Supercritical fluid extraction of bitumen using chemically modified carbon dioxide

Abstract

Surface minable oil sands are a significant source of heavy oil (bitumen) production in Canada. Supercritical fluid extraction (SFE) provides a potential means to recover bitumen, a complex mixture of hydrocarbons, from process and process waste streams generated during the extraction and processing of bitumen from surface mined oil sands. Dynamic extractions were conducted to determine the effect of two modifiers, toluene and methanol, on the extraction of hydrocarbons from bitumen using carbon dioxide (CO2) at supercritical conditions of 24 MPa and 333 K. Toluene was tested at concentrations of 5, 10 and 15 mol% whereas methanol was tested at these concentrations plus at 33.7 mol% in supercritical CO2 (SC-CO2). High temperature simulated distillation (HTSD) was used to determine the distillation profile of the extracted hydrocarbons. SC-CO2 only extracted 39 wt% of the bitumen while a methanol concentration of 33.7 mol% in SC-CO2 extracted 55 wt% and 15 mol% toluene in SC-CO2 extracted 76 wt% of the bitumen. Higher modifier concentrations lead to increased extraction efficiencies. Toluene consistently extracted more hydrocarbons than methanol. The hydrocarbons extracted when toluene was used as a modifier were consistently the heaviest hydrocarbon mixtures, with higher toluene concentrations increasing this compositional effect.