Micro-channel reaction tube bundle and device and method for continuously preparing hexafluoropropylene oxide

Abstract

The invention belongs to the field of fluorine chemical industry, and particularly relates to a microchannel reaction tube bundle and a device and method for continuously preparing hexafluoropropylene oxide. The micro-channel reaction tube bundle comprises one or more parallel micro-channel reactors; each micro-channel reactor comprises a plurality of continuous reaction units; and each reaction unit comprises an S-shaped ascending section and a vertical descending section. When the microchannel reaction device provided by the invention is used for preparing hexafluoropropylene oxide, continuous synthesis can be realized under the conditions of normal temperature and lower pressure. The reaction is carried out in the micro-channel reactor, an amplification experiment is carried out, and the productivity reaches a pilot scale.

Description

Technical Field

[0001] The invention belongs to the field of fluorine chemical industry, and specifically relates to a microchannel reaction tube bundle, a device and a method for continuously preparing hexafluoropropylene oxide. Background Art

[0002] Hexafluoropropylene oxide (HFPO) is an important intermediate in organic fluorine chemistry. The fluorine-containing fine chemical industry chain with hexafluoropropylene oxide as the source is an important part of the fluorine chemical industry. Hexafluoropropylene oxide is an important raw material for a variety of fluorine-containing fine chemicals. A variety of downstream products can be derived from hexafluoropropylene oxide, including perfluoropropionyl fluoride, perfluorosulfonyl vinyl ether, perfluoroalkyl vinyl ether, perfluoropolyether, hexafluoroacetone, etc., and these derivatives can be used to prepare perfluorosulfonic acid ion membranes, soluble polytetrafluoroethylene, fluorinated surfactants, fluorinated medical anesthetics and other products. The downstream products of hexafluoropropylene oxide are used in many industries, including chemical engineering, aerospace, electronics, medicine, environmental protection, construction, fire protection and other fields. Therefore, how to synthesize high-quality hexafluoropropylene oxide is an important topic in the field of fluorine-containing fine chemicals.

[0003] DuPont first reported the synthesis method of hexafluoropropylene oxide in the 1960s. As the demand for hexafluoropropylene oxide increases year by year around the world, research on the synthesis of hexafluoropropylene oxide has become a hot topic in the fluorine chemical industry. At present, most of the synthesis processes of hexafluoropropylene oxide use hexafluoropropylene (HFP) as raw material to prepare hexafluoropropylene oxide through epoxidation reaction. Commonly used oxidants include oxygen as a gas oxidant and sodium hypochlorite or hydrogen peroxide as a liquid oxidant.

[0004] Oxygen oxidation method is a method for preparing hexafluoropropylene oxide under high temperature and high pressure with the participation of fluorinated solvent. Although the cost of the oxidant is very low, it is necessary to add expensive fluorinated solvent to control the reaction and produce the by-product of acyl fluoride. The purification process is more complicated, and a certain amount of waste water will be produced in the purification process. The mainstream process of preparing hexafluoropropylene oxide propane by oxygen oxidation method is a batch process (US3600409, JP9052886, US3536733 and JP2003040879). Although the conversion rate of hexafluoropropylene and the selectivity of hexafluoropropylene oxide are higher in the process, the equipment utilization rate of the batch process is low. In order to ensure production capacity, the equipment volume is large, resulting in high construction cost and high risk.

[0005] In recent years, the continuous process of preparing hexafluoropropylene oxide propane by oxygen oxidation has been studied. Although patents CN101157669, CN201692802, and CN10651357 have achieved continuous production, the process is dangerous and the heat of reaction is not easy to diffuse. The reaction conditions are still harsh and still need to be carried out at a high temperature of more than 100°C and a pressure of more than 1.5MPa.

[0006] Liquid oxidant can be mainly divided into two oxidation systems of hydrogen peroxide and sodium hypochlorite, although liquid phase oxidation method can produce a certain amount of waste water, but the gas phase product produced by the method is relatively single, the oxidant adopted mainly comprises hydrogen peroxide (GB904877, US3858003 and JP63027487) and sodium hypochlorite (EP2409970, US4902810, US7405312 and CN102356072), the oxidation efficiency of liquid phase oxidation method is high, the reaction rate is fast, and no harmful acyl fluoride gas is produced in the reaction process. In addition, the reaction conditions of liquid oxidant are milder than oxygen oxidation, and the danger is low. Therefore, the reaction of hexafluoropropylene oxide is under mild conditions, and the target pursued in the fluorine chemical industry is always adopted to produce by continuous method. Summary of the invention

[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a microchannel reaction tube bundle, a device and a method for continuously preparing hexafluoropropylene oxide.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] A microchannel reaction tube bundle comprises one or more parallel microchannel reactors; each of the microchannel reactors comprises a plurality of continuous reaction units; each of the reaction units comprises an S-shaped ascending section and a vertical descending section.

[0010] The S segment is composed of two arc segments which are arranged opposite to each other.

[0011] The diameter of the pipeline constituting the reaction unit is 1.5-5 mm, preferably 4 mm.

[0012] The number of the reaction units is 1-20, preferably 4-8, and more preferably 4. The reaction units are made of a fluorine-containing plastic tube.

[0013] The present invention also includes a microchannel reaction device for continuously preparing hexafluoropropylene oxide, including a liquid distributor and the microchannel reaction tube bundle; the liquid distributor includes a liquid distributor body and a plurality of pipelines connected to the liquid distributor body; each of the pipelines is connected to one of the microchannel reactors.

[0014] Each of the pipelines is provided with a gas inlet connected to a gas storage tank; the liquid inlet on the liquid distributor body is connected to a liquid raw material preparation kettle; preferably, there are 10 pipelines.

[0015] A gas flow control valve is provided on the gas passage between the gas inlet and the gas storage tank; a reaction feed pump is provided on the liquid passage between the liquid inlet and the liquid raw material configuration kettle.

[0016] The outlet end of the microchannel reaction tube bundle is connected to the gas-liquid separation tank; the gas-liquid separation tank is provided with a liquid phase outlet and a gas phase outlet; the liquid phase outlet is respectively connected to the waste liquid discharge pipeline and the liquid recycling pipeline.

[0017] The present invention also includes a method for preparing hexafluoropropylene oxide using the microchannel reaction device, comprising the following steps: configuring a liquid raw material in a liquid raw material configuration kettle; the liquid raw material enters a liquid distributor and is mixed with a gas raw material, and then enters a microchannel reaction device for reaction, and after the reaction is completed, enters a gas-liquid separation tank for separation.

[0018] The liquid raw material includes the oxidant, potassium carbonate, potassium bicarbonate, a phase transfer catalyst and a solvent; the gas raw material is hexafluoropropylene;

[0019] Preferably, the oxidant is a sodium hypochlorite solution; the effective chlorine content of the sodium hypochlorite solution is 3.8%; the solvent is toluene, and the phase transfer catalyst is trioctylmethylammonium chloride;

[0020] Preferably, the mass ratio of the oxidant, potassium carbonate, potassium bicarbonate, solvent and phase transfer catalyst is (200-300):(1-10):(1-5):(10-50):(0.1-2); preferably 260:6:2:35:1.

[0021] The flow rate of the gas raw material entering the microchannel reactor is 0.3-0.58 kg / h; the flow rate of the liquid raw material entering the microchannel reactor is 36-72 kg / h; the reaction pressure of the microchannel reaction device is 0.1-0.4 MPa, and the temperature is -20°C to 50°C.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The microchannel reaction tube bundle of the present application is composed of one or more parallel microchannel reactors, each of which includes a plurality of continuous reaction units to form a reaction device of different lengths, and each of which includes an S-shaped ascending section and a vertical descending section. The reaction unit of gas and liquid presents an S-shape in the ascending stage, and the reaction unit of gas and liquid presents a straight line in the descending stage. In the entire microchannel reactor, when gas and liquid pass through, the gas moves forward along the pipeline direction, and the liquid moves downward due to gravity in the S-shaped ascending section perpendicular to the ground in the microchannel tube bundle reactor. In the narrow space of the microchannel reactor, due to space limitations, the degree of gas-liquid contact is aggravated, so that the gas and liquid are continuously tumbling in the S-shaped ascending section perpendicular to the ground, thereby achieving the purpose of sufficient mixing and contact between gas and liquid, which is beneficial to the reaction result; and the vertical descending section is a straight line, which can make the liquid with higher density reach the vertical bottom faster, seal the limited space of the microchannel, and facilitate full contact with the gas in the next S-shaped ascending section.

[0024] The use of the microchannel reaction device of the present application to prepare hexafluoropropylene oxide can achieve continuous synthesis under normal temperature and relatively low pressure conditions. The reaction is carried out in a microchannel reactor, and an amplification experiment is carried out, and the production capacity reaches the pilot scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the structure of a microchannel reaction tube bundle according to an embodiment of the present invention;

[0026] Figure 2 This is a schematic structural diagram of a microchannel reaction device for continuously preparing hexafluoropropylene oxide according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and the best embodiments.

[0028] Figure 1 A microchannel reaction tube bundle is shown, comprising one or more parallel microchannel reactors; each of the microchannel reactors comprises a plurality of continuous reaction units; each of the reaction units comprises an S-shaped ascending section and a vertical descending section.

[0029] As a preferred form, the S segment is composed of two relatively arranged arc segments connected. The diameter of the pipeline constituting the reaction unit is 1.5-5mm; preferably 4mm. The pipeline diameters of the S-shaped ascending section and the vertical descending section are independently 1.5-5mm, specifically 1.5mm, 2mm, 3mm, 4mm, 5mm. Below 1.5mm, the resistance of the gas and liquid to flow in the microchannel pipeline will increase, the pressure of the entire reaction device will increase, and the selectivity of the reaction will be affected; above 5mm, the space of the entire reactor is too large, the gas-liquid contact is insufficient, and it is difficult to form the effect of microchannel promoting the reaction.

[0030] Preferably, the vertical descending section is equal to the vertical length of the S-shaped ascending section;

[0031] The number of the reaction units is 1-20. If there are more than 20 reaction units, the gas-liquid contact time is too long, which will cause overreaction and reduce the selectivity of the reaction. In the embodiment of the present invention, the length of the pipe of each reaction unit is 5 meters, and 1-8 reaction units are used as a preferred example for illustrative description.

[0032] The reaction unit is made of a fluorine-containing plastic tube, and the material of the fluorine-containing plastic includes but is not limited to PTFE, PFA, FEP, PVDF, PVF, and PCTFE;

[0033] In the present invention, a plurality of microchannel reactors are arranged in parallel to form a microchannel reaction tube bundle, and the size of the microchannel reaction tube bundle can be flexibly increased or decreased according to the required reaction scale.

[0034] In the embodiments of the present invention, an exemplary description is given by taking 10 microchannel reactors to form a microchannel reaction tube bundle.

[0035] Figure 2 A microchannel reaction device for continuously preparing hexafluoropropylene oxide is shown, comprising a liquid distributor 5 and a microchannel reaction tube bundle 6; the liquid distributor comprises a liquid distributor body and a plurality of pipelines connected to the liquid distributor body; each of the pipelines is connected to one of the microchannel reactors.

[0036] The liquid inlet on the liquid distributor body is connected to the liquid raw material configuration kettle; the pipeline is provided with a gas inlet connected to the gas storage tank 1.

[0037] A gas mass flow controller 2 is provided on the gas passage between the gas inlet and the gas storage tank 1; a reaction feed pump 10 is provided on the liquid passage between the liquid inlet and the liquid raw material configuration kettle; the outlet end of the microchannel reaction tube bundle is connected to the gas-liquid separation tank through a discharge pipeline, and a reactor back pressure valve 7 is provided on the discharge pipeline; there are two gas-liquid separation tanks, namely a first gas-liquid separation tank 8 and a second gas-liquid separation tank 9, wherein the first gas-liquid separation tank 8 and the second gas-liquid separation tank 9 are used alternately as a backup; each gas-liquid separation tank is provided with a liquid phase outlet and a gas phase outlet; the liquid phase outlet is respectively connected to a waste liquid discharge pipeline and a liquid recycling pipeline 11; there are two liquid raw material configuration kettles, wherein the first liquid raw material configuration kettle 3 and the second liquid raw material configuration kettle 4 are used alternately as a backup;

[0038] The present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0039] The present invention firstly adopts a single-tube microchannel reactor to examine the number of reaction units and the microchannel diameter of the microchannel reaction device in a hexafluoropropylene epoxidation system.

[0040] The reaction system used in Examples 1-8 is a reaction system of sodium hypochlorite and toluene, with sodium hypochlorite as an oxidant, toluene as a reaction solvent, trioctylmethylammonium chloride as a phase transfer catalyst, and a potassium carbonate and potassium bicarbonate buffer system added to maintain a constant pH value of the reaction. Since the sodium carbonate and sodium bicarbonate buffer system has a strong buffering capacity, the pH value of the reaction system can be maintained stable to the maximum extent.

[0041] The specific reaction liquid mass ratio of the reaction system is: sodium hypochlorite aqueous solution (effective chlorine 3.8%): potassium carbonate: potassium bicarbonate: toluene: trioctylmethylammonium chloride = 260:6:2:35:1.

[0042] In Example 1-8, the reaction liquid is injected into the microchannel reactor from the liquid preparation kettle through a feed pump, the injection amount of the reaction liquid is 72 kg / h, hexafluoropropylene enters from the gas feed port, the gas input amount of the microchannel reactor is 0.58 kg / h, the reaction pressure is 0.2 MPa, the temperature is 0°C, the pipeline diameter of the reactor microchannel is 1.5-5 mm, the number of reaction units of the microchannel reactor is 1-8, and the number of microchannel reactors is 1; the specific results are shown in Table 1.

[0043] Table 1

[0044]

[0045]

[0046] According to the reaction results of Examples 1-8, when the pipe diameter of the microchannel reaction device is 4 mm and the number of reaction units is 6, the optimal reaction result is obtained, that is, Example 7. Based on Example 7, Examples 9-15 connect the reactors of Example 7 in parallel to form a reaction tube bundle, so that the reaction scale of Examples 9-15 is significantly enlarged to reach the pilot scale. In Examples 9-15, the reaction tube bundle is composed of 10 microchannel reaction devices, and the diameter of each microchannel is 4 mm;

[0047] A method for preparing hexafluoropropylene oxide in a pilot test using the microchannel reaction tube bundle comprises the following steps:

[0048] 1) preparing liquid raw materials in a liquid raw material preparation kettle; the oxidant is sodium hypochlorite; the solvent is toluene, and the phase transfer catalyst is trioctylmethylammonium chloride;

[0049] The mass ratio of the oxidant, potassium carbonate, potassium bicarbonate, solvent and phase transfer catalyst is 260:60:2:35:1, wherein the effective chlorine content of the oxidant sodium hypochlorite is 3.8%.

[0050] 2) The liquid raw material enters the liquid distributor and is mixed with the gas raw material hexafluoropropylene and then enters the microchannel reactor for reaction. After the reaction is completed, it enters the gas-liquid separation tank for separation.

[0051] Examples 9-14 investigated the temperature and pressure conditions of the reaction. The reaction liquid was injected into the entire microchannel reactor from the liquid preparation kettle through a feed pump. The total injection rate of the reaction liquid was 720 kg / h, and it entered 10 pipes on average through a liquid distributor. The liquid input rate of each microchannel reactor was 72 kg / h; each pipe inlet had a gas inlet, and hexafluoropropylene entered from the gas feed port. The total gas input rate was 5.76 kg / h, that is, the gas input rate of each microchannel reactor was 0.576 kg / h, the reaction pressure was 0.1-0.4 MPa, and the temperature was -20 to 50°C.

[0052] Table 2 shows the conversion rate and selectivity of the pilot-scale microchannel hexafluoropropylene oxide reaction tube bundle under different reaction conditions.

[0053] Table 2

[0054] Example Temperature(℃) Pressure(bar) HFP conversion rate (%) HFPO selectivity (%) 9 -20 0.2 75 88 10 -10 0.2 85 90 11 0 0.2 87 85 12 20 0.2 90 80 13 50 0.2 92 74 14 -10 0.1 83 90 15 -10 0.4 92 82

[0055] Comparative Example 1

[0056] The present invention conducted a comparative test. On the basis of Example 7 (the microchannel reaction device in Example 7 includes 6 reaction units, and the length of the reaction tube is about 30 meters), an equal-length U-shaped tube microchannel reactor was constructed in the comparative example, and other conditions were the same as those in Example 7. The results of the comparative test are listed in Table 3.

[0057] Table 3

[0058] experiment Reaction unit shape HFP conversion rate (%) HFPO selectivity (%) Example 7 S-shaped reaction unit 88 85 Comparative test U-tube reaction unit 73 79

[0059] In summary, the microchannel reaction device of the present application is composed of a plurality of continuous reaction units to form a reaction tube bundle. The reaction tube bundle of gas and liquid presents an S shape in the ascending stage, and the reaction tube bundle of gas and liquid presents a straight line in the descending stage. In the entire microchannel reaction device, when gas and liquid pass through, the gas always moves forward along the pipeline direction, and the liquid moves downward due to gravity in the S-shaped ascending section perpendicular to the ground in the microchannel tube bundle reactor. In the narrow space of the microchannel reactor, due to space limitations, the degree of gas-liquid contact is aggravated, so that the gas and liquid are continuously tumbling in the S section perpendicular to the ground, thereby achieving the purpose of sufficient mixing and contact of gas and liquid, which is beneficial to the reaction result; and the vertical descending section is a straight line, which can make the liquid with higher density reach the vertical bottom faster, seal the limited space of the microchannel, and facilitate full contact with the gas in the next S-shaped ascending section.

[0060] The microchannel reaction device of the present application is used to prepare hexafluoropropylene oxide, which can achieve continuous synthesis under normal temperature and relatively low pressure conditions. The reaction is carried out in a microchannel reactor, and an amplification experiment is carried out, and the production capacity reaches the pilot scale.

[0061] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A microchannel reaction tube bundle, characterized in that: It comprises one or more parallel microchannel reactors; each of the microchannel reactors comprises a plurality of continuous reaction units; each of the reaction units comprises an S-shaped ascending section and a vertical descending section.

2. The microchannel reaction tube bundle according to claim 1, characterized in that: The S segment is composed of two arc segments which are arranged opposite to each other.

3. The microchannel reaction tube bundle according to claim 1, characterized in that: The diameter of the pipeline constituting the reaction unit is 1.5-5 mm, preferably 4 mm.

4. The microchannel reaction tube bundle according to claim 1, characterized in that: The number of the reaction units is 1-20, preferably 4-8, and more preferably 6. The reaction units are made of a fluorine-containing plastic tube.

5. A microchannel reaction device for continuously preparing hexafluoropropylene oxide, characterized in that: It comprises a liquid distributor and the microchannel reaction tube bundle as described in any one of claims 1 to 4; the liquid distributor comprises a liquid distributor body and a plurality of pipelines connected to the liquid distributor body; each of the pipelines is connected to one of the microchannel reactors.

6. The microchannel reaction device for continuously preparing hexafluoropropylene oxide according to claim 5, characterized in that: Each of the pipelines is provided with a gas inlet connected to a gas storage tank; the liquid inlet on the liquid distributor body is connected to a liquid raw material preparation kettle; preferably, there are 10 pipelines.

7. The microchannel reaction device for continuously preparing hexafluoropropylene oxide according to claim 6, characterized in that: A gas flow control valve is provided on the gas passage between the gas inlet and the gas storage tank; a reaction feed pump is provided on the liquid passage between the liquid inlet and the liquid raw material configuration kettle.

8. The microchannel reaction device for continuously preparing hexafluoropropylene oxide according to claim 6, characterized in that: The outlet end of the microchannel reaction tube bundle is connected to the gas-liquid separation tank; the gas-liquid separation tank is provided with a liquid phase outlet and a gas phase outlet; the liquid phase outlet is respectively connected to the waste liquid discharge pipeline and the liquid recycling pipeline.

9. A method for preparing hexafluoropropylene oxide using the microchannel reaction device according to any one of claims 5 to 8, characterized in that: The method comprises the following steps: preparing liquid raw materials in a liquid raw material preparation kettle; the liquid raw materials enter a liquid distributor and are mixed with gas raw materials, and then enter a microchannel reaction device for reaction, and after the reaction is completed, enter a gas-liquid separation tank for separation.

10. The method for preparing hexafluoropropylene oxide according to claim 9, characterized in that: The liquid raw material includes the oxidant, potassium carbonate, potassium bicarbonate, a phase transfer catalyst and a solvent; the gas raw material is hexafluoropropylene; Preferably, the oxidant is a sodium hypochlorite solution; the effective chlorine content of the sodium hypochlorite solution is 3.8%; the solvent is toluene, and the phase transfer catalyst is trioctylmethylammonium chloride; Preferably, the mass ratio of the oxidant, potassium carbonate, potassium bicarbonate, solvent and phase transfer catalyst is (200-300):(1-10):(1-5):(10-50):(0.1-2); preferably 260:6:2:35:

1. The flow rate of the gas raw material entering the microchannel reactor is 0.3-0.58kg / h; the flow rate of the liquid raw material entering the microchannel reactor is 36-72kg / h; the reaction pressure of the microchannel reaction device is 0.1-0.4MPa, preferably 0.2-0.4MPa, and the temperature is -20℃ to 50℃; preferably -20℃ to 20℃.

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