Performance of bifunctional Pd/MxNyO (M = Mg, Ca; N = Zr, Al) catalysts for aldolization–hydrogenation of furfural–acetone mixtures

The performance of different bi-functional Pd catalysts (supported on Mg–Zr, Mg–Al and Ca–Zr mixed oxides) for the aqueous-phase aldol-condensation of acetone and furfural was studied in this work. Experiments were carried out in a batch slurry reactor at 323–393 K. Activity trends, as well as selectivity for the formation of the different adducts (C8 and C13), were correlated with the physico-chemical properties of the materials, mainly with the distribution of acid and basic sites. In general, it was observed that the catalyst with the lowest concentration of basic sites (Pd/Ca–Zr) presents the poorest performance. By contrast, the presence of medium-strength acid sites (as the observed in the case of one the Pd/Mg–Al catalyst) seems to enhance the catalytic activity of the material. Although selectivities trends were similar for the catalysts supported on Mg–Zr and Mg–Al catalysts, the ability of the materials for catalyzing the formation of the heaviest adducts depends mainly on the total concentration of basic sites.