Functional characterization of bimetallic CuPd_x nanoparticles in hydrothermal conversion of glycerol to lactic acid

The crude glycerol from biomass represents an abundant and inexpensive resource which can be utilized in producing food additives such as lactic acid. The direct transformation of bioderived glycerol to lactic acid under the catalysis of bimetallic CuPd_x nanoparticles as well as monometallic Cu and Pd was investigated in hydrothermal conditions. The properties of fresh and spent bimetallic CuPd_x nanoparticles were characterized with various physicochemical techniques viz. XRD, TEM, HRTEM, XPS, and AAS measurements. Catalytic activity of the prepared CuPd_x nanoparticles is superior to the monometallic ones due to the alloying trend and synergistic effects. At optimal experimental conditions (100 ml of glycerol and NaOH solution, catalyst/glycerol mass ratio 2:100, 220°C, and 2.0 hr), the desired lactic acid selectivity catalyzed by the bimetallic CuPd₂ , CuPd₃ , and CuPd₄ catalysts reached 95.3%, 91.4%, and 90.9%, respectively. PRACTICAL APPLICATIONS: Lactic acid, a widely used food additive, was traditionally produced by fermentation. However, due to the limitation such as time-consuming and complex separation procedure, interest has been attracted in developing an alternative approach toward efficient production of lactic acid. An attempt was made in present study to use the biodiesel byproduct, glycerol, and chemical conversion to high-valued lactic acid. Compared with traditional biological fermentation route, it was evidenced that glycerol selective transformation to lactic acid involves a new chemical reaction path for commodity lactic acid with a large availability and economic efficiency. This finding is significant for sustainable development of biodiesel industry and elimination of environmental issues arising from the abandoned crude glycerol.