Acetic acid (CH<sub>3</sub>COOH) and its decomposition over Pd (111) surface is a good model system for decomposition of small oxygenates, common in biomass conversion. Many catalytic processes, including biomass conversion, include co-adsorbates or even solvents but experimental studies have shown that different solvents can effect the selectivity of catalytic reactions. Understanding the reaction mechanism of acetic acid decomposition, at an atomic scale, and how different functional groups interact with co-adsorbates and solvent molecules can help us design more effective catalysts and catalyst systems. Using DFT calculations we have identified two major pathways for decarboxylation(DCX) and decarbonylation(DCN) of acetic acid as well as explored the role of co-adsorbed water in these reaction mechanisms. The minima energy path for the two different reaction routes follows the same dehydrogenation steps up until the CH<sub>2</sub>COO reaction intermediate where dehydrogenation, for the DCX pathway, and C-O scissoring, for the DCN pathway, have the same activation barrier but the DCX step is slightly less exothermic. Adding co-adsorbed water effects the two paths differently, changing the selectivity of the decomposition. These calculations give an insight into the complexity of decompositions of oxygenations, the interplay between the competitive reaction routes and the effects of co-adsorbed water on the critical reaction steps in the network.

Theoretical study of acetic acid decomposition and the role of co-adsorbates

2019 Fall National Meeting

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