Effect of modification by Gemini cationic surfactant on the properties of slurries prepared with petroleum coke: Experiments and molecular dynamics simulation

In order to improve the properties of petroleum coke water slurry (PWS), a quaternary ammonium Gemini cationic surfactant, 14-3(OH)-14(2Cl) (G14), was chosen to modify the surface chemistry of Lanqiao petroleum coke (LQ). Compared with the single additive of naphthalene sulfonate-formaldehyde condensate (NSF), the compound additive G14&NSF greatly decreased the apparent viscosity of PWS prepared with 73% solid loading of LQ from 789 mPa.s to 623 mPa.s at 25 °C. However, with the increase in temperature, the viscosity-reducing effect of G14 decreased. At the temperature range of this experiment, the static stability of PWS was enhanced remarkably to 7 d, without any deterioration of its rheological behavior. The modification mechanism of G14 on the properties of PWS was ascribed to the apparently strengthened NSF adsorption and the increased absolute zeta potential of LQ particles after pre-adsorption of G14. The adsorption mechanism of the compound additive G14&NSF on LQ particles was investigated by both experiments and MD simulations. The results showed that G14 was adsorbed on LQ particles by a lateral horizontal adsorption mode, which provided more active adsorption sites for NSF mainly via electrostatic interaction, cation-π interaction or the synergistic effect of these two interactions.