Catalyst containing rare earth

Use of Catalyst Containing Rare Earths. A number of jeolite catalysts containing polyvalent metals cations such as Ca and rare earth cations (RE3+) have been prepared and Investigated. 

Effective cathode catalysts for partial oxidation of hydrocarbons by the method in Figure 1 were looked for using cyclohexane as a model substrate. The metal salts to be tested as electrocatalysts were added to graphite by impregnation from aqueous solutions of their metal chlorides and were dried at 373 K. The reaction products were cyclohexanol and cyclohexanone and no CO2 was produced. The active cathode catalysts contained rare earth metal cations. 

Screening of Perovskite-type Catalysts Containing Rare Earths... 

The experimental results indicate that the order of the oxidation activities of the three perovskite-type catalysts containing rare earths is La 7Sr 3Co03 > LaCoOj > > LaMnO,. This order agrees well with the evaluation using a catalytic reactor [22,23]. 

The experimental results indicated that the order of oxidation activity for the purification of automotive exhaust gases of three perovskite catalysts containing rare earth is as follows Lag7Srg3Co03>LaCo03>LaMn03. The results were confirmed by evaluation using a reactor. 

As an additional probe of metal activity, we monitored benzene hydrogenation activity. As seen in Figure 9, Pt-containing rare earth catalysts have lower hydrogenation activity than chlorided alumina catalysts this result reflects inhibition of metal activity on these supports relative to conventional transitional alumina supports. Whereas the acid strength can be adjusted close to that of chlorided and flourided aluminas, metal activity is somewhat inhibited on these catalysts relative to halided aluminas. This inhibition is not due to dispersion, and perhaps indicates a SMSI interaction between Pt and the dispersed Nd203 phase. 

Rare earths are used as catalysts and catalyst promoters in a variety of processes such as oxidation, synthesis of alcohol, dehydration and production of specialty chemicals. Complex oxides containing rare earths are also used as electrode materials in electrochemical systems. 

Complex oxides of the perovskite structure containing rare earths like lanthanum have proved effective for oxidation of CO and hydrocarbons and for the decomposition of nitrogen oxides. These catalysts are cheaper alternatives than noble metals like platinum and rhodium which are used in automotive catalytic converters. The most effective catalysts are systems of the type Lai vSrvM03, where M = cobalt, manganese, iron, chromium, copper. Further, perovskites used as active phases in catalytic converters have to be stabilized on the rare earth containing washcoat layers. This then leads to an increase in rare earth content of a catalytic converter unit by factors up to ten compared to the three way catalyst. 

The use of catalytic converters to reduce the amount of unbumed hydrocarbons in exhaust gases is an additional example of the use of metals. Reactions of these unbumed hydrocarbons in the atmosphere are described later, in the section on photochemical smog. The catalyst currently used is a cordierite or alumina support treated with an AI2O3 wash coat containing rare earth oxides and 0.10% to 0.15% Pt, Pd, and/or Rh, which catalyzes the combustion of hydrocarbons in the exhaust gases to carbon dioxide and water. Platinum,... 

BASF has also claimed the use of metal-modified TS-1 catalysts [25]. Various catalyst compositions have been described, including (i) titanium or vanadium silicalites containing rare earth ions [25a] and (ii) titanium or vanadium silicalites containing noble metals (Ru, Rh, Pd, Os, Ir, Pt, Re, Au, Ag). In these systems the... 

Finally, new types of NOx and SOx abatement catalysts use rare earths in their formulations, helping to increase the activity and stability of transition-metal-containing zeolites. 

Rare earth pyrochlores, possessing the general formula Ln2Sn207, where Ln denotes a rare earth, are active catalysts for the oxidative coupling of methane 150]. Enhanced conversion to useful hydrocarbons (e.g., ethene) is observed with pyrochlores containing rare earths with mixed valence behavior, particularly Sm, Eu, and Yb. Since the rare earth site thus appears to be crucially linked to the catalytic behavior, the distribution of such rare earth species within the lattice is of intrinsic interest. 

The purpose of the present paper is to investigate the behavior of high temperature stable support in complete oxidation of methane, when sulfur species are present in the feed. Various characterization methods have been employed here in order to give a general picture of the deactivation of supported Pd catalysts in catalytic combustion of methane. This work will examine the reactivity of supported Pd catalysts, when the metal particles are dispersed over a thermally stable material, containing rare earth elements. Moreover, we will focus on the behavior of the catalysts when sulfur species are added to the feed, as sulfur can be present in significant amounts in natural gas. 

When SO2 is added to the gas stream, the catalysts respond differently depending on the nature of the support. We observed an increase of the T50 value of only 20 C, for PdAS. In contrast, for the modified supports containing rare earth elements, the activity of the catalysts is much more strongly affected. The increase in the light-off temperature exceeds 1 SO C. Moreover, when comparing the effect of La and Ba, PdBS has almost completely lost its catalytic activity, reaching only 10 % conversion at SSO "C. The conversion over PdBS is stable, or decreasing. On the other hand, PdLS is affected by the presence of sulfur in the feed, but its activity still increases with the temperature. 

Chapter 4 contains the background of the development of effective modified Ni catalysts, discusses the methods of preparation of different types of stable and active metal catalysts, and discusses the selection of effective modifiers and the most suitable substrate molecules having practical interests. On the basis of these studies a reaction mechanism for the new effective catalytic systems was suggested and experimentally examined. The Chapter discusses the preparation variables for the development of this new type of effective chiral modified Ni catalyst, the supported metal catalysts, the chiral modified bimetal and multimetal catalysts including rare earth metals, and the new chiral modified nickel-ruthenium and palladium catalysts. Attempts are undertaken to elucidate the mechanism of enantioselectivity and to reveal the general regularities of asymmetric actions. 

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