THE MOLECULAR NATURE OF PETROLEUM ASPHALTENES

The limitations and challenges of processing the heavier feedstocks (w hich include the naturally-occurring heavy oils and nonvolatile residu a) depend upon several factors, not the least of which is the amount o f higher molecular weight constituents (asphaltenes) present in the fe edstock. Different asphaltene contents lead to variations in the amoun t of thermal coke and also in the relative rates of catalytic reaction s as well as differing tendencies for catalyst deterioration and, henc e, in the methods chosen for refining different feedstocks. Thus, the aim of this review is to present some detail of the types of molecular species that have been identified and modeled as part of the asphalte ne matrix. The evolution of the modeling efforts will be presented. An d, although considerable debate still exists about the type of molecul ar models that should be used, new thoughts will be presented which il lustrate more novel structural designs for these species.