Patent GB-607948-A (GB)
Title: Improved process for the solvent extraction of naphthenes from hydrocarbon mixtures
IPC: C10G21/08
Filed: 1943-01-05
Abstract: <PICT:0607948/III/1> Liquid ammonia is employed as a solvent extractor for separating naphthenes from hydrocarbon mixtures containing paraffins and naphthenes, particularly from such mixtures containing constituents boiling within a relatively narrow range. The solvent power of the ammonia may be increased by the addition of modifying solvents such as the methylamines, higher glycols, ethers and ether-alcohols, methanol and other alcohols, alcohol-amines, aniline and pyridine, or decreased by the addition of solvents such as water, ethylene glycol, formamide, ethylene diamine and various paraffinic hydrocarbons.  The modifying solvents may be added either initially with the ammonia, or in at least a part of the extraction path.  Both types of solvent may also be used in some cases, a modifying solvent for increasing the solvent power being used in the first stage and a solvent for decreasing the solvent power being added at a later stage.  The proportion of ammonia to modifying solvent should always be more than 50 per cent, preferably 75 per cent by volume, the temperatures used should range from 70 DEG  to 150 DEG  F. and the pressure should be sufficient to maintain the solvent in the liquid phase.  Normally, the process is carried out in two stages or extraction zones, a stripping zone where the naphthenes are removed as completely as possible, and an enriching zone when the naphthenes are purified from the other components, usually by recycling a portion of the purified naphthenes from the extract discharge end of the apparatus.  Examples are given in which single naphthenic hydrocarbons are separated from mixtures containing them (see Group IV (b)).  The Figure shows an apparatus suitable for separating methylcyclohexane from n-heptane.  The feed enters a stripping tower 1 by line 2 while methylamine-ammonia mixture from tank 18 enters through line 3. The extract passes through line 5 to an enriching tower 12 when it meets methylcyclohexane from the line 23 byepassed by the line 32. The raffinate from tower 12 is returned to tower 1 through line 13 while the extract passes by line 14 to extraction tower 15 when it meets a counter-current of a higher boiling paraffinic mineral oil from the line 17.  This oil dissolves out all the methylcyclohexane so that ammonia methylamine mixture is discharged from the tower back to storage tank 18 by line 16, while a paraffinic extract of the naphthene passes through line 19 to evaporator 20 from which pure paraffinic oil is discharged through line 17.  Methylcyclohexane and some ammonia solvent pass from the evaporator 20 to a distillation column 22 from which solvent is discharged back to the tank 18 through line 27 while methylcyclohexane passes through line 23 partly to storage and partly to the tower 12.  The raffinate from tower 1 containing n-heptane is passed through line 4 to a distillation column 6 whence the ammonia solvent is returned to tank 18 while the heptane is discharged through line 7.  In cases where aromatics and unsaturated hydrocarbons are also present, the solvent power of the ammonia is adjusted so as to yield, in the first instance, a paraffinic raffinate and an extract containing the other hydrocarbons; this extract is further extracted with liquid p  ammonia of reduced solvent power to yield a final extract containing the aromatic and unsaturated hydrocarbons, a fraction rich in naphthenes being withdrawn at an intermediate point in the extraction path and treated separately with an ammonia solvent of appropriate solvent power to recover the naphthene hydrocarbons. Specifications 607,945, 607,946, 607,947 and 607,949 are referred to.ALSO:<PICT:0607948/IV(b)/1> Liquid ammonia is employed as a solvent extractor for separating naphthenes from hydrocarbon mixtures containing paraffins and naphthenes, particularly from such mixtures containing constituents boiling within a relatively narrow range.  The solvent power of the ammonia may be increased by the addition of modifying solvents such as the methylamines, higher glycols, ethers and ether-alcohols, methanol and other alcohols, alcohol-amines, aniline and pyridine, or decreased by the addition of solvents such as water, ethylene glycol, formamide, ethylene diamine, and various paraffinic hydrocarbons. The modifying solvents may be added either initially with the ammonia, or in at least a part of the extraction path.  Both types of solvent may also be used in some cases, a modifying solvent for increasing the solvent power being used in the first stage and a solvent for decreasing the solvent power being added at a later stage.  The proportion of ammonia to modifying solvent should always be more than 50 per cent, preferably 75 per cent by volume, the temperatures used should range from 70 DEG  to 150 DEG  F. and the pressure should be sufficient to maintain the solvent in the liquid phase.  Normally the process is carried out in two stages or extraction zones, a stripping zone where the naphthenes are removed as completely as possible and an enriching zone where the naphthenes are purified from the other components, usually by recycling a portion of the purified naphthenes from the extract discharge end of the apparatus.  Examples are given of the separation of (1) methylcyclohexane and n-heptane by extraction with liquid ammonia containing methylamine (2) methylnaphthalene, tetralin, and decane from a mixture containing them by means of liquid ammonia containing some water; methyl naphthalene is obtained as an extract, and the raffinate is extracted with liquid ammonia to give an extract of tetralin and a raffinate of decane; (3) cyclopentane from neohexane by extraction with liquid ammonia. The Figure shows an apparatus suitable for carrying out the first of the above separations.  The feed enters a stripping tower 1 by line 2 while methylamine-ammonia mixture from tank 18 enters through line 3.  The extract passes through line 5 to an enriching tower 12 when it meets methylcyclohexane from the line 23 bye-passed by the line 32.  The raffinate from tower 12 is returned to tower 1 through line 13, while the extract passes by line 14 to extraction tower 15 when it meets a counter current of a higher boiling paraffinic mineral oil from the line 17.  This oil dissolves out all the methylcyclohexane so that ammonia methylamine mixture is discharged from the tower back to storage tank 18 by line 16, while a paraffinic extract of the naphthene passes through line 19 to evaporator 20 from which pure paraffinic oil is discharged through line 17.  Methylcyclohexane and some ammonia solvent pass from the evaporator 20 to a distillation column 22 from which solvent is discharged back to the tank 18 through line 27 while methylcyclohexane passes through line 23 partly to storage and partly to the tower 12.  The raffinate from tower 1 containing n-heptane is passed through line 4 to a distillation column 6 whence the ammonia solvent is returned to tank 18 while the heptane is discharged through line 7.  In cases where aromatics and unsaturated hydrocarbons are also present, the solvent power of the ammonia is adjusted so as to yield, in the first instance a paraffinic raffinate and an extract containing the other hydrocarbons; this extract is further extracted with liquid ammonia of reduced solvent power to yield a final extract containing the aromatic and unsaturated hydrocarbons, a fraction rich in naphthenes being withdrawn at an intermediate point in the extraction path and treated separately with an ammonia solvent of appropriate solvent power to recover the naphthene hydrocarbons. Specifications 607,945, [Group III], 607,946, 607,947 and 607,949 are referred to.