Ruthenium Sponge

Fig. 5 HREM micrograph of ruthenium sponge-like particles obtained in pure methanol...

Ruthenium Sponge results on ignition of ammonium chlor-ruthenate. It readily dissolves in a solution of hydrogen chloride saturated with chlorine yielding halogen derivatives. Hydrobromic acid saturated with bromine likewise effects the solution of ruthenium sponge. 

Some data fitting results are displayed in Figures 12.1 and 12.3. The general conclusion is that both models describe the behaviours of the main components, lactose and lactitol very well, both for sponge nickel and ruthenium catalysts. In this respect, no real model discrimination is possible. Both models also describe equally well the behaviour of lactobionic acid (D), including its concentration maximum when the reversible step is included (ks) (Figure 12.3). 

Catalyst deactivation during consecutive lactose and xylose hydrogenation batches over Mo promoted sponge nickel (Activated Metals) and Ru(5%)/C (Johnson Matthey) catalysts were studied. Deactivation over sponge nickel occurred faster than on Ru/C in both cases. Product selectivities were high (between 97 and 100%) over both catalysts. However, related to the amount of active metal on the catalyst, ruthenium had a substantially higher catalytic activity compared to nickel. 

Catalyst deactivation often plays a central role in manufacturing of various alimentary products. Sugar alcohols, such as xylitol, sorbitol and lactitol, are industrially most commonly prepared by catalytic hydrogenation of corresponding sugar aldehydes over sponge nickel and ruthenium on carbon catalysts (5-10). However, catalyst deactivation may be severe under non-optimized process conditions. 

The R11 is purified by distilling with Cl2. Volatile ruthenium tetroxide is collected, A saturated solution of NFLiClis added, causing the precipitation of ammonium hexachlororuthenate(III). The precipitated salt is calcined in H2. yielding commercial Ru sponge. 

In a reaction that similarly relies on the acidity of benzylic protons in arene-ruthenium(II) complexes, the r 6-mesitylene complex 92 containing bidentate (C6F5)2PCH2CH2P(C6F5)2 loses two molecules of HF on treatment with proton sponge to give the di-strapped salt 93 in which each tether contains three carbon atoms [Eq. (18)]).83... 

Following the development of sponge-metal nickel catalysts by alkali leaching of Ni-Al alloys by Raney, other alloy systems were considered. These include iron [4], cobalt [5], copper [6], platinum [7], ruthenium [8], and palladium [9]. Small amounts of a third metal such as chromium [10], molybdenum [11], or zinc [12] have been added to the binary alloy to promote catalyst activity. The two most common skeletal metal catalysts currently in use are nickel and copper in unpromoted or promoted forms. Skeletal copper is less active and more selective than skeletal nickel in hydrogenation reactions. It also finds use in the selective hydrolysis of nitriles [13]. This chapter is therefore mainly concerned with the preparation, properties and applications of promoted and unpromoted skeletal nickel and skeletal copper catalysts which are produced by the selective leaching of aluminum from binary or ternary alloys. 

Properties of the palladium metals and platinum. Ruthenium, osmium, rhodium, iridium, palladium, platinum. Osmium tetroxidc. Chloropailadous acid, chlo-ropaliadic acid, chloroplatinous at id. rhloroplatinic acid. Platinum sponge, platinum black. Uses of the palladium and platinum metals. 

Cavallito (66) reports that neither it nor 3-benzoxypyridine was hydrogenated in the presence of Willstatter s palladium sponge catalyst (67). Under low pressure conditions in ether or dioxane Raney nickel and platinum oxide were ineffective. However, other examples show that reduction takes place readily under a variety of conditions. Biel used Raney nickel at 125° and 50 atm (68), excellent yield of 6-propyl-3-hydroxypiperidine resulted from reduction of the pyridine in acetic acid with platinum oxide (69). Ruthenium in the conversion of 3-hydroxypyridine in aqueous solution gave very high yield of the corre-... 

More recently, Llobet and coworkers reported the anodic electropolymerization of A -substituted pyrroles as a convenient method of anchoring a redox-active dinuclear ruthenium catalyst onto conducting solid supports, like vitreous carbon sponges (VCS) and fluorine-doped tin oxide (FTO). In the presence of Ce(IV) as the sacrificial oxidant, turnover numbers up to 76 have been achieved. A major improvement of the system is accomplished by the copolymerization with a robust non active redox species, able to further separate the catalytically active species on the solid support, obtaining up to 250 catalytic cycles. 

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