Modified CHA molecular sieve and preparation method thereof, methylamine catalyst and preparation method and application thereof, method for increasing monomethylamine production

Abstract

The present invention relates to the technical field of monomethylamine production, and discloses a modified CHA molecular sieve and a preparation method thereof, a methylamine catalyst and a preparation method and application thereof, and a method for increasing the production of monomethylamine. A modified CHA molecular sieve having a silicon content of 1-10% by weight and a total specific surface area of ​​300-550 m 2 / g, with an external surface area of ​​35‑65m 2 / g, micropore area of ​​300-550m 2 / g, with a total pore volume of 0.15-0.25cm 3 / g, micropore volume is 0.13-0.24cm 3 The modified CHA molecular sieve provided by the present invention can achieve the purpose of increasing the production of monomethylamine.

Description

Technical Field

[0001] The present invention relates to the technical field of monomethylamine production, and in particular to a modified CHA molecular sieve and a preparation method thereof, a methylamine catalyst and a preparation method and application thereof, and a method for increasing the production of monomethylamine. Background Art

[0002] Methylamine is an important organic chemical raw material, primarily comprising monomethylamine, dimethylamine, and trimethylamine. Methylamine has a wide range of industrial applications. For example, monomethylamine is used in pesticides, pharmaceuticals, surfactants, dyes, accelerators, ion exchange resins, dyes, developers, and solvents. Dimethylamine is used in the production of high-quality chemical fiber and polyurethane solvents—N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAC). Trimethylamine is primarily used in peripheral feed additives and reagent disinfectants. The three methylamines have distinct functions, resulting in varying demands from different companies, such as increasing monomethylamine production.

[0003] Molecular sieves are the most commonly reported raw materials for methylamine catalysts. Molecular sieves have the advantages of abundant pores and ease of post-processing. Existing reports often use molecular sieves as the main component to synthesize methylamine catalysts, such as ZSM-5 (US4082805), alkali magnesium zeolite (USP4254061), X-type, Y-type, and A-type zeolites (USP4436938), and ZK-5 (USP879444, Journal of Catalysis 1988 113:367).

[0004] Union Carbide Corporation (UCC) in the United States developed the SAPO-n series of molecular sieves in 1984. SAPO-34, a chabazite-like structure, features a three-dimensional octahedral pore system along the crystallographic a-, b-, and c-axes. It possesses uniquely small pores with an opening diameter of 3.8 angstroms. It also exhibits moderate acidity and good hydrothermal stability, making it widely used in methanol-to-olefin reactions. SAPO-44 molecular sieve has a CHA structure similar to SAPO-34. SAPO-47 also has small pores of 4.1 angstroms. Furthermore, the framework structure of LTA molecular sieves features a simple cubic arrangement of β-cages, interconnected by double quaternary crosslinks, forming an α-cage and a three-dimensional framework structure at the center of the unit cell. The LTA framework can be considered a simple cubic arrangement of α-cages with a central β-cage. It has a three-dimensional octahedral pore system with a pore diameter of 4.1 angstroms.

[0005] Currently, industrial plants use equilibrium catalysts. This means that the mixed methylamines synthesized from methanol and liquid ammonia exhibit a thermodynamic equilibrium distribution, with monomethylamine accounting for approximately 20-25% by weight. Therefore, increasing monomethylamine production is difficult to achieve under typical reaction conditions. Summary of the Invention

[0006] The present invention aims to overcome the difficulty in increasing the production of monomethylamine under typical reaction conditions in the prior art. The present invention provides a modified CHA molecular sieve and its preparation method, a methylamine catalyst and its preparation method and application, and a method for increasing the production of monomethylamine. The modified CHA molecular sieve provided by the present invention can achieve the goal of increasing the production of monomethylamine.

[0007] In order to achieve the above object, the first aspect of the present invention provides a modified CHA molecular sieve, wherein the silicon content in the modified CHA molecular sieve is 1-10% by weight, the total specific surface area is 300-550m 2 / g, with an external surface area of ​​35-65m 2 / g, micropore area is 300-550m 2 / g, with a total pore volume of 0.15-0.25cm 3 / g, micropore volume is 0.13-0.24cm 3 / g.

[0008] Preferably, the amount of strong acid in the molecular sieve is 0.05-0.6 mmol / g, preferably 0.05-0.2 mmol / g.

[0009] Preferably, the total acid content is 0.2-1.3 mmol / g, preferably 0.2-0.5 mmol / g.

[0010] A second aspect of the present invention provides a method for preparing a modified CHA molecular sieve, the method comprising the following steps:

[0011] (1) mixing a CHA molecular sieve with a basic silicon modifier in the presence of a solvent, and then performing a first heat treatment to obtain a first silicon-modified molecular sieve;

[0012] (2) In the presence of a solvent, the first silicon-modified molecular sieve is mixed with a pore-limiting silicon modifier, and then subjected to a second heat treatment to obtain a modified CHA molecular sieve.

[0013] A third aspect of the present invention provides a methylamine catalyst, which comprises the modified CHA molecular sieve described in the first aspect or the modified CHA molecular sieve prepared by the preparation method described in the second aspect.

[0014] A fourth aspect of the present invention provides a method for preparing a methylamine catalyst, the method comprising the following steps:

[0015] (1) mixing a CHA molecular sieve with a basic silicon modifier in the presence of a solvent, and then performing a first heat treatment to obtain a first silicon-modified molecular sieve;

[0016] (2) mixing the first silicon-modified molecular sieve with a pore-limiting silicon modifier in the presence of a solvent, and then performing a second heat treatment to obtain a modified CHA molecular sieve;

[0017] The method further comprises mixing the first silicon-modified molecular sieve with a carrier and / or a carrier precursor, and then optionally shaping it; or the method further comprises mixing the modified CHA molecular sieve with a carrier and / or a carrier precursor, and then optionally shaping it.

[0018] The fifth aspect of the present invention provides use of the methylamine catalyst described in the third aspect in a reaction for selectively producing monomethylamine.

[0019] A sixth aspect of the present invention provides a method for increasing the production of monomethylamine, wherein methanol and ammonia are reacted with the methylamine catalyst described in the third aspect under monomethylamine production conditions.

[0020] The present invention adopts a CHA molecular sieve with a relatively small pore size and simultaneously adopts a two-step silicon modification method. The first modification adopts an alkaline silanization agent to reduce the strong acid center, and the second modification further reduces the pore size, so that methylamine is retained in the monomethylamine stage as much as possible and the trimethylamine stage is reduced, thereby increasing the proportion of monomethylamine and thermodynamically inhibiting the generation of dimethylamine and trimethylamine, thereby achieving the purpose of increasing the production of monomethylamine. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 NH3-TPD characterization diagram of the molecular sieve after primary silicon modification and the unmodified molecular sieve in Example 1;

[0022] Figure 2 It is the BET characterization diagram of the catalyst prepared in Example 1 and the unmodified molecular sieve. DETAILED DESCRIPTION

[0023] The endpoints of the ranges and any values ​​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 endpoints of each range, the endpoints of each range and 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 to be specifically disclosed herein.

[0024] The first aspect of the present invention provides a modified CHA molecular sieve, wherein the silicon content of the modified CHA molecular sieve is 1-10% by weight, the total specific surface area is 300-550m 2 / g, with an external surface area of ​​35-65m2 / g, micropore area is 300-550m 2 / g, with a total pore volume of 0.15-0.25cm 3 / g, micropore volume is 0.13-0.24cm 3 / g.

[0025] According to the present invention, preferably, the silicon content in the modified CHA molecular sieve is 3-8 wt%.

[0026] According to the present invention, preferably, the total specific surface area of ​​the modified CHA molecular sieve is 400-530m 2 / g, with an external surface area of ​​45-55m 2 / g, micropore area is 300-450m 2 / g, with a total pore volume of 0.18-0.24 cm 3 / g, micropore volume is 0.15-0.20cm 3 / g.

[0027] By adopting the above method, the modified CHA molecular sieve with specific silicon content, total specific surface area, external surface area, micropore area, total pore volume and micropore volume is selected to meet the purpose of increasing the production of monomethylamine.

[0028] In the present invention, the silicon content in the modified CHA molecular sieve is measured by X-ray fluorescence analysis.

[0029] In the present invention, the total specific surface area, external surface area, micropore area, total pore volume and micropore volume of the modified CHA molecular sieve are obtained through BET characterization.

[0030] According to the present invention, there is no specific limitation on the type of modified CHA molecular sieve, and any conventional CHA molecular sieve in the art is suitable for the present invention. Preferably, the modified CHA molecular sieve is selected from one or more of SAPO-34, SAPO-44, SAPO-47, and X-type molecular sieves.

[0031] According to the present invention, in order to further reduce the pore size of the modified CHA molecular sieve and achieve the purpose of increasing the production of monomethylamine, preferably, the silicon-aluminum molar ratio of SAPO-34, SAPO-44 and SAPO-47 is 0.1-0.6, more preferably 0.1-0.3.

[0032] In a preferred embodiment, the silicon-aluminum molar ratio of the X-type molecular sieve is 1-3, more preferably 1-2.

[0033] According to the present invention, in one embodiment, the amount of strong acid in the molecular sieve is preferably 0.05-0.6 mmol / g, more preferably 0.05-0.2 mmol / g. When the amount of strong acid in the molecular sieve is within the above range, the molecular sieve has good performance and can further improve the selectivity of monomethylamine.

[0034] In order to increase the production of monomethylamine, the total acid content of the molecular sieve is adjusted in the present invention. Preferably, the total acid content is 0.2-1.3 mmol / g, more preferably 0.2-0.5 mmol / g.

[0035] In the present invention, the strong acid refers to an acid site having a desorption temperature of above 300° C. after the molecular sieve adsorbs ammonia.

[0036] In the present invention, the amount of strong acid and the total acid can be measured by an ammonia temperature-programmed desorption method.

[0037] A second aspect of the present invention provides a method for preparing a modified CHA molecular sieve, the method comprising the following steps:

[0038] (1) mixing a CHA molecular sieve with a basic silicon modifier in the presence of a solvent, and then performing a first heat treatment to obtain a first silicon-modified molecular sieve;

[0039] (2) In the presence of a solvent, the first silicon-modified molecular sieve is mixed with a pore-limiting silicon modifier, and then subjected to a second heat treatment to obtain a modified CHA molecular sieve.

[0040] According to the present invention, in order to reduce the strong acid centers of the CHA molecular sieve, the present invention performs the primary modification treatment of step (1) on the CHA molecular sieve. The present invention does not specifically limit the type of CHA molecular sieve used in step (1). Preferably, the CHA molecular sieve is selected from one or more of SAPO-34, SAPO-44, SAPO-47 and X-type molecular sieve.

[0041] According to the present invention, in order to achieve the purpose of increasing the production of monomethylamine, preferably, the silicon-aluminum molar ratio of SAPO-34, SAPO-44 and SAPO-47 is 0.1-0.6, more preferably 0.1-0.3.

[0042] In a preferred embodiment, the silicon-aluminum molar ratio of the X-type molecular sieve is 1-3, more preferably 1-2.

[0043] According to the present invention, there is no specific limitation on the type of the basic silicon modifier in step (1), as long as it can reduce the strong acid centers of the CHA molecular sieve. Preferably, the basic silicon modifier is selected from one or more of trimethylsilyl imidazole, trimethylsilyl pyridine, and 4-pyridine triethoxysilane.

[0044] According to the present invention, the mixing in step (1) produces a mixed product. Preferably, the concentration of the basic silicon modifier in the mixed product is 0.01-0.3 mg / mL, preferably 0.01-0.2 mg / mL. In this preferred embodiment, selecting an appropriate concentration of the basic silicon modifier can further control the strong acid centers of the CHA molecular sieve, thereby achieving the purpose of increasing the production of monomethylamine.

[0045] In a preferred embodiment, relative to 1 g of the CHA molecular sieve, the amount of the solvent used in step (1) is 2-13 mL, preferably 2-6.5 mL.

[0046] The present invention has no particular limitation on the mixing process of step (1), as long as the CHA molecular sieve and the alkaline silicon modifier are uniformly mixed. For example, the alkaline silicon modifier can be mixed with the solvent first, and then the CHA molecular sieve is added.

[0047] The solvent type selection range of step (1) of the present invention is relatively wide. Preferably, the solvent is selected from at least one of water and an organic solvent. The organic solvent is preferably ethanol and / or isopropanol.

[0048] According to the present invention, in step (1), the mixed product of the CHA molecular sieve and the alkaline silicon modifier is further subjected to a first heat treatment. Preferably, the conditions of the first heat treatment include: a temperature of 280-350°C for 3-5 hours; more preferably, a temperature of 280-330°C for 3-5 hours.

[0049] According to the present invention, preferably, the first heat treatment can be performed in a vapor deposition furnace.

[0050] According to a specific embodiment of the present invention, the method further comprises cooling the first silicon-modified molecular sieve under an inert atmosphere (which may be cooled to 20-50° C.) before the second heat treatment. The inert atmosphere is an atmosphere that does not react with the first silicon-modified molecular sieve, including but not limited to a nitrogen atmosphere.

[0051] According to the present invention, the type of pore-limiting silicon modifier in step (2) is not specifically limited, as long as it can further reduce the pore structure of the first silicon-modified molecular sieve. Preferably, the pore-limiting silicon modifier is selected from one or more of methyl silicone oil, dimethyl silicone oil, phenyl silicone oil, and phenylmethyl silicone oil; more preferably, methyl silicone oil and dimethyl silicone oil.

[0052] According to the present invention, the mixing in step (2) comprises adding the first silicon-modified molecular sieve to a mixture of a pore-limiting silicon modifier and a solvent, and impregnating the mixture at 20-50° C. for 2-8 hours. The present invention does not specifically limit the impregnation method, as long as the first silicon-modified molecular sieve can be completely immersed in the solution (the mixture of the pore-limiting silicon modifier and the solvent).

[0053] The present invention still has no particular limitation on the mixing in step (2). For example, the pore-limiting silicon modifier can be mixed with the solvent first, and then the pelletized catalyst can be added.

[0054] The solvent in step (2) of the present invention may be the same as or different from that in step (1), and the present invention has no particular limitation thereto. Preferably, the solvent in step (2) is selected from isopropanol and / or n-heptane.

[0055] According to the present invention, preferably, in step (2), the concentration of the pore-limiting silicon modifier in the mixed product is 0.5-2.5 mg / mL, more preferably 1.5-2 mg / mL. In this embodiment, selecting an appropriate concentration of the pore-limiting silicon modifier can further control the pore size of the CHA molecular sieve, thereby achieving the purpose of increasing the production of monomethylamine.

[0056] Preferably, relative to 1 g of the first silicon-modified molecular sieve, the amount of the solvent and the pore-limiting silicon modifier used in step (2) is 8-32 mL, preferably 9-18 mL.

[0057] According to the present invention, the solid product obtained after mixing is dried. The present invention does not specifically limit the drying method. There is no particular limitation on the method of obtaining the solid product, for example, it can be dried.

[0058] Preferably, the second heat treatment conditions include: temperature of 350-550°C for 1-4 hours, more preferably, temperature of 380-450°C for 1-3 hours. This preferred embodiment is more conducive to improving the monomethylamine selectivity of the prepared molecular sieve.

[0059] According to the present invention, preferably, the heating rate is 0.1-5°C / min, more preferably 0.5-2°C / min.

[0060] In a preferred embodiment, the temperature of the second heat treatment is higher than that of the first heat treatment, preferably 50-180°C higher, and more preferably 60-150°C higher. Advantages of this preferred embodiment include enhancing the effect of the alkaline modifying agent due to the immobilization of the alkaline modifying agent, and the step-by-step treatment facilitates the modification of the acidic and pore properties separately.

[0061] A third aspect of the present invention provides a methylamine catalyst, which comprises the modified CHA molecular sieve described in the first aspect or the modified CHA molecular sieve prepared by the preparation method described in the second aspect.

[0062] According to the present invention, preferably, the methylamine catalyst further comprises a carrier.

[0063] In the present invention, there is no particular limitation on the type of carrier, and any carrier commonly used in the art is suitable for the present invention. In order to further improve the selectivity of monomethylamine, preferably, the carrier is selected from at least one of aluminum oxide, silicon oxide, kaolin, montmorillonite, and aluminum sol.

[0064] According to a preferred embodiment of the present invention, the carrier is alumina.

[0065] In the present invention, the alumina may be at least one selected from δ-alumina, ρ-alumina, κ-alumina and χ-alumina, and the present invention has no particular limitation thereto.

[0066] In a preferred embodiment, based on the total amount of the catalyst, the content of the modified CHA molecular sieve is 10-80 wt%, and the content of the carrier is 20-90 wt%. Preferably, the content of the modified CHA molecular sieve is 30-70 wt%, and the content of the carrier is 30-70 wt%.

[0067] A methylamine catalyst with excellent performance is prepared by regulating the proportions of modified CHA molecular sieve and carrier in the methylamine catalyst, thereby improving the selectivity of monomethylamine.

[0068] A fourth aspect of the present invention provides a method for preparing a methylamine catalyst, the method comprising the following steps:

[0069] (1) mixing a CHA molecular sieve with a basic silicon modifier in the presence of a solvent, and then performing a first heat treatment to obtain a first silicon-modified molecular sieve;

[0070] (2) mixing the first silicon-modified molecular sieve with a pore-limiting silicon modifier in the presence of a solvent, and then performing a second heat treatment to obtain a modified CHA molecular sieve;

[0071] The method further comprises mixing the first silicon-modified molecular sieve with a carrier and / or a carrier precursor, and then optionally shaping it; or the method further comprises mixing the modified CHA molecular sieve with a carrier and / or a carrier precursor, and then optionally shaping it.

[0072] According to the present invention, step (1) and step (2) are the same as those described in the second aspect of the present invention and will not be described in detail here.

[0073] According to the preparation method of the present invention, there is no specific limitation on the timing of introducing the carrier and / or the carrier precursor. The carrier and / or the carrier precursor can be introduced after step (1), or after step (2), or partially after step (1) and partially after step (2). However, when the carrier and / or the carrier precursor is introduced after step (1), the first silicon-modified molecular sieve in step (2) is a catalyst semi-finished product containing the carrier and the first silicon-modified molecular sieve.

[0074] According to the preparation method of the present invention, after step (1), the first silicon-modified molecular sieve may be mixed with a carrier and then optionally shaped; or the first modified molecular sieve may be mixed with a precursor of the carrier and then optionally shaped. More preferably, the first modified molecular sieve is mixed with the carrier and then shaped.

[0075] According to the present invention, the types of carriers used have been described in the third aspect of the present invention and will not be repeated here.

[0076] According to the present invention, the precursor of the carrier can be any conventional carrier precursor in the art, and those skilled in the art can appropriately select one based on the specific carrier type. For example, when the carrier is alumina, the precursor of alumina can be selected from one or both of pseudoboehmite and boehmite. Pseudoboehmite is most preferred.

[0077] In a preferred embodiment, after step (2), the modified CHA molecular sieve may be mixed with a carrier, or the modified CHA molecular sieve may be mixed with a carrier precursor, and then optionally shaped.

[0078] In a specific preferred embodiment, the carrier is introduced after step (1). The advantages of adopting this preferred embodiment are that it is more conducive to the formation of the catalyst and the prepared catalyst has better selectivity for monomethylamine.

[0079] According to the present invention, an extrusion aid may be added during the molding process to improve the molding rate. The present invention does not specifically limit the type of the extrusion aid, and those skilled in the art can select the specific type of the extrusion aid according to conventional methods. For example, the extrusion aid is selected from at least one of sesbania powder, starch, and cellulose, preferably sesbania powder.

[0080] According to the present invention, during the molding process, a sol can be added to improve the molding rate. The type of the sol is not specifically limited in the present invention. For example, the sol is selected from at least one of hydrochloric acid, nitric acid, citric acid and oxalic acid, preferably nitric acid.

[0081] The present invention has no particular limitation on the amount of the extrusion aid and the sol, as long as the molding can be carried out smoothly. Preferably, the amount of the extrusion aid is 1-10%; preferably, the amount of the sol is 1-15%.

[0082] In the present invention, the molding can be extrusion molding. There is no particular limitation on the shape of the molded object, and it can be, for example, cylindrical, clover-shaped, butterfly-shaped, honeycomb-shaped, etc.

[0083] The method provided by the present invention preferably further comprises curing the resulting shaped article, followed by drying. The curing time can be selected over a wide range, preferably from 2 to 24 hours. In the present invention, there are no specific limitations on the drying method, as long as the shaped article is dried, for example at a temperature of 80-150°C for 4-8 hours. Preferably, forced air drying can be selected to rapidly dry the shaped article. This specific embodiment can prevent the carrier and / or carrier precursor in the shaped article from continuing to react with the sol.

[0084] The method provided by the present invention further includes calcining the formed article after drying. The present invention provides a wide range of calcination conditions. Preferably, the calcination temperature is 350-550°C and the calcination time is 1-4 hours.

[0085] According to the method provided by the present invention, after calcination, the calcined product is further pelletized. The pelletizing method is not specifically limited in the present invention. Preferably, the catalyst particles obtained after pelletizing have a diameter of 1.3-5.0 mm and a particle length of 5-25 mm.

[0086] The fifth aspect of the present invention provides use of the methylamine catalyst described in the third aspect in a reaction for selectively producing monomethylamine.

[0087] A sixth aspect of the present invention provides a method for increasing the production of monomethylamine, comprising: reacting methanol and ammonia with the methylamine catalyst described in the third aspect under monomethylamine production conditions.

[0088] According to the present invention, preferably, the monomethylamine production conditions include: under a reducing atmosphere or an inert atmosphere, a reaction temperature of 300-500°C, a gauge pressure of 0.1-5.0 MPa, and a raw material liquid hourly space velocity of 1-35 hours. -1 .

[0089] In one embodiment, the present invention does not particularly limit the type of reducing atmosphere or inert atmosphere. Specifically, the reducing atmosphere or inert atmosphere is provided by hydrogen and optionally an inert gas. The inert atmosphere is provided by an inert gas. Preferably, the inert gas is at least one of hydrogen, nitrogen, helium, argon, and carbon dioxide.

[0090] In a preferred embodiment, in order to further increase the production of monomethylamine, the reaction temperature can be selected from any value between 300-500°C, such as 300°C, 350°C, 400°C, 450°C, 500°C, or any value and any interval between any two values.

[0091] In a specific embodiment, the reaction pressure is preferably 0.1-5.0 MPa, more preferably 0.1-3.0 MPa, for example, it can be 0.1 MPa, 0.5 MPa, 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa, 5 MPa, and can also be any value and any range between any two values.

[0092] In one embodiment, the raw materials are methanol and ammonia. In order to further improve the methanol conversion rate and the selectivity of monomethylamine, preferably, the raw material liquid hourly space velocity is 1-35 hours. -1 , preferably 1-20 hours -1 .

[0093] In one embodiment, the liquid hourly space velocity of the raw material is 1-35 hours -1 Any value between, for example, 1 hour -1 1.5 hours -1 2 hours -1 2.5 hours -1 5 hours -1 , 10 hours -1 15 hours -1 20 hours -1 25 hours -1 30 hours -1 35 hours -1 , and can also be any value or any interval between any two values.

[0094] According to the present invention, the molar ratio of ammonia to methanol can be adjusted within a wide range. Preferably, the molar ratio of ammonia to methanol is 1.0-3.5, more preferably 1.0-2.5. This preferred embodiment can further improve the selectivity of monomethylamine.

[0095] According to the present invention, the reactor used in the production of methylamine can be any conventional device in the art, such as a riser, a reaction tower, a fixed bed, a fluidized bed or a moving bed.

[0096] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, all reagents used are commercially available products.

[0097] Example 1

[0098] At room temperature, 10 g of SAPO-34 molecular sieve with a silicon-aluminum ratio of 0.3 was weighed and placed in a beaker. 3 mL of trimethylsilyl imidazole was weighed and added to 50 mL of deionized water to prepare a silanization reagent solution with a concentration of 0.06 g / mL. After the trimethylsilyl imidazole was completely dissolved, the above-prepared SAPO-34 molecular sieve was added and heated in a 300°C vapor deposition furnace for 4 hours. Then, the mixture was switched to a nitrogen atmosphere and taken out after cooling to 25°C.

[0099] Add 5g of alumina carrier and 0.6g of sesbania powder and mix well. Add 13.5 aqueous solution containing 0.6g of nitric acid and knead. After extrusion, cure at room temperature overnight, dry at 120℃ for 3 hours, and then calcine in a muffle furnace at 550℃ for 2 hours to obtain the catalyst. Then cut into pellets with a particle size of 2mm and a particle length of 5-8mm.

[0100] Take 5 g of the above catalyst particles, add them into 30 mL of an isopropanol mixed solution containing 5 g of dimethyl silicone oil, soak at room temperature for 24 hours, then filter and dry, heat to 400 ° C at 1 ° C / min, and heat for 2 hours to obtain a modified catalyst.

[0101] The reaction evaluation was carried out in a fixed bed reactor under the following conditions: temperature 380°C, pressure 2 MPa, molar ratio of ammonia to methanol (N / C molar ratio) of 1.8, and volumetric space velocity of 15 h -1 After 2 hours of reaction, the methylamine product stream was removed for chromatographic analysis. The analysis showed a methanol conversion rate of 56%. Under the condition of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine, dimethylamine, and trimethylamine) were 57 / 26 / 17, respectively.

[0102] Example 2

[0103] At room temperature, 8 g of SAPO-34 molecular sieve with a silicon-aluminum ratio of 0.2 was weighed and placed in a beaker. 0.5 mL of trimethylsilyl imidazole was weighed and added to 50 mL of deionized water to prepare a silanization agent solution with a concentration of 0.01 mg / mL. After the trimethylsilyl imidazole was completely dissolved, the above-prepared SAPO-34 molecular sieve was added and heated in a 280°C vapor deposition furnace for 4 hours. Then, the solution was switched to a nitrogen atmosphere and taken out after cooling to 25°C.

[0104] Add 8g of alumina carrier and 0.6g of sesbania powder and mix well. Add 14.4 aqueous solution containing 0.6g of nitric acid and knead. After extrusion, cure at room temperature overnight, dry at 120℃ for 3 hours, and then calcine in a muffle furnace at 400℃ for 2 hours to obtain the catalyst. Then cut into pellets with a particle size of 2mm and a particle length of 5-8mm.

[0105] Take 5 g of the above catalyst particles, add them into 30 mL of an isopropanol mixed solution containing 5 g of dimethyl silicone oil, soak at room temperature for 24 hours, then filter and dry, heat to 400 ° C at 1 ° C / min, and heat for 2 hours to obtain a modified catalyst.

[0106] The reaction evaluation was carried out in a fixed bed reactor under the following conditions: temperature 380°C, pressure 2 MPa, molar ratio of ammonia to methanol (N / C molar ratio) of 1.8, and volumetric space velocity of 15 h -1 After 2 hours of reaction, the methylamine product stream was removed for chromatographic analysis. The analysis showed a methanol conversion rate of 56%. Under the condition of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine, dimethylamine, and trimethylamine) were 52 / 28 / 20, respectively.

[0107] Example 3

[0108] At room temperature, 8 g of SAPO-34 molecular sieve with a silicon-aluminum ratio of 0.2 was weighed and placed in a beaker. 3.5 mL of trimethylsilyl imidazole was weighed and added to 50 mL of ethanol to prepare a silanization reagent solution with a concentration of 0.07 mg / mL. After the trimethylsilyl imidazole was completely dissolved, the above-prepared SAPO-34 molecular sieve was added and heated in a 300°C vapor deposition furnace for 4 hours. Then, the mixture was switched to a nitrogen atmosphere and taken out after cooling to 25°C.

[0109] Add 8g of alumina carrier and 0.6g of sesbania powder and mix well. Add 14.4g of aqueous solution containing 0.6g of nitric acid and knead. After extrusion, cure at room temperature overnight, dry at 120℃ for 3 hours, and then calcine in a muffle furnace at 400℃ for 2 hours to obtain the catalyst. The catalyst is then cut into pellets with a particle size of 2mm and a particle length of 5-8mm.

[0110] Take 5g of the above catalyst particles, add them into 30mL of n-heptane mixed solution containing 6g of methyl silicone oil, soak at room temperature for 24 hours, then filter and dry, heat to 390℃ at 1℃ / min, and heat for 2 hours to obtain a modified catalyst.

[0111] The reaction evaluation was carried out in a fixed bed reactor under the following conditions: temperature 390°C, pressure 1.8 MPa, molar ratio of ammonia to methanol (N / C molar ratio) of 2, and volumetric space velocity 11 h -1 After 2 hours of reaction, the methylamine product stream was removed for chromatographic analysis. The analysis showed a methanol conversion rate of 51%. Under the condition of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine, dimethylamine, and trimethylamine) were 49 / 25 / 26, respectively.

[0112] Example 4

[0113] At room temperature, 8 g of SAPO-34 molecular sieve with a silicon-aluminum ratio of 0.2 was weighed and placed in a beaker. 3 mL of 4-pyridinetriethoxysilane was weighed and 30 mL of isopropanol was added to prepare a silanization reagent solution with a concentration of 0.01 mg / mL. After the 4-pyridinetriethoxysilane was completely dissolved, the above-prepared SAPO-34 molecular sieve was added and heated in a 330°C vapor deposition furnace for 4 hours. Then, the solution was switched to a nitrogen atmosphere and taken out after cooling to 25°C.

[0114] Add 8g of alumina carrier and 0.6g of sesbania powder and mix well. Add 13.5 aqueous solution containing 0.6g of nitric acid and knead. After extrusion, cure at room temperature overnight, dry at 120℃ for 3 hours, and then calcine in a muffle furnace at 400℃ for 2 hours to obtain the catalyst. Then cut into pellets with a particle size of 2mm and a particle length of 5-8mm.

[0115] Take 5 g of the above catalyst particles, add them into 40 mL of n-heptane solution containing 8 g of dimethyl silicone oil, soak at room temperature for 24 hours, then filter and dry, heat to 400 ° C at 1 ° C / min, and heat for 2 hours to obtain a modified catalyst.

[0116] The reaction evaluation was carried out in a fixed bed reactor under the following conditions: temperature 400°C, pressure 2.5 MPa, molar ratio of ammonia to methanol (N / C molar ratio) of 3.5, and volumetric space velocity of 11 h -1 After 2 hours of reaction, the methylamine product stream was removed for chromatographic analysis. The analysis showed a methanol conversion rate of 68%. Under the condition of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine, dimethylamine, and trimethylamine) were 66 / 21 / 13, respectively.

[0117] Example 5

[0118] At room temperature, 8 g of SAPO-34 molecular sieve with a silicon-aluminum ratio of 0.1 was weighed and placed in a beaker. 4 mL of trimethylsilyl pyridine was weighed and 20 mL of ethanol was added to prepare a silanization reagent solution with a concentration of 0.2 mg / mL. After the trimethylsilyl pyridine was completely dissolved, the above-prepared SAPO-34 molecular sieve was added and heated in a 310°C vapor deposition furnace for 4 hours. Then, the solution was switched to a nitrogen atmosphere and taken out after cooling to 25°C.

[0119] Add 18g of alumina carrier and 1.1g of sesbania powder and mix well. Add 24 aqueous solution containing 1.1g of nitric acid and knead. After extrusion, cure at room temperature overnight, dry at 120℃ for 3 hours, and then calcine in a muffle furnace at 400℃ for 2 hours to obtain the catalyst. Then cut into pellets with a particle size of 2mm and a particle length of 5-8mm.

[0120] Take 5 g of the above catalyst particles, add them into 50 mL of a mixed solution of n-heptane containing 5 g of dimethyl silicone oil, soak at room temperature for 24 hours, then filter and dry, heat to 380°C at 1°C / min, and heat for 2 hours to obtain a modified catalyst.

[0121] The reaction evaluation was carried out in a fixed bed reactor under the following conditions: temperature 390°C, pressure 2.1 MPa, molar ratio of ammonia to methanol (N / C molar ratio) of 2, and volumetric space velocity of 10 h -1 After 2 hours of reaction, the methylamine product stream was removed for chromatographic analysis. The analysis showed a methanol conversion rate of 61%. Under the condition of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine, dimethylamine, and trimethylamine) were 48 / 28 / 24, respectively.

[0122] Example 6

[0123] At room temperature, 8 g of SAPO-34 molecular sieve with a silicon-aluminum ratio of 0.3 was weighed and placed in a beaker. 6 mL of trimethylsilyl pyridine was weighed and 30 mL of ethanol was added to prepare a silanization reagent solution with a concentration of 0.2 mg / mL. After the trimethylsilyl pyridine was completely dissolved, the above-prepared SAPO-34 molecular sieve was added and heated in a 310°C vapor deposition furnace for 4 hours. Then, the solution was switched to a nitrogen atmosphere and taken out after cooling to 25°C.

[0124] Add 12g of alumina carrier and 0.8g of sesbania powder and mix well. Add 18.0 aqueous solution containing 0.8g of nitric acid and knead. After extrusion, cure at room temperature overnight, dry at 120℃ for 3 hours, and then calcine in a muffle furnace at 400℃ for 2 hours to obtain the catalyst. The catalyst is then cut into pellets with a particle size of 2mm and a particle length of 5-8mm.

[0125] Take 5g of the above catalyst particles, add them into 30mL of n-heptane mixed solution containing 5g of dimethyl silicone oil, soak at room temperature for 24 hours, then filter and dry, heat to 390℃ at 1℃ / min, and heat for 2 hours to obtain a modified catalyst.

[0126] The reaction evaluation was carried out in a fixed bed reactor under the following conditions: temperature 390°C, pressure 2.1 MPa, molar ratio of ammonia to methanol (N / C molar ratio) of 2, and volumetric space velocity of 10 h -1 After 2 hours of reaction, the methylamine product stream was removed for chromatographic analysis. The analysis showed a methanol conversion rate of 55%. Under the condition of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine, dimethylamine, and trimethylamine) were 51 / 27 / 22, respectively.

[0127] Example 7

[0128] At room temperature, 8 g of SAPO-34 molecular sieve with a silicon-aluminum ratio of 0.1 was weighed and placed in a beaker. 2.5 mL of trimethylsilyl pyridine was weighed and 50 mL of ethanol was added to prepare a silanization reagent solution with a concentration of 0.05 mg / mL. After the trimethylsilyl pyridine was completely dissolved, the above-prepared SAPO-34 molecular sieve was added and heated in a 350°C vapor deposition furnace for 4 hours. Then, the solution was switched to a nitrogen atmosphere and taken out after cooling to 25°C.

[0129] Add 3.4g of kaolin and 0.5g of sesbania powder and mix well. Add 10.3g of an aqueous solution containing 0.5g of nitric acid and knead. Dry at 120°C for 3 hours, then calcine in a muffle furnace at 400°C for 2 hours to obtain the catalyst, and cut into pellets with a particle size of 2mm and a particle length of 5-8mm.

[0130] Take 5 g of the above catalyst particles, add them into 30 mL of a mixed solution of n-heptane containing 5 g of phenylmethyl silicone oil, soak at room temperature for 24 hours, then filter and dry, heat to 390°C at 1°C / min, and heat for 2 hours to obtain a modified catalyst.

[0131] The reaction evaluation was carried out in a fixed bed reactor under the following conditions: temperature 390°C, pressure 4.5 MPa, molar ratio of ammonia to methanol (N / C molar ratio) of 2, and volume space velocity of 10 h -1 After 2 hours of reaction, the methylamine product stream was removed for chromatographic analysis. The analysis showed a methanol conversion rate of 57%. Under the condition of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine, dimethylamine, and trimethylamine) were 52 / 28 / 20, respectively.

[0132] Example 8

[0133] At room temperature, 8 g of SAPO-44 molecular sieve with a silicon-aluminum ratio of 0.2 was weighed and placed in a beaker. 2.5 mL of trimethylsilyl imidazole was weighed and added to 50 mL of ethanol to prepare a silanization reagent solution with a concentration of 0.05 mg / mL. After the trimethylsilyl imidazole was completely dissolved, the above-prepared SAPO-44 molecular sieve was added and heated in a 300°C vapor deposition furnace for 4 hours. Then, the mixture was switched to a nitrogen atmosphere and taken out after cooling to 25°C.

[0134] Add 32g of montmorillonite and 1.6g of sesbania powder and mix well. Add 36g of an aqueous solution containing 1.6g of nitric acid and knead. After extrusion, cure at room temperature overnight, dry at 120°C for 3 hours, and then calcine in a muffle furnace at 400°C for 2 hours to obtain the catalyst. The catalyst is then pelletized with a particle size of 2mm and a particle length of 5-8mm.

[0135] Take 5g of the above catalyst particles, add them into 30mL of n-heptane mixed solution containing 5g of phenyl silicone oil, soak at room temperature for 24 hours, then filter and dry, heat to 390℃ at 1℃ / min, and heat for 2 hours to obtain a modified catalyst.

[0136] The reaction evaluation was carried out in a fixed bed reactor under the following conditions: temperature 390°C, pressure 3 MPa, molar ratio of ammonia to methanol (N / C molar ratio) of 3, volumetric space velocity 10 h -1 After 2 hours of reaction, the methylamine product stream was removed for chromatographic analysis. The analysis showed a methanol conversion rate of 61%. Under the condition of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine, dimethylamine, and trimethylamine) were 53 / 27 / 20, respectively.

[0137] Example 9

[0138] At room temperature, 8 g of SAPO-47 molecular sieve with a silicon-aluminum ratio of 0.2 was weighed and placed in a beaker. 5 mL of trimethylsilyl imidazole was weighed and added with 100 mL of ethanol to prepare a silanization agent solution with a concentration of 0.05 mg / mL. After the trimethylsilyl imidazole was completely dissolved, the above-prepared SAPO-47 molecular sieve was added and heated in a 300°C vapor deposition furnace for 4 hours. Then, the mixture was switched to a nitrogen atmosphere and taken out after cooling to 25°C.

[0139] Add 12g of aluminum sol and 0.8g of sesbania powder and mix well. Add 18.0g of an aqueous solution containing 0.8g of nitric acid and knead. After extrusion, cure at room temperature overnight, dry at 120°C for 3 hours, and then calcine in a muffle furnace at 400°C for 2 hours to obtain the catalyst. The catalyst is then pelletized with a particle size of 2mm and a particle length of 5-8mm.

[0140] Take 5g of the above catalyst particles, add them into 30mL of a mixed solution of n-heptane containing 4g of methyl silicone oil, soak at room temperature for 24 hours, then filter and dry, heat to 450℃ at 1℃ / min, and heat for 2 hours to obtain a modified catalyst.

[0141] The reaction evaluation was carried out in a fixed bed reactor under the following conditions: temperature 390°C, pressure 2 MPa, molar ratio of ammonia to methanol (N / C molar ratio) of 2, volume space velocity 10 h -1 After 2 hours of reaction, the methylamine product stream was removed for chromatographic analysis. The analysis showed a methanol conversion rate of 60%. Under the condition of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine, dimethylamine, and trimethylamine) were 51 / 29 / 20, respectively.

[0142] Comparative Example 1

[0143] The method of Example 1 was followed, except that only the first modification step was performed, without the second modification step. The results are shown in Table 1. Analysis showed a methanol conversion rate of 51%. Under the conditions of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine, dimethylamine, and trimethylamine) produced were 26 / 27 / 47, respectively.

[0144] Comparative Example 2

[0145] The method of Example 1 was followed, except that only the second step of modification was performed without the first step. The results are shown in Table 1. Analysis showed a methanol conversion rate of 68%. Under the condition of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine, dimethylamine, and trimethylamine) produced were 31 / 26 / 43, respectively.

[0146] Performance Testing

[0147] The molecular sieve after the primary silicon modification was characterized by NH3-TPD. The NH3-TPD diagram of the molecular sieve after the primary silicon modification in Example 1 is shown in FIG. Figure 1 As shown. Figure 1 It can be seen that after one silicon modification, the amount of molecular sieve acid is significantly reduced.

[0148] The modified catalyst obtained by secondary modification was characterized by BET. The BET characterization diagram of the catalyst prepared in Example 1 is as follows: Figure 2 As shown. Figure 2 It can be seen that the catalyst provided by the present invention has a reduced pore size.

[0149] The silicon content and strong acid content of the catalysts of the above examples and comparative examples are listed in Table 1, and the physicochemical parameters are listed in Table 2.

[0150] Table 1

[0151]

[0152]

[0153] Table 2

[0154]

[0155]

[0156] From the results in Table 1, it can be seen that the total acid content and acid content of the modified CHA molecular sieve of the present invention are significantly reduced after modification, and the pore size is smaller. The modified CHA molecular sieve can achieve the purpose of increasing the production of monomethylamine and is suitable for industrial production.

[0157] 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, various simple variations of the technical approach of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing a modified CHA molecular sieve, the method comprising the following steps: (1) mixing a CHA molecular sieve with a basic silicon modifier in the presence of a solvent, and then performing a first heat treatment to obtain a first silicon-modified molecular sieve; (2) mixing the first silicon-modified molecular sieve with a pore-limiting silicon modifier in the presence of a solvent, and then performing a second heat treatment to obtain a modified CHA molecular sieve; The alkaline silicon modifier is selected from one or more of trimethylsilyl imidazole, trimethylsilyl pyridine and 4-pyridine triethoxysilane; The pore-limiting silicon modifier is selected from one or more of methyl silicone oil, dimethyl silicone oil, phenyl silicone oil and phenylmethyl silicone oil.

2. The preparation method according to claim 1, wherein In step (1), the concentration of the alkaline silicon modifier in the product obtained by mixing is 0.01-0.3 mg / mL.

3. The preparation method according to claim 2, wherein In step (1), the concentration of the alkaline silicon modifier in the product obtained by mixing is 0.01-0.2 mg / mL.

4. The preparation method according to claim 1 or 2, wherein Relative to 1 g of the CHA molecular sieve, the amount of the solvent used in step (1) is 2-13 mL.

5. The preparation method according to claim 4, wherein Relative to 1 g of the CHA molecular sieve, the amount of the solvent used in step (1) is 2-6.5 mL.

6. The preparation method according to claim 1 or 2, wherein The conditions of the first heat treatment include: temperature of 280-350° C. and time of 3-5 hours.

7. The preparation method according to claim 1 or 2, wherein In step (2), the concentration of the pore-limiting silicon modifier in the product obtained by mixing is 0.5-2.5 mg / mL.

8. The preparation method according to claim 7, wherein In step (2), the concentration of the pore-limiting silicon modifier in the product obtained by mixing is 1.5-2 mg / mL.

9. The preparation method according to claim 1 or 2, wherein Relative to 1 g of the first silicon-modified molecular sieve, the amount of the solvent and the pore-limiting silicon modifier used in step (2) is 8-32 mL.

10. The preparation method according to claim 9, wherein Relative to 1 g of the first silicon-modified molecular sieve, the amount of the solvent and the pore-limiting silicon modifier used in step (2) is 9-18 mL.

11. The preparation method according to claim 1 or 2, wherein The conditions of the second heat treatment include: temperature of 350-550° C. and time of 1-4 hours.

12. The preparation method according to claim 1 or 2, wherein The temperature of the second heat treatment is higher than the temperature of the first heat treatment.

13. The preparation method according to claim 12, wherein The temperature of the second heat treatment is higher than that of the first heat treatment, by 50-180°C.

14. The preparation method according to claim 13, wherein The temperature of the second heat treatment is higher than that of the first heat treatment, by 60-150°C.

15. The preparation method according to claim 1 or 2, wherein The CHA molecular sieve is selected from one or more of SAPO-34, SAPO-44 and SAPO-47.

16. The preparation method according to claim 15, wherein The silicon-aluminum molar ratio of SAPO-34, SAPO-44 and SAPO-47 is 0.1-0.

6.

17. The preparation method according to claim 16, wherein The silicon-aluminum molar ratio of SAPO-34, SAPO-44 and SAPO-47 is 0.1-0.

3.

18. A methylamine catalyst, comprising the modified CHA molecular sieve prepared by the preparation method according to any one of claims 1 to 17.

19. The methylamine catalyst according to claim 18, wherein The methylamine catalyst further includes a carrier.

20. The methylamine catalyst according to claim 19, wherein The carrier is selected from at least one of alumina, silica, kaolin, montmorillonite and alumina sol.

21. The methylamine catalyst according to claim 19, wherein Based on the total amount of the catalyst, the content of the modified CHA molecular sieve is 10-80% by weight, and the content of the carrier is 20-90% by weight.

22. The methylamine catalyst according to claim 21, wherein Based on the total amount of the catalyst, the content of the modified CHA molecular sieve is 30-70% by weight, and the content of the carrier is 30-70% by weight.

23. A method for preparing a methylamine catalyst, the method comprising the following steps: (1) mixing a CHA molecular sieve with a basic silicon modifier in the presence of a solvent, and then performing a first heat treatment to obtain a first silicon-modified molecular sieve; (2) mixing the first silicon-modified molecular sieve with a pore-limiting silicon modifier in the presence of a solvent, and then performing a second heat treatment to obtain a modified CHA molecular sieve; The method further comprises mixing the first silicon-modified molecular sieve with a carrier and / or a carrier precursor, and then optionally shaping it; or the method further comprises mixing the modified CHA molecular sieve with a carrier and / or a carrier precursor, and then optionally shaping it; The alkaline silicon modifier is selected from one or more of trimethylsilyl imidazole, trimethylsilyl pyridine and 4-pyridine triethoxysilane; The pore-limiting silicon modifier is selected from one or more of methyl silicone oil, dimethyl silicone oil, phenyl silicone oil and phenylmethyl silicone oil.

24. Use of the methylamine catalyst according to any one of claims 18 to 22 in the selective production of monomethylamine.

25. A method for increasing the production of monomethylamine, comprising: Under monomethylamine production conditions, methanol and ammonia are reacted with the methylamine catalyst according to any one of claims 18 to 22.

26. The method for increasing the production of monomethylamine according to claim 25, wherein: The monomethylamine production conditions include: under a reducing atmosphere or an inert atmosphere, a reaction temperature of 300-500° C., a gauge pressure of 0.1-5.0 MPa, and a raw material liquid hourly space velocity of 1-35 hours. -1 .

27. The method for increasing the production of monomethylamine according to claim 25, wherein: The molar ratio of ammonia to methanol is 1.0-3.5.

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