Effects of experimental conditions on the molecular composition of maltenes and asphaltenes derived from oilsands bitumen: Characterized by negative-ion ESI FT-ICR MS  

作　　者：WANG LiTao HE Chen LIU Yang ZHAO SuoQi ZHANG YaHe XU ChunMing CHUNG Keng H. SHI Quan 

机构地区：[1]State Key Laboratory of Heavy Oil Processing, China University of Petroleum [2]Well Resources Inc.

出　　处：《Science China Chemistry》2013年第7期863-873,共11页中国科学（化学英文版）

基　　金：supported by the National Natural Science Foundation of China(U1162204 and 21236009)

摘　　要：A vacuum topped Canadian oilsands bitumen （VTB） was subjected to solvent precipitation and subsequently characterized by elemental analysis, gel permeation chromatograph （GPC）, IH-NMR spectroscopy and negative-ion electrospray ionization （ESI） Fourier transform ion cyclotron resonance mass spectrometry （FT-ICR MS）. Effects of experimental conditions such as solvent types （n-Cs, n-C6, and n-C7）, solvent purity, and solvent washing time on asphaltenes yields, bulk composition, and molecular composition of detectable heteroatom compounds in ESI source were determined. Elemental nitrogen and sulfur were enriched in asphaltenes while elemental oxygen had comparable content in maltenes and asphaltenes. Molecular compo- sition of asphaltenes varies with separation conditions. The N1 and O1 species identified by ESI FT-ICR MS were enriched in maltenes. The 02 species exhibited two different double bond equivalents （DBE） distributions and solubility in normal paraffin solvents, indicating two types of molecular structures. Multi oxygen atom containing compounds mainly detected in asphal- tenes. Compound class distributions are similar for maltenes derived from n-Cs, n-C6, and n-C7 , as well as for asphaltenes. The cyclic paraffin impurities in normal paraffin solvents had a significant influence on asphaltenes yields and heteroatom molecu- lar composition. A portion of neutral N1 species and acidic 02 species adsorbed on asphaltenes could be dissolved by increas- ing washing time. Cautions should be exercised when interpreting the properties and composition of asphaltenes obtained with different experimental conditions.A vacuum topped Canadian oilsands bitumen (VTB) was subjected to solvent precipitation and subsequently characterized by elemental analysis, gel permeation chromatograph (GPC), 1 H-NMR spectroscopy and negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Effects of experimental conditions such as solvent types (n-C5 , n-C6 , and n-C7 ), solvent purity, and solvent washing time on asphaltenes yields, bulk composition, and molecular composition of detectable heteroatom compounds in ESI source were determined. Elemental nitrogen and sulfur were enriched in asphaltenes while elemental oxygen had comparable content in maltenes and asphaltenes. Molecular composition of asphaltenes varies with separation conditions. The N1 and O1 species identified by ESI FT-ICR MS were enriched in maltenes. The O2 species exhibited two different double bond equivalents (DBE) distributions and solubility in normal paraffin solvents, indicating two types of molecular structures. Multi oxygen atom containing compounds mainly detected in asphaltenes. Compound class distributions are similar for maltenes derived from n-C5 , n-C6 , and n-C7 , as well as for asphaltenes. The cyclic paraffin impurities in normal paraffin solvents had a significant influence on asphaltenes yields and heteroatom molecular composition. A portion of neutral N1 species and acidic O2 species adsorbed on asphaltenes could be dissolved by increasing washing time. Cautions should be exercised when interpreting the properties and composition of asphaltenes obtained with different experimental conditions.

关 键 词：asphaltene precipitation experimental conditions bulk properties molecular composition ESI FT-ICR MS 

分 类 号：TE626.86[石油与天然气工程—油气加工工程] O657.63[理学—分析化学]