Continuous production method of 1, 3-cyclohexyl dimethylamine

Abstract

The invention relates to the technical field of organic chemical industry, in particular to a continuous production method of 1, 3-cyclohexyldimethylamine, which adopts two fixed bed reactors connected in series to carry out two-step continuous hydrogenation reaction to obtain 1, 3-cyclohexyldimethylamine. In the first step of hydrogenation, isophthalonitrile is dissolved in a solvent to serve as a reactant, and a cobalt-iron catalyst loaded on a modified carrier and hydrogen are subjected to hydrogenation to generate an m-xylylenediamine reaction solution; in the second step of hydrogenation, the ruthenium-nickel catalyst loaded on the modified carrier and hydrogen are subjected to hydrogenation, and finally 1, 3-cyclohexyl dimethylamine is obtained. According to the continuous production method for industrially producing the 1, 3-cyclohexyl dimethylamine, provided by the invention, through two-step continuous hydrogenation reaction, the reaction time is shortened, the material transfer loss is reduced, a stagnation link in a batch intermittent process is avoided, and a relatively high conversion rate of isophthalonitrile and a relatively high total yield of the 1, 3-cyclohexyl dimethylamine are ensured.

Description

Technical Field

[0001] The invention relates to the technical field of organic chemical industry, and in particular to a continuous production method of 1,3-cyclohexyldimethylamine. Background Art

[0002] 1,3-Cyclohexanedimethanamine (1,3-BAC) is also known as 1,3-diaminomethylcyclohexane. It is an important fine chemical intermediate and also a pesticide intermediate. It is mainly used as a curing agent for epoxy resins because of its advantages such as fast curing speed, good toughness and excellent yellowing resistance. The polyurethane resin prepared by it has high heat resistance and can also be used in the production of coating hardeners, aging inhibitors, and coating resins. It has special applications in fiber and membrane materials, and can also be used as a raw material for dyes, detergents and pharmaceutical intermediates.

[0003] At present, the main foreign manufacturers producing 1,3-cyclohexyldimethylamine include Mitsubishi Gas, BASF and other companies. There are only a few domestic manufacturers. After MXDA is listed as a toxic chemical, the demand for 1,3-cyclohexyldimethylamine will gradually increase.

[0004] US5371293 uses a catalyst loaded with 5% Ru / Al2O3. In the presence of liquid ammonia, dioxane is used as a solvent. At a reaction temperature of 140°C and a reaction pressure of 15MPa, isophthalonitrile is hydrogenated to obtain 1,3-cyclohexyldimethylamine with a yield of 87.8%. At a reaction temperature of 100°C and a reaction pressure of 15MPa, the molar yield of 1,3-cyclohexyldimethylamine is 88.3%. If liquid ammonia is not added during the hydrogenation process, the yield of 1,3-cyclohexyldimethylamine is only 29%, and a large amount of deamination low-boiling byproducts will be generated.

[0005] EP0703213 uses a supported catalyst, and the solvents used in the reaction include methylamine, dimethylamine, ethylenediamine, etc. The reaction pressure is 5-15 MPa, the reaction temperature is 80° C.-130° C., and the yield can reach 94%.

[0006] CN101959848 uses non-supported Ni-Cu-Cr as a catalyst, and uses a fixed bed continuous reaction process to carry out a hydroamination reaction of 1,3-cyclohexanedimethanol at a reaction temperature of 190°C to 220°C and a reaction pressure of 17MPa to obtain 1,3-cyclohexanedimethylamine, with a maximum selectivity of 72.6%. Many intermediates and by-products are also produced in the product. In addition, since the boiling points of the product 1,3-cyclohexanedimethylamine and 1,3-cyclohexanedimethanol are close, separation is difficult.

[0007] CN113402396 discloses a method for producing m-xylylenediamine and 1,3-diaminomethylcyclohexane in combination. In the method, m-xylylenediamine and 1,3-diaminomethylcyclohexane are produced by contacting m-xylylenediamine with hydrogen in the presence of a catalyst. The ratio of the target product m-xylylenediamine and 1,3-diaminomethylcyclohexane can be adjusted by optimizing the process conditions of the hydrogen-nitrile ratio and combining with catalyst modulation, and the molar ratio of the two is about 9:1 to 1:1.

[0008] CN102911062 discloses a method for preparing 1,3-cyclohexyldimethylamine, wherein the method performs two-stage hydrogenation under the same solvent, wherein the first stage uses Raney nickel as a catalyst, methanol, methylamine or 1,4-dioxane as a solvent, and an organic amine, liquid ammonia, water or sodium hydroxide as an auxiliary agent, and isophthalonitrile and hydrogen react to obtain a m-phenylenediamine reaction liquid, and the second stage uses activated carbon loaded with ruthenium as a catalyst, and the m-phenylenediamine reaction liquid reacts with hydrogen to obtain 1,3-cyclohexyldimethylamine. The method uses two high-pressure reactors connected in series, which is an intermittent operation.

[0009] At present, there are many problems in the production of 1,3-cyclohexyldimethylamine. For example, the use of two high-pressure reactors in series cannot achieve truly continuous hydrogenation operation; there are many side reactions, which will generate by-products covering the catalyst surface, thereby reducing the life of the catalyst; the cyclohexanedimethanol hydrogenation method has problems such as high reaction temperature and reaction pressure, low raw material conversion rate, and low product selectivity; the hydrogenation of isophthalonitrile to prepare 1,3-cyclohexyldimethylamine requires the addition of inorganic additives such as liquid ammonia, which increases energy consumption and further increases production costs; it is impossible to effectively suppress the occurrence of deamination in the reaction system.

[0010] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art known to those skilled in the art. Summary of the invention

[0011] The technical problem to be solved by the present invention is to provide a continuous production method of 1,3-cyclohexyldimethylamine, which adopts two fixed bed reactors connected in series to carry out two-step hydrogenation, realizes continuous hydrogenation operation and reduces operation costs.

[0012] In order to achieve the above object, the technical solution adopted by the present invention is:

[0013] A continuous production method of 1,3-cyclohexyldimethylamine, which is obtained by performing two-step continuous hydrogenation reactions using two fixed bed reactors connected in series;

[0014] In the first step of hydrogenation, isophthalonitrile is dissolved in a solvent as a reactant, and a cobalt-iron catalyst supported on a modified carrier is used at a temperature of 80°C to 120°C, a pressure of 4MPa to 10MPa, and a solution space velocity of 0.3h -1 ~0.6h -1 Under the conditions of , hydrogenation is performed with hydrogen to generate a m-xylylenediamine reaction liquid; the first step hydrogenation catalyst used in the present invention can inhibit the polycondensation reaction during the hydrogenation of isophthalonitrile, thereby increasing the service life of the catalyst in the first step hydrogenation and reducing the frequency of catalyst replacement;

[0015] Furthermore, in the first step of hydrogenation, isophthalonitrile is dissolved in a solvent as a reactant, and a cobalt iron catalyst supported on a modified carrier is used at a temperature of 85°C to 95°C, a pressure of 9MPa to 10MPa, and a gas space velocity of 290h -1 ~310h -1 , the solution space velocity is 0.5h -1 ~0.6h -1 Under the condition of , hydrogenation is carried out with hydrogen to generate a m-xylylenediamine reaction liquid;

[0016] The second step of hydrogenation uses a ruthenium nickel catalyst on a modified carrier at a temperature of 120°C to 160°C, a pressure of 4MPa to 10MPa, and a solution space velocity of 0.1h -1 ~0.2h -1 Under the conditions of , 1,3-cyclohexyldimethylamine is finally obtained by hydrogenation with hydrogen. The second-step hydrogenation catalyst used in the present invention, wherein ruthenium provides excellent hydrogenation activity, and nickel enhances the selectivity for the target cyclic compound (1,3-cyclohexyldimethylamine), while reducing the generation of side reaction products, can effectively reduce the occurrence of deamination side reaction during the hydrogenation of meta-phenylenediamine, and greatly improves the yield of the target product 1,3-cyclohexyldimethylamine.

[0017] Furthermore, the second step of hydrogenation uses a ruthenium nickel catalyst supported on a modified carrier at a temperature of 140°C to 150°C, a pressure of 6MPa to 8MPa, and a gas space velocity of 290h -1 ~310h -1 , solution space velocity 0.1h -1 ~0.15h -1 The product is hydrogenated with hydrogen under the conditions of 1,3-cyclohexyldimethylamine.

[0018] Preferably, the modified carrier comprises a carrier and an alkali metal modifier loaded on the carrier, wherein the mass content of the alkali metal modifier is 3% to 5%; The clover alumina carrier, the alkali metal modifier is one or more of NaNO3, NaOH, KOH, preferably KOH.

[0019] Alkali metal modifiers can introduce alkaline centers on the surface of the alumina support. Taking KOH as an example, through KOH impregnation and calcination treatment, part of KOH decomposes to generate K2O. The oxide provides stable alkaline sites on the support surface. In the first step, it promotes the hydrogenation of nitrile groups to generate amine groups (meta-phenylenediamine) and avoids the formation of by-products such as amides. In the second step, it improves the selectivity of the hydrogenation cyclization reaction, avoids the formation of over-hydrogenation by-products, and improves the purity of the target product 1,3-cyclohexyldimethylamine.

[0020] As a preferred method, the preparation method of the modified carrier is:

[0021] The alkali metal modifier is prepared into an aqueous solution, heated to 55-65° C., sprayed evenly onto the carrier by an equal amount impregnation method, and then dried and calcined at 210-230° C. to obtain a modified carrier.

[0022] Preferably, the cobalt-iron catalyst loaded on the modified carrier includes a modified carrier, and metallic cobalt and metallic iron loaded on the modified carrier in sequence, wherein the mass content of metallic cobalt is 5% to 35%, and the mass content of metallic iron is 5% to 35%. This preparation method of first modifying the carrier and then loading cobalt and iron in sequence ensures that the modified carrier provides a good alkaline environment, so that cobalt and iron can be highly dispersed on the surface of the carrier, avoiding mutual shielding between metal active sites, thereby significantly improving the activity and selectivity of the catalyst. Cobalt, as the main active metal, is first loaded to ensure the formation of stable basic active sites, providing protection for the main hydrogenation step of the reaction. Iron, as a secondary metal after cobalt loading, can further modify the surface properties of cobalt and enhance the catalytic performance of cobalt. This secondary loading method can also avoid the shielding effect of iron particles on cobalt active sites.

[0023] Preferably, the preparation method of the cobalt-iron catalyst supported on the modified carrier comprises:

[0024] (1) preparing cobalt nitrate into a 60-65° C. aqueous solution, spraying it evenly on the modified carrier by an equal amount impregnation method, then drying it, and then calcining it at 440-460° C.; repeating this step until the cobalt content in the catalyst reaches the required level, thereby obtaining a cobalt-containing catalyst;

[0025] (2) preparing ferric nitrate into a 40-45°C aqueous solution, spraying it evenly on the cobalt-containing catalyst by an equal amount impregnation method, and then drying it, and then calcining it at 440-460°C, repeating this step until the iron content in the catalyst reaches the required level, thereby obtaining a cobalt-iron catalyst supported on a modified carrier.

[0026] Preferably, the ruthenium nickel catalyst loaded on the modified carrier includes a modified carrier, and metallic ruthenium and metallic nickel loaded on the modified carrier in sequence, wherein the mass content of metallic ruthenium is 0.1% to 3%, and the mass content of metallic nickel is 1% to 3%. The present invention first loads ruthenium on the modified carrier, and then loads nickel, forming a bimetallic catalytic system with high synergy. Ruthenium, as the main active metal, is responsible for the hydrogenation reaction, while nickel improves the selectivity of the target product during the cyclization process. The preparation of the modified carrier is carried out before the metal loading, ensuring that the alkaline modifier fully acts on the carrier surface, thereby optimizing the environment and dispersibility of the metal loading, and improving the overall performance of the catalyst. Ruthenium is first loaded to ensure that it forms a stable active site on the carrier surface, providing the main catalytic ability for the hydrogenation cyclization reaction, and the nickel loaded later can be more effectively distributed around the ruthenium to form a uniform ruthenium nickel synergistic catalytic structure, thereby maximizing its catalytic effect.

[0027] Preferably, the preparation method of the ruthenium nickel catalyst supported on the modified carrier comprises:

[0028] (1) preparing ruthenium chloride into a 65-70° C. aqueous solution, spraying it onto the carrier by an equal amount impregnation method, then drying it, and then calcining it at 440-460° C.; repeating this step until the ruthenium content requirement in the catalyst is reached, thereby obtaining a ruthenium-containing catalyst;

[0029] (2) nickel nitrate is prepared into a 60-70°C aqueous solution, and sprayed evenly on the ruthenium-containing catalyst of (2) by an equal amount impregnation method, followed by drying, and then calcining at 440-450°C. This step is repeated until the nickel content in the catalyst reaches the required level, thereby obtaining a ruthenium nickel catalyst supported on a modified carrier.

[0030] As preferably, isophthalonitrile needs to be dissolved with a solvent before use. After being dissolved in the solvent, isophthalonitrile changes from a solid particle state to a molecular state, can more fully contact with hydrogen and the active sites of the catalyst, helps to improve the adsorption rate of isophthalonitrile on the catalyst surface, promotes the activation of the nitrile group and the hydrogenation reaction. After dissolution, the concentration of isophthalonitrile accounts for 2-3wt% of the total amount of reactants. Too high a concentration may increase the amount of reactants loaded on the catalyst surface, causing catalyst poisoning or active sites to be occupied, thereby reducing catalyst performance, and a concentration range of 2-3wt% can provide a moderate reactant concentration for the catalyst, ensuring the high efficiency and long life of the catalyst.

[0031] Preferably, the solvent is one or more of methanol, N,N-dimethylethanolamine, N,N-dimethylacetamide, and tetrahydrofuran, preferably tetrahydrofuran. Tetrahydrofuran is an excellent polar organic solvent with good solubility for isophthalonitrile. Its moderate polarity can effectively dissolve isophthalonitrile and can be evenly distributed in the liquid phase reaction system to avoid solid particles or insoluble matter covering the catalyst surface.

[0032] Preferably, the cobalt-iron catalyst carried on a modified carrier and the ruthenium-nickel catalyst carried on a modified carrier need to be reduced with hydrogen before adding the raw materials; during the catalyst preparation process, the metals (cobalt, iron, ruthenium, nickel) exist in an oxidized state, and through the reduction process, hydrogen reacts with these metal oxides to generate zero-valent metals or low-valent metals. The reduced metals are in an active state and can participate in the hydrogenation reaction more effectively.

[0033] Among them, CoO and Fe2O3 have higher reduction temperatures, and the reduction temperature of the cobalt iron catalyst on the modified carrier is 370-385°C; RuO2 and NiO have lower reduction temperatures, and the reduction temperature of the ruthenium nickel catalyst on the modified carrier is 240-260°C. The optimized reduction temperature not only improves the activity and selectivity of the catalyst, but also effectively prolongs the service life of the catalyst, and significantly improves the reaction efficiency and purity of the target product, fully meeting the needs of industrial continuous production.

[0034] Preferably, the raw material used in the second step of hydrogenation is the reaction liquid obtained in the first step of hydrogenation, thereby achieving continuous production, avoiding the steps of separation, purification and storage of intermediate products, and retaining the active substances in the reaction system to the greatest extent.

[0035] The beneficial effects of the present invention are:

[0036] (1) The method for continuous production of 1,3-cyclohexyldimethylamine for industrial production provided by the present invention, through two-step continuous hydrogenation reaction, enables the first reaction (isophthalonitrile to meta-xylenediamine) and the second reaction (meta-xylenediamine to 1,3-cyclohexyldimethylamine) to be continuously carried out in two series-connected fixed-bed reactors, thereby reducing the reaction time and material transfer loss, avoiding the stagnation link in the batch intermittent process, and ensuring a high conversion rate of isophthalonitrile and a high total yield of 1,3-cyclohexyldimethylamine.

[0037] (2) In the first step, the present invention uses a cobalt-iron catalyst supported on a modified carrier to provide high activity for the nitrile hydrogenation reaction and promote the highly selective production of meta-xylylenediamine. In the second step, a ruthenium-nickel catalyst supported on a modified carrier is used to improve the efficiency of the cyclization reaction and reduce side reactions by regulating the hydrogenation activity of ruthenium and the selectivity of nickel. Different catalysts are selected for the two-step reaction, so that the catalyst can specifically catalyze the target reaction at each stage, rather than using a single catalyst to complete the two-step reaction at the same time, thereby avoiding the risk of decreased selectivity. The modified carrier is modified by alkali metal to optimize the metal dispersion and the electronic properties of the active site, thereby improving the selectivity of the target product.

[0038] (3) The reaction solvent such as tetrahydrofuran in the present invention can be recycled during the reaction process, reducing the loss and waste of the solvent, and the incompletely reacted isophthalonitrile and by-products can continue to participate in the subsequent reaction without generating additional waste. The first reaction liquid is directly used for the second step reaction, avoiding the use of solvents, energy consumption and waste discharge required for the separation and purification of meta-xylylenediamine in the traditional process. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0041] In the examples, the specifications of the carrier, modified carrier and catalyst were all ￠3, and all components were purchased from Aladdin.

[0042] Embodiment 1:

[0043] Carrier modification: It was measured that the water absorption rate of the aluminum oxide carrier was 70%. 10 grams of NaOH was added to 100 mL of deionized water, heated to 60°C, and prepared into a NaOH solution. The solution was then sprayed on 200 grams of the aluminum oxide carrier, dried, and calcined at 220°C to obtain a modified aluminum oxide carrier. It was measured that the water absorption rate of the modified carrier was still 70%. To obtain a larger amount of modified carriers, the aforementioned steps can be repeated or the aforementioned method can be scaled up in equal proportions.

[0044] Using the same method as above, the alumina support was modified with NaNO3 and KOH respectively to obtain a modified support.

[0045] The first step of hydrogenation catalyst preparation: (1) 9.39 g of Co(NO3)2·6H2O was dissolved in deionized water to obtain a total volume of 14 ml of cobalt nitrate solution, which was heated to 60°C, and the cobalt nitrate solution was evenly sprayed on 20 g of alumina carrier by an equal amount impregnation method, then dried, and then calcined at 450°C; (2) step (1) was repeated twice to obtain a cobalt-containing catalyst; (3) 10.33 g of Fe(NO3)3·9H2O was dissolved in deionized water to obtain a total volume of 14 ml of ferric nitrate solution, which was heated to 60°C, and the ferric nitrate solution was evenly sprayed on the cobalt-containing catalyst obtained in the above (2) by an equal amount impregnation method, then dried, and then calcined at 400°C; (4) step (3) was repeated once to obtain a cobalt-iron catalyst. The catalyst contains 20% cobalt and 10% iron, respectively.

[0046] The second step is the preparation of hydrogenation catalyst: (1) 0.27g of RuCl3·3H2O is dissolved in deionized water to obtain a ruthenium chloride solution with a total volume of 14ml, which is heated to 80°C, and the ruthenium chloride solution is evenly sprayed on the alumina carrier modified with NaNO3 by an equal amount impregnation method, then dried, and then calcined at 450°C to obtain a ruthenium-containing catalyst; (2) 2.13g of Ni(NO3)2·6H2O is dissolved in deionized water to obtain a nickel nitrate solution with a total volume of 14ml, which is heated to 40°C, and the iron nitrate solution is evenly sprayed on the cobalt-containing catalyst obtained in the above (1) by an equal amount impregnation method, then dried, and then calcined at 200°C to obtain a ruthenium-containing nickel catalyst. The catalyst contains 0.5% ruthenium and 2% nickel, respectively.

[0047] Hydrogenation reaction: (1) The catalysts prepared above are loaded into fixed bed reactors respectively, and first reduced with hydrogen. The catalyst reduction temperature in the first hydrogenation reactor is 380°C, and the catalyst reduction temperature in the second hydrogenation reactor is 250°C, until the reduction is completed; (2) Isophthalonitrile is dissolved in tetrahydrofuran solvent to prepare a reaction raw material liquid, so that the isophthalonitrile content is 3wt%; (3) The raw material liquid is introduced into a fixed bed reactor, and hydrogen is introduced at the same time. The control conditions of the first reactor are: reaction temperature 80°C, reaction pressure 10.0MPa, solution space velocity 0.6h -1 , gas space velocity 300h -1 The control conditions of the second reactor are: reaction temperature 160°C, reaction pressure 10.0MPa, solution space velocity 0.2h -1 , gas space velocity 280h -1 .

[0048] Embodiment 2:

[0049] Example 1 was repeated, except that the amount of raw materials was changed according to the composition change. In the first step of hydrogenation catalyst, the carrier was modified with KOH, and the cobalt and iron contents in the catalyst were 5wt% and 35wt%, respectively. The hydrogenation reaction conditions were: reaction temperature 120°C, reaction pressure 4.0MPa, solution space velocity 0.3h -1 , gas space velocity 280h -1 In the second step of hydrogenation catalyst, the carrier was modified with NaOH, and the contents of ruthenium and nickel were 0.1wt% and 3wt%, respectively. The reaction conditions were: reaction temperature 150°C, reaction pressure 8.0MPa, solution space velocity 0.15h -1 , gas space velocity 280h -1 .

[0050] Embodiment 3:

[0051] Example 1 was repeated, except that the amount of raw materials was changed according to the composition change. In the first step of hydrogenation catalyst, the carrier was modified with NaOH, the cobalt and iron contents in the catalyst were 10wt% and 20wt%, respectively, and the hydrogenation reaction conditions were: reaction temperature 110°C, reaction pressure 9.0MPa, solution space velocity 0.5h -1 , gas space velocity 300h -1 In the second step of hydrogenation catalyst, the carrier was modified with KOH, and the contents of ruthenium and nickel were 1wt% and 1.5wt% respectively. The reaction conditions were: reaction temperature 145°C, reaction pressure 7.0MPa, solution space velocity 0.12h -1 , gas space velocity 300h -1 .

[0052] Embodiment 4:

[0053] Example 1 was repeated, except that the amount of raw materials was changed according to the composition change. In the first step of hydrogenation catalyst, the carrier was modified with KOH, and the cobalt and iron contents in the catalyst were 15wt% and 15wt%, respectively. The hydrogenation reaction conditions were: reaction temperature 95°C, reaction pressure 8.0MPa, solution space velocity 0.4h -1 , gas space velocity 320h -1 In the second step of hydrogenation catalyst, the carrier was modified with KOH, and the contents of ruthenium and nickel were 2wt% and 1wt%, respectively. The reaction conditions were: reaction temperature 130°C, reaction pressure 6.0MPa, solution space velocity 0.1h -1 , gas space velocity 320h -1 .

[0054] Embodiment 5:

[0055] Example 1 was repeated, except that the amount of raw materials was changed according to the composition change. In the first step of hydrogenation catalyst, the carrier was modified with KOH, the cobalt and iron contents in the catalyst were 35wt% and 5wt%, respectively, and the hydrogenation reaction conditions were: reaction temperature 100°C, reaction pressure 5.0MPa, solution space velocity 0.35h -1 , gas space velocity 300h -1 In the second step of hydrogenation catalyst, the carrier was modified with KOH, and the contents of ruthenium and nickel were 3wt% and 1wt%, respectively. The reaction conditions were: reaction temperature 120℃, reaction pressure 4.0MPa, solution space velocity 0.15h -1 , gas space velocity 300h -1 .

[0056] Embodiment 6:

[0057] Example 1 was repeated, except that the amount of raw materials was changed according to the composition change. In the first step of hydrogenation catalyst, the carrier was modified with KOH, the cobalt and iron contents in the catalyst were 25wt% and 7wt%, respectively, and the hydrogenation reaction conditions were: reaction temperature 90°C, reaction pressure 7.0MPa, solution space velocity 0.45h -1 , gas space velocity 300h -1 In the second step of hydrogenation catalyst, the carrier was modified with NaNO3, and the contents of ruthenium and nickel were 0.6wt% and 2.5wt%, respectively. The reaction conditions were: reaction temperature 135°C, reaction pressure 9.0MPa, solution space velocity 0.12h -1 , gas space velocity 300h -1 .

[0058] Embodiment 7:

[0059] Example 1 was repeated, except that the amount of raw materials was changed according to the composition change. In the first step of hydrogenation catalyst, the carrier was modified with KOH, the cobalt and iron contents in the catalyst were 7wt% and 30wt%, respectively, and the hydrogenation reaction conditions were: reaction temperature 85°C, reaction pressure 6.0MPa, solution space velocity 0.4h -1 , gas space velocity 300h -1 In the second step of hydrogenation catalyst, the carrier was modified with KOH, and the contents of ruthenium and nickel were 0.8wt% and 2.3wt%, respectively. The reaction conditions were: reaction temperature 145°C, reaction pressure 5.0MPa, solution space velocity 0.16h -1 , gas space velocity 320h -1 .

[0060] Comparative Example: A catalyst was prepared in the same manner as in Example 1, except that the carriers used in preparing the catalyst were not modified, the contents of cobalt and iron in the first step hydrogenation catalyst were 10 wt% and 20 wt%, respectively, and the hydrogenation reaction conditions were: reaction temperature 110°C, reaction pressure 9.0 MPa, solution space velocity 0.5 h -1 , gas space velocity 300h -1 The ruthenium and nickel contents in the second step hydrogenation catalyst were 1wt% and 1.5wt% respectively, and the reaction conditions were: reaction temperature 145°C, reaction pressure 7.0MPa, solution space velocity 0.12h -1 , gas space velocity 300h -1 .

[0061] Performance Testing

[0062]

[0063] The performance of the catalyst prepared by modifying the carrier used in the present invention is significantly better than that of the catalyst prepared by using the unmodified carrier. At the same time, the method of the present invention can achieve true continuous operation, avoid many disadvantages of continuous reactor operation, effectively reduce operating costs, and improve operating efficiency.

[0064] Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A continuous production method of 1,3-cyclohexyldimethylamine, characterized in that: It is obtained by using two fixed bed reactors connected in series to carry out two-step continuous hydrogenation reaction; In the first step of hydrogenation, isophthalonitrile is dissolved in a solvent as a reactant, and a cobalt-iron catalyst supported on a modified carrier is used at a temperature of 80°C to 120°C, a pressure of 4MPa to 10MPa, and a solution space velocity of 0.3h -1 ~0.6h -1 Under the condition of , hydrogenation is carried out with hydrogen to generate a m-xylylenediamine reaction liquid; The second step of hydrogenation uses a ruthenium nickel catalyst on a modified carrier at a temperature of 120°C to 160°C, a pressure of 4MPa to 10MPa, and a solution space velocity of 0.1h -1 ~0.2h -1 The product is hydrogenated with hydrogen under the conditions of 1,3-cyclohexyldimethylamine.

2. The method for continuous production of 1,3-cyclohexyldimethylamine according to claim 1, characterized in that: The modified carrier includes a carrier and an alkali metal modifier loaded on the carrier, and the mass content of the alkali metal modifier is 3%~5%; the carrier is a Ø3 clover alumina carrier, and the alkali metal modifier is one or more of NaNO3, NaOH, and KOH.

3. The continuous production method of 1,3-cyclohexyldimethylamine according to claim 2, characterized in that: The preparation method of the modified carrier is: The alkali metal modifier is prepared into an aqueous solution, heated to 55-65° C., and evenly sprayed onto the carrier by an equal amount impregnation method, and then dried and calcined at 210-230° C. to obtain a modified carrier.

4. The method for continuous production of 1,3-cyclohexyldimethylamine according to claim 2, characterized in that: The cobalt-iron catalyst supported on a modified carrier comprises a modified carrier, and metal cobalt and metal iron supported on the modified carrier in sequence, wherein the mass content of the metal cobalt is 5% to 35%, and the mass content of the metal iron is 5% to 35%.

5. The method for continuous production of 1,3-cyclohexyldimethylamine according to claim 4, characterized in that: The preparation method of the cobalt-iron catalyst supported on the modified carrier comprises: (1) Cobalt nitrate is prepared into a 60-65°C aqueous solution, and is evenly sprayed on the modified carrier by an equal amount impregnation method, followed by drying, and then calcining at 440-460°C; this step is repeated until the required cobalt content in the catalyst is reached to obtain a cobalt-containing catalyst; (2) preparing ferric nitrate into a 40-45° C. aqueous solution, spraying it uniformly on the cobalt-containing catalyst by an equal amount impregnation method, and then drying it, and then calcining it at 440-460° C., repeating this step until the iron content in the catalyst reaches the required level, thereby obtaining the cobalt-iron catalyst supported on the modified carrier.

6. The method for continuous production of 1,3-cyclohexyldimethylamine according to claim 2, characterized in that: The ruthenium-nickel catalyst supported on a modified carrier comprises a modified carrier, and metal ruthenium and metal nickel supported on the modified carrier in sequence, wherein the mass content of the metal ruthenium is 0.1% to 3%, and the mass content of the metal nickel is 1% to 3%.

7. The method for continuous production of 1,3-cyclohexyldimethylamine according to claim 6, characterized in that: The preparation method of the ruthenium nickel catalyst supported on the modified carrier comprises: The ruthenium chloride is prepared into a 65-70°C aqueous solution, sprayed on the carrier by an equal amount impregnation method, and then dried, and then calcined at 440-460°C; this step is repeated until the ruthenium content in the catalyst reaches the required level, thereby obtaining a ruthenium-containing catalyst; (2) nickel nitrate is prepared into a 60-70°C aqueous solution, and sprayed uniformly on the ruthenium-containing catalyst of (2) by an equal amount impregnation method, followed by drying, and then calcining at 440-450°C, and this step is repeated until the nickel content in the catalyst reaches the required level, thereby obtaining the ruthenium nickel catalyst supported on the modified carrier.

8. The method for continuous production of 1,3-cyclohexyldimethylamine according to claim 1, characterized in that: Isophthalonitrile needs to be dissolved with a solvent before use, and the concentration of isophthalonitrile after dissolution accounts for 2~3wt% of the total amount of reactants.

9. The method for continuous production of 1,3-cyclohexyldimethylamine according to claim 1, characterized in that: The cobalt-iron catalyst carried on the modified carrier and the ruthenium-nickel catalyst carried on the modified carrier need to be reduced with hydrogen before adding the raw materials; the reduction temperature of the cobalt-iron catalyst carried on the modified carrier is 370-385°C, and the reduction temperature of the ruthenium-nickel catalyst carried on the modified carrier is 240-260°C.

10. The method for continuous production of 1,3-cyclohexyldimethylamine according to claim 1, characterized in that: The raw material used in the second step of hydrogenation is the reaction liquid obtained in the first step of hydrogenation.

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