Oxygen surface mobility and isotopic exchange on oxides: role of the nature and the structure of metal particles

Porous Clay Heteroestructures (PCH) have shown to be highly efficient supports for nickel oxide in the oxidative dehydrogenation of ethane. Thus NiO supported on silica with PCH structure shows productivity towards ethylene three times higher than if NiO is supported on a conventional silica. This enhanced productivity is due to an increase in the catalytic activity and especially to a drastic increase in the selectivity to ethylene.Additionally, PCH silica modified with columns of TiO2 have also been synthesized and used as supports for NiO. An enhanced activity and selectivity to ethylene was found compared to the TiO2-free PCH. The enhanced catalytic performance has been related to the high dispersion of nickel oxide particles on the support, which leads to a lower reducibility of the nickel oxide, hindering the oxidation of ethane into carbon oxides.More interestingly, the particle morphology plays an important role on the catalyst selectivity since a higher distortion of the NiO crystal lattice parameter has meant an enhanced selectivity to ethylene.

show abstract

“…41 which has been reported as non-selective, 22 with practically no participation of lattice oxygen species.…”

Section: Catalyst Characterizationmentioning

confidence: 92%

Nickel oxide supported on porous clay heterostructures as selective catalysts for the oxidative dehydrogenation of ethane

Solsona

Concepción

Nieto

et al. 2016

Catal. Sci. Technol.

View full text Add to dashboard Cite

show abstract

“…Experimental evidence for reverse oxygen spillover has been obtained by oxygen isotopic exchange studies on Rh/CeO 2 . [26,27] Additional evidence was obtained from temperature-programmed desorption (TPD) studies, for example, by Zafiris and Gorte on the same system, which suggested that lattice oxygen migration to the Rh particles occurs at about 400 K. [28] Finally, some additional evidence for the oxygen reverse spillover from CeO 2 to Pd was obtained by Smirnov and Graham. [29] The authors observed the oxidation of supported Pd particles while annealing the sample in ultrahigh vacuum (UHV) at temperatures above 473 K.…”

Section: Introductionmentioning

confidence: 94%

Microscopic Insights into Methane Activation and Related Processes on Pt/Ceria Model Catalysts

et al. 2010

View full text Add to dashboard Cite

Ceria-based supported noble-metal catalysts release oxygen, which may help to reduce the formation of carbonaceous residues, for example during hydrocarbon reforming. To gain insight into the microscopic origins of these effects, a model study is performed under ultrahigh-vacuum conditions using single-crystal-based supported model catalysts. The model systems are based on ordered CeO(2)(111) films on Cu(111), on which Pt nanoparticles are grown by physical vapor deposition. The growth and structure of the surfaces are characterized by means of scanning tunneling microscopy, and the electronic structure and reactivity are probed by X-ray photoelectron spectroscopy. Specifically, it is shown that the fully oxidized CeO(2) thin films undergo slight reduction upon Pt deposition (CeO(1.99)). This effect is enhanced upon annealing (CeO(1.96)), thus indicating facile oxygen release and reverse spillover. The model system is structurally stable up to temperatures exceeding 700 K. The activation of methane is investigated using high-kinetic-energy CH(4) (0.83 eV), generated by a supersonic molecular beam. It is shown that dehydrogenation occurs under rapid formation of CH or C species without detectable amounts of CH(3) being formed, even at low temperatures (100 K). The released hydrogen spills over to the CeO(2) support, which leads to the formation of OH groups. At 200 K and above, the OH groups start to decompose leaving additional Ce(3+) centers behind (CeO(1.97-1.94)). At up to 700 K, carbon deposits are quantitatively removed by reaction with oxygen, which is supplied by reverse spillover from the CeO(2) film, thus leading to substantial reduction of the support (approximately CeO(1.90-1.85)).

show abstract

“…This is primary determined by a much higher reactivity of Pt atoms both for methane [7,22,23] and O 2 [10,34] activation, so the surface steps are mainly controlled by the Pt reactivity, while supports mainly affects the relaxation features. This is also provided by a much higher rate of the surface diffusion as compared with the bulk diffusion [34].…”

Section: Resultsmentioning

confidence: 99%

“…Complex oxides with fluorite-like structure, such as CeO 2 -ZrO 2 system doped by rare-earth cations (Gd, La, Sm, Pr) [7][8][9][10][11][12][13] are now among the most broadly studied catalysts and supports. Doping of ceria-zirconia solid solution and promotion by supported platinum group metals allow to tune the bonding strength, mobility and reactivity of oxygen [14,15].…”

Section: Introductionmentioning

confidence: 99%

Effect of oxygen mobility in solid catalyst on transient regimes of catalytic reaction of methane partial oxidation at short contact times

et al. 2006

View full text Add to dashboard Cite

Mathematical modeling of the effect of the oxygen mobility in a solid oxide catalyst on the dynamics of transients of fast catalytic reactions has been carried out. The analysis was based upon the redox mechanistic scheme with a due regard for diffusion of oxygen from the bulk of catalyst to its surface. Parameters of kinetic and mathematical models were selected via fitting of the experimental data for methane selective oxidation into syngas on 1.4%Pt/Gd 0.2 Ce 0.4 Zr 0.4 O x catalyst. The range of the Thiele parameter (/) where the oxygen bulk diffusion affects the most strongly reaction transients corresponds to /2[0:3 Ä 7]. For highsurface-area oxide catalysts, the bulk oxygen diffusion coefficients corresponding to this range of the Thiele parameter are in the range of10 À18 Ä 10 À13 cm 2 /s.

show abstract

Oxygen surface mobility and isotopic exchange on oxides: role of the nature and the structure of metal particles

Cited by 89 publications

References 48 publications

Nickel oxide supported on porous clay heterostructures as selective catalysts for the oxidative dehydrogenation of ethane

Nickel oxide supported on porous clay heterostructures as selective catalysts for the oxidative dehydrogenation of ethane

Microscopic Insights into Methane Activation and Related Processes on Pt/Ceria Model Catalysts

Effect of oxygen mobility in solid catalyst on transient regimes of catalytic reaction of methane partial oxidation at short contact times

Contact Info

Product

Resources

About