Method for synthesizing high-silica RHO molecular sieve without fluorine by conversion method, high-silica RHO molecular sieve and application thereof

Abstract

The present invention provides a method for synthesizing high-silica RHO zeolite without fluorine by a conversion method, the high-silica RHO zeolite and its application, relating to the technical field of zeolites. In the present invention, 18-crown-6, sodium hydroxide, water and cesium hydroxide are mixed for a coordination reaction to obtain an organic template agent; the organic template agent is mixed with SSZ-13 zeolite, water and seeds for a crystallization reaction to obtain high-silica RHO zeolite. The present invention uses high-silica-alumina SSZ-13 zeolite as a conversion raw material to synthesize RHO zeolite by a conversion method; and the high-silica-alumina SSZ-13 zeolite, supplemented with a specific organic template and seeds, avoids adding fluorine-containing species to the system, thereby realizing the fluorine-free synthesis of high-silica RHO zeolite. The silicon-aluminum ratio of the high-silica RHO zeolite synthesized by the present invention is 6.2 to 9.8, and it is applied to the catalytic ammoniation of methanol to prepare monomethylamine and dimethylamine, with high methanol conversion rate and high total selectivity of monomethylamine and dimethylamine.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieves, and particularly relates to a method for synthesizing high-silica RHO molecular sieve without fluorine by a topotactic transformation method, a high-silica RHO molecular sieve, and its application. Background Art

[0002] Under certain conditions, methanol and ammonia can react through a series of reactions under the action of a catalyst to produce monomethylamine, dimethylamine, and trimethylamine. In a series of reactions of methanol amination, the thermodynamically most favorable product is trimethylamine, but monomethylamine and dimethylamine are more widely used in production and life. Under the catalysis of traditional catalysts, the main product of the methanol amination reaction is still trimethylamine, resulting in a great waste of resources and energy.

[0003] Zeolite molecular sieves are a series of aluminosilicate crystals formed by the ordered arrangement of alumina and silica tetrahedra with a clear microporous structure. Due to the regular structure, high thermal stability, and rich acidic sites of zeolite molecular sieves, they have excellent separation and catalytic reaction properties. When used as catalysts in the catalytic field, they are often remarkable for their excellent shape selectivity. In recent years, zeolite molecular sieves such as AFX, CHA, KFI, MOR, RHO, etc. have been continuously studied as catalysts for methanol amination reactions.

[0004] RHO molecular sieve is a small-pore molecular sieve with a three-dimensional eight-membered ring pore channel, and is a good catalyst for methanol amination reaction, having high methanol conversion rate and high total selectivity of monomethylamine and dimethylamine. The pore size of the RHO molecular sieve gives it shape selectivity for this reaction, which is beneficial to the formation of monomethylamine and dimethylamine and inhibits the production of trimethylamine.

[0005] However, the silicon-aluminum ratio of conventionally synthesized RHO is only 3-4, which severely limits its application in the catalytic field. Increasing the silicon-aluminum ratio is beneficial for it to exhibit more excellent performance in the catalytic field. The synthesis of high-silica RHO has rarely been reported, and most of them require adding highly toxic and highly polluting fluorine-containing species to the system. Therefore, obtaining high-silica RHO in a non-toxic and pollution-free manner has become the current demand. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a method for synthesizing high-silica RHO molecular sieve without fluorine by a topotactic transformation method, a high-silica RHO molecular sieve, and its application. The method provided by the present invention realizes the synthesis of high-silica RHO molecular sieve without fluorine.

[0007] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0008] The present invention provides a method for synthesizing high-silica RHO molecular sieve without fluorine by a topotactic transformation method, comprising the following steps:

[0009] (1) Mix 18-crown-6, sodium hydroxide, water and cesium hydroxide for a coordination reaction to obtain an organic template agent;

[0010] (2) Mix the organic template agent with SSZ-13 zeolite, water and seed crystals, and subject the obtained first mother liquor to a first crystallization reaction to obtain a high-silica RHO zeolite; the SSZ-13 zeolite is based on Al 2 O 3 and SiO 2 Calculated, in the first mother liquor, the molar ratio of Al 2 O 3 , SiO 2 , organic template agent and water is 1.0:(10 - 30):(0.5 - 5.0):(20 - 200), and the mass of the seed crystals is 5 - 20% of the mass of SiO 2 .

[0011] Preferably, in step (1), the molar ratio of 18-crown-6, sodium hydroxide, water and cesium hydroxide is (0.02 - 0.20):(0.01 - 0.10):1.00:(0.01 - 0.10).

[0012] Preferably, in step (1), the temperature of the coordination reaction is 20 - 90 °C and the time is 0.5 - 3 h.

[0013] Preferably, in step (2), the temperature of the first crystallization is 100 - 200 °C and the time is 1 - 10 d.

[0014] Preferably, the method for preparing the seed crystals in step (2) includes the following steps:

[0015] Mix water, cesium hydroxide, sodium hydroxide, 18-crown-6, an aluminum source and a silicon source, subject the obtained second mother liquor to a second crystallization reaction, and calcine the obtained crystallization product to obtain the seed crystals; the sodium hydroxide, cesium hydroxide, aluminum source and silicon source are based on the corresponding oxides, and in the second mother liquor, the molar ratio of Na 2 O, Cs 2 O, Al 2 O 3 , SiO 2 , 18-crown-6 and water is (1.3 - 1.8):0.3:1:10:(0.25 - 0.5):100.

[0016] Preferably, the temperature of the second crystallization reaction is 100 - 120 °C and the time is 2 - 8 d.

[0017] The present invention provides a high-silica RHO zeolite obtained by the method of the above technical solution, and the silica-alumina ratio of the high-silica RHO zeolite is 6.2 - 9.8.

[0018] The present invention provides the application of the high-silica RHO molecular sieve described in the above technical solution in the catalytic ammoniation of methanol to prepare methylamine and dimethylamine. Before carrying out the methanol ammoniation, the high-silica RHO molecular sieve is subjected to first calcination, ammonium ion exchange, and second calcination in sequence.

[0019] Preferably, the temperature of the first calcination is 500-700 °C, and the time is 4-8 h; the ammonium ion exchange is carried out in an aqueous ammonium chloride solution, the concentration of the aqueous ammonium chloride solution is 0.5-5 mol / L, the temperature of the ammonium ion exchange is 60-90 °C, the number of times of the ammonium ion exchange is 2-8 times, and the single time is 3-6 h; the temperature of the second calcination is 500-700 °C, and the time is 4-8 h.

[0020] Preferably, the conditions for the methanol ammoniation include: the particle size of the high-silica RHO molecular sieve is 20-100 mesh, and the loading amount is 0.3 g; the mass space velocity of methanol is 0.5-5 h -1 , the molar ratio of ammonia to methanol is (0.5-10):1, and the reaction temperature is 200-450 °C.

[0021] The present invention provides a method for synthesizing a high-silica RHO molecular sieve without fluorine by a conversion method, which includes the following steps: mixing 18-crown-6, sodium hydroxide, water, and cesium hydroxide for a coordination reaction to obtain an organic template agent; mixing the organic template agent with SSZ-13 molecular sieve, water, and seed crystals, and subjecting the obtained mother liquor to a crystallization reaction to obtain a high-silica RHO molecular sieve; the SSZ-13 molecular sieve is based on Al 2 O 3 and SiO 2 calculated, the molar ratio of Al 2 O 3 , SiO 2 , the organic template agent and water in the mother liquor is 1.0:(10-30):(0.5-5.0):(20-200), and the mass of the seed crystal is 5-20% of the mass of SiO 2 . The present invention uses a high-silica-alumina SSZ-13 molecular sieve as a conversion raw material to synthesize a RHO molecular sieve by a conversion method; and the high-silica-alumina SSZ-13 molecular sieve, supplemented with a specific organic template and seed crystals, avoids adding fluorine-containing species to the system, thereby realizing the fluorine-free synthesis of a high-silica RHO molecular sieve. The silicon-aluminum ratio of the high-silica RHO molecular sieve synthesized by the present invention is 6.2-9.8, which is applied to the catalytic ammoniation of methanol to prepare methylamine and dimethylamine, and has a high methanol conversion rate and a high total selectivity of methylamine and dimethylamine. The results of the examples show that when the high-silica RHO molecular sieve synthesized by the present invention and the RHO molecular sieve with the same silicon-aluminum ratio reported in the literature are used to catalyze the ammoniation of methanol under the same conditions, the catalytic effect of the RHO molecular sieve of the present invention on the methanol ammoniation reaction is better than that of the comparative sample. Description of the Drawings

[0022] Figure 1 XRD patterns of the high-silica RHO zeolites synthesized in Examples 1 to 10;

[0023] Figure 2 Electron micrograph of the seed crystals obtained in Example 1;

[0024] Figure 3 Electron micrograph of the high-silica RHO zeolite prepared in Example 1;

[0025] Figure 4 Electron micrograph of the high-silica RHO zeolite in Comparative Application Example 1. Detailed implementation mode

[0026] The present invention provides a method for synthesizing high-silica RHO zeolite without fluorine by a conversion method, comprising the following steps:

[0027] (1) Mix 18-crown-6, sodium hydroxide, water and cesium hydroxide for a coordination reaction to obtain an organic template agent;

[0028] (2) Mix the organic template agent with SSZ-13 zeolite, water and seed crystals, and subject the obtained first mother liquor to a first crystallization reaction to obtain a high-silica RHO zeolite; the SSZ-13 zeolite is based on Al 2 O 3 and SiO 2 calculated, in the first mother liquor, the molar ratio of Al 2 O 3 , SiO 2 , the organic template agent and water is 1.0:(10 - 30):(0.5 - 5.0):(20 - 200), and the mass of the seed crystals is 5 - 20% of the mass of SiO 2 .

[0029] In the present invention, unless otherwise specified, the raw materials involved are commercially available products well-known to those skilled in the art.

[0030] In the present invention, 18-crown-6, sodium hydroxide, water and cesium hydroxide are mixed for a coordination reaction to obtain an organic template agent. In the present invention, the molar ratio of 18-crown-6, sodium hydroxide, water and cesium hydroxide is preferably (0.02 - 0.20):(0.01 - 0.10):1.00:(0.01 - 0.10), more preferably (0.05 - 0.1):(0.05 - 0.1):1.00:(0.03 - 0.05); the cesium hydroxide is preferably added in the form of an aqueous cesium hydroxide solution, the mass concentration of the aqueous cesium hydroxide solution is preferably 50%, and the water in the aqueous cesium hydroxide solution is included in the above molar ratio. In the present invention, the temperature of the coordination reaction is preferably 20 - 90 °C, more preferably 60 - 80 °C, the time is preferably 0.5 - 3 h, more preferably 2 - 3 h, and the temperature of the coordination reaction is preferably achieved by a water bath; the coordination reaction is preferably carried out under stirring conditions. In the present invention, the coordination reaction is the coordination of 18-crown-6 with sodium ions in sodium hydroxide and cesium ions in cesium hydroxide. After the coordination reaction, in the present invention, the obtained coordination reaction solution is preferably allowed to stand. During the standing process, the coordination reaction solution is cooled to room temperature and layered, and the upper clear liquid is separated to obtain the organic template agent.

[0031] After obtaining the organic template agent, the present invention mixes the organic template agent with SSZ-13 zeolite, water and seeds, and the obtained first mother liquor is subjected to a first crystallization reaction to obtain high-silica RHO zeolite. In the present invention, the SSZ-13 zeolite (with a silica-to-alumina ratio of 5 - 15) is preferably purchased from Luoyang Jianlong Micro-Nano New Materials Co., Ltd.; the present invention uses SSZ-13 zeolite with a high silica-to-alumina ratio as the conversion zeolite raw material. SSZ-13 zeolite is a CHA zeolite, and it and RHO zeolite are both small-pore zeolites and have a certain degree of structural similarity. In the present invention, based on Al 2 O 3 and SiO 2 calculation, in the first mother liquor, the molar ratio of Al 2 O 3 , SiO 2 , the organic template agent and water is 1.0:(10 - 30):(0.5 - 5.0):(20 - 200), and the mass of the seeds is SiO 25% to 20% of the mass, preferably 10% to 15%. In the present invention, it is preferred to mix the organic template agent, SSZ-13 molecular sieve and water, and then add seeds thereto. In the present invention, the temperature of the first crystallization is preferably 100 to 200 °C, more preferably 120 to 150 °C, the time is preferably 1 to 10 days (d), more preferably 4 to 6 d; the first crystallization preferably places the mixed solution obtained by mixing the organic template agent, SSZ-13 molecular sieve, water and seeds in an oven under static conditions, and after the first crystallization, it is preferred to wash and dry the obtained reaction solution.

[0032] In the present invention, the preparation method of the seeds preferably includes the following steps: mixing water, cesium hydroxide, sodium hydroxide, 18-crown-6, an aluminum source and a silicon source, performing a second crystallization reaction on the obtained second mother liquor, and calcining the obtained crystallization product to obtain the seeds. The present invention has no special requirements for the aluminum source and the silicon source, and the aluminum source and the silicon source well-known to those skilled in the art can be used. In the examples of the present invention, the aluminum source is preferably sodium aluminate, and the silicon source is preferably silica sol. In the present invention, the sodium hydroxide, cesium hydroxide, aluminum source and silicon source are calculated in terms of the corresponding metal oxides. Specifically, taking sodium aluminate as the aluminum source and silica sol as the silicon source as an example, sodium hydroxide is calculated as Na 2 O, cesium hydroxide is calculated as Cs 2 O, sodium aluminate is calculated as Na 2 O and Al 2 O 3 , silica sol is calculated as SiO 2 The molar ratio of Na 2 O, Cs 2 O, Al 2 O 3 , SiO 2 , 18-crown-6 and water in the second mother liquor is preferably (1.3 to 1.8):0.3:1:10:(0.25 to 0.5):100; the cesium hydroxide is preferably added in the form of an aqueous cesium hydroxide solution, and the mass concentration of the aqueous cesium hydroxide solution is preferably 50%, and the water in the aqueous cesium hydroxide solution is included in the above molar ratio. In the present invention, it is preferred to mix water, cesium hydroxide, sodium hydroxide, 18-crown-6 and an aluminum source, stir until clear and then add the silicon source. In the present invention, the temperature of the second crystallization reaction is preferably 100 to 120 °C, more preferably 100 to 110 °C, the time is preferably 2 to 8 d, more preferably 4 to 5 d; the second crystallization reaction preferably places the mixed solution obtained by mixing water, cesium hydroxide, sodium hydroxide, 18-crown-6, an aluminum source and a silicon source in an oven under static conditions. After the second crystallization reaction, it is preferred to wash, filter by suction and perform solid-phase drying on the obtained reaction solution in sequence to obtain the crystallization product. In the present invention, the temperature of the calcination is preferably 550 °C, and the time is preferably 6 h.

[0033] The present invention uses a high-silica-alumina ratio SSZ-13 molecular sieve as the starting material for topotactic transformation to synthesize RHO molecular sieve by topotactic transformation method; moreover, the high-silica-alumina ratio SSZ-13 molecular sieve, supplemented with a specific organic template and seed crystals, avoids the addition of fluorine-containing species in the system, thereby realizing the fluorine-free synthesis of high-silica RHO molecular sieve.

[0034] The present invention provides a high-silica RHO molecular sieve obtained by the method of the above technical solution. The silica-alumina ratio of the high-silica RHO molecular sieve is 6.2 to 9.8, more preferably 7.9 to 8.7, and the morphology of the high-silica RHO molecular sieve is a rhombic dodecahedron.

[0035] The present invention provides the application of the high-silica RHO molecular sieve of the above technical solution in the catalytic ammoniation of methanol to prepare monomethylamine and dimethylamine. When applying, the high-silica RHO molecular sieve is first calcined, ammonium ion exchanged, and then second calcined. In the present invention, the temperature of the first calcination is preferably 500 to 700 °C, more preferably 600 °C, and the time is preferably 4 to 8 h, more preferably 6 h; the present invention removes the organic template in the pores of the RHO molecular sieve through the first calcination. In the present invention, the ammonium ion exchange is preferably carried out in an ammonium chloride aqueous solution. The concentration of the ammonium chloride aqueous solution is preferably 0.5 to 5 mol / L, more preferably 3 mol / L. The temperature of the ammonium ion exchange is preferably 60 to 90 °C, more preferably 80 °C. The number of times of ammonium ion exchange is preferably 2 to 8 times, more preferably 4 times, and the single time is preferably 3 to 6 h, more preferably 5 h; the ammonium ion exchange is preferably carried out under stirring conditions; after the ammonium ion exchange, the obtained ion exchange product is preferably washed with water, filtered by suction, and dried in sequence. The present invention exchanges the metal ions in the pores of the molecular sieve with ammonium ions through the ammonium ion exchange. In the present invention, the temperature of the second calcination is preferably 500 to 700 °C, more preferably 550 °C, and the time is preferably 4 to 8 h, more preferably 4 h. The present invention converts the ammonium ions in the molecular sieve into hydrogen ions through the second calcination.

[0036] In the present invention, the conditions for the ammoniation of methanol preferably include: the particle size of the high-silica RHO molecular sieve is 20 to 100 mesh, and the loading amount is 0.3 g; the mass space velocity of methanol is 0.5 to 5 h -1 , preferably 0.5 to 2 h -1, the molar ratio of ammonia to methanol is (0.5 - 10):1, preferably (2 - 5):1; the reaction temperature is 200 - 450 °C, preferably 300 - 350 °C. In the present invention, the ammonia is a gas, and the methanol is stored in a methanol pool in liquid form. However, during the methanol ammoniation reaction, nitrogen is used as a carrier gas to pass through the methanol pool, introducing the methanol into the reaction device in gaseous form, that is, both the ammonia and methanol participating in the catalytic reaction are in gaseous state; the generated monomethylamine, dimethylamine, trimethylamine, dimethyl ether, and the unreacted methanol remaining in the product gas stream all pass through a gas chromatograph in gaseous form and are then analyzed by the gas chromatograph to obtain the content.

[0037] The high-silica RHO zeolite synthesized in the present invention is applied to the catalytic ammoniation of methanol to prepare monomethylamine and dimethylamine, with high methanol conversion rate and high total selectivity of monomethylamine and dimethylamine. The results of the examples show that when the high-silica RHO zeolite synthesized in the present invention is used for the catalytic ammoniation of methanol, the conversion rate of methanol is 42.15 - 99.82%, and the total selectivity of monomethylamine and dimethylamine is 55.55 - 87.61%.

[0038] To further illustrate the present invention, the method for synthesizing high-silica RHO zeolite without fluorine by the conversion method, the high-silica RHO zeolite and its application provided by the present invention will be described in detail below with reference to examples, but they should not be construed as limiting the protection scope of the present invention.

[0039] Example 1

[0040] Mix 16 g of water, 3.6 g of cesium hydroxide aqueous solution (50 wt%), 0.6 g of sodium hydroxide, 2.6 g of 18-crown-6, and 4.2 g of sodium aluminate, stir until clear, and then add 30 g of silica sol (40 wt%). The mother liquor ratio is: the molar ratio of Na 2 O, Cs 2 O, Al 2 O 3 , SiO 2 , 18-crown-6 and H 2 O is 1.8:0.3:1:10:0.5:100. Let it stand in an oven at 110 °C for 4 d. After the reaction is completed, wash the product, filter it by suction, dry it, and calcine it at 550 °C for 6 h to obtain the seed crystals required for the reaction.

[0041] Mix 21 g of 18-crown-6, 3 g of sodium hydroxide, 14 g of water, and 8 g of cesium hydroxide aqueous solution (50 wt%), place it in a water bath at 80 °C and stir for 3 h. After cooling to room temperature, separate the upper clear liquid to obtain the organic template agent required for the reaction.

[0042] Mix 7.5 g of SSZ-13 molecular sieve (purchased from Luoyang Jianlong Micro-Nano New Materials Co., Ltd.), 10 g of water and 15.5 g of organic template, and then add seeds equivalent to 10 wt% of the silicon source. The mother liquor ratio is: Al 2 O 3 、SiO 2 、organic template and H 2 O with a molar ratio of 1.0:20:3.0:90. Let it stand in an oven at 150 °C for 4 days. After the reaction is completed, wash the product with water, filter it by suction, and dry it to obtain high-silica RHO molecular sieve, denoted as A1. Its XRD pattern is as shown in Figure 1 . It is measured that the silicon-aluminum ratio (Si / Al) of A1 is 8.6.

[0043] Figure 2 is the electron micrograph of the seeds obtained in Example 1. Figure 3 is the electron micrograph of the high-silica RHO molecular sieve prepared in Example 1. It can be seen from Figure 2 and Figure 3 that the seeds are spheres with a diameter of about 0.5 - 1.0 μm formed by stacking square particles with a smooth surface of 100 nm, while the high-silica RHO molecular sieve prepared in Example 1 is a rhombic dodecahedron with a smooth surface and a diameter of about 0.5 - 1.5 μm.

[0044] Example 2

[0045] Change the water bath temperature of the organic template in Example 1 to 20 °C, and the rest is the same as in Example 1 to synthesize high-silica RHO molecular sieve, denoted as A2. Its XRD pattern is as shown in Figure 1 . It is measured that the silicon-aluminum ratio (Si / Al) of A2 is 8.0.

[0046] Example 3

[0047] Change the water bath temperature of the organic template in Example 1 to 90 °C, and the rest is the same as in Example 1 to synthesize high-silica RHO molecular sieve, denoted as A3. Its XRD pattern is as shown in Figure 1 . It is measured that the silicon-aluminum ratio (Si / Al) of A3 is 8.7.

[0048] Example 4

[0049] Change the water bath time of the organic template in Example 1 to 0.5 h, and the rest is the same as in Example 1 to synthesize high-silica RHO molecular sieve, denoted as A4. Its XRD pattern is as shown in Figure 1 . It is measured that the silicon-aluminum ratio (Si / Al) of A4 is 8.1.

[0050] Example 5

[0051] Change the amount of seed crystals in Example 1 to 5 wt% of the silicon source, and the rest is the same as in Example 1 to synthesize high-silica RHO zeolite. The product is denoted as A5, and its XRD pattern is as Figure 1 shown. It was determined that the silica-alumina ratio (Si / Al) of A5 is 8.7.

[0052] Example 6

[0053] Change the amount of seed crystals in Example 1 to 20% of the mass of the silicon source, and the rest is the same as in Example 1 to synthesize high-silica RHO zeolite, denoted as A6, and its XRD pattern is as Figure 1 shown. It was determined that the silica-alumina ratio (Si / Al) of A6 is 8.2.

[0054] Example 7

[0055] Change the synthesis temperature of the high-silica RHO zeolite in Example 1 to 100 °C, and the rest is the same as in Example 1 to synthesize high-silica RHO zeolite, denoted as A7, and its XRD pattern is as Figure 1 shown. It was determined that the silica-alumina ratio (Si / Al) of A7 is 8.0.

[0056] Example 8

[0057] Change the synthesis temperature of the high-silica RHO zeolite in Example 1 to 200 °C, and the rest is the same as in Example 1 to synthesize high-silica RHO zeolite, denoted as A8, and its XRD pattern is as Figure 1 shown. It was determined that the silica-alumina ratio (Si / Al) of A8 is 8.7.

[0058] Example 9

[0059] Change the synthesis time of the high-silica RHO zeolite in Example 1 to 10 d, and the rest is the same as in Example 1 to synthesize high-silica RHO zeolite, denoted as A9, and its XRD pattern is as Figure 1 shown. It was determined that the silica-alumina ratio (Si / Al) of A9 is 8.7.

[0060] Example 10

[0061] Change the synthesis time of the high-silica RHO zeolite in Example 1 to 1 d, and the rest is the same as in Example 1 to synthesize high-silica RHO zeolite, denoted as A10, and its XRD pattern is as Figure 1 shown. It was determined that the silica-alumina ratio (Si / Al) of A10 is 7.9.

[0062] Comparative Example 1

[0063] Under other conditions the same as in Example 1, replace the conversion raw material SSZ-13 with an equal molar amount of pseudoboehmite and silica sol, and as a result, no RHO crystals were obtained.

[0064] Comparative Example 2

[0065] Other conditions were the same as those in Example 1, but no seed crystal was added during synthesis, and as a result, no RHO crystal was obtained.

[0066] Comparative Example 3

[0067] Other conditions were the same as those in Example 1, but the seed crystal was replaced with a high-silica RHO molecular sieve with a silicon-aluminum ratio (Si / Al) of 8.6 synthesized in a fluorine-containing system according to the method reported in the literature (Quanli Ke et al. Targeted Synthesis of Ultrastable High-Silica RHO Zeolite Through AlkaliMetal–Crown Ether Interaction. Chemistry–An Asian Journal 2017, 12(10), 1043-1047), that is, this high-silica RHO molecular sieve with a silicon-aluminum ratio of 8.6 was used as the seed crystal. As a result, no RHO crystal was obtained.

[0068] Application Example 1

[0069] The high-silica RHO molecular sieve A1 prepared in Example 1 was calcined at 600 °C for 6 h. The obtained product was stirred in a water bath at 80 °C in 3 mol / L ammonium chloride aqueous solution for 5 h, and this was repeated 4 times. The solid was washed with water, filtered by suction, and dried, and then calcined at 550 °C for 4 h. The obtained powdery solid was denoted as H-RHO(A1).

[0070] The H-RHO(A1) molecular sieve was loaded as a catalyst in a reactor, and nitrogen was used to carry methanol through the reactor. The composition of the gas at the outlet of the reactor was tested to evaluate the catalytic performance of the catalyst. The experimental parameters were as follows: the catalyst particles were 20 - 100 mesh, the catalyst loading was 0.3 g, the methanol mass space velocity was 0.8 h -1 , NH 3 and CH 3 OH injection molar ratio was 2, the reaction temperature was 350 °C, the analytical capillary column was CP-Volamine, and the product distribution and conversion rate were expressed in the form of carbon mole percentage. The obtained results are shown in Table 1.

[0071] Application Example 2

[0072] H-RHO(A1) was prepared by the method of Application Example 1, and the methanol amination test was carried out by the method of Application Example 1, but the NH 3 and CH 3 OH injection molar ratio was changed to 0.5. The obtained results are shown in Table 1.

[0073] Application Example 3

[0074] Prepare H-RHO(A1) by the method of Application Example 1, and conduct the methanol amination test by the method of Application Example 1, but change the molar ratio of NH 3 and CH 3 OH injection to 10. The obtained results are shown in Table 1.

[0075] Application Example 4

[0076] Prepare H-RHO(A1) by the method of Application Example 1, and conduct the methanol amination test by the method of Application Example 1, but change the reaction temperature to 200 °C. The obtained results are shown in Table 1.

[0077] Application Example 5

[0078] Prepare H-RHO(A1) by the method of Application Example 1, and conduct the methanol amination test by the method of Application Example 1, but change the reaction temperature to 450 °C. The obtained results are shown in Table 1.

[0079] Application Example 6

[0080] Prepare H-RHO(A1) by the method of Application Example 1, and conduct the methanol amination test by the method of Application Example 1, but change the methanol mass space velocity to 0.5 h -1 . The obtained results are shown in Table 1.

[0081] Application Example 7

[0082] Prepare H-RHO(A1) by the method of Application Example 1, and conduct the methanol amination test by the method of Application Example 1, but change the methanol mass space velocity to 5.0 h -1 . The obtained results are shown in Table 1.

[0083] Table 1 Methanol Amination Catalytic Performance of High-Silica H-RHO in Examples (Carbon Mole Percentage, %)

[0084]

[0085] Comparative Application Example 1

[0086] Synthesize a high-silica RHO molecular sieve with a silica-to-alumina ratio (Si / Al) = 8.6 in a fluorine-containing system according to the method reported in the literature (Quanli Ke et al. Targeted Synthesis of Ultrastable High-Silica RHO Zeolite Through Alkali Metal–Crown Ether Interaction. Chemistry–An Asian Journal 2017, 12(10), 1043-1047).

[0087] Figure 4It is the electron micrograph of the high-silica RHO molecular sieve prepared in this comparative example. From Figure 4 it can be seen that the high-silica RHO molecular sieve prepared in this comparative example is a sphere with a rough surface and a particle size of about 1-3 μm.

[0088] The high-silica RHO molecular sieve prepared in this comparative example was post-treated by the method of Application Example 1, and the methanol amination test was carried out. The obtained results are shown in Table 2.

[0089] Table 2 Catalytic performance of high-silica H-RHO in methanol amination (carbon mole percentage, %)

[0090]

[0091] It can be seen from the above examples that when the high-silica RHO molecular sieve synthesized in the present invention is applied to the catalytic amination of methanol to prepare monomethylamine and dimethylamine, it has a high methanol conversion rate, a high total selectivity of monomethylamine and dimethylamine, and when catalytically aminating methanol under the same conditions as the RHO molecular sieve with the same silica-alumina ratio reported in the literature, the RHO molecular sieve of the present invention has a better catalytic effect on the methanol amination reaction than this comparative sample.

[0092] The above is only the preferred embodiment of the present invention, and it does not impose any form of limitation on the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for synthesizing high-silica RHO zeolite without fluorine by the conversion method, characterized in that, it includes the following steps: (1) Mix 18-crown-6, sodium hydroxide, water and cesium hydroxide for a coordination reaction to obtain an organic template agent; the molar ratio of 18-crown-6, sodium hydroxide, water and cesium hydroxide in the step (1) is (0.02~0.20):(0.01~0.10):1.00:(0.01~0.10); (2) Mix the organic template agent with SSZ-13 zeolite, water and seeds, and subject the obtained first mother liquor to a first crystallization reaction to obtain high-silica RHO zeolite; the SSZ-13 zeolite is calculated based on Al 2 O 3 and SiO 2 . In the first mother liquor, the molar ratio of Al 2 O 3 , SiO 2 , the organic template agent and water is 1.0:(10 - 30):(0.5 - 5.0):(20 - 200), and the mass of the seeds is 5 - 20% of the mass of SiO 2 ; The preparation method of the seed crystals in the step (2) includes the following steps: Mix water, cesium hydroxide, sodium hydroxide, 18-crown-6, an aluminum source, and a silicon source, subject the obtained second mother liquor to a second crystallization reaction, and calcine the obtained crystallization product to obtain the seed crystal; the sodium hydroxide, cesium hydroxide, aluminum source, and silicon source are calculated as corresponding oxides, and the molar ratio of Na 2 O, Cs 2 O, Al 2 O 3 , SiO 2 , 18-crown-6, and water in the second mother liquor is (1.3 to 1.8):0.3:1:10:(0.25 to 0.5):

100.

2. According to the method described in claim 1, characterized in that, the temperature of the coordination reaction in the step (1) is 20~90°C, and the time is 0.5~3 h.

3. According to the method described in claim 1, characterized in that, the temperature of the first crystallization in the step (2) is 100~200°C, and the time is 1~10 d.

4. According to the method described in claim 1, characterized in that, the temperature of the second crystallization reaction is 100~120°C, and the time is 2~8 d.

5. The high-silica RHO zeolite obtained by the method described in any one of claims 1 to 4, and the silica-alumina ratio of the high-silica RHO zeolite is 6.2~9.

8.

6. Application of the high-silica RHO zeolite described in claim 5 in the catalytic ammoniation of methanol to prepare monomethylamine and dimethylamine. Before carrying out the methanol ammoniation, the high-silica RHO zeolite is subjected to first calcination, ammonium ion exchange and second calcination in sequence.

7. According to the application described in claim 6, characterized in that, the temperature of the first calcination is 500~700°C, and the time is 4~8 h; the ammonium ion exchange is carried out in an ammonium chloride aqueous solution, the concentration of the ammonium chloride aqueous solution is 0.5~5 mol / L, the temperature of the ammonium ion exchange is 60~90°C, the number of times of the ammonium ion exchange is 2~8 times, and the single time is 3~6 h; the temperature of the second calcination is 500~700°C, and the time is 4~8 h.

8. According to the application described in claim 6, characterized in that, The conditions for the methanol ammoniation include: the particle size of the high-silica RHO molecular sieve is 20 to 100 mesh, and the loading amount is 0.3 g; the mass space velocity of methanol is 0.5 to 5 h -1 , the molar ratio of ammonia to methanol is (0.5 to 10):1, and the reaction temperature is 200 to 450 °C.

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