Temperature programmed desorption study of water adsorbed on metal oxides. 2. Tin oxide surfaces

Egashira, Makoto; Nakashima, M.; Kawasumi, Shohachi; Selyama, Tetsuro

doi:10.1021/j150626a034

Cited by 137 publications

(70 citation statements)

References 4 publications

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“…It is assumed that during water addition surface hydroxyls will be formed first; as soon as the surface is saturated, molecularly adsorbed water starts to build up. This pattern of water uptake on the surface was observed on a-A1203 [ 161,TiO,[ 17,341 and SnO,[ 181. To verify this hypothesis TGA profiles of a 15 wt.-% Mn/Al,O, catalyst after water addition at 323 K during different exposure times were compared; see Fig. 10.…”

Section: Deactivation By Watermentioning

confidence: 69%

Inhibiting and deactivating effects of water on the selective catalytic reduction of nitric oxide with ammonia over MnO /Al2O3

Kijlstra

Daamen

Graaf

et al. 1996

Applied Catalysis B: Environmental

114

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Inhibiting and deactivating effects of water on the selective catalytic reduction (SCR) of NO with NH3 over MnOx/Al2O3 Kijlstra, W.S.; Daamen, J.C.M.L.; van de Graaf, J.M.; van der Linden, B.; Poels, E.K.; Bliek, A. Published in:Applied Catalysis B-Environmental DOI:10.1016/0926-3373(95) Link to publication Citation for published version (APA):Kijlstra, W. S., Daamen, J. C. M. L., van de Graaf, J. M., van der Linden, B., Poels, E. K., & Bliek, A. (1995). Inhibiting and deactivating effects of water on the selective catalytic reduction (SCR) of NO with NH3 over MnOx/Al2O3. Applied Catalysis B-Environmental, 7(3/4), 337-357. DOI: 10.1016/0926-3373(95)00052-6 General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. AbstractThe effect of water on the selective catalytic reduction (SCR) of nitric oxide with ammonia over alumina supported with 2-l 5 wt.-% manganese oxide was investigated in the temperature range 385-600 K, with the emphasis on the low side of this temperature window. Studies on the effect of l-5 vol.-% water vapour on the SCR reaction rate and selectivity were combined with TPD experiments to reveal the influence of water on the adsorption of the single SCR reactants. It turned out that the activity decrease due to water addition can be divided into a reversible inhibition and an irreversible deactivation. Inhibition is caused by molecular adsorption of water. TPD studies showed that water can adsorb competitively with both ammonia and nitric oxide. Additional kinetic experiments revealed that adsorbed ammonia is present in excess on the catalyst surface, even in the presence of water. Reduced nitric oxide adsorption is responsible for the observed reversible decrease in the reaction rate; the fractional reaction order changes from 0.79 in the absence of water to 1.07 in its presence. Deactivation is probably due to the dissociative adsorption of water, resulting in the formation of additional surface hydroxyls. As the amount of surface hydroxyls formed is limited to a saturation level, the deactivating effect on the catalyst is limited too. The additional hydroxyls condense and desorb in the temperature range 525-775 K, resulting in a lower degree of deactivation at higher temperature. A high temperature treatment at 775 K results in a complete regeneration....

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Section: Deactivation By Watermentioning

confidence: 69%

Inhibiting and deactivating effects of water on the selective catalytic reduction of nitric oxide with ammonia over MnO /Al2O3

Kijlstra

Daamen

Graaf

et al. 1996

Applied Catalysis B: Environmental

114

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“…metal oxide surfaces takes instead place at 473 K). 39 Similarly, we can exclude that the surface conductivity is due to the motion of the sodium species, as it has been shown that the sodium atoms remain tightly bound to the fullerene molecules up to at least 575 K. 14 A more likely explanation is that the surface-enhanced conductivity is due to charge propagation by hydrogen-bond exchange (proton-shuttling) between intact, physisorbed water molecules in higher hydration layers.…”

Section: B1 Effect Of the Surface Hydrationmentioning

confidence: 99%

Water-Triggered Conduction Mediated by Proton Exchange in a Hygroscopic Fulleride and Its Hydrate

et al. 2014

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Impedance spectroscopy is employed to probe the impact of water on the dc conductivity and ac dielectric response of the polycrystalline C 60 (ONa) 24 fulleride, both in its bulk-hydrate form, stable only below 370 K, and in the pure form, obtained by heating to high temperature. Exposure of the pure material to ambient air results in the condensation of water vapor on the crystallites' surface, which in turn leads to an enhancement of the room-temperature conductivity by four orders of magnitude due to charge transport through the hydration layer. Electrical conduction in the hydrate between 320 and 380 K is dominated by a non-equilibrium contribution associated with the structural water, which leads to a value of the dc conductivity that is higher than that of the pure material by almost two decades at 360 K. Both conductivity enhancements are most likely due to a proton exchange mechanism. All impedance spectra exhibit, in the radiofrequency range, a dielectric loss feature related to the accumulation of free charges at grain boundaries, whose strength is strongly affected by the presence of hydration water.

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“…Once this initial layer formed, it is no further affected by exposure to humidity. In the case of anatase, which is the phase of our titania sensors, it has been estimated that the desorption of the chemisorbed layer takes place around 200 • C [19].…”

Section: Basic Models Assumed For the Electrical Conduction And Polarmentioning

confidence: 99%

AC impedance spectroscopy: a new equivalent circuit for titania thick film humidity sensors

Faia

Furtado

Ferreira

2005

Sensors and Actuators B: Chemical

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The variation of the electrical signal with humidity in ceramic sensors is originated by the chemical and physical sorptions of water molecules existing in the atmosphere. The aim of the work described in the present paper is to establish an equivalent electrical circuit for the case of two titania thick-film samples. It is shown, at least for the temperature of 23• C, that the same type of circuit represents adequately these two samples for various relative humidities. Chemisorption and physisorption are responsible for the different charge transport mechanisms -ion hopping, ion diffusion and electrolytic conduction. Complex impedance data were obtained at the temperature of 23• C and various relative humidities, in the frequency range 0.1 Hz-40 MHz. The best and simpler circuit representation we found, which gives the best fitting for the Cole-Cole and Bode plots, consists of two RC parallel circuits in series with two constant-phase elements (CPEs). The values of the electrical components are tabled and, as an example, the Cole-Cole and Bode plots fitting obtained for one of our samples, the sample B, for 87.5% RH, in the frequency range 0.1 Hz-40 MHz is shown.

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Temperature programmed desorption study of water adsorbed on metal oxides. 2. Tin oxide surfaces

Cited by 137 publications

References 4 publications

Inhibiting and deactivating effects of water on the selective catalytic reduction of nitric oxide with ammonia over MnO /Al2O3

Inhibiting and deactivating effects of water on the selective catalytic reduction of nitric oxide with ammonia over MnO /Al2O3

Water-Triggered Conduction Mediated by Proton Exchange in a Hygroscopic Fulleride and Its Hydrate

AC impedance spectroscopy: a new equivalent circuit for titania thick film humidity sensors

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