Metal halides (NaCl, MgCl2, and CaCl2) are naturally present in oilsands deposits. The impact of these salts on bitumen upgrading are mainly described in terms of fouling and corrosion of equipment. Corrosion is caused by HCl formed during the hydrolysis of the metal halides or through the reaction of metal halides with naphthenic acids present in the oil at temperatures &gt;200 °C. In our previous study, it was observed that mild halogenation of asphaltenes resulted in a harder and more complex material compared to the raw asphaltenes. In addition, halogenation reaction changed the solubility of asphaltenes, i.e., asphaltenes were insoluble in both aromatic and paraffinic solvents, like coke. Considering that bitumen originally contains metal halides and asphaltenes are coke precursors during bitumen upgrading, it was postulated that the native metal halides could be involved in coke formation during bitumen upgrading in ways not previously appreciated. The objective of this work was to investigate the influence of metal halides on coke formation. The hypothesis that metal halides could affect the chemistry and consequently increase yield of coke was evaluated by thermal treating Athabasca vacuum residue at 400 °C for 1 h in the presence and absence of different metal halides (NaBr, CaBr2, MgBr2, CoBr2, and ZnBr2). Bromides were chosen instead of chlorides to facilitate analyses. It was expected to observe an increase in coke yield in the treatments performed in the presence of metal halides. As speculated, coke yield of the reactions performed in the presence of a metal halide was higher than the coke yield obtained in the absence of metal halides, except for NaBr, in which the coke yield (2.2 + 0.3 wt%) was similar to the control sample (2.5 + 0.2 wt%). The highest coke yield (10.2 + 0.8 wt%) was obtained with ZnBr2. Liquid and coke products were characterized by different analytical techniques. It is hypothesized that the metal halides can increase coke yield by participating in the free radical chain mechanism in coke formation, halogenating olefins and aromatic compounds, and/or the halide acid formed at high temperatures may catalyse Friedel-Crafts alkylation between olefins and aromatics that results in heavier material that will contribute to coke formation.

Influence of metal halides on coke formation

253rd National Meeting (2017)

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