Bimetallic AuPt/TiO₂Catalysts for Direct Oxidation of Glucose and Gluconic Acid to Tartaric Acid in the Presence of Molecular O₂

Abstract

Tartaric acid is an important industrial building block in the food and polymer industry. However, green manufacture of tartaric acid remains a grand challenge in this area. To date, chemical synthesis from nitric acid-facilitated glucose oxidation leads to only <10% yield with significant toxics as byproducts. We reported a one-pot aqueous-phase oxidation of glucose and gluconic acid using bimetallic AuPt/TiO2 catalysts in the presence of molecular O2, with ∼50% yield toward tartaric acid at 110 °C and 2 MPa. Structural characterization and density functional theory (DFT) calculation reveal that the lattice mismatch between fcc Pt and bcc Au induces the formation of twinned boundaries in nanoclusters and Jahn–Teller distortion in an electronic field. Such structural and electronic reconfiguration leads to enhanced σ-activation of the C–H bond competing with π–π electronic sharing of the CO bond on the catalyst surface. As a result, both C–H (oxidation) and C–C (decarboxylation) bond cleavage reactions synergistically occur on the surface of bimetallic AuPt/TiO2 catalysts. Therefore, glucose and gluconic acid can be efficiently transformed into tartaric acid in a base-free medium. Lattice distortion-enhanced reconfiguration of the electronic field in Pt-based bimetallic nanocatalysts can be utilized in many other energy and environmental fields for catalyzing synergistic oxidation reactions.

Structure–Reactivity Effects of Biomass‐based Hydroxyacids for Sustainable Electrochemical Hydrogen Production

“…In the case of oxidation of ethyl lactate to ethyl pyruvate, 59.7 and 103.4 kJ mol −1 were obtained using catalysts based on MoVNbO [65] and a titanium‐based zeolite, [66] respectively. E a values for GA oxidation to a range of different products (with ≈50 % tartaric acid selectivity) were also in the same order with 46.5 and 90.2 kJ mol −1 reported for Pt/TiO 2 and AuPt/TiO 2 heterogeneous catalysts, [40] respectively.…”

“…Formate was identified as one of the GA oxidation products and its oxidation to CO 2 has been widely reported with Pd‐based electrocatalysts [70,71] . The GA oxidation certainly follows a more complex reaction mechanism than the LA oxidation and proposed pathways for the detected products are represented in Figure 9 based on previous reports in the literature from the oxidation of similar species such as GA, glucose or glycerol [40,72–74] . Briefly, we propose that the GA oxidation takes place preferentially through the oxidation of the carbons furthest from the carboxylic group (C 6 and C 5 ).…”

“…GA is mainly used in the food industry as an acidity regulator, [33] but it might become a promising sustainable and cost‐effective platform chemical to produce an additional range of chemicals such as tartaric, oxalic or glucaric acids for further applications, with the latter being considered as one of the most valued chemical products that can be derived from biomass [39] . Whilst the valorization of GA by heterogeneous catalysis seems to be a promising and well‐investigated application, [40] it is still unknown if this hydroxyacid could become a good option for the sustainable production of H 2 by electrolysis since only a few and very limited studies regarding the electro‐oxidation of GA have been reported. For instance, GA electro‐oxidation on graphite electrodes has shown to produce arabinose with good selectivity, [41,42] but the lack of electrocatalytic properties of graphite required the application of a very high potential (+1.5 V vs. SHE).…”

Dealuminization for a Modified (Si–OH)n–Pt Interface: Self-Activation of Pt/NaY Catalysts for Oxidation of Ethylene Glycol in a Base-Free Medium

“…Based on the data presented in Figure a,b, it is strongly believed that metallic Pt 0 species, favoring σ-bond activation to eventually formulate Pt–H intermediates, contributes to good EG conversion (Figure c) . However, cationic Pt δ+ species in Pt/NaY samples often facilitate π-activation with O species rather than promote dehydrogenation reaction . As a result, the calcined Pt/NaY catalyst (Pt/NaY-0) with a dominant Pt δ+ content displays poor EG conversion compared with Pt/NaY-400 samples.…”

Effect of CeO2 morphology on the catalytic properties of Au/CeO2 for base-free glucose oxidation

“…However, in order to obtain a high catalytic performance in the absence of alkali, gold-based catalysts typically require harsh reaction conditions at high temperatures of 373–473 K with an oxygen pressure of 0.5–2.0 MPa. 11–13 And when it comes to reacting under milder conditions, the choice of support turns out to be crucial. For example, using Au nanoparticles on alkaline MgO or Mg(OH) 2 supports as catalysts, base-free oxidation of glucose can be performed at 60 °C under ambient pressure, showing high catalytic activity with 100% selectivity toward gluconic acid.…”