Isolation of polybutenylsuccinimide-type dispersants from multigrade lubricating oils by classical cation exchange chromatography

A macroporous cation exchanger is used for the efficient separation of ashless dispersants (polybutenylsuccinimide type) from base oil and additives (viscosity improver (VI), detergent, inhibitors, etc.) of multigrade lubricating oils. Due to the basic character of residual amine groups present in its polyamine chain, the dispersant is retained on the macroporous cation exchanger (H+ form) while base oil and additives are eluted with appropriate solvents. The highly purified dispersant is then recovered through elution with a strong and basic eluent constituted of chloroform-isopropanol-ammonia (35 : 60 : 5%, vv). The quality of the isolation is checked all along the separation by Fourier transform infrared (FTIR) spectrometry and size-exclusion chromatography (SEC).