Selective Dehydration of Glycerol to Hydroxyacetone over Cu-, Ag-, and AgFe-Mordenites

The increasing demands of the hydroxyacetone (also known as acetol) market require more efficient acetol production technologies. The development of new effective catalysts for glycerol dehydration to acetol at mild condition is an important task. In this study, dehydration of glycerol to acetol on microporous sodium mordenite (MOR) modified by conventional ion exchange with Cu²⁺, Ag⁺ and Ag⁺Fe²⁺ was investigated within a temperature range from 100 to 250°C. The transition metal content after ion exchange procedure was determined by EDX: 4.6 wt % of Cu for CuMOR, 2.8 wt % of Ag for AgMOR, 2.3 and 0.2 wt % of Ag and Fe, respectively, for AgFeMOR. H₂-TPR indicates the presence of different types of active sites (Cu²⁺, Ag⁺, ${\text{Ag}}_{m}^{{n + }}$, Fe⁺²). The glycerol conversion and the acetol yield over the zeolite samples increase in the CuMOR < AgFeMOR < AgMOR series. For AgMOR, glycerol conversion achieves ~90% at 175°C (with an acetol yield of about 76%), the presence of Fe²⁺ reduces the catalytic performance of the catalyst. The copper-exchanged catalyst exhibits the poorest catalytic performance. The proposed reaction mechanism of glycerol dehydration over mordenite involves a preparative step (glycerol as reducing media, forms a catalyst by interacting with cations introduced into the zeolite), and then on these formed neutral metallic sites the conversion of glycerol to the final product occurs; the selectivity of the reaction is mainly determined by steric constraints.