Preparation and dynamic adsorption properties of activated carbons with tailored micro- and mesoporosity

Abstract

Carbons containing controlled levels of micro- and mesoporosity are prepared using a combination of templating and activation. Analysis by nitrogen adsorption shows that the templated carbons are predominantly mesoporous. Subsequent activation of the template carbons increases the micro:mesopore ratio. Adsorption of pentane from a dry flowing airstream reveals that the dynamic uptakes are consistent with the uptake from adsorption isotherms. Comparison with the isotherm data shows that only a limited amount of the microporosity is utilized. Increase in the micropore volume results in an increase in breakthrough time and uptake. When in competition with water vapor, the breakthrough time and capacity for pentane are both significantly reduced. Introduction of high levels of microporosity can reduce performance, as a result of the high quantities of water present. The effect of water vapor is less pronounced for octane than for pentane, as a result of its lower volatility and hence higher partial pressure. This enables octane to more readily displace water from the micropore volume, thus limiting the reduction in breakthrough time and capacity. In this case, additional microporosity does provide a beneficial effect.