Role of binary solvent and ionic liquid in bitumen recovery from oil sands

摘要

A binary solvent of ethyl acetate and n-heptane was made and applied together with ionic liquids (ILs, 1-ethyl-3-methyl imidazolium tetrafluoroborate ([Emim]BF4)) to extract bitumen from oil sands at ambient conditions. Results of bottle tests show that the bitumen recovery is highly dependent on the volume ratio of ethyl acetate to n-heptane. The maximum recovery was obtained at the ethyl acetate-to-n-heptane ratio of 3:6. With external addition of ILs, an additional improvement of approximate to 10% of bitumen recovery was observed (from 83 to 93% at the ethyl acetate-to-n-heptane ratio of 3:6). Based on the intensive investigation of key operational parameters (i.e. ILs-to-solvent ratio, agitation time, and conditioning time), a set of recommended extraction conditions were proposed to maximize the bitumen recovery. Further fractionation of the extracted bitumen together with FTIR and SEM detection on the residual solids indicated that ILs addition could increase the dissolution of bitumen fractions into solvents, while reducing the entrapment of fine particles in the solvents. The improvement of bitumen recovery by ILs addition was attributed to the enhancement of the liberation of bitumen components from mineral solids surfaces during oil sands solvent extraction. However, the asphaltenes were observed to be rejected during processing due to their accumulation at the oil-ILs interface as a film.