Hydrodeoxygenation of C3–4 polyols to C3–4 diols over carbon-supported bimetallic MgCu@C catalysts prepared from ion exchange resin

Abstract

The selective hydrodeoxygenation (HDO) of C3–4 polyols (glycerol and erythritol) to value-added diol products was investigated over a series of Cu-based catalysts, namely, carbon-supported monometallic Cu@C and bimetallic MgCu@C prepared by using a weakly acidic cation-exchange resin as the carbon support precursors. High metal loading (> 50 wt%) and small metal particle size (< 15 nm) were realized by the catalyst prepared from ion-exchange resin. The addition of Mg decreased Cu particle size (10.0–13.5 nm) and improved metal dispersion. The largest metal surface area was achieved for the MgCu@C catalyst with Mg/Cu molar ratio of 1/9. Furthermore, HDO of C3–4 polyols was performed over the prepared catalysts at relatively low temperature (180 °C) under low initial H2 pressure (1.2 MPa). Over the MgCu@C catalyst with a nominal Cu/Mg atomic ratio of 9/1, a C3 polyol conversion of 94.0 C mol% was obtained with a high selectivity towards 1,2-propanediol (94.3 C mol%), while a low erythritol conversion of 18.75 C mol% with a selectivity toward butanediols of 43.0 C mol% was achieved after 360 h reaction. The different effects of the Mg addition on catalytic activity to C3 and C4 polyol HDO were likely attributed to the different reaction mechanism. The dehydration-hydrogenation mechanism was proposed for C3 HDO over Cu@C and MgCu@C, in which the addition of Mg species promoted the dehydration of glycerol to produce hydroxyacetone followed by the hydrogenation of hydroxyacetone to 1,2-propanediol.