Aromatization of Naphthenic Ring Structures and Relationships between Feed Composition and Coke Formation during Heavy Oil Carbonization

摘要

Selected characteristics and molecular structural parameters of a wide range of heavy oils originating from paraffinic, naphthenic, and intermediate crude oils were estimated, and carbonization was then performed in the form of delayed coking or the Conradson carbon residue (CCR) test to elucidate the aromatization fate of naphthenic ring structures and thus the feed composition, coke formation relationships during heavy oil carbonization. The results show that the heavy oils have very different characteristics such as density, viscosity, CCR content, asphaltene content, etc. Heavy oil may be rich in naphthenic ring structures found in molecules such as naphthenes of varying sizes; its aromaticity increases upon delayed coking, during which solid, liquid, and gaseous products are obtained. Further CCR tests of the heavy liquid products from delayed coking and the other heavy oils show that any single structural parameter such as aromaticity, aromatic ring size, or naphthenic ring size fail to account for coke product formation when heavy oils are carbonized under atmospheric pressure. However, the condensed ring (including aromatic and naphthenic) structures with no fewer than four rings fundamentally end in the coke product, showing essential aromatization and coke formation of the naphthenic structures. Because of the higher concentration of naphthenic structures, heavy oils from the naphthenic or intermediate crude oils tend to form more coke than those from the paraffinic ones.