The method of purification of 1,1,1,2-tetrafluoroethane from unsaturated halogenated derivatives of impurities

 

(57) Abstract:

Usage: when receiving perchlorethylene hydrocarbons ethane series, in particular when cleaning ozone-safe refrigerants, such as 1,1,1,2-Tetrafluoroethane (R-134a). The essence of the invention: purification of R-134a from unsaturated halogenated derivatives of impurities (R-1113, R-1122, R-1123, R-1243, R-1225) consists of passing the contaminated R-134a with a total content of the above-mentioned impurities to 10000 ppm through a layer of activated charcoal at 253 323 K and a pressure not exceeding the pressure of saturated vapor R-134a at a given temperature. The specific flow rate of the purified gas is not more than 0.35 kg/mm2C. the percentage of Total impurities after cleaning does not exceed 10 ppm. To improve the efficiency of the process before adsorption through the layer of sorbent miss R-134a, with no admixture of unsaturated kalogeropoulou. As the adsorbent used coal sulphur and potassium activation with the utmost amount of sorption space 0,50-0,80 cm3/, Regeneration of the adsorbent is carried out at 473 523 K and a pressure of 210-40.15 MPa, thus there is a complete desorption of the adsorbed products. The number of cycles of sorption is determined by the mechanical strength of the coal. table 2.purification ozone-safe refrigerants.

The process of purification of 1,1,1,2-Tetrafluoroethane (R-134a) is of considerable interest due to the prospects of its use as an ozone-friendly refrigerant substitute of difenilamina (R-12).

In the process of synthesis of R-134a by catalytic hydroperiodide 1,1,1-triptorelin (R-133a) or trichloroethylene is formed, the reaction mixture containing in addition to the target product, fluoride and R-a, also pentaborate (R-125), 1,1,1-trifluoroethane (R-143a), 1,1-differetn (R-152a), 1,1,1,2-tetrafluorochloroethane (R-124A beaches), a significant amount of unsaturated compounds: tryptophanate (R-1113), 1,1-di-fluoro-2-chlorethylene (R-1122), triptorelin (R-1123), 1,1,1-triptorelin (R-1243), 1,1,1,3,3-pentafluoropropane (R-1225), 1,1,1,2,3-pentafluoropropane and a number of other products.

During primary treatment of this mixture is the separation of the target product, R-134a, from most of the impurities. However, at this stage of purification is unable to fully remove impurities from the reaction mixture of unsaturated compounds. Due to the toxicity of the latter the use of contaminated their R-134a is not possible. Additional measures are necessary for the purification of R-134a.

In U.S. patent N 3819493 proposed a method of purification of R-134a methodology is However, this method requires sophisticated equipment and high energy costs. The method is ineffective when cleaning from the whole range of unsaturated impurities.

The company Du Pont de Nemours (application USA SN-1539), a method for oxidation of unsaturated impurities on hopcalite. This method is highly effective, but its use is associated with irreversible loss of the oxidant and its high environmental hazard.

Proposed by the company Allied Signal Inc. Pat. USA N 4906796, adsorption purification method R-134a is the absorption of 1,1-debtor-2-chloroethylene (R-1122) zeolites or carbon molecular sieves with an average pore size of 0.38-of 0.48 nm. Removal of R-1122 of R-134a is due to the use of molecular-sieve properties of the proposed adsorbents selectively absorbing those components, the size of the molecules which corresponds to or somewhat smaller than the pore size of the adsorbent. Because the size of the molecules R-1243 and R-1225 exceeds the average pore size of the proposed adsorbents, their removal from the R-134a does not occur. Thus, this method cannot be applied for purification of R-134a from R-1243, R-1225 and R-1113.

In Pat. EP 0389334 (the company Atochem, prototype) proposed a method of purification of R-134a from R-1122 when using as the adsorbent a number of industrial activated carbons. Due to the significantly greater blessing halogen derivatives of impurities on most charcoal is ineffective. You must use a special, high-performance grades of coal, as well as improving the efficiency of adsorption with additional measures.

Purification of R-134a from unsaturated halogenated derivatives of impurities consists of passing the contaminated R-134a with the content of the listed impurities to 10000 ppm through a fixed bed of activated carbon at temperatures from 253 to 323 K and a pressure not exceeding the pressure of saturated vapor R-134a at a given temperature. The specific flow rate of the purified gas is not more than 0.35 kg/ (m2.C). When this happens selective adsorption of unsaturated halogenated derivatives of impurities, the total content of which in purified refrigerant does not exceed 10 ppm.

To improve the efficiency of the adsorption process before it starts through the layer of adsorbent miss R-134a, with no admixture of unsaturated kalogeropoulou. This significantly increases the time of the protective action of the adsorbent.

As the adsorbent is proposed to use the coal sulfur and potassium activation with the utmost amount of sorption space 0,50-0,80 cm3/, Coals are characterized by advanced micro - and metophorically. Before using the adsorbent is subjected to heat is of Renta carried out at a temperature of 473-C and pressure 210-4-0,15 MPa, thus there is a complete desorption of the adsorbed products. The number of cycles of sorption is determined by the mechanical strength of the coals.

P R I m e R 1. 100 g of prepared coal SKT placed in the adsorber diameter of 25 mm, made of stainless steel. Refrigerant R-134a, which has in its composition a mixture of Pentafluoroethane (R-125), triptorelin (R-143a), tryptophanate (R-a), triptorelin (R-1123), triptoreline (R-1113), diperchlorate (R-1122), triptorelin (R-1243), pentafluoropropane (R-1225), passed through the layer of adsorbent with a volume flow rate of 200 standards.ml/min under the following conditions:

1 a pressure of 0.1 MPa, temperature of 298 K;

2 a pressure of 0.1 MPa, the temperature of 263 K;

3 the pressure 0.35 MPa, temperature 298 K.

Facing the gas flow analyze gas chromatography on a printed column length of 6 m and a diameter of 2 mm, filled with silochrome (fraction of 0.16-0.20 mm), modified potassium, at 296 K, using a flame ionization detector.

The results of the experiment are given in table. 1 and 2.

Analysis of the emerging gas stream indicates the absence of unsaturated kalogeropoulou and some increase in the content of other products associated with two.

Coal SKT almost completely absorbs R-1123, R-1113, R-1122, R-1243 and R-1225 and not adsorb other impurity components.

P R I m m e R 2. 100 g of prepared coal SKT placed in the adsorber diameter of 25 mm, made of stainless steel. Freon R-134a with low content of possible impurities (see example 1, table. 1) is passed through the layer of adsorbent with a volume flow rate of 200 standards. ml/min at atmospheric pressure and a temperature of 298 K for 3 h in 1.5 h analyze coming out of the gas adsorber. After completion of the adsorption determine the amount of absorbed product by weight of the adsorbent.

Desorption is carried out at atmospheric pressure and a temperature of 500 K for 3 h, after which determined the amount of desorbed product of loss of weight of the adsorbent.

The cycle of adsorption-desorption is repeated as many times as necessary.

The results are shown in table. 3.

The results of the experiments show that long-term cyclic operation leads to deterioration of the adsorption properties of coal. The service life of the sorbent, therefore, is determined by its mechanical strength.

P R I m e R 3. Two identical adsorber diameter of 25 mm and a height of 500 mm separatrice listed in example 1, table. 1, with a volume flow rate of 200 standards. ml/min To the input of the second adsorber is fed R-134a does not contain olefins, until complete saturation of the coal, and then begin to submit to be treated with R-134a with the same flow as the first adsorber. Determines the time the protective action of adsorbers until the output of total concentration of olefins 1ppm.

In the experiment it was established that the protective action of the second adsorber is 155 min, which is longer than the time of the protective action of the first adsorber (99 min) 1.6 times.

The METHOD of PURIFICATION of 1,1,1,2-TETRAFLUOROETHANE FROM UNSATURATED halogenated derivatives of IMPURITIES, which consists in the adsorption uptake of these contaminants carbon adsorbent, characterized in that the purified product is passed through a pre-saturated 1,1,1,2-Tetrafluoroethane sorbent coal sulphur and potassium activation with the utmost amount of sorption space 0,50 0,80 cm3/g in the temperature range 253 323K at a pressure of 1.3 MPa, with a flow rate of the purified gas to 0.35 kg/(m2(C) if the subsequent complete desorption.

 

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