scholarly journals Application of pulsed and high-frequency electron paramagnetic resonance techniques to study petroleum disperse systems

Georesursy ◽  
2020 ◽  
Vol 22 (4) ◽  
pp. 2-14
Author(s):  
Marat R. Gafurov ◽  
Andrey A. Ponomarev ◽  
Georgiy V. Mamin ◽  
Alexander A. Rodionov ◽  
Fadis F. Murzakhanov ◽  
...  

The spectral and relaxation characteristics of “free” organic radicals (FR) and vanadyl-porphyrin (VP) complexes in various petroleum disperse systems (PDS) like bitumen, petroleum, their high-molecular components and solutions were studied using stationary (conventional) and pulsed electron paramagnetic resonance (EPR) techniques in two frequency ranges (X- and W-bands, with the microwave radiation frequencies of about 9 GHz and 95 GHz, respectively). The features of the pulsed approaches (electron spin echo, modulation of the electron spin echo signal decay, electronic relaxation times) and high-frequency EPR for PDS investigations were examined. W-band EPR allows to resolve spectrally the lines from the different paramagnetic centers and more accurately determine their spectral characteristics. It is shown that the electron spin echo can be observed at room temperatures even at high magnetic fields of 3.4 T demonstrating the potential of application of pulsed EPR techniques for the low-cost oilfield measurements. Analysis of the VP transverse magnetization decay curve permits to identify electron-nuclear interactions with the 14N and 1H nuclei in situ while in the EPR spectra these hyperfine interactions usually cannot be detected. It is found from the W-band EPR measurements that FR lineshape cannot be fitted with isotropic parameters in contrast to the established X-band results. The observed effect of increasing the rates of electronic transverse relaxation in asphaltenes is described in the framework of a model of spectral diffusion between the fast- and slow-relaxing paramagnetic centers in supramolecular complexes of asphaltenes.

2010 ◽  
Vol 645-648 ◽  
pp. 1239-1242 ◽  
Author(s):  
Alexandra A. Soltamova ◽  
P.G. Baranov ◽  
Ivan V. Ilyin ◽  
A.Y. Vul' ◽  
S.V. Kidalov ◽  
...  

Electron paramagnetic resonance (EPR) and electron spin echo (ESE) at X-band (9.4 GHz) and W-band (94 GHz) have been used to study defects in natural diamond nanocrystals, detonation nanodiamond (ND) with a size of  4.5 nm and detonation ND after high-pressure high-temperature (HTHP) sintering with a size of  8.5 nm. Based on identification of atomic nitrogen centers N0 and nitrogen pairs N2+ detected by means of the high frequency EPR and ESE in natural diamond nanocrystals, atomic nitrogen centers N0 have been discovered in nanodiamond core in detonation ND and detonation ND after sintering. In addition EPR signal of multi-vacancy centers with spin 3/2 seems to be observed in diamond core of detonation ND.


2005 ◽  
Vol 85 (1-2) ◽  
pp. 3-18 ◽  
Author(s):  
M. Borgheresi ◽  
G. P. Bernardini ◽  
C. Cipriani ◽  
F. Di Benedetto ◽  
M. Romanelli

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