Gold reference catalyst

F. Porta, M. Rossi, J. Mol Catal A Chem. 553 (2003) 553. World Gold Council reference catalysts web site www. gold.org/discover/sci indu/gold catalysts/refcat.litml. 

Fig. 5. Conversion of n-butane as a function of time-on-stream during steam reforming in a flow reactor. The gray curve shows the conversion of the pure nickel catalyst, and the black curve represents the gold/nickel catalyst. From Reference (79).

In order to test our deposition-precipitation method, we have prepared gold on titania P25 (Table 1, entry 4) and compared it to a Au/P25 reference catalyst (Table 1, entry 5). It turns out that the average gold particle sizes and the size distributions are similar, around 3.7 1.5 nm. However, the gold loading as well as the sodium content are smaller in our case (by 2.3 and 3.9 times respectively), probably due to the extensive washing procedure that we have applied. This indicates that the interaction between the gold precursor and the support is still quite weak after 18 h reaction at 20°C. After treatment under reaction conditions, these two materials display similar rates both in the oxidation of CO under PROX conditions and in the oxidation of H2. However,... 

Au/Ti02 reference catalyst (Type A - Sample Number 53 from World Gold Council). 

World Gold Council reference catalysts, http //www.utilisegold.com/uses applications/catalysis/... 

Figure 1. TEM image of a titania supported gold catalyst (1.7wt.% Au) prepared by deposition-precipitation (gold particle size = 5.3+ 0.3 nm, dispersion = 36%). (Reprinted from Reference [84], 2000, with permission from American Chemical Society).

Figure 9. CO conversion as a function of temperature for supported gold catalysts (a) Au/Zr02, (b) Au/Ti02 (both PVA protected) (Reprinted from Reference [24], 2006, with permission from American Chemical Society).

It has recently been found that NEt3 is a gas-phase promoter for propene epoxidation by supported gold catalysts [245]. In more recent studies, Hughes et al. reported that catalytic amounts of peroxides could initiate the oxidation of alkenes with 02, without the need for sacrificial H2 [243]. The process worked for a range of substrates (cyclohexene, ds-stilbene, styrene and so on) and even in the absence of solvent hence, we may refer to this as green technology. 

Compensation trends found for decomposition of formic acid on metal (and other) catalysts are represented diagrammatically in Fig. 7. Line I (Table III, Q) refers to reactions over nickel and copper (3, 190, 194, 236), gold (5,189,237), cobalt (137,194), and iron (194) the observations included in this group were obtained by selection, since other metals, which showed large deviations, were omitted [see also (5), p. 422], Line I is close to that calculated for the reaction catalyzed by nickel metal (Table III, R) (3, 137, 189-194, 238). Lines II (19,233) and III (3, 234, 235) (Table III, O and P) refer to decomposition on silver. The other lines were found for the same rate process on IV, copper-nickel alloys (190) V, oxides (47, 137), VI, tungsten bronzes (239) and VII, Cu3Au (Table III, S) (240a). 

The purpose of this section is to introduce the main methods that are used to study the physical properties of small gold particles, to give their acronyms for subsequent use, and where necessary to add a few explanatory or cautionary words. These methods are already well described in the literature, so only brief treatments are necessary. A small selection of references to their use in studying gold catalysts will be included as an introduction to the relevant literature. 

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