Method for azeotropic dehydration of cyclohexene oxide by solution polymerization solvent and coupling method of cyclohexene oxide azeotropic dehydration and polymerization reaction

Abstract

The invention provides a method for carrying out azeotropic dehydration on cyclohexene oxide by using a solution polymerization solvent and a coupling method of the cyclohexene oxide and a polymerization reaction, and the method comprises the following steps: mixing water-containing cyclohexene oxide and the solution polymerization solvent, and carrying out azeotropic dehydration on the obtained mixed material to obtain a mixed material for polymerization; the mixed material for polymerization comprises dehydrated cyclohexene oxide and a solution polymerization solvent. According to the invention, the selected solution polymerization solvent can be azeotropic with water to remove water, and can be used as a polymerization reaction solvent, so that no new impurities are introduced into a polymerization reaction system; a mixture of cyclohexene oxide and a solvent can be added into the polymerization reaction kettle, so that the requirement on the purity of cyclohexene oxide is reduced, and the energy consumption of separation is reduced.

Description

Technical Field

[0001] The invention relates to the field of separation technology, in particular to a method for carrying out azeotropic dehydration of cyclohexene oxide using a solution polymerization solvent and a coupling method thereof with a polymerization reaction. Background Art

[0002] The preparation of aliphatic polycarbonates by ring-opening polymerization of carbon dioxide and propylene oxide is an important research direction for the utilization of carbon dioxide, but the glass transition temperature of polypropylene carbonate (PPC) prepared by it is low (30-40°C), which limits its use in high temperature environments. Cyclohexene oxide, because of its similar structure to propylene oxide and the presence of a rigid six-membered ring, has a high glass transition temperature (Tg>100°C) for polycyclohexene carbonate (PCHC) prepared by copolymerizing it with carbon dioxide, which greatly broadens the scope of use of carbon dioxide-based polycarbonates. By adjusting the ratio of carbon dioxide, propylene oxide and cyclohexene oxide, the glass transition temperature of the ternary copolymer product can be freely adjusted, broadening the scope of use while taking into account the economic efficiency of the product.

[0003] Impurities with active hydrogen (such as water) will affect the induction period of the copolymerization reaction of carbon dioxide and propylene oxide or cyclohexene oxide, reduce production efficiency, and even make the reaction impossible in severe cases. Generally, the water content of cyclohexene oxide participating in the polymerization reaction is required to be less than 200ppm. At present, the water content of cyclohexene oxide produced industrially exceeds 200ppm and cannot be directly used for polymerization reaction, and dehydration treatment is required.

[0004] There are many methods for dehydration in the prior art. For example, in CN117164840A, molecular sieves are used to dehydrate cyclohexene oxide to a water content of 173ppm. However, heat is released during the dehydration process of the molecular sieve, which is dangerous in industrial large-scale dehydration processes. CN116082276B discloses a distillation method for refining ultra-dry cyclohexene oxide, which uses n-hexane as an azeotropic entrainer to remove water. The purified cyclohexene oxide has a purity of more than 99.9% and a water content of less than 150ppm. It has the following disadvantages: 1) because it adopts the intermittent distillation operation mode, the operation is complicated, and in the industrial production process, some transition materials are inevitably present, which affects the overall yield of cyclohexene oxide; 2) using n-hexane azeotropic entrainer to first distill and remove water between 85 and 95° C., and then distill and remove the azeotropic entrainer after the water removal meets the standard, and finally heat up to 133° C. to distill and obtain cyclohexene oxide. The operating temperature needs to be heated or cooled at different stages. Obviously, this is a high-energy consumption treatment method.

[0005] In summary, the current existing technologies focus on how to dehydrate cyclohexene oxide, and do not consider how to adapt to the industrialization needs of the carbon dioxide-based polycarbonate production process. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a method for azeotropic dehydration of cyclohexane with a solution polymerization solvent and a coupling method thereof with a polymerization reaction. The selected solvent can azeotropically remove water with water and, as a solvent for preparing carbon dioxide-based polycarbonate by polymerization reaction, will not affect the polymerization reaction and reduce the purity requirement of the cyclohexane after dehydration, thereby reducing the separation requirement of the azeotropic dehydration and saving energy consumption; at the same time, the operating temperature of the bottom of the tower is reduced, and the side reactions such as hydrolysis / decomposition of the cyclohexane are reduced, so that the quality of the cyclohexane after the dehydration operation can be improved; in addition, no substances other than the polymerization reaction solvent are introduced, which will not affect the polymerization reaction and the quality of the polymerization product.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for azeotropic dehydration of cyclohexene oxide with a solution polymerization solvent, the method comprising: mixing water-containing cyclohexene oxide with a solution polymerization solvent, and azeotropically dehydrating the obtained mixture to obtain a polymerization mixture; the polymerization mixture comprises the dehydrated cyclohexene oxide and the solution polymerization solvent.

[0009] Specifically, conventional azeotropic dehydration in the prior art has the defect of high energy consumption for separating the entrainer from cyclohexene oxide, and inevitably has the defect of low recovery rate of cyclohexene oxide; in addition, according to the difficulty of separating the entrainer from cyclohexene oxide, the cyclohexene oxide after dehydration will contain 0.5-5wt% of the entrainer, and it is very difficult to obtain high-purity cyclohexene oxide and the energy consumption for separation is high. The presence of the entrainer will affect the downstream polymerization reaction, the main effects are: 1) increase the load of the devolatilization unit of the polymerization product; 2) there will be unexpected defects in the polymerization reaction, thereby affecting the polymerization reaction and product quality. This scheme is to overcome the defects of the above-mentioned conventional inherent methods and propose an azeotropic dehydration process of cyclohexane using a solution polymerization solvent as an azeotropic agent. The polymerization mixture obtained after azeotropic dehydration is directly applied to the downstream polymerization reaction containing cyclohexane and carbon dioxide. Because the azeotropic agent is the solvent of the polymerization reaction, the azeotropic agent is contained in the dehydrated mixture, which will not affect the subsequent polymerization reaction, thereby reducing the requirements for the purity of cyclohexane in conventional inherent technologies, and also reducing the separation requirements of azeotropic dehydration. Specifically, the reduction of separation requirements is specifically manifested in: 1) The operating temperature of the tower is reduced, saving energy consumption, and the reaction temperature of the downstream polymerization reaction is about 60 to 90°C. When the downstream polymerization reaction is carried out at a lower tower temperature, the heat exchange energy consumption can be reduced; 2) The operating temperature of the tower is reduced, and the side reactions such as hydrolysis and decomposition of cyclohexane can be reduced, thereby ensuring the quality of the cyclohexane after dehydration.

[0010] It should be noted that the solution polymerization solvent in the present invention needs to meet the following three key points: 1. The solution polymerization solvent can produce azeotropy with water, and the azeotropic system does not contain cyclohexene oxide, so that the solution polymerization solvent can achieve the effect of removing water from cyclohexene oxide; 2. The solution polymerization solvent does not chemically react with cyclohexene oxide or undergo polymerization or decomposition reaction itself under the operating conditions of azeotropic dehydration, which can ensure that the cyclohexene oxide product does not contain other impurities; 3. The solution polymerization solvent can be subsequently used in the polymerization reaction containing cyclohexene oxide, so that the dehydrated cyclohexene oxide can be directly sent to the subsequent polymerization reaction, avoiding the process of separating the azeotroping agent and cyclohexene oxide after dehydration in the prior art, greatly reducing energy consumption, and at the same time avoiding the problem of low purity of cyclohexene oxide caused by incomplete removal of the azeotroping agent, which leads to low quality of the polymerization product obtained by the subsequent polymerization reaction. However, since the solvent of the subsequent polymerization reaction is itself the azeotropic dehydration entrainer, the above-mentioned problem does not exist in the present invention.

[0011] Preferably, the polymerization mixture is directly used for a polymerization reaction containing cyclohexene oxide as a raw material, and the solution polymerization solvent is a solvent for the polymerization reaction. Specifically, the polymerization mixture obtained by the azeotropic dehydration method of this scheme is used to be directly transported to a downstream polymerization reaction.

[0012] Among them, it is necessary to keep the mass content of dehydrated cyclohexane as a reaction raw material in the polymerization mixture not less than 30wt%, so that the solution polymerization solvent used as the polymerization reaction does not need to be removed from the polymerization mixture; of course, if the solution polymerization solvent as the polymerization reaction is insufficient, the solvent can be directly added as needed. In addition, it is necessary to ensure the dehydration effect, reasonable energy consumption, and can be directly transported to the downstream polymerization reaction, and the mass content of dehydrated cyclohexane as a reaction raw material in the polymerization mixture is not higher than 90wt%. Therefore, the proportion of dehydrated cyclohexane in the polymerization mixture is 30-90wt%, for example, it can be 30wt%, 40wt%, 45wt%, 55wt%, 65wt%, 75wt%, 85wt% or 90wt%, preferably 40-86wt%.

[0013] The present invention has no special requirements for the polymerization reaction, and it can be a polymerization reaction containing cyclohexene oxide well known in the art, for example, it can be a polymerization reaction containing cyclohexene oxide and carbon dioxide to prepare carbon dioxide-based polycarbonate.

[0014] Preferably, the polymerization reaction includes any one of binary copolymerization, ternary copolymerization or tetrameric copolymerization.

[0015] Preferably, the binary copolymerization is a binary copolymerization of carbon dioxide and cyclohexene oxide.

[0016] Preferably, the terpolymerization is a terpolymerization of carbon dioxide, propylene oxide and cyclohexene oxide, and / or a terpolymerization of carbon dioxide, cyclohexene oxide and a third monomer, wherein the third monomer may be phthalic anhydride.

[0017] Preferably, the quaternary copolymerization is a quaternary copolymerization of carbon dioxide, propylene oxide, cyclohexene oxide and a fourth monomer, and the fourth monomer may be phthalic anhydride.

[0018] Preferably, the water content of the hydrous cyclohexane is 200ppm to 10000ppm. The solution copolymerization reaction containing cyclohexane and carbon dioxide requires that the water content of the cyclohexane participating in the polymerization is less than 200ppm. In order to ensure the quality of the polymerized product, dehydration treatment is required when the water content in the cyclohexane is higher than 200ppm. The water content in the cyclohexane is related to its preparation method, storage method, and saturated solubility of water in the cyclohexane, and generally does not exceed 10000ppm. If it exceeds 10000ppm, static stratification can be performed first, and then the cyclohexane can be extracted from the upper layer. The water content of commercially available cyclohexane is 1000ppm, 2000ppm, 3000ppm or 4000ppm, etc.

[0019] The selection of solution polymerization solvent and the proportion of solution polymerization solvent in the mixed material play a crucial role: 1) The proper selection of solvent is also related to the temperature of the tower, energy consumption, and water content of the tower bottom material (mixed material for polymerization). For example, by using dichloromethane as the solution polymerization solvent, by adjusting the proportion of the solution polymerization solvent in the mixed material containing water-containing cyclohexene oxide, the tower bottom operating temperature can be controlled at 50-65°C, that is, using a heat medium of 95-120°C can meet the heating requirements of the tower bottom reboiler. Therefore, the use of dichloromethane can effectively recover low-temperature heat sources such as steam condensate in the device and directly use them for heating the tower bottom reboiler, saving energy consumption and achieving a good dehydration effect. For another example, by using ethylene dichloride and adjusting the proportion of the solution polymerization solvent in the mixture containing water-containing cyclohexene oxide, a good water removal effect can be obtained while maintaining low energy consumption, and the polymerization mixture output from the bottom of the tower is maintained at 90-120°C. When coupled with the downstream polymerization reaction, the polymerization mixture needs to be combined with other reaction materials or additional reaction solvent, so as to achieve the effect of cooling the polymerization mixture, which can also save energy consumption to the greatest extent.

[0020] Therefore, 1) the solution polymerization solvent of the present invention is any one of dichloromethane, ethylene dichloride, chloroform, carbon tetrachloride, acrylonitrile or cyclohexane or a combination of at least two thereof. Typical but non-limiting combinations include a combination of ethylene dichloride and dichloromethane, a combination of chloroform and dichloromethane, a combination of cyclohexane and dichloromethane, a combination of carbon tetrachloride and dichloromethane, and a combination of carbon tetrachloride and acrylonitrile. 2) The amount of the solution polymerization solvent added of the present invention is 10 to 70 wt % of the mixed material. In summary, 1) and 2) are combined, and the present invention preferably uses the above-mentioned solution polymerization solvent as an azeotropic agent, which can have the three key points mentioned above, and the amount of the solution polymerization solvent added can achieve excellent dehydration rate while having low energy consumption and the ratio of the solution polymerization solvent and epoxy cyclohexane finally obtained is more suitable for the needs of subsequent polymerization reactions.

[0021] More specifically, the factors affecting the amount of solution polymerization solvent used as an azeotropic agent in the mixed material in this application are: 1) the minimum required amount of various solution polymerization solvents that can produce azeotropy with water; 2) the water content requirement in the polymerization material after azeotropic dehydration; 3) the comprehensive demand for energy consumption; 4) the proportion of solution polymerization solvent to the polymerization mixed material cannot exceed 70wt%, because the water content of the hydrous cyclohexene oxide to be treated is relatively low (200-10000ppm), that is, the proportion of solution polymerization solvent to the mixed material is kept at no more than 70wt%. Taking the above factors 1), 2), and 3) into consideration, the proportion of solution polymerization solvent to the mixed material needs to be greater than 10wt%.

[0022] In summary, in some preferred embodiments, the amount of the solution polymerization solvent added is 10 to 70 wt% of the mixed material, for example, it can be 10 wt%, 15 wt%, 17 wt%, 24 wt%, 30 wt%, 37 wt%, 44 wt%, 50 wt%, 57 wt%, 64 wt% or 70 wt%, etc., preferably 20 to 60 wt%.

[0023] Preferably, the top operating pressure of the azeotropic dehydration is 1 kPa(A) to 200 kPa(A), for example, it can be 1 kPa, 24 kPa, 46 kPa, 68 kPa, 90 kPa, 112 kPa, 134 kPa, 156 kPa, 178 kPa or 200 kPa.

[0024] In the present invention, the tower top operating pressure of 1 kPa(A) to 200 kPa(A) means that the absolute pressure range is 1 kPa to 200 kPa.

[0025] Preferably, the temperature of the bottom of the azeotropic dehydration tower is 50-120°C, for example, it can be 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C or 120°C; the top temperature is 40-95°C, for example, it can be 40°C, 42°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C or 95°C.

[0026] Preferably, the theoretical plate number of the azeotropic dehydration tower is 10 to 60, for example, 10, 16, 22, 27, 33, 38, 44, 49, 55 or 60.

[0027] Preferably, the tower feed position for the azeotropic dehydration is the 5th to 40th theoretical plate from the top of the tower, for example, it can be 5, 9, 13, 17, 21, 25, 29, 33, 37 or 40, etc. The feed position can be specifically selected based on the requirements for obtaining the mixed material for polymerization, low energy consumption and dehydration effect.

[0028] The present invention further preferably feeds at a feed position of (1 / 3 to 2 / 3)×the number of theoretical plates of the tower, which has a better dehydration effect and lower energy consumption.

[0029] Preferably, the azeotropic dehydration process comprises: the azeotropic gas phase formed by the solution polymerization solvent and water in the mixed material is enriched in the upper part of the azeotropic dehydration tower, and the oil-water phase is separated after condensation at the top of the tower. The mixed material after water removal is enriched in the lower part of the azeotropic dehydration tower, and the mixture of cyclohexene oxide and the solution polymerization solvent is taken out from the bottom of the tower, and the mixture is used as the mixed material for polymerization.

[0030] Preferably, after the oil and water phases are separated, the oil phase is completely refluxed into the azeotropic dehydration tower.

[0031] In the present invention, the oil phase is completely refluxed into the azeotropic dehydration tower, so that the solution polymerization solvent can be recovered.

[0032] Preferably, the water phase generated by the oil-water phase separation is subjected to wastewater post-treatment.

[0033] Preferably, the water content of the cyclohexene oxide after dehydration is less than 200 ppm, for example, it can be 10 ppm, 20 ppm, 31 ppm, 49 ppm, 52 ppm, 73 ppm, 80 ppm, 85 ppm, 94 ppm, 115 ppm, 136 ppm, 157 ppm, 178 ppm or 199 ppm, etc., a better result is less than 100 ppm, and the best result is less than 50 ppm.

[0034] Preferably, the polymerization mixture contains 10-70wt% of solution polymerization solvent, for example, it can be 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt% or 70wt%.

[0035] Preferably, the azeotropic dehydration is a continuous dehydration process or an intermittent dehydration process.

[0036] The method for azeotropic dehydration of cyclohexene oxide with a solution polymerization solvent in the present invention can be a continuous process to achieve continuous production, but for smaller-scale tests such as pilot plants, an intermittent dehydration process can also be used.

[0037] In a second aspect, the present invention provides a coupling method for azeotropic dehydration of cyclohexene oxide and polymerization reaction, wherein the coupling method feeds a polymerization mixture obtained by azeotropic dehydration of cyclohexene oxide with the solution polymerization solvent described in the first aspect into a polymerization reaction section to carry out polymerization reaction.

[0038] Compared with the prior art, the present invention has at least the following beneficial effects:

[0039] (1) Based on the advantage of coupling cyclohexene oxide with downstream polymerization reaction, the present invention provides a method for azeotropic dehydration of cyclohexene oxide with a solution polymerization solvent. The entrainer used in the method is also a solvent for the polymerization reaction. Therefore, the cyclohexene oxide in the tower bottom containing the entrainer will not affect the downstream polymerization reaction, reducing the purity requirement of the cyclohexene oxide in the tower bottom, thereby reducing the separation requirement of the azeotropic dehydration tower and saving energy consumption. Specifically, the purity of cyclohexene oxide in the polymerization mixture after dehydration in the tower bottom is maintained at 30-90wt%, the operating temperature of the tower bottom is 50-120°C, and the water content in the polymerization mixture is maintained below 200ppm, preferably maintained at 70-160ppm.

[0040] (2) The method for azeotropic dehydration of cyclohexene oxide using a solution polymerization solvent provided by the present invention, wherein the bottom of the azeotropic dehydration tower is a mixture of cyclohexene oxide and an azeotropic agent, which reduces the operating temperature of the bottom of the tower. The operating temperature of the bottom of the tower is 50 to 120° C., reduces side reactions such as hydrolysis / decomposition of cyclohexene oxide, and can improve the quality of cyclohexene oxide.

[0041] (3) The method for azeotropic dehydration of cyclohexene oxide using a solution polymerization solvent provided by the present invention can recover all the raw cyclohexene oxide in the bottom of the tower without loss, and the yield is basically 100%. No new impurities are introduced, and the polymerization reaction and product quality will not be affected by the reaction solvent, so the method has good application prospects.

[0042] (4) The process of coupling the dehydration of cyclohexene oxide and the polymerization reaction of the present invention can directly and continuously apply the polymerization mixture obtained by dehydration of cyclohexene oxide to the polymerization reaction, and the continuous operation is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The present invention provides a device and a flow chart of a process method for coupling dehydration and polymerization reaction of cyclohexene oxide according to a specific embodiment of the present invention.

[0044] Figure 1 Among them, C-101: azeotropic dehydration tower, E-101: condenser, E-102: tower bottom reboiler, V-101: phase separator, P-101: reflux pump, P-102: kettle liquid pump, X-101: polymerization unit.

[0045] Figure 1 In the figure, A represents a mixture of water-containing cyclohexane oxide and a solution polymerization solvent; B represents an aqueous phase produced by oil-water phase separation; C represents an oil phase after oil-water phase separation; D represents the material taken out from the bottom of the tower; E represents a polymerization mixture of cyclohexane oxide and a solution polymerization solvent taken out and entering the polymerization unit; F1 represents a refrigerant; and F2 represents a heat medium. DETAILED DESCRIPTION

[0046] For the convenience of understanding the present invention, the present invention lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0047] Those skilled in the art should understand that the present invention necessarily includes necessary pipelines, conventional valves and general pump equipment for realizing a complete process, but the above content does not belong to the main inventive point of the present invention. Those skilled in the art can add layouts on their own based on the process flow and equipment structure selection, and the present invention does not make special requirements and specific limitations on this.

[0048] As a specific embodiment of the present invention, a device for a process method of coupling dehydration and polymerization reaction of cyclohexene oxide is provided, and a schematic diagram of the device is shown in FIG. Figure 1As shown, the device includes an azeotropic dehydration tower C-101, a condenser E-101 and a phase separator V-101 are sequentially arranged on the top of the azeotropic dehydration tower C101, the phase separator V-101 is connected to the azeotropic dehydration tower C-101 through a reflux pump P-101, a kettle reboiler E-102 is arranged at the bottom of the azeotropic dehydration tower C-101, the kettle reboiler E-102 is connected to the bottom circulation of the azeotropic dehydration tower C-101, and a kettle liquid pump P-102 is arranged between the bottom outlet and the kettle reboiler E-102, and a mixture outlet is arranged at the outlet of the kettle liquid pump P-102, and the mixture outlet is connected to the polymerization unit X-101, and is used to transport the mixture extracted from the bottom of the tower to the polymerization unit X-101 for direct polymerization reaction.

[0049] Examples 1 to 9

[0050] Embodiments 1 to 9 provide a method for coupling dehydration and polymerization of cyclohexene oxide, the method being carried out using the above-mentioned device, and the method comprising the following steps:

[0051] The water-containing cyclohexyl oxide (water content is 200ppm-10000ppm) is mixed with a solution polymerization solvent, and the obtained mixture enters the middle part of an azeotropic dehydration tower, wherein the azeotropic gas phase formed by the solution polymerization solvent and water in the mixture is enriched toward the upper part of the azeotropic dehydration tower, and is discharged from the top of the tower and condensed in a condenser and then enters a phase separator for oil-water phase separation. The oil phase after the oil-water phase separation is completely refluxed to the top of the azeotropic dehydration tower, and the water phase is subjected to wastewater post-treatment; the mixture after water removal is enriched toward the lower part of the azeotropic dehydration tower, and a mixture of cyclohexyl oxide and the solution polymerization solvent is taken out from the bottom of the tower, which is a polymerization mixture, and the polymerization mixture is directly fed into a polymerization unit for a polymerization reaction containing cyclohexyl oxide as a raw material.

[0052] The amount of the solution polymerization solvent added is 10 to 70 wt% of the mixed material, the temperature of the bottom of the tower is 50 to 120°C, the temperature of the top of the tower is 40 to 95°C, the operating pressure of the top of the tower is 1 kPa(A) to 200 kPa(A), the number of theoretical plates is 10 to 60, and the feed position is the 5th to 40th theoretical plates below the top of the tower.

[0053] For the convenience of experiment, in Examples 1 to 9, normal pressure, i.e., 101.3 kPa, was used for the experiment, the feed rate was 2000 kg / h, the number of plates was 30 theoretical plates, and the feed position was the 15th theoretical plate. However, it does not mean that the present invention can only be carried out using the above feed rate, pressure, feed position and theoretical plate number. For the feed rate, the method provided by the present invention can be adapted to any feed rate, and for the pressure, the range defined by the claims of the present invention can be realized. The number of plates and the feed position can be adjusted according to the actual situation.

[0054] The specific raw material composition, parameter conditions in the separation process and separation results are shown in Table 1.

[0055] Table 1

[0056]

[0057]

[0058] It can be seen from Examples 1 to 9 that the method for azeotropic dehydration of cyclohexene oxide with a solution polymerization solvent provided by the present invention can achieve effective dehydration, and the water content in the final polymerization mixture is in the range of 40 to 193 ppm, preferably within 150 ppm, and more preferably within 100 ppm, and the cyclohexane content in the polymerization mixture obtained in the bottom of the tower is in the range of 24.9 to 94.9 wt%, preferably 49.9 wt% to 85.1 wt%, which can better meet the needs of downstream polymerization reactions, and the recovery rate of cyclohexane oxide reaches 100%.

[0059] Comparative Example 1, Example 4 and Example 5 can be seen that when the addition of the entrainer in Example 4 is on the low side, in order to achieve effective azeotropic dehydration, it is necessary to adjust the tower bottom temperature to 129 DEG C, and the power reaches 172kW simultaneously, and the energy consumption is relatively high, and the water content of the polymerization mixture finally obtained is still up to 193ppm, i.e., the dehydration effect is poor. And the entrainer addition in Example 5 is up to 75wt%, causing the content of cyclohexene oxide in the polymerization mixture finally obtained to be 24.9wt%, and the concentration of the reaction raw materials when directly applied to the downstream polyreaction is too low, which will affect the polyreaction process, if the polyreaction is carried out again after the supplement of cyclohexene oxide, the newly supplemented cyclohexene oxide water content is not up to standard, thus showing that the addition of the entrainer is preferably controlled within a reasonable range by the present invention, and the dehydration containing cyclohexene oxide material that more meets the downstream polyreaction demand can be obtained with lower energy consumption.

[0060] As can be seen from Examples 6 and 7, the operating temperature of the tower bottom using dichloromethane in the present invention is 58-65°C, so the temperature of the heat source for heating the tower bottom reboiler only needs to be greater than 95°C. In industrial devices, heat sources with a temperature of less than 120°C are difficult to recover. When dichloromethane is used, heat can be exchanged with a heat source with a temperature of 95°C < T < 120°C to recover heat, that is, no new heat needs to be introduced to heat the reboiler, and the power of the reboiler is 0 at this time. Therefore, when dichloromethane is used, the heat of low-temperature heat sources such as steam condensate at a temperature of less than 120°C in industrial devices can be effectively recovered, saving energy consumption.

[0061] It can be seen from Examples 2 to 3 and Examples 8 to 9 that these embodiments have better water removal effects, and the operating temperature of the tower bottom is between 85 and 120°C. When used in the downstream polymerization reaction process, since the polymerization reaction temperature is generally 60 to 80°C, the energy consumption required for heat exchange can also be saved.

[0062] Comparative Example 1

[0063] This comparative example provides a method for azeotropic dehydration of cyclohexene oxide, the number of plates and the feed composition are the same as those in Example 3, and what is finally obtained in the tower bottom is not a mixture of cyclohexene oxide and a solution polymerization solvent, but a rectification separation to obtain high-purity cyclohexene oxide. The operating conditions of the process are: the top reflux ratio is 0.5, the tower bottom operating temperature is 133°C, and the power of the tower bottom reboiler is 222kW. The tower bottom composition finally obtained is mainly cyclohexene oxide, wherein the purity of cyclohexene oxide is 98%, the water content is 195ppm, and the recovery rate of cyclohexene oxide is less than 95%.

[0064] This comparative example is different from Example 3 in that dehydration and polymerization coupling are not adopted, but conventional azeotropic distillation is used to remove dehydration and entrainer; the number of plates and feeding conditions remain unchanged, the purity of the tower bottom cyclohexene oxide needs to meet (as close to 100%) and the cyclohexane obtained needs to be maintained to meet the requirement of water content, so after adjusting the optimal tower bottom operating temperature and reboiler power, the purity of the obtained cyclohexene oxide is 98%, the water content is 161ppm, and the recovery rate of cyclohexene oxide is less than 95%. Compared with Example 3, if the coupling method is not adopted, more energy consumption will be achieved, and the purity is low and the recovery rate is low.

[0065] Comparative Example 2

[0066] This comparative example replaces the entrainer ethylene dichloride with benzene (not a polymerization solvent), so that cyclohexene oxide can carry out subsequent polymerization reaction, it is necessary to obtain cyclohexene oxide with higher purity in the dehydration process, therefore compared with Example 3, the number of plates and the feeding conditions remain unchanged, and the rectification dehydration, the cyclohexene oxide content of the tower reactor needs to meet (as close to 100%) and needs to maintain the cyclohexane obtained to meet the requirement of water content. The operating conditions of the process are: the tower top reflux ratio is 0.5, the tower reactor operating temperature is 133 DEG C, and the power of the tower reactor reboiler is 258kW. The tower reactor finally obtained is mainly composed of cyclohexene oxide, wherein the purity of cyclohexene oxide is 99%, and the water content is 166ppm, and the recovery rate of cyclohexene oxide is less than 95%.

[0067] In this comparative example, since the entrainer cyclohexane is not a solvent for solution polymerization, the cyclohexene oxide needs to be raised to a higher purity, which increases the energy consumption of the dehydration process. At the same time, the impurities remaining in the cyclohexene oxide (byproducts produced by decomposition at high temperature and the entrainer benzene, etc.) will accumulate in the polymerization and separation unit, thereby affecting the polymerization reaction and the quality of the product.

[0068] In addition, the bottom temperatures of Comparative Examples 1 and 2 are higher than those of Example 3, which results in the cyclohexene oxide being susceptible to side reactions such as hydrolysis / decomposition.

[0069] In summary, the present invention couples the polymerization process with the epoxy cyclohexane dehydration process, the solvent of the polymerization process is also the entrainer of the epoxy cyclohexane dehydration process, the entrainer is used to form the lowest azeotrope with water, and the trace amount of water in the epoxy cyclohexane is separated at the top of the tower; the entrainer of the epoxy cyclohexane in the tower bottom will not affect the polymerization reaction, and the purity requirement of the epoxy cyclohexane in the tower bottom is reduced, thereby reducing the separation requirement of the azeotropic dehydration tower, saving energy consumption; at the same time, the operating temperature of the tower bottom of the azeotropic dehydration tower is reduced, the side reactions such as the hydrolysis / decomposition of epoxy cyclohexane are reduced, and the quality of epoxy cyclohexane is improved. On the other hand, the present invention does not introduce new impurities, does not affect the polymerization reaction and product quality, and has a good application prospect.

[0070] The present invention illustrates the detailed features of the present invention through the above embodiments, but the present invention is not limited to the above detailed features, that is, it does not mean that the present invention must rely on the above detailed features to be implemented. Those skilled in the art should understand that any improvement to the present invention, equivalent replacement of the technical features selected by the present invention, addition of auxiliary technical features, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for azeotropic dehydration of cyclohexene oxide using a solution polymerization solvent, characterized in that: The method comprises: The water-containing cyclohexene oxide is mixed with a solution polymerization solvent, and the obtained mixed material is subjected to azeotropic dehydration to obtain a mixed material for polymerization; The polymerization mixture comprises dehydrated cyclohexene oxide and a solution polymerization solvent.

2. The method according to claim 1, characterized in that: The polymerization mixture is directly used for a polymerization reaction containing cyclohexene oxide as a raw material, and the solution polymerization solvent is a solvent for the polymerization reaction; Preferably, the polymerization reaction comprises a copolymerization reaction containing cyclohexene oxide and carbon dioxide as raw materials; Preferably, the copolymerization reaction is selected from any one of binary copolymerization, ternary copolymerization or quaternary copolymerization; Preferably, the binary copolymerization is a binary copolymerization of carbon dioxide and cyclohexene oxide; The terpolymerization is a terpolymerization of carbon dioxide, propylene oxide and cyclohexene oxide, and / or a terpolymerization of carbon dioxide, cyclohexene oxide and a third monomer; The quaternary copolymerization is a quaternary copolymerization of carbon dioxide, propylene oxide, cyclohexene oxide and a fourth monomer.

3. The method according to claim 1 or 2, characterized in that: The solution polymerization solvent is any one of dichloromethane, dichloroethane, chloroform, carbon tetrachloride, cyclohexane or acrylonitrile, or a combination of at least two thereof; And / or, the proportion of dehydrated cyclohexene oxide in the polymerization mixture is 30 to 90 wt %, preferably 40 to 86 wt %.

4. The method according to any one of claims 1 to 3, characterized in that: The water content of the water-containing cyclohexene oxide is 200ppm to 10000ppm.

5. The method according to any one of claims 1 to 4, characterized in that: The amount of the solution polymerization solvent added is 10-70 wt %, preferably 20-60 wt % of the mixed material.

6. The method according to any one of claims 1 to 5, characterized in that: The tower top operating pressure of the azeotropic dehydration is 1 kPa(A) to 200 kPa(A); Preferably, the temperature of the bottom of the azeotropic dehydration tower is 50-120° C., and the temperature of the top of the tower is 40-95° C. Preferably, the number of theoretical plates of the azeotropic dehydration tower is 10-60; Preferably, the tower feed position for the azeotropic dehydration is the 5th to 40th theoretical plates below the top of the tower.

7. The method according to any one of claims 1 to 6, characterized in that: The azeotropic dehydration process comprises: the azeotropic gas phase formed by the solution polymerization solvent and water in the mixed material is enriched in the upper part of the azeotropic dehydration tower, and the oil-water phase is separated after condensation at the top of the tower; the mixed material after water is removed is enriched in the lower part of the azeotropic dehydration tower, and the mixture of cyclohexene oxide and the solution polymerization solvent is taken out from the bottom of the tower, and the mixture is used as the mixed material for polymerization.

8. The method according to claim 7, characterized in that After the oil and water phases are separated, the oil phase is completely refluxed into the azeotropic dehydration tower; Preferably, the water phase generated by the oil-water phase separation is subjected to wastewater post-treatment.

9. The method according to any one of claims 1 to 9, characterized in that: The water content of the cyclohexene oxide after dehydration is less than 200 ppm; Preferably, the polymerization mixture contains 10 to 70 wt% of a solution polymerization solvent; Preferably, the azeotropic dehydration is a continuous dehydration process or an intermittent dehydration process.

10. A coupling method for azeotropic dehydration of cyclohexene oxide and polymerization reaction, characterized in that: In the coupling method, the polymerization mixture obtained by subjecting the solution polymerization solvent according to any one of claims 1 to 9 to azeotropic dehydration of cyclohexene oxide is fed into a polymerization unit to carry out a polymerization reaction.

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