Chemistry of hydrocarbon compounds – Purification – separation – or recovery – By addition of extraneous agent – e.g. – solvent – etc.
Patent
1994-04-29
1995-12-19
Pal, Asok
Chemistry of hydrocarbon compounds
Purification, separation, or recovery
By addition of extraneous agent, e.g., solvent, etc.
585854, 585857, 585860, 585866, 2082621, 2082625, C07C 700, C10G 1700
Patent
active
054769876
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a safe method for removing halogenated aromatic compounds from hydrocarbon oil contaminated by halogenated aromatic compounds such as polychlorinated biphenyl (hereinafter "PCB"), using chemical reaction processing and extraction.
2. Description of Related Art
It is known that it is extremely difficult to treat hydrocarbon oil that during use has become contaminated by PCB or other such halogenated aromatic compound. This has led to considerable efforts directed toward the removal or decompsition of halogenated aromatic compounds. Methods for accomplishing this using a reaction process that takes place in the presence of an alkali include the alumina-alkali process disclosed by U.S. Pat. No. 2,951,804. U.S. Pat. No. 4,532,028 discloses a method of reacting alkali and a PCB content of up to 50,000 ppm in a mixture of alkyl or alkylene sulfoxide and polyole, thereby reducing the content to several ppm. Other examples include Canadian Patent No. 1,181,771 which discloses a method employing melted sodium, and Italian Patent No. 1,206,508 which discloses a method using alkaline earth metal on which PEG is adsorbed.
Each method has its good points and, in the case of non-aromatic hydrocarbon and other such samples containing high concentrations of halogenated aromatic compounds are recognized as being effective techniques for reducing concentrations of halogenated aromatic compounds to a low level.
However, with the prior art techniques it is not possible to further remove halogenated aromatic compounds from samples having a low concentration thereof, so that the halogenated aromatic compound content is further reduced to the extent that the inclusion thereof is substantially not recognizable; it is not yet possible to reduce the halogenated aromatic compound concentration to 1 ppm or below. Moreover, processes that are specifically for extracting contaminants having low concentration levels are considered very difficult. Also, it is widely known that heating the extraction solvent used in the prior art methods to a high temperature of 120.degree. C. or over in the presence of an alkali or alkali metal has a chemically destablizing effect that promotes solvent decomposition and polymerization, degrading the basic function of the extraction solvent.
SUMMARY
The inventor of the present invention investigated various ways of eliminating such drawbacks and discovered a highly effective method of removing aromatic compounds from non-aromatic hydrocarbon oil. In accordance with the method, a heat-resistant alkaline polar solvent that has low compatibility with non-aromatic hydrocarbon oil, a high boiling point and good high-temperature stability with respect to alkalis is contacted with non-aromatic hydrocarbon oil containing a small amount of an aromatic compound, in the presence of an alkali and at a temperature ranging from about 100.degree. C. to about 300.degree. C.
Thus, in the method of the present invention for removing halogenated aromatic compounds from hydrocarbon oil which is constituted mainly of non-aromatic hydrocarbon oil and contains a small amount of halogenated aromatic compound, the non-aromatic hydrocarbon oil is contacted with a heat-resistant alkaline polar solvent, and the non-aromatic hydrocarbon oil and heat-resistant alkaline polar solvent are then separated.
Hence, the halogenated aromatic compound is PCB and analogous compounds thereof. Substances that may be used to constitute the heat-resistant alkaline polar solvent include 1, 3-dimethyl-2-imidazolidinone, sulfolane, ethylene glycol, diethylene glycol, triethylen glycol, polyethylene glycol, low alkyl-ethers of polyethylene glycol, trimethylene glycol, butylene glycol, and low alkyl-ethers thereof.
Industrially these heat-resistant alkaline polar solvents are used relatively extensively and have low toxicity and risk. What should be noted is their outstanding ability to extract halogenated aromatic compounds. However, if only an extraction process
REFERENCES:
patent: 2951804 (1960-09-01), Juliard
patent: 4327027 (1982-04-01), Howard et al.
patent: 4327027 (1982-04-01), Howard et al.
patent: 4532028 (1985-07-01), Peterson
Kitamura Shuji
Tanimoto Humio
Yano Tsuneo
Mitsui & Co. Ltd.
Pal Asok
Phan Nhat D.
Research Institute for Production Development
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