Transformation of petroleum asphaltenes in supercritical alcohols—A tool to change H/C ratio and remove S and N atoms from refined products

The aliphatic alcohols (methanol, ethanol, 1- and 2-propanol) were used for the upgrading of petroleum asphaltenes. The process was performed under supercritical (sc) conditions at 350 °C. CHNSO analysis and GC methods were used to characterize the elemental and chemical composition of the products preliminarily divided into three fractions: hexane-soluble (HSF), benzene-soluble (BSF), and insoluble residue (IR). It was shown that the sc alcohols leads to the decrease of total content of sulfur and nitrogen in the products (HSF + BSF + IR) by 18–23 and 31–33 wt%, correspondingly, as compared with the initial asphaltenes (IA). The highest yield of the soluble fractions (HSF and BSF) was observed for 1-propanol and ethanol. It appeared that the alcohols used as a reaction media are partially consumed by incorporating in the product molecules as alkoxy substituents. The H and O content of HSF and BSF for all alcohols was significantly higher than that for IA. The composition of hexane-soluble fraction obtained after sc upgrading is quite similar to chemical composition of the diesel fraction, specifically to straight-run gas oil. The efficiency of each supercritical alcohol used for the upgrading of asphaltenes is analyzed and discussed.