Aqueous phase reforming of industrially relevant sugar alcohols with different chiralities

The influence of substrate chirality was studied in the aqueous phase reforming (APR) over Pt/Al₂O₃ in a continuous fixed-bed reactor at 225 °C. Two epimeric sugar alcohols, namely sorbitol and galactitol, were used for performance comparison. For the very first time galactitol was used in the APR process. The reliability of the liquid-phase product analysis was considerably improved due to application of a spiking technique for qualitative analysis and subsequent peak fitting for quantification. A detailed analysis of the gas and liquid phases showed almost the same behavior of both polyols, apart from the formation of several intermediate oxygenates. This implies that industrially relevant feedstocks with different chiralities can be efficiently processed in APR, since the chirality of the initial substance does not affect the reaction rate and selectivity to the final products. However, the observed difference in the liquid phase composition should be considered, because the catalyst should be active in the conversion of both polyols and oxygenates. Finally, possible reaction pathways were proposed and discussed from a thermodynamic point of view.