Asfaltenli p-Diflorobenzen Süspansiyonunda DNP Parametrelerinin Yıla Bağlı Değişimi

Petrol asfaltenleri ham petrolün en ağır, en aromatik ve en kompleks bileşenidir ve asfaltenler paramanyetiktir. Overhauser Dinamik nükleer polarizasyon (ODNP), 1.53 mT'da asfalten/p-Diflorobenzen örneklerini incelemek için gerçekleştirildi. Oksijenden uzaklaştırılarak beş yıl bekletilen asfaltenli p-difluorobenzen çözgen üç farklı konsantrasyonda çalışıldı. ODNP deneyleri tekrar yapılarak, Dinamik nükleer polarizasyon parametreleri belirlendi. Çalışmalarımızın sonuçları ve hesaplanan parametreler, özellikle çiftlenme parametresi, çekirdek ve serbest elektron spinleri arasında dipolar etkileşmeler olduğunu göstermektedir. Bu dipolar etkileşmeler, beş yılın sonunda süspansiyondaki asfalten misellerinin topaklandığını ve molekül hareketlerini yavaşlattığını göstermektedir. Elde edilen dinamik nükleer polarizasyon parametreleri literatürdeki değerleri ile karşılaştırılmış ve parametrelerin zamanla bir miktar azaldığı görülmüştür.

Year-Dependent Change of DNP Parameters in p-Difluorobenzene Suspension with Asphaltene

Petroleum asphaltenes are the heaviest, most aromatic and most complex component of crude oil and asphaltenes are paramagnetic. Overhauser Dynamic nuclear polarization (ODNP) were performed to study samples of asphaltene/p-Difluorobenzene at 1.53 mT. p-difluorobenzen solvent with asfalten in three different concentrations waiting five years with oxygen removed have been stuied. Dynamic nuclear polarization parameters were determined by performing ODNP experiments again. The results of our studies and the calculated parameters, especially the coupling parameter, indicates that there were dipolar interactions between nuclei and free electron spins. These dipolar interactions indicate that, at the end of five years the the asphaltene micelles in suspension agglomerated and that make the molecule movements slower. The obtained dynamic nuclear polarization parameters were compared with their values in the literature and it was observed that the parameters decreased slightly with time.

PDF

___

[1] Headen T.F., Boek E.S., Skipper N.T. 2009. Evidence for Asphaltene Nanoaggregation in Toluene and Heptane from Molecular Dynamics Simulations. Energy Fuels, 23: 1220-1229.
[2] Liu J., Zhao Y., Ren S. 2015. Molecular Dynamics Simulation of Self-Aggregation of Asphaltenes at an Oil/Water Interface: Formation and Destruction of the Asphaltene Protective Film. Energy Fuels, 29: 1233-1242.
[3] Aydogdu D, Cimenoglu M.A, Yalcıner A. 2006. Dynamic Nuclear Polarization in Suspensions Consisting of Xylene Isomers and Asphaltene Extracted from MC-800 Liquid Asphalt. Journal of Dispersion Science and Technology, 27: 955-961.
[4] Gizatullin B., Gafurov M., Rodionov A., Mamin G., Mattea C., Stapf S., Orlinskii S. 2018. Proton−Radical Interaction in Crude Oil-A Combined NMR and EPR Study. Energy Fuels, 32: 11261-11268.
[5] Gutowsky H.S., Ray B.R., Rutledge R.L., Untenberger R.R. 1958. Carbonaceous free radicals in crude petroleum. Journal of Chemical Physics, 28: 744-745.
[6] Yen T.F., Chilingarian G.V. 1994. Asphaltenes and asphalts 1, Elsevier, New York, 1-379.
[7] Poindexter E.H. 1959. Overhauser effect in asphalt solutions. Journal of Chemical Physics, 31 (6): 1477-1480.
[8] Kirimli H.E., Ovalioglu H., Akay C. 2017. Intermolecular Effects of Fluorocarbons on MC800 Asphaltene and their Characterization. Acta Physica Polonica A, 131 (3): 336-338.
[9] Kirimli H.E., Peksoz A., Ovalioglu H., Yalciner A. 2011. The Effect of Sample Age on Dynamic Nuclear Polarization Parameters in Asphalt Suspensions. Energy Sources, Part A, 33: 604-611.
[10] Abragam A. 1961. The Principles of Nuclear Magnetism. Chap. 8, Oxford University Press, Oxford, 323-353.
[11] Armstrong B.D., Soto P., Shea J.E., Han S. 2009. Overhauser dynamic nuclear polarization and molecular dynamics simulations using pyrroline and piperidine ring nitroxide radicals. Journal of Magnetic Resonanace, 200: 137-141.
[12] Kramer K.D., Müller-Warmuth W. 1964. Über zusammenhänge der Overhauserkernpolarisation mit der molekülbewegung, der frequenz und der relaxation in flüssigkeiten [On the relationship between Overhauser-nuclear polarization, the molecular motion, the frequency and the relaxation in liquids]. Z. Naturforsch, 19a: 375-387.
[13] Ravera E., Luchinat C., Parigi G. 2016. Basic facts and perspectives of Overhauser DNP NMR. Journal of Magnetic Resonance, 264: 78-87.
[14] Levien M., Hiller M., Tkach I., Bennati M., Orlando T. 2020. Nitroxide Derivatives for Dynamic Nuclear Polarization in Liquids: The Role of Rotational Diffusion. Journal of Physical. Chemistry Letters, 11: 1629-1635.
[15] Akay C., Yalciner A. 1995. A new weak field double resonance NMR spectrometer. Z. Naturforsch, 50a: 177-185.