Patent GB-607947-A (GB)
Title: Improved process for the solvent extraction of olefins from hydrocarbon mixtures
IPC: C10G21/08
Filed: 1943-01-05
Abstract: Olefines are separated from oils or hydrocarbon mixtures containing them by a solvent-extraction 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.  If desired, the oil or mixture may first be extracted with liquid ammonia containing a substance which increases its solvent power, e.g. a higher glycol, an ether or ether-alcohol, methanol or other alcohol, an alcohol-amine, aniline, pyridine or any of the methylamines or other aliphatic amine of low molecular weight, whereafter the mixture is treated with liquid ammonia of reduced dissolving power to effect a further concentration of the olefines. When the oil or mixture contains aromatic hydrocarbons, which are more soluble than the olefines in the solvents employed, the extract may be re-extracted to yield a raffinate consisting mainly of olefines.  The process may be effected in a countercurrent system in which the solubility-modifying agent may be added at more than one point, 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 0-150 DEG  F., and the pressure should be sufficient to maintain the constituents in the liquid state. Examples are given in which propylene, butylenes, amylenes and hexenes are separated from mixtures with the corresponding paraffins (see Group IV (b)), and reference is made also to the separation of aromatic hydrocarbons containing olefinic side chains from those containing paraffinic side chains, e.g. the separation of styrene from xylenes and ethylbenzene.  An arrangement of plant identical with that shown in Specification 607,946 is described.  Specifications 607,948 and 607,949 also are referred to.ALSO:Olefines 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.  If desired, the oil or mixture may first be extracted with liquid ammonia containing a substance which increases its solvent power, e.g. a higher glycol, an ether or ether-alcohol, methanol or other alcohol, an alcohol-amine, aniline, pyridine or any of the methylamines or other aliphatic amine of low molecular weight, whereafter the mixture is treated with liquid ammonia of reduced dissolving power to effect a further concentration of the olefines.  When the oil or mixture contains aromatic hydrocarbons, which are more soluble than the olefines in the solvents employed, the extract may be re-extracted to yield a raffinate consisting mainly of olefines. The process may be effected in a counter-current system in which the solubility-modifying agent may be added at more than one point, 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 0-150 DEG  F., and the pressure should be sufficient to maintain the constituents in the liquid state. Examples are given in which (1) propylene is separated from a mixture with propane by extraction with a mixture of liquid ammonia and ethylene glycol, the concentration of the latter being raised to 30 per cent as the extraction proceeds; (2) butylenes are separated from a mixture with butanes by extraction with liquid ammonia containing a paraffinic oil boiling about 50 DEG  F. above the butane-butylene mixture; (3) amylenes are separated from a mixture with pentanes by extraction with liquid ammonia containing up to 35 per cent of ethylene diamine; (4) hexenes are separated from a mixture with hexanes by extracting the mixture with liquid ammonia and methylamine and then reducing the solvent power of the ammonia by addition of water and a paraffinic oil boiling about 50 DEG  F. above the hexene-hexane mixture.  Reference is made also to the separation of aromatic hydrocarbons containing olefinic side chains from those containing paraffinic side chains, e.g. the separation of styrene from xylenes and ethylbenzene.  An arrangement of plant identical with that shown in Specification 607,946 is described. Specifications 607,948 and 607,949 also are referred to.