Pyrimidine template agent and application thereof in preparation of SSZ-98 molecular sieve

Abstract

The invention relates to the technical field of molecular sieve materials, and particularly discloses a pyrimidine template agent and application thereof in preparation of an SSZ-98 molecular sieve, the structure of the pyrimidine template agent is shown as a general formula I: # imgabs0 #, in the formula I, R1 and R2 are independently selected from C1-C12 alkyl groups; the pyrimidine template agent provided by the invention has high hydrothermal stability, is difficult to decompose in the preparation process of the molecular sieve and has high utilization rate, so that the dosage of the pyrimidine template agent is reduced, and the production cost of the molecular sieve is reduced; and secondly, the consumption of the template agent is reduced, the amount of harmful gas generated in the high-temperature calcination process is also reduced, and the environmental pollution is less. The invention also provides application of the pyrimidine template agent in preparation of the SSZ-98 molecular sieve, and the pyrimidine template agent is suitable for SSZ-98 type molecular sieve skeleton growth, short in hydro-thermal synthesis period, high in production efficiency and high in product yield.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieve materials, and more specifically, to pyrimidine-based templating agents and their use in the preparation of SSZ-98 molecular sieves. Background Art

[0002] As a typical porous material, molecular sieves have important application values in the fields of adsorption separation, catalytic conversion, and ion exchange due to their high specific surface area, excellent shape-selective catalytic performance, and adjustable acidic characteristics. Among them, ERI-type molecular sieves (International Zeolite Association code: ERI) have attracted much attention due to their unique pore topology structure. Their frameworks usually contain double six-membered rings (d6R) and eight-membered ring pores / channels and cages. ERI-type molecular sieves include two types, SSZ-98 and ZSM-34, and are usually synthesized by hydrothermal crystallization method. The structure-directing agent (SDA) used in the synthesis process is a typical complex organic molecule, which induces the shaping of the molecular shape and pattern of the zeolite framework through hydrothermal reaction. The SDA acts as a mold for the formation of the molecular sieve, inducing the silicon-aluminum units to form a crystalline structure around it. After the hydrothermal reaction, the SDA is generally removed from the crystalline structure by a high temperature above 500 °C, leaving behind porous aluminosilicate cages. ERI-type molecular sieves have a relatively small pore size and good shape-selective selectivity, suitable for the passage of C1-C4 hydrocarbons. Therefore, they show important commercial value in industrial processes such as methanol-to-olefins (MTO) and light hydrocarbon catalytic conversion.

[0003] The synthesis of ERI-type molecular sieves began in 1960. The US Patent US2950925 first reported the hydrothermal synthesis method of T-type zeolite (ERI / OFF symbiotic body). With the development of molecular sieve synthesis chemistry, the US Patents US9409786 and US9416017 disclosed the use of N,N'-dimethyl-1,4-diazabicyclo[2.2.2]octane divalent cations as structure-directing agents to synthesize pure-phase SSZ-98 type molecular sieves. The Chinese Patent CN106470944B disclosed the use of N,N'-dimethyl-1,4-diazabicyclo[2.2.2]octane divalent cations and 18-crown-6 as double templating agents to synthesize pure-phase SSZ-98 type molecular sieves. The Chinese Patent CN108495815A disclosed the use of one or more of 1,1-diethylpyrrolidinium cations, 1-butyl-1-methylpiperidinium cations, 1,1-diethyl-4-methylpiperidinium cations, and 8-(pyridin-2-yl)-5,8-diazaspiro[4.5]decane-5-ium cations as structure-directing agents to synthesize pure-phase SSZ-98 type molecular sieves. However, the existing technologies for synthesizing SSZ-98 type molecular sieves using the above organic templating agents generally have the following significant limitations: 1. High cost of the template agent: The synthesis steps of the reported SDAs (such as bicyclic diamines, crown ether composite systems) are complex, and the raw materials are expensive, accounting for 60%-80% of the total manufacturing cost of molecular sieves; 2. Long crystallization period: The crystallization process of hydrothermal synthesis usually takes 3-7 days or even longer, resulting in high energy consumption and low production efficiency; 3. Low yield: Limited by the matching efficiency of the template agent and the silicon-aluminum precursor, the product yield is generally low, about 50%, and the template agent is difficult to recycle and reuse; 4. Environmental burden: A large amount of CO2 and nitrogen-containing waste gas are generated during the process of removing the template agent by high-temperature calcination (>500°C), which does not conform to the development trend of green chemistry.

[0004] Therefore, there is an urgent need for an efficient and cost-effective template agent, which needs to be applicable to the framework growth of SSZ-98 type molecular sieves, and can quickly synthesize zeolites, improve the yield of molecular sieves, so as to mass-produce SSZ-98 type molecular sieves and be widely used in selective catalytic reduction of nitrogen oxides. Based on the above statement, the present invention provides a pyrimidine-based template agent and its application in the preparation of SSZ-98 molecular sieves. Summary of the Invention

[0005] In order to solve the problems commonly existing in the prior art, such as high cost of the template agent, long crystallization period, low yield, difficulty in recycling and reusing the template agent, and easy environmental burden during the removal process, the present invention provides a pyrimidine-based template agent and its application in the preparation of SSZ-98 molecular sieves; the pyrimidine-based template agent has high hydrothermal stability, is not easily decomposed during the preparation process of molecular sieves, and has high utilization rate. Therefore, the dosage of the pyrimidine-based template agent is reduced, the production cost of molecular sieves is reduced, and the yield of molecular sieves is increased. Secondly, the reduction of the dosage of the template agent also reduces the amount of harmful gases generated during the high-temperature calcination process, less pollutes the environment, and is conducive to the industrial production and application of molecular sieves.

[0006] In the first aspect, the present invention provides a pyrimidine-based template agent, adopting the following technical scheme: The pyrimidine-based template agent has a structure as shown in general formula I: ; Formula I

[0007] In formula I, R1 and R2 are each independently selected from C1-C12 alkyl groups.

[0008] Preferably, R1 and R2 are each independently selected from methyl, ethyl, propyl, butyl, pentyl or hexyl.

[0009] Preferably, R1 and R2 are the same.

[0010] Preferably, the compound shown in formula I is selected from the following structures: 。

[0011] Preferably, taking R1 and R2 as the same as an example, the preparation method of the pyrimidine template agent shown in Formula I is described, including the following steps:

[0012] (1) In an autoclave, using a mixed solvent of methanol and water as the reaction solvent, under a nitrogen atmosphere, intermediate MA reacts with dialkyl carbonate ( ), to obtain intermediate MA-1; (2) Add the intermediate MA-1 prepared in step (1) into deionized water, add lithium hydroxide, and then add calcium hydroxide for reaction, to obtain the pyrimidine template agent shown in Formula I.

[0013] Preferably, the volume ratio of methanol to water in the reaction solvent of step (1) is 20-30:1.

[0014] In a second aspect, the present invention provides the use of the pyrimidine template agent shown in Formula I in the preparation of SSZ-98 zeolite.

[0015] In a third aspect, the present invention provides a preparation method of SSZ-98 zeolite, and the method uses the pyrimidine template agent shown in Formula I as an organic template agent.

[0016] Preferably, the preparation method of the SSZ-98 zeolite includes the following steps: First, mix the aluminum source with deionized water and stir, then sequentially add the aqueous solution of the pyrimidine template agent, the alkali source, and the silicon source, heat up to 30-70 °C, and stir for 2-4 h; then pour the material into an autoclave, close and heat up to 100-200 °C, carry out hydrothermal reaction for 20-30 h, take out the material, let it stand, filter, wash the filter cake with water until neutral, then remove water and dry, and then place it in a muffle furnace and calcine at 300-600 °C to obtain the alkali metal type SSZ-98 zeolite.

[0017] Preferably, the aluminum source uses Y zeolite.

[0018] Preferably, the Y zeolite has an appearance of white to off-white, SiO2 / Al2O3 = 5-50, and the Na2O content < 0.15%.

[0019] Preferably, the SiO2 / Al2O3 of the Y zeolite = 12.

[0020] Preferably, the silicon source uses silica sol.

[0021] Preferably, the silica sol is silica sol with a content of 25-35%.

[0022] Preferably, the silica sol is a silica sol with a content of 30%.

[0023] Preferably, the alkali source is sodium hydroxide or potassium hydroxide.

[0024] Preferably, the structure of the pyrimidine-based template agent is: .

[0025] In summary, the present invention has the following beneficial effects: The present invention provides a pyrimidine-based template agent, which has high hydrothermal stability, is not easily decomposed during the preparation of molecular sieves, has a high utilization rate. Therefore, the dosage of the pyrimidine-based template agent is reduced, and the production cost of the molecular sieve is reduced; secondly, the reduction of the template agent dosage also reduces the amount of harmful gases generated during the high-temperature calcination process, and has less environmental pollution.

[0026] The present invention also provides a preparation method of a pyrimidine-based template agent. The preparation method is simple in operation, mild in reaction conditions, can be prepared by reacting with cheap raw materials, and the industrial production cost is significantly reduced, which is conducive to the industrial production and application of molecular sieves.

[0027] The present invention provides the application of a pyrimidine-based template agent in the preparation of SSZ-98 molecular sieve, which is suitable for the framework growth of SSZ-98 type molecular sieve, has a short hydrothermal synthesis cycle, high production efficiency and high product yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification, and are used to explain the present invention together with the embodiments of the present invention, and do not constitute a limitation to the present invention.

[0029] Figure 1 It is a scanning electron microscope image of the SSZ-98 molecular sieve prepared in Application Example 1 of the present invention.

[0030] Figure 2 It is an XRD spectrum of the SSZ-98 molecular sieve prepared in Application Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The following further describes the present invention in detail with reference to the embodiments.

[0032] The materials, reagents, etc. used in the present invention can be obtained from commercial channels without special instructions.

[0033] Example 1: Synthesis of Compound P1

[0034] (1) In an autoclave, 16.4 g of intermediate M0, 20 g of dimethyl carbonate, 50 mL of methanol, and 2 mL of water were added. After sealing, the air was replaced with nitrogen three times, and then nitrogen was filled to 1.2 MPa. The temperature was raised to 90 °C and the reaction was carried out for 30 hours. After cooling, methanol and water were concentrated from the reaction solution to obtain a viscous substance containing intermediate M1. Without purification, the next reaction was directly carried out.

[0035] (2) The viscous substance containing intermediate M1 prepared in step (1) was added to 120 mL of deionized water, 0.50 g of lithium hydroxide was added, and then 10 g of calcium hydroxide was added. The temperature was raised to 70 °C and kept warm for 5 h. Unreacted calcium hydroxide and generated calcium carbonate were filtered out. Excess water and methanol were rotary evaporated to obtain 62 g of an aqueous solution of compound P1. It was titrated with 0.1 mol / L hydrochloric acid solution, and the mass concentration was 27.1%.

[0036] To obtain pure compound P1, the following experiment was carried out: Take 1.0 g of the above aqueous solution of P1 and add 10 mL Extract with ethyl acetate of 3. After the ethyl acetate layer was dried with anhydrous sodium sulfate, the desiccant was filtered off. It was placed at room temperature to slowly volatilize ethyl acetate until needle-like crystals appeared therein. The crystals were filtered and dried in vacuo to obtain pure compound P1. The elemental analysis results are as follows: Theoretical values (%) : C, 57.12; H, 8.63; N, 26.64, measured values (%) : C, 57.16; H, 8.60; N, 26.60.

[0037] Example 2: Synthesis of compound P2

[0038] Referring to the synthesis method of compound P1 in Example 1, only dimethyl carbonate in the raw materials was replaced with diethyl carbonate to obtain 66 g of an aqueous solution of compound P2. It was titrated with 0.1 mol / L hydrochloric acid solution, and the mass concentration was 25.3%.

[0039] Referring to the preparation method of pure compound P1, pure compound P2 was prepared. The elemental analysis results are as follows: Theoretical values (%) : C, 60.47; H, 9.30; N, 23.51, measured values (%) : C, 60.48; H, 9.28; N, 23.50.

[0040] Application Example 1: Using compound P1 of Example 1 as a template agent to prepare SSZ-98 zeolite The preparation method of SSZ-98 molecular sieve is as follows: First, mix 16 g of Y molecular sieve (SiO2 / Al2O3 = 5.5) with 150 g of deionized water, stir with a stirrer for 1 h, then sequentially add 40 g of an aqueous solution of compound P1 in Example 1 (mass concentration of 27.1%), 14 g of sodium hydroxide, and 175 g of silica sol with a 30% content, heat up to 50 °C, and stir for 3 h; then pour the material into an autoclave, close it and heat up to 160 °C for hydrothermal reaction for 24 h, take out the material, let it stand, filter, wash the filter cake with deionized water until neutral, remove water from the material and dry it, then place it in a muffle furnace, calcine at 450 °C for 15 hours, wash it again, and dry it at 150 °C for 12 hours to obtain 45 g (the theoretical value is 69 g) of SSZ-98 molecular sieve. The scanning electron microscope image of SSZ-98 molecular sieve is as shown in Figure 1 shown, and the XRD spectrum of SSZ-98 molecular sieve is as shown in Figure 2 shown. The X-ray fluorescence analysis result of SSZ-98 molecular sieve shows that SAR = 20.5.

[0041] Application Example 2: Use compound P1 in Example 1 as a template agent to prepare SSZ-98 molecular sieve The preparation method refers to Application Example 1, only changing the aqueous solution of compound P1 in Example 1 (mass concentration of 27.1%) from 40 g to 35 g, to obtain 47 g (the theoretical value is 69 g) of SSZ-98 molecular sieve. The X-ray fluorescence analysis result shows that SAR = 21.1.

[0042] Application Example 3: Use compound P1 in Example 1 as a template agent to prepare SSZ-98 molecular sieve The preparation method refers to Application Example 1, only changing 16 g of Y molecular sieve (SiO2 / Al2O3 = 5.5) in Example 1 to 16 g of Y molecular sieve (SiO2 / Al2O3 = 12), to obtain 53 g (the theoretical value is 69 g) of SSZ-98 molecular sieve. The X-ray fluorescence analysis result shows that SAR = 22.3.

[0043] Application Example 4: Use compound P2 in Example 2 as a template agent to prepare SSZ-98 molecular sieve The preparation method refers to Application Example 1, only changing the compound P1 solution to 40 g of an aqueous solution of compound P2 in Example 2 (mass concentration of 25.3%), to obtain 49 g (the theoretical value is 69 g) of SSZ-98 molecular sieve.

[0044] Comparative Application Example 1: The preparation method was referred to Application Example 1, except that the compound P1 solution therein was replaced with an aqueous solution of 50 g of 8-(pyridin-2-yl)-5,8-diazaspiro[4.5]decane-5-ium hydroxide with a mass content of 20%, and 37 g (the theoretical value was 69 g) of SSZ-98 molecular sieve was obtained.

[0045] The structure of 8-(pyridin-2-yl)-5,8-diazaspiro[4.5]decane-5-ium hydroxide is as follows:

[0046] In summary, it can be seen that using the pyrimidine-based template agent prepared in Examples 1-2 of the present invention to prepare SSZ-98 molecular sieve is beneficial to the growth of the molecular sieve framework, with a low template agent dosage, a short hydrothermal synthesis period, low production costs, high production efficiency, and high product yield.

[0047] This specific embodiment is only an explanation of the present invention, and it is not a limitation of the present invention. Those skilled in the art can make modifications to this embodiment without creative contributions according to needs after reading this specification, but as long as it is within the scope of the claims of the present invention, it is protected by the patent law.

Claims

1. A pyrimidine-based template agent, characterized in that, The structure is as shown in General Formula I: ； Formula I In Formula I, R1 and R2 are each independently selected from C1-C12 alkyl groups.

2. The pyrimidine-based template agent according to claim 1, wherein Said R1 and R2 are each independently selected from methyl, ethyl, propyl, butyl, pentyl or hexyl.

3. The pyrimidine template agent according to claim 1, wherein Said R1 and R2 are the same.

4. The pyrimidine-based templating agent according to claim 1, characterized in that, The compound shown in Formula I is selected from the following structures: 。 5. The pyrimidine templating agent according to claim 3, wherein The preparation method of the pyrimidine template agent includes the following steps: (1) In an autoclave, using a mixed solvent of methanol and water as the reaction solvent, under a nitrogen atmosphere, intermediate MA reacts with dialkyl carbonate to obtain intermediate MA-1; (2) Add the intermediate MA-1 prepared in step (1) to deionized water, add lithium hydroxide, and then add calcium hydroxide for reaction to obtain the pyrimidine template agent shown in Formula I.

6. Use of the pyrimidine template agent according to any one of claims 1-5 in the preparation of SSZ-98 zeolite.

7. Use of the pyrimidine-based template agent according to claim 6 in the preparation of SSZ-98 zeolite, characterized in that, The preparation method of the SSZ-98 zeolite includes the following steps: First, mix the aluminum source with deionized water and stir, then sequentially add an aqueous solution of the pyrimidine template agent, an alkali source, and a silicon source, heat up to 30-70 °C, and stir for 2-4 h; then pour the material into an autoclave, close and heat up to 100-200 °C, carry out hydrothermal reaction for 20-30 h, take out the material, let it stand, filter, wash the filter cake with water until neutral, then remove water and dry, and then place it in a muffle furnace and calcine at 300-600 °C to obtain SSZ-98 zeolite.

8. Use of the pyrimidine template agent according to claim 7 in the preparation of SSZ-98 zeolite, characterized in that, The aluminum source uses Y zeolite, the silicon source uses silica sol, and the alkali source is sodium hydroxide or potassium hydroxide.

9. Use of the pyrimidine-based templating agent according to claim 8 in the preparation of SSZ-98 zeolite, characterized in that, The SiO2 / Al2O3 of the Y zeolite is 5-50; the silica sol is silica sol with a mass content of 25-35%.

10. Use of the pyrimidine template agent according to claim 8 in the preparation of SSZ-98 zeolite, characterized in that, The structure of the pyrimidine template agent is as follows: .

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