Results 81 to 90 of about 225 (136)
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Molecular composition of vanadyl porphyrins in the gilsonite
Journal of Fuel Chemistry and Technology, 2020Abstract A gilsonite from Qingchuan (Sichuan province, China) was separated into several fractions and characterized by various techniques. The vanadyl porphyrins were determined by inductively coupled plasma optical emission spectrometer, ultraviolet-visible spectrophotometry, high-temperature gas chromatography-atomic emission detector, and ...
Quan Shi, Guangyou Zhu
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Thermal stability of the asphaltene/kerogen vanadyl porphyrins
Organic Geochemistry, 1996Abstract Thermal stability of vanadyl porphyrins incorporated into the asphaltene/kerogen structures of the Dead Sea asphalt “float”, the La Luna Mara limestone and the Serpiano marl was studied by electron spin resonance (ESR). Comparative studies were also made on alkyl vanadyl porphyrins such as deoxophylloerythroetioporphyrins and (extracted and ...
Göran S Nikolic, Pavle I Premović
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High-performance liquid chromatography of vanadyl porphyrins
Analytical Chemistry, 1985A rapid, highly reproducible high-performance liquid chromatographic method is described for the analysis of vanadyl porphyrins from fossil fuels. The ability to separate structural as well as positional isomers is also demonstrated. This method eliminates the problems and ambiguities associated with the demetalation of porphyrin mixtures which is ...
Padmanabhan Sundararaman
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Are vanadyl porphyrins products of asphaltene/kerogen thermal breakdown?
Fuel, 1997The idea was examined that during early stages of thermal maturation of source rocks or petroleums, the release of bound vanadyl (VO2+) porphyrins (P) from the immature asphaltenes or kerogen could contribute to an increase in extractable VO2+-P. To simulate such a change in the laboratory, the Dead Sea ‘floating’ asphalt and total organic (bitumen ...
Pavle I Premović
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Incorporation of vanadyl porphyrins into kerogen structures during catagenesis
Fuel, 2000Natural vanadyl (VO 21 )‐deoxophylloerythroetioporphyrins (DPEP) are shown to be capable of reacting and quantitatively incorporating into the immature kerogen model materials (torbanite, lignites, subbituminous coal and an immature lacustrine kerogen) at 2008C for 72 h in the absence/presence of air oxygen.
P.I Premović +3 more
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Chemistry of Vanadyl Porphyrins
Tetrahedron, 1978Abstract The chemistry of vanadyl porphyrins has been explored using vanadyl octaethylporphyrin as the type substance, and with special reference to the occurrence of such substances in petroporphyrins. Spectroscopic properties (electronic spectra, IR spectra, mass spectra) are described, and electronic spectra are employed to detect the occupation ...
R. Bonnett +3 more
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Diastereoisomers in sedimentary vanadyl porphyrins
Energy & Fuels, 1990The observation that the product of vanadyl insertion into the free-base porphyrin 15 I -methyl-15,17-propanoporphyrin separated into two near equal area peaks on HPLC analysis precipitated an investigation into the structure of both vanadyl porphyrins.
Christopher J. Boreham +2 more
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ChemInform Abstract: CHEMISTRY OF VANADYL PORPHYRINS
Chemischer Informationsdienst, 1978AbstractDurch Reaktion von Oktaethylporphyrin mit Vanadylsulfatdihydrat in Essigsäure‐Pyridin (2 : 1) in der Siedehitze wird die Verbindung (Ia) erhalten.
R. BONNETT, P. BREWER, K. NORO, T. NORO
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Electrochemical studies of tetraphenylporphyrin and vanadyl porphyrin
Science in China Series B: Chemistry, 1997The electrochemical reductions and oxidations of tetraphenylporphyrin (TPP) and vanadyl porphyrin (TPP-VO) were investigated in dimethylformamide at platinum, glass carbon and microdisk electrodes. A new electrode reaction mechanism of TPP and TPP-VO is proposed. The kinetic parameters have also been determined.
Qiankun Zhuang, Xiaoxia Gao
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Geochimica et Cosmochimica Acta, 1993
Abstract Correlations are demonstrated between steroid maturity parameters and the porphyrin maturity parameter (PMP) which is based on the ratio of specific vanadyl porphyrins C 28 E (C 28 E + C 32 D) measured by HPLC. Measurements from a global selection of > 100 rock extracts and oils show that PMP parallels changes in the
Padmanabhan Sundararaman +1 more
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Abstract Correlations are demonstrated between steroid maturity parameters and the porphyrin maturity parameter (PMP) which is based on the ratio of specific vanadyl porphyrins C 28 E (C 28 E + C 32 D) measured by HPLC. Measurements from a global selection of > 100 rock extracts and oils show that PMP parallels changes in the
Padmanabhan Sundararaman +1 more
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