Hydroconversion Behavior of Asphaltenes under Liquid-Phase Hydrogenation Conditions

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• 作者：Nan Jin ; Gang Wang ; Shuang Han ; Yiming Meng ; Chunming Xu ; Jinsen Gao
• 刊名：Energy & Fuels
• 出版年：2016
• 出版时间：April 21, 2016
• 年：2016
• 卷：30
• 期：4
• 页码：2594-2603
• 全文大小：570K
• 年卷期：0
• ISSN：1520-5029

文摘

To fully utilize deoiled end-cut (DOE) from selective asphaltene extraction process, Venezuela n-pentane DOE was subjected to hydroconversion in an autoclave reactor using tetralin as hydrogen donor. Venezuela DOE and its hydroconversion products were separated into gas, n-heptane maltenes (HM), n-heptane asphaltenes (HAs), and coke. The effects of reaction conditions including reaction temperature, solvent-to-feedstock (S/F) weight ratio, and reaction time on product distribution were investigated. High temperature, large S/F ratio, and long time benefited the generation of gas, HM, and coke to some extent. Under optimal conditions, over 50 wt % HAs in DOE was converted into HM fraction, with less than 3 wt % coke yield. The elemental compositions and molecular weights of HAs and HM, along with reaction time, were also analyzed. The hydrogen-to-carbon (H/C) ratio of HAs declined from 1.115 to 0.871, indicating that HAs underwent dehydrogenation and dealkylation reactions. However, the H/C ratio of HM initially increased from 1.405 to 1.548, showing that hydrogenation reaction occurred, and then decreased to 1.374 because of the cracking of HAs into HM and/or the secondary cracking of HM. The average molecular-weight decrease both for HAs and HM confirmed disaggregation and cracking reactions. The molecular composition and transformation of nitrogen and sulfur compounds before and after hydroconversion were determined by negative- and positive-ion electrospray ionization Fourier transform ion-cyclotron–resonance mass spectrometry, respectively. N₁, S₁, and O₂ classes were dominant in the feedstock. After hydroconversion, N₁ and S₂ compounds decreased in HAs, indicating that they were reactive species. N₁ compounds mainly cracked into small N₁ compounds and also condensed into N₂ compounds, while S₂ compounds generally decomposed into S₁ compounds.