Hydrothermal Treatment of Oilsands Bitumen Froth at 400 °C: Influence of Minerals and Water on Hydrogen Transfer, Cracking, and Addition Reactions

Abstract

Following prior evidence that water and mineral solids influenced the physicochemical properties of the products derived from the visbreaking of bitumen froth at 400 °C, the present study aimed to explore the effect of water and minerals on the reaction chemistry taking place during the thermal conversion of froth. The current study investigated the relative impact of water and mineral solids on hydrogen transfer, cracking, and addition reactions during the thermal treatment of froth at 400 °C. α-Methylstyrene (AMS) was employed as a probe molecule, and selected chemical species identified in the feed and thermally converted products were monitored. Water had a major effect on suppressing the conversion of AMS, whereas the hindrance of AMS conversion by mineral solids seemed to be minor. Substantial evidence of hydrogen and methyl transfer, hydration, and addition reactions was observed through the formation of specific AMS-derived products. The potential free radical and cationic pathways for the conversion of AMS were evaluated based on the product composition of the different reaction systems. There was an indication that the availability of hydrogen donors also influenced the conversion pathways of AMS. Both water and mineral solids favored the extent of hydrogen transfer during the treatment. However, their specific effect on promoting transfer hydrogenation could not be determined. AMS was not a good probe for cracking under the conditions of this study. Evidence of hydration was observed in the water-containing systems. The presence of water suppressed the formation of addition products, resulting in an overall formation of these products that was half of that observed in the absence of water. The presence of minerals during the treatment seemed to have a minor impact on the selectivity profile of addition products, although it had no apparent influence on the overall formation of these products.