Insights into the activity and selectivity trends in non-oxidative dehydrogenation of primary and secondary alcohols over the copper catalyst

Abstract Density functional theory (DFT) simulations are conducted to understand the differentiation of activity and selectivity trends between primary and secondary alcohols towards the non-oxidative dehydrogenation (NODH) reaction. Propanol and isopropanol are employed as model molecules to explore the NODH on the (111) facets of Cu. The initial dehydrogenation of propanol via the hydroxyl route exhibits a higher barrier (96.8 kJ/mol) as compared to that of isopropanol (61.4 kJ/mol). Furthermore, the second dehydrogenation step resulting in the formation of the carbonyl compound is also calculated to show higher barrier of primary alcohol (83 kJ/mol) than secondary alcohol (51.3 kJ/mol). Overall, for the consecutive dehydrogenation steps, propanol is observed to show higher activation barriers as opposed to that of isopropanol, indicating towards a higher conversion rate for isopropanol, similar to the trend observed experimentally. However, the subsequent dehydrogenation of the carbonyl compound formed shows a barrier of 112.8 kJ/mol for acetone and that of 70.6 kJ/mol for acetaldehyde owing to the higher stability of ketone. The formation of ester from the propionyl produced upon acetaldehyde dehydrogenation is calculated to show the lowest barrier (64.6 kJ/mol) amongst the dehydrogenation steps of primary alcohol dehydrogenation route, suggesting towards lower selectivity in case of NODH of propanol.