Preparation method of epoxypropane and device for preparing epoxypropane

Abstract

The invention relates to the field of organic chemical industry, and discloses a preparation method of epoxypropane and a device for preparing epoxypropane. The preparation method comprises the following steps: S1, in the presence of a first auxiliary agent and a first catalyst, carrying out a first epoxidation reaction on propylene and hydrogen peroxide to obtain a first epoxidation reaction product; s2, carrying out gas-liquid separation on a product obtained after the first epoxidation reaction; s3, in the presence of a second aid and a second catalyst, carrying out a second epoxidation reaction on the part A in the liquid-phase separated substance obtained in S2 and propylene to obtain a product after the second epoxidation reaction; and S4, returning the product after the second epoxidation reaction to S2 to obtain a gas-phase product and a liquid-phase product. According to the method, the concentration of residual hydrogen peroxide in a liquid phase obtained after gas-liquid separation and the mass percentage content of oxygen in the liquid phase are reduced, and the yield of the epoxypropane product can be improved.

Description

Technical Field

[0001] The invention relates to the field of organic chemical industry, and in particular to a method for preparing propylene oxide and a device for preparing propylene oxide. Background Art

[0002] With the development of petrochemicals and fine chemicals, propylene oxide has become the second largest derivative of propylene and an important petrochemical intermediate. The synthesis of propylene oxide by propylene epoxidation catalyzed by titanium silicon molecular sieve using hydrogen peroxide as an oxidant and low-carbon alcohols as solvents meets the requirements of green chemistry and atomic economic development concepts and is a green new process with great development prospects. In this process, the hydrogen peroxide concentration of the reactor outlet material must be strictly controlled, and the material must be hydrogenated and purified after removing propylene and propylene oxide to remove hydrogen peroxide and other impurities.

[0003] Regarding the removal of residual hydrogen peroxide in the product of epoxidation of olefins with hydrogen peroxide, CN1446206A and US7138534B2 disclose a continuous method for producing propylene oxide, wherein the epoxidation product of propylene and hydrogen peroxide is first fed into a distillation tower to remove propylene and propylene oxide from the top of the tower, and then the bottom discharge of the distillation tower containing methanol, water, epoxidation reaction by-products and hydrogen peroxide is fed into a fixed bed reactor equipped with a Group VIII metal or metal oxide catalyst to remove hydrogen peroxide at a temperature of 80-90°C under alkaline conditions, but other impurities are not removed.

[0004] CN1294125C discloses a method for hydrogenating and refining the recovered solvent in olefin epoxidation reaction, which can substantially remove carbonyl compounds such as formaldehyde and acetaldehyde, as well as hydrogen peroxide under the reaction conditions of 0.5-30 MPa and 80-150°C.

[0005] CN110354858A discloses an alcohol solvent hydrogenation refining catalyst for olefin epoxidation reaction process and its preparation method and application. The catalyst active component is Ni, the auxiliary component element is Mn or Fe, in addition, the catalyst also contains C, and the balance is an alumina carrier. The catalyst is at a temperature of 70-150°C, a pressure of 0.5-5MPa, a volume ratio of hydrogen to alcohol solvent of 20-500, and a liquid hourly space velocity of 1-10h -1 Under the conditions of good hydrogenation effect, it has good hydrogenation activity and high impurity removal rate for recovering various impurities in alcohol solvent.

[0006] In summary, the treatment of residual hydrogen peroxide in the HPPO process for synthesizing propylene oxide is generally carried out by removing hydrogen peroxide through hydrogenation during the separation process of the outlet materials of the epoxidation reaction, and there is no public report on the further epoxidation of residual hydrogen peroxide.

[0007] The residual hydrogen peroxide from epoxidation will decompose and release oxygen during the separation process, which poses a safety risk. Moreover, the higher the material temperature, the higher the concentration of hydrogen peroxide in the material, the faster the decomposition rate of hydrogen peroxide, and the greater the safety risk. The treatment of residual hydrogen peroxide in the current mainstream HPPO process for synthesizing propylene oxide is mainly carried out by hydrogenation removal under hydrogen conditions using catalysts containing Ni and the like. In the actual application of this process, the concentration of hydrogen peroxide in the material to be hydrogenated is strictly limited, but it still cannot avoid the oxidation of the active component Ni of the catalyst by strong oxidants such as hydrogen peroxide. These factors have prompted the use of more reasonable methods for the treatment and utilization of residual hydrogen peroxide in industrial applications. Summary of the invention

[0008] The purpose of the present invention is to overcome the problems of oxidation passivation of catalyst active components Ni and the like by hydrogen peroxide and inability to reasonably utilize residual hydrogen peroxide in the prior art, and to provide a method for preparing propylene oxide and a device for preparing propylene oxide. The method not only overcomes the oxidation passivation of catalyst active components Ni and the like by oxidant hydrogen peroxide, but also converts part of residual hydrogen peroxide into valuable products; the method has the characteristics of improving the utilization rate of hydrogen peroxide in the device, reducing separation energy consumption, improving the safety of the device, etc., being conducive to the performance of subsequent hydrogenation purification units, and greatly reducing the scale of hydrogenation purification units, and being particularly suitable for industrial application and optimization and improvement of industrial devices.

[0009] In order to achieve the above object, the first aspect of the present invention provides a method for preparing propylene oxide, the preparation method comprising:

[0010] S1. In the presence of a first auxiliary agent and a first catalyst, subjecting propylene and hydrogen peroxide to a first epoxidation reaction to obtain a first epoxidation reaction product;

[0011] S2, separating the gas-liquid product of the first epoxidation reaction;

[0012] S3, in the presence of a second auxiliary agent and a second catalyst, subjecting the portion A of the liquid phase separation obtained in S2 to a second epoxidation reaction with propylene to obtain a second epoxidation reaction product;

[0013] S4, returning the product after the second epoxidation reaction to S2 to obtain a gas phase product and a liquid phase product.

[0014] The second aspect of the present invention provides a device for preparing propylene oxide, the device comprising: an epoxidation reaction unit and a gas-liquid separation unit connected to each other; wherein the epoxidation reaction unit comprises a first epoxidation reactor 9, and the gas-liquid separation unit comprises a gas-liquid separator 6 and a second epoxidation reactor 5 connected to each other; wherein,

[0015] The side of the gas-liquid separator 6 is provided with a gas-liquid separator side line 2, which is used to lead the A part of the liquid phase separation after the first epoxidation reaction out of the gas-liquid separator 6 and send it to the second epoxidation reactor 5 from the bottom;

[0016] A second epoxidation product pipeline 3 is provided on the top of the second epoxidation reactor 5, for drawing out the second epoxidation product from the second epoxidation reactor 5 and returning it to the gas-liquid separator 6;

[0017] A propylene feed pipeline 8 and an auxiliary agent feed pipeline 7 are provided at the bottom of the second epoxidation reactor 5, which are used to transport propylene and auxiliary agents respectively, and are mixed with the material drawn out from the gas-liquid separator side line 2 and then fed into the second epoxidation reactor 5 from the bottom.

[0018] Through the above technical solution, the beneficial effects of the present invention are:

[0019] The product of the HPPO method for synthesizing propylene oxide has a low hydrogen peroxide concentration and a high propylene oxide concentration. If the reaction liquid is reacted again, the reaction process will cause propylene oxide to produce a large amount of by-products, resulting in a decrease in the overall yield. Therefore, the common practice in the art is to completely separate the propylene oxide in the reaction liquid, and then perform a "harmless" treatment of hydrogen peroxide on the liquid containing hydrogen peroxide by means of hydrogenation, etc. The treatment process does not produce benefits and increases production costs. The present invention couples the propylene epoxidation reaction process with the gas-liquid separation process, which can significantly reduce the generation of by-products in the further epoxidation reaction (second epoxidation reaction) process.

[0020] The residual hydrogen peroxide generates valuable products such as propylene oxide, etc. under the action of a small amount of propylene, auxiliary agents and catalysts, thereby improving the utilization rate of hydrogen peroxide and the economic benefits of the device. The hydrogen peroxide-containing material extracted from the gas-liquid separator side line reduces the concentration of hydrogen peroxide in the lower part (higher temperature) of the gas-liquid separator side line extraction line; thereby reducing the ineffective decomposition of hydrogen peroxide and improving the safety of the device. The reuse of epoxidation residual hydrogen peroxide greatly reduces the hydrogen peroxide concentration of the material treated by the hydrogenation purification unit, which is beneficial to the performance of the subsequent hydrogenation purification unit, can greatly reduce the scale of the hydrogenation purification unit, and improve the economic benefits of the device. Therefore, compared with the existing treatment method, the method for recycling residual hydrogen peroxide of the present invention has the following advantages: on the premise of increasing a small amount of equipment investment, it improves the yield of valuable products of the device and reduces the safety risk of the device, and is beneficial to the performance of the subsequent hydrogenation purification unit, and can greatly reduce the scale of the hydrogenation purification unit and improve the economic benefits of the device. It is particularly suitable for industrial applications and optimization and improvement of industrial devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a diagram of an apparatus for preparing propylene oxide in a preferred embodiment of the present invention.

[0022] Description of Reference Numerals

[0023] 1 Feed pipeline for product after the first epoxidation reaction 2 Side line of gas-liquid separator

[0024] 3 Second epoxidation reaction product pipeline 4 Bottom outlet

[0025] 5 Second epoxidation reactor 6 Gas-liquid separator 7 Auxiliary agent feed pipeline

[0026] 8 propylene feed line 9 first epoxidation reactor 10 top outlet DETAILED DESCRIPTION

[0027] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0028] A first aspect of the present invention provides a method for preparing propylene oxide, the preparation method comprising:

[0029] S1. In the presence of a first auxiliary agent and a first catalyst, subjecting propylene and hydrogen peroxide to a first epoxidation reaction to obtain a first epoxidation reaction product;

[0030] S2, separating the gas-liquid product of the first epoxidation reaction;

[0031] S3, in the presence of a second auxiliary agent and a second catalyst, subjecting the portion A of the liquid phase separation obtained in S2 to a second epoxidation reaction with propylene to obtain a second epoxidation reaction product;

[0032] S4, returning the product after the second epoxidation reaction to S2 to obtain a gas phase product and a liquid phase product.

[0033] S1 uses hydrogen peroxide direct oxidation of propylene method (HPPO method) to synthesize propylene oxide, and the obtained first epoxidation reaction product mainly includes the following components: propylene, methanol, water, propylene oxide, propylene glycol monomethyl ether, propylene glycol isomethyl ether, propylene glycol, hydrogen peroxide, etc. For example, the HPPO method propylene oxide synthesis reaction outlet material (first epoxidation reaction product) from the propylene oxide industrial test device of Sinopec Changling Branch includes the following components: 10wt% of propylene, 60.09wt% of methanol, 14.74wt% of water, 13.78wt% of propylene oxide, 0.13wt% of propylene glycol monomethyl ether, 0.10wt% of propylene glycol isomethyl ether, 0.06wt% of propylene glycol, 0.30wt% of hydrogen peroxide and 0.80wt% of other impurities.

[0034] S2 performs gas-liquid separation on the product after the first epoxidation reaction to obtain a liquid phase separation and a gas phase separation; wherein the liquid phase separation obtained after the gas-liquid separation of S2 mainly includes components such as hydrogen peroxide, methanol, water, propylene glycol monomethyl ether, propylene glycol isomethyl ether and propylene glycol; the gas phase separation mainly includes components such as oxygen, propylene, methanol, water, propylene oxide, propylene glycol monomethyl ether and propylene glycol isomethyl ether. The liquid phase separation obtained in S2 can be further divided into at least two parts, part A and part B. wherein S3 takes part A in the presence of a second auxiliary agent and a second catalyst, and makes the hydrogen peroxide contained therein react with the added propylene and auxiliary agent for a second epoxidation reaction to obtain a product after the second epoxidation reaction; the product after the second epoxidation reaction is returned to S2 and further subjected to gas-liquid separation.

[0035] The product of the HPPO method for synthesizing propylene oxide has a low hydrogen peroxide concentration and a high propylene oxide concentration. If the reaction liquid is reacted again, the reaction process will cause propylene oxide to produce a large amount of by-products, resulting in a decrease in the overall yield. Therefore, the common practice in the art is to completely separate the propylene oxide in the reaction liquid, and then perform a "harmless" treatment of hydrogen peroxide on the liquid containing hydrogen peroxide by means of hydrogenation, etc., which does not produce benefits and increases production costs. The present invention couples the propylene epoxidation reaction process with the gas-liquid separation process, which can significantly reduce the generation of by-products in the further epoxidation reaction (second epoxidation reaction) process.

[0036] According to the present invention, preferably, in S3, the portion A is 20-100 wt %, preferably 50-100 wt %, of the total weight of the liquid phase separation.

[0037] According to the present invention, preferably, the content of propylene oxide in the part A is less than or equal to 4 wt %, preferably less than or equal to 2 wt %. When the content of propylene oxide meets this condition, the occurrence of side reactions during the second epoxidation reaction can be effectively reduced.

[0038] According to the present invention, preferably, in S3, the conditions of the second epoxidation reaction include: a temperature of 65-85°C, a pressure of less than or equal to 3 MPa, a weight space velocity of the total weight of the A part, propylene and the second auxiliary agent of 0.5-50 h -1 Wherein, the temperature refers to the initial reaction temperature of the second epoxidation reaction. When the second epoxidation reaction meets this condition, the conversion rate of hydrogen peroxide can be effectively improved and a higher selectivity of propylene oxide can be obtained.

[0039] According to the present invention, preferably, in S3, the molar ratio of propylene to the hydrogen peroxide contained in the A part is (1-8): 1. When the amounts of propylene and hydrogen peroxide meet this range, the conversion of hydrogen peroxide can be promoted and the conversion rate of hydrogen peroxide can be improved.

[0040] According to the present invention, preferably, based on the total weight of the part A, the amount of the second auxiliary agent is 0.001-0.02 wt %.

[0041] According to the present invention, preferably, the first auxiliary agent and the second auxiliary agent are each independently selected from at least one of NaHCO3, KOH, NH3, NaOH, K2CO3, Na2CO3, KHCO3, Li2CO3, LiHCO3, Na2HPO4, (NH4)2Ac, ammonia water, triethylamine and pyridine.

[0042] According to the present invention, preferably, the first catalyst and the second catalyst are each independently a titanium silicon molecular sieve, preferably a spherical titanium silicon molecular sieve with an average particle size of 1-2 mm. In the present invention, the titanium silicon molecular sieve can be a titanium silicon molecular sieve raw powder, or a molded body prepared by a catalyst molding method such as spray molding, ball rolling molding, extrusion molding or tablet molding using the titanium silicon molecular sieve raw powder. Preparing the titanium silicon molecular sieve raw powder into a spherical titanium silicon molecular sieve with an average particle size of 1-2 mm can make the catalyst have a higher catalytic efficiency in the first epoxidation reaction and the second epoxidation reaction, and can reduce the occurrence of side reactions during the second epoxidation reaction. In order to facilitate industrial applications, the first catalyst and the second catalyst are preferably the same titanium silicon molecular sieve.

[0043] According to the present invention, preferably, the topological structure of the titanium silicalite is selected from at least one of MFI, BEA, MEL, MWW and MOR, preferably MFI. The titanium silicalite with the topological structure of MFI can obtain both a higher hydrogen peroxide conversion rate and a higher propylene oxide selectivity. If the titanium silicalite with other topological structures is selected, the hydrogen peroxide conversion rate and the propylene oxide selectivity may be low, and it is difficult to obtain a higher propylene oxide yield.

[0044] According to the present invention, preferably, in the titanium silicon molecular sieve, the molar ratio of titanium element to silicon element is 1:(20-200).

[0045] According to the present invention, preferably, the conditions of the first epoxidation reaction include: a temperature of 20-60°C, a pressure of less than or equal to 3 MPa, and a weight space velocity (the total weight of the first auxiliary agent, propylene and hydrogen peroxide) of 0.5-10 h -1 ; wherein the molar ratio of propylene to hydrogen peroxide is (1-8): 1; based on the weight of hydrogen peroxide, the amount of the first auxiliary agent is 0.001-0.02wt%.

[0046] According to the present invention, preferably, the product after the second epoxidation reaction comprises: propylene oxide, propylene glycol ether and propylene glycol.

[0047] According to the present invention, preferably, in S4, the content of hydrogen peroxide in the liquid phase product is less than or equal to 0.4wt%, preferably less than or equal to 0.1wt%; the content of oxygen in the gas phase product is less than or equal to 0.014wt%, preferably less than or equal to 0.008wt%. The second epoxidation reaction is carried out on the A part of the liquid phase separation product (liquid phase product of propylene oxide synthesized by HPPO method) after the first epoxidation reaction, which is beneficial to reduce the concentration of residual hydrogen peroxide in the liquid phase obtained after gas-liquid separation and the mass percentage of oxygen in the gas phase, and improve the yield of propylene oxide product in the gas phase.

[0048] The liquid product obtained after the gas-liquid separation in step S4 of the present invention still contains a small amount of hydrogen peroxide, which still leads to the generation of impurities that affect the product quality and poses certain safety hazards. Therefore, preferably, the preparation method further comprises: hydrogenating and purifying the liquid product to remove the residual hydrogen peroxide in the liquid product obtained after the gas-liquid separation.

[0049] The second aspect of the present invention provides a device for preparing propylene oxide, the device comprising: an epoxidation reaction unit and a gas-liquid separation unit connected to each other; wherein the epoxidation reaction unit comprises a first epoxidation reactor 9, and the gas-liquid separation unit comprises a gas-liquid separator 6 and a second epoxidation reactor 5 connected to each other; wherein,

[0050] The side of the gas-liquid separator 6 is provided with a gas-liquid separator side line 2, which is used to lead the A part of the liquid phase separation after the first epoxidation reaction out of the gas-liquid separator 6 and send it to the second epoxidation reactor 5 from the bottom;

[0051] A second epoxidation product pipeline 3 is provided on the top of the second epoxidation reactor 5, for drawing out the second epoxidation product from the second epoxidation reactor 5 and returning it to the gas-liquid separator 6;

[0052] A propylene feed pipeline 8 and an auxiliary agent feed pipeline 7 are provided at the bottom of the second epoxidation reactor 5, which are used to transport propylene and auxiliary agents respectively, and are mixed with the material drawn out from the gas-liquid separator side line 2 and then fed into the second epoxidation reactor 5 from the bottom.

[0053] The product after the first epoxidation reaction (the product of propylene oxide synthesized by the HPPO method) is separated through the gas-liquid separator 6, wherein components such as propylene and propylene oxide flow out from the top of the gas-liquid separator 6, and hydrogen peroxide flows out from the bottom of the gas-liquid separator 6. The present invention extracts a stream of liquid phase material from the side of the gas-liquid separator 6, so that the residual hydrogen peroxide in the liquid phase material generates valuable products such as propylene oxide under the action of adding a small amount of propylene, auxiliary agents and catalysts, thereby improving the utilization rate of hydrogen peroxide and the economic benefits of the device.

[0054] According to the present invention, preferably, the top of the gas-liquid separator 6 is provided with a top discharge port 10 for drawing out the gas phase product after gas-liquid separation; and the bottom is provided with a bottom discharge port 4 for drawing out the liquid phase product after gas-liquid separation.

[0055] According to the present invention, preferably, the second epoxidation reactor is selected from a fixed bed reactor or a slurry bed reactor.

[0056] According to the present invention, preferably, the gas-liquid separator 6 is a distillation tower.

[0057] The propylene epoxidation reaction is generally carried out in a tubular reactor in the prior art because of the huge reaction heat release, so that the reaction heat can be removed in time. The tubular reactor can only be filled with catalysts in the tubulars, the effective space utilization rate is low, and the technical requirements for the manufacture and use of the reactor are relatively high. The present invention couples the propylene epoxidation reaction process with the distillation process, and can use adiabatic or non-adiabatic reactors such as fixed bed or slurry bed, so as to realize the epoxidation reaction without increasing the production energy consumption of the device. In addition, coupling the fixed bed reactor or slurry bed reactor with the distillation process can further reduce the generation of by-products in the second epoxidation reaction process.

[0058] According to the present invention, preferably, a first epoxidation reaction product feed pipeline 1 is also provided on the side of the gas-liquid separator 6 for connecting the first epoxidation reactor 9 and the gas-liquid separator 6 and introducing the first epoxidation reaction product into the gas-liquid separator 6 .

[0059] According to the present invention, preferably, the inlet of the gas-liquid separator side line 2 is lower than the outlet of the first epoxidation reaction product feeding pipeline 1 .

[0060] According to the present invention, preferably, the ratio of the distance from the inlet of the gas-liquid separator side line 2 to the bottom of the gas-liquid separator 6 to the distance from the outlet of the first epoxidation reaction product feed pipeline 1 to the bottom of the gas-liquid separator 6 is 1:(1.1-10). When the extraction position of the extracted material meets this range, the amount of the material to be processed in the second epoxidation reactor can be effectively reduced, and the content of propylene oxide in the material can be greatly reduced, otherwise it is difficult to obtain an ideal hydrogen peroxide conversion rate and propylene oxide selectivity.

[0061] According to the present invention, preferably, the device further comprises a hydrogenation purification unit for removing hydrogen peroxide from the liquid phase product after gas-liquid separation.

[0062] According to a specific embodiment of the present invention, the present invention Figure 1 The method for preparing propylene oxide in the device shown specifically comprises the following steps:

[0063] In the first epoxidation reactor 9, propylene and hydrogen peroxide are subjected to a first epoxidation reaction (HPPO method for synthesizing propylene oxide) in the presence of a first auxiliary agent and a first catalyst to obtain a first epoxidation product; the first epoxidation product enters a gas-liquid separator 6 through a first epoxidation product feed pipeline 1 to separate propylene and propylene oxide, and at least a portion (portion A) of liquid phase material is extracted from a gas-liquid separator side line 2, and the ratio of the distance from the extraction position to the bottom of the gas-liquid separator to the distance from the outlet of the first epoxidation product feed pipeline 1 to the bottom of the gas-liquid separator 6 is 1:(1.1-10), and the flow rate of the liquid phase material extracted from the gas-liquid separator side line 2 accounts for 20-100wt% of the total liquid in the gas-liquid separator 6; and the added propylene and auxiliary agent are respectively mixed with the extracted material through a propylene feed pipeline 8 and an auxiliary agent feed pipeline 7 and then injected into a second epoxidation reactor 5. The reactor is filled with a catalyst, the material temperature is 65-85°C as the initial reaction temperature, the reaction pressure is less than or equal to 3MPa, and the weight space velocity of the total weight of the A part, propylene and the second auxiliary agent is 0.5-50h -1 Under the conditions of , an epoxidation reaction is carried out to obtain a reaction product stream containing epoxide, which flows out from the second epoxidation reaction product pipeline 3 and then returns to the gas-liquid separator 6, and can be returned to the gas-liquid separator 6 from the upper part, the middle part or the lower part of the gas-liquid separator 6, and is mixed with the HPPO method synthesized propylene oxide product material flowing into the gas-liquid separator 6 from the first epoxidation reaction product feed pipeline 1. Enter the distillation tower to complete separation; the gas phase product and the liquid phase product separated by the gas-liquid separator 6 flow out from the top discharge port 10 and the bottom discharge port 4 respectively; the liquid phase flowing out of the bottom discharge port 4 is introduced into the hydrogenation purification unit for hydrogenation purification, so as to remove the unremoved hydrogen peroxide.

[0064] The present invention will be described in detail below through examples and comparative examples. In the following examples, unless otherwise specified, all conventional methods are used; the reagents and materials used, unless otherwise specified, can be obtained from commercial sources. The raw materials and determination methods involved in each example and comparative example are as follows:

[0065] All materials come from the propylene oxide industrial test unit of Sinopec Changling Branch. The HPPO process involved in the synthesis of propylene oxide reaction outlet material composition: propylene 10wt%, methanol 60.09wt%, water 14.74wt%, propylene oxide 13.78wt%, propylene glycol monomethyl ether 0.13wt%, propylene glycol isomethyl ether 0.1wt%, propylene glycol 0.06wt%, hydrogen peroxide 0.3wt% and other impurities 0.8wt%.

[0066] The conversion of hydrogen peroxide and the selectivity of propylene oxide are calculated as follows:

[0067] Conversion rate of hydrogen peroxide % = (the number of moles of hydrogen peroxide converted ÷ the number of moles of hydrogen peroxide fed) × 100%;

[0068] Propylene oxide selectivity % = (the number of moles of propylene oxide produced ÷ the sum of the total number of moles of epoxides produced) × 100%;

[0069] The concentration of hydrogen peroxide was measured by iodine titration; the composition of the top material and bottom material of the distillation tower was analyzed and tested by gas chromatography.

[0070] The following examples are used to illustrate the Figure 1 The method for preparing propylene oxide using the apparatus shown.

[0071] Example 1

[0072] The flow rate of the outlet material of the HPPO method for synthesizing propylene oxide is 1 t / h, and the material enters a distillation tower for separation of propylene and propylene oxide, and the material is extracted from the side line of the distillation tower. The ratio of the distance from the extraction position to the bottom of the distillation tower to the distance from the feed position of the distillation tower to the bottom of the distillation tower is 1:7, and the flow rate of the extracted material accounts for 100wt% of the total liquid volume of the distillation tower; the content of propylene oxide in the material is 0.5wt%; the material is mixed with external propylene (propylene flow rate 7.41kg / h, propylene and hydrogen peroxide molar ratio in the extracted material is 2) and an auxiliary agent injected by an injection pump (NaHCO3 aqueous solution with a concentration of 1wt%, flow rate 0.2kg / h, and the added amount is 0.02wt% of the total mass of the extracted material), and then injected into a fixed bed stainless steel reactor. The reactor is filled with a molded titanium-silicon molecular sieve catalyst (titanium-silicon molar ratio of 1:35, topological structure of MFI, spheres with a diameter of 1.5±0.2 mm), with a material temperature of 70°C as the initial reaction temperature, a reaction pressure of 2 MPa, and a weight space velocity (the total amount of produced material, added propylene and additives) of 20 h-1 Under the conditions of , an epoxidation reaction was carried out to obtain a stream containing epoxide. The composition of the reaction outlet was analyzed, and the conversion rate of hydrogen peroxide was 90%, and the selectivity of propylene oxide was 95%. The stream was mixed with the outlet material of the HPPO method propylene oxide synthesis reaction and entered the distillation tower for separation.

[0073] The top material and bottom material of the distillation tower were sampled and analyzed. The composition of the top material was: oxygen 0.007wt%, propylene 25.5wt%, methanol 36.76wt%, water 2.59wt%, propylene oxide 34.84wt%, propylene glycol monomethyl ether 0.005wt%, propylene glycol isomonomethyl ether 0.005wt%, and other impurities 0.29wt%; the flow rate was 408.08kg / h.

[0074] The bottom material composition is: methanol 75.13wt%, water 22.93wt%, propylene glycol monomethyl ether 0.23wt%, propylene glycol isomethyl ether 0.18wt%, propylene glycol 0.12wt%, hydrogen peroxide 0.05wt%, and other impurities 1.35wt%; the flow rate is 599.53kg / h.

[0075] Example 2

[0076] The flow rate of the outlet material of the HPPO method for synthesizing propylene oxide is 1 t / h, and the material enters a distillation tower to separate propylene and propylene oxide, and the material is extracted from the side line of the distillation tower. The ratio of the distance from the extraction position to the bottom of the distillation tower to the distance from the feed position of the distillation tower to the bottom of the distillation tower is 1:4, and the flow rate of the extracted material accounts for 70wt% of the total liquid volume of the distillation tower; the content of propylene oxide in the material is 2wt%; the material is mixed with external propylene (propylene flow rate is 20.75kg / h, and the molar ratio of propylene to hydrogen peroxide in the extracted material is 8) and an auxiliary agent injected by an injection pump (ammonia water with a concentration of 3wt%, a flow rate of 0.1kg / h, and an added amount of 0.01wt% of the total mass of the extracted material), and then injected into a fixed bed stainless steel reactor. The reactor is filled with a molded titanium-silicon molecular sieve catalyst (titanium-silicon molar ratio of 1:35, topological structure of MFI, spheres with a diameter of 1.5±0.2 mm), with a material temperature of 85°C as the initial reaction temperature, a reaction pressure of 2 MPa, and a weight space velocity (the total amount of produced material, added propylene and additives) of 50 h -1 Under the conditions of , an epoxidation reaction was carried out to obtain a stream containing epoxide. The composition of the reaction outlet was analyzed, and the hydrogen peroxide conversion rate was 95%, and the propylene oxide selectivity was 95%. The stream was mixed with the outlet material of the HPPO method propylene oxide synthesis reaction and entered the distillation tower for separation.

[0077] The top material and bottom material of the distillation tower were sampled and analyzed. The composition of the top material was: oxygen 0.01wt%, propylene 28.15wt%, methanol 35.46wt%, water 2.52wt%, propylene oxide 33.57wt%, propylene glycol monomethyl ether 0.005wt%, propylene glycol isomonomethyl ether 0.005wt%, and other impurities 0.28wt%; the flow rate was 420.17kg / h.

[0078] The bottom material composition is: methanol 75.16wt%, water 22.87wt%, propylene glycol monomethyl ether 0.22wt%, propylene glycol isomethyl ether 0.17wt%, propylene glycol 0.1wt%, hydrogen peroxide 0.13wt%, and other impurities 1.35wt%; the flow rate is 600.68kg / h.

[0079] Example 3

[0080] The outlet material of the HPPO method for synthesizing propylene oxide has a flow rate of 1 t / h, enters a distillation tower for separation of propylene and propylene oxide, and extracts the material from the side line of the distillation tower. The ratio of the distance from the extraction position to the bottom of the distillation tower to the distance from the feed position of the distillation tower to the bottom of the distillation tower is 1:10, and the extraction material flow rate accounts for 50wt% of the total liquid volume of the distillation tower; the content of propylene oxide in the material is 0.1wt%; the material is mixed with external propylene (propylene flow rate 1.85kg / h, and the molar ratio of propylene to hydrogen peroxide in the extracted material is 1) and an auxiliary agent injected by an injection pump (aqueous solution of KHCO3 with a concentration of 2wt%, a flow rate of 0.01kg / h, and an amount added of 0.001wt% of the total mass of the extracted material), and then injected into a slurry bed reactor. The reactor is filled with titanium silicate molecular sieve catalyst (titanium silicate molecular sieve raw powder, titanium-silicon molar ratio of 1:30, topological structure of MFI), the material temperature is 65 ° C as the initial reaction temperature, the reaction pressure is normal pressure, the weight space velocity (the total amount of produced material, added propylene and additives) is 0.5h -1 Under the conditions of , an epoxidation reaction was carried out to obtain a stream containing epoxide. The composition of the reaction outlet was analyzed, and the conversion rate of hydrogen peroxide was 99%, and the selectivity of propylene oxide was 90%. The stream was mixed with the outlet material of the HPPO method propylene oxide synthesis reaction and entered the distillation tower for separation.

[0081] The top material and bottom material of the distillation tower were sampled and analyzed. The composition of the top material was: oxygen 0.011wt%, propylene 25.00wt%, methanol 36.99wt%, water 2.65wt%, propylene oxide 35.05wt%, propylene glycol monomethyl ether 0.005wt%, propylene glycol isomethyl ether 0.005wt%, and other impurities 0.3wt%; the flow rate was 400.07kg / h.

[0082] The bottom material composition is: methanol 75.12wt%, water 22.88wt%, propylene glycol monomethyl ether 0.23wt%, propylene glycol isomethyl ether 0.18wt%, propylene glycol 0.1wt%, hydrogen peroxide 0.24wt%, and other impurities 1.26wt%; flow rate 601.79kg / h.

[0083] Example 4

[0084] Propylene oxide was prepared according to the method of Example 2, except that a tank reactor was used to contact the side line material of the rectification tower with the added propylene, auxiliary agent and catalyst for epoxidation reaction to obtain a stream containing epoxide. Analysis of the reaction outlet composition showed a hydrogen peroxide conversion rate of 98% and a propylene oxide selectivity of 80%.

[0085] The top material and bottom material of the distillation tower were sampled and analyzed. The composition of the top material was: oxygen 0.014wt%, propylene 28.18wt%, methanol 35.50wt%, water 2.52wt%, propylene oxide 33.50wt%, propylene glycol monomethyl ether 0.005wt%, propylene glycol isomethyl ether 0.005wt%, and other impurities 0.28wt%; the flow rate was 419.77kg / h.

[0086] The bottom material composition is: methanol 75.08wt%, water 22.86wt%, propylene glycol monomethyl ether 0.27wt%, propylene glycol isomethyl ether 0.22wt%, propylene glycol 0.13wt%, hydrogen peroxide 0.1wt%, and other impurities 1.35wt%; flow rate 601.09kg / h.

[0087] Example 5

[0088] Propylene oxide was prepared according to the method of Example 2, except that the flow rate of the material extracted from the side line of the distillation tower accounted for 20wt% of the total liquid volume of the distillation tower, and the material was contacted with external propylene, an auxiliary agent and a catalyst for epoxidation reaction to obtain a stream containing epoxide. Analysis of the reaction outlet composition showed that the hydrogen peroxide conversion rate was 95% and the propylene oxide selectivity was 95%.

[0089] The top material and bottom material of the distillation tower were sampled and analyzed. The composition of the top material was: oxygen 0.012wt%, propylene 26.05wt%, methanol 36.66wt%, water 2.62wt%, propylene oxide 34.36wt%, propylene glycol monomethyl ether 0.005wt%, propylene glycol isomethyl ether 0.005wt%, and other impurities 0.29wt%; the flow rate was 403.77kg / h.

[0090] The bottom material composition is: methanol 75.16wt%, water 22.73wt%, propylene glycol monomethyl ether 0.22wt%, propylene glycol isomethyl ether 0.17wt%, propylene glycol 0.10wt%, hydrogen peroxide 0.37wt%, and other impurities 1.26wt%; flow rate 602.17kg / h.

[0091] Example 6

[0092] Propylene oxide was prepared according to the method of Example 2, except that the content of propylene oxide in the material taken out from the side line of the distillation tower was 4wt%. The material was contacted with external propylene, an auxiliary agent and a catalyst for epoxidation reaction to obtain a stream containing epoxide. Analysis of the reaction outlet composition showed that the hydrogen peroxide conversion rate was 94% and the propylene oxide selectivity was 91%.

[0093] The top material and bottom material of the distillation tower were sampled and analyzed. The composition of the top material was: oxygen 0.01wt%, propylene 28.16wt%, methanol 35.45wt%, water 2.52wt%, propylene oxide 33.54wt%, propylene glycol monomethyl ether 0.005wt%, propylene glycol isomethyl ether 0.005wt%, and other impurities 0.28wt%; the flow rate was 420.00kg / h.

[0094] The bottom material composition is: methanol 75.12wt%, water 22.86wt%, propylene glycol monomethyl ether 0.24wt%, propylene glycol isomethyl ether 0.19wt%, propylene glycol 0.11wt%, hydrogen peroxide 0.13wt%, and other impurities 1.35wt%; the flow rate is 600.85kg / h.

[0095] Example 7

[0096] Propylene oxide was prepared according to the method of Example 2, except that the content of propylene oxide in the material taken out from the side line of the distillation tower was 6wt%. The material was contacted with external propylene, an auxiliary agent and a catalyst for epoxidation reaction to obtain a stream containing epoxide. Analysis of the reaction outlet composition showed that the conversion rate of hydrogen peroxide was 92% and the selectivity of propylene oxide was 86%.

[0097] The top material and bottom material of the distillation tower were sampled and analyzed. The composition of the top material was: oxygen 0.011wt%, propylene 28.18wt%, methanol 35.50wt%, water 2.52wt%, propylene oxide 33.50wt%, propylene glycol monomethyl ether 0.005wt%, propylene glycol isomethyl ether 0.005wt%, and other impurities 0.28wt%; the flow rate was 419.78kg / h.

[0098] The bottom material composition is: methanol 75.07wt%, water 22.85wt%, propylene glycol monomethyl ether 0.27wt%, propylene glycol isomethyl ether 0.21wt%, propylene glycol 0.11wt%, hydrogen peroxide 0.14wt%, and other impurities 1.35wt%; flow rate 601.07kg / h.

[0099] Example 8

[0100] Propylene oxide was prepared according to the method of Example 2, except that the initial reaction temperature was 60°C, the reaction pressure was 4 MPa, and the weight space velocity was 55 h -1 Under the conditions of , an epoxidation reaction was carried out to obtain a stream containing epoxide. Analysis of the reaction outlet composition showed that the conversion rate of hydrogen peroxide was 70% and the selectivity of propylene oxide was 98%;

[0101] The top material and bottom material of the distillation tower were sampled and analyzed. The composition of the top material was: oxygen 0.012wt%, propylene 28.20wt%, methanol 35.53wt%, water 2.52wt%, propylene oxide 33.44wt%, propylene glycol monomethyl ether 0.005wt%, propylene glycol isomethyl ether 0.005wt%, and other impurities 0.28wt%; the flow rate was 419.41kg / h.

[0102] The bottom material composition is: methanol 75.15wt%, water 22.78wt%, propylene glycol monomethyl ether 0.22wt%, propylene glycol isomethyl ether 0.17wt%, propylene glycol 0.10wt%, hydrogen peroxide 0.24wt%, and other impurities 1.35wt%; the flow rate is 601.45kg / h.

[0103] Example 9

[0104] Propylene oxide was prepared according to the method of Example 2, except that the molar ratio of propylene to hydrogen peroxide in the produced material was 9. A stream containing epoxide was obtained, and the composition of the reaction outlet was analyzed, and the conversion rate of hydrogen peroxide was 93%, and the selectivity of propylene oxide was 96%;

[0105] The top material and bottom material of the distillation tower were sampled and analyzed. The composition of the top material was: oxygen 0.009wt%, propylene 28.60wt%, methanol 35.25wt%, water 2.50wt%, propylene oxide 33.35wt%, propylene glycol monomethyl ether 0.005wt%, propylene glycol isomethyl ether 0.005wt%, and other impurities 0.28wt%; the flow rate was 422.73kg / h.

[0106] The bottom material composition is: methanol 75.15wt%, water 22.87wt%, propylene glycol monomethyl ether 0.22wt%, propylene glycol isomethyl ether 0.17wt%, propylene glycol 0.10wt%, hydrogen peroxide 0.14wt%, and other impurities 1.35wt%; the flow rate is 600.72kg / h.

[0107] Example 10

[0108] Propylene oxide was prepared according to the method of Example 2, except that a shaped titanium silicon molecular sieve with a different topological structure was selected. Specifically, a shaped titanium silicon molecular sieve catalyst (a titanium-silicon molar ratio of 1:50, a topological structure of MWW, and a sphere with a diameter of 1.5±0.2 mm) was loaded into a fixed bed stainless steel reactor. A stream containing epoxide was obtained, and the reaction outlet composition was analyzed, with a hydrogen peroxide conversion rate of 97% and a propylene oxide selectivity of 83%.

[0109] The top material and bottom material of the distillation tower were sampled and analyzed. The composition of the top material was: oxygen 0.009wt%, propylene 28.18wt%, methanol 35.49wt%, water 2.52wt%, propylene oxide 33.51wt%, propylene glycol monomethyl ether 0.005wt%, propylene glycol isomethyl ether 0.005wt%, and other impurities 0.28wt%; the flow rate was 419.82kg / h.

[0110] The bottom material composition is: methanol 75.08wt%, water 22.85wt%, propylene glycol monomethyl ether 0.26wt%, propylene glycol isomethyl ether 0.21wt%, propylene glycol 0.11wt%, hydrogen peroxide 0.12wt%, and other impurities 1.36wt%; flow rate 601.04kg / h.

[0111] Embodiment 11

[0112] Propylene oxide was prepared according to the method of Example 2, except that a molded titanium silicon molecular sieve with a different titanium silicon ratio was selected. Specifically, a molded titanium silicon molecular sieve catalyst (a titanium silicon molar ratio of 1:210, a topological structure of MFI, and a sphere with a diameter of 1.5±0.2 mm) was loaded in a fixed bed stainless steel reactor. A stream containing epoxide was obtained, and the reaction outlet composition was analyzed, with a hydrogen peroxide conversion rate of 80% and a propylene oxide selectivity of 96%.

[0113] The top material and bottom material of the distillation tower were sampled and analyzed. The composition of the top material was: oxygen 0.011wt%, propylene 28.18wt%, methanol 35.50wt%, water 2.52wt%, propylene oxide 33.49wt%, propylene glycol monomethyl ether 0.005wt%, propylene glycol isomethyl ether 0.005wt%, and other impurities 0.28wt%; the flow rate was 419.70kg / h.

[0114] The bottom material composition is: methanol 75.13wt%, water 22.81wt%, propylene glycol monomethyl ether 0.22wt%, propylene glycol isomethyl ether 0.17wt%, propylene glycol 0.10wt%, hydrogen peroxide 0.22wt%, and other impurities 1.35wt%; flow rate 601.16kg / h.

[0115] Comparative Example 1

[0116] The outlet material flow rate of the HPPO process for synthesizing propylene oxide is 1 t / h, and enters the distillation tower for separation of propylene and propylene oxide; the side line material of the distillation tower is not taken out and the subsequent epoxidation reaction is not carried out.

[0117] The top material and bottom material of the distillation tower were sampled and analyzed. The composition of the top material was: oxygen 0.015wt%, propylene 25.15wt%, methanol 37.47wt%, water 2.52wt%, propylene oxide 34.62wt%, propylene glycol monomethyl ether 0.003wt%, propylene glycol isomonomethyl ether 0.003wt%, and other impurities 0.23wt%; the flow rate was 397.66kg / h.

[0118] The bottom material composition is: methanol 75.02wt%, water 22.83wt%, propylene glycol monomethyl ether 0.22wt%, propylene glycol isomonomethyl ether 0.17wt%, propylene glycol 0.1wt%, hydrogen peroxide 0.48wt%, and other impurities 1.19wt%; flow rate 602.34kg / h.

[0119] The results of the residual hydrogen peroxide concentration in the distillation tower kettle, the oxygen content at the top of the tower and the mass flow rate of propylene oxide at the top of the tower after treatment in each embodiment and comparative example are shown in Table 1:

[0120] Table 1

[0121]

[0122]

[0123] It can be seen from the results of each embodiment and comparative example and Table 1 that, compared with comparative example 1, when preparing propylene oxide in embodiments 1-11 of the present invention, when the outlet material of the HPPO method propylene oxide synthesis reaction enters the tower for separation, a stream of material is taken out of the tower side line for epoxidation reaction, which is beneficial to reducing the concentration of residual hydrogen peroxide in the tower bottom and the mass percentage of oxygen at the top of the tower, and improving the yield of propylene oxide product. Lower residual hydrogen peroxide in the tower bottom can reduce the load of the subsequent hydrogenation purification unit, which is beneficial to the performance of the hydrogenation purification unit and reduces its scale; lower mass percentage of oxygen at the top of the tower can improve the safety of the device and reduce the amount of nitrogen used; higher product mass flow rate is beneficial to improving the economic benefits of the device.

[0124] In addition, in Example 4, the side-line extracted liquid phase of the distillation tower is contacted with the added propylene, auxiliary agent and catalyst for epoxidation reaction using a tank reactor. Compared with Example 2, the selectivity of propylene oxide is significantly decreased, indicating that coupling the fixed bed reactor with the distillation process can reduce the generation of by-products in the second epoxidation reaction process; in Example 5, the amount of the side-line extracted material of the distillation tower is reduced. Compared with Example 2, the H2O2 content in the bottom of the tower is significantly increased, indicating that increasing the amount of the side-line extracted material of the distillation tower is beneficial to reducing the concentration of residual hydrogen peroxide in the bottom of the tower; in Examples 6 and 7, the content of propylene oxide in the side-line extracted material of the distillation tower is relatively high. Compared with Example 2, the H2O2 conversion rate and propylene oxide selectivity are both reduced to a certain extent, indicating that the content of propylene oxide in the extracted material has a greater influence on the utilization of H2O2 and the generation of by-products in the second epoxidation reaction process; in Example 8, in a fixed bed stainless steel reactor The initial reaction temperature is low. Compared with Example 2, the H2O2 content in the bottom of the tower has a certain increase, and the H2O2 conversion rate has a significant decrease, indicating that the reaction temperature of the second epoxidation reaction has a greater influence on the utilization of H2O2; in Example 9, more propylene is added. Compared with Example 2, the H2O2 conversion rate is slightly reduced, indicating that the ratio of added propylene to hydrogen peroxide in the produced material has a certain influence on the utilization of H2O2; in Example 10, titanium silicalite molecular sieves with different topological structures are used. Compared with Example 2, the selectivity of propylene oxide is significantly reduced, and the propylene oxide flow rate at the top of the tower is reduced, indicating that the use of titanium silicalite molecular sieves with different topological structures affects the propylene oxide yield; in Example 11, the titanium-silicon molar ratio of the titanium silicalite is changed. Compared with Example 2, the H2O2 content in the bottom of the tower has a significant increase, and the H2O2 conversion rate has a significant decrease, indicating that the use of titanium silicalite molecular sieves with a suitable titanium-silicon ratio is beneficial to improving the utilization of hydrogen peroxide.

[0125] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing propylene oxide, characterized in that: The preparation method comprises: S1. In the presence of a first auxiliary agent and a first catalyst, subjecting propylene and hydrogen peroxide to a first epoxidation reaction to obtain a first epoxidation reaction product; S2, separating the gas-liquid product of the first epoxidation reaction; S3, in the presence of a second auxiliary agent and a second catalyst, subjecting the portion A of the liquid phase separation obtained in S2 to a second epoxidation reaction with propylene to obtain a second epoxidation reaction product; S4, returning the product after the second epoxidation reaction to S2 to obtain a gas phase product and a liquid phase product.

2. The method according to claim 1, characterized in that In S3, the A portion is 20-100 wt%, preferably 50-100 wt%, of the total weight of the liquid phase separation.

3. The method according to claim 1 or 2, characterized in that: The content of propylene oxide in the part A is less than or equal to 4 wt %, preferably less than or equal to 2 wt %.

4. The method according to any one of claims 1 to 3, characterized in that: In S3, the conditions of the second epoxidation reaction include: a temperature of 65-85° C., a pressure of less than or equal to 3 MPa, a weight space velocity of the total weight of the A part, propylene and the second auxiliary agent of 0.5-50 h -1 .

5. The method according to any one of claims 1 to 4, characterized in that: In S3, the molar ratio of propylene to the hydrogen peroxide contained in the A part is (1-8):

1.

6. The method according to any one of claims 1 to 5, characterized in that: Based on the total weight of the A part, the amount of the second auxiliary agent is 0.001-0.02wt%; Preferably, the second auxiliary agent is selected from at least one of NaHCO3, KOH, NH3, NaOH, K2CO3, Na2CO3, KHCO3, Li2CO3, LiHCO3, Na2HPO4, (NH4)2Ac, aqueous ammonia, triethylamine and pyridine.

7. The method according to any one of claims 1 to 6, characterized in that: The second catalyst is titanium silicon molecular sieve; Preferably, the average particle size of the second catalyst is 1-2 mm; Preferably, the topological structure of the titanium silicalite molecular sieve is selected from at least one of MFI, BEA, MEL, MWW and MOR, preferably MFI; Preferably, in the titanium silicon molecular sieve, the molar ratio of titanium element to silicon element is 1:(20-200).

8. The method according to any one of claims 1 to 7, characterized in that: In S4, the content of hydrogen peroxide in the liquid product is less than or equal to 0.4wt%, preferably less than or equal to 0.1wt%; the content of oxygen in the gas product is less than or equal to 0.014wt%, preferably less than or equal to 0.008wt%; Preferably, the preparation method further comprises: purifying the liquid phase product by hydrogenation.

9. A device for preparing propylene oxide, characterized in that: The device comprises: an epoxidation reaction unit and a gas-liquid separation unit which are interconnected; wherein the epoxidation reaction unit comprises a first epoxidation reactor (9), and the gas-liquid separation unit comprises a gas-liquid separator (6) and a second epoxidation reactor (5) which are interconnected; wherein, A gas-liquid separator side line (2) is provided on the side of the gas-liquid separator (6) for drawing part A of the liquid phase separated product after the first epoxidation reaction out of the gas-liquid separator (6) and feeding it into the second epoxidation reactor (5) from the bottom; A second epoxidation product pipeline (3) is provided at the top of the second epoxidation reactor (5) for leading the second epoxidation product from the second epoxidation reactor (5) and returning it to the gas-liquid separator (6); A propylene feed pipeline (8) and an auxiliary agent feed pipeline (7) are provided at the bottom of the second epoxidation reactor (5), which are used to transport propylene and auxiliary agent respectively, and are mixed with the material drawn out from the gas-liquid separator side line (2) and then fed into the second epoxidation reactor (5) from the bottom.

10. The device according to claim 9, characterized in that The top of the gas-liquid separator (6) is provided with a top discharge port (10) for drawing out the gas phase product after gas-liquid separation; and the bottom is provided with a bottom discharge port (4) for drawing out the liquid phase product after gas-liquid separation.

11. The device according to claim 9 or 10, characterized in that The second epoxidation reactor is selected from a fixed bed reactor or a slurry bed reactor; Preferably, the gas-liquid separator (6) is a distillation tower.

12. The device according to any one of claims 9 to 11, characterized in that: A first epoxidation product feed pipeline (1) is also provided on the side of the gas-liquid separator (6), which is used to connect the first epoxidation reactor (9) and the gas-liquid separator (6) and introduce the first epoxidation product into the gas-liquid separator (6); Preferably, the inlet of the gas-liquid separator side line (2) is lower than the outlet of the first epoxidation reaction product feed pipeline (1); Preferably, the ratio of the distance from the inlet of the gas-liquid separator side line (2) to the bottom of the gas-liquid separator (6) to the distance from the outlet of the first epoxidation reaction product feed pipeline (1) to the bottom of the gas-liquid separator (6) is 1:(1.1-10).

13. The device according to any one of claims 9 to 11, characterized in that: The device also includes a hydrogenation purification unit for removing hydrogen peroxide from the liquid phase product after gas-liquid separation.

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