Patent GB-459442-A (GB)
Title: A process for the extraction of two or more liquid mixtures
IPC: B01D11/04
Filed: 1935-07-02
Abstract: In a process for extracting a series of two or more qualitatively different liquid mixtures A, B, C ... by means of a solvent S, the nth liquid mixture is extracted with the solvent charged with the extract obtained from the (n - 1)th liquid mixture, and the first liquid mixture is extracted with the solvent S charged with the extract obtained from the last liquid mixture.  The raffinates obtained are separated into their components in known manner, e.g. by distillation, cooling, crystallization, or washing.  By this process the recovery of the solvent S at intermediate stages is avoided. <PICT:0459442/IV/1> Three liquid mixtures L, M, H are extracted with a solvent S passed therethrough in series.  The several extract components are denoted by LE, and the raffinates by LR.  The extract S + LE originally formed in the first stage is used as extracting agent for M.  A part (LE<1>) of LE appears in the extract with ME, and the other part (LE<11>) in the raffinate MR.  The extracting agent (S + LE<1> + ME) for H is similarly split up in the second stage, one part (LE<1111> + MG<11>) appearing in the raffinate HR, and the other (LE<111> + ME<1>) in the extract with HE.  The latter extract with the solvent forms the extracting agent for the first mixture L.  The raffinates obtained containing only a small amount of the solvent are then fractionated into their components.  Extraction is preferably effected in countercurrent.  The process may be regulated so that a particular component is wholly removed, for example, by increasing the flow of the mixture M in the second column the whole of LE may be removed with the raffinate MR, leaving the extract S + ME at the top of the column.  The extraction process may be assisted by a temperature gradient control, or by "back-washing" with the solvent or an extract component as described in Specification 355,294, 380,954 or 417,617, [all in Group III].  In a modification, the extract obtained at one or more stages is distilled to remove a component before introduction to the next stage; in another the process is carried out in two series of mixing and settling vessels, Fig. 4 (not shown), in which the separated layers are conveyed to their respective next stages in a countercurrent order.  Mixtures which may be treated are, fractions of homologous substances which do not overlap in boiling range such as petroleum fractions with phenol (S); different mixtures of paraffin wax with oxidation products thereof, with alcohol (S); mixtures of chlorine compounds with their parent olefines or alcohols, with alcohol (S); mixtures of monovalent alcohols with the corresponding olefines, with water or a polyvalent alcohol (S); or mixtures of alcohols with fatty acids from which they are obtained by reduction, with monoethanolamine (S).  Dutch Specification 28730 also is referred to.ALSO:In a process for extracting a series of two or more qualitatively different liquid mixtures A, B, C, by means of a solvent S, the nth liquid mixture is extracted with the solvent S charged with extract obtained from the (n--1)th liquid mixture and the first liquid mixture is extracted with the solvent S charged with the extract formed in the last liquid mixture.  The raffinates obtained are separated into their components in known manner, e.g. distillation, cooling crystallization <PICT:0459442/III/1> or washing.  By this process the recovery of the solvent S at intermediate stages is rendered unnecessary.  Three liquid mixtures L M H are extracted with a solvent S passed therethrough in series. The extracted components from each stage is denoted by E, and the raffinates by R.  The extract S + LE originally formed in the first stage is used as extracting agent for M.  A part LE<1> of LE appears in the extract with ME, and the other part (LE<11>) in the raffinate MR.  The extracting agent (S + LE<1> + ME) for H is similarly split up in the second stage, one part (LE<1111>+ME<11>) appearing with the raffinate HR, and the other (LE<111>+ME<1>) in the extract with HE. The latter extract with the solvent forms the extracting agent for the first mixture L.  The raffinates obtained which contain only a small amount of solvent S are then fractionated into their components by distillation.  Extraction is preferably effected in counter current.  The process may be regulated so that a particular component is wholly removed, for example by increasing the flow of the mixture M in the second column the whole of LE may be removed with the raffinate MR leaving the extract S + ME at the top of the column.  In an example, L is gas oil, M is gasoline and S is liquid sulphur dioxide or furfural.  The extraction process yields (a) gas oil raffinate of high cetene number, (b) gas oil extract + gasoline raffinate which may be cracked, and (c) gasoline extract of high octane number.  In a second example, an asphalt (MR) mixed with aromatics (LE) is obtained by treating a crude kerosene and an asphaltic petroleum residue, with alcohol (S).  The extraction process may be assisted by " back-washing " with the solvent or an extract component, or temperature gradient control as described in Specification 355,294, 380,954, or 417,617.  In modifications, the extract obtained at one or more stages is distilled to remove a component before introduction to the next stage; the process is carried out in two series of mixing and settling vessels (for L and H, one passed through each of the series) in which the separated layers are conveyed to their respective next stages in a counter current order.  Mixtures which may be treated are, fractions of homologous substances which do not overlap in boiling range such as petroleum fractions with phenol (S); different mixtures of paraffin wax with oxidation products thereof with alcohol (S); mixtures of chlorine compounds with their parent olefines or alcohols, mixtures of monovalent alcohols with corresponding olefines with water or a polyvalent alcohol (S); or mixtures of alcohols with fatty acids from which they are obtained by reduction, and monethanolamine (S).  Dutch Specification 28730 also is referred to.