Propylene oxide separation and purification system and method

Abstract

The application relates to an epoxy propane separation and purification system and a separation and purification method, and belongs to the technical field of fine chemical industry. The epoxy propane separation and purification system comprises an epoxidation reactor, a propylene stripping tower, a crude PO separation tower, a PO purification tower and a propylene purification tower. The propylene stripping tower is arranged, the propylene stripping tower is operated at low temperature and low pressure, the hydrolysis reaction of epoxy propane is inhibited, and the loss rate of epoxy propane is effectively reduced; the crude PO separation tower is arranged, the crude PO separation tower is arranged as a divided wall distillation column, the operations originally required to be completed in the crude PO separation tower and a methanol separation tower are concentrated in one tower, the effects of short process, low investment, low energy consumption and small land occupation area are achieved; the PO purification tower is arranged, the PO purification tower is arranged as an extractive distillation tower, light hydrocarbon components are effectively reduced, and the purity of epoxy propane products is improved, and the purity reaches 99.9-99.99%.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fine chemical industry, and particularly relates to an epoxypropane separation and purification system and a separation and purification method. BACKGROUND

[0002] Epoxypropane (PO) is an important propylene derivative, which is mainly used for producing polyether polyols, propylene glycol, propylene glycol ether, isopropanolamine, propylene carbonate, 1,4-butylene glycol and the like, and is one of main raw materials for manufacturing polyurethane, non-ionic surfactant, emulsifier, oil field demulsifier, flame retardant, plasticizer, lubricating oil and the like, and has a wide application in petroleum, chemical industry, pesticide, textile, daily chemical industry and the like.

[0003] At present, the production methods of PO mainly include chlorohydrination method, co-oxidation method and hydrogen peroxide direct oxidation method (HPPO method). The chlorohydrination method has a large amount of three wastes emission, serious environmental pollution and great difficulty in comprehensive treatment, and has been listed in the restricted development. The co-oxidation method, also known as "Halcon method", includes isobutane co-oxidation method and ethylbenzene co-oxidation method, which respectively generates PO by co-oxidation reaction of isobutane or ethylbenzene and propylene, and simultaneously generates tertiary butanol (TBA) or styrene (SM), and the main defect of the method is high device investment cost, complex process flow, high requirement for raw material purity, and a large amount of joint products in the production process, and the economic nature is seriously dependent on the market demand and price of the joint products.

[0004] The HPPO method generally uses a large amount of methanol as a solvent, and dissolves excessive propylene in the methanol solution to react with hydrogen peroxide, so as to ensure high conversion rate of hydrogen peroxide and selectivity of epoxypropane. Generally, the reaction product is first subjected to a first step distillation, so as to separate the reaction product into overhead material containing epoxypropane, propylene and propane and oxygen, and bottom material containing solvent, water and high-boiling-point impurities, the overhead product can be further separated in a second distillation step, the overhead is light components containing propylene and propane, and the bottom is crude epoxypropane, or the overhead material of the first step distillation is subjected to partial condensation and stripping to remove propylene and the like light components, and then is separated by extraction distillation to obtain crude epoxypropane and methanol aqueous solution, the refined epoxypropane product is obtained from the overhead of the extraction distillation column, and the bottom is the extractant, methanol, water and other impurities.

[0005] Chinese patent CN103172594B discloses a method for refining and purifying propylene oxide, the epoxidation reaction product enters a propylene separation column for separation, the overhead material obtained contains propylene, with or without propane, propylene oxide, methanol, with or without water, the bottom material contains methanol, water, hydrogen peroxide and high-boiling-point by-products; the overhead material of the propylene separation column enters a propylene stripping column, the overhead gas contains propylene, with or without propane, a small amount of propylene oxide, and is recycled back to the reaction system after compression; the bottom material contains methanol, propylene oxide, a small amount of aldehyde and ketone impurities, with or without water, enters a reactor packed with basic ion exchange resin for reaction, removes methyl formate and acetaldehyde therefrom, and further refines to obtain high-purity propylene oxide through rectification.

[0006] Chinese patent CN108473452A discloses a method for epoxidizing propylene, comprising the following steps: epoxidizing propylene with hydrogen peroxide in the presence of methanol, first flash-evaporating the reaction product under reduced pressure, returning the compressed flash-evaporated gas to the reaction, feeding the flash-evaporated liquid into a pre-fractionation column, separating propylene, propylene oxide, methanol and the like from the top of the column, and obtaining a methanol aqueous solution from the bottom of the column, feeding the overhead material of the pre-fractionation column into a propylene column, separating propylene from the top of the column and recycling it back to the reaction, separating crude propylene oxide and a solvent mixture from the bottom of the column, using a compound reactive to acetaldehyde to extract distill the crude propylene oxide, hydrogenating the solvent mixture and the bottom product of the extractive distillation, recovering methanol from the hydrogenated mixture through distillation under acid addition, and recycling the recovered methanol to the epoxidation reaction.

[0007] Chinese patent CN102898405B discloses a process for preparing propylene oxide by directly epoxidizing propylene with hydrogen peroxide, which comprises the following steps: (1) mixing propylene and hydrogen peroxide thoroughly, and then performing an epoxidation reaction in a fixed-bed reactor packed with titanium-silicon molecular sieve to generate a crude propylene oxide product; (2) pumping the crude product into a crude separation column to perform a crude separation of unreacted propylene and propylene oxide; (3) feeding the crude product into a propylene flash-evaporation column, and then into a light component recovery column; (4) compressing the propylene and light components separated from the crude separation column and the light component recovery column by a compressor, and then feeding them into a non-condensing gas separation column, feeding the propylene from the bottom of the separation column into a recycling system, and discharging tail gas through a tail gas absorption device; and (5) treating the propylene oxide after the light component recovery column treatment in a propylene oxide purification column through extractive distillation to obtain a high-purity propylene oxide product.

[0008] Chinese patent CN104130216B discloses a process for continuously producing propylene oxide by directly oxidizing propylene / propane mixture with hydrogen peroxide. In the reaction process, a fluidized bed loop reactor is used, and a fine particle molecular sieve catalyst is applied. The slurry is discharged and then the low oxygen propylene / propane mixture and propylene oxide are respectively evaporated from the flash tower. The catalyst slurry and mother liquor are separated by a membrane separator. After the mother liquor is separated from methanol by flash evaporation, the recovered solvent methanol is used to recover the high oxygen propylene / propane mixture remaining after reaction in the high oxygen propylene / propane absorption tower, and the catalyst slurry is returned to the reactor after on-line partial regeneration for recycling.

[0009] Chinese patent CN106349188B provides a process for removing propylene and oxygen, which comprises: reacting propylene with hydrogen peroxide in an epoxy propylene reactor; feeding the material at the outlet of the epoxy propylene reactor into a high-pressure rectifying tower to obtain propylene at the top of the high-pressure rectifying tower; and feeding the material at the bottom of the high-pressure rectifying tower into a low-pressure stripping tower to further separate propylene and remove oxygen. The process provided by the invention simplifies the process of recovering propylene, and does not need to separately provide an oxygen stripping tower and high-pressure nitrogen supply. However, the reaction stream of the invention first enters the high-pressure rectifying tower, and the operating pressure is 1.8-2.4 MPaG. In actual verification, the operating temperature of the high-pressure rectifying tower is relatively high, which accelerates the hydrolysis reaction of propylene oxide, resulting in loss of propylene oxide.

[0010] As can be seen from the above, the existing separation process basically adopts a traditional rectification process of five or six distillation towers. In the first distillation tower after the reactor, propylene is discharged from the top together with propylene oxide. The material at the top of the first distillation tower is fed into a propylene stripping tower to separate propylene from propylene oxide and methanol. The propylene stripping tower is discharged at the bottom to separate propylene oxide and methanol for extractive distillation to obtain propylene oxide. Further purification is required to obtain refined propylene oxide. The methanol and water are discharged at the bottom of the first distillation tower and are separated by distillation. Alternatively, in the first distillation tower after the reactor, propylene is discharged from the top. The material at the top of the first distillation tower is fed into a propylene stripping tower to purify propylene. The material at the bottom of the first distillation tower is discharged to separate propylene oxide and methanol in a crude propylene oxide tower. The crude propylene oxide obtained at the top of the crude propylene oxide tower is subjected to extractive distillation to obtain propylene oxide. Further purification is required to obtain refined propylene oxide. The methanol and water are discharged at the bottom of the crude propylene oxide tower and are separated by distillation. The whole process is relatively long and has high energy consumption. There are deficiencies in energy saving and environmental protection. Moreover, propylene oxide cannot be separated from water in time at a high temperature, which increases the risk of hydrolysis reaction of propylene oxide and reduces the yield of propylene oxide. SUMMARY

[0011] The purpose of the present application is to provide an epoxy propylene separation and purification system to solve the technical problems of long process, high energy consumption and low yield of epoxy propylene in the prior art.

[0012] The embodiment of the present application provides an epoxy propane separation and purification system, comprising: an epoxidation reactor, the inlet of the epoxidation reactor is communicated with a feed source; a propylene stripping tower, the inlet of the propylene stripping tower is communicated with the outlet of the epoxidation reactor, the propylene stripping tower is provided with a first top outlet and a first bottom outlet; a crude PO separation tower, the crude PO separation tower is a divided wall distillation column, the inlet of the crude PO separation tower is communicated with the first bottom outlet, the crude PO separation tower is provided with a second top outlet, a second bottom outlet and a second side outlet, the second side outlet is communicated with the inlet of the epoxidation reactor through a methanol circulation pipe; a PO purification tower, the PO purification tower is an extractive distillation column, the inlet of the PO purification tower is communicated with the second top outlet, the PO purification tower is provided with a third top outlet and a third bottom outlet, the third bottom outlet is communicated with the inlet of the crude PO separation tower; a propylene purification tower, the inlet of the propylene purification tower is communicated with the first top outlet, the propylene purification tower is provided with a fourth top outlet, a fourth bottom outlet and a fourth side outlet, the fourth side outlet is communicated with the inlet of the epoxidation reactor through a propylene circulation pipe, and the fourth bottom outlet is communicated with the inlet of the crude PO separation tower.

[0013] The embodiment of the present application also provides an epoxy propane separation and purification method, which is separated and purified by using the above epoxy propane separation and purification system, and comprises the following steps.

[0014] Propylene, hydrogen peroxide and methanol are introduced into the epoxidation reactor to perform epoxidation reaction, and an epoxidation product is obtained at the outlet of the epoxidation reactor;

[0015] The epoxidation product is introduced into the propylene stripping tower to perform separation under a first condition, and a first bottom mixture is obtained at the first bottom outlet;

[0016] The first bottom mixture is introduced into the crude PO separation tower to perform rectification under a third condition, and a second top mixture is obtained at the second top outlet;

[0017] The second top mixture is introduced into the PO purification tower to perform extractive distillation under a fourth condition, and an epoxy propane product is obtained at the third top outlet;

[0018] Wherein, the mass percentage of the epoxy propane product is as follows:

[0019] The epoxidation product comprises 0.1-0.2% of oxygen, 10-30% of epoxy propane, 5-15% of propylene, 0-2% of propane, 30-70% of methanol, 20-40% of water, 0-0.1% of hydrogen peroxide and 0.5-1% of propylene glycol, and the rest is aldehyde ketone impurities;

[0020] The first bottom mixture comprises 20-50% of water, 20-50% of epoxy propane, 30-40% of methanol, 0.6-1.2% of propylene glycol and 0-0.1% of hydrogen peroxide, and the rest is aldehyde ketone impurities;

[0021] The second overhead mixture comprises: propylene oxide 93-97%, methanol 3-5%, water 0.5-1%;

[0022] The purity of the propylene oxide product is 99.9-99.99%.

[0023] Optionally, the method further comprises the following steps:

[0024] The first overhead mixture is obtained at the first overhead outlet;

[0025] The first overhead mixture is introduced into a propylene purification column, and separation is performed under a second condition, and a fourth bottom mixture is obtained at a fourth bottom outlet;

[0026] The fourth bottom mixture is introduced into a crude PO separation column for rectification;

[0027] The first overhead mixture comprises: oxygen 0.1-1%, propylene 70-80%, propane 0-2%, propylene oxide 10-15%, and methanol 5-10%; and the fourth bottom mixture comprises: propylene oxide 50-75% and methanol 25-50%.

[0028] The first overhead mixture comprises: oxygen 0.1-1%, propylene 70-80%, propane 0-2%, propylene oxide 10-15%, and methanol 5-10%; and the fourth bottom mixture comprises: propylene oxide 50-75% and methanol 25-50%.

[0029] Optionally, the method further comprises the following steps:

[0030] Circulating propylene is obtained at the fourth side outlet;

[0031] The circulating propylene is returned through the propylene circulation pipe and mixed with the feed.

[0032] Optionally, the method further comprises the following steps:

[0033] Circulating methanol is obtained at the second side outlet;

[0034] The circulating methanol is returned through the methanol circulation pipe and mixed with the feed.

[0035] Optionally, the method further comprises the following steps:

[0036] A third bottom mixture is obtained at the third bottom outlet;

[0037] The third bottom mixture is returned to the crude PO separation column for rectification again;

[0038] The first overhead mixture comprises: oxygen 0.1-1%, propylene 70-80%, propane 0-2%, propylene oxide 10-15%, and methanol 5-10%; and the fourth bottom mixture comprises: propylene oxide 50-75% and methanol 25-50%.

[0039] The third bottom mixture comprises: methanol 10-20%, water 80-90%, and propylene oxide 0.5-1%.

[0040] Optionally, the first condition comprises: the propylene stripping column has a pressure of 0.02-0.1 MPa(g); a reflux ratio of 0.5-4; a top temperature of 42-50 DEG C; and a bottom temperature of 50-70 DEG C.

[0041] Optionally, the second condition comprises: the propylene purification column has a pressure of 1.0-1.5 MPa(g); a reflux ratio of 0.5-4; a top temperature of 35-50 DEG C; and a bottom temperature of 75-85 DEG C.

[0042] Optionally, the third condition comprises: the crude PO separation column has a pressure of 0.02-0.2 MPa(g); a reflux ratio of 7-20; a top temperature of 50-70 DEG C; and a bottom temperature of 100-115 DEG C.

[0043] Optionally, the fourth condition comprises: the PO purification column has a pressure of 0.04-0.2 MPa(g); a reflux ratio of 0.5-4; a top temperature of 35-50 DEG C; and a bottom temperature of 80-90 DEG C.

[0044] The one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0045] The epoxy propane separation and purification system provided by the embodiments of the present application has the following advantages: the propylene stripping column is used to inhibit the hydrolysis reaction of epoxy propane and effectively reduce the loss rate of epoxy propane; the crude PO separation column is used as a divided wall column, so that the operations originally completed in the crude PO separation column and the methanol separation column are concentrated in one column, thereby achieving the effects of short process, low investment, low energy consumption and small land occupation; and the PO purification column is used as an extractive distillation column, which effectively reduces the carrying of light hydrocarbon components and improves the purity of the epoxy propane product.

[0046] The above description is only a summary of the technical solutions of the present application, in order to more clearly understand the technical means of the present application, the embodiments of the present application can be implemented according to the content of the specification, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following will describe the specific embodiments of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creating any creative labor.

[0048] Figure 1is a schematic diagram of a propylene oxide separation and purification system provided by an embodiment of the present application.

[0049] Figure 2 is a flow chart of a propylene oxide separation and purification method provided by an embodiment of the present application.

[0050] Reference signs: 10-epoxidation reactor; 20-propylene stripping column; 21-first top outlet; 22-first bottom outlet; 30-raw PO separation column; 31-second top outlet; 32-second bottom outlet; 33-second side outlet; 34-methanol circulation pipe; 40-PO purification column; 41-third top outlet; 42-third bottom outlet; 50-propylene purification column; 51-fourth top outlet; 52-fourth bottom outlet; 53-fourth side outlet; 54-propylene circulation pipe. DETAILED DESCRIPTION

[0051] The advantages and various effects of the present application will be more clearly presented hereinafter with specific embodiments and examples. Those skilled in the art should understand that these specific embodiments and examples are used to illustrate the present application, rather than limit the present application.

[0052] Throughout the specification, unless otherwise specifically indicated, the terms used herein are to be understood as having the meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. If there is a conflict, the present specification takes precedence. The professional terms used herein are only for the purpose of describing the specific embodiments, and are not intended to limit the protection scope of the present application. For example, room temperature can refer to a temperature in the range of 10-35℃.

[0053] Unless otherwise specifically indicated, the various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0054] The technical solution of the embodiments of the present application is to solve the above technical problems, and the general idea is as follows:

[0055] Please refer to Figure 1According to a typical embodiment of the present application, an epoxy propane separation and purification system is provided, comprising: an epoxidation reactor 10, an inlet of the epoxidation reactor 10 being in communication with a feed source; a propylene stripping column 20, an inlet of the propylene stripping column 20 being in communication with an outlet of the epoxidation reactor 10, the propylene stripping column 20 being provided with a first top outlet 21 and a first bottom outlet 22; a crude PO separation column 30, the crude PO separation column 30 being a divided wall distillation column, an inlet of the crude PO separation column 30 being in communication with the first bottom outlet 22, the crude PO separation column 30 being provided with a second top outlet 31, a second bottom outlet 32 and a second side outlet 33, the second side outlet 33 being in communication with the inlet of the epoxidation reactor 10 through a methanol circulation pipe 34; a PO purification column 40, the PO purification column 40 being an extractive distillation column, an inlet of the PO purification column 40 being in communication with the second top outlet 31, the PO purification column 40 being provided with a third top outlet 41 and a third bottom outlet 42, the third bottom outlet 42 being in communication with the inlet of the crude PO separation column 30; a propylene purification column 50, an inlet of the propylene purification column 50 being in communication with the first top outlet 21, the propylene purification column 50 being provided with a fourth top outlet 51, a fourth bottom outlet 52 and a fourth side outlet 53, the fourth side outlet 53 being in communication with the inlet of the epoxidation reactor 10 through a propylene circulation pipe 54, the fourth bottom outlet 52 being in communication with the inlet of the crude PO separation column 30. By providing the propylene stripping column 20, since the propylene stripping column 20 is operated at low temperature and low pressure, the hydrolysis reaction of the epoxy propane is inhibited, and the loss rate of the epoxy propane is effectively reduced. By providing the crude PO separation column 30 and setting it as a divided wall distillation column, the operations that were originally completed in two columns, i.e., the crude PO separation column and the methanol separation column, are concentrated in one column, achieving the effects of short process, low investment, low energy consumption and small land occupation. By providing the PO purification column 40 and setting it as an extractive distillation column, the light hydrocarbon components are effectively reduced, thereby improving the purity of the epoxy propane product. By providing the methanol circulation pipe 34 and the propylene circulation pipe 54, the recycling of the methanol and the propylene is respectively achieved, and the production cost is effectively reduced.

[0056] According to another typical embodiment of the present application, an epoxy propane separation and purification method is also provided, which is separated and purified by using the above-mentioned epoxy propane separation and purification system, comprising the following steps:

[0057] S1, introducing propylene, hydrogen peroxide and methanol into the epoxidation reactor 10 to perform an epoxidation reaction, and obtaining an epoxidation product at the outlet of the epoxidation reactor 10.

[0058] S2, introducing the epoxidation product into the propylene stripping column 20 to perform separation under a first condition, and obtaining a first bottom mixture at the first bottom outlet 22.

[0059] S3, introducing the first bottom mixture into the crude PO separation column 30 to perform distillation under a third condition, and obtaining a second top mixture at the second top outlet 31.

[0060] S4, passing the second top mixture into a PO purification column 40, performing extractive distillation under a fourth condition, and obtaining an epoxy propane product at a third top outlet 41.

[0061] wherein: in mass percentage,

[0062] The epoxidation product includes: oxygen 0.1-0.2%, epoxy propane 10-30%, propylene 5-15%, propane 0-2%, methanol 30-70%, water 20-40%, hydrogen peroxide 0-0.1%, propylene glycol 0.5-1%, and the rest is aldehyde ketone impurities.

[0063] The first bottom mixture includes: water 20-50%, epoxy propane 20-50%, methanol 30-40%, propylene glycol 0.6-1.2%, hydrogen peroxide 0-0.1%, and the rest is aldehyde ketone impurities.

[0064] The second top mixture includes: epoxy propane 93-97%, methanol 3-5%, water 0.5-1%.

[0065] The purity of the epoxy propane product is 99.9-99.99%.

[0066] The above steps can realize the separation and purification of epoxy propane. Specifically, by step S1, propylene, hydrogen peroxide and methanol are passed into the epoxidation reactor 10 as feed, an epoxidation reaction occurs, and propylene and hydrogen peroxide are subjected to epoxidation reaction in methanol solvent to generate epoxy propane product; by step S2, the excess propylene for reaction is separated from the reaction product; by step S3, epoxy propane, methanol and water are separated, crude epoxy propane is obtained at the top of the column, methanol is obtained at the middle of the column, and wastewater is obtained at the bottom of the column; by step S4, the crude epoxy propane is refined to remove the carried methanol and other impurities, and finally the epoxy propane product with a purity of 99.9-99.99% is obtained.

[0067] It should be noted that the extractant of the PO purification column 40 is preferably desalted water, deoxygenated water or steam turbine condensate, and more preferably deoxygenated water or steam turbine condensate.

[0068] In some embodiments, the following steps are further included:

[0069] S5, obtaining a first top mixture at the first top outlet 21;

[0070] S6, passing the first top mixture into a propylene purification column 50, performing separation under a second condition, and obtaining a fourth bottom mixture at a fourth bottom outlet 52;

[0071] S7, passing the fourth bottom mixture into a crude PO separation column 30 for rectification;

[0072] Wherein: in mass percentage,

[0073] The first top mixture comprises: oxygen 0.1-1%, propylene 70-80%, propane 0-2%, propylene oxide 10-15%, and methanol 5-10%.

[0074] The fourth bottom mixture comprises: propylene oxide 50-75% and methanol 25-50%.

[0075] The purpose and mechanism of the above steps are to purify and refine propylene in the first top mixture and recover the fourth bottom mixture.

[0076] In some embodiments, the method further comprises the following steps:

[0077] S8, obtaining circulating propylene at the fourth side outlet 53;

[0078] S9, recycling the circulating propylene through the propylene recycling pipe 54 and mixing it with the feed.

[0079] Through steps S8 and S9, the circulation of propylene is achieved, effectively reducing production costs.

[0080] In some embodiments, the method further comprises the following steps:

[0081] S10, obtaining circulating methanol at the second side outlet 33;

[0082] S11, recycling the circulating methanol through the methanol recycling pipe 34 and mixing it with the feed.

[0083] Through steps S10 and S11, the circulation of methanol is achieved, effectively reducing production costs.

[0084] In some embodiments, the method further comprises the following steps:

[0085] S12, obtaining a third bottom mixture at the third bottom outlet 42;

[0086] S13, recycling the third bottom mixture to the crude PO separation tower 30 for further rectification;

[0087] Wherein: in mass percentage,

[0088] The third bottom mixture comprises: methanol 10-20%, water 80-90%, and propylene oxide 0.5-1%.

[0089] The purpose and mechanism of the above steps are to recover methanol and propylene oxide and improve the recovery rate of propylene oxide.

[0090] In some embodiments, the first condition comprises: the pressure of the propylene stripping tower 20 is 0.02-0.1 MPa(g);

[0091] The reflux ratio is 0.5-4; the overhead temperature is 42-50℃; and the bottom temperature is 50-70℃.

[0092] Preferably, the propylene stripping column 20 has a pressure of 0.04-0.06 MPa(g); and a reflux ratio of 1-2.

[0093] The purpose and mechanism of controlling the working parameters of the propylene stripping column 20 under the first condition is to reduce the hydrolysis reaction of propylene oxide and improve the recovery rate of propylene oxide.

[0094] In some embodiments, the second condition includes that the propylene purification column 50 has a pressure of 1.0-1.5 MPa(g); a reflux ratio of 0.5-4; an overhead temperature of 35-50℃; and a bottom temperature of 75-85℃.

[0095] Preferably, the propylene purification column 50 has a pressure of 1.2-1.4 MPa(g); and a reflux ratio of 1-2.

[0096] The purpose and mechanism of controlling the working parameters of the propylene purification column 50 under the second condition is to improve the purity of propylene and control the oxygen content of non-condensable gas.

[0097] In some embodiments, the third condition includes that the crude PO separation column 30 has a pressure of 0.02-0.2 MPa(g); a reflux ratio of 7-20; an overhead temperature of 50-70℃; and a bottom temperature of 100-115℃.

[0098] Preferably, the crude PO separation column 30 has a pressure of 0.04-0.1 MPa(g); a reflux ratio of 7.5-9; an overhead temperature of 50-60℃; and a bottom temperature of 105-110℃.

[0099] The purpose and mechanism of controlling the working parameters of the crude PO separation column 30 under the third condition is to ensure product quality, make full use of low-temperature heat source, and reduce energy consumption.

[0100] In some embodiments, the fourth condition includes that the PO purification column 40 has a pressure of 0.04-0.2 MPa(g); a reflux ratio of 0.5-4; an overhead temperature of 35-50℃; and a bottom temperature of 80-90℃.

[0101] Preferably, the PO purification column 40 has a pressure of 0.04-0.1 MPa(g).

[0102] The purpose and mechanism of controlling the working parameters of the PO purification column 40 under the fourth condition is to improve the purity of propylene oxide and reduce energy consumption.

[0103] The application will be described in detail below with reference to examples, comparative examples and experimental data.

[0104] Example 1

[0105] The present embodiment provides an epoxy propane separation and purification system, comprising: an epoxidation reactor 10, the inlet of the epoxidation reactor 10 being in communication with a feed source; a propylene stripping column 20, the inlet of the propylene stripping column 20 being in communication with the outlet of the epoxidation reactor 10, the propylene stripping column 20 being provided with a first top outlet 21 and a first bottom outlet 22; a crude PO separation column 30, the crude PO separation column 30 being a divided wall rectifying column, the inlet of the crude PO separation column 30 being in communication with the first bottom outlet 22, the crude PO separation column 30 being provided with a second top outlet 31, a second bottom outlet 32 and a second side outlet 33, the second side outlet 33 being in communication with the inlet of the epoxidation reactor 10 through a methanol circulation pipe 34; a PO purification column 40, the PO purification column 40 being an extractive distillation column, the inlet of the PO purification column 40 being in communication with the second top outlet 31, the PO purification column 40 being provided with a third top outlet 41 and a third bottom outlet 42, the third bottom outlet 42 being in communication with the inlet of the crude PO separation column 30; a propylene purification column 50, the inlet of the propylene purification column 50 being in communication with the first top outlet 21, the propylene purification column 50 being provided with a fourth top outlet 51, a fourth bottom outlet 52 and a fourth side outlet 53, the fourth side outlet 53 being in communication with the inlet of the epoxidation reactor 10 through a propylene circulation pipe 54, the fourth bottom outlet 52 being in communication with the inlet of the crude PO separation column 30.

[0106] The present embodiment also provides an epoxy propane separation and purification method, which is carried out by using the above system and comprises the following steps:

[0107] S1, propylene, hydrogen peroxide and methanol are introduced into the epoxidation reactor 10 according to a molar ratio of 1.5:1:2 for epoxidation reaction, and an epoxidation product is obtained at the outlet of the epoxidation reactor 10, the composition of the epoxidation product being shown in Table 1.

[0108] Table 1 Composition of the epoxidation product of Example 1

[0109] Mass percent Oxygen % Propylene % Propane % Water % PO % Methanol % Propylene glycol % Example 1 0.1 11.04 0.23 26.56 28.7 32.55 0.82

[0110] S2, the epoxidation product is introduced into the propylene stripping column 20 for separation under the first condition, and a first bottom mixture is obtained at the first bottom outlet 22.

[0111] The first condition is that the pressure of the propylene stripping column 20 is 0.04 MPa(g); the reflux ratio is 1, the top temperature is 45.4℃, and the bottom temperature is 66.2℃.

[0112] S3, the first bottom mixture is introduced into the crude PO separation column 30 for rectification under the third condition, and a second top mixture is obtained at the second top outlet 31.

[0113] wherein: the third condition is that the pressure of the crude PO separation column 30 is 0.1 MPa(g); the reflux ratio is 8; the overhead temperature is 59°C; and the bottom temperature is 110°C. The energy consumption of the crude PO separation column 30 is 26.5 MW.

[0114] S4, passing the second overhead mixture into the PO purification column 40, and performing extractive distillation under the fourth condition to obtain the propylene oxide product at the third overhead outlet 41. The purity of the propylene oxide product is 99.95%, and the recovery rate is 99%.

[0115] wherein: the fourth condition is that the pressure of the PO purification column 40 is 0.04 MPa(g); the reflux ratio is 0.5; the overhead temperature is 36°C; and the bottom temperature is 88°C.

[0116] S5, obtaining the first overhead mixture at the first overhead outlet 21.

[0117] S6, passing the first overhead mixture into the propylene purification column 50, and performing separation under the second condition to obtain the fourth bottom mixture at the fourth bottom outlet 52.

[0118] wherein: the second condition is that the pressure of the propylene purification column 50 is 2.2 MPa(g); the reflux ratio is 1.0; the overhead temperature is 42°C; and the bottom temperature is 83°C.

[0119] S7, passing the fourth bottom mixture into the crude PO separation column 30 for rectification.

[0120] S8, obtaining the circulating propylene at the fourth side outlet 53.

[0121] wherein: the purity of the circulating propylene is 99.6%.

[0122] S9, refluxing the circulating propylene through the propylene circulation pipe 54 and mixing it with the feed.

[0123] S10, obtaining the circulating methanol at the second side outlet 33.

[0124] wherein: the purity of the circulating methanol is 98.9%.

[0125] S11, refluxing the circulating methanol through the methanol circulation pipe 34 and mixing it with the feed.

[0126] S12, obtaining the third bottom mixture at the third bottom outlet 42.

[0127] S13, refluxing the third bottom mixture to the crude PO separation column 30 for rectification again.

[0128] Example 2

[0129] The embodiment also provides a propylene oxide separation and purification method, which is performed by using the system provided in the embodiment 1 and comprises the following steps.

[0130] S1, propylene, hydrogen peroxide and methanol are introduced into an epoxidation reactor 10 according to a molar ratio of 3:1:4 to perform an epoxidation reaction, and an epoxidation product is obtained at the outlet of the epoxidation reactor 10, and the composition of the epoxidation product is shown in Table 2.

[0131] Table 2 Composition of the epoxidation product of the embodiment 2

[0132] Mass percent Oxygen % Propylene % Propane % Water % PO % Methanol % Propylene glycol % Example 2 0.12 27.62 0.1 11.8 11.5 48.76 0.1

[0133] S2, the epoxidation product is introduced into a propylene stripping column 20 to perform separation under a first condition, and a first bottom mixture is obtained at a first bottom outlet 22.

[0134] The first condition is that the pressure of the propylene stripping column 20 is 0.04 MPa (g), the reflux ratio is 1.2, the top temperature is 44 ℃ and the bottom temperature is 65 ℃.

[0135] S3, the first bottom mixture is introduced into a crude PO separation column 30 to perform rectification under a third condition, and a second top mixture is obtained at a second top outlet 31.

[0136] The third condition is that the pressure of the crude PO separation column 30 is 0.1 MPa (g), the reflux ratio is 7.5, the top temperature is 57 ℃ and the bottom temperature is 108 ℃. The energy consumption of the crude PO separation column 30 is 20.3 MW.

[0137] S4, the second top mixture is introduced into a PO purification column 40 to perform extractive distillation under a fourth condition, and a propylene oxide product is obtained at a third top outlet 41. The purity of the propylene oxide product is 99.96%, and the recovery rate is 99%.

[0138] The fourth condition is that the pressure of the PO purification column 40 is 0.04 MPa (g), the reflux ratio is 0.48, the top temperature is 35 ℃ and the bottom temperature is 87 ℃.

[0139] S5, a first top mixture is obtained at the first top outlet 21.

[0140] S6, the first top mixture is introduced into a propylene purification column 50 to perform separation under a second condition, and a fourth bottom mixture is obtained at a fourth bottom outlet 52.

[0141] The second condition is that the pressure of the propylene purification column 50 is 1.2 MPa (g), the reflux ratio is 1.3, the top temperature is 44 ℃ and the bottom temperature is 85 ℃.

[0142] S7, the fourth bottom mixture is introduced into the crude PO separation column 30 to perform rectification.

[0143] S8, obtaining the recycled propylene at the fourth side outlet 53.

[0144] wherein: the purity of the recycled propylene is 99.6%.

[0145] S9, recycling the recycled propylene through the propylene recycling pipe 54 and mixing with the feed.

[0146] S10, obtaining the recycled methanol at the second side outlet 33.

[0147] wherein: the purity of the recycled methanol is 99%.

[0148] S11, recycling the recycled methanol through the methanol recycling pipe 34 and mixing with the feed.

[0149] S12, obtaining the third bottom mixture at the third bottom outlet 42.

[0150] S13, recycling the third bottom mixture to the crude PO separation tower 30 for rectification again.

[0151] Comparative Example 1

[0152] The composition of the epoxidation reaction mixture is the same as that in Example 1, the crude PO separation tower is a conventional separation tower, and a methanol separation tower is added; the PO product of the PO purification tower is not taken out through a side line, but is obtained from the top of the tower, and then is sent to a PO refining tower, and the final PO product is obtained from the bottom of the refining tower. The process described herein is calculated using the Aspen Plus simulation program, and the purity of the final PO product is 99.8%; the energy consumption of the crude PO separation tower is 12.71 MW, and the energy consumption of the methanol separation tower is 29.09 MW.

[0153] Comparative Example 2

[0154] The composition of the epoxidation reaction mixture is the same as that in Example 2, the crude PO separation tower is a conventional separation tower, and a methanol separation tower is added; the PO product of the PO purification tower is not taken out through a side line, but is obtained from the top of the tower, and then is sent to a PO refining tower, and the final PO product is obtained from the bottom of the refining tower. The process described herein is calculated using the Aspen Plus simulation program, and the purity of the final PO product is 99.9%; the energy consumption of the crude PO separation tower is 11.8 MW, and the energy consumption of the methanol separation tower is 37.4 MW.

[0155] Experimental Example

[0156] According to the epoxidized propylene separation and purification method of Examples 1-2 and Comparative Examples 1-2, the purity of the epoxidized propylene product, the recovery rate and the total amount of system power consumption are calculated after the reaction is completed, and the calculation results are shown in Table 3.

[0157] Table 3

[0158] Propylene oxide purity % Recovery % Total system electricity consumption MW Example 1 99.95 99 43.67 Example 2 99.96 99 39.65 Comparative Example 1 99.94 99 58.97 Comparative Example 2 99.93 99 66.45

[0159] From Table 3, according to the comparison of Examples 1-2 and Comparative Examples 1-2, it can be seen that the propylene oxide separation and purification system and method provided by the present application can ensure effective separation and purification of propylene oxide under the condition of reducing two towers in the system, the product purity reaches 99.95-99.99%, the conversion rate reaches 99%, and the energy consumption of the whole system is greatly reduced, which is reduced by 15.3 MW and 26.8 MW compared with Comparative Examples 1 and 2, respectively.

[0160] Finally, it should be noted that the terms "comprising", "including", or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements, but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0161] Although preferred embodiments of the present application have been described, those skilled in the art can make further changes and modifications to these embodiments once they know the basic inventive concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0162] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A method for separating and purifying propylene oxide, characterized in that: The system used in the method is composed of the following components: Epoxidation reactor (10): the inlet of the epoxidation reactor (10) is connected to the feed source; Propylene stripping tower (20): the inlet of the propylene stripping tower (20) is directly connected to the outlet of the epoxidation reactor (10), and the propylene stripping tower (20) is provided with a first top outlet (21) and a first bottom outlet (22); A crude PO separation tower (30): the crude PO separation tower (30) is a dividing wall distillation tower, the inlet of the crude PO separation tower (30) is connected to the first bottom outlet (22), the crude PO separation tower (30) is provided with a second top outlet (31), a second bottom outlet (32) and a second side outlet (33), the second side outlet (33) is connected to the inlet of the epoxidation reactor (10) through a methanol circulation pipe (34), and the second bottom outlet (32) is used to discharge wastewater; PO purification tower (40): the PO purification tower (40) is an extractive distillation tower, the inlet of the PO purification tower (40) is connected to the second top outlet (31), the PO purification tower (40) is provided with a third top outlet (41) and a third bottom outlet (42), the third bottom outlet (42) is connected to the inlet of the crude PO separation tower (30), and the third top outlet (41) is used to discharge the propylene oxide product; Propylene purification tower (50): the inlet of the propylene purification tower (50) is connected to the first top outlet (21), the propylene purification tower (50) is provided with a fourth top outlet (51), a fourth bottom outlet (52) and a fourth side outlet (53), the fourth side outlet (53) is connected to the inlet of the epoxidation reactor (10) through a propylene circulation pipe (54), the fourth bottom outlet (52) is connected to the inlet of the crude PO separation tower (30), and the fourth top outlet (51) is used to discharge oxygen-containing non-condensable gas; The method comprises the following steps: Propylene, hydrogen peroxide and methanol are introduced into the epoxidation reactor (10) to carry out epoxidation reaction, and an epoxidation product is obtained at the outlet of the epoxidation reactor (10); Passing the epoxidation product into a propylene stripping tower (20), separating the epoxidation product under a first condition, and obtaining a first bottom mixture at a first bottom outlet (22); Passing the first bottom mixture into a crude PO separation tower (30), performing rectification under a third condition, and obtaining a second top mixture at a second top outlet (31); Passing the second top mixture into a PO purification tower (40), performing extractive distillation under a fourth condition, and obtaining a propylene oxide product at the third top outlet (41); In which: in mass percentage, The epoxidation product comprises: 0.1-0.2% oxygen, 10-30% propylene oxide, 5-15% propylene, 0-2% propane, 30-70% methanol, 20-40% water, 0-0.1% hydrogen peroxide, 0.5-1% propylene glycol, and the balance being aldehyde and ketone impurities; The first base mixture comprises: 20-50% water, 20-50% propylene oxide, 30-40% methanol, 0.6-1.2% propylene glycol, 0-0.1% hydrogen peroxide, and the balance being aldehyde and ketone impurities; The second top mix comprises: 93-97% propylene oxide, 3-5% methanol, and 0.5-1% water; The purity of the propylene oxide product is 99.9-99.99%; Obtaining a first top mixture at the first top outlet (21); Passing the first top mixture into a propylene purification tower (50), performing separation under the second condition, and obtaining a fourth bottom mixture at a fourth bottom outlet (52); Passing the fourth bottom mixture into a crude PO separation tower (30) for rectification; In which: in mass percentage, The first top mixture comprises: 0.1-1% oxygen, 70-80% propylene, 0-2% propane, 10-15% propylene oxide and 5-10% methanol; The fourth bottom mixture comprises: 50-75% propylene oxide and 25-50% methanol; The first condition includes: The pressure of the propylene stripping tower (20) is 0.02-0.1 MPa(g); the reflux ratio is 0.5-4; the tower top temperature is 42-50°C; and the tower bottom temperature is 50-70°C. The second condition includes: The pressure of the propylene purification tower (50) is 1.0-1.5 MPa(g); the reflux ratio is 0.5-4; the tower top temperature is 35-50°C; and the tower bottom temperature is 75-85°C. The third condition includes: The pressure of the crude PO separation tower (30) is 0.02-0.2 MPa(g); the reflux ratio is 7-20; the tower top temperature is 50-70°C; and the tower bottom temperature is 100-115°C. The fourth condition includes: The pressure of the PO purification tower (40) is 0.04-0.2 MPa(g); the reflux ratio is 0.5-4; the tower top temperature is 35-50°C; and the tower bottom temperature is 80-90°C.

2. The method for separating and purifying propylene oxide according to claim 1, wherein The following steps are also included: Obtaining recycled propylene at the fourth side outlet (53); The circulating propylene is refluxed through the propylene circulation pipe (54) and mixed with the feed.

3. The method for separating and purifying propylene oxide according to claim 1, wherein The following steps are also included: Obtaining circulating methanol at the second side outlet (33); The circulating methanol is refluxed through the methanol circulation pipe (34) and mixed with the feed.

4. The method for separating and purifying propylene oxide according to claim 1, wherein The following steps are also included: Obtaining a third bottom mixture at the third bottom outlet (42); The third bottom mixture is refluxed to the crude PO separation tower (30) and distilled again; In which: in mass percentage, The third base mixture includes: 10-20% methanol, 80-90% water and 0.5-1% propylene oxide.

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