A method for recycling of by-product cyclohexene distillation still bottoms

Abstract

The application discloses a recycling method of by-product cyclohexene distillation still residue, and belongs to the technical field of recycling of by-product cyclohexene distillation still residue. The still residue is analyzed by liquid chromatography-mass spectrometry, and the chlorocyclohexane in the still residue is reacted with sodium disulfide under the condition of a catalyst. After static separation, the oil phase is refined to obtain dicyclohexyl disulfide and cyclohexene, and the water phase can be recycled. The catalyst is composed of sulfonated castor oil and a phase transfer catalyst, can improve the conversion rate of chlorocyclohexane and the selectivity of dicyclohexyl disulfide, and greatly shortens the reaction time. The application can realize recycling and utilization of the still residue, avoids waste of resources and pollution to the environment, saves the chemical production cost, and meets the environmental protection concept of green chemical industry.

Description

Technical Field

[0001] This invention relates to the technical field of recycling residues from cyclohexene distillation kettles, specifically to a method for recycling residues from cyclohexene distillation kettles. Background Technology

[0002] Dicyclohexyl disulfide is an important fine chemical intermediate, a key intermediate in the preparation of N-cyclohexylthiophthalimide (CTP), a rubber additive and anti-scorching agent. It is also a new type of food flavoring approved by the Ministry of Health of my country, belonging to the thioether flavoring category. There are two main methods for synthesizing dicyclohexyl disulfide: the cyclohexyl mercaptan oxidation method and the halocyclohexane sulfidation method. The cyclohexyl mercaptan oxidation method is accompanied by a foul odor, and the raw materials and catalysts are difficult to obtain, so it has been largely phased out. The halocyclohexane sulfidation method is more economical in preparing dicyclohexyl disulfide, with milder reaction conditions, but the reaction time is longer. In the process of preparing dicyclohexyl disulfide by reacting chlorocyclohexane with disodium disulfide, in addition to the main product dicyclohexyl disulfide, a small amount of crude cyclohexene byproduct is also generated. After distillation, dicyclohexyl disulfide and cyclohexene are obtained separately. Cyclohexene can be used to produce adipic acid, adipic aldehyde, and cyclohexaldehyde. It is an important intermediate in organic reactions and can also be used as an extractant or a stabilizer for gasoline with a high octane number, and can be sold as a commercial product.

[0003] After the cyclohexene distillation process, a portion of high-boiling-point distillation vessel residue is generated. This residue mainly consists of unreacted cyclohexane chloride, incompletely separated cyclohexene, carried dicyclohexyl disulfide, and cyclohexene polymers. Due to its complex composition, it is difficult to separate and reuse, and is usually disposed of as hazardous waste, which not only impacts the environment but also increases costs and has low economic benefits. Furthermore, when the cyclohexane chloride in the residue reacts again with disodium disulfide, the conversion rate is extremely low, the reaction process is slow, and the product yield decreases accordingly. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for recycling the by-product cyclohexene distillation vessel residue. This method recovers and reuses the main components in the residue, namely chlorocyclohexane, cyclohexene and dicyclohexyl disulfide. The reaction conditions are mild, the operation is safe and simple, the reaction time is shortened, the utilization rate of the distillation vessel residue is improved, and the pollution to the environment and the waste of resources are reduced.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for recycling cyclohexene distillation vessel residue as a byproduct includes the following steps:

[0007] S1. Take a sample of the residue from the distillation of the by-product cyclohexene and perform qualitative and quantitative analysis using liquid chromatography-mass spectrometry to determine the contents of the main components chlorocyclohexane, cyclohexene and dicyclohexyl disulfide.

[0008] S2. Based on the content of chlorocyclohexane in the reactor residue, following the molar ratio of chlorocyclohexane:sodium sulfide:sulfur = 1:(0.4~0.8):(0.3~0.8), add sodium sulfide, sulfur and water or mother liquor and stir, then heat to 60~80℃ and keep warm for 0.5~1.5h until completely dissolved to obtain disodium disulfide solution;

[0009] S3. Add a measured amount of cyclohexene distillation vessel residue to the disodium disulfide solution obtained in step S2, and add a catalyst at the same time. Under the conditions of temperature of 80-110℃ and pressure of 0.8-2.5MPa, stir the reaction in a closed container for 4-6 hours, then cool down and let it stand to separate the phases. After separation, an oil phase containing crude dicyclohexyl disulfide and cyclohexene, an aqueous phase containing the catalyst, and sodium chloride are obtained respectively.

[0010] S4. Pass the oil phase obtained in step S3 through a distillation column, and after distillation, separate dicyclohexyl disulfide and cyclohexene. The sodium chloride obtained is separated and recovered, and the aqueous phase containing the catalyst can be recycled.

[0011] The catalyst is obtained by compounding sulfonated castor oil with a phase transfer catalyst.

[0012] Preferably, the molar ratio follows chlorocyclohexane:sodium sulfide:sulfur = 1:(0.5-0.6):(0.5-0.6).

[0013] Furthermore, the disodium disulfide solution has a mass fraction of 10-30%.

[0014] Furthermore, the sulfonated castor oil is 0.1 to 0.5‰ of the volume of the aqueous phase.

[0015] Furthermore, the phase transfer catalyst is one of polyethylene glycol-400, tetrabutylammonium bisulfate, tetrabutylammonium bromide, tetrabutylammonium chloride, and benzyltriethylammonium bromide.

[0016] Furthermore, the phase transfer catalyst is 0.5 to 1‰ of the mass of chlorocyclohexane.

[0017] Furthermore, the cyclohexene and dicyclohexyl disulfide originally present in the reactor residue enter the oil phase together.

[0018] Furthermore, the aqueous phase containing the catalyst can be used as a mother liquor to prepare a disodium disulfide solution for recycling.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] (1) A method for recycling cyclohexene distillation kettle residue, a byproduct of the present invention, utilizes a catalyst composed of sulfonated castor oil and a phase transfer catalyst. This method requires less material, has a fast reaction rate, high conversion efficiency, and reduces production costs. Sulfonated castor oil, as an anionic surfactant, consists of nonpolar lipophilic and polar hydrophilic groups. It can reduce the surface tension of liquids and form micelles in solution, exhibiting excellent emulsifying, penetrating, dispersing, solubilizing, and wetting properties. As a catalyst, sulfonated castor oil can reduce the surface tension between the organic and aqueous phases, promoting the reaction of chlorocyclohexane with disodium disulfide, increasing the conversion rate of chlorocyclohexane and the selectivity of dicyclohexyl disulfide. When sulfonated castor oil is combined with the phase transfer catalyst, the catalyst can carry sulfur anions from the aqueous phase into the organic phase, further accelerating the reaction and significantly shortening the reaction time. After the catalytic reaction is complete, the catalyst in the aqueous phase can be separated and recycled, reducing recovery costs. At the same time, using water as the reaction medium effectively reduces the use of organic solvents, making it an environmentally friendly green chemical process.

[0021] (2) A method for recycling cyclohexene distillation vessel residue, a byproduct of this invention, involves quantitatively analyzing the main component, chlorocyclohexane, in the residue and then, with a matching amount of disodium disulfide, converting it back into dicyclohexyl disulfide under the action of a catalyst. This improves the utilization rate of chlorocyclohexane and simultaneously recovers the vessel residue and the compounds obtained during the process. The resulting crude cyclohexene, after rectification, can be used industrially to produce adipic acid, adipaldehyde, and cyclohexaldehyde, which are important chemical raw materials. The recovery process is simple, avoids resource waste, saves production costs in the chemical industry, and reduces environmental pollution from the vessel residue, thus conforming to the environmental protection concept of green chemistry. Detailed Implementation

[0022] The present invention will now be further described in conjunction with specific embodiments. It should be noted that, without conflict, the embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0023] In the examples, 60% sodium sulfide, sulfur, sulfonated castor oil, and phase transfer catalyst are all chemical raw materials that can be purchased from the market.

[0024] Example 1

[0025] This embodiment provides a method for recycling cyclohexene distillation kettle residue as a byproduct, comprising the following steps:

[0026] S1. Qualitative and quantitative analysis of the residue sample after distillation of the by-product cyclohexene using liquid chromatography-mass spectrometry was performed. The results showed that the content of chlorocyclohexane was 40.32%, the content of cyclohexene was 14.99%, and the content of dicyclohexyl disulfide was 8.1%.

[0027] S2. Preparation of disodium disulfide: Weigh 660 kg of 60% sodium sulfide, 165 kg of sulfur, and 4000 L of water. Control the temperature at 70℃ and stir to dissolve for 1 hour to obtain a disodium disulfide solution.

[0028] S3. Add 3000L of reactor residue to the disodium disulfide solution, along with 0.5L of sulfonated castor oil and 1.2kg of polyethylene glycol-400. Under the conditions of 110℃ and 0.8MPa, stir the mixture in a sealed container for 6 hours, then cool it down and allow it to stand for phase separation.

[0029] S4. By liquid chromatography-mass spectrometry analysis, the crude dicyclohexyl disulfide content in the oil phase was found to be 45.62%, and the cyclohexene content was 16.86%.

[0030] S5. The separated oil phase is passed through a distillation column, and cyclohexene and dicyclohexyl disulfide are separated by distillation. The aqueous phase containing the catalyst is recycled, and sodium chloride is separated and recovered.

[0031] Example 2

[0032] This embodiment provides a method for recycling cyclohexene distillation kettle residue as a byproduct, comprising the following steps:

[0033] S1. Qualitative and quantitative analysis of the residue sample after distillation of the by-product cyclohexene using liquid chromatography-mass spectrometry was performed. The results showed that the content of chlorocyclohexane was 40.28%, the content of cyclohexene was 15.12%, and the content of dicyclohexyl disulfide was 7.6%.

[0034] S2. Preparation of disodium disulfide: Weigh 560 kg of 60% sodium sulfide, 140 kg of sulfur, and 2500 L of mother liquor. Control the temperature at 60℃ and stir to dissolve for 1.5 h to obtain disodium disulfide solution.

[0035] S3. Add 2500L of reactor residue to the disodium disulfide solution, along with 1.5L of sulfonated castor oil and 0.55kg of tetrabutylammonium bromide. Stir the mixture in a sealed container for 4 hours at 80℃ and 2.5MPa, then cool and allow it to stand for phase separation.

[0036] S4. By liquid chromatography-mass spectrometry analysis, the crude dicyclohexyl disulfide content in the oil phase was found to be 45.35%, and the cyclohexene content was 16.62%.

[0037] S5. The separated oil phase is passed through a distillation column, and cyclohexene and dicyclohexyl disulfide are separated by distillation. The aqueous phase containing the catalyst is recycled, and sodium chloride is separated and recovered.

[0038] Example 3

[0039] This embodiment provides a method for recycling cyclohexene distillation kettle residue as a byproduct, comprising the following steps:

[0040] S1. Qualitative and quantitative analysis of the residue sample after distillation of the by-product cyclohexene using liquid chromatography-mass spectrometry was performed. The results showed that the content of chlorocyclohexane was 41.64%, the content of cyclohexene was 14.55%, and the content of dicyclohexyl disulfide was 6.8%.

[0041] S2. Preparation of disodium disulfide: Weigh 468 kg of 60% sodium sulfide, 120 kg of sulfur, and 3500 L of water. Control the temperature at 65℃ and stir to dissolve for 1.5 h to obtain a disodium disulfide solution.

[0042] S3. Add 2000L of reactor residue to the disodium disulfide solution, along with 1L of sulfonated castor oil and 1kg of benzyltriethylammonium bromide. Stir the mixture in a sealed container for 5 hours at 100℃ and 1.5MPa, then cool and allow it to stand for phase separation.

[0043] S4. By liquid chromatography-mass spectrometry analysis, the crude dicyclohexyl disulfide content in the oil phase was found to be 46.44%, and the cyclohexene content was 16.32%.

[0044] S5. The separated oil phase is passed through a distillation column, and cyclohexene and dicyclohexyl disulfide are separated by distillation. The aqueous phase containing the catalyst is recycled, and sodium chloride is separated and recovered.

[0045] Example 4

[0046] This embodiment provides a method for recycling cyclohexene distillation kettle residue as a byproduct, comprising the following steps:

[0047] S1. Qualitative and quantitative analysis of the residue sample after distillation of the by-product cyclohexene using liquid chromatography-mass spectrometry was performed. The results showed that the content of chlorocyclohexane was 40.86%, the content of cyclohexene was 14.8%, and the content of dicyclohexyl disulfide was 7.4%.

[0048] S2. Preparation of disodium disulfide: Weigh 640 kg of 60% sodium sulfide, 157 kg of sulfur, and 3000 L of mother liquor. Control the temperature at 68℃ and stir to dissolve for 1.2 h to obtain disodium disulfide solution.

[0049] S3. Add 2800L of reactor residue to the disodium disulfide solution, along with 1.2L of sulfonated castor oil and 0.7kg of tetrabutylammonium hydrogen sulfate. Stir the mixture under sealed conditions at 90℃ and 2.0MPa for 5.5h, then cool and allow it to stand for phase separation.

[0050] S4. By liquid chromatography-mass spectrometry analysis, the crude dicyclohexyl disulfide content in the oil phase was found to be 45.76%, and the cyclohexene content was 16.05%.

[0051] S5. The separated oil phase is passed through a distillation column, and cyclohexene and dicyclohexyl disulfide are separated by distillation. The aqueous phase containing the catalyst is recycled, and sodium chloride is separated and recovered.

[0052] Example 5

[0053] This embodiment provides a method for recycling cyclohexene distillation kettle residue as a byproduct, comprising the following steps:

[0054] S1. Qualitative and quantitative analysis of the residue sample after distillation of the by-product cyclohexene using liquid chromatography-mass spectrometry was performed. The results showed that the content of chlorocyclohexane was 41.54%, the content of cyclohexene was 14.68%, and the content of dicyclohexyl disulfide was 6.9%.

[0055] S2. Preparation of disodium disulfide: Weigh 400 kg of 60% sodium sulfide, 124 kg of sulfur, and 2000 L of mother liquor. Control the temperature at 70℃ and stir to dissolve for 1 h to obtain disodium disulfide solution.

[0056] S3. Add 2200L of reactor residue to the disodium disulfide solution, along with 0.5L of sulfonated castor oil and 1kg of tetrabutylammonium hydrogen sulfate. Under conditions of 90℃ and 2.5MPa, stir the mixture in a sealed container for 6 hours, then cool and allow it to stand for phase separation.

[0057] S4. By liquid chromatography-mass spectrometry analysis, the crude dicyclohexyl disulfide content in the oil phase was found to be 46.12%, and the cyclohexene content was 16.45%.

[0058] S5. The separated oil phase is passed through a distillation column, and cyclohexene and dicyclohexyl disulfide are separated by distillation. The aqueous phase containing the catalyst is recycled, and sodium chloride is separated and recovered.

[0059] Comparative Example 1

[0060] This comparative example provides a method for recycling cyclohexene distillation vessel residue as a byproduct, comprising the following steps:

[0061] S1. A sample of the residue from the distillation of cyclohexene, the same byproduct as in Example 1, was subjected to qualitative and quantitative analysis by liquid chromatography-mass spectrometry. The results showed that the content of chlorocyclohexane was 40.32%, the content of cyclohexene was 14.99%, and the content of dicyclohexyl disulfide was 8.1%.

[0062] S2. Preparation of disodium disulfide: Weigh 660 kg of 60% sodium sulfide, 165 kg of sulfur, and 4000 L of water. Control the temperature at 70℃ and stir to dissolve for 1 hour to obtain a disodium disulfide solution.

[0063] S3. Add 3000L of reactor residue to the disodium disulfide solution, and add 0.5L of sulfonated castor oil at the same time. Under the conditions of 110℃ and 0.8MPa, stir and react in a closed container for 6 hours, and then cool down and let stand to separate the phases.

[0064] S4. By liquid chromatography-mass spectrometry analysis, the crude dicyclohexyl disulfide content in the oil phase was found to be 31.22%, the cyclohexene content was 15.59%, and the chlorocyclohexane content was 12.85%.

[0065] S5. The separated oil phase is passed through a distillation column, and cyclohexene and dicyclohexyl disulfide are separated by distillation. The aqueous phase containing the catalyst is recycled, and sodium chloride is separated and recovered.

[0066] Comparative Example 2

[0067] This comparative example provides a method for recycling cyclohexene distillation vessel residue as a byproduct, comprising the following steps:

[0068] S1. A sample of the residue from the distillation of cyclohexene, the same byproduct as in Example 1, was subjected to qualitative and quantitative analysis by liquid chromatography-mass spectrometry. The results showed that the content of chlorocyclohexane was 40.32%, the content of cyclohexene was 14.99%, and the content of dicyclohexyl disulfide was 8.1%.

[0069] S2. Preparation of disodium disulfide: Weigh 660 kg of 60% sodium sulfide, 165 kg of sulfur, and 4000 L of water. Control the temperature at 70℃ and stir to dissolve for 1 hour to obtain a disodium disulfide solution.

[0070] S3. Add 3000L of reactor residue to the disodium disulfide solution, and simultaneously add 1.2kg of polyethylene glycol-400. Under the conditions of 110℃ and 0.8MPa, stir and react in a sealed manner for 6h, and then cool down and let stand to separate the phases.

[0071] S4. By liquid chromatography-mass spectrometry analysis, the crude dicyclohexyl disulfide content in the oil phase was found to be 34.6%, the cyclohexene content was 16.82%, and the chlorocyclohexane content was 11.04%.

[0072] S5. The separated oil phase is passed through a distillation column, and after distillation, cyclohexene and dicyclohexyl disulfide are separated and recovered by sodium chloride.

[0073] Comparative Example 3

[0074] This comparative example provides a method for recycling cyclohexene distillation vessel residue as a byproduct, comprising the following steps:

[0075] S1. A sample of the residue from the distillation of cyclohexene, the same byproduct as in Example 1, was subjected to qualitative and quantitative analysis by liquid chromatography-mass spectrometry. The results showed that the content of chlorocyclohexane was 40.32%, the content of cyclohexene was 14.99%, and the content of dicyclohexyl disulfide was 8.1%.

[0076] S2. Preparation of disodium disulfide: Weigh 660 kg of 60% sodium sulfide, 165 kg of sulfur, and 4000 L of water. Control the temperature at 70℃ and stir to dissolve for 1 hour to obtain a disodium disulfide solution.

[0077] S3. Add 3000L of reactor residue to the disodium disulfide solution, and stir the mixture under closed conditions at 110℃ and 0.8MPa for 6 hours. Then cool down and allow the mixture to stand to separate the phases.

[0078] S4. By liquid chromatography-mass spectrometry analysis, the contents of chlorocyclohexane in the oil phase were found to be 25.86%, the contents of crude dicyclohexyl disulfide were 20.65%, and the contents of cyclohexene were 15.42%.

[0079] S5. The separated oil phase is passed through a distillation column, and after distillation, cyclohexene and dicyclohexyl disulfide are separated and recovered by sodium chloride.

[0080] Comparative Example 4

[0081] This comparative example provides a method for recycling cyclohexene distillation vessel residue as a byproduct, comprising the following steps:

[0082] S1. A sample of the residue from the distillation of cyclohexene, the same byproduct as in Example 1, was subjected to qualitative and quantitative analysis by liquid chromatography-mass spectrometry. The results showed that the content of chlorocyclohexane was 40.32%, the content of cyclohexene was 14.99%, and the content of dicyclohexyl disulfide was 8.1%.

[0083] S2. Preparation of disodium disulfide: Weigh 660 kg of 60% sodium sulfide, 165 kg of sulfur, and 4000 L of water. Control the temperature at 70℃ and stir to dissolve for 1 hour to obtain a disodium disulfide solution.

[0084] S3. Add 3000L of reactor residue to the disodium disulfide solution, and add 0.5L of sulfonated castor oil at the same time. Under the conditions of 110℃ and 0.8MPa, stir and react in a closed container for 10h, and then cool down and let stand to separate the phases.

[0085] S4. By liquid chromatography-mass spectrometry analysis, the crude dicyclohexyl disulfide content in the oil phase was found to be 40.26%, and the cyclohexene content was 15.84%.

[0086] S5. The separated oil phase is passed through a distillation column, and cyclohexene and dicyclohexyl disulfide are separated by distillation. The aqueous phase containing the catalyst is recycled, and sodium chloride is separated and recovered.

[0087] The results of Examples 1 and Comparative Examples 1-4 show that when sulfonated castor oil is used alone as a catalyst, it can promote the reaction of chlorocyclohexane with disodium disulfide over a longer reaction time, and the selectivity of dicyclohexyl disulfide is stronger. However, in a shorter reaction time, the yield of dicyclohexyl disulfide is low, the reaction is incomplete, and the catalytic effect of sulfonated castor oil cannot be fully utilized. When the phase transfer catalyst is used alone, although the reaction time is faster, the selectivity of dicyclohexyl disulfide decreases, and more cyclohexene is generated. Without the addition of a catalyst, the reaction between chlorocyclohexane and disodium disulfide solution is extremely poor, the yield of dicyclohexyl disulfide is low, and chlorocyclohexane is not completely removed, which is not conducive to the recovery of residues. In the catalytic system prepared in this invention, sulfonated castor oil can reduce the surface tension of the liquid, and the phase transfer catalyst can promote the ion exchange between the aqueous phase and the organic phase. The two work synergistically, exhibiting a faster reaction rate and higher product selectivity.

[0088] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for recycling cyclohexene distillation kettle residue as a byproduct, characterized in that, Includes the following steps: S1. Take a sample of the residue from the distillation of the by-product cyclohexene and perform qualitative and quantitative analysis using liquid chromatography-mass spectrometry to determine the contents of the main components chlorocyclohexane, cyclohexene and dicyclohexyl disulfide. S2. Based on the content of chlorocyclohexane in the reactor residue, following the molar ratio of chlorocyclohexane:sodium sulfide:sulfur = 1:(0.4~0.8):(0.3~0.8), add sodium sulfide, sulfur and water or mother liquor and stir, then heat to 60~80℃ and keep warm for 0.5~1.5h until completely dissolved to obtain disodium disulfide solution; S3. Add a measured amount of cyclohexene distillation vessel residue to the disodium disulfide solution obtained in step S2, and add a catalyst at the same time. Under the conditions of temperature of 80-110℃ and pressure of 0.8-2.5MPa, stir the reaction in a closed container for 4-6 hours, then cool down and let it stand to separate the phases. After separation, an oil phase containing crude dicyclohexyl disulfide and cyclohexene, an aqueous phase containing the catalyst, and sodium chloride are obtained respectively. S4. Pass the oil phase obtained in step S3 through a distillation column, and after distillation, separate dicyclohexyl disulfide and cyclohexene. The sodium chloride obtained is separated and recovered, and the aqueous phase containing the catalyst can be recycled. The catalyst was obtained by compounding sulfonated castor oil with a phase transfer catalyst. The phase transfer catalyst is one of polyethylene glycol-400, tetrabutylammonium bisulfate, tetrabutylammonium bromide, tetrabutylammonium chloride, and benzyltriethylammonium bromide.

2. The method for recycling the byproduct cyclohexene distillation vessel residue according to claim 1, characterized in that, The disodium disulfide solution has a mass fraction of 10-30%.

3. The method for recycling the byproduct cyclohexene distillation vessel residue according to claim 1, characterized in that, The sulfonated castor oil is 0.1 to 0.5‰ of the volume of the aqueous phase.

4. The method for recycling the byproduct cyclohexene distillation vessel residue according to claim 1, characterized in that, The phase transfer catalyst is 0.5 to 1‰ of the mass of chlorocyclohexane.

5. A method for recycling cyclohexene distillation vessel residue as a byproduct according to claim 1, characterized in that, The cyclohexene and dicyclohexyl disulfide originally present in the reactor residue entered the oil phase together.

6. The method for recycling the byproduct cyclohexene distillation vessel residue according to claim 1, characterized in that, The aqueous phase containing the catalyst can be used as a mother liquor to prepare disodium disulfide solution and recycled.