Asphaltene which is the cheapest fraction in bitumen was modified into a valuable product which can be added in refinement process. Bitumen is a kind of petroleum which has high viscosity and density and is recovered from oil sands. To separate bitumen from solid particle, water, and naphtha or paraffin are blended which is called froth treatment. Froth treatment can be classified two kinds; naphthenic froth treatment and paraffinic froth treatment. Because asphaltene is defined as n-pentane or n-heptane insoluble, but toluene soluble fraction, asphaltene is precipitated during paraffinic froth treatment. In paraffinic froth treatment, the removal of asphaltene is also important factor because deasphaltened oil is transported through pipeline to far refinery plants. Furthermore, asphaltene must be removed because it can cause plugging in pipeline, poisoning of catalyst, and increase of viscosity. Asphaltene forms colloidal dispersion by resin in crude oil. Asphaltene interacts with resin, asphaltene, or surfactant with $\pi-\pi$ interaction, hydrogen bonding, Coulombic interaction, and acid-base interaction. By controlling those interaction factors, dispersion or aggregation property of asphaltene can be adjusted. Thus, asphaltene was modified to increase polarity and the number of functional group because it will enable the increase of affinity. Among many methods to modify asphaltene, oxidation was selected because of cost of process in this thesis.
In chapter 2, a new method to facilitate the precipitation of asphaltene in water/n-heptane/bitumen emulsion was suggested with oxidized asphaltene. Two types of surfactants (alkylphenol-ethoxylate type and alkyl-ethoxylate type) were added to the emulsion to investigate the effect of aromatic group. Then asphaltene was precipitated when only alkylphenol-ethoxylate type surfactants were used which indicates aromatic ring is important factor in interaction between asphaltene and surfactant. Asphaltene was dissolved in dichloromethane solvent and oxidized with potassium permanganate ( $KMnO_4$ ). The oxidation degree of asphaltene was controlled by reaction time. By addition of oxidized asphaltene, about half of asphaltene and a quarter of resin was removed. Also, the precipitated asphaltene showed similar property with raw asphaltene. This result implies a possibility of the effect of oxidized asphaltene to facilitate the precipitation of asphaltene.
In chapter 3, ozonation of asphaltene was conducted as modification method of asphaltene. The oxidation process with potassium permanganate involves a lot of toxic waste such as, sulfuric acid, dichloromethane, and hydroperoxide. Thus, that process is unsuitable because of environmental problem. The asphaltene powder was grinded, strained with a sieve, and ozonized. The ozonation of asphaltene powder was interpreted by shrinking core model. The ozonized asphaltene was characterized with various analysis; element analysis, FT-IR, zeta potential, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). Then, ozonized asphaltene was added to water/n-pentane/bitumen emulsion to enhance the precipitation of asphaltene. Then, SARA removal efficiency was calculated with various dosage, solvent ratio, and degree of oxidation, when ozonized asphaltene was added. Furthermore, to evaluate the quality of deasphaltened oil, boiling point distribution of deasphaltened oil was measured. The interaction between asphaltene and ozonized asphaltene was studied by measuring size of cluster in toluene. Micron-size cluster was detected which proves the high interaction between asphaltene and ozonized asphaltene.
In chapter 4, ozonized asphaltene was applied to reduce viscosity of diluted bitumen (Dilbit) during transportation in pipeline. Naphthenic froth treatment leaves asphaltene in bitumen and diluted by naphtha to transport to upgrader. For efficient transportation of bitumen, ozonized asphaltene was added to bitumen as viscosity reducer. Particle size distribution in solution can influence on the viscosity of fluid. Because asphaltene aggregate size can be changed by ozonized asphaltene in oil phase, it was assumed that ozonized asphaltene can decrease the viscosity of diluted bitumen. Viscosity of diluted bitumen was controlled by degree of ozonation and the amount of ozonized asphaltene. Especially, the addition of ozonized asphaltene with low concentration (hundreds of ppm) and high degree reduced maximum 40 % which is equivalent to 3.1 % addition of solvent. Furthermore, the temperature dependence of viscosity and reduction efficiency was investigated. The shear modulus measurement also showed consistent result with viscosity data.
In this thesis, asphaltene was modified with potassium permanganate and ozone and used to control the size of asphaltene aggregate in bitumen. Oxidizing asphaltene resulted in higher affinity to asphaltene in oil phase. Oxidized asphaltene interacts with asphaltene by $\pi-\pi$ stacking, acid-base interaction, Coulombic interaction, and hydrogen bonding. Oxidized asphaltene tends to hide inside the asphaltene aggregate because of its hydrophilicity. As a result, the aggregate size increased and it changed the dispersion property of asphaltene aggregate. This characteristic was applied on refinement of bitumen as an additive to facilitate the precipitation of asphaltene in paraffinic froth treatment process and to reduce viscosity during transportation in pipeline.