Abstract: The calculations have been performed for model systems MCOMn+1(M=Ru, Rh, Pd; M₁ⁿ⁺=Na⁺, K⁺, Mg²⁺) by Gaussian programs at the HF/LANL2DZlevel. The influences of C—Obond and its mechanism have been studied after the COadsorbed on the main group metal cation M₁ⁿ⁺ promoted transition metal catalysts. And the products of COhydrogenation on these catalysts have been inferred. The calculations showed that the different interaction positions of the main group metal cation promoter and the various kinds of metal cation promoters both cause the changes of catalyst activity and selectivity. When M₁ⁿ⁺ cations affect the COthrough the Oatom of CO, the C—Obond is weakened largely and the products of COhydrogenation over these catalysts will shift to hydrocarbons. When the M₁ⁿ⁺ cations affect the COthrough the transition metal atom, the CObond is weakened slightly, so it is beneficial to form oxygenates. And there is no activity when M₁ⁿ⁺ cations bonded on the side of CO. It can also be concluded that the main group metal cation with stronger ability to accept the electrons may be a better promoter.

Key words: Chemisorption of CO, Promoter effect, Ab initio calculation