Molecular Changes in Asphaltenes within H2 Plasma

Abstract

In the present work, the chemical changes in asphaltenes, solid residues, when they are treated with hydrogen plasma were analyzed. H2 plasma was characterized by the presence of electrons, H+ and H2+ ions, at kinetic energies as low as 30 eV. These species can interact with the asphaltenes to produce changes in the chemical structure by different mechanisms such as bond cleavage, recombination, and condensation. Asphaltene samples were exposed to different treatment times (up to 120 min). The plasma was characterized by optical emission spectroscopy (OES) as well as by the different products created in the reactions of asphaltenes. The presence of C+, CH+, C2+, NH+, and V+ was confirmed. Spectroscopic techniques such as Fourier transform infrared spectroscopy (FT-IR), matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS), nuclear magnetic resonance spectroscopy (1H NMR and 13C NMR), and X-ray diffractometry (XRD) were used to characterize the chemical composition of asphaltenes at the different treatment times. Chemical changes were analyzed from the molecular structural parameters calculated by the above-mentioned spectroscopic techniques. Possible changes in the asphaltene cluster structures were analyzed using XRD. This work explores the application of plasma technologies to modify the chemical composition of asphaltenes and obtain valuable chemical products resulting from a plasma treatment process.