CN115254163B - Catalyst, preparation method thereof and application of catalyst in preparation process of hexafluorobutadiene - Google Patents

Abstract

The invention relates to the field of electron special gas, in particular to a catalyst, a preparation method thereof and application thereof in the preparation process of hexafluorobutadiene, wherein the catalyst comprises a substrate formed by layered structure minerals; the surface of the base material is coated with a carbon layer; the carbon layer is doped with nitrogen atoms; the carbon layer is also loaded with a metal halide. The catalyst in the invention can effectively reduce the energy required by converting 1, 4-dihalogen perfluorobutane into hexafluorobutadiene, so that the selectivity and the reaction speed of the reaction are also improved rapidly, the slurry method is adopted to prepare hexafluorobutadiene, the whole reaction is mild and controllable, the raw materials with high activity and easy decomposition are not needed, the difficulty in the reaction and the difficulty in subsequent treatment are greatly reduced, the reaction can be performed with high efficiency under milder conditions, the preparation method is simple, special protection treatment is not needed, the cost is low, and the industrial use can be facilitated.

Description

Catalyst, preparation method thereof and application of catalyst in preparation process of hexafluorobutadiene

Technical Field

The invention relates to the field of electron special gas, in particular to a catalyst, a preparation method thereof and application thereof in the preparation process of hexafluorobutadiene.

Background

Semiconductor chips have become the basic strategic industry as the basis of the information industry. Large scale integrated circuits and high speed high capacity memory chips are the core of the IT industry, and with the continuous development of the electronics industry, the etching line width requirements are narrower and narrower in the processing process. The core of the etching technology is the development of plasma etchants, hexafluorobutadiene (C ₄ F ₆ ) The etching gas is a new generation of integrated circuit etching gas with excellent performance, can be used for dry etching of ultra-large integrated circuits with the width smaller than 90nm and even narrower, has high selectivity and high accuracy, and is more suitable for etching process with high aspect ratio.

Hexafluorobutadiene has many etching advantages over C at 0.13 μm technology level ₄ F ₈ The photoresist and silicon nitride selectivity ratio is higher, the stability of etching can be improved when the photoresist and silicon nitride selectivity ratio is used, and the etching rate and uniformity are improved, so that the product yield is improved. Hexafluorobutadiene also has a very low greenhouse effect (GWP is only 290, and can be completely decomposed in the atmosphere for 2 d), has little harm to the ozone layer, and is an environment-friendly dry etching gas.

There are various methods for preparing hexafluorobutadiene, in which the routes capable of realizing industrial production can be divided into the following 5 types according to the raw materials and the number of reaction steps:

(1) 1, 2-difluoro dichloroethylene is used as a raw material, and hexafluorobutadiene is finally synthesized through 4 steps;

(2) With trifluorochloroethylene as a raw material, synthesizing hexafluorobutadiene through 3 steps;

(3) Taking trifluorobromoethylene as a raw material, and preparing hexafluorobutadiene through two steps of reactions;

(4) Tetrafluoroethylene is used as a reaction raw material, and hexafluorobutadiene is obtained through a two-step reaction;

(5) 1, 4-dihalogen perfluorobutane is used as a reaction raw material, and hexafluorobutadiene is prepared through one-step reaction.

For method 5, it has good development potential due to the advantage of short reaction route.

In 1985, bargigia6 reported for the first time a process for preparing hexafluorobutadiene by the dehydro-IF reaction of α, ω -diiodoperfluoroalkanes. The best hexafluorobutadiene preparation condition is that the hexane solution containing butyl lithium is added dropwise into the anhydrous diethyl ether solution containing 1.4-diiodoperfluorobutane at-80 ℃, then naturally heated to room temperature, boiled and kept for 30min, and finally the yield of hexafluorobutadiene can reach 97.5%.

Although the preparation of perfluorodiene by using alpha, omega-diiodoperfluoroalkane as raw material has the advantages of less steps and high yield, the industrial production difficulty is high because the organometallic compound is expensive, has high chemical activity, is easy to decompose and difficult to treat, and causes a certain danger in large-scale production.

MIKI, jun and Yoshimi et al report (EP 1247791) use I-CF ₂ -CF ₂ -CF ₂ -CF ₂ After mixing the-I and Zn, heating to 120 ℃, maintaining for 30 minutes, adding a certain amount of DMF to initiate reaction, and obtaining mixed gas after 30 minutes of reaction, wherein the perfluorobutadiene content is 65%. The yield thereof was found to be 54.4%.

Although the reaction operation is simple, the polar organic matters such as NN-dimethylformamide and the like are used, and the cyclization and hydrogen substitution reaction of the 1, 4-diiodoperfluorobutane can occur in the process, so that the yield of byproducts is too high, and the further development of the method is limited.

Disclosure of Invention

The invention provides a catalyst, a preparation method thereof and application thereof in the preparation process of hexafluorobutadiene, and aims to overcome the defects that the raw material risk is high and the byproduct yield is too high in the preparation process of hexafluorobutadiene in the prior art.

In order to achieve the aim of the invention, the invention is realized by the following technical scheme:

in a first aspect, the present invention provides a catalyst that can be used to catalyze the conversion of 1, 4-dihalo-perfluorobutane to hexafluorobutadiene;

the catalyst comprises a substrate composed of a layered structure mineral;

the surface of the base material is coated with a carbon layer;

the carbon layer is doped with nitrogen atoms;

the carbon layer is also loaded with a metal halide.

The catalyst comprises a substrate composed of layered structure minerals, wherein a large number of gaps are formed between the substrates due to the fact that the substrates are supported in a mode that the layers are scattered, reactants can be filled in the gaps in the process of catalytic reaction, and the whole reaction system can be divided into a plurality of micro-reaction areas by the gaps formed inside the substrate due to the fact that the reactants are adsorbed by the surfaces of the layers. Since each micro-reaction zone is independently carried out inside, and each micro-reaction zone is kept constant due to the reaction conditions, the reaction selectivity and reaction speed of the 1, 4-dihalo-perfluorobutane in the micro-reaction zone are also rapidly improved when the 1, 4-dihalo-perfluorobutane is converted into hexafluorobutadiene.

Meanwhile, the carbon layer is coated on the surface of the base material, so that the surface roughness of the base material is increased, reactants are more easily loaded, the reactants can stably stay in gaps among the base materials, and the stability of reaction conditions of a micro-reaction area is ensured. At the same time, the carbon layer has good conductivity, which can act as an electron mediator, thereby promoting electron transfer from the metal into the 1, 4-dihalo-perfluorobutane, and improving the reaction rate of the 1, 4-dihalo-perfluorobutane inside the microreaction region.

In addition, as the nitrogen atoms are doped in the carbon layer, the polarity of the carbon layer can be improved by doping the nitrogen atoms, and the nitrogen atoms can coordinate with the 1, 4-dihalo-perfluorobutane, so that the adsorption and adsorption effects on the 1, 4-dihalo-perfluorobutane are improved by combining the two effects, and the activation energy for the reaction is reduced.

Finally, as the metal halide is also loaded in the carbon layer, the metal halide can be used as a dehalogenation assisting agent to improve the dehalogenation effect of the metal on the 1, 4-dihalo-perfluorobutane in the micro-reaction area, compared with a control group without the metal halide, the conversion rate of an experimental group with the metal halide is obviously improved, and the reaction is milder.

Preferably, the layered structure mineral comprises one or more of mica, montmorillonite, pyrophyllite, serpentine, talcum, chlorite.

The layered structure minerals have the advantages of easily available raw materials and low cost, and compared with other porous materials in the prior art, the layered structure minerals have the characteristics of simple treatment method and no need of excessive maintenance. Therefore, the difficulty of industrial production is effectively reduced.

Preferably, the metal halide comprises any one or more of zinc, magnesium, aluminum, iron, manganese, copper halides.

In a second aspect of the present invention, there is provided a process for preparing the above catalyst,

the method comprises the following steps:

(1) Coating a carbon precursor on the surface of a substrate formed by layered structure minerals;

(2) Heat treating to convert the carbon precursor into a carbon layer;

(3) And immersing the substrate coated with the carbon layer in a metal halide solution to load the metal halide in the carbon layer, and drying to obtain the catalyst.

The catalyst provided by the invention has the advantages that the preparation method is simple, no special protection treatment is needed, and the industrial use can be facilitated. The catalyst provided by the invention only needs to fully strip the layered structure mineral into a sheet, then coat a layer of carbon precursor on the surface of the layered structure mineral, and then convert the carbon precursor into a carbon layer through a heat treatment mode.

The coated carbon precursor is various, for example, the substrate may be impregnated into a solution containing the carbon precursor by an impregnation method, and the carbon layer may be obtained after the impregnation is completed and dried.

Preferably, the carbon precursor is polydopamine or polyvinylpyrrolidone.

When the carbon precursor is polydopamine, the polydopamine layer, namely one of the carbon precursors, can be formed on the surface of the substrate by only immersing the substrate in a solution containing a dopamine component and adjusting the pH value of the solution.

When the carbon precursor is polyvinylpyrrolidone, the substrate is only required to be immersed in a solution containing polyvinylpyrrolidone, and after the immersion is finished, polyvinylpyrrolidone, namely another carbon precursor, can be formed on the surface of the substrate after drying.

The carbon precursor in the invention selects polydopamine or polyvinylpyrrolidone which has nitrogen atoms in the carbon precursor, so that the nitrogen atoms still remain in a carbon layer after heat treatment, and a component containing nitrogen elements is not required to be added to the carbon layer.

Preferably, the heat treatment conditions in the step (2) are as follows: and under the protection of inert gas, heating to 400-650 ℃ and keeping for 3-12 h.

In the process of forming the carbon layer on the surface of the substrate, in order to ensure the stable formation of the carbon layer, heat treatment is required under the protection of inert gas, so that the oxidation and thermal degradation of the carbon layer can be prevented. Meanwhile, the carbon precursor is carbonized at the temperature of 400-650 ℃ in the method, so that the layered structure mineral can be ensured not to be converted into a structure, and the stability is ensured.

In a third aspect of the present invention, there is also provided a method for producing hexafluorobutadiene,

the method comprises the following steps:

(S.1) mixing the catalyst, metal powder and an organic solvent to form slurry, and refluxing and stirring to enable zinc powder to enter interlayer gaps of the catalyst;

(S.2) dropwise adding 1, 4-dihalogen perfluorobutane into the slurry, uniformly mixing, and adding aluminum alkyl to initiate reaction;

(S.3) collecting the generated hexafluorobutadiene.

The hexafluorobutadiene of the invention is obviously different from the prior art in the preparation process: the reaction system of the prior art is usually in a solution system, whereas the reaction system of the present invention is in a slurry formed by mixing a catalyst, a metal powder and an organic solvent.

As already mentioned above, the present invention is such that the reaction mass fills the gaps formed in the gaps during the catalytic reaction to form micro-reaction regions, and thus each micro-reaction region is independently carried out inside, and each micro-reaction region is kept constant due to the reaction conditions, so that the energy required for converting 1, 4-dihalo-perfluorobutane into hexafluorobutadiene in the micro-reaction region is effectively reduced, and the selectivity of the reaction and the reaction speed are also rapidly improved.

In addition, the invention does not need to use high-activity easily-decomposed raw materials in the hexafluorobutadiene, greatly reduces the difficulty in the reaction and the difficulty in subsequent treatment, and ensures that the reaction can be performed with high efficiency under milder conditions.

Preferably, the reaction temperature in the step (s.2) is 60 to 85 ℃.

Preferably, in the step (s.1), the mass ratio of the catalyst to the metal powder to the organic solvent is (1 to 3): 1: (1-3);

preferably, in the step (s.1), the metal powder is a simple substance powder of any one of zinc, magnesium, aluminum, tin, copper, and iron or an alloy powder of a plurality of kinds.

Preferably, the solvent is a polar aprotic solvent.

Further preferably, the polar aprotic solvent comprises any one or a combination of more of dimethylsulfoxide, acetone, acetonitrile, dimethylformamide, dimethylacetamide or hexamethylphosphoramide.

Preferably, the particle size of the metal powder is in the range of 0.5 to 2 μm.

In some of the prior art, it is thought that the particle size of the metal powder will generally have a significant effect on the dehalogenation reaction, and it is thought that the particle size of the metal powder cannot be too small, and that too small metal powder will induce an increase in side reactions. The reaction process is carried out in the interlayer gaps of the base material, and the reaction in each micro-reaction area is relatively independent, so that the generation of side reaction can be reduced in the micro-reaction process, the metal powder with smaller particle size range can be selected in the process of selecting the particle size range of the metal powder, the generation of side reaction can be reduced when the metal powder reaches micro-nano scale, and the reaction rate can be effectively improved. When the particle diameter of the metal powder is too large, it is difficult to enter into the interlayer gap between the substrates, resulting in a decrease in the efficiency of the reaction.

Preferably, the amount of the substance of the alkyl aluminum initiator is 1-5% of the amount of the substance of the 1, 4-dihalo-perfluorobutane;

the amount of the 1, 4-dihalo-perfluorobutane is 10-50% of the amount of the metal powder.

Therefore, the invention has the following beneficial effects:

(1) The catalyst can effectively reduce the energy required by 1, 4-dihalogen perfluorobutane when converting into hexafluorobutadiene, so that the selectivity and the reaction speed of the reaction are also rapidly improved;

(2) According to the invention, the hexafluorobutadiene is prepared by a slurry method, the overall reaction is mild and controllable, and high-activity and easily-decomposed raw materials are not required to be used, so that the difficulty in the reaction and the difficulty in subsequent treatment are greatly reduced, and the reaction can be performed with high efficiency under milder conditions;

(3) The preparation method is simple, does not need special protection treatment, has low cost and can be favorable for industrialized use.

Drawings

Fig. 1 is an electron micrograph of catalyst A1.

FIG. 2 is an electron micrograph of monolithic mica in catalyst A1.

FIG. 3 is a gas phase diagram of crude hexafluorobutadiene in example 1.

Detailed Description

The invention is further described below with reference to the drawings and specific examples. Those of ordinary skill in the art will be able to implement the invention based on these descriptions. In addition, the embodiments of the present invention referred to in the following description are typically only some, but not all, embodiments of the present invention. Therefore, all other embodiments, which can be made by one of ordinary skill in the art without undue burden, are intended to be within the scope of the present invention, based on the embodiments of the present invention.

[ preparation of catalyst ]

The preparation method of the catalyst used in the invention is as follows:

catalyst A1: 100 parts of flaky mica powder is washed by acid washing and distilled water, then dispersed in 200 parts of water, then 20 parts of dopamine hydrochloride is added dropwise into the mixture, after stirring and dispersing uniformly, the pH is regulated to 9.5, stirring is continued for 1h, the mica powder is filtered out, the temperature is raised to 500 ℃ under the protection of nitrogen for heat treatment for 6h, the flaky mica coated with a carbon layer is obtained, then the flaky mica is immersed in a zinc chloride solution containing 5wt% for 30min, filtered and dried in vacuum for 3h at 100 ℃ to obtain the catalyst A1. The electron microscope photograph of the catalyst A1 and the monolithic mica therein is shown in figures 1-2.

Catalyst A2: 100 parts of flaky mica powder is washed by acid washing and distilled water, then dispersed in 200 parts of water, then 20 parts of dopamine hydrochloride is added dropwise into the mixture, after stirring and dispersing uniformly, the pH is regulated to 9.5, stirring is continued for 1h, the mica powder is filtered out, the temperature is raised to 500 ℃ under the protection of nitrogen for heat treatment for 6h, the flaky mica coated with a carbon layer is obtained, then the flaky mica is immersed in an aluminum chloride solution containing 5wt% for 30min, filtered and dried in vacuum for 3h at 100 ℃ to obtain the catalyst A2.

Catalyst A3: 100 parts of flaky mica powder is washed by acid washing and distilled water, then dispersed in 200 parts of water, then 20 parts of dopamine hydrochloride is added dropwise into the mixture, after stirring and dispersing uniformly, the pH is regulated to 9.5, stirring is continued for 1h, the mica powder is filtered out, the temperature is raised to 500 ℃ under the protection of nitrogen for heat treatment for 6h, the flaky mica coated with a carbon layer is obtained, then the flaky mica is immersed in a copper bromide solution containing 5wt% for 30min, filtered and dried in vacuum for 3h at 100 ℃ to obtain the catalyst A3.

Catalyst A4: 100 parts of flaky talcum powder is washed by acid washing and distilled water, then dispersed in 200 parts of water, then 20 parts of dopamine hydrochloride is added dropwise into the mixture, after stirring and dispersing uniformly, the pH is regulated to 9.5, stirring is continued for 1h, mica powder is filtered out, the temperature is raised to 650 ℃ under the protection of nitrogen for heat treatment for 4h, and the flaky mica coated with a carbon layer is obtained, then immersed in a zinc chloride solution containing 5wt% for 30min, filtered and dried in vacuum for 3h at 100 ℃ to obtain the catalyst A4.

Catalyst A5: 100 parts of flaky montmorillonite is washed by acid washing and distilled water, then dispersed in 200 parts of water containing 20% polyvinylpyrrolidone, stirred and dispersed for 1h, mica powder is filtered out, the temperature is raised to 400 ℃ under the protection of nitrogen for 12h, the flaky mica coated with a carbon layer is obtained, then the flaky mica is immersed in a zinc chloride solution containing 5wt% for 30min, filtered and dried in vacuum for 3h at 100 ℃ to obtain the catalyst A5.

Catalyst A6: 100 parts of flaky mica is washed by acid washing and distilled water, then dispersed in 200 parts of water containing 20% polyethylene oxide, stirred and dispersed for 1h, mica powder is filtered out, the temperature is raised to 400 ℃ under the protection of nitrogen for 12h, the flaky mica coated with a carbon layer is obtained, then the flaky mica is immersed in a zinc chloride solution containing 5wt% for 30min, filtered and dried in vacuum for 3h at 100 ℃ to obtain the catalyst A6.

Catalyst A7: 100 parts of flaky mica powder is washed by acid washing and distilled water, then dispersed in 200 parts of water, then 20 parts of dopamine hydrochloride is added dropwise into the mixture, after stirring and dispersing uniformly, the pH is regulated to 9.5, stirring is continued for 1h, the mica powder is filtered out, the temperature is raised to 500 ℃ under the protection of nitrogen, heat treatment is carried out for 6h, and the flaky mica coated with a carbon layer is obtained and naturally cooled, thus obtaining the catalyst A7.

[ preparation of hexafluorobutadiene ]

Example 1

A method for preparing hexafluorobutadiene, comprising the steps of:

after the whole air in 2000ml of the column bottom with the thermocouple was replaced with nitrogen, 200g of catalyst A1, 200g (3 mol) of nano zinc powder (average particle diameter 500 nm) and 400g of dimethyl sulfoxide were added, and the mixture was heated, refluxed and stirred for 1 hour, so that zinc powder was introduced into the inter-layer gaps of the catalyst to form a slurry. The temperature of the system is regulated to 80 ℃, 136g (0.3 mol) of 1, 4-diiodoperfluorobutane is added into the system, mixing is continued for 30min, then 0.35g (3 mmol) of triethylaluminum is added into the system to initiate reaction, the crude product is collected in a low-temperature cold trap at the temperature of minus 90 ℃ after 3h of reaction, the crude product is fully gasified at normal temperature after the reaction is finished, gasified gas is frozen into a high-pressure steel cylinder to be weighed, 45.8g (yield 94.2 percent and purity 98.3 percent) of crude hexafluorobutadiene is obtained, and the GC diagram is shown in figure 3.

Example 2

A method for preparing hexafluorobutadiene, comprising the steps of:

after the whole air in 2000ml of the autoclave equipped with a thermocouple was replaced with nitrogen, 300g of catalyst A2, 100g (1.5 mol) of ultrafine zinc powder (average particle diameter: 1 μm) and 300g of dimethyl sulfoxide were added, and the mixture was heated, refluxed and stirred for 1 hour to allow the zinc powder to enter into the gaps between the layers of the catalyst to form a slurry. The temperature of the system is regulated to 85 ℃, 340g (0.75 mol) of 1, 4-diiodoperfluorobutane is added into the system, the mixture is continuously mixed for 30min, then 4.38g (38 mmol) of triethylaluminum is added into the mixture to initiate the reaction, the crude product is collected in a low-temperature cold trap at the temperature of minus 90 ℃ after the reaction is carried out for 4h, the crude product is fully gasified at normal temperature after the reaction is finished, and gasified gas is frozen into a high-pressure steel cylinder to be weighed, thus 115.5g (yield 95.1% and purity 98.5%) of crude hexafluorobutadiene are obtained.

Example 3

A method for preparing hexafluorobutadiene, comprising the steps of:

after the whole air in 2000ml of the column bottom with thermocouple was replaced with nitrogen, 200g of catalyst A3, 100g (1.5 mol) of nano zinc powder (average particle diameter 500 nm) and 100g of dimethyl sulfoxide were added, and the mixture was heated, refluxed and stirred for 1 hour, so that zinc powder was introduced into the interlayer gap of the catalyst to form a slurry. The temperature of the system is regulated to 85 ℃, 136g (0.3 mol) of 1, 4-diiodoperfluorobutane is added into the system, the mixture is continuously mixed for 30min, then 0.7g (6 mmol) of triethylaluminum is added into the mixture to initiate the reaction, the crude product is collected in a low-temperature cold trap at the temperature of minus 90 ℃ after 4h of reaction, the crude product is fully gasified at normal temperature after the reaction is finished, and gasified gas is frozen into a high-pressure steel cylinder to be weighed, thus obtaining 40.5g (yield 93.5 percent, purity 99.3 percent) of crude hexafluorobutadiene.

Example 4

A method for preparing hexafluorobutadiene, comprising the steps of:

after the whole air in 2000ml of the column bottom with thermocouple was replaced with nitrogen, 200g of catalyst A4, 96g (4 mol) of ultrafine magnesium powder (average particle size 2 μm) and 250g of acetonitrile were added, and the mixture was heated, refluxed and stirred for 1 hour, so that the magnesium powder entered into the interlayer gap of the catalyst to form slurry. Regulating the temperature of the system to 60 ℃, adding 181g (0.4 mol) of 1, 4-diiodoperfluorobutane into the system, continuously mixing for 30min, then adding 1.16g (3 mmol) of triethylaluminum to initiate reaction, collecting a crude product after 2.5h of reaction, placing the crude product in a low-temperature cold trap at the temperature of minus 90 ℃, fully gasifying the crude product at normal temperature after the reaction is finished, freezing gasified gas into a high-pressure steel cylinder, and weighing to obtain 61.8g (yield 95.3% and purity 98.1%) of crude hexafluorobutadiene.

Example 5

A method for preparing hexafluorobutadiene, comprising the steps of:

after the whole air in 2000ml of the autoclave equipped with a thermocouple was replaced with nitrogen, 250g of catalyst A5, 54g (2 mol) of ultrafine aluminum powder (average particle diameter: 1 μm) and 250g of acetone were added, and the mixture was heated, refluxed and stirred for 1 hour to allow the aluminum powder to enter into the gaps between the layers of the catalyst to form a slurry. The temperature of the system is regulated to 65 ℃, 91g (0.2 mol) of 1, 4-diiodoperfluorobutane is added into the system, the mixture is continuously mixed for 30min, then 0.24g (3 mmol) of triethylaluminum is added into the mixture to initiate the reaction, the reaction is carried out for 3.5h, the crude product is collected and placed in a low-temperature cold trap at the temperature of minus 90 ℃, after the reaction is finished, the crude product is fully gasified at normal temperature, gasified gas is frozen into a high-pressure steel cylinder to be weighed, and 30.8g of crude hexafluorobutadiene (the yield is 95.1 percent and the purity is 97.9 percent) is obtained.

Example 6

A method for preparing hexafluorobutadiene, comprising the steps of:

after the whole air in 2000ml of the autoclave equipped with a thermocouple was replaced with nitrogen, 300g of catalyst A2, 100g (1.5 mol) of ultrafine zinc powder (average particle diameter: 1 μm) and 300g of dimethyl sulfoxide were added, and the mixture was heated, refluxed and stirred for 1 hour to allow the zinc powder to enter into the gaps between the layers of the catalyst to form a slurry. The temperature of the system is regulated to 85 ℃, 270g (0.75 mol) of 1, 4-dibromoperfluorobutane is added into the system, mixing is continued for 30min, then 0.86g (7.5 mmol) of triethylaluminum is added to initiate the reaction, the crude product is collected in a low-temperature cold trap at the temperature of minus 90 ℃ after 4h of reaction, the crude product is fully gasified at normal temperature after the reaction is finished, and gasified gas is frozen into a high-pressure steel cylinder for weighing, thus 116.1g of crude hexafluorobutadiene (yield 95.6 percent and purity 97.6 percent) is obtained.

Comparative example 1

A method for preparing hexafluorobutadiene, comprising the steps of:

after the whole air in 2000ml of the thermocouple-equipped column was replaced with nitrogen, 100g (1.5 mol) of nano zinc powder (average particle diameter 500 nm) and 100g of dimethyl sulfoxide were stirred at reflux with heating for 1 hour to form a slurry. The temperature of the system is regulated to 120 ℃, 136g (0.3 mol) of 1, 4-diiodoperfluorobutane is added into the system, mixing is continued for 30min, then 0.7g (6 mmol) of triethylaluminum is added to initiate reaction, the crude product is collected in a low-temperature cold trap at the temperature of minus 90 ℃ after 5h of reaction, the crude product is fully gasified at normal temperature after the reaction is finished, and gasified gas is frozen into a high-pressure steel cylinder for weighing, thus obtaining 20.0g (yield 46.3 percent, purity 88.6 percent) of crude hexafluorobutadiene.

Comparative example 2

A method for preparing hexafluorobutadiene, comprising the steps of:

after the whole air in 2000ml of the column bottom with thermocouple was replaced with nitrogen, 200g of catalyst A6, 100g (1.5 mol) of nano zinc powder (average particle diameter 500 nm) and 100g of dimethyl sulfoxide were added, and the mixture was heated, refluxed and stirred for 1 hour, so that zinc powder was introduced into the interlayer gap of the catalyst to form a slurry. The temperature of the system is regulated to 85 ℃, 136g (0.3 mol) of 1, 4-diiodoperfluorobutane is added into the system, the mixture is continuously mixed for 30min, then 0.7g (6 mmol) of triethylaluminum is added into the mixture to initiate the reaction, the crude product is collected in a low-temperature cold trap at the temperature of minus 90 ℃ after 4h of reaction, the crude product is fully gasified at normal temperature after the reaction is finished, and gasified gas is frozen into a high-pressure steel cylinder to be weighed, thus 31.4g of crude hexafluorobutadiene is obtained (yield is 72.6 percent, purity is 94.9 percent).

Comparative example 3

A method for preparing hexafluorobutadiene, comprising the steps of:

after the whole air in 2000ml of the column bottom with thermocouple was replaced with nitrogen, 200g of catalyst A7, 100g (1.5 mol) of nano zinc powder (average particle diameter 500 nm) and 100g of dimethyl sulfoxide were added, and the mixture was heated, refluxed and stirred for 1 hour, so that zinc powder was introduced into the interlayer gap of the catalyst to form a slurry. The temperature of the system is regulated to 85 ℃, 136g (0.3 mol) of 1, 4-diiodoperfluorobutane is added into the system, the mixture is continuously mixed for 30min, then 0.7g (6 mmol) of triethylaluminum is added into the mixture to initiate the reaction, the crude product is collected in a low-temperature cold trap at the temperature of minus 90 ℃ after 4h of reaction, the crude product is fully gasified at normal temperature after the reaction is finished, and gasified gas is frozen into a high-pressure steel cylinder to be weighed, thus 29.5g (yield 68.2 percent and purity 95.2 percent) of crude hexafluorobutadiene is obtained.

From the above results, it is understood that by comparing examples 1 to 5 with comparative example 1, the reaction temperature used in the preparation process of hexafluorobutadiene can be effectively reduced by applying the catalyst of the present invention, and the yield and purity can be maintained higher by a person at a lower reaction temperature.

Meanwhile, it was found by comparison with comparative example 2 that since the catalyst A6 of comparative example 2 does not contain nitrogen atoms in the carbon layer, the yield of crude hexafluorobutadiene during the reaction was greatly lowered, indicating that the addition of nitrogen atoms had a non-negligible effect on the conversion of diiodoperfluorobutane to hexafluorobutadiene.

Furthermore, as compared with comparative example 2, it was found that the catalyst A6 of comparative example 2 was also reduced in productivity due to the absence of the supported metal halide in the carbon layer thereof, indicating that the addition of the metal halide also had a non-negligible effect on the conversion of diiodoperfluorobutane to hexafluorobutadiene.

Claims (9)

1. A catalyst, which is characterized in that,

comprising a substrate made of a layered structure mineral;

the surface of the base material is coated with a carbon layer;

the carbon layer is doped with nitrogen atoms;

the carbon layer is also loaded with metal halide;

the metal halide comprises any one or a combination of more of zinc, magnesium, aluminum, iron, manganese and copper.

2. A catalyst according to claim 1, wherein,

the layered structure mineral comprises one or more of mica, montmorillonite, pyrophyllite, serpentine, talcum and chlorite.

3. A process for preparing a catalyst as claimed in claim 1 or 2, characterized in that,

the method comprises the following steps:

(1) Coating a carbon precursor on the surface of a substrate formed by layered structure minerals;

(2) Heat treating to convert the carbon precursor into a carbon layer;

(3) And immersing the substrate coated with the carbon layer in a metal halide solution to load the metal halide in the carbon layer, and drying to obtain the catalyst.

4. The method of claim 3, wherein the step of,

the carbon precursor is polydopamine or polyvinylpyrrolidone.

5. The method of claim 3, wherein the step of,

the heat treatment conditions in the step (2) are as follows: and under the protection of inert gas, heating to 400-650 ℃ and keeping for 3-12 h.

6. A preparation method of hexafluorobutadiene is characterized in that,

the method comprises the following steps:

(s.1) mixing the catalyst of claim 1 or 2 with a metal powder and an organic solvent to form a slurry, and refluxing and stirring the slurry so that the metal powder enters into the inter-layer gaps of the catalyst;

(S.2) dropwise adding 1, 4-dihalogen perfluorobutane into the slurry, uniformly mixing, and adding aluminum alkyl to initiate reaction;

(S.3) collecting the generated hexafluorobutadiene.

7. A process for producing hexafluorobutadiene as claimed in claim 6, wherein,

in the step (S.1), the mass ratio of the catalyst to the metal powder to the organic solvent is (1-5): 1: (1-5);

the metal powder is elemental powder of any one of zinc, magnesium, aluminum, tin, copper and iron or alloy powder of a plurality of kinds;

the solvent is a polar aprotic solvent.

8. A process for producing hexafluorobutadiene as claimed in claim 6 or 7, wherein,

the particle size range of the metal powder is 0.5-2 mu m.

9. A process for producing hexafluorobutadiene as claimed in claim 6, wherein,

the amount of the substance of the alkyl aluminum initiator in the step (S.2) is 1-5% of the amount of the substance of the 1, 4-dihalo-perfluorobutane;

the amount of the 1, 4-dihalo-perfluorobutane is 10-50% of the amount of the metal powder.

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