Metal supported cobalt-ruthenium catalysts

We are investigating bifunctional catalysts in which one component of the catalyst adsorbs or oxidizes CO and the other component dissociates water. Our present research is focusing on metal-support combinations to promote this bifunctional mechanism. The metallic component is chosen to adsorb CO at intermediate adsorption strengths (platinum [Pt], Ru, palladium [Pd], PtRu, PtCu, cobalt [Co], ruthenium [Ru], silver [Ag], iron [Fe], copper [Cu], and molybdenum [Mo]). The support is chosen to adsorb and dissociate water, typically a mixed-valence oxide with redox properties or oxygen... 

The addition of other metals to the heterogeneously cobalt-catalyzed reaction can have a beneficial effect on hydroformylation. For example, small amounts of ruthenium added to a carbon-supported cobalt catalyst (Co/AC) increased activity as well as Hb selectivity [64]. The effect was rationalized by the high dispersion and reducibUity of supported cobalt. When ruthenium was added, small particles of an unbalanced alloy were formed. These particles keep more CO in a nondisso-ciative state and lower the surface hydrogen pressure. This was in contrast to the related but uniformly distributed Pt-Co or Pd-Co alloys. Activity and regioselectivity increased with increased Ru loading. 

The main contaminants for the membrane are cationic species, such as metal ions, which may come from contaminated air and fuel streams when moisture is present, metal fuel cell components, balance-of-plant components, or nonmetal contaminated component materials. Other organic and inorganic materials can also contaminate the membrane, but the effects of these are less well documented. Component materials supplying contaminants may include the platinum catalyst or alloying metals, such as ruthenium or cobalt, which may leach out into the membrane the raw material source for the carbon materials (in the catalyst support, microporous layer, gas diffusion layer, or plate materials) may also have inherent metal or other chemical impurities and seal and gasketing materials, such as silicone, can decompose and contaminate the membrane. All of the membrane contaminants can also impact the ionomer materials present in the catalyst layers. 

Anilines have been reduced successfully over a variety of supported and unsupported metals, including palladium, platinum, rhodium, ruthenium, iridium, (54), cobalt, and nickel. Base metals require high temperatures and pressures (7d), whereas noble metals can be used under much milder conditions. Currently, preferred catalysts in both laboratory or industrial practice are rhodium at lower pressures and ruthenium at higher pressures, for both display high activity and relatively little tendency toward either coupling or hydrogenolysis,... 

The reactions are catalyzed by transition metals (cobalt, iron, and ruthenium) on high-surface-area silica, alumina, or zeolite supports. However, the exact chemical identity of the catalysts is unknown, and their characterization presents challenges as these transformations are carried out under very harsh reaction conditions. Typically, the Fischer-Tropsch process is operated in the temperature range of 150°C-300°C and in the pressure range of one to several tens of atmospheres [66], Thus, the entire process is costly and inefficient and even produces waste [67]. Hence, development of more economical and sustainable strategies for the gas-to-liquid conversion of methane is highly desirable. 

The elTiciency of cobalt and ruthenium catalysis is not very sensitive to the presence of promoters )21]. With cobalt, the addition of thorium and alkali promoters increases wax production and supports were incorporated to increase the active metal surface area. On the other hand, promoters and supports are essentia) for iron catalysts. 

The metal catalysts active for steam reforming of methane are the group VIII metals, usually nickel. Although other group VIII metals are active, they have drawbacks for example, iron rapidly oxidizes, cobalt cannot withstand the partial pressures of steam, and the precious metals (rhodium, ruthenium, platinum, and palladium) are too expensive for commercial operation. Rhodium and ruthenium are ten times more active than nickel, platinum, and palladium. However, the selectivity of platinum and palladium are better than rhodium [1]. The supports for most industrial catalysts are based on ceramic oxides or oxides stabilized by hydraulic cement. The commonly-used ceramic supports include a-alumina, magnesia, calcium-aluminate, or magnesium-alu-minate [4,8]. Supports used for low temperature reforming (< 770 K) are... 

Iron and its compounds (carbide, nitride), as well as ruthenium, cobalt, rhodium, and molybdenum compounds (sulfide, carbide), are used most frequently to produce high-molecular-weight hydrocarbons. Iron can be prepared as a high-surface-area catalyst (==300 m /g) even without using a microporous oxide support. 7-AI2O3, Ti02, and silica are frequently used as supports of the dispersed transition-metal particles. Recently zeolites, as well as thorium oxide and lanthanum oxide, have... 

When titania is used as a support for cobalt iron or ruthenium, veiy active catalysts are prepared, indicating the importance of certain oxide-metal interfaces as active sites for CO hydrogenation. 

Cobalt-based low temperature Fischer—Tropsch catalysts, appHed at approximately 220 °C and 30 atm, are usually supported on high-surface-area Y-AI2O3 (150—200 m g ) and typically contain 15—30% weight of cobalt. To stabihze them and decrease selectivity to methane, these catalysts may contain small amounts of noble metal promoters (typically 0.05—0.1 wt% of ruthenium, rhodium, platinum, or palladium) or an oxide promoter (e.g., zir-conia, lanthana, cerium oxide, in concentrations of 1—10 wt%) (409). 

One of the first metal oxides to be examined electrochemically on a diamond substrate was ruthenium dioxide [115, 116]. This material is important both for electrochemical capacitor and electrocatalytic applications (chlorine evolution). Another example is cobalt hydrous oxide, which has catalytic activity for oxygen evolution [117]. A very recent example is lead dioxide [118]. A metal oxide (V2O3) has also been supported on particulate diamond as a catalyst for an organic gas-phase reaction [119]. 

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