Pd metal (0.1-1 wt%) supported on Zn-II-Cr-III (1:10) mixed oxide was found to be an efficient bifunctional catalyst for the one-step synthesis of methyl isobutyl ketone (MIBK) from acetone and H-2 in gas-and liquid-phase processes. The reaction involves the acid-catalysed condensation of acetone to form mesityl oxide, followed by its hydrogenation to MIBK. The gas-phase reaction produces MIBK with a selectivity up to 78% at 40-66% acetone conversion (200-350 degrees C, ambient pressure). Diisobutyl ketone (DIBK) is the main byproduct, with a total MIBK + DIBK selectivity Of Lip to 93%. The catalyst reaches a steady state in ca. I h and shows constant activity and selectivity for at least 50 It on stream. The liquid-phase reaction yields MIBK with up to 83% selectivity and total selectivity to MIBK + DIBK up to 9 at 56% acetone conversion (200 degrees C 5 bar H2 pressure). As a catalyst support, the amorphous Zn-Cr oxide calcined at 300 degrees C provides higher catalytic activity than the crystalline Zn-Cr oxide calcined at 400 degrees C, probably due to the lower Surface area of the crystalline oxide. XRD of 0.3-1%Pd/Zn-Cr oxide showed no pattern of Pd metal, indicating a fine dispersion of Pd particles in the catalyst. (c) 2005 Elsevier Inc. All rights reserved.