Ruthenium alumina-supported

More recently, Chang reported a ruthenium-based Heck-type reaction in DME/H20 (1 1) by using alumina-supported ruthenium catalysts.154... 

Ruthenium catalysts, supported on a commercial alumina (surface area 155 m have been prepared using two different precursors RUCI3 and Ru(acac)3 [172,173]. Ultrasound is used during the reduction step performed with hydrazine or formaldehyde at 70 °C. The ultrasonic power (30 W cm ) was chosen to minimise the destructive effects on the support (loss of morphological structure, change of phase). Palladium catalysts have been supported both on alumina and on active carbon [174,175]. Tab. 3.6 lists the dispersion data provided by hydrogen chemisorption measurements of a series of Pd catalysts supported on alumina. is the ratio between the surface atoms accessible to the chemisorbed probe gas (Hj) and the total number of catalytic atoms on the support. An increase in the dispersion value is observed in all the sonicated samples but the effect is more pronounced for low metal loading. 

Alumina-supported Ru catalysts derived from supported ruthenium carbonyls have been reported to be effective for carbon dioxide methanation, showing higher activity than other catalysts prepared from RUCI3. The catalytic activity depended on the nuclearity of the carbonyl precursor [111]. 

The co-existence of at least two modes of ethylene adsorption has been clearly demonstrated in studies of 14C-ethylene adsorption on nickel films [62] and various alumina- and silica-supported metals [53,63—65] at ambient temperature and above. When 14C-ethylene is adsorbed on to alumina-supported palladium, platinum, ruthenium, rhodium, nickel and iridium catalysts [63], it is observed that only a fraction of the initially adsorbed ethylene can be removed by molecular exchange with non-radioactive ethylene, by evacuation or during the subsequent hydrogenation of ethylene—hydrogen mixtures (Fig. 6). While the adsorptive capacity of the catalysts decreases in the order Ni > Rh > Ru > Ir > Pt > Pd, the percentage of the initially adsorbed ethylene retained by the surface which was the same for each of the processes, decreased in the order... 

Comparison of Initial Methanation Activities for Zeolite and Alumina Supported Ruthenium Catalysts... 

Platinum, ruthenium, and mixed platinum-ruthenium species supported on silica Various alumina-supported nickel complexes Dispersion of metallic species during treatments in 02 and H2 at temperatures up to 473 K Reaction of nickel complexes and interaction with support at temperatures... 

Another ion exchange procedure involves the interaction of a metal acetylacetonate (acac) with an oxide support. Virtually all acetylacetonate complexes, except those of rhodium and ruthenium, react with the coordinatively unsaturated surface sites of 7 alumina to produce stable catalyst precursors. On thermal treatment and reduction these give alumina supported metal catalysts having relatively high dispersions. 38 Acetylacetonate complexes which are stable in the presence of acid or base such as Pd(acac)2, Pt(acac)2 and Co(acac)3, react only with the Lewis acid, Al" 3 sites, on the alumina. Complexes which decompose in base but not in acid react not only with the Al 3 sites but also with the surface hydroxy groups. Complexes that are sensitive to acid but not to base react only slightly, if at all, with the hydroxy groups on the surface. It appears that this is the reason the rhodium and ruthenium complexes fail to adsorb on an alumina surface. 38... 

The effect of suJfur poisoning on the coking tendency of alumina-supported ruthenium SNG catalyst has been studied. The clean KU/AI2O3 catalyst has exceptional coking resistance, and at 490 C and 25 atm, can tolerate steam to carbon ratios below stoichiometric (steam/carbori=0.6) with light naphtha before a continuous accumulation of carbon will occur. However, at this temperature (appropriate for SNG production), sulfur can adsorb on the active metal surfaces to a level which will cause a slow but steady accumulation of less reactive carbon. The critical sulfur coverage that adversely affected the steam to carbon ratio necessary to prevent continuous coking appears to fall just above one-half the maximum capacity of the catalyst. 

The reaction of ethylene with deuterium was studied (61) between 0 and 80° used alumina-supported catalysts. A selection of the results and some of the calculated distributions are shown in Table XXI. The addition reactions are first-order in deuterium and zero in ethylene. At < 50° some 50% of the initial products are exchanged ethylenes over ruthenium and some 25% over osmium. These figures are unaffected by alteration in the ethylene pressure but are suppressed by increasing deuterium pressure. The relative rates of both exchange processes increase with rising temperature, and the following activation energy differences have been derived ... 

Troduct Digtriindions from the Reaction of Ethylene with Deuterium over Alumina-Supported Ruthenium and Osmium (61)... 

Alumina supported ruthenium clusters were studied for the effect of cluster nuclearity on the rate of CO2 methanation. It was found that the reactivity paralleled the nuclearity of the catalyst precursor. 

CO2 Methanation. Finally, we have studied the catalytic activity and selectivity toward methanation of carbon dioxide using several alumina supported ruthenium clusters including Ru3(C0)i2>... 

Figure 4 compares the product distribution from ATR of diesel from three different catalysts at 850 °C. The y-Alumina supported ruthenium catalyst proved to be the most active catalyst in producing synthesis gas from diesel ATR. 

Surface-science studies using nickel single-crystal surfaces revealed that the methanation reaction is surface-structure-insensitive. Both the (111) and (100) crystal faces yield the same reaction rates over a wide temperature range. These specific rates are also the same as those found for alumina-supported nickel, further proving the structure insensitivity of the process. This is also the case for the reaction over ruthenium, rhodium, molybdenum, and iron. 

Alumina-supported ruthenium catalysts were prepared by impregnating alumina (Aerosil, 200 m /g) with ruthenium chloride from its aqueous solution. The catalysts composition was Ru Al203 = 2 98 by weight. The catalyst precursors were dried overnight at 120°C in an air oven, and were then calcined at 450 °C for 2 h to form a supported metal oxide [12,13]. The catalysts were reduced in a hydrogen flow at 150°C and 300 °C for 1 h each, and at 400 °C for 2 h in series and then passivated. They were reduced again at 400 °C for 2 h in situ before the catalytic reaction. 

Studying non-classical preparation procedures, it has been already shown that ultrasound play a relevant role in preparing high dispersed pure amorphous iron [3]. Moreover, it has been recently proposed that ultrasound can improve the metal dispersion in alumina supported ruthenium catalyst 14, 51. 

Suzuki et al. reported catalyst development for kerosene steam reforming [254]. They prepared a 2 wt.% ruthenium catalyst supported by an alumina carrier, which was stabilised by 20 wt.% yttria, lanthana and ceria, respectively. At 800 °C reaction temperature, S/C 3.5 and 8-bar pressure the ceria stabilised sample showed the best performance in the medium term in the presence of 51 ppm sulfur in the feed. With hydrodesulfiirised kerosene the catalyst showed a stable performance for 8000-h... 

Ammonia decomposition was investigated by Choudhary et al. [283] over nickel, iridium and ruthenium catalysts supported by various carrier materials such as ZSM-5 and Y-zeolites, alumina and silica. Ruthenium on silica was most active, followed by iridium and nickel [283]. 

Men et al. investigated selective methanation over nickel and ruthenium catalysts supported by different carriers [344]. A nickel catalyst containing 43wt% nickel, which was doped with 6 wt% calcium oxide and supported by alumina, turned out to be the most active sample. The catalyst produced methane exclusively, from both carbon monoxide and carbon dioxide in the presence of hydrogen. 90% conversion of carbon monoxide could be achieved at a 300 °C reaction temperature with 35% selectivity. The presence of steam reduced the activity of the catalyst but improved its selectivity towards carbon monoxide. When oxygen was added to the feed, the catalyst exclusively converted carbon monoxide into carbon dioxide, and methane formation did not start until all the oxygen had been consumed. 

Fan et al. (1995) studied how the pore size of the catalyst affected the transfer of reactants and products in the supercritical-phase FTS reaction. Alumina-supported ruthenium catalysts were prepared with different pore size. They conclude that the chain-growth probability of the Ru catalysts increased while the Ru dispersion decreased with the increase of the pore diameter. 

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. ... 

Vernon et al tested a series of noble metal catalysts, either Ru, Rh, Pt, Pd or Ir supported on AI2O3, or rare earth ruthenium pyrochlore materials. All materials yielded the equilibrium CPO conversion of methane to syngas at IITC and 1 atm. After the reaction, it was found that Ru had been reduced out of the pyrochlore structures. Claridge et al. studied coke formation over alumina-supported or pyrochlore-derived catalysts and reported that the coke forming rates decreased in the order Ni > Pd > Rh > Ir, as illustrated in Fig. 8.3. ... 

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