Thermal stability of the asphaltene/kerogen vanadyl porphyrins

Premović, Pavle; Jovanović, Ljubiša S.; Nikolić, Goran

doi:10.1016/s0146-6380(96)00084-8

Cited by 17 publications

(8 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The very good stability of VOTPP in SiO 2 is clearly shown by the intensity of the EPR spectra, which remains unchanged from room temperature to about 400 °C for VOTPP/BSA−SiO 2 and to about 350 °C for VOTPP−SiO 2 (Figure ). The EPR intensity rapidly decreases for heating steps at higher temperatures, indicating a degradation of VOTPP as previously observed for VO−P in asphaltene and kerogen . During this degradation, VO 2+ are oxidized in diamagnetic V(V) species.…”

Section: Resultssupporting

confidence: 67%

“…The EPR intensity rapidly decreases for heating steps at higher temperatures, indicating a degradation of VOTPP as previously observed for VO-P in asphaltene and kerogen. 24 During this degradation, VO 2+ are oxidized in diamagnetic V(V) species. It appears that the stability of VO 2+ is slightly higher in VOTPP/BSA-SiO 2 than that in VOTPP-SiO 2 (Figures 6 and 7) as the latter completely vanished after a treatment at 570 °C while the former still showed a detectable EPR spectrum at this temperature (Figures 7 and 8).…”

Section: Structure Of Vanadyl-porphyrin Trapped In Silica Continuous-...mentioning

confidence: 99%

“…VO 2+ is paramagnetic (vanadium is in the V(IV) state with a 3d 1 electron configuration), so that vanadyl−porphyrins in petroleum, coals, and rocks are easily detected with high sensitivity (criterion (iii)) by electron paramagnetic resonance (EPR) spectroscopy. , However, it is not known if the stability of such vanadyl−porphyrins is sufficiently high to protect them from complete destruction in rocks as old as 3.5−3.8 Ga, which contain some of the oldest putative traces of life and which are often deeply transformed by the effect of temperature and pressure . It is thus of fundamental interest to identify the degradation process and the degradation products of vanadyl−porphyrins in a mineral environment.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

EPR, ENDOR, and HYSCORE Study of the Structure and the Stability of Vanadyl−Porphyrin Complexes Encapsulated in Silica: Potential Paramagnetic Biomarkers for the Origin of Life

et al. 2010

View full text Add to dashboard Cite

The possibility of using vanadyl ions as paramagnetic biomarkers for the identification of traces of primitive life fossilized in silica rocks is studied by cw-EPR, ENDOR, HYSCORE, and DFT calculations. It is well-known that porphyrins, which are common to all living organisms, form vanadyl-porphyrin complexes in sediments deposited in oceans. However, the stability of these complexes over a very long time (more than 3 billion years) is not known. By encapsulating vanadyl-porphyrin complexes in silica synthesized by a sol-gel method to mimic SiO(2) sediments, we studied the structure and stability of these complexes upon step heating treatments by monitoring the evolution of the g factor and of the hyperfine interactions with (51)V, (1)H, (14)N, (13)C, and (29)Si nuclei. It is found that vanadyl-porphyrin complexes are progressively transformed into oxygenated vanadyl complexes by transfer of the VO(2+) ion from the porphyrin ring to the mineral matrix. The organic component is transformed into carbonaceous matter which contains paramagnetic centers (IOM(*) centers). To test the validity of this approach, we studied by EPR a 3490 million years old chert (polycrystalline SiO(2) rock) containing some of the oldest putative traces of life. This rock contains oxygenated vanadyl complexes and IOM(*) centers very similar to those found in the synthetic analogues.

show abstract

Section: Resultssupporting

confidence: 67%

Section: Structure Of Vanadyl-porphyrin Trapped In Silica Continuous-...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

EPR, ENDOR, and HYSCORE Study of the Structure and the Stability of Vanadyl−Porphyrin Complexes Encapsulated in Silica: Potential Paramagnetic Biomarkers for the Origin of Life

et al. 2010

View full text Add to dashboard Cite

show abstract

“…In spite of the unique opportunities, ESR spectroscopy is generally used to characterize asphaltenes and their stability as well as oil species for the presence of vanadyl paramagnetic centers and so called free radicals [33,34,35]. VO 2+ centers are known to be a part of vanadium and nickel organometallic compounds that exist mainly as petroporphyrine structures or other porphyrin-like coordination spheres around the metal in crude oils and their heavy fractions [3].…”

mentioning

confidence: 99%

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

et al. 2014

View full text Add to dashboard Cite

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

show abstract

“…Therefore, tetra-alkyl pyrroles may either have lost their metals over time and became covalently bound to the macromolecular fraction, which could shield them from further decay. (MacKenzie et al, 1980;Premovic ´et al, 1996;Killops and Killops, 2005).…”

Section: Downcore Sedimentsmentioning

confidence: 99%

The influence of oxygen exposure time on the composition of macromolecular organic matter as revealed by surface sediments on the Murray Ridge (Arabian Sea)

Nierop

Reichart

Veld

et al. 2017

Geochimica et Cosmochimica Acta

View full text Add to dashboard Cite

Thermal stability of the asphaltene/kerogen vanadyl porphyrins

Cited by 17 publications

References 32 publications

EPR, ENDOR, and HYSCORE Study of the Structure and the Stability of Vanadyl−Porphyrin Complexes Encapsulated in Silica: Potential Paramagnetic Biomarkers for the Origin of Life

EPR, ENDOR, and HYSCORE Study of the Structure and the Stability of Vanadyl−Porphyrin Complexes Encapsulated in Silica: Potential Paramagnetic Biomarkers for the Origin of Life

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

The influence of oxygen exposure time on the composition of macromolecular organic matter as revealed by surface sediments on the Murray Ridge (Arabian Sea)

Contact Info

Product

Resources

About