Catalyst barium oxide

The lithium oxide-promoted barium oxide also functions as a catalyst for the methane coupling reaction, but the mechanism is not clearly understood at the present time. The only comment that might be offered here is that the presence of ions on the surface of this material might etdrance the formation of methyl radicals drrough the formation of hydroxyl groups thus... 

The NOx storage-reduction (NSR) catalyst, developed by Toyota and other companies, offers a solution based on a two step process, in which the engine switches periodically between a long lean-burn stage and a very short fuel-rich stage. The NSR catalyst combines the oxidation activity of platinum with a NOx storage compound based on barium oxide. Figure 10.10 illustrates the principle of operation. 

Barium oxide is not a catalyst all reactions involving this component are entirely stoichiometric. Nevertheless, as Fig. 10.10 illustrates, even when the barium storage function is saturated, the NOx content in the outlet gas from the catalyst is lower than in the inlet, owing to the capability of platinum to reduce NOx by hydrocarbons in oxygen-rich exhausts. 

Examples of multi-disciplinary innovation can also be found in the field of environmental catalysis such as a newly developed catalyst system for exhaust emission control in lean burn automobiles. Japanese workers [17] have successfully merged the disciplines of catalysis, adsorption and process control to develop a so-called NOx-Storage-Reduction (NSR) lean burn emission control system. This NSR catalyst employs barium oxide as an adsorbent which stores NOx as a nitrate under lean burn conditions. The adsorbent is regenerated in a very short fuel rich cycle during which the released NOx is reduced to nitrogen over a conventional three-way catalyst. A process control system ensures for the correct cycle times and minimizes the effect on motor performance. 

Barium oxide and sodium hydride are more potent catalysts than silver oxide. With barium oxide catalysis, reactions occur more rapidly but O-acetyl migration is promoted. With sodiun hydride, even sterically hindered groups may be quantitatively alkylated but unwanted C-alkylation Instead of, or in addition to, 0-alkylatlon is a possibility. Sodium hydroxide is a suitable catalyst for the alkylation of carboxylic acids and alcohols [497J. 

See Barium oxide Cotton waste, Heavy metals Metal catalysts, all below... 

Synthesis from Geraniol or Nerol. ( )-Citronellal can be obtained by vapor-phase rearrangement of geraniol or nerol in the presence of, e.g., a barium-containing copper-chromium oxide catalyst [63]. 

Dihydrophenanthrene has been prepared from 2,2 -bis(bromomethyl)biphenyl and sodium 8 from the reduction of 2,2 -diiodobibenzy 1 in the presence of 1% palladium on barium carbonate catalyst 8 by the hydrogenation of phenanthrene in the presence of nickel8 or copper-chromium oxide catalyst 10 and by the coupling of 2,2 -bis(bromomethyl)biphenyl with lithium phenyl.11... 

Crystal structure of 60 revealed that the complex existed as a dimeric species where the two chromium centers are bridged through the indane oxygen and each chromium metal bears one molecule of water (Figure 17.6). It was therefore proposed, as for the inverse electron-demand hetero Diels-Alder reaction, that the barium oxide desiccant removed one molecule of bound water from the catalyst dimer, which opened one coordination site for binding of the substrate carbonyl.26... 

Zhang, G., Hattori, H. and Tanabe, K. Aldol addition of acetone, catalyzed by solid base catalysts magnesium oxide, calcium oxide, strontium oxide, barium oxide, lanthanum-(III) oxide and zirconium oxide, Appl. Catal., 1988, 36, 189-97. 

To our knowledge, the first Raman investigations of the states of the barium phase during ongoing NOv decomposition were reported by Lunsford and coworkers (Haller et al., 1996 Mestl et al., 1997a,b, 1998 Xie et al., 1997). They used a MgO-supported barium oxide model catalyst for their investigation of NO decomposition. It was found that the supported barium oxide phase stabilized peroxide species in the presence of molecular 02 in the feed, which in turn reacted with gas-phase NO to... 

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