Selective liquid-phase oxidation of Lactose to Lactobionic Acid

REGENHARDT, SILVINA; MEYER, CAMILO; GARETTO, TERESITA; MARCHI, ALBERTO

Pittsburgh, PA

Congreso; 24th North American Catalysis Society Meeting; 2015

THE NORTH AMERICAN CATALYSIS SOCIETY

Lactose (LA) is a major component of whey, the main by-product in cheese production in dairy industry. Cheese whey typically contains about 5 wt. % lactose, which can be converted to lactobionic acid (LBA) by selective oxidation. This acid has antioxidant properties and its largest commercial use is as an important constituent to preserve solutions for human organs during transplantation procedures. LBA is also employed as acidulant, complexing agent and antioxidant in food and pharmaceuticals. Nowadays, LBA is produced by microbiological oxidation of LA. The main disadvantages of this process are the long times required to achieve high levels of conversion and the formation of hydrogen peroxide as a byproduct. However, recently, there has been increasing interest in the LBA production by heterogeneous catalytic oxidation of LA. Some authors have studied LA oxidation using different metals and supports. It was found that metal, pH, temperature and O2 concentration has important influence on this reaction. The aim of this work is to analyze the effect of support, metal and initial lactose concentration in the liquid-phase LA oxidation at low temperature (65°C) and pH=9 in order to obtain high yield and selectivity to LBA. Pt-based catalysts were prepared by incipient wetness impregnation and Au-based catalysts by precipitation-deposition method.Oxidation experiments over Pt/SiO2, Pt/Al2O3 and Au/Al2O3 with an initial LA concentration of 0.012 M showed that after 180 min the LA conversion over Pt/SiO2 was only about 9%, while for Pt/Al2O3 was 23%. This activity difference could be assigned to the mayor dispersion of metallic Pt over Al2O3 compared with SiO2. Furthermore, Au/Al2O3 was much more active than Pt/Al2O3: a LA conversion of 85% after 180 min was achieved. In all cases, for the conditions used in this work, the only oxidation product detected was LBA. Experiments with different initial LA concentration, between 0.03 and 0.17 M were carried out with Au/Al2O3 in order to estimate the reaction order respect to LA. It was determined that, for a given reaction time, the LA conversion decreased as the initial concentration was raised. Total LA conversion with 100% selectivity to LBA was obtained using a highly dispersed and stable Au/Al2O3 catalyst