FR2575176A1 - Compositions based on chlorofluoro solvents for absorption machines - Google Patents

Abstract

Compositions of solvents and heat-generating fluids for absorption heating or cooling equipment. The compositions according to the invention contain a chlorofluorohydrocarbon with a boiling point of between -40 and +50 DEG C and at least one solvent with a boiling point above 100 DEG C, chosen from the compounds of formula: in which m is equal to 1, 2 or 3, x is an integer ranging from 0 to 4, n is an integer ranging from 1 to 4 and X denotes a hydrogen, chlorine or iodine atom.

Description

COMPOSITIONS BASED ON CHLOROFLUORO SOLVENTS
FOR ABSORPTION MACHINES -ooooo-
The present invention relates to solvent and heat transfer fluid compositions for use in heating or absorption cooling apparatus.

 These machines whose operating principle is based on the extraction by low-level heat energy absorption, borrowed for example from outside air for a heat pump or a refrigerating chamber for a refrigerant group, and on the return of this energy to the room to be heated or to the surrounding space in the second case, use a readily vaporizable compound (the calogene) and a low volatility compound which is preferably a good solvent of the first.

 In a heat pump, the solution enriched with heat transfer fluid after absorption returns to the boiler where the two fluids are again separated by heating. The heat pump is vaporized and sent to the pump circuit where it first undergoes condensation at high temperature, followed by expansion followed by evaporation before returning to the absorber.

The chosen pairs of heat and solvent must meet a number of criteria related to the operation of this type of machine
(a) The boiling points under normal pressure must be at least 150 to 2000 ° C apart to avoid the use of a solvent retrograde device.

 (b) The boiling point of the heat-generating medium must not be too low to avoid the use of large operating pressures, nor too high to meet the preceding condition.

 c) Both compounds must be fully miscible in the proportions of use over a wide range of temperatures.

 d) The solvent must remain liquid at low temperature and have a solidification point as low as possible to maintain an acceptable viscosity at temperatures of -20 to 0 ° C.

 e) The mixture must have excellent thermal and chemical stability in the temperature range involved in the thermodynamic cycle, that is to say in a temperature range of -10 ° C in the particular case of heat pumps. for the cold source (absorber) at 150-180 C for the boiler.

 (f) The selected products must not display any toxicity character.

 For reasons of safety and also to take into account their good thermal and chemical stability, most of the heat transfer fluids are chosen from fluorinated hydrocarbons and, more particularly, from chlorofluorocarbons with one or two carbon atoms which best correspond to volubility and solubility criteria defined above.The most widely used compounds are dichlorodifluoromethane (R 12), dichlorofluoromethane (R 21), chlorodifluoromethane (R 22), chlorofluoromethane (R 31), dichloro-1 , 2-tetrafluoro-1,1,2,2 ethane (R 114), 1,1-dichloro-1,2,2,2-tetrafluoroethane (R 114a), chloropentafluoroethane (R 115), dichloro-1, 2,2,2-trifluoroethane (R 123), 1,2-dichloro-1,2,2-trifluoroethane (R 123a), 1,1-dichloro-1,2,2-trifluoroethane (R 123 b), chloro-1-1,2,2,2-tetrafluoroethane (R 124), 1-chloro-1,1,2,2-tetrafluoroethane (R 124a), 1-chloro-1,2-trifluoroethane , 2 ethane (R 133), the chloro-1-trifluoro-2,2,2 ethane (R 133a), chloro-1-trifluoro-1,1,2 ethane (R 133b) and chloro-1-difluoro-1,1 ethane (R 142b).

 The best solvents, when the fluorinated hydrocarbon has one or more hydrogen atoms, are those capable of forming intermolecular associations by hydrogen bonding and are recruited in the classes of carbonyl derivatives (esters, ketones, amides, lactams), alcohols or ethers of polyethylene glycols.

Among the most used solvents, mention may be made of dimethyl ethers of tri- or tetraethyleneglycol (patent SU 150113 and applications JP 79-152257 and DE 3202377), N-methyl-pyrrolidone (patent SU 643524 and JP 79 applications). 145774 and JP 82-132545), N, N-dimethylformsmide (JP application 82-121759) and dibutyl phthalate (patent SU 346326). Imidazolines and phosphoramides (JP 82-132544 and DE 2944189) as well as derivatives of tetrahydrofurfuryl alcohol (U.S. Patent No. 4,215,132) have also been advocated as solvents.

In the boiler of the absorption machines the solutions enriched with working fluid are brought to high temperatures. the walls of the boiler are generally made of metal materials based on iron, aluminum or copper which, under the effect of temperature, may constitute a destabilizing element of the calogine-solvent pair; It is well known that a chlorofluorocarbon of the CnH2n + 2-x-yFxCly type, heated in the presence of one of the abovementioned metals and of a hydrogen-donor compound, undergoes a quantitative transformation with progressive substitution of the According to the reactivity of the donor and the structure of the fluorinated hydrocarbon, when n is equal to or greater than 2, a greater or lesser proportion of ethylenic derivatives is also formed. Thus, in the case of chloro-1-trifluoro-2,2,2 ethane (R 133a), these transformations are carried out according to the following reaction scheme

<tb> GF3- <SEP> o <SEP> + <SEP> RH <SEP> (solvent) <SEP> CF3CH3 <SEP> + <SEP> R.
<Tb>

1-chloro-1,2,2,2-tetrafluoroethane (R 124), heated in the presence of N-methylpyrrolidone and iron, gives 1,1,1,2-tetrafluoroethane (R 134a). and a mixture of 1,1-difluoroethylene and trifluoroethylene.

 This reaction is accompanied by the formation of tars at the expense of the solvent and a significant corrosion due to the action of metal halides formed. The modification of the nature of the calogenic couple / solvent, the effects of corrosion and in particular the formation of incondensable gases cause the deterioration of the operating conditions of the heat pump and can very quickly cause it to be put out of use.

 Various proposals have been made to remedy this disadvantage and to ensure a minimum reliability of the order of 10,000 hours. The most important is to stabilize the chlorofluorinated fluid / solvent mixture by introducing an additive in a proportion not substantially modifying the physicochemical and thermodynamic characteristics of the calogenic couple / solvent.

 Unfortunately, these additives have only a limited effectiveness over time and their action is mainly limited to an increase in the inhibition period.

 Another method is to replace the chlorofluorinated hydrocarbon with a polyfluorinated alcohol such as trifluoroethanol (JP applications 80-16315, 81-88485, 82-132545 and 83-98137). However, the relatively high boiling points of these alcohols (73.5 C for trifluoroethanol) lead to operate part of the installation (the evaporator) at a pressure much lower than the normal pressure.

 Finally, it is possible to nidrate the solvent and choose it from a family of products which, in the presence of metals and chlorofluorocarbons, do not give rise to the reactions described above.

In this respect, the structure identity has been used in the patents FR 2,075,236 and U.S. 4,003,215 which use chlorofluorocarbon couples as solvents and working fluids.

However, for the R 12 / R 11 and R 12 / R 113 couples cited in the examples, the small differences in boiling points (of the order of 40 to 80 ° C.) require the implementation of complex technological processes for carry out the solvent / calogene separation at the boiler outlet.

 the present invention therefore aims to overcome the disadvantages of the prior art and to provide chlorofluorinated chlorofluoroZcalogene solvent couples, stable at high temperature in the presence of metals and used especially in heating systems or refrigeration absorption.

It has now been found that chlorofluorinated compounds having a boiling point greater than 100 ° C and having the general formula
Wherein m is 1, 2 or 3, x is an integer from 0 to 4, n is an integer from 1 to 4, and wherein m is 1, 2 or 3; preferably equal to 2 or 3, and X represents a hydrogen, chlorine or iodine atom, form with the chlorofluorinated hydrocarbons serving as working fluid (heat generating) mixtures which are stable at high temperature in the presence of metallic materials, especially ferrous, and can therefore, without addition of stabilizer, beech used in the heating or refrigeration units by absorption without risk of decomposition. Their chemical inertia allows the use of common materials for the realization of the hot parts of the installation of which safety is increased by the absolutely non-flammable nature of said mixtures.

 The subject of the invention is therefore compositions comprising, on the one hand, a chlorofluorinated hydrocarbon having a boiling point of between 40 and + 500 ° C., preferably between -20 ° and + 200 ° C., and, on the other hand, at least one compound of formula (I) having a boiling point greater than 100 ° C.

 The compounds of formula (I), used as a solvent in the compositions according to the invention, can be prepared from trifluorochloroethylene according to well-known methods, either by thermal or radical telomerization using telogens such as chloroform and sodium iodides. perfluoroalkyl CrnF2ii + II either by redox telomerization using perhalogenated telogens such as carbon tetrachloride, trichloro-1,1,1,2,2,2-trifluoroethane and the aforementioned iodides (Boutevin et al., Tetrahedon Letters No. 12, 1973, pp. 887-890 and Eur Polym J. 1976, 12, 219), the initiation being obtained in this case using a metal that can take different degrees of oxidation such that, for example, iron or copper.The latter metal is particularly interesting because it allows to selectively obtain a monoaddition compound (n = 1) of the telogen trifluorochloroethylene.

 The viscosity and volatility of the compounds of formula (I) depend on the nature of the telogen, the degree of telomerization and the ratio F / C1. This ratio can optionally be modified by treating the telomer with elemental fluorine or any other fluorinating agent. By combining these different parameters, one obtains chlorofluorinated solvents with boiling points higher than 100 C preserving their liquid state on a broad field.

temperature. For example, the telomers of trifluorochlorethylene with chloroform have the following boiling points, calculated by the method of B.P.N. (boiling point number) according to J. Chem. Eng. Data 1967, p. 214.

Telomer PEb / 760 torr
CCl2-CF2-CFClH 142 C
CCl3- (CF2-CFCl) 2H 203 C
CCl3- (CF2-CFCl) 3H 256 C
Of the chlorofluorinated hydrocarbons according to the present invention, it is preferred to use chloro-1-1,2,2,2-tetrafluoroethane (R 124), chloro-1 2,2,2-trifluoroethane (R 133a) and the 1,2-dichloro-1,1,2,2-tetrafluoroethane (R 114).

 The compositions according to the invention have an extensive range of complete miscibility. The respective proportions of chlorofluorinated hydrocarbon and compound of formula (I) are not critical and are limited only by the mutual solubilities.

 The following tests A to C, carried out with chlorofluorinated hydrocarbon / N-methyl-pyrrolidone (NMP) pairs, are given as controls and are to be compared with Examples 1 to 7 which illustrate the invention without limiting it.

TEST A
5 mmol of R 124 are introduced into a thick-walled pyrex tube containing 3 g of NMP and a suitably cleaned 250 mg ordinary steel test tube. The tube is cooled to the temperature of liquid nitrogen, sealed under vacuum and then maintained at a temperature of 180 C for 100 hours. It is then re-dipped into liquid nitrogen, connected to a vacuum ramp and opened with a suitable device. Volatiles are recovered by low temperature purging and gas chromatographic analyzes. The analysis shows that 55.4% of the initial R 124 has been converted, of which about 50% is CF 3 -CH 2 F (R 134a).

 If the ordinary steel specimen is replaced by a test specimen of 620 mg of aluminum and heated at 1800 ° C for 1000 hours, the decomposition rate of R 124 reaches 97.4%.

TEST B
5 mmol of R 133a, 3 g of NMP and a 250 mg ordinary steel test tube are placed in a pyrex tube and the mixture is maintained at 1800 ° C. for 100 hours. After opening the tube, it is found that 76.1% of the initial R 133a were converted, of which about 62.5% CF3CH3 and 8.5% CF2-CH2.

TEST C
A mixture of 5 mmol of R 124, 3 g of NMP and 45 mg of tiutyl phosphate is placed, with a 250 mg test tube of ordinary steel, in a thick walled pyrex tube and the whole is kept at 180 ° C. 100 hours. After opening the tube, it is found that 28.9% of the initial R 124 were transformed, 25% of which in R 134a.

EXAMPLE 1
5 mmol of R 124, 3 g of 1,1,1,3,3-pentachloro-2,2,3-trifluoropropane and a test tube of 250 mg of ordinary steel are placed in a pyrex tube and the mixture is heated to 1800C for 100 hours. After opening the tube, only 1.3% of the
R 124 initial were transformed.

EXAMPLES 2 TO 7
The following table summarizes the results obtained by operating as in Example 1 with other compositions according to the invention.

In the last column is indicated the solubility of the chlorofluorinated hydrocarbon in the solvent of formula (I), this solubility being measured at ordinary temperature and pressure and expressed in grams of chlorofluorinated hydrocarbon dissolved per 10 g of mixture. the abbreviations S 416a and S 426 have the following meaning
S 416a: Hexachloro-1,1,1,3,5,5 hexafluoro-2,2,3,4,4,5 pentane
or CCl3-CF2-CFCl-CF2-CFCl2
S 426: Pentachloro-1,1,1,3,5 hexafluoro-2,2,3,4,4,5 pentane
or CCl3-CF2-CFCl-CF2-CFClH
The 1,1,1,3,3-pentachloro-2,2,3-trifluoropropane used in Example 1 and the solvent S 416a used in Examples 2, 4 and 6 are described in Eur. Polym. J. 1976, 12, 219. Their respective boiling points are 156 ° C. and 2170 ° C. under normal pressure. Hydrocarbon Decay rate
Chlorofluorinated Example Solvent (I) Hydrocarbon Solubility 2 R 124 S 416a 0.5% 12.8% 3 R 124 S 426 0.2% 12.0% 4 R 133a S 416a 1.7% 24.6 % 5 R 133a S 426 0.8% 26.3% 6 R 114 S 416a 0.3% 30.5% 7 R 114 S 426 0.2% 28.2%

Claims (6)

 Wherein m is 1.2 or 3, x is an integer from 0 to 4, n is an integer from 1 to 4 and represents an atom of hydrogen, chlorine or iodine.  = = = = = = = 1. Compositions for heating or absorption cooling apparatus, characterized in that they contain a chlorofluorinated hydrocarbon having a boiling point of between -40 and + 50 ° C. and at least one solvent having a d boiling above 100 C, selected from compounds of general formula Compositions according to claim 1, wherein n is 2 or 3. 3. Compositions according to claim 1, wherein the solvent is 1,1,1,3,3-pentachloro-2,2,3-trifluoro-propane, hexachloro1,1,1,3,5,5 hexafluoro-2 2,3,4,4,5 pentane or pentachloro-1,1,1,3,5 hexafluoro 2,2,3,4,4,5 pentane. 4. Compositions according to one of claims 1 to 3, wherein the chlorofluorinated hydrocarbon has a boiling point between -20 and + 200C. 5. Compositions according to one of claims 1 to 4, wherein the chlorofluorinated hydrocarbon contains one or two carbon atoms. 6. Compositions according to claim 5, in which the chlorofluorinated hydrocarbon is chloro-1-1,2,2,2-tetrafluoroethane, 1-diloro-2,2,2-trifluoroethane or 1,2-tetrafluoro-dichloroethane. -1,1,2,2 ethane.