Aerobic Oxidation of 5-Hydroxymethyl-furfural to 2,5-Furandicarboxylic Acid at 20 °C by Optimizing Adsorption on AgPd Alloy Nanoparticle Catalysts

Abstract

Production of 2,5-furandicarboxylic acid (FDCA, a platform chemical for the chemical industry in the future) by the selective aerobic oxidation of 5-hydroxymethyl-furfural is a crucial component to enable the FDCA production from sugars. The challenge is to achieve a high FDCA yield at low temperatures. Here, we report a catalyst composed of alloyed nanoparticles (containing 1.5 wt % Ag and 1.5 wt % Pd) supported on CeO2 nanofibers, which achieved an excellent FDCA yield (93%) at 20 °C. Interesting observations include yield deterioration at higher reaction temperatures; water is the source of the oxygen atom(s) added to the oxidized intermediates and product, while O2 molecules adsorbed onto the catalyst scavenge electrons, yielding OH• radicals from OH– ions in the reaction system to drive the oxidation. At 20 °C, we avoid side reactions, but there is no external energy provided for overcoming the activation barriers. The barriers for activating the alcohol groups are significant. We find that the appropriate chemisorption on the catalyst is critical for a high FDCA yield. By tuning the Ag/Pd ratio, we attained the most catalytically active sites, bimetallic surface sites, at the boundaries between Ag and Pd clusters. The chemisorption at these sites is strong enough to cause the selective oxidation of both the aldehyde and alcohol groups in HMF at 20 °C, avoiding side reactions at high temperatures. The knowledge acquired from this study is expected to have implications for other catalytic systems where competitive reactions proceed.

Nickel -supported PdM (M = Au and Ag) nanodendrites as formate oxidation (electro)catalytic anodes for direct fuel cells and hydrogen generation at room temperature

“…4e and f depict the EDS mapping of elements Pd and Ag, revealing that the concentration of Ag on the surface is higher than that of Pd on the surface, accordingly, signifying that the Ag element is enriched on the surface, while more Pd exists in the core, because of the lower surface energy of Ag than that of Pd. 49,50 The nickel-supported PdM (M = Au and Ag) nanodendrites before and after catalysis were further characterized by TEM and HRTEM, as shown in Fig. 5.…”

A Review on Green and Efficient Synthesis of 5-Hydroxymethylfurfural (HMF) and 2,5-Furandicarboxylic Acid (FDCA) from Sustainable Biomass

“…The catalyst used in HMF oxidation could also play an important role in deciding the reaction temperature to be maintained. For example, Jin et al 94 were able to synthesize FDCA with a high yield of 93% at a very low temperature of 20 °C, using a catalyst composed of alloyed nanoparticles (1.5 wt % Ag and 1.5 wt % Pd) supported on CeO 2 nanofibers. Water was used as oxygen atom source.…”

Industry-oriented method for the aqueous phase oxidation of crude 5-hydroxymethyl furfural (HMF) to 2,5-furandicarboxylic acid (FDCA)

“…It is known that hydroxymethyl (ÀCH 2 OH) and formyl (ÀCHO) groups in HMF are highly reactive and they induce complex side-reactions, such as condensation and polymerization, specifically under temperatures as low as 70 1C and under acidic conditions, which are used to convert sugars into HMF. [40][41][42] These side products are often called humins and are typically formed in higher concentrations when HMF concentrations are also high. These humins contain compounds with dimeric or larger structures and also several functional groups.…”