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Zhang Y.,China University of Petroleum - Beijing | Zhang L.,China University of Petroleum - Beijing | Xu Z.,China University of Petroleum - Beijing | Zhang N.,China University of Petroleum - Beijing | And 4 more authors.
Energy and Fuels | Year: 2014

Venezuela Orinoco extra-heavy-crude-oil-derived vacuum resid (VR) was subjected to supercritical fluid extraction and fractionation (SFEF) to prepare multiple narrow fractions. The SFEF fractions were analyzed by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with various ionization techniques, including positive-ion electrospray ionization (ESI), negative-ion ESI, positive-ion atmospheric pressure photoionization (APPI), and sulfur methylation followed by positive-ion ESI. The results showed that the SFEF separates the VR species by their molecular weights and degrees of molecular condensation. The mass ranges of compounds determined by various ionization techniques were comparable. The FT-ICR MS data were in agreement with the elemental analysis and molecular weight determined by gel permeation chromatography (GPC) and vapor pressure osmometry (VPO) for the extractable fractions. The molecular compositions of SFEF fractions determined by FT-ICR MS provide important clues for the understanding of the molecular composition for the unextractable end-cut (asphaltenes). Each ionization technique favors identification of certain compounds in heavy petroleum fractions and discriminates against others. APPI allows for a general overview of species present in heavy petroleum fractions, because of its ability to ionize a wide range of species. ESI is more selective toward polar species. A thorough characterization of species in heavy petroleum fractions cannot be achieved by using an ionization technique; however, it can be performed by combining various ionization techniques. © 2014 American Chemical Society. Source


Long H.,China University of Petroleum - Beijing | Shi Q.,China University of Petroleum - Beijing | Pan N.,China University of Petroleum - Beijing | Zhang Y.,China University of Petroleum - Beijing | And 4 more authors.
Energy and Fuels | Year: 2012

A commercial lignite gasification-derived middle-temperature coal tar (MTCT) was subjected to acid-base extraction to obtain acidic, basic, and neutral fractions. The neutral fraction was characterized by mass spectrometry (MS) for hydrocarbon-group-type analysis and further fractionated by extrography into six subfractions, which were characterized by gas chromatography-mass spectrometry (GC-MS). Saturate, aromatic, and resin fractions of the neutral fraction accounted for 16.4, 47.6, and 36.0 wt %, respectively. The GC-MS analysis showed that the first neutral subfraction (15.7 wt %) contained alkanes, alkenes, and cycloalkanes; the second subfraction (52.0 wt %) contained 1-6-ring aromatics; the third subfraction (4.6 wt %) contained neutral nitrogen compounds, such as indoles, carbazoles, and benzocarbazoles; the fourth subfraction (8.2 wt %) contained neutral polar compounds, such as C 8-C 28 alkyl nitriles and aliphatic and aromatic ketones, such as 4-, 5-, and 6-ketones and phenyl ketones, derived from a series of propiophenone to decanophenone; the fifth subfraction (14.9 wt %) contained 2-ketones and aromatic ketones, such as acetophenones, indanones, and acetonaphthones; and most of the sixth subfraction (1.3 wt %) cannot be eluted from GC. Electrospray ionization (ESI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to analyze the third neutral subfraction, which was enriched with neutral nitrogen compounds. In addition to indoles, carbazoles, and benzocarbazoles, FT-ICR MS analysis showed that dibenzocarbazoles and tribenzocarbazoles with various carbon numbers were present in the third neutral subfraction. © 2012 American Chemical Society. Source


Zhou X.,China University of Petroleum - Beijing | Zhou X.,Liaoning Medical University | Zhang Y.,China University of Petroleum - Beijing | Zhao S.,China University of Petroleum - Beijing | And 4 more authors.
Energy and Fuels | Year: 2014

Heavy petroleum fractions, which have distinct chemical and physical properties, are becoming important refinery feedstocks. In comparison to aromatic and heteroatom-containing compounds, the saturate compounds in heavy petroleum fractions have rarely been analyzed using recent advanced mass spectrometry methods. In this work, the compositions of saturate fractions derived from six vacuum residua (VR) of different geological origins were determined and compared. Saturate fractions were subjected to ruthenium-ion-catalyzed oxidation (RICO) derivatization and characterized with negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results showed that the VR-derived saturates consisted of n-paraffins, isoparaffins, and naphthenes with 1-10 rings. The maximum double bond equivalent (DBE) values of species in various VR-derived saturates were similar. The maximum carbon number of VR-derived saturates was up to 100. The maximum carbon numbers of naphthenes in VR-derived saturates were generally greater than that of paraffins. The relative abundances and ranges of carbon numbers of the various species in VR-derived saturates differed depending upon their geological origin and the distillation temperature of samples. Compounds with 0-6 naphthenic rings were highly abundant in the VR-derived saturates. On the basis of the results of this study, the RICO/ESI FT-ICR MS method shows promise as a potential semi-quantitative analysis for saturates in heavy petroleum fractions. © 2013 American Chemical Society. Source


Zhang Y.,China University of Petroleum - Beijing | Shi Q.,China University of Petroleum - Beijing | Li A.,China University of Petroleum - Beijing | Chung K.H.,Well Resources Incorporated | And 2 more authors.
Energy and Fuels | Year: 2011

Crude oil was subjected to extrography to obtain various acid compounds in multiple subfractions. Negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) and gas chromatography-mass spectrometry (GC-MS) were used to determine the acid compounds in the crude oil subfractions. Isoprenoidyl phenols with molecular formulas of C 27H 48O and C 28H 50O, which were previously deduced as sterol-type compounds, were highly enriched in a subfraction and confirmed by GC-MS. The mass peak with a molecular formula of C 27H 46O 2 was identified as δ-tocopherol. The eluting sequence of the various compounds in crude oil was N 1 carbazoles, followed by O 1 class acid compounds, then O 2 class acid compounds, and finally, N 1O 2, O 3, and O 4 class acid compounds. The results show that extrography is an adequate separation technique for partitioning crude oil acid compounds into various subfractions. © 2011 American Chemical Society. Source


Shi Q.,China University of Petroleum - Beijing | Shi Q.,Florida State University | Pan N.,China University of Petroleum - Beijing | Long H.,China University of Petroleum - Beijing | And 8 more authors.
Energy and Fuels | Year: 2013

Coal tar has been considered as a potential energy alternative because of dwindling supplies of petroleum. To determine if the coal tar could be refined and upgraded to produce clean transportation fuels, detailed investigation of its composition is necessary, particularly for identifying the acidic components that account for about one-quarter of the weight of the coal tar. A middle-temperature coal tar (MTCT) and its fractions were characterized by gas chromatography-mass spectrometry (GC-MS) and negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with different ion transmission modes for high-and low-mass ions. Analytical results of narrow distillation fractions from FT-ICR MS agreed reasonably well with those from GC-MS, although each technique has its own advantages and disadvantages. In this work, FT-ICR MS was demonstrated to be capable of characterizing small molecules of <100 Da using appropriate operation conditions, thus yielding mass distributions to compare to GC-MS results. A continuous distribution in double bond equivalent (DBE) and carbon number was observed with the distillates of increasing boiling point, while the composition of the distillation residue was much more complex than that of distillates. Acidic compounds containing 1-7 oxygen atoms were observed in the MTCT by FT-ICR MS, with O1 and O2 classes being dominant. Various phenolic compounds with 1-4 aromatic rings were identified on the basis of literature references, including some molecules having structures resembling known biomarkers in petroleum and coal. © 2012 American Chemical Society. Source

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