Methane Activation By Ni～0, NiH～+, NiO And MgO.-A Theoretical Study

Methane activation by Ni~+ atom, NiH+ diatomics, NiO diatomics and MgO diatomics, respectively, has been studied. The reaction paths in which the intermediates transfer from one to another via transition state have been rationalized by their energy, structure, frequency and natural bond orbital analysis. The main results are as the following:The reactions of Ni + CRt -* NiCH2 + H2, Ni + CR, -* NiCH3- + H-and Ni + CR, ?NiH- + CR3- have been studied on a singlet state potential energy curve by B3LYP method. The initial interaction between Ni and CRt is the formation of atom-molecule complex NiCR? The complex NiCRt was predicted for the first time in present work. The intermediate HNiCHs is the energetically preferred configuration in the reaction. The reactions of Ni + CH4 - NiCH2 + H2, Ni + CR, - NiCH3- + H- and Ni + CR, -NiH- + CH3 are predicted to be endothermic, and the reaction Ni + CRt -NiH- + CHj- is the easiest to occur.The reactions of Ni(d9s1 3D) + CH2(3B1) - H2 + NiC and Ni(d9s1 3D) + CH2(3Bi) trans-HNiCH have been studied on a singlet state potential energy curve by B3LYP method. At low energies, the formation of trans-HNiCH is favored, while at high energies, the formation of H2 + NiC is preferred.The reaction of NiH + CH4 - NiCH+ + 2H2 has been studied on a singlet state potential energy curve by B3LYP method. The initial interaction between NiH* and CRt is the formation of ion-molecule complex HNiCH4+.In the reaction, the ion-molecule complexes HNiCH/ and (HyNiCHs* are the energetically preferred configurations in the reaction.The reactions of NiO + CH4 Ni + CO + 2H2, NiO + CH4 Ni + CH3OH and NiO + CH4 NiCH2 + H2O have been studied on a singlet state potential energy curve by B3LYP method. The initial interaction between CH4 and NiO is the formation of two molecule-molecule complexes NiOCH4 and ONiCH4. The complex ONiCH4 is more stable than the complex NiOCH4. The calculation predicts that the intermediate HNiOCHa is the energetically preferred configuration in the reaction.The reactions of CHj + MgO -?MgOH- + CH3- and Cttt + MgO -Mg + CHaOH have been studied on a singlet state potential energy curve by B3LYP and MP2 methods. The initial interaction between CH4 and MgO is the formation of two molecule-molecule complexes MgOCH4 and OMgCRj. The calculation predicts that the former reaction may proceed more easily than the latter; and the complex HOMgCHs is the energetically preferred configuration in the reaction of MgO + CH4.