Adsorption of Hydrocarbons on Air-Reacted Activated Carbons. II. High and Low Pressure Hysteresis

Abstract

The adsorption-desorption isotherms of N 2 at 77 K and hydrocarbons (benzene, cyclohexane, 2,2-dimethylbutane, n -hexane and iso-octane) at 298 K have been determined on a series of carbons prepared by reaction of an activated carbon with dry air at 623 K. A detailed analysis of the evolution of high pressure hysteresis (HPH) and low pressure hysteresis (LPH) as a function of burn-off and the different factors conditioning their existence has been carried out. Both HPH and LPH increase with the extent of carbon burn-off; this increase in LPH has no antecedent in the literature and has been related, amongst other things, to the nature of the reaction gas, in this case air.