Unveiling the effect of metallic and oxidized phases of cobalt on acetone hydrodeoxygenation

Abstract

The impact of metallic and oxidized phases of cobalt and the nature of different catalytic sites in the gas-phase acetone hydrodeoxygenation were evaluated using Co3O4 nanopowder as catalyst. Mild pretreatments (reduction/oxidation up to 400 °C) were performed to vary the oxidation degree of the catalyst, aiming to favor the selective CO bond cleavage. We found that the Co3O4 nanopowder was not able to deoxygenate acetone at 200 °C, even by halving the acetone weight hourly space velocity (WHSV). At this temperature, only products of hydrogenation (isopropanol) and condensation (mesityl oxide) were obtained. A different selectivity was achieved by the pretreated catalysts. Methane formation was enhanced in the prereduced catalyst whereas isopropanol was the favored product after reoxidizing the catalyst at 400 °C. The best compromise was achieved when the prereduced catalyst was calcined at a lower temperature, 200 °C, achieving about 1:1 CC: CO bond cleavage ratio. The results pointed out the nature of different catalytic sites, and their correlation with the reaction pathways was proposed.