Isopropylbenzene recovery method

Abstract

The invention provides a recovery method of isopropyl benzene, and relates to the technical field of isopropyl benzene recovery processes. The method comprises the following steps: introducing an isopropylbenzene material into a recovery tower to obtain a gas-phase component, a heavy component and isopropylbenzene; the gas-phase component is cooled through a condenser arranged at the top of the recovery tower and then subjected to gas-liquid separation through a reflux tank to obtain non-condensable gas and reflux liquid in the reflux tank, the reflux liquid circulates to the recovery tower, the non-condensable gas in the reflux tank is cooled through an after-cooler, and then light components are extracted from an after-condensate tank; heavy components are discharged from the tower kettle; cumene is extracted from the side line of the recovery tower. The method not only can effectively remove ethylbenzene in circulating cumene, but also can reduce the loss of cumene in the process; the method has the advantages of economy, high efficiency and environmental protection.

Description

Technical Field

[0001] The invention relates to the technical field of cumene recovery technology, and in particular to a cumene recovery method. Background Art

[0002] Propylene oxide (PO) is an important organic chemical raw material, mainly used in the production of polyether polyols, propylene glycol, propylene glycol ethers, etc., of which the consumption of polyether polyols accounts for about 70%. At present, the main commercial production methods of PO are the chlorohydrin method, ethylbenzene co-oxidation method (PO / SM), isobutane co-oxidation method (PO / TBA or PO / MTBE), hydrogen peroxide direct oxidation method (HPPO) and hydrogen peroxide isopropylbenzene method (CHP). Among them, the CHP process has the following advantages: the conversion rate and selectivity of the whole process are very high, and the products are only PO and isopropylbenzene (IPB) circulating in the system; the process flow is relatively simple. In the CHP method of producing propylene oxide, a large amount of α,α-dimethylbenzyl alcohol (DMBA) is generated during the epoxidation of propylene, which needs to be generated by hydrogenolysis to participate in the reaction cycle again. In the CHP process, cumene (IPB) is the raw material of the oxidation unit, the reaction product of the hydrogenolysis of α,α-dimethylbenzyl alcohol, and also the solvent of the propylene epoxidation reaction process. The efficient circulation of cumene is crucial and significantly affects the technical and economic performance of the device. The ethylbenzene contained in the cumene raw material and the ethylbenzene generated by the side reaction need to be efficiently removed. The accumulation of ethylbenzene will affect the stable operation of the device. A method for recovering cumene is proposed in Chinese patent CN202011156375.9, which mainly emphasizes the removal of heavy components and does not involve the separation of ethylbenzene.

[0003] The accumulation of ethylbenzene in the circulating cumene will affect the stable operation of the system. In the conventional method, when a certain concentration of ethylbenzene accumulates in the circulating cumene, it is discharged, and the loss of cumene is large. The side-line extraction of cumene can enrich ethylbenzene at the top of the tower and reduce the loss of cumene. However, the light components such as water and organic acids in the reaction products of α,α-dimethylbenzyl alcohol hydrogenolysis are easily enriched at the top of the tower during the separation process. At the same time, 1,2-propylene glycol and / or its ether will also enter the top of the tower after azeotropy with cumene, and it is also easy to enrich in the tower bottom at the top of the tower. Excessive enrichment of water, organic acids, 1,2-propylene glycol and / or its ether in the tower top system will further promote the formation of propylene glycol oligomers and block the tower top system, so it is necessary to effectively remove them. Summary of the invention

[0004] In order to solve the technical problem of large cumene loss in the process of removing ethylbenzene from circulating cumene in the prior art, the present invention provides a cumene recovery method, which can efficiently remove light components of the system, has high ethylbenzene removal efficiency, high cumene recovery rate, low energy consumption, and can effectively avoid the accumulation of ethylbenzene in the system.

[0005] The present invention solves the technical problem by adopting the following technical solutions.

[0006] A method for recovering cumene, comprising:

[0007] The gas phase components, heavy components and cumene are obtained by introducing the cumene material into a recovery tower;

[0008] The gas phase component is first cooled by a condenser arranged at the top of the recovery tower, and then separated by gas-liquid separation in a reflux tank to obtain non-condensable gas and reflux liquid in the reflux tank, wherein the reflux liquid is circulated to the recovery tower, and the non-condensable gas in the reflux tank is cooled by an aftercooler, and then the light component is extracted in the after-condensate tank;

[0009] The heavy components are discharged from the bottom of the tower;

[0010] The cumene is taken out from the side line of the recovery tower.

[0011] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0012] 1. In a method for recovering cumene provided by the present invention, cumene is extracted from a side line, and ethylbenzene is extracted after being enriched at the top of a tower, thereby greatly reducing the energy consumption for separating ethylbenzene; steam is generated at the top of a cumene recovery tower to recover heat from the top of the tower; an aftercooler is provided, and light components at the top of the tower are extracted from the condensate of the aftercooler, so that ethylbenzene is further enriched in the condensate of the aftercooler, further reducing the amount of extraction from the top of the tower and reducing the loss of cumene; and online flushing measures are provided for the aftercooler process to ensure long-term stable operation of the device.

[0013] 2. The method of the present invention is used to recover cumene, which can efficiently remove light components rich in ethylbenzene in the system, with high ethylbenzene removal efficiency, high cumene recovery rate, low energy consumption, and can effectively avoid the accumulation of ethylbenzene in the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0015] Figure 1This is a schematic diagram of the method flow of Example 1 of the present invention;

[0016] Figure 2 It is a schematic diagram of the method flow of Comparative Example 1 in the present invention.

[0017] Icons: 1-feed inlet, 2-heavy component discharge pipe, 3-isopropylbenzene production pipe, 4-exhaust pipe, 5-condensate pipe, 6-reflux pipe, 7-reflux tank non-condensable gas discharge pipe, 8-online flushing unit, 9-aftercooler condensate discharge pipe, 10-non-condensable gas external discharge pipe, 11-water phase collection pipe, 12-oil phase collection pipe, 13-after-condensate circulation pipe, 14-ethylbenzene-rich light component production pipe, A-recovery tower, B-condenser, C-reflux tank, D-aftercooler, E-after-condensate tank. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0019] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to specific embodiments.

[0020] A method for recovering cumene, comprising:

[0021] The gas phase components, heavy components and cumene are obtained by introducing the cumene material into a recovery tower;

[0022] The gas phase component is first cooled by a condenser arranged at the top of the recovery tower, and then separated by gas-liquid separation in a reflux tank to obtain non-condensable gas and reflux liquid in the reflux tank, wherein the reflux liquid is circulated to the recovery tower, and the non-condensable gas in the reflux tank is cooled by an aftercooler, and then the light component is extracted in the after-condensate tank;

[0023] The heavy components are discharged from the bottom of the tower;

[0024] The cumene is taken out from the side line of the recovery tower.

[0025] In some preferred embodiments of the present invention, the cumene material is the reaction product of α,α-dimethylbenzyl alcohol and hydrogen in the process of preparing propylene oxide by cumene hydroperoxide method.

[0026] In some preferred embodiments of the present invention, the cumene material includes the following components in mass percentage: 95-99.5% cumene, 0.01-2% ethylbenzene, 0.001-0.05% organic acid, 0.001-0.1% water, 0.001-0.1% 1,2-propylene glycol, 0.001-0.1% alcohol ether and 0-4.0% heavy components.

[0027] In some preferred embodiments of the present invention, the operating conditions of the recovery tower include: a tower top pressure of 0 to 200 KPaG, and a tower top temperature of 130 to 200°C.

[0028] In some preferred embodiments of the present invention, the operating conditions of the recovery tower include: a tower top pressure of 20 to 100 KPaG, and a tower top temperature of 145 to 180°C.

[0029] In some preferred embodiments of the present invention, the temperature difference of the gas phase component before and after passing through the condenser is ≤60°C.

[0030] In some preferred embodiments of the present invention, the temperature difference of the gas phase component before and after passing through the condenser is ≤30°C.

[0031] It should be noted here that too low a condensation temperature will result in the inability to produce usable low-pressure steam at the top of the tower during the condensation process, and will cause the ethylbenzene content in the gas phase material flow at the outlet of the top reflux tank to be too low, making it impossible to further extract sufficient ethylbenzene-rich light components from the aftercooler condensate, thereby reducing the separation efficiency of ethylbenzene.

[0032] In some preferred embodiments of the present invention, the post-condensate tank is provided with an oil-water separation structure, and the water phase obtained by treatment with the oil-water separation structure is directly discharged, and the obtained oil phase is divided into two parts, one part of which is produced as the light component, and the other part is circulated to the reflux tank. The water phase obtained by treatment with the oil-water separation structure is directly discharged, and one part of the obtained oil phase is produced as the light component, and the other part is circulated to the reflux tank.

[0033] It should be noted here that free water is extracted from the heavy component, which mainly contains water, trace amounts of organic acids and 1,2-propylene glycol; the oil phase mainly contains isopropylbenzene and ethylbenzene.

[0034] In some preferred embodiments of the present invention, the oil-water separation structure adopts a gravity sedimentation structure, and no coalescer filter element is provided in the gravity sedimentation structure. It should be noted that gravity sedimentation is a conventional liquid-liquid separation structure, which uses the density of the water phase and the oil phase for separation, and the gravity sedimentation structure can avoid clogging of the filter element due to the use of a high-efficiency coalescer.

[0035] In some preferred embodiments of the present invention, the light components are separated and the cumene therein is recovered.

[0036] In some preferred embodiments of the present invention, the mass ratio of the production flow rate of the light component to the isopropylbenzene material is (0.1-2.0):100.

[0037] In some preferred embodiments of the present invention, the mass ratio of the production flow rate of the light component to the isopropylbenzene material is (0.3-1.0):100.

[0038] In some preferred embodiments of the present invention, the condensation temperature of the aftercooler is 30-80°C.

[0039] In some preferred embodiments of the present invention, the condensation temperature of the aftercooler is 40-55°C.

[0040] It should be noted here that since the trace amount of water in the isopropylbenzene raw material needs to be discharged, a water diversion facility needs to be set up. According to the conventional design scheme, a water diversion structure is set up in the reflux tank, which will lead to the enrichment of water in the process of the reflux tank and the aftercooler. In addition, since the temperature difference between the gas phase component before and after passing through the condenser is ≤60°C, the temperature of the reflux liquid is high, and the water content in the reflux liquid is high, which will lead to the enrichment of impurities such as water and organic acids in the top system, increasing the corrosiveness of the material. Therefore, the present invention preferably controls the condensation temperature of the aftercooler to 30-80°C, and further preferably to 40-55°C, and performs oil-water separation of water in the aftercooler condensate; the oil phase material part of the aftercooler condensate is used as the effluent rich in ethylbenzene, the ethylbenzene concentration is the highest, and the isopropylbenzene loss is minimal when the same ethylbenzene flow rate is discharged.

[0041] In some preferred embodiments of the present invention, the post-condensate tank is provided with an online flushing unit, and the online flushing unit uses a flushing liquid to flush the oil-water interface. The online flushing unit is provided in the post-condensate tank to destroy its emulsion layer and discharge the ethers therein. A sight glass is provided at the oil-water separation interface of the post-cooler condensate tank to regularly monitor the oil-water interface, and a tubular structure with small holes is provided in the flushing unit. The flushing method is selected as regular flushing, or flushing when an emulsion layer is found to appear at the oil-water interface. Studies have found that the mixture formed by azeotropy of 1,2-propylene glycol and / or its ether and isopropylbenzene in the system can undergo liquid-liquid phase separation after cooling, but alcohol ethers such as propylene glycol monomethyl ether contain hydroxyl groups and ether bonds, which are both lipophilic and hydrophilic, and are easy to form an emulsion layer between the aqueous phase and the organic phase. Excessive accumulation of the emulsion layer cannot be discharged from the device, and may further polymerize to form oligomers, thereby blocking the device, which will affect the stable operation of the device. Therefore, flushing the device is very necessary.

[0042] In some preferred embodiments of the present invention, the flushing liquid is water or cumene, so that the emulsified layer is dissolved in cumene or water and sent out as waste water, or discharged in the light component drainage rich in ethylbenzene.

[0043] The principle of the cumene recovery method provided by the present invention is as follows:

[0044] The raw material containing isopropylbenzene is fed into the recovery tower A from the feed port 1 located in the middle of the recovery tower A, the tower top temperature is controlled to be 130-200, the tower top pressure is controlled to be 0-200KPaG, and the isopropylbenzene product is discharged from the isopropylbenzene extraction pipe 3; the heavy components in the raw material (mainly containing acetophenone, isopropylbenzene, and oligomers of 1,2-propylene glycol) are discharged from the heavy component discharge pipe 2 located at the bottom of the recovery tower A, and the exhaust pipe 4 located at the top of the recovery tower A is used to collect gas phase components (the gas phase mainly contains isopropylbenzene, ethylbenzene, water, organic acid, 1,2-propylene glycol, alcohol ether impurities, etc.); the gas phase logistics then enters the condenser B for condensation, and the condensed gas phase enters the reflux tank C through the condensate pipe 5, and the liquid phase in the reflux tank C is continuously circulated back to the top of the recovery tower through the reflux pipe 6; the gas phase in the reflux tank C enters the rear through the reflux tank non-condensable gas discharge pipe 7 The condensate discharged from the aftercooler D enters the after-condensate tank E through the aftercooler condensate discharge pipe 9. A non-condensable gas external discharge pipe 10 is arranged on the top of the condensate tank E to discharge the gas phase that cannot be condensed in the system; an oil-water separation structure is arranged in the after-condensate tank E. The oil-water separation structure adopts a gravity sedimentation structure, which is a conventional liquid-liquid separation structure. The density of the water phase and the oil phase is used for separation. A high-efficiency coalescing filter element structure is no longer arranged. A partition is arranged inside. A water phase collection pipe 11 and an oil phase collection pipe 12 are respectively arranged on both sides of the partition. The water phase is extracted from the heavy phase and the water is discharged from the water phase collection pipe 11; the light phase is the oil phase, and the ethylbenzene-rich material is extracted from the oil phase collection pipe 12. Part of the extracted oil phase is discharged as a light component from the ethylbenzene-rich light component extraction pipe 14, and the other part of the discharged oil phase is circulated to the reflux tank C through the after-condensate circulation pipe 13 for further recovery.

[0045] The post-condensate tank E is provided with an online flushing unit 8, which uses a flushing liquid to regularly flush the oil-water interface, thereby destroying its emulsified layer and discharging the ethers therein.

[0046] Example 1

[0047] Please refer to Figure 1 The composition of the cumene material is (by mass percentage): 98.0% cumene, 1% ethylbenzene, 0.005% organic acid, 0.05% water, 0.01% 1,2-propylene glycol, 0.005% alcohol ether, 0.8% heavy component, and the rest are other trace impurity components.

[0048] The theoretical number of plates of the isopropylbenzene recovery tower is 40, the feed port is located at the 28th floor (from top to bottom), the side line production position is at the 15th floor (from top to bottom), and a condenser, reflux tank, aftercooler, and aftercooler separator tank with oil-water separation are set on the top of the tower. The light component rich in ethylbenzene is produced from the oil phase of the aftercooler condensate tank.

[0049] The tower top pressure is 30KPaG, the temperature of the gas phase component produced from the tower top (i.e., the tower top temperature) is 152°C, the temperature of the gas phase component produced from the tower top after condensation by the condenser is 135°C (i.e., the temperature difference of the gas phase component before and after passing through the condenser is 17°C), the condensation temperature of the aftercooler is 40°C, the tower bottom temperature is 235°C, the mass ratio of the reflux liquid flow in the reflux pipe to the side line production flow is 1.1:1, the mass ratio of the production flow of the light component to the isopropylbenzene material is 0.5:100,

[0050] In this embodiment, the loss rate of cumene in the extracted light component material is 0.22%, the removal rate of ethylbenzene is 25.4%, and the residual amount of ethylbenzene in the product is 0.76%.

[0051] The oil-water separation tank is flushed once a week. The flushing liquid is water. The flushing flow rate is 0.2% of the isopropylbenzene feed flow rate. The flushing time is 1 hour. This can effectively remove the emulsified layer and avoid the accumulation of impurities therein, so that the device can operate stably for a long time.

[0052] Example 2

[0053] This embodiment is basically the same as Embodiment 1, except that the mass ratio of the produced flow rate of the light component to the isopropylbenzene material is 0.9:100.

[0054] In this embodiment, the loss rate of cumene in the extracted light component material is 0.53%, the removal rate of ethylbenzene is 37.3%, and the residual amount of ethylbenzene in the product is 0.64%.

[0055] The oil-water separation tank is flushed once every two weeks. The flushing liquid is cumene. The flushing flow rate is 0.2% of the cumene feed flow rate. The flushing time is 1 hour. This can effectively remove the emulsion layer and avoid the accumulation of impurities therein, so that the device can operate stably for a long time.

[0056] Example 3

[0057] This embodiment is basically the same as Embodiment 1, except that the mass ratio of the produced flow rate of the light component to the isopropylbenzene material is 0.3:100.

[0058] In this embodiment, the loss rate of cumene in the extracted light component material is 0.03%, the removal rate of ethylbenzene is 25.0%, and the residual amount of ethylbenzene in the product is 0.76%.

[0059] The oil-water separation tank is flushed once every 6 days. The flushing liquid is cumene. The flushing flow rate is 0.2% of the cumene feed flow rate. The flushing time is 1 hour. It can effectively remove the emulsion layer and avoid the accumulation of impurities therein. The device can operate stably for a long time.

[0060] Comparative Example 1

[0061] Please refer to Figure 2 This comparative example is basically the same as Example 1, except that the light component extraction pipe is set at the liquid phase outlet of the reflux tank 301.

[0062] In this comparative example, the loss rate of cumene in the light components extracted was 0.26%, the removal rate of ethylbenzene was 23.1%, and the residual amount of ethylbenzene in the product was 0.78%. Compared with Example 1, the loss of cumene increased by 16%, and the removal rate of ethylbenzene decreased by 2.3%. In addition, due to the accumulation of impurities and the appearance of oligomers at the top of the tower, the device could not operate stably for a long period of time.

[0063] Comparative Example 2

[0064] This comparative example is basically the same as Example 1, except that an efficient coalescer filter element is provided in the oil-water separation structure in the aftercooler condensate tank. In this comparative example, compared with Example 1, the filter element is more easily clogged and needs to be cleared every three days.

[0065] Comparative Example 3

[0066] This comparative example is basically the same as Example 1, except that the temperature of the gas phase component taken out from the top of the tower is 152°C, and the temperature of the gas phase component taken out from the top of the tower after condensation by the condenser is 72°C (that is, the temperature difference of the gas phase component before and after passing through the condenser is 80°C).

[0067] In this comparative example, compared with Example 1, since the condensation temperature is too low, no condensation and no flow will occur (i.e., the flow in the non-condensable gas discharge pipe 7 is too low), resulting in impurities such as ethylbenzene, 1,2-propylene glycol, and alcohol ethers being unable to be discharged from the non-condensable gas discharge pipe 7, and will be enriched and accumulated in the condenser, reflux tank and related pipelines, blocking the system.

[0068] In this comparative example, the loss rate of cumene in the extracted light component material was 0%, the removal rate of ethylbenzene was 0%, and the residual amount of ethylbenzene in the product was 1%.

[0069] In summary, the cumene recovery method provided by the present invention can not only effectively remove ethylbenzene in the circulating cumene, but also reduce the loss of cumene in the process; in addition, an online flushing unit is added to the method provided by the present invention, which can ensure the long-term stable operation of the device.

[0070] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A method for recovering cumene, characterized in that: include: The gas phase components, heavy components and cumene are obtained by introducing the cumene material into a recovery tower; The gas phase component is first cooled by a condenser arranged at the top of the recovery tower, and then separated by gas-liquid separation in a reflux tank to obtain non-condensable gas and reflux liquid in the reflux tank, wherein the reflux liquid is circulated to the recovery tower, and the non-condensable gas in the reflux tank is cooled by an aftercooler, and then the light component is extracted in the after-condensate tank; The heavy components are discharged from the bottom of the tower; The cumene is taken out from the side line of the recovery tower.

2. The method according to claim 1, characterized in that The cumene material is the reaction product of α,α-dimethylbenzyl alcohol and hydrogen in the process of preparing propylene oxide by the cumene hydroperoxide method.

3. The method according to claim 1 or 2, characterized in that: The cumene material comprises the following components in percentage by mass: 95-99.5% of cumene, 0.01-2% of ethylbenzene, 0.001-0.05% of organic acid, 0.001-0.1% of water, 0.001-0.1% of 1,2-propylene glycol, 0.001-0.1% of alcohol ether and 0-4.0% of heavy components.

4. The method according to claim 3, characterized in that The operating conditions of the recovery tower include: a tower top pressure of 0 to 200 KPaG, and a tower top temperature of 130 to 200°C; preferably, the operating conditions of the recovery tower include: a tower top pressure of 20 to 100 KPaG, and a tower top temperature of 145 to 180°C.

5. The method according to any one of claims 1 to 4, characterized in that: The temperature difference of the gas phase component before and after passing through the condenser is ≤60°C; preferably, the temperature difference of the gas phase component before and after passing through the condenser is ≤30°C.

6. The method according to any one of claims 1 to 5, characterized in that: The post-condensate tank is provided with an oil-water separation structure, and the water phase obtained by the oil-water separation structure is directly discharged, a part of the obtained oil phase is produced as the light component, and the other part is circulated to the reflux tank; Preferably, the oil-water separation structure adopts a gravity sedimentation structure, and no coalescer filter element is provided in the gravity sedimentation structure; and / or, the light component is separated and treated to recover the isopropylbenzene therein.

7. The method according to any one of claims 1 to 6, characterized in that: The mass ratio of the withdrawal flow rate of the light component to the isopropylbenzene material is (0.1-2.0):100, preferably (0.3-1.0):

100.

8. The method according to any one of claims 1 to 7, characterized in that: The condensation temperature of the aftercooler is 30-80°C, preferably 40-55°C.

9. The method according to any one of claims 1 to 8, characterized in that: The post-condensate tank is provided with an online flushing unit, and the online flushing unit uses a flushing liquid to flush the oil-water interface.

10. The method according to claim 9, characterized in that The flushing liquid is water or cumene.

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