Ru on Alumina

XPS that the reducibility of rhenium compounds depends on their nature and the support used reduction was more difficult on y-alumina compared with sihca due to the stronger interaction of Re with the alumina surface. Experiments with HRe04-Al203 treated in vacuo at 773 K indicated some rhenium in an intermediate oxidation state, possibly Re , but subsequent calcination in air at 673 K resulted in re-oxidation to Re ,  

The dual-state behaviour of RU-AI2O3 catalysts may also arise from metal-support interaction. In the oxidized state, the catalyst was more selective for nitrogen formation in NO reduction than when in the reduced state. It was also active for the water-gas shift reaction whereas the reduced form was rather inactive and differences were also observed for ammonia decomposition and the CO-H2 reaction. The more active form does not appear to contain ruthenium oxide the reduced catalyst may have been de-activated by reaction with the support and its transformation to the more active form by oxidation may involve surface reconstruction and/or destruction of the metal-support interaction. 

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Metals such as Fe, Co, Ni, or Ru on alumina or other oxide supports convert CO and H2 to hydrocarbons. Using different catalysts and reaction conditions either CH4, liquid hydrocarbons, high molecular weight paraffins, methanol, higher alcohols, olefins, and aromatics can be obtained, though rarely (with the exception of CFL, and methanol) with high selectivity. Hydrocarbons typically exhibit a Schulz-Flory type molecular weight distribution. 

Ru on alumina catalyst. The water produced during the reaction permeates selectively through the membrane. Removing the product from the reaction zone increases the reactor conversion. In the range of the space velocities investigated (0.03-0.123 s ) and temperatures (480-719 K), a maximum 18 % increase in conversion over the reactor conversion attained in the absence of the membrane was observed. 

To accelerate the polymerization process, some water-soluble salts of heavy metals (Fe, Co, Ni, Pb) are added to the reaction system (0.01-1% with respect to the monomer mass). These additions facilitate the reaction heat removal and allow the reaction to be carried out at lower temperatures. To reduce the coagulate formation and deposits of polymers on the reactor walls, the additions of water-soluble salts (borates, phosphates, and silicates of alkali metals) are introduced into the reaction mixture. The residual monomer content in the emulsion can be decreased by hydrogenizing the double bond in the presence of catalysts (Raney Ni, and salts of Ru, Co, Fe, Pd, Pt, Ir, Ro, and Co on alumina). The same purpose can be achieved by adding amidase to the emulsion. 

Because both [PtClgl g) and Ru" are more equally adsorbed on alumina, the mobility of the Pt-precursor phase relative to the Ru-precursor phase is reduced. The data in Table III show that the increase in dispersion following dilution with pure alumina (Alon-C) is moderate with respect to that observed on silica. However, the redlsperslon of Pt is still substantially greater than that of Ru. 

The author wishes to thank Dr. J.B. Cohen for supplying samples of Pt and Pd on alumina and silica and Drs. J. Schwank and A.K. Dayte for samples of Ru and Au on magnesia and silica. This work was supported by the US Department of Energy under Contract DMR-76ER02995 and has make use of the resources of the ASU Faoiltity for High Resolution Electron Microscopy, supported by NSF grant DMR 8306501. 

Scheme 12 Total synthesis of (-)-xestospongin A (116), (+)-araguspongine B (129), and (+)-xestospongin C (130) [41]. Experimental conditions i. (a) NaH, THE, (b) -BuLi, (c) 132 a. Ru(II)-S-BINAP, H2, EtOH Hi. LiBH4, Et20 iv. PPTS, 2,2-dimethoxypropane, acetone v. Nal, acetone, reflux vi. 3-picoline, EDA, THE vii. HCl(aq.), EtOH viii. TsCl, EtsN, CH2CI2 ix. Nal, butanone, reflux x. LiBH4, MeOH, i-PrOH xi. DEAD, CH2CI2 xii. H2, Ni (Raney), MeOH xiii. Rh on alumina, MeOH, H2, then add alumina, reflux...

Supported Co, Ni, Ru, Rh, Pd and Pt as well as Raney Ni and Co catalysts were used for the hydrogenation of dodecanenitrile to amines in stirred SS autoclaves both in cyclohexane and without a solvent. The reaction temperature and the hydrogen pressure were varied between 90-140 °C and 10-80 bar, respectively. Over Ni catalysts NH3 and/or a base modifier suppressed the formation of secondary amine. High selectivity (93-98 %) to primary amine was obtained on Raney nickel, Ni/Al203 and Ru/A1203 catalysts at complete nitrile conversion. With respect to the effect of metal supported on alumina the selectivity of dodecylamine decreased in the order Co Ni Ru>Rh>Pd>Pt. The difference between Group VIII metals in selectivity can be explained by the electronic properties of d-band of metals. High selectivity to primary amine was achieved on base modified Raney Ni even in the absence of NH3. 

Grenoble and coworkers229 reported an important influence of the support on the water-gas shift activity of various metal catalysts. For example, the rate increased an order of magnitude when Pt was supported on alumina versus silica. Turnover numbers for alumina-supported metal catalysts decreased in the order Cu, Re, Co, Ru, Ni, Pt, Os, Au, Fe, Pd, Rh, and Ir, whereby the activity varied by 3 orders of magnitude, suggesting a correlation between activity of the metal and the heat of adsorption. To describe these differences in activity, the authors used a bifunctional model, involving chemisorption of water on alumina and CO on the metal, followed by association of the CO with the water to form a formic acid-like formate species, with subsequent decomposition via dehydrogenation on the metal sites (Scheme 55). 

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. 

Table 2 Hydrogenation of 4-amino-ethyl benzoate on alumina and carbon supported Ru, Rh and catalysts. Effect of catalyst, solvent and temperature...

D Ru on mesoporous silica E Pd on microporous alumina F Macroporous silica/alumina G Pt on mesoporous polystyrene... 

Some papers have been published that examine Ru/SiC>2 as a catalyst in the Methanation step. These papers looked at the effects of hydrogen and temperature as well as how a Cl-modified Ru/SiC)2 catalyst performs. The Cl decreased catalytic activity, but it enhanced selectivity for methane formation -even though it was present on the catalyst only during the initial stages of the reaction77, 8. For extremely low temperature applications (i.e., < 180°C), one company offers a catalyst with 0.3% ruthenium on alumina. This catalyst does not contain any NiO or CaO166. 

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