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UBC Theses and Dissertations

Nano-sized carbon-supported molybdenum disulphide particles for hydrodesulphurization Solnickova, Lucie


Canadian bitumen is a plentiful source of hydrocarbons. However, to obtain oils which may be sold to consumers, bitumen must be upgraded. Among other processes, bitumen upgrading includes lowering sulphur content and correcting the carbon to hydrogen ratio mostly by carbon rejection, which results in the formation of petroleum coke (PC), a byproduct which must be stored or disposed of. This study's focus was the preparation of a molybdenum disulphide (MoS₂) catalyst for a more facile removal of intercalated sulphur from bitumen, by synthesising nano-sized MoS₂ particles. Simultaneously, this study attempted to use PC as a catalyst support. Carbon-supported MoS₂ catalysts were successfully prepared by two methods using ammonium tetrathiomolybdate: reverse micelles using the water/IGEPAL CO-520/cyclohexane system, and incipient wetness impregnation from ultra pure water. MoS₂ prepared by impregnation was supported on PC, and MoS₂ prepared by reverse micelles was supported on both PC and activated carbon (AC). Catalysts prepared by reverse micelles contained nanosized MoS₂ with low stacking order, and the catalyst prepared by impregnation consisted of long sheets of MoS₂ with a higher stacking order. The catalysts were screened for hydrodesulphurization activity in a novel slurry-phase batch microreactor using dibenzothiophene as a model compound. The overall rate constant for DBT conversion per gram of molybdenum for the MoS₂/PC prepared by impregnation was greater than that for the catalysts prepared by reverse micelles in the temperature range of 350 - 375 °C. MoS₂ supported on AC and PC showed a similar activity toward catalysing the HDS of DBT when the MoS₂ was prepared by reverse micelles; therefore, PC is a good alternative support to AC for MoS₂/C catalysts prepared by this method. The rate constant associated with hydrogenation was an order of magnitude greater for the catalyst prepared by impregnation than that for the catalysts prepared by reverse micelles. It was concluded that the larger stacking order in MoS₂/PC prepared by impregnation provided more sites for hydrogenation, which resulted in an overall larger rate constant than that for the catalysts prepared by reverse micelles, whose MoS₂ stacking orders were minimal due to the small particle size.

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