Deuterium kinetic isotopic study for hydrogenolysis of ethyl butyrate

The hydrogenation of ethyl butyrate, n-butyric acid, and n-butyraldehyde to their corresponding alcohol(s) has been studied over a γ-Al2O3-supported cobalt catalyst using a high-pressure fixed-bed reactor in the temperature range of 473–493 K. H2–D2–H2 switching experiments show that ethyl butyrate and n-butyric acid follow an inverse kinetic isotope effect (KIE) (i.e. rH/rD = 0.50–0.54), whereas n-butyraldehyde did not display any KIE (i.e. rH/rD = 0.98). DRIFTS experiments were performed over the support and catalyst to monitor the surface species formed during the adsorption of ethyl butyrate and n-butyric acid at atmospheric pressure and the desired temperature. Butanoate and butanoyl species are the stable surface intermediates formed during hydrogenation of ethyl butyrate. Hydrogenation of butanoate to a partially hydrogenated intermediate is likely involved in the rate-determining step of ethyl butyrate and butyric acid hydrogenation.

Graphical abstractThe hydrogenation of ethyl butyrate and n-butyric acid to corresponding alcohols follows an inverse kinetic isotope effect on γ-Al2O3-supported cobalt catalyst. Butanoate and butanoyl are the stable surface intermediate species formed over the surface of catalyst, and hydrogenation of these intermediates is likely involved in the rate-limiting step.Figure optionsDownload full-size imageDownload high-quality image (48 K)Download as PowerPoint slide