Separation of Petroporphyrins from Asphaltenes by Chemical Modification and Selective Affinity Chromatography

Part of the metalloporphyrin fraction was separated from asphaltenes by a combination of reactive modification and affinity chromatography. The targeted vanadyl porphyrin complexes were modified by reaction with oxalyl chloride followed by a long chain alkylamine or perfluoroalkylaniline to produce an imido vanadium(IV) derivative bearing an octadecyl or perfluoroctyl side chain. This derivatized asphaltene was then chromatographed on C18-silica gel or perfluorous (-C8F17) silica gel to remove the tagged metalloporphyrins from the remaining asphaltene. With the C18-tagging and reverse-phase chromatography method, from 15 to 40% of the total vanadium content together with comparable percentages of nickel was removed, with less than 5% mass loss from the asphaltene fraction. The fluorous tagging process gave better removal of metals on one sample but was limited by the lower recovery of asphaltenes on other samples. This approach requires further optimization for quantitative selective separation of metal c...