A Computational Approach for the Rational Design of Bimetallic Clusters for Ethanol Formation from Syn-gas

A major challenge associated with the synthesis of ethanol from syn-gas is an inability to find a low-cost catalyst that promotes the proper combination of CO dissociation and CO insertion steps, so as to yield ethanol as the primary reaction product and inhibit the formation of methane, methanol, longer chain alkanes, and other coking reaction products. We used quantum mechanical simulations for the rational design of bimetallic catalysts. Several promising 13-atom bimetallic clusters were selected by the identification of key reaction descriptors for ethanol formation reaction. Density Functional Theory (DFT) simulations and Bronsted-Evans-Polanyi (BEP) relations were used to map out the full reaction mechanism from syn-gas to ethanol. Selectivity analysis was conducted including hydrocarbons, methanol, acetaldehyde and ethanol as products. Microkinetic models were built, considering all necessary adsorption and reaction steps as well as the diffusion of intermediate species between different metal surface sites. More general selectivity trends were identified by altering the surface concentrations of various metal sites. These simulations indicate the nature and stability of the various bimetallic nanocatalysts and more importantly identify specific metal combinations that are ideally suited for ethanol production