Spectroscopic Investigation of Asphaltene Aggregation in Carbon Tetrachloride Medium Containing Microquantities of Water

Abstract

By fluorescence spectroscopy it has been established that coal derived asphaltene (CDA) forms aggregates in CCl4 medium. The new feature of this compound is that even before aggregate formation it can incorporate water molecules and the critical aggregation concentration (CAC) in nonaqueous medium increases with increase in ω (= water:CDA mole ratio). The fluorescence spectroscopic determination of the equilibrium constant (K) of the molecular complex of [60] fullerenes with CDA in carbon tetrachloride medium has revealed that K increases on addition of microquantities of water. This observation has been rationalized by assuming that the nitrogenatoms at one end of CDA molecules attach themselves to the water micropool and thus producing a different conformation with a wider distance at the other end. This pre-organization further facilitates inclusion. By utilizing fluorescence variation of [60]fullerene/CDA complex in CCl4 as continuous medium with change in ω a critical ω (=5) has been found. The formation of CDA/[60]fullerene complex has also been established by NMR spectroscopy.