Patent GB-607946-A (GB)
Title: Improved process for the solvent extraction of diolefins from hydrocarbon mixtures
IPC: C07C7/10
Filed: 1943-01-05
Abstract: <PICT:0607946/III/1> Diolefines are separated from oils or hydrocarbon mixtures containing them by a solventextraction process of the kind described in Specification 607,945, i.e. by a single- or multistage extraction with liquid ammonia to which there is added, in at least one of the stages, a minor proportion of an agent which reduces its solvent power, e.g. water, ethylene glycol, formamide, ethylene diamine, toluene, or a paraffinic or naphthenic oil or hydrocarbon, e.g. propane, cetane, decane or decahydronaphthalene. When oils or mixtures of low diolefine content are treated they may first be extracted with liquid ammonia containing an addition which increases its solvent power, e.g. any of the methylamines, whereafter the extract is treated with liquid ammonia of reduced dissolving power to effect a further concentration of the diolefines.  When the oil or mixture contains aromatic hydrocarbons, which are more soluble than the diolefines in the solvents employed, the extract may be reextracted to yield a raffinate consisting mainly of diolefines. The process may be effected in a counter-current system in which the solubility-modifying agent may be added at one or more points, and is particularly applicable to oils or mixtures of narrow molecular-weight range, e.g. a range of 15-30.  The operating temperature may be -10 DEG  to 150 DEG  F., and the pressure should be sufficient to maintain the constituents in the liquid state. Examples are given in which butadiene, isoprene and cyclopentadiene are separated from mixtures with olefines and paraffins (see Group IV (b)), and reference is made also to the separation of dipentene from hydrocarbon mixtures containing it. An arrangement of plant is described in which the mixture to be treated is supplied by line 10 to a tower 11 down which it flows in counter-current to solvent supplied by line 13, the solvent comprising liquid ammonia and a little water.  The extract from tower 11 contains the diolefines and is passed through line 16 to a second tower 17 in which the relative concentration of diolefines in the extract is increased by cooling the extract or by injecting water at points 19.  The raffinate from tower 17 is returned to tower 11 by line 18 and the extract is passed by line 21 to a tower 22 in which it is treated with a paraffinic oil fed through line 23.  The oil dissolves the diolefines from the extract, and the stripped solvent is returned by line 24 to storage tank 12.  The solution of diolefines in paraffinic oil is partly returned by line 281 to tower 17, the remainder being passed to a still 27, the vapours from which pass to a partial condenser 32 in which any water present is condensed and returned to the tower 27 by line 33.  The diolefines and residual ammonia pass through line 34 to a still 35, from which diolefines are removed through line 40. Vapours from the still 35 are condensed in a condenser 38 and partly returned to the still by line 37, the remainder passing to tower 17 by line 39.  The residue from the still 27, comprising paraffinic oil and water, is passed to a settler 29, from which water is returned to the still by line 28 while the oil is passed to storage tank 42.  The raffinate from tower 11 is passed to a still 45 from which hydrocarbon vapours pass to a condenser 49 from which condensate is withdrawn through line 50, a part being returned as reflux through line 51.  A liquid phase is withdrawn at point 52 in the still and distilled in a still 53 to yield ammonia, which is returned to storage tank 12 by way of condenser 54.  The residue from the still 53 is returned to the still 45, the residue from which, comprising liquid hydrocarbons and water, passes to a settler 47, from which water is returned to still 45 by line 46 and oil is returned to storage tank 42 by line 58.  Specifications 607,947, 607,948 and 607,949 also are referred to.ALSO:<PICT:0607946/IV(b)/1> Diolefines are separated from oils or hydrocarbon mixtures containing them by a solvent-extraction process of the kind described in Specification 607,945, [Group III], i.e. by a single or multi-stage extraction with liquid ammonia to which there is added, in at least one of the stages, a minor proportion of an agent which reduces its solvent power, e.g. water, ethylene glycol, formamide, ethylene diamine, toluene, or a paraffinic or naphthenic oil or hydrocarbon, e.g. propane, cetane, decane or decahydronaphthalene.  When oils or mixtures of low diolefine content are treated they may first be extracted with liquid ammonia containing an addition which increases its solvent power, e.g. any of the methylamines, whereafter the extract is treated with liquid ammonia of reduced dissolving power to effect a further concentration of the diolefines.  When the oil or mixture contains aromatic hydrocarbons, which are more soluble than the diolefines in the solvents employed, the extract may be re-extracted to yield a raffinate consisting mainly of diolefines. The process may be effected in a counter-current system in which the solubility-modifying agent may be added at one or more points, and is particularly applicable to oils or mixtures of narrow molecular-weight range, e.g. a range of 15-30.  The operating temperature may be -10 DEG  to 150 DEG  F. and the pressure should be sufficient to maintain the constituents in the liquid state. Examples are given in which (1) butadiene is extracted from a mixture containing olefines and paraffins of four carbon atoms by treating the mixture at 50 DEG  F. with aqueous liquid ammonia containing 12 per cent of water or (example 2) at 32 DEG  F. with liquid ammonia containing 37.5 per cent of paraffinic oil; (3) isoprene is extracted from a mixture containing olefines and paraffins of five carbon atoms by treating the mixture at 75 DEG  F. with a 35 per cent solution of ethylene glycol in liquid ammonia; (4) cyclopentadiene is separated from olefines and paraffins of similar boiling point by means of liquid ammonia containing minor proportions of water and paraffinic oil.  The separation of dipentene from hydrocarbon mixtures containing it is also mentioned.  An arrangement of plant is described in which the mixture to be treated is supplied by line 10 to a tower 11 down which it flows in counter-current to solvent supplied by line 13, the solvent comprising liquid ammonia and a little water.  The extract from tower 11 contains the diolefines and is passed through line 16 to a second tower 17 in which the relative concentration of diolefines in the extract is increased by cooling the extract or by injecting water at points 19.  The raffinate from tower 17 is returned to tower 11 by line 18 and the extract is passed by line 21 to a tower 22 in which it is treated with a paraffinic oil fed through line 23.  The oil dissolves the diolefines from the extract, and the stripped solvent is returned by line 24 to storage tank 12.  The solution of diolefines in paraffinic oil is partly returned by line 281 to tower 17, the remainder being passed to a still 27, the vapours from which pass to a partial condenser 32 in which any water present is condensed and returned to the tower 27 by line 33.  The diolefines and residual ammonia pass through line 34 to a still 35, from which diolefines are removed through line 40. Vapours from the still 35 are condensed in a condenser 38 and partly returned to the still by line 37, the remainder passing to tower 17 by line 39.  The residue from the still 27, comprising paraffinic oil and water, is passed to a settler 29, from which water is returned to the still by line 28 while the oil is passed to storage tank 42. The raffinate from tower 11 is passed to a still 45 from which hydrocarbon vapours pass to a condenser 49 from which condensate is withdrawn through line 50, a part being returned as reflux through line 51.  A liquid phase is withdrawn at point 52 in the still and distilled in a still 53 to yield ammonia, which is returned to storage tank 12 by way of condenser 54.  The residue from the still 53 is returned to the still 45, the residue from which comprising liquid hydrocarbon and water, passes to a settler 47, from which water is returned to still 45 by line 46 and oil is returned to storage tank 42 by line 58.  Specifications 607,947, 607,948 and 607,949 also are referred to.