On the Nature of UV/Vis Absorption Spectra of Asphaltenes

Evdokimov, Igor N.; Losev, Aleksandr P.

doi:10.1080/10916460601186420

Cited by 28 publications

(30 citation statements)

References 13 publications

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“…A certain shift of the main band of the magnetic circular dichroism (570 nm) that occurs upon a decrease in the concentration of oil in the solu tion can be attributed to a decrease in the axial compo nent of the crystal field, i.e., to a slight change in the conformation of vanadyl. This possibility was previ ously observed in [11].…”

Section: Samples and Experimental Techniquementioning

confidence: 86%

“…Particular features in the absorption spectra of oil samples at these wavelengths were previ ously also observed by some authors. Thus, e.g., in [11], by subtracting the smooth curve of the strong absorption from the measured curve, an absorption maximum at 400 nm and a structured band in the range 550-650 nm were revealed, which were attrib uted by the authors of that work to porphyrin com plexes of vanadyl complexes.…”

Section: Samples and Experimental Techniquementioning

confidence: 97%

“…A specific brownish color of resins and asphaltenes is one of their characteristic features [7,8] and is determined by the occurrence of broad electronic absorption bands in the visible and UV ranges. The absorption spectra in these ranges have been studied in [9][10][11], in which the use of low concentration oil solutions made it possible to reveal a number of resonant bands in the UV and visible spec tral ranges. These works demonstrated the potential of the UV and visible spectroscopy for studying samples of crude oil.…”

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Magneto-optical activity of crude oil and its heavy fractions

et al. 2012

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INTRODUCTIONElectron spin resonance (ESR) and optical absorp tion spectroscopy methods have been widely used to reveal particular features of the molecular structure of oil and its high molecular components, primarily res ins and asphaltenes. The ESR method makes it possi ble to study the state of paramagnetic ions, in particu lar, V 4+ ions, which, as a rule, are contained in oil as porphyrin complexes of vanadyl VO 2+ [1,2]. In the ground state, the V 4+ ion has the 3d 1 configuration with the spin 1/2. A strong covalent bond, which is deter mined by a short V-O distance, leads to an axial dis tortion of the nearest environment of the vanadium ion and, as a consequence, to a strong dependence of optical and magnetic resonance spectra on the proper ties of the compound that contains VO 2+ complexes. This particular feature allowed researchers to success fully use the ESR method and the optical absorption spectroscopy for obtaining information on the local symmetry, degree of covalence, structure of electron levels, presence of defects in the matrix, etc., in com pounds that contain vanadyl complexes (e.g., [3][4][5]).In studies of the properties of oils and their heavy fractions, special attention is paid to the investigation of their IR spectra [6], which contain a large number of characteristic narrow peaks that make interpreta tion of molecular structures easier [6]. In most cases, the visible and UV spectra are described by rather smooth curves [3], which do not contain characteristic peaks and, therefore, are considered to be less infor mative. However, the absence itself of characteristic features in these spectra is directly related to the prop erties of heavy oil fractions. A specific brownish color of resins and asphaltenes is one of their characteristic features [7,8] and is determined by the occurrence of broad electronic absorption bands in the visible and UV ranges. The absorption spectra in these ranges have been studied in [9][10][11], in which the use of low concentration oil solutions made it possible to reveal a number of resonant bands in the UV and visible spec tral ranges. These works demonstrated the potential of the UV and visible spectroscopy for studying samples of crude oil.Methods of polarization spectroscopy that study natural optical activity and magneto optical effects could significantly complement the absorption spec troscopy. In both situations, the main effect under study is circular dichroism, more specifically, natural circular dichroism and magnetic circular dichroism. The natural optical activity of oil is mainly related to carbon atoms that occupy asymmetric positions, i.e., are related to four different atoms or radicals. The optical activity is very sensitive to any changes in the structure of the substance and to intermolecular inter action; therefore, it can yield valuable information on the nature of substituents in molecules (both organic and complex inorganic compounds) and on their con formations, internal rotation, etc. The magneto opti cal activity is related to t...

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Section: Samples and Experimental Techniquementioning

confidence: 86%

Section: Samples and Experimental Techniquementioning

confidence: 97%

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confidence: 99%

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Magneto-optical activity of crude oil and its heavy fractions

et al. 2012

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“…Estos, por lo general, se han usado para medir diferencias entre cambios en la concentración de asfaltenos en una misma disolución, por ejemplo, en estudios de adsorción de asfaltenos (7). Otros investigadores han propuesto un método que permite cuantificar el porcentaje de asfaltenos considerando una gran cantidad de crudos, basándose en medir la diferencia entre el crudo inicial diluido y los maltenos luego de precipitar los asfaltenos, a dos longitudes de onda distintas para corregir por línea de base y diferencias en los índices de refracción (8,9).…”

Section: Introductionunclassified

Estandarización del método espectroscópico UV-Visible para la determinación del contenido de asfaltenos en crudos pesados.

Samaniego

Rojas²,

Leone

et al. 2017

Ingeniería

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Este estudio pretende implementar una metodología para lograr determinar el contenido de asfaltenos en crudos pesados resultantes de la aplicación del proceso de desasfaltación para disminuir el tiempo de medición y reducir el volumen del disolvente en comparación con el método convencional ASTM D 3279-07. Se logró mejorar la reproducibilidad de los datos en comparación con el método convencional. El tiempo de medición se redujo a menos de 3 horas en vez de 2 días, mientras que el volumen del disolvente se disminuyó a una cuarta parte.

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“…The absorption behavior of crude oil strongly depends on the wavelength range employed. In particular, UV-Vis absorption of crude oils is due to the presence of a wide range of cyclic aromatic compounds, including asphaltenes, with the intensity and the spectral properties of this absorption being directly related to chemical composition [2].…”

Section: Introductionmentioning

confidence: 99%

Determination of Absorption and Fluorescence Spectrum of Iraqi Crude Oil

Hadi¹,

Mohammed²,

Rasheed³

et al. 2016

AJPA

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The fluorescence spectroscopy (FS) is increasingly used in petroleum technology due the availability of better optical detection techniques, because FS offers high sensitivity, good diagnostic potential, and relatively simple instrumentation. Absorption and fluorescence spectrum of crude oil was studied at room temperature using optical path cuvette 1 cm. In this work, the absorption spectra were scanned (190-1100) nm while the emission spectra were obtained at different excitation wavelengths (266, 337, 420, and 488) nm. Crude oil was diluted by absolute ethanol to prepare different concentrations of crude oil. Ethanol as a solvent was used to dilute crude oil to obtain a solution transparent and the light could be transmitted. This work considers as an additional spectroscopic tool to develop into a fast responsive system for charchtrize the crude oil.

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On the Nature of UV/Vis Absorption Spectra of Asphaltenes

Cited by 28 publications

References 13 publications

Magneto-optical activity of crude oil and its heavy fractions

Magneto-optical activity of crude oil and its heavy fractions

Estandarización del método espectroscópico UV-Visible para la determinación del contenido de asfaltenos en crudos pesados.

Determination of Absorption and Fluorescence Spectrum of Iraqi Crude Oil

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