Solvent recovery from lube oil filtrates with a polyimide membrane

A polyimide membrane manufactured from a co-polymer of diaminophenylindane with benzophenone tetracarboxylic dianhydride has been shown to have excell ent chemical resistance and economically viable flux and rejection characte ristics for the separation of light hydrocarbon solvents from lube oil filt rates. This asymmetric membrane was subjected to a series of bench scale hy perfiltration studies. After 2 months of continuous high pressure tests, th e membrane demonstrated recovery of chilled solvent (a mixture of methyl et hyl ketone and toluene at -10 degreesC) 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 inc reases in energy efficiency and solvent recovery capacity are realized. Sub sequently, 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 ba rrels per day) at Mobil's Beaumont, Texas refinery. This process, trademark ed MAX-DEWAX(R), provides a low capital method for expansion of solvent dew axing units and is available for licensing. (C) 2000 Elsevier Science B.V. All rights reserved.