Processes for the separation of aromatic hydrocarbons from a hydrocarbon mixture

A process for separating aromatic hydrocarbons from a feedstream containing aromatic and non-aromatic hydrocarbons, comprising:

• a) passing the feedstream to an upper fractionation zone of a reboiled extractive distillation column maintained at extractive distillation conditions including a temperature of from about 200.degree. to 400.degree. F. and a pressure of from about 15 to 100 psia effective to separate aromatic from non-aromatic hydrocarbons and contacting the feedstream within said distillation column with a cooled lean solvent stream comprising an aromatic-selective solvent and a stripping medium stream comprising water, said cooled lean solvent stream being introduced at the top of the upper fractionation zone and said stripping medium stream being introduced in a bottom fractionation zone;
• b) withdrawing a raffinate stream comprising non-aromatic hydrocarbons and water from the upper fractionation zone of said distillation column;
• c) withdrawing a side stream as a vapor side draw comprising aromatic hydrocarbons, water, and trace amounts of the aromatic-selective solvent from an intermediate fractionation zone of said distillation column;
• d) withdrawing a hot lean solvent stream comprising the aromatic-selective solvent from the bottom fractionation zone of said distillation column;
• e) passing the side stream to a first cyclone separator to provide an aromatic-rich overhead stream and a first aqueous stream and returning at least a portion of the first aqueous phase to the first cyclone separator;
• f) passing the aromatic-rich overhead stream to a first condenser and a first phase separator to provide an aromatic product and a second aqueous phase;
• g) passing the raffinate stream to a second cyclone separator to provide an overhead raffinate stream and a third aqueous phase;
• h) cooling and condensing the overhead raffinate stream to provide a raffinate byproduct and a fourth aqueous phase;
• i) combining at least a portion of the first, second, third and fourth aqueous phases to provide a stripping medium stream;
• and
• j) cooling said hot lean solvent stream to provide the cooled lean solvent stream.

A process for separating aromatic hydrocarbons from a feedstream containing aromatic and non-aromatic hydrocarbons, comprising;

• a) admixing the feedstream with at least a portion of a benzene product prior to passing the feedstream to an upper fractionation zone of a reboiled extractive distillation column maintained at extractive distillation conditions including a temperature of from about 200 to 400.degree. F. and a pressure of from about 15 to 100 psia effective to separate aromatic from non-aromatic hydrocarbons and contacting the feedstream within said distillation column with a cooled lean solvent stream comprising sulfolane and a stripping medium stream comprising water, said cooled lean solvent stream introduced at the top of the upper fractionation zone and said stripping medium introduced in a bottom fractionation zone;
• b) withdrawing a raffinate stream comprising non-aromatic hydrocarbons and water from the upper fractionation zone of said distillation column;
• c) withdrawing a side stream as a vapor side draw comprising aromatic hydrocarbons, water, and trace amounts of sulfolane from an intermediate fractionation zone of said distillation column;
• d) withdrawing a hot lean solvent stream comprising sulfolane from the bottom fractionation zone of said distillation column;
• e) passing the side stream to a first cyclone separator to provide an aromatic-rich overhead stream and a first aqueous stream;
• f) passing the aromatic-rich overhead stream to a first condenser and a first phase separator to provide an aromatic product and a second aqueous phase;
• g) recovering a benzene product from the aromatic product and recycling at least a portion of the benzene product to be admixed with the feedstream;
• h) passing the raffinate stream to a second cyclone separator to provide an overhead raffinate stream and a third aqueous phase;
• i) cooling and condensing the overhead raffinate stream to provide a raffinate product and a fourth aqueous phase;
• j) combining at least a portion of the first, second, third and fourth aqueous phases to provide a stripping medium stream and returning said stripping medium stream to the bottom fractionation zone;
• k) cooling the hot lean solvent stream by indirect heat exchange with the stripping medium stream to provide a first-cooled lean solvent stream, thereby at least partially vaporizing the stripping medium stream prior to passing it to the bottom fractionation zone of said distillation column;
• and
• l) further cooling the first-cooled lean solvent stream by indirect heat exchange with the feedstream to provide the cooled lean solvent stream, thereby at least partially vaporizing the feedstream prior to passing said feedstream to the upper fractionation zone.