Role of catalyst preparation on determining selective sites for hydrogenation of dimethyl adipate over RuSn/Al2O3

The hydrogenation of dimethyl adipate over RuSn/Al2O3 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 SnOx moieties and tailor the required Ru–SnOx selective sites.

Graphical abstractThe effects of the preparation method and pretreatment conditions on the selective production of 1,6-hexanediol was studied. The catalysts were prepared by co-impregnation and sol gel methods. The results presented in this work indicated that alumina-supported Ru–Sn bimetallic catalysts may be appropriate for 1,6-hexanediol production from DMA. 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 SnOx moieties and tailor the required Ru–SnOx selective sites as revealed by XPS and Mössbauer spectroscopy. Figure optionsDownload full-size imageDownload as PowerPoint slide