(275f) Enhanced Oil-Solid Separation By Multifunctional Switchable Solvents

A kind of process aids, switchable-hydrophilicity tertiary amines (SHTA), have been synthesized and applied to enhancing oil-solid separation with or without assistance of hydrocarbon solvent. This solvent can switch between its hydrophilic and hydrophobic states with the addition or removal of CO₂, respectively. When working together with the hydrocarbon solvent, it is observed that the addition of SHTA solution (e.g., triethylamine, N, N-dimethylcyclohexylamine, etc.) facilitates the recovery of heavy hydrocarbons and improves the quality of bitumen product by surface modification. When working individually or with water, the SHTA solution (e.g., N, N, N′, N′-tetraethyl-1, 3-propanediamine , TEPDA) is found to perform as two different roles: as an organic solvent and can be ionized in water to form cations. With these properties, TEPDA was proven to perform well with water in separating heavy oil from a carbonate solid surface, resulting in over 10% additional oil recovery. A mechanistic study shows that in this aqueous/non-aqueous hybrid process, TEPDA acts mainly as a solvent in softening and dissolving heavy hydrocarbons (dissolution effect). Meanwhile, a small amount of ionized TEPDA in the aqueous phase acts as a surface-active material accumulating at the oil-water and water-solid interfaces (interfacial modification). Both of these effects work to enhance the detachment of oil from solid surfaces. Similar to those in above hydrocarbon system, the quality of the recovered oil and the cleanliness of the residual solids are both improved. Further tests show that this water-assisted TEPDA process also performs well in detaching oil from other solid surfaces, such as metal and silica. The above results show that the switchable solvent would be a promising ‘green chemicals’ in oil production or soil remediation.

KEYWORDS: Switchable solvent; Solvent extraction; Unconventional oil; Oil-solid separation; Diamine

References:

[1] Xingang Li, Ziqi Yang, Hong Sui, Ashish Jain and Lin He, A hybrid process for oil-solid separation by a novel multifunctional switchable solvent, Fuel, 2018, 221: 303-310.

[2] Hong Sui, Lin Xu, Xingang Li and Lin He, Understanding the roles of switchable-hydrophilicity tertiary amines in recovering heavy hydrocarbons from oil sands, Chem Eng J, 2016, 290: 312–318.