A method for preparing hexafluoropropylene oxide by photooxidation of hexafluoropropene

Abstract

The present application relates to a kind of hexafluoropropylene photooxidation preparation hexafluoropropylene oxide method, belong to fluorine chemical industry field.The specific reaction kettle is replaced by nitrogen gas, vacuumizing, reaction kettle is heated and is passed into gaseous hexafluoropropylene and oxygen, catalytic oxidation under ultraviolet light, then join rare earth oxidation accelerator, continue to react at 80-100 ℃, the liquid product generated is discharged from the lower end of reaction kettle, after alcohol washing, alkali washing, drying is refined to obtain hexafluoropropylene oxide.This method has mild reaction condition, simple operation, simplifies processing means, meets the requirement of developing green environment-friendly chemistry, improves synthesis efficiency, reduces cost, has industrial synthesis value and prospect.

Description

Technical Field

[0001] This invention belongs to the field of fluorochemicals, specifically relating to a method for preparing hexafluoropropylene oxide by photo-oxidation of hexafluoropropylene. Background Technology

[0002] Perfluoropropylene oxide, also known as hexafluoropropylene oxide, CAS number: 428-59-1, molecular formula: C18H36F6O6, molecular weight: 462.4686. It is mainly used as an important fluorine-containing intermediate and also in the synthesis of high-grade fluorine-containing functional compounds.

[0003] CN116768827A discloses a method for the industrial production of hexafluoropropylene oxide, which uses hexafluoropropylene as raw material and prepares hexafluoropropylene oxide in one step through an epoxidation reaction in a novel MOF 5 / pyridine ionic liquid catalytic system.

[0004] CN111362887B relates to a method for the catalytic oxidation preparation of hexafluoropropylene oxide, comprising the following steps: 1) Preparation of catalyst: dissolving hexadecyltrimethylammonium bromide (CTAB) in distilled water, adding ammonia and tetraethyl orthosilicate (TEOS) sequentially; adding cesium fluoride solution and silver nitrate solution; adding to a reaction vessel with a polytetrafluoroethylene liner, crystallizing, then removing the sample, filtering, washing, drying, and calcining at high temperature in a muffle furnace to prepare the catalyst; 2) preparing the calcined catalyst in step 1) into 4060 mesh catalyst particles, loading them into a tubular reactor, heating; then sequentially introducing hexafluoropropylene and oxygen into the tubular reactor, and collecting the reaction products.

[0005] KR1020230086035A includes (a) introducing an aqueous solution of an organic solvent and an oxidant into a reactor, said oxidant being a fluorinated ether represented by Formula 1; (b) adding a phase change catalyst to the reactor; and (c) preparing hexafluoropropylene oxide, comprising preparing hexafluoropropylene oxide by injecting hexafluoropropylene into the reactor and allowing it to react. As a result, hexafluoropropylene oxide (HFPO) is oxidized in the presence of a phase change catalyst via a two-phase reaction in which an organic solvent and water are mixed, and hexafluoropropylene oxide (HFPO) is produced.

[0006] CN116178311A relates to the field of hexafluoropropylene oxide preparation technology, and more particularly to a hexafluoropropylene oxidation process, including an oxygen tank. The top of the oxygen tank is connected to a reaction vessel via a connecting pipe. A first ball valve and a gas flow meter are sequentially installed on the outside of the connecting pipe between the oxygen tank and the reaction vessel. The top of the reaction vessel is connected to a condenser via two connecting pipes. The top of the condenser is connected to a connecting pipe, and an online oxygen content analyzer and an exhaust solenoid valve are installed on the outside of this connecting pipe. The online oxygen content analyzer and the exhaust solenoid valve are interlocked by a signal. In this invention, oxygen enters the reaction system through a dense porous packing. The connecting pipe at the top of the condenser connects the online oxygen content analyzer and the exhaust solenoid valve. The exhaust solenoid valve is interlocked with the online oxygen content analyzer, and the oxygen content of the reaction system is controlled by opening and closing the exhaust solenoid valve.

[0007] In the existing process for preparing hexafluoropropylene from hexafluoropropylene, since the liquid-phase oxidation method advocates that the epoxidation reaction is carried out in the liquid phase, a large amount of solvent is often added to the reactor. The high feed ratio greatly reduces the space-time yield of the reactor and also makes the reaction pressure very high, resulting in increased equipment investment and safety hazards in production.

[0008] Previous reports on oxygen gas-phase catalytic oxidation methods have involved complex catalyst preparation processes, requiring multiple steps for loading and calcining of active components and modifiers. Furthermore, because the catalyst requires impregnation in multiple steps, it is difficult to achieve uniform dispersion of the support, active components, and modifiers. Additionally, the specific surface area of ​​the support material used in the reaction is relatively small, resulting in a lower conversion rate compared to oxygen liquid-phase oxidation methods. Summary of the Invention

[0009] To solve the above problems, the present invention adopts the following solution:

[0010] A method for preparing hexafluoropropylene oxide by photo-oxidation, the method comprising:

[0011] Step 1: Evacuate the air in the reactor and then introduce nitrogen gas, then evacuate again. Repeat this operation 3-7 times. If the pressure in the reactor remains unchanged for 30 minutes, it indicates that the airtightness is good.

[0012] Step 2: After heating the reactor to 80-120℃, introduce 30-70 parts of gaseous hexafluoropropylene and 5-10 parts of oxygen, and catalytically oxidize under ultraviolet light for 20-40 minutes.

[0013] Step 3: Add 0.05-0.3 parts of rare earth oxidation promoter, react at 80-100℃ for 20-40 minutes, and the generated liquid product is discharged from the bottom of the reactor. After washing with alcohol, washing with alkali, drying and distillation, the target product is obtained.

[0014] Preferably, the pressure in the reactor during the reaction is 1-10 MPa.

[0015] Preferably, the oxygen concentration in step 2 is 40%-60%.

[0016] Preferably, the oxygen flow rate in step 2 is 1 to 2 m³ / min.

[0017] Preferably, the ultraviolet light source in step 2 is selected from medium-pressure mercury lamps, high-pressure mercury lamps, metal halide lamps, or xenon lamps.

[0018] Preferably, the effective wavelength of the ultraviolet light source in step 2 is 200–400 nm.

[0019] Preferably, the unit volume power of the ultraviolet light generator in the reactor in step 2 is 5 to 195 W / L.

[0020] Furthermore, the method for preparing the oxidation accelerator is as follows:

[0021] Weigh 10-20 parts by weight of 3,3'-bipyridine-6,6'-diamino, 5-10 parts of titanium tetrachloride, and 0.4-2.8 parts of bismuth nitrate, add them to 100-200 parts of ethylene glycol, mix and stir at 70-80℃ for 50-100 min, then add 0.07-0.4 parts of dimercaptothiadiazole and 4-7 parts of triethylamine, mix and stir at 70-80℃ for 30-60 min, and remove the ethylene glycol by distillation to obtain the oxidation promoter.

[0022] Reaction mechanism

[0023] The reaction mechanism for the photooxidation of hexafluoropropylene to prepare hexafluoropropylene oxide is as follows:

[0024]

[0025] The reaction mechanism of the oxidation promoter is as follows:

[0026] 3,3'-Bipyridine-6,6'-diamino reacts with titanium and bismuth salts to form complexes, which are then added to dimercaptothiadiazole to yield an oxidation promoter containing titanium, bismuth, thiadiazole, and bipyridine complexes. This promotes the complete epoxidation of hexafluoropropylene.

[0027] Technical effect

[0028] 1. The photocatalytic reaction conditions are mild and the operation is simple, which simplifies the processing methods, meets the requirements for developing green and environmentally friendly chemistry, improves synthesis efficiency, reduces costs, and has industrial synthesis value and prospects.

[0029] 2. Building upon photocatalysis, the use of rare-earth oxidation promoters containing titanium, bismuth, thiadiazole, and bipyridine complexes can enhance the conversion rate of the hexafluoropropylene epoxidation reaction. This is achieved by providing highly reactive oxygen free radicals to promote the oxidation of hexafluoropropylene. Multiple mechanisms are employed to improve conversion rate and selectivity. The design and development of such promoters provide new ideas and methods for optimizing the hexafluoropropylene epoxidation reaction. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the reactor;

[0031] Figure 2 The chromatogram of hexafluoropropylene oxide is shown in Example 1. Detailed Implementation

[0032] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0033] Detection methods

[0034] The conversion rate of hexafluoropropylene and the selectivity of hexafluoropropylene oxide were determined by gas chromatography normalization.

[0035] Example 1

[0036] Step 1: After evacuating the air in the reactor, nitrogen gas is introduced, and then the reactor is evacuated again. Repeat this operation 5 times. If the pressure in the reactor remains unchanged for 30 minutes, it indicates that the airtightness is good. The pressure of the reactor should be controlled at 1 MPa.

[0037] Step 2: After heating the reactor to 80°C, 30 kg of gaseous hexafluoropropylene and 5 kg of oxygen with a concentration of 40% are introduced into the reactor at a flow rate of 1 m3 / min. Catalytic oxidation is carried out for 20 minutes under the ultraviolet light of a medium-pressure mercury lamp with an effective wavelength of 200 nm and a unit volume light source power of 5 W / L.

[0038] Step 3: Add 0.05 kg of rare earth oxidation promoter, react at 80°C for 20 minutes, and the generated liquid product is discharged from the bottom of the reactor. After alkali washing and drying, the target product is obtained by distillation.

[0039] The method for preparing the oxidation accelerator is as follows:

[0040] Weigh 100g of 3,3'-bipyridine-6,6'-diamino, 50g of titanium tetrachloride, and 4g of bismuth nitrate, add them to 1000g of ethylene glycol, mix and stir at 70℃ for 50min, then add 0.7g of dimercaptothiadiazole and 40g of triethylamine, mix and stir at 70℃ for 30min, and remove the ethylene glycol by distillation to obtain the oxidation promoter.

[0041] Example 2

[0042] Step 1: After evacuating the air in the reactor, nitrogen gas is introduced, and then the reactor is evacuated again. Repeat this operation 5 times. If the pressure in the reactor remains unchanged for 30 minutes, it indicates that the airtightness is good. The pressure of the reactor should be controlled at 5 MPa.

[0043] Step 2: After heating the reactor to 100℃, 50kg of gaseous hexafluoropropylene and 8kg of oxygen with a concentration of 50% are introduced into the reactor at a rate of 1.5m3 / min. Catalytic oxidation is carried out for 30 minutes under the action of an ultraviolet xenon lamp with an effective wavelength of 300nm and a unit volume light source power of 100W / L.

[0044] Step 3: Add 0.15 kg of rare earth oxidation promoter, react at 90°C for 30 minutes, and the generated liquid product is discharged from the bottom of the reactor. After washing with alcohol, washing with alkali, drying and distillation, the target product is obtained.

[0045] The method for preparing the oxidation accelerator is as follows:

[0046] Weigh 150g of 3,3'-bipyridine-6,6'-diamino, 80g of titanium tetrachloride, and 16g of bismuth nitrate, add them to 1500g of ethylene glycol, mix and stir at 75℃ for 80min, then add 2.5g of dimercaptothiadiazole and 60g of triethylamine, mix and stir at 75℃ for 45min, and remove the ethylene glycol by distillation to obtain the oxidation promoter.

[0047] Example 3

[0048] Step 1: After evacuating the air in the reactor, nitrogen gas is introduced, and then the reactor is evacuated again. Repeat this operation 5 times. If the pressure in the reactor remains unchanged for 30 minutes, it indicates that the airtightness is good. Control the pressure of the reactor at 10 MPa.

[0049] Step 2: After heating the reactor to 120°C, 70 kg of gaseous hexafluoropropylene and 10 kg of 60% oxygen are introduced into the reactor at a rate of 1.5 m3 / min. Catalytic oxidation is carried out for 40 minutes under the action of an ultraviolet high-pressure mercury lamp with an effective wavelength of 400 nm and a unit volume light source power of 195 W / L.

[0050] Step 3: Add 0.3 kg of rare earth oxidation promoter, react at 100°C for 40 minutes, and the generated liquid product is discharged from the bottom of the reactor. After washing with alcohol, washing with alkali, drying and distillation, the target product is obtained.

[0051] The method for preparing the oxidation accelerator is as follows:

[0052] Weigh 200g of 3,3'-bipyridine-6,6'-diamino, 100g of titanium tetrachloride, and 28g of bismuth nitrate, add them to 2000g of ethylene glycol, mix and stir at 80℃ for 100min, then add 4g of dimercaptothiadiazole and 70g of triethylamine, mix and stir at 80℃ for 60min, and remove the ethylene glycol by distillation to obtain the oxidation promoter.

[0053] Comparative Example 1

[0054] Without adding rare earth oxidation promoters, the rest of the technical solutions are the same as in Example 1.

[0055] Comparative Example 2

[0056] Dithiodiazole is not added to the rare earth oxidant; the rest of the technical solutions are the same as in Example 1.

[0057] Comparative Example 3

[0058] Triethylamine is not added to the rare earth oxidant, and the rest of the technical solutions are the same as in Example 1.

[0059] Table 1 shows the conversion rates and selectivity of the effective products for the reactions of Examples 1-3 and Comparative Examples 1-3.

[0060] Table 1

[0061] Example 1 97 98 Example 2 98 99 Example 3 99 99 Comparative Example 1 89 94 Comparative Example 2 92 96 Comparative Example 3 93 96

[0062] As shown in Table 1, 3,3'-bipyridine-6,6'-diamino forms a complex with titanium and bismuth salts, which then undergoes an addition reaction with dimercaptothiadiazole to obtain an oxidation promoter containing titanium, bismuth, thiadiazole, and bipyridine complexes, which can promote the complete epoxidation reaction of hexafluoropropylene.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing hexafluoropropylene oxide by photooxidation, characterized in that: The methods include: Step 1: Evacuate the air in the reactor and then introduce nitrogen gas, then evacuate again. Repeat this operation 3-7 times. If the pressure in the reactor remains unchanged for 30 minutes, it indicates that the airtightness is good. Step 2: After heating the reactor to 80-120℃, introduce 30-70 parts of gaseous hexafluoropropylene and 5-10 parts of oxygen, and catalytically oxidize under ultraviolet light for 20-40 minutes. Step 3: Add 0.05-0.3 parts of rare earth oxidation promoter, react at 80-100℃ for 20-40 minutes, and the generated liquid product is discharged from the bottom of the reactor. After alkali washing and drying, the target product is obtained by distillation. The method for preparing the rare earth oxidation promoter in step 3 is as follows: Weigh 10-20 parts by weight of 3,3'-bipyridine-6,6'-diamino, 5-10 parts of titanium tetrachloride, and 0.4-2.8 parts of bismuth nitrate, add them to 100-200 parts of ethylene glycol, mix and stir at 70-80℃ for 50-100 min, then add 0.07-0.4 parts of dimercaptothiadiazole and 4-7 parts of triethylamine, mix and stir at 70-80℃ for 30-60 min, and remove the ethylene glycol by distillation to obtain the oxidation promoter.

2. The method for preparing hexafluoropropylene oxide by photo-oxidation according to claim 1, characterized in that: The pressure in the reactor during the reaction process is 1-10 MPa.

3. The method for preparing hexafluoropropylene oxide by photo-oxidation according to claim 1, characterized in that: The oxygen concentration mentioned in step 2 is 40%-60%.

4. The method for preparing hexafluoropropylene oxide by photo-oxidation according to claim 1, characterized in that: The oxygen flow rate mentioned in step 2 is 1-2 m³ / min.

5. The method for preparing hexafluoropropylene oxide by photo-oxidation according to claim 1, characterized in that: The source of ultraviolet light mentioned in step 2 is selected from medium-pressure mercury lamps, high-pressure mercury lamps, metal halide lamps, or xenon lamps.

6. The method for preparing hexafluoropropylene oxide by photo-oxidation according to claim 1, characterized in that: The effective wavelength of the ultraviolet light source mentioned in step 2 is 200–400 nm.

7. The method for preparing hexafluoropropylene oxide by photo-oxidation according to claim 1, characterized in that: In step 2, the power of the ultraviolet light source per unit volume in the reactor is 5–195 W / L.

Images