Catalytic combustion of methane over palladium alumina modified by niobia

Alegre, Violeta Virginia; Silva, M.A.P. da; Schmal, Martín

doi:10.1016/j.catcom.2005.10.018

Cited by 35 publications

(10 citation statements)

References 20 publications

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“…The differences in the catalytic stability of catalysts (Pd/NiO-Al 2 O 3 > Pd/NiO-2Al 2 O 3 > Pd/2NiO-Al 2 O 3 ) likewise could not be explained directly by the differences in the surface area. The large surface area plays an important role in promoting the overall capability of catalyst, but it is not applicable in the present samples, being consistent with results reported in many studies [30,34,40,41]. A significant variation of Pd dispersion values, calculated by CO-chemisorption analysis, could be observed for three catalysts.…”

Section: Characterization Of Catalystsupporting

confidence: 80%

Enhanced hydrothermal stability of high performance lean fuel combustion alumina-supported palladium catalyst modified by nickel

Liu

Wang

Sun

et al. 2012

Applied Catalysis B: Environmental

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Section: Characterization Of Catalystsupporting

confidence: 80%

Enhanced hydrothermal stability of high performance lean fuel combustion alumina-supported palladium catalyst modified by nickel

Liu

Wang

Sun

et al. 2012

Applied Catalysis B: Environmental

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“…The same band around 280 nm, however, has been claimed previously to be due to (Gaspar and Dieguez 2000). A broad band in the d-d transition region from 450 to 500 nm (maximum at about 490 nm), which is much more pronounced in the spectra of sample 1, has been attributed to bulk PdO particles of different size with no interaction with the support (Alegre et al 2006;Ivanova et al 2010). This may indicate larger PdO particles (C 0 onsul et al 2006) sitting on the edge of the support of sample 1, which is a scenario that suites well to the lower Pd(O) dispersion found by XPS of the same sample (Table 2).…”

Section: Structural Investigationsupporting

confidence: 75%

Strong metal–support interaction as activity requirement of palladium-supported tin oxide sol–gel catalyst for water denitration

Bošković

Kovacevic

Kiss

et al. 2012

Int. J. Environ. Sci. Technol.

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Two nanocrystalline palladium-supported tin oxide catalysts for water denitration were synthesized by a modified sol-gel technique using appropriate chloride precursors for both support and active phases, and citric acid to tune the rate of hydrolysis and condensation. The difference among sample preparation procedures refers to the moment of the noble metal loading to the support, as well as to the calcination temperature altitude followed. Thus, mesoporous tin oxide was synthesized by a sol-gel method following calcination at 700°C. The palladium active phase was introduced afterwards by means of palladium chloride solution impregnation, followed by calcination at 400°C (sample 1). Alternatively, simultaneous complexation of both metal and support precursors followed by single calcination at 700°C was applied for preparation of sample 2. The former sample showed higher activity and selectivity in hydro-denitration of water model system initially containing 100 ppm of nitrates. This was explained by preferential textural, morphological and structural properties accomplished by early contact of metal and support nanoparticles, while achieved by calcination at high single temperature forcing diffusion of palladium ions into the tin oxide matrix. The outcome is very well distribution of palladium and strong metal-support interaction leading to multivalent tin. This indicates partly reduced tin oxide formation in the course of its reduction in hydrogen, which may act as active site in denitration reaction.

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“…The PdCl catalyst also has a broad reduction peak at 400-500 K that is not present in the TPR trace of the PdN sample. Some authors attribute this peak to the reduction of PdO species strongly interacting with the support [5,24,26]. Other authors suggest that the hydrogen consumption at these temperatures is due to the reduction of Pd x O y Cl z oxychlorinated species or the reduction of Pd 2?…”

Section: Catalytic Reaction Testsmentioning

confidence: 94%

Resistance to Sulfur and Oxygenated Compounds of Supported Pd, Pt, Rh, Ru Catalysts

et al. 2010

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The poisoning resistance to sulfided and oxygenated compounds of some VIII Group PYGAS selective hydrogenation catalysts based on metals was assessed. Low content alumina supported Rh, Pd, Ru and Pt catalysts (0.35 wt%) were prepared from chlorided precursors. In the case of the palladium catalysts a nitrogenated precursor was also used. The catalysts were mainly assessed in the catalytic test of selective styrene hydrogenation in the presence or absence of known poisons. Model feedstocks spiked with thiophene, thiophane and tetrahydrofuran were used. The catalysts were further characterized by means of chemical analysis, XPS, TPR and chemisorption. The results indicate that chlorided precursors yield more sulfur resistant catalysts. The effect was attributed in part to the formation of oxychlorinated species, refractory to reduction, that leave the metal in an electron deficient state, thus inhibiting the formation of strong poison-metal bonds, the chloride species could also be a steric factor that can contribute to the sulfur resistance of the catalyst. Pd based catalyts had the highest activity and resistance to poisons of all the metals tested. This superior performance was attributed in part to the total occupancy of the 4d electronic levels of the Pd metal that was supposed to promote the rupture of the H 2 bond during the hydrogenation reaction. Keywords Low metal loading catalysts Á Selective hydrogenation Á Sulfided and oxygenated poisons List of Symbols PF Poison free condition TE Thiophene TA Thiophane THF Tetrahydrofuran D Metal dispersion S Metal specific surface (m 2 g met -1 ) d Average metal particle size (Å ) V HAds (CNPT) Volume of hydrogen chemisorbed at normal conditions (cm 3 ) PA Atomic weight of the metal (g mol -1 ) w Metal content per unit gram of catalyst M Mass of sample (g) m Stoichiometry of chemisorption of the gas on the surface metal atoms V m CNPT Volume of the chemisorbed monolayer of the adsorbate at normal conditions (cm 3 g -1 ) N Avogadro's number (6.023 9 10 23 ) V N Molar volume of the adsorbate at normal conditions r Number of metal atoms per square meter (atoms m -2 ) xAdsorption stoichiometry (number of hydrogen atoms adsorbed per unit of metal atom) qDensity of the metal (g m -3 ) M Red /M Tot Reduced metal amount and total metal amount ratio wt M% Nobel metal content (weight percentage) T Red Reduction temperature (K) r°E S Initial styrene hydrogenation rate in poison free condition (mol g cat -1 min -1 ) DESRelative deactivation per concentration of poison (ppm -1 )

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Catalytic combustion of methane over palladium alumina modified by niobia

Cited by 35 publications

References 20 publications

Enhanced hydrothermal stability of high performance lean fuel combustion alumina-supported palladium catalyst modified by nickel

Enhanced hydrothermal stability of high performance lean fuel combustion alumina-supported palladium catalyst modified by nickel

Strong metal–support interaction as activity requirement of palladium-supported tin oxide sol–gel catalyst for water denitration

Resistance to Sulfur and Oxygenated Compounds of Supported Pd, Pt, Rh, Ru Catalysts

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