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

Abstract

･ 7Al 2 O 3 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 CaCO 3 and Al 2 O 3 . We attempted to fabricate 12CaO ･ 7Al 2 O 3 electride using limestone as a raw material instead of using high purity CaCO 3 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 CaCO 3 , 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 N 2 and O 2 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 CH 4 was identifi ed. It is implied that the desorbed CO originates from CO 2 in the atmosphere. This result indicates these samples might selectively adsorb CO 2 and CH 4 as compared with N 2 and O 2 . Furthermore, for the limestone derived samples, the selectivity of CO 2 and CH 4 adsorption was improved and this result indicated the possibility that the CO 2 adsorption capacity of these samples is higher than that made from high purity CaCO 3 . 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 ･ 7Al 2 O 3 electride.