Catalyst for selectively producing methylamine, preparation method and application thereof, and method for increasing production of monomethylamine

Abstract

The present invention relates to the technical field of methylamine production, and discloses a catalyst for selectively producing methylamine, its preparation method and application, and a method for increasing the production of monomethylamine. The catalyst for selectively producing methylamine comprises a metal selected from the fourth period and aluminum, wherein, on a molar basis, the metal selected from the fourth period contains 0.1-2% and the aluminum contains 98-99.9%. The catalyst for selectively producing methylamine has a weak acid content of 0.1-0.45 mmol / g and a total pore volume of 0.2-1.1 cm 3 / g, micropore volume is 0.1-0.55cm 3 The catalyst for selectively producing methylamine provided by the present invention can improve the selectivity of monomethylamine and achieve increased production of monomethylamine.

Description

Technical Field

[0001] The present invention relates to the technical field of methylamine production, and in particular to a catalyst for selectively producing methylamine, 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 solvents and polyurethane solvents. Trimethylamine is primarily used as a feed additive and reagent disinfectant. The three methylamines have distinct applications, resulting in varying demands from different companies. Some companies require dimethylamine, while others prioritize monomethylamine and trimethylamine.

[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), Y-type, A-type (USP4436938), and ZK-5 (USP879444, Journal of Catalysis 1988 113:367).

[0004] Currently, industrial plants utilize equilibrium catalysts. This means that the mixed methylamines synthesized from methanol and liquid ammonia exhibit a thermodynamic equilibrium product distribution, with monomethylamine constituting approximately 20-25% of the total weight of the mixed methylamines. Modifications to molecular sieves have also been reported (for example, patent application CN 102513147A). These modifications, such as those using alkali metals, rare earth elements, phosphorus, steam treatment, or alkaline treatment, alter the pore size or openings of the active phase molecular sieves, limiting the formation of macromolecular products within the pores and thereby altering the ratio of the three mixed amines. Generally speaking, the product distribution primarily increases dimethylamine, while decreasing trimethylamine. Therefore, increasing monomethylamine production is difficult to achieve under typical reaction conditions. Summary of the Invention

[0005] The present invention aims to overcome the problem in the prior art that increasing the production of monomethylamine is difficult to achieve under typical reaction conditions. The present invention provides a catalyst for selectively producing methylamine, a preparation method and application thereof, and a method for increasing the production of monomethylamine. The catalyst for selectively producing methylamine can improve the selectivity of monomethylamine and achieve increased production of monomethylamine.

[0006] To achieve the above object, the present invention provides a catalyst for selectively producing methylamine in a first aspect, the catalyst comprising a metal selected from the fourth period and aluminum, wherein the content of the metal selected from the fourth period is 0.1-2% and the content of aluminum is 98-99.9% on a molar basis;

[0007] The weak acid content of the catalyst for selectively producing methylamine is 0.1-0.45 mmol / g, and the total pore volume of the catalyst for selectively producing methylamine is 0.2-1.1 cm 3 / g, micropore volume is 0.1-0.55cm 3 / g.

[0008] A second aspect of the present invention provides a method for preparing a catalyst for selectively producing methylamine, the method comprising the following steps:

[0009] (1) providing a solution containing a pore-adjusting polymer compound and an aluminum-containing precursor, and then contacting the solution with a gas containing carbon dioxide to perform a gelling reaction to obtain a gelling product;

[0010] (2) The colloid product is mixed with a precursor of a metal selected from the fourth period and a metal complex dispersed polymer compound, and then dried and calcined.

[0011] The third aspect of the present invention provides a use of the catalyst for selectively producing methylamine described in the first aspect or the catalyst for selectively producing methylamine prepared by the preparation method described in the second aspect in a reaction for increasing the production of monomethylamine.

[0012] A fourth aspect of the present invention provides a method for increasing the production of monomethylamine, comprising: reacting methanol and ammonia with the catalyst for selectively producing methylamine described in the first aspect or the catalyst for selectively producing methylamine prepared by the preparation method described in the second aspect under monomethylamine production conditions.

[0013] The present invention reduces trimethylamine production by adjusting the synthesis method of a catalyst for selective methylamine production and adding a metal element to the catalyst. This controls the acid distribution in the catalyst, allowing the methylamine reaction to proceed at less acidic reactive sites. The addition of a metal, such as the specific metal selected in the present invention, produces a lattice substitution effect. The metal occupies the aluminum lattice in the alumina, creating charge imbalance points, thereby increasing the number of weakly acidic sites and further improving reactivity. Simultaneously, by unblocking pores, diffusion is accelerated, reducing the reaction toward dimethylamine and trimethylamine. This combined effect improves the retention rate of monomethylamine, achieving the goal of increasing monomethylamine production. DETAILED DESCRIPTION

[0014] 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.

[0015] A first aspect of the present invention provides a catalyst for selectively producing methylamine, the catalyst comprising a metal selected from the fourth period and aluminum, wherein the content of the metal selected from the fourth period is 0.1-2% and the content of aluminum is 98-99.9% on a molar basis;

[0016] The weak acid content of the catalyst for selectively producing methylamine is 0.1-0.45 mmol / g, and the total pore volume of the catalyst for selectively producing methylamine is 0.2-1.1 cm 3 / g, micropore volume is 0.1-0.55cm 3 / g.

[0017] By adopting the above technical solution, selecting a specific metal and aluminum for coordination, and the catalyst for selectively producing methylamine provided by the present invention having a specific weak acid amount, total pore volume and micropore volume, the catalyst for selectively producing methylamine can improve the selectivity of monomethylamine.

[0018] According to the present invention, the metal content of the fourth period is preferably 0.2-1.5%, and the aluminum content is preferably 98.5-99.8%, on a molar basis. By further regulating the metal and aluminum contents of the fourth period, the selectivity of the catalyst for selectively producing methylamine can be further improved, thereby achieving increased production of monomethylamine.

[0019] In the present invention, the metal content of the fourth period and the aluminum content are measured by X-ray fluorescence spectroscopy.

[0020] According to the present invention, in a preferred embodiment, the amount of weak acid in the catalyst for selectively producing methylamine is 0.2-0.4 mmol / g. When the amount of weak acid in the catalyst for selectively producing methylamine is within this range, the catalyst for selectively producing methylamine has better selectivity for monomethylamine, thereby further improving the selectivity for monomethylamine.

[0021] In the present invention, the weak acid refers to the acid corresponding to the ammonia desorption at a temperature below 200° C. after the material adsorbs ammonia.

[0022] In the present invention, the amount of weak acid can be measured by ammonia temperature-programmed desorption method.

[0023] In a preferred embodiment, the total pore volume of the catalyst for selectively producing methylamine is 0.5-0.8 cm3 / g, micropore volume is 0.3-0.45cm 3 / g.

[0024] In the present invention, the total pore volume and micropore volume of the catalyst for selectively producing methylamine are measured by BET characterization.

[0025] In the present invention, there is no particular limitation on the type of metal in the fourth period; all metals in the fourth period conventionally defined in the art are applicable to the present invention. Preferably, the metal is selected from one or more of Fe, Co, Ni, Cu, Ti, and Zr; more preferably, the metal is selected from one of Cu, Ti, and Zr.

[0026] A second aspect of the present invention provides a method for preparing a catalyst for selectively producing methylamine, the method comprising the following steps:

[0027] (1) providing a solution containing a pore-adjusting polymer compound and an aluminum-containing precursor, and then contacting the solution with a gas containing carbon dioxide to perform a gelling reaction to obtain a gelling product;

[0028] (2) The colloid product is mixed with a precursor of a metal selected from the fourth period and a metal complex dispersed polymer compound, and then dried and calcined.

[0029] According to the method provided by the present invention, the range of selection for the types of the pore-adjusting polymer compound in step (1) and the metal complex-dispersing polymer compound in step (2) is relatively wide, and those skilled in the art can select specific types according to specific needs. Among them, the pore-adjusting polymer compound only needs to meet the purpose of being blended with alumina. The metal complex-dispersing polymer compound only needs to meet the purpose of being able to disperse metal ions and blend with alumina. Preferably, the pore-adjusting polymer compound and the metal complex-dispersing polymer compound are each independently selected from one or more of polyacrylamide, polymethyl methacrylate, polyvinyl alcohol, polyethylene glycol, polyoxyethylene-polyoxypropylene ether block copolymer and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer.

[0030] In a preferred embodiment, the pore-adjusting polymer compound is selected from one or more of polyacrylamide, polymethyl methacrylate, polyvinyl alcohol, and polyethylene glycol, and more preferably one or more of polyacrylamide, polyvinyl alcohol, and polyethylene glycol.

[0031] In a preferred embodiment, the metal complexing dispersed polymer compound is at least one selected from polyoxyethylene-polyoxypropylene ether block copolymer, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer and polyacrylic acid.

[0032] The present invention has a wide range of molecular weight selection for the pore-adjusting polymer compound and the metal complex dispersed polymer compound. Preferably, the number average molecular weights of the pore-adjusting polymer compound and the metal complex dispersed polymer compound are independently 8-14 million.

[0033] The present invention has no particular limitation on the sources of the pore-adjusting polymer compound and the metal complex dispersing polymer compound. They can be prepared by any existing method or purchased commercially.

[0034] In a preferred embodiment, the amount of the pore-adjusting polymer compound is 0.1-3% by weight, preferably 0.5-1.5% by weight, of the aluminum-containing precursor, where the aluminum-containing precursor is calculated as aluminum hydroxide.

[0035] In a preferred embodiment, the added mass of the metal complex dispersing polymer compound is 0.5-5 times, preferably 0.5-3 times, the added mass of the pore-adjusting polymer compound.

[0036] According to the method provided by the present invention, the method for providing the solution containing the pore-adjusting polymer compound and the aluminum-containing precursor in step (1) is not particularly limited, as long as the pore-adjusting polymer compound and the aluminum-containing precursor are uniformly mixed. For example, the pore-adjusting polymer compound can be dissolved in the solution of the aluminum-containing precursor and stirred thoroughly.

[0037] According to the method provided by the present invention, the method of preparing the solution containing the aluminum precursor in step (1) is not particularly limited, as long as the aluminum precursor is dissolved.

[0038] The present invention has a wide range of solvents for the solution in step (1), including but not limited to water.

[0039] According to the method provided by the present invention, the concentration of the aluminum-containing precursor in the solution can be selected in a wide range. Preferably, in step (1), the concentration of the aluminum-containing precursor in the solution is 0.1-1 mol / L.

[0040] In the present invention, there is no particular limitation on the type of aluminum-containing precursor in step (1), and those skilled in the art can select the desired aluminum-containing precursor according to specific needs. Preferably, the aluminum-containing precursor is selected from one or more of sodium metaaluminate, sodium aluminate, aluminum nitrate, and aluminum sulfate, and more preferably sodium metaaluminate. There is no particular limitation on the source of the sodium metaaluminate, and it can be prepared by existing methods or purchased commercially.

[0041] According to the method provided by the present invention, in step (1), the solution is contacted with a carbon dioxide-containing gas to perform a gel-forming reaction. In the present invention, the carbon dioxide content in the carbon dioxide-containing gas can be selected within a wide range. For example, the carbon dioxide-containing gas can contain an inert gas in addition to carbon dioxide, and the volume fraction of carbon dioxide is 20-70%, preferably 25-65%, and more preferably 30-50%.

[0042] In a specific embodiment, the present invention does not specifically limit the type of inert gas. Preferably, the inert gas is one or more of hydrogen, nitrogen, helium and argon.

[0043] The method provided by the present invention allows for a wide range of conditions for the gelation reaction. Preferably, the gelation reaction conditions include: a temperature of 15-70°C, preferably 30-50°C; a duration of 30-90 minutes, preferably 60-90 minutes; and terminating the gelation reaction when the pH reaches 8-12, preferably 9-11. This preferred embodiment further improves the quality of the gelled product and, in turn, increases the selectivity of monomethylamine.

[0044] According to the method provided by the present invention, a gelled product is obtained after the gelling reaction in step (1) is completed. The method further comprises: aging the gelled product and then performing step (2).

[0045] According to the method provided by the present invention, the aging time can be selected over a wide range. Preferably, the aging time is 1-6 hours. The advantage of adopting this preferred embodiment is that the pore-modulating polymer compound and the alumina gel can be fully aged to facilitate the shaping and stabilization of the pores.

[0046] In a preferred embodiment, after the gelled product is aged, the aged gelled product is subjected to solid-liquid separation, and then step (2) is performed. In the present invention, there is no particular limitation on the method of solid-liquid separation, and those skilled in the art can select a specific method according to actual needs. For example, the solid-liquid separation method can be one of filtration, sedimentation, and centrifugation, preferably filtration.

[0047] According to the method provided by the present invention, the metal of the fourth period in step (2) has been mentioned in the first aspect and will not be elaborated here.

[0048] In a preferred embodiment, the amount of the precursor of the metal selected from the fourth period added is such that, in the prepared catalyst, the content of the metal selected from the fourth period is 0.1-2%, and the content of aluminum is 98-99.9%, calculated on a molar basis; further preferably, the content of the metal selected from the fourth period is 0.1-1.5%, and the content of aluminum is 98.5-99.9%.

[0049] The precursors of the metals in the fourth period in step (2) can each be selected from water-soluble compounds of the corresponding metals. In a preferred embodiment, the precursors of the metals in the fourth period in step (2) are selected from one or more of ferric nitrate, cobalt nitrate hexahydrate, titanium tetrachloride, nickel nitrate hexahydrate, zirconium oxychloride, and copper nitrate, preferably one or more of titanium tetrachloride, zirconium oxychloride, and copper nitrate.

[0050] The present invention does not specifically limit the mixing method of step (2), as long as the colloid product is uniformly mixed with the precursor of the metal selected from the fourth period and the metal complex dispersed polymer compound. Specifically, the mixing of step (2) is carried out in the presence of a solvent, and the solvent includes but is not limited to water.

[0051] Preferably, the mixing is performed under stirring conditions. The present invention does not particularly limit the speed of the stirring, as long as the mixing is uniform. The stirring method in the present invention is not particularly limited. For example, ultrasonic stirring can be used.

[0052] The order of mixing in step (2) is not particularly limited in the present invention. For example, the colloid product may be slurried before mixing, and then the metal complex dispersed polymer compound may be added to the wet slurry and mixed, and then the precursor of the metal selected from the fourth period may be added.

[0053] According to the method provided by the present invention, there is no specific limitation on the pulping method of the gelled product in step (2), as long as the gelled product is contacted with a solvent (such as water) to obtain a wet pulp.

[0054] In a preferred embodiment, the mixing time is 0.2-4 hours, more preferably 0.4-1 hour.

[0055] According to the method provided by the present invention, the mixture obtained by mixing in step (2) is dried. The present invention has a wide range of selection conditions for the drying. Preferably, the drying conditions include: a temperature of 80-200°C and a time of 2-24 hours.

[0056] According to the method provided by the present invention, the dried product can be calcined in step (2). Preferably, the calcination conditions in step (2) are: temperature of 350-550° C. and time of 1-4 hours.

[0057] The third aspect of the present invention provides use of the catalyst for selectively producing methylamine described in the first aspect or the catalyst for selectively producing methylamine prepared by the preparation method described in the second aspect in a reaction for increasing the production of monomethylamine.

[0058] A fourth aspect of the present invention provides a method for increasing the production of monomethylamine, comprising: reacting methanol and ammonia with the catalyst for selectively producing methylamine described in the first aspect or the catalyst for selectively producing methylamine prepared by the preparation method described in the second aspect under monomethylamine production conditions.

[0059] According to the present invention, preferably, the monomethylamine production conditions include: under a reducing atmosphere or an inert atmosphere, a reaction temperature of 350-450°C, a gauge pressure of 0.1-5.0 MPa, and a raw material liquid hourly space velocity of 1-35 hours. -1 .

[0060] 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 one or more of hydrogen, nitrogen, helium, argon, and carbon dioxide.

[0061] In a preferred embodiment, in order to further increase the production of monomethylamine, the reaction temperature can be selected from any value between 350-450°C, such as 350°C, 400°C, 450°C, or any value and any interval between any two values.

[0062] 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, 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, or any value or any interval between any two values.

[0063] In one embodiment, the raw materials are methanol and ammonia. In order to further improve the selectivity of monomethylamine, preferably, the raw material liquid hourly space velocity is 1-35 hours -1 , preferably 1-20 hours -1 .

[0064] In one embodiment, the liquid hourly space velocity of the raw material is 1-35 hours -1 , for example 1 hour -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.

[0065] 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.

[0066] 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.

[0067] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, the raw materials used in the present invention are all commercially available products, and their manufacturers and models are shown in the following table.

[0068] Table 1

[0069]

[0070]

[0071] Example 1

[0072] 31.2g of industrial-grade aluminum hydroxide powder was dissolved in sodium hydroxide to produce 1L of sodium metaaluminate solution at a concentration of 0.4mol / L. To this solution was added 0.31g of a polyacrylamide polymer compound, representing 1% of the mass of the aluminum hydroxide. The mixture was stirred evenly and a 50% carbon dioxide and air mixture was introduced with continuous stirring. The gelling temperature was controlled at 35°C for 60 minutes. When the pH reached 10, the carbon dioxide introduction was stopped. Stirring and aging were continued for 4 hours, followed by filtration. The resulting filter cake was then beaten into a wet slurry. Polyvinyl alcohol, a metal complex dispersing polymer, was added in an amount equal to 100% of the pore-adjusting polymer compound, i.e., 0.31g. Ferric nitrate was added, with the molar amount of iron being 1% of the molar amount of aluminum. Ultrasonic stirring was performed for 1 hour, and the mixture was dried at 120°C for 12 hours. The mixture was then calcined at 550°C for 3 hours to obtain the methylamine catalyst.

[0073] The reaction evaluation was carried out in a fixed bed reactor under the following conditions: temperature 400°C, pressure 2 MPa, molar ratio of ammonia to methanol (N / C molar ratio) of 2.5, liquid hourly 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 89%. Under the condition of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine / dimethylamine / trimethylamine) were 56 / 21 / 23, respectively.

[0074] Example 2

[0075] 7.8g of industrial-grade aluminum hydroxide powder was dissolved in sodium hydroxide to produce 1L of sodium metaaluminate solution at a concentration of 0.1mol / L. To this solution was added 0.08g of a polymethyl methacrylate polymer (1% by weight of the aluminum hydroxide). The mixture was stirred evenly and a 50% carbon dioxide and air mixture was introduced with constant stirring. The gelling temperature was maintained at 30°C for 60 minutes. When the pH reached 10, the carbon dioxide introduction was stopped. Stirring and aging were continued for 4 hours. The resulting filter cake was then filtered and beaten into a wet slurry. A metal complex dispersing polymer, polyethylene glycol, was added in an amount 1.5 times that of the pore-adjusting polymer, i.e., 0.12g. The metal complex dispersing polymer, polyethylene glycol, was added in an amount 1.5 times that of the pore-adjusting polymer. The cobalt nitrate hexahydrate (0.44g) was added, with the molar amount of cobalt being 1.5% of the molar amount of aluminum. Ultrasonic stirring was then performed for 1 hour, and the mixture was dried at 120°C for 12 hours. The mixture was then calcined at 550°C for 3 hours to obtain the methylamine catalyst.

[0076] The reaction evaluation was carried out in a fixed bed reactor under the following conditions: temperature 410°C, pressure 2.4 MPa, molar ratio of ammonia to methanol (N / C molar ratio) of 2.5, 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 85%. Under the condition of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine / dimethylamine / trimethylamine) were 55 / 22 / 23, respectively.

[0077] Example 3

[0078] Take 39g of technical-grade aluminum hydroxide powder and dissolve it in sodium hydroxide to produce 1L of sodium metaaluminate solution at a concentration of 0.5mol / L. Add 0.31g of polyvinyl alcohol polymer to this solution, the addition amount being 0.8% of the aluminum hydroxide mass. Stir evenly and introduce a mixture of 30% carbon dioxide and air, stirring continuously, controlling the gelling temperature at 30°C for 60 minutes. When the pH value reaches 11, stop introducing carbon dioxide gas. Continue stirring and aging for 4 hours, then filter the resulting filter cake, break the filter cake into a wet slurry, and add a metal complex dispersed polymer compound P123 (polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer) in an amount of 1.5 times the amount of the pore-adjusting polymer compound, i.e. 0.47g. Add 0.57g of titanium tetrachloride, the molar weight of titanium being 0.6% of the molar weight of aluminum. The mixture was stirred by ultrasonic for 1 hour, dried at 110° C. for 12 hours, and calcined at 530° C. for 3 hours to obtain a methylamine catalyst.

[0079] The reaction evaluation was carried out in a fixed bed reactor under the following conditions: temperature 410°C, pressure 2 MPa, molar ratio of ammonia to methanol (N / C molar ratio) of 2.5, volume space velocity 10 h -1After 2 hours of reaction, the methylamine product stream was removed for chromatographic analysis. The analysis showed a methanol conversion rate of 98%. Under the condition of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine / dimethylamine / trimethylamine) were 66 / 21 / 13, respectively.

[0080] Example 4

[0081] 39g of industrial-grade aluminum hydroxide powder was dissolved in sodium hydroxide to produce 1L of sodium metaaluminate solution at a concentration of 0.5mol / L. 0.47g of polyvinyl alcohol (PVA) was added to the solution, representing 1.2% of the mass of the aluminum hydroxide. The mixture was stirred evenly and introduced with a mixture of 65% carbon dioxide and air. The gelling temperature was maintained at 30°C for 90 minutes, and the CO2 addition was stopped when the pH reached 8. Stirring and aging were continued for 4 hours. The resulting filter cake was then filtered and beaten into a wet slurry. A metal complex dispersed polymer compound, P123 (polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer), was added in an amount of twice that of the pore-adjusting polymer, i.e., 0.94g. 0.87g of nickel nitrate hexahydrate was added, with the molar weight of nickel being 0.6% of the molar weight of aluminum. Ultrasonic stirring was performed for 1 hour, and the mixture was dried at 120°C for 8 hours. The mixture was then calcined at 500°C for 3 hours to obtain the methylamine catalyst.

[0082] The reaction evaluation was carried out in a fixed bed reactor under the following conditions: temperature 410°C, pressure 2.4 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 91%. Under the condition of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine / dimethylamine / trimethylamine) were 58 / 25 / 17, respectively.

[0083] Example 5

[0084] 46.8g of industrial-grade aluminum hydroxide powder was dissolved in sodium hydroxide to produce 1L of sodium metaaluminate solution at a concentration of 0.6mol / L. 0.70g of polyacrylamide polymer was added to this solution in an amount of 1.5% of the mass of the aluminum hydroxide. The mixture was stirred evenly and introduced into a mixture of 50% carbon dioxide and air, stirring continuously. The gelling temperature was controlled at 30°C for 30 minutes. When the pH value reached 10, the carbon dioxide gas was stopped. Stirring and aging were continued for 4 hours, and the resulting filter cake was then filtered and beaten into a wet slurry. A metal complex dispersed polymer compound P123 (polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer) was added in an amount of 2.5 times the amount of the pore-adjusting polymer compound, i.e., 1.76g. 0.68g of titanium tetrachloride was added, with the molar weight of titanium being 0.6% of the molar weight of aluminum. The mixture was ultrasonically stirred for 1 hour, dried at 120°C for 8 hours, and calcined at 500°C for 3 hours to obtain a methylamine catalyst.

[0085] The reaction evaluation was carried out in a fixed bed reactor under the following conditions: temperature 410°C, pressure 2 MPa, molar ratio of ammonia to methanol (N / C molar ratio) of 2.5, volume space velocity 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 90%. Under the condition of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine / dimethylamine / trimethylamine) were 59 / 24 / 17, respectively.

[0086] Example 6

[0087] 78g of industrial-grade aluminum hydroxide powder was dissolved in sodium hydroxide to produce 1L of sodium metaaluminate solution at a concentration of 1mol / L. 0.39g of polyacrylamide (0.5% by weight of the aluminum hydroxide) was added to the solution. The mixture was stirred evenly and introduced into a mixture of 40% carbon dioxide and air with continuous stirring. The gelling temperature was controlled at 50°C for 50 minutes. When the pH reached 12, the carbon dioxide introduction was stopped. Stirring and aging were continued for 4 hours. The resulting filter cake was then filtered and beaten into a wet slurry. A metal complex dispersed polymer compound, P123 (polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer), was added in an amount of 3 times the amount of the pore-adjusting polymer compound, i.e., 1.17g. 0.38g of titanium tetrachloride (the molar amount of titanium was 0.2% of the molar amount of aluminum) was added. Ultrasonic stirring was performed for 1 hour, and the mixture was dried at 120°C for 6 hours. The mixture was then calcined at 550°C for 2 hours to obtain the methylamine catalyst.

[0088] The reaction evaluation was carried out in a fixed bed reactor under the following conditions: temperature 410°C, pressure 1.5 MPa, molar ratio of ammonia to methanol (N / C molar ratio) of 1.9, volume space velocity 10 h -1After 2 hours of reaction, the methylamine product stream was removed for chromatographic analysis. The analysis showed a methanol conversion rate of 89%. Under the condition of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine / dimethylamine / trimethylamine) were 62 / 26 / 12, respectively.

[0089] Example 7

[0090] Take 39g of technical-grade aluminum hydroxide powder and dissolve it in sodium hydroxide to obtain 1L of sodium metaaluminate solution at a concentration of 0.5mol / L. Add 0.47g of the P123 compound (polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer) polymer compound to this solution, in an amount of 1.2% of the aluminum hydroxide mass. Stir evenly and introduce a mixed gas of 45% carbon dioxide and air, constantly stirring, controlling the gelling temperature at 45°C for 60 minutes. When the pH value reaches 10, stop introducing carbon dioxide gas. Continue stirring and aging for 4 hours, then filter the resulting filter cake and break it into a wet slurry. Add 0.6 times the amount of the pore-adjusting polymer compound F127 (polyoxyethylene-polyoxypropylene ether block copolymer), i.e. 0.28g, of the metal complex dispersed polymer compound. Add 0.45g of zirconium oxychloride, with the molar weight of zirconium being 0.5% of the molar weight of aluminum. The mixture was stirred by ultrasonic for 1 hour, dried at 120° C. for 12 hours, and calcined at 550° C. for 3 hours to obtain a methylamine catalyst.

[0091] The reaction evaluation was carried out in a fixed bed reactor under the following conditions: temperature 410°C, pressure 3 MPa, molar ratio of ammonia to methanol (N / C molar ratio) of 2.8, volume space velocity 20 h -1 After 2 hours of reaction, the methylamine product stream was removed for chromatographic analysis. The analysis showed a methanol conversion rate of 87%. Under the condition of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine / dimethylamine / trimethylamine) were 61 / 24 / 15, respectively.

[0092] Example 8

[0093] 39g of industrial-grade aluminum hydroxide powder was dissolved in sodium hydroxide to produce 1L of sodium metaaluminate solution at a concentration of 0.5mol / L. 0.47g of polyacrylamide (1.2% by mass of the aluminum hydroxide) was added to this solution. Stirring was continued, and a mixture of 50% carbon dioxide and air was introduced with continuous stirring. The gelling temperature was maintained at 60°C for 60 minutes. The carbon dioxide introduction was stopped when the pH reached 10. Stirring and aging were continued for 4 hours. The resulting filter cake was then filtered and beaten into a wet slurry. A metal complex dispersed polymer F127 (polyoxyethylene-polyoxypropylene ether block copolymer) was added in an amount of 1.2 times the amount of the pore-adjusting polymer, i.e., 0.56g. Titanium tetrachloride (0.76g) was added, with the molar weight of titanium being 0.8% of the molar weight of aluminum. Ultrasonic stirring was performed for 1 hour, and the mixture was dried at 120°C for 12 hours. The mixture was then calcined at 550°C for 3 hours to obtain the methylamine catalyst.

[0094] The reaction evaluation was carried out in a fixed bed reactor under the following conditions: temperature 440°C, pressure 2 MPa, molar ratio of ammonia to methanol (N / C molar ratio) of 2.5, volume space velocity 30 h -1 After 2 hours of reaction, the methylamine product stream was removed for chromatographic analysis. The analysis showed a methanol conversion rate of 88%. Under the condition of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine / dimethylamine / trimethylamine) were 60 / 23 / 17, respectively.

[0095] Example 9

[0096] 39g of industrial-grade aluminum hydroxide powder was dissolved in sodium hydroxide to produce 1L of sodium metaaluminate solution at a concentration of 0.5mol / L. 0.47g of F127 polymer (polyoxyethylene-polyoxypropylene ether block copolymer) was added to this solution, accounting for 1.2% of the mass of the aluminum hydroxide. The mixture was stirred evenly and introduced into a mixture of 45% carbon dioxide and air. The gelling temperature was maintained at 20°C for 60 minutes, and the carbon dioxide introduction was stopped when the pH reached 10. Stirring and aging were continued for 4 hours, after which the resulting filter cake was filtered and beaten into a wet slurry. A metal complexing dispersed polymer, polyvinyl alcohol, was added in an amount of 1.2 times the amount of the pore-adjusting polymer, i.e., 0.6g. The copper nitrate (0.56g) was added, with the molar amount of copper being 0.5% of the molar amount of aluminum. Ultrasonic stirring was performed for 1 hour, and the mixture was dried at 120°C for 6 hours. The mixture was then calcined at 550°C for 2 hours to obtain the methylamine catalyst.

[0097] The reaction evaluation was carried out in a fixed bed reactor under the following conditions: temperature 350°C, pressure 2 MPa, molar ratio of ammonia to methanol (N / C molar ratio) of 3, volume space velocity 5 h -1The reaction was continued for 2 hours, and the methylamine product stream was subjected to chromatographic analysis. The analysis showed that the methanol conversion rate was 89%. Under the condition of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine / dimethylamine / trimethylamine) were 59 / 25 / 16 respectively.

[0098] Example 10

[0099] 39g of industrial-grade aluminum hydroxide powder was dissolved in sodium hydroxide to produce 1L of sodium metaaluminate solution at a concentration of 0.5mol / L. To this solution was added 0.47g of a polyvinyl alcohol polymer compound, representing 1.2% of the mass of the aluminum hydroxide. The mixture was stirred evenly and a mixture of 45% carbon dioxide and air was introduced with continuous stirring. The gelling temperature was maintained at 30°C for 60 minutes. When the pH reached 10, the carbon dioxide introduction was stopped. Stirring and aging were continued for 4 hours. The resulting filter cake was then filtered and beaten into a wet slurry. A metal-complexing dispersing polymer, polyacrylamide, was added in an amount 1.2 times that of the pore-adjusting polymer, i.e., 0.56g. Zirconium oxychloride (0.45g) was also added, with the molar amount of zirconium being 0.5% of the molar amount of aluminum. Ultrasonic stirring was performed for 1 hour, and the mixture was dried at 120°C for 12 hours. The mixture was then calcined at 550°C for 3 hours to obtain the methylamine catalyst.

[0100] The reaction evaluation was carried out in a fixed bed reactor under the following conditions: temperature 410°C, pressure 2.5 MPa, molar ratio of ammonia to methanol (N / C molar ratio) of 2.5, 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 90%. Under the condition of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine / dimethylamine / trimethylamine) were 58 / 26 / 16, respectively.

[0101] Comparative Example 1

[0102] The method of Example 1 was followed, except that the polyacrylamide polymer was replaced with an equal mass of polystyrene. Analysis showed a methanol conversion rate of 42%, and the mass ratios of the three methylamines (monomethylamine, dimethylamine, and trimethylamine) produced in a single pass through the reactor were 18 / 20 / 62, respectively.

[0103] Comparative Example 2

[0104] The method of Example 3 was followed, except that titanium tetrachloride was replaced with calcium nitrate, the amount of calcium nitrate added being 0.49 g, and the metal complex dispersed polymer compound P123 (polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer) was replaced with polystyrene, the amount of which remained unchanged. Analysis showed a methanol conversion rate of 38%, and under conditions of a single pass through the reactor, the mass ratios of the three methylamines (monomethylamine / dimethylamine / trimethylamine) produced were 21 / 19 / 60, respectively.

[0105] Performance testing

[0106] The catalyst for the selective production of methylamine was characterized by BET.

[0107] The metal content, aluminum content, weak acid content and physicochemical parameters of the catalysts of the above examples and comparative examples are listed in Table 2.

[0108] Table 2

[0109]

[0110] Combining the examples with the data in Table 2, it can be seen that the catalyst for selectively producing methylamine prepared by the present invention can reduce the reaction toward dimethylamine and trimethylamine, improve the selectivity of monomethylamine, and achieve increased production of monomethylamine.

[0111] The preferred embodiments of the present invention have been 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 solution 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 catalyst for selectively producing methylamine, comprising a metal selected from the fourth period and aluminum, wherein the content of the metal selected from the fourth period is 0.1-2% and the content of aluminum is 98-99.9% on a molar basis; The weak acid content of the catalyst for selectively producing methylamine is 0.2-0.45 mmol / g, and the total pore volume of the catalyst for selectively producing methylamine is 0.5-1.1 cm 3 / g, micropore volume is 0.3-0.55cm 3 / g; The metal is selected from one or more of Fe, Co, Ni, Cu, Ti and Zr; The weak acid refers to the acid corresponding to the ammonia desorbed at a temperature below 200° C. after the catalyst for selectively producing methylamine adsorbs ammonia.

2. The catalyst according to claim 1, wherein The content of the metal selected from the fourth period is 0.2-1.5% by mole, and the content of aluminum is 98.5-99.8% by mole.

3. The catalyst according to claim 1 or 2, wherein The weak acid content of the catalyst for selectively producing methylamine is 0.2-0.4 mmol / g.

4. The catalyst according to claim 1 or 2, wherein The total pore volume of the catalyst for selectively producing methylamine is 0.5-0.8 cm 3 / g, micropore volume is 0.3-0.45cm 3 / g.

5. The catalyst according to claim 1 or 2, wherein The metal is selected from one of Cu, Ti and Zr.

6. A method for preparing the catalyst for selectively producing methylamine according to any one of claims 1 to 5, comprising the steps of: (1) providing a solution containing a pore-adjusting polymer compound and an aluminum-containing precursor, and then contacting the solution with a gas containing carbon dioxide to perform a gelling reaction to obtain a gelling product; (2) mixing the colloid product with a precursor of a metal selected from the fourth period and a metal complex dispersed polymer compound, and then drying and calcining; The pore-adjusting polymer compound is selected from one or more of polyacrylamide, polymethyl methacrylate, polyvinyl alcohol, polyethylene glycol, polyoxyethylene-polyoxypropylene ether block copolymer, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer and polyacrylic acid.

7. The preparation method according to claim 6, wherein The metal complexing dispersed polymer compound is selected from one or more of polyacrylamide, polymethyl methacrylate, polyvinyl alcohol, polyethylene glycol, polyoxyethylene-polyoxypropylene ether block copolymer, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer and polyacrylic acid.

8. The preparation method according to claim 6 or 7, wherein The pore-adjusting polymer compound is selected from one or more of polyacrylamide, polymethyl methacrylate, polyvinyl alcohol, and polyethylene glycol.

9. The preparation method according to claim 7, wherein The metal complex dispersed polymer compound is selected from at least one of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polyoxyethylene-polyoxypropylene ether block copolymer and polyacrylic acid.

10. The preparation method according to claim 6 or 7, wherein The amount of the pore-adjusting polymer compound used is 0.1-3% by weight of the aluminum-containing precursor, and the aluminum-containing precursor is calculated as aluminum hydroxide.

11. The preparation method according to claim 9, wherein The added mass of the metal complexing and dispersing polymer compound is 0.5-5 times the added mass of the pore-adjusting polymer compound.

12. The preparation method according to claim 6 or 7, wherein In the solution of step (1), the concentration of the aluminum precursor is 0.1-1 mol / L.

13. The preparation method according to claim 6 or 7, wherein The aluminum-containing precursor is selected from one or more of sodium metaaluminate, sodium aluminate, aluminum nitrate and aluminum sulfate.

14. The preparation method according to claim 13, wherein The aluminum-containing precursor is sodium metaaluminate.

15. The preparation method according to claim 6 or 7, wherein The volume fraction of carbon dioxide in the carbon dioxide-containing gas is 20-70%.

16. The preparation method according to claim 6 or 7, wherein The gelling reaction conditions include: temperature of 15-70° C., time of 30-90 minutes, and stopping the gelling reaction when the pH value reaches 8-12.

17. The preparation method according to claim 16, wherein The conditions for the gelling reaction include: a temperature of 30-50° C.; and a time of 60-90 minutes.

18. The preparation method according to claim 6 or 7, wherein The method further comprises: aging the gelled product and then performing step (2).

19. The preparation method according to claim 18, wherein The aging time is 1-6 hours, and the aging temperature is 60-90°C.

20. The preparation method according to claim 6 or 7, wherein: In step (2), the mixing is carried out under stirring conditions.

21. The preparation method according to claim 20, wherein The mixing time is 0.5-8 hours.

22. The preparation method according to claim 6 or 7, wherein: The calcination conditions in step (2) include: a temperature of 350-550° C. and a time of 1-4 hours.

23. Use of the catalyst for selectively producing methylamine according to any one of claims 1 to 5 or the catalyst for selectively producing methylamine obtained by the preparation method according to any one of claims 6 to 22 in a reaction for increasing the production of monomethylamine.

24. A method for increasing the production of monomethylamine, comprising: Under monomethylamine production conditions, methanol and ammonia are reacted with the catalyst for selectively producing methylamine according to any one of claims 1 to 5 or the catalyst for selectively producing methylamine prepared by the preparation method according to any one of claims 6 to 22.

25. The method according to claim 24, wherein The monomethylamine production conditions include: under a reducing atmosphere or an inert atmosphere, a reaction temperature of 350-450° C., a gauge pressure of 0.1-5.0 MPa, and a raw material liquid hourly space velocity of 1-35 hours. -1 .

26. The method according to claim 24 or 25, wherein The molar ratio of ammonia to methanol is 1.0-3.5.

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