The method of obtaining pentafluoroethane dismutase of tetrafluoromethane

 

Application: getting fluorocarbons. Essence: are dismutation of CHLOROTETRAFLUOROETHANE in the presence of the applied catalyst, and the catalyst is a mixture of oxide of trivalent chromium with at least the oxide of the alkali earth metal selected from Mg, CA, Sr and BA. Technical result: getting more pure Pentafluoroethane. 7 C.p. f-crystals, 2 tab.

The invention relates to a method, which allows to obtain high yields of very pure F2-CF3(HFC 125) penaflorida.

HFC 125 is a safe fluorocarbon for the ozone layer and therefore meets the requirements of the Montreal agreement (the Montreal Treaty). For commercial use of this connection requires its high purity.

The possibility of obtaining pure Pentafluoroethane depends on the type of impurities that are formed during the synthesis. For example, CFC-115 (CHLOROPENTAFLUOROETHANE CF2Cl-CF3) represents the impurity, which can hardly be removed from the HFC 125, so its presence does not allow to obtain a connection with a high level of purity. In order to get pentaverate that meets these requirements, you should use the ways in which CFC 115 not obrazu HCFC 124 (tetraphthalate C2HF4Cl) as a starting compound. HCFC 124 is subjected to fluorination HF on a suitable catalyst or turn (by dismutation) in a mixture of HFC 125+HCFC 123 (dichlorotrifluoroethane C2HF3Cl2), operating at a suitable temperature and in the presence of a catalyst. In the patent application WO 95/16654 describes a method for Pentafluoroethane on the basis of previously obtained gas mixture containing as a main component CHLOROTETRAFLUOROETHANE and lower amounts of chlorofluorocarbons (CFCs) with two carbon atoms. In the first stage chlorofluorocarbons separated in order to have HCFC 124, almost pure for the reaction with HF, in particular free from dichlorotetrafluoroethane (C2Cl2F4) CFC 114, which in these conditions must interact, forming CFC 115. Therefore, this patent discloses that in order to obtain pure HFC 125 by reacting HF with HCFC 124 source connection must be pre-cleaned by removing impurities chlorofluorocarbon2(114).

The way dismutation HCFC 124 more suitable compared to the reaction with HF, as the purity of the original connection is less significant, in addition, the selectivity is higher. This method has the disadvantage that the pre is Italia.

There is a need for a method of producing HFC 125, based on HCFC 124, in which you can increase the amount of HFC 125, reducing the amount of impurities in comparison with the synthesis of fluorocarbon described by known methods.

Surprisingly and unexpectedly, the applicant has discovered that the above problem can be solved, and it is the purpose of this invention, using a gas-phase method, in which pentaverate get dismutase of CHLOROTETRAFLUOROETHANE, in the presence of a catalyst comprising a mixture of oxide of trivalent chromium with at least the oxide of the alkali earth metal selected from Mg, CA, Sr and BA.

The reaction temperature is in the range 150C-250C, preferably 180C-240C.

The contact time with the catalyst, defined as the ratio between the volume of the catalyst and the volume of gas flow at the operating temperature and pressure is in the range 5-30 seconds, preferably 10 to 20 seconds.

Pressure is not essential, but is preferably between 1 and 10 bar.

The reaction is carried out, passing gaseous HCFC 124, optionally diluted with an inert gas, such as, nuchae the catalyst particles should have a size suitable for this installation type.

The ratio g (g) atoms between chromium and alkali-earth metals ranges from 50:1 to 3:1, preferably from 20:1 to 5:1.

The catalyst preferably is applied.

Preferably the substrate of the catalyst is aluminum fluoride, which can be obtained by fluorination of alumina, and having a fluorine content not lower than 90%, preferably not lower than 95% relative to the stoichiometric.

Usually used lF3formed from the gamma phase, as described in French patent 1383927, and has a surface area typically in the range of 25-35 m2/, When using the catalyst in the fluidized bed, the substrate has a grain size distribution that is appropriate for this type of rector, as is well known to specialists in this field of technology.

In the deposited catalyst the amount of interest contents contained chromium and alkali earth metal is in the range of 5-15%, by weight, preferably 10-15%.

The catalyst preferably is obtained by impregnation of the substrate with an aqueous solution of soluble salts of chromium and alkaline earth metals. The impregnation of the substrate can be accomplished in any way known in the prior art, for example In accordance with this method, the impregnation is carried out, pouring on a substrate, one after another, in accordance with the method described here below, portions of the impregnating solution so that the total volume was no higher than the pore volume of aluminum fluoride. The solution for impregnation is obtained by dissolution in water of the required quantities of the corresponding salts, preferably chlorides, trivalent chromium and alkaline earth metals. The solution is poured out portions on the substrate, after each addition carry out the drying at 110With several hours to evaporate the water from the pores of the substrate.

After impregnation, the catalyst must be activated: the operation can be done directly in the reactor used for the dismutation by calcination in a stream of inert gas, at a temperature of approximately 400C for 4-8 hours and then by treatment with 360With anhydrous HF in 12-24 hours.

Several examples are for illustrative purposes and are not limiting application of the present invention.

EXAMPLE 1A

Getting chrome/calcium/lF3catalyst

400 g of aluminum fluoride having a pore volume of 0.25 cm3/g and a grain size distribution that is appropriate is holding 252,5 g rl36N2O and 7.7 g of anhydrous CaCl2and further activate, as described above.

Thus obtained catalyst contains 10% by weight of chromium and 0.5% by weight of calcium.

EXAMPLE 1V

Dismutase 124 on chrome-calcium catalyst of Example 1A at a temperature of 200

350 g of the catalyst obtained in accordance with Example 1A, placed in 5-cm tubular Inconel600 reactor, equipped with a porous membrane at its base, and is heated by means of an electrical device. The catalyst is heated up to 200With in a stream of nitrogen. At this temperature, enter 2 mol/h (273 g/h) mixture 95/5, moles, HCFC 124 and HCFC 124A beaches isomers. Gases leaving the reactor, washed in water in order to absorb trace amounts of acidity, and analyzed by gas chromatography with detection thermoprotect. The results of the analysis of the reaction mixture by gas chromatography are shown in Table 1.

The Table shows that the conversion of HCFC 124 is 59.7% and that the yield of the BORE 125 (defined as received 125/reacted 124) is 51,4%. Moles/hour obtained HFC 125 are 0,61. Specific performance obtained HFC 125 (grams) in units of the who, than the limit of detection of the method of gas chromatography (100 million shares). Analysis of this mixture is repeated using a method GC-MS (GC-MS), but it is not possible to determine the admixture as its content lower than the limit of detection (1 million shares).

HCFC 124 and 1110 recycle in this way. So, as I believe, the latter is no admixture of way.

EXAMPLE 1C

Dismutase HCFC 124 on chrome-calcium catalyst of Example 1A at temperatures 220C and 240With, respectively,

The reaction of dismutation again, following the method described in the previous Example 1B, at temperatures 220C and 240C, respectively.

The results are presented in Table 1.

The Table shows that the number of CFC 115 at a temperature of 220With not measurable by the detector thermoprotect, and that, moreover, at a temperature of 240With the number of CFC 115 remains lower than 100 million shares. At this temperature, the conversion of HCFC 124 is approximately 80%, and output, as defined above, is equal to 54.7 per cent. Moles/hour obtained HFC 125 consists of 0.87. Therefore, the specific productivity at 240

EXAMPLE 2A

Getting chrome-strontium/lF3catalyst

400 g of aluminum fluoride having a pore volume of 0.25 cm3/g granules suitable for use in the fluidized bed, repeatedly impregnate a total volume of 240 cm3an aqueous solution containing 264 g rl36N2O and 15.7 g SrCl26H2O, and further activate, as described in the method of producing catalyst. Thus obtained catalyst contains 10% by weight of chromium and 1% by weight of strontium.

EXAMPLE 2B

Dismutase HCFC 124 on chrome-strontium catalyst of Example 2A at a temperature of 220

300 g of the catalyst obtained in accordance with Example 2A, is placed in the previously described tubular reactor and heated to 220With in a stream of nitrogen. Once this temperature is reached, enter 2 mol/h (273 g/h) approximately 95/5 mixture of HCFC 124 and HCFC 124A beaches isomers. Gases leaving the reactor, washed in water in order to absorb the traces of acidity, and analyzed by gas chromatography. The results are presented in Table 1.

The Table shows that the conversion of HCFC 124 is 55.8 per cent. The output is of 51.2%. Moles/hour obtained HFC 125 is 0 daysa measurement detector thermoprotect. The analysis is repeated using the GC-MS gives the number of CFC 115 approximately 55 million shares. The ratio of CFC-115/HFC 125 is lower than 200 million shares.

EXAMPLE 2C

Dismutase HCFC 124 on chrome-strontium catalyst of Example 2A at a temperature of 240

The test of Example 2 is repeated at a temperature of 240C. the Results are presented in Table 1, from which it follows that if 240With the amount of CFC 115 100 million shares, the conversion of HCFC 124 is 68.5 per cent and the output is 52.7 percent. At this temperature, moles/hour obtained HFC 125 are 0,72. Therefore, specific performance equal to 125 289 (g/kg catalyst/hour.

EXAMPLE 3A

Obtaining chromium-magnesium/lF3catalyst

500 g of aluminum fluoride having a pore volume equal to 0.25 CC/g, grain size distribution suitable for use in the fluidized bed, repeatedly impregnate total 327 CC of an aqueous solution containing 327 g rl36N2O and 50 g MDS26N2O. the Catalyst is further activated, as previously described. Thus obtained catalyst contains 10% by weight of chromium and 0.9% by weight of magnesium.

EXAMPLE 3B

Dismutase HCFC 124 on chrome-magnetotactic with Example 3A, placed in the previously described tubular reactor and heated to 220With in a stream of nitrogen. After the catalyst is stabilized at this temperature, enter 2 mol/h (273 g/h) approximately 95/5 (molar ratio) mixture of HCFC 124 and HCFC 124A beaches isomers. Gases leaving the reactor, washed in water in order to absorb the traces of acidity, and analyzed by gas chromatography. Get the following results, mol.%:

125 31,4

124 38,3

123 29,9

other: 0.4

Conversion of HCFC 124 is equal to 61.7 per cent. Output, as defined above, is of 50.9%. Moles/hour obtained HFC 125 are 0,63. The ratio of CFC-115/HFC 125 is 100 million shares (GC-MS analysis). Specific performance equal to 125 251 (g/kg catalyst/hour.

EXAMPLE 4A (COMPARATIVE)

Getting chrome/lF3catalyst

400 g of aluminum fluoride having a pore volume of 0.25 cm3/g and a grain size distribution suitable for use in the fluidized bed, repeatedly impregnate a total volume of 420 cm3an aqueous solution containing 275 g rl36N2O, and further activate, as described previously. Thus obtained catalyst contains 10.5% by weight of chromium.

EXAMPLE 4B (COMPARATIVE)

The reaction of dismutation HCFC 124 on r/176.gif">With 260With 280With 300C and 320With, respectively,

Approximately 400 g of the catalyst obtained in accordance with Example 4A, placed in the previously described tubular reactor and heated to reaction temperature in a stream of nitrogen. After the catalyst to adopt an appropriate temperature, enter 2 mol/h (273 g/h) approximately 95/5 mixture of HCFC 124 and HCFC 124A beaches isomers. Gases leaving the reactor, washed in water in order to absorb the traces of acidity, and analyzed by gas chromatography. The results obtained at different temperatures are presented in Table 2.

The Table shows that at a temperature of 180With the conversion 124 is 43.5%. Moles/hour obtained HFC 125 amount of 0.45. Specific capacity is 135 (g/kg catalyst/hour. Contents 115 125 defined by the GC method is <100 million shares.

Using the same above-described experimental conditions, carry out the reaction at 220With 240With 260With 280With 300C and 320With for the 6.gif">With, moles/hour obtained HFC 125 increase, but the ratio 115/125 has very high values, since temperature 240(0,13%). In addition, when the temperature decreases to increase the purity of the product specific productivity decreases. For example, at a temperature of 220With the conversion 124 is 52,8% with the release of 125-51%. Therefore, the specific capacity is about 125 161 g/kg catalyst/hour.

Claims

1. Gas-phase acquisition method Pentafluoroethane by dismutation of CHLOROTETRAFLUOROETHANE, in the presence of a catalyst comprising a mixture of oxide of trivalent chromium with at least the oxide of the alkali earth metal selected from SB, CA, Sr and BA.

2. The method according to p. 1, where the reaction temperature is in the range of 150-250C., preferably 180-240C.

3. The method according to PP.1 and 2, where the contact time with the catalyst is in the range of 5-30, preferably 10-20 C.

4. The method according to any of paragraphs.1-3, where the ratio of g atoms between chromium and alkaline earth metals ranges from 50:1 to 3:1, preferably from 20:1 to 5:1.

5. The method according to any of paragraphs.1-4, where the catalyst is applied.

6. The way in which the fluorine content not lower than 90%, preferably not lower than 95% relative to the stoichiometric.

7. The method according to p. 6, where the aluminum fluoride, mainly formed of the gamma phase and has a surface area typically in the range of 25-35 m2/,

8. The method according to any of paragraphs.5-7, where in the deposited catalyst amount percentage contents of chromium and alkaline earth metals is in the range of 5-15% by weight, preferably 10-15%.

 

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