Adsorption of methane on magnesium oxide studied by temperature-programmed desorption and ab initio molecular orbital methods

Theoretical Study on the Mechanism of the Reaction of CH4 + MgO

“…12,13 To understand the nature of the interaction between methane and MgO, the adsorption and dissociation of methane on MgO catalyst have been extensively investigated experimentally. [2][3][4][5][6][10][11][12][13][14][15][16][17][18] In 1985, Driscoll and co-workers 10,11 found that when methane is passed over MgO at temperatures above 800 K, CH 3 • radicals are formed, then released into the gas phase, and detected after collection in an argon matrix. Later, Ito and co-workers 15,16 proposed that methane pretreated above 973 K on MgO could be adsorbed in a heterolytically dissociated form, CH 3 -on Mg 2+ and H + on O 2-, even below room temperature.…”

“…18 The rate-determining step in the conversion of methane to higher derivatives has been shown to be the abstraction of hydrogen at the surface. 4 To obtain further information about this process, many theoretical studies of the interaction of methane with metal oxide heve been performed using an oxometal cluster model 9,16,[18][19][20][21] and gaseous metal oxide molecules. [22][23][24][25][26][27] Of particular interest is the direct oxidation of methane by metal oxide fragments, [22][23][24][25][26][27] because this process can be justifiably regarded as providing models for the more complicated processes of heterogeneous or enzymatic methane monooxygenase catalysis.…”

Ab initio density functional study of MgO (001) surface with topological defects

“…Other case providing further evidence of the importance of defective surfaces is the chemisorption of methane on oxide surfaces. Ito et al 8 have shown that methane heterolytically dissociates on the nearest pair of three‐coordinated surface magnesium and oxygen atoms, which are part of defect sites and are the most active sites. In other work, Di Valentin et al 9 investigated how the chemisorption and heterolytic dissociation of methanol occur only at defect sites on MgO surfaces.…”

Theoretical study of MgO(001) surfaces: Pure, doped with Fe, Ca, and Al, and with and without adsorbed water

“…The effect of surface morphology is also not completely understood as well as, in particular, the role of fivefold coordinate terrace sites and lower coordinate defects such as steps, kinks, and vacancies. The problem is exacerbated by the use of the wide variety of MgO smokes, powdered MgO, thin films of MgO grown on a variety of substrates, and single‐crystal MgO subject to various cleaning procedures 19, 20, 22–27.…”

“…The surfaces of MgO have been previously investigated by various theoretical ab intio and semiempirical methods 24, 25, 27–47. Anchel et al 28 investigated the interactions of water molecules at three‐coordination sites of small (MgO) 4 and (MgO) 8 clusters including full geometry optimization and correlation energy at the MP2 level of theory for the (MgO) 4 cluster, and predicted that H 2 O chemidissociates without a barrier directly onto adjacent three‐coordinated sites.…”