Gold-on-carbon catalysts

Porta F, Prati L. Selective oxidation of glycerol to sodium glycerate with gold-on-carbon catalyst an insight into reaction selectivity. J Catal. 2004 224 397-403. 

Rossi and co-workers studies [360,361] showed that gold on carbon catalyst is a valid alternative to most of the investigated multi-metallic catalysts based on Pd and/or Pt metals. Moreover, gold has a unique property, i.e., it operates without the external control of pH, thus ensuring total conversion at all pH values, and total selectivity to gluconic acid. 

Porta, F. and Prati, L. (2004). Selective Oxidation of Glycerol to Sodium Glycerate with Gold-On-Carbon Catalyst An Insight into Reaction Selectivity, Journal of Catalysis, 224(2), pp. 397 03. 

L. Prati and M. Rossi, Gold on carbon as a new catalyst for selective liquid phase oxidation of diols, J. Catal. 176(2), 552-560 (1998). 

Consequently, gold on carbon has considerable potential as a commercial catalyst for the manufacture of vinyl chloride (see Sect. 6.5.2). 

Rossi and co-workers have studied the oxidation of organic substrates in the liquid phase, and shown that gold on carbon is the preferred catalyst [27,357-364]. One of the best preparation methods is the immobilisation of colloidal particles [27,140, 357-360, 362-364], which can readily be prepared... 

Thus, it was shown that gold on carbon was much better than the more complicated multi-metallic Pt/Pd/Bi catalysts evaluated previously [365,386-392] for the liquid-phase oxidation of D-glucose, giving 100% selectivity to gluconic acid [360,361], Claus and co-workers also studied a series of Au/C catalysts prepared by the sol-gel method and got conversions and selectivities... 

F. Moreau, G. C. Bond, A. O. Taylor, Gold on titania catalysts for the oxidation of carbon monoxide Control of pH during preparation with various gold contents, ]. Catal. 231 (2005) 105. 

Palladium-gold on alumina catalysts are examples of bifunctional catalysts (3,4), in which the alumina carrier itself possesses acidic sites that are involved in the reactions. This property of the system impedes a detailed understanding of the effect of the gold in suppressing the formation of C,-C6 alkanes. However, when alkanes or cycloalkanes are contacted with simpler metal catalysts, specifically, metals which are either unsupported or supported on a relatively nonacidic carrier such as silica, a similar marked suppression in the formation of products of lower carbon number than the reactants is observed when a Group IB metallic element is incorporated with a Group VIII metal. Examples are given in our 1971 patent (5), for which the... 

Scheme 13.3 was then adopted by us and other different research groups also for gas-phase applications. Coprecipitation, deposition-precipitation and colloidal particles immobilisation, discussed in Section 13.2, were the preferred methods for preparing catalysts. In our case, supporting finely dispersed gold on carbon by means of metal sol immobilisation led to the discovery of an active and selective catalyst for liquid phase oxidation. 

Prati, L. and Rossi, M. (1998). Gold on Carbon as a New Catalyst for Selective Liquid Phase Oxidation of Diols, J. Catal, 176, pp. 552-560. 

Propylene oxide is also produced in Hquid-phase homogeneous oxidation reactions using various molybdenum-containing catalysts (209,210), cuprous oxide (211), rhenium compounds (212), or an organomonovalent gold(I) complex (213). Whereas gas-phase oxidation of propylene on silver catalysts results primarily in propylene oxide, water, and carbon dioxide as products, the Hquid-phase oxidation of propylene results in an array of oxidation products, such as propylene oxide, acrolein, propylene glycol, acetone, acetaldehyde, and others. 

The oxidation of CO at low temperatures was the first reaction discovered as an example of the highly active catalysis by gold [1]. Carbon monoxide is a very toxic gas and its concentration in indoor air is regulated to 10-50 ppm depending on the conditions [61]. An important point is that CO is the only gas that cannot be removed from indoor air by gas adsorption with activated carbon. On the other hand, metal oxides or noble metal catalysts can oxidize CO at room temperature. 

The strategy for preparing gold catalysts for liquid-phase oxidation is based on environment friendly and cheap methodologies with the aim to produce 3-5 nm particles, well dispersed on carbon supports, to be applied also to large-scale preparations. 

Maye et al. studied gold nanoparticles supported on carbon black for ORR in both acidic and alkaline media.210 The gold nanoparticles were of a core-shell type where the particle consisted of a gold nanocrystal core of 1-6 nm in diameter that was surrounded by an organic monolayer shell.214 While the Au/C catalyst was found to be active for ORR, its activity was much lower than that of Pt/C, PtRu/C and AuPt/C. The electron transfer in 0.5 M H2S04 was reported as 2.9 0.2, indicating a mixed reduction pathway.210... 

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