On the active site of MgO/CaO mixed oxide for oxidative coupling of methane

Study on the Kinetics and Mechanism of Grain Growth during the Thermal Decomposition of Magnesite

“…Analogous to the surface hydroxyl groups formed on MgO in the presence of water vapor, whether some kinds of surface structure are formed on MgO by the adsorption of CO 2 . These surface structures resulted from the adsorption of CO 2 have been relatively well confirmed by several workers [15][16][17][18][19] using the infra-red study as shown in Figure 2. They used the active MgO as the raw material and the adsorption of CO 2 was carried out either at room temperature or at temperature varied from 473 K to 773 K. Four major vibrational frequencies for unidentate carbonates (Figure 2 .…”

Carbon dioxide adsorption characteristics of synthesized MgO with various porous structures achieved by varying calcination temperature

“…9 shows the in-situ horizontal attenuated total reflectance Fourier transform infrared spectroscopy of the synthesized samples. The adsorption band at 857, 1057 and 1654 cm −1 were assigned to bidentate carbonate [26,27], monodentate carbonate [28,29] and bicarbonate [26,29] respectively. It is seen that the most remarkable adsorption band ranging from 1254 cm −1 to 1630 cm −1 was observed, indicating the combined strength of bicarbonate, monodentate carbonate and bidentate carbonate [30].…”

REACTION OF CO2 WITH MgO(100) SURFACES

“…For example, MgO has been shown to be a suitable support for the production of syn-gas from mixed steam and CO 2 reforming of methane 1 and for oxidative coupling of methane. 2,3 However, an understanding of the interaction of CO 2 with metal oxides is not only of considerable interest for technological issues but also for environmental and "global climate change" issues since CO 2 is a major greenhouse gas contributing to global warming. 4 Surprisingly few studies have examined the interaction of CO 2 with single crystal metal oxide surfaces (except for ZnO used for the synthesis of methanol from a mixture of CO, H 2 and CO 2 5,6 ).…”

“…7 The chemisorption of this molecule on the surface of basic oxides leads to two different compounds, depending on whether it interacts with hydroxyl groups (formation of hydrogen carbonate species, HOCO − 2 , which is easily desorbed between 100 and 200 • C 2, 8,9 ) or with surface oxygen (formation of carbonates, CO 2− 3 ). Two main types of carbonate can be formed: (1) unidentate (the CO 2 molecule is bound to only one surface oxygen) and (2) bidentate (bound to one surface oxygen and one surface Mg). The relative amounts of unidentate and bidentate species, as well as their thermal stabilities, are still matters of debate; 2,[8][9][10][11][12] however, all of these results confirm the formation of carbonate species after exposure of MgO powders to CO 2 at room temperature.…”

“…Two main types of carbonate can be formed: (1) unidentate (the CO 2 molecule is bound to only one surface oxygen) and (2) bidentate (bound to one surface oxygen and one surface Mg). The relative amounts of unidentate and bidentate species, as well as their thermal stabilities, are still matters of debate; 2,[8][9][10][11][12] however, all of these results confirm the formation of carbonate species after exposure of MgO powders to CO 2 at room temperature.…”