Article pubs.acs.org/EF
Size Distributions of Sulfur, Vanadium, and Nickel Compounds in Crude Oils, Residues, and Their Saturate, Aromatic, Resin, and Asphaltene Fractions Determined by Gel Permeation Chromatography Inductively Coupled Plasma High-Resolution Mass Spectrometry German Gascon,†,‡,§ Vicmary Vargas,‡,§,∥ Llinaber Feo,† Olga Castellano,† Jimy Castillo,∥ Pierre Giusti,⊥ Socrates Acavedo,∥ Charles-Philippe Lienemann,# and Brice Bouyssiere*,‡,§ †
PDVSA Intevep, Apartado 76343, Caracas 1070-A, Venezuela Institut des Sciences Analytiques et de Physico-Chimie pour l’Environnement et les Materiaux, UMR 5254, Centre National de la Recherche Scientifique (CNRS)/Université de Pau et des Pays de l’Adour, 64000 Pau, France § Joint Laboratory C2MC: Complex Matrices Molecular Characterization, Total Research & Technology, Gonfreville, BP 27, F-76700 Harfleur, France ∥ Escuela de Química, Facultad de Ciencias, Universidad Central de Venezuela (UCV), Caracas 1053, Venezuela ⊥ TOTAL Raffinage Chimie (TRTG), BP 27, 76700 Harfleur, France # IFP Energies nouvelles-Lyon, Rond-point de l’échangeur de Solaize, BP 3, 69360 Solaize, France ‡
ABSTRACT: The size distributions of sulfur (S), vanadium (V), and nickel (Ni) compounds in four crude oils, two residues, and their saturate, aromatic, resin, and asphaltene (SARA) fractions were determined using gel permeation chromatography (GPC) coupled to inductively coupled plasma high-resolution mass spectrometry (ICP HR MS). The results show trimodal distributions of V, Ni, and S compounds in the crude oils and residues. V and Ni compounds are present in both resins and asphaltenes. Trimodal distributions are clearly apparent in the resins but not apparent in the asphaltenes. In the latter, the predominant compounds have a high molecular weight (HMW), even when the solution of asphaltenes is diluted by 40000-fold. In the resins, compounds with a medium molecular weight (MMW) were expected; however, HMW compounds were observed, indicating that nanoaggregates or large molecules exist in both the asphaltenes and resins. Low-molecular-weight (LMW) compounds are predominantly present in the resins and do not represent more than 22% of V and Ni present in crude oil. These compounds appear to have molecular weights similar to simple metalloporphyrins.
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porphyrinic compounds has been proposed.14−17 These compounds include other ring systems, such as chlorophylls, chlorins, corrins (reduced porphyrins), highly substituted aromatic porphyrins, and porphyrins with ultraviolet−visible (UV−vis) properties (unlike porphyrins that exhibit the Soret band).14 However, much controversy exists regarding nonporphyrinic compounds18,19 and several hypotheses suggesting that all V and Ni present in crude oil are MPs20 and that some may be trapped in either asphaltene aggregates in solution,21−25 in a supramolecular assembly of molecules,26 or in large molecules.27,28 Large compounds containing V and Ni have been investigated using size-exclusion chromatography (SEC) or gel permeation chromatography (GPC) coupled with inductively coupled plasma optical emission spectroscopy (ICP OES)17,29 or inductively coupled plasma mass spectrometry (ICP MS),2 and a bimodal distribution of V has been found with maxima at approximate molecular weights (MWs) of 800 and 9000 [polystyrene (PS) equivalent].17 In contrast,
INTRODUCTION Crude oil is a very complex mixture primarily composed of carbon, hydrogen, sulfur, nitrogen, and trace metals [nickel (Ni) and vanadium (V)].1 The oil quality is defined by the types of hydrocarbons and potential contaminant species that are present. Among the metals naturally present in crude oil, V and Ni are the most abundant.1 Because of their high boiling point, minimal V and Ni are contained in the distillates (
