Propylene oxide synthesis reaction system and synthesis method

Abstract

The application belongs to the technical field of heterocyclic compounds, and particularly relates to an epoxypropane synthesis reaction system and a synthesis method. The epoxypropane synthesis reaction system comprises a mixer, a mixing pipe arranged at the top of the mixer, a circulating pipe arranged at the bottom of the mixer, a methanol raw material tank connected to the middle of the mixer, a propylene raw material tank connected to the top of the mixing pipe, a circulating pump connected to the circulating pipe, a feeding pipe arranged at the upper part of the mixer, a thermostat connected to the feeding pipe, a pipeline reactor connected to the thermostat, a hydrogen peroxide raw material tank connected between the feeding pipe and the thermostat, a plurality of groups of reaction units arranged in parallel in the pipeline reactor, and a deoxidation tower connected to the pipeline reactor and provided with a liquid sprayer and a gas nozzle inside. The application realizes a green new method for producing epoxypropane.

Description

Technical Field

[0001] This invention belongs to the field of heterocyclic compound technology, specifically relating to a propylene oxide synthesis reaction system and synthesis method. Background Technology

[0002] Propylene oxide is an extremely important organic chemical intermediate, widely used in the production of various products such as polyether polyols, propylene glycol, and nonionic surfactants. For a long time, the production of propylene oxide has mainly relied on the chlorohydrin process and the co-oxidation process, but these two methods suffer from serious environmental pollution, highly corrosive equipment, and the generation of large quantities of low-value-added co-products.

[0003] To align with the trend of green and sustainable development in the chemical industry, developing new processes with high atom economy and environmental friendliness is imperative. Therefore, those skilled in the art have developed the direct hydrogen peroxide oxidation method. This method uses hydrogen peroxide as an oxidant, reacting directly with propylene to produce propylene oxide and water, theoretically without any byproducts, and is hailed as a "green process." Among the many direct hydrogen peroxide oxidation process routes, the system using methanol as a solvent and titanium-silicon molecular sieves as a catalyst is currently one of the most technologically mature and widely used industrial solutions.

[0004] Chinese patent CN116283833A discloses a process for the direct oxidation of propylene to prepare propylene oxide. This patent protects the reaction environment through N2 and propylene replacement, conducts the reaction under an excess propylene atmosphere, and simultaneously adds the target product and byproduct propylene glycol to the reaction system. This effectively suppresses the formation of byproducts during the reaction process and improves the conversion rate of reactants and the selectivity of the target product. However, this patent suffers from problems such as solvent loss, high separation energy consumption, and increased difficulty in wastewater treatment.

[0005] The direct hydrogen peroxide oxidation method, with its core advantages of being green, environmentally friendly, and highly efficient in atom economy, has become the future development direction for propylene oxide production technology. The main products of the reaction are only propylene oxide and water, completely eliminating the problems of chlorine-containing wastewater from the traditional chlorohydrin method and co-product issues from the co-oxidation method. Propylene conversion rate and propylene oxide selectivity are significantly improved, and large-scale industrial application has been achieved, proving its technical feasibility and economic viability. However, this production process still faces a series of serious challenges:

[0006] 1. The supply chain is highly dependent on a stable and low-cost source of hydrogen peroxide, and the supply of this high-risk chemical increases the complexity and cost of the supply chain.

[0007] 2. Methanol, as a solvent, itself can initiate ring-opening side reactions, which is the most fatal drawback of methanol in this reaction. The three-membered ring in the propylene oxide molecule has high strain and is prone to ring-opening under acidic or nucleophilic conditions. As a nucleophile, methanol can nucleophilically attack the carbon atoms of propylene oxide at acidic sites of the catalyst or at high temperatures, causing a ring-opening reaction and generating byproducts such as 1-methoxy-2-propanol and 2-methoxy-1-propanol, which are propylene glycol methyl ether byproducts. This leads to a decrease in product yield and increased difficulty in subsequent separation and purification.

[0008] 3. The lifespan, regeneration frequency, and deactivation issues of expensive titanium-silicon molecular sieve catalysts directly increase operating costs;

[0009] 4. The reaction system is a gas-liquid-solid three-phase system. Traditional fixed-bed reactors suffer from mass transfer efficiency bottlenecks, potentially limiting the reaction rate. Furthermore, ensuring stable removal of reaction heat, preventing localized overheating, and achieving long-term stable operation in large-scale plants remain challenging engineering problems requiring continuous optimization. Propylene epoxidation is a strongly exothermic reaction. Traditional batch or fixed-bed reactors, due to their low heat transfer efficiency, easily cause the catalyst surface to heat up to over 200°C, forming localized high-temperature zones. These high temperatures not only accelerate hydrogen peroxide decomposition but also trigger chain reactions, including propylene oxide ring-opening to form propylene glycol methyl ether, deep oxidation producing low-carbon waste such as CO / CO2, and catalyst sintering and deactivation. The catalyst requires frequent maintenance during use, with a maximum service life of no more than 300 days, severely impacting production schedules.

[0010] 5. During the reaction process, there is also a risk of the accumulation of substances such as oxygen in the reaction liquid, which can form an explosive mixture, thus increasing the risk in subsequent production stages. Summary of the Invention

[0011] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a propylene oxide synthesis reaction system, which improves the synthesis efficiency and yield of propylene oxide by modular design of each step of the reaction; the present invention also provides a method for synthesizing propylene oxide.

[0012] The technical solution adopted by this invention to solve its technical problem is:

[0013] The propylene oxide synthesis reaction system of the present invention includes a mixer, a mixing pipe at the top of the mixer, a circulation pipe at the bottom of the mixer, the circulation pipe and the mixing pipe being connected through a mixing nozzle, a methanol feed tank connected to the middle of the mixer, a propylene feed tank connected to the top of the mixing pipe, a circulation pump connected to the circulation pipe and connected to the upper part of the mixer, a feed pipe at the upper part of the mixer, a thermostat connected to the feed pipe, a pipeline reactor connected to the thermostat, a hydrogen peroxide feed tank connected between the feed pipe and the thermostat, several reaction units arranged in parallel inside the pipeline reactor, a deoxygenation tower connected to the pipeline reactor, a liquid sprayer and a gas nozzle inside the deoxygenation tower, a settling zone at the top of the deoxygenation tower, an absorption tower connected to the top of the settling zone, and a buffer tank connected to the bottom of the deoxygenation tower.

[0014] in:

[0015] The circulation pipe includes a main pipe and several branch pipes vertically arranged on the main pipe, and the mixing pipe includes a series of pipes and several manifolds vertically arranged on the series of pipes, with the branch pipes and manifolds arranged in combination.

[0016] The mixing nozzle includes an propylene nozzle and a circulating liquid nozzle. The propylene nozzle is located inside the circulating liquid nozzle, and a manifold passes through the side wall of the circulating liquid nozzle and connects to the propylene nozzle.

[0017] A feed pump is installed between the feed pipe and the thermostat, a hydrogen peroxide pump is installed between the hydrogen peroxide raw material tank and the thermostat, a methanol heating tank is connected to the end of the pipeline reactor near the thermostat, and a methanol recovery tank is connected to the end of the pipeline reactor near the deoxygenation tower.

[0018] The reaction unit is arranged in a rhomboid shape, with several groups of reaction units connected end to end in sequence. The reaction unit includes a unit inlet at the top and a unit outlet at the bottom. Several reaction micro-elements are arranged at intervals inside the reaction unit, and several filter screens are arranged between adjacent reaction micro-elements. The filter screens are connected to each other to separate the reaction micro-elements into a honeycomb structure. A heat dissipation hole is arranged in the middle of the reaction micro-element, and several catalyst particles are filled inside the reaction micro-element. The catalyst particles are located outside the heat dissipation hole.

[0019] The filter screen has a pore size of 3-5 mm, and the catalyst particles within the reaction micro-element are filled to a thickness of 30-70 mm. The catalyst particles are titanium-silicon molecular sieve catalyst particles, spherical in shape, with an average diameter of 10-15 mm. The filter screen is made of 316L stainless steel, and the open area of ​​the filter screen is >50%.

[0020] The gas nozzle is connected to a nitrogen tank, and the pipeline reactor is connected to a liquid sprayer located above the gas nozzle. The liquid sprayer and gas nozzle are positioned opposite each other. A liquid recovery tank is connected to the bottom of the absorption tower, and a tail gas treatment area is connected to the top of the absorption tower. The liquid recovery tank is connected to a buffer tank. Methanol is contained inside the absorption tower for absorption.

[0021] The synthesis method using the aforementioned propylene oxide synthesis reaction system includes the following steps:

[0022] A1. Propylene from the propylene feed tank and methanol from the methanol feed tank are transported to a mixer to be mixed to obtain a mixture. Hydrogen peroxide from the hydrogen peroxide feed tank is mixed with the mixture and transported to a thermostat for heating. Then it is transported to a pipeline reactor with several sets of reaction units to carry out a cyclization reaction to obtain a reaction solution.

[0023] A2. The reaction liquid is transported to the deoxygenation tower and deoxygenated by convection with nitrogen to obtain deoxygenated liquid. The gas carried by nitrogen is transported to the absorption tower for absorption to obtain absorbent liquid and tail gas. The tail gas is transported to the tail gas treatment area, and the absorbent liquid is recovered to the liquid recovery tank. Then, it is transported together with the deoxygenated liquid to the buffer tank to obtain crude propylene oxide. The crude propylene oxide is refined to obtain propylene oxide product.

[0024] In step A1, the mixing temperature is 10-25℃, the mixing pressure is 2-3MPa, the hydrogen peroxide concentration is 45-55wt.%, the molar ratio of hydrogen peroxide in hydrogen peroxide to propylene in the mixture is 1:1.02-1.04, the heating temperature is 40-50℃, the cyclization reaction temperature is 50-60℃, and the cyclization reaction time in each reaction unit is 3-5min. In step A2, the nitrogen pressure is 1.5-2MPa, and the nitrogen temperature is -20 to 0℃.

[0025] In step A1, after the cyclization reaction, heated methanol is transported to the pipeline reactor through a methanol heating tank at a temperature of 150-165°C for 4-6 hours, and then recovered to a methanol recovery tank.

[0026] The beneficial effects of this invention are:

[0027] This invention achieves a new, green method for the continuous production of propylene oxide with higher efficiency, greater safety, and continuous operation through modular design of mixers, pipeline reactors, and deoxygenation towers. It improves reaction efficiency and selectivity by suppressing side reactions at their source: the structural design of reaction units and honeycomb-shaped reaction micro-elements achieves breakthroughs in both quantity and quality. The reaction units within the pipeline reactor increase the contact efficiency of propylene, hydrogen peroxide, and catalyst by orders of magnitude, significantly accelerating the main reaction rate. The cooling process within the reaction units through heat dissipation holes fundamentally eliminates localized overheating, greatly suppressing hydrogen peroxide decomposition and propylene oxide ring-opening side reactions, thereby significantly improving the selectivity and yield of propylene oxide.

[0028] This invention heats a mixture and hydrogen peroxide in a thermostat before flowing into the reaction unit of a pipeline reactor. After entering the reaction unit, the mixture and hydrogen peroxide are dispersed through a filter and enter different reaction micro-elements within the reaction unit, where they come into contact with catalyst particles filled in the micro-elements. Under the catalysis of the catalyst particles, propylene and hydrogen peroxide react on the catalyst surface to produce propylene oxide. At the same time, unreacted raw materials enter the next reaction micro-element. Through flow and mixing in the reaction micro-elements, dispersion and convection are formed to achieve a complete reaction, thus realizing the conversion of propylene. This can promote the complete conversion of propylene and greatly improve the product yield.

[0029] The mixer uses a circulating pump and mixing nozzles to generate forced circulation and mixing of liquids. Methanol and propylene are separately injected into the mixer and forcibly mixed through the mixing nozzles. Based on the height of the liquid level rise in the mixer, the circulating pump is activated to further promote the flow and mixing of methanol and propylene. Under optimized pressure and temperature parameters, liquid propylene is efficiently dissolved in methanol to form a homogeneous and stable mixture, which facilitates the feeding reaction. The mixing nozzles spray propylene and methanol out through a unified outlet for deep mixing in the mixer. Subsequently, the mixture is further homogenized by the circulating pump and mixed with the newly added propylene and methanol from the mixing nozzles to obtain more mixture. This achieves a dual process of supplementary feeding and material mixing, resulting in a more stable mixture. This pretreatment process provides ideal reaction raw materials for the pipeline reactor, ensuring that the main reaction proceeds under optimal conditions.

[0030] After the reaction is complete, a deoxygenation tower is set up. High-pressure, low-temperature nitrogen is used to purge the reaction liquid online to obtain a deoxygenated liquid. The reaction liquid enters the deoxygenation tower from top to bottom, while the nitrogen enters from bottom to top. The low-temperature nitrogen purging can remove oxygen from the reaction liquid, ensuring safer post-processing operations. The deoxygenated reaction liquid is stored for easy separation and purification operations. The liquid entrained by nitrogen comes into contact with other liquids in the settling zone, forming larger droplets that fall. Some organic phase enters an absorption tower with methanol as the solvent along with nitrogen and oxygen for absorption. The liquid that is not settled or vaporized is transported to a liquid recovery tank, mainly containing propylene, a small amount of methanol, and a small amount of propylene oxide. The unabsorbed gases, nitrogen, oxygen, and a small amount of organic matter, enter the tail gas treatment. The oxygen in the reaction liquid is removed through secondary gas separation, and all the product is stored, reducing the loss of propylene oxide and ensuring the safety of post-processing operations. This design effectively removes dissolved oxygen accumulated in the system before it enters the post-processing stage, fundamentally eliminating the risk of explosion, stabilizing the crude propylene oxide, achieving inherent safety, and ensuring the safe and stable operation of subsequent distillation and storage units.

[0031] This invention solves the core problem of "reaction efficiency and selectivity" through a pipeline reactor. It addresses the pain points of safe and continuous production through innovative raw material mixing, cyclization reaction unit, deoxygenation design and modular operation, ultimately improving product yield while reducing overall operating costs. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the synthesis reaction system structure of the present invention;

[0033] Figure 2 yes Figure 1 Enlarged view of point A in the middle;

[0034] Figure 3 This is a schematic diagram of the mixing pipe structure of the present invention;

[0035] Figure 4 This is a schematic diagram of the circulation pipe structure of the present invention;

[0036] Figure 5 This is a schematic diagram of the cross-sectional structure of the reaction unit of the present invention;

[0037] Figure 6 yes Figure 5 Enlarged view at point B in the middle;

[0038] Figure 7 This is a schematic diagram of the filter structure of the present invention;

[0039] Figure 8 This is a schematic diagram of the reaction unit structure of the present invention;

[0040] In the diagram: 1. Propylene feedstock tank; 2. Methanol feedstock tank; 3. Mixing pipe; 4. Mixer; 5. Circulation pump; 6. Circulation pipe; 7. Mixing nozzle; 8. Feed pipe; 9. Hydrogen peroxide feedstock tank; 10. Feed pump; 11. Hydrogen peroxide pump; 12. Thermostat; 13. Pipeline reactor; 14. Reaction unit; 15. Liquid sprayer; 16. Nitrogen tank; 17. Gas nozzle; 18. Deoxidizer; 19. Settling zone; 20. Buffer tank ; 21. Absorption tower; 22. Liquid recovery tank; 23. Tail gas treatment area; 24. Methanol heating tank; 25. Methanol recovery tank; 301. Tube; 302. Manifold; 601. Main pipe; 602. Branch pipe; 701. Propylene nozzle; 702. Circulating liquid nozzle; 1401. Unit inlet; 1402. Filter screen; 1403. Reaction element; 1404. Catalyst particles; 1405. Unit outlet; 1406. Heat dissipation hole. Detailed Implementation

[0041] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0042] Example 1

[0043] like Figure 1-8 As shown, the propylene oxide synthesis reaction system includes a mixer 4, a mixing pipe 3 at the top of the mixer 4, and a circulation pipe 6 at the bottom of the mixer 4. The circulation pipe 6 and the mixing pipe 3 are connected through a mixing nozzle 7. A methanol feed tank 2 is connected to the middle of the mixer 4, and a propylene feed tank 1 is connected to the top of the mixing pipe 3. A circulation pump 5 is connected to the circulation pipe 6 and is connected to the upper part of the mixer 4. A feed pipe 8 is installed at the upper part of the mixer 4 and is connected to a thermostat 12. The thermostat 12 is connected to the pipeline reactor 13. The feed pipe 8 is connected to the thermostat 12 via a hydrogen peroxide raw material tank 9. Several sets of reaction units 14 are arranged in parallel inside the pipeline reactor 13. The pipeline reactor 13 is connected to a deoxygenation tower 18. The deoxygenation tower 18 is equipped with a liquid sprayer 15 and a gas nozzle 17. A settling zone 19 is set at the top of the deoxygenation tower 18. An absorption tower 21 is connected to the top of the settling zone 19. A buffer tank 20 is connected to the bottom of the deoxygenation tower 18.

[0044] The circulation pipe 6 includes a main pipe 601 and several branch pipes 602 vertically arranged on the main pipe 601. The mixing pipe 3 includes a tube 301 and several manifolds 302 vertically arranged on the tube 301. The branch pipes 602 and the manifolds 302 are arranged in a coordinated manner.

[0045] The mixing nozzle 7 includes an propylene nozzle 701 and a circulating liquid nozzle 702. The propylene nozzle 701 is located inside the circulating liquid nozzle 702, and the manifold 302 passes through the side wall of the circulating liquid nozzle 702 and connects to the propylene nozzle 701.

[0046] A feed pump 10 is installed between the feed pipe 8 and the thermostat 12, a hydrogen peroxide pump 11 is installed between the hydrogen peroxide raw material tank 9 and the thermostat 12, a methanol heating tank 24 is connected to one end of the pipeline reactor 13 near the thermostat 12, and a methanol recovery tank 25 is connected to one end of the pipeline reactor 13 near the deoxygenation tower 18.

[0047] The reaction unit 14 is arranged in a rhomboid shape. Several groups of reaction units 14 are connected end to end in sequence. The reaction unit 14 includes a unit inlet 1401 at the top and a unit outlet 1405 at the bottom. Several reaction micro elements 1403 are arranged at intervals inside the reaction unit 14. Several filters 1402 are arranged between adjacent reaction micro elements 1403. The filters 1402 are connected to each other to separate the reaction micro elements 1403 to form a honeycomb structure. A heat dissipation hole 1406 is arranged in the middle of the reaction micro element 1403. Several catalyst particles 1404 are filled inside the reaction micro element 1403. The catalyst particles 1404 are located outside the heat dissipation hole 1406.

[0048] The filter screen 1402 has a pore size of 5 mm, and the catalyst particles 1404 in the reaction micro-element 1403 have a filling thickness of 70 mm. The catalyst particles 1404 are titanium-silicon molecular sieve catalyst particles, and the catalyst particles 1404 are spherical in shape with an average diameter of 10 mm.

[0049] The gas nozzle 17 is connected to the nitrogen tank 16, the pipeline reactor 13 is connected to the liquid sprayer 15, the liquid sprayer 15 is located above the gas nozzle 17, and the liquid sprayer 15 and the gas nozzle 17 are arranged opposite to each other. The bottom of the absorption tower 21 is connected to the liquid recovery tank 22, and the top of the absorption tower 21 is connected to the tail gas treatment area 23. The liquid recovery tank 22 is connected to the buffer tank 20.

[0050] The synthesis method using a propylene oxide synthesis reaction system includes the following steps:

[0051] A1. Propylene from propylene feedstock tank 1 and methanol from methanol feedstock tank 2 are transported to mixer 4 and mixed at 15°C and 2MPa. When the methanol level exceeds the top of the bottom mixing nozzle 7, circulation pump 5 is turned on to promote dynamic circulation and mixing of methanol and propylene to obtain a mixture. When the level of the mixture rises to the top of mixer 4, 50wt.% hydrogen peroxide from hydrogen peroxide feedstock tank 9 is mixed with the mixture at a molar ratio of hydrogen peroxide in hydrogen peroxide to propylene in the mixture of 1:1.03 and transported to thermostat 12 to be heated to 45°C. Then it is transported to pipeline reactor 13, which is equipped with 9 sets of reaction units 14, and cyclization reaction is carried out at 55°C. In reaction unit 14, hydrogen peroxide and mixture pass through unit inlet 1401 and filter screen 1402 and enter reaction micro-element 1403 filled with TS-1 catalyst particles to carry out cyclization reaction. The cyclization reaction time in each set of reaction units 14 is 3min to obtain reaction solution.

[0052] After the cyclization reaction, heated methanol is transported to the pipeline reactor 13 through the methanol heating tank 24 at a heating temperature of 160°C for 5 hours. Then it is recovered to the methanol recovery tank 25. The interval between transporting heated methanol is 340 days.

[0053] A2. The reaction liquid is transported to the deoxygenation tower 18 and dispersed into droplets by the liquid sprayer 15. It then undergoes deoxygenation by convection with nitrogen gas sprayed from the gas nozzle 17 at 1.5 MPa and -20°C, resulting in a deoxygenated liquid. During the deoxygenation process, some liquid will be mixed with the oxygen carried by the nitrogen gas. After preliminary separation in the settling zone 19, the liquid is transported to the absorption tower 21 for absorption to obtain the absorbent liquid and tail gas. The tail gas is transported to the tail gas treatment zone 23 for treatment before being discharged. The absorbent liquid is recovered to the liquid recovery tank 22 and then transported together with the deoxygenated liquid to the buffer tank 20 to obtain crude propylene oxide. The conversion rate of hydrogen peroxide is 98%, and the selectivity of propylene is 97%.

[0054] During the refining process, crude propylene oxide is first separated into propylene-rich gas and propylene oxide liquid by flash evaporation at 1 MPa and 60°C. The propylene-rich gas is then liquefied and separated at 0.09 MPa and 96°C, and refined at 0.05 MPa and 80°C. It is then washed with alcohol at 0.02 MPa and 10°C, and finally separated into propane waste gas at 2.1 MPa and 65°C. Propylene is recovered and recycled at 2.1 MPa and 100°C. The propylene oxide liquid is pre-separated at 0.09 MPa and 87°C, and then refined through a three-stage refining tower. Water, hydrazine, and NaOH are added in the middle section of the refining tower for extraction reaction. Finally, water and propylene oxide are efficiently separated in the top rectification section of the tower to obtain high-purity propylene oxide.

[0055] Methanol in methanol recovery tank 25 is hydrogenated at 0.6 MPa and 90°C to remove residual hydrogen peroxide, then impurities are adsorbed in a resin tower at 0.45 MPa and 45°C, and finally pure methanol is recovered through two distillations. The waste liquid is then evaporated.

[0056] The absorbent in liquid recovery tank 22 is subjected to four-effect evaporation and dehydration at -0.03MPa to 0.8MPa, and then stripped at -0.085MPa and 135℃ to remove organic matter. Finally, through fractionation operations such as light removal, separation of propylene glycol at -0.085MPa and 135℃, purification, and ether removal at atmospheric pressure and 129℃, byproducts such as propylene glycol, propylene glycol monomethyl ether, and propylene glycol isomonomethyl ether are separated.

[0057] After refining the crude propylene oxide, a propylene oxide product with a purity of 99.98% was obtained.

[0058] Example 2

[0059] The propylene oxide synthesis reaction system is the same as in Example 1.

[0060] The synthesis method using a propylene oxide synthesis reaction system includes the following steps:

[0061] A1. Propylene from propylene feedstock tank 1 and methanol from methanol feedstock tank 2 are transported to mixer 4 and mixed at 10°C and 3MPa. When the methanol level exceeds the top of the bottom mixing nozzle 7, circulation pump 5 is turned on to promote dynamic circulation and mixing of methanol and propylene to obtain a mixture. When the level of the mixture rises above mixer 4, 45wt.% hydrogen peroxide from hydrogen peroxide feedstock tank 9 is mixed with the mixture at a molar ratio of hydrogen peroxide in hydrogen peroxide to propylene in the mixture of 1:1.02 and transported to thermostat 12 to be heated to 50°C. Then it is transported to pipeline reactor 13, which is equipped with 9 sets of reaction units 14, and cyclization reaction is carried out at 50°C. In reaction unit 14, hydrogen peroxide and mixture pass through unit inlet 1401 and filter screen 1402 and enter reaction micro-element 1403 filled with TS-1 catalyst particles to carry out cyclization reaction. The cyclization reaction time in each set of reaction units 14 is 4min to obtain reaction solution.

[0062] After the cyclization reaction, heated methanol is transported to the pipeline reactor 13 through the methanol heating tank 24 at a heating temperature of 165°C for 4 hours. It is then recovered to the methanol recovery tank 25. The interval between transporting heated methanol is 352 days.

[0063] A2. The reaction liquid is transported to the deoxygenation tower 18 and dispersed into droplets by the liquid sprayer 15. It then undergoes deoxygenation by convection with nitrogen gas sprayed from the gas nozzle 17 at 1.5 MPa and -10°C, resulting in a deoxygenated liquid. During the deoxygenation process, some liquid will be mixed with the oxygen carried by the nitrogen gas. After preliminary separation in the settling zone 19, the liquid is transported to the absorption tower 21 for absorption to obtain the absorbent liquid and tail gas. The tail gas is transported to the tail gas treatment zone 23 for treatment before being discharged. The absorbent liquid is recovered to the liquid recovery tank 22 and then transported together with the deoxygenated liquid to the buffer tank 20 to obtain crude propylene oxide. The conversion rate of hydrogen peroxide is 97.8%, and the selectivity of propylene is 96.5%.

[0064] The refining and recycling process is the same as in Example 1.

[0065] After refining the crude propylene oxide, a propylene oxide product with a purity of 99.96% was obtained.

[0066] Example 3

[0067] The propylene oxide synthesis reaction system is the same as in Example 1.

[0068] The synthesis method using a propylene oxide synthesis reaction system includes the following steps:

[0069] A1. Propylene from propylene feedstock tank 1 and methanol from methanol feedstock tank 2 are transported to mixer 4 and mixed at 25°C and 2MPa. When the methanol level exceeds the top of the bottom mixing nozzle 7, circulation pump 5 is turned on to promote dynamic circulation and mixing of methanol and propylene to obtain a mixture. When the level of the mixture rises above mixer 4, 55wt.% hydrogen peroxide from hydrogen peroxide feedstock tank 9 is mixed with the mixture at a molar ratio of hydrogen peroxide in hydrogen peroxide to propylene in the mixture of 1:1.04 and transported to thermostat 12 to be heated to 40°C. Then it is transported to pipeline reactor 13, which is equipped with 9 sets of reaction units 14, and cyclization reaction is carried out at 60°C. In reaction unit 14, hydrogen peroxide and mixture pass through unit inlet 1401 and filter screen 1402 and enter reaction micro-element 1403 filled with TS-1 catalyst particles to carry out cyclization reaction. The cyclization reaction time in each set of reaction units 14 is 5min to obtain reaction solution.

[0070] After the cyclization reaction, heated methanol is transported to the pipeline reactor 13 through the methanol heating tank 24 at a heating temperature of 150°C for 6 hours. It is then recovered to the methanol recovery tank 25. The interval between transporting heated methanol is 348 days.

[0071] A2. The reaction liquid is transported to the deoxygenation tower 18 and dispersed into droplets by the liquid sprayer 15. It then undergoes deoxygenation by convection with nitrogen gas at 2MPa and 0℃ sprayed from the gas nozzle 17 to obtain a deoxygenated liquid. During the deoxygenation process, some liquid will be mixed with the oxygen carried by the nitrogen gas. After preliminary separation in the settling zone 19, it is transported to the absorption tower 21 for absorption to obtain the absorbent liquid and tail gas. The tail gas is transported to the tail gas treatment zone 23 for treatment and then discharged. The absorbent liquid is recovered to the liquid recovery tank 22 and then transported together with the deoxygenated liquid to the buffer tank 20 to obtain crude propylene oxide. The conversion rate of hydrogen peroxide is 97.4%, and the selectivity of propylene is 97.2%.

[0072] The refining and recycling process is the same as in Example 1.

[0073] After refining the crude propylene oxide, a propylene oxide product with a purity of 99.97% was obtained.

[0074] Comparative Example 1

[0075] Remove the mixing nozzle 7 inside the mixer 4, and follow the same steps as in Example 1. The conversion rate of hydrogen peroxide is 94.8%, and the selectivity of propylene is 95%.

[0076] Comparative Example 2

[0077] The reaction unit 14 inside the pipeline reactor 13 was removed, and the remaining steps were the same as in Example 1. The conversion rate of hydrogen peroxide was 93.5%, and the selectivity of propylene was 94.1%.

[0078] Comparative Example 3

[0079] Remove the gas nozzle 17 inside the deoxygenation tower 18, and follow the same steps as in Example 1. The crude propylene oxide contains a lot of oxygen and cannot be stored stably.

Claims

1. A propylene oxide synthesis reaction system, comprising a mixer (4), characterized in that, The mixer (4) has a mixing pipe (3) at the top and a circulation pipe (6) at the bottom. The circulation pipe (6) includes a main pipe (601) and several branch pipes (602) vertically arranged on the main pipe (601). The mixing pipe (3) includes a tube (301) and several manifolds (302) vertically arranged on the tube (301). The branch pipes (602) and manifolds (302) are configured to cooperate. The circulation pipe (6) and the mixing pipe (3) are connected through a mixing nozzle (7). The mixing nozzle (7) includes an propylene nozzle (701) and a circulating liquid nozzle (702). The propylene nozzle (701) is equipped with... Inside the circulating liquid nozzle (702), a manifold (302) is connected to the propylene nozzle (701) through the side wall of the circulating liquid nozzle (702). A methanol feed tank (2) is connected to the middle of the mixer (4), and a propylene feed tank (1) is connected to the top of the mixing pipe (3). A circulation pump (5) is connected to the circulation pipe (6), and the circulation pump (5) is connected to the upper part of the mixer (4). A feed pipe (8) is provided on the upper part of the mixer (4), and a thermostat (12) is connected to the feed pipe (8). A pipeline reactor (13) is connected to the thermostat (12). The feed pipe (8) and the thermostat (12) are connected to each other. There is a hydrogen peroxide raw material tank (9), and a pipeline reactor (13) with several sets of reaction units (14) inside. The reaction units (14) are arranged in a rhomboid shape. The reaction units (14) are connected end to end in sequence. The reaction unit (14) includes a unit inlet (1401) at the top and a unit outlet (1405) at the bottom. The reaction unit (14) is equipped with several reaction micro-elements (1403) at intervals. Several filter screens (1402) are arranged between adjacent reaction micro-elements (1403). The filter screens (1402) are connected to each other to separate the reaction micro-elements (1403) to form The reactor has a honeycomb structure with a heat dissipation hole (1406) in the middle of the reaction element (1403). The reaction element (1403) is filled with a number of catalyst particles (1404), which are located outside the heat dissipation hole (1406). The pipeline reactor (13) is connected to a deoxygenation tower (18). The deoxygenation tower (18) is equipped with a liquid sprayer (15) and a gas nozzle (17). The top of the deoxygenation tower (18) is equipped with a settling zone (19). The top of the settling zone (19) is connected to an absorption tower (21). The bottom of the deoxygenation tower (18) is connected to a buffer tank (20). The mixer generates forced circulation and mixing of liquids through a circulation pump and mixing nozzles. Methanol and propylene are injected into the mixer separately and mixed by forced injection through the mixing nozzles. The circulation pump is turned on according to the height of the liquid level rise in the mixer to further promote the flow and mixing of methanol and propylene. The mixing nozzles spray propylene and methanol out through a unified outlet.

2. The propylene oxide synthesis reaction system according to claim 1, characterized in that, A feed pump (10) is installed between the feed pipe (8) and the thermostat (12), a hydrogen peroxide pump (11) is installed between the hydrogen peroxide raw material tank (9) and the thermostat (12), a methanol heating tank (24) is connected to one end of the pipeline reactor (13) near the thermostat (12), and a methanol recovery tank (25) is connected to one end of the pipeline reactor (13) near the deoxygenation tower (18).

3. The propylene oxide synthesis reaction system according to claim 1, characterized in that, The filter screen (1402) has a pore size of 3-5 mm, and the catalyst particles (1404) in the reaction micro-element (1403) have a filling thickness of 30-70 mm. The catalyst particles (1404) are titanium-silicon molecular sieve catalyst particles, and the catalyst particles (1404) are spherical in shape with an average diameter of 10-15 mm.

4. The propylene oxide synthesis reaction system according to claim 1, characterized in that, A gas nozzle (17) is connected to a nitrogen tank (16), a pipeline reactor (13) is connected to a liquid sprayer (15), the liquid sprayer (15) is located above the gas nozzle (17), the liquid sprayer (15) and the gas nozzle (17) are arranged opposite to each other, a liquid recovery tank (22) is connected to the bottom of the absorption tower (21), a tail gas treatment area (23) is connected to the top of the absorption tower (21), and the liquid recovery tank (22) is connected to the buffer tank (20).

5. A synthesis method using the propylene oxide synthesis reaction system according to any one of claims 1-4, characterized in that, Includes the following steps: A1. Propylene in propylene raw material tank (1) and methanol in methanol raw material tank (2) are transported to mixer (4) to mix and obtain a mixture. Hydrogen peroxide in hydrogen peroxide raw material tank (9) is mixed with the mixture and transported to thermostat (12) for heating. Then it is transported to pipeline reactor (13) with several sets of reaction units (14) for cyclization reaction to obtain reaction liquid. A2. The reaction liquid is transported to the deoxygenation tower (18) and deoxygenated by convection with nitrogen to obtain deoxygenated liquid. The gas carried by nitrogen is transported to the absorption tower (21) to absorb and obtain absorbent liquid and tail gas. The tail gas is transported to the tail gas treatment area (23). The absorbent liquid is recovered to the liquid recovery tank (22) and then transported together with the deoxygenated liquid to the buffer tank (20) to obtain crude propylene oxide. The crude propylene oxide is refined to obtain propylene oxide product.

6. The synthesis method according to claim 5, characterized in that, In step A1, the mixing temperature is 10-25℃, the mixing pressure is 2-3MPa, the hydrogen peroxide concentration is 45-55wt.%, the molar ratio of hydrogen peroxide in hydrogen peroxide to propylene in the mixture is 1:1.02-1.04, the heating temperature is 40-50℃, the cyclization reaction temperature is 50-60℃, the cyclization reaction time in each reaction unit (14) is 3-5min, and in step A2, the nitrogen pressure is 1.5-2MPa and the nitrogen temperature is -20-0℃.

7. The synthesis method according to claim 5, characterized in that, After the cyclization reaction in step A1, heated methanol is transported to the pipeline reactor (13) through the methanol heating tank (24) at a heating temperature of 150-165℃ for 4-6 hours, and then recovered to the methanol recovery tank (25).

Images