Emissions of greenhouse gases (especially carbon dioxide) into the atmosphere have cause
many environmental problems in recent years. Therefore, finding a suitable method to
reduce the amount of carbon dioxide in the atmosphere is very important. Among the
existing methods, the use of adsorbents and adsorption method is one of the most effective
methods. So far, many adsorbents for CO2 adsorption have been prepared and evaluated,
among which calcium oxide adsorbents are of special importance due to their low cost,
great activity, easy access and high porosity. However, due to the high temperature, this
adsorbent is associated with a decrease in adsorption capacity and resistance during the
calcium looping. In this study, in order to increase the mechanical and thermal resistance
of calcium oxide adsorbent, the chemical structure of this adsorbent was modified by
alumina and zirconia by precipitation method. Four CaO, CaO-10% Al2O3, CaO-10%
ZrO2 and CaO-5% Al2O3-5% ZrO2 adsorbents were prepared and evaluated under different
operating conditions in a fixed bed reactor during five carbonation-calcination cycles (The
adsorbents of the first group are exposed to 20 ml/min of pure CO2 flow for the carbonation
process and 20 ml/min of pure argon gas for the calcination process, the second group of
adsorbents are exposed to 40 ml/min of pure CO2 flow for the carbonation process and 40
ml/min of pure argon for the calcination process and the adsorbents of the third group are
exposed to 10 ml/min of CO2 flow and 20 ml/min of argon gas for the carbonation process
and 20 ml/min of pure argon gas for the calcination process). The results showed that the
two modified adsorbents CaO-10% Al2O3 and CaO-10% ZrO2 have higher stability and
resistance than the unmodified adsorbent. According to the results of XRD analysis, the
reason for the increase in the stability of these two adsorbents compared to the unmodified
adsorbent of calcium oxide was attributed to the formation of two comp