Asphaltene concentration and compositional alterations upon solar irradiation of petroleum

An Arabian light crude and an intermediate Brazilian crude petroleum were subjected to tropical solar irradiation. In both cases there was an immediate and progressive increase in the asphaltenic content that was perceptible after only 5 h. This asphaltene was characterized using fluorescence, FT-IR, proton NMR, and TGA analyses. In both cases the asphaltene became progressively less fluorescent but more aromatic, and also revealed some oxidation.