5 years ago

Transformation of Petroleum Asphaltenes in Supercritical Alcohols Studied via FTIR and NMR Techniques

Transformation of Petroleum Asphaltenes in Supercritical Alcohols Studied via FTIR and NMR Techniques
Anton S. Shalygin, Oleg N. Martyanov, Andrey M. Chibiryaev, Ivan V. Kozhevnikov
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.

Publisher URL: http://dx.doi.org/10.1021/acs.energyfuels.7b01630

DOI: 10.1021/acs.energyfuels.7b01630

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