Abstract
Glycerol hydrogenolysis to 1,2-propanediol (1,2-PDO) was performed over activated carbon supported copper-based catalysts. The catalysts were prepared by impregnation using a pristine carbon support and thermally-treated carbon supports (450, 600, 750, and 1000 °C). The final hydrogen adsorption capacity, porous structure, and total acidity of the catalysts were found to be important descriptors to understand catalytic performance. Oxygen surface groups on the support controlled copper dispersion by modifying acidic and adsorption properties. The amount of oxygen species of thermally modified carbon supports was also found to be a function of its specific surface area. Carbon supports with high specific surface areas contained large amount of oxygen surface species, inducing homogeneous distribution of Cu species on the carbon support during impregnation. The oxygen surface groups likely acted as anchorage centers, whereby the more stable oxygen surface groups after the reduction treatment produced an increase in the interaction of the copper species with the carbon support, and determined catalytic performances.
Highlights
Glycerol is produced in large amounts as a reaction by-product during biodiesel production [1,2].Glycerol has been identified by the Department of Energy of United States (DOE) as one of the top-12 building block chemicals that can be derived from sugar and converted to high-value bio-based chemicals or materials [3]
Previous research has shown that hydrogenolysis of glycerol to 1,2-PDO proceeds via dehydration of glycerol to acetol on acid catalysts and consecutive hydrogenation over metal catalysts
The accessibility to the copper atoms on this sample which exhibited the highest hydrogen adsorption capacity. These findings suggest that the effect of oxygen surface groups of the support on copper dispersion is an important factor in this reaction
Summary
Glycerol is produced in large amounts as a reaction by-product during biodiesel production [1,2]. Suppes et al [9] proposed that C–O cleavage leading to the formation of propylene glycol is a metal-catalyzed reaction. In this route, glycerol is directly dehydrated on the metal site to form acetol as an intermediate, which can be hydrogenated over the metal to form propylene glycol (1,2-PDO). Previous research has shown that hydrogenolysis of glycerol to 1,2-PDO proceeds via dehydration of glycerol to acetol on acid catalysts and consecutive hydrogenation over metal catalysts. The present work investigates the effect of thermal treatment of activated carbon as supports for copper catalysts for glycerol conversion. It is expected that oxygen surface groups will have a crucial influence on the final accessibility to the exposed copper species on the catalyst
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