Unraveling the CO and CO2 reactivity on Li2MnO3: Sorption and catalytic analyses

Abstract

Lithium manganate (Li2MnO3) was synthesized, characterized and then tested as possible carbon oxides captor material. Thus, Li2MnO3 was dynamic and isothermally tested under different CO2 or CO atmospheres. This ceramic exhibited excellent CO oxidation and subsequent chemisorption properties under reductive atmospheres, while CO2 or CO in oxygen presence were not trapped. Li2MnO3 is the first lithium-containing ceramic reported for a selective CO sorption, in reductive atmospheres, which would be of great interest in different physicochemical processes. In fact, the CO-Li2MnO3 system evolution showed that o-LiMnO2 is produced as an intermediate crystalline phase. Based on that, o-LiMnO2 was analyzed to complement the CO chemisorption analysis. The whole atypical and unique reaction path was evidenced and supported by different structural and chemical analysis performed on the isothermal products, where lithium diffusion and reactivity with CO is performed through partial Mn reduction, allowing oxygen release for CO oxidation to form CO2 which can be captured. Moreover, isothermal data was kinetically analyzed and fitted to the Jander-Zhang mathematical model. Finally, cyclic CO oxidation-carbonation and decarbonation on Li2MnO3 showed interesting efficiencies, which however would be enhanced. Hence, Li2MnO3 presents interesting properties as CO oxidant and captor material, in non-oxidative conditions.