Sorption and recovery of heavy oils using exfoliated graphite Part IV: Discussion of high oil sorption of exfoliated graphite

The correlation between sorption capacity for heavy oil with a viscosity of 0.004 kg/m s and pore volume measured by a mercury porosimeter was studied on exfoliated graphite samples with different bulk densities. Pore volume measured by using the conventional dilatometer (N-type cell), which gives information on the pore size from 0.004 to 4 μm, was too low to explain the sorption capacity measured. However, pore volume measured by a special dilatometer (U-type cell) for large pore sizes up to 600 μm was very closed to sorption capacity. Pore volume measured by this U-type cell showed a linear relation to sorption capacity of exfoliated graphite samples, of which the slope was the same value as the density of heavy oil used (860 kg/m³). Therefore, large pores, which are reasonably assumed to be inter-particle pores among entangled worm-like particles of exfoliated graphite, were responsible for the large sorption capacity of heavy oils. Intra-particle pores inside and cleavage-like pores on the surface of worm-like particles were assumed to assist the capillary pumping of heavy oil.