Gas-phase conversion of acetone to methyl isobutyl ketone over bifunctional metal/carbon catalysts. 2. Examination of the hydrogenation potential of different metals

The single-stage self-condensation and subsequent hydrogenation of acetone to methyl isobutyl ketone (MIBK) in the gas phase was carried out using catalysts consisting of hydrogenating metals supported on active carbon (Me/C). The reaction was conducted in a continuously operated, ideally backmixed Berty reactor at 1 MPa and 623 K. Platinum, palladium, nickel, and copper were applied as metal components, and their hydrogenation activity decreased in the order Pt > Pd > Ni > Cu. The impact of the hydrogenation reactions in the reaction network can also be enhanced by increasing the molar ratio of hydrogen to acetone in the feed, and by raising the metal content of the Me/C catalysts. A low hydrogenation activity negatively affects the acetone conversion and promotes the production of mesityl oxide. Hydrogenation conditions being too severe may favor the unwanted hydrogenation of acetone to 2-propanol and of MIBK to methyl isobutyl carbinol, but this effect is less detrimental to the MIBK selectivity than an unsufficient hydrogenation activity. The best performance showed a Pt/C catalyst with 0.5% m/m Pt and a Ni/C catalyst with a higher Ni loading (2.71% m/m); the optimum H-2/acetone feed ratio was 0.5, which is the stoichiometric value for the idealized formation of MIBK from acetone. Despite the higher metal content required, the Ni/C catalyst allows for a considerable reduction of the costs for catalyst production.