One-step synthesis of methyl isobutyl ketone from acetone catalysed by Pd supported on ZnII–CrIII mixed oxide

Pd metal (0.1–1 wt%) supported on ZnII–CrIII image mixed oxide was found to be an efficient bifunctional catalyst for the one-step synthesis of methyl isobutyl ketone (MIBK) from acetone and H2 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 °C, ambient pressure). Diisobutyl ketone (DIBK) is the main byproduct, with a total MIBK + DIBK selectivity of up to 93%. The catalyst reaches a steady state in ca. 1 h and shows constant activity and selectivity for at least 50 h 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 °C, 5 bar H2 pressure). As a catalyst support, the amorphous Zn–Cr oxide calcined at 300 °C provides higher catalytic activity than the crystalline Zn–Cr oxide calcined at 400 °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.