Bubble generator, reactor and method for preparing propylene carbonate by absorbing carbon dioxide by propylene oxide

Abstract

The present invention relates to the field of chemical engineering technology and discloses a bubble generator, a reactor, and a system for enhancing a gas-liquid reaction using microbubbles, as well as a method for producing propylene carbonate by absorbing carbon dioxide with propylene oxide. A reaction solution consisting of propylene oxide, a catalyst, an auxiliary agent, and a solvent, propylene carbonate, is added to a reactor, in which a bubble generator is disposed. The carbon dioxide feed gas is passed through the microbubble generator to form carbon dioxide microbubbles, which then contact and react with the reaction solution at a specific temperature and pressure to produce propylene carbonate. The present invention utilizes the positioning of the bubble generator and the design of its branches to generate CO2 microbubbles suitable for the reaction under high temperature and high pressure, effectively enhancing the reaction between carbon dioxide and propylene oxide and improving the mass transfer efficiency and reaction speed of the gas-liquid reaction. The present invention also features a high yield of propylene carbonate.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical engineering, in particular to a bubble generator, a reactor and a method for preparing propylene carbonate by absorbing carbon dioxide with propylene oxide. Background Art

[0002] Carbon dioxide is the end product of the oxidation and combustion of fossil fuels, particularly coal and oil. Since the advent of industrial production, the extensive use of fossil energy has led to a gradual increase in the concentration of carbon dioxide in the atmosphere, making it a major greenhouse gas, directly contributing to rising global temperatures and climate anomalies, posing a serious threat to the human environment. On the other hand, CO₂ is the most abundant C₁ resource, making its conversion and utilization of CO₂ of significant importance in both environmental protection and resource management. However, the CO₂ molecule itself is very stable and difficult to react with other substances. Currently, few industrial production routes using CO₂ as a raw material exist, and the synthesis of propylene carbonate (PC) from CO₂ and propylene oxide (PO) is one such route.

[0003] The reaction of carbon dioxide with epoxides to form five-membered cyclic carbonates has been extensively studied. Cyclic carbonates are used in a variety of applications, including as aprotic polar solvents, battery electrolytes, polycarbonate precursors, pharmaceuticals, and intermediates in fine chemical synthesis. Propylene carbonate (PC), also known as propylene carbonate, is a heterocyclic ketone with the molecular formula C4H6O3. It is a colorless, odorless, pale yellow, transparent liquid that is soluble in water and carbon tetrachloride and miscible with ether, acetone, and benzene. It is an excellent polar solvent with an intrinsic molecular weight of 102.09, a melting point of -48.8°C, a boiling point of 242°C, and a relative density of 1.2069. Propylene carbonate has a high solubility for acidic gases such as CO2 and H2S, but has a low solubility for gases such as H2, N2, CO, and CH4. Therefore, it is an ideal and highly effective solvent for carbon dioxide (CO2) and sulfur removal in industries such as ammonia synthesis feed gas purification, natural gas purification, and hydrogen production. PC has a low vapor pressure and can absorb CO2 at room temperature. Solvent regeneration requires only depressurizing or bubbling the CO2-absorbed rich solution with air, without consuming heat. This is energy-efficient and environmentally friendly, with a simple process and low equipment investment. Due to its low toxicity, PC is also used as a solvent in the textile printing and dyeing industry, a dispersant for pigments and water-soluble organic dyes, and an extractant for olefins and aromatic hydrocarbons. It is also an excellent solvent for insoluble substances such as oil extraction, metal extraction, and lacquer plasticizers. Furthermore, propylene carbonate, as an electrolyte in second-generation lithium batteries, can protect graphite electrodes in harsh environments. It is currently in high demand in the US and European markets and serves as an excellent dielectric in high-energy batteries and capacitors in the electronics industry. Propylene carbonate and isocyanate, mixed in a certain ratio, can be used as a high-strength wood adhesive. Recently, propylene carbonate has also been used in a transesterification reaction with methanol to produce dimethyl carbonate, a widely used green chemical. Due to its wide range of uses, demand for propylene carbonate has surged. The conventional gas-liquid reaction of propylene oxide with CO2 can both recycle CO2 and address the greenhouse effect caused by its emissions.

[0004] In the prior art, the conventional reaction of carbon dioxide and propylene oxide has harsh reaction conditions, generally requiring a high temperature of over 100°C and a reaction pressure of about 4 MPa, and a long reaction cycle, generally requiring 4-24 hours. Summary of the Invention

[0005] To address the problems of harsh reaction conditions and long reaction cycles in the conventional reaction of carbon dioxide and propylene oxide in the prior art, the present invention provides a bubble generator, a reactor, and a method for preparing propylene carbonate by absorbing carbon dioxide by propylene oxide. The present invention can effectively reduce the reaction condition requirements, lower the reaction pressure, improve the mass transfer efficiency, and accelerate the efficiency of the reaction.

[0006] In order to achieve the above object, the present invention provides a bubble generator in one aspect, comprising: a main air inlet pipe having an air inlet, for passing raw gas into the bubble generator;

[0007] At least three first-level transverse branches are arranged in the radial direction of the main air intake pipe, each of the first-level transverse branches is radially provided with at least one first-level longitudinal branch, each of the first-level longitudinal branches is radially provided with at least three second-level transverse branches, each of the second-level transverse branches is radially provided with at least one second-level longitudinal branch, and the second-level longitudinal branches are provided with air outlets, and each of the air outlets is fixedly provided with an air outlet plate having multiple bubble holes for cutting the raw gas to form microbubbles.

[0008] Preferably, the inner diameter of each of the first-level transverse branches is 5 / 9 to 7 / 8 of the inner diameter of the main air intake pipe, and more preferably is arranged at a distance of 1 / 5 to 1 / 4 from the top end of the main air intake pipe.

[0009] Preferably, the inner diameter of each of the first-level longitudinal branches is 5 / 12 to 7 / 10 of the inner diameter of the main air intake pipe, and more preferably is arranged at a distance of 1 / 3 to 2 / 3 from the top end of the first-level transverse branch.

[0010] Preferably, the inner diameter of each of the secondary transverse branches is 5 / 18 to 7 / 17 of the inner diameter of the main air intake pipe, and more preferably is arranged at a distance of 1 / 3 to 2 / 3 from the top end of the primary longitudinal branch.

[0011] Preferably, the inner diameter of each of the secondary longitudinal branches is 5 / 36 to 7 / 34 of the inner diameter of the main air intake pipe, and more preferably is arranged at a distance of 1 / 3 to 2 / 3 from the top end of the secondary transverse branch.

[0012] Preferably, the inner diameter of each of the air outlets is 5 / 72 to 7 / 68 of the inner diameter of the main air inlet pipe.

[0013] Preferably, the diameter of each of the gas outlet plates is the same as the outer diameter of the gas outlet, the thickness is 0.5-2 mm, the porosity is 50%-70%, and the diameter of the bubble pores is 1-20 μm, preferably 5-20 μm.

[0014] Preferably, the bubble generator is adapted to the reactor, and more preferably, the inner diameter of the main air inlet pipe is 1 / 7 to 1 / 5 of the inner diameter of the reactor.

[0015] Preferably, the inner diameter of each of the first-level transverse branches is 1 / 9 to 1 / 8 of the inner diameter of the reactor, and more preferably is arranged at a distance of 1 / 5 to 1 / 4 from the top end of the main air inlet pipe.

[0016] Preferably, the inner diameter of each of the first-level longitudinal branches is 1 / 12 to 1 / 10 of the inner diameter of the reactor, and more preferably is arranged at a distance of 1 / 3 to 2 / 3 from the top of the first-level transverse branch.

[0017] Preferably, the inner diameter of each of the secondary transverse branches is 1 / 18 to 1 / 17 of the inner diameter of the reactor, and more preferably is arranged at a distance of 1 / 3 to 2 / 3 from the top of the primary longitudinal branch.

[0018] Preferably, the inner diameter of each of the secondary longitudinal branches is 1 / 34 to 1 / 36 of the inner diameter of the reactor, and is placed at a distance of 1 / 3 to 2 / 3 from the top of the secondary transverse branch.

[0019] Preferably, the inner diameter of each gas outlet is 1 / 68 to 1 / 72 of the inner diameter of the reactor.

[0020] Preferably, the diameter of each of the gas outlet plates is the same as the outer diameter of the gas outlet, the thickness is 0.5-2 mm, the porosity is 50%-70%, and the diameter of the bubble pores is 1-20 μm, preferably 5-20 μm.

[0021] A second aspect of the present invention provides a reactor, comprising at least two bubble generators according to the present invention, which are respectively arranged at the bottom of the reactor and on the inner wall at a distance of 1 / 2 to 2 / 3 from the bottom of the reactor.

[0022] Preferably, each of the bubble generators is wrapped by a stainless steel cover having a top plate, and the top plate has the same bubble aperture as that of the gas outlet plate, and is used for secondary cutting of the bubbles generated by the bubble generator.

[0023] Preferably, the inner diameter of the stainless steel cover is 1.2-1.5 times the overall length of the bubble generator, and the height is 1.1-1.5 times the overall height of the bubble generator.

[0024] Preferably, the reactor comprises at least a raw gas inlet corresponding to the bubble generator inlet on the bottom and the inner wall, and a liquid phase feed inlet.

[0025] A third aspect of the present invention provides a method for preparing propylene carbonate by absorbing carbon dioxide by propylene oxide, which is carried out in the reactor described in the present invention and comprises the following steps:

[0026] (1) dissolving propylene oxide, a catalyst, and an auxiliary agent in propylene carbonate to form a reaction solution;

[0027] (2) removing oxygen from the reactor and adding the reaction solution described in step 1) into the reactor through the liquid phase feed port;

[0028] (3) Carbon dioxide is introduced into each bubble generator through the raw gas inlet of the reactor and the main air inlet pipe of the bubble generator on the bottom and inner wall. After carbon dioxide microbubbles are formed by the bubble generator, they flow out from the air outlet plate and react with the reaction solution to obtain propylene carbonate.

[0029] Preferably, the catalyst in step 1) is a catalytic system comprising a potassium iodide catalyst and a crown ether auxiliary.

[0030] Preferably, the crown ethers are 18-crown 5 and 15-crown 5.

[0031] More preferably, the mass ratio of potassium iodide to propylene oxide is in the range of 1:400-1:50, and the mass ratio of the auxiliary agent to potassium iodide is in the range of 1:4-1:1.

[0032] Preferably, the catalyst in step 1) is an ammonium salt, preferably tetraethylammonium bromide.

[0033] More preferably, the mass ratio of tetraethylammonium bromide to propylene oxide is in the range of 1:400-1:50.

[0034] Preferably, the flow rate of the carbon dioxide in step 3) is 10-40 ml / min.

[0035] Preferably, the contact reaction conditions in step 3) include: reaction pressure of 0.5-4 MPa; reaction temperature of 80-120°C.

[0036] The technical solution of the present invention utilizes a specific microbubble generator to produce CO2 microbubbles suitable for the reaction at high temperature and pressure, thereby enhancing the reaction process. By enhancing gas-liquid reaction mass transfer through microbubbles, the reaction pressure and temperature required for the reaction of propylene oxide and carbon dioxide under conventional conditions can be effectively reduced, the reaction time can be shortened, the propylene carbonate yield can be increased, and the reaction efficiency can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is the relationship between the yield and time in the reaction of carbon dioxide and propylene oxide in reactor No. 1 of the present invention;

[0038] Figure 2 This is the relationship between the yield and time in the reaction of carbon dioxide and propylene oxide in a conventional tank reactor No. 2;

[0039] Figure 3 is the relationship between yield and temperature in the reaction of carbon dioxide and propylene oxide in reactor No. 1 of the present invention;

[0040] Figure 4 is the relationship between yield and pressure in the reaction of carbon dioxide and propylene oxide in Reactor No. 1 of the present invention;

[0041] Figure 5The size of microbubbles generated by the gas outlet plates with different micropore diameters at different gas flow rates in reactor No. 1 of the present invention is as follows;

[0042] Figure 6 is the relationship between the yield and the quality of the catalyst in the reaction of carbon dioxide and propylene oxide in Reactor No. 1 of the present invention;

[0043] Figure 7 is a schematic structural diagram of a bubble generator according to an embodiment of the present invention;

[0044] Figure 8 Schematic diagram of the structure of a reactor according to one embodiment of the present invention.

[0045] Description of Reference Numerals

[0046] 1 reactor; 2 stainless steel cover; 3 bubble generator; 4 air inlet; 5 main air inlet pipe; 6 first-level horizontal branch pipe; 7 first-level longitudinal branch pipe; 8 second-level horizontal branch pipe; 9 second-level longitudinal branch pipe; 10 air outlet; 11 air outlet plate. DETAILED DESCRIPTION

[0047] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0048] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0049] In the present invention, unless otherwise specified, directional words such as "up, down, left, right" generally refer to up, down, left, right as shown in the reference drawings; "inside, outside" refer to inside and outside relative to the outline of each component itself.

[0050] like Figure 8As shown, the first aspect of the present invention provides a bubble generator, the bubble generator 3 includes: a main air inlet pipe 5 with an air inlet 4, for passing the raw gas into the bubble generator 3; at least three first-level transverse branches 6 are arranged in the radial direction of the main air inlet pipe 5, each of the first-level transverse branches 6 is radially provided with at least one first-level longitudinal branch 7, each of the first-level longitudinal branches 7 is radially provided with at least three second-level transverse branches 8, each of the second-level transverse branches 8 is radially provided with at least one second-level longitudinal branch 9, the second-level longitudinal branch 9 is provided with an air outlet 10, each of the air outlets 10 is fixedly provided with an air outlet plate 11 with multiple bubble holes, for cutting the raw gas to form microbubbles, wherein the bubble generator of the present invention includes at least one air inlet 4 and at least 9 evenly distributed air outlets 10.

[0051] The conventional reaction of carbon dioxide and propylene oxide in the prior art has stringent reaction conditions, generally requiring temperatures above 100°C and reaction pressures of around 4 MPa, and a long reaction cycle, typically requiring 4-24 hours. The present invention utilizes a specific microbubble generator to generate CO2 microbubbles suitable for the reaction, enhancing the reaction process and effectively reducing reaction conditions and pressure, while improving mass transfer efficiency and accelerating the reaction.

[0052] According to a preferred embodiment of the present invention, the inner diameter of each of the first-level transverse branches 6 is 5 / 9 to 7 / 8 of the inner diameter of the main air intake pipe 5 , and is preferably placed at a distance of 1 / 5 to 1 / 4 from the top end of the main air intake pipe 5 .

[0053] According to a preferred embodiment of the present invention, the inner diameter of each of the first-level longitudinal branches 7 is 5 / 12 to 7 / 10 of the inner diameter of the main air intake pipe 5 , and is preferably placed at a distance of 1 / 3 to 2 / 3 from the top of the first-level transverse branch 6 .

[0054] According to a preferred embodiment of the present invention, the inner diameter of each of the secondary transverse branches 8 is 5 / 18 to 7 / 17 of the inner diameter of the main intake pipe 5 , and is preferably placed at a distance of 1 / 3 to 2 / 3 from the top of the primary longitudinal branch 7 .

[0055] According to a preferred embodiment of the present invention, the inner diameter of each of the secondary longitudinal branches 9 is 5 / 36 to 7 / 34 of the inner diameter of the main intake pipe 5 , and is preferably placed at a distance of 1 / 3 to 2 / 3 from the top end of the secondary transverse branch 8 .

[0056] According to a preferred embodiment of the present invention, the inner diameter of each of the air outlets 10 is 5 / 72 to 7 / 68 of the inner diameter of the main air inlet pipe 5 .

[0057] According to a preferred embodiment of the present invention, the diameter of each outlet plate 11 is the same as the outer diameter of the outlet port 10, the thickness is 0.5-2 mm, the porosity is 50%-70%, and the bubble pore diameter is 1-20 μm, preferably 5-20 μm.

[0058] According to a preferred embodiment of the present invention, the bubble generator 3 is adapted to the reactor, and preferably the inner diameter of the main air inlet pipe 5 is 1 / 7 to 1 / 5 of the inner diameter of the reactor.

[0059] According to a preferred embodiment of the present invention, the inner diameter of each of the first-level transverse branches 6 is 1 / 9 to 1 / 8 of the inner diameter of the reactor, and is preferably placed at a distance of 1 / 5 to 1 / 4 from the top of the main air inlet pipe 5.

[0060] According to a preferred embodiment of the present invention, the inner diameter of each of the first-level longitudinal branches 7 is 1 / 12 to 1 / 10 of the inner diameter of the reactor, and is preferably placed at a distance of 1 / 3 to 2 / 3 from the top of the first-level transverse branch 6.

[0061] According to a preferred embodiment of the present invention, the inner diameter of each of the secondary transverse branches 8 is 1 / 18 to 1 / 17 of the inner diameter of the reactor, and is preferably placed at a distance of 1 / 3 to 2 / 3 from the top of the primary longitudinal branch 7 .

[0062] According to a preferred embodiment of the present invention, the inner diameter of each of the secondary longitudinal branches 9 is 1 / 34 to 1 / 36 of the inner diameter of the reactor, and is preferably placed at a distance of 1 / 3 to 2 / 3 from the top of the secondary transverse branch 8.

[0063] According to a preferred embodiment of the present invention, the inner diameter of each gas outlet 10 is 1 / 68 to 1 / 72 of the inner diameter of the reactor, wherein the gas outlet 10 is arranged at the center of the top surface of the secondary longitudinal branch 9, and the sudden reduction of the inner diameter can increase the gas flow rate.

[0064] According to a preferred embodiment of the present invention, the diameter of each of the air outlet plates 11 is the same as the outer diameter of the air outlet 10, the thickness is 0.5-2 mm, the porosity is 50%-70%, and the diameter of the bubble pores is 1-20 μm, preferably 5-20 μm, wherein the air outlet plate 11 is preferably a microporous plate sintered from stainless steel, welded to the top of the air outlet 10.

[0065] like Figure 7 As shown, the second aspect of the present invention provides a reactor, which comprises at least two bubble generators 3 described in the present invention, which are respectively arranged at the bottom of the reactor 1 and on the inner wall at a distance of 1 / 2 to 2 / 3 from the bottom of the reactor 1.

[0066] In the present invention, the position of the bubble generator and the design and coordination of each branch pipe of the bubble generator can effectively enhance the reaction of carbon dioxide and propylene oxide, and improve the mass transfer efficiency and reaction speed of the gas-liquid reaction.

[0067] According to a preferred embodiment of the present invention, each bubble generator 3 is wrapped by a stainless steel cover 2 having a top plate, and the top plate has the same bubble aperture as the gas outlet plate 11, which is used for secondary cutting of the bubbles generated by the bubble generator 3.

[0068] According to a preferred embodiment of the present invention, the stainless steel cover 2 is cylindrical, and its bottom surface is connected to the bottom surface or wall surface of the reactor.

[0069] According to a preferred embodiment of the present invention, preferably, the inner diameter of the stainless steel cover 2 is 1.2-1.5 times the overall length of the bubble generator 3 , and the height is 1.2-1.5 times the overall height of the bubble generator 3 .

[0070] According to a preferred embodiment of the present invention, the reactor comprises at least a raw gas inlet corresponding to the gas inlet 4 of the bubble generator 3 on the bottom and the inner wall, and a liquid phase feed port.

[0071] The reactor of the present invention also includes a heating device, temperature and pressure measuring auxiliary reaction devices in the prior art and is connected to other equipment such as a high-pressure gas dissolving tank, a gas-liquid buffer tank and a condensation reflux device. Various pipelines or valves and components that may be needed in the industry can be added between each device or equipment as needed. The present invention has no special requirements for this and will not be described in detail here.

[0072] The present invention provides a method for preparing propylene carbonate by absorbing carbon dioxide by propylene oxide. The method is carried out in the reactor described in the present invention and comprises the following steps:

[0073] (1) Propylene oxide, a catalyst, and an auxiliary agent are dissolved in propylene carbonate to form a reaction solution.

[0074] (2) removing oxygen from the reactor and adding the reaction solution in step 1) into the reactor through the liquid phase feed port.

[0075] (3) Carbon dioxide is introduced into each bubble generator through the reactor's feed gas inlet and the main inlet pipe 5 of the bubble generator 3 on the bottom and inner wall. After being formed into carbon dioxide microbubbles by the bubble generator 3, the carbon dioxide bubbles flow out of the outlet plate 11 and react with the reaction solution to produce propylene carbonate. After the reaction is completed, the reaction products are qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and chromatography.

[0076] The present invention strengthens gas-liquid reaction mass transfer by microbubbles, and compared with the reaction of propylene oxide and carbon dioxide under conventional conditions, can effectively reduce the pressure and temperature required for the reaction, shorten the reaction time, increase the yield of propylene carbonate, and improve the reaction efficiency.

[0077] According to a preferred embodiment of the present invention, the catalyst in step 1) is a catalytic system comprising a potassium iodide catalyst and a crown ether auxiliary.

[0078] According to a preferred embodiment of the present invention, the preferred crown ethers are 18-crown 5 and 15-crown 5.

[0079] According to a preferred embodiment of the present invention, more preferably, the mass ratio of potassium iodide to propylene oxide is in the range of 1:400-1:50, and the mass ratio of the auxiliary agent to potassium iodide is in the range of 1:4-1:1.

[0080] According to a preferred embodiment of the present invention, the catalyst in step 1) is an ammonium salt, preferably tetraethylammonium bromide.

[0081] According to a preferred embodiment of the present invention, the mass ratio of tetraethylammonium bromide to propylene oxide is more preferably in the range of 1:400-1:50.

[0082] According to a preferred embodiment of the present invention, the flow rate of the carbon dioxide in step 3) is 10-40 ml / min.

[0083] According to a preferred embodiment of the present invention, the contact reaction conditions in step 3) include: reaction pressure of 0.5-4 MPa; reaction temperature of 80-120°C.

[0084] According to a preferred embodiment of the present invention, the bubble particle size range of the bubble generator generated in step 3) is 100-400 μm.

[0085] The present invention is further described below through examples and comparative examples, but the device and method of the present invention are not limited thereto.

[0086] The method of the present invention is further described below with reference to the embodiments.

[0087] Example 1

[0088] like Figure 8As shown, a micro bubble generator 3 is provided at the bottom of the reactor 1 and at the inner wall 1 / 2 from the bottom, and each bubble generator 3 is wrapped by a stainless steel cover 2. The inner diameter of the reactor 1 is 70 mm, the inner diameter of the main air inlet pipe 5 of the bubble generator 3 is 10 mm, the inner diameter of the first-level transverse branch 6 is 8 mm, and it is 1 / 5 of the distance from the top of the main air inlet pipe 5; the inner diameter of the first-level longitudinal branch 7 is 6 mm, and it is 2 / 3 of the distance from the top of the first-level transverse branch 6; the inner diameter of the second-level transverse branch 8 is 4 mm, and it is 1 / 4 of the distance from the top of the first-level transverse branch 6. The longitudinal branch 7 is at a distance of 1 / 3 from the top; the inner diameter of the secondary longitudinal branch 9 is 2 mm, and it is at a distance of 1 / 3 from the top of the secondary transverse branch 8; the inner diameter of the gas outlet 10 is 1 mm and the outer diameter is 2 mm; the diameter of the gas outlet plate 11 is 2 mm, the thickness is 1 mm, the porosity is 60%, the bubble pore diameter is 10 μm, the inner diameter of the stainless steel cover 2 is 45 mm, and the height is 28 mm. The reactor in this embodiment is defined as No. 1, and the reactor also includes auxiliary devices such as a heating jacket, a temperature control device, and a pressure control device.

[0089] The reaction was carried out in the reactor in Example 1, 20 g of propylene oxide was weighed and dissolved in 200 ml of propylene carbonate solution, and potassium iodide (KI) was added as a catalyst in a mass ratio of 1:50 to propylene oxide, and an auxiliary agent 18-crown 5 was added in a mass ratio of 1:2 to the catalyst to form a reaction solution, which was added to the reactor through a liquid phase feed port. Nitrogen was purged to remove oxygen in the reactor, and the reaction apparatus was heated to 120° C. using a heating jacket. CO2 was introduced from the two raw gas inlets of the reactor through a bubble generator 3 to form microbubbles. The flow rates of the bottom raw gas inlet and the side wall raw gas inlet were both 30 ml / min. The reaction pressure was adjusted to 2 MPa, and the carbon dioxide microbubble rate was maintained at 15 ml / min. Microbubbles were used to enhance the reaction of propylene oxide and CO2. The reaction temperature was maintained for 1 hour, the heating device was turned off, and the reaction apparatus was cooled with an ice-water mixture. After turning off CO2, the reaction solution was taken out, and the resultant was tested using GC to measure the yield of propylene carbonate (PC) in the resultant.

[0090] Comparative Example 1

[0091] Provided are a reaction apparatus and operating method for the reaction of carbon dioxide and propylene oxide in a conventional reactor. The apparatus primarily comprises a high-pressure reactor, designated as reactor No. 2, a heating jacket, a temperature control device, and a pressure control device. The operating method is as follows: 20 g of propylene oxide is weighed and dissolved in 200 ml of a propylene carbonate solution, followed by the addition of a catalyst, potassium iodide (KI), in a mass ratio of 1:50 to propylene oxide, and an auxiliary agent, 18-crown 5, in a mass ratio of 1:2 to the catalyst, to form a reaction solution, which is then transferred to a reactor. Nitrogen is purged three times to remove oxygen from the reactor, and the reactor is heated to 120° C. using a heating jacket. CO2 is introduced to adjust the reaction pressure to 2 MPa, and the reaction is carried out for 1 hour. The heating device is then turned off, and the reactor is cooled with an ice-water mixture to remove the reaction solution. The product is then tested using a GC to measure the yield of propylene carbonate (PC) in the product.

[0092] Test results of Example 1 and Comparative Example 1:

[0093] Experimental results of propylene oxide absorbing carbon dioxide reaction:

[0094] In the above experiment, in the No. 1 and No. 2 reactors used for the reaction of propylene oxide and carbon dioxide, the reactants are continuously converted into the product propylene carbonate as time goes by. Figure 1 and Figure 2 The figures show the relationship between PC yield and time in reactors 1 and 2, respectively. As can be seen from the figure, the yield of the ordinary reactor is only about 56% after 1 hour, and only reaches 74% after 1.5 hours, while the yield of the microbubble reactor is about 97% after 1 hour.

[0095] It can be seen that the use of a reactor containing a bubble generator can effectively enhance the reaction of carbon dioxide and propylene oxide. Microbubbles can effectively enhance the transfer efficiency of the gas-liquid reaction and increase the reaction speed.

[0096] Figure 3 This is the relationship between the PC generation rate and the reaction temperature in Reactor No. 1 of the present invention. It can be seen that as the temperature increases, under the same time conditions, when the temperature is low, the reactant conversion rate increases rapidly when the temperature is increased, and when the temperature is high, the reactant conversion rate does not change much when the temperature is increased. The reaction selectivity shows a trend of first increasing and then decreasing as the temperature increases. Therefore, choosing the optimal reaction temperature for the reaction can effectively improve the reaction efficiency.

[0097] same Figure 4 This is the relationship between the PC production rate and the reaction pressure in reactor No. 1 of the present invention. It can be seen that under the condition of 1 h, as the pressure increases, the PC yield continues to increase, but after 2 MPa, the reaction yield does not change much.

[0098] Figure 5In the reactor No. 1 of the present invention, gas outlet plates with different micropore diameters are used to generate microbubbles. The sizes of the microbubbles under different gas flow rates are as follows. In this experimental system, 30 ml / min is the optimal reaction flow rate. Because in this experimental system, the gas flow rate affects the state of the microbubbles, using microbubbles in better state can further accelerate the reaction rate and increase the yield of PC.

[0099] Figure 6 is the relationship between the yield and the quality of the catalyst in the reaction of carbon dioxide and propylene oxide in reactor No. 1 of the present invention; Figure 6 It can be seen that when the catalyst solubility is low, increasing the catalyst concentration can increase the reaction yield, but when the mass ratio of catalyst to propylene oxide is greater than 1:50, the improvement is no longer obvious.

[0100] The preferred embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various specific technical features in any appropriate manner. In order to avoid unnecessary repetition, the present invention will no longer describe various possible combinations separately. However, these simple modifications and combinations should also be regarded as the contents disclosed by the present invention, and all belong to the protection scope of the present invention; the present invention clearly and completely describes the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

Claims

1. A reactor, characterized in that The reactor (1) comprises at least two bubble generators (3), which are respectively arranged at the bottom of the reactor (1) and at a distance from the bottom of the reactor (1). to On the inner wall of the distance; The bubble generator (3) comprises: A main air inlet pipe (5) having an air inlet (4) for passing the raw gas into the bubble generator (3); At least three first-level transverse branches (6) are arranged radially on the main air inlet pipe (5), each of the first-level transverse branches (6) is radially provided with at least one first-level longitudinal branch (7), each of the first-level longitudinal branches (7) is radially provided with at least three second-level transverse branches (8), each of the second-level transverse branches (8) is radially provided with at least one second-level longitudinal branch (9), each of the second-level longitudinal branches (9) is provided with an air outlet (10), and each of the air outlets (10) is fixedly provided with an air outlet plate (11) having a plurality of bubble holes for cutting the raw gas to form microbubbles; The inner diameter of each of the first-level transverse branch pipes (6) is 5 / 9 to 7 / 8 of the inner diameter of the main air intake pipe (5); The inner diameter of each of the first-level longitudinal branch pipes (7) is equal to the inner diameter of the main air inlet pipe (5). to ; The inner diameter of each of the secondary transverse branches (8) is equal to the inner diameter of the main air intake pipe (5). Until July 17; The inner diameter of each secondary longitudinal branch pipe (9) is 5 / 36 to 1 / 36 of the inner diameter of the main air inlet pipe (5). ; The inner diameter of each of the air outlets (10) is 5 / 72 to 7 / 68 of the inner diameter of the main air inlet pipe (5); The diameter of each of the air outlet plates (11) is the same as the outer diameter of the air outlet (10), the thickness is 0.5-2 mm, the porosity is 50%-70%, and the diameter of the bubble pores is 1-20 μm.

2. The reactor according to claim 1, wherein Each of the first-level transverse branch pipes (6) is placed at a distance from the top of the main air inlet pipe (5). to distance; and / or Each of the first-level longitudinal branches (7) is placed at a distance from the top of the first-level transverse branch (6). to distance; and / or Each of the secondary transverse branches (8) is placed at a distance from the top of the primary longitudinal branch (7). to distance; and / or Each of the secondary longitudinal branches (9) is placed at a distance from the top of the secondary transverse branch (8). to distance; and / or The diameter of the bubble pores is 5-20 μm.

3. The reactor according to claim 1, wherein The bubble generator (3) is adapted to the reactor (1); and / or The inner diameter of each of the first-level transverse branches (6) is equal to the inner diameter of the reactor (1). to and / or The inner diameter of each of the first-level longitudinal branches (7) is equal to the inner diameter of the reactor (1). to and / or The inner diameter of each of the secondary transverse branches (8) is equal to the inner diameter of the reactor (1). to and / or The inner diameter of each of the secondary longitudinal branches (9) is 1 / 2 of the inner diameter of the reactor (1). to and / or The inner diameter of each gas outlet (10) is equal to the inner diameter of the reactor (1). to .

4. The reactor according to claim 3, wherein The inner diameter of the main air inlet pipe (5) is equal to the inner diameter of the reactor (1). to and / or Each of the first-level transverse branch pipes (6) is placed at a distance from the top of the main air inlet pipe (5). to distance; and / or Each of the first-level longitudinal branches (7) is placed at a distance from the top of the first-level transverse branch (6). to distance; and / or Each of the secondary transverse branches (8) is placed at a distance from the top of the primary longitudinal branch (7). to distance; and / or Each of the secondary longitudinal branches (9) is placed at a distance from the top of the secondary transverse branch (8). to Distance.

5. The reactor according to claim 1, wherein Each bubble generator (3) is wrapped by a stainless steel cover (2) having a top plate, wherein the top plate has the same bubble aperture as the gas outlet plate (11) and is used for secondary cutting of bubbles generated by the bubble generator (3).

6. The reactor according to claim 5, wherein The inner diameter of the stainless steel cover (2) is 1.2-1.5 times the overall length of the bubble generator (3), and the height is 1.2-1.5 times the overall height of the bubble generator (3).

7. The reactor according to claim 1, wherein The reactor (1) comprises at least a raw gas inlet corresponding to the gas inlet (4) of the bubble generator (3) on the bottom and the inner wall, and a liquid phase feed inlet.

8. A method for preparing propylene carbonate by absorbing carbon dioxide with propylene oxide, characterized in that: The method is carried out in a reactor according to any one of claims 1 to 7, and comprises the following: 1) Propylene oxide, catalyst and additive are dissolved in propylene carbonate to form a reaction solution; 2) removing oxygen from the reactor, and adding the reaction solution of step 1) into the reactor (1) through the liquid phase feed port; 3) Carbon dioxide is introduced into each bubble generator through the raw gas inlet of the reactor and the air inlet (4) of the main air inlet pipe (5) of the bubble generator (3) on the bottom and inner wall. After carbon dioxide microbubbles are formed by the bubble generator, they flow out from the air outlet plate (11) and react with the reaction solution to obtain propylene carbonate.

9. The method according to claim 8, wherein The catalyst in step 1) is a catalytic system comprising a potassium iodide catalyst and a crown ether auxiliary.

10. The method according to claim 9, wherein: In step 1), the catalyst includes crown ethers such as 18-crown 5 and 15-crown 5.

11. The method according to claim 10, wherein: The mass ratio of potassium iodide to propylene oxide is in the range of 1:400-1:50, and the mass ratio of the additive to potassium iodide is in the range of 1:4-1:

1.

12. The method according to claim 8, wherein In step 1), the catalyst is an ammonium salt.

13. The method according to claim 12, wherein: In step 1), the catalyst is tetraethylammonium bromide.

14. The method according to claim 13, wherein The mass ratio of tetraethylammonium bromide to propylene oxide is in the range of 1:400-1:

50.

15. The method according to claim 8, wherein Step 3) The flow rate of the carbon dioxide is 10-40 ml / min; and / or The contact reaction conditions in step 3) include: reaction pressure of 0.5-4 MPa; reaction temperature of 80-120°C.

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