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Anion and cation effects of ionic liquids and ammonium salts evaluated as dehydrating agents for super-heavy crude oil: Experimental and theoretical points of view.

Authors :
Flores, César A.
Flores, Eugenio A.
Hernández, Edgar
Castro, Laura V.
García, Antonieta
Alvarez, Fernando
Vázquez, Flavio S.
Source :
Journal of Molecular Liquids. Aug2014, Vol. 196, p249-257. 9p.
Publication Year :
2014

Abstract

Abstract: One series of ionic liquids (IL), [TOA]+ [Y] (where [Y]− =[Cl]−, [HSO4]− or [H2PO4]−), and new ammonium salts, [OCD]+ [Y]− (where [Y]=[HSO4]−, [MeSO3]− or [MePhSO3]−), were evaluated as demulsifying agents for super-heavy crude oil, at API=6.39° (MO1) and API=7.13° (MO2), with 8.46 and 8.94wt.% of asphaltenes, respectively, at dosages of 1000 and 1500ppm, using a conventional heating bottle test. At 1000ppm, the ranking of water removal efficiency for the [TOA]+ [Y]− series (in MO1 and MO2, in order to reach 96.7% and 95.4%, respectively) was [Cl]− >[HSO4]− >[H2PO4]−. For the [OCD]+ [Y]− series, the rankings for efficiency at 360min were [HSO4]− >[MeSO3]−, reaching approximately 27% in MO2, whereas [MePhSO3]− reached 1% in MO2. At a dosage of 1500ppm, the [TOA]+ [Y]− series achieved 100% water removal, showing the same order at 1000ppm. For [OCD]+ [Y]−, the order at 24h was [HSO4]− >[MeSO3]− >[MePhSO3]− for MO1 and MO2 at maximums of 85.5% and 92.3%, respectively. [OCD]+ [HSO4]− was an efficient demulsifier in tests of long duration. Quantum parameters were obtained at the semiempirical RM1 level, in order to establish a correlation with the experimental results. The molecular volume (V M), molecular refractivity (MR), dipolar moment (μ) and mean polarizability (α) of the cation and anion fragments were important factors driving the dewatering process. V M, MR and α were shown to have a direct relationship with water removal efficiency. Furthermore, absolute softness and the electrophilicity index of the cation fragments were calculated at the density functional theory (DFT) level. An increase in the softness and electrophilicity of the cations correlated with lesser effectiveness as demulsifiers. Finally, the partition coefficient of the cations showed that if the viscosity of the crude oil is low, it is possible to use ILs with a low partition coefficient (log P), but if the viscosity is high, the log P of IL should be near the [TOA]+ [Cl]− value. [Copyright &y& Elsevier]

Details

Language :
English
ISSN :
01677322
Volume :
196
Database :
Academic Search Index
Journal :
Journal of Molecular Liquids
Publication Type :
Academic Journal
Accession number :
96242291
Full Text :
https://doi.org/10.1016/j.molliq.2014.03.044