Abstract
Solvent deasphalting (SDA) is a well-known process where asphaltenes are removed from the oil using a paraffinic solvent to produce a lighter and better quality deasphalted oil (DAO). SDA has uses in refineries and bitumen upgraders. In the latter use, the DAO still needs further upgrading to make it a transportable oil that meets pipeline specifications. This doctoral thesis covers the use of thermal cracking as a DAO upgrading technology, as well as catalytic steam cracking using innovative Ni/K and Ni/Ce ultradispersed (UD) and Ni/Ce fixed-bed (FB) catalyst formulations as an alternative path to further improve upon the thermal cracking performance. A detailed reactivity study and comprehensive kinetic modeling for these DAO processing methods is conducted and discussed throughout the work.
The experimental data for the reactivity experiments is obtained in a research-scale pilot plant equipped with an up-flow open tubular reactor, which was procured, designed and constructed as part of this doctoral project. A complete set of characterization techniques is used for detailed evaluation of the performance of the processes and the analysis of relevant properties related to the quality of the liquid and gas products.
The effect of operating conditions on DAO thermal cracking including Liquid Hourly Space Velocity (LHSV), reaction temperature, total pressure and steam partial pressure was assessed and was found to be consistent with results in the literature regarding thermal cracking of residual hydrocarbons. Considerable generation of asphaltenes during thermal cracking was found to be the main drawback of this process and their production was analyzed from a kinetic point of view. Catalytic steam cracking was found to have the same relevant kinetic and rate controlling steps as that of thermal cracking in terms of conversion and the effect of operating variables, however having a catalytic effect to promote water dissociation to induce hydrogenation and enhancement of the overall product quality. Operating conditions, as well as the state of oxidation of the catalyst active phase were found to play a critical role for the appropriate performance of the catalytic process.
