Exxon Research and Engineering Company

Stephen F Perry

Thomas E Broadhurst

Ralph R Hall

James D Eagan

An improved DILCHILL* dewaxing process wherein waxy lubricating oil stocks are solvent dewaxed by contacting them with successive increments of cold dewaxing solvent at a plurality of points along the height of a vertical tower divided into a plurality of stages while agitating the oilsolvent mixture in each stage to provide substantially instantaneous mixing of the waxy oil and solvent thereby precipitating wax from the oil while avoiding the well known shock chilling effect. The improvement resides in adjusting the cold solvent addition to each stage in a manner so as to modify the temperature profile along the tower to ensure that the temperature drop per stage in the initial stages in which wax precipitation occurs is greater than the temperature drop per stage in the final or later stages in which wax precipitation occurs.

Dilution chilling dewaxing by modification of tower temperature profile

Ketone dewaxing solvent is separated and recovered from dewaxed oil and a wax slurry through the use of flash vaporization or distillation followed by steam stripping. Water is removed from the recovered solvent through the use of a combination of a decanting drum to form a solvent phase and a water phase, a deketonizer tower which strips solvent from the water phase, and a simple distillation tower which functions as a solvent dehydrator. It has been found that feeding a portion of the overhead vapors from the flash vaporization step directly to the bottom of the dehydrator provides enough heat to eliminate the need for a reboiler on the dehydrator tower.

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Westfield, NJ, United States of America

Stephen F Perry