Oxidation of d‐Glucose to Glucaric Acid Using Au/C Catalysts

Abstract

The reactivity of Au and AuBi nanoparticles supported on activated carbon AC was investigated in the direct oxidation of glucose to glucaric acid. The catalysts were very active, regardless of the Au nanoparticles size, but the catalyst with the smallest average particle diameter was the least selective to glucaric acid because of the enhanced consecutive oxidative degradation of the intermediately formed gluconic acid. The reaction network included the fast oxidation of glucose to gluconic acid, which was the only primary product, and its consecutive oxidation into either glucaric acid or lighter mono and dicarboxylic acids. The best glucaric acid yield obtained with a AuBi/AC catalyst (Au/Bi 3:1) was 31 %, with 18 % residual gluconic acid. The control of reaction parameters was essential to achieving the best selectivity. Specifically, the glucose concentration turned out to be a critical parameter in relation to O2 pressure and to glucose/metal ratio.

Advances in Base-Free Oxidation of Bio-Based Compounds on Supported Gold Catalysts

“…Indeed, at 70 • C and after 4 h of reaction in the presence of K 2 CO 3 , a noncatalyzed (thermal) oxidative degradation of glucose was observed. Similar results already described in the literature [28][29][30] confirmed the formation of formic, acetic, and propionic acids, as well as of 24 hydrocarboxylic acids and 12 corresponding lactones. The aldehyde and alcohol functions of monosaccharides (such as glucose) can be oxidized giving high added-value compounds (see Scheme 1).…”

“…Studies confirmed that the best catalytic activity and the highest TOF were observed with a mass ratio of 70/20/10 [48]. Recently, Hutchings's group [28] studied several Au bimetallic catalysts for the oxidation of glucose and cellobiose. They found that the preparation method plays a crucial role in the catalytic activity of supported Au catalysts especially in the case of base-free oxidation processes.…”

“…The following step of this reaction is the oxidation of the primary hydroxyl to yield glucaric acid. Although the oxidation of glucose directly to dicarboxylic acids was already demonstrated to occur on a Pt/C catalyst using oxygen as an oxidant [53][54][55], the oxidation of free gluconic acid into glucaric acid was also demonstrated on Au/C catalysts [28]. It has been reported that the rate of the reaction between the chemisorbed oxygen and the adsorbed gluconic acid is much lower than that of the reaction between the chemisorbed oxygen and the adsorbed glucose [55].…”

Furfural Oxidation on Gold Supported on MnO2: Influence of the Support Structure on the Catalytic Performances

“…In recent decades, supported gold nanoparticles have been extensively studied because of their unusual catalytic properties [1][2][3][4]. It is well recognized that the size of gold nanoparticles determines both the activity and the selectivity of the final catalyst [4,5].…”

“…It is well recognized that the size of gold nanoparticles determines both the activity and the selectivity of the final catalyst [4,5]. It is also considered that the drastic change of the catalytic properties of nanoparticles is due to their new properties (physical and chemical) which are created when their size decreases, mainly due to the significant increase in the number of atoms on the surface [5][6][7].…”