Preparation method of 1, 1, 1, 2, 3, 3-hexafluoropropane

Abstract

The invention belongs to the technical field of organic chemistry, and particularly relates to a preparation method of 1, 1, 1, 2, 3, 3-hexafluoropropane. The invention relates to a preparation method of 1, 1, 1, 2, 3, 3-hexafluoropropane, which comprises the following step: carrying out hydrogenation reaction on hexafluoropropylene serving as a raw material under the action of a Pd-loaded carbon nitride catalyst to obtain the 1, 1, 1, 2, 3, 3-hexafluoropropane. According to the preparation method of 1, 1, 1, 2, 3, 3-hexafluoropropane provided by the invention, through the innovative design of the nitrogen-doped carbon carrier, the anti-sintering performance and catalytic efficiency of the palladium-based catalyst are remarkably improved, so that the catalyst has high conversion rate, high selectivity and ultra-long service life in the selective hydrogenation reaction of hexafluoropropylene; the core defect that a traditional palladium carbon catalyst is prone to sintering deactivation is successfully overcome, and reliable technical support is provided for industrial continuous production of 1, 1, 1, 2, 3, 3-hexafluoropropane.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic chemistry, and particularly relates to a method for preparing 1,1,1,2,3,3-hexafluoropropane. Background Art

[0002] 1,1,1,2,3,3-Hexafluoropropane (R236ea) is a hydrofluorocarbon that can be used as a refrigerant, fire extinguishing agent, cleaning agent, foaming agent, etching agent, heat transfer medium, etc. Especially in the synthesis process of the fourth-generation refrigerant 2,3,3,3-tetrafluoropropene, R236ea is one of the important intermediates and has wide application and industrial utilization value. Therefore, it is of great significance to develop a preparation process with high purity and low cost.

[0003] Currently, among the synthesis methods of R236ea, only the hexafluoropropene hydrogenation process has achieved industrial application due to its advantages such as convenient raw material source, simple process, high raw material utilization rate, and low energy consumption. And supported palladium catalysts are the most important catalysts in the existing hexafluoropropene hydrogenation process due to their high activity and high selectivity.

[0004] For example, Chinese Patent Application CN102026947A discloses a method for synthesizing 1,1,1,2,3,3-hexafluoropropane by hydrogenating hexafluoropropene using a 0.5% palladium / activated carbon (Pd / AC) catalyst. From the data provided in its Example 1, it can be seen that in the case of co-feeding the binary components 1,2,3,3,3-pentafluoropropene (Z-1225ye) and hexafluoropropene, the conversion rate of hexafluoropropene is still 85.8%, and at this conversion rate, the selectivity of 1,1,1,2,3,3-hexafluoropropane is still 93.1%. Another example is Chinese Patent CN101921168B, which discloses a method for catalytic hydrogenation synthesis of R236ea by reacting hexafluoropropene with hydrogen under the catalysis of a supported palladium catalyst, where palladium is the active component and the carrier is α-aluminum oxide. At the highest reaction temperature of 121 °C, the conversion rate of hexafluoropropene can reach 100%, and the selectivity of R236ea can reach 99.34%. Still another example is Chinese Patent CN105107491B, which discloses a method for manufacturing and applying a hexafluoropropene hydrogenation catalyst. The catalyst consists of a main catalyst, an auxiliary agent, and a carrier. The main catalyst is palladium, and the auxiliary agent is a lanthanide metal including one or more of La, Ce, and Pr. The main catalyst and the auxiliary agent are supported on an activated carbon carrier. The Pd / AC catalyst prepared by steps such as rapid reduction treatment in its preparation method has a uniform distribution of metallic Pd, high dispersion, and small particle size, and has excellent reaction performance. In the gas-phase hydrogenation reaction of hexafluoropropene, the conversion rate of hexafluoropropene is greater than 99%, and the selectivity of R236ea is greater than 99.5%, showing high activity and high selectivity.

[0005] However, although the above-mentioned prior art discloses a method for hydrogenating hexafluoropropene using a Pd / AC catalyst as a hydrogenation catalyst, which can have a relatively high reaction conversion rate and selectivity for the target product, the inventors of the present application found in the experiment of synthesizing R236ea by hydrogenating hexafluoropropene using a Pd / AC catalyst that there is a phenomenon of Pd particle sintering during the reaction, resulting in a relatively low service life of the Pd / AC catalyst and making it difficult to be applied industrially. Summary of the Invention

[0006] In order to solve the problems existing in the prior art, the object of the present invention is to provide a method for preparing 1,1,1,2,3,3-hexafluoropropane. The method for preparing 1,1,1,2,3,3-hexafluoropropane provided by the present invention significantly improves the anti-sintering performance and catalytic efficiency of the palladium-based catalyst through the innovative design of the nitrogen-doped carbon support, enabling the catalyst to have high conversion rate, high selectivity and ultra-long service life in the selective hydrogenation reaction of hexafluoropropene, successfully solving the core defect of easy sintering and deactivation of the traditional palladium-carbon catalyst, and providing reliable technical support for the industrial continuous production of 1,1,1,2,3,3-hexafluoropropane.

[0007] The technical solution of the present invention is as follows: A method for preparing 1,1,1,2,3,3-hexafluoropropane, comprising the following steps: using hexafluoropropene as a raw material, and carrying out a hydrogenation reaction under the action of a Pd-loaded carbon nitride catalyst to obtain 1,1,1,2,3,3-hexafluoropropane.

[0008] Further, the preparation method of the Pd-loaded carbon nitride catalyst comprises the following steps: Step (1): Mix an ionic liquid and tetraethyl orthosilicate evenly by magnetic stirring, then calcine under nitrogen protection, cool, obtain a black solid, grind the black solid into powder, then add an ammonium bifluoride solution, stir magnetically at room temperature, filter after stirring, wash the filter cake, dry, and grind it into powder to obtain a nitrogen-doped carbon material; Step (2): Add water to the nitrogen-doped carbon material obtained in step (1), carry out ultrasonic treatment, then add a palladium chloride solution, continue ultrasonic treatment, then add a sodium borohydride solution, continue ultrasonic treatment, and filter to obtain a Pd-loaded carbon nitride catalyst.

[0009] Preferably, the ionic liquid in the step (1) is one of N-butyl-3-methylpyridinium dicyanamide (3-MBP-dca, CAS No. 712355-12-9), 1-ethyl-3-methylimidazolium dicyanamide (EMIM-dca, CAS No. 923019-22-1), 1-butyl-3-methylimidazolium dicyanamide (BMIm-dca, CAS No. 448245-52-1), and 1-octyl-3-methylimidazolium dicyanamide (OMIm-dca, CAS No. 905972-84-1); More preferably, the ionic liquid is one of N-butyl-3-methylpyridinium dicyanamide (3-MBP-dca) and 1-ethyl-3-methylimidazolium dicyanamide (EMIM-dca); Particularly preferably, the ionic liquid is N-butyl-3-methylpyridinium dicyanamide (3-MBP-dca).

[0010] Preferably, the mass ratio of the ionic liquid to tetraethyl orthosilicate in the step (1) is 3-7:1; More preferably, the mass ratio of the ionic liquid to tetraethyl orthosilicate is 4-6:1; Particularly preferably, the mass ratio of the ionic liquid to tetraethyl orthosilicate is 5:1.

[0011] Preferably, the mass ratio of the ammonium bifluoride solution to tetraethyl orthosilicate in the step (1) is 3-8:1; More preferably, the mass ratio of the ammonium bifluoride solution to tetraethyl orthosilicate is 3-5:1; Particularly preferably, the mass ratio of the ammonium bifluoride solution to tetraethyl orthosilicate is 4-5:1.

[0012] Preferably, the mass ratio of the palladium chloride solution in the step (2) to the nitrogen-doped carbon material obtained in the step (1) is 0.2-1:1; More preferably, the mass ratio of the palladium chloride solution to the nitrogen-doped carbon material is 0.3-0.8:1; Particularly preferably, the mass ratio of the palladium chloride solution to the nitrogen-doped carbon material is 0.3-0.5:1.

[0013] Preferably, the mass ratio of the palladium chloride solution in the step (2) to the sodium borohydride solution is 1:3-10; More preferably, the mass ratio of the palladium chloride solution to the sodium borohydride solution is 1:4-8; Particularly preferably, the mass ratio of the palladium chloride solution to the sodium borohydride solution is 1:4-6.

[0014] Preferably, the calcination temperature in step (1) is 900 - 1000 °C, and the mass concentration of the ammonium bifluoride solution is 20%; the concentration of the palladium chloride solution in step (2) is 0.01 - 0.05 g / mL; the mass concentration of the sodium borohydride solution is 0.2% - 0.5%.

[0015] More preferably, the calcination temperature is 900 °C; the concentration of the palladium chloride solution is 0.01 g / mL; the mass concentration of the sodium borohydride solution is 0.2%.

[0016] In addition, a preparation method of 1,1,1,2,3,3 - hexafluoropropane provided by the present invention specifically adopts a hydrogenation reaction: in a fixed - bed reactor, hexafluoropropene and H 2 are introduced, and the reaction is carried out under the action of a Pd - loaded carbon nitride catalyst to obtain 1,1,1,2,3,3 - hexafluoropropane.

[0017] Preferably, the reaction temperature in the preparation method is 80 - 120 °C, and the reaction pressure is 0.01 - 0.3 MPa; More preferably, the reaction temperature is 80 - 110 °C, and the reaction pressure is 0.01 - 0.1 MPa; Most preferably, the reaction temperature is 90 - 110 °C, and the reaction pressure is 0.05 - 0.1 MPa.

[0018] Preferably, the reaction space velocity of hexafluoropropene is 50 - 120 h -1 ; More preferably, the reaction space velocity of hexafluoropropene is 80 - 110 h -1 ; Most preferably, the reaction space velocity of hexafluoropropene is 90 - 110 h -1 .

[0019] Preferably, the molar ratio of hexafluoropropene to H 2 is 1:10 - 30; More preferably, the molar ratio of hexafluoropropene to H 2 is 1:15 - 30; Most preferably, the molar ratio of hexafluoropropene to H 2 is 1:15 - 20.

[0020] The present invention provides an innovative method for efficiently preparing 1,1,1,2,3,3 - hexafluoropropane. The core lies in the development of an anti - sintering Pd - loaded carbon nitride catalyst to solve the key problems such as short lifespan and difficulty in industrialization caused by Pd particle sintering during the hydrofluorination of hexafluoropropene in traditional palladium / activated carbon (Pd / AC) catalysts. The specific method is as follows: Using a cyanide - containing ionic liquid as a precursor, combined with the tetraethyl orthosilicate hard - template method, a nitrogen - doped carbon support with a hierarchical porous structure is directionally synthesized through a high - temperature carbonization process. During this process, the specific type of ionic liquid selected in the present invention has a high boiling point, high thermal stability, and extremely low vapor pressure. After high - temperature treatment, the polymerization and carbonization of the cyanide group in the ionic liquid can obtain a nitrogen - doped carbon material, and the structure of the ionic liquid can be easily adjusted to obtain a carbon material with a high nitrogen content.

[0021] Furthermore, after introducing nitrogen atoms into the carbon skeleton, the properties of the carbon material are optimized to a great extent. The introduced nitrogen atoms result in basic sites on the surface of the nitrogen - doped carbon material, including Bronsted basic sites and Lewis basic sites. These basic sites can bind to Pd metal, enhance the attachment of Pd metal on the material surface, promote the activity of metal sites, and reduce the sintering of Pd atoms. The catalyst prepared thereby exhibits high conversion and high selectivity in the hydrofluorination reaction of hexafluoropropene, and at the same time significantly extends the service life, maintaining stable activity and mechanical strength during continuous operation, successfully overcoming the bottleneck of industrial application caused by sintering deactivation of traditional catalysts.

[0022] Compared with the prior art, the preparation method of 1,1,1,2,3,3 - hexafluoropropane provided by the present invention has the following advantages: The preparation method of 1,1,1,2,3,3 - hexafluoropropane provided by the present invention significantly improves the anti - sintering performance and catalytic efficiency of the palladium - based catalyst through the innovative design of the nitrogen - doped carbon support: constructing a nitrogen - rich porous carbon skeleton using an ionic liquid precursor and the template method, and generating strong chemical bonding between the introduced nitrogen atoms and palladium nanoparticles, effectively inhibiting the migration and aggregation of palladium particles at high temperatures, while optimizing the electronic structure of palladium to enhance the hydrogenation activity, enabling the catalyst to have high conversion, high selectivity, and an extremely long service life in the selective hydrofluorination reaction of hexafluoropropene, successfully solving the core defect of easy sintering and deactivation of traditional palladium - carbon catalysts, and providing reliable technical support for the industrial continuous production of 1,1,1,2,3,3 - hexafluoropropane. Specific Embodiments

[0023] The present invention is further described below through the description of specific embodiments, but this is not a limitation of the present invention. Those skilled in the art can make various modifications or improvements according to the basic idea of the present invention, but as long as they do not depart from the basic idea of the present invention, they are within the protection scope of the present invention.

[0024] In the following examples and comparative examples, reagents not specifically described are conventional reagents and can be purchased from regular reagent production and sales companies. The methods used, unless otherwise specified, are all prior arts.

[0025] Example 1 A preparation method of 1,1,1,2,3,3 - hexafluoropropane, comprising the following steps: In a fixed - bed reactor, hexafluoropropene and H 2 are introduced, and a reaction is carried out under the action of a Pd - loaded carbon nitride catalyst to obtain 1,1,1,2,3,3 - hexafluoropropane. The reaction temperature is 100 °C, the reaction pressure is 0.05 MPa, the reaction space velocity of hexafluoropropene is 80 h -1 , and the molar ratio of hexafluoropropene to H 2 is 1:20.

[0026] Among them, the preparation method of the Pd - loaded carbon nitride catalyst is as follows: Step (1): Using ionic liquid N - n - butyl - 3 - methylpyridinium dicyanamide (3 - MBP - dca) as a precursor and tetraethyl orthosilicate as a hard template, the mass ratio of N - n - butyl - 3 - methylpyridinium dicyanamide (3 - MBP - dca) to tetraethyl orthosilicate is 5:1. Add both to a crucible and magnetically stir for 1 hour to make the ionic liquid precursor and the template mix evenly. Then place the crucible in a muffle furnace and calcine under nitrogen protection at 900 °C. After cooling to room temperature, take it out to obtain a black solid. Grind it into powder, then transfer it to a wide - mouth bottle, add an ammonium bifluoride solution with a mass concentration of 20%, and the mass ratio of the ammonium bifluoride solution to tetraethyl orthosilicate is 4:1. Magnetically stir at room temperature for 48 hours to remove silicon dioxide; after the stirring ends, filter, and wash the obtained filter cake with deionized water multiple times and dry it overnight in an oven at 70 °C. Grind it into powder to obtain a nitrogen - doped carbon material; Step (2): Place the nitrogen - doped carbon material obtained in step (1) in a beaker, add deionized water, and ultrasonicate for 10 minutes. Then add an aqueous solution of palladium chloride with a concentration of 0.01 g / mL, and the mass ratio of the palladium chloride solution to the nitrogen - doped carbon material is 0.3:1. Continue to ultrasonicate for 10 minutes, then add a sodium borohydride solution with a mass concentration of 0.2%, and the mass ratio of the palladium chloride solution to the sodium borohydride solution is 1:5. Ultrasonicate for 30 minutes, and the solid obtained after filtration is the Pd - loaded carbon nitride catalyst.

[0027] Example 2

[0028] A preparation method of 1,1,1,2,3,3 - hexafluoropropane, comprising the following steps: In a fixed - bed reactor, hexafluoropropene and H 2, the reaction is carried out under the action of a Pd-loaded carbon nitride catalyst to obtain 1,1,1,2,3,3-hexafluoropropane. The reaction temperature is 80 °C, the reaction pressure is 0.01 MPa, and the reaction space velocity of hexafluoropropene is 50 h -1 , hexafluoropropene and H 2 The molar ratio of is 1:10.

[0029] Among them, the preparation method of the Pd-loaded carbon nitride catalyst is as follows: Step (1): Using ionic liquid 1-ethyl-3-methylimidazolium dicyanamide (EMIM-dca) as a precursor and tetraethyl orthosilicate as a hard template, the mass ratio of the 1-ethyl-3-methylimidazolium dicyanamide (EMIM-dca) to tetraethyl orthosilicate is 3:1. Add both to a crucible and magnetically stir for 1 hour to mix the ionic liquid precursor and the template evenly. Then place the crucible in a muffle furnace and calcine it under nitrogen protection at 1000 °C. After cooling to room temperature, take it out to obtain a black solid. Grind it into powder, then transfer it to a wide-mouth bottle, add an ammonium bifluoride solution with a mass concentration of 20%, and the mass ratio of the ammonium bifluoride solution to tetraethyl orthosilicate is 3:1. Magnetically stir at room temperature for 48 hours to remove silicon dioxide; after the stirring ends, filter, wash the obtained filter cake with deionized water multiple times, dry it overnight in an oven at 70 °C, and grind it into powder to obtain a nitrogen-doped carbon material; Step (2): Place the nitrogen-doped carbon material obtained in step (1) in a beaker, add deionized water, and ultrasonicate for 10 minutes. Then add an aqueous solution of palladium chloride with a concentration of 0.02 g / mL, and the mass ratio of the palladium chloride solution to the nitrogen-doped carbon material is 0.2:1. Continue to ultrasonicate for 10 minutes, then add a sodium borohydride solution with a mass concentration of 0.3%, and the mass ratio of the palladium chloride solution to the sodium borohydride solution is 1:3. Ultrasonicate for 30 minutes, and the solid obtained after filtration is the Pd-loaded carbon nitride catalyst.

[0030] Example 3 A method for preparing 1,1,1,2,3,3-hexafluoropropane, comprising the following steps: In a fixed-bed reactor, introduce hexafluoropropene and H 2 , the reaction is carried out under the action of a Pd-loaded carbon nitride catalyst to obtain 1,1,1,2,3,3-hexafluoropropane. The reaction temperature is 90 °C, the reaction pressure is 0.1 MPa, and the reaction space velocity of hexafluoropropene is 90 h -1 , hexafluoropropene and H 2 The molar ratio of is 1:15.

[0031] Among them, the preparation method of the Pd-loaded carbon nitride catalyst is as follows: Step (1): Using ionic liquid 1-butyl-3-methylimidazolium dicyanamide (BMIm-dca) as the precursor and tetraethyl orthosilicate as the hard template, with the mass ratio of 1-butyl-3-methylimidazolium dicyanamide (BMIm-dca) to tetraethyl orthosilicate being 6:1. Add both to a crucible and magnetically stir for 1 hour to evenly mix the ionic liquid precursor and the template. Then place the crucible in a muffle furnace and calcine it under nitrogen protection at 900 °C. After cooling to room temperature, take it out to obtain a black solid. Grind it into powder, then transfer it to a wide-mouth bottle, add an ammonium bifluoride solution with a mass concentration of 20%, and the mass ratio of the ammonium bifluoride solution to tetraethyl orthosilicate is 5:1. Magnetically stir at room temperature for 48 hours to remove silicon dioxide. After stirring, filter, and wash the obtained filter cake with deionized water multiple times and dry it overnight in an oven at 70 °C. Grind it into powder to obtain the nitrogen-doped carbon material. Step (2): Place the nitrogen-doped carbon material obtained in step (1) in a beaker, add deionized water, and ultrasonicate for 10 minutes. Then add an aqueous solution of palladium chloride with a concentration of 0.03 g / mL, and the mass ratio of the palladium chloride solution to the nitrogen-doped carbon material is 0.5:1. Continue ultrasonication for 10 minutes, then add a sodium borohydride solution with a mass concentration of 0.4%, and the mass ratio of the palladium chloride solution to the sodium borohydride solution is 1:8. Ultrasonicate for 30 minutes, and the solid obtained after filtration is the Pd-loaded carbon nitride catalyst.

[0032] Example 4

[0033] A preparation method of 1,1,1,2,3,3-hexafluoropropane, comprising the following steps: In a fixed-bed reactor, introduce hexafluoropropene and H 2 , and carry out the reaction under the action of the Pd-loaded carbon nitride catalyst to obtain 1,1,1,2,3,3-hexafluoropropane. The reaction temperature is 110 °C, the reaction pressure is 0.3 MPa, the reaction space velocity of hexafluoropropene is 110 h -1 , and the molar ratio of hexafluoropropene to H 2 is 1:30.

[0034] Among them, the preparation method of the Pd-loaded carbon nitride catalyst is as follows: Step (1): Using ionic liquid 1-octyl-3-methylimidazolium bis(dicyanamide) (OMIm-dca) as the precursor and tetraethyl orthosilicate as the hard template, with the mass ratio of 1-octyl-3-methylimidazolium bis(dicyanamide) (OMIm-dca) to tetraethyl orthosilicate being 7:1, add both to a crucible and magnetically stir for 1 hour to evenly mix the ionic liquid precursor and the template. Then place the crucible in a muffle furnace and calcine under nitrogen protection at 1000 °C. After cooling to room temperature, take it out to obtain a black solid. Grind it into powder, then transfer it to a wide-mouth bottle, add an ammonium bifluoride solution with a mass concentration of 20%, with the mass ratio of the ammonium bifluoride solution to tetraethyl orthosilicate being 8:1, and magnetically stir at room temperature for 48 hours to remove silicon dioxide. After the stirring ends, filter, and wash the obtained filter cake with deionized water multiple times and then dry it overnight in an oven at 70 °C. Grind it into powder to obtain a nitrogen-doped carbon material; Step (2): Place the nitrogen-doped carbon material obtained in step (1) in a beaker, add deionized water, and ultrasonicate for 10 minutes. Then add an aqueous solution of palladium chloride with a concentration of 0.05 g / mL, with the mass ratio of the palladium chloride solution to the nitrogen-doped carbon material being 0.8:1, continue to ultrasonicate for 10 minutes, then add a sodium borohydride solution with a mass concentration of 0.5%, with the mass ratio of the palladium chloride solution to the sodium borohydride solution being 1:10, and ultrasonicate for 30 minutes. The solid obtained after filtration is the Pd-loaded carbon nitride catalyst.

[0035] Comparative Example 1

[0036] Compared with Example 1, the difference lies in that the ionic liquid N-butyl-3-methylpyridinium dicyanamide in the preparation step (1) of the Pd-loaded carbon nitride catalyst is replaced with 1,3-dimethylimidazolium hexafluorophosphate (CAS No. 243664-15-5), and other raw materials and preparation methods are the same as those in Example 1.

[0037] Comparative Example 2 Compared with Example 1, the difference lies in that the Pd-loaded carbon nitride catalyst is replaced with a Pd-loaded activated carbon catalyst, and the preparation method of the Pd-loaded activated carbon catalyst is as follows: Place the activated carbon in a beaker, add deionized water, and ultrasonicate for 10 minutes. Then add an aqueous solution of palladium chloride with a concentration of 0.01 g / mL, with the mass ratio of the palladium chloride solution to the activated carbon being 0.3:1, continue to ultrasonicate for 10 minutes, then add a sodium borohydride solution with a mass concentration of 0.2%, with the mass ratio of the palladium chloride solution to the sodium borohydride solution being 1:5, and ultrasonicate for 30 minutes. The solid obtained after filtration is the Pd-loaded activated carbon catalyst.

[0038] Other raw materials and preparation methods are the same as those in Example 1.

[0039] Comparative Example 3 Compared with Example 1, the difference lies in that tetraethyl orthosilicate in the preparation step (1) of the Pd-loaded carbon nitride catalyst is replaced by silica sol, and other raw materials and preparation methods are the same as those in Example 1.

[0040] Test Example 1. Detection of the yield and service life of 1,1,1,2,3,3-hexafluoropropane prepared by the present invention The products obtained by the preparation methods of Examples 1 to 4 and Comparative Examples 1 to 3 of the present invention were subjected to gas chromatography detection and analysis, and the conversion rate (%) of hexafluoropropene and the selectivity (%) of 1,1,1,2,3,3-hexafluoropropane are shown in Table 1.

[0041] When the catalysts prepared in Examples 1 to 4 and Comparative Examples 1 to 3 of the present invention were continuously used for 500 h, the products after the reaction were subjected to gas chromatography detection and analysis, and the conversion rate (%) of hexafluoropropene and the selectivity (%) of 1,1,1,2,3,3-hexafluoropropane are shown in Table 2.

[0042] Table 1 Group Conversion rate of hexafluoropropene (%) Selectivity of 1,1,1,2,3,3-hexafluoropropane (%) Example 1 99.98 99.53 Example 2 99.82 99.18 Example 3 99.91 99.33 Example 4 99.94 99.47 Comparative Example 1 95.42 99.12 Comparative Example 2 99.13 99.31 Comparative Example 3 96.19 99.16 。

[0043] Table 2 Group Conversion rate of hexafluoropropene (%) Selectivity of 1,1,1,2,3,3-hexafluoropropane (%) Example 1 99.45 99.23 Example 2 99.27 99.12 Example 3 99.36 99.21 Example 4 99.13 98.92 Comparative Example 1 90.89 98.18 Comparative Example 2 70.92 97.49 Comparative Example 3 95.74 98.43 。

[0044] As can be seen from Table 1, the selectivity of 1,1,1,2,3,3-hexafluoropropane obtained by gas chromatography detection and analysis of the products prepared by the methods of Examples 1 to 4 of the present invention is all above 99%. It can be seen that the Pd-loaded carbon nitride catalysts prepared by Examples 1 to 4 of the present invention can effectively improve the selectivity of 1,1,1,2,3,3-hexafluoropropane.

[0045] As can be seen from Table 2, after the Pd-loaded carbon nitride catalysts prepared by Examples 1 to 4 of the present invention were continuously catalyzed for 500 h respectively, 1,1,1,2,3,3-hexafluoropropane still had a high selectivity, indicating that the Pd-loaded carbon nitride catalysts prepared by the method of the present invention can not only improve the selectivity of 1,1,1,2,3,3-hexafluoropropane, but also effectively extend its service life.

[0046] The above embodiments only illustrate the principle and its efficacy of the present invention by way of example, rather than limiting the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing 1,1,1,2,3,3-hexafluoropropane, characterized in that: The method comprises the following steps: using hexafluoropropylene as a raw material, carrying out a hydrogenation reaction under the action of a Pd-supported carbon nitride catalyst to obtain 1,1,1,2,3,3-hexafluoropropane; The preparation method of the Pd-supported carbon nitride catalyst comprises the following steps: Step (1): the ionic liquid and tetraethyl orthosilicate are mixed uniformly by magnetic stirring, and then calcined under nitrogen protection, cooled to obtain a black solid, ground the black solid into powder, then added with ammonium bifluoride solution, magnetically stirred at room temperature, filtered after stirring, washed the filter cake, dried, and ground into powder to obtain a nitrogen-doped carbon material; Step (2): adding water to the nitrogen-doped carbon material obtained in step (1), performing ultrasonic treatment, then adding palladium chloride solution, continuing ultrasonic treatment, then adding sodium borohydride solution, continuing ultrasonic treatment, filtering, and obtaining a Pd-loaded carbon nitride catalyst; The ionic liquid in step (1) is one of N-n-butyl-3-methylpyridine dicyanamide, 1-ethyl-3-methylimidazole dicyanamide, 1-butyl-3-methylimidazole dicyanamide and 1-octyl-3-methylimidazole dicyanamide.

2. The method for preparing 1,1,1,2,3,3-hexafluoropropane according to claim 1, characterized in that: The mass ratio of the ionic liquid to tetraethyl orthosilicate in the step (1) is 3-7:

1.

3. The method for preparing 1,1,1,2,3,3-hexafluoropropane according to claim 1, characterized in that: In the step (1), the mass ratio of the ammonium bifluoride solution to tetraethyl orthosilicate is 3-8:

1.

4. The method for preparing 1,1,1,2,3,3-hexafluoropropane according to claim 1, characterized in that: The mass ratio of the palladium chloride solution in step (2) to the nitrogen-doped carbon material obtained in step (1) is 0.2-1:

1.

5. The method for preparing 1,1,1,2,3,3-hexafluoropropane according to claim 1, characterized in that: The mass ratio of the palladium chloride solution to the sodium borohydride solution in step (2) is 1:3-10.

6. The method for preparing 1,1,1,2,3,3-hexafluoropropane according to claim 1, characterized in that: The calcination temperature in step (1) is 900-1000° C., the mass concentration of the ammonium bifluoride solution in step (1) is 20%; the concentration of the palladium chloride solution in step (2) is 0.01-0.05 g / mL; and the mass concentration of the sodium borohydride solution in step (2) is 0.2%-0.5%.

7. The method for preparing 1,1,1,2,3,3-hexafluoropropane according to claim 1, characterized in that: The reaction temperature is 80-120° C., and the reaction pressure is 0.01-0.3 MPa.

8. The method for preparing 1,1,1,2,3,3-hexafluoropropane according to claim 1, characterized in that: The reaction space velocity of hexafluoropropylene is 50-120h -1 , the molar ratio of hexafluoropropylene to H2 is 1:10-30.