Patent GB-701577-A (GB)
Title: Improved process for separating the constituents of hydrocarbon mixtures
IPC: C10G31/06
Filed: 1950-07-14
Abstract: Hydrocarbon mixtures, comprising normal paraffins, isoparaffins and naphthenes, all of about 12-18 carbon atoms per molecule, are fractionated by progressively cooling the mixture to- 10 DEG C. or lower, in the presence of a simple or mixed solvent having anti-solvent properties in respect of paraffins and solvent properties in respect of naphthenes at such temperature, and removing first the normal paraffins and then the isoparaffins which crystallize out.  The hydrocarbon mixtures which are fractionated may be derived from petroleum, synthetic hydrocarbon oils, shale oils or coal oils, particularly the kerosene and the light gas oil fractions of petroleum, and may first be freed of aromatic, olefinic and sulphur-containing constituents by refining with sulphuric acid and/or a selective solvent such as liquid sulphur dioxide.  Solvents mentioned are acetone-dichloroethane mixtures, acetone-methyl ethyl ketone mixtures, acetone-benzene mixtures, acetone-toluene mixtures, ethyl alcohol-diethyl ether mixtures, acetone, trichloroethylene, methyl ethyl ketone and dichloroethane.  In modifications of the process, (i) the whole of the paraffinic hydrocarbons are separated by cooling a solution of the hydrocarbon mixture in the solvent to -60 DEG C. or lower and then filtering off the crystals formed, and the paraffinic fraction in the presence of a solvent is separated into a normal paraffinic fraction and an isoparaffinic fraction by fractional crystallization at a temperature between -10 DEG C. and -60 DEG C., (ii) the normal paraffins and a part of the isoparaffins are crystallized by cooling a solution of the hydrocarbon mixture in the solvent to a temperature between -30 DEG C. and -60 DEG C., and the crystallized paraffins after filtering off are separated into normal paraffins and isoparaffins by redissolving in solvent and fractionally crystallizing, and (iii) a fraction enriched in paraffins is crystallized by cooling a solution of the hydrocarbon mixture in the solvent to a temperature between -20 DEG C. and -60 DEG C., leaving in solution a fraction enriched in naphthenes, and the crystallized paraffinic fraction after filtering off is redissolved in solvent and fractionally crystallized.ALSO:Hydrocarbon mixtures, comprising normal paraffins, isoparaffins and naphthenes, all of about 12-18 carbon atoms per molecule, are fractionated by progressively cooling the mixture to-10 DEG C. or lower, in the presence of a simple or mixed solvent having anti-solvent properties in respect of paraffins and solvent properties in respect of naphthenes at such temperature, and removing first the normal paraffins and then the isoparaffins which crystallize out.  The hydrocarbon mixtures which are fractionated may be derived from petroleum, synthetic hydrocarbon oils, shale oils or coal oils, particularly the kerosene and light gas oil fractions of petroleum, and may first be freed of aromatic, olefinic and sulphur-containing constituents by refining with sulphuric acid and/or a selective solvent such as liquid sulphur dioxide.  Solvents mentioned are acetone-dichloroethane mixtures, acetone-methyl ethyl ketone mixtures, acetone-benzene mixtures, acetone-toluene mixtures, ethyl alcohol-diethyl ether mixtures, acetone, trichloroethylene, methylethyl ketone and dichloroethane.  In modifications of the process, (i) the whole of the paraffinic hydrocarbons are separated by cooling a solution of the hydrocarbon-mixture in the solvent to -60 DEG C. or lower and then filtering off the crystals formed, and the paraffinic fraction in the presence of a solvent is separated into a normal paraffinic fraction and an isoparaffinic fraction by fractional crystallization at a temperature between -10 DEG C. and -60 DEG C., (ii) the normal paraffins and a part of the isoparaffins are crystallized by cooling a solution of the hydrocarbon mixture in the solvent to a temperature between -30 DEG C. and -60 DEG C. and the crystallized paraffins after filtering off are separated into normal paraffins and isoparaffins by redissolving in solvent and fractionally crystallizing and (iii) a fraction enriched in paraffins is crystallized by cooling a solution of the hydrocarbon mixture in the solvent to a temperature between -20 DEG C. and -60 DEG C. leaving in solution a fraction enriched in naphthenes, and the crystallized paraffinic fraction after filtering off is redissolved in solvent and fractionally crystallized.