Chemical transformations of acetone on ZnO powder

• We investigate adsorption and thermal transformations of acetone on ZnO powder.
• We use infrared spectroscopy and computational calculations for analysis.
• We reconcile previous low-coverage and high-coverage observations.
• We investigate the possible pathways for catalyzed acetone self-reaction on ZnO powder.
• We explain the spectroscopic signatures of the observed species.

Acetone transformations on ZnO powder encompass a number of practical implications for heterogeneous catalysis, and the interest towards this system has fueled a substantial debate over the nature of the adsorbed molecule and its possible self-reactions. This work combines vibrational analysis and computational density functional theory investigation to reconcile some of the disagreements posed by the previous studies spanning wide range of experimental conditions and a variety of ZnO surfaces. The formation of rehybridized and non-rehybridized enolate species following acetone adsorption is analyzed by varying the molecular coverage in computational investigation using cluster models representing ZnO surfaces, and the resulting vibrational spectra are compared with the experimental measurements. In addition, self-aldol-condensation is explored to offer possible surface-catalyzed reaction pathways. Aldol condensation of acetone results in a stable species – enolized diacetone alcohol. Further transformation of this species into mesityl oxide is found to have a very high kinetic barrier.

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