Changes in Molecular Aggregate of Vacuum Residue Fractions Analyzed by Slow Step Scan XRD.

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  • SAKANISHI Kinya
    Institute of Advanced Material Study, Kyushu University National Institute for Resources and Environment
  • MANABE Toru
    Institute of Advanced Material Study, Kyushu University
  • WATANABE Izumi
    Institute of Advanced Material Study, Kyushu University
  • MOCHIDA Isao
    Institute of Advanced Material Study, Kyushu University

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  • ＸＲＤを用いる減圧残油中の分子凝集とその変化の解析
  • XRD オ モチイル ゲンアツ ザンユチュウ ノ ブンシ ギョウシュウ ト ソノ ヘンカ ノ カイセキ

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Abstract

A vacuum residue (VR) and its fractions of hexane-soluble (HS) and hexane-insoluble (HI) were analyzed by using a horizontal-type X-ray diffractmeter by slow step scan mode at variable temperatures, in order to clarify the changes in molecular aggregate structure during heating, solvation, adsorption, and hydrotreatment. The VR fractions showed a broad peak around 20° with sharp peaks around 22 and 24° which are ascribed to aliphatic chain entanglement and ordered packing of n-paraffins, respectively. They also showed a shoulder around 26° which is ascribed to aromatic ring stacking interactions. The asphaltene (HI) and the polar fraction in HS showed a rather clear peak around 26°, reflecting their stronger aromatic ring stacking. The peak of 26° in the HI decreased by the heating to 300°C with or without the existence of the HS, although the extent was smaller without HS solvent. The addition of toluene was also effective for the reduction of the peak around 26°. Ketjen Black (KB: carbon nanoparticles) rather selectively adsorbed the asphaltene fraction from VR at 60°C. The adsorbate (THF insoluble: THFI) strongly adsorbed on KB even after THF extraction and washing showed a broad peak around 26°, while the peak of THF extracted fraction (HI but THF soluble: HI-THFS) decreased by the adsorption treatment. The aggregate structure of the asphaltene through the aromatic plane stacking may be loosened by the heating or solvent addition. The hydrotreatment with NiMo/KB or a commercial NiMo/Al2O3 catalyst decreased the content of the asphaltene (HI) fraction by its conversion to maltene (HS) fraction at reaction temperatures below 400°C, while the hydrotreatment at 420°C increased the content of HI with its aromaticity. Based on the above results, the designs of proper solvent and the nanoparticle carbon catalysts with meso-pores are suggested very important for the solvation, depolymerization, demetallation, hydrocracking of the asphaltene without retrogressive reactions such as coke formation.

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