Gas Adsorption Properties of 12CaO・7Al2O3 Electride Derived from Limestone

12CaO･7Al2O3 electride is one of the outstanding materials expected to be applied in various fields such as electronics and catalyst, and generally fabricated by sintering high purity CaCO3 and Al2O3. We attempted to fabricate 12CaO･7Al2O3 electride using limestone as a raw material instead of using high purity CaCO3 aiming at further industrial use, and investigated the gas adsorption properties of the fabricated samples. Three samples, two from limestone and one from high purity CaCO3, were prepared and exposed to the atmosphere for about 9 hours, and then the gas adsorption properties of them were analyzed by Py-GC/MS. As a result, desorption of N2 and O2 which are abundant in the atmosphere was not observed by heating the samples exposed to the atmosphere up to 700℃, while desorption of CO and CH4 was identified. It is implied that the desorbed CO originates from CO2 in the atmosphere. This result indicates these samples might selectively adsorb CO2 and CH4 as compared with N2 and O2. Furthermore, for the limestone derived samples, the selectivity of CO2 and CH4 adsorption was improved and this result indicated the possibility that the CO2 adsorption capacity of these samples is higher than that made from high purity CaCO3. One reason of this phenomena is inferred the changes in the electronic state of material surfaces due to the doping of impurities contained in limestones, such as Mg, Sr, and Cu, into the Ca sites of the cage-like structure in 12CaO･7Al2O3 electride.