Improvements in or relating to the production of substantially oil-free wax and dewaxed oil from wax-bearing lubricating oil stock

摘要

Wax-bearing lubricating oil is dewaxed by treating with a liquid which is a solvent for oil but not for wax at dewaxing temperatures and in which water is partially miscible, filtering to obtain dewaxed oil dissolved in solvent and primary wax containing some solvent and oil; mixing the primary wax with wet solvent, filtering to obtain secondary wax of low oil content and a filtrate comprising solvent and a little oil, at such a temperature that the moisture in the solvent is crystallized and separated as ice with the wax; and recycling the dry filtrate to the first dewaxing step. The secondary wax may be heated to, for example, 130 DEG F. and the liquid wax separated from the water. The solvent recovered from the primary dewaxed oil may be separated by steam stripping and may be recycled to the secondary dewaxing zone. Solvents referred to are mixtures of aromatic hydrocarbons such as benzene and toluene with ketones such as acetone, methylethyl ketone, methylisobutyl ketone, methyl normal butyl ketone and methyl normal propyl ketone, aldehydes, chlorinated hydrocarbons, such as methylene chloride, esters, such as propyl and amyl acetate and low boiling paraffins such as pentane and hexane; single solvents may also be used. An example is given of dewaxing a wax distillate oil with methylethyl ketone and toluene; a dewaxing temperature of -10 DEG F. is used in both dewaxingsteps and the wet solvent contained 1 per cent of water.