The
aliphatic alcohols (methanol, ethanol, and 1- and 2-propanols)
were used for the first time as a reaction media for the upgrading
of crude oil asphaltenes. The process was realized in a batch reactor
under supercritical conditions (at 350 °C). The three main fractions
of the products (hexane- and benzene-soluble fractions, HSF and BSF,
and insoluble residue, IR) were analyzed using attenuated total reflection
Fourier tranform infrared (ATR-FTIR) and 1H and 13C nuclear magnetic resonance (NMR) spectroscopy to characterize structural
changes of the initial asphaltenes (IA). According to NMR data, the
aliphatics are the main part of the hexane-soluble fraction (HSF)
and benzene-soluble fraction (BSF). The alcohols were appeared to
influence the content of both aliphatics and aromatics in the products.
The content of aliphatics in the HSF increases in the line from “lighter”
to “heavier” alcohols used but reduces in the BSF. However,
the content of aromatics in the HSF increases from “heavier”
to “lighter” alcohols, while this order is reversed
for the BSF. According to the ATR-FTIR spectroscopy data, the aromatics-to-aliphatics
ratios observed for the insoluble residues are 2–3 times higher
as compared with the initial asphaltenes but 2 times lower for the
HSF. The BSF are composed of less-condensed aromatics than those of
the IA. It is shown that the alcohols used as a reaction media are
incorporated in the product molecules as alkoxy substituents in aromatic
ethers Ar–OAlk. According to NMR and ATR-FTIR data obtained,
the alkylation–dealkylation and alkoxylation reactions make
a crucial contribution to the chemical transformations of the asphaltenes.