Solvent effects in the hydrogenation of 2-butanone

In liquid-phase reaction systems, the role of the solvent is often limited to the simple requirement of dissolving and/or diluting substrates. However, the correct choice, either pure or mixed, can significantly influence both reaction rate and selectivity. For multi-phase heterogeneously catalysed reactions observed variations may be due to changes in mass transfer rates, reaction mechanism, reaction kinetics, adsorption properties and combinations thereof. The liquid-phase hydrogenation of 2-butanone to 2-butanol over a Ru/SiO2 catalyst, for example, shows such complex rate behaviour when varying water/isopropyl alcohol (IPA) solvent ratios. In this paper, we outline a strategy which combines measured rate data with physical property measurements and molecular simulation in order to gain a more fundamental understanding of mixed solvent effects for this heterogeneously catalysed reaction. By combining these techniques, the observed complex behaviour of rate against water fraction is shown to be a combination of both mass transfer and chemical effects.

The complex rate behaviour observed during the hydrogenation of 2-butanone using water/IPA mixtures is attributed to a combination of mass transfer and structural dynamics effects. This work highlights the potential beneficial role of water in both lowering the activation barrier as well as increasing the proton diffusion coefficient.Figure optionsDownload high-quality image (108 K)Download as PowerPoint slideHighlights
► We investigate mixed solvent effects during the hydrogenation of 2-butanone.
► Complex rate/composition behaviour is observed and correlated to mass transfer and kinetics.
► Strong correlation found between hydrogen bonding structure and increased reaction rates.
► Results show that catalytic performance can be tailored through controlling structural dynamics.