Advances in the applications of size exclusion chromatography to the characterization of carbon materials from petroleum derivatives by using NMP/chloroform mixtures as eluent

摘要

This paper describes advances made in the application of size-exclusion chromatography (SEC) to the characterization of petroleum derived materials. The method employs a novel mixed solvent as SEC eluent. A mixture of NMP/CHCl_3 as eluent shows superior calibration behaviour for a variety of polymeric molecular mass standards and model PAH and heterocyclic compounds compared to THF, chloroform or toluene. Using a mixture of NMP/CHCl_3 (6:1) as SEC eluent improves the solubility of petroleum samples, usually partially insoluble in NMP alone, whilst maintaining the benefits of NMP as SEC eluent. Elution times of a set of PAHs and heterocyclic compounds in the mixed eluent gave a calibration line with a different slope to larger polymeric standards (> 500 Da). The NMP/CHCl_3 as the eluent appears to extend the elution times of these aromatic and polar compounds, possibly due to the marginal promotion of surface effects. The application of this SEC system to a Maya asphaltene showed the NMP insoluble fraction is of larger size (and higher in mass) than the NMP soluble fraction.The work has shown that careful consideration of solvent properties may be instrumental in bringing together data from structurally very different polymeric standards. We have seen that the combination of NMP with chloroform has generated an SEC system, with its corresponding calibration, able to dissolve and elute petroleum asphaltene samples that were only partly characterized when using pure NMP as eluent.