Pyrimidine templates and their application in the preparation of SSZ-98 molecular sieves

Abstract

The present invention relates to the field of molecular sieve material technology, specifically discloses pyrimidine template and its application in preparing SSZ 98 molecular sieve, the structure of the pyrimidine template is shown in general formula I: # imgabs0# formula I In formula I, R1, R2 are each independently selected from C1 C12 alkyl; The pyrimidine template of the present invention has high hydrothermal stability, is not easy to decompose during molecular sieve preparation, and utilization rate is high, therefore, reduces the consumption of the pyrimidine template, reduces the production cost of molecular sieve; Secondly, the template dosage is reduced, and the amount of harmful gases produced during high-temperature calcination is also reduced, and environmental pollution is less. The present invention also provides the application of pyrimidine template in preparing SSZ 98 molecular sieve, which is applicable to SSZ 98 type molecular sieve framework growth, and the hydrothermal synthesis cycle is short, and production efficiency is high and product yield is high.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieve materials, and more particularly to a pyrimidine template and its application in the preparation of SSZ-98 molecular sieve. Background Art

[0002] Molecular sieves, a typical porous material, have significant applications in adsorption separation, catalytic conversion, and ion exchange due to their high specific surface area, excellent shape-selective catalytic performance, and tunable acidity. Among them, ERI-type molecular sieves (Zeolite Association International code: ERI) have attracted considerable attention due to their unique pore topology. Their framework typically consists of double six-ring (d6R) and eight-membered ring pore / channel units and cages. ERI-type molecular sieves, including SSZ-98 and ZSM-34, are typically synthesized via hydrothermal crystallization. The structure-directing agent (SDA) used in the synthesis is a typical complexing organic molecule that, through the hydrothermal reaction, induces the formation of the molecular shape and pattern of the zeolite framework. The SDA acts as a mold for the molecular sieve, inducing the formation of a crystalline structure around the silica-alumina units. After the hydrothermal reaction, the SDA is removed from the crystalline structure, typically at temperatures above 500°C, leaving behind a porous aluminosilicate cage. ERI type molecular sieves have a small pore size and good shape selectivity, making them suitable for the passage of C1-C4 hydrocarbons. Therefore, they show important commercial value in industrial processes such as methanol to olefins (MTO) and catalytic conversion of light hydrocarbons.

[0003] The synthesis of ERI-type molecular sieves began in 1960, with U.S. Patent No. 2,950,925 reporting the first hydrothermal synthesis of T-type zeolite (ERI / OFF intergrowth). With the advancement of molecular sieve synthesis chemistry, U.S. Patents No. 9,409,786 and No. 9,416,017 disclosed the use of N,N'-dimethyl-1,4-diazabicyclo[2.2.2]octane divalent cations as structure-directing agents to synthesize pure SSZ-98 molecular sieves. Chinese Patent No. CN106470944B discloses the use of N,N'-dimethyl-1,4-diazabicyclo[2.2.2]octane divalent cations and 18-crown-6 as dual templates to synthesize pure SSZ-98 molecular sieves. Chinese patent CN108495815A discloses the use of one or more structure-directing agents selected from the group consisting of 1,1-diethylpyrrolidinium, 1-butyl-1-methylpiperidinium, 1,1-diethyl-4-methylpiperidinium, and 8-(pyridin-2-yl)-5,8-diazaspiro[4.5]decane-5-ium to synthesize pure SSZ-98 molecular sieves. However, the prior art for synthesizing SSZ-98 molecular sieves using these organic templates generally suffers from the following significant limitations:

[0004] 1. High cost of templates: The reported SDAs (such as bicyclic diamines and crown ether complex systems) have complex synthesis steps and expensive raw materials, accounting for 60%-80% of the total manufacturing cost of molecular sieves;

[0005] 2. Long crystallization cycle: The crystallization process of hydrothermal synthesis usually takes 3-7 days or even longer, resulting in high energy consumption and low production efficiency;

[0006] 3. Low yield: Limited by the matching efficiency between the template and the silicon-aluminum precursor, the product yield is generally low, usually around 50%, and the template is difficult to recycle and reuse;

[0007] 4. Environmental burden: The process of high-temperature calcination (>500°C) to remove the template produces a large amount of CO2 and nitrogen-containing waste gas, which is not in line with the development trend of green chemistry.

[0008] Therefore, there is an urgent need for an efficient and cost-effective template suitable for the growth of the SSZ-98 molecular sieve framework, capable of rapidly synthesizing zeolites and improving molecular sieve yield, thereby enabling mass production of SSZ-98 molecular sieves and their widespread application in the selective catalytic reduction of nitrogen oxides. Based on the foregoing, the present invention provides a pyrimidine template and its use in the preparation of SSZ-98 molecular sieves. Summary of the Invention

[0009] In order to solve the problems of the prior art such as high template cost, long crystallization cycle, low yield, difficulty in recycling and reusing templates, and easy environmental burden caused by the removal process, the present invention provides a pyrimidine template and its application in the preparation of SSZ-98 molecular sieve; the pyrimidine template has high hydrothermal stability, is not easy to decompose during the preparation of molecular sieve, has high utilization rate, and therefore reduces the amount of pyrimidine template, reduces the production cost of molecular sieve, and improves the yield of molecular sieve. Secondly, the reduced amount of template also reduces the amount of harmful gases produced during high-temperature calcination, has less pollution to the environment, and is beneficial to the industrial production and application of molecular sieve.

[0010] In the first aspect, the present invention provides a pyrimidine template, which adopts the following technical solution:

[0011] The pyrimidine template has a structure as shown in the general formula I:

[0012] ;

[0013] Formula I

[0014] In formula I, R1 and R2 are each independently selected from a C1-C12 alkyl group.

[0015] Preferably, R1 and R2 are each independently selected from methyl, ethyl, propyl, butyl, pentyl or hexyl.

[0016] Preferably, R1 and R2 are the same.

[0017] Preferably, the compound represented by formula I is selected from the following structures:

[0018] .

[0019] Preferably, taking R1 and R2 as an example, the preparation method of the pyrimidine template represented by Formula I is described, comprising the following steps:

[0020]

[0021] (1) In an autoclave, a mixture of methanol and water was used as the reaction solvent. Under nitrogen atmosphere, the intermediate MA and dialkyl carbonate ( ) to react to obtain intermediate MA-1;

[0022] (2) The intermediate MA-1 prepared in step (1) is added to deionized water, lithium hydroxide is added, and then calcium hydroxide is added to react to obtain the pyrimidine template agent shown in formula I.

[0023] Preferably, the volume ratio of methanol to water in the reaction solvent of step (1) is 20-30:1.

[0024] In a second aspect, the present invention provides the use of a pyrimidine template agent represented by formula I in the preparation of SSZ-98 molecular sieve.

[0025] In a third aspect, the present invention provides a method for preparing SSZ-98 molecular sieve, wherein the method uses a pyrimidine template agent represented by formula I as an organic template agent.

[0026] Preferably, the preparation method of the SSZ-98 molecular sieve comprises the following steps:

[0027] First, the aluminum source and deionized water are mixed and stirred, and then an aqueous solution of a pyrimidine template agent, an alkali source, and a silicon source are added in sequence. The temperature is raised to 30-70°C and stirred for 2-4 hours. The material is then poured into an autoclave, sealed and heated to 100-200°C, and hydrothermally reacted for 20-30 hours. The material is taken out, allowed to stand, filtered, and the filter cake is washed with water until neutral. The filter cake is then dehydrated and dried, and then placed in a muffle furnace and calcined at 300-600°C to obtain an alkali metal type SSZ-98 molecular sieve.

[0028] Preferably, the aluminum source is Y molecular sieve.

[0029] Preferably, the Y molecular sieve has a white to off-white appearance, SiO2 / Al2O3=5-50, and a Na2O content of <0.15%.

[0030] Preferably, the Y molecular sieve has SiO2 / Al2O3=12.

[0031] Preferably, the silicon source is silica sol.

[0032] Preferably, the silica sol has a content of 25-35%.

[0033] Preferably, the silica sol has a silica sol content of 30%.

[0034] Preferably, the alkali source is sodium hydroxide or potassium hydroxide.

[0035] Preferably, the pyrimidine template structure is: .

[0036] In summary, the present invention has the following beneficial effects:

[0037] The present invention provides a pyrimidine template agent. The pyrimidine template agent has high hydrothermal stability, is not easily decomposed during the preparation of molecular sieves, and has a high utilization rate. Therefore, the amount of the pyrimidine template agent used is reduced, and the production cost of the molecular sieve is reduced. Secondly, the reduced amount of the template agent also reduces the amount of harmful gases generated during the high-temperature calcination process, thereby reducing environmental pollution.

[0038] The present invention also provides a preparation method of a pyrimidine template agent. The preparation method is simple to operate, has mild reaction conditions, can be prepared by reaction of cheap raw materials, and significantly reduces the cost of industrial production, thereby facilitating the industrial production and application of molecular sieves.

[0039] The present invention provides the use of a pyrimidine template in the preparation of SSZ-98 molecular sieves. The pyrimidine template is suitable for the growth of the SSZ-98 molecular sieve framework, has a short hydrothermal synthesis cycle, high production efficiency and high product yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0041] Figure 1 This is a scanning electron microscope image of the SSZ-98 molecular sieve prepared in Application Example 1 of the present invention.

[0042] Figure 2 This is the XRD spectrum of the SSZ-98 molecular sieve prepared in Application Example 1 of the present invention. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below with reference to the examples.

[0044] Unless otherwise specified, the materials, reagents, etc. used in the present invention can be obtained from commercial sources.

[0045] Example 1: Synthesis of Compound P1

[0046]

[0047] (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 autoclave was replaced with nitrogen three times, and then filled with nitrogen to 1.2 MPa. The temperature was raised to 90 °C and the reaction was carried out for 30 hours. The temperature was lowered, and the methanol and water were concentrated to obtain a viscous substance containing intermediate M1. The product was directly used for the next step without purification.

[0048] (2) The viscous substance containing the 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. The unreacted calcium hydroxide and the generated calcium carbonate were filtered out, and the excess water and methanol were evaporated to obtain 62 g of an aqueous solution of compound P1. The solution was calibrated with 0.1 mol / L hydrochloric acid solution, and the mass concentration was 27.1%.

[0049] In order to obtain pure compound P1, the following experiment was performed:

[0050] Take 1.0 g of the aqueous solution of P1 above and add 10 ml 3 was extracted with ethyl acetate. The ethyl acetate layer was dried over anhydrous sodium sulfate, the desiccant was filtered off, and the mixture was allowed to stand at room temperature to allow the ethyl acetate to evaporate slowly until needle-shaped crystals appeared. The crystals were filtered and dried under vacuum to obtain pure compound P1. The elemental analysis results are as follows:

[0051] Theoretical value (%): C, 57.12; H, 8.63; N, 26.64, Found value (%): C, 57.16; H, 8.60; N,26.60.

[0052] Example 2: Synthesis of Compound P2

[0053]

[0054] Referring to the synthesis method of compound P1 in Example 1, only the raw material dimethyl carbonate was replaced with diethyl carbonate to obtain 66 g of an aqueous solution of compound P2, which was calibrated with 0.1 mol / L hydrochloric acid solution to have a mass concentration of 25.3%.

[0055] Pure compound P2 was prepared by referring to the preparation method of pure compound P1. The elemental analysis results are as follows:

[0056] Theoretical value (%): C, 60.47; H, 9.30; N, 23.51, Found value (%): C, 60.48; H, 9.28; N,23.50.

[0057] Application Example 1: Preparation of SSZ-98 molecular sieve using compound P1 of Example 1 as template

[0058] The preparation method of SSZ-98 molecular sieve is as follows: first, 16g of Y molecular sieve (SiO2 / Al2O3=5.5) is mixed with 150g of deionized water, stirred with a stirrer for 1h, then 40g of an aqueous solution of compound P1 of Example 1 (mass concentration is 27.1%), 14g of sodium hydroxide, and 175g of 30% silica sol are added in sequence, the temperature is raised to 50°C, and stirred for 3h; then the material is poured into an autoclave, sealed and heated to 160°C, hydrothermally reacted for 24h, the material is taken out, allowed to stand, filtered, and the filter cake is washed with deionized water until neutral, the material is dehydrated and dried, and then placed in a muffle furnace, calcined at 450°C for 15 hours, then washed with water, and dried at 150°C for 12 hours to obtain 45g (theoretical value is 69g) of SSZ-98 molecular sieve. The scanning electron microscope image of SSZ-98 molecular sieve is as follows Figure 1 As shown, the XRD spectrum of SSZ-98 molecular sieve is as follows Figure 2 As shown, the X-ray fluorescence analysis results of SSZ-98 molecular sieve showed SAR=20.5.

[0059] Application Example 2: Preparation of SSZ-98 molecular sieve using compound P1 of Example 1 as a template

[0060] The preparation method was similar to that of Application Example 1, except that the amount of the aqueous solution of Compound P1 (27.1% mass concentration) from Example 1 was changed from 40 g to 35 g. This yielded 47 g (theoretical value: 69 g) of SSZ-98 molecular sieve. X-ray fluorescence analysis showed a SAR of 21.1.

[0061] Application Example 3: Preparation of SSZ-98 molecular sieve using compound P1 of Example 1 as template

[0062] The preparation method was similar to that of Application Example 1, except that the 16 g Y molecular sieve (SiO₂ / Al₂O₃=5.5) in Example 1 was replaced with 16 g Y molecular sieve (SiO₂ / Al₂O₃=12). 53 g (theoretical value: 69 g) of SSZ-98 molecular sieve was obtained. X-ray fluorescence analysis showed a SAR of 22.3.

[0063] Application Example 4: Preparation of SSZ-98 molecular sieve using compound P2 of Example 2 as template

[0064] The preparation method refers to Application Example 1, except that the solution of Compound P1 is replaced with 40 g of an aqueous solution of Compound P2 of Example 2 (mass concentration is 25.3%) to obtain 49 g (theoretical value is 69 g) of SSZ-98 molecular sieve.

[0065] Comparative application example 1:

[0066] The preparation method is the same as that of Application Example 1, except that the compound P1 solution is replaced with 50 g of a 20% by weight aqueous solution of 8-(pyridin-2-yl)-5,8-diazaspiro[4.5]decane-5-ium hydroxide to obtain 37 g (theoretical value is 69 g) of SSZ-98 molecular sieve.

[0067] The structure of 8-(pyridin-2-yl)-5,8-diazaspiro[4.5]decan-5-ium hydroxide is as follows:

[0068]

[0069] In summary, the use of the pyrimidine template 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, has low template dosage, short hydrothermal synthesis cycle, low production cost, high production efficiency, and high product yield.

[0070] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed. However, as long as such modifications are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A pyrimidine template, characterized in that: The structure is shown in general formula I: ； Formula I In formula I, R1 and R2 are each independently selected from a C1-C12 alkyl group.

2. The pyrimidine template according to claim 1, characterized in that The R1 and R2 are each independently selected from methyl, ethyl, propyl, butyl, pentyl or hexyl.

3. The pyrimidine template according to claim 1, characterized in that The R1 and R2 are the same.

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

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

7. Use of the pyrimidine template according to claim 6 in the preparation of SSZ-98 molecular sieve, characterized in that: The preparation method of the SSZ-98 molecular sieve comprises the following steps: First, the aluminum source and deionized water are mixed and stirred, and then an aqueous solution of a pyrimidine template agent, an alkali source, and a silicon source are added in sequence. The temperature is raised to 30-70°C and stirred for 2-4 hours. The material is then poured into an autoclave, sealed and heated to 100-200°C, and hydrothermally reacted for 20-30 hours. The material is taken out, allowed to stand, filtered, and the filter cake is washed with water until neutral. The filter cake is then dehydrated and dried, and then placed in a muffle furnace and calcined at 300-600°C to obtain SSZ-98 molecular sieve.

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

9. Use of the pyrimidine template according to claim 8 in the preparation of SSZ-98 molecular sieve, characterized in that: The SiO2 / Al2O3 of the Y molecular sieve is 5-50; the silica sol has a mass content of 25-35%.

10. Use of the pyrimidine template according to claim 8 in the preparation of SSZ-98 molecular sieve, characterized in that: The structure of the pyrimidine template is: .

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