Reductive condensation of acetone to methyl isobutyl ketone on a bifunctional catalyst

The methyl isobutyl ketone (MIBK) was obtained in vapour phase, from aceton e and hydrogen in a single step, using Pd/(Zn) H-ZSM-5 as a catalyst. The c hemical transformation occurs in a sequence of two steps, acetone condensat ion to mesityl oxide on the acidic sites of zeolite, followed by the mesity l oxide hydrogenation to MIBK on the palladium metallic sites. The experiments were performed in a continuous fixed bed reactor at 0.5 MPa , 135-210 degrees C, hydrogen/acetone mole ratios of 0.5-9, and acetone mas s hourly space velocity of 0.15-1 h(-1) The experimental data showed that t he hydrogenation step occurs very fast compared with the condensation one, the intermediary mesityl oxide not being identified in the reaction mixture . The obtained acetone conversion was up to 55 % and MIBK selectivity betwe en 83 % and 94 %. A kinetic model was also proposed, assuming that the over all process rate is controlled by the acetone condensation step.