The preparation of large surface area lanthanum based perovskite supports for AuPt nanoparticles: tuning the glycerol oxidation reaction pathway by switching the perovskite B site

Abstract

Gold and gold alloys, in the form of supported nanoparticles, have been shown over the last three decades to be highly effective oxidation catalysts. Mixed metal oxide perovskites, with their high structural tolerance, are ideal for investigating how changes in the chemical composition of supports affect the catalysts' properties, while retaining similar surface areas, morphologies and metal co-ordinations. However, a significant disadvantage of using perovskites as supports is their high crystallinity and small surface area. We report the use of a supercritical carbon dioxide anti-solvent precipitation methodology to prepare large surface area lanthanum based perovskites, making the deposition of 1 wt% AuPt nanoparticles feasible. These catalysts were used for the selective oxidation of glycerol. By changing the elemental composition of the perovskite B site, we dramatically altered the reaction pathway between a sequential oxidation route to glyceric or tartronic acid and a dehydration reaction pathway to lactic acid. Selectivity profiles were correlated to reported oxygen adsorption capacities of the perovskite supports and also to changes in the AuPt nanoparticle morphologies. Extended time on line analysis using the best oxidation catalyst (AuPt/LaMnO3) produced an exceptionally high tartronic acid yield. LaMnO3 produced from alternative preparation methods was found to have lower activities, but gave comparable selectivity profiles to that produced using the supercritical carbon dioxide anti-solvent precipitation methodology.

Glycerol Oxidation Using MgO‐ and Al2O3‐supported Gold and Gold–Palladium Nanoparticles Prepared in the Absence of Polymer Stabilizers

“…The materials prepared with and without PVA were employed for selective aqueous phase glycerol oxidation to investigate the effect of the polymer stabiliser on the catalytic performance. The general reaction pathway is illustrated in Scheme , which is based on the observations obtained in this study and of reaction pathways reported in the literature . The first oxidative dehydrogenation step forms glyceraldehyde or dihydroxyacetone, which are in equilibrium.…”

“…This is notable, since TEM characterization indicated that the preparation without capping agent resulted in larger, ill‐shaped Au NPs (Figure and Supporting Information). It is generally described in the literature that smaller Au NPs show an improved catalytic activity for glycerol oxidation . Hence, this observation might imply that, besides the detrimental effect on the particle morphology, the absence of PVA can have a positive impact on the catalytic performance.…”

Preparing and Optimization of Cerium-Lanthanum-Cobalt Ternary Mixed Oxide as Catalyst for SO₂ Reduction to Sulfur

“…In general, the acidity of catalysts corresponded to the unsaturated M cations (Ce, La, and Co) exposed on the surface [37]. Entry of La and Co cations (La 3+ and Co 3+ ) in the structure of ternary catalyst affects the acidic sites.…”

Effect of Post‐Treatment on Structure and Catalytic Activity of CuCo‐based Materials for Glycerol Oxidation

“…Thus, we cannot support this proposed reaction pathway as the sole reason for glycolic acid formation. Glycolic acid is rather formed by C−C cleavage of glyceric acid or directly as primary product. The direct formation of glycolic acid through glyceraldehyde or dihydroxyacetone intermediates was reported by Ketchie et al.…”