The method of obtaining pentafluoroethane

 

(57) Abstract:

The invention relates to the field of chemical technology of fluorine compounds. Pentaverate obtained by gas-phase catalytic hydroperiodide of perchloroethylene or a mixture of perchloroethylene and hydrogen of glodeanu at a temperature 330-465C, molar ratio HF : hydroporinae products 4-40: 1, contact time 5-60 with the catalyst containing 8-24 wt.% fluoride chromium3+uniformly distributed in the magnesium fluoride. Increases the yield of the final product. 7 table.

Pentaborate (HFC 125) is ozone friendly product (ODP=0) and is considered as a promising refrigerant for low temperature refrigeration machines [gidaspow B. C., Maksimov, B. N. Refrigeration, No. 3, 1989, S. 2]. In addition, in the present studies on the use of Pentafluoroethane as fire extinguishing agent, capable in some applications to replace traditional ozone-dangerous fire extinguishing substance - trifloromethyl, diperchlorate, 1,2-dibromotetrafluoroethane. A number of leading foreign companies are developing processes for the production of Pentafluoroethane associated with gas-phase catalytic methods Shin is the vector of fluoride. Fluorination of hydrocarbons on the vector fluorine encounters difficulties during the implementation process associated with a large dissipation in the synthesis reaction and the need to use it to restore the health carrier of elemental fluorine. Another line of research to obtain Pentafluoroethane are studies on its synthesis by gas-phase catalytic hydrogenation of pentafluorobutane. So in the patent [Application Japan N 91/99026, C 07 C 19/08, op. 24/04/91] it is proposed to carry out the hydrogenation pentafluorobutane in the presence of cations of platinum and other metals of group VIII deposited on activated carbon. At a temperature of 320oC, the molar ratio hydrogen:pentafluorobutane = 3:1, the conversion of pentafluorobutane amounted to 89%, and the selectivity for pentaverate - 99%. However, getting Pentafluoroethane method gas-phase catalytic hydrogenation involves the implementation process with a potentially explosive atmosphere, as well as with the need to organize large recycle streams of hydrogen.

In patents Italy [EP 0282005, C 07 C 19/08, op. 14/09/88] and [EP 0408004, C 07 C 19/08, op. 16/01/91], obtained on the production of halon 123, by catalytic hydroperiodide of perchloroethylene in Savoy patents represented impregnated Cr3+the aluminum fluoride with a developed surface. Differing essentially only using different allotropic forms of aluminum fluoride and compounds of trivalent chromium (in the first case - CrCl3the second Cr2O3), patented production methods provide the most optimal conditions, the receipt of freon 123 and 124 not more than 40%, and halon 125 to 10%, with the maximum attainable conversion of perchloroethylene to 68%. In the patent firm Du Pont [EP 313061, C 07 C 19/08, op. 26/04/89] when gas-phase catalytic gidroftorirovaniya tetrachloroethylene (the molar ratio of HF:C2Cl4= 6:1) on the catalyst based on chromium oxide at a temperature of 250oC and contact time of 90 with the mixture of products containing 68,3% 1,1,1-Cryptor-2,2-dichloroethane; 20,2% - 1,1,1,2-tetrafluorochloroethane and 8% Pentafluoroethane. In accordance with this patent as a starting product for the synthesis can be used and halogeton composition C2HCl5-xFx(where x=0-2).

In the patent [U.S. Patent N 5395999, C 07 C 19/08, op. 07/03/95] proposed a method of obtaining Pentafluoroethane of trichloroethylene at a temperature of 200-375oC in the presence of a catalyst Cr2O3obtained by the pyrolysis of bichromate of ammonia (NH4)2Cr2O

In U.S. patent [U.S. Patent N 4766260, C 07 C 17/20, op. 23/08/88] hydroperiodide tetrachloroethylene were performed on catalysts based on aluminum fluoride obtained from aluminum oxide with additives of metals of variable valence of Cr, Mn, Ni, Co, along with the main products of the synthesis trichotillomania and tetrafluorochloroethane turns (depending on deposited on aluminum oxide cation of a metal of variable valence) to 0.5-9.8% of Pentafluoroethane. It should be noted that gas-phase catalytic hydroperiodide tetrachloroethylene does not provide a sufficiently high conversion in pentaborate in one pass of the original mixture (HF and C2Cl4through a reaction zone and, consequently, the organization of industrial process Pentafluoroethane this method is associated with a significant recirculation flows of intermediate products of the fluorination.

In the patent [WO 92/16479, C 07 C 17/00, op. 01/10/92] (prototype) announced the receipt of freon 123, 124 and 125 by gas-phase hydroperiodide fully halogenated ethylene (applicable for our case - perchloroethylene) on the catalyst comprising a fluorinated alumina, impregnated up to 40% metal, which morietur of the periodic system of elements. Under the most optimal conditions was achieved conversion 90,5%, the selectivity for three declared products - 88,2% and the content of HFC 125 reached 10.0 percent.

The aim of the present invention to provide an industrial method for the synthesis of Pentafluoroethane hydropericardium of perchloroethylene and recycled products, consisting of neproreagirovavshikh of perchloroethylene and products of incomplete fluorination of TETRAFLUOROMETHANE and trichotillomania, providing a high yield of HFC 125 and a high selectivity to the amount of hydrogenous glodeanu (freon 125, 124, 124A beaches, 123, 123A and others) and full utilization of the source of organic raw materials. This objective is achieved in that pentaverate obtained by gas-phase hydroperiodide of perchloroethylene or a mixture of perchloroethylene and return intermediate reaction products on the catalyst containing a compound of trivalent chromium, hydroperiodide at elevated temperature and pressure.

The technical essence of the invention consists in gidroftorirovaniya of perchloroethylene or a mixture of perchloroethylene and recycled products of incomplete fluorination catalyst of hydroperiodide representing gramotnosti HF:hydroporinae products 4-40:1 and the contact time between 5-60 C.

Studies have shown that when gidroftorirovaniya of perchloroethylene in this catalyst are mainly formed isomers tetrafluorochloroethane and trichotillomania containing-CF3group. This gives an additional effect in the organization of the technological process and return you to the synthesis of products of incomplete fluorination, because hydroperiodide 1,1,1,2-tetrafluorochloroethane proceeds with an endothermic effect and helps to reduce the total exothermic effect of process hydroperiodide of perchloroethylene that would allow a process with a smaller excess of hydrogen fluoride or at high feed rates of perchloroethylene in the synthesis reactor.

Studies have shown that the organization of recycling unreacted and intermediate products has allowed almost completely to use the original perchlorethylene to obtain HFC 125.

The authors argue that the proposed facility meets the criterion of "novelty", since on the basis of scientific-technical and patent information were found similar means to achieve these goals, and it was found that to obtain Pentafluoroethane with a high degree to the catalyst (a mixture of magnesium fluoride and fluoride trivalent chromium).

Example 1.

The process of hydroperiodide carried out in a Nickel reactor with a volume of 0.25 l with a stationary catalyst bed. The reactor was equipped with electric heating and a pocket for a thermocouple that allows temperature measurements over the entire height of the reaction zone. The reactor was loaded chromogenicity the catalyst in the form of granules with a diameter of 5-6 mm and a height of 6-7 mm or granules 3x4 mm

Dosing of perchloroethylene was carried out by the dosing pump CN-2 directly into the evaporator, mounted in front of the entrance to the reactor through a capillary flowmeter was also filed hydrogen fluoride, at a temperature of 120oC. If necessary, to the evaporator through a capillary flowmeter has been tetraphthalate, where it was mixed with a stream of hydrogen fluoride. In the evaporator, the mixture of the initial components were heated to fusion temperature and fed into the reactor, which is maintained overpressure 0.27 - 0.3 MPa.

The reaction gas was passed through a vessel filled with water, a solution of potassium alkali, the drying with zeolite NaA and are condensed in a trap cooled with dry ice (liquid nitrogen), or collected in a Gasometer. Liquid organic material that separates the washing capacity is thesis was performed by gas chromatography, as well as fractionation with subsequent study of fractions by X and chromato-mass-spectrometry.

Table 1 shows the compositions of the tested catalysts, as well as the efficiency of their application in the process of hydroperiodide of tetrafluorochloroethane. As the source tetrafluorochloroethane used a mixture consisting of 90.1% of mol. holdem. 124A beaches and 9.1 mol%. holdem. 124. Chromogenicity the catalyst produced according to the patent of the Russian Federation [RF Patent N 2005539, B 01 J 37/04, op.15/01/94]. The method which involves treating compound magnesium hydrofluoric acid at 20-80oC until the pH of the suspension equal to 3-6. Precipitated magnesium fluoride was dried at 300-550oC, was mixed with a solution of chromium chloride3+. The resulting mass was molded into pellets, which are then subjected to heat treatment.

Catalysts based on a mixture of magnesium fluoride with a fluoride trivalent chromium are quite effective in the studied synthesis.

Magnesium fluoride that does not contain fluoride, chromium has a low activity in this process (output Pentafluoroethane 1.5%). When fluoride chromium3+in the catalyst is less than 8 and more than 24 wt.% the output Pentafluoroethane significantly reduced (38,7% mol. and 50.3% MSSA on catalysts such composition due to the need for organizations large recycle streams. Thus, the most effective in this process was the catalyst containing 8-24 wt.% fluoride chromium3+.

Table 2 shows the results of hydroperiodide of perchloroethylene.

As can be seen from table 2, pentaverate can be obtained with high yield on the used catalyst. Lowering the synthesis temperature leads to a decrease in the conversion of perchloroethylene, but the selectivity for freon 123, 124 and 125 increases. The decrease in the ratio of HF/C2Cl4also reduces the conversion of PCE and selectivity for freon 123 and 124, while the selectivity to HFC 125 increases.

Example 2

The process of hydroperiodide was performed with the setup described in example 1. Hydroperiodide were subjected to a mixture of perchloroethylene, 1,1,1-trichotillomania (halon 123), 1,1,1,2 - tetrafluorochloroethane (halon 124) and 1,1,2,2-tetrafluorochloroethane (halon 124A beaches), and perchlorethylene and halon 123 filed in the evaporator by the dosing pump CN-2, and freon 124 and 124A beaches - via capillary flow.

The composition supplied to the mixture were analyzed by the method of gas-phase chromatography by sampling before entering the reactor.

The results are shown in table. 3.

This position allows you to process in a fairly wide range of both temperature and ratio of organic components supplied to the mixture, without significant deviations from the expected output Pentafluoroethane.

Example 3.

The experiments were carried out in a Nickel reactor with a volume of 0.2 m3(diameter 0.25 m), filled chromomagnetic catalyst. The reactor was equipped with devotional thermocouple. Supply of components in the reactor was carried out as follows: perchlorethylene - pump-dispenser (6-30 kg/h); tetraphthalate - bonding (10-40 kg/h); hydrogen fluoride - extrusion of nitrogen (10-40 kg/h). The components were evaporated and, after electrophoregrams, was admitted to the synthesis reactor. The reaction gas was washed with water, neutralized, drained and served on the stage of rectification, which was allocated Halocarbon 125 and return organic products.

The results of fluorination of perchloroethylene are given in table. 4.

In the example in table experimental data was observed almost complete conversion of perchloroethylene, the selectivity to the desired components of tolstanov, described in example 3. Hydroperiodide were subjected to a mixture of perchloroethylene and tetrafluorochloroethane. The results hydroperiodide are given in table. 5.

Perchlorethylene reacted almost completely (conversion amounted to more than 99%). The content of Pentafluoroethane in the reaction mixture depending on the synthesis temperature and the ratio of tetraphthalate:perchlorethylene was 20-60 vol.%.

Example 5.

Experiments were performed with the setup described in example 1. A mixture of perchloroethylene and trichotillomania filed in the evaporator by the dosing pump. The results hydroperiodide mixture of trichotillomania and perchloroethylene are shown in table 6.

Hydroperiodide mixtures containing 30-40% of perchloroethylene, proceeded with almost complete conversion at temperatures 340-365oC.

Studies have shown that by reducing the ratio of HF: hydroporinae products less than 4:1, in the reaction mixture significantly increased the amount of HFC 115, which dramatically reduces the selectivity of the process and increases the amount of products, the return of which is impossible in the technological process (freon 113, 114, a).

The increase in molar ratio more than the tx2">

When the temperature in the reaction zone below 330oC conversion of the feedstock becomes negligible, which requires very large recycle streams and also leads to increased energy costs. At temperatures above 465oC is rapidly deteriorating the selectivity of the process and increases the amount of by-products that cannot be returned into the process. As can be seen from the data in table. 7, the process when the contact time less than 5 s does not provide a sufficient conversion of raw materials and increase contact time with more than 60 reduces the selectivity of the process and performance of the reaction site.

The method of obtaining Pentafluoroethane by gas-phase hydroperiodide of perchloroethylene or a mixture of perchloroethylene and hydrogen-containing halogenated of Atanov at elevated temperature and pressure in excess of anhydrous hydrogen fluoride in the presence of a catalyst containing compounds of chromium, characterized in that the catalyst used magnesium fluoride using as compounds of chromium - chromium fluoride3+the number of 8-24% by weight of the catalyst and the process is conducted at a temperature 330-465oC, molar aspect]

 

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9 cl, 4 ex

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