KR890002822B1 - Process for the manufacture of chloropenta fluoroethane by the action of hydro fluoric acid - Google Patents

Abstract

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Description

Method for synthesizing chloropentafluoroethane from dichlorotetrafluoroethane and hydrofluoric acid

The present invention relates to a method for synthesizing chloropentafluoroethane from dichlorotetrafluoroethane and hydrofluoric acid. More specifically, the present invention relates to a process for producing chloropentafluoroethane by gas phase catalytic reaction of dichlorotetrafluoroethane C ₂ F ₄ Cl ₂ and hydrofluoric acid HF.

Chloropenta fluoroethane used as a solvent, propellant or coolant is prepared by known methods, for example from perchloroethylene, chlorine and hydrofluoric acid (West German Patent No. 117,580) or in the presence of aluminum trifluoride. It can be prepared by gas phase reaction of trichlorotrifluoroethane C ₂ F ₃ Cl ₃ with hydrofluoric acid (Japanese Patent Publication No. 48-26, 729/73).

US Pat. No. 3,087,974 describes the addition of hydrofluoric acid without vapor phase disproportionation of chlorofluoro compounds on a catalyst. Disproportionation of dichlorotetrafluoroethane occurs according to the following reaction.

2C ₂ Cl ₂ F ₄ → C ₂ ClF ₅ + C ₂ Cl ₃ F ₃

This catalyst is activated alumina with a large surface area treated with a fluorocarbon compound before being used for disproportionation. The conversion of CF ₂ ClCF ₂ Cl to C ₂ ClF ₅ does not exceed 34% on a molar basis, and a high proportion of C ₂ Cl ₃ F ₃ is prepared as a byproduct.

US Pat. No. 3,258,500 describes vapor phase catalyst fluorination with hydrofluoric acid.

Dichlorotetrafluoroethane CF ₂ Cl-CF ₂ Cl and hydrofluoric acid HF are reacted at 400 ° C. on a chromium oxide catalyst with a molar ratio of [HF / CF ₂ Cl-CF ₂ Cl] within the range of 4-5. The proportion of hexafluoroethane C ₂ F ₆ formed is 0.19 on a molar basis relative to C ₂ F ₅ Cl.

L. Marangoni et al. 'The Preparation of Chloropentafluoroethane from Dichlorotetrafluoroethane' (Journal of Fluorine Chemistry 19, 1981/82, pages 21-34) also included C ₂ F ₄ Cl ₂ and C ₂ F from HF. A catalyst based on chromium oxide for gas phase production of ₅ Cl is described. The conversion of C ₂ Cl ₂ F ₄ is in the range of 72-75% and the yield of C ₂ F ₅ Cl is in the range of 89-92%, but hexafluoroethane still accounts for 8% of C ₂ F ₅ Cl formation on a molar basis. Is formed.

M. A study on the vapor phase production of chlorofluoroethanes (Journal of Fluorine Chemistry, 4, 1974, pages 111-139) by Vecchio et al. Is based on aluminum fluoride based addition of nickel, iron and chromium halides. The same reactions are described for the same papers as above except for the catalyst phase. The conversion of C ₂ F ₄ Cl ₂ does not exceed 41% and the molar percentage at the reactor outlet is 38%.

The catalysts in the prior art have mediocre yields and selectivities for C ₂ F ₅ Cl, but suffer from manufacturing difficulties.

The present invention provides a simple, flexible and economical C ₂ F ₅ Cl production method that overcomes all these disadvantages. The method of the present invention reacts an activated alumina having a sodium oxide content of 300 ppm or less and a pore diameter of 40 mm or more with a volume of 0.7 cm ³ / g or more in a gaseous mixture of hydrofluoric acid or hydrofluoric acid with air, nitrogen or a fluorine compound. It is characterized in that the dichlorotetrafluoroethane C ₂ Cl ₂ F ₄ and hydrofluoric acid HF in the presence of a catalyst prepared by the reaction in the gas phase.

C ₂ F ₅ Cl is obtained with high conversion and high yield of at least 80% of the starting material. Another advantage of the present invention lies in the lifetime of the catalyst. Activated alumina is prepared by controlled heating of alumina hydrate to remove most of the water formed (Kirk-Ottmer, Encyclopedia of Chemical Technology, 3rd edition, Volume 2, page 225).

Alumina used for preparing the catalyst is alumina commercially available. It is sufficient to select activated alumina having a volume of pores of 40 mu m or more in the range of 0.70 m ² / g or more, preferably in the range of 0.75 to 1 cm ³ / g. The alumina is advantageously in the form of granules, beads or extrudate of a size smaller than a sphere of diameter 20 mm, preferably several millimeters, for convenient handling during the dripping and draining of the reactor.

As mentioned above, the Na ₂ O content should be 300 ppm or less, preferably as low as possible. It is also advantageous to select alumina containing up to 0.5% silica and up to 0.2% iron oxide Fe ₂ O ₃ by weight. Such alumina is converted to a mixture of aluminum trifluoride AlF ₃ and alumina by reaction with HF itself or with HF mixed with air, nitrogen or fluoro compounds.

For example, a mixture of dichlorotetrafluoroethane C ₂ Cl ₂ F ₄ and hydrofluoric acid can be used to initiate a reaction that passes over alumina at a sufficient temperature to convert the alumina to aluminum trifluoride. At this time, it is advantageous to perform within the temperature range of 150 ~ 500 ℃. The operation is preferably carried out at atmospheric pressure with a contact time of 5 to 15 seconds. Experts in this field can easily perform the reaction by adjusting the ratio, temperature, pressure and contact time of C ₂ F ₄ Cl ₂ and HF to prevent damage of alumina due to high temperature due to the exothermicity of the reaction. .

The alumina is converted to a catalyst if the composition of the gas no longer changes after passing over the alumina.

This catalyst can be used after washing with water if appropriate in order to fluorinate C ₂ F ₄ Cl ₂ with C ₂ F ₂ Cl according to the invention.

According to a preferred embodiment of the invention the catalyst can also be prepared by reacting alumina in a fluidized bed with a hot air stream containing hydrofluoric acid. This is advantageously performed in the temperature range of 150 ~ 500 ℃. It is advantageous to use a mixture of HF and air on a molar basis between 0.1 and 30%, preferably between 1.5 and 3%. Emissions are advantageously in the range of 200-250 moles / hour for 1 liter of catalyst. The operation is preferably carried out at atmospheric pressure of 350 ° C or higher. It is convenient to control the exothermicity of the reaction by changing the HF concentration in the air. When no more HF is consumed the reaction is terminated and the catalyst is considered to be used for fluorination of C ₂ F ₄ Cl ₂ .

The reaction between dichlorotetrafluoroethane C ₂ F ₄ Cl ₂ and anhydrous hydrofluoric acid HF is carried out on a catalyst which can be prepared according to any of the two routes above in the gas phase. The temperature is advantageously in the range of 300 to 500 ° C, preferably 380 to 500 ° C. The molar ratio of HF / C ₂ Cl ₂ F ₄ is advantageously between 0.5 and 1.5, preferably between 0.9 and 1.1.

The reaction can be carried out at any pressure if it is gaseous, but it is simpler to carry out with a contact time between 0.5 and 4 bar, preferably near atmospheric pressure, between 5 and 15 seconds, preferably between 6 and 13 seconds. The present invention will be described in detail with reference to the following examples without limiting the invention. C ₂ F ₄ Cl ₂ used in all examples contains 92.7% symmetric isomers.

Example 1

Activated pure alumina manufactured by Kayser Corporation in the form of 0.8 mm (1/32 ") extrudates having the following characteristics is used:

Volume of pores with a radius of 40 mm or more = 0.91 cm ³ / g

Total BET Specific Surface = 161m ² / g

Average pore radius = 106 mm

Apparent density (dense volume) = 0.47

= 105m ² / g of small pore with radius within 50 ~ 250Å

Surface area

Fe ₂ O ₃ content: 0.08% by weight

SiO ₂ content: 0.13% by weight

Na ₂ O content: 0.015% by weight

0.12 liters of alumina was packed into a fixed bed in a tubular reactor with an internal diameter of 28 mm and converted to a catalyst according to the table below.

After washing the oxygen-free acid with water and aqueous sodium hydroxide solution at the end of the treatment, the proportion of C ₂ ClF ₅ in the gas leaving the reactor amounts to 23.6% compared to only 0.7% at 350 ° C.

The amount of C ₂ Cl ₂ F ₄ is the same as before and the temperature of the reactor is raised to 450 ° C. The results are shown in Table I below. The molar discharge is described for a reactor pressure of 1 bar of catalyst of 0.1 l and a temperature of 450 ° C. The working time of the catalyst described includes a preliminary step in which alumina is converted into a catalyst.

In all the tests described above, unconverted dichlorotetrafluoroethane (about 15% of the C ₂ Cl ₂ F ₄ compound used on a molar basis) contains 20-25% of the symmetric isomer CF ₂ Cl-CF ₂ Cl. . After operating for 550 hours under the above operating conditions and regenerated with pure air at 450 ° C., the catalyst gives the exact same result as above.

Example 2

Activated alumina in the same 0.8 mm extrudate form as in Example 1 is taken and converted to catalyst using fluid bed technology. 0.125 liter of Kayser 4192 alumina, or 51.3 g, is taken and heated to 350 ° C. in a nitrogen stream, and then the following gas mixture is introduced under atmospheric pressure for 24 hours.

Air: 27.2 mol / hour, HF: 0.77 mol / hour

After performing this treatment for 24 hours, the catalyst contains 62% fluorine, in other words 91.4% aluminum fluoride and 8.6% unconverted alumina. Its weight is increased to 77.9 g.

Take the 68.1 g (0.1 liter) of the catalyst and repeat the test of Example 1 in the same 28 mm diameter tubular reactor as in Example 1. The results are shown in Table II below.

The catalysis time described in this table corresponds to the period in which the reactor starts to fill the fixed acid and does not include the conversion of alumina to the catalyst.

Example 3

The method of Example 2 is repeated with the same activated alumina as in Example 2, except after the reactor is charged to the stationary phase to fluorine C ₂ F ₄ Cl ₂ and after the alumina is converted to a catalyst. The molar ratio of HF / C ₂ Cl ₂ F ₄ starts the reaction at about 1 instead of 0.4 of Example 2. The results are shown in Table III. The activity or selectivity of the catalyst does not change by the starting method. The operating time described is the time from when the reactor is charged to the stationary phase and does not include the conversion of alumina to the catalyst.

Example 4 (comparative)

The method of Example 2 is repeated except that the activated alumina and the pore volume used in the process of the invention use different activated aluminas; The alumina used is SCM 250 having the following properties:

Chemical purity

Na ₂ O 800 ppm

Fe ₂ O ₃ 300 ppm

SiO ₂ 200ppm

Physical properties:

Shape: Bead, Diameter 2 ~ 4mm

Specific Surface (BET) = 270m ² / g

Total volume of pores with a radius of 40Å or more = 0.63cm ³ / g

Average pore diameter 90Å

Bulk Density: 0.66g / ml

A catalyst is obtained with an AlF ₃ content of 87.7% by weight and the remainder being unconverted alumina. The results are shown in Table IV, 1; The action time is measured as in Example 2.

The same SCM 250 alumina is used as a sphere of 2-4 mm and converted to a catalyst as described above. However, after conversion, it is mechanically decomposed into smaller pieces of 1 mm or less, which is similar in size to the Kayser alumina of Examples 1, 2 and 3. This catalyst is then used in the same manner as above.

The results are shown in Tables IV and 2.

The working times listed in the table do not include the time required for the conversion of alumina to the catalyst.

Example 5

CS331-1 from Catalyst and Chemicals Europe (CCE) is used.

Important physical properties are as follows:

Form: Extruded diameter 1/16 "(~ 1.6mm)

Active surface area (BET): 255m ² / g

Average pore diameter: 90Å

Volume of pores with a radius of 40Å or more: 0.76cm ³ / g

Bulk Density: 0.60g / ml

Na ₂ O 200 ppm

Fe ₂ O ₃ 800 ppm

SiO ₂ 300ppm

The catalyst was prepared as in Example 2 so that the AlF ₃ concentration of the catalyst was 92% and the concentration of unconverted alumina was 8%.

The corresponding test results are shown in Table V below; From the obtained results, it can be seen that it is much superior to that of Comparative Example 4 (SEM 250 alumina).

The operating time described does not include the conversion time of the alumina to the catalyst.

Example 6 (comparative)

According to a method different from the present invention, C ₂ F ₄ Cl ₂ is fluorinated with HF. Instead of taking alumina and converting it into a catalyst as described above, commercially available aluminum trifluoride powder containing about 8% alumina is used.

Important physicochemical properties are as follows:

Average particle size of powder: 50-80 microns

Total specific area (BET) = 1.6m ² / g

Volume of pores with radius above 40 ℃: 0.25cm ³ / g

The following method is the same as the above example in which C ₂ F ₄ Cl ₂ is fluorinated with HF, except that a fluidized bed is used instead of a fixed bed.

The results are shown in Table VI.

Example 7

The method of Example 2 was repeated using the same type of alumina (Cayser 4192) except that the contact time was shortened.

The results are shown in Table VII. At this time, the action time does not include the conversion time of the alumina to the catalyst.

It was found that the specific extrusion amount of C ₂ ClF ₅ can be increased significantly without compromising yield.

Table VIII describes the results obtained under similar conditions and shows the effect of Na ₂ O content.

TABLE I

TABLE II

Operation condition

Fixed bed catalyst (volume = 0.1 liters)

Temperature: 450 ℃

Pressure: atmospheric pressure

TABLE III

Operation condition

Fixed Bed Catalyst Prepared According to Example 2 (Volume = 0.1 L)

Temperature = 450 ℃

Pressure: atmospheric pressure

TABLE IV, 1

General operating conditions for testing

Fixed bed catalyst (volume = 0.1 liter) in the form of 2-4mm bead

Temperature = 450 ℃

Atmospheric pressure

TABLE IV, 2

Operation condition

Fixed bed catalyst (volume = 0.1 liters)

Temperature = 450 ° C until 139 hours, then 500 ° C

Atmospheric pressure

TABLE V

Operation condition

Fixed bed catalyst (volume = 0.1 liters) in the form of 1.6 mm extrudates prepared according to Example 2

Temperature = 450 ℃

Atmospheric pressure

Table VI

Operation condition

Catalyst in the form of a fluidized bed (volume = 0.14 liters) with a particle size of 50 to 80 microns

Temperature = 450 ℃

Atmospheric pressure

TABLE VII

Operation condition

Fixed bed catalyst (volume = 0.1 liter) in the form of 0.8 mm extrudate

Temperature = 450 ℃

Atmospheric pressure

TABLE VIII

Operation condition

Fixed bed catalyst (volume = 0.1 liter) in the form of 0.8 mm extrudate

Temperature = 450 ℃

Atmospheric pressure

Claims (16)

A method for producing chloropentafluoroethane by reacting dichlorotetrafluoroethane and hydrofluoric acid in a gaseous phase in the presence of a catalyst, wherein the volume of pores having a sodium oxide content of 300 ppm or less and a radius of 40 mm or more is 0.7 cm ³ as a catalyst. fluorinated alumina prepared by reacting an active alumina of / g or more with hydrofluoric acid or hydrofluoric acid and a mixture of air, nitrogen or a fluoro compound in the gas phase. The method according to claim 1, wherein the volume of the pores having an alumina of 40 mu m or more in the range of 0.75 to 1 cm ³ / g is used. The method of claim 1 or 2, wherein the alumina has a purity of at least 99.2% by weight. The method according to claim 1 or 2, characterized in that the alumina is in the form of particles smaller in size than a sphere having a diameter of 20 mm. 3. Process according to claim 1 or 2, characterized in that the catalyst is prepared by acting on air or a mixture of nitrogen and hydrofluoric acid on alumina at a temperature between 150 and 500 ° C. 6. The method of claim 5 wherein the HF content in the mixture of HF and air or nitrogen is 0.1-30% on a molar basis. The method of claim 5 wherein the operation is carried out at atmospheric pressure of 350 ° C. or higher. The process according to claim 1 or 2, characterized in that the alumina is subjected to a gas phase reaction at a temperature of 150 to 500 ° C. with a mixture of hydrofluoric acid and dichlorotetrafluoroethane. The method of claim 8, wherein the operation is performed at atmospheric pressure with a contact time of 5-15 seconds. 3. Process according to claim 1 or 2, characterized in that the fluorinated dichlorotetrafluoroethane with HF at a molar ratio of 0.5 to 1.5 of HF / dichlorotetrafluoroethane and at a temperature of 350 to 500 < 0 > C. The method of claim 10 wherein the operation is performed at 0.5-4 bar. The method of claim 11 wherein the operation is performed at atmospheric pressure with a contact time of 5-15 seconds. 7. The method of claim 6, wherein the HF content in the mixture of HF and air or nitrogen is 1.5-3% on a molar basis. The method of claim 10, wherein the molar ratio of HF / dichlorotetrafluoroethane is 0.9 to 1.1. The method of claim 10, wherein the temperature is 380 ~ 500 ℃. 13. The method of claim 12 wherein the contact time is 6-13 seconds.