Readsorption and Adsorption-Assisted Desorption of CO2 on Basic Solids

Abstract

The desorption of 13CO2 from the surface of basic oxides based on modified MgO was examined at conditions of chemical equilibrium using a 13CO2/12CO2 isotopic switch method. 13CO2 desorption rates increase with increasing concentration of 12CO2 in the gas phase and with increasing carrier gas flow rate, both during isotopic switch and transient temperature-programmed desorption of CO2. These effects are caused by a decrease in the probability of 13CO2 readsorption and not by faster desorption steps assisted by gas-phase 12CO2. This isotopic switch method allows the determination of desorption rates and of the density of sites that can bind CO2 reversibly at conditions typical of steady-state catalytic reactions. These measurements require, however, that we include in data analysis protocols any effects of readsorption processes.