CN111217669A - Method for preparing vinylidene fluoride by resource conversion of trifluoromethane - Google Patents
Method for preparing vinylidene fluoride by resource conversion of trifluoromethane Download PDFInfo
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Abstract
The invention discloses a method for preparing vinylidene fluoride by reacting trifluoromethane and methane under the action of a composite catalyst, wherein the composite catalyst comprises a component 1 and a component 2, the component 1 comprises lanthanide series metal, and the component 2 comprises IIA group metal. The method provided by the invention has the characteristics of high vinylidene fluoride selectivity, high methane conversion rate, low reaction temperature and the like.
Description
Technical Field
The invention relates to a method for resource conversion of trifluoromethane, in particular to a method for preparing vinylidene fluoride by resource conversion of trifluoromethane.
Background
Trifluoromethane, which is an ultra-strong greenhouse gas due to its potential greenhouse effect (GWP) 14800 times that of carbon dioxide, has been banned from use as a refrigerant. Trifluoromethane is also a by-product of the industrial production of monochlorodifluoromethane (HCFC-22, R22) which, due to its high temperature chamber effect potential, cannot be directly vented to the atmosphere and needs to be disposed of.
In general, the incineration method is used in industry to treat trifluoromethane, and the trifluoromethane is completely calcined and decomposed into substances such as hydrogen fluoride, carbon dioxide and the like. However, the incineration treatment needs to be equipped with special incineration equipment, the investment is large, and the decomposition product hydrogen fluoride is easy to corrode the equipment. If the trifluoromethane can be recycled to convert other useful compounds, the method has important social and economic benefits.
The resource transformation of the trifluoromethane is reported less, wherein a representative transformation method is to utilize the trifluoromethane, the methane and the oxygen to carry out the cocracking synthesis on the fluoroform (CH) which is an important monomer for producing the polyvinylidene fluoride and the fluororubber2＝CF2). Methane and trifluoromethane have high stability and hardly react at a high temperature of 700 ℃ without adding a catalyst.
The Greenhouse Gases, Science and Technology 7(5) (2017) 891-902, improved upon, report that the synthesis of vinylidene fluoride by the co-cracking of trifluoromethane with methane and oxygen using rare earth oxides as catalysts, has a vinylidene fluoride selectivity of 50% and a methane conversion of 5% at 700 ℃. Although the method can make the trifluoromethane react with the methane and the oxygen at the temperature of 700 ℃, the target product vinylidene fluoride has low selectivity and low yield, and the catalyst needs to be pretreated by the trifluoromethane at high temperature before use. In order to increase the activity of the catalyst, the reaction temperature is increased to 800 ℃ in this method, and when the reaction temperature is 800 ℃, although the activity of the catalyst is increased to some extent, the thermal stability of the catalyst is poor.
Therefore, improvement of the method for preparing vinylidene fluoride by resource conversion of trifluoromethane is needed, and particularly, improvement of the catalyst thereof is needed.
Disclosure of Invention
The invention aims to provide a method for preparing vinylidene fluoride by resource conversion of trifluoromethane, which has the characteristics of high vinylidene fluoride selectivity, high methane conversion rate, low reaction temperature and the like.
The invention provides the following technical scheme:
a process for making vinylidene fluoride from trifluoromethane, the process comprising:
under the action of a composite catalyst, reacting trifluoromethane with methane to prepare vinylidene fluoride;
the composite catalyst comprises a component 1 and a component 2, wherein the component 1 comprises lanthanide series metal, and the component 2 comprises IIA group metal.
In the prior art, when rare earth metal oxide is used as a catalyst, the reaction temperature needs to be kept above 800 ℃ in order to improve the activity of the catalyst. The reaction of trifluoromethane and methane for preparing vinylidene fluoride is generally carried out in a metal reaction tube, and when the temperature is higher than 800 ℃, the energy consumption is high, and the metal material is easily softened and easily corroded by a reaction byproduct HF and the like at high temperature, so that the service life of the metal reaction tube is shortened. Meanwhile, above 800 ℃ reaction temperature, the stability of the rare earth metal oxide catalyst is poor. Accordingly, the present invention provides a composite catalyst for preparing vinylidene fluoride from trifluoromethane, comprising a component 1 and a component 2, wherein the component 1 comprises a lanthanide metal and the component 2 comprises a group IIA metal. The present invention adds a component 2 comprising a group IIA metal to a component 1 comprising a lanthanide metal to form a composite catalyst.
In the composite catalyst provided by the invention, the component 1 is preferably selected from LaF2、CeF2And SmF2At least one of (1). Namely: the component 1 comprises a material selected from LaF2、CeF2And SmF2One, two or three of them.
In the composite catalyst provided by the invention, the component 2 is preferably selected from BaF2、CaF2And MgF2At least one of (1). Namely: the component 2 comprises BaF2、CaF2And MgF2One, two or three of (1).
According to the composite catalyst provided by the invention, the molar ratio of the component 1 to the component 2 meets the requirement that the reaction for preparing the vinylidene fluoride by reacting the trifluoromethane and the methane is smoothly carried out. As a preferable mode, the molar ratio of the component 1 to the component 2 is 0.15-4.5. More preferably, the molar ratio of the component 1 to the component 2 is 0.15-4.5, and the component 1 comprises LaF2、CeF2And SmF2One, two or three, the component 2 comprises BaF2、CaF2And MgF2One, two or three of (1).
The invention also provides a preparation method of the composite catalyst, which is prepared by carrying out lattice replacement on the component 1 and the component 2 at high temperature to generate a solid solution.
The preparation method of the composite catalyst provided by the invention can comprise the following steps:
(1) preparing an aqueous solution containing lanthanide metal soluble salt and IIA metal soluble salt, wherein the ion concentration ratio of lanthanide metal to IIA metal is 0.2-4.5: 1;
(2) adding a hydrogen fluoride solution into the aqueous solution at the temperature of 60-90 ℃ to enable the ion concentration ratio of fluoride ions to lanthanide metal ions and IIA metal ions in the aqueous solution to be 20-25: 1, so as to obtain a precipitate;
(3) and drying the precipitate and roasting at 600-950 ℃ to obtain the composite catalyst.
In the preparation method of the composite catalyst provided by the invention, the lanthanide metal soluble salt used can be a lanthanide metal soluble salt capable of being dissolved in water. In a preferred embodiment, the soluble lanthanide metal salt is at least one selected from the group consisting of a nitrate, an acetate, a carbonate, a chloride and a hydroxide of a lanthanide metal. Namely: the lanthanide metal soluble salt is selected from one, two, three, four or five of lanthanide metal nitrate, acetate, carbonate, chloride and hydroxide.
In the preparation method of the composite catalyst provided by the invention, the group IIA metal soluble salt used can be a group IIA metal soluble salt capable of being dissolved in water. In a preferred embodiment, the group IIA metal soluble salt is at least one selected from group IIA metal nitrates, acetates, chlorides, and hydroxides. Namely: the IIA metal soluble salt is selected from one, two, three or four of nitrate, acetate, chloride and hydroxide of IIA metal.
In the preparation method of the composite catalyst provided by the invention, in order to enable the prepared composite catalyst to be more favorable for preparing vinylidene fluoride by reacting trifluoromethane and methane, the aqueous solution containing lanthanide metal soluble salt and IIA metal soluble salt prepared in the step (1) is prepared, wherein the ion concentration ratio of lanthanide metal to IIA metal is 0.2-4.5: 1. Preferably, the ratio of the ion concentration of the lanthanide metal to the ion concentration of the group IIA metal is 0.25-2.0: 1.
In the preparation method of the composite catalyst provided by the invention, in the step (3), the precipitate is dried and roasted at 600-950 ℃ to obtain the composite catalyst. As a preferable scheme, the roasting of the precipitate comprises roasting at a temperature of 600-800 ℃ at a speed of 1-5 ℃/min.
According to the method for preparing the vinylidene fluoride from the trifluoromethane, when the composite catalyst provided by the invention is used for the reaction of the trifluoromethane and the methane for preparing the vinylidene fluoride, the trifluoromethane and the methane can react within a wider temperature range. The trifluoromethane and methane may be reacted at a reaction temperature of 1100 ℃ or less, at a reaction temperature of 750 ℃ or less, or at a reaction temperature of 700 ℃ or less. On the basis of comprehensively considering the selectivity of vinylidene fluoride, the conversion rate of methane and energy consumption, the reaction temperature is preferably within 750 ℃, and further preferably within 700 ℃. When the reaction temperature is within 750 ℃, the reaction temperature is 550-750 ℃ as a preferable mode; in a further preferable mode, the reaction temperature is 600 to 700 ℃; in a further preferred embodiment, the reaction temperature is 650 to 700 ℃.
According to the method for preparing the vinylidene fluoride from the trifluoromethane, the molar ratio of the methane to the trifluoromethane is satisfied, so that the reaction can be smoothly carried out. In a preferred embodiment, the molar ratio of methane to trifluoromethane is 0.5-3: 1.
The method for preparing the vinylidene fluoride from the trifluoromethane, which is provided by the invention, is used for preparing the vinylidene fluoride by the reaction of the trifluoromethane and the methane, and is a preferable technical scheme that the reaction is carried out by selecting water vapor, air and Cl2、CO2And O2In the presence of at least one gas. Namely: the reaction is carried out in a reaction chamber selected from the group consisting of steam, air, Cl2、CO2And O2In the presence of one, two, three, four or five gases.
When the reaction is carried out in a reaction system selected from the group consisting of steam, air, Cl2、CO2And O2Is carried out in the presence of at least one gas selected from the group consisting of water vapor, air, Cl2、CO2And O2At least one gas may be used in an amount sufficient to allow the reaction to proceed smoothly. As a preferred technical scheme, the solvent is selected from water vapor, air and Cl2、CO2And O2The using amount of at least one gas in the (1-10%) is 1-10% of the total volume of the feed gas of the trifluoromethane and the methane.
According to the method for preparing the vinylidene fluoride from the trifluoromethane, the used raw material trifluoromethane can be the by-product trifluoromethane in the production process of HCFC-22. When the used raw material is the by-product trifluoromethane in the production process of HCFC-22, the by-product trifluoromethane does not need to be purified too much and can be directly used for reaction.
Compared with the prior art, the method for preparing the vinylidene fluoride from the trifluoromethane has the following advantages that:
(1) the vinylidene fluoride has high selectivity, high methane conversion rate, low reaction temperature and mild reaction conditions;
(2) the provided composite catalyst not only has good activity, but also has good high temperature resistance and good stability.
Detailed Description
The present invention is further illustrated by the following examples, which are not intended to limit the invention to these embodiments. It will be appreciated by those skilled in the art that the present invention encompasses all alternatives, modifications and equivalents as may be included within the scope of the claims.
First, catalyst preparation
Example 1: catalyst preparation
Firstly, 58.8g of barium nitrate and 10.8g of lanthanum nitrate (the molar ratio of barium to lanthanum is Ba: La ═ 9:1) are dissolved in 500ml of distilled water, the mixture is heated and stirred in a water bath at 80 ℃, meanwhile, diluted hydrofluoric acid solution is slowly added into the barium-lanthanum mixed solution, the ratio of fluorine ions to metal ions (the sum of barium ions and lanthanum ions) is kept at 22.5, the hydrofluoric acid solution is added while stirring vigorously, and when the hydrofluoric acid solution is added dropwise and no white precipitate appears any more, the hydrofluoric acid solution is filtered and washed twice, and then white precipitate is obtained. And transferring the obtained white precipitate to a 100 ℃ forced air drying oven for drying for 12h, putting the dried white precipitate into a muffle furnace after the residual liquid is completely removed, heating to 800 ℃ at the heating rate of 2 ℃/min, keeping the temperature for 2h, and then automatically cooling to obtain the composite barium lanthanum fluoride catalyst.
Example 2: catalyst preparation
Firstly, 51g of barium nitrate and 21.5g of lanthanum nitrate (the molar ratio of barium to lanthanum is Ba: La ═ 4:1) are dissolved in 500ml of distilled water, the mixture is heated and stirred in a water bath at 80 ℃, meanwhile, diluted hydrofluoric acid solution is slowly added into the barium-lanthanum mixed solution, the ratio of fluorine ions to metal ions (the sum of barium ions and lanthanum ions) is kept at 22.5, the hydrofluoric acid solution is added while stirring vigorously, and when the hydrofluoric acid solution is dropwise added and no white precipitate appears any more, the white precipitate is obtained after the hydrofluoric acid solution is filtered and washed twice. And transferring the obtained white precipitate to a 100 ℃ forced air drying oven for drying for 12h, putting the dried white precipitate into a muffle furnace after the residual liquid is completely removed, heating to 800 ℃ at the heating rate of 2 ℃/min, keeping the temperature for 2h, and then automatically cooling to obtain the composite barium lanthanum fluoride catalyst.
Example 3: catalyst preparation
Firstly, 39g of barium nitrate and 43.3g of lanthanum nitrate solution (the molar ratio of barium to lanthanum is Ba: La ═ 3:2) are dissolved in 500ml of distilled water, the solution is heated and stirred in a water bath at 80 ℃, meanwhile, diluted hydrofluoric acid solution is slowly added into the barium-lanthanum mixed solution to keep the ratio of fluoride ions to metal ions (the sum of barium ions and lanthanum ions) to be 22.5, the solution is vigorously stirred while being added, when the hydrofluoric acid solution is dropwise added and no colored precipitate appears, the solution is filtered, washed twice by water and then transferred to a 100 ℃ blast drying oven for drying for 12 hours, the solution is placed in a muffle furnace after the residual liquid is completely removed, the temperature is increased to 800 ℃ at the heating rate of 2 ℃/min and kept for 2 hours, then the temperature is automatically reduced to obtain the composite barium-lanthanum fluoride catalyst, and finally the barium-lanthanum fluoride catalyst is crushed to 10-20 meshes for later use after being pressed and formed by 20 MPa.
Example 4: catalyst preparation
Dissolving 32.6g of barium nitrate and 54.1g of lanthanum nitrate (the molar ratio of barium to lanthanum is Ba: La is 1:1) in 500ml of distilled water, heating and stirring in a water bath at 80 ℃, slowly adding a diluted hydrofluoric acid solution into a barium-lanthanum mixed solution while keeping the ratio of fluoride ions to metal ions (the sum of barium ions and lanthanum ions) to be 22.5, violently stirring while adding, filtering and washing twice after the hydrofluoric acid solution is dropwise added and no white precipitate appears, then transferring to a 100 ℃ forced air drying oven for drying for 12 hours, placing in a muffle furnace after the residual liquid is completely removed, heating to 800 ℃ at the heating rate of 2 ℃ min and keeping for 2 hours, and then automatically cooling to obtain the composite barium-lanthanum fluoride catalyst.
Example 5: catalyst preparation
Firstly, 27g of barium nitrate and 64.5g of lanthanum nitrate (the molar ratio of barium to lanthanum is Ba: La ═ 2:3) are dissolved in 500ml of distilled water, the mixture is heated and stirred in a water bath at 80 ℃, meanwhile, diluted hydrofluoric acid solution is slowly added into the barium-lanthanum mixed solution to keep the ratio of fluoride ions to metal ions (the sum of barium ions and lanthanum ions) to be 22.5, the mixture is vigorously stirred while being added, when the hydrofluoric acid solution is dropwise added and no white precipitate appears any more, the mixture is filtered, washed twice by water and then transferred to a 100 ℃ blast drying oven for drying for 12 hours, the mixture is placed in a muffle furnace after residual liquid is completely removed, the temperature is increased to 800 ℃ at the heating rate of 2 ℃/min and kept for 2 hours, then the temperature is automatically reduced to obtain the composite barium-lanthanum fluoride catalyst, and finally the barium-lanthanum fluoride catalyst is crushed to 10-20 meshes for later use after being pressed and formed at 20 MPa.
Example 6: catalyst preparation
Dissolving 15g of barium nitrate and 86g of lanthanum nitrate (the molar ratio of barium to lanthanum is Ba: La is 1:4) in 500ml of distilled water, heating and stirring in a water bath at 80 ℃, slowly adding a diluted hydrofluoric acid solution into a barium-lanthanum mixed solution while keeping the ratio of fluorine ions to metal ions (the sum of barium ions and lanthanum ions) to be 22.5, violently stirring while adding, filtering and washing twice after the hydrofluoric acid solution is dropwise added and no white precipitate appears, transferring to a blast drying oven at 100 ℃ for drying for 12 hours, placing in a muffle furnace after the residual liquid is completely removed, heating to 800 ℃ at a heating rate of 2 ℃/min and keeping for 2 hours, automatically cooling to obtain a composite barium-lanthanum fluoride catalyst, tabletting and molding at 20MPa, and crushing to 10-20 meshes for later use.
Example 7: catalyst preparation
Firstly, 6.5g of barium nitrate and 97.4g of lanthanum nitrate (the molar ratio of barium to lanthanum is Ba: La is 1:9) are dissolved in 500ml of distilled water, the mixture is heated and stirred in a water bath at 80 ℃, meanwhile, diluted hydrofluoric acid solution is slowly added into the barium-lanthanum mixed solution to keep the ratio of fluoride ions to metal ions (the sum of barium ions and lanthanum ions) to be 22.5, the mixture is vigorously stirred while being added, when the hydrofluoric acid solution is dropwise added and no white precipitate appears any more, the mixture is filtered, washed twice by water and then transferred to a 100 ℃ blast drying oven for drying for 12 hours, after the residual liquid is completely removed, the mixture is placed in a muffle furnace, the temperature is raised to 800 ℃ at the rate of 2 ℃ min and kept for 2 hours, and then the temperature is automatically lowered to obtain the composite barium-lanthanum fluoride catalyst.
Example 8: catalyst preparation
Firstly, 35.42g of calcium nitrate and 43.3g of lanthanum nitrate (the molar ratio of calcium to lanthanum is Ca: La is 3:2) are dissolved in 500ml of distilled water, the solution is heated and stirred in a water bath at 80 ℃, meanwhile, diluted hydrofluoric acid solution is slowly added into the calcium-lanthanum mixed solution to keep the ratio of fluoride ions to metal ions (the sum of calcium ions and lanthanum ions) to be 22.5, the solution is vigorously stirred while being added, when the hydrofluoric acid solution is dropwise added and no colored precipitate appears, the solution is filtered and washed twice, then the solution is transferred to a blast drying oven at 100 ℃ for drying for 12 hours, the solution is placed in a muffle furnace after the residual liquid is completely removed, the temperature is increased to 800 ℃ at the heating rate of 2 ℃/min and kept for 2 hours, then the temperature is automatically reduced to obtain the composite fluoride catalyst, and finally, the composite fluoride catalyst is crushed to 10-20 meshes for later use after being pressed and formed by 20 MPa.
Example 9: catalyst preparation
Dissolving 22.2g of magnesium nitrate and 43.3g of lanthanum nitrate (the molar ratio of magnesium to lanthanum is Mg: La is 3:2) in 500ml of distilled water, heating and stirring in a water bath at 80 ℃, slowly adding a diluted hydrofluoric acid solution into a magnesium-lanthanum mixed solution while keeping the ratio of fluoride ions to metal ions (the sum of magnesium ions and lanthanum ions) to be 22.5, violently stirring while adding, filtering and washing twice after the hydrofluoric acid solution is dropwise added and no colored precipitate appears, then transferring to a 100 ℃ blast drying oven for drying for 12 hours, placing in a muffle furnace after the residual liquid is completely removed, heating to 800VC at the heating rate of 2 ℃/min and keeping for 2 hours, then automatically cooling to obtain the composite fluoride catalyst, and finally crushing the composite fluoride catalyst to 10-20 meshes for later use after tabletting and forming at 20 MPa.
Example 10: catalyst preparation
Firstly, 39g of barium nitrate and 43.4g of cerium nitrate (the molar ratio of barium to cerium is Ba: La ═ 3:2) are dissolved in 500ml of distilled water, the mixture is heated and stirred in a water bath at 80 ℃, meanwhile, diluted hydrofluoric acid solution is slowly added into the barium-cerium mixed solution to keep the ratio of fluoride ions to metal ions (the sum of barium ions and cerium ions) to be 22.5, the mixture is vigorously stirred while being added, when the hydrofluoric acid solution is dropwise added and no colored precipitate appears, the mixture is filtered, washed with water twice and then transferred to a 100 ℃ blast drying oven for drying for 12 hours, the mixture is placed in a muffle furnace after residual liquid is completely removed, the temperature is increased to 800 ℃ at the heating rate of 2 ℃/min and kept for 2 hours, then the temperature is automatically reduced to obtain the composite fluoride catalyst, and finally the composite fluoride catalyst is crushed to 10-20 meshes for later use after being pressed and formed by 20 MPa.
Example 11: catalyst preparation
Firstly, 39g of barium nitrate and 44.4g of samarium nitrate (the molar ratio of barium to samarium is Ba: La is 3:2) are dissolved in 500ml of distilled water, the mixture is heated and stirred in a water bath at 80 ℃, meanwhile, diluted hydrofluoric acid solution is slowly added into the barium-cerium mixed solution to keep the ratio of fluorine ions to metal ions (the sum of barium ions and samarium ions) to be 22.5, the mixture is vigorously stirred while being added, when the hydrofluoric acid solution is dropwise added and no colored precipitate appears, the mixture is filtered, washed with water twice and then transferred to a 100 ℃ blast drying oven for drying for 12 hours, the mixture is placed in a muffle furnace after the residual liquid is completely removed, the temperature is raised to 800 ℃ at the heating rate of 2 ℃/min and kept for 2 hours, then the composite fluoride catalyst can be obtained by self-cooling, and finally the composite fluoride catalyst is crushed to 10-20 meshes for standby after being pressed and formed by 20 MPa.
Comparative example 1: catalyst preparation
Weighing a certain amount of La (NO)3)3·6H2O is prepared into 1mol/L salt solution (prepared by a 25ml volumetric flask), then the salt solution and ammonia water (the ammonia water is prepared by 32ml ammonia water and 60ml water) are simultaneously and dropwise added into a beaker of 200ml deionized water, the pH of the solution is kept to be 9 in the whole dropping process (the pH is measured by a fine pH test paper), white milky precipitate is observed to be generated, after the dropping is finished, the precipitate solution is aged for 6 hours at room temperature, then the centrifugation and the washing are carried out, the solution is dried for 10 hours at 110 ℃ overnight, and the solution is roasted for 6 hours at 600 ℃ to obtain La2O3A catalyst.
Preparation of di-and vinylidene fluoride
Example 12: preparation of vinylidene fluoride
The composite barium lanthanum fluoride catalyst prepared in example 3 was used as a catalyst to examine the changes in reaction conversion and selectivity at different reaction temperatures. The reaction for preparing vinylidene fluoride from trifluoromethane is carried out in a normal-pressure fixed bed reaction device. The reaction tube is a pure nickel tube with the inner diameter of 1 cm. The catalyst was packed in pure nickel tubes. The reaction gas is N2、CHF3、CH4、O2The feeding ratio is 9:1:1:0.06, and the reaction temperature is 550-750 ℃. The conversion and selectivity data for the reaction are shown in table 1.
TABLE 1 influence of reaction temperature on the reaction
Example 13: preparation of vinylidene fluoride
The reaction for preparing vinylidene fluoride from trifluoromethane is carried out in a normal-pressure fixed bed reaction device. The reaction tube is a pure nickel tube with the inner diameter of 1 cm. The catalyst was packed in pure nickel tubes. The reaction gas is N2、CHF3、CH4、O2The feed ratio was 9:1:1:0.06, with nitrogen acting as the internal standard gas. At normal pressure, 700 deg.C and 900 hr-1The catalysts prepared in examples 1 to 11 and comparative examples were used, respectively, at space velocity and the conversion and selectivity data of the reactions are shown in table 2.
Table 2 shows the results of the tests using the catalysts prepared in examples 1 to 11 and comparative examples 1 and 2 under the same reaction conditions. Table 2 shows the conversion rates of trifluoromethane and methane and the selectivity of vinylidene fluoride as a product as a test index.
Comparative example 2: preparation of vinylidene fluoride
Reacting gas N2、CHF3、CH4、O2The reaction was carried out at a feed ratio of 9:1:1:0.06, at normal pressure, 700 ℃ and 900h, through a reactor without catalyst addition-1The empty tube performance of the vinylidene fluoride synthesized by the co-cracking of the trifluoromethane and the methane under the airspeed. The reaction results are shown in Table 2.
TABLE 2 reaction results at 700 deg.C
| Catalyst and process for preparing same | CH4Conversion (%) | CHF3Conversion (%) | Vinylidene fluoride Selectivity (%) |
| Example 1 | 7.8 | 20.1 | 61.1 |
| Example 2 | 9.6 | 22.5 | 70.5 |
| Example 3 | 11.3 | 24.3 | 74.4 |
| Example 4 | 9.4 | 21.3 | 62.3 |
| Example 5 | 10.9 | 22.1 | 64.6 |
| Example 6 | 12.5 | 22.7 | 58.2 |
| Example 7 | 10.8 | 20.4 | 53.6 |
| Example 8 | 7.4 | 11.5 | 45.3 |
| Example 9 | 7.8 | 12.5 | 44.8 |
| Example 10 | 6.3 | 11.9 | 45.9 |
| Example 11 | 6.8 | 13.1 | 46.1 |
| Comparative example 1 | 5.5 | 9.8 | 42.1 |
| Comparative example 2 | 4.3 | 8.7 | 40.5 |
From the data in table 2, it can be seen that: the empty tube test without using the catalyst has the advantages that the methane conversion rate, the trifluoromethane conversion rate and the vinylidene fluoride selectivity are low, and almost no reaction occurs; only the catalyst of metal lanthanum is used, and the methane conversion rate, the trifluoromethane conversion rate and the vinylidene fluoride selectivity are also lower; and the composite catalyst provided by the application has the advantages that the methane conversion rate, the trifluoromethane conversion rate and the vinylidene fluoride selectivity are improved, and compared with the reaction using the catalyst of metal lanthanum, the methane conversion rate is improved by about 2-7%, the trifluoromethane conversion rate is improved by about 2-12%, and the vinylidene fluoride selectivity is improved by about 3-30%.
Claims (13)
1. A process for producing vinylidene fluoride from trifluoromethane, characterized in that the process comprises:
under the action of a composite catalyst, reacting trifluoromethane with methane to prepare vinylidene fluoride;
the composite catalyst comprises a component 1 and a component 2, wherein the component 1 comprises lanthanide series metal, and the component 2 comprises IIA group metal.
2. The method for preparing vinylidene fluoride from trifluoromethane according to claim 1, wherein the composite catalyst comprises a component 1 and a component 2, wherein the component 1 comprises a material selected from LaF2、CeF2And SmF2At least one of, the component 2 comprises BaF2、CaF2And MgF2At least one of (1).
3. The method for preparing vinylidene fluoride from trifluoromethane according to claim 1, wherein the composite catalyst comprises a component 1 and a component 2, and the molar ratio of the component 1 to the component 2 is 0.15-4.5.
4. The method for preparing vinylidene fluoride from trifluoromethane according to claim 1, wherein the composite catalyst is prepared by subjecting component 1 and component 2 to lattice substitution at a high temperature to generate a solid solution.
5. The method for preparing vinylidene fluoride from trifluoromethane according to claim 1, wherein the composite catalyst is prepared by a method comprising:
(1) preparing an aqueous solution containing lanthanide metal soluble salt and IIA metal soluble salt, wherein the ion concentration ratio of lanthanide metal to IIA metal is 0.2-4.5: 1;
(2) adding a hydrogen fluoride solution into the aqueous solution at the temperature of 60-90 ℃ to enable the ion concentration ratio of fluoride ions to lanthanide metal ions and IIA metal ions in the aqueous solution to be 20-25: 1, so as to obtain a precipitate;
(3) and drying the precipitate and roasting at 600-950 ℃ to obtain the composite catalyst.
6. The process for producing vinylidene fluoride from trifluoromethane according to claim 5, wherein in the step (1):
the lanthanide metal soluble salt is selected from at least one of nitrate, acetate, carbonate, chloride and hydroxide of lanthanide metal;
the group IIA metal soluble salt is selected from at least one of nitrate, acetate, chloride and hydroxide of group IIA metal;
the ratio of the ion concentration of the lanthanide metal to the ion concentration of the IIA metal is 0.25-2.0: 1.
7. The process for producing vinylidene fluoride from trifluoromethane according to claim 5, wherein in the step (3): the roasting of the precipitate comprises roasting at a temperature of 600-800 ℃ at a speed of 1-5 ℃/min.
8. The process for preparing vinylidene fluoride from trifluoromethane according to claim 1, wherein: the reaction is carried out in a reaction chamber selected from the group consisting of steam, air, Cl2、CO2And O2In the presence of at least one gas.
9. The process for preparing vinylidene fluoride from trifluoromethane according to claim 8, wherein: said is selected from water vapor, air, Cl2、CO2And O2The using amount of at least one gas in the (1-10%) is 1-10% of the total volume of the feed gas of the trifluoromethane and the methane.
10. The process for preparing vinylidene fluoride from trifluoromethane according to claim 1, wherein:
the reaction temperature is within 1100 ℃;
the molar ratio of the methane to the trifluoromethane is 0.5-3: 1.
11. The process for preparing vinylidene fluoride from trifluoromethane according to claim 10, wherein the reaction temperature is up to 750 ℃.
12. The process for preparing vinylidene fluoride from trifluoromethane according to claim 11, wherein the reaction temperature is within 700 ℃.
13. The process for producing vinylidene fluoride from trifluoromethane according to claim 1, wherein the trifluoromethane is a by-product trifluoromethane produced in the production of HCFC-22.
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