Neutral fraction compounds: A representative sample of petroleum asphaltenes

In recent years many attempts to characterize petroleum asphaltenes have been made. However, these efforts have been hampered by difficulties in obtaining adequate samples, and in particular by the formation, in asphaltene solutions, of molecular aggregates of unknown association degree. These problems have hindered a better knowledge of fundamental properties of asphaltenes, such as average molecular weight and molecular weight distributions (MWD). Here they present evidence which suggests that the less polar asphaltene fraction, here called neutral, can be considered a representative sample of the total asphaltene mixture. It is thus possible to avoid the difficulties inherent in working with the total mixture.