Efficient recovery of extra-heavy oil using a naturally abundant green solvent: Toward a more sustainable oil-solid-water separation

Abstract

Non-aqueous extraction (NAE) at ambient temperature is a promising substitute to the current commercial hot water process for mined oil sand, but several challenges remain largely due to the use of hazardous conventional organic solvents (COS) such as toluene or heptane. In this work, a more sustainable process for separating extra-heavy oil from oil sands ore using β-pinene, a naturally abundant green solvent was developed. The method used to facilitate phase separation was two-stage centrifugation. Experimental parameters investigated included centrifugal force, solvent dosage and extraction time. Results indicated that oil recovery and supernatant product quality using β-pinene were affected by these process parameters, but there was little to no sensitivity to the grade of ore tested. The β-pinene extraction, after two stages of centrifugation, achieved oil recoveries of 96% to 99% for different-grades of ore, the highest yield compared to those often obtained using either toluene or n-heptane. The total water and solids content in the supernatant of the β-pinene extract could be controlled to 0.09 wt% and this is comparable to extraction by toluene. Importantly, the quantity of β-pinene solvent residual in sand after evaporation, although inversely relating to oil recovery, was limited in the range of about 5 to 60 ppm, a level well below the regulation target for a COS. The application of β-pinene solvent as a green alternative in NAE could reduce the safety, environmental, and health concerns associated with the use of a COS.