A high-conversion, high-yield propylene oxide production system and method

Abstract

The present application provides a propylene oxide production system and method with high conversion rate and high yield, which divides the reactor into two sections, provides three kinds of material precise feeding ratio and segmented control distribution feeding mode, adds propylene and most of the solvent diluted hydrogen peroxide into the first reaction section at the bottom through a primary feeding distributor, then adds the remaining solvent and hydrogen peroxide reaction mixture through a secondary feeding distributor in the second reaction section, which is beneficial to the uniform mixing of the reaction materials, avoids the problem of uneven mixing caused by one-time addition or non-distributed addition of materials, and improves the conversion rate of the materials. Meanwhile, the present application provides fins outside the catalytic tube to increase the heat exchange area, timely discharge the reaction heat, avoid the decomposition of hydrogen peroxide, and further improve the selectivity and yield of the product propylene oxide.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of propylene oxide production, and further relates to a propylene oxide production system and method with high conversion rate and high yield. BACKGROUND

[0002] Propylene oxide (PO) is an important propylene derivative with low boiling point and flammability. Its main use is to produce polyether polyols and propylene glycol (PG), and it is also the main raw material for producing propylene glycol ether, flame retardant, non-ionic surfactant and plasticizer. Among them, polyether polyol is an important raw material for producing polyurethane foam, thermal insulation material, elastomer, adhesive and paint, and various non-ionic surfactants are widely used in petroleum, chemical, pesticide, textile and daily chemical industries.

[0003] The propylene oxide production technology (HPPO) by direct oxidation of propylene with hydrogen peroxide is internationally recognized as a green and environmentally friendly production technology. Compared with the traditional chlorohydrination method and co-oxidation method, it has great advantages in product yield and environmental protection. The characteristics of this technology are short process, simple process, high atomic utilization rate, low investment, mild reaction conditions, low energy consumption, basically no pollution, high product yield and less by-products.

[0004] Although the HPPO method has great advantages compared with the traditional process route, there are still some bottleneck problems to be solved, such as low utilization rate of hydrogen peroxide and low yield of propylene oxide due to imperfect design of the reaction system. In order to solve the above problems, the following patents provide various solutions.

[0005] Patent CN109180611B provides a device and method for preparing propylene oxide by HPPO method with raw material segmented injection, which adopts at least two groups of reaction units connected in series, each group of reaction units including a mixing device and a reaction device, and the outlet of the reaction device of the previous group of reaction units is connected to the mixing device of the next group of reaction units. The raw materials are segmented into the reaction device of each group of reaction units, and are mixed uniformly before entering. The present application solves the problem of uneven distribution of hydrogen peroxide in the reactor by changing the feeding process, improves the conversion rate of hydrogen peroxide and the yield of propylene oxide, and reduces the safety hazard. However, the defect of this patent is that multiple reactors are used to solve the reaction task of one reactor originally, which has high investment and complex device operation. Moreover, the conversion rate of hydrogen peroxide in this patent is between 80% and 98%, and the selectivity of propylene oxide is between 95% and 98.2%.

[0006] Patent CN201821367379.X provides a reaction equipment for preparing propylene oxide by hydrogen peroxide method, which includes a mixing and emulsifying device and an emulsification reaction device of plate reactor. Although the emulsion can improve the mass and heat transfer efficiency, there are problems of small catalyst particle size and difficult separation due to the complexity of the reaction system.

[0007] Patent CN200710099853.5 provides a method for continuous production of propylene oxide, using original powder titanium silicalite molecular sieve as catalyst, the titanium silicalite molecular sieve is uniformly mixed with the reactant material in the form of slurry, the reactor is provided with a solid-liquid separation device outside the reactor for separating the molecular sieve from the liquid reactant, the molecular sieve is circulated in the circulation pipeline composed of the reactor and the separation device, and part of the liquid product flows out of the reaction system to obtain the target product. The conversion rate of hydrogen peroxide in this patent is greater than 95%, and the selectivity of propylene oxide is higher than 90%. Although the conversion rate of hydrogen peroxide is improved, the off-site filtration of powder molecular sieve is a difficulty and bottleneck of the device.

[0008] Therefore, it is urgent to develop an epoxy propane production system and production process to effectively solve the problems of low hydrogen peroxide conversion rate, low epoxy propane selectivity, and complex operation in the prior art. SUMMARY

[0009] In view of the problems of low raw material conversion rate and utilization rate, low selectivity of epoxy propane product, etc. in the existing epoxy propane production, the purpose of the present application is to provide a high-conversion-rate and high-yield epoxy propane production system and method. The reactor is divided into upper and lower two sections, three kinds of material precise feeding ratio are provided, and the distribution feeding mode is controlled in sections. Propylene and most of the hydrogen peroxide diluted by solvent are added into the first reaction section at the bottom through a primary feeding distributor for reaction, and then the remaining solvent and hydrogen peroxide reaction mixture are added in the second reaction section through a secondary feeding distributor, which is beneficial to uniform mixing of the reaction materials and avoids the problem of temperature overhigh and hydrogen peroxide decomposition caused by uneven mixing of materials due to one-time addition or undistributed addition, thereby improving the conversion rate of materials. Meanwhile, the present application provides fins outside the catalytic tube to increase the heat exchange area, timely discharge the reaction heat, avoid hydrogen peroxide decomposition, and further improve the selectivity and yield of the product propylene oxide.

[0010] In order to achieve the above purpose, the present application provides the following technical solutions:

[0011] The application discloses a high-conversion-rate and high-yield propylene oxide production system, which comprises a reactor, a raw material supply unit, a pH adjusting unit and a control unit; the inside of the reactor is divided into a first reaction section and a second reaction section along the material flow direction, and a plurality of catalyst-filled catalytic tubes are arranged in the first reaction section and the second reaction section; the raw material supply unit comprises a hydrogen peroxide supply pipeline, a solvent supply pipeline, a propylene supply pipeline, a primary feed distributor and a secondary feed distributor; the primary feed distributor is arranged at the inlet of the first reaction section and is connected with the hydrogen peroxide supply pipeline, the solvent supply pipeline and the propylene supply pipeline respectively; the secondary feed distributor is arranged at the inlet of the second reaction section and is connected with the hydrogen peroxide supply pipeline and the solvent supply pipeline respectively; the pH adjusting unit is used for adjusting the pH value of the reaction material in the reactor; and the control unit is electrically connected with the reactor and the raw material supply unit respectively, and controls the raw material supply unit to supply materials into the first reaction section and the second reaction section according to the set material ratio according to the reaction state of the material in the reactor.

[0012] In some embodiments, the raw material supply unit further comprises a primary feed mixer, a primary hydrogen peroxide dilution mixer and a secondary hydrogen peroxide dilution mixer; the inlet of the primary hydrogen peroxide dilution mixer is connected with the hydrogen peroxide supply pipeline and the solvent supply pipeline respectively; the outlet of the primary hydrogen peroxide dilution mixer and the propylene supply pipeline are connected with the inlet of the primary feed mixer respectively; and the outlet of the primary feed mixer is connected with the primary feed distributor; the inlet of the secondary hydrogen peroxide dilution mixer is connected with the hydrogen peroxide supply pipeline and the solvent supply pipeline respectively; and the outlet of the secondary hydrogen peroxide dilution mixer is connected with the secondary feed distributor.

[0013] In some embodiments, the pH adjusting unit comprises a pH adjusting agent distributor and a pH adjusting agent supply pipeline; the pH adjusting agent distributor is arranged at the inlet of the first reaction section; and the pH adjusting agent supply pipeline is connected with the pH adjusting agent distributor.

[0014] In some embodiments, the catalytic tubes in the first reaction section and the second reaction section are arranged in an equilateral triangle mode; the outer wall of the catalytic tube is provided with spiral fins; the spiral pitch of the fins is 8mm-30mm; the diameter D1 of the catalytic tube is 14-38mm; the thickness of the fins is 0.5-1.5mm; the width D2 of the fins is 0.25-0.5 times the diameter D1 of the catalytic tube; and the center distance L1 between any two adjacent catalytic tubes is 1.05-1.15 times the sum of the diameter D1 of the catalytic tube and the width D2 of the fins.

[0015] In some embodiments, the primary feed distributor, the secondary feed distributor and the pH regulator distributor are each provided with a feed main pipe and a plurality of distribution branch pipes parallel to each other in horizontal direction, the distribution branch pipes being in communication with the feed main pipe; the bottom of the distribution branch pipe is provided with two rows of distribution holes with uniform hole spacing, the two rows of distribution holes are symmetrically distributed in vertical direction, and the included angle a between the distribution holes and the vertical direction is 45°-90°; the two rows of distribution holes on the same distribution branch pipe are staggered.

[0016] In some embodiments, the diameter D3 of the distribution hole is 5-10 mm; in the same row, the center distance L2 between adjacent distribution holes is 3-6 times the diameter D3 of the distribution hole.

[0017] In some embodiments, the secondary feed distributor is 50-150 mm away from the top of the first reaction section; the pH regulator distributor is 100-200 mm away from the bottom of the first reaction section; the pH regulator distributor is arranged above the primary feed distributor and is 50-150 mm away from the primary feed distributor.

[0018] The application also provides a high-conversion and high-yield propylene oxide production method using the propylene oxide production system described above, comprising the following steps:

[0019] The hydrogen peroxide and the solvent are uniformly mixed in a certain proportion to form a reaction mixture, a part of the reaction mixture is uniformly mixed with propylene in a feed ratio, and then is fed into the bottom of the reactor through the primary feed distributor; the reaction material is adjusted in pH, and then is fed into the catalytic tube in the first reaction section; under the action of the catalyst, the reaction mixture generated by the reaction of propylene and hydrogen peroxide rises into the catalytic tube in the second reaction section; another part of the reaction mixture is fed into the catalytic tube in the second reaction section through the secondary feed distributor, and continues to react with the reaction mixture; and the final reaction product is discharged from the top of the reactor;

[0020] The feed mass ratio of the hydrogen peroxide, the propylene and the solvent is: hydrogen peroxide: propylene: solvent = 1: (2-4): (4-7);

[0021] The feed mass ratio of the hydrogen peroxide in the first reaction section and the second reaction section is: primary hydrogen peroxide feed: secondary hydrogen peroxide feed = (0.5-2): 1;

[0022] The feed mass ratio of the solvent in the first reaction section and the second reaction section is: primary solvent feed: secondary solvent feed = (4-8): 1;

[0023] The pH of the reaction material is 6-8.

[0024] In some embodiments, the mass ratio of the hydrogen peroxide, the propylene and the solvent is:

[0025] hydrogen peroxide: propylene: solvent = 1: (2.5-3.5): (5-6); and / or,

[0026] The mass ratio of the hydrogen peroxide in the first reaction section and the second reaction section is:

[0027] primary hydrogen peroxide feed: secondary hydrogen peroxide feed = 1: 1; and / or,

[0028] The mass ratio of the solvent in the first reaction section and the second reaction section is:

[0029] primary solvent feed: secondary solvent feed = (4-8): 1; and / or,

[0030] The reaction temperature is 20-60℃; and / or, the reaction pressure is 2.5-3.2 MPa; and / or, the pH of the reaction material is 6.5-7.5; and / or,

[0031] The liquid hourly space velocity of the reaction is 1-3 h -1 .

[0032] In some embodiments, the catalyst is a TS-1 type silicon-titanium molecular sieve catalyst, the specific surface area of the TS-1 type silicon-titanium molecular sieve catalyst is 350-450 m 2 / g, the pore volume is 0.2-0.25 cm 3 / g, and the average pore size is 2-2.5 nm; and / or, the concentration of the hydrogen peroxide is 50%-70%.

[0033] Compared with the prior art, the propylene oxide production system and method provided by the application has the following beneficial effects:

[0034] 1. The reactor provided by the application is provided with two reaction sections, and the hydrogen peroxide and a part of the hydrogen peroxide diluted by the solvent are fed into the first reaction section at the bottom in proportion, and the remaining hydrogen peroxide and solvent are added in the second reaction section, so that the uniformity of the mixing of the three materials is improved, the materials can be fully reacted, the conversion rate and utilization rate of the materials are improved, and the risks of low conversion rate caused by uneven mixing, excessive local heat production causing hydrogen peroxide decomposition and increased side reactions caused by one-time feeding of the materials are avoided.

[0035] 2. The primary feed distributor and the secondary feed distributor arranged at the entrances of the two sections can also ensure the uniformity of the distribution of the materials in the internal space of the reactor, facilitate the full mixing of the reaction materials, and make the temperature distribution in the internal space of the reaction section more uniform, so that the local temperature is not too high and the decomposition of the hydrogen peroxide is avoided.

[0036] 3、The present application is provided with the fin which is spirally wound and arranged on the outer wall of the catalytic tube, the heat exchange area is increased, the heat exchange coefficient is improved, the heat generated by the oxidation reaction is discharged in time, the temperature in the reaction section is effectively controlled, the reaction is smoothly carried out, the decomposition of hydrogen peroxide due to high temperature is avoided, the utilization rate of hydrogen peroxide is improved, and the yield of propylene oxide is improved;

[0037] 4、The present application adjusts the pH of the reaction material, controls the pH value in the neutral (alkaline) range, can avoid the promoting effect of the acid center on the by-product in the reaction process, inhibits the ring-opening reaction of propylene oxide, and improves the selectivity and yield of propylene oxide;

[0038] 5、The present application provides the material ratio of segmented feeding, most of the solvent is input into the first reaction section to dilute and uniform temperature, the solvent added in the second reaction section is to dilute the added hydrogen peroxide, improve the uniformity of hydrogen peroxide in the second reaction section, and also provides the total feeding ratio of three materials, reduces the solvent ratio, and reduces the energy consumption of subsequent solvent recovery. BRIEF DESCRIPTION OF DRAWINGS

[0039] The above-mentioned characteristics, technical features, advantages and implementation modes of the present application will be further described in a clear and easy-to-understand manner in combination with the preferred embodiments and the accompanying drawings.

[0040] Figure 1 The structure schematic diagram of the propylene oxide production system provided by the present application is shown in the figure.

[0041] Figure 2 The structure schematic diagram of the two-stage feeding distributor provided by the present application is shown in the figure.

[0042] Figure 3 The structure schematic diagram of the distribution branch pipe provided by the present application is shown in the figure.

[0043] Explanation of the figure reference number:

[0044] 1-Reactor; 101-First reaction section; 102-Second reaction section; 103-Tube plate; 104-Catalytic tube; 105-Fin; 106-First-stage feeding distributor; 107-Second-stage feeding distributor; 108-pH regulator distributor;

[0045] 2-Hydrogen peroxide supply pipeline; 3-Solvent supply pipeline; 4-Propylene supply pipeline; 5-First-stage feeding mixer; 6-First-stage hydrogen peroxide dilution mixer; 7-Second-stage hydrogen peroxide dilution mixer; 8-pH regulator supply pipeline; 9-Control unit; 10-Feeding main pipe; 11-Distribution branch pipe; 12-Distribution hole. DETAILED DESCRIPTION

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, specific implementations of the present application will be described below with reference to the drawings. Obviously, the drawings in the following description only represent some of the embodiments of the present application, and for those skilled in the art, other drawings can be obtained from these drawings without creative effort, and other embodiments can also be obtained.

[0047] For the sake of simplicity of the drawings, only the parts related to the present application are shown in each drawing, and they do not represent the actual structure of the product. In addition, in order to make the drawings simple and easy to understand, in some drawings, only one of the components with the same structure or function is shown schematically, or only one of them is marked. In this document, "one" not only means "only one", but also means "more than one" in some cases.

[0048] It should be further understood that the term "and / or" used in the present application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0049] In this document, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0050] In addition, in the description of the present application, the terms "first", "second", etc. are only used for differentiation and description, and cannot be understood as indicating or implying relative importance.

[0051] Example 1

[0052] Chemical principle for producing propylene oxide in the present application:

[0053] The main reaction is the oxidation reaction of hydrogen peroxide and propylene in the presence of TS-1 titanium silicalite to produce propylene oxide and water. The reaction equation is as follows:

[0054]

[0055] The main side reaction is the reaction of propylene oxide with water and alcohol to produce diol and ether. The reaction equation is as follows:

[0056]

[0057] and the ineffective decomposition of hydrogen peroxide into oxygen and water:

[0058] H202H20+02

[0059] The invalid decomposition of hydrogen peroxide not only reduces the utilization rate of hydrogen peroxide, but also brings safety risks due to the mixing of oxygen generated by decomposition and propylene oxide.

[0060] Therefore, in view of the above defects, the present application provides a propylene oxide production system with high yield and high raw material conversion rate, as shown in the accompanying drawings, comprising a reactor 1, a raw material supply unit, a pH adjusting unit and a control unit 9. Figure 1

[0061] The inside of the reactor 1 is divided into a first reaction section 101 and a second reaction section 102 along the material flow direction, and a plurality of catalyst-filled catalytic tubes 104 are arranged in the first reaction section 101 and the second reaction section 102, and a heat exchange medium is arranged between the outer wall of the catalytic tube 104 and the inner wall of the reactor 1.

[0062] The tangential heights of the first reaction section 101 and the second reaction section 102 are the same.

[0063] Specifically, a plurality of tube sheets 103 are arranged inside the reactor 1, and the tube sheets 103 divide the inside of the reactor 1 into the first reaction section 101 and the second reaction section 102 from bottom to top.

[0064] The raw material supply unit includes a hydrogen peroxide supply pipeline 2, a solvent supply pipeline 3, a propylene supply pipeline 4, a primary feed distributor 106 and a secondary feed distributor 107, and the hydrogen peroxide, the solvent and the propylene are fed in liquid phase, and the primary feed distributor 106 and the secondary feed distributor 107 are arranged inside the reactor 1 to uniformly distribute the raw materials.

[0065] Specifically, the primary feed distributor 106 is arranged at the inlet of the first reaction section 101, i.e. below the tube sheet 103 at the bottom of the first reaction section 101, and the primary feed distributor 106 is connected with the hydrogen peroxide supply pipeline 2, the solvent supply pipeline 3 and the propylene supply pipeline 4, respectively, and the hydrogen peroxide, the solvent and the propylene are mixed uniformly at a certain ratio and then enter the catalytic tube 104 in the first reaction section 101 for reaction.

[0066] ​The secondary feed distributor 107 is arranged at the inlet of the second reaction section 102, i.e. between the tube plate 103 at the top of the first reaction section 101 and the tube plate 103 at the bottom of the second reaction section 101, and is connected with the hydrogen peroxide supply pipeline 2 and the solvent supply pipeline 3 respectively, so that the raw material supply unit can introduce the hydrogen peroxide and the solvent into the second reaction section 102, and the reaction mixture generated by the reaction between the hydrogen peroxide and the propylene in the first reaction section 101 can rise into the catalytic tube 104 in the second reaction section 102 to continue the reaction with the hydrogen peroxide and the solvent uniformly distributed through the secondary feed distributor 107, so as to generate the final reaction product which is discharged from the top of the reactor 1 and then purified to obtain the propylene oxide.

[0067] The two-stage reactor is adopted in the present application, and the hydrogen peroxide is input in stages, so that the reaction bed temperature can be controlled and the invalid decomposition of the hydrogen peroxide due to excessively high temperature can be avoided.

[0068] In some embodiments, in order to obtain better reaction effect, the raw material supply unit further comprises a primary feed mixer 5, a primary hydrogen peroxide dilution mixer 6 and a secondary hydrogen peroxide dilution mixer 7.

[0069] The primary feed distributor 106 is connected with the hydrogen peroxide supply pipeline 2, the solvent supply pipeline 3 and the propylene supply pipeline 4 through the primary feed mixer 5, more specifically, the inlet of the primary feed mixer 5 is connected with the propylene supply pipeline 4 and the outlet of the primary hydrogen peroxide dilution mixer 6 respectively, and the outlet of the feed mixer 5 is connected with the inlet of the primary feed distributor 106.

[0070] The inlet of the primary hydrogen peroxide dilution mixer 6 is connected with the hydrogen peroxide supply pipeline 2 and the solvent supply pipeline 3 respectively, and the hydrogen peroxide and the solvent are mixed in the primary hydrogen peroxide dilution mixer 6 at a certain ratio, and then introduced into the feed mixer 5, mixed with the propylene added at a certain ratio, and then uniformly distributed into the catalytic tube 104 of the first reaction section 101 through the primary feed distributor 106.

[0071] The present application first dilutes the oxidant hydrogen peroxide with the solvent, and then uniformly mixes the hydrogen peroxide with the propylene, so that the three can be more uniformly mixed, the increase of by-products due to local excessive reaction caused by non-uniform mixing can be avoided, and the decomposition of the hydrogen peroxide caused by overheating can be avoided, and the utilization rate of the hydrogen peroxide can be improved.

[0072] The secondary feed distributor 107 is connected with the hydrogen peroxide supply pipeline 2 and the solvent supply pipeline 3 through the secondary hydrogen peroxide dilution mixer 7, more specifically, the inlet of the secondary hydrogen peroxide dilution mixer 7 is connected with the hydrogen peroxide supply pipeline 2 and the solvent supply pipeline 3 respectively, the outlet of the secondary hydrogen peroxide dilution mixer 7 is connected with the secondary feed distributor 107, and the hydrogen peroxide and the solvent are mixed in the secondary hydrogen peroxide dilution mixer 7 in a certain proportion, and then are uniformly distributed into the catalytic tube 104 of the second reaction section 102 by the secondary feed distributor 107, and continue to react with the reaction mixture rising from the first reaction section 101.

[0073] In the embodiment, the primary feed mixer 5 can be a commercially available SL type or SH type helical flow static mixer, and the number of mixing units of the static mixer is 4-8.

[0074] The primary hydrogen peroxide dilution mixer 6 and the secondary hydrogen peroxide dilution mixer 7 can be a commercially available SK type or SL type or SX type static mixer, and the number of mixing units of the static mixer is 4-8.

[0075] In some embodiments, the pH adjusting unit adjusts the pH value of the reaction material in the reactor 1, and specifically includes: a pH adjusting agent distributor 108 arranged in the reactor 1 and a pH adjusting agent supply pipeline 8.

[0076] Specifically, the pH adjusting agent distributor 108 is arranged at the inlet of the first reaction section 101, i.e. the pH adjusting agent distributor 108 is arranged below the tube plate 103 at the bottom of the first reaction section 101, and is preferably arranged between the tube plate 103 at the bottom of the first reaction section 101 and the primary feed distributor 106.

[0077] The pH adjusting agent supply pipeline 8 is connected with the pH adjusting agent distributor 108, and the pH adjusting agent is input into the reactor 1, and the mixture material (hydrogen peroxide, solvent and propylene) is mixed with the pH adjusting agent, and is adjusted to a set pH, and then enters the catalytic tube 104 of the first reaction section 101 under the action of the pressure difference to perform reaction.

[0078] Preferably, the secondary feed distributor 107 is away from the top of the first reaction section 101 by 50-150 mm, i.e. the distance between the secondary feed distributor 107 and the tube plate 103 at the top of the first reaction section 101 is 50-150 mm.

[0079] The pH regulator distributor 108 is 100-200 mm away from the bottom of the first reaction section 101, i.e. the distance between the pH regulator distributor 108 and the tube plate 103 at the bottom of the first reaction section 101 is 100-200 mm. If the distance is too short, the target material entering the reaction section is not uniformly mixed. If the distance is too long, the effect of uniform mixing is not greatly improved, and the equipment investment is increased. The primary feed distributor 106 is located below the pH adjustment distributor 108 and is 50-150 mm away from the pH adjustment distributor 108.

[0080] The pH regulator described above is an inorganic salt solution such as ammonia, sodium hydroxide, potassium hydroxide, etc. Preferably, ammonia is used as the pH regulator to avoid bringing too much water into the reaction system and reducing the energy consumption of recovery.

[0081] In some embodiments, the catalytic tubes 104 in the first reaction section 101 and the second reaction section 102 are arranged in an equilateral triangle. The diameter D1 of the catalytic tubes 104 is 14-38 mm to maintain a high flow rate and high turbulent state of the cooling medium.

[0082] The outer wall of the catalytic tube 104 is provided with a spiral fin 105. The fin 105 is preferably a heat-conducting metal plate. The thickness of the fin 105 is 0.5-1.5 mm. The width D2 of the fin 105 is 0.25-0.5 times the diameter D1 of the catalytic tube 104, i.e. D2=(0.25-0.5)×D1. The spiral pitch of the fin 105 is 8-30 mm. Such a fin 105 structure can obtain a higher heat transfer area and improve the heat transfer efficiency.

[0083] The center distance L1 between any two adjacent catalytic tubes 104 is 1.05-1.15 times the sum of the diameter D1 of the catalytic tube 104 and the width D2 of the fin 105, i.e. L1=(1.05-1.15)×(D1+D2).

[0084] In some embodiments, as shown in Figure 2 and Figure 3 The primary feed distributor 106, the secondary feed distributor 107 and the pH regulator distributor 108 are each provided with a feed main pipe 10 and a plurality of distribution branch pipes 11 parallel to each other in the horizontal direction. The distribution branch pipes 11 communicate with the feed main pipe 10. The feed main pipe 10 is used to input raw materials.

[0085] The bottom of the distribution branch pipe 11 is provided with two rows of distribution holes 12 with uniform hole spacing. The two rows of distribution holes 12 are symmetrically distributed in the vertical direction, and the included angle α between the distribution holes 12 and the vertical direction is 45°-90°.

[0086] The two rows of distribution holes 12 on the same distribution branch pipe 11 are staggered, the diameter D3 of the distribution hole 12 is 5-10 mm, and in the same row, the center distance L2 between adjacent distribution holes 12 is 3-6 times the diameter D3 of the distribution hole 12, that is, L2=(3-6)×D3.

[0087] The number and diameter of the distribution branch pipe 11 can meet the requirement that the flow rate of the fluid in the distribution branch pipe 11 is 0.5-2 m / s. If the flow rate is too fast, the pressure drop of the distribution branch pipe 11 is large, and if the flow rate is too low, the diameter of the distribution branch pipe 11 is too large.

[0088] The control unit is electrically connected with the reactor 1 and the raw material supply unit respectively to control automatic operation of the entire propylene oxide production system. The control unit controls the raw material supply unit to supply the first reaction section 101 and the second reaction section 102 with materials in a set material ratio according to the reaction state of the materials in the reactor 1 (and the operation state of the two reaction sections, such as temperature and pressure) to realize segmented material supply. The control unit controls the hydrogen peroxide supply pipeline 2, the solvent supply pipeline 3 and the propylene supply pipeline 4 to supply the first reaction section 101 with materials in a certain material ratio according to the reaction state of the materials in the first reaction section 101 (such as material pH and temperature). Similarly, the control unit controls the hydrogen peroxide supply pipeline 2 and the solvent supply pipeline 3 to supply the second reaction section 102 with hydrogen peroxide and solvent in a certain ratio according to the reaction state of the materials in the second reaction section 102.

[0089] Preferably, the control unit comprises a controller, a display and detection elements arranged on the reactor 1, such as temperature sensors, pressure sensors and pH sensors. The control unit also comprises electrically controlled valves and metering devices installed on the pipelines. An electrically controlled valve and a flow meter are arranged on the hydrogen peroxide supply pipeline 2, the solvent supply pipeline 3, the propylene supply pipeline 4 and the pH regulator supply pipeline 8.

[0090] The controller is electrically connected with the reactor 1, the detection elements, the electrically controlled valves and the metering devices. The controller automatically collects real-time parameters such as temperature, pressure, pH and material flow. The control program built in the controller automatically controls the operation state of the reactor 1 and the electrically controlled valves according to the collected information. The display is communicatively connected with the controller. The operating personnel can observe the operation state of each device on the display screen at any time and can also set the operation parameters. This greatly improves the degree of automatic and accurate control of the production system, facilitates the operation of the device under the best operating conditions and improves the product yield.

[0091] Example 2

[0092] On the basis of example 1, the present application provides a propylene oxide production method with high yield and high raw material conversion rate. The propylene oxide production system in example 1 is used, and the method comprises the following steps:

[0093] The hydrogen peroxide and the solvent are mixed in a certain ratio to form a reaction mixture, and a part of the reaction mixture is mixed with propylene in a certain ratio and then fed into the bottom of the reactor 1 through a first-stage feeding distributor 106, and then fed into the catalytic column 104 in the first reaction section 101 after adjusting the pH, and the propylene and the hydrogen peroxide are oxidized to form a reaction mixture which is then fed into the catalytic column 104 in the second reaction section 102.

[0094] Another part of the reaction mixture is fed into the catalytic column 104 in the second reaction section 102 through a second-stage feeding distributor 107, and the reaction mixture continues to react, and the final reaction product is discharged from the top of the reactor 1.

[0095] The concentration of the hydrogen peroxide is 50% to 70%, and the purity of the solvent and the propylene is more than 99%.

[0096] The solvent is an alcohol solution, such as methanol, ethanol, propanol, isopropanol, etc., and methanol is preferred as the solvent because of its high polarity and high solubility of propylene and propylene oxide.

[0097] The catalyst is a TS-1 type silicon-titanium molecular sieve catalyst, and the specific surface area of the TS-1 type silicon-titanium molecular sieve catalyst is 350 to 450 m 2 / g, the pore volume is 0.2 to 0.25 cm 3 / g, and the average pore size is 2 to 2.5 mm.

[0098] The pH is adjusted by using a pH adjuster, such as an inorganic salt solution of ammonia, sodium hydroxide, potassium hydroxide, etc., and ammonia is preferred.

[0099] In some embodiments, the feeding mass ratio of the hydrogen peroxide, the propylene and the solvent is: hydrogen peroxide: propylene: solvent = 1: (2 to 4): (4 to 7).

[0100] The feeding mass ratio of the three raw materials is preferably: hydrogen peroxide: propylene: solvent = 1: (2.5 to 3.5): (5 to 6). If the ratio is too high, the energy consumption of the circulation increases, and if the ratio is too low, the hydrogen peroxide is easily decomposed, which not only leads to low utilization rate of the hydrogen peroxide, but also causes the ring-opening of the propylene oxide to produce alcohol and ether by-products. A high ratio of the solvent is beneficial to the reaction, but a too high ratio will lead to high energy consumption.

[0101] In some embodiments, the feeding mass ratio of the hydrogen peroxide in the first reaction section 101 and the second reaction section 102 is: first-stage hydrogen peroxide feeding: second-stage hydrogen peroxide feeding = (0.5 to 2): 1.

[0102] The preferred ratio is: primary hydrogen peroxide feed: secondary hydrogen peroxide feed = 1:1. If the hydrogen peroxide feed ratio in the first reaction section 101 is too high or too low, the effect of graded feeding will not be achieved.

[0103] In some embodiments, the feed mass ratio of the solvent to the first reaction section 101 and the second reaction section 102 is: primary solvent feed : secondary solvent feed = (4-8) : 1.

[0104] Preferably, the ratio of primary solvent feed to secondary solvent feed is (5-6):1. Most of the solvent and hydrogen peroxide are mixed in the primary hydrogen peroxide dilution mixer 6 before entering the reactor 1 to achieve dilution and temperature equalization. The remaining solvent enters the secondary hydrogen peroxide dilution mixer 7 only to dilute the hydrogen peroxide and improve the uniformity of the secondary hydrogen peroxide feed distribution in the reactor 1.

[0105] In some embodiments, the reaction temperature of propylene and hydrogen peroxide is 20°C to 60°C, preferably 30°C to 50°C. Too high a temperature will cause hydrogen peroxide to decompose, while too low a temperature will reduce the reaction rate and lead to incomplete reaction.

[0106] The reaction pressure for the reaction of propylene with hydrogen peroxide is 2.5–3.2 MPa, preferably 2.8–3.0 MPa. If the reaction pressure is too low, the reaction cannot be guaranteed to be a fully liquid phase reaction, while if the pressure is too high, energy consumption and investment will increase.

[0107] The pH of the reactants (a mixed solution of hydrogen peroxide, propylene, and solvent) is 6–8, preferably 6.5–7.5. Too low a pH leads to a high rate of side reactions, while too high a pH results in a large consumption of pH adjuster without significantly improving the yield. This invention utilizes an alkaline pH adjuster to neutralize the acidic centers generated during the reaction that can lead to ring-opening and chain scission of propylene oxide to form alcohols and ethers, thereby improving the selectivity of propylene oxide.

[0108] The liquid hourly space velocity (LHSV) of the reaction between propylene and hydrogen peroxide ranges from 1 to 3 h⁻¹. -1 Preferably, it is 1.5 to 2.5 hours. -1 If the liquid hourly space velocity is too low, not only will the equipment investment be high, but it will also easily lead to the ring-opening production of propylene oxide as a byproduct.

[0109] In combination with the above Figure 1 The propylene oxide production system shown below has the following specific process flow:

[0110] Under the control of the control unit, the hydrogen peroxide supply pipeline 2 inputs hydrogen peroxide into the first-stage hydrogen peroxide dilution mixer 6 and the second-stage hydrogen peroxide dilution mixer 7 respectively according to the feeding proportion, the solvent supply pipeline 3 inputs solvent into the first-stage hydrogen peroxide dilution mixer 6 and the second-stage hydrogen peroxide dilution mixer 7 respectively according to the feeding proportion, and the propylene supply pipeline 4 inputs propylene into the first-stage feeding mixer 5 according to the feeding proportion.

[0111] The hydrogen peroxide and the solvent in the first-stage hydrogen peroxide dilution mixer 6 and the second-stage hydrogen peroxide dilution mixer 7 are uniformly mixed to form a reaction mixture, the reaction mixture in the first-stage hydrogen peroxide dilution mixer 6 enters the first-stage feeding mixer 5, is uniformly mixed with liquid propylene, and then enters the bottom of the reactor 1, is uniformly distributed through the first-stage feeding distributor 106, is uniformly mixed with the pH adjuster distributed through the pH adjuster distributor 108, and then, under the action of pressure difference, rises into the catalytic tube 104 in the first reaction section 101, propylene is oxidized with hydrogen peroxide to produce propylene oxide under the action of the catalyst, and the reaction heat is removed from the reactor 1 by the cooling medium outside the catalytic tube 104.

[0112] The reaction mixture from the first reaction section 101 continues to rise, is uniformly mixed with the mixture of hydrogen peroxide and solvent distributed through the second-stage feeding distributor 107, and then enters the second reaction section 102 for further reaction, and the final reaction product is discharged from the top of the reactor 1 after the reaction is completed.

[0113] The effects of the propylene oxide production system and method provided by the present application will be described below in combination with specific examples.

[0114] The hydrogen peroxide conversion rate, the effective utilization rate of hydrogen peroxide and the effective utilization rate of H2O2 mentioned in the following examples are explained as follows:

[0115] The hydrogen peroxide conversion rate refers to the difference between the total amount of hydrogen peroxide in the feeding of the reaction system and the total amount of hydrogen peroxide in the discharging divided by the total amount of hydrogen peroxide in the feeding, and the hydrogen peroxide conversion rate is expressed in percentage form.

[0116]

[0117] The effective utilization rate of hydrogen peroxide is the hydrogen peroxide conversion rate minus the ineffective conversion rate of hydrogen peroxide decomposed into water and oxygen.

[0118] The effective utilization rate of H2O2 = the conversion rate of H2O2 minus the conversion rate of H2O2 decomposed into water and oxygen.

[0119] Example 3

[0120] In combination Figure 1As shown, the distance between the secondary feed distributor 107 and the tube sheet 103 at the top of the first reaction section 101 is set to 100 mm, and the distance between the pH adjuster distributor 108 and the tube sheet 103 at the bottom of the first reaction section 101 is set to 200 mm.

[0121] The diameter D1 of the catalytic cracking tube 104 is set to 25 mm, the thickness of the fin 105 is 1 mm, the width D2 of the fin 105 is 12 mm, the helical pitch of the fin 105 is 15 mm, and the center distance L1 between any two adjacent catalytic cracking tubes 104 is (25+12)×1.1=40.7 mm.

[0122] The structures of the secondary feed distributor 107 and the pH adjuster distributor 108 are as follows: Figure 2 As shown, the diameter of the distribution branch pipe 11 is set to satisfy the fluid flow velocity of 1m / s, the diameter D3 of the distribution hole 12 is 5mm, the center distance L2 between two adjacent distribution holes 12 in the same row is 20mm, and the angle α between the distribution hole 12 and the vertical direction is 60°.

[0123] The primary feed mixer 5 is set to use a commercially available SH-type spiral flow static mixer with 4 mixing units; the primary hydrogen peroxide dilution mixer 6 and the secondary hydrogen peroxide dilution mixer 7 are both commercially available SL-type static mixers with 5 mixing units.

[0124] The specific surface area of ​​the TS-1 type silicon-titanium molecular sieve catalyst is set at 400 m². 2 / g, pore volume 0.25cm 3 / g, with an average pore size of 2.5nm; hydrogen peroxide concentration of 50%, methanol as solvent, and ammonia as pH adjuster.

[0125] The feed mass ratio of the three materials is set as follows:

[0126] Hydrogen peroxide:propylene:solvent = 1:2.8:5.6;

[0127] The feed mass ratio of hydrogen peroxide to the first reaction section 101 and the second reaction section 103 is set as follows:

[0128] Primary hydrogen peroxide feed: Secondary hydrogen peroxide feed = 1:1;

[0129] The feed mass ratio of methanol solvent to the first reaction section 101 and the second reaction section 103 is set as follows:

[0130] Primary solvent feed: Secondary solvent feed = 4:1;

[0131] The reaction temperature was set at 38℃, the reaction pressure at 3.0 MPa, the pH of the reactants at 7.0, and the liquid hourly space velocity (LISH) range at 1.5 h⁻¹. -1 .

[0132] The results of the reaction are shown in Table 1.

[0133] Example 4

[0134] The difference from Example 3 is that:

[0135] The reaction temperature was set to 45°C, and the liquid hourly space velocity of the reaction was set to 2.5 h -1 .

[0136] The rest was the same as Example 3, and the results of the reaction are shown in Table 1.

[0137] Example 5

[0138] The difference from Example 3 is that:

[0139] The reaction temperature was set to 25°C, and the liquid hourly space velocity of the reaction was set to 1.0 h -1 .

[0140] The rest was the same as Example 3, and the results of the reaction are shown in Table 1.

[0141] Example 6

[0142] The difference from Example 3 is that:

[0143] The reaction temperature was set to 55°C, and the liquid hourly space velocity of the reaction was set to 3 h -1 . The rest was the same as Example 3, and the results of the reaction are shown in Table 1.

[0144] Example 7

[0145] The difference from Example 3 is that:

[0146] The pH of the reaction material was set to 6.8.

[0147] The rest was the same as Example 3, and the results of the reaction are shown in Table 1.

[0148] Example 8

[0149] The difference from Example 3 is that:

[0150] The pH of the reaction material was set to 7.5.

[0151] The rest was the same as Example 3, and the results of the reaction are shown in Table 1.

[0152] Example 9

[0153] The difference from Example 3 is that:

[0154] The pH of the reaction material was set to 6.5.

[0155] The rest was the same as Example 3, and the results of the reaction are shown in Table 1.

[0156] Example 10

[0157] The difference from Example 3 is that:

[0158] The reaction pressure is set to 2.8 MPa.

[0159] The rest is the same as Example 3, and the reaction results are shown in Table 1.

[0160] Example 11

[0161] The difference from Example 3 is that:

[0162] The mass ratio of the three materials is set to:

[0163] Hydrogen peroxide: propylene: solvent = 1:3.5:6.

[0164] The rest is the same as Example 3, and the reaction results are shown in Table 1.

[0165] Example 12

[0166] The difference from Example 3 is that:

[0167] The concentration of hydrogen peroxide is set to 70%.

[0168] The rest is the same as Example 3, and the reaction results are shown in Table 1.

[0169] Example 13

[0170] The difference from Example 3 is that:

[0171] The angle α between the distribution hole 12 and the vertical direction is set to 85°.

[0172] The rest is the same as Example 3, and the reaction results are shown in Table 1.

[0173] Example 14

[0174] The difference from Example 3 is that:

[0175] The helical pitch of the fin 105 is set to 10 mm.

[0176] The rest is the same as Example 3, and the reaction results are shown in Table 1.

[0177] Example 15

[0178] The difference from Example 3 is that:

[0179] The helical pitch of the fin 105 is set to 30 mm, and the center distance L1 between any two adjacent catalytic cracking pipes 104 is (25+12)×1.05=38.85 mm.

[0180] The rest are the same as example 3, and the reaction results are shown in Table 1.

[0181] Example 16

[0182] The difference from example 3 is that:

[0183] The diameter D1 of the catalytic cracking pipe 104 is set to 30 mm, and the center distance L1 between any two adjacent catalytic cracking pipes 104 is (30+12) x 1.1 = 46.2 mm.

[0184] The rest are the same as example 3, and the reaction results are shown in Table 1.

[0185] Example 17

[0186] The difference from example 3 is that:

[0187] The specific surface area of the TS-1 type silicon-titanium molecular sieve catalyst is set to 350 m 2 / g, the pore volume is 0.2 cm 3 / g, and the average pore size is 2 nm.

[0188] The rest are the same as example 3, and the reaction results are shown in Table 1.

[0189] Comparative example 1

[0190] The difference from example 3 is that:

[0191] The outer wall of the catalytic cracking pipe 104 is not provided with fins.

[0192] The rest are the same as example 3, and the reaction results are shown in Table 1.

[0193] Comparative example 2

[0194] The difference from example 3 is that:

[0195] The two-stage reaction bed is not provided in the reactor 1, and the three materials directly enter from the bottom of the reactor 1.

[0196] The rest are the same as example 3, and the reaction results are shown in Table 1.

[0197] Comparative example 3

[0198] The difference from example 3 is that:

[0199] No pH adjuster is added, and the pH value of the reaction material is not controlled.

[0200] The rest are the same as example 3, and the reaction results are shown in Table 1.

[0201] Table 1 shows the reaction results of Examples 3-17 and Comparative Examples 1-3.

[0202]

[0203]

[0204] As shown in Table 1, Examples 3-17, using the propylene oxide production system and method provided by this invention, improved the utilization rate of reaction raw materials and the yield of propylene oxide. The hydrogen peroxide conversion rate was greater than 99.72%, the hydrogen peroxide utilization rate was above 93.95%, the propylene oxide yield was above 93.11%, and the propylene oxide selectivity was above 95.46%. The byproducts in the reaction were significantly reduced, with the yields of propylene glycol methyl ether, propylene glycol, and total aldehydes below 3.18%, 1.27%, and 0.18%, respectively.

[0205] Compared with Comparative Example 1, Example 3 has fins installed on the outer wall of the catalytic tube, which increases the heat transfer area, facilitates the timely discharge of heat generated during the reaction, avoids high-temperature decomposition of hydrogen peroxide, improves the utilization and conversion rate of hydrogen peroxide, thereby increasing the yield of propylene oxide and reducing the generation of by-products.

[0206] Compared with Comparative Example 2, the segmented feeding in Example 3 improved the uniformity of the mixing of the three materials (propane, hydrogen peroxide and solvent), thereby ensuring the full reaction of the materials, improving the conversion rate and utilization rate of the materials, and avoiding risks such as low conversion rate due to uneven mixing caused by a single feeding of materials, excessive heat generation causing hydrogen peroxide decomposition, and increased side reactions.

[0207] Compared with Comparative Example 3, in Example 3, adjusting the pH value of the reactants can avoid the promoting effect of acidic centers on by-products during the reaction process, thereby improving the selectivity and yield of propylene oxide.

[0208] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-conversion, high-yield propylene oxide production system, characterized in that, include: Reactor, raw material supply unit, pH adjustment unit, and control unit; The reactor is divided into a first reaction section and a second reaction section along the material flow direction. Both the first and second reaction sections are equipped with multiple catalyst tubes filled with catalyst. The outer wall of the catalyst tubes is provided with fins arranged in a spiral. The raw material supply unit includes a hydrogen peroxide supply pipeline, a solvent supply pipeline, a propylene supply pipeline, a primary feed distributor, a secondary feed distributor, a primary feed mixer, a primary hydrogen peroxide dilution mixer, and a secondary hydrogen peroxide dilution mixer; The primary feed distributor is located at the inlet of the first reaction section, and is connected to the hydrogen peroxide supply pipeline, the solvent supply pipeline and the propylene supply pipeline respectively. The secondary feed distributor is located at the inlet of the second reaction section and is connected to the hydrogen peroxide supply pipeline and the solvent supply pipeline, respectively. The inlet of the first-stage hydrogen peroxide dilution mixer is connected to the hydrogen peroxide supply pipeline and the solvent supply pipeline, respectively. The outlet of the first-stage hydrogen peroxide dilution mixer and the propylene supply pipeline are connected to the inlet of the first-stage feed mixer, respectively. The outlet of the first-stage feed mixer is connected to the first-stage feed distributor. The inlet of the secondary hydrogen peroxide dilution mixer is connected to the hydrogen peroxide supply pipeline and the solvent supply pipeline, respectively, and the outlet of the secondary hydrogen peroxide dilution mixer is connected to the secondary feed distributor; The pH adjustment unit includes a pH adjuster distributor installed at the inlet of the first reaction section and a pH adjuster supply pipeline connected thereto, used to adjust the pH value of the reactants in the reactor; The control unit is electrically connected to the reactor and the raw material supply unit respectively. The control unit controls the raw material supply unit to supply materials to the first reaction section and the second reaction section according to the material reaction state in the reactor and the set material ratio.

2. The propylene oxide production system according to claim 1, characterized in that, The catalytic tubes in the first reaction section and the second reaction section are arranged in an equilateral triangle, and the helical pitch of the fins is 8mm to 30mm. The diameter D1 of the catalytic tube is 14–38 mm; The thickness of the fins is 0.5 to 1.5 mm, and the width D2 of the fins is 0.25 to 0.5 times the diameter D1 of the catalytic tube. The center-to-center distance L1 between any two adjacent catalytic tubes is 1.05 to 1.15 times the sum of the diameter D1 of the catalytic tubes and the width D2 of the fins.

3. The propylene oxide production system according to claim 1, characterized in that, The primary feed distributor, the secondary feed distributor, and the pH adjuster distributor are all equipped with a main feed pipe and multiple horizontally parallel distribution branches, which are connected to the main feed pipe. The bottom of the distribution branch pipe is provided with two rows of evenly spaced distribution holes. The two rows of distribution holes are symmetrically distributed along the vertical direction, and the angle α between the distribution holes and the vertical direction is 45° to 90°. The two rows of distribution holes on the same distribution branch pipe are arranged alternately.

4. The propylene oxide production system according to claim 3, characterized in that, The diameter D3 of the distribution hole is 5-10 mm; In the same row, the center-to-center distance L2 between adjacent distribution holes is 3 to 6 times the diameter D3 of the distribution hole.

5. The propylene oxide production system according to claim 1, characterized in that, The secondary feed distributor is 50-150 mm away from the top of the first reaction section; The pH adjuster distributor is 100-200 mm away from the bottom of the first reaction section; The pH adjuster distributor is positioned above the primary feed distributor and is 50–150 mm away from it.

6. A method for producing propylene oxide with high conversion and high yield, using the propylene oxide production system according to any one of claims 1-5, characterized in that, Includes the following steps: Hydrogen peroxide and solvent are uniformly mixed in a certain proportion to prepare a reaction mixture. A portion of the reaction mixture is uniformly mixed with propylene according to the feed ratio and then fed into the bottom of the reactor through the primary feed distributor. The reaction material is adjusted to pH and then fed into the catalytic tube in the first reaction section. Under the action of the catalyst, the reaction mixture generated by the reaction of propylene and hydrogen peroxide rises into the catalytic tube in the second reaction section. Another portion of the reaction mixture enters the catalytic tube array of the second reaction section through the secondary feed distributor, where it continues to react with the reaction mixture, and the final reaction product is discharged from the top of the reactor. The feed mass ratio of the hydrogen peroxide, the propylene, and the solvent is: Hydrogen peroxide:propylene:solvent = 1:(2-4):(4-7); The feed mass ratio of hydrogen peroxide in the first reaction section and the second reaction section is: Primary hydrogen peroxide feed: Secondary hydrogen peroxide feed = (0.5~2):1; The feed mass ratio of the solvent in the first reaction section and the second reaction section is: Primary solvent feed: Secondary solvent feed = (4-8): 1; The pH of the reactants is controlled within the range of 6 to 8.

7. The method for producing propylene oxide according to claim 6, characterized in that, The feed mass ratio of the hydrogen peroxide, the propylene, and the solvent is: Hydrogen peroxide:propylene:solvent = 1:(2.5-3.5):(5-6); and / or, The feed mass ratio of hydrogen peroxide in the first reaction section and the second reaction section is: Primary hydrogen peroxide feed: Secondary hydrogen peroxide feed = 1:1; and / or, The feed mass ratio of the solvent in the first reaction section and the second reaction section is: Primary solvent feed: Secondary solvent feed = (5-6):1; and / or, The reaction temperature is 20℃~60℃; and / or, The reaction pressure is 2.5–3.2 MPa; and / or, The pH of the reactants is 6.5–7.5; and / or, The liquid hourly space velocity (LHSV) of the reaction ranged from 1 to 3 h⁻¹. -1 .

8. The method for producing propylene oxide according to claim 6, characterized in that, The catalyst is a TS-1 type silicon-titanium molecular sieve catalyst, and the specific surface area of ​​the TS-1 type silicon-titanium molecular sieve catalyst is 350-450 m². 2 / g, pore volume 0.2~0.25cm 3 / g, with an average pore size of 2–2.5 nm; and / or, The concentration of the hydrogen peroxide is 50% to 70%.

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