Low Temperature Fluorescence Studies of Crude Petroleum Oils

We have studied the low-temperature (133–298 K) fluorescence emission of crude petroleum oils using a combination of steady-state and time-resolved measurements. This was done, first, to see if we could generate linear correlations between the oil composition information and the fluorescence measurements and, second, to better understand how static and dynamic quenching affect fluorescence emission. It was observed that the fluorescence intensity and the lifetime of the crude oils increased rapidly with decreasing temperature down to the freezing point, and then, they either remained constant or, surprisingly, began to decrease slightly. These changes could not be correlated accurately with the compositional data available. However, despite the very large variations in sample composition, it was found that these lifetime–temperature changes followed simple Arrhenius and Eyring behavior. For the cold liquid phase, an Arrhenius model enabled the calculation of an intrinsic lifetime, the magnitude of which w...