Effect of the Water Content on Silica Gel for the Isolation of Interfacial Material from Athabasca Bitumen
2015
Clingenpeel, Amy C. | Robbins, Winston K. | Corilo, Yuri E. | Rodgers, Ryan P.
The role of the water content adsorbed to silica gel for the selective isolation of petroleum interfacially active material was examined. Systematic variation of the amount of water adsorbed on the silica surface and its effect on retained petroleum species (interfacially active) revealed that gravimetric yields of isolated interfacial material (IM) were inversely proportional to the amount of water loaded onto the silica gel. However, with the exception of the water-saturated silica gel (66.6% water g–¹ silica gel), all silica gels investigated (11.1–53.8% water g–¹ silica gel) were stained after IM isolation, indicating that >53.8% water g–¹ silica gel is required to prevent irreversible, oil–silica interactions. Moreover, emulsion stability tests reveal that IM isolated from the water-saturated silica gel (66.6% water g–¹ silica gel) forms the most stable emulsion relative to IM isolated from the unsaturated silica gels. Molecular-level analysis of isolated IM fractions as a function of the silica water loading by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) exposes a gradual shift to a lower carbon number and double bond equivalents (DBE) in the interfacially active, OₓSy, N₁Oₓ, and N₁OₓS₁ classes as a function of the increasing silica water content. The results suggest that lower carbon number/DBE, more surface-active compounds are isolated with the water-saturated silica gel. Conversely, IM Oₓ species isolated with water saturated silica gel have similarly low carbon number ranges, but higher DBE, and occupy compositional space characteristic of asphaltenic species.
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