BOC-MP Study on the Mechanism of Reactions of Methanol on Transition Metals

The mechanism of dissociation of methanol and its reactions with oxygen on transition metal surfaces,Ag (111),Cu (111),Pd (111),Ni (111) and Pt (111),are analyzed by the Bond-Order-Conservation-Morse-Potential (BOC-MP) approach.It is shown that the cleavage of the C-O bond or C-H bond of methanol may takes place,resulting the formation of the CH_x(x=2,3) species.However,in the presence of oxygen,the methanol is directly oxidized to formaldehyde.
The calculation values of activation barrier by BOC-MP approach are in good agreement with the experimental values.The results showed that the HCOH is very easy oxidized into CO or CO₂ on the surface of Ni,Pd,Pt,Cu and Ag.So,the very small amount of oxygen must be controlled for the system oxidizing mathanol to formaldehyde by transition metal catalysts.
The easy order is Ni＞Pd＞Pt＞Cu＞Ag for dissociation of mathanol over transition metal catalysts.However,in very low oxygen content,the carbon deposition is more easy on Ni,Pd and Pt than Cu adn Ag surface.Therfore,The Cu and Ag rather than Ni,Pd and Pt are used in the commercial catalysts for the oxidation of mathanol to formaldehyde.