CN110372516B - Method for preparing cyclohexylamine - Google Patents
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- CN110372516B CN110372516B CN201910732002.2A CN201910732002A CN110372516B CN 110372516 B CN110372516 B CN 110372516B CN 201910732002 A CN201910732002 A CN 201910732002A CN 110372516 B CN110372516 B CN 110372516B
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- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
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- C07C209/00—Preparation of compounds containing amino groups bound to a carbon skeleton
- C07C209/04—Preparation of compounds containing amino groups bound to a carbon skeleton by substitution of functional groups by amino groups
- C07C209/14—Preparation of compounds containing amino groups bound to a carbon skeleton by substitution of functional groups by amino groups by substitution of hydroxy groups or of etherified or esterified hydroxy groups
- C07C209/16—Preparation of compounds containing amino groups bound to a carbon skeleton by substitution of functional groups by amino groups by substitution of hydroxy groups or of etherified or esterified hydroxy groups with formation of amino groups bound to acyclic carbon atoms or to carbon atoms of rings other than six-membered aromatic rings
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- C07—ORGANIC CHEMISTRY
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- C07C209/00—Preparation of compounds containing amino groups bound to a carbon skeleton
- C07C209/68—Preparation of compounds containing amino groups bound to a carbon skeleton from amines, by reactions not involving amino groups, e.g. reduction of unsaturated amines, aromatisation, or substitution of the carbon skeleton
- C07C209/70—Preparation of compounds containing amino groups bound to a carbon skeleton from amines, by reactions not involving amino groups, e.g. reduction of unsaturated amines, aromatisation, or substitution of the carbon skeleton by reduction of unsaturated amines
- C07C209/72—Preparation of compounds containing amino groups bound to a carbon skeleton from amines, by reactions not involving amino groups, e.g. reduction of unsaturated amines, aromatisation, or substitution of the carbon skeleton by reduction of unsaturated amines by reduction of six-membered aromatic rings
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Abstract
The invention discloses a method for preparing high-yield and high-purity cyclohexylamine. The method comprises the following steps: (1) reacting raw materials of aniline, ammonia gas, hydrogen and water in a fixed bed reactor filled with a hydrogenation catalyst under a gas-phase reaction condition to obtain a reaction solution; (2) and (2) reacting the reaction liquid obtained in the step (1) with a sulfhydryl compound, and then rectifying to obtain a cyclohexylamine product. The method has the advantages that the used catalyst is used for continuously synthesizing cyclohexylamine, and has the advantages of mild reaction conditions, long service life of the catalyst, difficult pulverization, difficult influence on the post-treatment process and high yield of cyclohexylamine; meanwhile, the cyclohexylamine product obtained by the method has high purity, does not contain Schiff base, and is suitable for industrial large-scale production.
Description
Technical Field
The invention relates to a preparation method of an organic compound, and more particularly relates to a method for preparing cyclohexylamine with high yield and high purity.
Background
Cyclohexylamine is an important fine chemical intermediate and a raw material with extremely wide application in organic synthesis industry, and can be used for preparing cyclohexanol, cyclohexanone, caprolactam, acetate fiber, nylon 6 and the like. The cyclohexylamine is a solvent and can be applied to resins, coatings, fats and paraffin oil. It can also be used for preparing desulfurizer, rubber antioxidant, vulcanization accelerator, plastic and textile chemical auxiliary agent, boiler feed water treatment agent, metal corrosion inhibitor, emulsifier, antiseptic, antistatic agent, latex coagulant, petroleum additive, bactericide, pesticide and dye intermediate. The synthesis method mainly comprises five methods: aniline catalytic hydrogenation, nitrocyclohexylamine reduction, cyclohexanol catalytic ammonolysis, phenol hydroammoniation and nitrobenzene one-step cyclohexylamine preparation. At present, besides a few foreign enterprises adopt a cyclohexanol catalytic ammonolysis method to produce cyclohexylamine, domestic manufacturers all adopt an aniline catalytic hydrogenation reduction method to produce cyclohexylamine due to lack of corresponding ammonolysis catalysts. The aniline hydrogenation method is divided into gas phase hydrogenation and liquid phase hydrogenation, the liquid phase method is to carry out liquid phase catalytic hydrogenation in a kettle type reactor, according to the report of the patent US2822392, the liquid phase method needs to be carried out under the conditions that the hydrogen pressure is 1.7-69 MPa and the temperature is about 200-; the gas phase method is a hydrogenation reaction carried out in a fixed bed reactor of a gas-solid phase catalyst, and the gas phase method has the advantages of simple process, easy operation, high safety, low equipment investment and the like, so the gas phase method is the most commonly used method for synthesizing cyclohexylamine by domestic manufacturers at present.
Chinese patent publication CN102633649B discloses a method for synthesizing cyclohexylamine by aniline gas-phase catalytic hydrogenation. The method mixes fresh hydrogen and circulating hydrogen, and then mixes the mixed hydrogen with aniline according to a molar ratio of 15: 1-19: 1 mixing and gasifying aniline in an aniline evaporator; and (3) carrying out hydrogenation reaction on the gasified mixed gas in a fixed bed hydrogenation reactor with a cobalt ruthenium catalyst or a nickel ruthenium catalyst in advance under the conditions of the reaction temperature of 165-179 ℃ and the reaction pressure of 0.2-0.3MPa to obtain a cyclohexylamine reaction liquid. The invention has low reaction pressure and low requirement on the material of equipment, but has the defects of lower yield of the cyclohexylamine which is only about 93 percent, and simultaneously does not explain the conversion rate of the aniline and the quality conditions of byproducts and a rectification product of the cyclohexylamine.
U.S. patent publication No. 5705700 discloses the preparation of a mixture of cyclohexylamine and dicyclohexylamine by catalytic hydrogenation of aniline at elevated temperature and pressure in a two-stage reactor system comprising two reduced, unsupported catalysts A and B, both of which are extruded from oxide or hydroxide powders. The catalyst A comprises one or more of Fe, Co and Ni, and also comprises one or more of Mn, Cu and Ca, Sr and Ba; catalyst B comprises one or more of Fe, Co, Ni, and also comprises Mn, Si and Mg. The invention has the advantages that the yield of the cyclohexylamine and the dicyclohexylamine with different proportions can be obtained by changing the temperature and the space velocity of the reaction, and the range is wide. Under the optimal process conditions: the reaction temperature is 190 ℃, the reaction pressure is 30MPa, the yield of the cyclohexylamine is only 90.6 percent, the yield is low, in addition, the high reaction temperature can influence the service life of the catalyst, the reaction pressure is high, the catalyst is a great hazard source for factories, and the requirements on the material and the type selection of equipment are very high.
U.S. patent publication No. 3196179A discloses a method for preparing cyclohexylamine from aniline under the action of rhodium catalyst, which comprises subjecting aniline, hydrogen and catalyst to liquid phase hydrogenation in autoclave, wherein the reaction time varies with the reaction temperature, pressure and catalyst amount, and the yield of cyclohexylamine is more than 96%, and the maximum yield of cyclohexylamine is 97.6%, the invention has the advantages of high yield of cyclohexylamine and the disadvantages of: 1. expensive catalyst is used, so that the production cost is high; 2. the reaction is an intermittent process, the production automation degree is low, the labor intensity is high, and safety accidents are easy to happen.
According to the research of the inventor, in the process of producing cyclohexylamine from aniline, a Schiff base substance is generated due to inevitable certain amount of moisture in raw materials, and the structure of the Schiff base substance is shown as follows.
Its formation mechanism is as follows:
although the boiling point of the Schiff base is high, the Schiff base is unstable at high temperature and can undergo a reversible reaction to generate cyclohexanone and cyclohexylamine, the cyclohexanone is carried to the top of the tower in the rectification process and generates the Schiff base at the top of the tower, and the Schiff base can generate macromolecular substances with the cyclohexylamine and the cyclohexanone to cause product loss. According to the analysis of cyclohexylamine products in the market, the products contain a certain amount of Schiff base, the content of the Schiff base can influence the downstream use, generally cannot exceed 0.1 wt% in high-end application, and in addition, the Schiff base contained in the raw materials can easily cause the product to turn yellow to influence the phase.
The prior art has the following defects:
(1) the process for preparing cyclohexylamine adopts an intermittent process, the operation process is complex, the automation degree is low, and the catalyst is easy to break under the action of a stirring paddle and leaks to a post-treatment system, so that the product decomposition and some safety problems are caused.
(2) The prior art adopts a process for preparing cyclohexylamine by fixed bed gas phase hydrogenation, and the yield of the cyclohexylamine is low. Further, according to the present inventors' study on the process for synthesizing cyclohexylamine by the gas phase method, it was found that the deamination light component is easily produced and the catalyst life is short although the reaction rate is high and the treatment ability per catalyst is high when the reaction temperature is high.
(3) The cyclohexylamine product contains a certain amount of Schiff base, so that high-quality cyclohexylamine cannot be obtained, and the product loss is caused.
Disclosure of Invention
Aiming at the defects of the technology, the invention provides a method for continuously preparing cyclohexylamine from aniline, ammonia gas, hydrogen and water, which can obtain high-yield and high-purity cyclohexylamine.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a process for preparing cyclohexylamine, comprising the steps of:
(1) reacting raw materials of aniline, ammonia gas, hydrogen and water in a gas-phase reaction condition through a fixed bed reactor filled with a hydrogenation catalyst to obtain a reaction solution;
(2) and (2) reacting the reaction liquid obtained in the step (1) with a sulfhydryl compound, and then rectifying to obtain a cyclohexylamine product.
As a preferred technical scheme, the preparation method of cyclohexylamine of the invention comprises the following steps:
(1) aniline, ammonia gas, hydrogen and water as raw materials pass through a fixed bed reactor filled with a Co-precipitation Co-based catalyst under certain reaction conditions to obtain reaction liquid;
(2) and (2) reacting the reaction liquid obtained in the step (1) with a mercapto compound, and then rectifying to obtain a cyclohexylamine product.
In the invention, the raw materials of aniline, ammonia gas, hydrogen and water have a molar ratio of hydrogen to aniline of 5-25: 1, preferably 8 to 15: 1. the volume ratio of ammonia to hydrogen is 1-15: 1, preferably 5 to 10: 1. the mass ratio of water to aniline is 0.001-0.05: 1, preferably 0.002 to 0.03: 1. the addition of ammonia has two effects: the first is to inhibit the deamination reaction of cyclohexylamine from generating dicyclohexylamine, if the volume concentration of ammonia gas is too low, the generation amount of dicyclohexylamine is too large, and if the volume concentration of ammonia gas is too high, the partial pressure of hydrogen is insufficient, and the conversion rate of aniline is too low; the second function is that under the condition of the present catalytic system and the existence of ammonia gas, the byproduct cyclohexanol is easy to produce hydroamination reaction to generate cyclohexylamine. The main product cyclohexylamine is easier to adsorb on the surface of the catalyst than the raw material, and the solubility of water to cyclohexylamine is higher, so that the adsorption of cyclohexylamine on the surface of the catalyst can be reduced by adding water, the aniline is easier to perform hydrogenation reaction on the surface of the catalyst, and the water also plays a role in cleaning the catalyst, so that the service life of the catalyst is prolonged; too low water content, insufficient aniline conversion rate and too high water content can increase the schiff base content of byproducts and the cyclohexanol content in cyclohexanone hydrogenation, which affects the yield of cyclohexylamine. It should be noted that the proportions of the raw materials must be such that the catalyst is contacted with the raw materials under the reaction conditions, which is a gas-solid reaction, but not a gas-liquid reaction, because the gas-liquid reaction can cause the catalyst to be easily deactivated.
In the invention, the reaction temperature in the step (1) is 150-180 ℃, preferably 155-170 ℃; the reaction pressure is 0.1-0.5MPa (absolute pressure), preferably 0.2-0.4MPa (absolute pressure); the space velocity (based on aniline) is from 0.1 to 1g/g (cat)/h, preferably from 0.2 to 0.5g/g (cat)/h.
The Co-precipitated Co-based catalyst of the present invention comprises: the content of cobalt oxide is 15-50wt%, preferably 30-40wt%, the content of copper oxide is 5-10wt%, preferably 4-8wt%, the content of silver oxide is 0.5-3wt%, preferably 1-2wt%, and the balance is carrier barium carbonate.
The preparation method of the Co-precipitation Co-based catalyst comprises the following steps:
1) preparing soluble cobalt salt, soluble copper salt, soluble silver salt and soluble barium salt into aqueous solution according to corresponding proportion, dripping a precipitator into the aqueous solution at the reaction temperature of 80-90 ℃, and aging after the reaction is finished to obtain suspension of a corresponding mixture;
2) and (4) carrying out suction filtration on the turbid liquid to obtain a solid phase and a liquid phase, washing the solid phase, drying, roasting, and tabletting to obtain the catalyst.
As a preferred embodiment, the preparation method of the Co-precipitated Co-based catalyst of the present invention comprises the following steps:
1) preparing aqueous solution from cobalt nitrate, copper nitrate, silver nitrate and barium nitrate according to corresponding proportion, dropwise adding a precipitator into the aqueous solution at the reaction temperature of 80-90 ℃, controlling the PH value to be 9-10 in the reaction process, and preserving heat and aging for 2-4 hours at the temperature of 60-70 ℃ after the reaction is finished to obtain suspension of a corresponding mixture;
2) and carrying out vacuum filtration on the suspension to obtain a solid-liquid two phase, washing the solid phase with deionized water until the content of alkali metal is less than 0.2wt%, drying at the temperature of 100-750 ℃ for 24-36h, roasting at the temperature of 650-750 ℃ for 6-8h, and finally tabletting and forming to obtain the oxidized catalyst.
The catalyst is required to be reduced before use, the reduction step is a conventional scheme in the field, and for example, the catalyst can be fully reduced for 24 hours by using a mixed gas of hydrogen and nitrogen (in a volume ratio of 1: 5) at 220 ℃ and 1 MPa.
The coprecipitator can be one or more of sodium carbonate, potassium carbonate and ammonium carbonate, and sodium carbonate is preferred.
The mercapto compound in step (2) of the present invention may be one or more selected from the group consisting of mercaptopyridine, mercaptoethylamine, 1-mercaptododecane, mercaptooctane, and octadecanethiol, preferably mercaptooctane.
The reaction temperature in the step (2) of the invention is 25-100 ℃, preferably 40-80 ℃, the reaction pressure is normal pressure, and the reaction time is 15min-2 h.
In the system, the addition of water is favorable for separating cyclohexylamine from the surface of the catalyst, so that the catalyst has higher activity, the reaction can be carried out at low temperature, and the content of light components such as cyclohexane, cyclohexene and benzene generated by deamination is low; the barium carbonate carrier is difficult to dissolve in water, and the surface of the catalyst is washed by water vapor, which is equivalent to the on-line regeneration of the catalyst, so the service life of the catalyst is longer. Although the addition of water also leads to an increased content of imine to cyclohexanone, the latter mainly occurs in the following two reactions.
The cyclohexanone is directly hydrogenated to generate cyclohexanol.
Cyclohexanone reacts with cyclohexylamine to produce schiff base.
However, in the present catalytic system and in the presence of ammonia, a portion of the cyclohexanol produced will undergo hydroamination reaction with ammonia to produce cyclohexylamine, as follows.
The Schiff base can also generate a hydrogenation reaction to generate dicyclohexylamine under the catalytic system, and the reaction is as follows.
However, a small amount of Schiff base is inevitably generated in the reaction, and the Schiff base is converted into a heavy component by utilizing the fact that the sulfhydryl compound is very easy to perform addition reaction with the Schiff base, so that the subsequent rectification is not influenced, and a high-purity cyclohexylamine product without the Schiff base is obtained.
The amount of the mercapto compound of the present invention is determined according to the schiff base content in the reaction solution, and the molar ratio of the mercapto compound to the schiff base is 1.01 to 1.50, preferably 1.05 to 1.10: 1. the amount of the schiff base is calculated by detecting the content of the schiff base in the reaction solution obtained in the step (1) by gas chromatography and multiplying the total mass of the reaction solution.
In the invention, the rectification conditions in the step (2) are as follows: under normal pressure, the theoretical plate number of the rectifying column is 10-30, preferably 15-20; the reflux ratio is from 1 to 10:1, preferably from 2 to 5: 1.
The beneficial effects of the invention are:
(1) surprisingly, the addition of water can improve the activity of the catalyst, the conversion rate of the aniline is more than 99.9 percent, so that the aniline does not need to be refined and recycled, the energy consumption and the difficulty of post-treatment are reduced, and in addition, the water carries out on-line regeneration on the catalyst, so the service life of the catalyst can be prolonged.
(2) Under the environment of the catalytic system and ammonia gas, most of the byproduct cyclohexanol can be converted into cyclohexylamine, so that the yield of the cyclohexylamine is improved, the byproduct treatment is reduced, and the technology is more green and environment-friendly. In addition, the method has mild reaction conditions, effectively reduces the occurrence of side reactions, and is also beneficial to prolonging the service life of the catalyst.
(3) A small amount of Schiff base as a byproduct reacts with a sulfhydryl compound to generate a heavy component, so that subsequent separation is not influenced, and a high-quality cyclohexylamine product without Schiff base can be obtained, wherein the yield of the cyclohexylamine can be more than or equal to 98.5%, and the purity can be more than or equal to 99.9%.
(4) The invention is a fixed bed continuous process, has high automation degree, low labor intensity and simple process operation, and simultaneously, compared with a series of thermal decomposition safety problems caused by the decomposition of post-treatment products due to easy crushing and filtration leakage of a catalyst in an intermittent process, the continuous process is safer and is suitable for industrial mass production. The catalyst prepared by the invention is used for continuously synthesizing cyclohexylamine, and has the advantages of mild reaction conditions, long service life, difficult pulverization, difficult influence on post-treatment process and high yield of cyclohexylamine; meanwhile, the cyclohexylamine product obtained by the method has high purity, does not contain Schiff base, and is suitable for industrial large-scale production.
Detailed Description
The invention is further illustrated by the following examples, but is not limited to the examples set forth.
The conditions for gas chromatographic analysis in the following examples were: an Agilent DB-5 chromatographic column, wherein the injection port temperature is 280 ℃, the FID detector temperature is 300 ℃, the column flow rate is 1.5ml/min, the hydrogen flow rate is 40ml/min, the air flow rate is 400ml/min, the temperature programming mode is that the temperature is kept for 5min at 60 ℃, and the temperature is increased to 280 ℃ at 15 ℃/min and kept for 5 min.
Example 1
Preparation of No. 1 Co-precipitated Co-based catalyst:
310.74g of cobalt nitrate hexahydrate, 37.73g of copper nitrate, 2.93g of silver nitrate and 135.08g of barium nitrate are dissolved in 2000ml of deionized water and heated to 90 ℃ to form a uniform solution, 25 wt% of sodium carbonate aqueous solution is slowly added into the solution, the pH value is controlled to be 9-10 in the reaction process, after the reaction is finished, the temperature is kept and the aging is carried out for 4 hours at 60 ℃ to obtain a suspension of a corresponding mixture, then the suspension is subjected to vacuum filtration and separation, a solid phase is washed by the deionized water until the sodium content is less than 0.2wt%, the solid phase is naturally dried and then is dried at 120 ℃ for 24 hours, then is roasted at 700 ℃ for 6 hours, and finally, tabletting and forming is carried out to obtain the catalyst in an oxidation state of 3 x 3mm, wherein the cobalt oxide content is 40wt%, the copper oxide content is 8wt%, the silver oxide content is 1 wt%, and the balance is carrier barium carbonate.
Example 2
Preparation of # 2 Co-precipitated Co-based catalyst:
271.90g of cobalt nitrate hexahydrate, 28.30g of copper nitrate, 5.86g of silver nitrate and 150.98g of barium nitrate are dissolved in 2000ml of deionized water and heated to 85 ℃ to form a uniform solution, 25 wt% of sodium carbonate aqueous solution is slowly added into the solution, the pH value is controlled to be 9-10 in the reaction process, after the reaction is finished, the temperature is kept and the aging is carried out for 2 hours at 70 ℃ to obtain a suspension of a corresponding mixture, then the suspension is subjected to vacuum filtration and separation, a solid phase is washed by the deionized water until the sodium content is less than 0.2wt%, the solid phase is naturally dried, then dried for 36 hours at 110 ℃, then roasted for 6 hours at 750 ℃, and finally, tabletting and forming are carried out to obtain the catalyst in an oxidation state of 3 x 3mm, wherein the cobalt oxide content is 35 wt%, the copper oxide content is 6 wt%, the silver oxide content is 2wt%, and the balance is carrier barium carbonate.
Example 3
Preparation of No. 3 Co-precipitated Co-based catalyst:
116.53g of cobalt nitrate hexahydrate, 47.16g of copper nitrate, 1.47g of silver nitrate and 197.33g of barium nitrate are dissolved in 2000ml of deionized water, the mixture is heated to 80 ℃ to form a uniform solution, 25 wt% of sodium carbonate aqueous solution is slowly added into the solution, the pH value is controlled to be 9-10 in the reaction process, after the reaction is finished, the mixture is subjected to heat preservation and aging for 2 hours at 65 ℃ to obtain a suspension of the corresponding mixture, then vacuum filtration and separation are carried out, a solid phase is washed by the deionized water until the sodium content is less than 0.2wt%, the solid phase is naturally dried, then is dried for 48 hours at 100 ℃, then is roasted for 8 hours at 650 ℃, and finally tabletting and forming are carried out to obtain the catalyst in an oxidation state of 3 x 3mm, wherein the cobalt oxide content is 15 wt%, the copper oxide content is 10wt%, the silver oxide content is 0.5 wt%, and the balance is carrier barium carbonate.
Example 4
The reaction is carried out on a fixed bed reactor, the inner diameter is 20mm, the length of the tube is 1000mm, quartz sand of 10-20 meshes washed by 5 wt% of dilute nitric acid is filled at the upper part and the bottom of the fixed bed, and 100g of No. 1 Co-precipitation Co-based catalyst is filled in the middle part.
Before the catalyst is used, the catalyst is fully reduced for 24 hours by using a mixed gas of hydrogen and nitrogen (the volume ratio is 1: 5) at 220 ℃ and 1 MPa.
Aniline, ammonia gas, hydrogen and water enter a reactor from the top of a fixed bed, and raw materials are mixed and gasified and then enter a bed layer containing a catalyst for reaction. The reaction temperature is 155 ℃, the reaction pressure is 0.3MPa, the space velocity of the aniline is 0.2g/g (cat)/h, the molar ratio of the hydrogen to the aniline is 10:1, the mass ratio of the water to the aniline is 0.01:1, and the volume ratio of the ammonia gas to the hydrogen gas is 10: 1. After the reaction is stably operated for 24 hours, the reaction liquid is subjected to gas-liquid separation, condensation and gas chromatography analysis by sampling, and the conversion rate of the aniline is 100%, the selectivity of the cyclohexylamine is 99.05%, the selectivity of the dicyclohexylamine is 0.65%, the selectivity of the Schiff base is 0.18% and the selectivity of the cyclohexanol is 0.08%.
Taking 500g of the reaction liquid to react with mercaptooctane at the temperature of 60 ℃, wherein the molar ratio of the added mercaptooctane to the Schiff base is 1.10:1, directly carrying out normal pressure rectification after reacting for 30 minutes, and the rectification conditions are as follows: the theoretical plate number of the rectifying column is 15, the reflux ratio is 3:1, the fraction obtained at the tower top temperature of 134 ℃ is analyzed by gas chromatography, the purity of the cyclohexylamine is 99.98 percent, and Schiff base is not contained.
Example 5
The reaction is carried out on a fixed bed reactor, the inner diameter is 20mm, the length of the tube is 1000mm, the upper part and the bottom of the fixed bed are filled with 10-20 meshes of quartz sand washed by 5 wt% of dilute nitric acid, and the middle part is filled with 100g of a No. 2 Co-precipitation Co-based catalyst.
Before the catalyst is used, the catalyst is fully reduced for 24 hours by using a mixed gas of hydrogen and nitrogen (the volume ratio is 1: 5) at 220 ℃ and 1 MPa.
Aniline, ammonia gas, hydrogen and water enter a reactor from the top of a fixed bed, and raw materials are mixed and gasified and then enter a bed layer containing a catalyst for reaction. The reaction temperature is 160 ℃, the reaction pressure is 0.2MPa, the space velocity of the aniline is 0.3g/g (cat)/h, the molar ratio of the hydrogen to the aniline is 12:1, the mass ratio of the water to the aniline is 0.005:1, and the volume ratio of the ammonia gas to the hydrogen is 5: 1. After the reaction is stably operated for 24 hours, the reaction liquid is subjected to gas-liquid separation, condensation and gas chromatography analysis by sampling, so that the conversion rate of the aniline is 100%, the selectivity of the cyclohexylamine is 98.84%, the selectivity of the dicyclohexylamine is 0.83%, the selectivity of the Schiff base is 0.15% and the selectivity of the cyclohexanol is 0.06%.
Taking 500g of the reaction liquid to react with octadecanethiol at 50 ℃, wherein the molar ratio of the octadecanethiol addition to the Schiff base is 1.05:1, after reacting for 30 minutes, directly carrying out normal pressure rectification under the following rectification conditions: the theoretical plate number of the rectifying column is 20, the reflux ratio is 2:1, the fraction obtained at the tower top temperature of 134 ℃ is analyzed by gas chromatography, the purity of the cyclohexylamine is 99.95 percent, and Schiff base is not contained.
Example 6
The reaction is carried out on a fixed bed reactor, the inner diameter is 20mm, the length of the tube is 1000mm, the upper part and the bottom of the fixed bed are filled with 10-20 meshes of quartz sand washed by 5 wt% of dilute nitric acid, and the middle part is filled with 100g of 3# precipitation type Co-based catalyst.
The catalyst was fully reduced with a mixed gas of hydrogen and nitrogen (volume ratio 1: 5) at 220 ℃ under 1MPa for 24 hours before use.
Aniline, ammonia gas, hydrogen and water enter a reactor from the top of a fixed bed, and raw materials are mixed and gasified and then enter a bed layer containing a catalyst for reaction. The reaction temperature is 180 ℃, the reaction pressure is 0.1MPa, the space velocity of the aniline is 0.5g/g (cat)/h, the molar ratio of the hydrogen to the aniline is 15:1, the mass ratio of the water to the aniline is 0.03:1, and the volume ratio of the ammonia gas to the hydrogen is 10: 1. After the reaction is stably operated for 24 hours, the reaction liquid is subjected to gas-liquid separation, condensation and gas chromatography analysis by sampling, so that the conversion rate of the aniline is 100%, the selectivity of the cyclohexylamine is 98.60%, the selectivity of the dicyclohexylamine is 1.01%, the selectivity of the Schiff base is 0.23% and the selectivity of the cyclohexanol is 0.08%. Taking 500g of the reaction liquid to react with mercaptooctane at the temperature of 80 ℃, wherein the molar ratio of the added mercaptooctane to the Schiff base is 1.20:1, directly carrying out normal pressure rectification after reacting for 30 minutes, and the rectification conditions are as follows: the theoretical plate number of the rectifying column is 30, the reflux ratio is 1:1, the fraction obtained at the tower top temperature of 134 ℃ is analyzed by gas chromatography, the purity of the cyclohexylamine is 99.92 percent, and Schiff base is not contained.
The 3# precipitation type Co-based catalyst is adopted to carry out a catalyst life test, the reaction conditions are the same, the catalyst still keeps a good state when the catalyst runs on a reactor for 3000 hours, and the catalyst is stable in form and free from the phenomena of pulverization and the like. The lifetime test data are detailed in table 1.
TABLE 1 data of life test results
Comparative example 1
The reaction is carried out on a fixed bed reactor, the inner diameter is 20mm, the length of the tube is 1000mm, the upper part and the bottom of the fixed bed are filled with 10-20 meshes of quartz sand washed by 5 wt% of dilute nitric acid, and the middle part of the fixed bed is filled withCo-based catalyst (active component Co) special for preparing cyclohexylamine by filling commercial aniline3O4The carrier is Ca (OH) with the content of 54.5 percent2)。
Before the catalyst is used, the catalyst is fully reduced for 24 hours by using a mixed gas of hydrogen and nitrogen (the volume ratio is 1: 5) at 220 ℃ and 1 MPa.
Aniline, ammonia gas and hydrogen gas enter a reactor from the top of a fixed bed, and raw materials are mixed and gasified and then enter a bed layer containing a catalyst for reaction. The reaction temperature is 180 ℃, the reaction pressure is 0.1MPa, the space velocity of the aniline is 0.5g/g (cat)/h, the molar ratio of the hydrogen to the aniline is 15:1, and the volume ratio of the ammonia gas to the hydrogen is 10: 1. After the reaction is stably operated for 24 hours, the reaction liquid is subjected to gas-liquid separation, condensation and gas chromatography analysis by sampling, so that the conversion rate of aniline is 99.50%, the selectivity of cyclohexylamine is 95.41%, the selectivity of dicyclohexylamine is 3.78%, the selectivity of Schiff base is 0.11% and the selectivity of cyclohexanol is 0.05%.
When the catalyst is used for a catalyst life experiment, the reaction conditions are the same, the catalyst is operated on a reactor for 1000 hours, the activity of the catalyst is gradually reduced, the conversion rate of aniline is gradually reduced, and the selectivity of cyclohexylamine is also gradually reduced. The lifetime test data are detailed in table 2.
Table 2 data of life test results
Claims (10)
1. A process for preparing cyclohexylamine, comprising the steps of:
(1) reacting raw materials of aniline, ammonia gas, hydrogen and water in a gas-phase reaction condition through a fixed bed reactor filled with a hydrogenation catalyst to obtain a reaction solution;
(2) reacting the reaction liquid obtained in the step (1) with a sulfhydryl compound, and then rectifying to obtain a cyclohexylamine product;
the hydrogenation catalyst in the step (1) is a coprecipitation Co-based catalyst, and the catalyst comprises: the cobalt oxide content is 15-50wt%, the copper oxide content is 5-10wt%, the silver oxide content is 0.5-3wt%, and the balance is carrier barium carbonate, wherein the mercapto compound in the step (2) is selected from one or more of mercaptopyridine, mercaptoethylamine, 1-mercaptododecane, mercaptooctane and octadecanethiol.
2. The method of claim 1, wherein the Co-precipitated Co-based catalyst comprises: the content of cobalt oxide is 30-40wt%, the content of copper oxide is 4-8wt%, the content of silver oxide is 1-2wt%, and the balance is barium carbonate as a carrier.
3. The method according to claim 1 or 2, characterized in that said Co-precipitated Co-based catalyst is prepared by the following steps: 1) preparing soluble cobalt salt, soluble copper salt, soluble silver salt and soluble barium salt into aqueous solution according to corresponding proportion, dripping a precipitator into the aqueous solution at the reaction temperature of 80-90 ℃, and aging after the reaction is finished to obtain suspension of a corresponding mixture; 2) and (4) carrying out suction filtration on the suspension to obtain a solid-liquid two phase, washing the solid phase, drying, roasting, and tabletting to obtain the catalyst.
4. The method as claimed in claim 3, wherein in step 1), the reaction process is controlled to have a pH value of 9-10, the mixture is aged at 60-70 ℃ for 2-4 hours, and in step 2), the solid phase is washed with deionized water until the alkali metal content is less than 0.2wt%, dried at 100-120 ℃ for 24-36 hours, and then calcined at 650-750 ℃ for 6-8 hours.
5. The method according to claim 3, wherein the precipitant is selected from one or more of sodium carbonate, potassium carbonate and ammonium carbonate.
6. The process according to any one of claims 1-2, wherein the molar ratio of hydrogen to aniline is from 5 to 25: 1; the volume ratio of ammonia to hydrogen is 1-15: 1; the mass ratio of water to aniline is 0.001-0.05: 1.
7. the method as claimed in any one of claims 1-2, wherein the reaction temperature in step (1) is 150-180 ℃; the reaction pressure is 0.1-0.5 MPa; the space velocity is 0.1-1g/g cat/h based on aniline.
8. The method according to any one of claims 1-2, wherein the mercapto compound in step (2) is selected from mercaptooctane; the amount of the mercapto compound is determined according to the Schiff base content in the reaction solution obtained in the step (1), and the molar ratio of the mercapto compound to the Schiff base is 1.01-1.50.
9. The method according to any one of claims 1 to 2, wherein in the step (2), the reaction temperature is 25 to 100 ℃; the reaction time is 15min-2 h.
10. The method according to any one of claims 1-2, wherein in step (2), the rectification conditions are: the number of theoretical plates of the rectifying column is 10-30; the reflux ratio is 1-10: 1.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JPS5168539A (en) * | 1974-12-10 | 1976-06-14 | Shin Nippon Rika Kk | Shikanjiaminno seizoho |
| WO2012018310A1 (en) * | 2010-08-02 | 2012-02-09 | Duslo, A.S. | Process for the production of highly pure dicyclohexylamine from by-products resulting from the producton of cyclohexylamine |
| CN102516087A (en) * | 2011-10-25 | 2012-06-27 | 江苏诺盟化工有限公司 | Resource utilization preparation method for high-purity dicyclohexyl amine |
| CN105237434A (en) * | 2015-10-29 | 2016-01-13 | 中石化南京工程有限公司 | Method for producing cyclohexanone oxime |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5168539A (en) * | 1974-12-10 | 1976-06-14 | Shin Nippon Rika Kk | Shikanjiaminno seizoho |
| WO2012018310A1 (en) * | 2010-08-02 | 2012-02-09 | Duslo, A.S. | Process for the production of highly pure dicyclohexylamine from by-products resulting from the producton of cyclohexylamine |
| CN102516087A (en) * | 2011-10-25 | 2012-06-27 | 江苏诺盟化工有限公司 | Resource utilization preparation method for high-purity dicyclohexyl amine |
| CN105237434A (en) * | 2015-10-29 | 2016-01-13 | 中石化南京工程有限公司 | Method for producing cyclohexanone oxime |
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