Excellent performance in hydrogenation of esters over Cu/ZrO2 catalyst prepared by bio-derived salicylic acid

Abstract

Herein, Cu/ZrO₂ catalysts have been prepared using bio-derived organic carboxylic acids (ORCOOH) as complex agents. The one using salicylic acid (SA) as a complex agent exhibits both small CuO particles and abundant crystalline ZrO₂, regardless of being calcined at 550 or 750 °C. As a result, the catalyst calcined at 550 °C shows excellent selectivities towards ethanol of 93.1% and 98.9% in the hydrogenation of dimethyl oxalate (DMO) and ethyl acetate under higher weight liquid hourly space velocity, respectively. Besides, a selectivity towards ethylene glycol of 97.9%, which corresponds to 100% conversion of DMO, is achieved over the catalyst calcined at 750 °C. In this case, a high turnover frequency of 64.5 h⁻¹ is maintained over more than 120 h on stream. In brief, the aromatic ring skeleton with a large conjugated π-system in SA influenced the structures and properties of the obtained complexes. After thermal treatment, the interaction between Cu and crystalline ZrO₂ further supports retention of higher metal dispersion to improve the catalytic activity.