CuO/CeO₂ catalysts for glycerol selective conversion to lactic acid

Abstract

Ceria supported copper oxide catalysts were produced by a deposition-precipitation method, at a high copper loading (up to >25 wt%). These materials demonstrated excellent properties for glycerol selective conversion to lactic acid, with a conversion reaching up to 87% with a selectivity to lactic acid of 74% (8 h reaction, 220 °C, under N2 pressure). These catalysts also exhibited high stability upon 5 successive reaction cycles. The formation of a crystalline CuO phase was demonstrated in the nanocomposites at a high Cu loading, with elongated shaped particles formed on the cerium oxide surface. Such particles were however, not observed at low Cu loadings. XPS analysis revealed that Cu(ii) was the main Cu species on the fresh catalyst, and that this species was reduced to Cu(i) during the reaction. Complementary characterization over the spent catalyst clearly showed the morphological modifications of the CuO phase, however, did not impact significantly either glycerol conversion or selectivity to lactic acid upon recycling. For instance, apparently, the catalytic activity of CuO largely depends on the Cu(ii) species.

Glycerol valorization to lactic acid catalyzed by hydroxyapatite‐supported palladium particles

“…According to Palacio et al, the absence of a catalyst, paired with selected reaction conditions (220 °C, 100 mL of NaOH 0.6 mol L −1 , 5 wt% glycerol), had a marked effect on glycerol conversion. Reportedly, lactic acid was formed with selectivity of 52% and after 8 h reaction time, the glycerol conversion only reached 30% …”

“…Glycerol, with three functional hydroxyl groups, allows various selective catalytic transformations to chemicals (e.g. acrolein, acrylic acid, propanediol and lactic acid). Notably, glycerol selective oxidation to lactic acid has received growing attention, because it supports a new chemical route for large‐scale lactic acid production.…”

“…The production capacity of polylactic acid is predicted to be 830 kt in 2020 . Lactic acid can be produced either chemically or biotechnologically by fermentation routes . The chemical route using HCN and acetaldehyde is of less interest nowadays due to environmental concerns.…”

“…The chemical route using HCN and acetaldehyde is of less interest nowadays due to environmental concerns. The fermentation route, with various carbohydrates as starting resources, can produce optically pure l ‐(+)‐ or d ‐(−)‐lactic acid yet suffers from low productivity and efficiency . Thus, the fermentation route may be not insufficient to meet the increasing demand of lactic acid in the chemical industry.…”

Functional characterization of bimetallic CuPdxnanoparticles in hydrothermal conversion of glycerol to lactic acid

“…Until recently, lactic acid has been primary produced via fermentation routes using natural carbohydrates as starting sources. The fermentation route, producing optically pure L ‐(+)‐ or D ‐(−)‐lactic acid, dissatisfy the environmental and technical goals due to relatively low productivity and efficiency (Cubas‐Cano, González‐Fernández, & Tomás‐Pejó, ; Noraini & Ahmad, ; Palacio et al, ). The growing market demand for pure lactic acid has been estimated to 260,000 ton in 2008.…”