A rare earth molecular sieve, its preparation method and application

Abstract

The present invention discloses a rare earth molecular sieve, a preparation method thereof and an application thereof, belonging to the technical field of NH3-SCR catalysis; by using a trivalent aluminum source, a tetravalent silicon source and a monovalent base source as reaction raw materials; a copper amine complex and a quaternary ammonium salt compound as co-template agents; a rare earth source and a rare earth chelate as complexing agents; a rare earth molecular sieve is prepared by using a hydrothermal reaction in cooperation with a microwave ultrasonic reaction. The preparation process of the present invention is simple, and a rare earth molecular sieve with excellent catalytic purification of diesel vehicle exhaust gas NO x under hydrothermal aging can be prepared.

Description

Technical Field

[0001] The present invention belongs to the technical field of NH 3 -SCR catalysis, and particularly relates to a rare earth molecular sieve, a preparation method thereof and an application. Background Art

[0002] NH 3 Selective catalytic reduction of nitrogen oxides (NH 3 -SCR) is currently widely used for the elimination of nitrogen oxides in the diesel vehicle exhaust after-treatment system. The Cu-SSZ-13 molecular sieve has NH 3 -SCR catalytic performance, and thus is widely used in the purification of diesel vehicle exhaust NO x ; however, with the increasingly strict requirements of diesel vehicle exhaust emission regulations, the catalytic activity of such molecular sieve catalysts needs to be further improved; in addition, in the diesel vehicle exhaust after-treatment NH 3 -SCR system, since the urea solution and the biodiesel additive 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 amount and the amount of active sites of the Cu-SSZ-13 molecular sieve, resulting in a reduction in catalytic activity.

[0003] CN108128784A discloses a preparation method of a Cu-Ce-La-SSZ-13 molecular sieve catalyst. Preparation of solution A: Dissolve sodium aluminate in a sodium hydroxide solution and stir until the solution is clear and transparent; Preparation of solution B: Slowly drop tetraethylenepentamine into a copper sulfate solution, carry out a complexation reaction at 25-30 °C, and after the reaction ends, sequentially add cerium nitrate hexahydrate and lanthanum nitrate hexahydrate, stir and react, and obtain solution B after the reaction ends. Slowly add solution B to solution A, mix evenly, then slowly drop silica sol, stir and age, subject the obtained sol-gel precursor to homogeneous hydrothermal reaction at 140-160 °C for 72 h-96 h, after crystallization ends, centrifuge and separate, wash with water until pH = 7, dry, and then calcine at 500-550 °C for 4-8 h to obtain the Cu-Ce-La-SSZ-13 molecular sieve. This molecular sieve is an aluminum-rich molecular sieve with a silica-alumina ratio <10, and the catalytic ability of the molecular sieve under hydrothermal aging is weak and the alkali metal poisoning resistance performance 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 agent, 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 subjected to a second hydrothermal reaction to obtain a second reaction product; the second reaction product and a rare earth source are mixed and then subjected to a third hydrothermal reaction to obtain a third reaction product; the third reaction product is separated to obtain a solid reaction product, and the solid reaction product is calcined to obtain a molecular sieve containing rare earth elements. The silicon-aluminum ratio of this molecular sieve is <20, and the steps of adding the copper source and the 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 under fresh and hydrothermal aging conditions, and alkali metal poisoning resistance. Summary of the Invention

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

[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 preparation method of a rare earth molecular sieve, comprising the following steps:

[0010] Using a trivalent aluminum source, a tetravalent silicon source and a monovalent base source as reaction raw materials, a copper amine complex and a quaternary ammonium salt compound as co-template agents; a rare earth source and a rare earth chelate as complexing agents; and using a hydrothermal reaction in combination 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-trimethyladamantylammonium, benzyltrimethylammonium, tetraethylammonium hydroxide or tetrapropylammonium hydroxide. More preferably, the quaternary ammonium salt compound is N,N,N-trimethyladamantylammonium.

[0012] Preferably, the rare earth source is selected from one or more of rare earth nitrates, rare earth acetates, rare earth chlorides or rare earth oxides; wherein, the rare earth elements include 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 metaaluminate; more preferably sodium metaaluminate or aluminum sol.

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

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

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

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

[0018] (2) Sequentially add a quaternary ammonium salt compound, a monovalent base 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 and mix evenly;

[0019] (3) Subject the mixed solution obtained in step (2) to hydrothermal reaction and microwave ultrasonic reaction in sequence, and dry and calcine 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 a temperature of 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] Add the product after the hydrothermal reaction to an ammonium source solution, and react for 10 - 24 h under the conditions of a temperature of 40 - 90 °C, a microwave power of 100 - 1500 W and an ultrasonic power of 100 W - 1000 W.

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

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

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

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

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

[0029] As described above, the application of a rare earth molecular sieve in purifying NO in diesel vehicle exhaust x .

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

[0031] The preparation method of a rare earth-based molecular sieve denitration catalyst disclosed by the present invention is simple, easy to implement, has a wide application range, saves production costs, and is suitable for industrial production;

[0032] Moreover, the rare earth molecular sieve prepared by the method of the present invention has a wide range of silica-alumina ratios, broadening its application in eliminating nitrogen oxides in the after-treatment system of diesel vehicle exhaust; further, the molecular sieves with silica-alumina ratios of 20 or 25 prepared in Example 1 and Example 2 of the present invention also prove that they have excellent fresh catalytic performance and hydrothermal aging performance; in addition, the rare earth-based molecular sieve denitration catalyst prepared by the present invention also has good alkali metal poisoning resistance, 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 this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation to this application. In the drawings:

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

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

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

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

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

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

[0040] Figure 7 is the conversion rate graph of NO catalyzed by the molecular sieves prepared in Examples 1-2 and Comparative Examples 1-3 x ;

[0041] Figure 8 The conversion rate diagram of NO catalyzed by the molecular sieves prepared by using Examples 1-2 and Comparative Examples 1-3 after hydrothermal aging. x is shown in the figure. Detailed implementation manners

[0042] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation to the present invention, but should be understood as a more detailed description of certain aspects, characteristics and implementation schemes of the present invention.

[0043] It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0044] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can 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 related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0045] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the present invention specification, which are obvious to those skilled in the art. Other implementation manners obtained from the present invention specification are obvious to those skilled in the art. The present invention specification and examples are only exemplary.

[0046] Regarding "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0047] The present 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 base 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 a rare earth molecular sieve; wherein the copper amine complex is obtained by mixing a divalent copper source with a tetraethylene pentamine 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 metaaluminate. Preferably, the trivalent aluminum source is selected from sodium metaaluminate or aluminum sol. More preferably, the aluminum source is sodium metaaluminate. Among them, the aluminum sol has a solid content of 8-20 wt%, a pH of 3-6, a viscosity of 35-50 Pa·s, and a particle size of 5-15 nm.

[0057] In some preferred embodiments, the tetravalent silicon source is selected from one or more of silicate esters, fumed silica, and silica sol. Preferably, the silicon source is selected from one or two of silica sol or fumed silica. More preferably, the silicon source is silica sol. The silica sol has a solid content of 15-30 wt%, a pH of 3-10, and a density of 1-2 g / cm 3 , and a particle size of 5-15 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 silica, and the rare earth molecular sieve synthesized in this way has a wide silica-alumina ratio.

[0059] In some preferred embodiments, the monovalent base source is selected from inorganic bases or organic bases; among them, the inorganic bases are selected from sodium hydroxide and / or potassium hydroxide; the organic bases are selected from one or more of sodium alkoxide, potassium alkoxide or tetraethylammonium hydroxide. Preferably, the inorganic base is selected from one or a mixture of sodium hydroxide and potassium hydroxide, which is beneficial to improving the catalytic activity of the molecular sieve at high temperatures; the molar ratio of the monovalent base source to the trivalent aluminum source is: 1-10:1, preferably: 2-7:1, the base source is calculated as sodium hydroxide, and the aluminum source is calculated as aluminum oxide, and the molecular sieve formed in this way 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. Among them, the quaternary ammonium salt compound is selected from one or more of N,N,N-trimethyladamantylammonium, benzyltrimethylammonium, tetraethylammonium hydroxide or tetrapropylammonium hydroxide. Preferably, N,N,N-trimethyladamantylammonium and the copper amine complex are co-template agents. The molar ratio of the co-template agent to the aluminum source can be 1.3-10:1; preferably 1.3-7.5:1; the molar ratio of N,N,N-trimethyladamantylammonium to the aluminum source is: 1-5:1, preferably: 1-4:1. The aluminum source is calculated as alumina. Selecting the two as co-template agents can broaden the width of the synthesized silica-alumina ratio, 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 copper glutamate chelate. Preferably, the copper source is copper sulfate, which is beneficial to form a stable copper-amine complex with tetraethylenepentamine. On the one hand, the formed copper-amine complex can participate in the formation of the molecular sieve framework, and on the other hand, it can enable copper to enter the ring of the molecular sieve in the form of more active copper, which is beneficial 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 - 5:1; preferably 0.3 - 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 alumina, the base source is calculated as sodium hydroxide, and the rare earth source is calculated as rare earth element. The molar ratio of the silicon source:aluminum source:base:divalent copper ions: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 the hydrothermal reaction method, and the specific steps are as follows:

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

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

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

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

[0068] (3) Crystallize (hydrothermal react) the fourth mixture, and wash and dry the crystallized product.

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

[0070] In some preferred embodiments, the hydrothermal reaction temperature in 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, where the temperature of microwave drying is 60 - 110°C and the time of microwave drying is 3 - 24 h. More preferably, it is microwave drying at 100°C for 12 h.

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

[0073] In some preferred embodiments, the ammonium source is selected from one or two 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 - 24 h. Preferably, the temperature of the microwave ultrasonic reaction is 70°C - 90°C and the reaction time is 12 - 20 h; where the microwave power is 100 - 1500 W, and its preferred power range is 700 W - 1000 W, and the power of the ultrasonic wave is 100 W - 1000 W, and its preferred power range is 500 W - 700 W.

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

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

[0076] All raw materials used in the present invention are obtained by purchasing in the market.

[0077] The technical solution of the present invention is further described below through examples.

[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, and 0.0035 mol of tetraethylenepentamine is slowly added dropwise to the aqueous solution, and stirred well to form a first mixture;

[0080] (2) Mix 0.0105 mol of N,N,N-trimethyladamantammonium evenly with the first mixture to form a second mixture; add 0.0105 mol of sodium hydroxide, 0.007 mol of sodium metaaluminate, 0.33 mmol of cerium acetate, and 2 mmol of N-(2-hydroxyethyl)ethylenediamine-N,N,N-triacetic acid trisodium salt solution to the second mixture, stir evenly under heating reflux at a temperature of 40 °C to form a third mixture, and mix 0.07 mol of silica sol (solid content: 30%, pH: 9.1, density: 1.2 g / cm 3 ) with the third mixture, stir until a homogeneous gel is formed to form a fourth mixture;

[0081] (3) Load the fourth mixture into a hydrothermal reaction kettle lined with polytetrafluoroethylene, crystallize at 160 °C for 4 days, wash the crystallized product, and dry it in a microwave (microwave power: 2000 W) at 100 °C for 12 h;

[0082] (4) Add the dried product to 100 mL of ammonium nitrate solution with a concentration of 1.25 mol / L, and under the conditions of a microwave power of 1000 W, a constant ultrasonic power of 600 W, and a temperature of 80 °C, treat it for 12 h, wash and filter, and then dry it in a microwave at 110 °C for 12 h to obtain a second dried product; calcine the second dried product in a microwave (microwave power: 1000 W) at 600 °C for 4 h to obtain a rare earth molecular sieve.

[0083] Example 2

[0084] (1) At room temperature, add 0.0072 mol of copper sulfate to 2.23 mol of distilled water to form an aqueous solution, and slowly drop 0.0072 mol of tetraethylenepentamine into the aqueous solution, stir well to form a first mixture;

[0085] (2) Mix 0.010 mol of N,N,N-trimethyladamantammonium evenly with the first mixture to form a second mixture; add 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 diethylenetriaminepentaacetic acid pentasodium salt to the second mixture, stir evenly under heating reflux at a temperature of 30 °C to form a third mixture, and mix 0.12 mol of silica sol (solid content: 30%, pH: 9.1, density: 1.2 g / cm 3 ) with the third mixture, stir until a homogeneous gel is formed to form a fourth mixture;

[0086] (3) Load the fourth mixture into a hydrothermal reactor lined with polytetrafluoroethylene, crystallize it at 170 °C for 4 days, wash the crystallized product, and dry it in a microwave oven (microwave power: 2000 W) at 100 °C for 12 h;

[0087] (4) Add the dried product to 100 mL of ammonium nitrate solution with a concentration of 1.5 mol / L, and under the conditions of a microwave power of 1000 W, a constant ultrasonic power of 600 W, and a temperature of 70 °C, treat it for 12 h, wash and filter it, and then dry it in a microwave oven at 110 °C for 12 h to obtain a second-dried product; calcine the second-dried product in a microwave oven (microwave power: 1000 W) at 600 °C for 3 h to obtain a rare earth molecular sieve.

[0088] Comparative Example 1

[0089] Add 0.0035 mol of copper sulfate, 0.0105 mol of N,N,N-trimethyladamantylammonium, 0.0105 mol of sodium hydroxide, and 0.007 mol of sodium metaaluminate 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 ), stir until a homogeneous gel is formed, carry out a hydrothermal reaction on the mixture, crystallize it at 160 °C for 4 days, wash the crystallized product, and dry it at 100 °C for 12 h. Add the once-dried product obtained by drying to 100 mL of ammonium nitrate solution with a concentration of 1.25 mol / L, treat it at room temperature for 12 h, wash and filter it, and then dry it at 110 °C for 12 h to obtain a second-dried product; calcine the second-dried product in air at 600 °C for 4 h to obtain a copper-containing molecular sieve.

[0090] Comparative Example 2

[0091] Add 0.0072 mol of copper sulfate, 0.010 mol of N,N,N-trimethyladamantylammonium, 0.011 mol of potassium hydroxide, and 0.0048 mol of aluminum sol (solid content 10 wt%, pH 4, viscosity 43 mPa·s, particle size 10 nm) 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 ), stir until a homogeneous gel is formed, crystallize it at 170 °C for 4 days, wash the crystallized product, and dry it at 100 °C for 12 h to obtain a once-dried product; dissolve 0.15 mol of ammonium nitrate in 100 mL of aqueous solution, add the once-dried product (i.e., copper CHA zeolite containing K ions) to it and treat it at room temperature for 12 hours, wash and filter it, and then dry it at 110 °C for 12 h to obtain a second-dried product. Calcine it in air at 600 °C for 4 h to obtain a copper-containing zeolite molecular sieve.

[0092] Comparative Example 3

[0093] (1) At room temperature, 0.0035 mol of copper sulfate was added to 2.23 mol of distilled water to form an aqueous solution. 0.0035 mol of tetraethylenepentamine was slowly added dropwise to the aqueous solution, and the mixture was stirred well 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 ) were added to the above-mentioned mixture, and the mixture was stirred until a homogeneous gel was formed. The gel was crystallized in a hydrothermal reaction kettle at 160 °C for 4 days. The crystallized product was washed and dried at 100 °C for 12 h. The obtained first-dried product was added to 100 mL of ammonium nitrate solution with a concentration of 1.5 mol / L, and the mixture was treated at room temperature for 12 h, washed and filtered, and then dried at 110 °C for 12 h to obtain a second-dried product. The second-dried product was calcined in air at 600 °C for 4 h.

[0095] The physicochemical 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 6 XRD patterns of the molecular sieves prepared in Examples 1-2 and Comparative Examples 1-3 of the present invention are shown. It can be seen from the figure that Examples 1-2 have a typical CHA configuration structure, indicating that SSZ-13 molecular sieve can be synthesized by using copper amine complex and N,N,N-trimethyladamantyl ammonium as co-template agents. At the same time, no corresponding rare earth peaks and copper peaks were observed, indicating that rare earth and copper mainly entered the rings in the molecular sieve; for Comparative Examples 1-2, CHA characteristic peaks and CuO characteristic peaks can be observed, indicating that molecular sieve SSZ-13 can be synthesized by using only N,N,N-trimethyladamantyl ammonium, but copper mainly exists in the form of CuO; for Comparative Example 3, a large peak at 20-30° is the characteristic peak of SiO 2 , and no CHA characteristic peak was observed, indicating that it is not feasible to synthesize a high-silica-alumina ratio molecular sieve by using only Cu-TEPA. At the same time, a CuO characteristic peak was observed, indicating that copper mainly exists in the form of CuO.

[0099] Effect verification

[0100] NH 3 -SCR activity tests were carried out on the molecular sieve catalysts prepared in Examples 1-2 and Comparative Examples 1-3:

[0101] (1) The NOx conversion rate results of the fresh samples are shown in Table 2 and Figure 7 as follows. The test conditions are: [NO] = 500 ppm; [NH 3 = 500 ppm; [O 2 = 10 vol%; [C 3 H 6 = 200 ppm; [CO] = 8 vol%; [H 2 O] = 5 vol%; N 2 is used as the balance gas; the total flow rate is 750 mL / min; the space velocity = 150000 h -1 .

[0102] Table 2

[0103]

[0104] (2) The hydrothermal aging conditions of the catalyst are: aging at 800 °C for 16 h, and the water amount is 10 vol% of the total gas volume.

[0105] The catalysts in Examples 1-2 and Comparative Examples 1-3 were subjected to NH 3 -SCR activity tests. The NOx conversion rate results of the aged samples are shown in Table 3 and Figure 8 as follows.

[0106] Table 3

[0107]

[0108] Conclusion: As shown in Tables 2-3 and Figures 7-8 as follows, whether the silica-alumina ratio is 20 or 25, the catalytic activity of the rare earth molecular sieve synthesized by the present invention using a dual template agent and a rare earth chelating agent is superior to that of the molecular sieve with a single template agent. At the same time, under the condition that the silica-alumina ratio > 15, using only copper ammonium complex as a single template agent cannot synthesize a molecular sieve. Therefore, using a dual template agent can broaden the range of the silica-alumina ratio of the molecular sieve, and the in-situ added rare earth and copper are prone to strong interaction, simplifying its production steps, and showing excellent fresh catalytic performance and hydrothermal aging performance.

[0109] (3) The catalysts in Examples 1-2 and Comparative Examples 1-3 were prepared into alkali-poisoned catalysts and subjected to NH 3 -SCR activity tests. The NOx conversion rate results are shown in Table 4. The alkali poisoning method is as follows:

[0110] Take 5 g of the catalysts prepared in Examples 1-2 and Comparative Examples 1-3, dissolve 0.37 g of NaNO 3 in deionized water, and use the equal-volume impregnation method, and then NaNO 3The aqueous solution was added dropwise to the above molecular sieve, impregnated at room temperature for 6 h, dried overnight by microwave at 110 °C (microwave power was 2000 W), and calcined by microwave at 500 °C for 2 h (microwave power was 1000 W) to obtain Na + a catalyst with a Na loading of 2% Na / gcat.

[0111] The test conditions were: [NO] = 500 ppm; [NH 3 = 500 ppm; [O 2 = 10 vol%; [C 3 H 6 = 200 ppm; [CO] = 8 vol%; [H 2 O]0 = 5 vol%; N 2 was used as the balance gas; the total flow rate was 750 mL / min; the space velocity = 150000 h -1 .

[0112] Table 4

[0113]

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

[0115] The above is only the preferred specific embodiment 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 those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to 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: 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; a hydrothermal reaction is used in coordination with a microwave ultrasonic reaction to prepare a rare earth molecular sieve; The quaternary ammonium salt compound includes one or more of N,N,N-trimethyladamantanammonium, benzyltrimethylammonium, tetraethylammonium hydroxide or tetrapropylammonium hydroxide; The specific conditions of the hydrothermal reaction are: at 120-200°C, the reaction time is 2-7 days; The specific conditions of the microwave ultrasonic reaction 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.

2. 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.

3. The method for preparing a rare earth molecular sieve according to claim 1 or 2, 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).

4. 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.

5. A rare earth molecular sieve, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 4.

6. A rare earth molecular sieve according to claim 5, 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.

7. A rare earth molecular sieve as claimed in claim 5 or 6 for purifying NOx from diesel exhaust x Application in.

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