Sodium Conversion of Asphaltenes

Abstract

Asphaltenes are a solubility class and it is the material in oil that is insoluble in a paraffinic matrix. It is a major contributor to problems in many petroleum operations such as production, transportation, refining, precipitation, crude oil emulsification, and de-emulsification, and high hydrogen consumption during hydroprocessing. Alternative strategies to current industrial practice for the upgrading of asphaltenes are therefore sought out. Alkali metals can easily give electrons and form donor-acceptor ion pairs. The electron transferred from sodium is delocalized in the aromatic. With the presence of a hydrogen source, hydrogenation of the aromatic system might take place. At the same time, for heteroatoms, there are reports about the bond cleavage and ring-opening reactions by alkali metals, which may help with desulfurization or denitrogenation. Asphaltenes from the Nexen Long Lake Upgrader was converted with metallic sodium at different temperatures below 250°C to avoid the contribution of thermal reactions. Although Na does not have a significant effect on increasing liquid yield, the aromatic H-content decreased compared to that of the feed asphaltenes. The Na did help with heteroatom removal. The results from the conversion of the asphaltenes suggested Na could react with some oxygen, sulfur and nitrogen groups in asphaltenes, which decreased oxygen, sulfur and nitrogen content. In order to understand the reaction network better, model compounds were investigated with Na as well. It was found that sulfur can be extruded from S-containing heterocycles, but nitrogen and oxygen cannot be extruded from heterocycles. In addition, multinuclear aromatics are hydrogenated by hydrogen transfer.