Preparation system of epoxypropane

Abstract

The utility model provides a preparation system of epoxypropane. The system comprises an oxidation reactor and an epoxidation reactor, a circulating pipeline is arranged on one side of the oxidation reactor, an inlet of the circulating pipeline is communicated with the bottom of the oxidation reactor, an outlet of the circulating pipeline is communicated with the oxidation reactor, and the outlet is higher than the inlet in the vertical direction and lower than the liquid level of the oxidation reactor in the vertical direction; the circulating pipeline is connected with an ethylbenzene pipeline; a first enhanced mass transfer unit is arranged in the circulating pipeline and close to an outlet of the circulating pipeline, the first enhanced mass transfer unit is connected with an oxygen pipeline, and oxygen in the oxygen pipeline enters the circulating pipeline after being treated by the first enhanced mass transfer unit so as to enhance the mass transfer effect between the oxygen and ethylbenzene; the side wall of the epoxidation reactor is connected with a propylene pipeline, and propylene enters the epoxidation reactor through the propylene pipeline so as to react with ethylbenzene hydroperoxide in the epoxidation reactor to generate epoxypropane. The system is simple in overall structure, and the occupied area and the production cost can be reduced easily.

Description

Technical Field

[0001] The utility model relates to the technical field of propylene oxide preparation technology, in particular to a propylene oxide preparation system. Background Art

[0002] The propylene oxide-styrene (PO / SM) co-production process, also known as the co-oxidation process, is an important chemical production technology. The PO / SM co-production process technology route mainly uses propylene and ethylbenzene as raw materials and adopts the co-oxidation process to produce propylene oxide and styrene product monomers. The process first directly oxidizes ethylbenzene with air or oxygen to produce ethylbenzene hydroperoxide (EBHP), and then EBHP and propylene undergo epoxidation reaction under the action of a molybdenum-based catalyst to produce methylbenzyl alcohol (phenylethanol) and propylene oxide. The epoxidation reaction liquid is distilled to obtain propylene oxide (PO) products, and phenylethanol is dehydrated at 260°C and normal pressure to produce styrene (SM) products.

[0003] In the related art, ethylbenzene peroxidation reaction is usually carried out in multiple (for example, two) non-catalytic, liquid-phase oxidation reactors connected in series. The concentration of EBHP in the reaction product obtained after passing through multiple oxidation reactors is usually only 8-10wt%. The concentration of EBHP needs to be concentrated to about 40wt% by a concentration device before it can participate in the next epoxidation reaction. The overall reaction efficiency is low, and more equipment is required, which occupies a large area and has high production costs.

[0004] In view of this, the present utility model is proposed. Utility Model Content

[0005] The first object of the utility model is to provide a system for preparing propylene oxide, which can improve the reaction efficiency and product yield of ethylbenzene peroxidation reaction by arranging a circulation pipeline used in conjunction with an oxidation reactor and arranging a first enhanced mass transfer unit in the circulation pipeline, so that the reaction product of the ethylbenzene peroxidation reaction can be directly input into the epoxidation reactor without further concentrating the reaction product of the ethylbenzene peroxidation reaction, thereby reducing production costs and reducing the area occupied by the system.

[0006] The second purpose of the utility model is to provide a method for preparing propylene oxide. By adopting the above system, the preparation method can improve the efficiency and yield of ethylbenzene epoxidation reaction, thereby improving the preparation efficiency of propylene oxide.

[0007] In order to achieve the above-mentioned purpose of the utility model, the following technical solutions are adopted:

[0008] The utility model provides a preparation system of propylene oxide, comprising: an oxidation reactor and an epoxidation reactor, wherein a delivery pipeline is arranged between the oxidation reactor and the epoxidation reactor, wherein the inlet of the delivery pipeline is connected to the product outlet of the oxidation reactor, and the outlet of the delivery pipeline is connected to the epoxidation reactor; a circulation pipeline is arranged on one side of the oxidation reactor, wherein the inlet of the circulation pipeline is connected to the bottom of the oxidation reactor; the outlet of the circulation pipeline is connected to the oxidation reactor, wherein the outlet of the circulation pipeline is higher than the inlet of the circulation pipeline in the vertical direction and the outlet of the circulation pipeline is lower than the liquid level of the oxidation reactor in the vertical direction; and the product outlet is higher than the outlet of the circulation pipeline in the vertical direction. The circulating pipeline is connected to an ethylbenzene pipeline, and the ethylbenzene in the ethylbenzene pipeline enters the oxidation reactor through the circulating pipeline; a first enhanced mass transfer unit is arranged in the circulating pipeline near the outlet of the circulating pipeline, and the first enhanced mass transfer unit is connected to an oxygen pipeline, and the oxygen in the oxygen pipeline enters the circulating pipeline after being processed by the first enhanced mass transfer unit, so as to enhance the mass transfer effect between oxygen and ethylbenzene; a propylene pipeline is connected to the side wall of the epoxidation reactor, and propylene enters the epoxidation reactor through the propylene pipeline to react with ethylbenzene hydroperoxide in the epoxidation reactor to generate propylene oxide.

[0009] In the related art, ethylbenzene peroxidation is usually carried out in multiple (e.g., two) non-catalytic, liquid-phase series oxidation reactors. The concentration of EBHP in the reaction product obtained after multiple oxidation reactors is usually only 8-10wt%. It is necessary to concentrate the concentration of EBHP to about 40wt% through a concentration device before participating in the next step of epoxidation. The overall reaction efficiency is low, and the required equipment is large, the floor space is large, and the production cost is high. Meanwhile, the utility model person has found through research that the reaction of ethylbenzene oxidation to generate hydrogen peroxide has the characteristics of slow reaction rate, temperature sensitivity, large influence by product concentration, medium reaction heat effect, etc., thus, the reactor of the reaction should meet the requirements of large liquid holdup, high heat transfer efficiency, stable operation, easy control of reaction conditions, etc. However, the utility model person has further found that the liquid phase backmixing in the reactor (e.g., bubble tower reactor) with large liquid holdup is serious, and the ethylbenzene peroxidation reaction is very sensitive to the concentration of product EBHP, and the liquid phase backmixing will reduce the selectivity of the reaction and is not conducive to the control of the reaction. In addition, when the reactor height-diameter ratio is large, bubbles will coalesce, the bubble dispersion effect will deteriorate, the gas-liquid contact area will be reduced, and the gas-liquid mass transfer efficiency will be affected. In view of the above technical background and research, the embodiment of the utility model provides a preparation system of propylene oxide, which uses only one oxidation reactor in the ethylbenzene peroxidation reaction stage, can reduce the occupied area, and help reduce production costs; by setting a circulation pipeline connected to the oxidation reactor, the circulation pipeline can be used to extract the material at the bottom of the oxidation reactor, and transport it back to the oxidation reactor through the circulation pipeline outlet, thereby, the material in the oxidation reactor can be stirred, and the uniformity of the distribution of microbubbles in the material inside the oxidation reactor is promoted, which helps to further improve the reaction efficiency and product yield; by setting a first enhanced mass transfer unit in the circulation pipeline, the first enhanced mass transfer unit can be used to disperse and crush the oxygen transported by the oxygen pipeline, which can increase the gas-liquid contact area between oxygen and ethylbenzene and improve the reaction efficiency. At the same time, since the first enhanced mass transfer unit is arranged in the circulation pipeline, when the first enhanced mass transfer unit disperses and crushes oxygen, the oxygen pipeline can be used to simultaneously disperse and crush the oxygen conveying power and the material conveying power in the circulation pipeline, thereby further improving the dispersion and crushing effect of the gas phase raw material. In addition, the microbubbles output by the first enhanced mass transfer unit can flow back to the oxidation reactor together with the circulating material under the impact of the material in the circulation pipeline, and the microbubbles can be further dispersed and crushed under the impact of the material, and the microbubbles can be more evenly distributed in the circulating material under the impact of the material, thereby avoiding the occurrence of bubble aggregation, thereby helping to further increase the gas-liquid contact area, thereby helping to further improve the reaction efficiency and reaction yield.In summary, the scheme helps to improve the reaction efficiency and product yield of the ethylbenzene peroxidation reaction, and because the concentration of ethylbenzene hydroperoxide in the reaction product of the ethylbenzene peroxidation reaction is relatively high, it can be directly input into the epoxidation reactor without further concentrating the reaction product of the ethylbenzene peroxidation reaction, and therefore, there is no need to set up a separate concentrating device, thereby further reducing the production cost and reducing the footprint of the system.

[0010] Preferably, a baffle is provided in the oxidation reactor, the top of the baffle is higher than the liquid level of the oxidation reactor in the vertical direction, and the distance between the bottom of the baffle and the bottom of the inner cavity of the oxidation reactor is a preset distance; a circulation channel is formed between the baffle and the side wall of the oxidation reactor, and the outlet of the circulation pipe is connected to the circulation channel.

[0011] In the above preferred embodiment, by providing a baffle in the oxidation reactor, it is possible to prevent the materials circulating back in the circulation pipeline from impacting the materials that have completed the reaction in the oxidation reactor, thereby preventing back mixing and ensuring that the reaction in the oxidation reactor proceeds in an orderly manner. The circulating materials can flow into the bottom of the oxidation reactor along the circulation channel, which helps to extend the reaction path of this part of the materials, thereby helping to improve the conversion rate of the reaction raw materials.

[0012] Preferably, a second enhanced mass transfer unit is provided in the oxidation reactor, and the oxygen pipeline is connected to the second enhanced mass transfer unit. The oxygen in the oxygen pipeline enters the oxidation reactor after being processed by the second enhanced mass transfer unit to enhance the mass transfer effect between oxygen and ethylbenzene. In this solution, by providing the second enhanced mass transfer unit in the oxidation reactor, the gaseous raw material can enter the oxidation reactor after being processed by the second enhanced mass transfer unit, thereby timely replenishing sufficient oxygen into the oxidation reactor to ensure that the reaction in the oxidation reactor proceeds in an orderly manner, and the second enhanced mass transfer unit can disperse and break the oxygen into micro-bubbles at the micron level, thereby increasing the gas-liquid contact area between oxygen and ethylbenzene, improving the gas-liquid mass transfer efficiency, and thus improving the reaction efficiency.

[0013] Preferably, the distance between the first enhanced mass transfer unit and the inner wall of the oxidation reactor is smaller than the distance between the baffle and the inner wall of the oxidation reactor, and the distance between the baffle and the inner wall of the oxidation reactor is smaller than the distance between the baffle and the second enhanced mass transfer unit; preferably, the baffle is provided with a plurality of protrusions from top to bottom on one side close to the side wall of the oxidation reactor; preferably, the first enhanced mass transfer unit is provided at the outlet of the circulation pipeline. In this scheme, considering that the material flows faster in the circulation pipeline, some microbubbles in the first enhanced mass transfer unit may not have time to break smaller before being sent to the circulation pipeline, resulting in poor consistency of the microbubble scale of the microbubbles output by the first enhanced mass transfer unit (which can be referred to as the first microbubble flow), and bubbles may coalesce in the process of entering the circulation channel through the circulation pipeline, affecting the contact area between gas and liquid. And because the scale of some microbubbles output by the first enhanced mass transfer unit is greater than the scale of the microbubbles output by the second enhanced mass transfer unit, after these microbubbles enter the inside of the oxidation reactor (here mainly refers to the chamber in the oxidation reactor except the circulation channel), the scale of microbubbles in the oxidation reactor may be inconsistent, which leads to uneven gas distribution in the oxidation reactor and affects the reaction efficiency. In addition, the rising speed of microbubbles of different scales in the oxidation reactor is different, which may cause the microbubbles of different scales to gather and then further affect the reaction efficiency of ethylbenzene peroxidation. In the scheme of the present embodiment, by specifically setting the relative position relationship between the first enhanced mass transfer unit, the baffle plate and the second enhanced mass transfer unit, the first microbubble flow can be made to quickly enter the circulation channel, and in the process of the first microbubble flow entering the circulation channel, it collides with the baffle plate, so that the microbubbles in the first microbubble flow can be further dispersed and broken, and bubbles are avoided to gather and merge. At the same time, the microbubbles in the first microbubble flow gradually decrease during the process of entering the oxidation reactor along the circulation channel, and when the microbubbles output by the first enhanced mass transfer unit flow to the vicinity of the second enhanced mass transfer unit, the scale of the microbubbles in the first microbubble flow is nearly the same as the scale of the microbubbles output by the second enhanced mass transfer unit, thereby avoiding the reaction efficiency of the ethylbenzene peroxidation reaction being affected by the different scales of the microbubbles. In a further preferred embodiment, the first enhanced mass transfer unit is arranged at the outlet of the circulation pipeline. Thus, the first microbubble flow can be directly input into the circulation channel to avoid the first microbubble flow from condensing during the flow in the circulation pipeline. In a further preferred embodiment, a plurality of protrusions are sequentially arranged on the baffle from top to bottom, thereby, when the microbubbles output by the first enhanced mass transfer unit flow in the circulation channel, they can collide with these protrusions, so that the microbubbles are further broken, which helps to further reduce the scale difference between the microbubbles output by the first enhanced mass transfer unit and the microbubbles output by the second enhanced mass transfer unit.

[0014] Preferably, a first heat exchanger is provided on the circulation pipeline, and the material in the circulation pipeline is heated by the first heat exchanger and then circulated to the oxidation reactor. As mentioned above, the ethylbenzene peroxidation reaction is sensitive to temperature. In this solution, by providing the first heat exchanger on the circulation pipeline, the material temperature in the oxidation reactor can be controlled to maintain the stability of the reaction temperature, thereby helping to further improve the conversion rate and selectivity of the reaction and improve the yield of the reaction product.

[0015] Preferably, there are multiple second enhanced mass transfer units, and the multiple second enhanced mass transfer units are all lower than the product outlet in the vertical direction. In the above scheme, by setting multiple second enhanced mass transfer units, the dispersion and crushing efficiency of the gas phase raw material can be improved.

[0016] Preferably, the plurality of second enhanced mass transfer units are arranged in sequence from top to bottom along the vertical direction. This solution helps to improve the uniformity of microbubble distribution in the oxidation reactor by arranging the plurality of second enhanced mass transfer units in sequence from top to bottom along the vertical direction, thereby further increasing the gas-liquid contact area.

[0017] Preferably, the outlets of the plurality of second enhanced mass transfer units face downward. It is understood that in this solution, the flow direction of the reaction raw materials is from bottom to top, and the final reaction product is discharged from the product outlet at the top. Therefore, compared with the top of the second enhanced mass transfer unit, the ethylbenzene concentration at the bottom of the second enhanced mass transfer unit is higher. By adding the microbubbles after the oxygen is dispersed and broken to the bottom of the second enhanced mass transfer unit, it is helpful to make the ethylbenzene at the bottom react with the oxygen more fully, thereby further improving the reaction efficiency and product yield.

[0018] Preferably, it also includes a heat exchange pipe, the inlet and outlet of the heat exchange pipe are both connected to the oxidation reactor, and the inlet of the heat exchange pipe is arranged below the outlet of the heat exchange pipe in the vertical direction; a second heat exchanger is arranged on the heat exchange pipe. By arranging the heat exchange pipe, the second heat exchanger can be used to control the temperature of the material in the oxidation reactor, prevent the reaction temperature from fluctuating violently due to the heat release of the oxidation reaction, maintain the stability of the reaction temperature, thereby helping to improve the conversion rate and selectivity of the reaction, and improve the yield of the reaction product. In addition, the heat exchange pipe can play a local stirring role on the material inside the oxidation reactor during the heat exchange process of the material, which helps to evenly distribute the microbubbles in the oxidation reactor and avoid the aggregation of bubbles, thereby helping to further improve the reaction efficiency and product yield.

[0019] Preferably, there are multiple heat exchange pipes, and the multiple heat exchange pipes are arranged sequentially from top to bottom. By arranging multiple heat exchange pipes sequentially from top to bottom, the solution can more accurately control the reaction temperature in the oxidation reactor, thereby helping to further improve the conversion rate and selectivity of the reaction. In addition, the multiple heat exchange pipes can stir different positions in the oxidation reactor, thereby further improving the uniformity of the microbubble distribution in the oxidation reactor, thereby helping to further improve the reaction efficiency and product yield.

[0020] Preferably, multiple layers of first baffles are staggered from top to bottom in the oxidation reactor, and the multiple layers of first baffles are located below the liquid surface of the oxidation reactor. This solution can avoid the occurrence of liquid phase backmixing as much as possible by staggering multiple layers of first baffles from top to bottom in the oxidation reactor, so that the reaction can proceed more orderly.

[0021] Preferably, a third enhanced mass transfer unit is provided in the epoxidation reactor, the third enhanced mass transfer unit is connected to the outlet of the delivery pipeline, and the material transported in the delivery pipeline is processed by the third enhanced mass transfer unit before entering the epoxidation reactor to enhance the mass transfer effect with propylene. By providing the third enhanced mass transfer unit in the epoxidation reactor, the third enhanced mass transfer unit can be used to disperse and crush the material transported in the delivery pipeline into micro droplets of micrometer level, and then feed them into the epoxidation reactor, thereby increasing the contact area between ethylbenzene hydroperoxide in the material and propylene, thereby improving the mass transfer effect between ethylbenzene hydroperoxide and propylene, and further contributing to improving the reaction efficiency of the epoxidation reaction.

[0022] Preferably, multiple layers of second baffles are staggered from top to bottom in the epoxidation reactor, and the multiple layers of second baffles are located between the liquid surface of the epoxidation reactor and the third enhanced mass transfer unit. By setting multiple layers of second baffles, this solution can avoid the occurrence of liquid phase backmixing as much as possible, so that the epoxidation reaction can proceed more orderly.

[0023] Preferably, it also includes a propylene separation tower, a propylene oxide separation tower, an ethylbenzene separation tower, a dehydration tower and a styrene refining tower connected in sequence, the propylene separation tower is connected to the epoxidation reactor, the bottom outlet of the styrene refining tower is connected to a hydrogenation reactor to transport the separated acetophenone to the hydrogenation reactor; the outlet of the hydrogenation reactor is connected to the dehydration tower; a fourth enhanced mass transfer unit is arranged in the hydrogenation reactor, the fourth enhanced mass transfer unit is connected to a hydrogen pipeline, and the hydrogen transported by the hydrogen pipeline enters the hydrogenation reactor after being processed by the fourth enhanced mass transfer unit to enhance the mass transfer effect between hydrogen and acetophenone. The above technical scheme can use the fourth enhanced mass transfer unit to disperse and break the hydrogen into micro-bubbles at the micron level by arranging the fourth enhanced mass transfer unit in the hydrogenation reactor, and then send it into the hydrogenation reactor for hydrogenation reaction, thereby increasing the contact area between hydrogen and acetophenone, thereby increasing the mass transfer effect between hydrogen and acetophenone, thereby helping to improve the reaction efficiency of the hydrogenation reaction, and helping to reduce the pressure required for the hydrogenation reaction.

[0024] Preferably, a gas distributor is further provided in the hydrogenation reactor, the bottom inlet of the gas distributor is connected to the outlet of the fourth enhanced mass transfer unit, the top of the gas distributor is provided with a plurality of outlets facing different directions, and the microbubbles output by the fourth enhanced mass transfer unit enter the hydrogenation reactor through the gas distributor. By providing a gas distributor, this solution can improve the uniform distribution effect of microbubbles and avoid bubble aggregation, thereby helping to further improve the reaction efficiency of the hydrogenation reaction.

[0025] Those skilled in the art can understand that the enhanced mass transfer reactor adopted in the present invention has been embodied in the prior patents of the present invention, such as patents with application numbers CN201610641119.6, CN201610641251.7, CN201710766435.0, CN106187660, CN105903425A, CN109437390A, CN205833127U and CN207581700U. The prior patent CN201610641119.6 describes in detail the specific product structure and working principle of the micron bubble generator (i.e., bubble breaker). The application document states that "the micron bubble generator includes a main body and a secondary crushing member, a cavity is provided in the main body, an inlet connected to the cavity is provided on the main body, the first and second opposite ends of the cavity are open, wherein the cross-sectional area of ​​the cavity decreases from the middle of the cavity to the first and second ends of the cavity; the secondary crushing member is provided at at least one of the first and second ends of the cavity, a part of the secondary crushing member is provided in the cavity, and an annular channel is formed between the secondary crushing member and the through holes open at both ends of the cavity. The micron bubble generator also includes an air inlet pipe and a liquid inlet pipe." From the specific structure disclosed in the application document, it can be known that its specific working principle is: the liquid enters the micron bubble generator tangentially through the liquid inlet pipe, rotates at ultra-high speed and cuts the gas, so that the gas bubbles are broken into micron-level microbubbles, thereby increasing the mass transfer area between the liquid phase and the gas phase, and the micron bubble generator in the patent is a pneumatic bubble breaker.

[0026] In addition, the prior patent 201610641251.7 records that the primary bubble breaker has a circulating liquid inlet, a circulating gas inlet and a gas-liquid mixture outlet, and the secondary bubble breaker connects the feed port with the gas-liquid mixture outlet, indicating that the bubble breaker requires gas-liquid mixture to enter. In addition, it can be seen from the following figures that the primary bubble breaker mainly uses circulating liquid as power, so the primary bubble breaker actually belongs to a hydraulic enhanced reactor, and the secondary bubble breaker simultaneously passes the gas-liquid mixture into an elliptical rotating ball for rotation, thereby achieving bubble breaking during the rotation process, so the secondary bubble breaker actually belongs to a gas-liquid linkage type bubble breaker. In fact, whether it is a hydraulic bubble breaker or a gas-liquid linkage type bubble breaker, it is a specific form of a bubble breaker. However, the enhanced mass transfer reactor adopted by the utility model is not limited to the above-mentioned forms. The specific structure of the bubble breaker recorded in the prior patent is only one of the forms that can be adopted by the utility model.

[0027] In addition, the prior patent 201710766435.0 records that "the principle of the bubble breaker is a high-speed jet to achieve mutual collision of gases"; and the prior patent CN106187660 also has relevant records on the specific structure of the bubble breaker, see paragraphs

[0031] -

[0041] in the specification, and the drawings, which explain in detail the specific working principle of the bubble breaker S-2. The top of the bubble breaker is a liquid phase inlet, and the side is a gas phase inlet. The liquid phase coming in from the top provides suction power, thereby achieving the effect of crushing into ultrafine bubbles. It can also be seen in the drawings that the bubble breaker has a conical structure, and the diameter of the upper part is larger than the diameter of the lower part, so that the liquid phase can better provide suction power.

[0028] Since the bubble breaker was just developed in the early stage of the prior patent application, it was named micron bubble generator (CN201610641119.6) in the early stage. With the continuous technical improvement, it was renamed as bubble breaker in the later stage. Now the enhanced mass transfer reactor in the utility model is equivalent to the previous micron bubble generator, micro interface generator, etc., but the name is different. In summary, the enhanced mass transfer reactor of the utility model belongs to the prior art.

[0029] The utility model also provides a method for preparing propylene oxide, which adopts the above-mentioned system and comprises: breaking oxygen into micro-bubbles at the micron level through enhanced mass transfer, mixing the oxygen with ethylbenzene for oxidation reaction to generate ethylbenzene hydroperoxide; mixing the generated ethylbenzene hydroperoxide with propylene, and performing epoxidation reaction under the catalysis of a catalyst to generate propylene oxide.

[0030] Compared with the prior art, the beneficial effects of the utility model are:

[0031] 1. In the utility model, only one oxidation reactor is used in the ethylbenzene peroxidation reaction stage, which can reduce the occupied area and help reduce production costs.

[0032] 2. The utility model provides a circulation pipeline connected to the oxidation reactor, and can use the circulation pipeline to extract the material at the bottom of the oxidation reactor and transport it back to the oxidation reactor through the circulation pipeline outlet. Therefore, the material in the oxidation reactor can be stirred, and the uniformity of the distribution of microbubbles in the material inside the oxidation reactor can be promoted, which helps to further improve the reaction efficiency and product yield.

[0033] 3. The utility model can use the first enhanced mass transfer unit to disperse and crush the oxygen transported by the oxygen pipeline by arranging the first enhanced mass transfer unit in the circulation pipeline, thereby increasing the gas-liquid contact area between oxygen and ethylbenzene and improving the reaction efficiency. At the same time, since the first enhanced mass transfer unit is arranged in the circulation pipeline, when the first enhanced mass transfer unit disperses and crushes the oxygen, the oxygen pipeline can be used to simultaneously disperse and crush the oxygen and the material in the circulation pipeline, thereby further improving the dispersion and crushing effect on the gas phase raw material. In addition, the microbubbles output by the first enhanced mass transfer unit can flow back to the oxidation reactor together with the circulating material under the impact of the material in the circulation pipeline, and the microbubbles can be further dispersed and crushed under the impact of the material, and the microbubbles can be more evenly distributed in the circulating material under the impact of the material, thereby avoiding the occurrence of bubble aggregation, thereby helping to further improve the gas-liquid contact area, thereby helping to further improve the reaction efficiency and reaction yield.

[0034] 4. The utility model can improve the reaction efficiency and product yield of ethylbenzene peroxidation reaction by matching the circulation pipeline, the first enhanced mass transfer unit and the oxidation reactor, and the concentration of ethylbenzene hydrogen peroxide in the reaction product of ethylbenzene peroxidation reaction can meet the needs of epoxidation reaction, and there is no need to further concentrate the reaction product of ethylbenzene peroxidation reaction, so there is no need to set up an additional concentrating device, thereby further reducing production costs and reducing the footprint of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] By reading the detailed description of the preferred embodiment below, various other advantages and benefits will become clear to those of ordinary skill in the art. The accompanying drawings are only used for the purpose of illustrating the preferred embodiment and are not considered to be limiting of the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0036] Figure 1 A schematic diagram showing a system for preparing propylene oxide according to an embodiment of the utility model;

[0037] Figure 2 A schematic diagram of an oxidation reactor according to an embodiment of the present invention is shown.

[0038] Among them: 1. oxidation reactor; 101. tail gas outlet; 102. product outlet; 2. oxygen pipeline; 3. ethylbenzene pipeline; 4. first enhanced mass transfer unit; 5. circulation pump; 6. circulation pipeline; 7. first heat exchanger; 8. baffle; 9. second enhanced mass transfer unit; 10. first screen; 11. heat exchange pump; 12. heat exchange pipeline; 13. second heat exchanger; 14. epoxidation reactor; 15. propylene pipeline; 16. second screen; 17. third enhanced mass transfer unit; 18. propylene separation tower; 19. propylene oxide separation tower; 20. propylene oxide refining tower; 21. ethylbenzene separation tower; 22. dehydration tower; 23. styrene refining tower; 24. hydrogenation reactor; 25. fourth enhanced mass transfer unit; 26. gas distributor; 27. hydrogen pipeline; 28. delivery pipeline; 29. ​​protrusion. DETAILED DESCRIPTION

[0039] The technical solution of the utility model will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but those skilled in the art will understand that the embodiments described below are part of the embodiments of the utility model, rather than all of the embodiments, and are only used to illustrate the utility model, and should not be considered as limiting the scope of the utility model. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the utility model. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0040] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0041] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] According to one aspect of the utility model, a system for preparing propylene oxide is provided. Figure 1 A schematic diagram of a system for preparing propylene oxide according to an embodiment of the utility model is shown. Figure 2 A schematic diagram of an oxidation reactor according to an embodiment of the present invention is shown. Figure 1-2 As shown, the preparation system includes: an oxidation reactor 1 and an epoxidation reactor 14, a delivery pipeline 28 is arranged between the oxidation reactor 1 and the epoxidation reactor 14, the inlet of the delivery pipeline 28 is connected to the product outlet 102 of the oxidation reactor 1, and the outlet of the delivery pipeline 28 is connected to the epoxidation reactor 14; a circulation pipeline 6 is arranged on one side of the oxidation reactor 1, the inlet of the circulation pipeline 6 is connected to the bottom of the oxidation reactor 1; the outlet of the circulation pipeline 6 is connected to the oxidation reactor 1, the outlet of the circulation pipeline 6 is higher than the inlet of the circulation pipeline 6 in the vertical direction and the outlet of the circulation pipeline 6 is lower than the liquid level of the oxidation reactor 1 in the vertical direction; the product outlet 102 is higher than the outlet of the circulation pipeline 6 in the vertical direction, And the product outlet 102 is located below the liquid surface of the oxidation reactor 1 in the vertical direction; the circulation pipeline 6 is connected to the ethylbenzene pipeline 3, and the ethylbenzene in the ethylbenzene pipeline 3 enters the oxidation reactor 1 through the circulation pipeline 6; a first enhanced mass transfer unit 4 is arranged in the circulation pipeline 6 near the outlet of the circulation pipeline 6, and the first enhanced mass transfer unit 4 is connected to the oxygen pipeline 2, and the oxygen in the oxygen pipeline 2 enters the circulation pipeline 6 after being processed by the first enhanced mass transfer unit 4 to enhance the mass transfer effect between oxygen and ethylbenzene; the side wall of the epoxidation reactor 14 is connected to the propylene pipeline 15, and the propylene enters the epoxidation reactor 14 through the propylene pipeline 15 to react with the ethylbenzene hydroperoxide in the epoxidation reactor 14 to generate propylene oxide.

[0043] It is understood that the oxygen pipeline 2 can be used to transport the gaseous material of the ethylbenzene peroxidation reaction, and the gaseous material can be oxygen or air. Figure 1 In the illustrated embodiment, the gaseous material in the oxygen pipeline 2 may be air.

[0044] In an embodiment of the present invention, the oxidation reactor 1 may be a bubble tower reactor.

[0045] In the embodiment of the utility model, a first enhanced mass transfer unit 4 is arranged inside the circulation pipeline 6. Optionally, the enhanced mass transfer unit can be composed of one or more enhanced mass transfer reactors. When the oxidation reactor 1 is working, oxygen can be dispersed and broken into micro-bubbles of micron level by the first enhanced mass transfer unit 4 to increase the interfacial mass transfer area between oxygen and ethylbenzene, thereby enhancing the mass transfer effect between oxygen and ethylbenzene. Figure 1 In the illustrated embodiment, the first intensified mass transfer unit 4 comprises an intensified mass transfer reactor.

[0046] Preferably, if Figure 2 As shown, a baffle 8 is provided in the oxidation reactor 1, the top of the baffle 8 is higher than the liquid level of the oxidation reactor 1 in the vertical direction, and the distance between the bottom of the baffle 8 and the bottom of the inner cavity of the oxidation reactor 1 is a preset distance; a circulation channel is formed between the baffle 8 and the side wall of the oxidation reactor 1, and the outlet of the circulation pipe 6 is connected to the circulation channel.

[0047] Preferably, if Figure 2 As shown, a first heat exchanger 7 is provided on the circulation pipeline 6 , and the material in the circulation pipeline 6 is heated by the first heat exchanger 7 and then circulated to the oxidation reactor 1 .

[0048] exist Figure 2 In the illustrated embodiment, a circulation pump 5 is further provided on the circulation pipeline 6 , and the first heat exchanger 7 is arranged behind the circulation pump 5 along the material flow direction in the circulation pipeline 6 , thereby helping to reduce the circulation resistance of the circulation pump 5 .

[0049] Preferably, if Figure 2 As shown, a second enhanced mass transfer unit 9 is provided in the oxidation reactor 1, and the oxygen pipeline 2 is connected to the second enhanced mass transfer unit 9. The oxygen in the oxygen pipeline 2 enters the oxidation reactor 1 after being processed by the second enhanced mass transfer unit 9 to enhance the mass transfer effect between oxygen and ethylbenzene. Figure 1 In the illustrated embodiment, the second enhanced mass transfer unit 9 includes an enhanced mass transfer reactor. It is understood that the oxygen pipeline 2 connected to the second enhanced mass transfer unit 9 and the oxygen pipeline 2 connected to the first enhanced mass transfer unit 4 can be the same oxygen pipeline. In this case, the oxygen pipeline 2 can be provided with a plurality of branch pipelines to be respectively connected to different enhanced mass transfer units. Of course, the oxygen pipeline 2 connected to the second enhanced mass transfer unit 9 and the oxygen pipeline 2 connected to the first enhanced mass transfer unit 4 can also be independent oxygen pipelines, which will not be described in detail.

[0050] Preferably, if Figure 2 As shown, there are multiple second intensified mass transfer units 9, and the multiple second intensified mass transfer units 9 are all lower than the product outlet 102 in the vertical direction.

[0051] Preferably, if Figure 2 As shown, a plurality of second enhanced mass transfer units 9 are arranged in sequence from top to bottom along the vertical direction.

[0052] Preferably, if Figure 2 As shown, the outlets of the plurality of second intensified mass transfer units 9 face downward.

[0053] Preferably, if Figure 2 As shown, the distance between the first enhanced mass transfer unit 4 and the inner wall of the oxidation reactor 1 is smaller than the distance between the baffle 8 and the inner wall of the oxidation reactor 1, and the distance between the baffle 8 and the inner wall of the oxidation reactor 1 is smaller than the distance between the baffle 8 and the second enhanced mass transfer unit 9.

[0054] Preferably, if Figure 2 As shown, the first enhanced mass transfer unit 4 is arranged at the outlet of the circulation pipeline 6.

[0055] Preferably, if Figure 2 As shown, a plurality of protrusions 29 are sequentially arranged from top to bottom on one side of the baffle plate 8 close to the side wall of the oxidation reactor 1 .

[0056] Preferably, if Figure 2 As shown, it also includes a heat exchange pipe 12, the inlet and outlet of the heat exchange pipe 12 are both connected to the oxidation reactor 1, and the inlet of the heat exchange pipe 12 is arranged below the outlet of the heat exchange pipe 12 in the vertical direction; a second heat exchanger 13 is arranged on the heat exchange pipe 12.

[0057] Preferably, if Figure 2 As shown, there are multiple heat exchange pipes 12, and the multiple heat exchange pipes 12 are arranged in sequence from top to bottom. Figure 1 In the illustrated embodiment, the number of the heat exchange pipes 12 is two.

[0058] exist Figure 2 In the illustrated embodiment, a heat exchange pump 11 is further provided on the heat exchange pipe 12 . The heat exchange pump 11 is arranged in front of the first heat exchanger 7 along the material flow direction in the heat exchange pipe 12 to reduce the operation resistance of the heat exchange pump 11 .

[0059] Preferably, if Figure 2 As shown, multiple layers of first baffles 10 are alternately arranged from top to bottom in the oxidation reactor 1 , and the multiple layers of first baffles 10 are located below the liquid surface of the oxidation reactor 1 .

[0060] Preferably, if Figure 1 As shown, the epoxidation reactor 14 is provided with a third enhanced mass transfer unit 17, which is connected to the outlet of the delivery pipeline 28. The material transported in the delivery pipeline 28 is processed by the third enhanced mass transfer unit 17 and then enters the epoxidation reactor 14 to enhance the mass transfer effect with propylene. Figure 1 In the illustrated embodiment, the third intensified mass transfer unit 17 comprises an intensified mass transfer reactor.

[0061] Preferably, if Figure 1 As shown, multiple layers of second baffles 16 are alternately arranged from top to bottom in the epoxidation reactor 14 , and the multiple layers of second baffles 16 are located between the liquid surface of the epoxidation reactor 14 and the third enhanced mass transfer unit 17 .

[0062] Preferably, if Figure 1As shown, it also includes a propylene separation tower 18, a propylene oxide separation tower 19, an ethylbenzene separation tower 21, a dehydration tower 22 and a styrene refining tower 23 which are connected in sequence. The propylene separation tower 18 is connected to the epoxidation reactor 14. The bottom outlet of the styrene refining tower 23 is connected to a hydrogenation reactor 24 to transport the separated acetophenone to the hydrogenation reactor 24. The outlet of the hydrogenation reactor 24 is connected to the dehydration tower 22. A fourth enhanced mass transfer unit 25 is arranged in the hydrogenation reactor 24. The fourth enhanced mass transfer unit 25 is connected to a hydrogen pipeline 27. The hydrogen transported by the hydrogen pipeline 27 enters the hydrogenation reactor 24 after being processed by the fourth enhanced mass transfer unit 25 to enhance the mass transfer effect between hydrogen and acetophenone. Figure 1 In the illustrated embodiment, the fourth intensified mass transfer unit 25 includes an intensified mass transfer reactor.

[0063] Preferably, if Figure 1 As shown, a gas distributor 26 is also provided in the hydrogenation reactor 24. The bottom inlet of the gas distributor 26 is connected to the outlet of the fourth enhanced mass transfer unit 25. The top of the gas distributor 26 is provided with multiple outlets facing different directions. The microbubbles output by the fourth enhanced mass transfer unit 25 enter the hydrogenation reactor 24 through the gas distributor 26.

[0064] The utility model also provides a method for preparing propylene oxide, which adopts the above system and includes: breaking oxygen into micron-level microbubbles through enhanced mass transfer, mixing with ethylbenzene for oxidation reaction to generate ethylbenzene hydroperoxide; mixing the generated ethylbenzene hydroperoxide with propylene, and performing epoxidation reaction under the catalysis of a catalyst to generate propylene oxide. Preferably, the catalyst in the epoxidation reaction process is a molybdenum-based catalyst.

[0065] by Figure 1 Take the preparation process of propylene oxide as an example to illustrate. Figure 1In the embodiment shown, oxygen is dispersed and broken into micro-bubbles of micron level by the first enhanced mass transfer unit 4 and the second enhanced mass transfer unit 9, and then mixed with ethylbenzene for oxidation reaction to generate ethylbenzene hydroperoxide, and the tail gas in the ethylbenzene peroxidation reaction is discharged through the tail gas outlet 101 at the top of the oxidation reactor 1. The reaction product in the oxidation reactor 1 enters the epoxidation reactor 14, and the reaction product is dispersed and broken into micro-droplets of micron level by the third enhanced mass transfer unit 17, and then mixed with propylene, wherein the ethylbenzene hydroperoxide and propylene are subjected to epoxidation reaction under the catalysis of the catalyst to generate propylene oxide. The epoxidation reaction product (including propylene oxide) of the epoxidation reactor 14 enters the propylene separation tower 18, and the propylene in the epoxidation reaction product is separated and refluxed to the propylene pipeline 15, and other materials (which can be called the first separation product) are input to the propylene oxide separation tower 19 through the bottom of the propylene separation tower 18. In the propylene oxide separation tower 19, the propylene oxide in the first separation product is output from the top of the propylene oxide separation tower 19 to the propylene oxide refining tower 20 for refining, and the refined propylene oxide is extracted from the top of the tower. Other materials in the first separation product (which may become the second separation product, and the second separation product includes ethylbenzene, phenylethyl alcohol, acetophenone, etc.) are input to the ethylbenzene separation tower 21 through the bottom of the propylene oxide separation tower 19. In the ethylbenzene separation tower 21, the ethylbenzene in the second separation product is extracted from the top of the tower, and other materials (which may become the third separation product, mainly including phenylethyl alcohol and acetophenone) are input to the dehydration tower 22 through the bottom of the tower. The phenylethyl alcohol in the third separation product undergoes a dehydration reaction in the dehydration tower 22 to generate crude styrene. The generated crude styrene is transported to the styrene refining tower 23 for refining. The refined styrene is extracted from the top of the styrene refining tower 23, and the other components at the bottom of the tower (which can be called the fourth separation product, mainly including acetophenone and unreacted phenylethanol) can be transported to the hydrogenation reactor 24. In the hydrogenation reactor 24, the hydrogen is dispersed and broken into micro-bubbles of micrometer level by the fourth enhanced mass transfer unit 25 and then enters the hydrogenation reactor 24, and undergoes a hydrogenation reaction with the acetophenone in the fourth separation product to generate phenylethanol. The generated phenylethanol can be transported to the dehydration tower 22.

[0066] Preferably, the reaction pressure in the hydrogenation reactor 24 is 1-1.5 MPa.

[0067] In order to more clearly explain the technical solution of the present invention, it is described in the form of specific embodiments below.

[0068] Example 1

[0069] In this embodiment, the Figure 1The system shown prepares propylene oxide. The reaction temperature in the oxidation reactor is 145°C and the pressure is 0.24 MPa. The reaction temperature in the epoxidation reactor is 100°C and the reaction pressure is 4 MPa. The reaction temperature in the hydrogenation reactor is 55°C and the reaction pressure is 1 MPa.

[0070] The concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor, the molar selectivity of propylene oxide to ethylbenzene hydroperoxide in the epoxidation reactor, and the conversion rate of acetophenone in the hydrogenation reactor were detected respectively.

[0071] According to the test, the concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor was 48 wt %, the molar selectivity of propylene oxide to ethylbenzene hydroperoxide in the epoxidation reactor was 95%, and the conversion rate of acetophenone in the hydrogenation reactor was 97%.

[0072] Example 2

[0073] The difference between this embodiment and embodiment 1 is that this embodiment does not have a circulation pipeline, the first enhanced mass transfer unit is arranged in the circulation channel, and the liquid inlet pipeline is directly connected to the circulation channel. The reaction pressure in the hydrogenation reactor is 1.5 MPa.

[0074] The concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor was found to be 44 wt %, the molar selectivity of propylene oxide to ethylbenzene hydroperoxide in the epoxidation reactor was 93%, and the conversion rate of acetophenone in the hydrogenation reactor was 95%.

[0075] Comparing the concentration of ethylbenzene hydroperoxide in the ethylbenzene peroxidation product obtained in Example 1 and the concentration of ethylbenzene hydroperoxide in Example 2, it can be seen that the concentration of ethylbenzene hydroperoxide in the product of Example 1 is significantly higher than that in Example 2. This is because Example 1 can stir the material in the oxidation reactor by setting a circulation pipeline, improve the uniformity of the distribution of microbubbles in the internal material of the oxidation reactor, and the microbubbles output by the first enhanced mass transfer unit can flow back to the oxidation reactor with the circulating material under the impact of the material in the circulation pipeline, and the microbubbles can be further dispersed and broken under this impact, and the microbubbles can be more evenly distributed in the circulating material under the impact of the material, avoiding the occurrence of bubble aggregation, thus, helping to further improve the gas-liquid contact area, thereby helping to further improve the reaction efficiency and reaction yield. In short, the scheme of Example 1 helps to improve the concentration of ethylbenzene hydroperoxide in the ethylbenzene peroxidation product by combining the circulation pipeline with the first enhanced mass transfer unit.

[0076] Example 3

[0077] The difference between this embodiment and embodiment 1 is that the second mass transfer enhancement unit is not provided. The reaction pressure in the hydrogenation reactor is 1.3 MPa. The molar selectivity of propylene oxide to ethylbenzene hydroperoxide in the epoxidation reactor is 94%, and the conversion rate of acetophenone in the hydrogenation reactor is 97%.

[0078] According to the detection, the concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor was 43 wt %.

[0079] By comparing the concentration of ethylbenzene hydroperoxide in the product obtained in Example 3 with the concentration of ethylbenzene hydroperoxide in the product obtained in Comparative Example 1, it can be seen that the concentration of ethylbenzene hydroperoxide in the product of Example 1 is significantly higher than that of Example 3. This may be because Example 1 can increase the gas-liquid contact area by setting multiple second enhanced mass transfer units, and the oxygen pipeline can supplement oxygen to different height sections of the oxidation reactor through multiple second enhanced mass transfer units to ensure that oxygen is always sufficient, thereby improving the reaction yield and raw material conversion rate, and increasing the concentration of ethylbenzene hydroperoxide in the product.

[0080] Example 4

[0081] The difference between this embodiment and embodiment 1 is that in this embodiment, a plurality of second enhanced mass transfer units are arranged in sequence along the horizontal direction.

[0082] The concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor was found to be 45 wt %. The molar selectivity of propylene oxide to ethylbenzene hydroperoxide in the epoxidation reactor and the conversion rate of acetophenone in the hydrogenation reactor were almost the same as those in Example 1.

[0083] By comparing the concentration of ethylbenzene hydroperoxide in the ethylbenzene peroxidation product obtained in Example 1 with the concentration of ethylbenzene hydroperoxide in the product obtained in Example 4, it can be seen that the concentration of ethylbenzene hydroperoxide in the product of Example 1 is higher than that in Example 4. This may be due to the fact that the microbubbles output by the horizontally arranged multiple second enhanced mass transfer units are all at the same height section of the oxidation reactor, causing the bubbles to coalesce and affect the reaction efficiency and yield. As a result, the concentration of ethylbenzene hydroperoxide in the reaction product of the ethylbenzene peroxidation in Example 4 is relatively low.

[0084] Example 5

[0085] The only difference between this embodiment and embodiment 1 is that no baffle is provided in this embodiment.

[0086] The concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor was found to be 45 wt %. The molar selectivity of propylene oxide to ethylbenzene hydroperoxide in the epoxidation reactor and the conversion rate of acetophenone in the hydrogenation reactor were almost the same as those in Example 1.

[0087] Comparing the concentration of ethylbenzene hydroperoxide in the ethylbenzene peroxidation product obtained in Example 1 and the concentration of ethylbenzene hydroperoxide in the product obtained in Example 5, it can be seen that the concentration of ethylbenzene hydroperoxide in the product of Example 1 is higher than that in Example 5. This may be due to the impact of the material circulating back to the oxidation reactor in the circulation pipeline in Example 5 on the reaction product in the oxidation reactor, causing the reaction product to be back-mixed, thereby suppressing the occurrence of ethylbenzene peroxidation. As a result, the concentration of ethylbenzene hydroperoxide in the reaction product of its ethylbenzene peroxidation is relatively low.

[0088] Example 6

[0089] The only difference between this embodiment and embodiment 1 is that in this embodiment, the distance between the baffle and the inner wall of the oxidation reactor is greater than the distance between the baffle and the second enhanced mass transfer unit.

[0090] The concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor was found to be 44 wt %. The molar selectivity of propylene oxide to ethylbenzene hydroperoxide in the epoxidation reactor and the conversion rate of acetophenone in the hydrogenation reactor were almost the same as those in Example 1.

[0091] Comparing the concentration of ethylbenzene hydroperoxide in the ethylbenzene peroxidation product obtained in Example 1 and the concentration of ethylbenzene hydroperoxide in the product obtained in Example 6, it can be seen that the concentration of ethylbenzene hydroperoxide in the product of Example 1 is higher than that in Example 6. This may be due to the fact that the distance between the baffle and the inner wall of the oxidation reactor in Example 6 is greater than the distance between the baffle and the second enhanced mass transfer unit. At this time, the width of the circulation channel is large, and the internal material flow rate is relatively slow. At this time, the microbubbles with inconsistent scales in the first microbubble flow may have bubble aggregation inside, generating microbubbles with larger scales. When these microbubbles flow to the vicinity of the second enhanced mass transfer unit, the microbubbles near the second enhanced mass transfer unit are unevenly distributed, affecting the reaction efficiency. At the same time, since the distance between the baffle and the second enhanced mass transfer unit is relatively close at this time, the first microbubble flow with uneven scales and containing larger microbubbles flowing out of the circulation channel directly flows to the vicinity of the second enhanced mass transfer unit, and may directly collide with the microbubble flow output by the second enhanced mass transfer unit, and gather and generate larger microbubbles, which further aggravates the uneven distribution of microbubbles near the second enhanced mass transfer unit. Based on the above reasons, the concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor in Example 6 is lower than that in Example 1.

[0092] Example 7

[0093] The only difference between this embodiment and embodiment 1 is that in this embodiment, the distance between the baffle and the inner wall of the oxidation reactor is greater than the distance between the first enhanced mass transfer unit and the inner wall of the oxidation reactor.

[0094] The concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor was found to be 45 wt %. The molar selectivity of propylene oxide to ethylbenzene hydroperoxide in the epoxidation reactor and the conversion rate of acetophenone in the hydrogenation reactor were almost the same as those in Example 1.

[0095] By comparing the concentration of ethylbenzene hydroperoxide in the ethylbenzene peroxidation product obtained in Example 1 with the concentration of ethylbenzene hydroperoxide in the product obtained in Example 7, it can be seen that the concentration of ethylbenzene hydroperoxide in the product of Example 1 is higher than that in Example 7. This may be because the distance between the baffle and the inner wall of the oxidation reactor in Example 7 is greater than the distance between the first enhanced mass transfer unit and the inner wall of the oxidation reactor. At this time, bubbles may have coalesced during the flow of the first microbubble flow in the circulation pipeline, generating larger microbubbles, thereby increasing the scale difference between the microbubbles in the first microbubble flow and the microbubbles output by the second enhanced mass transfer unit, resulting in uneven distribution of microbubbles near the second enhanced mass transfer unit, affecting the reaction efficiency. As a result, the concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor in Example 7 is lower than that in Example 1.

[0096] Combining the data of Example 1, Example 6 and Example 7, it can be seen that the solution of Example 1 of the utility model effectively improves the reaction efficiency of ethylbenzene peroxidation reaction by specifically setting the relative position relationship between the first enhanced mass transfer unit, the baffle and the second enhanced mass transfer unit.

[0097] Example 8

[0098] The only difference between this embodiment and Embodiment 1 is that this embodiment does not provide a first heat exchanger.

[0099] The concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor was found to be 47 wt %. The molar selectivity of propylene oxide to ethylbenzene hydroperoxide in the epoxidation reactor and the conversion rate of acetophenone in the hydrogenation reactor were almost the same as those in Example 1.

[0100] By comparing the concentration of ethylbenzene hydroperoxide in the ethylbenzene peroxidation product obtained in Example 1 with the concentration of ethylbenzene hydroperoxide in the product obtained in Example 8, it can be seen that the concentration of ethylbenzene hydroperoxide in the product of Example 1 is higher than that in Example 8. This may be because the first heat exchanger is provided on the circulation pipeline of Example 1, which can better control the reaction temperature, making the reaction temperature in the oxidation reactor more stable, and thus the concentration of ethylbenzene hydroperoxide in the reaction product of the ethylbenzene peroxidation reaction is higher.

[0101] Example 9

[0102] The difference between this embodiment and Embodiment 1 is that the first grid is not provided in this embodiment.

[0103] The concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor was found to be 44 wt %. The molar selectivity of propylene oxide to ethylbenzene hydroperoxide in the epoxidation reactor and the conversion rate of acetophenone in the hydrogenation reactor were almost the same as those in Example 1.

[0104] By comparing the concentration of ethylbenzene hydroperoxide in the ethylbenzene peroxidation product obtained in Example 1 with the concentration of ethylbenzene hydroperoxide in the product obtained in Example 9, it can be seen that the concentration of ethylbenzene hydroperoxide in the product of Example 1 is higher than that in Example 9. This may be because in Example 1, by providing the first barrier, liquid phase backmixing is further avoided, thereby ensuring the orderly progress of the ethylbenzene peroxidation reaction, and thus the concentration of ethylbenzene hydroperoxide in the obtained product is higher.

[0105] Example 10

[0106] The difference between this embodiment and embodiment 1 is that in this embodiment, a plurality of heat exchange pipes are arranged in sequence along the horizontal direction.

[0107] The concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor was found to be 46 wt %. The molar selectivity of propylene oxide to ethylbenzene hydroperoxide in the epoxidation reactor and the conversion rate of acetophenone in the hydrogenation reactor were almost the same as those in Example 1.

[0108] By comparing the concentration of ethylbenzene hydroperoxide in the ethylbenzene peroxidation product obtained in Example 1 with the concentration of ethylbenzene hydroperoxide in the product obtained in Example 10, it can be seen that the concentration of ethylbenzene hydroperoxide in the product of Example 1 is higher than that in Example 10. This may be because in Example 1, a plurality of heat exchange pipes are respectively arranged at different heights, which has a better control effect on the temperature in the oxidation reactor, and thus the concentration of ethylbenzene hydroperoxide in the obtained ethylbenzene peroxidation product is higher.

[0109] Embodiment 11

[0110] The only difference between this embodiment and Embodiment 1 is that the second heat exchanger is not provided.

[0111] The concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor was found to be 45 wt %. The molar selectivity of propylene oxide to ethylbenzene hydroperoxide in the epoxidation reactor and the conversion rate of acetophenone in the hydrogenation reactor were almost the same as those in Example 1.

[0112] By comparing the concentration of ethylbenzene hydroperoxide in the product obtained in Example 1 with the concentration of ethylbenzene hydroperoxide in the product obtained in Example 11, it can be seen that the concentration of ethylbenzene hydroperoxide in the product of Example 1 is significantly higher than that in Example 11. This may be because in Example 1, by providing a second heat exchanger, the temperature in the oxidation reactor can be more accurately controlled, making the temperature in the oxidation reactor more stable, and thus the concentration of ethylbenzene hydroperoxide in the obtained product is higher.

[0113] Example 12

[0114] The only difference between this embodiment and embodiment 1 is that no heat exchange pipeline is provided.

[0115] The concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor was found to be 41 wt %. The molar selectivity of propylene oxide to ethylbenzene hydroperoxide in the epoxidation reactor and the conversion rate of acetophenone in the hydrogenation reactor were almost the same as those in Example 1.

[0116] By comparing the concentration of ethylbenzene hydroperoxide in the product obtained in Example 1 with the concentration of ethylbenzene hydroperoxide in the product obtained in Example 12, it can be seen that the concentration of ethylbenzene hydroperoxide in the product of Example 1 is significantly higher than that in Example 12. This may be because Example 1, by providing a heat exchange pipe, can stir the material on the one hand, thereby improving the uniformity of the distribution of microbubbles in the oxidation reactor, and on the other hand, the heat exchange pipe can maintain the reaction temperature in the oxidation reactor through the second heat exchanger to make the reaction more orderly. Therefore, the concentration of ethylbenzene hydroperoxide in the obtained product is higher.

[0117] Example 13

[0118] The only difference between this embodiment and embodiment 1 is that the third enhanced mass transfer unit is not provided.

[0119] After testing, the concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor and the conversion rate of acetophenone in the hydrogenation reactor were almost consistent with those in Example 1. The molar selectivity of propylene oxide to ethylbenzene hydroperoxide in the epoxidation reactor was 63%.

[0120] By comparing the molar selectivity of propylene oxide to ethylbenzene hydroperoxide in Example 1 and the molar selectivity of propylene oxide to ethylbenzene hydroperoxide in Example 13, it can be seen that the molar selectivity of propylene oxide to ethylbenzene hydroperoxide in Example 1 is significantly higher than that in Example 13. This is because the scheme of Example 1 of the utility model increases the contact area between ethylbenzene hydroperoxide and propylene oxide by setting the third enhanced mass transfer unit in the epoxidation reactor, thereby improving the reaction efficiency and the molar selectivity of propylene oxide to ethylbenzene hydroperoxide.

[0121] Embodiment 14

[0122] The difference between this embodiment and embodiment 1 is that the second grid is not provided in this embodiment.

[0123] After testing, the concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor and the conversion rate of acetophenone in the hydrogenation reactor were almost consistent with those in Example 1. The molar selectivity of propylene oxide to ethylbenzene hydroperoxide in the epoxidation reactor was 82%.

[0124] By comparing the molar selectivity of propylene oxide to ethylbenzene hydroperoxide in Example 1 and the molar selectivity of propylene oxide to ethylbenzene hydroperoxide in Example 14, it can be seen that the molar selectivity of propylene oxide to ethylbenzene hydroperoxide in Example 1 is significantly higher than that in Example 14. This may be because in Example 1, by providing the second barrier, liquid phase backmixing is avoided, thereby ensuring the orderly progress of the epoxidation reaction and improving the molar selectivity of propylene oxide to ethylbenzene hydroperoxide.

[0125] Embodiment 15

[0126] The only difference between this embodiment and embodiment 1 is that the fourth enhanced mass transfer unit is not provided in this embodiment.

[0127] The conversion rate of acetophenone in the hydrogenation reactor was 72%. The concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor and the molar selectivity of propylene oxide to ethylbenzene hydroperoxide in the epoxidation reactor were almost the same as those in Example 1.

[0128] Comparing the conversion rate of acetophenone in Example 1 and the conversion rate of acetophenone in Example 15, it can be seen that the conversion rate of acetophenone in Example 1 is significantly higher than that in Example 15. This is because the scheme of Example 1 of the utility model increases the contact area between hydrogen and acetophenone by setting the fourth enhanced mass transfer unit in the hydrogenation reactor, thereby improving the reaction efficiency and the conversion rate of acetophenone.

[0129] Example 16

[0130] The only difference between this embodiment and embodiment 1 is that a gas distributor is not provided in this embodiment.

[0131] The conversion rate of acetophenone in the hydrogenation reactor was 92%. The concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor and the molar selectivity of propylene oxide to ethylbenzene hydroperoxide in the epoxidation reactor were almost the same as those in Example 1.

[0132] By comparing the conversion rate of acetophenone in Example 1 with the conversion rate of acetophenone in Example 16, it can be seen that the conversion rate of acetophenone in Example 1 is significantly higher than that in Example 16. This is because the scheme of Example 1 of the utility model provides a gas distributor to make the distribution of hydrogen microbubbles more uniform, avoid the aggregation of microbubbles and increase the contact area between hydrogen and acetophenone, thereby improving the reaction efficiency and the conversion rate of acetophenone.

[0133] Embodiment 17

[0134] In this embodiment, two fixed bed reactors connected in series are used to replace the hydrogenation reactor in Example 1. The reaction temperature in the hydrogenation reactor is 55° C. and the reaction pressure is 2 MPa.

[0135] The conversion rate of acetophenone at the outlet of the second fixed bed reactor was 95%. The concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor and the molar selectivity of propylene oxide to ethylbenzene hydroperoxide in the epoxidation reactor were almost the same as those in Example 1.

[0136] The configuration of Example 17 is the reaction device used in the hydrogenation reaction of acetophenone in the related art. By comparing Example 1 with Example 17, it can be found that the conversion rate of acetophenone in Example 1 is slightly higher than that in Example 17, which shows that the scheme of Example 1 can achieve or even exceed the conversion rate of acetophenone that requires two fixed bed reactors in the related art by combining the fourth enhanced mass transfer unit, the gas distributor and the hydrogenation reactor with only one hydrogenation reactor. And the required reaction pressure in the scheme of Example 1 is only half of that in the related art, which will greatly save reaction energy consumption and help improve reaction safety.

[0137] Comparative Example 1

[0138] The only difference between this embodiment and embodiment 1 is that this embodiment does not have a first enhanced mass transfer unit.

[0139] The concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor was found to be 46 wt %. The molar selectivity of propylene oxide to ethylbenzene hydroperoxide in the epoxidation reactor and the conversion rate of acetophenone in the hydrogenation reactor were almost the same as those in Example 1.

[0140] By comparing the concentration of ethylbenzene hydroperoxide in the ethylbenzene peroxidation product obtained in Example 1 with the concentration of ethylbenzene hydroperoxide in the product obtained in Comparative Example 1, it can be seen that the concentration of ethylbenzene hydroperoxide in the product of Example 1 is higher than that in Comparative Example 1. This may be because in the scheme of Example 1, a first enhanced mass transfer unit is provided in the circulation pipeline, and the first enhanced mass transfer unit is used to enhance the dispersion and crushing effect of the gas phase raw material, thereby further increasing the concentration of ethylbenzene hydroperoxide in the product.

[0141] Comparative Example 2

[0142] In this embodiment, two non-catalytic, liquid-phase oxidation reactors connected in series are used as reactors for the ethylbenzene peroxidation reaction.

[0143] According to the test, the concentration of ethylbenzene hydroperoxide in the reaction product in the oxidation reactor was 10 wt %, the molar selectivity of propylene oxide to ethylbenzene hydroperoxide in the epoxidation reactor was 91%, and the conversion rate of acetophenone in the hydrogenation reactor was 90%.

[0144] Comparative Example 2 is a solution adopted in the related art. By comparing Examples 1-17 with Comparative Example 2, it can be seen that the concentration of ethylbenzene hydroperoxide in the reaction products of Examples 1-17 is significantly higher than that of Comparative Example 2. This shows that the ethylbenzene enhanced oxidation reaction system of the utility model can significantly improve the reaction efficiency and product yield of the ethylbenzene peroxidation reaction, and the concentration of ethylbenzene hydroperoxide in Examples 1-17 basically meets the requirements of the downstream epoxidation reaction (i.e., the concentration of ethylbenzene hydroperoxide in the product reaches about 40wt%), thus, the product of the oxidation reactor of the utility model can be directly input into the epoxidation reactor to participate in the epoxidation reaction, without the need to set up a concentration unit, thereby further reducing the floor space of the preparation system and helping to reduce production costs.

[0145] In summary, the technical solution of the utility model is helpful to improve the reaction efficiency and product yield of the ethylbenzene peroxidation reaction, and because the concentration of ethylbenzene hydroperoxide in the reaction product of the ethylbenzene peroxidation reaction is relatively high, it can be directly input into the epoxidation reactor without further concentrating the reaction product of the ethylbenzene peroxidation reaction, so there is no need to set up a separate concentrating device, thereby further reducing the production cost and reducing the footprint of the system.

[0146] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the utility model.

Claims

1. A system for preparing propylene oxide, characterized in that: include: An oxidation reactor and an epoxidation reactor, wherein a delivery pipeline is disposed between the oxidation reactor and the epoxidation reactor, wherein the inlet of the delivery pipeline is connected to the product outlet of the oxidation reactor, and the outlet of the delivery pipeline is connected to the epoxidation reactor; A circulation pipeline is provided on one side of the oxidation reactor, the inlet of the circulation pipeline is communicated with the bottom of the oxidation reactor; the outlet of the circulation pipeline is communicated with the oxidation reactor, the outlet of the circulation pipeline is higher than the inlet of the circulation pipeline in the vertical direction and the outlet of the circulation pipeline is lower than the liquid level of the oxidation reactor in the vertical direction; the product outlet is higher than the outlet of the circulation pipeline in the vertical direction and the product outlet is located below the liquid level of the oxidation reactor in the vertical direction; The circulation pipeline is connected to an ethylbenzene pipeline, and the ethylbenzene in the ethylbenzene pipeline enters the oxidation reactor through the circulation pipeline; A first enhanced mass transfer unit is arranged in the circulation pipeline near the outlet of the circulation pipeline, and the first enhanced mass transfer unit is connected to an oxygen pipeline. The oxygen in the oxygen pipeline enters the circulation pipeline after being processed by the first enhanced mass transfer unit, so as to enhance the mass transfer effect between oxygen and ethylbenzene; The side wall of the epoxidation reactor is connected with a propylene pipeline, and propylene enters the epoxidation reactor through the propylene pipeline to react with ethylbenzene hydroperoxide in the epoxidation reactor to generate propylene oxide.

2. The system according to claim 1, characterized in that A baffle is arranged in the oxidation reactor, the top of the baffle is higher than the liquid level of the oxidation reactor in the vertical direction, and the distance between the bottom of the baffle and the bottom of the inner cavity of the oxidation reactor is a preset distance; a circulation channel is formed between the baffle and the side wall of the oxidation reactor, and the outlet of the circulation pipe is connected to the circulation channel.

3. The system according to claim 2, characterized in that A second enhanced mass transfer unit is arranged in the oxidation reactor, and the oxygen pipeline is connected to the second enhanced mass transfer unit. The oxygen in the oxygen pipeline enters the oxidation reactor after being processed by the second enhanced mass transfer unit to enhance the mass transfer effect between oxygen and ethylbenzene.

4. The system according to claim 3, characterized in that The distance between the first enhanced mass transfer unit and the inner wall of the oxidation reactor is smaller than the distance between the baffle and the inner wall of the oxidation reactor, and the distance between the baffle and the inner wall of the oxidation reactor is smaller than the distance between the baffle and the second enhanced mass transfer unit.

5. The system according to claim 1, characterized in that The circulation pipeline is provided with a first heat exchanger, and the material in the circulation pipeline is heated by the first heat exchanger and then circulated to the oxidation reactor.

6. The system according to claim 1, characterized in that It also includes a heat exchange pipe, the inlet and outlet of which are both connected to the oxidation reactor, and the inlet of the heat exchange pipe is arranged below the outlet of the heat exchange pipe in the vertical direction; a second heat exchanger is arranged on the heat exchange pipe.

7. The system according to claim 1, characterized in that Multiple layers of first baffles are staggered from top to bottom in the oxidation reactor, and the multiple layers of first baffles are located below the liquid surface of the oxidation reactor.

8. The system according to any one of claims 1 to 7, characterized in that: A third enhanced mass transfer unit is arranged in the epoxidation reactor, and the third enhanced mass transfer unit is connected with the outlet of the conveying pipeline. The material conveyed in the conveying pipeline enters the epoxidation reactor after being processed by the third enhanced mass transfer unit, so as to enhance the mass transfer effect with propylene.

9. The system according to claim 8, characterized in that Multiple layers of second baffles are staggered from top to bottom in the epoxidation reactor, and the multiple layers of the second baffles are located between the liquid surface of the epoxidation reactor and the third enhanced mass transfer unit.

10. The system according to any one of claims 1 to 7, characterized in that: It also includes a propylene separation tower, a propylene oxide separation tower, an ethylbenzene separation tower, a dehydration tower and a styrene refining tower which are connected in sequence, wherein the propylene separation tower is connected to the epoxidation reactor, and the bottom outlet of the styrene refining tower is connected to a hydrogenation reactor to transport the separated acetophenone to the hydrogenation reactor; the outlet of the hydrogenation reactor is connected to the dehydration tower; A fourth enhanced mass transfer unit is arranged in the hydrogenation reactor, and the fourth enhanced mass transfer unit is connected to a hydrogen pipeline. The hydrogen transported by the hydrogen pipeline enters the hydrogenation reactor after being processed by the fourth enhanced mass transfer unit, so as to enhance the mass transfer effect between hydrogen and acetophenone.

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