A method and system for producing propylene oxide

Abstract

A method and system for producing propylene oxide, propylene and hydrogen peroxide are mixed and contacted in the presence of an oxidation catalyst in a reactor to carry out an oxidation reaction, and a post-reaction stream is separated to obtain propylene oxide; a device for producing propylene oxide comprises a riser reactor (5), a liquid-solid separator (8), a liquid-liquid separator (13) and a tubular mixer (4), the top of the reactor is connected to the inlet of the liquid-solid separator through an external circulation pipe (7), the trapped liquid outlet of the liquid-solid separator is connected to the bottom of the reactor through an external circulation pipe and a tubular mixer, and the clear liquid outlet (10) of the liquid-solid separator is connected to the inlet of the liquid-liquid separator; hydrogen peroxide and solvent in the reactant are either a dispersed phase or a continuous phase. The method for producing propylene oxide provided by the application strengthens liquid-liquid mass transfer, can improve reaction conversion rate and selectivity, and realizes long-period operation of the device.

Description

Technical Field

[0001] The present invention relates to a method and a reaction system for producing propylene oxide, and more particularly to a method and a reaction system for producing propylene oxide by catalyzing the oxidation of propylene with hydrogen peroxide using a liquid-liquid-solid multiphase reaction device. Technical Background

[0002] Propylene oxide (PO) is an important basic organic chemical raw material and the third largest organic chemical product in terms of production volume among propylene derivatives, after polypropylene and acrylonitrile. It is widely used in the chemical, light industry, pharmaceutical, food, textile, and other industries, and has a profound impact on the chemical industry and national economic development. With the expansion of PO's applications and the growing demand for downstream products, the PO market is growing. Currently, the industrial production of PO primarily utilizes the chlorohydrin process and the co-oxidation process. The chlorohydrin process suffers from severe equipment corrosion, consumes large amounts of toxic gases, and produces significant amounts of wastewater, failing to meet the requirements of green chemistry and clean production, and will be gradually phased out. The co-oxidation process, however, is lengthy, has high investment costs, and its byproducts are subject to market constraints. The HPPO process, which synthesizes PO by direct epoxidation of propylene with hydrogen peroxide using titanium silicalite as a catalyst, offers mild, environmentally friendly, and pollution-free conditions, in line with current green chemistry development concepts and is a new green process for producing PO.

[0003] Because the intermiscibility of the reaction raw materials propylene and hydrogen peroxide in the process of synthesizing propylene oxide by direct epoxidation of propylene by hydrogen peroxide is very poor, the method for the liquid-liquid mixing of oil and water phases mainly includes the following: first, by adding a cosolvent to improve the intermiscibility of the two phases. For example, a method for producing propylene oxide is disclosed in CN 101293813A, which adopts an emulsifying agent to form an oil-in-water emulsion with C4 and water and then carries out an olefin hydration reaction, which can increase the conversion rate of isobutylene to about 70%. In the process of synthesizing propylene oxide by hydrogen peroxide and propylene, methanol is also often adopted as a solvent in order to improve the mutual contact of the two phases (CN102898405A, CN 102442979A, CN 106632148A), but the adding of such non-raw material may cause the generation of a series of side reactions, and has a greater impact on subsequent separation and product purity. In addition, for the strengthening of the liquid-liquid mixing process in conventional means, the methods commonly used in industry include mechanical stirring, designing tortuous flow channels, high-speed impact of liquids, etc., the purpose of which is to generate fluid turbulence to increase the mixing efficiency of the liquid. The most commonly used reactor form is a stirred tank, which utilizes the mechanical stirring effect of an agitator to achieve mixing and reaction of raw materials. However, due to the limitations of stirred tank equipment, the time scale of mixing is between a few minutes or even a few hours, which is commonly used in reaction systems with slow reaction rates. For example, CN202527171A discloses a reaction device for gas-liquid-liquid-solid multiphase reaction, in which a draft tube is installed inside the reactor, and an agitator is installed in the draft tube to achieve contact reaction of raw materials by stirring. Commonly used pipeline static mixers use tortuous flow channels to strengthen mixing of fluids, but their mixing effect is relatively poor.

[0004] The reactor that adopts for the synthesis of propylene oxide from hydrogen peroxide and propylene process at present mainly contains the following several forms, such as fixed-bed reactor (EP 0659473, CN 1671678A) or shell and tube reactor, or adopt the method for stirring (CN101279957A), or slurry bed reactor (CN 101314596A), or the series / parallel use of multiple reactor forms, such as the process of adopting fixed-bed pipeline reactor and slurry bed reactor combination in CN104311513A, CN 106632148A discloses a method for epoxidation reaction by combining a bubble tower slurry bed reactor and a stirred tank slurry bed reactor. The main purpose of the above-mentioned different methods is to improve interphase mass transfer and reaction heat extraction. For solving the heat release problem and process amplification problem in the chemical reaction process.

[0005] According to existing literature and patent reports, the process of synthesizing propylene oxide from hydrogen peroxide and propylene still has many problems in its actual application. Therefore, it is necessary to develop a new propylene epoxidation process, especially an innovative reactor form, so as to simply and efficiently solve many problems existing in the process of synthesizing propylene oxide from hydrogen peroxide and propylene, such as incomplete hydrogen peroxide conversion, low effective utilization rate of hydrogen peroxide, low selectivity of product propylene oxide, and high exothermic reaction that may lead to temperature runaway. Summary of the Invention

[0006] One of the technical problems to be solved by the present invention is to provide a method for producing propylene oxide by oxidizing propylene with hydrogen peroxide in the presence of a solid molecular sieve catalyst.

[0007] The second technical problem to be solved by the present invention is to provide a reaction system for producing propylene oxide.

[0008] A method for producing propylene oxide comprises mixing and contacting propylene and hydrogen peroxide in a reactor in the presence of an oxidation catalyst to carry out an oxidation reaction, and separating the post-reaction stream to obtain propylene oxide. The device for producing propylene oxide comprises a riser reactor 5, a liquid-solid separator 8, a liquid-liquid separator 13, and a tubular mixer 4. The bottom of the riser reactor is provided with a dispersed phase inlet 1 and a catalyst discharge outlet 6, the top of the reactor is connected to the solid-liquid separator inlet via an external circulation pipe 7, the retentate outlet of the solid-liquid separator is connected to the bottom of the reactor via the external circulation pipe and the tubular mixer, the clear liquid outlet 10 of the solid-liquid separator is connected to the liquid-liquid separator inlet, the liquid-liquid separator is provided with a water phase outlet and an oil phase outlet, and the water phase outlet or the oil phase outlet is connected to the inlet of the tubular mixer 4.

[0009] Preferably, the hydrogen peroxide in the reaction material serves as the dispersed phase and propylene serves as the continuous phase.

[0010] A system for producing propylene oxide comprises a device for producing propylene oxide, a reaction system consisting of water-oil two-phase reaction raw materials and oxidation catalyst particles, wherein the water phase is hydrogen peroxide with or without a solvent, the oil phase is propylene, and the particle size of the oxidation catalyst particles is 0.05-3.0 mm. The device for producing propylene oxide comprises a riser reactor 5, a liquid-solid separator 8, a liquid-liquid separator 13 and a tubular mixer 4, wherein the bottom of the riser reactor is provided with a dispersed phase inlet 1 and a catalyst discharge outlet 6, the top of the reactor is connected to the solid-liquid separator inlet via an external circulation pipe 7, the retentate outlet of the solid-liquid separator is connected to the bottom of the reactor via the external circulation pipe and the tubular mixer, the clear liquid outlet 10 of the solid-liquid separator is connected to the liquid-liquid separator inlet, the liquid-liquid separator is provided with a water phase outlet and an oil phase outlet, and the water phase outlet or the oil phase outlet is connected to the inlet of the tubular mixer 4.

[0011] The novel multiphase reaction system provided by the present invention and its beneficial effects in the propylene oxide preparation process are as follows:

[0012] Compared to the prior art, the present invention provides a method for producing propylene oxide by direct oxidation of hydrogen peroxide using a dedicated reaction apparatus. A dispersed phase feeder disperses one phase of the reactants into a tiny liquid. A small-particle molecular sieve oxidation catalyst is used, enhancing interphase mass transfer through microdroplets and microparticles, thereby significantly improving reaction efficiency. Furthermore, the use of a cosolvent is eliminated or minimized, reducing the occurrence of side reactions and lowering subsequent separation difficulty and energy consumption. The method couples the reaction with the liquid-liquid separation process, allowing for internal circulation of a large amount of propylene, with newly added propylene only required to replenish chemical consumption. Furthermore, the presence of a high concentration of continuous propylene in the reaction system facilitates improved hydrogen peroxide reaction selectivity. Because the solid-phase catalyst is in a circulating flow state within the reaction system, online catalyst renewal is facilitated, thereby extending the device's downtime and maintenance cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A schematic flow chart of a first embodiment of a method for producing propylene oxide provided by the present invention.

[0014] Figure 2 A schematic flow diagram of a second embodiment of a reaction apparatus for producing propylene oxide.

[0015] Description of reference numerals:

[0016] 1-Dispersed phase inlet 2-Continuous phase inlet 3-Dispersed phase feeder

[0017] 4- Tubular mixer 5- Reactor 6- Catalyst discharge port

[0018] 7-External circulation pipe 8-Liquid-solid separator 9-Lower section of external circulation pipe

[0019] 10-Clear liquid outlet 11-Catalyst inlet 12-Backwash liquid inlet

[0020] 13-Liquid-liquid separator 14-Water phase outlet 15-Oil phase outlet

[0021] 16-Product Separation System I-Tube Side II-Shell Side DETAILED DESCRIPTION

[0022] The specific embodiments of the present invention are described in detail below.

[0023] A method for producing propylene oxide, propylene and hydrogen peroxide are mixed and contacted in the presence of an oxidation catalyst in a reactor to perform an oxidation reaction, and a post-reaction stream is separated to obtain propylene oxide; a device for producing propylene oxide comprises a riser reactor 5, a liquid-solid separator 8, a liquid-liquid separator 13 and a tubular mixer 4, wherein the riser reactor is provided with a dispersed phase inlet 1 and a catalyst discharge outlet 6 at the bottom, and the top of the reactor is connected to the inlet of the liquid-solid separator through an external circulation pipe 7, the trapped liquid outlet of the liquid-solid separator is connected to the inlet of the liquid-liquid separator through an external circulation pipe and a tubular mixer, and the clear liquid outlet 10 of the liquid-solid separator is connected to the inlet of the liquid-liquid separator, the liquid-liquid separator is provided with a water phase outlet and an oil phase outlet, and the water phase outlet or the oil phase outlet is connected to the inlet of the tubular mixer 4.

[0024] In the method for producing propylene oxide provided by the application, hydrogen peroxide, with or without solvent, is in the aqueous phase and can be used as the dispersed phase or the continuous phase; propylene is in the oil phase and is another phase. Preferably, hydrogen peroxide and the solvent are used as the dispersed phase, and propylene is used as the continuous phase. The solvent is preferably methanol.

[0025] In the method for producing propylene oxide provided by the application, hydrogen peroxide and propylene are subjected to an oxidation reaction in the presence of an oxidation catalyst to obtain propylene oxide; the oxidation reaction conditions are as follows: the pressure is 0.1-3.0 MPa, the temperature is 30-80℃, the reaction residence time is 0.3-3 h, the molar ratio of fresh propylene feed to hydrogen peroxide is (1.0-3.0):1, and the molar ratio of the solvent to hydrogen peroxide is (0-10):1. Preferably, the solvent is added to the reaction material, and the molar ratio of the solvent to hydrogen peroxide is (0.5-10):1.

[0026] In the method for producing propylene oxide provided by the application, the oxidation catalyst is a titanium-silicon molecular sieve with MFI structure, and the particle diameter of the oxidation catalyst is 0.05-3.0 mm.

[0027] In the method for producing propylene oxide provided by the application, in the device for producing propylene oxide, preferably, the riser reactor is divided into a tube and a shell, the tube and the shell are separated by a tube wall, the tube and the shell are not connected, and the streams in the tube and the shell can exchange heat, wherein the tube provides a reaction space for the reaction material, the shell is connected to the bottom of the reactor through a heat exchange medium inlet and a heat exchange medium outlet, and the heat exchange medium inlet and the heat exchange medium outlet are connected to the tube and the shell.

[0028] In the device for producing propylene oxide provided by the application, preferably, the dispersed phase inlet 1 is provided with a dispersed phase feeder 3, and the dispersed phase feeder is a porous pipe, a sintered metal pipe, an inorganic membrane pipe or an atomizing nozzle.

[0029] Preferably, the front-to-rear pressure drop of the dispersed phase feeder 2 is 0.05-3.0 MPa, and the initial liquid flow rate at the outlet of the dispersed phase feeder is 5-40 m / s.

[0030] Preferably, the riser reactor is a shell and tube reactor, wherein the interior of tube side I provides a reaction space for the reaction materials, and a cooling medium is introduced into shell side II to exchange heat with the reaction materials in the tube side to dissipate the reaction heat. The number of tube sides is preferably a plurality of circular tubes evenly arranged inside the reactor shell, and the tube side and shell side materials are separated by providing top and bottom baffles. The dispersed phase inlet is provided with a dispersed phase feeder 2. When a plurality of circular tubes are provided in the straight pipe section, a dispersed phase feeder is provided at the bottom of each circular tube. In the production of propylene oxide, the dispersed phase can be either an oil phase or an aqueous phase. The dispersed phase feeder has a significant throttling effect, and it is necessary to ensure that the pressure difference before and after the feeder is preferably in the range of 0.05 to 3.0 MPa, and the liquid flow rate at the feed inlet is 5 to 40 m / s.

[0031] In the device for producing propylene oxide, preferably, the liquid-solid separator is a filter assembly, the filter assembly includes a shell and a filter tube, and the filter tube is selected from one or a combination of inorganic ceramic membranes, metal tube membranes, metal screens, and metal sintered tubes.

[0032] In the device for producing propylene oxide, preferably, a catalyst addition port is further provided on the shell of the liquid-solid separator.

[0033] In the device for producing propylene oxide, preferably, in the liquid-solid separator, a backwash pipeline is provided on the filter assembly.

[0034] In the device for producing propylene oxide, preferably, the outer circulation pipe is one or more, wherein the pipe connecting the reactor outlet and the liquid-solid separator is the upper section of the outer circulation pipe, and the pipe connecting the retentate outlet of the liquid-solid separator and the tubular mixer is the lower section of the outer circulation pipe;

[0035] Preferably, the inner diameter of the upper section of the outer circulation pipe is the same as that of the lower section of the outer circulation pipe.

[0036] Preferably, the ratio of the diameter of the external circulation pipe to that of the reactor is (0.3-3):1, preferably (0.5-2):1.

[0037] In the device for producing propylene oxide, preferably, the tubular mixer is a jet mixer, wherein the lower section of the circulation pipe is connected to the main fluid inlet of the jet mixer, and the water phase outlet of the liquid-liquid mixer is connected to the high-speed jet inlet of the jet mixer.

[0038] The jet mixer has a main fluid inlet, a high-speed jet fluid inlet and a jet outlet. During the reaction process, the flow rate of the high-speed jet fluid at the jet outlet of the jet mixer is 3-30 m / s.

[0039] Preferably, the high-speed jet inlet of the jet mixer is also connected to the continuous phase inlet so as to replenish the reaction raw materials during the reaction process.

[0040] Preferably, the liquid-liquid separator is selected from one or a combination of a conventional gravity settling tank, an oil-water coalescing separator and a fiber membrane surface separator.

[0041] There are one or more external circulation pipes, one end of which is connected to the top of the reactor and the other end is connected to the bottom of the reactor to form a circulation loop. Preferably, the inner diameter of the upper section of the external circulation pipe and the inner diameter of the lower section of the external circulation pipe are the same, and the ratio of the diameter of the external circulation pipe to the straight section of the reactor is (0.3-3):1, preferably (0.5-2:1).

[0042] Preferably, the liquid-solid separator is a filter assembly for liquid-solid separation of materials from the top of the reactor. The filter assembly includes a housing and a filter tube, and the filter tube is selected from one or a combination of inorganic ceramic membranes, metal tube membranes, metal screens, metal sintered tubes, etc. The filter assembly can be one or more groups. The filter assembly is provided with a clear liquid outlet and a retained liquid outlet. The clear liquid outlet is connected to the liquid-liquid separator, and the retained liquid outlet is connected to the bottom of the reactor through the lower section of the downcomer. During use, the retained liquid is returned to the bottom of the reactor as a circulating material through the jet mixer.

[0043] The filter assembly is provided with a filter backwash liquid inlet, and preferably the backwash liquid inlet pipeline and the clear liquid outlet pipeline obtained by liquid-solid separation share a common interface on the filter assembly housing. The backwash liquid is selected from the clear liquid after filtration or fresh raw material liquid.

[0044] The lower section of the external circulation pipe is connected to a jet mixer. The circulating material from the retentate outlet of the liquid-solid separator serves as the suction fluid for the jet mixer, while the feedstock from the continuous phase inlet and the circulating liquid phase from the aqueous phase outlet of the liquid-liquid separator serve as high-speed jets. The jet flow rate is preferably 3-30 m / s. The two streams are mixed in the jet mixer and then enter the bottom of the reactor.

[0045] The method for producing propylene oxide provided by the present invention employs a granular oxidation catalyst, which is added to the reaction apparatus via a catalyst inlet provided on a liquid-solid separator. Because some catalyst wear and deactivation are inevitable during the reaction process, to ensure overall catalyst activity, it is necessary to regularly monitor catalyst activity and wear. A portion of the catalyst is then discharged from a catalyst discharge port at the bottom of the riser reactor to achieve online catalyst renewal, thus avoiding equipment downtime that could affect the operating cycle.

[0046] A system for producing propylene oxide comprises a propylene oxide production apparatus, a reaction system consisting of water-oil two-phase reaction raw materials, and oxidation catalyst particles, wherein the aqueous phase comprises hydrogen peroxide and a solvent, the oil phase comprises propylene, and the oxidation catalyst particles have a particle size of 0.05 to 3.0 mm. The propylene oxide production apparatus comprises a riser reactor, a liquid-solid separator, a liquid-liquid separator, and a tubular mixer. The bottom of the riser reactor is provided with a dispersed phase inlet and a catalyst discharge outlet, the top of the reactor is connected to the solid-liquid separator inlet via an external circulation pipe, the retentate outlet of the solid-liquid separator is connected to the bottom of the reactor via the external circulation pipe and the tubular mixer, the clear liquid outlet of the solid-liquid separator is connected to the liquid-liquid separator inlet, the liquid-liquid separator is provided with an aqueous phase outlet and an oil phase outlet, and the aqueous phase outlet or the oil phase outlet is connected to the inlet of the tubular mixer. The aqueous phase serves as the dispersed phase or the continuous phase. Preferably, hydrogen peroxide and the solvent serve as the dispersed phase.

[0047] The method and system for producing propylene oxide of the present invention will be further described below with reference to the accompanying drawings, but the present invention is not limited thereto.

[0048] Attachment Figure 1 This is a schematic diagram of the process for producing propylene oxide. Figure 1 As shown, the reaction device for producing propylene oxide used is composed of a reactor 5, a liquid-solid separator 8, a liquid-liquid separator 13 and a tubular mixer 4, wherein the bottom of the riser reactor is provided with a dispersed phase inlet 1 and a catalyst unloading outlet 6, the top of the reactor is connected to the inlet of the solid-liquid separator 8 through an external circulation pipe 7, the retentate outlet of the solid-liquid separator 8 is connected to the bottom of the reactor through the tubular mixer 4, the clear liquid outlet 10 of the solid-liquid separator is connected to the inlet of the liquid-liquid separator 13, the liquid-liquid separator 13 is provided with an aqueous phase outlet 14 and an oil phase outlet 15, and the aqueous phase outlet 14 is connected to the inlet of the tubular mixer 4.

[0049] Attachment Figure 2 Schematic diagram of the second embodiment of the method for producing propylene oxide. Figure 1 The difference is that the reactor is divided into a tube side I and a shell side II, which are not interconnected. The shell side is provided with a heat exchange medium inlet 20 and a heat exchange medium outlet 21 at the upper and lower ends, respectively. The tube side provides a reaction space for the reactants, while the heat exchange medium introduced into the shell side exchanges heat with the reactants within the tube side, removing the heat of reaction to control the reaction temperature. The oil phase separated by the liquid-liquid separator 13 is returned to the bottom of the reactor 5 through the oil phase outlet 15 for a cyclic reaction. The separated aqueous phase enters the product separation system 16 through the aqueous phase outlet 14 for further separation. In addition, a continuous phase inlet 2 is provided at the bottom of the reactor 5.

[0050] As attached Figure 2 As shown, the method for producing propylene oxide provided by the present invention is illustrated using hydrogen peroxide as the dispersed phase. A certain amount of oxidation catalyst, preferably a titanium silicalite with an MFI structure and a particle diameter of 0.05 to 3.0 mm, is pre-introduced into the riser reactor 5. Fresh propylene feedstock, serving as the continuous phase, enters the reactor through the continuous phase inlet 2 and fills the entire reactor. A certain amount of hydrogen peroxide (typically containing water) mixed with a solvent, preferably methanol, in a certain proportion, enters the bottom of the reactor tube 5 through the dispersed phase inlet 1 and through the dispersed phase feeder 3. To achieve optimal dispersion and ensure good circulation within the reactor, the pressure drop across the dispersed phase feeder 3 is required to be 0.05 to 3.0 MPa, and the initial liquid flow rate at the dispersed phase feeder outlet must be 5 to 40 m / s, with the resulting dispersed phase droplets having a diameter of less than 1 mm. Within the reactor tube 1, the titanium silicalite catalyzes the oxidation of propylene with hydrogen peroxide to produce propylene oxide. The superficial liquid velocity within the reactor tube is controlled to exceed 20% to 120% of the critical settling velocity of the catalyst particles or the droplets (whichever is greater). Heat exchange medium is introduced into the reactor shell II to extract the reaction heat and control the required reaction temperature. Preferably, the cooling medium flows in the opposite direction to the reaction material or in a cross-flow direction.

[0051] After the reaction, the material is withdrawn from the top of the reactor 5 and enters the external circulation pipe 7, then enters the liquid-solid separator 8 for liquid-solid separation. The liquid-solid separator 8 is a filter assembly comprising a housing and a filter tube. The mixed material undergoes cross-flow filtration in the filter assembly. When too many particles accumulate on the filter tube wall, or optionally when the pressure difference across the filter tube is greater than 0.2 MPa, the process switches to a backwash phase, where a backwashing stream is introduced through the backwash medium inlet 12 to backwash the particles accumulated on the filter tube, thereby restoring the permeability of the filter tube. The backwash liquid inlet 12 preferably shares a common interface with the filtered clear liquid outlet 10. The backwash liquid can be selected from the filtered clear liquid or fresh raw material liquid. The retentate from the liquid-solid separator 8 is passed as the circulating material through the lower section of the external circulation pipe into the jet mixer, where it is mixed with the continuous phase feed and then enters the bottom of the riser reactor 5. The circulating material serves as the suction fluid, and the continuous liquid phase feed serves as the high-speed jet fluid. To ensure a good mixing effect, the jet flow rate is preferably 3 to 30 m / s.

[0052] After filtration in the liquid-solid separator, the clear liquid enters the liquid-liquid separator 13 through the clear liquid outlet 10. The liquid-liquid separator 13 is primarily used to separate the oil phase from the aqueous phase and can employ a conventional gravity settling tank, a surface coalescing separator, a fiber membrane surface separator, a centrifugal separator, a cyclone separator, or a combination thereof. The separated propylene-based oil phase returns to the reactor via the oil phase outlet 15 to participate in the reaction again. The separated propylene oxide-rich aqueous phase is withdrawn via the aqueous phase outlet 14 and enters the subsequent product separation system 16 for separation of the target product. The product separation system 16 can employ a variety of different unit operation modes, such as conventional distillation separation, liquid-liquid extraction, and adsorption separation, or a combination thereof.

[0053] The catalyst inlet 11 is preferably located on the liquid-solid separator 8, and the catalyst discharge outlet 6 is preferably located at the bottom of the reactor. Since some catalyst wear and deactivation are inevitable during the reaction process, to ensure the overall activity of the catalyst, it is necessary to regularly monitor the activity and wear of the catalyst. Depending on the situation, a portion of the catalyst is discharged from the discharge outlet and a portion of fresh catalyst is added to achieve online catalyst renewal, thereby avoiding plant downtime that affects the plant's operating cycle.

[0054] The following specific examples further illustrate the application effects of the method and system for producing propylene oxide provided by the present invention, but the present invention is not limited thereto.

[0055] In the Examples and Comparative Examples, the raw propylene had a purity greater than 99.6%, and the titanium silicalite catalyst used was HTS (Hunan Jianchang Company). Commercially available hydrogen peroxide was used at a concentration of 30 wt %. The residual hydrogen peroxide concentration was determined by KMnO₄ titration, and the product composition was analyzed by gas chromatography.

[0056] Comparative Example 1

[0057] Comparative Example 1 uses a conventional fixed-bed reactor to oxidize propylene with hydrogen peroxide to produce propylene oxide, and the reactor has a height-to-diameter ratio of 20. Logistics enter from the top and exit from the bottom, and a side-gap inlet distributor is provided at the reactor inlet, so that logistics in the reactor are naturally distributed.

[0058] The reaction inlet material was a mixture of propylene, hydrogen peroxide, and the solvent methanol, with a molar ratio of methanol to hydrogen peroxide of 40:1 and a molar ratio of propylene to hydrogen peroxide of 2:1. The reaction inlet temperature was 35°C, the pressure was 1.6 MPa, and the apparent residence time of the reaction materials in the reactor was 1.0 h. The reactor outlet temperature was 78°C.

[0059] The hydrogen peroxide conversion rate obtained by sampling and analyzing the reaction results was less than 90%, and the propylene oxide selectivity was 82%.

[0060] The hydrogen peroxide conversion rate is the ratio of the consumed hydrogen peroxide to the amount of hydrogen peroxide added. The propylene oxide selectivity is the ratio of the amount of substance of propylene oxide generated to the amount of substance of hydrogen peroxide consumed.

[0061] Example 1

[0062] Example 1 illustrates the effect of the method for producing propylene oxide provided by the present application.

[0063] The reaction device and process for producing propylene oxide are shown in the attached Figure 2 The mixed solution of hydrogen peroxide and methanol is used as the dispersed phase, wherein the molar ratio of methanol to hydrogen peroxide is 2.0, the molar ratio of fresh propylene feed to hydrogen peroxide is 1.5, and the diameter of the catalyst particles is 10-200 μm. The reactor contains three uniformly distributed tubes, each tube corresponding to a dispersed phase feeder at the bottom, the top of the dispersed phase feeder being a 6 mm sintered metal tube, the average pore size of the sintered tube being 7 μm, the three dispersed phase feeders being connected to the dispersed phase feed tube through a ring, and the total pressure drop of the feeders being 0.25 MPa. A metal sintered tube filtering assembly with an average filtering pore size of 6 μm is arranged on the external circulation pipeline of the reactor. The liquid-solid mixture on the interception side of the filtering assembly is circulated back to the reactor, the filtrate collected from the filtering assembly is introduced into a gravity settling tank for liquid-liquid separation, the upper oil phase obtained by the separation is returned to the reactor, and the lower aqueous phase is collected for product separation and analysis.

[0064] The reaction inlet temperature is 45°C, the reactor outlet temperature is controlled by passing cooling water through the reactor shell to be 68°C, the reaction partial pressure is 1.2 MPa, and the apparent residence time of the reaction material in the reactor is 1.0 h.

[0065] The hydrogen peroxide conversion rate is greater than 96% and the propylene oxide selectivity is 95% according to the sampling analysis and calculation of the reaction results.

Claims

1. A method for producing propylene oxide, wherein propylene and hydrogen peroxide are mixed and contacted in a reactor in the presence of an oxidation catalyst to carry out an oxidation reaction, and the reaction stream is separated to obtain propylene oxide; characterized in that: The device for producing propylene oxide is composed of a riser reactor (5), a liquid-solid separator (8), a liquid-liquid separator (13) and a tubular mixer (4), wherein the bottom of the riser reactor is provided with a dispersed phase inlet (1) and a catalyst discharge outlet (6), the top of the reactor is connected to the solid-liquid separator inlet via an external circulation pipe (7), the retentate outlet of the solid-liquid separator is connected to the bottom of the reactor via the external circulation pipe and the tubular mixer, the clear liquid outlet (10) of the solid-liquid separator is connected to the liquid-liquid separator inlet, the liquid-liquid separator is provided with a water phase outlet and an oil phase outlet, and the oil phase outlet is connected to the inlet of the tubular mixer (4); the riser reactor is divided into a tube side and a shell side, the upper and lower ends of the shell side are provided with a heat exchange medium inlet and a heat exchange medium outlet respectively, wherein the tube side provides a reaction space for the reaction material, and the shell side is introduced with a heat exchange medium to control the temperature; the hydrogen peroxide in the reaction material is used as the dispersed phase, and propylene is used as the continuous phase; The dispersed phase inlet (1) is provided with a dispersed phase feeder (3), the front and rear pressure drop of the dispersed phase feeder is 0.05-3.0 MPa, and the initial liquid flow rate at the dispersed phase feeder outlet is 5-40 m / s.

2. The method for producing propylene oxide according to claim 1, wherein The oxidation catalyst is a titanium silicon molecular sieve with an MFI structure, and the diameter of the oxidation catalyst particles is 0.05-3.0 mm.

3. The method for producing propylene oxide according to claim 1, wherein The oxidation reaction conditions are: pressure 0.1~3.0MPa, temperature 30~80℃, reaction residence time 0.3~3h, molar ratio of fresh feed propylene to hydrogen peroxide (1.0~3.0):1, wherein solvent may or may not be added to the reaction material, and the molar ratio of solvent to hydrogen peroxide is (0~10):

1.

4. The method for producing propylene oxide according to claim 3, wherein The solvent is methanol.

5. The method for producing propylene oxide according to any one of claims 1 to 3, characterized in that The dispersed phase feeder is a porous tube, a sintered metal tube, an inorganic membrane tube or an atomizing nozzle.

6. The method for producing propylene oxide according to any one of claims 1 to 3, characterized in that The liquid-solid separator is a filter assembly, which includes a shell and a filter tube. The filter tube is selected from one or a combination of inorganic ceramic membranes, metal tube membranes, metal screens, and metal sintered tubes.

7. The method for producing propylene oxide according to any one of claims 1 to 3, characterized in that The liquid-solid separator shell is also provided with a catalyst adding port.

8. The method for producing propylene oxide according to claim 6, wherein In the liquid-solid separator, a backwash pipeline is provided on the filter assembly.

9. The method for producing propylene oxide according to claim 1, wherein The outer circulation pipe is one or more, wherein the upper section of the outer circulation pipe connects the reactor outlet with the liquid-solid separator, and the lower section of the outer circulation pipe connects the retentate outlet of the liquid-solid separator with the tubular mixer.

10. The method for producing propylene oxide according to claim 9, wherein The inner diameters of the upper section of the outer circulation pipe and the lower section of the outer circulation pipe are the same.

11. The method for producing propylene oxide according to claim 9 or 10, characterized in that The ratio of the diameter of the external circulation pipe to that of the reactor is (0.3~3):

1.

12. The method for producing propylene oxide according to claim 11, wherein The ratio of the diameter of the external circulation pipe to that of the reactor is (0.5~2):

1.

13. The method for producing propylene oxide according to any one of claims 1 to 3, characterized in that The tubular mixer is a jet mixer, wherein the lower section of the circulation pipe is connected to the main fluid inlet of the jet mixer, and the oil phase outlet of the liquid-liquid mixer is connected to the high-speed jet inlet of the jet mixer.

14. A system for producing propylene oxide, characterized in that: The invention comprises a device for producing propylene oxide and a reaction system consisting of water-oil two phases and oxidation catalyst particles, wherein the water phase is hydrogen peroxide and a solvent, the oil phase is propylene, and the particle size of the oxidation catalyst particles is 0.05-3.0 mm. The device for producing propylene oxide comprises a riser reactor, a liquid-solid separator, a liquid-liquid separator and a tubular mixer, wherein a dispersed phase inlet and a catalyst discharge outlet are provided at the bottom of the riser reactor, the top of the reactor is connected to the solid-liquid separator inlet via an external circulation pipe, the retentate outlet of the solid-liquid separator is connected to the bottom of the reactor via the external circulation pipe and the tubular mixer, the clear liquid outlet of the solid-liquid separator is connected to the liquid-liquid separator inlet, the liquid-liquid separator is provided with a water phase outlet and an oil phase outlet, and the oil phase outlet is connected to the inlet of the tubular mixer.

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