The way to clean octafluorocyclobutane

 

(57) Abstract:

The invention relates to a method of cleaning OCTAFLUOROCYCLOBUTANE from impurities tetrafluorochloroethane. The process is carried out in an absorption column in which the contacting of the gaseous OCTAFLUOROCYCLOBUTANE with water containing chlorine compounds and fluorine in the amount of 1 - 100 mg/l In the reduced impurity content of TETRAFLUOROMETHANE in purified OCTAFLUOROBUT. table 1.

The invention relates to the technology for the production of fluorine-containing ethane series, used as refrigerants, propellants, pore-formers in various branches of engineering, namely to clean OCTAFLUOROCYCLOBUTANE (R S) of the admixture of TETRAFLUOROMETHANE (R 124).

The method of rectification is widely used for cleaning various compounds, including organofluorine (Kasatkin, A., Basic processes and apparatus of chemical technology, Goskomizdat, 1955). However, cleaning OCTAFLUOROCYCLOBUTANE hampered the ability of the latter to form an azeotropic mixture with tetrafluorochloroethane. Therefore, when the rectification of OCTAFLUOROCYCLOBUTANE containing, for example, to 38.2 wt.% tetrafluorochloroethane on column efficiency 40 teoretic and tetrafluorochloroethane, probably can be removed by extractive distillation using organic compounds as separating reagents (Nikiforov, B. L., Drums Century, Technological methods of purification of halocarbons and formononetin, Journal of applied chemistry, I. 68, Issue 7, page 1175). However, extractive distillation is very energy intensive way to separate the components.

Closest to the proposed invention by a combination of traits and the achieved result is a way for U.S. patent (US 2384821 from 18.09.45).

Division of OCTAFLUOROCYCLOBUTANE and tetrafluorochloroethane by chlorination of impurities which are not separated by distillation. In the chlorination mixture tetrafluorochloroethane formed tetraphenylborate (R 114), which is easily separated from OCTAFLUOROCYCLOBUTANE distillation.

A significant disadvantage of the prototype is a high rate of depletion of the ozone layer (ODP = 0.85) formed tetrafluorodichloroethane, resulting in the production and use of this product is prohibited in accordance with the Vienna Convention in 1985 and the Montreal Protocol of 1987 (Industrial organofluorine products Handbook, ed. "Chemistry" C.-P., 1996, the sponding properties (ODP = 0.022) and in addition, tetraphthalate is the raw material for the synthesis of ozone-safe refrigerant Pentafluoroethane (R 125).

The chlorination process pollutes the processed mixture of acidic components and requires an additional stage of neutralization.

The task of the invention is to eliminate the disadvantages of the prototype, namely to reduce ozone danger of resulting products and to reduce the number of stages of the cleanup process.

This goal is achieved by contacting gaseous OCTAFLUOROCYCLOBUTANE containing an admixture of TETRAFLUOROMETHANE in a mass transfer column with water containing small amount of chlorine and fluorine, namely 10 - 100 mg/l as chlorine and fluorine can be used, for example, NaCl, CaCl2, MgCl2, NaF, and others.

The essence of the proposed technical solutions more disclosed in the examples.

Example 1. Gaseous OCTAFLUOROCYCLOBUTANE containing 38.2 wt.% impurity tetrafluorochloroethane, served in the lower part of the absorption column with a diameter of 15 mm and a height of the Packed parts 1000 mm, filled with nichrome coils 3x3 mm column Pressure is maintained in peterjames 2.5 mg/l CaCl2(counting on chlorine-ion), and 2.0 mg/l NaF (counting on fluoride ion). Water consumption was 4 - 5 DM3/PM

From the upper part of the column is given a gas containing 0.02 wt.% tetrafluorochloroethane and of 99.98 wt.% OCTAFLUOROCYCLOBUTANE.

From the bottom of the column gave the absorbent containing dissolved tetraphthalate, which was isolated from the water by vacuum to a residual pressure 0.0014 - 0.002 MPa. Selected from water tetraphthalate contained 3.2 wt.% OCTAFLUOROCYCLOBUTANE. Cleared organofluorine impurities absorbent return pump up the absorption columns for purification of OCTAFLUOROCYCLOBUTANE. The degree of purification from tetrafluorochloroethane in this example amounted to 99.97% Loss OCTAFLUOROCYCLOBUTANE with water from the bottom of the column 2.04%.

Example 2. In conditions described in example 1, the absorbance was served water with different salt content of chlorine and fluorine.

The results are presented in the table.

As seen from the above examples, the use of water containing chlorine compounds and fluorine as absorbent, allows 99.95-99.97% reduction in the impurity content of TETRAFLUOROMETHANE in purified OCTAFLUOROCYCLOBUTANE. When reducing the content of chlorine ion and fluoride ion in the mixture tetrafluorochloroethane in the purified gas.

As a result of the separation process are formed less ozone-dangerous products than the prototype, poetomu not require additional stages of neutralization.

The way to clean OCTAFLUOROCYCLOBUTANE from impurities TETRAFLUOROMETHANE in a mass transfer column, characterized in that as the mass-transfer columns using an absorption column in which the contacting of the gaseous OCTAFLUOROCYCLOBUTANE with water containing chlorine compounds and fluorine in the amount of 1 - 100 mg/L.

 

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SUBSTANCE: hexafluorobuta-1,3-diene, suitable as bifunctional monomer in production and cross-linking of perfluorinated elastomers but also as agent for dry plasma etching in manufacture of semiconductor articles, is first subjected to low-temperature rectification and then additionally purified on zeolite sorbents and submitted to vacuum degassing and filtration. Low-temperature rectification is carried out in two steps: first at overpressure in column from 1.0 atm to 0.05 atm and still temperature 15-25оС, and then, respectively, 0.3 to 0.2 atm and 15-25оС. After first or second low-temperature rectification step product additionally undergoes cleaning on carbon sorbents.

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5 cl, 2 tbl, 5 ex

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SUBSTANCE: invention relates to a method for purifying octafluorocyclobutane. Method is carried out by interaction of crude octafluorocyclobutane containing impurities with the impurity-decomposing agent at increased temperature and then with adsorbent that is able to eliminate indicated impurities up to the content less 0.0001 wt.-% from the mentioned crude octafluorocyclobutane. Impurity-decomposing agent comprises ferric (III) oxide and compound of alkaline-earth metal in the amount from 5 to 40 wt.-% of ferric oxide and from 60 to 95 wt.-% of compound of alkaline-earth metal as measured for the complete mass of the impurity-decomposing agent. Ferric (III) oxide represents γ-form of iron hydroxyoxide and/or γ-form of ferric (III) oxide. Impurity represents at least one fluorocarbon taken among the group consisting of 2-chloro-1,1,1,2,3,3,3-heptafluoropropane, 1-chloro-1,1,2,2,3,3,3-heptafluoropropane, 1-chloro-1,1,2,2,3,3,3-heptafluoropropane, 1-chloro-1,2,2,2-tetrafluoroethane, 1-chloro-1,1,2,2-tetrafluoroethane, 1,2-dichloro-1,1,2,2-tetrafluoroethane, hexafluoropropene and 1H-heptafluoropropane. Adsorbent represents at least one of representatives taken among the group including activated carbon, carbon molecular sieves and activated coal. Crude octafluorocyclobutane interacts with the mentioned impurity-decomposing agent at temperature from 250oC to 380oC. Invention proposes gas, etching gas and purifying gas including octafluorocyclobutane with purity degree 99.9999 wt.-% and above and comprising fluorocarbon impurity in the concentration less 0.0001 wt.-%. Invention provides enhancing purity of octafluorocyclobutane.

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26 cl, 13 tbl, 10 ex

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13 cl, 11 tbl, 12 ex

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6 cl, 7 ex, 7 tbl, 3 dwg

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1 tbl

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5 tbl

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