The Density Functional Theory Study Of Adsorption For CO And CO₂

There are two aspects in this paper. One is the short-range interactions between solvents and solutes, and the other is the infulunce of water gas reaction during the synthesis of ethonal by syngas.It is well-known that the continuous solvation model COSMO is always used in the theoretical study of solvent effects which is a cutting-edge subject. The model is used to simulate the long-range interactions between solvents and solutes while ignore the short-range interactions, for which the interactions between CO and saturated straight chain alkanes with C8-C16are calculated. Consequently, some abnormal results are obtained. There are chemical interactions between CO and straight chain saturated alkane molecule with even carbon atoms on the middle two carbon atoms and generate ketone compounds, which can not react with other carbons in the same situation. The same interaction can only occur for C9H2o aomong odd numbers of straight chain saturated alkane molecules.We found that Cu+has an important role in the selectivity of ethanol by our group as well as the catalytic active center for the water gas reaction. Therefore, the interactions between CO2as well as CO and Cu2O are researched in the reaction process. There are lots of study for the interactions between CO and Cu2O, so the interactions between CO2and Cu2O are researched in the second part.The results are as follows:(1) The adsorption of CO2on perfect Cu2O(111) surface is non-activated physical adsorption, in which the "O-perpendicular to Cucus" and "two horizontal type adsorption of Ocus-Cucus" are the more stable adsorption sites.(2) The adsorption of CO2on oxygen vacancy Cu2O(111) surface is non-activated physical adsorption, in which the "O-perpendicular to CuCUS-1" and "two horizontal type adsorption of Cuv0-Cucus" are the more stable adsorption sites.(3) The exist of oxygen vacancy reduces the adsorption ability of relative adsorption sites on Cu2O(111)surface.(4) The dissociation adsorption of CO2on oxygen vacancy Cu2O(111) surface is thermodynamically unfeasible while its inverse process is thermodynamically favored.(5) Although Cu+can prove the selectivity of ethanol and water gas reaction, the adsorption of CO on Cu2O(111) surface is chemical adsorption while there are physical adsorption for the adsorption of CO2on Cu2O(111) surface. As a result, the effect of water gas reaction on synthetic ethanol should be considered in theory, and the suppression of water gas reaction is the important topic in the synthesis of ethanol.