A method for economically and rapidly synthesizing Cu / SSZ-13 molecular sieve

Abstract

The invention discloses a method for economically and rapidly synthesizing a Cu / SSZ-13 molecular sieve. The method selects a suitable silicon source, an aluminum source, an alkali source, a metal copper salt, a template agent and an auxiliary agent and mixes them in a suitable proportion, strictly controls the experimental conditions, accelerates the zeolite nucleation rate, shortens the zeolite crystallization time, and rapidly synthesizes the Cu / SSZ-13 molecular sieve in one step. The method has the advantages of low cost, low pollution and high economy, simple operation, safety and reliability, good repeatability, etc., and has broad market application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of catalyst preparation, and in particular to a method for economically and rapidly synthesizing a Cu / SSZ-13 molecular sieve. Background Art

[0002] SSZ-13 molecular sieve is an aluminum silicate material with a CHA topological structure and a three-dimensional pore system with a pore size of 0.38 nm. It is widely used in denitrification reactions, methanol to olefin reactions and gas separation. SSZ-13 is usually prepared by hydrothermal synthesis using an expensive organic template N,N,N-trimethyl-1-adamantyl ammonium hydroxide (TMAdaOH) as a template. A patent (CN103601211A) reported an economical synthesis method using cheap choline chloride as a template. At present, a variety of templates for preparing SSZ-13 have been developed, mainly including benzyltrimethylammonium hydroxide, tetraethylammonium hydroxide and Cu-tetraethylenepentamine. SSZ-13 molecular sieves can be successfully prepared using the above templates, but the traditional hydrothermal synthesis time is long, usually 4-6 days. Although the preparation time can be shortened to 2 days by adding seed crystals, it is still time-consuming and the catalyst preparation efficiency is low.

[0003] Cu-SSZ-13 is a SSZ-13 molecular sieve loaded with metallic copper. It has very good catalytic performance in catalytic redox reactions, and has more excellent low-temperature catalytic activity and hydrothermal stability. It is mainly used in direct oxidation of methane to methanol, methanol to olefins, gas adsorption, especially in the removal of NO from automobile exhaust. x The research field of Cu-SSZ-13 has received extensive attention. The traditional preparation method of Cu-SSZ-13 molecular sieve is liquid phase ion exchange method, that is, by first synthesizing SSZ-13 molecular sieve crystallization product, then exchanging it with ammonium to obtain H-type SSZ-13 molecular sieve, and then exchanging it with copper ions and calcining it to obtain Cu / SSZ-13 catalyst. At present, the above method has the characteristics of a long reaction cycle, usually 2-6 days, which increases the cost of preparing molecular sieve Cu-SSZ-13 and is not conducive to large-scale production. Summary of the invention

[0004] The purpose of the present invention is to improve the preparation efficiency of Cu / SSZ-13 catalyst, introduce auxiliary urea into the synthesis gel to chelate aluminum species and copper species therein, accelerate the zeolite nucleation rate, shorten the zeolite crystallization time, and synthesize the Cu / SSZ-13 molecular sieve denitration catalyst economically and quickly in one step.

[0005] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0006] A method for economically and rapidly synthesizing Cu / SSZ-13 molecular sieves comprises the following steps:

[0007] (a) mixing a metal copper salt, urea, an aluminum source and deionized water, and stirring until completely dissolved; then adding an alkali source and a template agent, stirring and dissolving, and then adding a silicon source, stirring evenly at room temperature, adjusting the pH value to 12-13, and aging at room temperature for 4 hours to obtain a synthetic gel;

[0008] (b) The synthesized gel is transferred into a reaction vessel for crystallization, and the crystallized solid product is washed, separated, dried and calcined to obtain a Cu / SSZ-13 molecular sieve.

[0009] Preferably, the initial molar ratios of the synthesized gel in step (a) are SiO2 / Al2O3=2-30:1, urea / Al2O3=0.5-4:1, template / Al2O3=1-4:1, and H2O / SiO2=400-1200:1.

[0010] Preferably, the alkali source is an organic base, including one or a combination of triethylamine, diethylamine, triethanolamine, tripropylamine and ammonia water.

[0011] Preferably, the silicon source is one of sodium silicate, silica sol and solid silica gel.

[0012] Preferably, the metal copper salt is at least one of copper chloride, copper nitrate and copper sulfate, and the amount of copper element added accounts for 1-5wt% of SiO2.

[0013] Preferably, the aluminum source is one or a combination of pseudo-boehmite, sodium aluminate, aluminum nitrate, aluminum isopropoxide and aluminum sulfate.

[0014] Preferably, the template agent is one or more of choline chloride, tetraethylammonium hydroxide, Cu-tetraethylenepentamine, and N,N,N-trimethyl-1-adamantylammonium hydroxide.

[0015] Preferably, the crystallization temperature is 140-180° C., and the crystallization time is 1-12 h.

[0016] Preferably, the calcination temperature is 550° C. and the calcination time is 6 hours.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1) The Cu / SSZ-13 molecular sieve is synthesized by a hydrothermal method without the need for ammonium exchange and copper exchange. The auxiliary agent urea is introduced into the synthetic gel to chelate the aluminum species and copper species therein, thereby accelerating the zeolite nucleation rate and shortening the zeolite crystallization time. The Cu / SSZ-13 molecular sieve denitrification catalyst is synthesized economically and quickly in one step. It has the advantages of low cost, low pollution and high economy, simple operation, safety and reliability, good repeatability, and is convenient for market-scale production.

[0019] 2) The Cu-SSZ-13 prepared by the present invention has a higher crystallinity, and the surface is no longer a flat cubic surface. These surface defects and the small size of the crystal provide a large specific surface area and have better catalytic activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the XRD pattern of the Cu / SSZ-13 molecular sieve prepared in Example 4 of the present invention;

[0021] Figure 2 This is a SEM image of the Cu / SSZ-13 molecular sieve prepared in Example 4 of the present invention;

[0022] Figure 3 This is a SEM image of the Cu / SSZ-13 molecular sieve prepared in the comparative example of the present invention. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described below in conjunction with specific embodiments, but is not limited thereto.

[0024] Example 1

[0025] A method for economically and rapidly synthesizing Cu / SSZ-13 molecular sieves comprises the following steps:

[0026] (a) mixing a metal copper salt, urea, an aluminum source and deionized water, and stirring until completely dissolved; then adding an alkali source and a template agent, stirring and dissolving, and then adding a silicon source, stirring evenly at room temperature, adjusting the pH value to 12-13, and aging at room temperature for 4 hours to obtain a synthetic gel;

[0027] (b) The synthesized gel was transferred into a reaction vessel for crystallization at 150°C for 2 h, and the crystallized solid product was washed, separated, dried, and calcined at 550°C for 6 h to obtain Cu / SSZ-13 molecular sieve.

[0028] The initial molar ratios of the synthesized gel in step (a) are SiO2 / Al2O3=2:1, urea / Al2O3=0.5:1, template / Al2O3=1:1, and H2O / SiO2=400:1.

[0029] The alkali source is triethylamine, the silicon source is sodium silicate, the metal copper salt is copper chloride, and the amount of copper added accounts for 5wt% of SiO2, the aluminum source is pseudo-boehmite, and the template agent is choline chloride.

[0030] Example 2

[0031] A method for economically and rapidly synthesizing Cu / SSZ-13 molecular sieves comprises the following steps:

[0032] (a) mixing a metal copper salt, urea, an aluminum source and deionized water, and stirring until completely dissolved; then adding an alkali source and a template agent, stirring and dissolving, and then adding a silicon source, stirring evenly at room temperature, adjusting the pH value to 12-13, and aging at room temperature for 4 hours to obtain a synthetic gel;

[0033] (b) The synthesized gel was transferred into a reaction vessel for crystallization at 160°C for 5 h, and the crystallized solid product was washed, separated, dried, and calcined at 550°C for 6 h to obtain Cu / SSZ-13 molecular sieve.

[0034] The initial molar ratios of the synthesized gel in step (a) are SiO2 / Al2O3=20:1, urea / Al2O3=2:1, template / Al2O3=2:1, and H2O / SiO2=800:1.

[0035] The alkali source is triethanolamine, the silicon source is silica sol, the metal copper salt is copper nitrate, and the amount of copper added accounts for 1wt% of SiO2, the aluminum source is sodium metaaluminate, and the template agent is tetraethylammonium hydroxide.

[0036] Example 3

[0037] A method for economically and rapidly synthesizing Cu / SSZ-13 molecular sieves comprises the following steps:

[0038] (a) mixing a metal copper salt, urea, an aluminum source and deionized water, and stirring until completely dissolved; then adding an alkali source and a template agent, stirring and dissolving, and then adding a silicon source, stirring evenly at room temperature, adjusting the pH value to 12-13, and aging at room temperature for 4 hours to obtain a synthetic gel;

[0039] (b) The synthesized gel was transferred into a reactor for crystallization at 180°C for 1 h, and the crystallized solid product was washed, separated, dried, and calcined at 550°C for 6 h to obtain Cu / SSZ-13 molecular sieve.

[0040] The initial molar ratios of the synthesized gel in step (a) are SiO2 / Al2O3=30:1, urea / Al2O3=4:1, template / Al2O3=4:1, and H2O / SiO2=1200:1.

[0041] The alkali source is tripropylamine, the silicon source is solid silica gel, the metal copper salt is copper sulfate, and the amount of copper added accounts for 3wt% of SiO2, the aluminum source is aluminum nitrate, and the template agent is Cu-tetraethylenepentamine.

[0042] Example 4

[0043] A method for economically and rapidly synthesizing Cu / SSZ-13 molecular sieves comprises the following steps:

[0044] (a) mixing a metal copper salt, urea, an aluminum source and deionized water, and stirring until completely dissolved; then adding an alkali source and a template agent, stirring and dissolving, and then adding a silicon source, stirring evenly at room temperature, adjusting the pH value to 12-13, and aging at room temperature for 4 hours to obtain a synthetic gel;

[0045] (b) The synthesized gel was transferred into a reactor for crystallization at 140°C for 10 h, and the crystallized solid product was washed, separated, dried, and calcined at 550°C for 6 h to obtain Cu / SSZ-13 molecular sieve.

[0046] The initial molar ratios of the synthesized gel in step (a) are SiO2 / Al2O3=15:1, urea / Al2O3=3:1, template / Al2O3=3:1, and H2O / SiO2=1000:1.

[0047] The alkali source is diethylamine; the silicon source is silica sol; the metal copper salt is copper chloride, and the amount of copper added accounts for 4wt% of SiO2; the aluminum source is aluminum isopropoxide; and the template agent is N,N,N-trimethyl-1-adamantyl ammonium hydroxide.

[0048] Comparative Example

[0049] A method for synthesizing Cu / SSZ-13 molecular sieve in a conventional manner comprises the following steps:

[0050] (a) mixing a metal copper salt, an aluminum source and deionized water, and stirring until completely dissolved; then adding an alkali source and a template agent, stirring and dissolving, and then adding a silicon source, stirring evenly at room temperature, adjusting the pH value to 12-13, and aging at room temperature for 4 hours to obtain a synthetic gel;

[0051] (b) The synthesized gel was transferred into a reaction vessel for crystallization treatment at 140°C for 144 hours, and the crystallized solid product was washed, separated, dried, and calcined at 550°C for 6 hours to obtain Cu / SSZ-13 molecular sieve.

[0052] The initial molar ratios of the synthesized gel in step (a) are SiO2 / Al2O3=15:1, template / Al2O3=3:1, and H2O / SiO2=1000:1.

[0053] The alkali source is diethylamine; the silicon source is silica sol; the metal copper salt is copper chloride, and the amount of copper added accounts for 1-5wt% of SiO2; the aluminum source is aluminum isopropoxide; and the template agent is N,N,N-trimethyl-1-adamantyl ammonium hydroxide.

[0054] Except for not containing urea, the other aspects of the comparative example are the same as those of Example 4.

[0055] Performance Testing

[0056] The Cu-SSZ-13 molecular sieve prepared in Example 4 was subjected to X-ray diffraction test, and its XRD spectrum is shown in Figure 1 ,Will Figure 1 Compared with the standard card, it can be seen that the Cu-SSZ-13 molecular sieve sample synthesized by the method of the present invention shows a CHA characteristic diffraction peak, indicating that the sample synthesized by the method of the present invention has a typical CHA structure crystal form, and the spectrum line is flat, there is no impurity peak, and the crystallinity is good.

[0057] The Cu-SSZ-13 molecular sieves prepared in Example 4 and the comparative example were tested by scanning electron microscopy. Figure 2 and Figure 3 It can be seen that the particle size of the product prepared in the embodiment of the present invention is 0.5-2 μm, and the particle dispersibility is good, while the product prepared in the comparative example is a dispersion of regular larger micron-sized cubic particles.

[0058] The Cu-SSZ-13 molecular sieves prepared in Examples 1-4 and the comparative example were used to purify diesel exhaust gas at an air velocity of 400,000 h -1 The test was carried out under the conditions of reaction temperature 250℃, NO x The conversion results are shown in Table 1.

[0059] Table 1 Test results

[0060]

[0061] From the results in Table 1, it can be seen that the product NO prepared by the present invention x The conversion rates are all above 95%, with excellent catalytic activity.

[0062] It should be noted that the above embodiments are only partial embodiments of the preferred methods of implementing the present invention, rather than all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

Claims

1. A method for economically and rapidly synthesizing Cu / SSZ-13 molecular sieves, characterized in that: It includes the following steps: (a) mixing a metal copper salt, urea, an aluminum source and deionized water, and stirring until completely dissolved; then adding an alkali source and a template agent, stirring and dissolving, and then adding a silicon source, stirring evenly at room temperature, adjusting the pH value to 12-13, and aging at room temperature for 4 hours to obtain a synthetic gel; (b) transferring the synthesized gel into a reaction kettle for crystallization, and washing, separating, drying and calcining the crystallized solid product to obtain a Cu / SSZ-13 molecular sieve; The initial molar ratio of the synthesized gel in step (a) is SiO2 / Al2O3=2-30:1, urea / Al2O3=0.5-4:1, template / Al2O3=1-4:1, H2O / SiO2=400-1200:1; The crystallization temperature is 140-180° C., and the crystallization time is 1-12 h; The calcination temperature is 550°C and the calcination time is 6 hours; The alkaline source is an organic base, including one or more of triethylamine, diethylamine, triethanolamine, tripropylamine and ammonia water; The metal copper salt is at least one of copper chloride, copper nitrate and copper sulfate, and the amount of copper element accounts for 1-5wt% of SiO2.

2. The method for economically and rapidly synthesizing Cu / SSZ-13 molecular sieve according to claim 1, characterized in that: The silicon source is one of sodium silicate, silica sol and solid silica gel.

3. The method for economically and rapidly synthesizing Cu / SSZ-13 molecular sieve according to claim 1, characterized in that: The aluminum source is one or a combination of pseudo-boehmite, sodium aluminate, aluminum nitrate, aluminum isopropoxide and aluminum sulfate.

4. The method for economically and rapidly synthesizing Cu / SSZ-13 molecular sieve according to claim 1, characterized in that: The template agent is one or more of choline chloride, tetraethylammonium hydroxide, Cu-tetraethylenepentamine, and N,N,N-trimethyl-1-adamantylammonium hydroxide.

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