Heats of adsorption and desorption of CO 2, CH 4, SO 2, O 2 AND N 2 on microporous carbons

Abstract

Flow adsorption experiments have been carried out on CH 4, O 2, N 2 and H 2O with active carbons at a range of pressures and temperatures. The equipment used was a new model Microscal Flow Adsorption Microcalorimeter in which the adsorption and the associated heat evolution could be measured simultaneously with the aid of appropriate down stream detectors. The flow methods permitted to study the sequential adsorption and desorption of the gases, and repetition of the cycles to an assessment of the adsorption reversibility. The effect of temperature on the reversibility was investigated up to 220 °C. The pressures used for the adsorption of the permanent gases ranged from atmospheric to 50 bar g. The use of the flow adsorption microcalorimeter methods have led to the discovery and a confirmation of the following surface properties of active carbons. 1. (1) The relatively high affinity of O 2 for the carbon surfaces compared with that of N 2. 2. (2) Strong effect of pressure on the heats of sorption of CH 4 and N 2. 3. (3) Partly irreversible adsorption of CO 2 from helium and its activation of the adsorption of O 2. 4. (4) Partly irreversible adsorption of SO 2 from helium and its activation of the subsequent adsorption of CO 2.