CO2 Hydrogenation on NixMg1−xAl2O4: A Comparative Study of MgAl2O4 and NiAl2O4

Abstract

Due to the increasing attention focused on global warming, many studies on reducing CO2 emissions and developing sustainable energy strategies have recently been performed. One of the approaches is CO2 methanation, transforming CO2 into methane. Such transformation (CO2 + 4H2 → CH4 + 2H2O) provides advantages of carbon liquification, storage, etc. In this study, we investigated CO2 methanation on nickel–magnesium–alumina catalysts both experimentally and computationally. We synthesized the catalysts using a precipitation method, and performed X-ray diffraction, temperature-programmed reduction, and N2 adsorption–desorption tests to characterize their physical and chemical properties. NiAl2O4 and MgAl2O4 phases were clearly observed in the catalysts. In addition, we conducted CO2 hydrogenation experiments by varying with temperatures to understand the reaction. Our results showed that CO2 conversion increases with Ni concentration and that MgAl2O4 exhibits high selectivity for CO. Density functional theory calculations explained the origin of this selectivity. Simulations predicted that adsorbed CO on MgAl2O4(100) weakly binds to the surface and prefers to desorb from the surface than undergoing further hydrogenation. Electronic structure analysis showed that the absence of a d orbital in MgAl2O4(100) is responsible for the weak binding of CO to MgAl2O4. We believe that this finding regarding the origin of the CO selectivity of MgAl2O4 provides fundamental insight for the design methanation catalysts.

Platinum on High-Entropy Aluminate Spinels as Thermally Stable CO Oxidation Catalysts

“…Thus, these samples retained active sites despite the sintering of platinum during aging. Transition metal aluminate spinels were previously observed to be effective CO adsorbents, in which the strength of interaction is heavily influenced by the divalent cation [25][26][27][28]. The previous literature further observed that CO adsorption on aluminate spinels was significantly enhanced through the incorporation of multiple transition metal elements, as well as under-coordinated defect sites [29][30][31].…”

Tunability of domain structure in partially inverse spinels NiAl2O4

“…Owing to excellent thermal, chemical & mechanical stability & unique electro-optic characteristics, it has been under study for metal containing ceramic-composites, and radiation protection applications [ [14] , [15] , [16] , [17] , [18] , [19] , [20] ]. It has also been extensively deliberated for catalytic applications owing to its unique porous structure [ [21] , [22] , [23] , [24] ]. The most important claim for NiAl 2 O 4 is its potential application as metamaterial owing to its distinctive dielectric response [ 25 ].…”