Titania‐Supported Gold Nanoparticles as Efficient Catalysts for the Oxidation of Cellobiose to Organic Acids in Aqueous Medium

Abstract

Titania‐supported gold nanoparticles were prepared by using the deposition–precipitation method, followed by reduction under a hydrogen flow. The catalytic activity of these as‐prepared catalysts was explored in the oxidation of cellobiose to gluconic acid with molecular oxygen, and the properties of these catalysts were examined by using XRD, TEM, temperature‐programmed desorption of NH3, energy‐dispersive X‐ray spectroscopy, UV/Vis, and X‐ray photoemission spectroscopy (XPS). The catalyst sample reduced at high temperature demonstrated an excellent catalytic activity in the oxidation of cellobiose. The characterization results revealed the strong metal–support interaction between the gold nanoparticles and titania support. Hydrogen reduction at higher temperatures (usually >600 °C) plays a vital role in affording a unique interface between gold nanoparticles and titania support surfaces, which thus improves the catalytic activity of gold/titania by fine‐tuning both the electronic and structural properties of the gold nanoparticles and titania support.

High-temperature reduction improves the activity of rutile TiO2 nanowires-supported gold-copper bimetallic nanoparticles for cellobiose to gluconic acid conversion

“…These reactions have been studied recently due to the application of gluconic acid in pharmaceutical processes and as water-soluble cleansers and additives in the food industry [28]. Furthermore, the effect and possible role of titania nanowires as compared other forms of titania (TiO 2 -P25 and TiO 2 (75% Anatase-25% Rutile) powder, the effect of hydrogen reduction as compared to calcination in air of Au-Cu/TiO 2 NWs and the role of Cu as an active catalyst for replacing part of gold by enabling the replacement of high gold loading catalyst with a lower gold loading catalysts were investigated toward the conversion of cellobiose to gluconic acid as compared to our earlier work [29], where we investigated the influence of hydrogen reduction on titania supported-gold nanoparticles monometallic catalysts and compared their catalytic performance with gold supported on zeolite-HY, Carbon nanotube and Al 2 O 3 supports. Efforts were made to illustrate the interactions between gold and copper and also to investigate the surface composition of the as-synthesized catalyst.…”

Electrocatalytic Oxidation of Cellulose to Gluconate on Carbon Aerogel Supported Gold Nanoparticles Anode in Alkaline Medium

“…This might be attributed to its favorable adsorption to oxygen atoms of the 1-4-glycosidic bonds in cellulose molecules, so as to benefit the catalytic performance. Moreover, the introduce of surface oxidized functional groups to carbon support can also increase the interaction between Au nanoparticles and support, and at the same time, promote the selectivity of gluconic acid [7,9]. In addition, although Au is one of the most active electrocatalysts for the oxidation of cellulose [9,33], the high yield and high selectivity to gluconic acid (or gluconate) depends mainly on the size, dispersion and electronic state of Au.…”

“…Considering that oxygen usually plays important roles in the selective oxidation of glucose to gluconic acid, particularly Au-based catalysts [4,7,28], the effect of oxygen was also studied on cellulose electrochemical oxidation by whether bubbling air into the reaction system or not. Experiment results show that the products of cellulose electrolysis are constant regardless of with or without air aeration, accompanying with a nearly unchanged products distribution.…”

“…A 97% yield to gluconic acid was achieved over Au/CS 1.7 H 1.3 PW 12 O 40 at 145˝C and 0.5 MPa O 2 , which was attributed to the high acidity of the catalyst. Moreover, the same catalyst afforded a 70% conversion of a ball-milled cellulose by oxidation at 145˝C under 1 MPa of O 2 , resulting in a 60% yield to gluconic acid after 11 h. By using Au/TiO 2 as catalyst, Borgna et al [7] achieved a 93% conversion of cellobiose and a 73.7% selectivity of goluconic acid. The high catalytic activity of Au/TiO 2 is considered to depend on the catalyst as a whole, especially the strong metal-support interaction between gold nanoparticles and titania support, rather than the sole size range of Au nanoparticles.…”

“…Moreover, the network of intra-and intermolecular hydrogen bonds formed between the hydroxyl groups in adjacent cellulose makes it insoluble in water and in most organic solvents under mild conditions, which further aggravates the restriction for its utilization. In previous studies, various approaches including mineral acids hydrolysis, hydrothermal oxidation, enzymes hydrolysis, heterogeneous acids catalysis, metal and metal oxide catalysis, etc., were attempted to transform cellulose [3][4][5][6][7][8]. High value-added chemicals and fuels, such as glucose, polyols and organic acids, have been obtained.…”