A data-mining
and Bayesian learning approach is used to model the
reaction network of a low-temperature (150–400 °C) visbreaking
process for field upgrading of oil sands bitumen. Obtaining mechanistic
and kinetic descriptions for the chemistry involved in this process
is a significant challenge because of the compositional complexity
of bitumen and the associated analytical challenges. Lumped models
based on a preconceived reaction network might be unsatisfactory in
describing the key conversion steps of the actual process. Fourier
transform infrared spectra of products produced at different operating
conditions (temperature and time of processing) of the visbreaking
process were collected. Bayesian agglomerative hierarchical cluster
analysis was employed to obtain groups of pseudospecies with similar
spectroscopic properties. Then, a Bayesian structure-learning algorithm
was used to develop the corresponding reaction network. The final
reaction network model was compared to the anticipated reaction network
of thermal cracking of a model alkyl tricyclic naphthenoaromatic compound,
and the agreement was encouraging. The reaction model also indicates
that the outcome of thermal processing is the increase in lighter
and more aliphatic products, which is consistent with experimental
findings. Pseudokinetics were obtained for the reactions between the
pseudospecies based on the estimated parameters of the Bayesian network.
An attractive feature of the model is that it can be embedded into
a process control system to perform real-time online analysis of the
reactions both qualitatively and quantitatively.