Comment on “Towards understanding the bifunctional hydrodeoxygenation and aqueous phase reforming of glycerol” [J. Catal. 269 (2010) 411–420]

A recent experimental study of 1- and 2-propanol in water feed over Pt/Al2O3 yielded dehydrogenation of 2-propanol to acetone, but formation of CO2 and ethane from 1-propanol. To rationalize this reactivity difference of primary and secondary alcohols, we explored computationally the dehydrogenation of 1- and 2-propanol over Pt(111) as model. As product of 2-propanol, our calculations confirm acetone which adsorbs only weakly; thus, desorption occurs readily as the subsequent dehydrogenation would exhibit a high barrier. For 1-propanol we determined propionyl as strongly adsorbed intermediate which eventually undergoes C-C bond breaking.

The experimentally observed dissimilar dehydrogenation behavior of 1- and 2- propanol on Pt surfaces is rationalized via DFT model calculations. The most stable dehydrogenation product of the primary alcohol, propionyl, strongly adsorbs whereas for the secondary alcohol, acetone is determined as product which desorbs easily.Figure optionsDownload high-quality image (95 K)Download as PowerPoint slideHighlights
► Different dehydrogenation (DH) reactivity calculated for 1- and 2-propanol over Pt.
► Substantially lower barrier in the crucial DH step of 1-propanol.
► Acetone from 2-propanol rather desorbs than overcoming a high DH barrier.
► Approximate solvation model confirms acetone desorption from the surface.