Catalyst perovskite

Electrochemical Promotion of Particulate Matter (Soot) Combustion Using a Ceria-Gadolinia Solid Electrolyte and a Dispersed Perovskite Catalyst... 

In the case of H2 oxidation the two investigated classes of catalysts show different behaviors. Again perovskite type catalysts calcined at 973 K show higher combustion activity than hexaaluminates calcined at 1573 K, but characteristic values of parent activation energy (5-7 Kcal/mole) have been calculated for perovskite catalysts that are markedly lower than... 

Catalyst recycling. The solid Pd-doped perovskite catalysts are easily filtered from the reaction mixtnre for reuse. The activity of the recycled BaCco 95Pdo.o502 95 catalyst was investigated in the coupling of 4-bromoanisole with 4-phenylboronic acid. The results in Table 27.3 show that high activity was retained even after seven cycles of catalyst use. 

Scheme 27.1. Proposed mechanism for Suzuki coupling by Pd-doped perovskite catalysts.

Nishibata, Y., Mizuki, J., Akao, T. et al. (2002) Self-regeneration of a Pd-perovskite catalyst for automotive emissions control, Nature 418, 164. 

The activities of the perovskite-type oxides are strongly dependent on pretreatment in reducing or oxidizing atmospheres at a.600°C. This was found for other perovskite catalysts as well (1). Reducing pretreatments lead to more active catalysts (Figures 5 and 6). The reason for this is not known, but better binding of CO to the reduced surface is a possible explanation. 

This destruction is considered as the main reason leading to the permanent deactivation of the perovskite catalyst. 

Leanza, R Rossetti, 1 Fabbrini, L Oliva, C Fomi, L. Perovskite catalysts for the catalytic flameless combustion of methane Preparation by flame-hydrolysis and charaeterisation by TPD-TPR-MS and EPR. Appl. Catal, B Environmental, 2000, Volume 28, Issue 1, 55-64. 

Chien, MW Pearson, IM Nobe, K. Reduction and absorption kinetics of nitric oxide on colbalt perovskite catalysts. Ind. Eng. Chem., Prod. Res. Dev., 1975, Volume 14, 131-134. 

Figure 26 The effect of 5 and 50 ppm sulfur on H2 production from ATR of a gasoline benchmark fuel over perovskite catalysts (Lao,8 ro,2Cro.9Nioj03, Lao.8 ro.2Mno.9NiojOs, and Lao.8Sro.2peo.9Nio.i03) ...

Figure 6.27 Possible metal precursors for making stable doped perovskite catalysts with the general formula AA BB 03, for diesel-soot filter regeneration in situ.

Patent USA 4812300. Selective perovskite catalysts to oxidize ammonia to nitric oxide. Qumian M.A., Ramanathan R., Wise H. 

J.G. McCarty and H. Wise, Perovskite catalysts for methane combustion, CataL Today 5 231 (1990). 

Podyacheva O., Ketov A., Ismagilov Z., Ushakov V., Bos A. and Veringa H., Development of supported perovskite catalysts for high temperature combustion, in Environment Catalysis, Centi G. et al., eds, SCI Publ., Rome, (1995), p. 599. 

Studies of perovskite and other oxide electrocatalysts continue to be of great interest [115-118]. The high activities of perovskite catalysts for the oxidation of organic substances [119,120] has stimulated related electrocatalytic studies [121-123]. Perovskites are also convenient inactive substrates for electroanalytical purposes [124]. These investigations are intrinsically related to the electrochemistry of HTSC and serve therefore to extend the circle of well-characterized electrode materials. 

The main problem connected to practical use of this kind of perovskite catalyst in an operating plant is probably low surface area and the tendency to form fine particles during the catalytic action. This must be solved by using a binder or a certain support, like a-Al203. The latter study has just been undergoing in our laboratory. 

A,B-site modified LaNi03 and LaCo03 were demonstrated to be active autothermal reforming catalysts and appear to be structurally stable under the reducing reaction conditions. Sulfur tolerance is still an issue based on the rapid decrease in the H2 concentration in the reformate when reforming sulfur-containing fuels. Future work will focus on improving the activity and the sulfur tolerance of these perovskite catalysts. 

An interesting example of the application of perovskites as electrodes was published by Muller et al. (1994). Lao.6Cao4Co03 has excellent catalytic properties for O2 reduction and evolution as shown by Shimizu et al. (1990). In order to obtain a more durable electrode material, Muller et al. (1994) used graphitized carbon (70 m2/g) as support of the perovskite catalysts. They described in detail the technique used to prepare the electrode which was assayed using an experimental setup adequate for the intended application of this electrode, namely Zn/air batteries. Their main advance over previous formulations was to achieve longer durability of the electrode with some reduction in current density when compared to the previous work of Shimizu et al. (1990). The authors also suggest routes to improve the overall performance of this attractive system. 

The amount of information available in the literature concerning the use of perovskite catalysts for the water gas shift reaction is very minimal. However it has been shown that some ABO3 perovskites have exhibited significant activity for the reaction. GdFeOs is such an example whose activity is attributed to their p-type semi-conductivity due to a limited number of Fe cations, existing in their crystal lattice and associated with the presence of some cation vacancies [10]. 

Here, we present preliminary characterisation results of perovskite catalysts developed with a view to application in PEM-based fuel cell applications, as developed in Forschungszentrum Juelich. CO is a poison to the Pt-based anode catalyst and thus deep... 

---