Electrochemical behavior study towards demetallization and selective separation of vanadyl oxide tetraphenyl porphyrin from heavy oil
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2012
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Abstract
Vanadium is one of the most troublesome heavy metals present in the asphaltenic portion of oil sands deposits, mainly in the form of metalloporphyrins. These metal complexes can easily lead to the deactivation of desulfurization and cracking catalysts during the hydrotreatment and hydrocracking refining processes as well as the emission of vanadium pentoxide during combustion in stacks downstream. The problem is more pronounced for the Alberta heavy oil and oil sands producers, since bitumen contains much higher concentrations of vanadium than conventional crude.
The first part of the thesis explores a way of improving the electrochemical redox reactions by introducing dispersed nickel nanoparticles. The electrochemical behavior of the well know probe potassium ferricyanide (PFC) is monitored in aqueous and (w/o) microemulsion systems. The electrochemical behavior of PFC in aqueous solutions is well documented in the literature, while (w/o) microemulsion systems are good heavy oil model solutions. Observations and interpretations made on the PFC behavior are extended to the study of the removal of a model vanadyl compound, vanadyl oxide tetraphenyl porphyrin (VOTPP), from heavy oil model systems. In presence of dichloromethane and tetrabuhtylammonium perchlorate as a supporting electrolyte the cyclic voltammetry shows that VOTPP behaves quasi-reversibly. In heavy oil model solutiontype dichloromethane/HepTol, on the other hand, the cyclic voltammograms show an irreversible behavior as confirmed by the Randles-Sevcik plots.
The second part of the thesis investigates, in details; an observation made during electrochemical demetallization of VOTPP, and led to selective removal of VOTPP from heavy oil in tetrahydrofuran (THF) and methanol by salting-out as a result of stepwise addition of 1.0 M NaCl aqueous solution.
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Bibliography: p. 85-91
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Ouled Ameur, Z. (2012). Electrochemical behavior study towards demetallization and selective separation of vanadyl oxide tetraphenyl porphyrin from heavy oil (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/4827