Supported gold nanoparticle catalysts for wet peroxide oxidation

Kinetics of wet peroxide oxidation of phenol with a gold/activated carbon catalyst

“…Hydrogen peroxide was determined by colorimetric titration with a UV 2100 Shimadzu UV-VIS spectrophotometer using the titanium sulfate method [11]. A more detailed description of these analytical procedures can be found elsewhere [9].…”

“…No traces of gold were detected in the liquid samples by TXRF, therefore, deactivation by gold leaching was discarded. On the other hand, it is well-known that carboxylate species [8,9,19,20] strongly adsorb on gold nanoparticles which ultimately lead to catalyst poisoning. In particular in CWPO, dicarboxylic acids, which are typical oxidation by-products, have been considered responsible of gold deactivation [8,21].…”

“…Recent studies on the catalytic applications of gold nanoparticles show that CWPO is a promising area in that respect [6][7][8][9]. So far, gold nanoparticles deposited on hydroxyapatite (Au/HAP) [6], diamond (Au/npD) [8] or activated carbon (Au/AC) [9] have shown fairly high activity. However, frankly different efficiencies of hydrogen peroxide consumption were observed with those catalysts, which are attributed to the nature of the support, crucial for the activity of gold [9].…”

“…In our previous studies [9,10], a reaction mechanism and an oxidation pathway for phenol with Au/AC catalyst were proposed based on the experimental evidences. CWPO proceeds through a complex scheme of reactions involving a number of intermediates, such as aromatic compounds (mainly resorcinol, hydroquinone and p-benzoquinone) and low molecular weight carboxylic acids (maleic, malonic, oxalic, acetic and formic), according to the following steps: (i) adsorption of phenol and, preferentially, hydrogen peroxide on the gold-support interface, (ii) production of hydroxyl and hydroperoxyl radicals mainly on the gold surface though in some extension also occurs on the carbon surface and (iii) reaction between hydroxyl radicals and phenol molecules on the gold surface.…”

Graphite and carbon black materials as catalysts for wet peroxide oxidation

“…Homogeneous CWPO technology has been commercialized under different proprietary processes, US Peroxide, OXY-PURE ® , OHP ® and PROX T.E.C [1]. These commercial systems are attractive because of their simple design and cost-effective operation.…”