Selective Hydrogenolysis of Glycerol to 1,2-Propylene Glycol on Ultrafine Copper Particles

Abstract

Hydrogenolysis of glycerol to 1,2-propylene glycol at 200°C in the presence of Cu/Al₂O₃ catalysts prepared by coprecipitation from copper nitrate and aluminum nitrate using NaOH and NH₄OH has been studied. The kinetics of the reaction is described by the first-order rate law. It has been found that the selectivity for the target product for all catalyst samples is 98% and the activity of the catalysts depends on their synthesis conditions. By using X-ray diffraction analysis, transmission electron microscopy, energy dispersive X-ray analysis, and X-ray photoelectron spectroscopy, it has been revealed that the active phase of Cu/Al₂O₃ samples is made of particles with an average size of 20 to 140 nm, whose surface consisted of CuO and Cu₂O. The catalysts with different particle sizes the active phase but close chemical composition exhibits comparable activity (67.5 ± 5 h^–1mol^—1). This finding indicates that the hydrogenolysis reaction run in the presence of Cu/Al₂O₃ is not structure-responsive. A decrease in concentration of the Cu₂O phase of the catalyst leads to a decrease in the hydrogenolysis rate, thereby this indicating a higher activity of the Cu₂O phase in comparison with the CuO phase.