BECAS
HERNANDEZ NUÑEZ Maury Sabrina
artículos
Título:
EFFECT OF TEMPERATURE ON THE EPR SPECTRUM OF ASPHALTENES
Autor/es:
MAURY HERNÁNDEZ; OLGA CASTELLANO ; PEDRO SILVA
Revista:
ACTA CIENTIFICA VENEZOLANA
Editorial:
Acta Cientifica Venezolana
Referencias:
Lugar: Caracas Distrito Capital; Año: 2015 vol. 66 p. 157 - 162
ISSN:
0001-5504
Resumen:
Electron paramagnetic resonance (EPR) is used to analyze asphaltenes from different crude oils and vacuum residues from the ?Hugo Chávez? Orinoco Oil Belt in the temperature range 90 < T < 670 K. Critical temperatures Tc1 obtained for free radicals are in accord with those determined for the most intense signal in the vanadium multiplet. Only three of the samples studied have critical temperature Tc2 and cracking temperature. Curie temperatures obtained for free radicals are in the range −23 < Tc < −200 K. For the most intense signal in the vanadium multiplet, we observe that 1/AN increases as a function of temperature for all the studied samples. This behavior may indicate a possible change in the oxidation state of vanadium undetectable by EPR. Critical temperatures Tc2 and cracking temperatures are not observed. Curie temperatures for the most intense signal in the vanadium multiplet are in the range −19 < Tc < 67 K.