth elements in the rare earth source include one or more of lanthanum, cerium, praseodymium, neodymium, samarium, europium, ytterbium, and yttrium; The trivalent aluminum source is selected from one or more of boehmite, aluminum hydroxide, aluminum sol or sodium metaaluminate; The tetravalent silicon source is selected from one or more of silicate, fumed silica or silica sol.

4. The method for preparing a rare earth molecular sieve according to claim 1 or 3, characterized in that: The molar ratio of the trivalent aluminum source, the tetravalent silicon source and the monovalent alkali source is: 1:(10-50):(1-10).

5. The method for preparing a rare earth molecular sieve according to claim 1, characterized in that: The following steps are involved: (1) preparing a copper amine complex solution; (2) adding a quaternary ammonium salt compound, a monovalent alkali source, a trivalent aluminum source, a rare earth source, a rare earth chelating agent and a tetravalent silicon source to the copper amine complex solution in sequence and mixing them evenly; (3) subjecting the mixed solution obtained in step (2) to a hydrothermal reaction and a microwave ultrasonic reaction in sequence, and drying and calcining the obtained product to prepare the rare earth molecular sieve.

6. The method for preparing a molecular sieve according to claim 5, characterized in that: The specific conditions of the hydrothermal reaction in step (3) are: At 120-200°C, the reaction time is 2-7 days.

7. The method for preparing a rare earth molecular sieve according to claim 5, characterized in that: The specific conditions of the microwave ultrasonic reaction in step (3) are: The product after the hydrothermal reaction is added to an ammonium source solution, and the reaction is carried out for 10 to 24 hours at a temperature of 40 to 90° C., a microwave power of 100 to 1500 W, and an ultrasonic power of 100 W to 1000 W.

8. A rare earth molecular sieve, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 7.

9. A rare earth molecular sieve according to claim 8, characterized in that: The specific surface area of ​​the molecular sieve is greater than 600m 2 / g; pore volume is 0.1~0.5mL / g, pore diameter is 1~2nm; The hydrogen consumption of the molecular sieve is 1 to 2.5 mmol / g; The acid content of the molecular sieve is 1 mmol / g to 2 mmol / g.

10. A rare earth molecular sieve as claimed in claim 8 or 9 for purifying NOx from diesel exhaust x Application in.

Images