Prediction of the Distillate and SARA Content of Visbroken Bitumen, Vacuum Bottoms, and Deasphalted Oil

Methods to predict the final properties of visbroken bitumen and bitumen fractions are useful for the design of upgrading processes. Previously, correlations were proposed for the density, viscosity, and stability of visbroken products as a function of the measured feed properties, conversion, and product composition. The composition was defined in terms of the distillate content (D) and the saturate, aromatic, resin, and pentane-insoluble asphaltene contents of the distillation residue (SARA). However, for design purposes, it is necessary to predict rather than measure the product composition. The objective of this study was to develop correlations for the product distillates, saturates, aromatics, resins, and asphaltenes (DSARA) composition. To do so, seven different feeds including three Western Canadian bitumens, two partially deasphalted bitumens, a fully deasphalted bitumen, and a vacuum residue fraction were thermally cracked in two different continuous visbreakers at constant pressure over a range of conversions. The simulated distillation assay, gas yield, pentane-insoluble asphaltene content, toluene-insoluble (TI) content, distillate content, and residue SARA contents of each feed and product were measured. Conversions were determined from the SimDist assays and ranged from 5 to 46%. First, correlations were developed for the product DSARA contents as functions of the measured conversion and feed composition. The average absolute deviation (AAD) for the correlated composition was within the experimental error (±1.0 to ±3.0 wt % depending on the component). Next, the correlations were applied with a conversion determined from the reactor temperature profile and space time by using a previously developed method. Finally, the correlations were applied with feed DSARA content determined from readily available feed oil measurements (SimDist assay, oil density, and asphaltene content) using a previously developed method. In all cases, the AAD remained within experimental error.