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AssigneeShowa Denko K.K.
InventorsHiromoto Ohno, Toshio Ohi
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Tetrachloroethylene containing a stabilizer is contacted with a zeolite having an average pore size of 3.4 to 11 Å and/or a carbonaceous adsorbent having an average pore size of 3.4 to 11 Å in a liquid phase to obtain a high purity tetrachloroethylene. A halogenated alkene and/or a halogenated alkane are reacted with hydrogen fluoride in the presence of a fluorination catalyst to produce a first hydrofluorocarbon, a halogenated alkene and/or a halogenated alkane are reacted with hydrogen fluoride in the presence of a fluorination catalyst to produce a second hydrofluorocarbon, and the products are joined and then distilled to obtain the first and second hydrofluorocarbons.
A method for purifying tetrachloroethylene, comprising contacting tetrachloroethylene containing, as a stabilizer, a hydroxyl group-containing aromatic compound with a zeolite having an average pore size of 3.4 to 11 Å and/or a carbonaceous adsorbent having an average pore size of 3.4 to 11 Å, in a liquid phase, to reduce the amount of said stabilizer.
A process for producing a hydrofluorocarbon, comprising (A) a step of reacting hydrogen fluoride with a halogenated alkene and/or a halogenated alkane in the presence of a fluorination catalyst to produce a first hydrofluorocarbon, (B) a step of reacting hydrogen fluoride with halogenated alkene and/or a halogenated alkane in the presence of a fluorination catalyst to produce a second hydrofluorocarbon, and (C) a step of joining and then distilling the products obtained in the steps (A) and (B) to obtain the first hydrofluorocarbon and the second hydrofluorocarbon.
Dependencies are inferred from the claim text.
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Of halogen atoms by other halogen atoms: with simultaneous increase of the number of halogen atoms
Two or more compounds being involved in the reaction: the other compound being HX
Preparation of halogenated hydrocarbons: separation; Purification; Stabilisation; Use of additives
Separation; Purification; Stabilisation; Use of additives: by adsorption on solids
Term end not estimated
The present invention relates to a method for purifying tetrachloroethylene and a process for producing a hydrofluorocarbon.
As for the production of tetrachloroethylene (CCl2═CCl2) (hereinafter sometimes referred to as “PCE”), for example, (1) a method of thermally decomposing carbon tetrachloride, (2) a method of simultaneously conducting chlorination and dehydrochlorination of a chloroolefin, and (3) a method of using chlorine and a hydrocarbon such as natural gas or LPG as starting materials are known. In the methods, a stabilizer is added so as to ensure the stability of tetrachloroethylene and, in general, the stabilizer is added in an amount of hundreds to thousands of ppm. As for uses, tetrachloroethylene is used, for example, as a dry cleaning solvent, a starting material for the production of a fluorocarbon gas, or a solvent.
On the other hand, as for the production of pentafluoroethane (CF3CHF2), for example, (1) a method of fluorinating tetrachloroethylene or a fluorinated product thereof with hydrogen fluoride (see, Japanese International Application Domestic Publication No. 9-511515, etc.), (2) a method of hydrogenolyzing chloropentafluoroethane (CClF2CF3) (see, Japanese Unexamined Patent Publication No. 5-97728 (JP-A-5-97728), etc.) and (3) a method of reacting a fluorine gas with halogen-containing ethylene (see, Japanese Unexamined Patent Publication No. 1-38034 (JP-A-1-38034)) are known.
FIG. 1 is a schematic view of an apparatus for carrying out the process for producing a hydrofluorocarbon according to the present invention.
FIG. 2 is a schematic view of another apparatus for carrying out the process for producing a hydrofluorocarbon according to the present invention.
The present invention will be described in detail below with respect to preferred embodiments.
The method for purifying tetrachloroethylene will be explained first.
The zeolite for use in the purification method of tetrachloroethylene according to the present invention suitably has an average pore size of 3.4 to 11 Å, preferably 3.4 to 10 Å. If the zeolite has an average pore size exceeding 11 Å, the amount of tetrachloroethylene adsorbed increases, whereas if the average pore size is less than 3.4 Å, the zeolite is reduced in the capability of adsorbing the stabilizer.