GB733863A - Improvements in or relating to an extraction process for separating aromatic and saturated hydrocarbons - Google Patents

Abstract

An extraction process for separating aromatic and saturated hydrocarbons, contained in an oil boiling below 350 DEG C. and containing less than 5 per cent by weight of tar acids, comprises counter-currently extracting the oil in a vertical extraction zone, by feeding a naphtha boiling from 60-130 DEG C. and having a density of less than 0.8 into the bottom of the zone, and an aqueous methanol solution containing 75-96 per cent methanol into the top. A naphtha solution of the saturated hydrocarbons, and a methanol extract containing the aromatic compounds and any tar acids and other oxygen-containing compounds, and nitrogen- and sulphur-containing compounds present, are obtained; methanol and naphtha are stripped off to recover the hydrocarbons. Any tar acids present may be phenols, cresols, xylenols and higher alkylated phenols. The extraction tower may be a packed tower, a pierced plate column, a bubble plate column, or a column containing alternate zones of turbulence and quiescence. The process may be carried out by feeding in the oil at the centre of the column, with the naphtha as the continuous phase and the interface at the bottom of the column; in a modification, a solution of neutral oils (from which tar acids have been removed by a double solvent-extraction process) in naphtha is fed to the bottom of the extraction column and the aqueous methanol to the top, the methanol solution being the continuous phase and the interface at the top of the column. The extraction column may be operated at 60-120 DEG F. An example is given of the treatment of a tar acid free neutral oil produced from a low-temperature coal carbonization tar fraction, boiling from 160-325 DEG C.ALSO:An extraction process for separating aromatic and saturated hydrocarbons, contained in an oil boiling below 350 DEG C. and containing less than 5 per cent by weight of tar acids, comprises countercurrently extracting the oil in a vertical extraction zone, by feeding a naphtha boiling from 60-130 DEG C. and having a density of less than 0.8 into the bottom of the zone, and an aqueous methanol solution containing 75-96 per cent methanol into the top. A naphtha solution of the saturated hydrocarbons, and a methanol extract containing the aromatic compounds and any tar acids and other oxygen-containing compounds, and nitrogen- and sulphur-containing compounds present, are obtained; methanol and naphtha are stripped off to recover the hydrocarbons. Any tar acids present may be phenols, cresols, xylenols and higher alkylated phenols. The extraction tower may be a packed tower, a pierced plate column, a bubble plate column, or a column containing alternate zones of turbulence and quiescence. The process may be carried out by feeding in the oil at the centre of the column, with the naphtha as the continuous phase and the interface at the bottom of the column; in a modification, a solution of neutral oils (from which tar acids have been removed by a double solvent extraction process) in naphtha is fed to the bottom of the extraction column and the aqueous methanol to the top, the methanol solution being the continuous phase and the interface at the top of the column. The extraction column may be operated at 60-120 DEG F. An example is given of the treatment of a tar acid free neutral oil produced from a low-temperature coal carbonization tar fraction, boiling from 160-325 DEG C.