High-conversion-rate and high-yield epoxypropane production system and method

Abstract

According to the epoxypropane production system and method with the high conversion rate and the high yield, the interior of the reactor is divided into the upper section and the lower section through the production system, the accurate feeding proportion of three materials is provided, and the mode of segmented control and distributed feeding is provided; propylene and most of hydrogen peroxide diluted by a solvent are added into a first reaction section at the bottom through a first-stage feeding distributor for reaction, and then a reaction mixed solution of the residual solvent and hydrogen peroxide is supplemented into a second reaction section through a second-stage feeding distributor, so that reaction materials are uniformly mixed for reaction; the problem that the temperature is too high and hydrogen peroxide is decomposed due to uneven mixing caused by one-time adding or non-distributed adding of materials is avoided, the conversion rate of the materials is increased, meanwhile, fins are arranged on the outer sides of the catalytic tubes, the heat exchange area is increased, reaction heat is discharged in time, hydrogen peroxide decomposition is avoided, and the catalytic effect is improved. The selectivity and the yield of the product epoxypropane are further improved.

Description

Technical Field

[0001] The invention relates to the technical field of propylene oxide production, and further to a system and method for producing propylene oxide with high conversion rate and high yield. Background Art

[0002] Propylene oxide (PO) is an important propylene derivative with a low boiling point and flammability. Its main use is to produce polyether polyols and propylene glycol (PG). It is also the main raw material for preparing propylene glycol ethers, flame retardants, non-ionic surfactants and plasticizers. Among them, polyether polyols are important raw materials for the production of polyurethane foams, thermal insulation materials, elastomers, adhesives and coatings, and various non-ionic surfactants are widely used in the petroleum, chemical, pesticide, textile and daily chemical industries.

[0003] The technology of producing propylene oxide by direct oxidation of propylene with hydrogen peroxide (HPPO) is internationally recognized as a green and environmentally friendly production technology. Compared with the traditional chlorohydrin 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, low investment, mild reaction conditions, low energy consumption, basically no pollution, high product yield, and few other by-products.

[0004] Although the HPPO method has great advantages over the traditional process route, it also has bottleneck problems such as low hydrogen peroxide utilization and low propylene oxide yield due to imperfect reaction system design that need to be solved. In order to solve the above problems, the following patents propose a variety of solutions.

[0005] Patent CN109180611B provides a device and method for preparing propylene oxide by HPPO method with segmented raw material injection, which uses at least two groups of reaction units in series, each group of reaction units includes 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 enter the reaction device of each group of reaction units in stages and are mixed evenly before entering. The present invention 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 safety hazards. However, the defect of this patent is that multiple reactors are used to solve the reaction task of the original one reactor, the investment is high, and the operation of the device is complicated. Moreover, the hydrogen peroxide conversion rate of 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 device for preparing propylene oxide by hydrogen peroxide method, including an emulsification reaction device of a mixing emulsification device and a plate reactor. Although the emulsion can improve the mass transfer and heat transfer efficiency, due to the complexity of the reaction system, there are problems such as small catalyst particle size and difficult separation.

[0007] Patent CN200710099853.5 provides a method for continuously producing propylene oxide, using powdered titanium silicon molecular sieve as a catalyst, uniformly mixing the titanium silicon molecular sieve with the reaction materials to react in a slurry state, and setting a solid-liquid separation device outside the reactor to separate the molecular sieve from the liquid reaction materials. The molecular sieve circulates in a 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 external filtration of the powdered molecular sieve is the difficulty and bottleneck of the device.

[0008] Therefore, it is urgent to develop a propylene oxide production system and production process to effectively solve the defects of the prior art such as low hydrogen peroxide conversion rate, low propylene oxide selectivity, and complex operation. Summary of the invention

[0009] In view of the problems that the existing propylene oxide production has low raw material conversion rate and utilization rate, low selectivity of propylene oxide products, etc., the purpose of the present invention is to provide a high conversion rate and high yield propylene oxide production system and method, the reactor is divided into two sections, an upper section and a lower section, three materials are accurately fed in a ratio and a feeding mode is controlled and distributed in sections, propylene and most of the hydrogen peroxide diluted by a solvent are added to the first reaction section at the bottom through a primary feeding distributor for reaction, and then the remaining solvent and the reaction mixture of hydrogen peroxide are added to the second reaction section through a secondary feeding distributor, which is conducive to uniform mixing and reaction of the reaction materials, avoids the problem of hydrogen peroxide decomposition caused by excessively high temperature due to uneven mixing caused by the materials being added at one time or added without distribution, and improves the conversion rate of the materials. At the same time, the outer side of the catalytic tube provided by the present invention is provided with fins to increase the heat exchange area, discharge the reaction heat in time, avoid the decomposition of hydrogen peroxide, and further improve the selectivity and yield of the product propylene oxide.

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

[0011] A high-conversion and high-yield propylene oxide production system comprises: a reactor, a raw material supply unit, a pH adjustment unit and a control unit; the interior of the reactor is divided into a first reaction section and a second reaction section along the material flow direction, and a plurality of catalytic tubes filled with catalysts 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 entrance of the first reaction section, and is respectively connected to the hydrogen peroxide supply pipeline, the solvent supply pipeline and the propylene supply pipeline; the secondary feed distributor is arranged at the entrance of the second reaction section, and is respectively connected to the hydrogen peroxide supply pipeline and the solvent supply pipeline; the pH adjustment unit is used to adjust the pH value of the reaction material in the reactor; the control unit is respectively electrically connected to the reactor and the raw material supply unit, and the control unit controls the raw material supply unit to feed materials into the first reaction section and the second reaction section according to the set material ratio according to the reaction state of the materials in the reactor.

[0012] In some embodiments, the raw material supply unit further includes: 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 respectively connected to the hydrogen peroxide supply pipeline and the solvent supply pipeline, the outlet of the primary hydrogen peroxide dilution mixer and the propylene supply pipeline are respectively connected to the inlet of the primary feed mixer, and the outlet of the primary feed mixer is connected to the primary feed distributor; the inlet of the secondary hydrogen peroxide dilution mixer is respectively connected to the hydrogen peroxide supply pipeline and the solvent supply pipeline, and the outlet of the secondary hydrogen peroxide dilution mixer is connected to 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 disposed at the inlet of the first reaction section, and the pH adjusting agent supply pipeline is connected to 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, and the outer walls of the catalytic tubes are provided with spirally arranged fins, and the spiral pitch of the fins is 8 mm to 30 mm; the diameter D1 of the catalytic tubes is 14 to 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 tubes; the 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.

[0015] In some embodiments, the first-level feed distributor, the second-level feed distributor and the pH adjuster distributor are all provided with a feed main pipe and a plurality of distribution branches parallel to each other in the horizontal direction, and the distribution branches are connected to the feed main pipe; two rows of distribution holes with uniform hole spacing are provided at the bottom of the distribution branch, and the two rows of distribution holes are symmetrically distributed in 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 are staggered.

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

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

[0018] The present invention also provides a method for producing propylene oxide with high conversion rate and high yield, using the above-mentioned propylene oxide production system, 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 according to the feed ratio, and then fed into the bottom of the reactor through the primary feed distributor, the reaction materials are fed into the catalytic tubes in the first reaction section after adjusting the pH, and the reaction mixture generated by the reaction of propylene and the hydrogen peroxide rises into the catalytic tubes of the second reaction section under the action of the catalyst; another part of the reaction mixture enters the catalytic tubes of the second reaction section through the secondary feed distributor, and continues to react with the reaction mixture, and finally the 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 stage and the second reaction stage is: first-stage hydrogen peroxide feed: second-stage hydrogen peroxide feed = (0.5-2): 1;

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

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

[0024] In some embodiments, the feed 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 feed mass ratio of the hydrogen peroxide in the first reaction section and the second reaction section is:

[0027] First-stage hydrogen peroxide feed: second-stage hydrogen peroxide feed = 1:1; and / or,

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

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

[0030] The reaction temperature is 20°C to 60°C; and / or, the reaction pressure is 2.5 to 3.2 MPa; and / or, the pH of the reaction mass is 6.5 to 7.5; and / or,

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

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

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

[0034] 1. The reactor provided by the present invention is provided with two reaction sections, propane and a part of hydrogen peroxide diluted with a solvent are introduced into the first reaction section at the bottom in proportion, and the remaining hydrogen peroxide and solvent are added into the second reaction section. The segmented feeding method improves the uniformity of mixing the three materials, enables the materials to react fully, improves the conversion rate and utilization rate of the materials, and avoids the risks of low conversion rate caused by uneven mixing of materials introduced at one time, decomposition of hydrogen peroxide caused by excessive local heat generation, and increased side reactions;

[0035] 2. The primary feed distributor and the secondary feed distributor respectively arranged at the entrance of the two sections can also ensure the uniform distribution of materials in the internal space of the reactor, which is conducive to the full mixing of the reaction materials, and the temperature distribution inside the reaction section is more uniform, so that the local temperature will not be too high, and the decomposition of hydrogen peroxide will be avoided;

[0036] 3. The present invention provides spirally wound fins on the outer wall of the catalytic tubes to increase the heat exchange area, improve the heat exchange coefficient, discharge the heat generated by the oxidation reaction in time, effectively control the temperature in the reaction section, make the reaction proceed smoothly, avoid the decomposition of hydrogen peroxide due to high temperature, improve the utilization rate of hydrogen peroxide, and thus improve the yield of propylene oxide;

[0037] 4. The present invention adjusts the pH of the reaction materials to control the pH value in a neutral (alkaline) range, thereby avoiding the promotion of by-products by the presence of acidic centers during the reaction, inhibiting the ring-opening reaction of propylene oxide, and improving the selectivity and yield of propylene oxide;

[0038] 5. The present invention provides a material ratio for staged feeding, wherein most of the solvent is input into the first reaction stage to achieve the effect of dilution and temperature equalization, and the solvent added in the second reaction stage is used to dilute the added hydrogen peroxide and improve the distribution uniformity of the hydrogen peroxide in the second reaction stage. The present invention also provides a total feed ratio of the three materials, reduces the solvent ratio, and can reduce the energy consumption of subsequent solvent recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The preferred implementation modes will be described below in a clear and understandable manner with reference to the accompanying drawings to further illustrate the above-mentioned characteristics, technical features, advantages and implementation methods of the present invention.

[0040] Figure 1 A schematic diagram of the structure of a propylene oxide production system provided by the present invention;

[0041] Figure 2 A schematic diagram of the structure of a secondary feed distributor provided by the present invention;

[0042] Figure 3 This is a schematic diagram of the structure of the distribution branch pipe provided by the present invention.

[0043] Description of Figure Numbers:

[0044] 1—reactor; 101—first reaction section; 102—second reaction section; 103—tube sheet; 104—catalytic tubes; 105—fins; 106—primary feed distributor; 107—secondary feed distributor; 108—pH regulator distributor;

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

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings and other implementation methods can be obtained based on these drawings without creative work.

[0047] In order to simplify the drawings, only the parts related to the invention are schematically shown in each figure, and they do not represent the actual structure of the product. In addition, in order to simplify the drawings and facilitate understanding, in some figures, only one of the parts with the same structure or function is schematically drawn or marked. In this article, "one" not only means "only one", but also means "more than one".

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

[0049] In this document, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

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

[0051] Example 1

[0052] The chemical principle of producing propylene oxide in the present invention:

[0053] The main reaction is that in the presence of TS-1 titanium silicalite, hydrogen peroxide and propylene undergo oxidation reaction in a solvent 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 form diols and ethers. The reaction equation is:

[0056]

[0057] And hydrogen peroxide ineffectively decomposes into oxygen and water:

[0058] H202H20+02

[0059] The ineffective decomposition of hydrogen peroxide not only reduces the utilization rate of hydrogen peroxide, but also the oxygen produced by the decomposition mixed with propylene oxide will bring safety risks.

[0060] Therefore, in view of the above-mentioned defects, the present invention provides a propylene oxide production system with high yield and high raw material conversion rate, such as Figure 1 As shown, it includes: a reactor 1, a raw material supply unit, a pH adjustment unit and a control unit 9.

[0061] The interior of the reactor 1 is divided into a first reaction section 101 and a second reaction section 102 along the material flow direction. The first reaction section 101 and the second reaction section 102 are both provided with a plurality of catalytic tubes 104 filled with catalysts, and a heat exchange medium is provided between the outer wall of the catalytic tubes 104 and the inner wall of the reactor 1.

[0062] The tangent 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 provided inside the reactor 1 , and the tube sheets 103 separate the inside of the reactor 1 into a first reaction section 101 and a 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. Hydrogen peroxide, solvent and propylene are all fed in liquid phase. The primary feed distributor 106 and the secondary feed distributor 107 are both arranged inside the reactor 1 to evenly distribute the raw materials.

[0065] Specifically: the first-level feed distributor 106 is arranged at the entrance of the first reaction section 101, that is, the first-level feed distributor 106 is arranged below the tube plate 103 at the bottom of the first reaction section 101, and the first-level feed distributor 106 is respectively connected to the hydrogen peroxide supply pipeline 2, the solvent supply pipeline 3 and the propylene supply pipeline 4. After the hydrogen peroxide, the solvent and the propylene are evenly mixed in a certain proportion, they enter the catalytic tube array 104 in the first reaction section 10 through the first-level feed distributor 106 to react.

[0066] The secondary feed distributor 107 is arranged at the entrance of the second reaction section 102, that is, the secondary feed distributor 107 is arranged between the tube sheet 103 at the top of the first reaction section 101 and the tube sheet 103 at the bottom of the second reaction section 101. The secondary feed distributor 107 is connected to the hydrogen peroxide supply pipeline 2 and the solvent supply pipeline 3 respectively. The raw material supply unit introduces hydrogen peroxide and solvent into the second reaction section 102. The reaction mixture generated by the reaction of hydrogen peroxide and propylene in the first reaction section 101 rises into the catalytic tubes 104 in the second reaction section 102, and continues to react with the hydrogen peroxide and solvent evenly distributed by the secondary feed distributor 107. The final reaction product is discharged from the top of the reactor 1 and enters the subsequent process to purify propylene oxide.

[0067] The present invention adopts a two-stage reactor and inputs hydrogen peroxide in stages to control the rate and stabilize the temperature of the reaction bed, thereby avoiding ineffective decomposition of hydrogen peroxide due to excessively high temperature.

[0068] In some embodiments, in order to obtain a better reaction effect, the raw material supply unit further includes: 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 to the hydrogen peroxide supply pipeline 2, the solvent supply pipeline 3 and the propylene supply pipeline 4 respectively through the primary feed mixer 5. More specifically, the inlet of the primary feed mixer 5 is connected to 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 to the inlet of the primary feed distributor 106.

[0070] The inlet of the primary hydrogen peroxide dilution mixer 6 is connected to the hydrogen peroxide supply pipeline 2 and the solvent supply pipeline 3 respectively. The hydrogen peroxide and the solvent are mixed in a certain proportion in the primary hydrogen peroxide dilution mixer 6, and then introduced into the feed mixer 5, propylene is added in proportion and mixed evenly, and then the primary feed distributor 106 evenly distributes them into the catalytic tube array 104 of the first reaction stage 101.

[0071] The invention first dilutes the oxidant hydrogen peroxide with a solvent and then mixes it with propylene evenly, so that the three are mixed more evenly, thereby avoiding the increase of byproducts caused by local overreaction due to uneven mixing and the decomposition of hydrogen peroxide caused by overheating, and improving the utilization rate of hydrogen peroxide.

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

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

[0074] The primary hydrogen peroxide dilution mixer 6 and the secondary hydrogen peroxide dilution mixer 7 can be commercially available SK type, SL type, or SX type static mixers, and the number of mixing units of the static mixer is 4 to 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 and a pH adjusting agent supply pipeline 8 disposed inside the reactor 1 .

[0076] Specifically: the pH regulator distributor 108 is arranged at the entrance of the first reaction section 101, that is, the pH regulator distributor 108 is arranged below the tube sheet 103 at the bottom of the first reaction section 101, preferably between the tube sheet 103 at the bottom of the first reaction section 101 and the primary feed distributor 106.

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

[0078] Preferably, the secondary feed distributor 107 is 50 to 150 mm away from the top of the first reaction section 101, that is, the distance between the secondary feed distributor 107 and the tube sheet 103 at the top of the first reaction section 101 is 50 to 150 mm.

[0079] The pH regulator distributor 108 is 100 to 200 mm away from the bottom of the first reaction section 101, that is, the distance between the pH regulator distributor 108 and the tube plate 103 at the bottom of the first reaction section 101 is 100 to 200 mm. If this distance is too short, the target materials entering the reaction section are not mixed evenly. If the distance is too long, not only will the mixing effect not be greatly improved, but also the equipment investment will become higher. The primary feed distributor 106 is located below the pH regulator distributor 108 and is 50 to 150 mm away from the pH regulator distributor 108.

[0080] The pH regulator mentioned above is an inorganic salt solution such as ammonia, sodium hydroxide, potassium hydroxide, etc. Ammonia is preferably used as the pH regulator to avoid introducing too much water into the reaction system and reduce recovery energy consumption.

[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, and the diameter D1 of the catalytic tubes 104 is 14 to 38 mm to maintain a high flow rate and high turbulence state of the cooling medium.

[0082] The outer wall of the catalytic tube 104 is provided with spirally arranged fins 105, which are preferably heat-conducting metal plates. The thickness of the fin 105 is 0.5-1.5 mm, and the width D2 of the fin 105 is 0.25-0.5 times the diameter D1 of the catalytic tube 104, that is, D2=(0.25-0.5)×D1. The spiral pitch of the fin 105 is 8mm-30mm. 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 to 1.15 times the sum of the diameter D1 of the catalytic tubes 104 and the width D2 of the fins 105, that is, L1 = (1.05 to 1.15) × (D1 + D2).

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

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

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

[0087] The number and diameter of the distribution branch pipes 11 can meet the requirement that the flow velocity of the fluid therein is 0.5 to 2 m / s. If the flow velocity is too fast, the pressure drop of the distribution branch pipes 11 is large. If the flow velocity is too low, the diameter of the distribution branch pipes 11 is too large.

[0088] The propylene oxide production system provided by the present invention is further provided with a control unit, which is electrically connected to the reactor 1 and the raw material supply unit respectively to control the automatic operation of the entire propylene oxide production system. The control unit controls the raw material supply unit to supply materials to the first reaction section 101 and the second reaction section 102 according to the set material ratio according to the reaction state of the materials in the reactor 1 (it can also be combined with the operation state of the two reaction sections, such as temperature, pressure, etc.), so as to realize segmented feeding: the control unit controls the hydrogen peroxide supply pipeline 2, the solvent supply pipeline 3 and the propylene supply pipeline 4 to supply materials to the first reaction section 101 according to a certain material ratio according to the reaction state of the materials in the first reaction section 101 (material pH, temperature and other parameters); similarly, the control unit controls the hydrogen peroxide supply pipeline 2 and the solvent supply pipeline 3 to supply hydrogen peroxide and solvent in a certain ratio to the second reaction section 102 according to the reaction state of the materials in the second reaction section 102.

[0089] Preferably, the control unit includes a controller, a display and detection elements arranged on the reactor 1, such as a temperature sensor, a pressure sensor and a pH sensor, etc. It also includes an electric control valve and a metering device installed on each pipeline, and an electric control 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 adjuster supply pipeline 8.

[0090] The controller is electrically connected to the reactor 1, the detection element, the electric control valve and the metering device respectively. The controller automatically collects real-time parameters such as temperature, pressure, pH, and the flow rate of each material. The built-in control program of the controller automatically controls the operating status of the reactor 1 and each electric control valve according to the collected information. The display is connected to the controller for communication. The operator can observe the operating status of each device at any time from the display screen and can also set the operating parameters, which greatly improves the degree of automated and precise control of the production system, facilitates the maintenance of the device under optimal operating conditions, and improves the product yield.

[0091] Example 2

[0092] On the basis of Example 1, the present invention provides a method for producing propylene oxide with high yield and high raw material conversion rate, using the propylene oxide production system in Example 1, comprising the following steps:

[0093] Hydrogen peroxide and solvent are uniformly mixed in a certain proportion to form a reaction mixture. A part of the reaction mixture is uniformly mixed with propylene according to the feed ratio and then fed into the bottom of the reactor 1 through the primary feed distributor 106. After adjusting the pH, it is fed into the catalytic tube array 104 in the first reaction section 101. Under the action of the catalyst, propylene and hydrogen peroxide undergo an oxidation reaction to generate a reaction mixture that rises and enters the catalytic tube array 104 in the second reaction section 102.

[0094] Another part of the reaction mixture enters the catalytic tubes 104 of the second reaction section 102 through the secondary feed distributor 107 and continues to react with the reaction mixture. Finally, the 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 propylene is both above 99%.

[0096] The above-mentioned solvent is an alcohol solution, such as methanol, ethanol, propanol, isopropanol, etc. Since methanol has a larger polarity and a high solubility in propylene and propylene oxide, methanol is preferably used as the solvent in the present invention.

[0097] The above catalyst is a TS-1 silicon-titanium molecular sieve catalyst, and the specific surface area of ​​the TS-1 silicon-titanium molecular sieve catalyst is 350 to 450 m 2 / g, pore volume is 0.2~0.25cm 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 ammonia, sodium hydroxide, potassium hydroxide and other inorganic salt solutions, preferably ammonia.

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

[0100] The feed mass ratio of the above three raw materials is preferably hydrogen peroxide: propylene: solvent = 11: (2.5-3.5): (5-6). If the ratio is too high, the cycle energy consumption increases, and if the ratio is too low, it is easy to cause ineffective decomposition of hydrogen peroxide, which not only leads to low hydrogen peroxide utilization, but also excessive hydrogen peroxide will cause propylene oxide to open the ring and produce alcohol and ether by-products. A high ratio of solvent is conducive to the reaction, but a high ratio will lead to excessive energy consumption.

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

[0102] Preferably, the ratio of primary hydrogen peroxide feed to secondary hydrogen peroxide feed is 1:1. If the ratio of hydrogen peroxide feed to the first reaction stage 101 is too high or too low, the effect of graded feeding cannot be achieved.

[0103] In some embodiments, the feed mass ratio of the solvent in 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 is mixed with hydrogen peroxide in the primary hydrogen peroxide dilution mixer 6 and then enters 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 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 the decomposition of hydrogen peroxide, and too low a temperature will reduce the reaction rate, resulting in incomplete reaction.

[0106] The reaction pressure of the reaction of propylene and hydrogen peroxide is 2.5-3.2 MPa, preferably 2.8-3.0 MPa. If the reaction pressure is too low, a full liquid phase reaction cannot be guaranteed. If the pressure is too high, both energy consumption and investment will increase.

[0107] The pH of the reaction material (mixed solution of hydrogen peroxide, propylene and solvent) is 6 to 8, preferably 6.5 to 7.5. A low pH value will lead to a high incidence of side reactions, while a high pH value will lead to a large consumption of pH regulators and will not significantly improve the yield. The present invention utilizes an alkaline pH regulator to neutralize the acidic center generated during the reaction process that can open the ring and break the chain of propylene oxide to generate alcohols and ethers, thereby improving the selectivity of propylene oxide.

[0108] The liquid hourly space velocity range of the reaction between propylene and hydrogen peroxide is 1 to 3 h -1 , preferably 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 cause the product propylene oxide to open its ring and produce by-products.

[0109] Combined with the above Figure 1 The propylene oxide production system shown in the figure, the specific process flow of the propylene oxide production method is as follows:

[0110] Under the control of the control unit, the hydrogen peroxide supply pipeline 2 inputs hydrogen peroxide to the primary hydrogen peroxide dilution mixer 6 and the secondary hydrogen peroxide dilution mixer 7 according to the feed ratio, the solvent supply pipeline 3 inputs solvent to the primary hydrogen peroxide dilution mixer 6 and the secondary hydrogen peroxide dilution mixer 7 according to the feed ratio, and the propylene supply pipeline 4 inputs propylene to the primary feed mixer 5 according to the feed ratio.

[0111] The hydrogen peroxide and the solvent in the primary hydrogen peroxide dilution mixer 6 and the secondary hydrogen peroxide dilution mixer 7 are uniformly mixed to form a reaction mixture. The reaction mixture in the primary hydrogen peroxide dilution mixer 6 enters the primary feed mixer 5, is uniformly mixed with liquid propylene, and then enters the bottom of the reactor 1. After being uniformly distributed by the primary feed distributor 106 and uniformly mixed with the pH regulator distributed by the pH regulator distributor 108, it rises into the catalytic tube 104 in the first reaction section 101 under the action of the pressure difference. Under the action of the catalyst, propylene and hydrogen peroxide undergo an oxidation reaction to produce propylene oxide, and the reaction heat is removed out of 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, and after being uniformly mixed with the mixture of hydrogen peroxide and solvent distributed by the secondary feed distributor 107, enters the second reaction section 102 to continue the reaction. After the reaction is completed, the final reaction product is discharged from the top of the reactor 1.

[0113] The effects of the propylene oxide production system and method provided by the present invention are described below in conjunction with specific embodiments.

[0114] Explanation of the hydrogen peroxide conversion rate, hydrogen peroxide effective utilization rate and H2O2 effective utilization rate mentioned in the following examples:

[0115] The hydrogen peroxide conversion rate refers to the difference between the total amount of hydrogen peroxide fed into the reaction system and the total amount of hydrogen peroxide discharged divided by the total amount of hydrogen peroxide fed. The hydrogen peroxide conversion rate is expressed as a percentage:

[0116]

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

[0118] Effective utilization rate of H2O2 = H2O2 conversion rate - conversion rate of H2O2 decomposition into water and oxygen.

[0119] Example 3

[0120] 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 regulator 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 set to 1 mm, the width D2 of the fin 105 is set to 12 mm, the spiral pitch of the fin 105 is set to 15 mm, and the center distance L1 between any two adjacent catalytic cracking tubes 104 is set to (25+12)×1.1=40.7 mm.

[0122] The structures of the secondary feed distributor 107 and the pH regulator distributor 108 are as follows: Figure 2 As shown, the diameter of the distribution branch pipe 11 is set to meet the fluid flow rate of 1m / s, the diameter D3 of the distribution hole 12 is 5mm, the center distance L2 of 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 first-stage feed mixer 5 is set to adopt a commercially available SH-type spiral flow static mixer with 4 mixing units; the first-stage hydrogen peroxide dilution mixer 6 and the second-stage hydrogen peroxide dilution mixer 7 are both set to adopt a commercially available SL-type static mixer with 5 mixing units.

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

[0125] Set the feed mass ratio of the three materials to:

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

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

[0128] First-stage hydrogen peroxide feed: second-stage hydrogen peroxide feed = 1:1;

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

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

[0131] The reaction temperature was set to 38°C, the reaction pressure was 3.0 MPa, the pH value of the reaction material was 7.0, and the liquid hourly space velocity range of the reaction was 1.5 h -1 .

[0132] The reaction results 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 range was set to 2.5h -1 .

[0136] The rest are the same as in Example 3. The reaction results 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 range was set to 1.0 h -1 .

[0140] The rest are the same as in Example 3. The reaction results 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 range was set to 3h. -1 The rest is the same as Example 3, and the reaction results are shown in Table 1.

[0144] Example 7

[0145] The difference from Example 3 is that:

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

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

[0148] Example 8

[0149] The difference from Example 3 is that:

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

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

[0152] Example 9

[0153] The difference from Example 3 is that:

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

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

[0156] Example 10

[0157] The difference from Example 3 is that:

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

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

[0160] Embodiment 11

[0161] The difference from Example 3 is that:

[0162] Set the feed mass ratio of the three materials to:

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

[0164] The rest are the same as in Example 3. 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 was set to 70%.

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

[0169] Embodiment 13

[0170] The difference from Example 3 is that:

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

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

[0173] Embodiment 14

[0174] The difference from Example 3 is that:

[0175] The spiral pitch of the fin 105 was set to 10 mm.

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

[0177] Embodiment 15

[0178] The difference from Example 3 is that:

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

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

[0181] Example 16

[0182] The difference from Example 3 is that:

[0183] Assuming that the diameter D1 of the catalytic cracking tube 104 is 30 mm, the center distance L1 between any two adjacent catalytic cracking tubes 104 is (30+12)×1.1=46.2 mm.

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

[0185] Embodiment 17

[0186] The difference from Example 3 is that:

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

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

[0189] Comparative Example 1

[0190] The difference from Example 3 is that:

[0191] It is assumed that the outer wall of the catalytic cracking tube 104 is not provided with fins.

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

[0193] Comparative Example 2

[0194] The difference from Example 3 is that:

[0195] It is assumed that there are no two-stage reaction beds in the reactor 1, and the three materials directly enter from the bottom of the reactor 1.

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

[0197] Comparative Example 3

[0198] The difference from Example 3 is that:

[0199] It is assumed that no pH adjuster is added and the pH value of the reaction material is not controlled.

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

[0201] Table 1 Reaction results of Examples 3-17 and Comparative Examples 1-3

[0202]

[0203]

[0204] As can be seen from Table 1, Examples 3-17 use the propylene oxide production system and method provided by the present invention, and the utilization rate of the reaction raw materials and the product of propylene oxide are improved, the hydrogen peroxide conversion rate is greater than 99.72%, the hydrogen peroxide utilization rate is above 93.95%, the yield of propylene oxide is above 93.11%, and the selectivity of propylene oxide is above 95.46%. The by-products in the reaction are greatly reduced, and the yields of propylene glycol methyl ether, propylene glycol and total aldehydes are below 3.18%, 1.27% and 0.18% respectively.

[0205] Compared with Comparative Example 1, Example 3 provides fins on the outer wall of the catalytic tubes, which increases the heat transfer area, facilitates the timely discharge of reaction heat, avoids high-temperature decomposition of hydrogen peroxide, improves the utilization rate and conversion rate of hydrogen peroxide, and further increases the yield of propylene oxide and reduces the generation of by-products.

[0206] Compared with Comparative Example 2, Example 3 improves the uniformity of mixing the three materials (propane, hydrogen peroxide and solvent) by staged feeding, thereby ensuring full reaction of the materials, improving the conversion rate and utilization rate of the materials, and avoiding the risks of low conversion rate caused by uneven mixing of the materials fed at one time, decomposition of hydrogen peroxide caused by excessive heat generated by the reaction, and increased side reactions.

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

[0208] The above are only preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A high conversion rate and high yield propylene oxide production system, characterized in that: include: Reactor, raw material supply unit, pH adjustment unit and control unit; The interior of the reactor is divided into a first reaction section and a second reaction section along the material flow direction, and a plurality of catalytic tubes filled with catalysts are arranged in the first reaction section and the second reaction section; The raw material supply unit includes 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 entrance of the first reaction section, and the primary feed distributor is respectively connected to the hydrogen peroxide supply pipeline, the solvent supply pipeline and the propylene supply pipeline; The secondary feed distributor is arranged at the entrance of the second reaction section, and the secondary feed distributor is respectively connected to the hydrogen peroxide supply pipeline and the solvent supply pipeline; The pH adjustment unit is used to adjust the pH value of the reaction material 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 a set material ratio according to a reaction state of the materials in the reactor.

2. The propylene oxide production system according to claim 1, characterized in that: The raw material supply unit also includes: 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 to 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 to the inlet of the primary feed mixer respectively, and the outlet of the primary feed mixer is connected to the primary 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.

3. The propylene oxide production system according to claim 1, characterized in that: The pH adjustment unit comprises: a pH adjuster distributor and a pH adjuster supply pipeline, The pH regulator distributor is arranged at the inlet of the first reaction section, and the pH regulator supply pipeline is connected to the pH regulator distributor.

4. 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 outer wall of the catalytic tubes is provided with fins arranged in a spiral, and the spiral pitch of the fins is 8mm to 30mm; The diameter D1 of the catalytic tubes is 14 to 38 mm; The thickness of the fin is 0.5 to 1.5 mm, and the width D2 of the fin is 0.25 to 0.5 times the diameter D1 of the catalytic tube; The 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 tube and the width D2 of the fin.

5. The propylene oxide production system according to claim 3, characterized in that: The primary feed distributor, the secondary feed distributor and the pH adjuster distributor are all provided with a feed main pipe and a plurality of distribution branches parallel to each other in the horizontal direction, and the distribution branches are connected to 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 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 in a staggered manner.

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

7. The propylene oxide production system according to claim 3, characterized in that: The secondary feed distributor is 50 to 150 mm away from the top of the first reaction section; The pH regulator distributor is 100 to 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 to 150 mm away from the primary feed distributor.

8. A method for producing propylene oxide with high conversion rate and high yield, using the propylene oxide production system according to claims 1-7, characterized in that: The following steps are involved: 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 fed into the bottom of the reactor through the primary feed distributor, the reaction materials are fed into the catalytic tubes in the first reaction section after adjusting the pH, and the reaction mixture generated by the reaction of propylene and hydrogen peroxide under the action of the catalyst rises and enters the catalytic tubes in the second reaction section; Another part of the reaction mixture enters the catalytic tubes of the second reaction stage through the secondary feed distributor, and continues to react with the reaction mixture, and finally the 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 the hydrogen peroxide in the first reaction section and the second reaction section is: First-stage hydrogen peroxide feed: Second-stage hydrogen peroxide feed = (0.5-2): 1; The feed mass ratio of the solvent in the first reaction stage and the second reaction stage is: Primary solvent feed: secondary solvent feed = (4-8): 1; The pH of the reaction material is controlled within the range of 6 to 8.

9. The method for producing propylene oxide according to claim 8, 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 the hydrogen peroxide in the first reaction section and the second reaction section is: First-stage hydrogen peroxide feed: second-stage hydrogen peroxide feed = 1:1; and / or, The feed mass ratio of the solvent in the first reaction stage and the second reaction stage is: Primary solvent feed: secondary solvent feed = (5-6): 1; and / or, The reaction temperature is 20°C to 60°C; and / or, The reaction pressure is 2.5 to 3.2 MPa; and / or, The pH of the reaction mass is 6.5 to 7.5; and / or, The liquid hourly space velocity range of the reaction is 1 to 3 h -1 .

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

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