Direct oxidation of glucose with enhanced selectivity to glucaric acid with tartronic and oxalic acids as coproducts is reported using bimetallic PtPd/TiO 2 catalysts under mild conditions. Bimetallic PtPd catalysts display significantly enhanced catalytic activity (turnover frequency (TOF) 2404 h −1 ) and improved selectivity to glucaric acid (S 44%) in glucose oxidation compared to monometallic catalysts (TOF 248 h −1 , S 4%). Oxidation of glucose follows a consecutive reaction with gluconic acid as an intermediate with inhibition of the second step (to glucaric acid and C−C cleavage reactions) by the presence of glucose. Surface characterization using TEM, SEM, chemisorption, UV−vis spectroscopy, and XRD distinguished the particle morphologies and provided insights into structure−activity relations. A reaction pathway for glucose oxidation is proposed based on the product distribution. These results provide new insights into the design of bimetallic catalysts for the oxidation of glucose to glucaric acid.
In
this paper, the performance of cobalt-based catalysts was reported
for oxidation of glycerol to dicarboxylic acids such as tartronic
and oxalic acids. Cobalt catalysts supported on Mg3Al(OH)
y(CO3)
z
structures prepared by a two-step modified sol–gel method
showed 100% glycerol conversion with 64% and 24% selectivity toward
tartronic and oxalic acids under mild conditions (55–70 °C
and 0.1 MPa O2). Surface and bulk characterization by N2 adsorption/desorption, X-ray diffraction, and temperature-programmed
reduction reveals that the cobalt sites interacting with surface hydroxides
are catalytically more active than those incorporated into a framework
leading to selective glycerol oxidation to dicarboxylic acids in one
pot. On the basis of the experiments at different cobalt contents,
temperatures, and concentration–time profiles, possible reaction
pathways are discussed to explain the selectivity profile. Deactivation
of the catalyst under certain conditions has been discussed as a result
of loss of surface area due to structural changes.
By exploiting the large difference in lattice constants between Pt and Fe metals, anisotropic growth of bimetallic PtFe clusters with high index numbers have been prepared to investigate their catalytic performance in oxidation of biopolyols. Surface characterization using transmission electron microscopy shows that etching effects caused by Fe 3+ and anisotropic growth induced by lattice mismatch contributed to the final nanocrystal geometry. The bimetallic PtFe heterocluster is shown to exhibit an unprecedented six-fold enhanced catalytic activity and threefold higher selectivity compared to monometallic Pt and Fe catalysts, in oxidation of biomass-derived polyols to dicarboxylic acids. A detailed study on structure-dependent kinetics of oxidation of glycerol, based on concentration-time profiles on Pt and PtFe catalysts, reveals that the presence of Fe in Pt catalysts significantly enhances the rate of oxidation and decreases the activation barriers for primary and secondary oxidation steps leading to enhanced catalytic activity and selectivity. The lattice mismatch methodology employed in this work provides a unique tool for designing high index catalytically active materials for various other industrial applications.
Phase
transformation in anisotropic nanocrystals is critical for
enhanced surface properties of bimetallic catalysts. In this work,
we report a series of phase transformed PtFe nanocomposites as catalysts
for facile oxidation of glycerol to value-added tartronic acid at
mild operating conditions. The lattice mismatch between Pt and Fe
intrinsically drives structure reconstruction from face centered cubic
(fcc) to ordered and lattice distorted face centered
tetragonal (fct) phase. Surface characterization
reveals that there exists an interdiffusion of Pt and Fe during phase
transformation and a downward shift of binding energy for Pt species.
Such transformation induces the formation of strained PtFe nanocomposites
and enhanced structural coherence leading to 3-fold enhancement in
catalytic activity for one-pot glycerol oxidation to tartronic acid
compared with the fcc structure.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations –citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.