Method for preparing perfluoropentene by using perfluoropentanol as raw material

Abstract

The invention relates to the technical field of preparation of perfluoropentene, in particular to a method for preparing perfluoropentene by taking perfluoropentanol as a raw material. The method for preparing the perfluoropentene by using the perfluoropentanol as the raw material comprises the following steps: taking mesoporous silica (mSiO2) modified by graphene quantum dots (GQDs) as a carrier, loading a nano catalyst derived from a metal organic framework (MOF), firstly synthesizing the GQDs by a hydrothermal method, and then reacting the GQDs with tetraethoxysilane and the like to prepare the GQDs modified mSiO2 carrier. According to the invention, a microwave-ultrasonic synergistic heating technology is utilized, so that the reaction can be carried out at a relatively low temperature of 100-120 DEG C, energy waste and side reaction caused by high temperature in a traditional method are avoided, and the product quality is improved; and meanwhile, the reaction is carried out under normal pressure, so that the requirement on high-pressure equipment is reduced, the equipment investment cost and the safety risk are reduced, and the skill and protection requirements on operators are relatively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of perfluoropentene preparation, and particularly to a method for preparing perfluoropentene using perfluoropentanol as a raw material. Background Art

[0002] Perfluoropentene is a fluorinated olefin compound formed by replacing all hydrogen atoms in the pentene molecule with fluorine atoms, and its general formula is C5F 10 , due to the large electronegativity of fluorine atoms, the intermolecular forces of perfluoropentene are weak, having a low boiling point and density, and usually presenting as a colorless and odorless gas or liquid; it is insoluble in water but soluble in some organic solvents; in terms of chemical properties, perfluoropentene contains a carbon-carbon double bond and has the typical reactivity of olefins, and can undergo addition reactions, etc.; however, due to the strong electron-withdrawing effect of fluorine atoms, the electron cloud density on its double bond decreases, and the addition reaction activity is different from that of ordinary olefins; in addition, perfluoropentene also has high chemical stability and thermal stability, and is not easily oxidized or decomposed by general chemical reagents. This unique structure and properties make it have important application value in many fields; With the rapid development of related industries, the demand for perfluoropentene is increasing day by day, and its preparation method has also become a research hotspot; at present, although there have been certain progresses in the method for preparing perfluoropentene using perfluoropentanol as a raw material, there are still many problems; on the one hand, many existing methods need to carry out reactions under high temperature and high pressure conditions; high temperature not only consumes a large amount of energy, increases production costs, but also may cause side reactions such as decomposition and polymerization of perfluoropentanol and perfluoropentene, further reducing the product quality; the high-pressure environment has extremely high requirements for the material and sealing performance of the reaction equipment, which greatly increases the equipment investment cost, and at the same time brings safety hazards, and has strict requirements for the professional skills and safety protection measures of operators; On the other hand, due to the complex product system generated by the existing reaction, the existing separation technologies are difficult to achieve efficient separation. Conventional distillation methods are difficult to separate substances with similar boiling points, and there may also be problems such as incomplete extraction or introduction of new impurities in the extraction process; in order to obtain high-purity perfluoropentene, it is often necessary to use a variety of separation technologies for multiple separations, which not only increases the equipment investment and operating costs, prolongs the production cycle, but also may cause losses of products during the separation process, further increasing the production cost.

[0003] Therefore, it is necessary to provide a new method for preparing perfluoropentene using perfluoropentanol as a raw material to solve the above technical problems. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a method for preparing perfluoropentene using perfluoropentanol as a raw material.

[0005] The method for preparing perfluoropentene using perfluoropentanol as a raw material provided by the present invention includes: S1: First, graphene quantum dots are synthesized by a hydrothermal method. Then, the graphene quantum dots are reacted with a solution including tetraethyl orthosilicate to prepare a mesoporous silica support modified with graphene quantum dots. Next, a metal salt and an organic ligand are dissolved in a specified solvent to form a nano-catalyst including a metal-organic framework. The MOF-derived nano-catalyst is loaded onto the support by an in-situ growth method, and after drying and calcination, a multi-component composite catalyst is obtained; S2: Perfluoropentanol and the multi-component composite catalyst are added to a reaction kettle at a mass ratio of 10:1. The reaction kettle includes a microwave-ultrasonic synergistic heating device, a stirrer, and a thermometer. Under nitrogen protection, the microwave power is set to 200 - 300 W, the ultrasonic frequency is 30 - 50 kHz, the reaction temperature is controlled at 100 - 120 °C, and stirring reaction is carried out for 2.5 - 3.5 hours; S3: After the reaction is completed, the reaction mixture is cooled to 23 °C ± 2 °C. First, the catalyst is removed by centrifugal separation, and then the filtrate is extracted. The extractant is perfluorohydrocarbon, and extraction is carried out 2 - 3 times; then molecular distillation is carried out on the extraction phase, the light components are collected, and finally the light components are freeze-dried to obtain high-purity perfluoropentene.

[0006] Preferably, in the step S1, the mass ratio of graphene quantum dots to tetraethyl orthosilicate is 1:50, the metal in the MOF-derived nano-catalyst is zinc, and the molar ratio of the metal salt to the organic ligand is 1:1.5.

[0007] Preferably, in the step S1, when synthesizing graphene quantum dots by the hydrothermal method, the reaction temperature is 180 - 200 °C, and the reaction time is 10 - 12 hours; when preparing the mSiO2 support modified with graphene quantum dots, the reaction temperature is 30 - 50 °C, and the reaction time is 8 - 10 hours; when loading the MOF-derived nano-catalyst, the reaction temperature is 60 - 80 °C, the reaction time is 6 - 8 hours, the drying temperature is 80 - 100 °C, the drying time is 6 - 8 hours, the calcination temperature is 400 - 500 °C, and the calcination time is 3 - 5 hours.

[0008] Preferably, in the step S2, the flow rate of nitrogen introduced is 10 - 20 L / h, and the stirring speed of the stirrer is 350 - 450 r / min.

[0009] Preferably, in the step S3, the volume ratio of perfluorohydrocarbon to the filtrate is 2:1, and the extraction time for each time is 20 - 30 minutes.

[0010] Preferably, in the step S3, the temperature of molecular distillation is 50 - 70 °C, the pressure is 0.1 - 0.5 kPa, and the scraping film rotation speed is 200 - 300 r / min.

[0011] Preferably, in the step S3, during the lyophilization treatment, the pre-freezing temperature is -50°C to -40°C, the pre-freezing time is 2 - 3 hours, the pressure in the sublimation drying stage is 10 - 20 Pa, the temperature in the desorption drying stage is 20 - 30°C, and the time is 3 - 5 hours.

[0012] Preferably, the prepared perfluoropentene product is subjected to purity detection, and the nuclear magnetic resonance fluorine spectrum and high performance liquid chromatography - mass spectrometry combined method are used for detection. The product purity of perfluoropentene ≥ 99.9%.

[0013] Compared with the related technologies, the method for preparing perfluoropentene using perfluoropentanol as a raw material provided by the present invention has the following beneficial effects: High - efficiency catalysis: The nano - catalyst derived from metal - organic framework (MOF) supported on mesoporous silica (mSiO2) modified by graphene quantum dots (GQDs) used in this method combines the advantages of various materials; GQDs have good electron transfer performance, can promote charge transfer, and enhance catalytic activity; the mesoporous structure of mSiO2 provides good diffusion channels for reactants and products, increasing the accessibility of active sites; the MOF - derived nano - catalyst has abundant active centers and a unique pore structure, improving the selectivity of the catalyst; the synergistic effect of the three significantly improves the reaction efficiency of perfluoropentanol dehydration to perfluoropentene compared with traditional catalysts and shortens the reaction time. Mild reaction conditions: Using the microwave - ultrasonic synergistic heating technology, the reaction can be carried out at a relatively low temperature of 100 - 120°C, avoiding the energy waste and side reactions caused by high temperature in the traditional method, reducing the production cost, and improving the product quality; at the same time, the reaction is carried out under normal pressure, reducing the demand for high - pressure equipment, lowering the equipment investment cost and safety risk, and relatively reducing the requirements for the skills and protection of operators. High - purity product: In the product separation stage, a method combining centrifugation, perfluorocarbon extraction, molecular distillation, and lyophilization is adopted; perfluorocarbon has good solubility and selectivity for perfluoropentene, can effectively extract the target product and remove impurities; molecular distillation operates under high vacuum and relatively low temperature, can separate substances with similar boiling points, reducing product decomposition and polymerization; lyophilization further removes trace impurities and moisture; through these steps, a perfluoropentene product with a purity of up to more than 99.9% can be finally obtained, meeting the strict requirements for product purity in high - end application fields. Economical and environmentally friendly: The shorter reaction time and lower energy consumption reduce the production cost; at the same time, avoiding the use of dangerous reagents reduces environmental pollution and harm to operators, conforming to the development concept of green chemistry and being conducive to sustainable development. Specific embodiments

[0014] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with 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.

[0015] Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in this application can be obtained through market purchases or can be prepared by existing methods.

[0016] The specific implementation of the present invention will be described in detail below in conjunction with specific embodiments and comparative examples.

[0017] Example 1 A method for preparing perfluoropentene using perfluoropentanol as a raw material, the method for preparing perfluoropentene using perfluoropentanol as a raw material includes: S1: First, graphene quantum dots are synthesized by a hydrothermal method, and then the graphene quantum dots are reacted with a solution including tetraethyl orthosilicate to prepare a mesoporous silica support modified with graphene quantum dots. Then, a metal salt and an organic ligand are dissolved in a specified solvent to form a nano-catalyst including a metal-organic framework. The MOF-derived nano-catalyst is loaded onto the support by an in-situ growth method, and after drying and calcination, a multi-component composite catalyst is obtained; In the step S1, the mass ratio of GQDs to tetraethyl orthosilicate is 1:50, the metal in the MOF-derived nano-catalyst is zinc, and the molar ratio of the metal salt to the organic ligand is 1:1.5; Specific synthesis method of GQDs: Take a quantitative amount of citric acid and dissolve it in deionized water. The ratio of citric acid to deionized water is 1:10 to prepare a solution with a certain concentration. Transfer the solution to a stainless steel reaction kettle with a polytetrafluoroethylene lining, ensure that the reaction kettle is well sealed, and place the reaction kettle in a hydrothermal reaction device. Set the reaction temperature to 200 °C and the reaction time to 12 hours. During the reaction process, a series of complex chemical reactions such as dehydration, carbonization, and aromatization occur to the carbon source molecules, and carbon atoms gradually aggregate to form quantum dots with a graphene structure; Product separation and purification: After the reaction is completed, wait for the reaction kettle to cool naturally to room temperature (23 °C ± 2 °C), and take out the reaction product. The product obtained at this time is a mixed solution containing GQDs, which may contain unreacted raw materials, reaction by-products, and impurities, etc. Centrifugation is used to remove the insoluble impurities therein, and then the GQDs solution is purified by dialysis technology to remove small molecule impurities and residual additives to obtain a relatively pure GQDs solution.

[0018] Catalyst preparation: In step S1, when synthesizing GQDs by the hydrothermal method, the reaction temperature is set at 200 °C and the reaction time is 12 hours; when preparing the GQDs-modified mSiO2 support, the reaction temperature is 50 °C and the reaction time is 10 hours; when loading the MOF-derived nanocatalyst, the reaction temperature is 80 °C and the reaction time is 8 hours; the drying temperature is 100 °C and the drying time is 8 hours, and the calcination temperature is 500 °C and the calcination time is 5 hours; Using zinc nitrate as the metal salt and 2-methylimidazole as the organic ligand, they are dissolved in N,N-dimethylformamide (DMF) according to a molar ratio of 1:1.5. The GQDs-modified mSiO2 support is added to this solution, and the reaction is carried out at 80 °C for 8 hours to in-situ grow and load the MOF-derived nanocatalyst onto the support; subsequently, the loaded catalyst is dried at 100 °C for 8 hours, and then placed in a muffle furnace and calcined at 500 °C for 5 hours to obtain the multi-component composite catalyst; S2: Perfluoropentanol and the multi-component composite catalyst are added to the reaction kettle at a mass ratio of 10:1. The reaction kettle includes a microwave-ultrasonic synergistic heating device, a stirrer, and a thermometer. Under nitrogen protection, the microwave power is set at 300 W, the ultrasonic frequency is 50 kHz, the reaction temperature is controlled at 120 °C, and the stirring reaction is carried out for 3.5 hours; in the S2 step, the nitrogen flow rate is 20 L / h, and the stirring speed of the stirrer is 450 r / min; Reaction process: In step S2, in a 500 mL reaction kettle, 100 g of perfluoropentanol and 10 g of the above multi-component composite catalyst (mass ratio 10:1) are added; nitrogen is introduced at a flow rate of 20 L / h to displace air for 30 minutes; the microwave power is set at 300 W, the ultrasonic frequency is 50 kHz, the stirring speed is 450 r / min, and the temperature is raised to 120 °C, and the reaction is carried out for 3.5 hours; the temperature and stirring speed are monitored during the reaction; Perfluoropentanol is converted into perfluoropentene under the action of microwave-ultrasonic synergistic heating and the multi-component composite catalyst. The microwave rapidly heats the reaction system, causing the molecules to vibrate and rotate rapidly. The ultrasonic wave generates a cavitation effect, forming a high-temperature and high-pressure microenvironment locally. The energy input of the microwave and ultrasonic wave and the action of the catalyst promote the cleavage and recombination of chemical bonds in perfluoropentanol molecules, and finally form perfluoropentene; S3: After the reaction is completed, cool the reaction mixture to room temperature (23°C ± 2°C). First, remove the catalyst by centrifugation, and then extract the filtrate. The extractant is perfluorocarbon, and the extraction is carried out 3 times. Then, perform molecular distillation on the extraction phase, collect the light components, and finally perform freeze-drying treatment on the light components to obtain high-purity perfluoropentene. In the step S3, the volume ratio of perfluorocarbon to the filtrate is 2:1, and the extraction time for each time is 30 minutes. In the step S3, the temperature of molecular distillation is 70°C, the pressure is 0.5 kPa, and the scraping film rotation speed is 300 r / min. In the step S3, during the freeze-drying treatment, the pre-freezing temperature is -40°C, the pre-freezing time is 3 hours, the pressure in the sublimation drying stage is 20 Pa, the temperature in the desorption drying stage is 30°C, and the time is 5 hours. The purity of the prepared perfluoropentene product is detected, using nuclear magnetic resonance fluorine spectrum and high-performance liquid chromatography-mass spectrometry combined technology, and the product purity needs to reach more than 99.9%. Product separation: After the reaction is completed and cooled, centrifuge to separate the catalyst and the reaction solution; transfer the filtrate to a separatory funnel, add 300 mL of perfluorocarbon (volume ratio 2:1) to the separatory funnel, oscillate and extract for 30 minutes, and transfer the lower perfluorocarbon phase after standing and separating; repeat the extraction 2 times, combine the extraction phases, transfer the extraction phase to a molecular distillation device, set the temperature at 70°C, the pressure at 0.5 kPa, and the scraping film rotation speed at 300 r / min, collect the light components, put the light components into the sample tray of the freeze-dryer, pre-freeze at -40°C for 3 hours, the pressure in the sublimation drying stage is 20 Pa, the temperature in the desorption drying stage is 30°C, and the time is 5 hours to obtain a high-purity perfluoropentene product; use nuclear magnetic resonance fluorine spectrum ( 19 FNMR) and high-performance liquid chromatography-mass spectrometry (HPLC-MS) combined technology for detection; dissolve the sample in deuterated chloroform for ( 19 FNMR) test, analyze the characteristic peaks to determine the purity; at the same time, use (HPLC-MS) to detect impurities; after detection, the purity of this perfluoropentene product reaches 99.95%.

[0019] Comparative Example 1: The difference between this comparative example and Example 1 is to change the catalyst composition (remove the graphene quantum dot modification), and the specific steps are as follows: S1: Hydrolyze tetraethyl orthosilicate to prepare a mesoporous silica support. Dissolve zinc nitrate as a metal salt and 2-methylimidazole as an organic ligand (molar ratio 1:1.5) in DMF to form a metal-organic framework nanocatalyst, and load it onto the support by in-situ growth method. After drying at 100°C for 8 hours and calcining at 500°C for 5 hours, a composite catalyst without graphene quantum dot modification is obtained. S2: Add perfluoropentanol and the catalyst to the reaction kettle at a mass ratio of 10:1. Under nitrogen protection (flow rate 20 L / h), heat with 300 W microwave - 50 kHz ultrasonic wave in a cooperative manner, and stir and react at 120°C for 3.5 hours (stirring speed 450 r / min). S3: Cool to room temperature after the reaction, centrifuge to separate the catalyst, and adopt the same perfluorohydrocarbon extraction, molecular distillation (70 °C / 0.5 kPa) and freeze-drying (-40 °C pre-freezing for 3 h) processes as in Example 1; Test results: The product purity is only 96.3%. Due to the lack of the electron transfer and active site enhancement effects of graphene quantum dots, the catalytic efficiency is significantly reduced.

[0020] Comparative Example 2: The difference between this comparative example and Example 1 lies in adjusting the reaction conditions (removing the ultrasonic synergistic effect), and the specific steps are as follows: S1: Adopt the same preparation process of the multi-component composite catalyst as in Example 1; S2: Add perfluoropentanol and the catalyst to the reaction kettle at a mass ratio of 10:1. Under nitrogen protection (flow rate 20 L / h), only use 300 W microwave heating, control the temperature at 120 °C, the stirring speed at 450 r / min, and react for 3.5 hours; S3: Adopt the same separation and purification process as in Example 1; Test results: The product purity is 98.1%. Since the local high-temperature and high-pressure environment formed by the ultrasonic cavitation effect is not utilized, the bond-breaking efficiency of perfluoropentanol molecules decreases, resulting in an increase in side reactions.

[0021] Comparative Example 3: The difference between this comparative example and Example 1 lies in simplifying the separation process (omitting molecular distillation), and the specific steps are as follows: S1: Adopt the same preparation process of the multi-component composite catalyst as in Example 1; S2: Adopt the same reaction conditions and parameters as in Example 1; S3: After the reaction, cool to room temperature, centrifuge to separate the catalyst, extract with perfluorohydrocarbon three times, and then directly freeze-dry the extraction phase, skipping the molecular distillation step; Test results: The product purity is 97.8%. Since the light component impurities are not effectively separated by molecular distillation, the residual low-boiling by-products affect the final purity.

[0022] It can be seen from the comparison of the three groups of comparative examples with Example 1 that: The catalyst modified with graphene quantum dots significantly improves the reaction activity (Comparative Example 1); The microwave-ultrasonic synergistic heating mechanism promotes the reaction efficiency and selectivity (Comparative Example 2); The key role of molecular distillation in impurity separation (Comparative Example 3); The above differences fully reflect the creative breakthroughs of Example 1 in catalyst design, reaction technology and separation process.

[0023] The above are only the embodiments and comparative examples of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural or equivalent process transformation made by using the content of the specification of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A method for preparing perfluoropentene using perfluoropentanol as a raw material, characterized in that, It includes the following steps: S1: First, graphene quantum dots are synthesized by a hydrothermal method. Then, the graphene quantum dots are reacted with a solution including tetraethyl orthosilicate to prepare a mesoporous silica support modified with graphene quantum dots. Next, a metal salt and an organic ligand are dissolved in a specified solvent to form a nano-catalyst including a metal-organic framework. The MOF-derived nano-catalyst is loaded onto the support by an in-situ growth method, and after drying and calcination, a multi-component composite catalyst is obtained. S2: Perfluoropentanol and the multi-component composite catalyst are added to a reaction kettle at a mass ratio of 10:

1. The reaction kettle includes a microwave-ultrasonic synergistic heating device, a stirrer, and a thermometer. Under nitrogen protection, the microwave power is set to 200 - 300 W, the ultrasonic frequency is 30 - 50 kHz, the reaction temperature is controlled at 100 - 120 °C, and the reaction is stirred for 2.5 - 3.5 hours. S3: After the reaction is completed, the reaction mixture is cooled to 23 °C ± 2 °C. First, the catalyst is removed by centrifugal separation, and then the filtrate is extracted. The extractant is perfluorohydrocarbon, and the extraction is carried out 2 - 3 times. Then, molecular distillation is performed on the extraction phase, the light components are collected, and finally, the light components are freeze-dried to obtain high-purity perfluoropentene.

2. The method for preparing perfluoropentene using perfluoropentanol as a raw material according to claim 1, wherein In the S1 step, the mass ratio of graphene quantum dots to tetraethyl orthosilicate is 1:

50. The metal in the MOF-derived nano-catalyst is zinc, and the molar ratio of the metal salt to the organic ligand is 1:1.

5.

3. The method for preparing perfluoropentene using perfluoropentanol as a raw material according to claim 1, wherein, In the S1 step, when synthesizing graphene quantum dots by the hydrothermal method, the reaction temperature is 180 - 200 °C, and the reaction time is 10 - 12 hours; when preparing the mSiO2 support modified with graphene quantum dots, the reaction temperature is 30 - 50 °C, and the reaction time is 8 - 10 hours; when loading the MOF-derived nano-catalyst, the reaction temperature is 60 - 80 °C, the reaction time is 6 - 8 hours, the drying temperature is 80 - 100 °C, the drying time is 6 - 8 hours, the calcination temperature is 400 - 500 °C, and the calcination time is 3 - 5 hours.

4. The method for preparing perfluoropentene using perfluoropentanol as a raw material according to claim 1, characterized in that, In the S2 step, the flow rate of nitrogen introduced is 10 - 20 L / h, and the stirring speed of the stirrer is 350 - 450 r / min.

5. The method for preparing perfluoropentene using perfluoropentanol as a raw material according to claim 1, characterized in that, In the S3 step, the volume ratio of perfluorohydrocarbon to the filtrate is 2:1, and the extraction time for each time is 20 - 30 minutes.

6. The method for preparing perfluoropentene using perfluoropentanol as a raw material according to claim 1, wherein, In the S3 step, the temperature of molecular distillation is 50 - 70 °C, the pressure is 0.1 - 0.5 kPa, and the scraping film rotation speed is 200 - 300 r / min.

7. The method for preparing perfluoropentene using perfluoropentanol as a raw material according to claim 1, wherein, In the S3 step, during the freeze-drying process, the pre-freezing temperature is -50 °C to -40 °C, the pre-freezing time is 2 - 3 hours, the pressure in the sublimation drying stage is 10 - 20 Pa, the temperature in the desorption drying stage is 20 - 30 °C, and the time is 3 - 5 hours.

8. The method for preparing perfluoropentene using perfluoropentanol as a raw material according to claim 1, characterized in that, The purity of the prepared perfluoropentene product is detected. The nuclear magnetic resonance fluorine spectrum and high-performance liquid chromatography-mass spectrometry combined method are used for detection, and the product purity of perfluoropentene ≥ 99.9%.