Role of catalyst preparation on determining selective sites for hydrogenation of dimethyl adipate over RuSn/Al 2O 3

Abstract

The hydrogenation of dimethyl adipate over RuSn/Al 2O 3 catalysts was studied. Attention was given to the effects of the preparation method and pretreatment conditions on the selective production of 1,6-hexanediol. The catalysts were prepared by co-impregnation and sol gel methods. The liquid phase catalytic reaction revealed that hexanediol can only be produced over the catalyst obtained by co-impregnation and calcined at low temperature. This system allowed 49% selectivity at practically total ester conversion. No diol could be formed when the same system was formerly calcined at 600 °C or over the sol gel catalyst. Mössbauer spectra revealed the occurrence of the same tin species in all catalysts; the distinct performance was thus attributed to the location of such species on the surface as evidenced by XPS. The results presented in this work indicated that alumina-supported Ru–Sn bimetallic catalysts may indeed be appropriate for 1,6-hexanediol production from DMA. However, the generation of tin oxidic species is not solely decisive for the formation of catalytically active sites. A suitable preparation method must be applied in order to better localize the SnO x moieties and tailor the required Ru–SnO x selective sites.