POTENTIAL OF UV-VISIBLE ABSORPTION SPECTROSCOPY FOR CHARACTERIZING CRUDE PETROLEUM OILS
Igor N. Evdokimov, Alexandr P. Losev Department of Physics, Gubkin Russian State University of Oil and Gas
New experimental data as well as analysis of published databases show that the potential of UV-Visible absorption (UVVA) spectroscopy for classification/evaluation of petroleum may be strongly underestimated. Even the simplest “coloration” approach, when monotonous UVVA spectra are characterized by a single numerical parameter, allows distinguishing various types of crude oils. Subjected to proper processing, apparently “featureless” UVVA spectrum shows a multiple peak structure superimposed on a general monotonous background providing a basis for UVVA employment for compositional analysis of crude oils. The main practical problem is that generally crude oils are opaque and have to be diluted for UVVA analysis. Our experiments show that oil dilution may strongly affect the measured UVVA spectra apparently due to de-aggregation of asphaltenes in a solution. Further development of UVVA techniques requires better understanding of the nature/composition of asphaltenes. A useful approach may be consideration of “molecular diversity” models, being developed for other systems with continuous UVVA spectra, in particular for humic acids and melanins