Gold catalysts for the liquid phase oxidation of o-hydroxybenzyl alcohol

Gold supported on iron oxy-hydroxides: a versatile tool for the synthesis of fine chemicals

“…Hematite (␣-Fe 2 O 3 ) is the prevailing crystallographic phase, but goethite (␣-FeOOH) and ferrihydrite have been also found [5]. Upon dispersing gold, through the deposition-precipitation, the ferrihydrite phase almost disappears (entry 10).…”

“…It is likely that during the deposition of gold, ferrihydrite is transformed into the more ordered hematite phase [29]. It is interesting to note that after 1 h reduction of the catalyst in H 2 , at 343 K in ethanol (entry 11), the chemical state of iron oxide is substantially unmodified with respect to that of the "as prepared sample" [5]. Au(III), instead is converted to Au metal [6].…”

“…Gold supported on iron oxy-hydroxides, hydrogenates, citral and cinnamaldehyde to the corresponding ␣,␤ unsaturated alcohols with a selectivity higher than 85%, without the addition of promoters [3,5].…”

“…Ponec et al have reported that the rate of hydrogenation of the C=O bond of propanal is dramatically enhanced by addition of Sn(II), Ga(III) or Fe(III) to a Pt/SiO 2 catalyst, whereas the rate of hydrogenation of acetone is only hardly increased [20]. Selective hydrogenation of ␣,␤ unsaturated ketones to the corresponding unsaturated alcohols, with molecular H 2 , has been instead achieved on Au supported on iron oxyhydroxides catalysts [4][5][6]. In particular, in the hydrogenation of benzalacetone and 4-methyl,3-penten,2-one the selectivity towards the formation of unsaturated alcohol was higher than 60% up to quantitative conversion of the substrates.…”

Gold nanoclusters as colloidal catalysts for oxidation of long chain aliphatic 1,2-diols in alcohol solvents

“…Gold metal catalysis has already been successfully used in gas phase reactions like the low temperature oxidation of CO (2,3), the acetylene hydrochlorination (4), the water-gas shift (5) and the epoxidation of propylene (6). Examples of liquid phase metallic gold catalyzed reactions are redox reactions such as the oxidation of alcohols and aldehydes (7)(8)(9), the hydrogenation of unsaturated ketones to allylic alcohols (10) and the synthesis of H 2 O 2 (11). Particularly in the liquid phase oxidation of 1,2-diols like 1,2-ethanediol and 1,2-propanediol, Prati and Rossi showed that gold is a suitable alternative for platinum group catalysts, because the surface of Au is not readily overoxidized and is hardly sensitive to chemical poisoning by acid adsorption (12).…”