Abstract Solvent extraction of a solid material which is contaminated with at least one hydrocarbon and water which comprises, in a first extraction stage consisting of one or more extraction steps, extracting a contaminated solid material with a mixture of an alcohol and a hydrocarbon with which it forms an azeotrope, the alcohol and azeotrope forming hydrocarbon respectively being employed at a ratio by volume within the range 30:70 to 70:30. Preferably in a second extraction stage consisting of one or more extraction steps, following the first extraction stage, the treated solid material from the first stage is extracted with a solvent comprising or consisting of the alcohol, thereafter recovering the treated solid material. Suitably the azeotrope-forming hydrocarbon is normal hexane. Suitably the alcohol is ethanol, propanol, isopropanol or a butanol. Suitably the process of the invention is applied to a crude or partially refined product of the growth of a micro-organism on a hydrocarbon substrate in the presence of an aqueous nutrient medium. Preferably the micro-organism is a yeast.
A process according to claim 1 wherein the extract fractions recovered from the extraction stages are fed, separately or after blending, to a distillation stage, consisting of one or more distillation steps, for the separate recovery of (a) an azeotropic mixture of the alcohol and the azeotrope-forming hydrocarbon, (b) an azeotropic mixture of the alcohol and water and (c) a residue fraction, thereafter blending part of the azeotropic mixture of the alcohol and water with part of the azeotropic mixture of the alcohol and azeotrope-forming hydrocarbon, the parts being selected to give a mixture of the alcohol and azeotrope-forming hydrocarbon containing these materials respectively at a ratio by volume in the range 30:70 to 70:30 and recycling this mixture to the first extraction stage.
Claim 2
Dependent Claim
13 words
A process according to claim 1 which the azeotrope-forming hydrocarbon is normal hexane.
Claim 3
Dependent Claim
17 words
A process according to claim 1 in which the alcohol is ethanol, propanol, isopropanol or a butanol.
Claim 4
Dependent Claim
25 words
A process according to claim 1 in which at least one solvent extraction step is carried out at a temperature in the range 30*-100* C.
Claim 5
Dependent Claim
30 words
A process according to claim 1 in which the micro-organism contains at least 20 percent of water in excess of the water present in the micro-organism in the dry state.