Abstract: EHMO calculations and orbital analyses of fragments have been performed for the formation of oxygenates in Fischer-Tropsch synthesis on the butterfly model for four different metal (Ni,Ru,Rh,Pd) catalysts supported on SiO₂.Calculations were made for the four processes,i.e.,CO-dissociation;Coupling of CO and Hto produce CHO;Insertion of CO to M-CH₃;insertion of CH₂ to M-CH₃ On the basis of comparing the degree of CObonds activation and the energy barriers of the foregoing processes for these four catalysts,it is concluded that Ni/SiO₂ can be used as the methanation catalyst.On Ru/SiO₂ and Rh/SiO₂ C₂-oxygenated compound can be produced (acetaldehyde),especially Rh/SiO₂ is the even better catalyst,and Pd/SiO₂ is a methanol synthesis catalyst.

Key words: EHMO calculation, Fischer-Tropsch synthesis, Mechanism of producing oxygenates, Group Ⅷ supported metal catalysts