CN109180420B - Preparation method of 1, 1-difluoroethylene - Google Patents

Preparation method of 1, 1-difluoroethylene Download PDF

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CN109180420B
CN109180420B CN201811134073.4A CN201811134073A CN109180420B CN 109180420 B CN109180420 B CN 109180420B CN 201811134073 A CN201811134073 A CN 201811134073A CN 109180420 B CN109180420 B CN 109180420B
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difluoroethylene
composite catalyst
chloroethane
difluoro
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CN109180420A (en
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韩文锋
王志昆
刘兵
李西良
唐浩东
李瑛�
刘化章
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Zhejiang University of Technology ZJUT
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Zhejiang University of Technology ZJUT
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C17/00—Preparation of halogenated hydrocarbons
    • C07C17/25—Preparation of halogenated hydrocarbons by splitting-off hydrogen halides from halogenated hydrocarbons
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/06—Halogens; Compounds thereof
    • B01J27/132—Halogens; Compounds thereof with chromium, molybdenum, tungsten or polonium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/06—Halogens; Compounds thereof
    • B01J27/138—Halogens; Compounds thereof with alkaline earth metals, magnesium, beryllium, zinc, cadmium or mercury
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
    • B01J37/0027—Powdering
    • B01J37/0036—Grinding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/03—Precipitation; Co-precipitation
    • B01J37/031—Precipitation

Abstract

The invention discloses a preparation method of 1, 1-difluoroethylene, which comprises the following steps: filling a composite catalyst into a tubular reactor, introducing 1, 1-difluoro-1-chloroethane or 1, 1-difluoro-2-chloroethane serving as a raw material into the tubular reactor, and performing a gas-phase catalytic cracking reaction to obtain 1, 1-difluoroethylene; the composite catalyst is a metal composite fluoride. The method for preparing 1, 1-difluoroethylene provided by the invention has the characteristics of low reaction temperature, high product selectivity, high yield, strong catalyst regenerability, mild preparation process conditions, simple operation and the like.

Description

Preparation method of 1, 1-difluoroethylene
Technical Field
The invention relates to a preparation method of 1, 1-difluoroethylene.
Background
1, 1-difluoro-1-chloroethane (HCFC-142 b, or R142 b) is colorless gas at normal temperature, slightly aromatic and easily soluble in oil and water. HCFC-142b is an important organic intermediate used in various fields such as refrigerants, blowing agents, etc., but it is most mainly used as a monomer for producing polyvinylidene fluoride (PVDF), 1, 1-difluoroethylene (VDF). To date, vinylidene fluoride has been produced second to tetrafluoroethylene in fluoromonomers, and is widely used in various fields. 1, 1-difluoroethylene (also known as vinylidene fluoride) is one of the important varieties of fluoroolefins, and is mainly used for producing polyvinylidene fluoride resin, fluororubber, and fluorine-containing copolymers such as vinylidene fluoride-hexafluoropropylene, vinylidene fluoride-vinylidene fluoride, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene, and the like. In addition, fluororubber obtained by copolymerizing vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene becomes one of indispensable and alternative basic materials in modern industries, particularly in high-tech fields, due to excellent high temperature resistance, oil resistance, solvent resistance and physical and mechanical properties of the fluororubber. HCFC-142 is a byproduct generated in the production of HCFC-142b, has no application value in industry, and can greatly reduce the production cost and the waste treatment cost if the HCFC-142 is recycled.
The production method of the vinylidene fluoride is divided according to raw materials, and mainly comprises a cracking preparation method of dehydrogenation, defluorination and dechlorination of C2 halogenated hydrocarbon, a co-cracking preparation method of C1 halogenated hydrocarbon and a deep cracking preparation method of C3-C5. The raw materials comprise C2, HCFC-142b (1, 1-difluoro-1-chloroethane and 1, 1-difluoro-2-chloroethane), R152a (1, 1-difluoroethane), VDC (1, 1-dichloroethylene), R132b (1, 2-dichloro-1, 1-difluoroethane) and the like; C1R 22 (1-fluoro-1-chloromethane), R12 (dichloromethane), R13 (1-chloro-trifluoromethane), etc. From the preparation method, catalytic cracking, thermal cracking, dilution cracking and promoter cracking are included.
For the dehydrochlorination reaction of HCFC-142b, because two fluorine atoms combined with the same carbon atom in HCFC-142b molecule strengthen the C-Cl bond, the dehydrochlorination of HCFC-142b needs to be thermally cracked at high temperature without the existence of catalyst, however, the reaction at high temperature is easy to cause side reaction and disproportionation reaction, thereby affecting the selectivity and yield of the reaction. The thermal cracking has the advantages of high yield, less control conditions, simple operation and the like, so the thermal cracking of HCFC-142b and the cracking of a diluent and an accelerant are the main methods for industrially producing VDF. However, the thermal cracking method requires reaction at high temperature, so that the energy consumption of industrial production is high, and the high temperature cracking easily generates carbon deposition to block the pipeline.
Many of the problems associated with the pyrolysis of HCFC-142b can be solved by catalytic cracking. The catalytic cracking can obviously reduce the reaction activation energy of HCFC-142b dehydrochlorination, thereby reducing the reaction temperature and energy consumption. Also, catalytic cracking can suppress the occurrence of side reactions and thus is advantageous in improving the selectivity of the product. Catalytic cracking has therefore been the subject of intense research in the dehydrochlorination of HCFC-142b because of its many advantages. In Chinese patent CN201710034557.0, a compound catalyst is adopted as a catalyst, and VDF selectivity of more than 90 percent can be obtained at a reaction temperature of 250-550 ℃. Patent CN106588563A uses Ba-based compound as main catalyst and adds transition metal as assistantThe catalyst can obtain different HCFC-142b conversion rates and VDF selectivity. In the US patent US3444251, HCFC-142b is adopted to pass through a catalyst layer in a tubular reactor at the space velocity of 60-100 v/v.h and the temperature of 420 ℃, and the catalyst is ZnCl2The impregnated alpha aluminum, aluminum fluoride and the like can obtain VDF with different yields. MeCClF is mentioned in US27747993，MeCCl2F or CH2ClCHF2By catalysis of MgF2Heating the copper pipe to 630-660oAnd C, the contact time is 5-30 s, and 96-98% of VDF can be obtained. The HCFC-142b of German patent DE1625568 is reacted at 300 ℃ with iron fluoride on activated carbonoC is reacted at a certain flow rate, the conversion rate of HCFC-142b is 93 percent, and the VDF/vinyl fluoride chloride in the product is about 99: 1.
HCl is a major by-product of the cracking reaction of HCFC-142b and HCFC-142, and high concentrations of HCl present a serious challenge to the lifetime of the catalyst. Highly corrosion-resistant compounds such as metal chlorides, metal fluorides, metal oxides, Activated Carbon (AC), and metal salts impregnated on activated carbon are often used as catalysts in a highly corrosive HCl atmosphere. Although the catalytic cracking has many advantages, it also has disadvantages, especially the poor stability and life of the catalyst are the main reasons for the failure of the catalytic cracking to be industrialized. Therefore, it is necessary to develop a catalyst system which has long service life, good stability, HCl and HF corrosion resistance and can be applied to industrial production for catalytic cracking of HCFC-142b and selective dehydrochlorination of HCFC-142.
Disclosure of Invention
In view of the above technical problems in the prior art, the present invention aims to provide a method for preparing 1, 1-difluoroethylene, which is simple, has good stability, high selectivity of 1, 1-difluoroethylene, simple process steps and easy industrialization.
The preparation method of the 1, 1-difluoroethylene is characterized in that a composite catalyst is filled into a tubular reactor, and 1, 1-difluoro-1-chloroethane or 1, 1-difluoro-2-chloroethane is used as a raw material and is introduced into the tubular reactor for gas-phase catalytic cracking reaction to prepare the 1, 1-difluoroethylene; the composite catalyst is a metal composite fluoride.
The preparation method of the 1, 1-difluoroethylene is characterized in that the metal in the metal composite fluoride is transition metal, alkaline earth metal or lanthanide metal, the transition metal is Fe, Co, Cr, Zr or Zn, the alkaline earth metal is Mg, Ca, Sr or Ba, and the lanthanide metal is La, Ce or Sm.
The preparation method of the 1, 1-difluoroethylene is characterized in that the metal in the metal composite fluoride is at least two of Fe, Co, Cr, Zr, Zn, Mg, Ca, Sr, Ba, La, Ce and Sm, and the mole percentage of any one metal is not more than 75% based on 100% of the total mole percentage of metal elements.
The preparation method of 1, 1-difluoroethylene is characterized in that N is adopted as 1, 1-difluoro-1-chloroethane or 1, 1-difluoro-2-chloroethane2Diluting and introducing into a tubular reactor for reaction, N2The feeding volume ratio of the raw materials to 1, 1-difluoro-1-chloroethane or 1, 1-difluoro-2-chloroethane is 1-9: 1.
The preparation method of the 1, 1-difluoroethylene is characterized in that the temperature of the gas phase catalytic cracking reaction is 250-550 ℃, the reaction pressure is normal pressure, and the feeding airspeed of the 1, 1-difluoro-1-chloroethane or the 1, 1-difluoro-2-chloroethane is 20-6000 h-1。
The preparation method of the 1, 1-difluoroethylene is characterized in that the tubular reactor is a nickel tube.
The preparation method of the 1, 1-difluoroethylene is characterized in that the preparation method of the composite catalyst comprises a precipitation method and a solid-phase grinding method;
the preparation process of the precipitation method is as follows:
(1) adding soluble salts of at least two metals into a container, adding water, mixing and stirring uniformly, and adding solid NH4F, forming a precipitate, and continuously stirring for more than 2 hours to obtain a precipitate mixed solution;
(2) filtering the precipitate mixed liquor obtained in the step (1), and drying and roasting filter residues to obtain the composite catalyst;
the preparation process of the solid phase grinding method is as follows:
s1: grinding of carbonates or hydroxides of at least two metalsAfter mixing well, (NH) is added4)2SiF6Continuously grinding for at least 0.5h to obtain a grinding mixture;
s2: and drying and roasting the ground mixture obtained in the step S1 for 5 hours to obtain the composite catalyst.
The preparation method of 1, 1-difluoroethylene is characterized in that the drying and roasting conditions of filter residue in a precipitation method and a ground mixture in a solid phase grinding method are the same, and specifically the method comprises the following steps: drying at 100-120 ℃ for at least 10h, and then roasting at 400-600 ℃ for at least 4 h. Before filling the composite catalyst into the tubular reactor, the composite catalyst is dried in a drying oven at 110 ℃ for at least 2 hours.
The preparation method of the 1, 1-difluoroethylene is characterized by comprising the following specific steps: filling the dried composite catalyst into a tubular reactor and introducing N2Raising the temperature of the composite catalyst bed layer from room temperature to 200 ℃ at a temperature rise rate of 5 ℃/min under the condition of N2And under the condition of unchanged flow, introducing 1, 1-difluoro-1-chloroethane or 1, 1-difluoro-2-chloroethane for treatment for 2h, and then raising the temperature of the composite catalyst bed to 250-550 ℃ at the heating rate of 5 ℃/min for catalytic reaction to generate 1, 1-difluoroethylene.
By adopting the method, compared with the prior method, the method has the following beneficial effects:
1) the invention adopts 1, 1-difluoro-1-chloroethane or 1, 1-difluoro-2-chloroethane as the raw material, the raw material is cheap and easy to obtain, and the cost is low, the invention takes the raw material as the raw material, and the raw material is converted into the fluorine-containing monomer with high added value and environmental protection, and the catalytic cracking route belongs to the green and environmental-friendly process route, and the method has obvious green and environmental-friendly, social and economic benefits, wherein the 1, 1-difluoro-2-chloroethane (HCFC-142) is taken as the raw material, so that the waste can be utilized, and the production and treatment cost can be reduced;
2) according to the method for preparing the vinylidene fluoride, the cheap compound metal catalyst is used as the catalyst, so that the cost is low, the preparation is simple, convenient and efficient, and the method is green and environment-friendly;
3) the method for preparing the vinylidene fluoride overcomes the defects of high energy consumption, serious carbon deposition, short continuous production time and the like of the prior art, and achieves the purposes of high yield, few steps and easy industrialization. The invention can realize the production of high-purity vinylidene fluoride by selecting reactants and controlling reaction conditions.
Detailed Description
The present invention is further illustrated by the following examples, which should not be construed as limiting the scope of the invention.
Example 1:
first, 0.01mol of each of the two transition metal nitrates was added to a vessel and 100mL of water was added. Mixing and stirring evenly, and then adding 0.04-0.06mol of solid NH4F (required for two metals to form precipitate)-Calculated) a precipitate formed and was filtered after 2h of continued stirring. And drying the solid obtained after filtration at 110 ℃ for 12h, and roasting at 500 ℃ for 4h to obtain the transition metal fluoride compound catalyst.
And then catalyzing 1, 1-difluoro-1-chloroethane to remove HCl by using the obtained composite catalyst to prepare the vinylidene fluoride. The reaction is carried out in a plug flow tubular reactor, the reaction tube of the plug flow tubular reactor adopts a Ni tube with the inner diameter of 20mm and the length of 800mm, and the composite catalyst is filled in the plug flow tubular reactor and is placed in a heating furnace for heating and raising the temperature to 350 ℃ for reaction. The reaction pressure was normal pressure.
Before the reaction, N is introduced2(space velocity 1000 h)-1) Under the condition of (1), the temperature of the composite catalyst bed layer is increased to 200 ℃ from room temperature at the heating rate of 5 ℃/min for drying for 2h, then is increased to 400 ℃ at the heating rate of 5 ℃/min for processing for 2h, and then is cooled to 200 ℃. In N2Under the condition of constant flow, HCFC-142b is introduced (the space velocity is 600 h)-1) The catalyst was reprocessed for 2 h. The HCFC-142b feed was then stopped and the temperature was raised to the reaction temperature of 350 ℃. Then introducing HCFC-142b and N2The mixed gas is subjected to gas phase catalytic reaction (the total space velocity is 1200 h)-1HCFC-142b and N2Feed volume ratio 1: 1). Quenching, alkali washing, water washing, drying, compressing, rectifying and purifying the tail gas generated by the reaction to obtain the vinylidene fluoride. Based on the consumption of HCFC-142bThe conversion and selectivity of the obtained partial catalyst are shown in the following table 1:
TABLE 1
Figure DEST_PATH_IMAGE001
Example 2
First, 0.01mol of each of the two alkaline earth metal nitrates was added to a vessel and 100mL of water was added. Mixing and stirring evenly, and then adding 0.04mol of solid NH4F forms a precipitate and is filtered after stirring for a further 2 h. And drying the solid obtained after filtration at 110 ℃ for 12h, and roasting at 500 ℃ for 4h to obtain the composite catalyst of the alkaline earth metal fluoride.
And then catalyzing 1, 1-difluoro-1-chloroethane to remove HCl by using the obtained composite catalyst to prepare the vinylidene fluoride. The reaction is carried out in a plug flow tubular reactor, the reaction tube of the plug flow tubular reactor adopts a Ni tube with the inner diameter of 20mm and the length of 800mm, and the composite catalyst is filled in the plug flow tubular reactor and is placed in a heating furnace for heating and raising the temperature to 350 ℃ for reaction. The reaction pressure was normal pressure.
Before the reaction, N is introduced2(space velocity 1000 h)-1) Under the condition of (1), the temperature of the composite catalyst bed layer is increased to 200 ℃ from room temperature at the heating rate of 5 ℃/min for drying for 2h, then is increased to 400 ℃ at the heating rate of 5 ℃/min for processing for 2h, and then is cooled to 200 ℃. In N2Under the condition of constant flow, HCFC-142b is introduced (the space velocity is 600 h)-1) The catalyst was reprocessed for 2 h. The HCFC-142b feed was then stopped and the temperature was raised to the reaction temperature of 350 ℃. Then introducing HCFC-142b and N2The mixed gas is subjected to gas phase catalytic reaction (the total space velocity is 1200 h)-1HCFC-142b and N2Feed volume ratio 1: 1). Quenching, alkali washing, water washing, drying, compressing, rectifying and purifying the tail gas generated by the reaction to obtain the vinylidene fluoride. The conversion and selectivity of the partial catalyst, calculated on the basis of the consumption of HCFC-142b, are shown in the following table 2:
TABLE 2
Figure DEST_PATH_IMAGE002
Example 3
Firstly, 0.01mol of each of two alkaline earth metal hydroxides is added into grinding, and 0.02mol (NH) is added after the two alkaline earth metal hydroxides are mixed and stirred evenly4)2SiF6And continuously grinding for at least 0.5h, drying the obtained solid at 110 ℃ for 12h, and roasting at 500 ℃ for 4h to obtain the composite catalyst of the alkaline earth metal fluoride.
And then catalyzing 1, 1-difluoro-1-chloroethane to remove HCl by using the obtained composite catalyst to prepare the vinylidene fluoride. The reaction is carried out in a plug flow tubular reactor, the reaction tube of the plug flow tubular reactor adopts a Ni tube with the inner diameter of 20mm and the length of 800mm, and the composite catalyst is filled in the plug flow tubular reactor and is placed in a heating furnace for heating and raising the temperature to 350 ℃ for reaction. The reaction pressure was normal pressure.
Before the reaction, N is introduced2(space velocity 1000 h)-1) Under the condition of (1), the temperature of the composite catalyst bed layer is increased to 200 ℃ from room temperature at the heating rate of 5 ℃/min for drying for 2h, then is increased to 400 ℃ at the heating rate of 5 ℃/min for processing for 2h, and then is cooled to 200 ℃. In N2Under the condition of constant flow, HCFC-142b is introduced (the space velocity is 600 h)-1) The catalyst was reprocessed for 2 h. The HCFC-142b feed was then stopped and the temperature was raised to the reaction temperature of 350 ℃. Then introducing HCFC-142b and N2The mixed gas is subjected to gas phase catalytic reaction (the total space velocity is 1200 h)-1HCFC-142b and N2Feed volume ratio 1: 1). Quenching, alkali washing, water washing, drying, compressing, rectifying and purifying the tail gas generated by the reaction to obtain the vinylidene fluoride. The catalytic activity and VDF selectivity were substantially the same as those in example 2, calculated on the basis of the consumption of HCFC-142b, but the solid phase milling method had the advantage over the precipitation method of not requiring the treatment of the waste water produced during the preparation of the catalyst and of the SiF produced by calcination4Can be repeatedly used, and the like.
Example 4
The composite catalyst in embodiment 3 is used for catalytic cracking of 1, 1-difluoro-2-chloroethane to remove HCl to prepare vinylidene fluoride.
The reaction is carried out in a plug flow tubular reactor, the reaction tube of the plug flow tubular reactor adopts a Ni tube with the inner diameter of 20mm and the length of 800mm, and the composite catalyst is filled in the plug flow tubular reactor and is placed in a heating furnace for heating and raising the temperature to 400 ℃ for reaction. The reaction pressure was normal pressure.
Before the reaction, N is introduced2(space velocity 1000 h)-1) Under the condition of (1), the temperature of the composite catalyst bed layer is increased to 200 ℃ from room temperature at the heating rate of 5 ℃/min for drying for 2h, then is increased to 400 ℃ at the heating rate of 5 ℃/min for processing for 2h, and then is cooled to 200 ℃. In N2Under the condition of constant flow, HCFC-142b is introduced (the space velocity is 600 h)-1) The catalyst was reprocessed for 2 h. The HCFC-142b feed was then stopped and the temperature was raised to a reaction temperature of 400 ℃. Then introducing HCFC-142b and N2The mixed gas is subjected to gas phase catalytic reaction (the total space velocity is 1200 h)-1HCFC-142b and N2Feed volume ratio 1: 1). Quenching, alkali washing, water washing, drying, compressing, rectifying and purifying the tail gas generated by the reaction to obtain the vinylidene fluoride. The conversion and selectivity of the partial catalyst, calculated on the basis of the consumption of HCFC-142, are given in the following Table 3:
TABLE 3
Figure DEST_PATH_IMAGE003
Example 5
Firstly, 0.01mol of each of lanthanide metal nitrate lanthanum nitrate and cerium nitrate is added into a container, and 100mL of water is added. Mixing and stirring evenly, and then adding 0.06mol of solid NH4F forms a precipitate and is filtered after stirring for a further 2 h. And drying the solid obtained after filtration at 110 ℃ for 12h, and roasting at 500 ℃ for 4h to obtain the composite catalyst of lanthanide metal fluoride.
And then catalyzing 1, 1-difluoro-1-chloroethane to remove HCl by using the obtained composite catalyst to prepare the vinylidene fluoride. The reaction is carried out in a plug flow tubular reactor, the reaction tube of the plug flow tubular reactor adopts a Ni tube with the inner diameter of 20mm and the length of 800mm, and the composite catalyst is filled in the plug flow tubular reactor and is placed in a heating furnace for heating and raising the temperature to 350 ℃ for reaction. The reaction pressure was normal pressure.
Before the reaction, N is introduced2(space velocity 1000 h)-1) Under the condition of (1), the temperature of the composite catalyst bed layer is increased to 200 ℃ from room temperature at the heating rate of 5 ℃/min for drying for 2h, then is increased to 400 ℃ at the heating rate of 5 ℃/min for processing for 2h, and then is cooled to 200 ℃. In N2Under the condition of constant flow, HCFC-142b is introduced (the space velocity is 600 h)-1) The catalyst was reprocessed for 2 h. The HCFC-142b feed was then stopped and the temperature was raised to the reaction temperature of 350 ℃. Then introducing HCFC-142b and N2The mixed gas is subjected to gas phase catalytic reaction (the total space velocity is 1200 h)-1HCFC-142b and N2Feed volume ratio 1: 1). Quenching, alkali washing, water washing, drying, compressing, rectifying and purifying the tail gas generated by the reaction to obtain the vinylidene fluoride.
Calculated on the basis of the consumption of HCFC-142b, LaCeF6The conversion rate of HCFC-142b is 65 percent, and the selectivity of VDF reaches 80 percent.
Example 6
Firstly, 0.01mol of each of lanthanide metal nitrate cerium nitrate and alkaline earth metal nitrate barium nitrate is added into a container, and 100mL of water is added. Mixing and stirring evenly, and then adding 0.05mol of solid NH4F forms a precipitate and is filtered after stirring for a further 2 h. And drying the solid obtained after filtration at 110 ℃ for 12h, and roasting at 500 ℃ for 4h to obtain the composite catalyst of lanthanide metal-alkaline earth metal fluoride.
And then catalyzing 1, 1-difluoro-1-chloroethane to remove HCl by using the obtained composite catalyst to prepare the vinylidene fluoride. The reaction is carried out in a plug flow tubular reactor, the reaction tube of the plug flow tubular reactor adopts a Ni tube with the inner diameter of 20mm and the length of 800mm, and the composite catalyst is filled in the plug flow tubular reactor and is placed in a heating furnace for heating and raising the temperature to 350 ℃ for reaction. The reaction pressure was normal pressure.
Before the reaction, N is introduced2(space velocity 1000 h)-1) In the case of (2), will beThe temperature of the catalyst bed layer is heated to 200 ℃ from room temperature at the heating rate of 5 ℃/min for drying for 2h, then heated to 400 ℃ at the heating rate of 5 ℃/min for processing for 2h, and then cooled to 200 ℃. In N2Under the condition of constant flow, HCFC-142b is introduced (the space velocity is 600 h)-1) The catalyst was reprocessed for 2 h. The HCFC-142b feed was then stopped and the temperature was raised to the reaction temperature of 350 ℃. Then introducing HCFC-142b and N2The mixed gas is subjected to gas phase catalytic reaction (the total space velocity is 1200 h)-1HCFC-142b and N2Feed volume ratio 1: 1). Quenching, alkali washing, water washing, drying, compressing, rectifying and purifying the tail gas generated by the reaction to obtain the vinylidene fluoride.
Calculated on the basis of the consumption of HCFC-142b, BaCeF5The conversion rate of HCFC-142b is 60 percent, and the selectivity of VDF reaches 86 percent.
Example 7
First, 0.01mol of each of two alkaline earth metal nitrates (strontium nitrate and barium nitrate) and one transition metal nitrate, zinc nitrate, was added to a vessel and 100mL of water was added. Mixing and stirring evenly, and then adding 0.06-0.08mol of solid NH4F (required for three metals to form precipitate)-Calculated) a precipitate formed and was filtered after 2h of continued stirring. And drying the solid obtained after filtration at 110 ℃ for 12h, and roasting at 500 ℃ for 4h to obtain the composite catalyst of the alkaline earth metal-transition metal fluoride.
And then catalyzing 1, 1-difluoro-1-chloroethane to remove HCl by using the obtained composite catalyst to prepare the vinylidene fluoride. The reaction is carried out in a plug flow tubular reactor, the reaction tube of the plug flow tubular reactor adopts a Ni tube with the inner diameter of 20mm and the length of 800mm, and the composite catalyst is filled in the plug flow tubular reactor and is placed in a heating furnace for heating and raising the temperature to 350 ℃ for reaction. The reaction pressure was normal pressure.
Before the reaction, N is introduced2(space velocity 1000 h)-1) Under the condition of (1), the temperature of the composite catalyst bed layer is increased to 200 ℃ from room temperature at the heating rate of 5 ℃/min for drying for 2h, then is increased to 400 ℃ at the heating rate of 5 ℃/min for processing for 2h, and then is cooled to 200 ℃. In N2Under the condition of constant flow, H is introducedCFC-142b (space velocity of 600 h)-1) The catalyst was reprocessed for 2 h. The HCFC-142b feed was then stopped and the temperature was raised to the reaction temperature of 350 ℃. Then introducing HCFC-142b and N2The mixed gas is subjected to gas phase catalytic reaction (the total space velocity is 1200 h)-1HCFC-142b and N2Feed volume ratio 1: 1). Quenching, alkali washing, water washing, drying, compressing, rectifying and purifying the tail gas generated by the reaction to obtain the vinylidene fluoride.
Calculated on the basis of the consumption of HCFC-142b, BaSrZnF6The conversion rate of HCFC-142b is 50 percent, and the selectivity of VDF reaches 95 percent.
The description is given for the sole purpose of illustrating embodiments of the inventive concept and should not be taken as limiting the scope of the invention to the particular forms set forth in the embodiments, but rather as being limited only to the equivalents thereof as may be contemplated by those skilled in the art based on the teachings herein.

Claims (5)

1. A preparation method of 1, 1-difluoroethylene is characterized in that a composite catalyst is filled into a tubular reactor, 1-difluoro-1-chloroethane is used as a raw material and is introduced into the tubular reactor for a gas phase catalytic cracking reaction to prepare 1, 1-difluoroethylene; the composite catalyst is BaSrZnF6；
The preparation method of the composite catalyst comprises the following steps: firstly, 0.01mol of each of two alkaline earth metal nitrates of strontium nitrate and barium nitrate and one transition metal nitrate of zinc nitrate are added into a container, and 100mL of water is added; mixing and stirring evenly, and then adding 0.06-0.08mol of solid NH4F, forming a precipitate, continuously stirring for 2 hours, and filtering; and drying the solid obtained after filtration at 110 ℃ for 12h, and roasting at 500 ℃ for 4h to obtain the composite catalyst of the alkaline earth metal-transition metal fluoride.
2. The process for preparing 1, 1-difluoroethylene as claimed in claim 1, wherein the 1, 1-difluoro-1-chloroethane is N2Diluting and introducing into a tubular reactor for reaction, N2The feeding volume ratio of the raw materials to the 1, 1-difluoro-1-chloroethane is 1-9: 1.
3. The method for preparing 1, 1-difluoroethylene according to claim 1, wherein the temperature of the gas phase catalytic cracking reaction is 250-550 ℃, the reaction pressure is normal pressure, and the feeding space velocity of the 1, 1-difluoro-1-chloroethane is 20-6000 h-1。
4. The process according to claim 1, 1-difluoroethylene, wherein the tubular reactor is a nickel tube.
5. The preparation method of 1, 1-difluoroethylene according to claim 1, characterized by comprising the following steps: filling the dried composite catalyst into a tubular reactor and introducing N2Raising the temperature of the composite catalyst bed layer from room temperature to 200 ℃ at a temperature rise rate of 5 ℃/min under the condition of N2And under the condition of unchanged flow, introducing 1, 1-difluoro-1-chloroethane for treatment for 2h, and then raising the temperature of the composite catalyst bed to 250-550 ℃ at the heating rate of 5 ℃/min for catalytic reaction to generate 1, 1-difluoroethylene.
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