Producing and purifying device and method for epoxypropane

Abstract

The invention provides a production and purification device for epoxypropane. The production and purification device comprises an epoxidation reactor; a public stripping section, a partition area and a public rectifying section are sequentially arranged in the divided-wall rectifying tower from bottom to top, a partition plate is vertically arranged in the partition area and divides the partition area into a feeding area and a discharging area, the upper end of the epoxidation reactor is communicated with the feeding area, and the lower end of the epoxidation reactor is communicated with the discharging area. The lower end of the epoxidation reactor is communicated with the upper end of the public rectifying section; the extractive distillation tower is communicated with the discharging area; the methanol recovery system is communicated with the lower end of the public rectifying section and the lower end of the extractive distillation tower, and the methanol recovery system is also communicated to the lower end of the epoxidation reactor. According to the invention, short process and low energy consumption can be realized, epoxypropane can be timely separated from water, and side reactions are reduced.

Description

Technical Field

[0001] The present invention relates to the field of chemical industry, and in particular to the production of propylene oxide. Background Art

[0002] Propylene oxide (PO) is an important propylene derivative, mainly used in the production of polyether polyols, propylene glycol, propylene glycol ether, isopropanolamine, propylene carbonate, etc. It is one of the main raw materials for the manufacture of polyurethane, non-ionic surfactants, emulsifiers, oilfield demulsifiers, flame retardants, plasticizers, lubricants, etc. It is widely used in the petroleum, chemical, pesticide, textile, daily chemical and other industries.

[0003] At present, the main methods for producing PO include chlorohydrin method, co-oxidation method and direct oxidation method with hydrogen peroxide (HPPO method). Chlorohydrin method has large discharge of three wastes, serious environmental pollution and great difficulty in comprehensive treatment, and has been listed as restricted development. Co-oxidation method includes isobutane co-oxidation method and ethylbenzene co-oxidation method, which respectively co-oxidize isobutane or ethylbenzene with propylene to produce PO, and simultaneously co-produce tert-butyl alcohol (TBA) or styrene (SM). The main disadvantages of this method are high equipment investment cost, complex process flow, high requirements for raw material purity, a large number of co-products in the production process, and economic efficiency is seriously dependent on the market demand and price of co-products. HPPO method uses propylene and industrial hydrogen peroxide as raw materials, and directly oxidizes to produce propylene oxide under the catalysis of titanium silicon molecular sieve catalyst. The process flow is simple, the reaction conditions are mild, the whole production process has no harmful gas emissions, and the wastewater produced can meet the discharge standards after general treatment. Its advantages of green environmental protection and low production cost have made it one of the fastest-growing and most promising processes.

[0004] The HPPO method generally uses a large amount of methanol as a solvent, dissolving excess propylene in a methanol solution to react with hydrogen peroxide, thereby ensuring a high conversion rate of hydrogen peroxide and selectivity of propylene oxide. The reaction mixture generally contains 10wt% to 30wt% of propylene oxide, 30wt% to 70wt% of methanol, 5wt% to 15wt% of propylene, 20wt% to 40wt% of water and unreacted hydrogen peroxide and a small amount of high-boiling by-products. After obtaining the reaction mixture, it is necessary to further separate it to purify propylene oxide and recover raw materials such as methanol and propylene. The existing separation process basically adopts the traditional distillation process of five distillation towers or six distillation towers. In the first distillation tower after the reactor, propylene oxide is discharged from the top of the tower along with propylene. The top material of the first distillation tower enters the propylene stripping tower to separate propylene from propylene oxide and methanol. The propylene oxide and methanol are discharged from the bottom of the propylene stripping tower for extractive distillation to obtain propylene oxide, and then further refined to obtain refined propylene oxide. Methanol and water are discharged from the bottom of the first distillation tower, and then methanol and water are separated by distillation. Alternatively, propylene is discharged from the top of the first distillation tower after the reactor, and the top material of the first distillation tower enters the propylene stripping tower to purify propylene. The propylene oxide and methanol discharged from the bottom of the first distillation tower enter the crude propylene oxide tower to separate propylene oxide from methanol and water. The crude propylene oxide obtained from the top of the crude propylene oxide tower is then subjected to extractive distillation to obtain propylene oxide, and then further refined to obtain refined propylene oxide. Methanol and water are discharged from the bottom of the crude propylene oxide tower, and then methanol and water are separated by distillation. The entire process is relatively long and has high energy consumption, and is insufficient in terms of energy conservation and environmental protection. In addition, propylene oxide cannot be separated from water in time at high temperatures, which increases the risk of propylene oxide hydrolysis reaction and reduces the propylene oxide yield. Summary of the invention

[0005] The embodiments of the present application provide a production and purification device and method for propylene oxide to solve the technical problems of the existing propylene oxide separation process being long, energy consumption being high, and propylene oxide being unable to be separated from water in time at a high temperature.

[0006] In a first aspect, an embodiment of the present application provides a production and purification device for propylene oxide, the production and purification device for propylene oxide comprising:

[0007] An epoxidation reactor for producing propylene oxide by the HPPO process;

[0008] A dividing wall distillation tower, wherein a common stripping section, a partitioning zone and a common distillation section are sequentially arranged inside the dividing wall distillation tower from bottom to top, a partition is vertically arranged in the partitioning zone, and the partitioning zone is divided into a feed zone and a discharge zone by the partitioning zone, the upper end of the epoxidation reactor is connected to the feed zone, and the lower end of the epoxidation reactor is connected to the upper end of the common distillation section;

[0009] A distillation system, wherein the distillation system comprises an extractive distillation tower, and the extractive distillation tower is connected to the discharge area;

[0010] A methanol recovery system is connected to the lower end of the common distillation section and the lower end of the extractive distillation tower, and the methanol recovery system is also connected to the lower end of the epoxidation reactor.

[0011] In some embodiments of the present application, the methanol recovery system includes a low-pressure methanol tower and a high-pressure methanol tower, the lower end of the low-pressure methanol tower is connected to the middle of the high-pressure methanol tower, the lower end of the common distillation section and the lower end of the extractive distillation tower are both connected to the middle of the low-pressure methanol tower, and the tops of the low-pressure methanol tower and the high-pressure methanol tower are both connected to the lower end of the epoxidation reactor.

[0012] In some embodiments of the present application, the distillation system further includes a first reboiler, which is connected to the lower portion of the extractive distillation tower and is used to heat the material in the lower portion of the extractive distillation tower.

[0013] In some embodiments of the present application, the top of the high-pressure methanol tower is connected to the lower end of the epoxidation reactor through the first reboiler.

[0014] In some embodiments of the present application, the methanol recovery system further includes a second reboiler, which is connected to the lower portion of the low-pressure methanol tower and is used to heat the material in the lower portion of the low-pressure methanol tower.

[0015] In some embodiments of the present application, the top of the high-pressure methanol tower is also connected to the lower end of the epoxidation reactor through the second reboiler.

[0016] In a second aspect, an embodiment of the present application provides a method for producing and purifying propylene oxide, the method being implemented by the propylene oxide production and purification device described in any embodiment of the first aspect, the method comprising:

[0017] introducing external raw materials, propylene from the common distillation section and materials from the methanol recovery system into the epoxidation reactor, and performing epoxidation reaction in the epoxidation reactor;

[0018] The product of the epoxidation reaction is introduced into the dividing wall distillation tower, and the product is distilled and separated by the dividing wall distillation tower, the propylene enriched in the common distillation section is returned to the epoxidation reactor, the first solution enriched in the common stripping section is introduced into the methanol recovery system, and the crude propylene oxide enriched in the discharge zone is introduced into the extractive distillation tower;

[0019] Purifying the crude propylene oxide by the extractive distillation tower, collecting the propylene oxide product from the upper end of the extractive distillation tower, and introducing the second solution enriched at the lower end of the extractive distillation tower into the methanol recovery system;

[0020] The first solution and the second solution are treated and methanol is recovered by the methanol recovery system, and the recovered methanol is returned to the epoxidation reactor.

[0021] In some embodiments of the present application, the operating pressure of the dividing wall distillation tower is 1.2-2.0 MPaG; and / or,

[0022] The operating temperature of the common distillation section is 30-45°C; and / or,

[0023] The operating temperature of the common stripping section is 152-160°C; and / or,

[0024] The number of theoretical plates in the feed zone is 5-20; and / or,

[0025] The number of theoretical plates of the common stripping section, the discharging zone and the common rectifying section is 55-85; and / or,

[0026] The number of theoretical plates of the common distillation section is 20-35; and / or,

[0027] The number of theoretical plates of the common stripping section is 15-30.

[0028] In some embodiments of the present application, the operating pressure of the extractive distillation tower is 0-0.2 MPaG; and / or,

[0029] The top temperature of the extractive distillation tower is 60-75° C.; and / or,

[0030] The bottom temperature of the extractive distillation tower is 80-95°C.

[0031] In some embodiments of the present application, the extractant used in the extractive distillation tower is at least one of desalted water, deoxygenated water or steam condensate.

[0032] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0033] The production and purification device of propylene oxide provided in the embodiment of the present application separates the epoxidation reaction product through a dividing wall distillation tower, and integrates the operations that need to be completed in at least two towers such as a propylene separation tower and a crude propylene oxide tower into one tower, which has a short process and low energy consumption, and can also separate propylene oxide from water in a timely manner to reduce side reactions. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0035] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0036] Figure 1 A schematic diagram of the structure of a propylene oxide production and purification device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0038] Unless otherwise specified, the terms used herein should be understood as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. In the event of a conflict, this specification takes precedence.

[0039] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0040] The existing propylene oxide separation process has technical problems such as a long process, high energy consumption, and the inability to separate propylene oxide from water in a timely manner at a high temperature.

[0041] The technical solution provided by the embodiments of the present application is to solve the above technical problems, and the overall idea is as follows:

[0042] In the first aspect, the present application embodiment provides a production and purification device for propylene oxide, please refer to Figure 1 , the propylene oxide production and purification device comprises:

[0043] Epoxidation reactor R1 for producing propylene oxide by HPPO process;

[0044] A dividing wall distillation tower T1, wherein a common stripping section, a partitioning zone and a common distillation section are sequentially arranged inside the dividing wall distillation tower T1 from bottom to top, a partition is vertically arranged in the partitioning zone, and the partitioning zone is divided into a feed zone and a discharge zone by the partitioning zone, the upper end of the epoxidation reactor R1 is connected to the feed zone, and the lower end of the epoxidation reactor R1 is connected to the upper end of the common distillation section;

[0045] A distillation system, wherein the distillation system comprises an extractive distillation tower T2, and the extractive distillation tower T2 is connected to the discharge area;

[0046] A methanol recovery system is connected to the lower end of the common distillation section and the lower end of the extractive distillation tower T2, and is also connected to the lower end of the epoxidation reactor R1.

[0047] The present application is directed to the separation and purification of the product of propylene oxide produced by the HPPO method. The HPPO method uses hydrogen peroxide and propylene as raw materials and methanol as solvent, and its product generally contains oxygen, propylene oxide, propylene, with or without propane, methanol, water, with or without hydrogen peroxide, propylene glycol methyl ether, propylene glycol, and a small amount of aldehyde and ketone impurities. In actual production, the product of the HPPO epoxidation reaction generally contains 0.1wt%-0.2wt% oxygen, 10wt%-30wt% propylene oxide, 5wt%-15wt% propylene, with or without propane, 30wt%-70wt% methanol, 20wt%-40wt% water, 0.5wt%-2wt% propylene glycol, propylene glycol methyl ether, a small amount of aldehyde and ketone impurities, and may contain hydrogen peroxide. It should be noted that the present application can be used to process the epoxidation reaction product with the above-mentioned weight range, but the scope that can be processed by the present application is not limited to this.

[0048] The epoxidation reaction product enters the bulkhead distillation tower T1 from the upper section of the epoxidation reactor R1. The bulkhead distillation tower T1 can separate multiple components in the epoxidation reaction product. After the epoxidation reaction product enters the bulkhead distillation tower T1, the light components are enriched in the common distillation section, and the light components mainly include propylene and oxygen-containing non-condensable gas. Skilled and technical personnel can separate non-condensable gas and propylene by conventional means in the art, for example, setting a condensation reflux tank connected to the common distillation section. If a condensation reflux tank is set, a part of the condensed material is refluxed into the common distillation section, and its reflux ratio can be, for example, 0.5-2, and the other part is returned to the lower end of the oxidation reactor. The non-condensable gas remains in a gaseous state in the condensation reflux tank. To ensure safety, the non-condensable gas can be diluted with nitrogen first, and then the tail gas is incinerated after further recovering propylene through washing. The condensed material is mainly unreacted propylene, which contains propylene, or does not contain propane, and a small amount of propylene oxide.

[0049] The heavy component enriched in the common distillation section is called the first solution, which contains water, methanol, propylene glycol methyl ether, propylene glycol, and possibly hydrogen peroxide, mainly methanol and water. The first solution is sent to the methanol recovery system to recover methanol.

[0050] The components of the discharge zone are crude propylene oxide, which includes propylene oxide, methanol, and may contain water. Mainly propylene oxide and methanol are sent to the propylene oxide product tower for refining and purifying propylene oxide.

[0051] The present application integrates the operations that need to be completed in at least two towers, such as a propylene separation tower and a crude propylene oxide tower, into one tower by setting a dividing wall distillation tower T1, and has the characteristics of short process, low investment, low energy consumption, and small footprint. At the same time, the method operates at low temperature, can quickly separate propylene oxide from water, inhibits the hydrolysis reaction of propylene oxide, improves the yield of propylene oxide, reduces the loss of propylene oxide, and reduces the operating cost of the device.

[0052] The dividing wall distillation tower T1 is a distillation equipment with a partition in the middle of a conventional distillation tower. The middle partition is installed vertically to prevent the liquid and gas phases on both sides from mixing horizontally. The internal structure of the dividing wall distillation tower T1 is divided into a common distillation section, a feed area, a discharge area and a common stripping section. The feed area is divided into a feed stripping section and a feed distillation section from bottom to top, and the discharge area is divided into a discharge stripping section and a discharge distillation section from bottom to top. The feed area can perform a rough fractionation on the feed. The discharge area, the common distillation section and the common stripping section are collectively called the main tower, which separates light, medium and heavy components. The dividing wall distillation tower T1 can also be equipped with conventional facilities such as a condenser and a reboiler.

[0053] The crude propylene oxide enters the extractive distillation tower for refining. The extractive distillation tower can obtain a high-purity propylene oxide product. The liquid phase obtained at the bottom of the tower is called the second solution, which includes methanol, water, and may contain propylene oxide. The second solution is sent to the methanol recovery system to recover methanol. The extractive distillation tower is provided with an extractant inlet L for introducing an extractant, and a propylene oxide feed port for introducing crude propylene oxide. The extractive distillation tower is divided into a rectifying section, an extractive rectifying section, and a stripping section, wherein the rectifying section is located above the extractant inlet L, the distillation section between the extractant inlet L and the propylene oxide feed port is the extractive rectifying section, and the stripping section is located below the propylene oxide feed port. In some embodiments, the number of theoretical plates in the rectifying section is 30-60, the number of theoretical plates in the extraction section is 20-40, and the number of theoretical plates in the stripping section is 15-30. The extractive distillation tower T2 top can obtain 99.9wt%-99.99wt% of propylene oxide products.

[0054] The methanol recovery system is used to recover methanol in the first solution and the second solution. The main components of the first solution and the second solution are water and methanol. Those skilled in the art can recover methanol in a conventional manner.

[0055] The present application separates the epoxidation reaction product through a dividing wall distillation tower T1, and integrates the operations that need to be completed in at least two towers such as a propylene separation tower and a crude propylene oxide tower into one tower, which has a short process and low energy consumption, and can also separate propylene oxide from water in a timely manner to reduce side reactions.

[0056] In some embodiments of the present application, the methanol recovery system includes a low-pressure methanol tower T3 and a high-pressure methanol tower T4, the lower end of the low-pressure methanol tower T3 is connected to the middle of the high-pressure methanol tower T4, the lower end of the common distillation section and the lower end of the extractive distillation tower T2 are both connected to the middle of the low-pressure methanol tower T3, and the tops of the low-pressure methanol tower T3 and the high-pressure methanol tower T4 are both connected to the lower end of the epoxidation reactor R1.

[0057] The first solution and the second solution are processed together in the low-pressure methanol tower T3. The first solution and the second solution mainly include water, methanol, propylene glycol monomethyl ether, propylene glycol, aldehyde and ketone impurities, and may contain a small amount of hydrogen peroxide. In some embodiments, the number of theoretical plates of the low-pressure methanol tower T3 is 20-35, the operating pressure is 0.1-0.2MPa, the tower top temperature is 65-85°C, the tower bottom temperature is 75-90°C, and the tower top methanol recovery rate can reach 20%-50%.

[0058] The liquid phase obtained at the bottom of the low-pressure methanol tower T3 is called the third solution. In some embodiments, the third solution includes 65%-75% methanol, 25%-32% water, and 0.5%-3%. The third solution is sent to the high-pressure methanol tower T4 to recover the remaining methanol. In some embodiments, the high-pressure methanol tower T4 has a theoretical plate number of 20-35, an operating pressure of 0.3-0.5 MPa, a tower top temperature of 105-125°C, and a tower bottom temperature of 143-158°C.

[0059] Methanol with a purity greater than 99% can be obtained from the top of the low-pressure methanol tower T3 and the high-pressure methanol tower T4, and the obtained methanol is returned to the oxidation reactor.

[0060] In some embodiments of the present application, the distillation system further includes a first reboiler E1, which is connected to the lower part of the extractive distillation tower T2 and is used to heat the material in the lower part of the extractive distillation tower T2.

[0061] In some embodiments of the present application, the top of the high-pressure methanol tower T4 is connected to the lower end of the epoxidation reactor R1 through the first reboiler E1.

[0062] It is easy to understand that the methanol collected from the top of the high-pressure methanol tower T4 has a higher temperature and can be used as a heat source for the first reboiler E1.

[0063] In some embodiments of the present application, the methanol recovery system further includes a second reboiler E2, which is connected to the lower portion of the low-pressure methanol tower T3 and is used to heat the material in the lower portion of the low-pressure methanol tower T3.

[0064] In some embodiments of the present application, the top of the high-pressure methanol tower T4 is also connected to the lower end of the epoxidation reactor R1 through the second reboiler E2.

[0065] It is easy to understand that the methanol recovered from the top of the high-pressure methanol tower T4 has a higher temperature and can be used as a heat source for the second reboiler E2.

[0066] In a second aspect, an embodiment of the present application provides a method for producing and purifying propylene oxide, the method being implemented by the propylene oxide production and purification device described in any embodiment of the first aspect, the method comprising:

[0067] S1: introducing external raw materials, propylene from the common distillation section and materials from the methanol recovery system into the epoxidation reactor R1, and performing epoxidation reaction in the epoxidation reactor R1;

[0068] S2: introducing the product of the epoxidation reaction into the dividing wall distillation tower T1, performing distillation separation on the product through the dividing wall distillation tower T1, returning the propylene enriched in the common distillation section to the epoxidation reactor R1, introducing the first solution enriched in the common stripping section into the methanol recovery system, and introducing the crude propylene oxide enriched in the discharge zone into the extractive distillation tower T2;

[0069] S3: purifying the crude propylene oxide through the extractive distillation tower T2, collecting the propylene oxide product from the upper end of the extractive distillation tower T2, and introducing the second solution enriched at the lower end of the extractive distillation tower T2 into the methanol recovery system;

[0070] S4: The first solution and the second solution are treated and methanol is recovered by the methanol recovery system, and the recovered methanol is returned to the epoxidation reactor R1.

[0071] In some embodiments of the present application, the operating pressure of the dividing wall distillation tower T1 is 1.2-2.0 MPaG; and / or,

[0072] The operating temperature of the common distillation section is 30-45°C; and / or,

[0073] The operating temperature of the common stripping section is 152-160°C; and / or,

[0074] The number of theoretical plates in the feed zone is 5-20; and / or,

[0075] The number of theoretical plates of the common stripping section, the discharging zone and the common rectifying section is 55-85; and / or,

[0076] The number of theoretical plates of the common distillation section is 20-35; and / or,

[0077] The number of theoretical plates of the common stripping section is 15-30.

[0078] As mentioned above, the discharge zone, the common distillation section, and the common stripping section are collectively referred to as the main tower, which separates light, medium, and heavy components. They are functionally integrated, and the theoretical plate numbers of the common stripping section, the discharge zone, and the common distillation section are the theoretical plate numbers of the main tower.

[0079] In some embodiments, the operating pressure of the dividing wall distillation tower T1 is 1.3-1.4 MPaG.

[0080] In some embodiments, the number of theoretical plates in the feed zone is 12-15.

[0081] In some embodiments, the main column has 65-82 theoretical plates.

[0082] In some embodiments, the common distillation section has 24-30 theoretical plates.

[0083] In some embodiments, the common stripping section has 20-26 theoretical plates.

[0084] In some embodiments of the present application, the operating pressure of the extractive distillation tower T2 is 0-0.2 MPaG; and / or,

[0085] The top temperature of the extractive distillation tower T2 is 60-75° C.; and / or,

[0086] The bottom temperature of the extractive distillation tower T2 is 80-95°C.

[0087] In some embodiments of the present application, the extractant used in the extractive distillation tower T2 is at least one of desalted water, deoxygenated water or steam condensate.

[0088] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0089] Example

[0090] This embodiment provides a production and purification device for propylene oxide. Figure 1, the propylene oxide production and purification device comprises:

[0091] Epoxidation reactor R1 for producing propylene oxide by HPPO process;

[0092] A dividing wall distillation tower T1, wherein a common stripping section, a partitioning zone and a common distillation section are sequentially arranged inside the dividing wall distillation tower T1 from bottom to top, a partition is vertically arranged in the partitioning zone, and the partitioning zone is divided into a feed zone and a discharge zone by the partitioning zone, the upper end of the epoxidation reactor R1 is connected to the feed zone, and the lower end of the epoxidation reactor R1 is connected to the upper end of the common distillation section;

[0093] A distillation system, wherein the distillation system comprises an extractive distillation tower T2, and the extractive distillation tower T2 is connected to the discharge area;

[0094] A methanol recovery system is connected to the lower end of the common distillation section and the lower end of the extractive distillation tower T2, and is also connected to the lower end of the epoxidation reactor R1.

[0095] The methanol recovery system includes a low-pressure methanol tower T3 and a high-pressure methanol tower T4, the lower end of the low-pressure methanol tower T3 is connected to the middle of the high-pressure methanol tower T4, the lower end of the common distillation section and the lower end of the extractive distillation tower T2 are both connected to the middle of the low-pressure methanol tower T3, and the tops of the low-pressure methanol tower T3 and the high-pressure methanol tower T4 are both connected to the lower end of the epoxidation reactor R1.

[0096] The extractive distillation column is provided with an extractant inlet L for introducing an extractant.

[0097] The distillation system further includes a first reboiler E1, which is connected to the lower part of the extractive distillation tower T2 and is used to heat the material in the lower part of the extractive distillation tower T2.

[0098] The top of the high-pressure methanol tower T4 is connected to the lower end of the epoxidation reactor R1 through the first reboiler E1.

[0099] The methanol recovery system further includes a second reboiler E2, which is connected to the lower part of the low-pressure methanol tower T3 and is used to heat the material in the lower part of the low-pressure methanol tower T3.

[0100] The top of the high-pressure methanol tower T4 is also connected to the lower end of the epoxidation reactor R1 through the second reboiler E2.

[0101] In addition, in this embodiment, the dividing wall distillation tower T1 and the extractive distillation tower T2 are both provided with a condenser and a reflux tank at the top in a conventional manner, and the dividing wall distillation tower T1 is also provided with a reboiler at the bottom in a conventional manner.

[0102] This embodiment also provides a method for producing and purifying propylene oxide, which is implemented by the propylene oxide production and purification device described in this embodiment, and the method comprises:

[0103] Sa: introducing external raw materials, propylene from the common distillation section and materials from the methanol recovery system into the epoxidation reactor R1, and performing epoxidation reaction in the epoxidation reactor R1;

[0104] Sb: introducing the product of the epoxidation reaction into the dividing wall distillation tower T1, performing distillation separation on the product through the dividing wall distillation tower T1, returning the propylene enriched in the common distillation section to the epoxidation reactor R1, introducing the first solution enriched in the common stripping section into the methanol recovery system, and introducing the crude propylene oxide enriched in the discharge zone into the extractive distillation tower T2;

[0105] Sc: purifying the crude propylene oxide through the extractive distillation tower T2, collecting the propylene oxide product from the upper end of the extractive distillation tower T2, and introducing the second solution enriched at the lower end of the extractive distillation tower T2 into the methanol recovery system;

[0106] Sd: The first solution and the second solution are treated and methanol is recovered by the methanol recovery system, and the recovered methanol is returned to the epoxidation reactor R1.

[0107] In the above steps, the operating pressure of the dividing wall distillation tower T1 is 1.35MPaG, the operating temperature of the common distillation section is 30-45°C, the operating temperature of the common stripping section is 152-160°C, the number of theoretical plates in the feed zone is 5-20, the number of theoretical plates in the common stripping section, the discharge zone and the common distillation section is 82, the number of theoretical plates in the common distillation section is 20-35, and the number of theoretical plates in the common stripping section is 15-30.

[0108] The operating pressure of the extractive distillation tower T2 is 0.04 MPaG, the top temperature of the extractive distillation tower T2 is 60-75°C, and the bottom temperature of the extractive distillation tower T2 is 80-95°C.

[0109] The extractant used in the extractive distillation tower T2 is at least one of deionized water, deoxygenated water or steam condensate.

[0110] The pressure of the low-pressure methanol tower T3 is 0.05 MPaG, the number of theoretical plates of the low-pressure methanol tower T3 is 26, and the methanol recovery rate reaches 47%.

[0111] The pressure of the low-pressure methanol tower T3 is 0.35 MPaG, and the number of theoretical plates of the low-pressure methanol tower T3 is 26.

[0112] The molar ratio of the reaction raw materials is hydrogen peroxide: propylene: methanol = 1: 1.5: 2. The composition of the epoxidation reaction mixed product is shown in Table 1

[0113] The purity of the propylene returned to the epoxidation reactor R1 in step Sb is 99.5wt%, and the purity of the methanol returned to the epoxidation reactor R1 in step Sd is 99wt%. The purity of the propylene oxide product recovered in step Sc is 99.95wt%, and the recovery rate is 99%.

[0114] The composition of the product of the epoxidation reaction in step Sb is shown in Table 1.

[0115]

[0116]

[0117] Table 1

[0118] The process described herein was calculated using the AspenPlus simulation program. The heat load conditions of each tower in this embodiment are shown in Table 2.

[0119] name Reboiler heat duty, MW Tower top condensing load, MW Dividing wall distillation tower T1 28.07 Extraction distillation tower T2 8.23 Low pressure methanol tower T3 23.8 High-pressure methanol tower T4 34.65 32.93

[0120] Table 2

[0121] Comparative Example

[0122] In this comparative example, the dividing wall distillation tower is replaced by a propylene distillation tower and a propylene oxide distillation tower, and propylene is recovered and propylene oxide is separated in a traditional manner. The other parts are the same as those in the embodiment.

[0123] The reaction product of this team first enters the propylene distillation tower, and the top of the tower obtains the same quality of circulating propylene as in the embodiment, and the bottom of the tower obtains the material containing propylene oxide, methanol, water, a small amount of propylene glycol and propylene glycol methyl ether; the material at the bottom of the propylene tower enters the propylene oxide distillation tower, and the top of the tower obtains crude propylene oxide, which is sent to the extractive distillation tower for purification to obtain a propylene oxide product with a purity of 99.95% (weight), and the methanol-water material at the bottom of the crude propylene oxide separation tower and the methanol-water material at the bottom of the propylene oxide refining tower are sent to the methanol distillation tower for treatment. The process described in this paper is calculated using the Aspen Plus simulation program, and the heat load of each tower is shown in Table 3.

[0124] name Reboiler heat duty, MW Propylene distillation tower 24.98 Propylene oxide distillation tower 13.88 Extractive distillation tower 9.17 Methanol distillation tower 50.64

[0125] Table 3

[0126] It can be seen that the embodiment requires lower external heat input, and the total heat load is 32.72MW. Compared with the comparative example, the heat load is reduced by 35.95MW, and the energy saving reaches 36.4%.

[0127] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0128] In the present application, in the absence of any contrary description, the directional words used, such as "upper" and "lower", are specifically the directions of the drawings in the accompanying drawings. In addition, in the description of the present application specification, the terms "including", "comprising", etc. refer to "including but not limited to". Moreover, the terms "including", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of further restrictions, the elements defined by the sentence "including..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements. In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that there can be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone. For the association relationship of more than three associated objects described by "and / or", it means that any one of these three associated objects can exist alone, or any at least two of them exist at the same time. For example, for A, and / or B, and / or C, it can be represented that any one of A, B, and C exists alone, or any two of them exist at the same time, or three of them exist at the same time. In this article, "at least one" refers to one or more, and "multiple" refers to two or more. "At least one", "the following at least one (individual)" or similar expressions refer to any combination of these items, including any combination of single (individual) or plural (individual). For example, "at least one (individual) of a, b, or c", or "at least one (individual) of a, b, and c", can all represent: a, b, c, ab (i.e. a and b), ac, bc, or abc, wherein a, b, and c can be single or multiple, respectively.

[0129] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A production and purification device for propylene oxide, characterized in that: The production and purification device of propylene oxide comprises: An epoxidation reactor for producing propylene oxide by the HPPO process; A dividing wall distillation tower, wherein a common stripping section, a partitioning zone and a common distillation section are sequentially arranged inside the dividing wall distillation tower from bottom to top, a partition is vertically arranged in the partitioning zone, and the partitioning zone is divided into a feed zone and a discharge zone by the partitioning zone, the upper end of the epoxidation reactor is connected to the feed zone, and the lower end of the epoxidation reactor is connected to the upper end of the common distillation section; A distillation system, wherein the distillation system comprises an extractive distillation tower, and the extractive distillation tower is connected to the discharge area; A methanol recovery system is connected to the lower end of the common distillation section and the lower end of the extractive distillation tower, and the methanol recovery system is also connected to the lower end of the epoxidation reactor.

2. The production and purification device for propylene oxide according to claim 1, characterized in that: The methanol recovery system comprises a low-pressure methanol tower and a high-pressure methanol tower, the lower end of the low-pressure methanol tower is connected to the middle of the high-pressure methanol tower, the lower end of the common distillation section and the lower end of the extractive distillation tower are both connected to the middle of the low-pressure methanol tower, and the tops of the low-pressure methanol tower and the high-pressure methanol tower are both connected to the lower end of the epoxidation reactor.

3. The production and purification device for propylene oxide according to claim 2, characterized in that: The distillation system further comprises a first reboiler, which is communicated with the lower part of the extractive distillation tower and is used for heating the material in the lower part of the extractive distillation tower.

4. The production and purification device for propylene oxide according to claim 3, characterized in that: The top of the high-pressure methanol tower is connected to the lower end of the epoxidation reactor through the first reboiler.

5. The production and purification device for propylene oxide according to claim 2, characterized in that: The methanol recovery system also includes a second reboiler, which is connected to the lower part of the low-pressure methanol tower and is used to heat the material in the lower part of the low-pressure methanol tower.

6. The production and purification device for propylene oxide according to claim 5, characterized in that: The top of the high-pressure methanol tower is also connected to the lower end of the epoxidation reactor through the second reboiler.

7. A method for producing and purifying propylene oxide, characterized in that: The method is implemented by the propylene oxide production and purification device according to any one of claims 1 to 6, and the method comprises: introducing external raw materials, propylene from the common distillation section and materials from the methanol recovery system into the epoxidation reactor, and performing epoxidation reaction in the epoxidation reactor; The product of the epoxidation reaction is introduced into the dividing wall distillation tower, and the product is distilled and separated by the dividing wall distillation tower, the propylene enriched in the common distillation section is returned to the epoxidation reactor, the first solution enriched in the common stripping section is introduced into the methanol recovery system, and the crude propylene oxide enriched in the discharge zone is introduced into the extractive distillation tower; Purifying the crude propylene oxide by the extractive distillation tower, collecting the propylene oxide product from the upper end of the extractive distillation tower, and introducing the second solution enriched at the lower end of the extractive distillation tower into the methanol recovery system; The first solution and the second solution are treated and methanol is recovered by the methanol recovery system, and the recovered methanol is returned to the epoxidation reactor.

8. The method for producing and purifying propylene oxide according to claim 7, characterized in that: The operating pressure of the dividing wall distillation tower is 1.2-2.0 MPaG; and / or, The operating temperature of the common distillation section is 30-45°C; and / or, The operating temperature of the common stripping section is 152-160°C; and / or, The number of theoretical plates in the feed zone is 5-20; and / or, The number of theoretical plates of the common stripping section, the discharging zone and the common rectifying section is 55-85; and / or, The number of theoretical plates of the common distillation section is 20-35; and / or, The number of theoretical plates of the common stripping section is 15-30.

9. The method for producing and purifying propylene oxide according to claim 7, characterized in that: The operating pressure of the extractive distillation tower is 0-0.2 MPaG; and / or, The top temperature of the extractive distillation tower is 60-75° C.; and / or, The bottom temperature of the extractive distillation tower is 80-95°C.

10. The method for producing and purifying propylene oxide according to claim 7, characterized in that: The extractant used in the extractive distillation tower is at least one of deionized water, deoxygenated water or steam condensate.

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