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Kissinger plots for heavy oil oxidation in nano-porous and coarse-porous media (top is for LTO, bottom is for HTO)
Source publication
Increasing interest to study hydrocarbon behavior in fine porous media, awakened by the shale revolution, requires the application of suitable model porous media. In the current study we prepared nano-porous synthetic opal, profoundly investigated its morphological and textural properties, and studied the kinetics of combustion of heavy oil impregn...
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Citations
... Measurements in the W-band require a much smaller volume of the substance (tubes with a diameter of 0.1-0.8 mm, sample length 3-10 mm), which can be considered as an additional advantage of measuring specimens of limited size, studying inhomogeneous samples, series of PDS samples after thermal and catalytic treatments, etc. (Al-Muntaser et al., 2020;Mehrabi-Kalajahi et al., 2018;Galukhin et al., 2018;Mukhamatdinov et al., 2020). ...
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 14 N and 1 H 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.
... The four components of the oil, such as saturates, aromatics, resins, and asphaltenes (SARA), were separated and quantified by extraction (n-alkane) and further chromatographic separation of the nonasphaltic oil components through columns filled with alumina. 46,47 Elemental analysis of crude oil was carried out on a PerkinElmer 2400 Series II elemental analyzer based on dynamic flash combustion of the sample. 46 The corresponding data are presented in Table 1. ...
The presence of paramagnetic species such as vanadyl complexes (VO2+) and free carbon radicals in petroleum disperse systems (PDS) like crude oil, bitumen, or kerogen causes significant interest of studying the structure of PDS high molecular weight components and its effects on the physical and chemical properties of PDS products by magnetic resonance techniques. However, the lack of detailed studies keeps the exact structure, aggregation mechanism and interaction with complex composites of PDS still disputable. In this contribution, detailed EPR and NMR investigations, including advanced fast field cycling dynamic nuclear polarization, of heavy crude oil focused on vanadyl complexes are presented. A perceptible room temperature 1H DNP solid effect at X-band (magnetic field of 300-400 mT corresponding to the EPR frequency of 9.5 GHz and NMR frequency of 14.6 MHz), with enhancement ± 5 is observed at moderate microwave irradiation power in crude oil with a high concentration of VO2+, while no Overhauser DNP contribution is found. Using NMR T2-encoding, DNP spectra and molecular dynamics, two components are distinguished, from which the one with slower dynamics exhibits higher DNP enhancement via VO2+ complexes. The observed difference is discussed in terms of electron-nuclear interaction and relative parts of hyperpolarized nuclear spins using an advanced model for DNP data simulation.
... From the analysis of 1 H ENDOR spectra, it could be supposed that vanadyl porphyrin complexes participate in the formation of asphaltene aggregates (at least in the studied films) through the functional groups rather than π − π interactions. It appears that application of double resonance techniques, especially at high frequencies (high magnetic fields), could significantly improve the understanding of the mechanisms of the aggregation (complex formation, self-organization) of various oil constituents and other high-molecular disordered systems of biogenic and synthetic origins [66,67]. ...
Vanadyl porphyrin complexes in asphaltenes from heavy (Karmalinskoye) oil and in asphaltene films obtained as a result of adsorption on the surface of aluminum oxide were studied by electron paramagnetic resonance (EPR) and double electron-nuclear resonance (ENDOR) in the W-band frequency range (microwave frequency of 95 GHz, magnetic field of 3.4 T). Mims ENDOR spectra from 1 H and 27 Al nuclei are observed. ENDOR spectra are different for native oil and asphaltenes from one side and the adsorbed samples from the other side while no significant changes in X-(microwave frequency of 9 GHz) or W-band EPR spectra are found. The results allow supposing that vanadyl porphyrin complexes (at least in the studied asphaltene films) participate in the formation of asphaltene aggregates through the functional groups rather than π − π interactions. The data show the feasibility of the commercial pulsed ENDOR approaches for the investigation of crude oils and their constituents under external influence.
... Therefore, silica colloidal crystals may find other important applications where nanoporous materials are critical, such as in studying the nanoconfinement effect. 14 However, such applications require to better define the pore size and pore size distribution (PSD) of colloidal crystals. These characteristics affect diffusion permeability, 15,16 adsorption, and other properties related to mass transfer and heat transfer 17,18 in porous systems. ...
We prepared silica colloidal crystals with different pore sizes using isothermal heating evaporation-induced self-assembly in quantities suitable for nitrogen porosimetry and studied their porous structure. We observed pores of two types in agreement with the description of silica colloidal crystals as fcc packed structure containing octahedral and tetrahedral voids. We calculated the sizes of these pores using Derjaguin-Broekhoff-de Boer theory of capillary condensation for spherical pores. We also described the pore geometry mathematically and showed that the octahedral pore radii measured experimentally matched closely the radii of the spheres of the same pore volume. In the case of the tetrahedral pores the proposed approach underestimated the pore radius by ca. 40%. Overall, this simple geometrical description provides good representation of the porous system in silica colloidal crystals.
