Adsorption of C20-C36 linear paraffins on the amorphous microporous silica-alumina ERS-8 was studied at vapor phase and liquid phase conditions. Henry adsorption constants and low coverage adsorption enthalpies were determined using the pulse chromatographic method at temperatures between 90 and 370 degrees C in gas phase. The low coverage adsorption enthalpy increases linearly with carbon number with 5.5 kJ/mol per additional methyl group. Competitive adsorption in liquid and dense vapor phase conditions was studied by performing column breakthrough experiments with various binary C20-C36 n-paraffin mixtures diluted in short chain length alkane solvents or undiluted as bulk mixture, at temperatures ranging from 25 to 300 degrees C and pressures from 3 to 110 bar. Both the adsorption capacity and the selectivity are strongly temperature and pressure dependent. At low temperature and high pressure, all n-paraffins are adsorbed equally and no separation is possible. With increasing temperature and decreasing pressure, the density of the bulk phase decreases, and a transition from a pure liquid paraffin stream to a dense vapor stream occurs. In such conditions, longer n-paraffins are adsorbed preferentially compared to the shorter n-paraffins. The selectivity increases with increasing difference in chain length between the adsorbing n-paraffins.