Patent GB-613770-A (GB)
Title: Process for extracting an aromatic hydrocarbon from a mixture containing other hydrocarbons
IPC: C07C7/10
Filed: 1946-07-02
Abstract: Aromatic hydrocarbons are extracted from their mixtures with other hydrocarbons containing less than 10 per cent of olefins by contact with a solvent comprising sulphuric acid or a mixture of sulphuric and sulphonic acids having dissolved therein silver sulphate, oxide or carbonate.  Substantially saturated fractions such as straight run gasoline may be purified by extraction of aromatics.  The sulphuric acid is usually of a concentration of 65-100 per cent, or more, preferably 75-100 per cent, and contains a high content of silver compound for example a 10 per cent solution of 96 per cent acid. Sulphonic acids formed by reaction of such solutions with aromatic hydrocarbons, as a separate step or during the separation process, increase the solubility of the silver compound.  Aliphatic or naphthenic sulphonic acids, and acids containing substituent groups such as hydroxy, nitro, carboxyl, and alkoxy, may also be used. "Stabilized" solutions containing such proportions of silver and acids that they do not effect further sulphonation of aromatic hydrocarbons are also utilized.  Sulphonic acids of, for example, toluene, mesitylene, amyl- and diamyl-naphthalene are too insoluble to give solutions utilizable at atmospheric temperature.  The separation of aromatic hydrocarbons is effected at temperatures from sub-atmospheric up to 65 DEG  C. or more, preferably 10-40 DEG  C. Pressure sufficient to maintain liquid phase is preferably used. Batch or continuous methods of extraction are used.  To recover the aromatic hydrocarbons the extract phase may be treated with a secondary solvent which is immiscible with the separating agent, such as propane, butane, pentane or cetane.  Alternatively, reduction of pressure or increase in the temperature may be used or water added to effect a separation.ALSO:Aromatic hydrocarbons are extracted from their mixtures with other hydrocarbons containing less than 10 per cent of olefins by contact with a solvent comprising sulphuric acid or a mixture of sulphuric and sulphonic acids having dissolved therein silver sulphate, oxide or carbonate.  Substantially saturated fractions such as straight run gasoline may be purified by extraction of aromatics.  The sulphuric acid is usually of a concentration of 65-100 per cent or more, preferably 75-100 per cent, and contains a high content of silver compound, for example a 10 per cent solution in 96 per cent acid.  Sulphonic acids formed by reaction of such solutions with aromatic hydrocarbons, as a separate step or during the separation process, increase the solubility of the silver compound.  Aliphatic or naphthenic sulphonic acids, and acids containing substituent groups such as hydroxy, nitro, carboxyl and alkoxy, may also be used. "Stabilized" solutions containing such proportions of silver and acids that they do not effect further sulphonation of aromatic hydrocarbons are also utilized.  Sulphonic acids of, for example, toluene, mesitylene, amyl- and diamyl-naphthalene are too insoluble to give solutions utilizable at atmospheric temperature. The separation of aromatic hydrocarbons is effected at temperatures from sub-atmospheric up to 65 DEG  C. or more, preferably 10-40 DEG  C.  Pressure sufficient to maintain liquid phase is preferably used.  Batch or continuous methods of extraction are used.  To recover the aromatic hydrocarbon, the extract phase may be treated with a secondary solvent which is immiscible with the separating agent, such as propane, butane, pentane or cetane. Alternatively, reduction of pressure or increase in temperature may be used or water added to effect a separation.  In examples: (1) comparative figures are given for benzene solubility in a saturated solution of silver sulphate in 85 per cent sulphuric acid, and an aqueous silver nitrate solution; (2) a similar part saturated solution of silver sulphate is used to extract a benzene, n-heptane mixture; (3) figures are given for the extraction by various secondary solvents of benzene dissolved in acid silver sulphate solution; (4) figures are given to show that the percentage of benzene extracted by pentane from separating agents containing various concentrations of benzene does not vary considerably; (5)-(8) ice and hydrogen chloride are added to separating agents containing dissolved benzene or cumene to recover the latter, part of which is, however, lost by sulphonation; (9) 96 per cent sulphuric acid is reacted with aromatic hydrocarbons in the presence of silver sulphate to give a "stabilized" separating agent which is enriched with silver sulphate and used as a solvent for benzene, toluene and cumene; (10) the same agents are used to separate benzene from mixtures with heptane; (11) figures are given for solubilities of benzene, toluene, m-xylene, mesitylene, ethylbenzene, cumene, amylbenzene, "Tetralin" (R.T.M.), and amylnaphthalene in separating agents containing sulphonic acids of benzene or the aromatic hydrocarbon being dissolved where such are utilizable; (12) and (13) silver sulphate, sulphuric acid, benzene sulphonic acid solution is used to separate benzene from mixtures with heptane, and such benzene solutions extracted with pentane.