Hydrogenation mthenium catalysts

Aminoalkoxy pentaerythritols are obtained by reduction of the cyanoethoxy species obtained from the reaction between acrylonitrile, pentaerythritol, and lithium hydroxide in aqueous solution. Hydrogen in toluene over a mthenium catalyst in the presence of ammonia is used (34). The corresponding aminophenoxyalkyl derivatives of pentaerythritol and trimethyl olpropane can also be prepared (35). 

Glycohc acid [79-14-1], HOOCCH2OH, mol wt 76.05, can be obtained by the electrolytic reduction of oxaUc acid or the catalytic reduction of oxaUc acid with hydrogen in the presence of a mthenium catalyst. Because of its acidity it is used as a cleaning agent for metal surface treatments and for boiler cleaning. It also serves as an ingredient in cosmetics (qv). 

In aqueous hydrochloric acid solutions, mthenium(II) chloride catalyzed the hydrogenation of water-soluble olefins such as maleic and fumaric acids [6]. After learning so much of so many catalytic hydrogenation reactions, the kinetics of these simple Ru(II)-catalyzed systems still seem quite fascinating since they display many features which later became established as standard steps in the mechanisms of hydrogenation. The catalyst itself does not react with hydrogen, however, the mthenium(II)-olefin complex... 

Hexaruthenium carbonyl complexes have been used to prepare Ti02-supported mthenium catalysts for the sulfur dioxide reduction with hydrogen [112, 113], A catalyst derived from [Ru6C(CO)i6] showed higher activity in the production of elemental sulfur at low temperatures than that prepared from RUCI3 as precursor. This catalytic behavior is related with the formation of an amorphous ruthenium sulfide phase that takes place during the reaction over the ex-carbonyl catalyst [112]. 

This ruthenium catalyst efficiently transforms cis-3-en-l-yne d3-9 into cyclopenta-dienyl species d3-ll selected examples are depicted in Table 6.1. The cyclization works not only for cis-3-en-l-ynes bearing a benzylic hydrogen but also for those bearing aliphatic C—H bonds. Table 6.1 also manifests additional use of this cyclization that 5-siloxyl-3-en-l-ynes were transformed into cydopentenone derivatives using the same mthenium catalyst. 

In the early syntheses of alkenyl alkylidene-mthenium catalysts, the first generation of Grubbs catalyst, it was observed that propargyl chloride could be a convenient source of the vinylcarbene initiator [53] with respect to the previous one arising from activation of cyclopropene [4] (Equation 8.3). In this synthesis the alkylidene hydrogen atom arises from the ruthenium hydride. 

Saturated sulfides have been prepared from unsaturated sulfides by low-pressure hydrogenation with a combination of heterogeneous and homogeneous mthenium catalysts as RuzO and Rii (()(OAc) AcO- in satisfactory to good yields, thus minimizing side reactions <1996SC899>. 

Hydrogenation of CO2 to formic acid and its derivatives such as methyl formate and N,N-dimethylformamide is an attractive process. Among transition metal catalysts, homogeneous mthenium catalysts are especially effective for these reactions. 

CHB is readily obtained from benzene via (a) selective hydrogenation to cyclohexene, using a mthenium catalyst (4), followed by Friedel-Crafts alkylation or... 

B. Bachilier-Baeza, A. Guerrero-Ruiz and I. Rodrigez-Ramos, "Role of the residual chlorides in platinum and mthenium catalysts for the hydrogenation of a,p-unsaturated aldehydes" Appl. Catal. A General, 192, 289 (2000). 

The use of chiral mthenium catalysts can hydrogenate ketones asymmetrically in water. The introduction of surfactants into a water-soluble Ru(II)-catalyzed asymmetric transfer hydrogenation of ketones led to an increase of the catalytic activity and reusability compared to the catalytic systems without surfactants. Water-soluble chiral mthenium complexes with a P-cyclodextrin unit can catalyze the reduction of aliphatic ketones with high enantiomeric excess and in good-to-excellent yields in the presence of sodium formate (Eq. 8.3). The high level of enantioselectivity observed was attributed to the preorganization of the substrates in the hydrophobic cavity of fl-cyclodextrin. 

A study of a ceramic reactor for on-site hydrogen production from propane at temperatures between 800 and 1000 °C was reported by Mitchell and Kenis [46]. They showed that the ceramic microreactor can be used with an S C ratio as low as 1.095 without coking or deactivation of the mthenium catalyst deposited on the SiC porous monoUths. 

Several studies have reported the catalytic conversion of cellulose into sorbitol. Among the metal catalysts used, Ru and Ft promoted both hydrolysis and hydrogenation steps (Dhepe et al., 2008). A catalytic system containing molecular acids such as H2SO4, HCl, or heteropolyacids combined with supported metal catalysts like Ft, Pd, and Ru could efficiently catalyze the conversion of cellulose to sorbitol (Anand et al., 2012 Palkovits, 2010,2011 Geboers et al., 2010 Dhepe et al., 2008). The highest yield of sugar alcohols (81%) could be achieved by the combination of heteropolyacids with supported mthenium catalysts (Palkovits et al., 2011). 

The direct, one-step production of DMF from carbon monoxide, hydrogen, and ammonia has also been reported. A mthenium carbonyl catalyst is used, either ia a polar organic solvent (20) or ia a phosphonium molten salt medium (21). 

Reduction of the aromatic nuclei contained in catalytic C-9 resins has also been accomplished in the molten state (66). Continuous downward concurrent feeding of molten resin (120°C softening point) and hydrogen to a fixed bed of an alumina supported platinum—mthenium (1.75% Pt—0.25% Ru) catalyst has been shown to reduce approximately 100% of the aromatic nuclei present in the resin. The temperature and pressure required for this process are 295—300°C and 9.8 MPa (lOO kg/cni2), respectively. The extent of hydrogenation was monitored by the percent reduction in the uv absorbance at 274.5 nm. 

Ruthenium. Ruthenium, as a hydroformylation catalyst (14), has an activity signiftcandy lower than that of rhodium and even cobalt (22). Monomeric mthenium carbonyl triphenylphosphine species (23) yield only modest normal to branched regioselectivities under relatively forcing conditions. For example, after 22 hours at 120°C, 10 MPa (1450 psi) of carbon monoxide and hydrogen, biscarbonyltristriphenylphosphine mthenium [61647-76-5] ... 

Catalytic asymmetric hydrogenation was one of the first enantioselective synthetic methods used industrially (82). 2,2 -Bis(diarylphosphino)-l,l -binaphthyl (BINAP) is a chiral ligand which possesses a Cg plane of symmetry (Fig. 9). Steric interactions prevent interconversion of the (R)- and (3)-BINAP. Coordination of BINAP with a transition metal such as mthenium or rhodium produces a chiral hydrogenation catalyst capable of inducing a high degree of enantiofacial selectivity (83). Naproxen (41) is produced in 97% ee by... 

Phenol Vi Cyclohexene. In 1989 Mitsui Petrochemicals developed a process in which phenol was produced from cyclohexene. In this process, benzene is partially hydrogenated to cyclohexene in the presence of water and a mthenium-containing catalyst. The cyclohexene then reacts with water to form cyclohexanol or oxygen to form cyclohexanone. The cyclohexanol or cyclohexanone is then dehydrogenated to phenol. No phenol plants have been built employing this process. 

Addition of ammonia to the hydrogenator, 1.5 to 5 parts per 100 parts aniline, has been reported to selectively yield cyclohexylamine (49). The reduction is carried out at 160 to 180°C and 2 to 5 MPa (20 to 50 atm) with a mthenium-on-carbon catalyst. 

Hydrogenation Catalysts. The key to catalytic hydrogenation is the catalyst, which promotes a reaction which otherwise would occur too slowly to be useful. Catalysts for the hydrogenation of nitro compounds and nitriles are generally based on one or more of the group VIII metals. The metals most commonly used are cobalt, nickel, palladium, platinum, rhodium, and mthenium, but others, including copper (16), iron (17), and tellurium... 

Hydrogenation. Gas-phase catalytic hydrogenation of succinic anhydride yields y-butyrolactone [96-48-0] (GBL), tetrahydrofiiran [109-99-9] (THF), 1,4-butanediol (BDO), or a mixture of these products, depending on the experimental conditions. Catalysts mentioned in the Hterature include copper chromites with various additives (72), copper—zinc oxides with promoters (73—75), and mthenium (76). The same products are obtained by hquid-phase hydrogenation catalysts used include Pd with various modifiers on various carriers (77—80), Ru on C (81) or Ru complexes (82,83), Rh on C (79), Cu—Co—Mn oxides (84), Co—Ni—Re oxides (85), Cu—Ti oxides (86), Ca—Mo—Ni on diatomaceous earth (87), and Mo—Ba—Re oxides (88). Chemical reduction of succinic anhydride to GBL or THF can be performed with 2-propanol in the presence of Zr02 catalyst (89,90). 

Succinic acid can also be produced by catalytic hydrogenation of aqueous solutions of maleic or fumaric acid in the presence of noble metal catalysts, ie, palladium, rhodium, mthenium, or their mixtures, on different carriers (135—139) or on Raney nickel (140). 

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