A hybrid process for oil-solid separation by a novel multifunctional switchable solvent

摘要

A switchable solvent with a diamine structure called N, N, N', N'-tetraethyl-1, 3-propanediamine (TEPDA) has been synthesized through an alkylation reaction. This solvent can switch between its hydrophilic and hydrophobic states with the addition or removal of CO2, respectively. It is found that TEPDA can be applied 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 aqueouson-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. Additionally, the quality of the recovered heavy oil and the cleanliness of the residual solids are both improved. After extraction, TEPDA can be efficiently recycled by CO2 and N-2 bubbling without huge energy consumption compared to distillation. Further tests show that this water-assisted TEPDA process also performs well in detaching oil from other solid surfaces, such as metal and silica.