Methods for enhanced extractive distillation employing extractive distillation compositions comprising sulfolane and compatibility agent

A process for separating hydrocarbon compounds of similar boiling points by extractive distillation, comprising the steps of:

• a) introducing a feed mixture into an extractive distillation zone having an upper portion and a lower portion, wherein the feed mixture comprises at least
• i) a first hydrocarbon compound comprising a C7-C10 aliphatic compound, and
• ii) a second hydrocarbon compound comprising benzene, toluene, ortho xylene, meta xylene, para xylene, or a mixture thereof;
• b) introducing an extractive distillation composition into the upper portion of the extractive distillation zone;
• c) distilling the feed mixture to at least partially separate the feed mixture into an overhead stream rich in the first hydrocarbon compound, and a bottoms stream rich in the second hydrocarbon compound;
• wherein the extractive distillation composition comprises:
• i) about 100 parts by weight of sulfolane or a sulfolane derivative having the formula:
• wherein S1, S2, S3, and S4 are independently hydrogen or an alkyl having one to six carbon atoms, and
• ii) from about 5 to about 35 parts by weight of a compatibility agent or a mixture of compatibility agents, wherein the compatibility agent composes an unsubstituted or substituted derivative of acetophenone, propiophenone, benzonitrile, a dialkyl phthalate ester, a cinnamate ester, a C6-C12 alkyl ester of acetic, propionic, or butyric acid, isophorone, a nitrobenzene, quinoline, or an isoquinoline.

A process for separating a BTX stream by extractive distillation that employs an extractive distillation composition, wherein the improvement comprises the use of an extractive distillation composition comprising:

• a) sulfolane and/or a sulfolane derivative having the formula:
• wherein S1, S2, S3, and S4 are independently hydrogen or an alkyl having one to six carbon atoms, and
• b) at least one compatibility agent, wherein the at least one compatibility agent:
• i) has a Hansen's Solubility Polar Parameter from about 2.7 to about 6.4 (calories/cm3)½, and a Hansen's Solubility Hydrogen Bonding Parameter from about 1.0 to about 4.4 (calories/cm3)½:
• ii) has a boiling point higher than the boiling point of the BTX stream;
• and
• iii) does not comprise an N-substituted-2-thiopyrrolidone compound or residue.