Preparative Group Separation of Complex Mixtures Extrography of Mineral Oil Residues

摘要

A method, called extrography, was developed for the preparative separation of complex mixtures having a wide polarity range. Optimal conditions have been found for the separation of crude oil vacuum residues. The advantages of extrography over other methods described in the literature are, that large samples (ca. 40 g) can be separated in a short time (ca. 2 hours), using small amounts of solvents and adsorbents. The apparatus required is simple and the separation can be carried out in an inert atmosphere. Using an optimized system the vacuum residue of a Kirkuk crude oil could be separated to yield about 10% by weight of a white paraffinic fraction, with a number averaged molecular weight of about 800. The most polar fracton obtained from this separation was of typically asphaltenic character (high Heteroatom content and molecular weight ca 5000). Extrography can be used both to obtain a group separation according to polarity and to characterise high boiling crude oil fractions. The mechanism of extrography has been studied and a simple model is proposed. It consists of a preseparation of the sample components on the polar surface of the support which is followed by a mixture of simple extraction and chromatographic separation. (ERA citation 08:035136)