A continuous process for the production of 1,3-cyclohexyl dimethylamine

Abstract

The present application relates to the field of organic chemical technology, and more particularly to a continuous production method of 1,3-cyclohexyl dimethylamine, which is obtained by two-step continuous hydrogenation reaction using two fixed-bed reactors in series; in the first step, m-phthalonitrile is dissolved in a solvent as a reactant, and a cobalt-iron catalyst supported on a modified carrier is used to react with hydrogen to generate m-xylylenediamine reaction solution; in the second step, a ruthenium-nickel catalyst supported on a modified carrier is used to react with hydrogen to finally obtain 1,3-cyclohexyl dimethylamine. The continuous production method of 1,3-cyclohexyl dimethylamine provided by the present application reduces the reaction time and material transfer loss through two-step continuous hydrogenation reaction, avoids the stagnation link in batch intermittent process, and ensures a high conversion rate of m-phthalonitrile and a high total yield of 1,3-cyclohexyl dimethylamine.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of organic chemical technology, and particularly relates to a continuous production method of 1,3-cyclohexyl dimethylamine. BACKGROUND

[0002] 1,3-cyclohexyl dimethylamine (1,3-BAC) is also called 1,3-diamine methyl cyclohexane, and its English name is 1,3-cyclohexanedimethanamine. It is an important fine chemical intermediate and also a pesticide intermediate. Because it has the advantages of fast curing speed, good toughness and excellent yellowing resistance, it is mainly used as a curing agent for epoxy resin. The polyurethane resin prepared by using the 1,3-cyclohexyl dimethylamine as a curing agent has high heat resistance, and can be applied to the production of coating hardening agents, aging polymerization inhibitors and coating resins, and has special applications in fiber and film materials, and can also be used as a raw material for dyes, detergents and pharmaceutical intermediates.

[0003] At present, there are few manufacturers in China to produce 1,3-cyclohexyl dimethylamine, and the demand for 1,3-cyclohexyl dimethylamine will gradually increase after MXDA is listed as a toxic chemical.

[0004] US5371293 uses a catalyst of 5% Ru / Al2O3, and in the presence of liquid ammonia, dioxane is used as a solvent, and the m-phthalonitrile is subjected to hydrogenation at a reaction temperature of 140℃ and a reaction pressure of 15MPa, and the yield of the prepared 1,3-cyclohexyl dimethylamine is 87.8%. If the reaction temperature is 100℃ and the reaction pressure is 15MPa, the molar yield of the prepared 1,3-cyclohexyl dimethylamine is 88.3%. If liquid ammonia is not added in the hydrogenation process, the yield of the prepared 1,3-cyclohexyl dimethylamine is only 29%, and a large amount of deamination low-boiling-point by-products are generated.

[0005] EP0703213 uses a supported catalyst, and the solvent used in the reaction is methylamine, dimethylamine, ethylenediamine and the like, the reaction pressure is 5-15MPa, the reaction temperature is 80℃-130℃, and the yield can reach 94%.

[0006] CN101959848 uses a non-supported Ni-Cu-Cr catalyst, and through a fixed-bed continuous reaction process, the 1,3-cyclohexyl dimethylamine is obtained by subjecting 1,3-cyclohexyl dimethyl alcohol to a hydrogenation reaction under the conditions of a reaction temperature of 190℃-220℃ and a reaction pressure of 17MPa, and the selectivity is highest at 72.6%, and a large amount of intermediates and by-products are generated in the product. In addition, because the boiling points of the 1,3-cyclohexyl dimethylamine and the 1,3-cyclohexyl dimethyl alcohol are close, separation is difficult.

[0007] CN113402396 discloses a production method of m-xylylenediamine co-producing 1,3-diamine methylcyclohexane, which reacts m-xylylene cyanide with hydrogen in the presence of a catalyst to generate m-xylylenediamine and 1,3-diamine methylcyclohexane. Through hydrogen cyanide ratio process condition optimization, combined with catalyst modulation, the ratio of target products m-xylylenediamine and 1,3-diamine methylcyclohexane can be adjusted, and the molar ratio of the two is about 9:1 to 1:1.

[0008] CN102911062 discloses a method for preparing 1,3-cyclohexyl dimethylamine, wherein the method is carried out in two stages of hydrogenation in the same solvent, 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 additive, m-xylylene cyanide and hydrogen are reacted to obtain m-xylylenediamine reaction liquid, and the second stage uses activated carbon loaded with ruthenium as a catalyst, and m-xylylenediamine reaction liquid and hydrogen are reacted to obtain 1,3-cyclohexyl dimethylamine. The method uses two high-pressure reaction kettles in series for intermittent operation.

[0009] Currently, there are many problems in the production of 1,3-cyclohexyl dimethylamine, for example: the use of two high-pressure reaction kettles in series cannot realize true continuous hydrogenation operation; there are many side reactions, which will generate by-products covering the surface of the catalyst, thereby reducing the service life of the catalyst; the cyclohexane dimethylol hydrogenation method has problems such as high reaction temperature, high reaction pressure, low raw material conversion rate, and low product selectivity; the preparation of 1,3-cyclohexyl dimethylamine by hydrogenation of m-xylylene cyanide requires the addition of inorganic additives such as liquid ammonia, which increases energy consumption and further increases production cost; and the reaction system cannot effectively inhibit the occurrence of deamination.

[0010] The information disclosed in this BACKGROUND section is only intended to enhance the understanding of the general background of the application and should not be taken as recognition or admission that this information is prior art. SUMMARY

[0011] The technical problem to be solved by the present application is to provide a continuous production method of 1,3-cyclohexyl dimethylamine, which uses two fixed-bed reactors in series for two-step hydrogenation to realize continuous hydrogenation operation and reduce operating costs.

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

[0013] A continuous production method of 1,3-cyclohexyl dimethylamine, which uses two fixed-bed reactors in series for two-step continuous hydrogenation reaction to obtain;

[0014] The first step, hydrogenation, involves dissolving isophthalonitrile in a solvent as a reactant, using a cobalt-iron catalyst supported on a modified support, at a temperature of 80℃–120℃, a pressure of 4 MPa–10 MPa, and a solution space velocity of 0.3 h⁻¹. -1 ~0.6h -1 Under certain conditions, the hydrogen is added to produce a reaction solution of m-phenylenediamine; the first-step hydrogenation catalyst used in this invention can inhibit the condensation reaction during the hydrogenation of isophthalonitrile, thereby improving the service life of the catalyst during 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, using a cobalt-iron catalyst supported on a modified support, at a temperature of 85℃~95℃, a pressure of 9MPa~10MPa, and a gas space velocity of 290h⁻¹. -1 ~310h -1 The solution space velocity is 0.5 h⁻¹. -1 ~0.6h -1 Under certain conditions, it reacts with hydrogen to produce m-phenylenediamine.

[0016] The second step of hydrogenation uses a ruthenium-nickel catalyst supported on a modified support, at a temperature of 120℃~160℃, a pressure of 4MPa~10MPa, and a solution space velocity of 0.1h. -1 ~0.2h -1 Under specific conditions, hydrogenation with hydrogen gas yields 1,3-cyclohexyldimethylamine. The second-step hydrogenation catalyst used in this invention utilizes ruthenium to provide excellent hydrogenation activity, while nickel enhances selectivity for the target cyclic compound (1,3-cyclohexyldimethylamine) and reduces the formation of by-products. This effectively reduces the occurrence of deamination side reactions during the hydrogenation of m-phenylenediamine, significantly improving the yield of the target product, 1,3-cyclohexyldimethylamine.

[0017] Furthermore, the second-step hydrogenation employs a ruthenium-nickel catalyst supported on a modified support, at a temperature of 140℃~150℃, a pressure of 6MPa~8MPa, and a gas space velocity of 290h⁻¹. -1 ~310h -1 Solution space velocity 0.1 h⁻¹ -1 ~0.15h -1 Under certain conditions, hydrogenation with hydrogen gas yields 1,3-cyclohexyldimethylamine.

[0018] Preferably, the modified carrier includes 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 carrier is... Clover-shaped alumina carrier, with an alkali metal modifier being one or more of NaNO3, NaOH, and KOH, preferably KOH.

[0019] The alkali metal modifier can introduce basic centers on the surface of the alumina carrier. Taking KOH as an example, through impregnation and calcination treatment of KOH, part of the KOH is decomposed to generate K2O, which provides stable basic sites on the surface of the carrier. In the first step, the nitrile group is promoted to generate an amine group (m-xylylenediamine), avoiding the generation of amide and other by-products. In the second step, the selectivity of the hydrogenation cyclization reaction is improved, avoiding the generation of over-hydrogenated by-products, and the purity of the target product 1,3-cyclohexyl dimethylamine is improved.

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

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

[0022] As preferred, the cobalt-iron catalyst supported on the modified carrier includes the modified carrier, and metal cobalt and metal iron sequentially supported on the modified carrier. The mass content of the metal cobalt is 5%-35%, and the mass content of the metal iron is 5%-35%. This preparation method of first modifying the carrier and then sequentially supporting cobalt and iron ensures that the modified carrier provides a good basic 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, its first loading can ensure the formation of stable basic active sites, providing protection for the main hydrogenation step of the reaction. Iron as a secondary metal after the loading of cobalt 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] As preferred, the preparation method of the cobalt-iron catalyst supported on the modified carrier includes:

[0024] (1) The cobalt nitrate is prepared into an aqueous solution at 60-65°C, uniformly sprayed onto the modified carrier by equal impregnation method, then dried, and calcined at 440-460°C. This step is repeated until the cobalt content in the catalyst meets the requirement, to obtain a cobalt-containing catalyst;

[0025] (2) The iron nitrate is prepared into an aqueous solution at 40-45°C, uniformly sprayed onto the cobalt-containing catalyst by equal impregnation method, then dried, and calcined at 440-460°C. This step is repeated until the iron content in the catalyst meets the requirement, to obtain the cobalt-iron catalyst supported on the modified carrier.

[0026] As preferred, the ruthenium-nickel catalyst supported on the modified carrier comprises the modified carrier, and the metal ruthenium and the metal nickel successively supported on the modified carrier, the mass content of the metal ruthenium being 0.1% to 3%, and the mass content of the metal nickel being 1% to 3%. The present application forms a bimetallic catalytic system with high synergy by supporting the ruthenium on the modified carrier first and then supporting the nickel. The ruthenium as the main active metal is responsible for the hydrogenation reaction, and the nickel improves the selectivity of the target product in the cyclization process. The preparation of the modified carrier precedes the metal supporting, which ensures that the alkaline modifier fully acts on the surface of the carrier, thereby optimizing the environment and dispersibility of the metal supporting, improving the overall performance of the catalyst, and the first supporting of the ruthenium ensures the formation of stable active sites on the surface of the carrier, which provides the main catalytic capacity for the hydrogenation-cyclization reaction, and the subsequent supporting of the nickel can be more effectively distributed around the ruthenium, forming a uniform ruthenium-nickel synergistic catalytic structure, thereby maximizing its cocatalytic effect.

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

[0028] (1) The ruthenium chloride is prepared into a 65-70℃ aqueous solution, which is sprayed on the carrier by the equal-amount impregnation method, then dried, and then calcined at 440-460℃; the step is repeated until the ruthenium content in the catalyst reaches the requirement, thereby obtaining a ruthenium-containing catalyst;

[0029] (2) The nickel nitrate is prepared into a 60-70℃ aqueous solution, which is uniformly sprayed on the ruthenium-containing catalyst of (2) by the equal-amount impregnation method, then dried, and then calcined at 440-450℃; the step is repeated until the nickel content in the catalyst reaches the requirement, thereby obtaining the ruthenium-nickel catalyst supported on the modified carrier.

[0030] As preferred, the isophthalonitrile needs to be dissolved in a solvent before use. After being dissolved in the solvent, the isophthalonitrile changes from a solid particle state to a molecular state, which can be more fully contacted with hydrogen and the active sites of the catalyst, helping to improve the adsorption rate of the isophthalonitrile on the surface of the catalyst and promote the activation of the nitrile group and the hydrogenation reaction. The concentration of the isophthalonitrile after dissolution accounts for 2-3wt% of the total amount of the reactants. Too high a concentration may increase the amount of reactants loaded on the surface of the catalyst, leading to catalyst poisoning or occupation of the active sites, thereby reducing the performance of the catalyst. The 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] As preferred, the solvent is one or more of methanol, N,N-dimethylethanolamine, N,N-dimethylacetamide, tetrahydrofuran, preferably tetrahydrofuran. Tetrahydrofuran is an excellent polar organic solvent, which has good solubility for isophthalonitrile, and its moderate polarity can effectively dissolve isophthalonitrile and can be uniformly distributed in the liquid phase reaction system, avoiding the coverage of solid particles or insoluble substances on the surface of the catalyst.

[0032] As preferred, the cobalt-iron catalyst supported on the modified carrier and the ruthenium-nickel catalyst supported on the modified carrier need to be reduced by hydrogen before the raw material is added; in the catalyst preparation process, the metal (cobalt, iron, ruthenium, nickel) exists in an oxidized state, through the reduction process, hydrogen reacts with these metal oxides to generate zero-valent metal or low-valent metal, and the reduced metal is in an active state, which can more effectively participate in the hydrogenation reaction.

[0033] Among them, CoO and Fe2O3 have a high reduction temperature, and the reduction temperature of the cobalt-iron catalyst supported on the modified carrier is 370-385 DEG C; the reduction temperature of RuO2 and NiO is relatively low, and the reduction temperature of the ruthenium-nickel catalyst supported on the modified carrier is 240-260 DEG 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 the purity of the target product, fully meeting the needs of industrial continuous production.

[0034] As preferred, the raw material used for the second hydrogenation is the reaction liquid obtained by the first hydrogenation. Continuous production is achieved, avoiding the steps of intermediate product separation, purification and storage, and the active substances in the reaction system are maximally reserved.

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

[0036] (1) The continuous production method of 1,3-cyclohexyl dimethylamine provided by the present application realizes the continuous hydrogenation reaction in two steps, so that the first reaction (isophthalonitrile to m-phenylenediamine) and the second reaction (m-phenylenediamine to 1,3-cyclohexyl dimethylamine) are continuously carried out in two fixed-bed reactors in series, reducing the reaction time and material transfer loss, avoiding the stagnation link in batch intermittent process, and ensuring the high conversion rate of isophthalonitrile and the high total yield of 1,3-cyclohexyl dimethylamine.

[0037] (2) The present application uses a cobalt-iron catalyst supported on a modified carrier in the first step, which provides high activity for the nitrile group hydrogenation reaction and promotes the high selectivity of m-xylylenediamine, and uses a ruthenium-nickel catalyst supported on a modified carrier in the second step, which improves the efficiency of the cyclization reaction by the hydrogenation activity of ruthenium and the selectivity regulation of nickel, reduces side reactions, and selects different catalysts for each step to target the reaction, rather than using a single catalyst to complete both steps, avoiding the risk of reduced selectivity. The modified carrier is modified by alkali metal, which optimizes the metal dispersion and electronic properties of the active sites, thereby improving the selectivity of the target product.

[0038] (3) The reaction solvent such as tetrahydrofuran in the present application can be recycled during the reaction process, reducing solvent loss and waste. The unreacted m-xylylene cyanide and by-products can continue to participate in the subsequent reaction, without generating additional waste. The first reaction solution 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 m-xylylenediamine in the traditional process. DETAILED DESCRIPTION

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

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

[0041] In the embodiments, the specifications of the carrier, the modified carrier and the catalyst are all 3, and each component is purchased from Aldrin.

[0042] Embodiment 1:

[0043] Carrier modification: According to the measurement, the water absorption rate of the alumina carrier is 70%, 10 grams of NaOH is added to 100 mL of deionized water, heated to 60°C, and prepared into a NaOH solution, then the solution is sprayed on 200 grams of alumina carrier, dried and calcined at 220°C to obtain a modified alumina carrier. According to the measurement, the water absorption rate of the modified carrier is still 70%. To obtain a larger amount of modified carrier, the above steps can be repeated or scaled up by the above method.

[0044] Using the same method as described above, the alumina carrier is modified with NaNO3 and KOH to obtain a modified carrier.

[0045] First step 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, heated to 60°C, and the cobalt nitrate solution was evenly sprayed on 20 grams of aluminum oxide carrier by equal 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 iron nitrate solution, heated to 60°C, and the iron nitrate solution was evenly sprayed on the cobalt-containing catalyst obtained in (2) above by equal impregnation method, then dried, and then calcined at 400°C; (4) step (3) was repeated once to obtain a cobalt-iron-containing catalyst. The catalyst contains cobalt and iron at 20% and 10%, respectively.

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

[0047] Hydrogenation reaction: (1) the catalyst prepared above was loaded into a fixed bed reactor, first reduced with hydrogen, the catalyst reduction temperature in the first hydrogenation reactor was 380°C, and the catalyst reduction temperature in the second hydrogenation reactor was 250°C, until reduction was complete; (2) the m-xylylene cyanide was dissolved in tetrahydrofuran solvent to prepare a reaction raw material solution, with a m-xylylene cyanide content of 3 wt%; (3) the raw material solution was passed into the fixed bed reactor, while hydrogen was passed in, the first reactor control conditions were: reaction temperature 80°C, reaction pressure 10.0 MPa, solution space velocity 0.6 h -1 , gas space velocity 300 h -1 ; the second reactor control conditions were: reaction temperature 160°C, reaction pressure 10.0 MPa, solution space velocity 0.2 h -1 , gas space velocity 280 h -1 .

[0048] Example 2:

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

[0050] Example 3:

[0051] Example 1 was repeated, except that the raw material amount was changed according to the composition change, the support was modified with NaOH in the first step hydrogenation catalyst, 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 ; the support was modified with KOH in the second step hydrogenation catalyst, the ruthenium and nickel contents 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 .

[0052] Example 4:

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

[0054] Example 5:

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

[0056] Example 6:

[0057] Example 1 was repeated, except that the raw material amount was changed according to the composition change, the carrier was modified with KOH in the first step hydrogenation catalyst, 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 7.0 MPa, solution space velocity 0.45 h -1 , gas space velocity 300 h -1 ; the carrier was modified with NaNO3in the second step hydrogenation catalyst, the ruthenium and nickel contents were 0.6wt% and 2.5wt% respectively, and the reaction conditions were: reaction temperature 135°C, reaction pressure 9.0 MPa, solution space velocity 0.12 h -1 , gas space velocity 300 h -1 .

[0058] Example 7:

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

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

[0061] Performance test

[0062]

[0063] The performance of the catalyst prepared by modifying the carrier is obviously superior to that of the catalyst prepared by using the unmodified carrier, and the method of the present application can realize continuous operation in a true sense, avoid many disadvantages of continuous reaction kettle operation, effectively reduce the operation cost, and improve the operation efficiency.

[0064] Those skilled in the art should understand that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application, and various changes and improvements can be made without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A process for the continuous production of 1,3-cyclohexyl dimethylamine, characterized in that, The two-step continuous hydrogenation reaction is carried out by using two fixed-bed reactors connected in series to obtain; The first step hydrogenation dissolves the isophthalonitrile in a solvent as a reactant, uses a cobalt-iron catalyst carried on a modified carrier, and carries out hydrogenation with hydrogen gas under the conditions of a temperature of 80-120℃, a pressure of 4-10 MPa, a solution air speed of 0.3-0.6 h -1 -0.6 h -1 , to generate an isophthalonitrile amine reaction solution. The second step hydrogenation is carried out with a ruthenium-nickel catalyst supported on a modified carrier under the conditions of a temperature of 120-160°C, a pressure of 4-10 MPa, a solution space velocity of 0.1-0.2 h -1 -1 and hydrogen to obtain 1,3-cyclohexyl dimethyl amine finally.​ The modified carrier comprises a carrier and an alkali metal modifier supported on the carrier, and the mass content of the alkali metal modifier is 3-5%; the carrier is a 3-leaf clover-shaped aluminum oxide carrier, and the alkali metal modifier is one or more of NaNO3, NaOH and KOH.

2. The process for the continuous production of 1,3-cyclohexyl dimethylamine according to claim 1, characterized in that, The preparation method of the modified carrier is as follows: The alkali metal modifier is prepared into an aqueous solution, heated to 55-65 DEG C, uniformly sprayed onto the carrier, and then dried and calcined at 210-230 DEG C to obtain the modified carrier.

3. The process for continuous production of 1,3-cyclohexyl dimethyl amine as claimed in claim 1 wherein, The cobalt-iron catalyst supported on the modified carrier comprises the modified carrier, and metal cobalt and metal iron supported on the modified carrier in sequence, and the mass content of the metal cobalt is 5-35% and the mass content of the metal iron is 5-35%.

4. The process for the continuous production of 1,3-cyclohexyl dimethylamine according to claim 3, characterized in that, The preparation method of the cobalt-iron catalyst supported on the modified carrier comprises: (1) the cobalt nitrate is prepared into an aqueous solution at 60-65 DEG C, uniformly sprayed onto the modified carrier, and then dried and calcined at 440-460 DEG C; the operation is repeated until the cobalt content in the catalyst reaches the requirement to obtain a cobalt-containing catalyst; (2) the ferric nitrate is prepared into an aqueous solution at 40-45 DEG C, uniformly sprayed onto the cobalt-containing catalyst, and then dried and calcined at 440-460 DEG C; the operation is repeated until the iron content in the catalyst reaches the requirement to obtain the cobalt-iron catalyst supported on the modified carrier.

5. The process for continuous production of 1,3-cyclohexyl dimethyl amine as claimed in claim 1 wherein, The ruthenium-nickel catalyst supported on the modified carrier comprises the modified carrier, and metal ruthenium and metal nickel supported on the modified carrier in sequence, and the mass content of the metal ruthenium is 0.1-3% and the mass content of the metal nickel is 1-3%.

6. The process for the continuous production of 1,3-cyclohexyl dimethylamine according to claim 5, characterized in that, The preparation method of the ruthenium-nickel catalyst supported on the modified carrier comprises: The ruthenium chloride is prepared into an aqueous solution at 65-70 DEG C, uniformly sprayed onto the modified carrier, and then dried and calcined at 440-460 DEG C; the operation is repeated until the ruthenium content in the catalyst reaches the requirement to obtain a ruthenium-containing catalyst; (2) the nickel nitrate is prepared into an aqueous solution at 60-70 DEG C, uniformly sprayed onto the ruthenium-containing catalyst, and then dried and calcined at 440-450 DEG C; the operation is repeated until the nickel content in the catalyst reaches the requirement to obtain the ruthenium-nickel catalyst supported on the modified carrier.

7. The process for continuous production of 1,3-cyclohexyl dimethyl amine as claimed in claim 1, wherein, The isophthalonitrile needs to be dissolved in a solvent before use, and the concentration of the isophthalonitrile after dissolution accounts for 2-3 wt% of the total amount of the reactants.

8. The process for continuous production of 1,3-cyclohexyl dimethyl amine as claimed in claim 1, wherein, The cobalt-iron catalyst supported on the modified carrier and the ruthenium-nickel catalyst supported on the modified carrier need to be reduced by hydrogen before the raw materials are added; the reduction temperature of the cobalt-iron catalyst supported on the modified carrier is 370-385 DEG C, and the reduction temperature of the ruthenium-nickel catalyst supported on the modified carrier is 240-260 DEG C.

9. The process for continuous production of 1,3-cyclohexyl dimethyl amine as claimed in claim 1, wherein, The raw material for the second-step hydrogenation is the reaction liquid obtained by the first-step hydrogenation.

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