Molecular distillation of petroleum residues and physical-chemical characterization of distillate cuts obtained in the process

Abstract

Molecular distillation is presented as an alternative technique for the separation of petroleum residues. The technique was used to obtain 13 heavy petroleum cuts from three atmospheric residues (ARs) at 673.15 K and above. The cuts present initial and final boiling points between (673.15 and 951.15) K. To evaluate the efficiency of the technique, chemical characterization of residues and distillate cuts, which included SARA fractionation, 13C NMR, elemental composition, and density and viscosity analysis, was performed. In addition, extended true boiling point curves of crude oils by simulated distillation and by molecular distillation were compared. An increase in the viscosity and in the density was observed in all cuts with an increased molecular distillation temperature. Such behavior demonstrates that highly polar components that have a high structural complexity, such as resins and asphaltenes, are concentrated at the higher temperatures of the process. A sensitivity analysis of these two properties, together with the temperature, showed that viscosity and density decreased with increased temperature. On the other hand, the thermal expansion coefficient values obtained were equivalent to those reported in literature for petroleum products. Furthermore, a complete characterization of crude oils was made using the molecular distillation process to extend the true boiling point (TBP) curves.