Ru/C catalyst

Figure 7. Cyclic voltammetry polarization curves for MEA made with different Pt-Ru/C catalysts [25], 3M (Pt/Ru = 1 1), 3M (Pt/ Ru = 1 2) and 3 M (Pt/Ru = 2 1) represent the catalysts prepared using the unprotected metal nanoclusters as building blocks E-tek (Pt/ Ru = 1 1) represents the commercially available catalyst (C14-30). All the catalysts have the same total metal loading of 30wt.%.

Very precise kinetic experiments were performed with sponge Ni and Ru/C catalysts in a laboratory-scale pressurized slurry reactor (autoclave) by using small catalyst particles to suppress internal mass transfer resistance. The temperature and pressure domains of the experiments were 20-70 bar and 110-130°C, respectively. Lactitol was the absolutely dominating main product in all of the experiments, but minor amounts of lactulose, lactulitol, lactobionic acid, sorbitol and galactitol were observed as by-products on both Ni and Ru catalysts. The selectivity of the main product, lactitol typically exceeded 96%. 

Figure 12.4. Galactitol (left) and sorbitol (right) concentrations versus lactose conversion comparison of consecutive model (1-3, 4b upper figures) and parallel model (1-3, 4a, lower figmes). Reaction conditions 120°C, 50 bar (left) and 60 bar (right), Ru/C catalyst.

Direct hydrogenation of amino acids to amino alcohols was first examined by Adkins et al. (3) via the esters, and recently studied by Antons and Beitzke in patents (4). Using Ru/C catalysts at high pressures (>14 MPa) and mild temperatures (70-150 °C), Antons demonstrated the conversion of carboxylic acids and amino acids with retention of optical activity in the product alcohols. High yields (>80%) and high enantiomeric purity (>97% in many cases) were achieved. Broadbent et al. had demonstrated earlier that under certain conditions hydrogenation of amino acids can be accompanied by deamination (8). 

Under relatively mild conditions the Ru/C catalyst poisoned with Sn (lines 1 and 2), the Ir/C catalyst (lines 14 and 15), and the Raney-cobalt catalyst modified with CoCl2 (line 19) seem likely systems to try when initiating a search for an effective method for selectively hydrogenating the C=0 bond in an a, 3-unsaturated aldehyde. 

There are several examples of one-pot reactions with bifunctional catalysts. Thus, using a bifunctional Ru/HY catalyst, water solutions of corn starch (25 wt.%) have been hydrolyzed on acidic sites of the Y-type zeolite, and glucose formed transiently was hydrogenated on ruthenium to a mixture of sorbitol (96%), mannitol (1%), and xylitol (2%) [68]. Similarly a one-pot process for the hydrolysis and hydrogenation of inulin to sorbitol and mannitol has been achieved with Ru/C catalysts where the carbon support was preoxidized to generate acidic sites [69]. Ribeiro and Schuchardt [70] have succeeded in converting fructose into furan-2,5-dicarboxylic acid with 99% selectivity at 72% conversion in a one-pot reaction... 

An exception is the hydrogenation with Ru/C catalyst shown in equation 1451. Another exception is the Pd-catalyzed hydrogenation of 1,3-cyclohexadiene, where benzene and cyclohexane are formed52. 

Ruthenium/carbon catalysts have also been promoted by the addition of Fe. Bron et al. reported the addition of Fe to a preformed Ru/C catalyst via adsorption of Fe complexes, followed by heat treatment. They found an increase in oxygen reduction activity of three to five times over unmodified Ru/C. It was suggested that the surfaces of Ru particles were covered with FeN,Cy sites. As discussed previously, the Pd alloys have shown significant MeOH tolerance toward oxygen reduction and appear to have activities closest to that of Ft. 

Cellulose and sawdust were gasified in supercritical water to produce hydrogen-rich gas, and Ru/C, Pd/C, CeO particles, nano-CeO and nano-(CeZr)v02 were selected as catalysts. The experimental results showed that the catalytic activities were Ru/C > Pd/C > nano-(CeZr)xOj > nano-CeOj > CeO particle in turn. The 10 wt.% cellulose or sawdust with CMC can be gasified almost completely with a Ru/C catalyst to produce 2-4 g hydrogen yield and 11-15 g potential hydrogen yield per 100 g feedstock at the condition of 773 K, 27 MPa, 20 min residence time in supercritical water (Hao et al., 2005). 

In textbooks of fullerene chemistry, hydrogenation is the simplest reaction and fullerene hydrides are the simplest derivatives of fullerenes. Hydrogenation can be conducted under pressure and elevated temperatures. Heating at 400°C and 80 atm H yields red solid, [40]. Up to 48 H atoms can be added to under more forcing conditions. Catalytic hydrogenation at 280°C and 160 atm with use of Ru/C catalyst produce hydrofulerenes up to [41]. Hydrogenation is quite... 

The experiments were carried out using Pt/C, Pt-Sn/C and Pt-Sn-Ru/C catalysts and in each case no other reaction products than AAL, AA and CO2 were detected. The addition of tin to platinum not only increases the activity of the catalyst towards the oxidation of ethanol and therefore the electrical performance of the DEFC, but also changes greatly the product distribution the formation of CO2 and AAL is lowered, whereas that of AA is greatly increased (Table 1.2). 

Deactivation of Sponge Nickel and Ru/C Catalysts in Lactose and Xylose... 

Figure 1. A. Consecutive xylose hydrogenation batches over 2.5 wt-% sponge nickel and 1.5 wt-% Ru/C catalyst. B. Catalyst deactivation during consecutive lactose hydrogenation batches over 5 wt-% sponge nickel and 2 wt-% Ru/C catalyst.

The Ru/C catalyst was provided by PMC, Inc. and consists of 5.0 wt% Ru on activated carbon support. The Ni/Re/C cataiyst comprises 2.5 wt% Ni and 2.5 wt% Re on activated carbon. Both cataiysts were characterized via N2 physisorption and H2 chemisorption using a Micromeritics ASAP 2010 apparatus the resuits are presented in Table 1. 

Figure 5.25. Cu-Ru/C catalyst in H2 (a) sintered larger Cu particles Ru nanoparticles remain stable b) enlarged area in the square showing Ru nanoparticles (with lattice spacings of 0.27 nm).

Figure 5.26. In situ ethane reaction and dynamic ED patterns a) Cu-Ru/C catalyst (room temperature) (Z ) 300 °C with extra rings (c) model of CuRu3 structure observed in dynamic ED. (After Smith et al 1994.)...

On the other hand, reduction of a,p-unsaturated compounds under the same conditions leads to the corresponding saturated ketones. This result can be reached in two cases of industrial interest such as the reduction of P-ionone into dihydro-P-ionone (entry 3), a valuable intermediate for the flavors and fragrances industry, and the reduction of 4-(6-methoxy-2-naphthyl)-3-buten-2-one into nabumetone (entry 4), a nonsteroidal anti-inflammatory drug [33], The selective hydrogenation of P-ionone can be performed in 89% yield using Raney nickel alloy treated with sodium hydroxide [34], with a Ru-C catalyst [35] or with Ph3SnH [36]. On the other hand Pd/C [37, 38] and Rh(T0A)/Al203 systems [39] are reported to be selective for the preparation of nabumetone. 

The effect of the structure of the catalysts on their electroactivity was first evaluated by CO stripping. The oxidation of a saturated layer of adsorbed CO occurs at lower potentials on the codeposited Pt0 8+Ru0 2/C catalyst than on the Pt0 8Ru0 2/C coreduced one, and the mixture of a Pt/C catalyst with a Ru/C catalyst gives the worst activity (Figure 9.16a). The activity for methanol electro-oxidation is also higher at the nonalloyed codeposited catalyst than at the alloyed... 

Liang G, Wu C, He L, et al. Selective conversion of concentrated microcrystalline cellulose to isosorbide over Ru/C catalyst. Green Chem. 2011 13 839 42. 

The rates, the products, and the stereochemistry of the hydrogenation of ketones over platinum metals may depend greatly on catalyst, solvent, and acidic or alkaline additive, impurities, as well as the structure of ketones. Breitner et al.97 studied the rates of hydrogenation of isobutyl methyl ketone, cyclohexanone, and cyclopentanone over 5% Pd-C, Pt-C, Rh-C, and Ru-C catalysts in various solvents (AcOH, H20, 0.5M aqueous NaOH, 0.5M aqueous HC1, MeOH, and EtOAc). Palladium was always not active irrespective of the solvents used. Over Pt-C all three ketones were hydrogenated most rapidly in H20 and 0.5M aqueous HC1, while in 0.5M aqueous NaOH only cyclohexanone was hydrogenated in a satisfactory rate. With Rh-C and Ru-C all the ketones were hydrogenated best in H20 and 0.5M aqueous NaOH, and the presence of HC1 depressed the rates of hydrogenation, especially for Ru-C. 

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