Supports of ruthenium catalysts

The effect of the raw materials of activated carbon on the activity of catalysts is shown in Table 6.2. ° It can be seen from Table 6.2, that the effect of the raw materials of activated carbons on the properties of catalyst is very great. Therefore, we should be cautious in choosing the raw material of activated carbon as the support of ruthenium catalyst. 

Oxides, as supports of ruthenium catalysts, have high mechanical strength, good stability and highly basic sites, which can provide electrons in order to activation of N2 and enhance the catalytic activity of synthetic ammonia. However, the low dispersion of ruthenium is a common problem. Therefore, it is a common topic on how to increase the dispersion of ruthenium. 

Table 6.8 Role of promoter and support of ruthenium catalyst (N2 +3H2 = 80 kPa) and isotopic equilibrium (N2 = 20 kPa) ...

Although the process is of significance, it has not well studied. Since the initial development of the CTA hydropurification process in 1960s , only a few papers have been published, mainly regarding catalyst deactivation [2]. Recently, Samsung Corporation, in collaboration with Russian scientists, developed a novel carbon material-CCM supported palladium-ruthenium catalyst and its application to this process [3]. However, pathways and kinetics of CTA hydrogenation, which are crucial to industrialization, are not reported hitherto. 

Fig. 5a. TEM image of CNF-supported 5w4 % ruthenium catalyst, reduced and treated at 773 K in N2...

In the present work, we investigated the influence of the metal precursor and of the nature of the support on the performences of ruthenium catalysts for the wet air oxidation of p-hydroxybenzoic (p-HBZ) acid chosen as a model of phenolic pollutants. Titanium and zirconium oxides were selected as supporting materials. The preparation method adopted for supports was sol-gel combined with the use of supercritical drying. The motivation of such combination is to prepare aerogel supports with high BET surface area and unique morphological and chemical properties [9,10]. 

In a more recent study, Li et al. [15] investigated the catalytic behavior of ruthenium catalysts supported on carbon materials with different porous and graphitic structures in the catalytic ammonia decomposition. They found that the catalytic activity followed the trend Ru/GC (graphitic carbon)> Ru/CNTs (carbon nantoubes) > Ru/CB-S (carbon black) > Ru/CB-C > Ru/CMK-3 (meso-porous carbon) = Ru/AC. It was concluded that the graphitic structure of the carbons was critical to the activity of the ruthenium catalysts, whereas the surface area and porosity were less important. 

Summary on Sn-Ru/AkO Catalysts. - In the last decade supported tin-ruthenium catalysts have been extensively studied because of their activity and high selectivity in the hydrogenation of unsaturated aldehydes, esters or acids into the corresponding alcohols. The increased performance of metal catalysts with the addition of promoters such as tin is attributed to the presence of promoter-cations on the surface or at the periphery of metal nanocluster, which activate the C=0 bond through the interaction with the lone electron pair of the carbonyl group oxygen. 

A. N. Basinska, L. KelpinAski, F. Domka, The effect of support on WGSR activity of ruthenium catalysts, Appl. Catal. A Gen. 183 (1999) 143-153. 

Rauhe BR, Mclamon FR, Cairns EJ (1995) Direct anodic-oxidation of methanol on supported platinum ruthenium catalyst in aqueous cesium carbonate. J Electrochem Soc 142(4) 1073-1084... 

Faita Rodrigues, M. F., Gomez Coho, A. J. (2010). Influence of the support nature and morphology on the performance of ruthenium catalysts for partial hydrogenation of benzene in liquid phase. Catalysis Today, 149, 321—325. http //dx.doi.org/10.1016/ j. cattod.2009.07.113. 

The aim of our investigatbns was to prepare and characterize some supported nnodffied ruthenium catalysts for enantbselective hydrogenatbn of D-fructose to D-mannitol. Two different molecular sieves zeolite L and APO-34 were used as support and as ligand high molecules without an optical active carbon. 

Figure 10.19. C Is XP spectra (left panel), and UVP spectra (right panel) of all Rn-based samples, as prepared and after reduction [159]. (Reproduced from Applied Surface Science, 238(1—4), Guraya M, Sprenger S, Rarog-Pilecka W, Szmigiel D, Kowalczyk Z, Muhler M. The effect of promoters on the electronic structure of ruthenium catalysts supported on carbon, 77-81, 2004, with permission from Elsevier.)...

Munke et al. [196] reported a technique (Figure 10.31) of in situ electrochemical FTIR and used it to study a real carbon-supported platinum + ruthenium catalyst. Different adsorptions were observed when methanol was electrooxidized at bulk Pt, Pt particles, and carbon-black-supported Pt -I- Ru electrodes, particularly with regard to the nature of the adsorbed CO species (Figure 10.32). 

Guraya M, Sprenger S, Rarog-Pilecka W, Szmigiel D, Kowalczyk Z, Muhler M. The effect of promoters on the electronic structure of ruthenium catalysts supported on carbon. Appl Surf Sci 2004 238 77-81. 

Levulinic acid (4-oxopentanoic acid) obtained from cellulose and hemicellulose materials by acid-catalysed hydrolysis can be hydrogenated to y-valerolactone (5-methyldihydrofuran-2(3H)-one) which is a useful platform chemical precursor to liquid fuels, polymers and fine chemicals. Carbon-supported tin-ruthenium catalysts were active and selective in the hydrogenation of levulinic acid (Scheme 21.4). ... 

For the ruthenium catalyst supported on activation carbon, the methanation reaction of the carbon support can also be catalyzed by ruthenium. This is another shortcoming of ruthenium catalyst which results in the loss of carbon support and impact on the catalyst lifetime. However, researchers have found that methanation reaction occurs at higher temperatures than ammonia synthesis reaction, so that the loss of carbon via methanation might be avoided when the reaction is performed at relatively low temperatures. 

The performances of ruthenium catalysts supported on activated carbons are... 

Kowalczy et al investigated five kinds of ruthenium catalysts supported on activated carbons treated under ultra high vacuum at the temperature range of 2,000 K-2,200 K and made the correlations between the pore structures and the distribution of active components. The experimental results show that the smface areas and the pore volumes are different (Table 6.4) in different activated carbons. The dispersions of ruthenium are closely related with the pore structures of activated carbons. The fuller development of pore structures in activated carbon, the higher the dispersion of ruthenium is (Table 6.5). 

When activated carbon is used as support, the support degradation by Ru-catalyzed methanation imder ammonia synthesis conditions can occur, so it affects the fife of catalysts. Therefore, many researchers have tried to use metal oxides to replace the activated carbons as the supports for ruthenium catalysts. Supported catalysts with high dispersion and high activity can be obtained when noble metals in precursor forms are supported on hardly reduced metal oxide. The oxides which are commonly used as ruthenium catalyst support include oxides of alkaline earth metals, lanthanide,and alumina. ... 

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