Bifunctional catalyst synthesis using ion-exchange resins for the methyl isobutyl ketone production

Abstract

This project is focused on the preparation of bifunctional catalysts, using ion exchange resins as a supporting material, for the biomass transformation. The acetone hydrogenation to produce methyl isobutyl ketone (MIBK), under the one-pot synthesis approach was selected as a model reaction. Acidic ion exchange resins, AmberlystTM 15 (A15) and Dowex 50WX2 (Dow2), were selected as the supporting material due to their ability to carry out the reactions at milder conditions. These resins were doped with noble metals (Pd and Ru) and non-noble metals (Cu) by wet impregnation. The catalytic activity test consisted on hydrogenating 40 g of acetone with a 5 wt.% catalyst loading for 4 h at 120 °C, a hydrogen pressure of 30 barg at 300 rpm. Palladium doped resins resulted to be the more catalytically active being able to convert more than 30 % of the acetone being totally selective to the MIBK formation. Similar results were accomplished by a commercial catalyst, namely AmberlystTM CH28 (ACH28). Although Dow2 doped with 1 wt.% achieved the highest yield, 37 %, it was less catalytically active than ACH28 according to the turnover number which were, respectively, 1500 and 1839 mols of acetone converted per mole of metal supported on the catalyst. Cu-based catalyst resulted to be the least catalytically active converting less than 20 % of the acetone with a selectivity towards the product of interest inferior to 10 %. Cu- and Pd-catalysts were characterized. It was observed that the nominal and actual metal content were seen to match at 1 wt.%. Additionally, no acidic sites were lost during the catalytic test, although the Pd-catalyst lost some acidic sites during its preparation. The transmission electron microscope proved that the Dow2-1%Pd catalyst had the smallest size distribution, which makes it a great catalyst while the scanning electron microscopy proved that the metal was homogeneously distributed on the polymeric resin surface. Finally, the Dow2-1%Pd catalyst was assayed at different temperatures (110-130 °C), being able to convert 45 % of the initial acetone without a selectivity loss. However, its reusability is not feasible, although the TON number remains constant, because almost no production of MIBK was observed when tested in three consecutive experimental runs.