Patent GB-768034-A (GB)
Title: Fractionation of oils and other organic substances by selective extraction
IPC: C11B7/00
Filed: 1954-08-23
Abstract: Oil is refined or fractionated in at least two stages by solvent extraction with liquid mixture consisting of at least one component which is liquid at the operating temperature and pressure and one which is a permanent gas at the operating temperature, but which is dissolved in the liquid component and by its presence decreases the solvent power of the solvent mixture, the content of dissolved gas in the liquid mixtures varying from stage to stage, the "saturation pressure" of the solvent-containing extract from each stage being increased after separation of this extract so that at least part of the dissolved oil therein is precipitated, this precipitate being separated and the residue of the solvent-containing extract after separation of the precipitate being returned to one of the fractionation stages. Oils mentioned are petroleum, its higher fractions and distillation residues such as topped crudes and short residues, tar oils, shale oils, fats and fatty oils including tall oil and polymerized oils such as stand oils and boiled linseed oils, fatty acids including tall oil fatty acids and fatty acids obtained by the oxidation of paraffin wax, and essential oils.  Solvent mixtures mentioned are solutions of methane in liquid propane or pentane, methane in petroleum ether or in a propane-propylene mixture, methane in a petroleum ether-white spirit mixture, propane in gasoline, nitrogen or nitrous oxide in liquid carbon dioxide, nitrous oxide in dichloromethane or liquid sulphur dioxide and methane or nitrous oxide in difluoro-dichloromethane. Ethane or a mixture of methane and ethane may also be used as the gaseous component of the solvent mixture.  Auxiliary solvents, such as white spirit, benzene, toluene, chlorinated hydrocarbons, alcohols, esters and ketones, may also be incorporated in the solvent mixtures.  A method of measuring "saturation pressures" is described.  The "saturation pressure" of the solvent-containing extract from each stage may be increased by pressing more gas into the extract and/or by increasing the temperature of the extract.  In an example the process is applied to the fractionation of boiled linseed oil, using methane dissolved in petroleum ether as the solvent mixture and employing a batch procedure, to give fractions of varying colour, acid number and viscosity.  Various forms of apparatus are also described in which the process is carried out in a continuous manner.ALSO:Oil is refined or fractionated in at least two stages by solvent extraction with liquid mixtures consisting of at least one component which is liquid at the operating temperature and pressure and one which is a permanent gas at the operating temperature, but which is dissolved in the liquid component and by its presence decreases the solvent power of the solvent mixture, the content of dissolved gas in the liquid mixtures varying from stage to stage, the "saturation pressure" of the solvent-containing extract from each stage being increased after separation of this extract so that at least part of the dissolved oil therein is precipitated, this precipitate being separated and the residue of the solvent-containing extract after separation of the precipitate being returned to one of the fractionation stages. Oils mentioned are petroleum, its higher fractions and distillation residues, tar oils, shale oils, fats and fatty oils including tall oil and polymerized oils, fatty acids including tall oil fatty acids and fatty acids obtained by the oxidation of paraffin wax, and essential oils.  The term "oil" is also used to embrace terpenes, rosins, rosin oils, and artificial resins such as alkyd resins, modified alkyd resins, polyester resins, modified epoxy and phenol resins, polyvinyl esters and ethers, poly-acrylates and -methacrylates, and co-polymers.  Solvent mixtures mentioned are solutions of methane in liquid propane or pentane, methane in petroleum ether or in a propane propylene mixture, methane in a petroleum ether-white spirit mixture, propane in gasoline, nitrogen or nitrous oxide in liquid carbon dioxide, nitrous oxide in dichloromethane or liquid sulphur dioxide and methane or nitrous oxide in difluoro-dichloromethane. Ethane of a mixture of methane and ethane may also be used as the gaseous component of the solvent mixture.  Auxiliary solvents, such as white spirit, benzene, toluene, chlorinated hydrocarbons, alcohols, esters and ketones, may also be incorporated in the solvent mixtures.  A method of measuring "saturation pressure" of the solvent-containing extract from each stage may be increased by pressing more gas into the extract and/or by increasing the temperature of the extract.  In an example, the process is applied to the fractionation of boiled linseed oil, using methane dissolved in petroleum ether as the solvent mixture and employing a batch procedure, to obtain fractions of varying colour, acid number and viscosity.  Various forms of apparatus are also described in which the process is carried out in a continuous manner.