Patent GB-1410773-A (GB)
Title: Hydrocarbon separation process
IPC: C07C15/02
Filed: 1972-09-15
Abstract: 1410773 Solvent extraction UNION CARBIDE CORP 15 Sept 1972 [16 Sept 1971] 42800/72 Heading C5E A continuous solvent extraction-steam distillation process for the recovery of aromatic hydrocarbons having boiling points in the range of 80 to 175 C. from a feedstock containing aliphatic hydrocarbons and aromatic hydrocarbons comprises: (a) contacting the feedstock in an extraction zone with a mixture of water in a solvent, which is water-miscible organic liquid having a boiling point of at least 200 C. and stable under the conditions of the process and with reflux hydrocarbons comprising reflux aliphatic hydrocarbons to provide an extract comprising aromatic hydrocarbons, reflux aliphatic hydrocarbons, solvent, and water and a raffinate comprising essentially aliphatic hydrocarbons; (b) contacting the extract with steam in a distillation zone to provide an overhead distillate comprising a reflux hydrocarbons phase and a water phase, a side cut distillate comprising an aromatic hydrocarbons phase and a water phase, and bottoms comprising a mixture of solvent and water; (c) contacting the raffinate with the water phase of the overhead distillate to provide an aliphatic hydrocarbons phase and water phase; (d) contacting the water phase of step (c) with an aromatic hydrocarbons stream containing at least 95% aromatic hydrocarbons, the amount of said latter stream being in the range of 0À1% to 5% by weight of the total aromatic hydrocarbons in the feedstock, to form an aromatic hydrocarbons phase and a water phase; (e) contacting the aromatic hydrocarbons phase of the side-cut distillate with the water phase of (d) to form an aromatic hydrocarbons phase and a water phase; (f) recycling the water phase of step (e) to the distillation or where said water phase is essentially converted to steam; (g) recycling the reflux hydrocarbons phase of the overhead distillate and the bottoms of step (b) to the extraction zone to provide reflux hydrocarbons and mixture of water and solvent, respectively, for step (a); and (h) recovering the aromatic hydrocarbons phase formed by step (e) and the aliphatic hydrocarbons phase formed by step (c). In an alternative embodiment the water phase of the overhead distillate of step (b) is divided into first and second streams and the following steps carried out: (c) contacting the raffinate with the first stream to provide an aliphatic hydrocarbons phase and a water phase, (d) contacting the second stream with the aromatic hydrocarbon stream as used in step (d) of the first embodiment, (e) contacting the aromatic hydrocarbons phase of the side-cut distillate with the water phase of (d) to form an aromatic hydrocarbons phase and a water phase; (f) contacting the water phase of step (e) with an aromatic hydrocarbons stream containing at least 95% aromatic hydrocarbons, the amount of said latter stream being in the range of 0À1% to 5% by weight of the total aromatic hydrocarbons in the feedstock, to form an aromatic hydrocarbons phase and a water phase; (g) recycling the water phases of steps (e) and (f) to the distillation zone where said water phases are essentially converted to steam; and treating the reflux hydrocarbons as with first embodiment. The preferred solvent is tetraethylene glycol.