Study of the Thermal Performance and Interaction of Petroleum Residue Fractions during the Coking Process

Abstract

SARA fractions (i.e., saturates, aromatics, resins, and asphaltenes) were prepared from vacuum residues of a Venezuelan crude oil and a Chinese Liaohe crude oil. Thermal performance of the fractions and their blends, plus interactions between the fractions, was then quantitatively studied by thermogravimetric analysis (TGA), derivative thermogravimetric analysis (DTG), and differential scanning calorimetry (DSC). Results indicated that the thermal processes of saturates, aromatics, and resins are endothermic to varying degrees because of thermal cracking. In contrast, both asphaltenes show exothermic behavior throughout the process. Then, it was found that there is a good linear dependency of enthalpy of fractions and blends upon the coke yield. The thermodynamic characteristic of a feedstock would change from endothermic to exothermic when its coke yield rises to some point, which is 49.1 wt % in this study. Furthermore, the difference in the coke yields and enthalpies between theoretical and experimental values revealed that synergic interactions between fractions could change the underlying chemical reaction pathway and, thus, in turn, influence the enthalpy of the thermal process. Proper selection of the blending feedstocks might therefore reduce energy consumption in coking processes in addition to inhibiting coke formation.