Measurement of Vacuum Residue and Asphaltene Fluid Properties at Process Conditions

The vacuum residue fraction of petroleum, comprising material with a normal boiling point of over 524°C, is a complex mixture of components with a wide range of molecular weight and chemical structure. The emphasis in process development and design for conversion of the vacuum residue fraction has tended to focus on the chemistry of the feed and the cracked products, and to some extent the chemistry of the transformation between the two. Most observations of the changes during the reactions of vacuum residue are based on laboratory measurements at room temperature and pressure. Consequently, we focus on the yields of solubility fractions such as the toluene-insoluble fraction (i.e. coke) and the toluene-soluble-heptane insoluble fraction (i.e. asphaltene), or the mesophase characteristics of the coke solids. To a significant degree, however, these observations fail to define some of the key fluid properties that govern the operation of reactor systems. In addition to defining the fluid phases that are present in a reactor during conversion of vacuum residue, we need to consider their interactions with each other, surfaces in the reactor, and catalysts. The properties of the vacuum residue fluids and reaction products that control these interactions are the viscosity, the surface tension and the contact angle. This review will first summarize the phenomena in conversion of vacuum residue that depend critically on fluid properties, then present recent work on the measurement of fluid properties at actual reactor conditions. We will then close with a summary of the key fluid properties that remain to be determined.