in the refining process used
to separate reactive components (unsaturated
hydrocarbons) from lube distillates in
order to improve the oil’s oxidation
stability, viscosity index (V.I.),
and response to additives. Commonly used
extraction media (solvents) are:
phenol, N-methylpyrrolidone (NMP),
furfural, liquid sulfur dioxide, and
nitrobenzene. The oil and solvent are mixed in an extraction tower,
resulting in the formation of two liquid phases: a heavy phase consisting of
the undesirable unsaturates (see
unsaturated hydrocarbon) dissolved in the solvent, and a light phase
consisting of high quality oil with some solvent dissolved in it. The phases
are separated and the solvent recovered from each by
distillation. The unsaturates portion, or
extract, while undesirable in lubricating oils, is useful in other
applications, such as rubber extender oils (see
rubber oil) and plasticizer oils.
Application
Notes:
