Application of PFG NMR in spectral resolution mode to study water-oil emulsions

UDK: 622.276.8:543.422.25

Key words: emulsion, nuclear magnetic resonance (NMR), diffusion, pulsed field gradient (PFG)

Authors: D.L. Melnikova, O.I. Gnezdilov, V.D. Skirda (Kazan Federal University, RF, Kazan)

The main purpose of current work is the detailed investigation of the opportunities of modern PFG NMR methods for studying the dynamic and structural properties of emulsions. As the example of emulsion for this study, the sample of direct emulsion “MC-90”, which contains 8, 90 and 2 % of oil, water and surfactant (SAS) respectively, has been created. The molecular composition of this mixture is similar to the composition of direct water-oil emulsion, which allows to use obtained results on real water-oil emulsions. To determine nuclear magnetic relaxation times 2D relaxometry methods have been used. It has been defined, that all molecular components have similar values of corresponding relaxation times (T1/T2~1). Thereby, all components satisfy the high-temperature approximation, i.e. have small correlation times of molecular motion. In particular, it has been found, that the equal diffusion coefficients for surfactant and water components - is the necessary and sufficient condition for existence of direct emulsion in the system. At the same time, by PFG NMR in spectral resolution mode it has been shown, that the feature of the investigated emulsion structure is a bimodal size distribution of dispersed in water oil-SAS formations. These results demonstrate the unique capabilities of PFG NMR for studies of complex disperse molecular structures, which include water-oil emulsions.
References
1. Nebogina N.A., Prozorova I.V., Yudina N.V., Research of emulsion formation
and precipitation in highly paraffinaceous oils (In Russ.), Oil&Gas Journal,
2008, no. 6, pp. 94–97.
2. Gamal M. E., Mohamed A.-M.O., Zekri A.Y., Effect of asphaltene, carbonate,
and clay mineral contents on water cut determination in water – oil
emulsions, J. Petrol. Sci. Eng., 2005, V. 46, no. 3, pp. 109–224.
3. Zimon A.D., Leshchenko N.F., Kolloidnaya khimiya (Colloid chemistry),
Moscow: AGAR Publ., 2001, 320 p.
4. Levchenko D.N., Begshteyn N.V., Nikolaeva N.M., Tekhnologiya obessolivaniya
na nefteperabatyvayushchikh predpriyatiyakh (Desalination technology
in oil refineries), Moscow: Khimiya Publ., 1985, 168 p.
5. Panteleeva A.R., Lodochnikov V.G., Popov K.A. et al., Implementation of
reagent Reapon-IK for in-tube demulsification and separator oil conditioning
(In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2005, no. 3, pp. 93–95.
6. Chizhik V.I., Yadernaya magnitnaya relaksatsiya (Nuclear magnetic relaxation),
St.Petersburg: Publ. of St. Petersburg University, 2004, 388 p.
7. Farrar T.C., Becker E.D., Pulse and Fourier Transform NMR, Acad. Press, 1971.
8. Song Yu-Q., Venkataramanan L., Hurlimann M.D. et al., T1-T2 correlation
spectra obtained using a fast two-dimensional Laplace inversion, Magn.
Reson. J., 2002, no. 154, pp. 261–268.
9. Peemoeller H., Shenoy R.K., Pintar M.M., Two-dimensional time evolution
correlation spectroscopy in wet lysozyme, J. Magn. Reson., 1981, no. 45,
193 p.
10. Skirda V.D., Maklakov A.I., Pimenov G.G. et al., Development gradient
NMR in studies of st ructure and dynamics of complex molecular systems
(In Russ.), Struktura i dinamika molekulyarnykh sistem, 2008, no. 2, pp. 1–6.
11. Maklakov A.I., Skirda V.D., Fatkullin N.F., Samodiffuziya v rastvorakh i rasplavakh
polimerov (Self-diffusion in solutions and polymer melts), Kazan': Publ.
of KSU, 1987, 224 p.
12. Arkhipov R.V., Kosarev V.E., Nurgaliev D.K. et al., Features of coupling between
rheological properties of oil and natural bitumen and the self-diffusion
data obtained by NMR method (In Russ.), Neftyanoe khozyaystvo = Oil Industry,
2013, no. 6, pp. 60–63.
13. Skirda V.D., Arkhipov R.V., Shkalikov N.V., Metodika opredeleniya opredelenie
massovoy doli vody i lineynykh razmerov kapel' vody v syrykh neftyakh i
vodno-neftyanykh emul'siyakh (Methods determination of mass fraction of
the water and the linear dimensions of the water droplets in crude oil and
water-oil emulsions), Kazan': Publ. of KSU, 2011, 11 p.
14. Pretsch E., Bhlmann P., Badertscher M., Structure determination of organic
compounds - Tables of spectral data, Softcover, 2009, 491 p.
15. Khaliullina A.V., Filippov A.V., Issledovanie samodiffuzii belkov v rastvore
metodom YaMR (The study of self-diffusion of proteins in solution by NMR),
Kazan': Publ. of KSU, 2013, 47 p.