Patent GB-866330-A (GB)
Title: A process for splitting up mixtures into their components by multiplicative distribution
IPC: B01D11/04
Filed: 1957-03-06
Abstract: A mixture is split into two components by distribution between two substantially immiscible solvents of different densities passed in countercurrent, one of the solvents being moved substantially continuously relatively to the points of introduction and withdrawal of the solvents and the other solvent being moved intermittently relatively to said points.  The mixture, which may be liquid or solid, is introduced either continuously or discontinuously at intervals corresponding to the intervals between the commencement of successive intermittent movements of the intermittently moved solvent.  Advantageously, the relative proportions by volume of the continuously moving solvent and the intermittently moving solvent in each stage are adjusted so that the ratio of the quantity of a substance dissolved in the continuously moving solvent to the quantity dissolved in the intermittently moving solvent is smaller than 1 and preferably smaller than 0,1.  Preferably, a system of apparatus comprising a plurality of units arranged side by side and each consisting of a mixing chamber provided with mechanical stirring and a settling chamber is used and in which the continuously moving solvent is moved from stage to stage by the stirring forces and/or by the difference between the densities of the solvents.  In such apparatus the intermittent movement of the intermittently moved solvent may be provided by disconnecting the end stage at which the continuously moved solvent is introduced and simultaneously connecting a charged unit at the other end. The mixture may be introduced in the middle of the system or at an end, and one of the components of the mixture may constitute one of the solvents. Alternatively, a system comprising distribution centrifuges or distribution columns may be used.  In the latter case the intermittently moving solvent is the coherent phase and the continuously moving solvent is the disperse phase.  If the mixture to be separated is in solid form it is added as such. Examples describe: (i) the separation of a 1:1 by weight mixture of oxalic acid and succinic acid using n-butanol and water; (ii) the extraction of aqueous acetic acid by n-pentanone-(2) in which the water of the mixture acts as the intermittently moved solvent, and the mixture is introduced into the last stage.ALSO:A mixture is split into two components by distribution between two substantially immiscible solvents of different densities passed in counter-current, one of the solvents being moved substantially continuously relatively to the points of introduction and withdrawal of the solvents and the other solvent being moved intermittently relatively to said points.  The mixture, which may be liquid or solid, is introduced either continuously or discontinuously at intervals corresponding to the intervals between the commencement of successive intermittent movements of the intermittently moved solvent.  Advantageously, the relative proportions by volume of the continuously-moving solvent and the intermittently moving solvent in each stage are adjusted so that the ratio of the quantity of a substance dissolved in the continuously-moving solvent to the quantity dissolved in the intermittently-moving solvent is smaller than 1 and preferably smaller than 0.1.  Preferably, a system of apparatus comprising a plurality of units arranged side-by-side and each consisting of a mixing-chamber provided with mechanical stirring and a settling chamber is used and in which the continuously moving solvent is moved from stage to stage by the stirring forces and/or by the difference between the densities of the solvents.  In such apparatus the intermittent movement of the intermittently-moved solvent may be provided by disconnecting the end stage at which the continuously-moved solvent is introduced and simultaneously connecting a charged unit at the other end. The mixture may be introduced in the middle of the system or at an end, and one of the components of the mixture may constitute one of the solvents. Alternatively, a system comprising distribution centrifuges or distribution columns may be used.  In the latter case the intermittently moving solvent is the coherent phase and the continuously-moving solvent is the disperse phase.  If the mixture to be separated is in solid form it is added as such. Examples describe: (i) the separation of a 1 : 1 by weight mixture of oxalic acid and succinic acid using n-butanol and water; (ii) the extraction of aqueous acetic acid by n-pentanone-(2) in which the water of the mixture acts as the intermittently-moved solvent, and the mixture is introduced into the last stage.