Conversion of glycerol to dihydroxyacetone over Au catalysts on various supports

Abstract

BACKGROUND Glycerol, which is a coproduct of biodiesel production, has been identified as a key platform compound for producing various valuable chemicals. The selective catalytic oxidation of glycerol to dihydroxyacetone is very attractive. RESULTS A series of Au catalysts supported on metallic oxides, i.e. ZnO, CuO, Al2O3, Fe2O3 and NiO, were studied for selective catalytic oxidation of glycerol to dihydroxyacetone under base‐free conditions. Among the catalysts, Au/CuO showed the best catalytic activity (glycerol conversion of 89% and dihydroxyacetone selectivity of 82.6% at 80 °C under 10 bar of O2), followed by Au/ZnO ≫ Au/NiO > Au/Al2O3 ≈ Au/CuO‐SD ≈ Au/Fe2O3. The catalytic behaviors of these supported Au catalysts varied depending on the Au particle size, Au oxidation state, Au–support interactions and lattice oxygen reducibility. CONCLUSION The main reasons for the high catalytic activity of Au/CuO are as follows. Firstly, the catalyst has small metallic Au particles, which are more active in cleavage of the secondary CH bond in glycerol molecules. Secondly, the interactions between Au and CuO facilitate lattice oxygen reduction, and this increases oxygen mobility, which may promote regeneration of Au–support perimeter active sites by gaseous oxygen. © 2019 Society of Chemical Industry

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

“…Therefore, it is plausible that gluconic acid tends to follow the C 1 −C 5 cleavage reaction via the decarboxylation reaction (orange route in Figure 2) over the Au/TiO 2 catalyst; thus, XYLA is formed as the major product. 30 However, for the Pt/ TiO 2 catalyst, gluconic acid (GA in Figure 2) seems to undergo subsequent C−C cleavage and oxidation, which eventually gives XYLA and TA as major products (orange and green routes). 22 Again, the bimetallic AuPt/TiO 2 * catalyst shows improved conversion compared with Au/TiO 2 and Pt/ TiO 2 catalysts, promoting consecutive C−C cleavage of gluconic acid (via orange and green routes); thus, TA is formed as the main product with almost 40% selectivity.…”

“…Results in Figure show that for oxidation of gluconic acid, Pt/TiO 2 (15.5%) outperforms the Au/TiO 2 catalyst (8.4%) in terms of conversion at 110 °C after 4 h. It is clear that Au/TiO 2 gives XA (a C 5 product) as the major product, while the Pt/TiO 2 material leads to the formation of both TA and XA (combined selectivity > 70%). Therefore, it is plausible that gluconic acid tends to follow the C 1 –C 5 cleavage reaction via the decarboxylation reaction (orange route in Figure ) over the Au/TiO 2 catalyst; thus, XYLA is formed as the major product . However, for the Pt/TiO 2 catalyst, gluconic acid (GA in Figure ) seems to undergo subsequent C–C cleavage and oxidation, which eventually gives XYLA and TA as major products (orange and green routes) .…”

The support influence of Au‐based catalysts in glycerin selective oxidation to glyceric acid

“…Nano‐CuO was synthesized by the hydrothermal method 19,20 . Na 2 CO 3 solution (1 mol L −1 ) was quickly added in Cu(NO 3 ) 2 solution (0.25 mol L −1 ), maintaining stirring and pH = 10.…”

Recent Advances in Glycerol Catalytic Valorization: A Review

“…A tuneable acidity can be generated through support synthesis methodologies that induce oxygen vacancies in the material, and these have been studied in different works concerning the influence of the support in the reaction [114]. Among them, materials such as carbon [115][116][117], metal oxides [118][119][120][121][122][123][124][125], zeolites [116,[126][127][128][129][130][131], and mixed oxides [120,[132][133][134][135] that exhibited high acidity were applied, in order to benefit the dehydration step [120,128,136]. In these cases, selectivity to 1,2-PDO can be explained if glycerol adsorption over support acid sites controlled by a steric effect is considered.…”