Method for producing dimethylamine with high selectivity

Abstract

The invention relates to the field of methylamine production, and discloses a method for producing dimethylamine. The method comprises the following steps: methanol and ammonia are subjected to a contact reaction with a catalyst; the catalyst comprises a silicon modified SSZ-13 molecular sieve, a binder and a matrix, wherein on the basis of the total mass of the SSZ-13 molecular sieve, the mass content of silicon in terms of oxide is 5-18%. By adopting the method provided by the invention, the purpose of high-selectivity yield increase of dimethylamine can be achieved.

Description

Technical Field

[0001] The invention relates to the field of methylamine production, and in particular to a method for producing dimethylamine with high selectivity. Background Art

[0002] Methylamine is an important organic chemical raw material product, and its product categories mainly include monomethylamine, dimethylamine, and trimethylamine. Methylamine has a wide range of industrial uses. For example, monomethylamine can be used in pesticides, pharmaceuticals, surfactants, dyes, promoters, ion exchange resins, dyes, developers, solvents, etc., and dimethylamine can be used to produce high-quality chemical fiber solvents and polyurethane solvents. Trimethylamine is mainly used as a peripheral feed additive and reagent disinfectant. The three methylamines have different uses, so different companies have different demands for the three methylamines. Some companies need dimethylamine, while others have more demand for monomethylamine and trimethylamine.

[0003] Molecular sieves are the raw materials of methylamine catalysts that are reported more frequently. Molecular sieves have the advantages of abundant pores and easy post-treatment. 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] At present, the catalysts used in industrial devices are equilibrium-type, that is, the mixed methylamine products synthesized from methanol and liquid ammonia are thermodynamic equilibrium products, in which the total equilibrium composition of monomethylamine and dimethylamine accounts for about 40-50wt% of the mixed methylamine. In order to produce more dimethylamine, the trimethylamine produced by the reaction is usually recycled back to the reaction system for further reaction to increase the production of monomethylamine and dimethylamine, but the energy consumption of this process is relatively high.

[0005] There is an urgent need to develop a highly selective dimethylamine catalyst to reduce the recycling of trimethylamine and achieve energy saving in the plant. Summary of the invention

[0006] The purpose of the present invention is to overcome the problem of low dimethylamine yield in the existing methylamine production process and provide a method for producing dimethylamine with high selectivity. The method provided by the present invention can achieve the purpose of increasing the yield of dimethylamine with high selectivity.

[0007] In order to achieve the above object, the present invention provides a method for producing dimethylamine, the method comprising: contacting methanol and ammonia with a catalyst for reaction; the catalyst comprises a silicon-modified SSZ-13 molecular sieve, a binder and a matrix;

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

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

[0010] Compared with the prior art, the advantages of the technical solution of the present invention include:

[0011] The method provided by the present invention adopts a specific type of catalyst, which can achieve the purpose of increasing the production of dimethylamine with high selectivity, effectively avoid the adverse effects of byproducts in the returned materials during the recycling of trimethylamine on the device and the catalyst, and also achieve energy saving of the device. Preferably, the method of the present invention adopts a fluidized bed reaction process, which can continuously regenerate the catalyst, so that the reaction can be carried out continuously, and the production efficiency can be improved. DETAILED DESCRIPTION

[0012] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

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

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

[0015] In the present invention, based on the total mass of the SSZ-13 molecular sieve, the mass content of silicon in terms of 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 in the range formed by any two of these point values. The use of this preferred embodiment is conducive to maintaining a high activity of the catalyst.

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

[0017] In the present invention, the content of silicon in the silicon-modified SSZ-13 molecular sieve in terms of oxide is calculated by weighing: using a precision balance, the mass change of the molecular sieve before and after modification is weighed, 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%, 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 in the range formed by any two of these point values; the mass content of the modified silica-alumina molecular sieve is 40-70%, preferably 42-65%; for example, it can be 40%, 42%, , 45%, 47%, 50%, 52%, 55%, 57%, 60%, 62%, 65%, 67%, 70%, and any value in the range formed by any two of these point 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 in the range formed by any two of these point values. The catalyst of the present invention is controlled within the above range, so that the catalyst has higher wear resistance, and the wear index is less than 5%.

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

[0021] The sum of the contents of the various components in the catalyst of the present invention is 100%.

[0022] The present invention has no particular limitation on the type of the binder, and it can be a conventional choice in the art. Preferably, the binder is alumina. This preferred embodiment is conducive to improving the wear resistance of the catalyst.

[0023] The present invention has no particular limitation on the type of the matrix, which can be selected conventionally in the art. Preferably, the matrix is ​​kaolin and / or diatomaceous earth. This preferred embodiment is beneficial to improving the wear resistance of the catalyst.

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

[0025] According to the present invention, preferably, the viscosity of the silanization agent is not less than 5000cps, preferably 5000-30000cps, for example, 5000cps, 6000cps, 7000cps, 8000cps, 9000cps, 10000cps, 11000cps, 12000cps, 13000cps, 14000cps, 15000cps, 16000cps, 17000cps, 18000cps, 19000cps, 20000cps, 25000cps, 30000cps, and any value in the range formed by any two of these point values. This preferred embodiment is conducive to obtaining higher catalytic activity and dimethylamine selectivity. When a silanization agent with a viscosity lower than 5000 cps is used, the activity of the catalyst will be seriously reduced; when a silanization agent with a viscosity higher than 30000 cps is used, the selectivity of dimethylamine will be reduced.

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

[0027] According to the present invention, preferably, the silanization agent is a methyl-containing silicone oil, preferably methyl silicone oil and / or dimethyl silicone oil. The above silanization agents can be obtained commercially.

[0028] The inventors of the present invention have found that the use of the above-mentioned specific type of silanization agent to modify the silica-alumina molecular sieve is beneficial to improving the selectivity of dimethylamine.

[0029] The present invention has no particular limitation on the preparation method of the above-mentioned catalyst, as long as the catalyst of the above-mentioned composition can be prepared. In order to more clearly illustrate the preparation of the catalyst, a specific preparation method is now provided, but the present invention is not limited thereto.

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

[0031] (1) impregnating the SSZ-13 molecular sieve in a silanization agent, and then performing optional drying and a first calcination to obtain a modified SSZ-13 molecular sieve;

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

[0033] (3) The obtained microspheres are optionally dried and subjected to a second calcination.

[0034] According to the present invention, preferably, the silanization agent is provided in the form of a mixed solution, and 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 silanization agent in the mixed solution is not higher than 10wt%, preferably not higher than 7wt%. This preferred embodiment is conducive to improving the uniformity of silicon oxide loading, so that the activity of the catalyst and the selectivity of dimethylamine are relatively high.

[0036] It should be noted that when the silanization agent is used at a concentration higher than 10 wt %, the silicon oxide loading is uneven, resulting in poor performance of the modified catalyst.

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

[0038] The present invention has no particular limitation on the number of times of the impregnation, and the impregnation may be performed once or multiple times, and the mass content of silicon calculated as oxide shall be within the above range.

[0039] The present invention does not particularly limit the temperature of the impregnation in step (1), and it can be carried out according to conventional methods, such as room temperature. The present invention does not particularly limit the time of the impregnation in step (1), as long as the required amount of silanization agent can be loaded on the silicon-aluminum 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 particularly limit the environment of the impregnation 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 comprises: separating the impregnation product of step (1) to obtain a solid product, and then performing optional drying and a first calcination.

[0041] The present invention has no particular limitation on the separation method, and the separation can be carried out using conventional techniques in the art.

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

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

[0044] In the present invention, unless otherwise specified, the term "optionally" means containing or not containing, adding or not adding, adopting or not adopting. Specifically, the step (1) and the following step (3) of the present invention may be dried or not.

[0045] The present invention does not particularly limit the drying conditions of step (1), and the drying can be carried out according to conventional methods in the art.

[0046] According to the present invention, preferably, the conditions of 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 static atmosphere. By adopting this preferred embodiment, silicon dioxide 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 has a wide range of choices for the type of solvent in step (2), which can be a conventional choice in the art. In the embodiment of the present invention, water is preferably used as the solvent.

[0048] The present invention has no particular limitation on the type of the binder precursor in step (2), and it can be any conventional choice in the art. For example, it can be aluminum sol, pseudo-boehmite, hydrated alumina with a diaspore structure, hydrated alumina with a gibbsite structure, hydrated alumina with a Bayerite structure, aluminum hydroxide, α-alumina, η-alumina, θ-alumina, γ-alumina, etc.

[0049] The present invention has no particular limitation on the order of adding the solvent, modified SSZ-13 molecular sieve, binder precursor and matrix in the mixing process of step (2), and they can be added separately or together. The embodiment of the present invention adopts the order of adding together as an example.

[0050] The present invention has no particular limitation on the mixing process in step (2), as long as the mixing 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 of the present invention.

[0052] The present invention has no particular limitation on the spray drying method, and the method can be carried out according to conventional methods in the art, so that the particle size of the obtained microspheres is within the above range.

[0053] The present invention does not particularly limit the drying conditions in step (3), and the drying can be carried out according to conventional methods in the art.

[0054] Preferably, the conditions of the second calcination in step (3) include: a temperature of 600-750°C 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 static atmosphere.

[0055] The present invention has no particular limitation on the reaction conditions, and the reaction can be carried out according 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 space velocity of 1-35 h -1 .

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

[0057] At present, the methanol amination reaction generally adopts a fixed bed reactor, which requires frequent shutdown to replace the catalyst, resulting in high production cost and relatively low production efficiency. The present invention uses a fluidized bed reactor, which can continuously regenerate the catalyst, so that the reaction can be carried out continuously, which is conducive to improving production efficiency, thereby achieving the purpose of continuous production of dimethylamine. Preferably, the reaction is carried out in a fluidized bed reactor.

[0058] In the present invention, the "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 examples.

[0060] In the following examples, the mass content of silicon in the silicon-modified SSZ-13 molecular sieve as oxide is calculated by weighing, specifically, using a precision balance to weigh the mass change of the molecular sieve before and after modification, and calculate it according to the following formula;

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

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

[0063] Preparation Example 1

[0064] The preparation examples of the present invention are used to illustrate the preparation of the catalyst of the present invention.

[0065] Prepare a n-hexane solution containing 5 wt% dimethyl silicone oil with dimethyl silicone oil (Sinopharm Reagent Company, viscosity 5000cps). Take 200 grams of H-SSZ-13 molecular sieve (SiO2 / Al2O3 molar ratio 12), immerse it in the above solution for 2 hours, and then filter to obtain a solid product. Dry the solid product at 110°C and calcine at 500°C for 4 hours. Repeat the immersion-filtration-drying-calcination steps twice to obtain a modified H-SSZ-13 molecular sieve.

[0066] 60 g of modified H-SSZ-13 molecular sieve, 63 g of kaolin, 100 g of aluminum sol (alumina content 20 wt%) and 100 g of water were mixed, mixed by colloid mill for 30 minutes, and then spray dried to obtain microspheres with a particle size of 50-200 μm. The microspheres were dried at 110° C. for 12 hours and calcined at 600° C. 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 with dimethyl silicone oil (Sinopharm Reagent Company, viscosity 10000 cps). Take 200 grams of H-SSZ-13 molecular sieve (SiO2 / Al2O3 molar ratio 36), immerse it in the above solution for 2 hours, and then filter to obtain a solid product. The solid product was dried at 110°C and calcined at 550°C for 3 hours. Repeat the immersion-filtration-drying-calcination steps twice to obtain a modified H-SSZ-13 molecular sieve.

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

[0070] Preparation Example 3

[0071] A 3 wt % methyl silicone oil n-heptane solution was prepared with dimethyl silicone oil (Sinopharm Reagent Company, viscosity 30000 cps), 200 g H-SSZ-13 molecular sieve (SiO2 / Al2O3 molar ratio 25) was immersed in the above solution for 2 hours, and then filtered to obtain a solid product. The solid product was dried at 110°C, calcined at 530°C for 3 hours, and the immersion-filtration-drying-calcination steps were repeated 4 times to obtain a modified H-SSZ-13 molecular sieve.

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

[0073] Comparative Preparation Example 1

[0074] The method of Example 1 was followed, except that ZSM-5 molecular sieve was used instead of H-SSZ-13 molecular sieve to obtain catalyst D. The composition of catalyst D is shown in Table 1.

[0075] Comparative Preparation Example 2

[0076] The method of Example 1 was followed, except that mercerized molecular sieve was used instead of H-SSZ-13 molecular sieve to obtain catalyst E. The composition of catalyst E is shown in Table 1.

[0077] Comparative Preparation Example 3

[0078] The method of Example 1 was followed, except that 60 g of H-SSZ-13 molecular sieve was not modified but directly mixed with kaolin, aluminum 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 in the fluidized bed reactor, and then methanol amination reaction was carried out: the reaction temperature was 400°C, the volume space velocity of ammonia and methanol was 18h -1 , reaction pressure 2MPa, ammonia to methanol molar ratio of 2. The reaction results of 1h reaction are listed in Table 2.

[0083] Example 2

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

[0085] Table 2

[0086]

[0087]

[0088] It can be seen from the results in Table 2 that the dimethylamine obtained by the method of the present invention has significantly higher selectivity.

[0089] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for producing dimethylamine, the method comprising: The methanol and ammonia are contacted with a catalyst for reaction; the catalyst comprises a silicon-modified SSZ-13 molecular sieve, a binder and a matrix; Wherein, based on the total mass of the SSZ-13 molecular sieve, the mass content of silicon calculated as oxide is 5-18%.

2. The method according to claim 1, wherein: Based on the total mass of the SSZ-13 molecular sieve, the mass content of silicon calculated as oxide 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%, preferably 12-36%; the mass content of the silicon-modified SSZ-13 molecular sieve is 40-70%, preferably 42-65%; the mass content of the matrix is ​​20-50%, preferably 22-46%.

4. The method according to any one of claims 1 to 3, wherein: The binder is aluminum oxide; Preferably, the matrix is ​​kaolin and / or diatomaceous earth.

5. The method according to any one of claims 1 to 4, wherein: The modified SSZ-13 molecular sieve is prepared by modifying the SSZ-13 molecular sieve with a silanization agent; Preferably, the viscosity of the silanization agent is not less than 5000 cps, preferably 5000-30000 cps; Preferably, the silanization agent is selected from methyl-containing silicone oils, preferably methyl silicone oil and / or dimethyl silicone oil.

6. The method according to claim 5, wherein: The preparation method of the catalyst comprises: (1) impregnating the SSZ-13 molecular sieve in a silanization agent, and then performing optional drying and a first calcination to obtain a modified SSZ-13 molecular sieve; (2) in the presence of a solvent, the modified SSZ-13 molecular sieve, a binder precursor and a matrix are mixed, and then spray-dried to obtain microspheres; (3) The obtained microspheres are optionally dried and subjected to a second calcination.

7. The method according to claim 6, wherein: The silanization agent is provided in the form of a mixed solution, and the solvent in the mixed solution is selected from at least one of n-hexane, cyclohexane and n-heptane; Preferably, the content of the silanization agent in the mixed solution is not higher than 10 wt %, preferably not higher than 7 wt %.

8. The method according to claim 6 or 7, wherein: The SiO2 / Al2O3 molar ratio of the SSZ-13 molecular sieve is 8-45, preferably 10-40; Preferably, the SSZ-13 molecular sieve is a hydrogen-type SSZ-13 molecular sieve; Preferably, the conditions for the first calcination in step (1) include: a temperature of 500-550° C. and a time of 3-8 h.

9. The method according to any one of claims 6 to 8, wherein: The particle size of the microspheres obtained in step (2) is 50-200 microns; Preferably, the conditions for the second calcination in step (3) include: a temperature of 600-750° C. and a time of 3-6 hours.

10. The method according to any one of claims 1 to 9, wherein: The molar ratio of ammonia to methanol is 1-4; Preferably, the conditions for the methanol amination reaction include: temperature of 300-450°C, pressure of 0.5-5 MPa, volume space velocity of 1-35 h -1 ; Preferably, the methanol amination reaction is carried out in a fluidized bed reactor.

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