Isolation of polybutenylsuccinimide-type dispersant from monograde and multigrade lubricating oils by classical liquid-adsorption chromatography on a Florisil column

A method is described for efficient separation of ashless dispersants (polybutenylsuccinimide type) from base oil and other additives (viscosity improver, detergent, inhibitors, etc.) of monograde and multigrade lubricating oils. Due to the complexity of modern engine motor oils a first enrichment in the dispersant is provided by a process including dialysis, liquid-liquid extraction and anion-exchange chromatography. The dispersant is then fully isolated through classical liquid chromatography on a Florisil (a hard, highly porous, activated magnesium silicate, convenient for the star polymer structure of the dispersant) column. The quality of the separation is checked by Fourier transform infrared spectrometry and size-exclusion chromatography.