重油梯級分離與轉化的化學基礎

趙鎖奇 史權 王麗濤

摘 要：建立了基于酸、堿改性硅膠為固定相的萃取色譜分離方法，對VTB中的石油酸和含氮化合物進行分離。分離結果表明，羧酸約占VTB的3～5wt%，中性氮和堿性氮化物約占18wt%和13wt%。電噴霧（ESI）電離直接分析重油中含氮化合物和強酸性含氧化合物結果能夠正確反映這些化合物的實際組成。通過萃取色譜分離，實現低含量和/或難電離化合物的組成分析。采用萃取色譜結合瀝青質分離方法、CID、1H/13C-NMR和ESI FT-ICR MS等分析方法對可溶質、瀝青質中的石油酸、氮化物和在堿改性硅膠上具有不可逆吸附的極性化合物進行了系統的分離和分子組成表征。可溶質中的石油酸主要是較低環數的環烷酸類化合物，而瀝青質中則主要包含多環的環烷酸、芳羧酸類化合物。ESI FT-ICR MS分析瀝青質得到的分子組成為瀝青質中所含的酸性組分的組成信息，瀝青質中占90wt%以上的非酸性組分無法在ESI電離源中電離。原料中能夠被ESI FT-ICR MS檢測的氮化物基本上都分布在膠質中，主要呈現出“孤島”結構。瀝青質雖然具有較高的氮元素含量，但無法在ESI電離源中電離。

關鍵詞：石油酸 萃取色譜 組分分離 ESI FT-ICR MS 分子組成

Abstract：Extragraphic separation methods were established to isolate the petroleum acids and nitrogen compounds， based on using modified silica gel as stationary phase. There are about 3～5 wt% acid fraction， 18 wt% nonbasic nitrogen fraction， and 13 wt% basic nitrogen fractions in VTB. By extragraphic fractionation， the composition of molecules with low content and/or hard to be ionized was obtained. It is confirmed that a direct analysis of the nitrogen compounds and strong acids in heavy oil by ESI could reflect their real composition in raw material. Petroleum acids in maltenes are those naphthenic acids with small naphthenic rings， while multi naphthenic ring acids and aromatic acids are enriched in asphaltenes. The analyzable nitrogen compounds by ESI FT-ICR MS mainly distribute in resins， and mainly present as “island”structure. Materials in acid-free fraction which accounts for more than 90.0 wt% of asphaltene is not ionizable in an ESI source. About 3 wt% irreversible adsorption fractions were recovered from alkali treated silica gel and characterized to be strong polar compounds with highly condensed structure and short alkyl side chain.

Key Words：Petroleum acid；Extraction chromatography；ESI FT-ICR MS

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