FLOW ADSORPTION MICROCALORIMERTY FOR DETERMINATION OF THE HEATS OF ADSORPTION AND DESORPTION ONTO VARIOUS MICROPOROUS CARBONS

Toxic vapors may be removed from passing air streams with an activated carbon bed. The heat evolved during the removal process can affect the removal rates of the toxic vapors with the carbon bed. Flow microcalorimetry (FMC), in which the heat generated by adsorption of molecules from a gas or liquid flow stream is monitored and measured, can provide a wealth of information on the heat evolved and the adsorptive properties of activated carbon adsorbents. Heats of adsorption and desorption for each of toluene, trichioroethylene, and carbon tetrachloride from a nitrogen carrier gas stream on Ambersorb 572, a microporous activated carbon, have been evaluated and compared using FMC. In addition to Ambersorb 572, the heats of adsorption of toluene on Ambersorb 563, Maxorb AW20, Maxorb AW30, and West Vaco-A1100 activated carbons have been also determined by FMC and compared. The integral molar heat of adsorption of toluene on Maxorb AW20, a high surface area microporous activated carbon, as an example, was evaluated by two ways. a) Combining the FMC thermal results and the adsorption amount of toluene simultaneously determined with a photoionization down stream detector. b) Combining the FMC thermal results and the adsorption amount of toluene concluded from the equilibrium adsorption isotherm, determined gravimetrically using a microbalance, of toluene on Maxorb AW20. The molar heats determined by the two methods were in a qualitative agreement with each other.