Copper-based molecular sieve as well as preparation method and application thereof

Abstract

The invention relates to a copper-based molecular sieve and a preparation method and application thereof, and the preparation method comprises the following steps: (1) carrying out first mixing on a silicon source, an aluminum source, an alkali source, a first template agent and a first solvent to prepare a solution A; a copper source, a second template agent and a second solvent are subjected to second mixing, and a solution B is prepared; and (2) carrying out third mixing on the solution A and the solution B, carrying out reaction crystallization, and carrying out one-step post-treatment on the system after reaction crystallization to obtain the copper-based molecular sieve, wherein a reagent adopted in the one-step post-treatment comprises an acid solution and / or an ammonium salt solution. According to the method, through the regulation and control of the mixing process, the crystallization process and the one-step post-treatment process, the synthesis method of the copper-based molecular sieve is optimized through the mutual synergistic effect of the three processes, meanwhile, the preparation yield of the copper-based molecular sieve is effectively improved, and the catalytic activity and the hydrothermal stability of the obtained copper-based molecular sieve are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieve preparation, and in particular to a copper-based molecular sieve and a preparation method and application thereof. Background Art

[0002] At present, my country is facing the problem of PM2.5 and ozone combined pollution. x ) is an important precursor to PM2.5 and ozone formation, and has a significant impact on NO x NH3 selective catalytic reduction technology (NH3-SCR) is a NO x The mainstream technology of catalytic purification, copper-based molecular sieve as a catalyst has excellent NH3-SCR performance, and is widely used in NO removal in mobile and fixed sources. x It is used in removal.

[0003] In the prior art, various copper-based molecular sieves are crystallized under alkaline conditions, but these molecular sieves are generally prepared by subjecting prepared Na-type molecular sieves to multi-step ion exchange reactions.

[0004] Prior art CN103212436A discloses a method for synthesizing an ion exchange type Cu-ETS-10 catalyst for SCR reaction, wherein ETS-10 is subjected to 6 ion exchanges using an aqueous ammonium nitrate solution to remove alkali metals (Na, K), and then ion exchange is performed again using a copper acetate solution to obtain calcined Cu-ETS-10.

[0005] The prior art CN111943224A discloses a preparation method of a Cu-SSZ-13 molecular sieve catalyst, the obtained product and application. An alkali source, a silicon source, deionized water, a template agent and a type A molecular sieve are stirred to form a crystallization starting gel, the starting gel is placed in an oven to fully evaporate the gel water, dry it and grind it into powder to obtain a molecular sieve precursor dry gel, crystallize it to obtain a Na-SSZ-13 molecular sieve, and the obtained Na-SSZ-13 molecular sieve is subjected to a multi-step ion exchange reaction with an ammonium salt solution and a divalent copper salt solution in sequence to obtain Cu-SSZ-13.

[0006] The above methods all have multiple post-treatment processes such as ammonium exchange and copper exchange, which are complex in process and high in production cost.

[0007] In addition, another currently used method for preparing copper-based molecular sieves is a process of directly mixing the raw materials with the template and then crystallizing them. The activity of the copper-based molecular sieves prepared by this process method needs to be improved. More importantly, the copper material in the molecular sieve prepared by this method is easy to agglomerate and the dispersion becomes poor, which leads to the poor catalytic performance of the copper-based molecular sieve as a catalyst.

[0008] Therefore, providing a preparation process for optimizing the synthesis process of copper-based molecular sieves and obtaining copper-based molecular sieves with excellent catalytic performance is a technical problem that needs to be solved urgently. Summary of the invention

[0009] In order to solve the above technical problems, the present invention aims to provide a copper-based molecular sieve and a preparation method and application thereof. The present invention optimizes the synthesis method of the copper-based molecular sieve by regulating the mixing process, and adopting the crystallization process and the one-step post-treatment process, and the synergistic effect between the three, and at the same time, effectively improves the preparation yield of the copper-based molecular sieve, and improves the catalytic activity and hydrothermal stability of the obtained copper-based molecular sieve.

[0010] To achieve this object, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides a method for preparing a copper-based molecular sieve, the preparation method comprising the following steps:

[0012] (1) a silicon source, an aluminum source, an alkali source, a first template and a first solvent are first mixed to prepare a solution A;

[0013] The copper source, the second template and the second solvent are mixed for a second time to prepare a solution B;

[0014] (2) mixing solution A and solution B for a third time, reacting and crystallizing, and performing a post-treatment on the system after the reaction and crystallization to obtain the copper-based molecular sieve;

[0015] Wherein, the reagents used in the one-step post-treatment include acid solution and / or ammonium salt solution.

[0016] In the present invention, there is no limitation on the order of preparing solution A and solution B, and those skilled in the art can select the order as needed.

[0017] The present invention obtains a copper-based molecular sieve by crystallization under an alkaline environment, omits the cumbersome process of multi-step ion exchange reaction, reduces the preparation process, saves production costs, and prepares a copper-based molecular sieve with excellent catalytic activity and hydrothermal stability. Secondly, the present invention helps to disperse and dissolve each substance in the raw material by regulating the mixing process of silicon source, aluminum source, copper source and template agent in the raw material, improves the crystallization rate and the crystallinity of the product molecular sieve, and effectively improves the yield of preparing copper-based molecular sieve. Furthermore, the present invention uses an acid solution or an ammonium salt solution to treat the reaction system after crystallization through a one-step post-treatment, regulates the existence state of Cu species in the molecular sieve, on the one hand, improves the dispersibility of Cu species in the molecular sieve, and on the other hand, improves the activity of the copper-based molecular sieve, thereby further improving the catalytic performance of the molecular sieve.

[0018] The present invention optimizes the synthesis method of copper-based molecular sieves by regulating the mixing process, adopting the crystallization process and the one-step post-treatment process, and the synergistic effect of the three processes. At the same time, the preparation yield of copper-based molecular sieves is effectively improved, and the catalytic activity and hydrothermal stability of the obtained copper-based molecular sieves are improved.

[0019] Preferably, the first template in step (1) includes any one of 2,6-dimethyl-N-pyridine, tetraethyldimethyldiazacyclo-6, N,N,N,N-tetraethyl-exo,exo-bicyclo[2.2.2]oct-7-ene-2,3,5,6-ditetrahydropyridine iodide ammonium salt, hydroxyl type N,N-dimethylpiperidine or 18-crown ether-6.

[0020] In the present invention, by using a first template of a specific substance, a specific type of copper-based molecular sieve is prepared accordingly. In addition, the copper-based molecular sieves prepared by the present invention are of various types, and the application range of the preparation process provided is wide.

[0021] Preferably, when the first template is 2,6-dimethyl-N-pyridine, the obtained copper-based molecular sieve is a Cu-RTH molecular sieve.

[0022] Preferably, when the first template is tetraethyldimethyldiazacyclo-6, the obtained copper-based molecular sieve is Cu-AFX molecular sieve.

[0023] Preferably, when the first template is N,N,N,N-tetraethyl-exo,exo-bicyclo[2.2.2]oct-7-ene-2,3,5,6-bitetrahydropyridone iodine ammonium salt, the copper-based molecular sieve obtained is Cu-UZM-35 molecular sieve.

[0024] Preferably, when the first template is hydroxy-type N,N-dimethylpiperidine, the obtained copper-based molecular sieve is a Cu-ERI molecular sieve.

[0025] Preferably, when the first template is 18-crown-6, the obtained copper-based molecular sieve is Cu-RHO molecular sieve.

[0026] Preferably, the silicon source in step (1) comprises any one of silica sol, sodium silicate, fumed silica, silica gel, Y molecular sieve, Beta molecular sieve or ZSM-5 molecular sieve, or a combination of at least two thereof.

[0027] Preferably, the aluminum source in step (1) comprises any one of sodium aluminate, aluminum hydroxide, aluminum sulfate, pseudo-boehmite, Y molecular sieve, Beta molecular sieve or ZSM-5 molecular sieve, or a combination of at least two thereof.

[0028] The Y molecular sieve, Beta molecular sieve and ZSM-5 molecular sieve provided by the present invention all include silicon and aluminum elements, so the above molecular sieves can be used as both a silicon source and an aluminum source.

[0029] Preferably, the alkali source in step (1) comprises sodium hydroxide and / or potassium hydroxide.

[0030] Preferably, the copper source in step (1) comprises any one of copper sulfate, copper acetate, copper nitrate or copper chloride, or a combination of at least two thereof.

[0031] Preferably, the second template in step (1) comprises any one of tetraethylenepentamine, triethylenetetramine, diethylenetriamine or ammonia water, or a combination of at least two thereof.

[0032] The second template used in the present invention has the function of complexing with copper ions. By regulating the specific type of the second template, a distribution effect that is beneficial to the Cu species in the molecular sieve can be produced.

[0033] Preferably, in step (1), the first solvent comprises water.

[0034] Preferably, in step (1), the second solvent comprises water.

[0035] Preferably, the molar ratio of the silicon element in the silicon source in step (1) to the aluminum element in the aluminum source is (1-50):1, for example, 1:1, 3:1, 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1 or 50:1, etc., preferably (5-40):1, and more preferably (10-20):1.

[0036] Preferably, the molar ratio of the silicon source to the alkali source in step (1) is (1-30):1, for example 1:1, 3:1, 5:1, 7:1, 9:1, 11:1, 13:1, 15:1, 17:1, 19:1, 21:1, 23:1, 25:1, 27:1, 29:1 or 30:1, etc., preferably (5-15):1, more preferably (5-10):1.

[0037] Preferably, the molar ratio of the silicon source to the first template in step (1) is (1-30):1, for example 1:1, 3:1, 5:1, 7:1, 9:1, 11:1, 13:1, 15:1, 17:1, 19:1, 21:1, 23:1, 25:1, 27:1, 29:1 or 30:1, etc., preferably (5-15):1, more preferably (5-10):1.

[0038] In the present invention, the molecular sieve crystallization effect can be optimized by adjusting the molar ratio of the silicon source to the first template. If the molar ratio of the silicon source to the first template is too small, impurities will be generated in the product and the catalyst performance will be poor; if the molar ratio of the silicon source to the first template is too large, the molecular sieve cannot be crystallized and the catalyst yield is low.

[0039] Preferably, the molar ratio of the copper source to the second template in step (1) is (0.1-1.5):1, for example 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1 or 1.5:1, etc., preferably (0.5-1):1.

[0040] Preferably, in the third mixing of step (2), the molar ratio of the silicon source to the copper source is (1-1000):1, for example 1:1, 5:1, 10:1, 50:1, 100:1, 150:1, 200:1, 250:1, 300:1, 350:1, 400:1, 450:1, 500:1, 550:1, 600:1, 650:1, 700:1, 750:1, 800:1, 850:1, 900:1, 950:1 or 1000:1, etc., preferably (5-100):1, more preferably (10-50):1.

[0041] Preferably, the temperatures of the first mixing, the second mixing and the third mixing are independently selected from 10-80°C, such as 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C or 80°C.

[0042] Preferably, the rotation speeds of the first mixing, the second mixing and the third mixing are independently selected from 10-2000r / min, for example, they can be 10r / min, 100r / min, 200r / min, 300r / min, 400r / min, 500r / min, 600r / min, 700r / min, 800r / min, 900r / min, 1000r / min, 1100r / min, 1200r / min, 1300r / min, 1400r / min, 1500r / min, 1600r / min, 1700r / min, 1800r / min, 1900r / min or 2000r / min, etc., preferably 100-500r / min.

[0043] Preferably, the time for the first mixing, the second mixing and the third mixing is independently selected from 0.5-16 h, such as 0.5 h, 2 h, 4 h, 6 h, 8 h, 10 h, 12 h, 14 h or 16 h, etc.

[0044] In the present invention, the mixing method is not specifically limited, including but not limited to stirring, ultrasound or ball milling, etc., and those skilled in the art can select it according to needs.

[0045] Preferably, the temperature of the reaction crystallization in step (2) is 120-200°C, for example, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 170°C, 180°C, 190°C, or 200°C, etc.

[0046] Preferably, the reaction crystallization time in step (2) is 1-336 h, for example, 1 h, 3 h, 6 h, 9 h, 12 h, 24 h, 48 h, 72 h, 96 h, 120 h, 144 h, 192 h, 240 h, 288 h or 336 h.

[0047] Preferably, the reaction crystallization in step (2) is carried out under non-stirring closed conditions.

[0048] Preferably, in step (2), the product after the reaction crystallization is further subjected to cooling and separation treatment.

[0049] Preferably, the cooling temperature is below 50°C, for example, 50°C, 45°C, 40°C, 35°C, 30°C, 25°C or 20°C.

[0050] In the present invention, there is no specific limitation on the separation method, including but not limited to filtration, centrifugation or sedimentation separation, etc. Those skilled in the art can select according to their needs.

[0051] Preferably, in the post-treatment process of step (2), the H + The concentration is 0.01-0.2mol / L, for example 0.01mol / L, 0.02mol / L, 0.04mol / L, 0.06mol / L, 0.08mol / L, 0.10mol / L, 0.12mol / L, 0.14mol / L, 0.16mol / L, 0.18mol / L or 0.20mol / L, etc.

[0052] In the present invention, if the concentration of the acid solution used in the post-treatment process is too low, the excess Cu ions cannot be effectively cleaned, thereby affecting the catalytic performance of the obtained copper-based molecular sieve; if the concentration of the acid solution is too high, the framework of the copper-based molecular sieve will be destroyed.

[0053] Preferably, in the post-treatment process of step (2), the concentration of the ammonium salt solution used is 0.01-0.5 mol / L, for example, 0.01 mol / L, 0.03 mol / L, 0.05 mol / L, 0.15 mol / L, 0.20 mol / L, 0.25 mol / L, 0.30 mol / L, 0.35 mol / L, 0.40 mol / L, 0.45 mol / L or 0.50 mol / L, etc.

[0054] In the present invention, if the concentration of the ammonium salt solution used in the post-treatment process is too low, the Cu ions cannot be effectively washed away, thereby affecting the catalytic performance of the obtained copper-based molecular sieve; if the concentration of the ammonium salt solution is too high, the framework of the copper-based molecular sieve will be destroyed.

[0055] Preferably, the time for the post-treatment in step (2) is 1-24 h, such as 1 h, 5 h, 10 h, 15 h, 20 h or 24 h, etc., preferably 5-10 h.

[0056] Preferably, the acid in the acid solution includes any one of hydrochloric acid, nitric acid or sulfuric acid, or a combination of at least two of them. Typical combinations include, but are not limited to, a combination of hydrochloric acid and nitric acid, a combination of hydrochloric acid and sulfuric acid, a combination of nitric acid and sulfuric acid, or a combination of hydrochloric acid, nitric acid and sulfuric acid, etc.

[0057] Preferably, the ammonium salt in the ammonium salt solution includes any one of ammonium chloride, ammonium nitrate or ammonium sulfate, or a combination of at least two of them.

[0058] Preferably, the preparation method further comprises: washing, drying and calcining the product after the one-step post-treatment to obtain the copper-based molecular sieve.

[0059] In the present invention, there is no specific limitation on the number of washing times, including but not limited to 3 times, 4 times, 5 times or 6 times, etc., and those skilled in the art can select according to needs.

[0060] In the present invention, there is no specific limitation on the washing solvent, including but not limited to water or ethanol, etc., and those skilled in the art can select it according to needs.

[0061] In the present invention, there is no specific limitation on the drying method, including but not limited to vacuum drying or natural air drying, and those skilled in the art can select according to needs.

[0062] Preferably, the drying temperature is 40-160°C, for example 40°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C or 160°C, etc.

[0063] Preferably, the heating rate of the calcination is 0.5-5°C / min, for example, 0.5°C / min, 1°C / min, 2°C / min, 3°C / min, 4°C / min or 5°C / min.

[0064] Preferably, the calcination temperature is 500-900°C, for example, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C or 900°C.

[0065] Preferably, the calcination holding time is 5-10 h, for example, 5 h, 6 h, 7 h, 8 h, 9 h or 10 h.

[0066] In a second aspect, the present invention provides a copper-based molecular sieve, which is prepared by the method for preparing the copper-based molecular sieve described in the first aspect.

[0067] The copper-based molecular sieve provided by the present invention has excellent catalytic activity and hydrothermal stability, wherein the copper species in the molecular sieve has high activity and good dispersion uniformity in the molecular sieve.

[0068] Preferably, the copper-based molecular sieve includes any one of Cu-RTH molecular sieve, Cu-AFX molecular sieve, Cu-UZM-35 molecular sieve, Cu-ERI molecular sieve, Cu-RHO molecular sieve, Cu-CHA molecular sieve or Cu-AEI molecular sieve.

[0069] Preferably, the copper-based molecular sieve includes any one of Cu-RTH molecular sieve, Cu-AFX molecular sieve, Cu-UZM-35 molecular sieve, Cu-ERI molecular sieve or Cu-RHO molecular sieve.

[0070] In a third aspect, the present invention provides an application of the copper-based molecular sieve according to the second aspect in the conversion of nitrogen oxides.

[0071] Compared with the prior art, the present invention has at least the following beneficial effects:

[0072] (1) The present invention obtains a copper-based molecular sieve by crystallization under an alkaline environment, omits the cumbersome process of multi-step ion exchange reaction, reduces the preparation process, saves production costs, and prepares a copper-based molecular sieve with excellent catalytic activity and hydrothermal stability. Secondly, the present invention helps to disperse and dissolve each substance in the raw material by regulating the mixing process of silicon source, aluminum source, copper source and template agent in the raw material, improves the crystallization rate and the crystallinity of the product molecular sieve, and effectively improves the yield of preparing copper-based molecular sieve. Furthermore, the present invention uses an acid solution or an ammonium salt solution to treat the reaction system after crystallization through a one-step post-treatment, regulates the existence state of Cu species in the molecular sieve, on the one hand, improves the dispersibility of Cu species in the molecular sieve, and on the other hand, improves the activity of the copper-based molecular sieve, thereby further improving the catalytic performance of the molecular sieve.

[0073] (2) The copper-based molecular sieve provided by the present invention has excellent catalytic activity and hydrothermal stability, wherein the copper in the molecular sieve has high activity and good dispersion uniformity in the molecular sieve. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 This is a graph showing the nitrogen oxide conversion rate of the copper-based molecular sieve prepared in Example 2 before and after aging as a catalyst. DETAILED DESCRIPTION

[0075] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0076] The Y molecular sieves used in the following examples were sourced from the Catalyst Factory of Nankai University.

[0077] The preparation process of 2,6-dimethyl-N-pyridine (relative molecular weight 107) used in the following examples is as follows:

[0078] Add 54 g of 2,6-dimethylpyridine to 200 g of ethanol and add 85 g of iodomethane. Seal the reaction vessel and react for 12 hours at 70°C with constant stirring in the dark and condensation reflux. After the reaction is completed, evaporate until only a small amount of liquid remains in the container, add ether to the solid product for cleaning, filter, and vacuum dry for 2 hours to finally obtain iodine-type 2,6-dimethyl-N-pyridine solid. Dissolve the iodine-type 2,6-dimethyl-N-pyridine solid in water, add hydroxide exchange resin (AmberliteIRN-78 ion exchange resin), stir for 12 hours, filter the liquid, and obtain a hydroxide-type 2,6-dimethyl-N-pyridine solution. Evaporate the solution to OH -The concentration is 0.5 mol / L, and the target concentration of hydroxy-2,6-dimethyl-N-pyridine template agent is finally obtained.

[0079] The preparation process of tetraethyldimethyldiazacyclo-6 (relative molecular weight 281) used in the following examples is as follows:

[0080] 24.4 g of 1,6-dibromohexane and 21.8 g of N,N-diethylmethylamine were dissolved in 250 mL of acetonitrile, stirred and reacted under reflux for 24 h to obtain a product containing bromide cations. After cooling to room temperature, the solid product was filtered, washed with anhydrous ether and dried overnight under vacuum. Then, the product containing bromide cations was converted to the hydroxide form by using a hydroxide exchange resin (Amberlite IRN-78 ion exchange resin) in water to obtain Et4Me2-diquat-6 (tetraethyl dimethyl diazacyclo-6) solution.

[0081] The preparation process of N,N,N,N-tetraethyl-exo,exo-bicyclo[2.2.2]oct-7-ene-2,3,5,6-bitetrahydropyridone iodide ammonium salt (relative molecular weight 431) used in the following examples is as follows:

[0082] First, add 80 g of ethylamine aqueous solution, and then add 25 g of bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride while stirring. Stir at room temperature for 2 hours, then heat to 70°C and reflux for 48 hours, and then heat to 100°C and reflux for 24 hours.

[0083] Mix 350ml of anhydrous tetrahydrofuran and 5g of lithium aluminum tetrahydride powder, add the product obtained in the previous step and mix. Stir at room temperature for 2h, heat to 68℃ and reflux for 24h. Add water and NaOH aqueous solution in sequence, filter with dichloromethane, and collect the filtrate. Add 50ml of water to the filtrate, adjust the pH to 3-4 with concentrated hydrochloric acid, add 50wt% NaOH solution to adjust the pH to 10, add 70ml of dichloromethane, and collect the lower organic phase.

[0084] Add 32 ml of anhydrous ethanol to the above organic phase product, slowly add 24 g of iodomethane dropwise using a constant pressure funnel under light protection, and add 15 ml of anhydrous ethanol to the upper layer of the constant liquid funnel. Reflux at 80°C for 24 hours, filter, wash with acetone, and vacuum dry to obtain N,N,N,N-tetraethyl-exo,exo-bicyclo[2.2.2]oct-7-ene-2,3,5,6-bitetrahydropyridine iodide ammonium salt.

[0085] The preparation process of the hydroxyl-type N,N-dimethylpiperidine (relative molecular weight of 130) used in the following examples is as follows:

[0086] Hydroxylated N,N-dimethylpiperidine is obtained by exchanging N,N-dimethylpiperidinium chloride with a hydroxide exchange resin (Amberlite IRN-78 ion exchange resin). N,N-dimethylpiperidinium chloride is commercially available on Gaide Chemical Network with a CAS number of 24307-26-4.

[0087] The 18-crown ether-6 used in the following examples has a relative molecular mass of 264 and is sourced from Sinopharm Reagent Company.

[0088] Example 1

[0089] This embodiment provides a method for preparing a copper-based molecular sieve, which specifically comprises the following steps:

[0090] (I) 15 g of sodium silicate (Na4SiO4), 0.5 g of sodium aluminate (NaAlO2), 0.5 g of sodium hydroxide and 1 g of 2,6-dimethyl-N-pyridine were stirred and mixed in 20 mL of deionized water for 10 h at a temperature of 60° C. and a speed of 200 r / min to obtain a solution A;

[0091] 0.5 g of anhydrous copper nitrate and 0.6 g of triethylenetetramine were stirred and mixed in 20 mL of deionized water solution for 10 h at a stirring temperature of 60° C. and a stirring speed of 200 r / min to obtain solution B;

[0092] (II) stirring and mixing the solution A and solution B prepared in step (I) at a temperature of 60° C. and a rotation speed of 400 r / min for 5 hours to obtain a mixed system, placing the mixed system in a sealed reaction kettle, reacting and crystallizing at 180° C. for 24 hours, and after the reaction is completed, cooling to 50° C., and separating by sedimentation to obtain a solid phase product;

[0093] (III) The solid phase product obtained in step (II) is immersed in a 0.1 mol / L ammonium chloride solution for a one-step post-treatment for 6 hours. The solid phase product after the one-step post-treatment is taken out, washed with deionized water for 5 times, dried at 80°C for 10 hours, and then heated to 700°C in a tubular furnace at a heating rate of 3°C / min for 8 hours to obtain a Cu-RTH molecular sieve.

[0094] Example 2

[0095] This embodiment provides a method for preparing a copper-based molecular sieve, which specifically comprises the following steps:

[0096] (I) 5 g of Y molecular sieve (wherein the molar ratio of silicon to aluminum is 12:1) and 0.6 g of sodium hydroxide and 15 mL of tetraethyldimethyldiazacyclo-6 solution (concentration is 0.75 M) are stirred and mixed in 20 mL of deionized water solution for 1 h at a temperature of 70° C. and a speed of 500 r / min to obtain solution A;

[0097] 0.8 g of anhydrous copper sulfate and 1.2 g of tetraethylene pentamine were stirred and mixed in 20 mL of deionized water solution for 1 hour at a stirring temperature of 70° C. and a stirring speed of 500 r / min to obtain solution B;

[0098] (II) stirring and mixing the solution A and solution B prepared in step (I) at a temperature of 60° C. and a rotation speed of 300 r / min for 2 hours to obtain a mixed system, placing the mixed system in a sealed reaction kettle, reacting and crystallizing at 140° C. for 96 hours, and after the reaction is completed, cooling to 50° C., and separating by sedimentation to obtain a solid phase product;

[0099] (III) The solid phase product obtained in step (II) is immersed in a 0.1 mol / L hydrochloric acid solution for a one-step post-treatment for 6 hours. The solid phase product after the one-step post-treatment is taken out, washed with deionized water for 4 times, dried at 70°C for 12 hours, and then heated to 600°C in a tubular furnace at a heating rate of 5°C / min for calcination for 6 hours to obtain a Cu-AFX molecular sieve.

[0100] Example 3

[0101] This embodiment provides a method for preparing a copper-based molecular sieve, which specifically comprises the following steps:

[0102] (I) 15 g of sodium silicate (Na4SiO4), 0.6 g of aluminum hydroxide, 0.4 g of sodium hydroxide and 6 g of N,N,N,N-tetraethyl-exo,exo-bicyclo[2.2.2]oct-7-ene-2,3,5,6-bitetrahydropyridone iodide ammonium salt were stirred and mixed in 20 mL of deionized water for 15 h at a temperature of 80° C. and a speed of 100 r / min to obtain a solution A;

[0103] 1 g of anhydrous copper chloride and 1 g of diethylenetriamine were stirred and mixed in 20 mL of deionized water solution for 15 hours at a stirring temperature of 80° C. and a stirring speed of 100 r / min to obtain solution B;

[0104] (II) stirring and mixing the solution A and solution B prepared in step (I) at a temperature of 80° C. and a rotation speed of 300 r / min for 5 hours to obtain a mixed system, placing the mixed system in a sealed reaction kettle, reacting and crystallizing at 130° C. for 5 days (120 hours), and after the reaction is completed, cooling to 50° C., and separating by sedimentation to obtain a solid phase product;

[0105] (III) The solid phase product obtained in step (II) is immersed in 0.3 mol / L ammonium nitrate for 8 hours of one-step post-treatment, the solid phase product after the one-step post-treatment is taken out, washed with deionized water 4 times, dried at 60°C for 15 hours, and then heated to 900°C in a tubular furnace at a heating rate of 4°C / min for calcination for 5 hours to obtain Cu-UZM-35 molecular sieve.

[0106] Example 4

[0107] This embodiment provides a method for preparing a copper-based molecular sieve, which specifically comprises the following steps:

[0108] (1) 20 g of sodium silicate (Na4SiO4), 0.5 g of sodium aluminate (NaAlO2), 0.8 g of potassium hydroxide and 2 g of hydroxy-type N,N-dimethylpiperidine were stirred and mixed in 20 mL of deionized water for 15 h at a temperature of 80° C. and a speed of 100 r / min to obtain a solution A;

[0109] 0.5 g of anhydrous copper nitrate and 0.6 g of triethylenetetramine were stirred and mixed in 20 mL of deionized water solution for 15 hours at a stirring temperature of 80° C. and a stirring speed of 100 r / min to obtain solution B;

[0110] (II) stirring and mixing the solution A and solution B prepared in step (I) at a temperature of 20° C. and a rotation speed of 200 r / min for 12 hours to obtain a mixed system, placing the mixed system in a sealed reaction vessel, reacting and crystallizing at 150° C. for 6 days (144 hours), and after the reaction is completed, cooling to 50° C., and separating by sedimentation to obtain a solid phase product;

[0111] (III) The solid phase product obtained in step (II) is immersed in a 0.05 mol / L sulfuric acid solution for a one-step post-treatment for 10 hours, the solid phase product after the one-step post-treatment is taken out, washed with deionized water for 3 times, dried at 80°C for 12 hours, and then heated to 500°C in a tubular furnace at a heating rate of 1°C / min for 10 hours to obtain a Cu-ERI molecular sieve.

[0112] Example 5

[0113] This embodiment provides a method for preparing a copper-based molecular sieve, which specifically comprises the following steps:

[0114] (I) 10 g of sodium silicate (Na4SiO4), 0.2 g of pseudo-boehmite (chemical formula: AlOOH), 0.5 g of potassium hydroxide and 1.5 g of 18-crown-6 were stirred and mixed in 20 mL of deionized water solution for 3 h at a temperature of 20° C. and a speed of 500 r / min to obtain a solution A;

[0115] 0.5 g of anhydrous copper acetate and 0.7 g of tetraethylenepentamine were stirred and mixed in 20 mL of deionized water solution for 3 hours at a stirring temperature of 20° C. and a stirring speed of 500 r / min to obtain solution B;

[0116] (II) stirring and mixing the solution A and solution B prepared in step (I) at a temperature of 50° C. and a rotation speed of 400 r / min for 2 hours to obtain a mixed system, placing the mixed system in a sealed reaction kettle, reacting and crystallizing at 160° C. for 6 days (144 hours), and after the reaction is completed, cooling to 50° C., and separating by sedimentation to obtain a solid phase product;

[0117] (III) The solid phase product obtained in step (II) is immersed in a 0.02 mol / L nitric acid solution for a one-step post-treatment for 5 hours, the solid phase product after the one-step post-treatment is taken out, washed with deionized water for 4 times, dried at 100° C. for 10 hours, and then heated to 900° C. in a tubular furnace at a heating rate of 5° C. / min for 6 hours to obtain a Cu-RHO molecular sieve.

[0118] Example 6

[0119] The difference between this embodiment and embodiment 1 is that the amount of 2,6-dimethyl-N-pyridine added in step (I) is 5 g, that is, the molar ratio of sodium silicate to 2,6-dimethyl-N-pyridine is 1.74:1. The rest is the same as embodiment 1.

[0120] Example 7

[0121] The difference between this embodiment and embodiment 1 is that the amount of 2,6-dimethyl-N-pyridine added in step (I) is 0.5 g, that is, the molar ratio of sodium silicate to 2,6-dimethyl-N-pyridine is 35:1. The rest is the same as embodiment 1.

[0122] Example 8

[0123] The difference between this embodiment and embodiment 1 is that the concentration of the ammonium chloride solution used in the post-treatment in step (III) is 0.005 mol / L. The rest is the same as embodiment 1.

[0124] Example 9

[0125] The difference between this embodiment and embodiment 1 is that the concentration of the ammonium chloride solution used in the post-treatment in step (III) is 0.6 mol / L. The rest is the same as embodiment 1.

[0126] Example 10

[0127] The difference between this embodiment and embodiment 2 is that the concentration of hydrochloric acid used in the post-treatment in step (III) is 0.005 mol / L. The rest is the same as embodiment 2.

[0128] Embodiment 11

[0129] The difference between this embodiment and embodiment 2 is that the concentration of hydrochloric acid used in the post-treatment in step (III) is 0.3 mol / L. The rest is the same as embodiment 2.

[0130] Comparative Example 1

[0131] The difference between this comparative example and Example 1 is that in the preparation method of the copper-based molecular sieve provided in this comparative example, 15g of sodium silicate (Na4SiO4), 0.5g of sodium aluminate (NaAlO2), 0.5g of sodium hydroxide, 1g of 2,6-dimethyl-N-pyridine, 0.5g of anhydrous copper nitrate and 0.6g of triethylenetetramine are stirred and mixed in 40mL of deionized water for 10h, the stirring and mixing temperature is 60°C, and the speed is 200r / min to obtain a mixed system. The rest is the same as Example 1.

[0132] Comparative Example 2

[0133] The difference between this comparative example and Example 1 is that in the preparation method of the copper-based molecular sieve provided in this comparative example, the post-treatment process of step (III) is omitted, that is, the solid phase product separated in step (II) is washed with deionized water for 5 times, dried at 80°C for 10 hours, and then heated to 700°C in a tube furnace at a heating rate of 3°C / min for 8 hours to obtain a Cu-RTH molecular sieve. The rest is the same as Example 1.

[0134] Comparative Example 3

[0135] The difference between this comparative example and Example 2 is that in the preparation method of the copper-based molecular sieve provided in this comparative example, the post-treatment process of step (III) is omitted, that is, the solid phase product separated in step (II) is washed with deionized water 4 times, dried at 70°C for 12 hours, and then heated to 600°C in a tube furnace at a heating rate of 5°C / min for 6 hours to obtain a Cu-AFX molecular sieve. The rest is the same as Example 2.

[0136] Performance Test:

[0137] (1) Yield test: Yield = mass of sample after drying and calcination / (mass of SiO2+Al2O3 in raw materials) × 100. The results are shown in Table 1.

[0138] (2) Test of catalytic performance: The copper-based molecular sieves prepared in the above examples and comparative examples were pressed into tablets and sieved, and molecular sieves with a mesh size of 40-600 were used as catalysts for experiments or treatments.

[0139] The obtained copper-based molecular sieve catalyst was placed in a quartz tube, placed in a fixed bed reactor, and hydrothermally aged at 750°C for 16 hours in a 10 vol% H2O / Air atmosphere to investigate the hydrothermal stability of the catalyst.

[0140] The molecular sieves before and after aging were placed in a temperature range of [NO] = [NH3] = 500 ppm, [O2] = [H2O] = 5 vol%, N2 as the balance gas, and a total flow rate of 500 ml / min. The air velocity was 400,000 h -1 The catalytic reaction test was carried out under the conditions of , and the results are shown in Table 1:

[0141] Table 1

[0142]

[0143]

[0144] The test results show that:

[0145] (1) It can be seen from Examples 1 to 5 that the present invention optimizes the synthesis method of copper-based molecular sieves by regulating the mixing process, adopting the crystallization process and the one-step post-treatment process, and the synergistic effect between the three, and at the same time, effectively improves the preparation yield of copper-based molecular sieves, and improves the catalytic activity and hydrothermal stability of the obtained copper-based molecular sieves. In addition, the present invention obtains a specific type of copper-based molecular sieve by adopting a first template of a specific substance. In addition, the copper-based molecular sieves prepared by the present invention are of various types, and the application range of the preparation process provided is wide.

[0146] Figure 1 The nitrogen oxide conversion rate curve of the copper-based molecular sieve prepared in Example 2 before and after aging as a catalyst is shown. It can be seen from the figure that the Cu-AFX molecular sieve prepared in Example 2 has excellent catalytic activity and hydrothermal stability.

[0147] (2) It can be seen from Example 1 and Examples 6-7 that in the present invention, if the molar ratio of the silicon source to the first template is too small, impurities will be generated in the product and the catalyst performance will be poor; if the molar ratio of the silicon source to the first template is too large, the molecular sieve cannot be crystallized and the catalyst yield is low.

[0148] (3) It can be seen from Examples 1 and 8-9, and Examples 2 and 10-11 that in the one-step post-treatment process adopted by the present invention, if the concentration of the acid solution or the ammonium salt solution is too low, the Cu ions will not be effectively washed away, thereby affecting the catalytic performance of the obtained copper-based molecular sieve, making the prepared copper-based molecular sieve catalyst have poor high-temperature activity; if the concentration of the acid solution or the ammonium salt solution is too high, the skeleton of the copper-based molecular sieve will be destroyed, and the catalyst will have poor low-temperature activity.

[0149] (4) By comparing Example 1 with Comparative Example 1, it can be seen that if the raw materials for preparing the copper-based molecular sieve are mixed together in the present invention, the dissolution of the raw materials will be incomplete, and agglomeration of the raw materials will occur during the mixing process, resulting in poor crystallinity of the product, thereby resulting in a low yield of the prepared copper-based molecular sieve.

[0150] (5) By comparing Example 1 and Comparative Example 2, and Example 2 and Comparative Example 3, it can be seen that if one post-treatment process is omitted in the present invention, the dispersion and activity of the copper substance in the obtained molecular sieve will be low, and the catalytic performance of the copper-based molecular sieve cannot be effectively improved.

[0151] In summary, the present invention obtains copper-based molecular sieves by crystallization under alkaline environment, omits the cumbersome process of multi-step ion exchange reaction, reduces the preparation process, saves production cost, and prepares copper-based molecular sieves with excellent catalytic activity and hydrothermal stability. Secondly, the present invention helps to disperse and dissolve each substance in the raw material by regulating the mixed process of silicon source, aluminum source, copper source and template agent in the raw material, improves the crystallization rate and the crystallinity of the product molecular sieve, and effectively improves the yield of preparing copper-based molecular sieves. Furthermore, the present invention uses an acid solution or an ammonium salt solution to treat the reaction system after crystallization by a one-step post-treatment, regulates the existence state of Cu species in the molecular sieve, on the one hand, improves the dispersibility of Cu species in the molecular sieve, and on the other hand, improves the activity of copper-based molecular sieves, thereby further improving the catalytic performance of the molecular sieve.

[0152] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a copper-based molecular sieve, characterized in that: The preparation method comprises the following steps: (1) a silicon source, an aluminum source, an alkali source, a first template and a first solvent are first mixed to prepare a solution A; The copper source, the second template and the second solvent are mixed for a second time to prepare a solution B; (2) mixing solution A and solution B for a third time, reacting and crystallizing, and performing a post-treatment on the system after the reaction and crystallization to obtain the copper-based molecular sieve; Wherein, the reagents used in the one-step post-treatment include acid solution and / or ammonium salt solution.

2. The preparation method according to claim 1, characterized in that: Step (1) The first template agent includes any one of 2,6-dimethyl-N-pyridine, tetraethyldimethyldiazacyclo-6, N,N,N,N-tetraethyl-exo,exo-bicyclo[2.2.2]oct-7-ene-2,3,5,6-bitetrahydropyridine iodide ammonium salt, hydroxyl type N,N-dimethylpiperidine or 18-crown ether-6; Preferably, when the first template is 2,6-dimethyl-N-pyridine, the obtained copper-based molecular sieve is a Cu-RTH molecular sieve; Preferably, when the first template is tetraethyldimethyldiazacyclo-6, the obtained copper-based molecular sieve is Cu-AFX molecular sieve; Preferably, when the first template is N,N,N,N-tetraethyl-exo,exo-bicyclo[2.2.2]oct-7-ene-2,3,5,6-bipyridone iodide ammonium salt, the obtained copper-based molecular sieve is Cu-UZM-35 molecular sieve; Preferably, when the first template is hydroxy-type N,N-dimethylpiperidine, the obtained copper-based molecular sieve is Cu-ERI molecular sieve; Preferably, when the first template is 18-crown-6, the obtained copper-based molecular sieve is Cu-RHO molecular sieve.

3. The preparation method according to claim 1 or 2, characterized in that: The silicon source in step (1) comprises any one of silica sol, sodium silicate, fumed silica, silica gel, Y molecular sieve, Beta molecular sieve or ZSM-5 molecular sieve, or a combination of at least two thereof; Preferably, the aluminum source in step (1) comprises any one of sodium aluminate, aluminum hydroxide, aluminum sulfate, pseudo-boehmite, Y molecular sieve, Beta molecular sieve or ZSM-5 molecular sieve, or a combination of at least two thereof; Preferably, the alkali source in step (1) comprises sodium hydroxide and / or potassium hydroxide; Preferably, the copper source in step (1) comprises any one of copper sulfate, copper acetate, copper nitrate or copper chloride, or a combination of at least two thereof; Preferably, the second template in step (1) comprises any one of tetraethylenepentamine, triethylenetetramine, diethylenetriamine or ammonia water, or a combination of at least two thereof.

4. The preparation method according to any one of claims 1 to 3, characterized in that In step (1), the molar ratio of the silicon element in the silicon source to the aluminum element in the aluminum source is (1-50):1, preferably (5-40):1, and more preferably (10-20):1; Preferably, in step (1), the molar ratio of the silicon source to the alkali source is (1-30):1, preferably (5-15):1, and more preferably (5-10):1; Preferably, the molar ratio of the silicon source to the first template in step (1) is (1-30):1, preferably (5-15):1, and more preferably (5-10):1; Preferably, the molar ratio of the copper source to the second template in step (1) is (0.1-1.5):1, preferably (0.5-1):1; Preferably, in the third mixing of step (2), the molar ratio of the silicon source to the copper source is (1-1000):1, preferably (5-100):1, and more preferably (10-50):

1.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The temperatures of the first mixing, the second mixing and the third mixing are independently selected from 10-80°C; Preferably, the rotation speeds of the first mixing, the second mixing and the third mixing are independently selected from 10-2000 r / min, preferably 100-500 r / min; Preferably, the time of the first mixing, the second mixing and the third mixing is independently selected from 0.5-16h; Preferably, the temperature of the reaction crystallization in step (2) is 120-200°C; Preferably, the reaction crystallization time in step (2) is 1-336h; Preferably, the reaction crystallization in step (2) is carried out under non-stirring closed conditions; Preferably, in step (2), the product after the reaction crystallization is further subjected to cooling and separation treatment.

6. The preparation method according to any one of claims 1 to 5, characterized in that: In the post-treatment process of step (2), the H + The concentration is 0.01-0.2 mol / L; Preferably, in the post-treatment process of step (2), the concentration of the ammonium salt solution used is 0.01-0.5 mol / L; Preferably, the post-treatment time in step (2) is 1-24 h, preferably 5-10 h; Preferably, the acid in the acid solution includes any one of hydrochloric acid, nitric acid or sulfuric acid, or a combination of at least two thereof; Preferably, the ammonium salt in the ammonium salt solution includes any one of ammonium chloride, ammonium nitrate or ammonium sulfate, or a combination of at least two of them.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The preparation method further comprises: washing, drying and calcining the product after the one-step post-treatment to obtain the copper-based molecular sieve; Preferably, the drying temperature is 40-160°C; Preferably, the heating rate of the calcination is 0.5-5°C / min; Preferably, the calcination temperature is 500-900°C; Preferably, the calcination holding time is 5-10 hours.

8. A copper-based molecular sieve, characterized in that The copper-based molecular sieve is prepared by the preparation method of the copper-based molecular sieve according to any one of claims 1-7.

9. The copper-based molecular sieve according to claim 8, characterized in that: The copper-based molecular sieve includes any one of Cu-RTH molecular sieve, Cu-AFX molecular sieve, Cu-UZM-35 molecular sieve, Cu-ERI molecular sieve, Cu-RHO molecular sieve, Cu-CHA molecular sieve or Cu-AEI molecular sieve; Preferably, the copper-based molecular sieve includes any one of Cu-RTH molecular sieve, Cu-AFX molecular sieve, Cu-UZM-35 molecular sieve, Cu-ERI molecular sieve or Cu-RHO molecular sieve.

10. Use of the copper-based molecular sieve according to claim 8 or 9 in the conversion of nitrogen oxides.

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