In Situ Electron Spin Resonance Study of Molecular Dynamics of Asphaltenes at Elevated Temperature and Pressure

Abstract

A comparison of the behavior of asphaltene molecules extracted from crude oil and dissolved in aromatic solvent as a model system with the behavior of vanadium-containing molecules in real crude oils via ESR in-situ technique showed that the changes of rotational mobility of asphaltene molecules can be related to the changes of the local viscosity and environment of the asphaltenes as well as the characteristic sizes of vanadyl-containing fragments due to aggregation/disaggregation processes in crude oils. The information about the mobility of asphaltene molecules in different local environments at different temperatures and pressures is 1

Asphaltenes: Separations, structural analysis and applications

“…There has been an inspiring research in paramagnetic centers of petroleum derivatives for last five years by EPR and ESR, especially for vanadyl porphyrin (VO 2 + ). The high sensitivity of EPR and ESR could detect low concentrations of vanadium species in asphaltenes, provide in situ information of sizes of vanadium molecules and their aggregates, distinguish different types of environments of vanadium species, and monitor environmental dynamics [31,[149][150][151] . The mechanisms of hydrodemetallization were also investigated using EPR [149,152] .…”

High-Field (3.4 T) ENDOR Investigation of Asphaltenes in Native Oil and Vanadyl Complexes by Asphaltene Adsorption on Alumina Surface

“…Different aspects of application of various electron paramagnetic resonance (EPR) and double resonance (ENDOR) techniques for the elucidation of the asphaltene architecture and the oil PC nature are covered in refs. [2,19,[32][33][34][35][36][37][38][39][40][41][42][43][44][45][46].…”

“…The effectiveness of the use of the VP as a native probe for the investigation of asphaltenes is determined by the resolved anisotropic spectral parameters (g-factor and hyperfine components, zero-field splitting, quadrupole tensors) in the EPR/ENDOR spectra, which makes VP to be orientationselective even in disordered media [40][41][42][43][44][45][46][47][48][49][50][51]. Using X-band (microwave frequency ν MW of 9 GHz, magnetic field B 0 of 0.34 T) and high-frequency (ν MW of 95 GHz, B 0 of 3.4 T, W-band) conventional and pulsed EPR/ENDOR techniques, we have shown that, on the one hand, the EPR and ENDOR spectra for VP in the initial oil samples of different genesis are similar while, on other hand, the relaxation parameters of VP (the electron longitudinal (T 1e ) and transverse (T 2e ) relaxation times) and the temperature dependences of the EPR spectra depend strongly on the nature of the sample and the method of the fractionation procedure [49][50][51][52].…”

Isolation of Porphyrins from Heavy Oil Objects

“…To study the concentrates of oil metal porphyrins other methods can be used, such as EPR spectroscopy [14,15], LDI mass-spectrometry [16], Fourier transform ion cyclotron resonance mass spectrometry [17], and high definition inductively coupled plasma mass spectrometry [18].…”