LaCrO3 perovskite and
transition-metal (Co, Rh, Ir)-doped
perovskite-based catalysts were fabricated using the Pechini method
and applied to the dry reforming reaction of CH4 using
CO2. One of the prepared perovskite-based catalysts, the
LaCr0.95Ir0.05O3−δ catalyst,
showed the highest CH4 conversion (81%) at 750 °C
via the preactivation of the catalyst with H2 gas. It also
showed highly stable catalytic activity for 72 h without coke formation
on the catalyst surface. Through X-ray photoelectron spectroscopy
and transmission electron microscopy analyses, it is confirmed that
the improved catalytic activity of the LaCr0.95Ir0.05O3−δ perovskite-based catalyst was based
on the exsolution of Ir nanoparticles on the catalyst surface, which
catalyzes the cleavage of the C–H bond for CH4.
Density functional theory calculations revealed that the exsolution
of a dopant Ir in LaCr0.95Ir0.05O3−δ is more exothermic with/without an oxygen vacancy condition by 1.01
eV/0.43 eV, which suggests the agglomeration of Ir on the surface.
In many materials for CO2 sorption, hydrotalcite is attracting substantial attention as a high temperature (200-500 °C) CO2 sorbent because of its fast sorption/desorption kinetics and easy regenerability. However, the CO2-sorption capacity of conventional hydrotalcite is relatively low for large-scale commercial use. To enhance CO2-sorption capacity, hydrotalcite is conventionally impregnated with alkali metals such as K2CO3. Although K2CO3-impregnated hydrotalcite has high CO2-sorption capacity, the preparation method takes long time and is inconvenient because hydrotalcite synthesis step and alkali metal impregnation step are separated. In this study, K2CO3-promoted hydrotalcite was newly synthesized from hydroxide-form percursors by a simple and eco-friendly method without a solvent-consuming washing step. Analysis based on X-ray diffraction indicated that the prepared samples had structures of well-defined hydrotalcite crystalline and un-reacted Mg(OH)2 precursor. Moreover, K2CO3 was successfully incorporated in hydrotalcite during the synthesis step. The prepared K2CO3-promoted hydrotalcite showed high CO2-sorption capacity and had potential for use as a high-temperature CO2 sorbent.
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