Process for the highly selective production of dimethylamine

Abstract

The application relates to the field of methylamine production and discloses a method for producing dimethylamine. The method comprises the following steps: reacting methanol and ammonia with a catalyst; the catalyst comprises a silicon-modified SSZ-13 molecular sieve, a binder and a matrix; wherein the mass content of silicon in the form of an oxide is 5-18% based on the total mass of the SSZ-13 molecular sieve. The method provided by the application can realize the purpose of increasing the production of dimethylamine with high selectivity.

Description

Technical Field

[0001] This invention relates to the field of methylamine production, and more specifically to a method for highly selectively producing dimethylamine. Background Technology

[0002] Methylamine is an important organic chemical raw material, with main product categories including monomethylamine, dimethylamine, and trimethylamine. Methylamine has a wide range of industrial applications. For example, monomethylamine can be used in pesticides, pharmaceuticals, surfactants, dyes, accelerators, ion exchange resins, developing agents, and solvents. Dimethylamine can be used to produce high-quality chemical fiber solvents and polyurethane solvents. Trimethylamine is mainly used in feed additives and reagent disinfectants. Because the uses of the three types of methylamine differ, different companies have different demands for them; some companies require dimethylamine, while others have a greater demand for monomethylamine and trimethylamine.

[0003] Molecular sieves are a widely reported raw material for methylamine catalysts. They have the advantages of abundant pores and easy post-processing. In existing reports, there are many reports on the synthesis of methylamine catalysts using molecular sieves as the main component, such as ZSM-5 (US4082805), alkali magnesium zeolite (USP4254061), Y-type, A-type (USP4436938), ZK-5 (USP879444, Journal of Catalysis 1988 113:367), etc.

[0004] Currently, industrial plants use equilibrium catalysts, meaning the mixed methylamine products synthesized from methanol and liquid ammonia are in thermodynamic equilibrium, with monomethylamine and dimethylamine accounting for approximately 40-50 wt% of the total mixed methylamine. To increase dimethylamine production, the trimethylamine produced in the reaction is typically recycled back into the reaction system for further reaction, thereby increasing the production of monomethylamine and dimethylamine. However, this process is energy-intensive.

[0005] There is an urgent need to develop a highly selective dimethylamine catalyst to reduce the reprocessing of trimethylamine and achieve energy savings in the equipment. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem of low dimethylamine yield in existing methylamine production processes and to provide a method for highly selectively producing dimethylamine. The method provided by this invention can achieve the goal of highly selectively increasing the production of dimethylamine.

[0007] To achieve the above objectives, the present invention provides a method for producing dimethylamine, the method comprising: reacting methanol and ammonia with a catalyst; wherein the catalyst comprises a silicon-modified SSZ-13 molecular sieve, a binder, and a matrix;

[0008] Based on the total mass of SSZ-13 molecular sieve, the silicon content, calculated as oxides, is 5-18%.

[0009] Preferably, the methanol amination reaction is carried out in a fluidized bed reactor.

[0010] Compared with existing technologies, the advantages of the technical solution of this invention include:

[0011] The method provided by this invention employs a specific type of catalyst, achieving highly selective production of dimethylamine while effectively avoiding the adverse effects of byproducts returned to the material during the reprocessing of trimethylamine on the equipment and catalyst. It also achieves energy savings in the equipment. Preferably, the method of this invention uses a fluidized bed reaction process, which allows for continuous catalyst regeneration, ensuring a sustained reaction and improving production efficiency. Detailed Implementation

[0012] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0013] The first aspect of this invention provides a method for producing dimethylamine, the method comprising: reacting methanol and ammonia with a catalyst; the catalyst comprising a silicon-modified SSZ-13 molecular sieve, a binder, and a matrix;

[0014] Based on the total mass of SSZ-13 molecular sieve, the silicon content, calculated as oxides, is 5-18%.

[0015] In this invention, based on the total mass of the SSZ-13 molecular sieve, the silicon content (calculated as oxide) is 5-18%, preferably 8-13%, for example, it can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, and any value within the range formed by any two of these values. This preferred embodiment is beneficial for maintaining high catalyst activity.

[0016] In this invention, it should be noted that the silicon content here refers to the silicon loading during silicon modification in the catalyst preparation process, and does not include the silicon contained in the SSZ-13 molecular sieve itself.

[0017] In this invention, the silicon content in the silicon-modified SSZ-13 molecular sieve, calculated as oxides, is obtained by weighing: a precision balance is used to weigh the mass change of the molecular sieve before and after modification, and the mass content of silicon is calculated.

[0018] The mass content of silicon = (mass of silicon-modified molecular sieve - mass of unmodified molecular sieve) / mass of unmodified molecular sieve × 100%.

[0019] According to the present invention, preferably, based on the total mass of the catalyst, the mass content of the binder is 10-40%, more preferably 12-36%, for example, it can be 10%, 12%, 15%, 17%, 20%, 22%, 25%, 27%, 30%, 32%, 35%, 36%, 37%, 40%, and any value within any range formed by any two of these values; the mass content of the modified silica-alumina molecular sieve is 40-70%, preferably 42-65%; for example, it can be 40%, 42%. The content of the catalyst is 20-50%, preferably 22-46%, for example, it can be 20%, 22%, 25%, 27%, 30%, 32%, 35%, 37%, 40%, 42%, 45%, 46%, 47%, 50%, and any value within the range formed by any two of these values; the content of the matrix is ​​20-50%, preferably 22-46%, for example, it can be 20%, 22%, 25%, 27%, 30%, 32%, 35%, 37%, 40%, 42%, 45%, 46%, 47%, 50%, and any value within the range formed by any two of these values. Controlling the catalyst of the present invention within the above range results in a catalyst with high wear resistance and a wear index of less than 5%.

[0020] The content of each component in the catalyst of the present invention is calculated by the amount of feed.

[0021] The total content of all components in the catalyst of this invention is 100%.

[0022] The present invention does not particularly limit the type of binder, and any conventional choice in the art can be used. Preferably, the binder is alumina. This preferred embodiment is beneficial for improving the wear resistance of the catalyst.

[0023] The present invention does not particularly limit the type of matrix, and can use conventional choices in the art. Preferably, the matrix is ​​kaolin and / or diatomaceous earth. This preferred embodiment is beneficial for improving the wear resistance of the catalyst.

[0024] According to the present invention, preferably, the modified SSZ-13 molecular sieve is prepared by modifying SSZ-13 molecular sieve with a silanizing agent.

[0025] According to the present invention, preferably, the viscosity of the silanizing agent is not less than 5000 cps, more preferably 5000-30000 cps, for example, it can be 5000 cps, 6000 cps, 7000 cps, 8000 cps, 9000 cps, 10000 cps, 11000 cps, 12000 cps, 13000 cps, 14000 cps, 15000 cps, 16000 cps, 17000 cps, 18000 cps, 19000 cps, 20000 cps, 25000 cps, 30000 cps, and any value within the range formed by any two of these point values. Using this preferred embodiment is beneficial for obtaining higher catalytic activity and dimethylamine selectivity. When using silanizing agents with a viscosity below 5000 cps, the activity of the catalyst will decrease significantly; when using silanizing agents with a viscosity above 30000 cps, the selectivity of dimethylamine will decrease.

[0026] The viscosity described in this invention is the viscosity at 25°C.

[0027] According to the present invention, preferably, the silanizing agent is a methyl-containing silicone oil, more preferably methyl silicone oil and / or dimethyl silicone oil. All of the above-mentioned silanizing agents are commercially available.

[0028] The inventors of this invention have discovered that modifying silica-alumina molecular sieves with the aforementioned specific types of silanizing agents is beneficial for improving the selectivity of dimethylamine.

[0029] This invention does not impose any particular limitation on the preparation method of the above-mentioned catalyst, as long as the catalyst with the above composition can be prepared. In order to more clearly illustrate the preparation of the catalyst, a specific preparation method is provided, but this invention is not limited thereto.

[0030] According to the present invention, preferably, the method for preparing the catalyst includes:

[0031] (1) SSZ-13 molecular sieve is impregnated in silanizing agent, and then optionally dried and calcined for the first time to obtain modified SSZ-13 molecular sieve;

[0032] (2) In the presence of a solvent, the modified SSZ-13 molecular sieve, binder and matrix are mixed and then spray-dried to obtain microspheres;

[0033] (3) The obtained microspheres are optionally dried and then calcined.

[0034] According to the present invention, preferably, the silanizing agent is provided in the form of a mixed solution, wherein the solvent in the mixed solution is selected from at least one of n-hexane, cyclohexane and n-heptane.

[0035] Preferably, the content of the silanizing agent in the mixed solution is not higher than 10 wt%, and more preferably not higher than 7 wt%. This preferred embodiment helps to improve the uniformity of the silica loading, resulting in higher catalyst activity and dimethylamine selectivity.

[0036] It should be noted that when using silanizing agents with a concentration higher than 10 wt%, the silica loading is uneven, resulting in poor performance of the modified catalyst.

[0037] The present invention does not specifically limit the method of impregnation in step (1). The impregnation method can be impregnation with excess liquid or impregnation with equal volume, depending on the amount of impregnation liquid used.

[0038] The present invention does not have a particular limitation on the number of times the impregnation is performed; it can be performed once or multiple times, provided that the mass content of silicon, calculated as oxide, is within the above-mentioned range.

[0039] The present invention does not impose a particular limitation on the impregnation temperature in step (1), and it can be carried out according to conventional methods, such as at room temperature. The present invention also does not impose a particular limitation on the impregnation time in step (1), as long as the required amount of silanizing reagent is loaded onto the silica-alumina molecular sieve. Once the required impregnation amount and conditions are determined, it is easy to select a suitable impregnation time. The present invention does not impose a particular limitation on the impregnation environment in step (1), and it can be carried out under sealed conditions or in an open environment according to conventional methods in the art.

[0040] Preferably, the method for preparing the catalyst further includes: separating the impregnation product from step (1) to obtain a solid product, and then optionally drying and first calcining.

[0041] The present invention does not impose any particular limitation on the separation method, and conventional technical means in the art can be used.

[0042] According to the present invention, preferably, the SSZ-13 molecular sieve is a hydrogen-form SSZ-13 molecular sieve.

[0043] According to the present invention, preferably, the SiO2 / Al2O3 molar ratio of the silica-alumina molecular sieve is 8-45, more preferably 10-40.

[0044] In this invention, unless otherwise specified, "optionally" means containing or not containing, adding or not adding, using or not using. Specifically, step (1) and step (3) below may or may not involve drying.

[0045] The present invention does not impose any particular limitation on the drying conditions described in step (1), and can be carried out in accordance with conventional methods in the art.

[0046] According to the present invention, preferably, the conditions for the first calcination in step (1) include: a temperature of 500-550°C and a time of 3-8 hours. The first calcination is generally carried out in an air atmosphere, which may include a flowing atmosphere or a stationary atmosphere. By adopting this preferred embodiment, silica can be uniformly loaded on the outer surface of the molecular sieve, and the molecular sieve can maintain a high activity.

[0047] The present invention allows for a wide range of solvent selection options in step (2), which can be conventional choices in the field. In this embodiment, water is preferably used as the solvent.

[0048] The present invention does not particularly limit the type of binder precursor described in step (2), and can use conventional choices in the art. For example, it can be alumina sol, boehmite, hydrated alumina with a monohydrate structure, hydrated alumina with a trihydrate structure, hydrated alumina with a Bayer structure, aluminum hydroxide, α-alumina, η-alumina, θ-alumina, γ-alumina, etc.

[0049] This invention does not impose any particular limitation on the order in which the solvent, modified SSZ-13 molecular sieve, binder precursor, and matrix are added during the mixing process in step (2). They can be added separately or together. The embodiment of this invention uses the order in which they are added together as an example.

[0050] The present invention does not have any particular limitation on the mixing process in step (2), as long as the mixture is uniform.

[0051] According to the present invention, preferably, the microspheres obtained in step (2) have a particle size of 50-200 micrometers. This preferred embodiment is compatible with the reaction described in the present invention.

[0052] The present invention does not particularly limit the spray drying method, and can refer to conventional methods in the art, as long as the obtained microsphere particle size is within the above range.

[0053] The present invention does not impose any particular limitation on the drying conditions described in step (3), and can be carried out in accordance with conventional methods in the art.

[0054] Preferably, the conditions for the second calcination in step (3) include: a temperature of 600-750℃ and a time of 3-6 hours. The first calcination is generally carried out in an air atmosphere, which may include a flowing atmosphere or a stationary atmosphere.

[0055] The present invention does not impose particular limitations on the reaction conditions, and can be carried out with reference to conventional methods in the art. Preferably, the reaction conditions include: a reaction temperature of 300-450°C, a reaction pressure of 0.5-5 MPa, and a volume hourly space velocity of 1-35 h⁻¹. -1 .

[0056] According to the present invention, preferably, the molar ratio of ammonia to methanol is 1-4.

[0057] Currently, methanol amination reactions commonly employ fixed-bed reactors, requiring frequent shutdowns for catalyst replacement, resulting in high production costs and relatively low production efficiency. This invention utilizes a fluidized-bed reactor, allowing for continuous catalyst regeneration and enabling the reaction to proceed continuously, thus improving production efficiency and achieving continuous production of dimethylamine. Preferably, the reaction is carried out in a fluidized-bed reactor.

[0058] In this invention, the terms "first" and "second" do not limit the substances and operations, but are only used to distinguish the substances introduced in different steps and the operations performed in different stages.

[0059] The present invention will be described in detail below through embodiments.

[0060] In the following examples, the mass content of silicon in the silicon-modified SSZ-13 molecular sieve, calculated as oxides, was obtained by weighing. Specifically, a precision balance was used to weigh the mass change of the molecular sieve before and after modification, and the result was calculated according to the following formula.

[0061] Silicon mass content = (mass of silicon-modified molecular sieve - mass of unmodified molecular sieve) / mass of unmodified molecular sieve × 100%

[0062] The content of each component in the catalyst described in this invention is calculated by the amount of feed.

[0063] Preparation Example 1

[0064] The preparation examples described in this invention are used to illustrate the preparation of the catalyst described in this invention.

[0065] A hexane solution containing 5 wt% dimethyl silicone oil (from Sinopharm Reagent Company, viscosity 5000 cps) was prepared. 200 g of H-SSZ-13 molecular sieve (SiO2 / Al2O3 molar ratio 12) was immersed in the above solution for 2 hours, then filtered to obtain a solid product. The solid product was dried at 110℃ and calcined at 500℃ for 4 hours. The impregnation-filtration-drying-calcination steps were repeated twice to obtain the modified H-SSZ-13 molecular sieve.

[0066] 60 g of modified H-SSZ-13 molecular sieve, 63 g of kaolin, 100 g of alumina sol (20 wt% alumina content) and 100 g of water were mixed and milled in a colloid mill for 30 minutes, then spray-dried to obtain microspheres with a particle size of 50-200 micrometers. The microspheres were dried at 110℃ for 12 hours and calcined at 600℃ for 3 hours to obtain catalyst A. The composition of catalyst A is shown in Table 1.

[0067] Preparation Example 2

[0068] A cyclohexane solution containing 7 wt% dimethyl silicone oil was prepared using dimethyl silicone oil (Sinopharm Reagent Company, viscosity 10000 cps). 200 g of H-SSZ-13 molecular sieve (SiO2 / Al2O3 molar ratio 36) was impregnated in the above solution for 2 hours, then filtered to obtain a solid product. The solid product was dried at 110℃ and calcined at 550℃ for 3 hours. The impregnation-filtration-drying-calcination steps were repeated twice to obtain the modified H-SSZ-13 molecular sieve.

[0069] 70 g of modified H-SSZ-13 molecular sieve, 40 g of kaolin, 100 g of alumina sol (20 wt% alumina content) and 100 g of water were mixed and blended in a colloid mill for 30 minutes, then spray-dried to obtain microspheres with a particle size of 50-200 micrometers. The microspheres were dried at 110℃ for 12 hours and calcined at 680℃ for 2 hours to obtain catalyst B. The composition of catalyst B is shown in Table 1.

[0070] Preparation Example 3

[0071] A heptane solution containing 3 wt% dimethyl silicone oil was prepared using dimethyl silicone oil (Sinopharm Reagent Company, viscosity 30000 cps). 200 g of H-SSZ-13 molecular sieve (SiO2 / Al2O3 molar ratio 25) was immersed in the above solution for 2 hours, followed by filtration to obtain a solid product. The solid product was dried at 110℃ and calcined at 530℃ for 3 hours. This impregnation-filtration-drying-calcination process was repeated four times to obtain the modified H-SSZ-13 molecular sieve.

[0072] 60 g of modified H-SSZ-13 molecular sieve, 40 g of kaolin, 120 g of alumina sol (20 wt% alumina content) and 100 g of water were mixed and blended in a colloid mill for 30 minutes, followed by spray drying to obtain microspheres with a particle size of 50-200 micrometers. The microspheres were dried at 110℃ for 12 hours and calcined at 650℃ for 3 hours to obtain catalyst C. The composition of catalyst C is shown in Table 1.

[0073] Comparative Preparation Example 1

[0074] The procedure was carried out according to Example 1, except that ZSM-5 molecular sieve was used instead of H-SSZ-13 molecular sieve. Catalyst D was obtained. The composition of catalyst D is shown in Table 1.

[0075] Comparative Preparation Example 2

[0076] The procedure was carried out according to Example 1, except that instead of H-SSZ-13 molecular sieve, a silicate molecular sieve was used. Catalyst E was obtained. The composition of catalyst E is shown in Table 1.

[0077] Comparative preparation example 3

[0078] The procedure was carried out according to Example 1, except that 60g of H-SSZ-13 molecular sieve was not modified and was directly mixed with kaolin, alumina sol and water to obtain catalyst F. The composition of catalyst F is shown in Table 1.

[0079] Table 1

[0080]

[0081] Example 1

[0082] The catalysts (AF) prepared in the preparation example and the comparative preparation example were respectively loaded into a fluidized bed reactor, and then a methanol amination reaction was carried out: the reaction temperature was 400℃, and the volume hourly space velocity of ammonia and methanol was 18 h⁻¹. -1 The reaction pressure was 2 MPa, and the molar ratio of ammonia to methanol was 2. The reaction results after 1 hour are listed in Table 2.

[0083] Example 2

[0084] The catalyst A prepared in Preparation Example 1 was packed into a fluidized bed reactor, and then a methanol amination reaction was carried out: the reaction temperature was 370°C, and the volume hourly space velocity of ammonia and methanol was 10 h⁻¹. -1 The reaction pressure was 3 MPa, and the molar ratio of ammonia to methanol was 3.8. The reaction results after 1 hour are listed in Table 2.

[0085] Table 2

[0086]

[0087]

[0088] As can be seen from the results in Table 2, the dimethylamine obtained by the method described in this invention has significantly higher selectivity.

[0089] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for producing dimethylamine, the method comprising: Methanol and ammonia are reacted with a catalyst; the catalyst comprises a silicon-modified SSZ-13 molecular sieve, a binder, and a matrix; Based on the total mass of SSZ-13 molecular sieve, the silicon content, calculated as oxides, is 5-18%. The modified SSZ-13 molecular sieve is prepared by modifying SSZ-13 molecular sieve with a silanizing agent; the silanizing agent is selected from methyl-containing silicone oil. The preparation method of modified SSZ-13 molecular sieve includes: impregnating SSZ-13 molecular sieve in silanizing agent, and then optionally drying and first calcining to obtain modified SSZ-13 molecular sieve.

2. The method according to claim 1, wherein, Based on the total mass of SSZ-13 molecular sieve, the silicon content, calculated as oxides, is 8-13%.

3. The method according to claim 1, wherein, Based on the total mass of the catalyst, the mass content of the binder is 10-40%; the mass content of the silicon-modified SSZ-13 molecular sieve is 40-70%; and the mass content of the matrix is ​​20-50%.

4. The method according to claim 3, wherein, Based on the total mass of the catalyst, the mass content of the binder is 12-36%; the mass content of the silicon-modified SSZ-13 molecular sieve is 42-65%; and the mass content of the matrix is ​​22-46%.

5. The method according to any one of claims 1-4, wherein, The adhesive is aluminum oxide; The matrix is ​​kaolin and / or diatomaceous earth.

6. The method according to any one of claims 1-4, wherein, The viscosity of the silanizing agent is not less than 5000 cps.

7. The method according to claim 6, wherein, The viscosity of the silanizing agent is 5000-30000 cps.

8. The method according to any one of claims 1-4, wherein, The silanizing agent is selected from methyl silicone oil and / or dimethyl silicone oil.

9. The method according to any one of claims 1-4, wherein, The method for preparing the catalyst includes: (1) The SSZ-13 molecular sieve is impregnated in a silanizing agent, and then optionally dried and calcined to obtain the modified SSZ-13 molecular sieve. (2) In the presence of a solvent, the modified SSZ-13 molecular sieve, binder precursor and matrix are mixed and then spray-dried to obtain microspheres; (3) The obtained microspheres are optionally dried and then calcined.

10. The method according to claim 9, wherein, The silanizing agent is provided in the form of a mixed solution, wherein the solvent in the mixed solution is selected from at least one of n-hexane, cyclohexane, and n-heptane; The content of the silanizing agent in the mixed solution is not higher than 10 wt%.

11. The method according to claim 10, wherein, The content of the silanizing agent in the mixed solution is not higher than 7 wt%.

12. The method according to claim 9, wherein, The SiO2 / Al2O3 molar ratio of the SSZ-13 molecular sieve is 8-45.

13. The method according to claim 12, wherein, The SiO2 / Al2O3 molar ratio of the SSZ-13 molecular sieve is 10-40.

14. The method according to claim 9, wherein, The SSZ-13 molecular sieve is a hydrogen-type SSZ-13 molecular sieve.

15. The method according to claim 9, wherein, Step (1) The conditions for the first roasting include: a temperature of 500-550℃ and a time of 3-8h.

16. The method according to claim 9, wherein, The microspheres obtained in step (2) have a particle size of 50-200 micrometers.

17. The method according to claim 9, wherein, Step (3) The conditions for the second roasting include: a temperature of 600-750℃ and a time of 3-6h.

18. The method according to any one of claims 1-4, wherein, The molar ratio of ammonia to methanol is 1-4.

19. The method according to any one of claims 1-4, wherein, The conditions for the methanol amination reaction include: a temperature of 300-450℃, a pressure of 0.5-5 MPa, and a volume hourly space velocity of 1-35 h⁻¹. -1 .

20. The method according to any one of claims 1-4, wherein, The methanol amination reaction is carried out in a fluidized bed reactor.

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