Patent GB-585166-A (GB)
Title: Improvements in and relating to the separation of aromatic hydrocarbons having conjugated unsaturated side groups from their mixtures with other aromatic hydrocarbons having no such characteristics, and especially to the purification of styrene, indene and similar compounds
IPC: C07C7/10
Filed: 1941-06-16
Abstract: Aromatic hydrocarbons having unsaturated side groups with a double bond in conjugated position to those of the aromatic nucleus are separated from their mixtures with aromatic hydrocarbons having no side groups or saturated side groups by distribution between two solvent layers which are immiscible or only partially miscible, and which dissolve preferentially hydrocarbons of the first and second types respectively, namely the solvent systems liquid sulphur dioxide-paraffinic hydrocarbons or aqueous alcohols-paraffinic hydrocarbons, and then separating the layers.  Hydrocarbons of the first type include styrene, indene, a-methyl-, p-methyl-, and m-ethyl-styrenes, propenylbenzene, alkyl derivatives of indene, and polycyclic hydrocarbons such as vinyl-naphthalene.  The second class includes benzene, naphthalene, anthracene, and derivatives with saturated side chains or saturated cyclic side groups such as toluene, ethylbenzene, xylene, and hydrindene.  Mixtures of these occur in coal carbonization products, for example, benzoles and tars of which the 130-150 DEG C. fraction contains xylenes, ethylbenzene, and styrene, and the 170 DEG -190 DEG C. fraction contains indene with other aromatics; products of catalytic cracking or aromatization according to the processes of Specifications 552,115, 552,216, 574,963, 574,973, 575,766, 575,768, and 575,769, [all in Group IV], which contain styrene, and its derivatives, and indene; and dehydrogenation products of ethylbenzene.  The paraffinic solvents may be either single paraffins such as liquid propane, isopentane or heptane or petroleum fractions of sufficiently different boiling range from the hydrocarbons to be separated.  The aqueous alcohols are mixtures of water with one or more alcohols capable of dissolving 5-50 per cent. by weight thereof, e.g., methyl, ethyl, propyl, isopropyl, sec. and tert. butyl, ethylene chlorhydrin, ethylene glycol mono-alkyl ethers, propylene glycol and its mono-alkyl ethers. The aromatics with conjugated unsaturated side groups concentrate in the sulphur dioxide or aqueous alcohol, and the others in the upper paraffinic layer. Repeated distribution gives complete separation. Temperatures below normal are preferable.  Multiple counter-current extraction in towers may be used continuously introducing the light and heavy solvents at bottom and top respectively, and the solute intermediately.  Examples describe the extraction with liquid propane and sulphur dioxide at -50 or -55 DEG C. of mixtures of styrene with ethylbenzene or xylol, and indene with alkylbenzenes, and the extraction with isopentane and aqueous methanol or sulphur dioxide of styrene and ethylbenzene.ALSO:Aromatic hydrocarbons having unsaturated side groups with a double bond in conjugated position to those of the aromatic nucleus are separated from their mixtures with aromatic hydrocarbons having no side groups or saturated side groups by distribution between two solvent layers which are immiscible or only partially miscible, and which dissolve preferentially hydrocarbons of the first and second types respectively, namely the solvent systems liquid sulphur dioxide-paraffinic hydrocarbons or aqueous alcohols-paraffinic hydrocarbons, and then separating the layers.  Hydrocarbons of the first type include styrene, indene, a -methyl-, p-methyl-, and m-ethyl-styrenes, propenylbenzene, alkyl derivatives of indene, and polycyclic hydrocarbons such as vinyl-naphthalene.  The second class includes benzene, naphthalene, anthracene, and derivatives with saturated side chains or saturated cyclic side groups such as toluene, ethylbenzene, xylene, and hydrindene.  Mixtures of these occur in coal carbonisation products, for example benzoles and tars of which the 130-150 DEG  C. fraction contains xylenes, ethylbenzene, and styrene, and the 170-190 DEG  C. fraction contains indene with other aromatics; products of catalytic cracking or aromatization according to the processes of Specifications 552,115, 552,216, 574,963, 574,973, 575,766, 575,768 and 575,769 which contain styrene and its derivatives, and indene; and dehydrogenation products of ethylbenzene.  The paraffinic solvents may be either single paraffins such as liquid propane, isopentane or heptane or petroleum fractions of sufficiently different boiling range from the hydrocarbons to be separated.  The aqueous alcohols are mixtures of water with one or more alcohols capable of dissolving 5-50 per cent by weight thereof, e.g. methyl, ethyl, propyl, isopropyl, sec. and tert. butyl, ethylene chlorhydrin, ethylene glycol mono-alkyl ethers, propylene glycol, and its mono-alkyl ethers.  The aromatics with conjugated unsaturated side groups concentrate in the sulphur dioxide or aqueous alcohol, and the others in the upper paraffinic layer. Repeated distribution gives complete separation.  Temperatures below normal are preferable. Multiple counter-current extraction in towers may be used continuously introducing the light and heavy solvents at bottom and top respectively, and the solute intermediately.  Examples describe the extraction with liquid propane and sulphur dioxide at - 50 or - 55 DEG  C. of mixtures of styrene with ethylbenzene or xylol, and indene with alkylbenzenes, and the extraction with isopentane and aqueous methanol or sulphur dioxide of styrene and ethylbenzene.