Polyalkylene glycol compositions for enhanced aromatic extraction

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;
• and
• b. introducing an extractive distillation composition into the upper portion of the extractive distillation zone;
• and
• c. distilling the feed mixture to at least partially separate the feed mixture into a first stream rich in the first hydrocarbon compound, and a second stream rich in the second hydrocarbon compound;
• wherein the extractive distillation composition comprises:
• i. about 100 parts by weight of at least one alkylene glycol, 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 comprises 2-ethyl-1-hexanol, dipropylene glycol methyl ether acetate, 1-octanol, 1-tridecanol, oleyl alcohol, 1-decanol (decyl alcohol), ethylene glycol dibutyrate, 1,2-decane carbonate, 1,2-dodecane carbonate, N-(2-aminoethyl)piperazine, aniline, 1,2-butylene carbonate, isobutyl heptyl ketone, dimethyl adipate, dimethyl glutarate, dimethylsuccinate, di-n-butyl sebacate, o-dichlorobenzene, diethyl succinate, diisobutylcarbinol, ethylene glycol butyl ether, ethyl decanoate, 2-ethylhexyl acetate, a hexyl acetate, a heptyl acetate, an octyl acetate, a nonyl acetate, a decyl acetate, N-formyl morpholine, hexamethylphosphoramide, 1,2-hexane carbonate, 1-isopropyl-2-methyl imidazole, 3-isopropyl-2-oxazolidinone, methoxyisopropyl acetamide, methoxyisopropyl formamide, methoxypropyl acetamide, methoxypropy formamide, methyl oleate, nonylphenol, 2-octanol, propylene glycol diacetate, pine oil, iso-propyl palmitate, alpha-terpineol, tri-n-butyl phosphate, acetophenone, benzonitrile, di-n-butyl phthalate, diethyl phthalate, dimethyl phthalate, ethyl cinnamate, isophorone, nitrobenzene, or quinoline.

A process for separating a mixture of hydrocarbon compounds by extractive distillation that employs an extractive distillation composition, wherein the improvement comprises the use of a mixture comprising at least one alkylene glycol compound, and at least one compatibility agent, wherein the at least one compatibility agent:

• a. 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;
• b. has a boiling point higher than the boiling point of the mixture of hydrocarbon compounds;
• and
• c. does not comprise
• i. an N-hydrocarbyl-substituted pyrrolidone compound or residue, or an N-hydrocarbyl-substituted-2-thiopyrrolidone compound or residue, or
• ii. a polyalkyleneglycol ether compound of the formula:
• R4O—[CHR5—(CHR6)x—O]y—R7
• wherein R4, R5, R6 and R7 may be hydrogen alkyl, aryl, aralkyl, alkylaryl and mixtures thereof, and wherein R4 or R7 are not both hydrogen.