Pd/Al2O3-La2O3 catalysts prepared by sol–gel: characterization and catalytic activity in the NO reduction by H2

Barrera, A.; Viniegra, M.; Bosch, P.; Lara, V.H.; Fuentes, S.

doi:10.1016/s0926-3373(01)00206-5

Cited by 67 publications

(37 citation statements)

References 33 publications

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“…As indicated in table 6, a higher value is obtained for the ratio k H /k NO on the pre-reduced Pd/LaCoO 3 . Such a result seems to be in relative good agreement with previous statements [53,54] highlighting that the extent of interactions between Pd and the reduced support would preserve the metallic character of Pd sites. Consequently, the competitive adsorptions would be more in favour of H 2 on the pre-reduced Pd/LaCoO 3 than on Pd/Al 2 O 3 .…”

Section: Kinetic Of the No+h 2 Reaction On Pd/al 2 Osupporting

confidence: 91%

An overview: Comparative kinetic behaviour of Pt, Rh and Pd in the NO + CO and NO + H2 reactions

Granger¹,

Dhainaut²,

Pietrzik

et al. 2006

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This paper reports a comparative kinetic investigation of the overall reduction of NO in the presence of CO or H 2 over supported Pt-, Rh-and Pd-based catalysts. Different activity sequences have been established for the NO+H 2 reaction . It was found that both reactions differ from the rate determining step usually ascribed to the dissociation of chemisorbed NO molecules. The rate enhancement observed for the NO+H 2 reaction has been mainly related to the involvement of a dissociation step of chemisorbed NO molecules assisted by adjacent chemisorbed H atoms. The calculation of the kinetic and thermodynamic constants from steadystate rate measurements and subsequent comparisons show that Pd and Rh are predominantly covered by chemisorbed NO molecules in our operating conditions which could explain either changes in activity or in selectivity with the lack of ammonia formation on Rh/Al 2 O 3 during the NO+H 2 reaction. Interestingly, Pd and Rh exhibit similar selectivity behaviour towards the production of nitrous oxide (N 2 O) irrespective of the nature of the reducing agent (CO or H 2 ). A weak partial pressure dependency of the selectivity is observed which can be related to the predominant formation of N 2 via a reaction between chemisorbed NO molecules and N atoms, while over Pt-based catalysts the associative desorption of two adjacent N atoms would occur simultaneously. Such tendencies are still observed under lean conditions in the presence of an excess of oxygen. However, a detrimental effect is observed on the selectivity with an enhancement of the competitive H 2 +O 2 reaction, and on the activity behaviour with a strong oxygen inhibiting effect on the rate of NO conversion, particularly on Rh.

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Section: Kinetic Of the No+h 2 Reaction On Pd/al 2 Osupporting

confidence: 91%

An overview: Comparative kinetic behaviour of Pt, Rh and Pd in the NO + CO and NO + H2 reactions

Granger¹,

Dhainaut²,

Pietrzik

et al. 2006

Top Catal

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“…Surface area (S BET ), pore volume (Vp), Palladium dispersions (D Pd ), Steam Reforming of Methane Reaction Rate, Turnover Frequency (TOF) at 783 K and Apparent Activation Energy (E a Barrera et al[10] also obtained similar results while studying c-Al 2 O 3 samples promoted with 15 wt. % of La.…”

mentioning

confidence: 59%

“…% a reduction peak appeared, around 740 K, the H 2 -comsuption is higher compared to the amount of PdO (Table 1), resulting in the H 2 consumption/PdO ratio higher than the stoichiometric. There are some controversies about how to assign the H 2 consumption at 740 K [10,[12][13][14][15][16] but several authors suggest that this peak may be related to the reduction of small quantities of La 2 O 3 to LaO x [10]. However, TPR experiments done with (x)La-Al 2 O 3 supports (not showed) reveal that there is no H 2 consumption up to 1,273 K. Therefore, it could be suggested that this peak is due to the reduction of the lanthana support that supposedly is associate with the cleavage of the H-H bond on highly dispersed Pd 0 particles, which promote the reduction of the lanthana.…”

Section: Resultsmentioning

confidence: 99%

Effect of CeO2 and La2O3 on the Activity of CeO2−La2O3/Al2O3-Supported Pd Catalysts for Steam Reforming of Methane

et al. 2007

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The effect of the addition of CeO 2 or La 2 O 3 on the surface properties and catalytic behaviors of Al 2 O 3 -supported Pd catalysts was studied in the steam reforming of methane. The FTIR spectroscopy of adsorbed CO and the Pd dispersion suggest the partial coverage of Pd 0 by ceria or lanthana species. This could lead to the formation of an adduct MPd x O (M = Ce or La) at the surface of the metal crystallites. The addition of ceria or lanthana resulted in an increase of the turnover rate and specific rate for steam reforming of methane. One possible explanation if that the Pd 0 *Pd d+ O-M interfacial species (M = Ce or La) are oxidized by H 2 O or CO 2 , promoting the O* transfer to the metal surface. This could facilitate the removal of C* species from the metal surface, resulting in the increase of specific reaction rate and increase of the accessibility of CH 4 to metal active sites.

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“…The double cathodic peak present on the CVs of activated carbon-supported palladium systems indicates the presence of various forms of palladium oxides on the activated Fig. 8 Cyclic voltammograms of activated carbon based electrodes at rising anodic reverse potentials carbon surface [34,35]. Palladium electro-oxidation does not affect the oxidation or reduction of hydrogen during cathodic polarization for AC (see Figs.…”

Section: Resultsmentioning

confidence: 99%

Cyclovoltammetric studies of carbon materials-supported palladium

Hofman

Świątkowski

Pakuła

et al. 2012

Reac Kinet Mech Cat

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Various Pd amounts (5 and 20 %wt) were chemically deposited on two different carbon materials (activated carbon and carbon black). Support materials were characterized using low-temperature N 2 adsorption and FTIR spectroscopy. SEM images and X-ray diffraction patterns were obtained for the samples tested. Cyclic voltammetric curves in 0.1 M H 2 SO 4 were recorded over a variable sweep potential range for carbon materials with and without Pd. For comparison, the same electrochemical measurements were performed for powdered palladium. The hydrogen electro-oxidation potential decreased and the removal of adsorbed hydrogen by activated carbon-supported palladium was facilitated, which enables these systems to be used as anodes in hydrogen-oxygen fuel cells.

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Pd/Al2O3-La2O3 catalysts prepared by sol–gel: characterization and catalytic activity in the NO reduction by H2

Cited by 67 publications

References 33 publications

An overview: Comparative kinetic behaviour of Pt, Rh and Pd in the NO + CO and NO + H2 reactions

An overview: Comparative kinetic behaviour of Pt, Rh and Pd in the NO + CO and NO + H2 reactions

Effect of CeO2 and La2O3 on the Activity of CeO2−La2O3/Al2O3-Supported Pd Catalysts for Steam Reforming of Methane

Cyclovoltammetric studies of carbon materials-supported palladium

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