MECHANISMS OF ASPHALTENE AGGREGATION IN TOLUENE-HEPTANE MIXTURES

The kinetics of asphaltene aggregation in toluene-heptane mixtures has been studied by photon correlation spectroscopy (PCS). The PCS techni que was adapted for investigation of opaque Liquids. We examined the n atural asphaltenes of various origin as well as the same ones with che mically modified metal-porphyrin kernels. The concentration of asphalt enes in toluene varied from I to 10 g/l. The theoretical model develop ed employs Smoluchowski fundamental approach. It allowed us to describ e quantitatively the experimental curves for which the universal behav ior was found. At asphaltene concentrations below the critical micelle concentration the diffusion limited aggregation (DLA) solely is obser ved. Above the CMC the reaction limited aggregation (RLA) occurs in th e initial stage of particle growth. Then, the aggregation mechanism go es to the DLA. The results obtained prove asphaltene aggregation in hy drocarbon solutions is similar to that of typical colloids. (C) 1998 P ublished by Elsevier Science B.V. All rights reserved.