A kind of synthetic method of cyclohexane

Abstract

The invention discloses a method for synthesizing cyclohexane, and belongs to the technical field of organic synthesis. The above-mentioned method comprises the following steps: hydrogen and benzene are mixed and added to a heat exchanger to be heated and evaporated into a gas phase, and then a modified nickel catalyst is added at 180-230°C and 36-53 atmospheric pressure to react and separate to obtain cyclohexane. Using the preparation method of the invention, the yield of the prepared cyclohexane is not less than 96%, and the selectivity is not less than 98%.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and particularly relates to a method for synthesizing cyclohexane. Background Art

[0002] Cyclohexane is an important chemical raw material and intermediate with a wide range of uses. About 20% is used in solvents and adhesives, and 80% is used in organic synthesis, mainly for the production of cyclohexanol, cyclohexanone, adipic acid, caprolactam and other products.

[0003] Cyclohexane exists in crude oil. The main methods for industrial production of cyclohexane are petroleum fraction separation and benzene catalytic hydrogenation. The petroleum fraction separation method is to separate the gasoline containing cycloalkanes into a fraction with a boiling range of 65.6-85.3°C, which mainly contains cyclohexane and methylcyclopentane, and then perform isomerization treatment to convert methylcyclopentane into cyclohexane. The treated product is separated and purified to obtain cyclohexane with a purity of more than 95%. The benzene hydrogenation method is currently a commonly used method for producing cyclohexane, that is, benzene is hydrogenated under the action of a catalyst, and the purity of the resulting cyclohexane is higher than that of the petroleum fraction separation method. The catalyst for preparing cyclohexane by hydrogenation of benzene can be Pt, Rh, Ni, Mo and Co. The noble metal Pt and Rh catalysts have high activity and can undergo hydrogenation reactions at room temperature; while the Ni catalyst needs to be at a higher temperature to have sufficient hydrogenation activity, and the metal catalyst has a small particle size and is prone to aggregation, thereby reducing the specific surface area of ​​the gold nanocomposite material and reducing the catalytic activity. In addition, since precious metal materials are expensive and their resources are limited, it is particularly important to increase the number of recycling times of metal catalysts and improve the catalytic efficiency of precious metals to reduce the cost of the catalyst itself.

[0004] Therefore, developing a high-efficiency, high-purity synthesis route for cyclohexane is a technical problem that urgently needs to be solved. Summary of the invention

[0005] The object of the present invention is to provide a method for synthesizing cyclohexane to solve the technical problem of low synthesis efficiency of cyclohexane in the prior art.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A method for synthesizing cyclohexane comprises the following steps:

[0008] Hydrogen and benzene are mixed and added to a heat exchanger to be heated and evaporated into a gas phase, and then a modified nickel catalyst is added at 180-230°C and 36-53 atmospheres to react and separate to obtain cyclohexane.

[0009] As a further embodiment of the present invention, the molar ratio of hydrogen to benzene is (3.5-6):1.

[0010] As a further solution of the present invention, the amount of the modified nickel catalyst used is 20-30% of the mass of benzene.

[0011] As a further embodiment of the present invention, the modified nickel catalyst is prepared by the following steps:

[0012] Add nickel chloride, modified carbon nanotubes and ammonium chloride into deionized water and stir, add concentrated ammonia water and continue stirring, heat to 95-100°C and react for 10-12 hours, naturally cool to room temperature, wash and filter, centrifuge, vacuum dry, grind and sieve; calcine at 580-600°C in a nitrogen atmosphere for 3-5 hours, cool to room temperature, and collect the product, which is the modified nickel catalyst.

[0013] As a further embodiment of the present invention, the usage ratio of nickel chloride, modified carbon nanotubes, ammonium chloride, deionized water and concentrated ammonia water is 0.09-0.10 g: 1.0-1.1 g: 0.53-0.55 g: 70 mL: 1 mL.

[0014] As a further solution of the present invention, the mesh size of the grinding and sieving is 300-500.

[0015] As a further embodiment of the present invention, the modified carbon nanotubes are prepared by the following steps:

[0016] After adding silane coupling agent KH-570 into anhydrous ethanol and stirring to dissolve, adding carbon nanotube aqueous solution, ultrasonic dispersion, stirring reaction, adjusting pH, heating to 50-70°C to continue reaction, cooling to room temperature, centrifugation washing, and drying to obtain modified carbon nanotubes.

[0017] As a further solution of the present invention, the usage ratio of silane coupling agent KH-570, anhydrous ethanol and carbon nanotube aqueous solution is 1g:25mL:20mL; the usage ratio of carbon nanotubes and water in the carbon nanotube aqueous solution is 2g:20mL.

[0018] As a further embodiment of the present invention, the pH is adjusted to 5-6.

[0019] Beneficial effects of the present invention:

[0020] The modified nickel catalyst prepared in the present invention effectively inhibits the agglomeration of the catalyst in the solvent, and the nickel nanoparticles are uniformly loaded on the modified carbon nanotubes without agglomeration. The modified carbon nanotubes have a large specific surface area, a porous structure and excellent thermal stability, and have a strong adsorption force on metal nickel, so that the metal nickel can be uniformly dispersed on the surface and is not easy to fall off, thereby overcoming the disadvantage of poor durability, prolonging the catalyst action time and improving the synthesis conversion efficiency; and the preparation method has low cost and is easy to operate, and the modified nickel catalyst is easy to recover in subsequent treatment, has good recyclability, and is suitable for large-scale production processes.

[0021] The modified carbon nanotubes in the present invention are prepared by reacting carbon nanotubes grafted with silane coupling agent KH-570, which improves the dispersion performance of carbon nanotubes in solvents, further improves the stability of nickel loaded on carbon nanotubes in solvents, prolongs the action time, and improves the catalytic efficiency.

[0022] The preparation method of synthetic cyclohexane of the present invention has a yield of cyclohexane of not less than 96% and a selectivity of not less than 98%. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Example 1

[0025] The embodiment provides a modified nickel catalyst, and the specific preparation steps are as follows:

[0026] 0.09 g of nickel chloride, 1 g of modified carbon nanotubes and 0.53 g of ammonium chloride were added to 70 mL of deionized water and stirred. 1 mL of concentrated ammonia solution was added and the stirring was continued for 0.5 h. The temperature was raised to 100 ° C. and the reaction was stirred for 10 h. The mixture was naturally cooled to room temperature. The mixture was washed with distilled water and anhydrous ethanol for 3 times respectively. The precipitate was filtered and centrifuged. It was dried at 60 ° C. under vacuum conditions for 12 h and ground through a 300-mesh sieve. The mixture was calcined at 600 ° C. in a nitrogen atmosphere for 5 h. The mixture was cooled to room temperature and the product was collected, which is a modified nickel catalyst.

[0027] The modified carbon nanotubes are prepared by the following steps:

[0028] 1 g of silane coupling agent KH-570 was added to 25 mL of anhydrous ethanol and stirred to dissolve, then 20 mL of carbon nanotube aqueous solution (carbon nanotube: water is 2 g: 20 mL) was added, ultrasonically dispersed, stirred, and the pH was adjusted to 5.5 with hydrochloric acid, and the temperature was raised to 65 ° C and the reaction was continued for 5 h. The mixture was cooled to room temperature, washed by centrifugation, and dried in an oven at 40 ° C to obtain modified carbon nanotubes.

[0029] Example 2

[0030] The only difference from Example 1 is that:

[0031] 0.095 g of nickel chloride, 1 g of modified carbon nanotubes and 0.54 g of ammonium chloride were added to 70 mL of deionized water and stirred. 1 mL of concentrated ammonia solution was added and the stirring was continued for 0.5 h. The temperature was raised to 100 ° C. and the reaction was stirred for 12 h. The mixture was naturally cooled to room temperature. The mixture was washed with distilled water and anhydrous ethanol for 3 times respectively. The precipitate was filtered and centrifuged. It was dried at 60 ° C. under vacuum conditions for 12 h and ground through a 300 mesh sieve. The mixture was calcined at 600 ° C. in a nitrogen atmosphere for 5 h. The mixture was cooled to room temperature and the product was collected, which is a modified nickel catalyst.

[0032] The remaining materials and steps are the same as those in Example 1.

[0033] Example 3

[0034] The only difference from Example 1 is that:

[0035] 0.10 g of nickel chloride, 1.05 g of modified carbon nanotubes and 0.54 g of ammonium chloride were added to 70 mL of deionized water and stirred. 1 mL of concentrated ammonia solution was added and the stirring was continued for 0.5 h. The temperature was raised to 100 ° C. and the reaction was stirred for 11 h. The mixture was naturally cooled to room temperature. The mixture was washed with distilled water and anhydrous ethanol for 3 times respectively. The precipitate was filtered and centrifuged. It was dried at 80 ° C. under vacuum conditions for 10 h and ground through a 500-mesh sieve. The mixture was calcined at 600 ° C. in a nitrogen atmosphere for 5 h. The mixture was cooled to room temperature and the product was collected, which is a modified nickel catalyst.

[0036] The remaining materials and steps are the same as those in Example 1.

[0037] Example 4

[0038] This embodiment provides a method for synthesizing cyclohexane:

[0039] According to the molar ratio of hydrogen to benzene being 3.5:1, hydrogen and benzene are mixed and added into a heat exchanger to be heated and evaporated into a gas phase, and then the modified nickel catalyst in Example 1 is added at 200°C and 45 atmospheres. The amount of the modified nickel catalyst in Example 1 is 20% of the mass of benzene, and cyclohexane is obtained by reaction and separation.

[0040] Example 5

[0041] This embodiment provides a method for synthesizing cyclohexane:

[0042] Hydrogen and benzene were mixed at a molar ratio of 3.5:1 and added to a heat exchanger for heating and evaporation into a gas phase. Then, the modified nickel catalyst in Example 2 was added at 200° C. and 45 atmospheres. The amount of the modified nickel catalyst in Example 2 was 25% of the mass of benzene. The mixture was reacted and separated to obtain cyclohexane.

[0043] Example 6

[0044] This embodiment provides a method for synthesizing cyclohexane:

[0045] Hydrogen and benzene were mixed at a molar ratio of 3.5:1 and added to a heat exchanger to be heated and evaporated into a gas phase. The modified nickel catalyst in Example 3 was added at 200°C and 45 atmospheres. The amount of the modified nickel catalyst in Example 3 was 30% of the mass of benzene. The mixture was reacted and separated to obtain cyclohexane.

[0046] Example 7

[0047] This embodiment provides a method for synthesizing cyclohexane:

[0048] Hydrogen and benzene are mixed at a molar ratio of 6:1 and added to a heat exchanger for heating and evaporation into a gas phase. Then, the modified nickel catalyst in Example 3 is added at 190° C. and 36 atmospheres. The amount of the modified nickel catalyst in Example 3 is 30% of the mass of benzene. The mixture is reacted and separated to obtain cyclohexane.

[0049] Comparative Example 1

[0050] This comparative example provides a method for synthesizing cyclohexane:

[0051] According to the molar ratio of hydrogen to benzene being 3.5:1, hydrogen and benzene are mixed and added into a heat exchanger to be heated and evaporated into a gas phase, and then a nickel catalyst is added at 200°C and 45 atmospheres. The amount of the nickel catalyst is 20% of the mass of the benzene, and the reaction is carried out and separated to obtain cyclohexane.

[0052] Comparative Example 2

[0053] This comparative example provides a method for synthesizing cyclohexane:

[0054] According to the molar ratio of hydrogen to benzene being 3.5:1, hydrogen and benzene are mixed and added into a heat exchanger to be heated and evaporated into a gas phase, and then a nickel catalyst is added at 200°C and 45 atmospheres. The amount of the nickel catalyst is 60% of the mass of the benzene, and cyclohexane is obtained by reaction and separation.

[0055] Comparative Example 3

[0056] This comparative example provides a method for synthesizing cyclohexane:

[0057] Hydrogen and benzene are mixed at a molar ratio of 8:1 and added to a heat exchanger for heating and evaporation into a gas phase. Then, the modified nickel catalyst in Example 3 is added at 190° C. and 36 atmospheres. The amount of the modified nickel catalyst in Example 3 is 30% of the mass of benzene. Cyclohexane is obtained by reaction and separation.

[0058] Performance tests were performed on Examples 4 to 7 and Comparative Examples 1 to 3: The yield and selectivity of cyclohexane generated by the reactions in the Examples and Comparative Examples were tested, and the test results are shown in Table 1:

[0059] Table 1

[0060] project Example 4 Example 5 Example 6 Example 7 Comparative Example 1 Comparative Example 2 Comparative Example 3 Yield (%) 96.9 97.1 97.2 96.8 93.2 95.1 95.4 Selectivity (%) 98.2 98.5 98.3 98.5 94.6 95.6 96.6

[0061] From the data in Examples 4-7 and Comparative Examples 1-3 in Table 1, it can be seen that the modified nickel catalyst prepared in the present invention can efficiently convert benzene and hydrogen into cyclohexane with a high yield and a selectivity of cyclohexane of more than 98%. It can be seen that the synthetic route for synthesizing cyclohexane in the present invention has excellent synthetic efficiency.

[0062] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0063] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for synthesizing cyclohexane, characterized in that: The following steps are involved: The hydrogen and benzene are mixed and added to a heat exchanger to be heated and evaporated into a gas phase, and then a modified nickel catalyst is added at 180-230°C and 36-53 atmospheric pressure to react and separate to obtain cyclohexane; wherein the molar ratio of hydrogen to benzene is 3.5-6:1; The modified nickel catalyst is prepared by the following steps: Add nickel chloride, modified carbon nanotubes and ammonium chloride into deionized water and stir, add concentrated ammonia water and continue stirring, heat to 95-100°C and react for 10-12 hours, cool naturally to room temperature, wash and filter, centrifuge, vacuum dry, grind and sieve; calcine at 580-600°C in a nitrogen atmosphere for 3-5 hours, cool to room temperature, and collect the product, which is the modified nickel catalyst; The modified carbon nanotubes are prepared by the following steps: After adding silane coupling agent KH-570 to anhydrous ethanol and stirring to dissolve, adding carbon nanotube aqueous solution, ultrasonic dispersion, stirring reaction, adjusting pH, heating to 50-70°C to continue reaction, cooling to room temperature, centrifugal washing, and drying to obtain modified carbon nanotubes; wherein the pH is adjusted to 5-6.

2. The method for synthesizing cyclohexane according to claim 1, characterized in that: The amount of the modified nickel catalyst used is 20-30% of the mass of benzene.

3. The method for synthesizing cyclohexane according to claim 1, characterized in that: The usage ratio of nickel chloride, modified carbon nanotubes, ammonium chloride, deionized water and concentrated ammonia water is 0.09-0.10 g: 1.0-1.1 g: 0.53-0.55 g: 70 mL: 1 mL.

4. The method for synthesizing cyclohexane according to claim 1, characterized in that: The mesh size of the grinded material is 300-500.

5. The method for synthesizing cyclohexane according to claim 1, characterized in that: The dosage ratio of silane coupling agent KH-570, anhydrous ethanol and carbon nanotube aqueous solution is 1g:25mL:20mL; the dosage ratio of carbon nanotubes and water in the carbon nanotube aqueous solution is 2g:20mL.