Methane-assisted catalytic light oil desulfurization: Catalyst design, sulfur product distribution analysis and mechanistic study

Abstract

The desulfurization of natural oil feedstock for fuel purposes is crucial for environmental protection and sustainable development. Methane is the main component of natural gas resources with low added value. Distinctive characteristics are demonstrated if methane can be directly used for oil desulfurization, instead of being converted into hydrogen via methane stream reforming for hydrodesulfurization. Here, the methane-assisted catalytic desulfurization process is specifically developed for light oils such as marine diesel oil. First, different catalyst supports are selected and compared, among which Al2O3 is confirmed to provide the most favorable reaction performances. Then, the reaction is operated under different gas atmospheres including CH4, N2, and H2, to reveal the uniqueness of methane for a desulfurization process. Next, model compound oils are selected with thiophene as the sulfur-containing oil component. Heptane and toluene are used as solvents to represent paraffin-rich and aromatic-rich oil, respectively. It is found that the structural characteristic of the oil significantly influences the desulfurization performance and product distribution, based on which the respective reaction mechanism networks are proposed. It is concluded that despite the unparalleled desulfurization performance under hydrogen, the methane-assisted desulfurization process demonstrates distinctive characteristics to prevent light end loss and oversaturation as well as the formation of H2S as the primary desulfurization product, which can be better utilized under certain circumstances.