| In upstream exploration and production of heavy and extra heavy oil, catalytic aquathermolysis is a process where steam (along with catalyst) is injected into the reservoir to improve oil production. The improvement of oil production has been associated with the reduction of heavy oil's viscosity due to the degradation of large hydrocarbon molecules (resin and asphaltene fractions) which mostly the result of desulphurization of organosulphur compounds. In this work, the potential of hematite (alpha-Fe2O3) nanoparticles, a nontoxic, inexpensive and the most stable phase of iron oxide, was investigated for aquathermolysis application. This dissertation encompasses the synthesis, surface modification, catalytic activity, and catalysis mechanism of hematite nanoparticles in aquathermolysis. In the first part of this study, a simple hydrothermal method was successfully developed to synthesize hematite nanoparticles with high purity and good crystallinity. Using this method, the size, crystal's growth rate, shape, and dispersity of the nanoparticles can be controlled by the amount of iron precursor, precipitation agent, temperature and reaction time. Furthermore, the surface chemistry of hematite nanoparticle was modified in order to improve particle dispersibility in hydrocarbon phase. Based on the result, oleic acid (OA) was successfully grafted on the surface of hematite nanoparticles by forming a monodentate interaction and changed the surface property of the nanoparticles from hydrophilic to hydrophobic. As the result, nanoparticles were able to be transferred from aqueous phase to non-polar phase, vice versa, depending on the amount of oleic acid used for modification. In the third part of this work, the catalytic activity and catalytic mechanism of hematite nanoparticles to catalyze desulphurization reaction were studied. It is found that hematite nanoparticles have a good catalytic activity to decompose a highly stable aromatic organosulphur compound, i.e. thiophene at considerably mild condition. Based on the analyses, it is suggested that the catalytic mechanism involves a cyclic phase transformation of some hematite surfaces into magnetite as thiophene was oxidatively decomposed to produce maleic acid, SO2 and CO2. However, in the presence of water as the source of active oxygen, these magnetite surfaces could be reconstructed back into hematite surfaces. In addition, it is also found that the catalytic activity of hematite can be improved by changing its surface property from hydrophilic into slightly more hydrophobic. However, further improvement on hydrophobicity reduces the activity due to the blockage of the catalytic site. Finally, when both bare and surface-modified hematite nanocatalysts were used in aquathermolysis reaction of heavy crude oil sample, the viscosity of heavy oil sample was significantly decreased by 61.52% and 74.33%, respectively. In addition, the quality of heavy oil can also be upgraded as the amount of saturated and aromatic fractions were significantly increased while asphaltene and resin fractions were reduced. |
