阅读说明：本技术 一种碳结构限域金属氟化物的制备方法 (Preparation method of carbon structure limited domain metal fluoride ) 是由 韩文锋 陆佳勤 王海丽 刘永南 俞威 杨虹 刘兵 李西良 唐浩东 李瑛� 于 2019-09-20 设计创作，主要内容包括：本发明公开了一种碳结构限域金属氟化物的制备方法,其特征在于包括以下过程：将PVDF与金属可溶性盐一并分散到有机溶剂中,然后搅拌至少12h,直至得到粘稠均匀的溶液,然后将所得溶液中的溶剂在80~160℃下蒸干,蒸干所得固体在高纯气氛下进行高温煅烧,即得到所述碳结构限域金属氟化物；其中所述金属可溶性盐为铝盐、镁盐、铬盐中的一种或两种以上混合物。本发明制备的碳结构限域金属氟化物,氟化铝活性中心被碳均匀分隔开,从而提高了催化剂的烧结能力,通过本发明方法制备的碳结构限域金属氟化物,在1,1,1,2-四氟乙烷裂解制备三氟乙烯反应中具有良好的活性和稳定性,且所述碳结构限域金属氟化物不易烧结失活。(The invention discloses a preparation method of carbon structure limited domain metal fluoride, which is characterized by comprising the following steps: dispersing PVDF and metal soluble salt into an organic solvent, stirring for at least 12 hours until a viscous and uniform solution is obtained, evaporating the solvent in the obtained solution to dryness at 80-160 ℃, and calcining the solid obtained by evaporation to dryness at high temperature under a high-purity atmosphere to obtain the carbon structure limited metal fluoride; wherein the metal soluble salt is one or a mixture of more than two of aluminum salt, magnesium salt and chromium salt. The carbon structure limited metal fluoride prepared by the method has good activity and stability in the reaction of preparing trifluoroethylene by cracking 1,1,1, 2-tetrafluoroethane, and is not easy to sinter and inactivate.)

1. A preparation method of carbon structure limited domain metal fluoride is characterized by comprising the following steps:

1) dispersing PVDF and metal soluble salt into an organic solvent, and then stirring for at least 12 hours until a viscous and uniform solution is obtained; wherein the metal soluble salt is one or a mixture of more than two of aluminum salt, magnesium salt and chromium salt;

2) evaporating the solvent in the solution obtained in the step 1) to dryness at 80-160 ℃, and calcining the solid obtained by evaporation to dryness at high temperature in a high-purity atmosphere to obtain the carbon structure confined metal fluoride.

2. The method of claim 1, wherein in step 1), the organic solvent is DMF; the concentration of the metal soluble salt in the organic solvent is 0.05-1 mol/L, and the mass ratio of the PVDF to the metal soluble salt is 1: 1-15: 1.

3. The method for preparing carbon-structure-confined metal fluoride according to claim 1, wherein the high-temperature calcination in step 2) is carried out by: calcining for 3-15 hours at the temperature of 300-800 ℃ in a high-purity atmosphere.

4. A method of preparing a carbon-structure-confined metal fluoride as claimed in claim 3, wherein said highly pure atmosphere is nitrogen, air, oxygen, carbon dioxide or carbon monoxide having a purity of 99.9% or more.

5. The method for preparing carbon-structure-confined metal fluoride according to claim 3, wherein the carbon-structure-confined metal fluoride prepared in the step 2) is carbon-doped AlF₃、MgF₂And CrF₃At least one of (1).

6. The method for preparing carbon-structure-restricted metal fluoride according to claim 1, wherein in the step 1), the metal soluble salt is one or a mixture of aluminum nitrate, magnesium chloride, chromium nitrate, chromium oxide and magnesium acetate.

Technical Field

The invention relates to a preparation method of carbon structure limited domain metal fluoride.

Background

1,1,1, 2-tetrafluoroethane (HFC-134 a) belongs to the third generation refrigerant, is nontoxic, colorless, tasteless, has ozone depletion potential of 0, and has no harm to the ozone layer when being discharged into the atmosphere. It is mainly used as refrigerant of automobile air conditioner, refrigerator, central air conditioner, etc. and is also aerosol propellant and fire retardant for pesticide, cosmetics, medicine, etc. But HFC-134a has a relatively high greenhouse potential (GWP) reaching CO₂1400 times of the gas, so HFC-134a is one of the gases which are controlled and discharged by the Kyoto protocol. The product of cracking HFC-134a to remove HF is trifluoroethylene (TrFE), which is an important polymer monomer, can produce some high molecular polymers or fine fluorine chemicals by polymerization or addition polymerization, and is widely applied to the production of fluorine-containing resin, fluorine-containing rubber and the like. Thus, the conversion of HFC-134a to high value added trifluoroethylene is very advantageousIs of great significance.

Chinese patent CN107233903A reports that when the aluminum fluoride catalyst is prepared by mechanical mixing roasting method and used for the dehydrof removal of 1,1,1, 2-tetrafluoroethane to prepare trifluoroethylene, the conversion rate of 1,1,1, 2-tetrafluoroethane is about 38% at 450 ℃, and the selectivity of trifluoroethylene is higher than 99%. Chinese patent CN201710353517 reports prepared theta-AlF₃When the catalyst is used for preparing trifluoroethylene by removing HF from 1,1,1, 2-tetrafluoroethane, the conversion rate of 1,1,1, 2-tetrafluoroethane is about 30% at 450 ℃, and the selectivity of trifluoroethylene is higher than 99%. Patent FR2710054A1 also reports the use of aluminum fluoride as a catalyst for the catalytic HF removal of 1,1,1, 2-tetrafluoroethane to prepare trifluoroethylene. Chinese patent CN108722449A reports that when aluminum-based catalyst is used for catalyzing 1,1,1, 2-tetrafluoroethane to remove HF to prepare trifluoroethylene, the conversion rate of 1,1,1, 2-tetrafluoroethane is about 35% at 450 ℃. Patent CN108114732A reports that when a zinc aluminate coated aluminum fluoride catalyst is prepared by a coating method and applied to the cracking of 1,1,1, 2-tetrafluoroethane to prepare trifluoroethylene, the conversion rate of 1,1,1, 2-tetrafluoroethane is above 30% at 450 ℃, and the selectivity of trifluoroethylene is higher than 99%. In the Chinese patent CN106000428A, aluminum fluoride containing OH groups, P-doped aluminum fluoride containing OH groups and zinc-doped aluminum fluoride containing OH groups are used as catalysts to catalyze the dehydrofluorination of 1,1,1, 2-tetrafluoroethane to prepare trifluoroethylene, the conversion rate of the 1,1,1, 2-tetrafluoroethane is 20-60% at 450-500 ℃, and the selectivity of the trifluoroethylene is higher than 99%. Likewise, U.S. Pat. No. 4, 5856593A reports the use of AlF₃When the catalyst is used as a catalyst for preparing trifluoroethylene by dehydrofluorination of HFC-134a, the conversion rate of 1,1,1, 2-tetrafluoroethane is about 35 percent by reaction at 600 ℃.

AlF as described above₃Is an important inorganic material, is often used for preparing trifluoroethylene by removing HF from 1,1,1, 2-tetrafluoroethane, and is also a main catalyst for F/Cl exchange, HF removal, HCl removal, fluorination reaction and replacement reaction. The specific surface area, crystal structure and surface acidity of the catalyst are all key factors influencing the catalytic activity. MgF with stronger Lewis acid₂And CrF₃The same applies to the HF removal from 1,1,1, 2-tetrafluoroethane. However, the existing catalyst has the disadvantages of high reaction temperature, easy sintering, low catalytic activity, serious carbon deposition and inactivationAnd the like.

Disclosure of Invention

In view of the above technical problems in the prior art, the present invention aims to provide a method for preparing carbon-structure-limited metal fluoride.

The preparation method of the carbon structure limited domain metal fluoride is characterized by comprising the following steps:

1) dispersing PVDF and metal soluble salt into an organic solvent, and then stirring for at least 12 hours until a viscous and uniform solution is obtained (aiming at uniformly mixing PVDF and metal soluble salt); wherein the metal soluble salt is one or a mixture of more than two of aluminum salt, magnesium salt and chromium salt;

2) evaporating the solvent in the solution obtained in the step 1) to dryness at 80-160 ℃, and calcining the solid obtained by evaporation to dryness at high temperature in a high-purity atmosphere to obtain the carbon structure confined metal fluoride.

The preparation method of the carbon structure limited domain metal fluoride is characterized in that in the step 1), the organic solvent is DMF; the concentration of the metal soluble salt in the organic solvent is 0.05-1 mol/L, and the mass ratio of the PVDF to the metal soluble salt is 1: 1-15: 1.

The preparation method of the carbon structure limited metal fluoride is characterized in that in the step 2), the high-temperature calcination process comprises the following steps: calcining for 3-15 hours at the temperature of 300-800 ℃ in a high-purity atmosphere.

The preparation method of the carbon structure limited metal fluoride is characterized in that the high-purity atmosphere is nitrogen, air, oxygen, carbon dioxide or carbon monoxide with the purity of more than 99.9 percent.

The preparation method of the carbon structure limited metal fluoride is characterized in that the carbon structure limited metal fluoride prepared in the step 2) is carbon-doped AlF₃、MgF₂And CrF₃At least one of (1).

The preparation method of the carbon structure limited metal fluoride is characterized in that in the step 1), the metal soluble salt is one or a mixture of aluminum nitrate, magnesium chloride, chromium nitrate, chromium oxide and magnesium acetate.

Compared with the prior art, the invention has the following beneficial effects:

in the process of preparing the carbon structure limited domain metal fluoride, PVDF and metal soluble salt are dissolved in an organic solvent, the organic solvent is dried and removed after the PVDF and the metal soluble salt are uniformly stirred and mixed, and then the PVDF fiber is wrapped by the metal soluble salt, and then the PVDF fiber is calcined at high temperature. In the calcining process, the metal soluble salt is firstly decomposed into the metal oxide, the PVDF can also generate some carbon-containing oligomers except for generating HF in the high-temperature decomposition process, HF released by the decomposition of the PVDF fluorinates the metal oxide decomposed by the metal soluble salt into the metal fluoride, so that the finally formed metal fluoride can be doped with carbon, the metal fluoride is separated and limited by carbon left by the decomposition of the PVDF, and the metal fluoride with a carbon structure limited domain is formed, so that the sintering resistance of the catalyst is improved, and better stability can be kept in the reaction process. Wherein the atmosphere of high temperature calcination requires a purity higher than 99.9%, different calcination atmospheres will result in metal fluorides with different carbon contents, which determines the exposed number of active sites and the number of active species limited by carbon.

According to the carbon structure limited metal fluoride prepared by the method, the aluminum fluoride active centers are uniformly separated by carbon, so that the sintering capacity of the catalyst is improved. The aluminum fluoride catalyst with different carbon contents can be obtained by roasting under different atmospheres. The method has mild process conditions and simple operation, and the carbon structure limited domain metal fluoride prepared by the method has anti-sintering capability because the aluminum fluoride is embedded in the carbon structure, has good activity and stability in the reaction of preparing trifluoroethylene by cracking 1,1,1, 2-tetrafluoroethane, and is not easy to sinter and inactivate.

Drawings

FIG. 1 is a SEM characterization of the aluminum fluoride catalyst prepared in example 1;

FIG. 2 is a SEM characterization of the aluminum fluoride catalyst prepared in example 2;

FIG. 3 is a SEM characterization of the aluminum fluoride catalyst prepared in example 3;

fig. 4 is a SEM characterization result graph of the aluminum fluoride catalyst prepared in example 4.

Detailed Description

The present invention is further illustrated by the following examples, which should not be construed as limiting the scope of the invention.

In the following examples, the purity of nitrogen, air, oxygen, carbon dioxide and carbon monoxide used was 99.9% or more.