A method for recycling a methylene dianiline by-product

Abstract

The application provides a recycling method of high-boiling-point products in the synthesis of m-xylylenediamine, comprising: subjecting the high-boiling-point products to a hydrogenation ammonolysis reaction in the presence of hydrogen and ammonia and under the action of a catalyst. The method of the application not only recycles the generated high-boiling-point secondary amine and tertiary amine compound into the target product m-xylylenediamine, maximizes the conversion of raw materials into the target product, reduces the loss of raw materials, and improves the yield of m-xylylenediamine in the existing process; at the same time, the generation amount of high-boiling-point mixtures is greatly reduced, the discharge amount of three wastes in the treatment of these products is also significantly reduced, the pollution is reduced, the environmental protection is enhanced, and thus the green production is guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of m-phenylenediamine production and relates to a method for recycling m-phenylenediamine byproducts. Background Technology

[0002] m-Phenylenediamine (MXDA) is an aliphatic diamine compound containing an aromatic ring. It can be used as a basic raw material for advanced polymer materials such as epoxy resin curing agents, special nylons, and nanofiltration membranes. It has a wide range of applications in aerospace, automotive lightweight materials, high-end equipment manufacturing, and water treatment, and has a broad market prospect.

[0003] Industrially, m-phenylenediamine is prepared by hydrogenation of isophthalonitrile, and the reaction process is as follows:

[0004]

[0005] The hydrogenation of isophthalonitrile is a process that converts two nitrile (-C≡N) functional groups in the raw material molecule into aminomethyl (-CH₂NH₂). However, during hydrogenation, the nitrile (-C≡N) functional groups first generate an imine intermediate (-CH=NH). This imine intermediate is highly reactive and readily undergoes self-condensation or polycondensation / crosslinking reactions with primary amines (-CH₂NH₂), inevitably leading to the formation of high-boiling-point products such as secondary and tertiary amines during the hydrogenation process (e.g., amines). Figure 1 (As shown). These high-boiling-point products are separated from the main product by a distillation process and then enriched in the distillation column.

[0006] Depending on the reaction process and hydrogenation catalyst, the content of high-boiling-point products generated by the hydrogenation of isophthalonitrile ranges from 10% to 25%. These high-boiling-point products reduce the yield of the target product MXDA and the utilization rate of the feedstock isophthalonitrile, increasing material losses in the process. Furthermore, these products have complex compositions, high viscosity, high boiling points, and deep colors, making further separation not only complex but also uneconomical. Due to the complex composition and difficulty in separating the generated high-boiling-point products, they are generally directly incinerated in industrial processes. This increases the material consumption of the entire reaction process, reducing its economic efficiency; moreover, the incineration process increases the carbon emissions of the entire process, as the nitrogen element in the high-boiling-point mixture is converted into nitrogen oxides (NOx) during incineration. x This has an adverse impact on the environment. For example, Chinese patent application CN200780004389.5 discloses a method for separating and purifying m-phenylenediamine, in which the high-boiling-point product separated is directly incinerated.

[0007] Chinese patent application CN03145486.0 discloses the production of phenylenediamine and / or cyanobenzylamine by liquid-phase catalytic hydrogenation of phthalonitrile compounds. Gas chromatography analysis of the hydrogenation products showed that the conversion rate of the raw material phthalonitrile was 99.6 mol%, the yield of m-phenylenediamine was 75.7 mol%, and the yield of 3-cyanobenzylamine was 0.3 mol%. The byproducts were mainly high-boiling-point substances, accounting for about 24 mol%. However, the document did not mention how to treat or utilize the high-boiling-point byproducts. Chinese patent application CN200710107071.1 discloses a method for preparing phenylenediamine by secondary hydrogenation. The final hydrogenation product, as determined by chromatographic analysis, contains 93.1 wt% m-phenylenediamine, 0.6 wt% 3-cyanobenzylamine, 0.02 wt% 3-methylbenzylamine, and no isophthalonitrile was detected. The remaining components, approximately 6 wt%, are oligomers of m-phenylenediamine or high-boiling-point polymers undetectable by gas chromatography. The document does not mention how to treat the resulting high-boiling-point polymers.

[0008] Therefore, there is a need in the art for a method to recover and utilize byproducts from the synthesis process of m-phenylenediamine. Summary of the Invention

[0009] To address the problems existing in the prior art, this invention provides a method for recovering and utilizing byproducts in the synthesis process of m-phenylenediamine. This method not only recovers and converts the generated high-boiling-point secondary and tertiary amine compounds into the target product MXDA, maximizing the conversion of raw materials into the target product, reducing raw material loss, and improving the MXDA yield in existing processes; it also significantly reduces the amount of high-boiling-point mixtures generated, thereby significantly reducing the amount of waste gas, wastewater, and solid waste emitted during the treatment of these products, reducing pollution and enhancing environmental protection, thus providing a guarantee for green production.

[0010] Specifically, the present invention provides a method for recovering and utilizing high-boiling-point products in the synthesis of m-phenylenediamine. The method includes: subjecting the high-boiling-point products to a hydrogenation ammonolysis reaction in the presence of hydrogen and ammonia and under the action of a catalyst to obtain a product containing m-phenylenediamine.

[0011] In one or more embodiments, the high-boiling product is a mixture of condensates generated by an imine condensation reaction during the hydrogenation of isophthalonitrile to prepare isophthalic dimethylamine.

[0012] In one or more embodiments, the boiling point of the high-boiling product is ≥280°C.

[0013] In one or more embodiments, the high-boiling-point product comprises one or more compounds selected from the following: and

[0014] In one or more embodiments, the hydrogenation ammonolysis reaction is carried out in a solvent, which is liquid ammonia or a mixture of liquid ammonia and an organic solvent; preferably, the organic solvent comprises one or more selected from organic hydrocarbon solvents, lower aliphatic amide compounds, and lower alcohol compounds; preferably, the organic hydrocarbon solvent is selected from one or two of toluene and xylene; preferably, the lower aliphatic amide compound is a C1-C6 aliphatic amide, such as one or two selected from dimethylformamide and dimethylacetamide; preferably, the lower alcohol compound is a C1-C4 alcohol, such as one or more selected from methanol, ethanol, and propanol.

[0015] In one or more embodiments, in the hydrogenation ammonolysis reaction system, the mass of the solvent is 10-90 wt% of the total mass of the solvent and the high-boiling product, preferably 20-90 wt%.

[0016] In one or more embodiments, the solvent contains 5-100 wt% liquid ammonia, preferably 10-100 wt%.

[0017] In one or more embodiments, the catalyst is a noble metal catalyst with catalytic hydrogenation function; the noble metal catalyst preferably contains Pt and / or Pd; the noble metal catalyst is preferably a supported noble metal catalyst; the support for the supported noble metal catalyst is preferably selected from one or more of Al2O3, C and SiO2; the content of noble metal in the noble metal catalyst is preferably 0.1-10 wt%, more preferably 0.5-5 wt%.

[0018] In one or more embodiments, the reactor for the hydrogenation ammonolysis reaction is a continuous reactor; preferably, in the hydrogenation ammonolysis reaction, the space velocity of the reactants is 0.1-5 h⁻¹. -1 Preferably 0.1-1h -1 Preferably, the hydrogen flow rate is 50-1000 mL / min, more preferably 80-500 mL / min; preferably, in the hydrogenation ammonolysis reaction, the total pressure of the reaction system is 5-15 MPa, more preferably 8-10 MPa.

[0019] In one or more embodiments, the continuous reactor is a fixed-bed reactor or a suspended-bed reactor; the fixed-bed reactor is preferably a tubular reactor.

[0020] In one or more embodiments, the reactor for the hydrogenation ammonolysis reaction is a batch reactor; preferably, the reaction time for the hydrogenation ammonolysis reaction is 1-5 hours; preferably, the hydrogen pressure in the hydrogenation ammonolysis reaction is 1-20 MPa, more preferably 2-15 MPa, and more preferably 3-10 MPa.

[0021] In one or more embodiments, the batch reactor is a batch reactor.

[0022] In one or more embodiments, the temperature of the hydrogenation ammonolysis reaction is 80-200°C, preferably 100-180°C, and more preferably 100-150°C.

[0023] In one or more embodiments, the recycling method further includes: separating m-phenylenediamine from the product of the hydrogenation ammonolysis reaction after a hydrogenation ammonolysis reaction.

[0024] In one or more embodiments, the recycling method further includes: separating the high-boiling-point product from the mixture containing m-phenylenediamine and the high-boiling-point product before carrying out the hydrogenation ammonolysis reaction; preferably, the mixture containing m-phenylenediamine and the high-boiling-point product is a reaction product of the hydrogenation of m-phenylenedionitrile to prepare m-phenylenediamine.

[0025] This invention also provides a method for preparing m-phenylenediamine, the method comprising:

[0026] (1) Hydrogenation reaction of isophthalonitrile to obtain a product containing isophthalic dimethylamine and a high-boiling product, and then separation of isophthalic dimethylamine and the high-boiling product.

[0027] (2) The high-boiling-point product is recycled using the recycling method described in any of the embodiments herein.

[0028] The present invention also provides a reaction system for recovering and utilizing high-boiling-point products in the synthesis of m-phenylenediamine. The reaction system includes a first separation device and a hydrogenation reactor. The first separation device is used to separate the high-boiling-point products from a mixture containing m-phenylenediamine and the high-boiling-point products. The hydrogenation reactor is used to perform a hydrogenation ammonolysis reaction on the high-boiling-point products.

[0029] In one or more embodiments, the first separation device is a distillation separation and purification device.

[0030] In one or more embodiments, the hydrogenation reactor is a continuous reactor or a batch reactor; preferably, the continuous reactor is a fixed-bed reactor or a suspended-bed reactor; preferably, the fixed-bed reactor is a tubular reactor; preferably, the batch reactor is a batch reactor.

[0031] In one or more embodiments, the reaction system further includes a high-boiling-point product storage tank for storing high-boiling-point products separated by the first separation device.

[0032] In one or more embodiments, the reaction system further includes a second separation device for separating m-phenylenediamine from the products of the hydrogenation ammonolysis reaction.

[0033] In one or more embodiments, the reaction system further includes a gas-liquid separation device disposed between the hydrogenation reactor and the second separation device for removing gas from the products of the hydrogenation ammonolysis reaction.

[0034] In one or more embodiments, the reaction system is used to implement the recycling method described in any embodiment of the text. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the imine condensation reaction during the hydrogenation of isophthalonitrile. Figure 1 In the diagram, (A), (B), and (C) represent three possible reaction routes.

[0036] Figure 2 This is a schematic flowchart of a method for recycling m-phenylenediamine byproducts in some embodiments of the present invention. Detailed Implementation

[0037] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0038] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0039] In this document, the terms “contains,” “includes,” “containing,” and similar terms encompass the meanings of “basically composed of” and “composed of.” For example, when this document discloses “A contains B and C,” “A is basically composed of B and C” and “A is composed of B and C” should be considered as having been disclosed in this document.

[0040] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0041] Unless otherwise specified, percentages refer to mass percentages and proportions refer to mass ratios in this article.

[0042] In this document, when describing embodiments or examples, it should be understood that it is not intended to limit the invention to those embodiments or examples. Rather, all alternatives, modifications, and equivalents of the methods and materials described herein are covered within the scope defined by the claims.

[0043] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0044] The present invention discloses a method for recovering and utilizing high-boiling-point byproducts in the synthesis process of m-phenylenediamine, which converts the high-boiling-point byproducts into MXDA products through a hydrogenation ammonolysis reaction.

[0045] In this invention, "high-boiling-point byproduct," "high-boiling-point product," and "high-boiling-point mixture of secondary and tertiary amines" have the same meaning, referring to a mixture of condensates generated by an imine condensation reaction during the hydrogenation of isophthalonitrile to prepare m-phenylenediamine, containing secondary and / or tertiary amines, with a boiling point ≥280°C. In this invention, the high-boiling-point product includes one or more compounds selected from the following: and

[0046] In some implementation schemes, such as Figure 1 As shown, the method for recovering and utilizing the high-boiling-point byproduct of m-phenylenediamine according to the present invention includes: firstly, the crude MXDA product generated by hydrogenation of isophthalonitrile is separated by a first separation device to obtain ammonia, inert substances, MXDA product, and high-boiling-point product; the high-boiling-point product enters a high-boiling-point product storage tank; using the high-boiling-point product as raw material, it is mixed with an ammonia-containing solvent and then introduced into a hydrogenation reactor containing a catalyst for hydrogenation ammonolysis reaction. The obtained product is separated into hydrogen and ammonia by a gas-liquid separation device and then introduced into a second separation device to obtain the solvent, MXDA product, and unreacted high-boiling-point product; wherein, the solvent can be reused, for example, the solvent can be mixed with the high-boiling-point product for hydrogenation ammonolysis reaction; the MXDA product generated by hydrogenation ammonolysis reaction can be incorporated into the crude MXDA product generated by hydrogenation of isophthalonitrile and enter the first separation device; the unreacted high-boiling-point product is collected and then centrally processed.

[0047] In this invention, the hydrogenation ammonolysis reaction is carried out in the liquid phase. The solvent is liquid ammonia or a mixture of liquid ammonia and an organic solvent, wherein the organic solvent may contain one or more selected from organic hydrocarbon solvents, lower aliphatic amide compounds, and lower alcohol compounds. Available organic hydrocarbon solvents include toluene, xylene, etc. The lower aliphatic amide compounds may be C1-C6 aliphatic amides, such as dimethylformamide and dimethylacetamide. The lower alcohol compounds may be C1-C4 alcohols, such as methanol, ethanol, and propanol. The organic solvent is preferably the solvent used in the hydrogenation reaction of isophthalonitrile, which helps to avoid the need for additional separation equipment and processes, thus improving the economic efficiency of the process. The mass of the solvent may be 10-90 wt% of the total mass of the solvent and the high-boiling-point product, preferably 20-90 wt%, for example, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, or 80 wt%. In the solvent, the mass fraction of liquid ammonia can be 5-100 wt%, preferably 10-100 wt%, for example 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, or 90 wt%.

[0048] The hydroammonolysis reaction is carried out in a hydrogen-containing atmosphere. This atmosphere may contain other impurity gases that do not participate in the hydrogenation process, such as nitrogen. However, if the content of these impurity gases is too high, the total reaction pressure must be significantly increased to achieve the necessary hydrogen partial pressure, which is industrially disadvantageous. The purity of the hydrogen used in the hydroammonolysis reaction is preferably ≥90 mol%, for example ≥95 mol%, ≥99 mol%, or 100 mol%.

[0049] The catalyst for the hydroammonolysis reaction can be a known noble metal catalyst with catalytic hydrogenation function, such as a supported noble metal catalyst. The noble metal catalyst is preferably a catalyst containing Pt and / or Pd. The support for the supported noble metal catalyst is preferably Al₂O₃, C, or SiO₂. Available noble metal catalysts include Pd / Al₂O₃, Pd / C, Pd / SiO₂, Pt / Al₂O₃, Pt / C, Pt / SiO₂, etc. In the noble metal catalyst, the content of the noble metal (e.g., Pt or Pd) can be 0.1-10 wt%, preferably 0.5-5 wt%, for example 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 4 wt%. The diameter of the catalyst can be 10-50 mesh, for example 20-40 mesh.

[0050] The reactor for the hydroammonolysis reaction can be a continuous reactor such as a fixed-bed reactor or a suspended-bed reactor, or a batch reactor such as a stirred tank reactor. A fixed-bed reactor can be a tubular reactor.

[0051] When using a batch reactor, such as a stirred tank reactor, for the hydrogenation ammonolysis reaction, the hydrogenation reaction time is preferably 1-5 hours, for example 2 hours, 3 hours, or 4 hours. When using a batch reactor, such as a stirred tank reactor, for the hydrogenation ammonolysis reaction, the hydrogen pressure is preferably 1-20 MPa, more preferably 2-15 MPa, and particularly preferably 3-10 MPa, for example 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, or 9 MPa.

[0052] When using a continuous reactor, such as a fixed-bed reactor, for continuous hydrogenation ammonolysis, the space velocity of the reactants can be 0.1-5 h⁻¹. -1 Preferably 0.1-1h -1 For example, 0.2h -1 0.5h -1 0.75h -1 0.8h -1 In this paper, the reactants consist of high-boiling-point products and solvents. The hydrogen flow rate in the continuous reactor, such as a fixed-bed reactor, can be 50-1000 mL / min, preferably 80-500 mL / min, for example 100 mL / min, 150 mL / min, 200 mL / min, 250 mL / min, 300 mL / min, 350 mL / min, or 400 mL / min. The reaction pressure (i.e., the total pressure of the reaction system) in the continuous reactor, such as a fixed-bed reactor, can be 5-15 MPa, preferably 8-10 MPa.

[0053] In this invention, the preferred temperature for the hydroammonolysis reaction is 80–200°C, more preferably 100–180°C, and particularly preferably 100–150°C, such as 110°C, 120°C, 130°C, or 140°C. The reaction pressure for the hydroammonolysis reaction can be 1–25 MPa, such as 5 MPa, 8 MPa, 9 MPa, 10 MPa, 13 MPa, 15 MPa, or 20 MPa.

[0054] In this invention, the high-boiling-point product can be separated from the mixture containing m-phenylenediamine and the high-boiling-point product before the hydrogenation ammonolysis reaction. Preferably, the mixture containing m-phenylenediamine and the high-boiling-point product is the reaction product of the hydrogenation of isophthalonitrile to prepare m-phenylenediamine, such as crude MXDA. In some embodiments, the content of m-phenylenediamine in the mixture containing m-phenylenediamine and the high-boiling-point product is 75-95 wt%, for example 80 wt%, 85 wt%, or 90 wt%, and the content of the high-boiling-point product is 5-25 wt%, for example 10 wt%, 15 wt%, or 20 wt%. The reaction product of the hydrogenation of isophthalonitrile to prepare m-phenylenediamine may also contain 3-cyanobenzylamine and / or 3-methylbenzylamine. In the mixture containing m-phenylenediamine and the high-boiling-point product, the content of 3-cyanobenzylamine can be 0-1 wt%, and the content of 3-methylbenzylamine can be 0-0.1 wt%. In some embodiments, the mixture containing m-phenylenediamine and the high-boiling product consists of MXDA, 3-cyanobenzylamine, 3-methylbenzylamine, and the high-boiling product. A first separation device can be used to separate the high-boiling product from the mixture containing m-phenylenediamine and the high-boiling product. The first separation device can be a distillation and purification unit.

[0055] In this invention, m-phenylenediamine can be separated from the product of the hydrogenation ammonolysis reaction after the reaction. A second separation device can be used to separate m-phenylenediamine from the product of the hydrogenation ammonolysis reaction. This second separation device can be a distillation and purification device.

[0056] In this invention, the product of the hydrogenation ammonolysis reaction can be first subjected to gas-liquid separation, and then m-phenylenediamine can be separated from the product after gas-liquid separation.

[0057] The method for preparing m-phenylenediamine according to the present invention includes: (1) subjecting isophthalonitrile to a hydrogenation reaction to obtain a product containing m-phenylenediamine and a high-boiling-point product, and then separating the m-phenylenediamine and the high-boiling-point product; (2) recycling the high-boiling-point product using the method for recycling the high-boiling-point product in the synthesis of m-phenylenediamine according to the present invention. m-phenylenediamine can be prepared by hydrogenation reaction of isophthalonitrile using known processes in the art.

[0058] This invention also provides a reaction system for recovering high-boiling-point products in the synthesis of m-phenylenediamine, which can be used to implement the method of this invention. The reaction system includes a first separation unit and a hydrogenation reactor. The first separation unit separates the high-boiling-point product from a mixture containing m-phenylenediamine and the high-boiling-point product. The hydrogenation reactor performs a hydrogenation ammonolysis reaction on the high-boiling-point product. The reaction system of this invention may further include a high-boiling-point product storage tank for storing the high-boiling-point product separated by the first separation unit. The reaction system of this invention may further include a second separation unit for separating m-phenylenediamine from the products of the hydrogenation ammonolysis reaction. The reaction system of this invention may further include a gas-liquid separation unit, which can be disposed between the hydrogenation reactor and the second separation unit for removing gas from the products of the hydrogenation ammonolysis reaction. The available first separation unit, hydrogenation reactor, and second separation unit can be as described in any of the preceding embodiments.

[0059] The present invention achieves the following beneficial effects: The present invention provides a method for recovering and utilizing high-boiling-point byproducts in the synthesis process of m-phenylenediamine. Through hydrogenation ammonolysis reaction, the high-boiling-point products generated during the hydrogenation reaction of isophthalonitrile are recovered and converted into the target product MXDA, maximizing the conversion of raw materials into the target product, reducing raw material loss, and improving the yield of MXDA in existing processes. At the same time, the amount of waste after residue recovery and treatment is significantly reduced, reducing costs and increasing economic benefits while reducing pollution and enhancing environmental protection, thereby providing a guarantee for green production.

[0060] The features of this invention are: (1) by catalytic hydrogenation ammonolysis, high-boiling-point products are converted into the target product MXDA, thereby improving the utilization rate of the reaction raw materials in the process; (2) the yield of high-boiling-point products in the entire process is reduced, while avoiding the CO2 and NO generated by the combustion of high-boiling-point products. x Emissions are reduced, significantly minimizing adverse environmental impacts.

[0061] The present invention will be described below by way of specific embodiments. It should be understood that these embodiments are merely illustrative and are not intended to limit the scope of the invention. The methods, reagents, and materials used in the embodiments are conventional methods, reagents, and materials in the art, unless otherwise stated. The raw material compounds in the embodiments are all commercially available.

[0062] In this invention, the contents of MXDA, 3-cyanobenzylamine, 3-methylbenzylamine, and m-xylene in the product were obtained by analysis using an Agilent 8890 gas chromatograph. The chromatographic column was DB624, and the temperature was set as follows: injection port 230°C, detector 295°C, and the column oven temperature was programmed to rise from 100°C to 260°C (after holding at 100°C for 10 minutes, the temperature was increased at a rate of 5°C / min).

[0063] The high-boiling-point products in the examples and comparative examples include and

[0064] The hydrogen used in the examples and comparative examples had a purity of 99.999 mol%.

[0065] Example 1

[0066] Isophthalonitrile is hydrogenated to produce crude MXDA, which contains 88.6 wt% MXDA, 0.6 wt% 3-cyanobenzylamine, 0.02 wt% 3-methylbenzylamine, and 10.78 wt% undetectable high-boiling byproducts by chromatography. Based on isophthalonitrile, the yield of MXDA in the hydrogenation reaction of isophthalonitrile to MXDA is 88.6 wt%, the yield of 3-cyanobenzylamine is 0.6 wt%, the yield of 3-methylbenzylamine is 0.02 wt%, and the yield of secondary and tertiary amine high-boiling products is 10.78 wt%.

[0067] The crude MXDA product is fed into a distillation and purification unit, where it is separated to distill out ammonia and inert substances, MXDA product, and a mixture of secondary and tertiary amines with high boiling points.

[0068] A high-boiling-point mixture of distilled secondary and tertiary amines (referred to as high-boiling-point products) was used as raw material, mixed with liquid ammonia and methanol to form a solution, wherein the high-boiling-point products accounted for 10 wt%, liquid ammonia for 30 wt%, and methanol for 60 wt%. This solution was then passed into a Φ14 mm x 1000 mm stainless steel tubular hydrogenation reactor. The reactor was packed with a 20-40 mesh Pt / Al₂O₃ catalyst (manufactured by Shanghai Sinochem Technology Co., Ltd.), with a Pt loading of 3 wt% and the remainder as a support. The reaction was carried out at a temperature of 120℃, a pressure of 10 MPa, and a liquid hourly space velocity (LHSV) of 0.2 h⁻¹. -1 The hydrogenation-ammonolysis reaction was carried out under the condition that the hydrogen flow rate was 100 mL / min.

[0069] After the reaction, the products were separated to remove methanol and ammonia, and the product composition was analyzed by gas chromatography. The product contained 72.8 wt% MXDA, 16.7 wt% 3-methylbenzylamine, 8.5 wt% m-xylene, and 2 wt% undetectable high-boiling-point products. In the entire process, based on isophthalonitrile, the yield of MXDA was 96.44 wt%, the yield of 3-cyanobenzylamine was 0.6 wt%, the yield of 3-methylbenzylamine was 1.82 wt%, and the yield of high-boiling-point products was 0.22 wt%. In this paper, the yield of a particular product refers to its mass fraction among all products. The total MXDA yield of the entire hydrogenation process = MXDA yield of hydrogenation reaction + MXDA yield of hydrogenation ammonolysis reaction = MXDA yield of hydrogenation reaction + high-boiling-point product yield of hydrogenation reaction × MXDA content in the hydrogenation ammonolysis reaction product.

[0070] Example 2

[0071] Using the high-boiling-point mixture of secondary and tertiary amines distilled from the crude MXDA product in Example 1 as raw material, a reaction solution was prepared by mixing with liquid ammonia and methanol, containing 10 wt% high-boiling-point product, 10 wt% liquid ammonia, and 80 wt% methanol. This solution was then passed into a Φ14 mm x 1000 mm stainless steel tubular hydrogenation reactor. The reactor was packed with a 20-40 mesh Pt / Al₂O₃ catalyst (manufactured by Shanghai Sinochem Technology Co., Ltd.), with a Pt loading of 3 wt% and the remainder as a support. The reaction was carried out at a temperature of 150 °C, a pressure of 10 MPa, and a liquid hourly space velocity (LHSV) of 0.2 h⁻¹. -1 The hydrogenation ammonolysis reaction was carried out under the condition that the hydrogen flow rate was 100 mL / min.

[0072] After the reaction, the product was separated to remove methanol and ammonia, and its composition was analyzed by gas chromatography. The product contained 70.8 wt% MXDA, 13.2 wt% 3-methylbenzylamine, 14.5 wt% m-xylene, and 1.5 wt% undetectable high-boiling-point products. In the entire process, based on the raw material isophthalonitrile, the yields of MXDA were 96.23 wt%, 3-cyanobenzylamine 0.6 wt%, 3-methylbenzylamine 1.44 wt%, and high-boiling-point products 0.16 wt%.

[0073] Example 3

[0074] Using the high-boiling-point mixture of secondary and tertiary amines distilled from the crude MXDA product in Example 1 as raw material, a reaction solution was prepared by mixing with liquid ammonia and methanol, containing 10 wt% high-boiling-point product, 50 wt% liquid ammonia, and 40 wt% methanol. This solution was then passed into a Φ14 mm x 1000 mm stainless steel tubular hydrogenation reactor. The reactor was packed with a 20-40 mesh Pt / SiO2 catalyst (manufactured by Shanghai Sinochem Technology Co., Ltd.), with a Pt loading of 2 wt% and the remainder as a support. The reaction was carried out at a temperature of 100°C, a pressure of 8 MPa, and a liquid hourly space velocity (LHSV) of 0.5 h⁻¹. -1 The hydrogenation ammonolysis reaction was carried out under a hydrogen flow rate of 100 mL / min.

[0075] After the reaction, the product was separated to remove methanol and ammonia, and its composition was analyzed by gas chromatography. The product contained 78.8 wt% MXDA, 8.2 wt% 3-methylbenzylamine, 2.5 wt% m-xylene, and 10.5 wt% high-boiling-point products that were undetectable by chromatography. In the entire process, based on the raw material isophthalonitrile, the yields of MXDA were 97.09 wt%, 3-cyanobenzylamine 0.6 wt%, 3-methylbenzylamine 0.289 wt%, and high-boiling-point products 1.13 wt%.

[0076] Example 4

[0077] Using the high-boiling-point mixture of secondary and tertiary amines distilled from the crude MXDA product in Example 1 as raw material, a reaction solution was prepared by mixing with liquid ammonia and ethanol, containing 10 wt% high-boiling-point product, 10 wt% liquid ammonia, and 80 wt% ethanol. This solution was then passed into a Φ14 mm x 1000 mm stainless steel tubular hydrogenation reactor. The reactor was packed with a 20-40 mesh Pd / Al₂O₃ catalyst (manufactured by Shanghai Sinochem Technology Co., Ltd.), with a Pd loading of 1.5 wt% and the remainder as a support. The reaction was carried out at a temperature of 130 °C, a pressure of 9 MPa, and a liquid hourly space velocity (LHSV) of 0.75 h⁻¹. -1 The hydrogenation ammonolysis reaction was carried out under the condition that the hydrogen flow rate was 250 mL / min.

[0078] After the reaction, the product was separated to remove ammonia and ethanol solvent, and its composition was analyzed by gas chromatography. The product contained 62.8 wt% MXDA, 18.2 wt% 3-methylbenzylamine, 16.5 wt% m-xylene, and 2.5 wt% undetectable high-boiling-point products. In the entire process, based on the raw material isophthalonitrile, the yields of MXDA were 95.36 wt%, 3-cyanobenzylamine 0.6 wt%, 3-methylbenzylamine 1.98 wt%, and high-boiling-point products 0.27 wt%.

[0079] Example 5

[0080] Using the high-boiling-point mixture of secondary and tertiary amines distilled from the crude MXDA product in Example 1 as raw material, a reaction solution was prepared by mixing with liquid ammonia and ethanol, containing 10 wt% high-boiling-point product, 5 wt% liquid ammonia, and 85 wt% ethanol. This solution was then passed into a Φ14 mm x 1000 mm stainless steel tubular hydrogenation reactor. The reactor was packed with a 20-40 mesh Pd / Al₂O₃ catalyst (manufactured by Shanghai Sinochem Technology Co., Ltd.), with a Pd loading of 3 wt% and the remainder as a support. The reaction was carried out at a temperature of 130 °C, a pressure of 9 MPa, and a liquid hourly space velocity (LHSV) of 0.75 h⁻¹. -1 The hydrogenation ammonolysis reaction was carried out under a hydrogen flow rate of 350 mL / min.

[0081] After the reaction, the product was separated to remove ethanol solvent and ammonia, and its composition was analyzed by gas chromatography. The product contained 52.8 wt% MXDA, 28.2 wt% 3-methylbenzylamine, 13.5 wt% m-xylene, and 5.5 wt% undetectable high-boiling-point products. In the entire process, based on the raw material isophthalonitrile, the yields of MXDA were 94.29 wt%, 3-cyanobenzylamine 0.6 wt%, 3-methylbenzylamine 3.06 wt%, and high-boiling-point products 0.59 wt%.

[0082] Example 6

[0083] In a 100 mL stainless steel stirred tank hydrogenation reactor, 2 g of Pt / C catalyst (manufactured by Shanghai Sinochem Technology Co., Ltd., with a Pt loading of 1 wt% and the remainder as a support) with a diameter of 20-40 mesh was added. A mixture of high-boiling-point secondary and tertiary amines distilled from the crude MXDA product in Example 1 and liquid ammonia were added as reactants. The high-boiling-point product content in the reactants was 10 wt%, and the liquid ammonia content was 90 wt%. The total mass of the reactants was 10 g. Hydrogen gas was then introduced into the reactor at 4 MPa, and the temperature was raised to 130 °C for hydrogenation ammonolysis at a pressure of 15 MPa for 5 h.

[0084] After the reaction, the product was separated, ammonia was removed, and the product composition was analyzed by gas chromatography. The product contained 82.6 wt% MXDA, 13.7 wt% 3-methylbenzylamine, 2.5 wt% m-xylene, and 1.2 wt% high-boiling-point product that was undetectable by chromatography. In the entire process, based on isophthalonitrile, the yield of MXDA was 97.50 wt%, the yield of 3-cyanobenzylamine was 0.6 wt%, the yield of 3-methylbenzylamine was 1.49 wt%, and the yield of high-boiling-point product was 0.13 wt%.

[0085] Example 7

[0086] In a 100 mL stainless steel stirred tank hydrogenation reactor, 2 g of Pt / Al₂O₃ catalyst (manufactured by Shanghai Sinochem Technology Co., Ltd., with a Pt loading of 0.5 wt% and the remainder as a support) with a diameter of 20-40 mesh was added. A mixture of high-boiling-point secondary and tertiary amines distilled from the crude MXDA product in Example 1 and liquid ammonia were added as reactants. The high-boiling-point product content in the reactants was 10 wt%, and the liquid ammonia content was 90 wt%. The total mass of the reactants was 10 g. Hydrogen gas at 3 MPa was then introduced into the reactor, and the temperature was raised to 110 °C for hydrogenation ammonolysis at a pressure of 13 MPa for 2 hours.

[0087] After the reaction, the product was separated, ammonia was removed, and the product composition was analyzed by gas chromatography. The product contained 58.8 wt% MXDA, 28.4 wt% 3-methylbenzylamine, 2.5 wt% m-xylene, and 10.3 wt% undetectable high-boiling-point products. In the entire process, based on isophthalonitrile, the yield of MXDA was 94.93 wt%, the yield of 3-cyanobenzylamine was 0.6 wt%, the yield of 3-methylbenzylamine was 3.08 wt%, and the yield of high-boiling-point products was 1.11 wt%.

[0088] Experimental data from Examples 1-7 show that the method of the present invention can effectively convert high-boiling-point products into MXDA and low-boiling-point compounds by hydrogenation, reduce the formation of high-boiling-point products by about 90%, and improve the overall MXDA yield of the process.

[0089] Comparative Example 1

[0090] Using the high-boiling-point mixture of secondary and tertiary amines distilled from the crude MXDA in Example 1 as raw material, a reaction solution was prepared by mixing with ethanol, containing 10 wt% high-boiling-point product and 90 wt% ethanol. This solution was then passed into a Φ14 mm x 1000 mm stainless steel tubular hydrogenation reactor. The reactor was packed with a 20-40 mesh Pd / Al₂O₃ catalyst (manufactured by Shanghai Sinochem Technology Co., Ltd.), with a Pd loading of 3 wt% and the remainder as a support. The reaction was carried out at a temperature of 130 °C, a pressure of 7 MPa, and a liquid hourly space velocity (LHSV) of 0.15 h⁻¹. -1 The hydrogenation reaction was carried out at a hydrogen flow rate of 250 mL / min.

[0091] After the reaction, the products were separated, and the ethanol solvent was removed. The product composition was analyzed by gas chromatography. The product contained 22.8 wt% MXDA, 58.2 wt% 3-methylbenzylamine, 16.5 wt% m-xylene, and approximately 2.5 wt% of high-boiling-point products that were undetectable by chromatography. In the entire process, based on isophthalonitrile, the yields of MXDA were 91.05 wt%, 3-cyanobenzylamine 0.6 wt%, 3-methylbenzylamine 6.29 wt%, and high-boiling-point products 0.27 wt%.

[0092] This shows that when the reaction system does not contain NH3, the high-boiling-point product undergoes excessive ammonolysis, resulting in a decrease in the yield of the target product MXDA.

[0093] Comparative Example 2

[0094] In a 100 mL stainless steel stirred tank hydrogenation reactor, 2 g of Pt / Al₂O₃ catalyst (manufactured by Shanghai Sinochem Technology Co., Ltd., with a Pt loading of 0.5 wt% and the remainder as a support) with a diameter of 20-40 mesh was added. The high-boiling-point mixture of secondary and tertiary amines distilled from the crude MXDA product in Example 1 and liquid ammonia were added as reactants. The high-boiling-point product content in the reactants was 10 wt%, and the liquid ammonia content was 90 wt%. The total mass of the reactants was 10 g. Hydrogen gas at 5 MPa was then introduced into the reactor, and the temperature was raised to 90 °C for hydrogenation ammonolysis at a pressure of 11 MPa for 3 hours.

[0095] After the reaction, the product was separated, ammonia was removed, and the product composition was analyzed by gas chromatography. The product contained 18.8 wt% MXDA, 20.4 wt% 3-methylbenzylamine, 5.7 wt% m-xylene, and 55.1 wt% undetectable high-boiling-point product. In the entire process, based on isophthalonitrile, the yield of MXDA was 90.62 wt%, the yield of 3-cyanobenzylamine was 0.6 wt%, the yield of 3-methylbenzylamine was 2.21 wt%, and the yield of high-boiling-point product was 5.93 wt%.

[0096] Therefore, it is evident that a reaction temperature that is too low is not conducive to the hydrogenation and ammonolysis of high-boiling-point products into the target product MXDA.

[0097] The yields of MXDA and high-boiling products prepared by hydrogenation of isophthalonitrile before and after hydrogenation ammonolysis in Examples 1-7 and Comparative Examples 1-2 are summarized in Table 1.

[0098] Table 1: Comparison of MXDA yield and high-boiling-point product yield before and after hydroammonolysis

[0099]

[0100]

Claims

1. A method for recycling high-boiling products in the synthesis of m-xylylenediamine, characterized in that, The recycling method comprises: subjecting the high-boiling-point product to a hydroamination reaction in the presence of hydrogen and ammonia and under the action of a catalyst to obtain a product comprising m-xylylenediamine; The high-boiling-point product is a mixture of condensates generated by imine condensation reaction in the preparation of m-xylylenediamine from m-xylylene cyanide by hydrogenation; The boiling point of the high-boiling-point product is ≥ 280℃; and the high boiling point product comprises one or more of the following compounds: , and ; The temperature of the hydroamination reaction is 100-180℃.

2. The recycling method of claim 1, wherein, The hydroamination reaction is carried out in a solvent, and the solvent is liquid ammonia or a mixture of liquid ammonia and an organic solvent; the organic solvent is selected from one or more of organic hydrocarbon solvents, lower aliphatic amide compounds and lower alcohol compounds; the organic hydrocarbon solvent is selected from one or both of toluene and xylene; the lower aliphatic amide compound is a C1-C6 aliphatic amide; and the lower alcohol compound is a C1-C4 alcohol.

3. The recycling method of claim 2, wherein, The lower aliphatic amide compound is selected from one or both of dimethylformamide and dimethylacetamide, and the lower alcohol compound is selected from one or more of methanol, ethanol and propanol.

4. The recycling method of claim 2, wherein, In the hydroamination reaction system, the mass of the solvent is 10-90wt% of the total mass of the solvent and the high-boiling-point product; and in the solvent, the mass fraction of liquid ammonia is 5-100wt%.

5. The recycling method of claim 2, wherein, In the hydroamination reaction system, the mass of the solvent is 20-90wt% of the total mass of the solvent and the high-boiling-point product; and in the solvent, the mass fraction of liquid ammonia is 10-100wt%.

6. The recycling method of claim 1, wherein, The catalyst is a noble metal catalyst having a catalytic hydrogenation function; the noble metal catalyst contains Pt and / or Pd; and the noble metal catalyst is a supported noble metal catalyst; the support of the supported noble metal catalyst is selected from one or more of Al2O3, C and SiO2; and in the noble metal catalyst, the content of noble metal is 0.1-10wt%.

7. The recycling method of claim 6, wherein, In the noble metal catalyst, the content of noble metal is 0.5-5wt%.

8. The recycling method of claim 1, wherein, The reactor of the hydrogenative aminolysis reaction is a continuous reactor; in the hydrogenative aminolysis reaction, the space velocity of the reaction raw material is 0.1-5h -1 , the hydrogen flow rate is 50-1000mL / min, and the total pressure of the reaction system is 5-15MPa; the continuous reactor is a fixed bed reactor or a suspended bed reactor; and the fixed bed reactor is a tubular reactor.

9. The recycling method of claim 8, wherein, The space velocity of the reaction raw material in the hydrogenation aminolysis reaction is 0.1-1h -1 , the hydrogen flow rate is 80-500 mL / min, and the total pressure of the reaction system is 8-10 MPa.

10. The recycling method of claim 1, wherein, The reactor for the hydroamination reaction is a batch reactor; the reaction time of the hydroamination reaction is 1-5h; in the hydroamination reaction, the hydrogen pressure is 1-20MPa; and the batch reactor is a kettle reactor.

11. The recycling method of claim 10, wherein, In the hydroamination reaction, the hydrogen pressure is 2-15MPa.

12. The recycling method of claim 10, wherein, In the hydroamination reaction, the hydrogen pressure is 3-10MPa.

13. The recycling method of claim 1, wherein, The temperature of the hydroamination reaction is 100-150℃.

14. The recycling method according to claim 1, wherein The recycling method further comprises: after the hydroamination reaction, separating m-xylylenediamine from the product of the hydroamination reaction; and / or The recycling method further comprises: before the hydroamination reaction, separating the high-boiling-point product from a mixture containing m-xylylenediamine and the high-boiling-point product; the mixture containing m-xylylenediamine and the high-boiling-point product is the reaction product of the preparation of m-xylylenediamine from m-xylylene cyanide by hydrogenation.

15. A method for preparing m-xylylenediamine, characterized by, The preparation method comprises: (1) subjecting m-xylylene cyanide to a hydrogenation reaction to obtain a product comprising m-xylylenediamine and a high-boiling-point product, and then separating m-xylylenediamine and the high-boiling-point product; (2) recycling the high-boiling product using the recycling method of any one of claims 1-14.

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