Selective Hydrogenation of Glycolic Acid to Renewable Ethylene Glycol over Supported Ruthenium Catalysts

Abstract

The production of industrially demanded polymer precursor ethylene glycol (EG) from biomass-accessible aqueous glycolic acid (GA) was investigated in this study. The systematic investigation of different active metals as well as, for the first time, various support materials revealed Ru/TiO2 and Ru/ZrO2 to be the most active catalysts in the heterogeneously catalyzed reduction of GA with molecular H2. Catalytic activity is enhanced by facilitated reduction of the active Ru species due to metal-support interactions. An assessment of several other catalyst properties (metal surface area, acid properties, porosity) revealed that high metal dispersion is also beneficial. Up to 94 % GA conversion and 95 % selectivity for EG were obtained under optimized and mild reaction conditions (105 °C, 60 bar H2 pressure, 23 h, Ru/TiO2 as catalyst). This shows that the heterogeneously catalyzed reduction of biomass-derived aqueous GA solutions can be a promising alternative for the renewable production of EG.