Laboratory pyrolysis of asphaltene/kerogen vanadyl porphyrins

摘要

The thermal stability of vanadyl (VO~(2+)) porphyrins (P) incorporated into the asphaltene/kerogen structures of the Dead Sea (DS) asphalt "float", the La Luna Mara (LLM) limestone and the Serpiano (Se) marl was studied by electron spin resonance (ESR). Comparative studies were also made of synthetic alkyl VO~(2+)-P: (C_(32)) deoxophyl- loerythroetioporphyrin (DPEP). According to these studies, alkyl VO~(2+)-P predominate by far within the asphaltene/kerogen framework. These P are stable up to 400 ℃ during laboratory heating and at this temperature their content sharply decreases. At 500 ℃ and 600 ℃, the asphaltene/kerogen VO~(2+)-P content follows a similar pattern to that at 400 ℃, except that at 600 ℃ it was reduced to a non-detectable point in less than 12 h. In addition, it is implied that a high proportion (ca. 60% of original asphaltene/kerogen alkyl VO~(2+)-P) is transformed during this pyrolysis into relatively stable (at temperature ≥ 400 ℃) multiaryl VO~(2+)-P incorporated into the asphaltene/kerogen matrix.