Role of the surface chemistry of carbon xerogel-based supports and Cu catalysts in the oxidation reaction of glycerol

Abstract

Carbon xerogel with pore size of about 10 nm were obtained using the sol–gel method and applying different thermal treatments. Catalysts were prepared depositing 3 wt% of copper on the xerogel. The catalytic activities of catalysts and supports were evaluated in the selective oxidation of glycerol (GLY). The supports showed good conversion and selectivity to glyceric acid (GA) and lactic acid (LA), with higher preference to GA. For the catalysts, the conversions were slightly higher, and the order of selectivity changed, benefiting the production of LA. Changes in selectivity between supports and catalysts were mainly associated with the different acid-base surface characteristics and the presence of the Cu domains in the catalysts. In the supports, even if the thermal treatment applied modifies the type and content of oxygenated functional groups (OFG) on the surface, predominates a superficial acid character, addressing the selectivity to GA. On the other hand, the basic character of the catalysts due to the Cu presence and the large metallic domain sizes favoured the production of LA. During the recycle test, supports and catalysts showed a decrease in catalytic activity. After three recycles, the catalytic performances of catalysts and supports were similar due to metal leaching.