Scrutinizing the CO Chemical Capture Path in Li₂MnO₃ Samples with Different Microstructural Properties

Abstract

Hydrothermal and ball-milling procedures combined with the solid-state reaction method were proposed as alternative synthesis routes to modify microstructural Li2MnO3 powders. All these materials were compared against Li2MnO3 prepared by following the solid-state reaction method only. To totally understand the effect of the synthesis routes proposed, the modified samples were structurally and microstructurally analyzed and subsequently subjected to the CO chemisorption process. Li2MnO3-modified samples exhibited important differences and improvements during the CO chemisorption process, in comparison to the powders obtained through the solid-state reaction method, associated with important variations on their microstructural features. Specifically, the sample prepared by the hydrothermal bottom-up approach and labeled as HSS700 showed the best CO chemisorption. This result was explained based on its crystal and particle sizes, morphology, and specific surface area. Moreover, the whole analysis performed on all the samples allowed one to determine that the solid–gas interphase controls the CO chemisorption over the CO-Li2MnO3 kinetics.

Enhanced hydrogen production via assisted biomass gasification using lithium manganate as a bifunctional material

“…In the first stage, between 410 °C and 615 °C, the CO production was lower in the presence of Li 2 MnO 3 , matching the temperature range of CO capture in Li 2 MnO 3 . 45–47 Despite this phenomenon, in the second stage ( T > 615 °C), the CO production increased twice in the presence of Li 2 MnO 3 . This must be explained due to the release of oxygen from the crystal lattice, which oxidizes the glucose pyrolysis byproducts, diminishing the available oxygen.…”

“…These results are in agreement with previous solid-state synthesis reports on this material. 45,46,50…”

“…Therefore, the solid–gas interphase must be modified, decreasing the CO capture, and finally resulting in lower positive mass percentages. 46 Furthermore, two crests are depicted in this temperature range. The first one (∼250 °C and 440 °C) can be ascribed to the surface CO x sorption-desorption equilibrium, while the latter (∼440 °C and 740 °C) should involve CO x chemical capture controlled by the Li + and O 2− diffusion mechanisms, 56 together with the occurrence of some thermal stress.…”

“…44 In this case, only lithium manganate (Li 2 MnO 3 ) has demonstrated selective CO catalytic ( T < 500 °C) and chemisorption ( T ≥ 500 °C, reaction (1), maintaining some catalytic activity) capabilities under inert or non-oxidative conditions. 45,46 Moreover, this material was tested using a synthetic syngas mixture for H 2 purification, showing a very low ceramic interaction with H 2 . 47 Li 2 MnO 3(s) + CO (g) → Li 2 CO 3(s) + MnO (s) …”