Solvent recovery from lube oil filtrates with a polyimide membrane

Abstract

A polyimide membrane manufactured from a co-polymer of diaminophenylindane with benzophenone tetracarboxylic dianhydride has been shown to have excellent chemical resistance and economically viable flux and rejection characteristics for the separation of light hydrocarbon solvents from lube oil filtrates. This asymmetric membrane was subjected to a series of bench scale hyperfiltration studies. After 2 months of continuous high pressure tests, the membrane demonstrated recovery of chilled solvent (a mixture of methyl ethyl ketone and toluene at −10°C) from the lube filtrates at a purity of better than 99% with a steady permeate rate. When a membrane system is combined with a conventional solvent lube dewaxing process, significant increases in energy efficiency and solvent recovery capacity are realized. Subsequently, this work led to the installation of a commercial membrane plant designed for a maximum feed rate of 11 500 cubic meters per day (72 000 barrels per day) at Mobil’s Beaumont, Texas refinery. This process, trademarked MAX-DEWAX ®, provides a low capital method for expansion of solvent dewaxing units and is available for licensing.