Control method for solvent refining lubricating oils

摘要

In a solvent refining process a naphthenic lubricating oil feedstock is solvent extracted to yield a primary aromatics-lean raffinate and a primary aromatics-rich extract. Polynuclear aromatic content of primary raffinate is controlled by manipulating extraction temperature and solvent dosage. Primary extract is separated (settled) to form a secondary raffinate and a secondary extract. Secondary raffinate is recycled to solvent extraction. The refractive index of secondary raffinate is controlled by manipulating settling temperature and antisolvent dosage. The refractive index of secondary raffinate is maintained at or below the refractive index of feedstock. An improved yield of primary raffinate of a specified polynuclear aromatic content is achieved.