Sorption and elution of asphaltenes from porous silica surfaces

Adsorption of asphaltene from toluene on silica sorbents of various porosities and on montmorillonite pillared with Al2O3 was studied. Asphaltene is adsorbed on the surface of pillared montmorillonite in relatively large amounts; however, the extent of adsorption is decreased by preliminary hydrophobization of the surface of the adsorbents. Asphaltene elution experiments were carried out in a flow system at high temperature (T=50, 90°C) and pressure (p=10, 40, 80 bar). Eluents used were pure toluene and toluene containing 2.5, 5.0 or 10% N-methyl-pyrrolidone (1-methyl-2-pyrrolidone). Elution experiments carried out at high pressure and at various temperatures show that the desorption of asphaltene from silica gel is strongly dependent on pressure and on the concentration of the additive included as a peptizator, N-methyl-pyrrolidone. Structural changes in the surface brought about by the adsorption and desorption of asphaltene were monitored by N2-adsorption, small-angle X-ray diffraction and FT-IR spectroscopy.