Determination of molecular weight distributions of polymerized petroleum pitch by gel permeation chromatography with quinoline eluent

Abstract

The technique of gel permeation chromatography (GPC) using quinoline eluent has been applied to measure molecular weight distributions in thermally polymerized petroleum pitches. The molecules present in the toluene-soluble fraction of polymeric pitch eluted ideally in quinoline. A study of low molecular weight model pericondensed polynuclear aromatic hydrocarbons, which elute nonideally in most GPC eluents, revealed that the elution volume in quinoline was closely related to the maximum length of the molecule. The molecules present in the toluene-insoluble-quinoline-soluble fraction of polymerized pitch eluded nonideally, and the elution volume was a function of the concentration of these molecules after reductive hydrogenation. A linear GPC polymerized pitch calibration curve was obtained for the 450 to 2000 molecular weight range. The technique is applicable for obtaining molecular weight distributions of petroleum pitch mesophases and semicokes which have quinoline-insoluble contents approaching 100%.