Nitrogen-doped carbon-coated catalyst, preparation method thereof and method for preparing m-xylylenediamine from m-xylylene cyanide

Abstract

The application provides a nitrogen-doped carbon-coated catalyst, a preparation method thereof and a method for preparing m-xylylenediamine from m-xylylene cyanide, the nitrogen-doped carbon-coated catalyst is a core-shell structure with a metal active component as an inner core and a nitrogen-doped carbon material as a coating layer, and the loading amount of the metal active component is 9-50 wt% based on 100 wt% of the mass fraction of the nitrogen-doped carbon-coated catalyst. The nitrogen-doped carbon-coated catalyst provided by the application does not need to be activated and can directly be used to show excellent catalytic activity, selectivity and stability for the hydrogenation reaction of m-xylylene cyanide, the selectivity and yield of m-xylylenediamine can be significantly improved under relatively mild reaction conditions, and the catalyst is easy to separate from the product and convenient for recycling.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of catalytic chemistry and nanoscience and technology, and particularly relates to a nitrogen-doped carbon-coated catalyst, a preparation method thereof and a method for preparing m-xylylenediamine from m-xylylene dicyanide. BACKGROUND

[0002] M-xylylenediamine is a widely used chemical raw material, commonly used as a low-toxicity curing agent for epoxy resins at room temperature, a rubber stabilizer, also used as a solvent, a pharmaceutical, a photosensitive plastic, a rubber additive, a polyurethane resin and coating production raw material and an organic synthesis intermediate.

[0003] The production route of m-xylylenediamine (m-XDA) by catalytic hydrogenation of m-xylylene dicyanide (IPN) using a batch autoclave or a continuous fixed-bed hydrogenation process has been widely used due to its mild reaction conditions, simple production process and low-cost raw materials. The catalysts used are mainly supported catalysts with Group VIII metals as active components, such as Raney Ni, Raney Co, etc. Raney Ni or modified Raney Ni catalysts are mainly used in industry, but they have low mechanical strength and poor stability, resulting in high catalyst consumption and increased industrial production costs. Supported composite catalysts have good mechanical strength, and the selectivity of m-XDA can be improved by optimizing the catalyst composition.

[0004] US6881864 discloses a process for preparing m-xylylenediamine by two-stage hydrogenation of m-xylylene dicyanide using a supported catalyst containing nickel or cobalt. The reaction temperature of the first-stage hydrogenation is 60-90℃, and the reaction temperature of the second-stage hydrogenation is 110-130℃. The conversion rate of m-xylylene dicyanide in the first-stage hydrogenation is greater than 90%, and the conversion rate of m-xylylene dicyanide in the second-stage hydrogenation is close to 99%, with a total yield of benzene dicyanide of 86.6%-92.4%. Although this process can reduce the influence of intermediate products on catalytic activity and increase the conversion rate, it has a long process flow, high production cost, and affects the economy of the process, and the total yield of benzene dicyanide is not high.

[0005] CN104148080A discloses a catalyst and a method for preparing m-xylylenediamine by hydrogenating m-xylylene dinitrile, the catalyst comprises the following components in parts by weight: 5.0-40.0 parts of metal nickel or its oxide; 0.01-25.0 parts of at least one element selected from A in the periodic table of elements or its oxide; 0.01-10.0 parts of at least one element selected from Mo, Zr and Ti or its oxide; 0.01-10.0 parts of at least one element selected from Sn, Fe and Cu or its oxide; 0.01-6.0 parts of at least one element selected from rare earth elements or its oxide; 9-95 parts of carrier silicon dioxide. The catalyst is not easy to coking and deactivation, and is suitable for fixed bed continuous hydrogenation production of m-xylylenediamine, but the yield of benzene dinitrile is not high.

[0006] CN110152642A discloses a catalyst and application for preparing m-xylylenediamine, the catalyst comprises a carrier, the carrier is alumina or a magnesium-aluminum mixture, the active element is Ni with a mass content of 18% to 40%, the auxiliary agent 1 is one of Co and Mn with a mass content of 0.2% to 5%, the auxiliary agent 2 is one of Na and K with a mass content of 0.02% to 0.5%; the catalyst first needs to prepare the carrier, then the carrier is sequentially soaked in the active component solution, the auxiliary agent 1 solution and the auxiliary agent 2 solution, and finally the catalyst product is obtained after activation. The preparation process of the catalyst is relatively complicated, and the catalyst needs to be activated before use.

[0007] Therefore, it is urgent to develop a new type of supported composite catalyst, which can further improve the catalytic activity, selectivity and stability of the catalyst on the basis of simplifying the preparation process, and is crucial for further improving the selectivity and yield of benzene dinitrile. SUMMARY

[0008] In view of the deficiencies in the prior art, the purpose of the present application is to provide a nitrogen-doped carbon-coated catalyst, a preparation method thereof and a method for preparing m-xylylenediamine from m-xylylene dinitrile. The nitrogen-doped carbon-coated catalyst provided by the present application can exhibit excellent catalytic activity, selectivity and stability in the hydrogenation reaction of m-xylylene dinitrile without activation, and can significantly improve the selectivity and yield of m-xylylenediamine under relatively mild reaction conditions.

[0009] To achieve this purpose, the technical scheme adopted by the present application is as follows:

[0010] In a first aspect, the present application provides a nitrogen-doped carbon-coated catalyst, which is a core-shell structure with a metal active component as the core and a nitrogen-doped carbon material as the coating layer. The loading of the metal active component is 9-50 wt%, for example, 9 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt% or 50 wt%, but is not limited to the listed values, and other values not listed in this range are also applicable.

[0011] The nitrogen-doped carbon-coated catalyst in the present application is a core-shell structure, in which the metal active component is the core and the nitrogen-doped carbon material is the coating layer. This structure can effectively improve the stability of the catalyst, and the synergistic effect between the metal active components can further improve the catalytic activity and selectivity of the catalyst.

[0012] The nitrogen-doped carbon-coated catalyst provided by the present application does not need to be activated and can directly be used to exhibit excellent catalytic activity, selectivity and stability for the hydrogenation reaction of isophthalonitrile. The selectivity and yield of m-xylylenediamine can be significantly improved under relatively mild reaction conditions, saving production costs. In addition, the nitrogen-doped carbon-coated catalyst provided by the present application has strong magnetism, is easy to separate from the product, and is convenient for recycling.

[0013] As a preferred technical solution of the present application, the metal active component comprises a first metal active component.

[0014] Preferably, the first metal active component comprises cobalt and / or nickel.

[0015] Preferably, the first metal active component comprises cobalt and nickel.

[0016] Preferably, the molar ratio of cobalt to nickel in the first metal active component is (0.2-5):1, for example, 0.2:1, 0.5:1, 1:1, 2:1, 3:1, 4:1 or 5:1, but is not limited to the listed values, and other values not listed in this range are also applicable.

[0017] As a preferred technical solution of the present application, the metal active component further comprises a second metal active component.

[0018] Preferably, the second metal active component comprises any one or a combination of at least two of copper, cesium, iron, potassium, lithium, molybdenum, manganese, magnesium or zinc.

[0019] Preferably, the molar ratio of the first metal active component to the second metal active component is (0.2-5):1, for example, it can be 0.2:1, 0.5:1, 1:1, 2:1, 3:1, 4:1 or 5:1, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0020] The first metal active component is denoted as M1, the second metal active component is denoted as M2, and the nitrogen-doped carbon material is denoted as CN in the present application; when the metal active component only includes the first metal active component, the nitrogen-doped carbon-coated catalyst can be represented as xM1@CN z (M1 is coated with CN on the surface, x represents the loading amount of the metal active component, and z represents the mass ratio of the carbon source and the nitrogen source), wherein M1 can be Co, Ni or Co y Ni (y represents the molar ratio of Co to Ni); when the metal active component includes both the first metal active component and the second metal active component, the nitrogen-doped carbon-coated catalyst can be represented as xM1M2@CN z (M1M2 is coated with CN on the surface, x represents the loading amount of the metal active component, and z represents the mass ratio of the carbon source and the nitrogen source), wherein M1 can be Co, Ni or Co y Ni (y represents the molar ratio of Co to Ni), and M2 can be any one of Cu, Ce, Fe, K, Li, Mo, Mn, Mg or Zn or a combination of at least two thereof, wherein M2 is preferably a combination of Mn and Ce, a combination of Cu and Mg or a combination of Fe and Zn.

[0021] In a second aspect, the present application provides a preparation method of the nitrogen-doped carbon-coated catalyst of the first aspect, which comprises:

[0022] After mixing the carbon source, the nitrogen source, the metal source and the solvent, a precursor solid material is obtained by evaporation treatment, and the nitrogen-doped carbon-coated catalyst is obtained by calcining the precursor solid material.

[0023] The present application successfully prepares the nitrogen-doped carbon-coated catalyst with good catalytic activity, selectivity and stability by using a simple one-step pyrolysis method, and the preparation process is simple, does not require an activation step, is low in cost, and has a high catalyst yield, which is suitable for large-scale industrial production.

[0024] In addition, preferably, the carbon source, the nitrogen source, the metal source and the solvent are stirred and mixed at room temperature to form a mixed solution of 25 mL.

[0025] As a preferred technical solution of the present application, the mass ratio of the carbon source to the nitrogen source is 1:(0.2-5), which can be 1:0.2, 1:0.5, 1:1, 1:2, 1:3, 1:4 or 1:5, but is not limited to the listed values, and other values not listed in the range are also applicable; the mass ratio of the carbon source to the nitrogen source is preferably 1:3.

[0026] The present application limits the mass ratio of the carbon source to the nitrogen source to 1:(0.2-5). When the amount of the nitrogen source is too large and the amount of the carbon source is too small, the coating effect of the nitrogen-doped carbon material on the metal active component core is poor, which can result in poor stability of the obtained catalyst material. When the amount of the nitrogen source is too small, the selectivity and yield of the catalyst material to m-xylylenediamine are reduced, because the pyridine nitrogen formed by the nitrogen source can provide basic sites for the catalyst material to improve the selectivity and yield of m-xylylenediamine and inhibit the generation of by-products. Preferably, the carbon source includes glucose.

[0027] Preferably, the nitrogen source includes urea.

[0028] Preferably, the metal source includes a metal nitrate.

[0029] Preferably, the solvent is any one of deionized water, ethanol or methanol; preferably deionized water.

[0030] Preferably, the mixing is carried out under stirring.

[0031] Preferably, the stirring time is 1-5h, which can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h, but is not limited to the listed values, and other values not listed in the range are also applicable; the stirring time is preferably 2h.

[0032] Preferably, the evaporation treatment temperature is 50-70℃, which can be 50℃, 52℃, 55℃, 58℃, 60℃, 62℃, 65℃, 68℃ or 70℃, and other values not listed in the range are also applicable.

[0033] Preferably, the evaporation treatment is carried out under vacuum.

[0034] As a preferred technical solution of the present application, the heating rate of the calcination is 1-5℃ / min, which can be 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min, 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min or 5℃ / min, and other values not listed in the range are also applicable; the heating rate is preferably 2℃ / min.

[0035] Preferably, the final calcination temperature is 700-1000℃, for example, it can be 700℃, 750℃, 800℃, 850℃, 900℃, 950℃ or 1000℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] Preferably, the holding time at the final temperature during calcination is 1 to 5 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours or 5 hours, but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0037] Preferably, the calcination is carried out under a protective gas atmosphere.

[0038] Preferably, the flow rate of the protective gas is 60-100 mL / min, for example, it can be 60 mL / min, 65 mL / min, 70 mL / min, 75 mL / min, 80 mL / min, 85 mL / min, 90 mL / min, 95 mL / min or 100 mL / min, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable; preferably 100 mL / min.

[0039] After the calcination and heat preservation are completed, the material can be naturally cooled in a protective gas atmosphere.

[0040] Thirdly, the present invention provides a method for preparing m-phenylenediamine from m-phthalonitrile, the method comprising:

[0041] isophthalonitrile, catalyst and solvent are mixed in a reaction apparatus, and a displacement gas is introduced to replace the air in the reaction apparatus. Then hydrogen is introduced to carry out a hydrogenation reaction to obtain m-phenylenediamine.

[0042] The catalyst is the nitrogen-doped carbon-coated catalyst described in the first aspect.

[0043] The nitrogen-doped carbon-coated catalyst provided by this invention exhibits excellent catalytic performance in the hydrogenation reaction of isophthalonitrile without activation, and can significantly improve the conversion rate of isophthalonitrile, as well as the selectivity and yield of isophthalic diamine.

[0044] In addition, the replacement gas in this invention can be nitrogen. After adding isophthalonitrile, catalyst and solvent to the reaction device, the reaction device is sealed, nitrogen is used to check the airtightness of the reaction device and replace the air in the reaction device, and then hydrogen is introduced to carry out the hydrogenation reaction.

[0045] As a preferred embodiment of the present invention, the mass ratio of isophthalonitrile to the catalyst is 1:(0.1 to 1), for example, it can be 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9 or 1:0.1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] Preferably, the solvent includes toluene and methanol.

[0047] Preferably, the volume ratio of toluene to methanol is (1-5):1, for example, it can be 1:1, 2:1, 3:1, 4:1 or 5:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] The present invention specifies that the volume ratio of toluene to methanol is (1-5):1. This is because isophthalonitrile is easily soluble in toluene, and methanol is highly polar, which is beneficial to CN bond polarization.

[0049] As a preferred technical solution of the present invention, the temperature of the hydrogenation reaction is 80 to 160°C, for example, it can be 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C or 160°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0050] Preferably, the pressure of the hydrogenation reaction is 2 to 12 MPa, for example, 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, 11 MPa or 12 MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0051] Preferably, the hydrogenation reaction time is 1 to 4 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0052] The use of the nitrogen-doped carbon-coated catalyst provided by this invention, and the control of the temperature, pressure and time of the hydrogenation reaction to a specific range, is more conducive to the hydrogenation reaction, thereby improving the conversion rate of isophthalonitrile and giving isophthalic dimethylamine a higher yield and selectivity. At the same time, compared with traditional catalysts, the reaction conditions of the hydrogenation reaction in this invention are milder, which can save production costs.

[0053] Preferably, the space velocity of the isophthalonitrile during the hydrogenation reaction is 0.2–2 h⁻¹. -1 For example, it could be 0.2h -10.4h -1 0.6h -1 0.8h -1 1h -1 1.2h -1 1.4h -1 1.6h -1 1.8h -1 or 2h -1 However, this does not limit the listed values; other unlisted values ​​within the range are also applicable.

[0054] As a preferred embodiment of the present invention, the method further includes:

[0055] Before the hydrogenation reaction, an alkaline inhibitor is added to the reaction apparatus.

[0056] In the catalytic hydrogenation of isophthalonitrile to prepare m-phenylenediamine, a basic inhibitor is usually added to suppress side reactions such as the condensation reaction between the highly reactive intermediate imine and amine, and the hydrogenation or deamination of the benzene ring in m-phenylenediamine, thereby further improving the yield of m-phenylenediamine. However, when using the nitrogen-doped carbon-coated catalyst provided in this invention, only a small amount of basic inhibitor is needed to suppress side reactions.

[0057] Preferably, the alkaline inhibitor includes any one of ammonia, ammonia water, sodium hydroxide, or potassium hydroxide.

[0058] In this aspect, when the alkaline inhibitor is ammonia, ammonia can be introduced after the air in the reaction apparatus is replaced with nitrogen, followed by hydrogen to the set pressure; when the alkaline inhibitor is liquid or solid, it can be added to the reaction apparatus when isophthalonitrile, catalyst and solvent are added.

[0059] Preferably, the reaction apparatus includes a reaction vessel or a fixed-bed reactor.

[0060] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0061] The nitrogen-doped carbon-coated catalyst provided by this invention exhibits excellent catalytic activity, selectivity, and stability in the hydrogenation reaction of isophthalonitrile without the need for activation. Under relatively mild reaction conditions, it significantly improves the selectivity and yield of m-phenylenediamine. Furthermore, under optimized hydrogenation conditions, the selectivity and yield of m-phenylenediamine can both reach over 99%, saving production costs. In addition, the nitrogen-doped carbon-coated catalyst provided by this invention possesses strong magnetic properties, is easily separated from the product, and is convenient for recycling. Moreover, the nitrogen-doped carbon-coated catalyst can be successfully prepared using a simple one-step pyrolysis method. The preparation process is simple, requires no activation step, is low-cost, and yields a high amount of catalyst, making it suitable for large-scale industrial production. Detailed Implementation

[0062] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0063] Example 1

[0064] This embodiment provides a method for preparing a nitrogen-doped carbon-coated catalyst, the method comprising:

[0065] A 25 mL aqueous solution was prepared by mixing 4 g glucose, 4 g urea, 2 g Co(NO3)2·6H2O, 2 g Ni(NO3)2·6H2O and deionized water. The solution was stirred at room temperature for 2 h and then evaporated at 60 °C to obtain a precursor solid material. Subsequently, the precursor solid material was heated to 800 °C for 2 h in a high-purity N2 stream at a flow rate of 100 mL / min and held at 2 °C / min. After natural cooling, a nitrogen-doped carbon-coated catalyst was obtained, denoted as 33%Co1Ni1@C1N1.

[0066] This embodiment also provides a method for preparing m-phenylenediamine by hydrogenation of isophthalonitrile, the method comprising:

[0067] 1g of isophthalonitrile, 1g of 33% Co1Ni1@C1N1 catalyst and solvent (toluene and methanol in a volume ratio of 4:1) were placed in a high-pressure reactor. The high-pressure reactor was sealed, and the airtightness of the reactor was checked with nitrogen and the air inside was replaced. Ammonia was introduced until the pressure reached 0.6MPa, and then hydrogen was introduced until the pressure reached 6MPa. The hydrogenation reaction was carried out at 140℃ for 2 hours to obtain m-phenylenediamine.

[0068] Example 2

[0069] This embodiment provides a method for preparing a nitrogen-doped carbon-coated catalyst, the method comprising:

[0070] 2g glucose, 6g urea, 2g Co(NO3)2·6H2O, 2g Ni(NO3)2·6H2O and deionized water were mixed to form a 25mL aqueous solution. After stirring at room temperature for 2h, the solution was evaporated at 60℃ to obtain a precursor solid material. Subsequently, the precursor solid material was heated to 800℃ for 2h in a high-purity N2 stream at a flow rate of 100mL / min and held at 2℃ / min. After natural cooling, a nitrogen-doped carbon-coated catalyst was obtained, denoted as 33%Co1Ni1@C1N3.

[0071] This embodiment also provides a method for preparing m-phenylenediamine by hydrogenation of isophthalonitrile. The only difference between this method and Example 1 is that a 33% Co1Ni1@C1N3 catalyst is used, while the other process parameters and operating conditions are the same as in Example 1.

[0072] Example 3

[0073] This embodiment provides a method for preparing a nitrogen-doped carbon-coated catalyst, the method comprising:

[0074] 2g glucose, 6g urea, 4g Co(NO3)2·6H2O, 4g Ni(NO3)2·6H2O and deionized water were mixed to form a 25mL aqueous solution. After stirring at room temperature for 2h, the solution was evaporated at 60℃ to obtain a precursor solid material. Subsequently, the precursor solid material was heated to 800℃ for 2h in a high-purity N2 stream at a flow rate of 100mL / min and held at 2℃ / min. After natural cooling, a nitrogen-doped carbon-coated catalyst was obtained, denoted as 50%Co1Ni1@C1N3.

[0075] This embodiment also provides a method for preparing m-phenylenediamine by hydrogenation of isophthalonitrile. The only difference between this method and Example 1 is that a 50% Co1Ni1@C1N3 catalyst is used, while the other process parameters and operating conditions are the same as in Example 1.

[0076] Example 4

[0077] This embodiment provides a method for preparing a nitrogen-doped carbon-coated catalyst, the method comprising:

[0078] 2g glucose, 6g urea, 4g Co(NO3)2·6H2O and deionized water were mixed to form a 25mL aqueous solution. After stirring at room temperature for 2h, the solution was evaporated at 60℃ to obtain a precursor solid material. Subsequently, the precursor solid material was heated to 800℃ for 2h in a high-purity N2 stream at a flow rate of 100mL / min and held at 2℃ / min. After natural cooling, a nitrogen-doped carbon-coated catalyst, denoted as 33%Co@C1N3, was obtained.

[0079] This embodiment also provides a method for preparing m-phenylenediamine by hydrogenation of isophthalonitrile. The only difference between this method and Example 1 is that a 33% Co@C1N3 catalyst is used, while the other process parameters and operating conditions are the same as in Example 1.

[0080] Example 5

[0081] This embodiment provides a method for preparing a nitrogen-doped carbon-coated catalyst, the method comprising:

[0082] 2g glucose, 6g urea, 4g Ni(NO3)2·6H2O and deionized water were mixed to form a 25mL aqueous solution. After stirring at room temperature for 2h, the solution was evaporated at 60℃ to obtain a precursor solid material. Subsequently, the precursor solid material was heated to 800℃ for 2h in a high-purity N2 stream at a flow rate of 100mL / min and held at 2℃ / min. After natural cooling, a nitrogen-doped carbon-coated catalyst was obtained, denoted as 33%Ni@C1N3.

[0083] This embodiment also provides a method for preparing m-phenylenediamine by hydrogenation of isophthalonitrile. The only difference between this method and Example 1 is that a 33% Ni@C1N3 catalyst is used, while the other process parameters and operating conditions are the same as in Example 1.

[0084] Example 6

[0085] This embodiment provides a method for preparing a nitrogen-doped carbon-coated catalyst, the method comprising:

[0086] A 25 mL aqueous solution was prepared by mixing 2 g glucose, 10 g urea, 0.8 g Co(NO3)2·6H2O, 0.2 g Ni(NO3)2·6H2O, 0.3 g Fe(NO3)3·9H2O, and deionized water. The solution was stirred at room temperature for 1 h and then evaporated at 50 °C to obtain a precursor solid material. Subsequently, the precursor solid material was heated to 1000 °C for 1 h in a high-purity N2 stream at a flow rate of 110 mL / min and heated at a rate of 5 °C / min. After natural cooling, a nitrogen-doped carbon-coated catalyst was obtained, denoted as 9%Co4NiFe@C1N5 (where the molar ratio of Co:Ni:Fe is 4:1:1).

[0087] This embodiment also provides a method for preparing m-phenylenediamine by hydrogenation of isophthalonitrile. The only difference between this method and Example 1 is that a 9% Co4NiFe@C1N5 catalyst is used for a 4-hour hydrogenation reaction, while the other process parameters and operating conditions are the same as in Example 1.

[0088] Example 7

[0089] This embodiment provides a method for preparing a nitrogen-doped carbon-coated catalyst, the method comprising:

[0090] A 25 mL aqueous solution was prepared by mixing 10 g glucose, 2 g urea, 2 g Co(NO3)2·6H2O, 1 g Ni(NO3)2·6H2O, 3 g Mg(NO3)3·6H2O, and deionized water. The solution was stirred at room temperature for 3 h, then evaporated at 70 °C to obtain a precursor solid material. Subsequently, the precursor solid material was heated to 700 °C for 5 h in a high-purity N2 stream at a flow rate of 90 mL / min and a heating rate of 1 °C / min. After natural cooling, a nitrogen-doped carbon-coated catalyst, denoted as 33%Co2NiMg, was obtained. 3.4 @C1N 0.2 (The molar ratio of Co:Ni:Cu is 2:1:3.4).

[0091] This embodiment also provides a method for preparing m-phenylenediamine by hydrogenation of isophthalonitrile. The only difference between this method and Example 1 is that 33% Co2NiMg is used. 3.4 @C1N 0.2 The catalyst, and the remaining process parameters and operating conditions are the same as in Example 1.

[0092] Example 8

[0093] The only difference between this embodiment and Example 2 is that the amount of urea added is 0.2g, resulting in a nitrogen-doped carbon-coated catalyst, denoted as 33%Co1Ni1@C1N. 0.1 And using 33% Co1Ni1@C1N 0.1 The catalyst was used to catalyze the hydrogenation of isophthalonitrile to prepare isophthalic dimethylamine, and the remaining process parameters and operating conditions were the same as in Example 2.

[0094] Example 9

[0095] The only difference between this embodiment and Example 2 is that the amount of urea added is 12g, resulting in a nitrogen-doped carbon-coated catalyst, denoted as 33%Co1Ni1@C1N6. The 33%Co1Ni1@C1N6 catalyst is used to catalyze the hydrogenation of isophthalonitrile to prepare isophthalic dimethylamine. The remaining process parameters and operating conditions are the same as in Example 2.

[0096] The products of the hydrogenation reaction of isophthalonitrile catalyzed by the nitrogen-doped carbon-coated catalysts prepared in Examples 1-9 were detected and analyzed by gas chromatography (RTX-5 column, FID detector). The results are shown in Table 1.

[0097] Table 1

[0098]

[0099]

[0100] To further optimize the reaction conditions for the catalytic hydrogenation of isophthalonitrile, this invention selected the 33% Co1Ni1@C1N3 catalyst prepared in Example 2 to prepare isophthalic acid under different hydrogenation reaction conditions.

[0101] Example 10

[0102] The difference between this embodiment and Embodiment 2 is that hydrogen gas is introduced until the pressure reaches 5 MPa, while the other process parameters and operating conditions are the same as in Embodiment 2.

[0103] Example 11

[0104] The difference between this embodiment and Embodiment 2 is that hydrogen gas is introduced until the pressure reaches 4 MPa, while the other process parameters and operating conditions are the same as in Embodiment 2.

[0105] Example 12

[0106] The difference between this embodiment and Embodiment 2 is that hydrogen gas is introduced until the pressure reaches 5 MPa, and the hydrogenation reaction time is 3 hours. The remaining process parameters and operating conditions are the same as in Embodiment 2.

[0107] Example 13

[0108] The difference between this embodiment and Embodiment 2 is that hydrogen gas is introduced until the pressure reaches 5 MPa, and the hydrogenation reaction time is 4 hours. The remaining process parameters and operating conditions are the same as in Embodiment 2.

[0109] Example 14

[0110] The difference between this embodiment and Embodiment 2 is that hydrogen gas is introduced until the pressure reaches 5 MPa, and the hydrogenation reaction temperature is 130°C. The remaining process parameters and operating conditions are the same as in Embodiment 2.

[0111] Example 15

[0112] The difference between this embodiment and Embodiment 2 is that hydrogen gas is introduced until the pressure reaches 5 MPa, and the hydrogenation reaction temperature is 100°C. The remaining process parameters and operating conditions are the same as in Embodiment 2.

[0113] The products of the hydrogenation reaction of intermediate phthalonitrile in Examples 10-15 were detected and analyzed by gas chromatography (RTX-5 column, FID detector), and the results are shown in Table 2.

[0114] Table 2

[0115]

[0116] Comparative Example 1

[0117] The difference between this comparative example and Example 2 is that the amount of Co(NO3)2·6H2O added is 0.2g, and the amount of Ni(NO3)2·6H2O added is 0.2g, resulting in a nitrogen-doped carbon-coated catalyst, denoted as 5%Co1Ni1@C1N3. The 5%Co1Ni1@C1N3 catalyst is used to catalyze the hydrogenation of isophthalonitrile to prepare isophthalic dimethylamine. The remaining process parameters and operating conditions are the same as in Example 2.

[0118] Comparative Example 2

[0119] The only difference between this comparative example and Example 2 is that the amount of Co(NO3)2·6H2O added is 6g, and the amount of Ni(NO3)2·6H2O added is 6g, resulting in a nitrogen-doped carbon-coated catalyst, denoted as 60%Co1Ni1@C1N3. The 60%Co1Ni1@C1N3 catalyst is used to catalyze the hydrogenation of isophthalonitrile to prepare isophthalic dimethylamine. The remaining process parameters and operating conditions are the same as in Example 2.

[0120] The products of the hydrogenation reaction of intermediate phthalonitrile in Comparative Examples 1-2 were detected and analyzed by gas chromatography (RTX-5 column, FID detector), and the results are shown in Table 3.

[0121] Table 3

[0122]

[0123] From the data analysis in Table 1, we can conclude that:

[0124] (1) The nitrogen-doped carbon-coated catalysts prepared in Examples 1-7 exhibited high catalytic activity without activation during the hydrogenation of isophthalonitrile to prepare isophthalic dimethylamine. The conversion rate of isophthalonitrile reached 100%, and the selectivity and yield of isophthalic dimethylamine both reached over 92.9%. Among them, under the optimized catalyst composition, the selectivity and yield of isophthalic dimethylamine can both reach about 99%.

[0125] (2) When the nitrogen-doped carbon-coated catalysts prepared in Examples 8 and 9 were used in the process of hydrogenating isophthalonitrile to prepare isophthalic dimethylamine, the selectivity and yield of isophthalic dimethylamine were lower than those in Example 2. This is because the amount of nitrogen source added in Example 8 was too low. Since the pyridine nitrogen formed by the nitrogen source provides basic sites for the catalyst material, it can improve the selectivity and yield of isophthalic dimethylamine and inhibit the formation of by-products. Therefore, when the amount of nitrogen source added is too low, the selectivity and yield of the catalyst material for isophthalic dimethylamine will decrease. In Example 9, the amount of nitrogen source added was too high, and the coating effect of the nitrogen-doped carbon material on the core of the metal active component was poor, which would lead to poor stability of the obtained catalyst material. This shows that adjusting the amount of carbon source and nitrogen source added to an appropriate range can further improve the activity of the catalyst.

[0126] From the data analysis in Table 2, we can conclude that:

[0127] Within the temperature, pressure, and reaction time ranges of the catalytic hydrogenation of isophthalonitrile provided by this invention, the selectivity and yield of m-phenylenediamine both reach over 97%. Furthermore, under the preferred reaction conditions of 140°C, 5 MPa (containing 0.6 MPa ammonia), and 2 h, the selectivity and yield of m-phenylenediamine can reach 99.1%. This demonstrates that using the nitrogen-doped carbon-coated catalyst provided by this invention, and controlling the temperature, pressure, and time of the hydrogenation reaction to a specific range, is more conducive to the hydrogenation reaction, thereby improving the conversion rate of isophthalonitrile and giving m-phenylenediamine a higher yield and selectivity. Simultaneously, compared to traditional catalysts, the reaction conditions for the hydrogenation reaction in this invention are milder, which can save production costs.

[0128] From the data analysis in Table 3, we can conclude that:

[0129] When the nitrogen-doped carbon-coated catalyst prepared in Comparative Example 1 was used in the process of hydrogenating isophthalonitrile to prepare m-phenylenediamine, the selectivity and yield of m-phenylenediamine were lower than those in Example 2. This was because the loading of the metal active component in the comparative example was too low. When the nitrogen-doped carbon-coated catalyst prepared in Comparative Example 2 was used in the process of hydrogenating isophthalonitrile to prepare m-phenylenediamine, the selectivity and yield of m-phenylenediamine were basically the same as those in Example 2. This shows that when the loading of the metal active component is too high, the catalytic activity of the catalyst will not be significantly improved, but will instead increase the production cost.

[0130] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A process for the preparation of m-xylylenediamine from m-xylylene dinitrile, characterized in that, The method comprises: The isophthalonitrile, the catalyst and the solvent are mixed in a reaction device, a replacement gas is introduced to replace air in the reaction device, and then hydrogen is introduced to carry out a hydrogenation reaction to obtain isophthalodiamine; The catalyst is a nitrogen-doped carbon-coated catalyst, the nitrogen-doped carbon-coated catalyst is a core-shell structure with a metal active component as a core and a nitrogen-doped carbon material as a coating layer, and the loading amount of the metal active component is 9-50wt% based on 100wt% of the mass fraction of the nitrogen-doped carbon-coated catalyst. The metal active component comprises a first metal active component; the first metal active component comprises cobalt and nickel; and the molar ratio of cobalt to nickel in the first metal active component is (0.2-5):

1.

2. The method of claim 1, wherein, The metal active component further comprises a second metal active component.

3. The method of claim 2, wherein, The second metal active component comprises any one or a combination of at least two of copper, cesium, iron, potassium, lithium, molybdenum, manganese, magnesium or zinc.

4. The method of claim 3, wherein, The molar ratio of the first metal active component to the second metal active component is (0.2-5):

1.

5. The method of claim 1, wherein, The preparation method of the nitrogen-doped carbon-coated catalyst comprises: The carbon source, the nitrogen source, the metal source and the solvent are mixed, and then evaporation treatment is performed to obtain a precursor solid material, and the precursor solid material is calcined to obtain the nitrogen-doped carbon-coated catalyst.

6. The method of claim 5, wherein, The mass ratio of the carbon source to the nitrogen source is 1:(0.2-5).

7. The method of claim 5, wherein, The carbon source comprises glucose.

8. The method of claim 5, wherein, The nitrogen source comprises urea.

9. The method of claim 5, wherein, The metal source comprises a metal nitrate.

10. The method of claim 5, wherein, The solvent is any one of deionized water, ethanol or methanol.

11. The method of claim 5, wherein, The mixing is performed under stirring.

12. The method of claim 11, wherein, The stirring time is 1-5h.

13. The method of claim 5, wherein, The evaporation treatment temperature is 50-70℃.

14. The method of claim 5, wherein, The evaporation treatment is performed under vacuum.

15. The method of claim 5, wherein, The calcination heating rate is 1-5℃ / min.

16. The method of claim 5, wherein, The final temperature of the calcination is 700-1000℃.

17. The method of claim 5, wherein, The holding time of the calcination at the final temperature is 1-5h.

18. The method of claim 5, wherein, The calcination is performed in a protective gas atmosphere.

19. The method of claim 18, wherein, The flow rate of the protective gas is 60-100mL / min.

20. The method of claim 1, wherein, The mass ratio of the isophthalonitrile to the catalyst is 1:(0.1-1).

21. The method of claim 1, wherein, The solvent comprises toluene and methanol.

22. The method of claim 21, wherein, The volume ratio of the toluene to the methanol is (1-5):

1.

23. The method of claim 1, wherein, The hydrogenation reaction temperature is 80-160℃.

24. The method of claim 1, wherein, The hydrogenation reaction pressure is 2-12MPa.

25. The method of claim 1, wherein, The hydrogenation reaction time is 1-4h.

26. The method of claim 1, wherein, The space velocity of the isophthalonitrile in the hydrogenation reaction process is 0.2-2 h -1 .

27. The method of claim 1, wherein, The method further comprises: Before the hydrogenation reaction, a basic inhibitor is added to the reaction device.

28. The method of claim 27, wherein, The basic inhibitor comprises any one of ammonia, ammonia water, sodium hydroxide or potassium hydroxide.

29. The method of claim 1, wherein, The reaction device comprises a reaction kettle or a fixed bed reactor.

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