Pulsed discharge plasma induced hydrogenation of aromatic compound in heavy oil: Reaction mechanism upon impact by operating conditions

Abstract

Hydrogenation is an essential step for heavy oil upgrading by raising the H/C ratio but commonly requires high H2 pressure and high temperature. Non-thermal plasma provides a highly promising method for heavy oil hydrogenation at ambient conditions without a catalyst. Here we demonstrate a new approach to in-situ hydrogenation of ethylbenzene as heavy oil model compound using a pulsed dielectric barrier discharge plasma and examine the reaction mechanism upon impact by operating conditions. Results show that a higher H density is conducive to the aromatic ring hydrogenation, and the average H number added to the aromatic ring increases by ∼50% as the pulse repetition frequency increases. The high-energy electrons positively associated with the H radical density result in excessive cracking of ethylbenzene or the hydrogenated products, and the hydrogenation process is inhabited at high temperatures. Overall, a higher pulse repetition frequency, appropriate voltage amplitude, and lower temperature are determined to ensure the hydrogenation process. The present work may provide guiding principles for optimizing the reaction conditions for plasma-enabled aromatic ring hydrogenation and contribute to the future upgrading of heavy oils.