A Density Functional Theory Study of CO Adsorption on Cu-ZSM5 and Cu-Y

Dimethyl carbonate (DMC) and dimethoxy methane (DMM) are of commercial interest because they are good fuel additives and building blocks for organic synthesis. Both products can be produced using Cu-exchanged ZSM-5 and Y from a mixture containing O2, CO, and CH3OH. Experimental studies done in our research group [1,2] have shown that at identical reaction conditions, very different product selectivity, catalytic properties, and adsorption modes are observed for Cu-exchanged ZSM-5 and Y. Thus, for example, high DMC selectivity is observed for Cu-Y and high DMM selectivity is observed using Cu-ZSM-5. To understand the origins of these differences, we have carried out a theoretical analysis of density functional theory (DFT) of CO adsorption on Cu site in Cu-ZSM-5 and Cu-Y. The goal of this work is to establish how changes in the local structure of the Cu exchange center affects the electronic properties of isolated Cu cations and the strength of interaction of Cu with adsorbed CO.