Raney ruthenium

This type of catalyst is not limited to nickel other examples are Raney-cobalt, Raney-copper and Raney-ruthenium. When dry, these catalysts are pyrophoric upon contact with air. Usually they are stored under water, which enables their use without risk. The pyrophoric character is due to the fact that the metal is highly dispersed, so in contact with oxygen fast oxidation takes place. Moreover, the metal contains hydrogen atoms and this adds to the pyrophoric nature. Besides the combustion of the metal also ignition of organic vapours present in the atmosphere can occur. Before start of the reaction it is a standard procedure to replace the water by organic solvents but care should be taken to exclude oxygen. Often alcohol is used. The water is decanted and the wet catalyst is washed repeatedly with alcohol. After several washes with absolute alcohol the last traces of water are removed. 

It is further important to note that all the current/voltage characteristics depicted in Fig. 6 are unchanged by the presence of liquid fuels such as methanol, formaldehyde, formic acid, or hydrazine. The phthalocyanine electrode remains completely inert toward such substances. For this reason, no mixed potential can be formed at a phthalocyanine electrode, as for example can occur at a platinum electrode, when it is used as cathode in a methanol cell containing sulfuric acid. This is shown by a comparison (see Fig. 7) of the stationary characteristics of the platinum alloy we found to be the most active in the presence of methanol, namely a Raney ruthenium—rhodium electrode, with an iron phthalocyanine electrode, both measured in 4.5 N H2SO4+2M CH3OH. 

Other specialized alloys have also been used to prepare skeletal metal catalysts. Raney ruthenium has been prepared from the ruthenium aluminum alloy. 20 A colloidal platinum has been prepared by the action of acetic acid on a platinum lithium alloy. l Skeletal nickel catalysts have been made from a number of intermetallic compounds of nickel with the rare earth elements, lanthanum and samarium. The rare earth element is removed from the alloy by reaction with diiodoethane or dibromoethane which convert the rare earths to the soluble halide salts. 22 Several multicomponent catalysts have also been prepared from the corresponding aluminum alloys. 23-126... 

It should be pointed out that the activity for nitrides of Sr and Ba is considerably high. Their activity per area is highest in all elements reported. However, the estimated activity per mass of SrNo.s is lower than that of Raney ruthenium and higher than that of 5% Ru-K/AC. The high activity for barium nitride is considered as various nitrides exist on its surface (Ba2N, BaN and BasN2) which can lead to elongation of bond to make dissociation easy. 

Analysis of Raney ruthenium and alumina-supported ruthenium by IR spectroscopy has shown the presence of a band at 2020 cm attributed to the N—N... 

Catalytic hydrogenation is mostly used to convert C—C triple bonds into C C double bonds and alkenes into alkanes or to replace allylic or benzylic hetero atoms by hydrogen (H. Kropf, 1980). Simple theory postulates cis- or syn-addition of hydrogen to the C—C triple or double bond with heterogeneous (R. L. Augustine, 1965, 1968, 1976 P. N. Rylander, 1979) and homogeneous (A. J. Birch, 1976) catalysts. Sulfur functions can be removed with reducing metals, e. g. with Raney nickel (G. R. Pettit, 1962 A). Heteroaromatic systems may be reduced with the aid of ruthenium on carbon. 

Ruthenium is excellent for hydrogenation of aliphatic carbonyl compounds (92), and it, as well as nickel, is used industrially for conversion of glucose to sorbitol (14,15,29,75,100). Nickel usually requires vigorous conditions unless large amounts of catalyst are used (11,20,27,37,60), or the catalyst is very active, such as W-6 Raney nickel (6). Copper chromite is always used at elevated temperatures and pressures and may be useful if aromatic-ring saturation is to be avoided. Rhodium has given excellent results under mild conditions when other catalysts have failed (4,5,66). It is useful in reduction of aliphatic carbonyls in molecules susceptible to hydrogenolysis. 

The sequence has been applied to the synthesis of 1,4-cyclohexanedione from hydroquinone 10), using W-7 Raney nickel as prepared by Billica and Adkins 6), except that the catalyst was stored under water. The use of water as solvent permitted, after hltration of the catalyst, direct oxidation of the reaction mixture with ruthenium trichloride and sodium hypochlorite via ruthenium tetroxide 78). Hydroquinone can be reduced to the diol over /o Rh-on-C at ambient conditions quantitatively (20). 

Epimerization of 50 at C-3 furnished carba-a-DL-allopyranose (60). Stepwise, 0-isopropylidenation of 50 with 2,2-dimethoxypropane afforded compound 56. Ruthenium tetraoxide oxidation of 56 gave the 3-oxo derivative 57, and catalytic hydrogenation over Raney nickel converted 57 into the 3-epimer 58 exclusively. Hydrolysis of 58, and acetylation, provided the pentaacetate 59, which was converted into 60 on hydrolysis. ... 

When we first contemplated thermochemical products available from Glu, a search of the literature revealed no studies expressly directed at hydrogenation to a specific product. Indeed, the major role that Glu plays in hydrogenation reactions is to act as an enantioselectivity enhancer (17,18). Glu (or a number of other optically active amino acids) is added to solutions containing Raney nickel, supported nickel, palladium, or ruthenium catalysts and forms stereoselective complexes on the catalyst surface, leading to enantioselective hydrogenation of keto-groups to optically active alcohols. Under the reaction conditions used, no hydrogenation of Glu takes place. 

Raney predicted that many other metal catalysts could be prepared with this technique, but he did not investigate them [8], Copper and cobalt catalysts were soon reported by others [4,5], These catalysts were not nearly as active as Raney s nickel catalyst and therefore have not been as popular industrially however they offer some advantages such as improved selectivity for some reactions. Skeletal iron, ruthenium and others have also been prepared [9-13], Wainwright [14,15] provides two brief overviews of skeletal catalysts, in particular skeletal copper, for heterogeneous reactions. Table 5.1 presents a list of different skeletal metal catalysts and some of the reactions that are catalyzed by them. 

More recently Hartog and Zwietering (103) used a bromometric technique to measure the small concentrations of olefins formed in the hydrogenation of aromatic hydrocarbons on several catalysts in the liquid phase. The maximum concentration of olefin is a function of both the catalyst and the substrate for example, at 25° o-xylene yields 0.04, 1.4, and 3.4 mole % of 1,2-dimethylcyclohexene on Raney nickel, 5% rhodium on carbon, and 5% ruthenium on carbon, respectively, and benzene yields 0.2 mole % of cyclohexene on ruthenium black. Although the cyclohexene derivatives could not be detected by this method in reactions catalyzed by platinum or palladium, a sensitive gas chromatographic technique permitted Siegel et al. (104) to observe 1,4-dimethyl-cyclohexene (0.002 mole %) from p-xylene and the same concentrations of 1,3- and 2,4-dimethylcyclohexene from wi-xylene in reductions catalyzed by reduced platinum oxide. 

Many catalysts, certainly those most widely used such as platinum, palladium, rhodium, ruthenium, nickel, Raney nickel, and catalysts for homogeneous hydrogenation such as tris(triphenylphosphine)rhodium chloride are now commercially available. Procedures for the preparation of catalysts are therefore described in detail only in the cases of the less common ones (p. 205). Guidelines for use and dosage of catalysts are given in Table 1. 

Also, Klabunovskii reported pressure dependences of the OYs in enantio-differentiating hydrogenations of ethyl acetoacetate (EAA) with ruthenium (67), Raney cobalt (65), and RNi catalysts (69) modified with TA, c. Additives. Additives which are added to the reaction system often exert a remarkable effect on the OY of the enantio-differentiating hydrogenation of M A A (23-25). Water is one such additive. For example, in most hydrogenations with amino acid MRNis, the direction of differentiation was reversed by the addition of small amounts of water as shown in Fig. 14 (23, 25). 

Raney nickel. Ruthenium-Silica. Sodium hydride-Nickel aoetate-f-Amyl oxide. 

Sumimoto introduced a new sebacic acid process including several catalytic hydrogenation reactions.342 The synthesis starts with naphthalene, which is first partially hydrogenated to tetralin over cobalt oxide or molybdenum oxide, then to decalin over ruthenium or iridium on carbon. The selectivity to cw-decalin is better than 90%. In a later phase of the synthesis 5-cyclododecen-l-one is hydrogenated over Raney nickel to obtain a mixture of cyclododecanone and cyclodode-canol in a combined yield of 90%. The selectivity of this step is not crucial since subsequent oxidation of either compound leads to the endproduct sebacic acid. 

As shown in figure 2 for glucitol conversion at 493 K for platinum and ruthenium as additives, the first atoms exchanged with copper are strong poisons for the copper catalyst until M/Cus = 0,10 to 0,15. In the range (A), the selectivity observed is that of Raney copper (DOH mainly, RC, RM). No cyclodehydration products have been detected. 

Pseudo-cc-DL-allopyranose (61) has been prepared from 54 by epimerization of the C-3 configuration as follows. O-Isopropylidenation of 54 with 2,2-dimethoxypropane gave l,2 4,6-di-0-isopropylidene-pseudo-a-DL-glucopyranose (56). On oxidation with ruthenium tetroxide and sodium metaperiodate, 56 gave the 3-oxo derivative (57), which was converted into l,2 4,6-di-0-isopropylidene-pseudo-a-DL-allopyranose (58) exclusively by catalytic hydrogenation under the presence of Raney nickel. Conven-. tional acetylation of 58 furnished the 3-O-acetyl derivative (59). Hydrolysis of 59 with aqueous acetic acid, followed by acetylation afforded pseudo-a-DL-allopyranose pentaacetate (60), which gave the free pseudo-sugar 61 on usual alkaline hydrolysis [22] (Scheme 13). 

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. 

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