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Title: Isotopic transient studies of sodium promotion of Pt/Al 2 O 3 for the water–gas shift reaction

Authors:
; ; ; ;
Publication Date:
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1341151
Grant/Contract Number:
FG02-03ER15466
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Journal of Catalysis
Additional Journal Information:
Journal Volume: 339; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-10-04 09:36:42; Journal ID: ISSN 0021-9517
Publisher:
Elsevier
Country of Publication:
United States
Language:
English

Citation Formats

Cybulskis, Viktor J., Wang, Jun, Pazmiño, Jorge H., Ribeiro, Fabio H., and Delgass, W. Nicholas. Isotopic transient studies of sodium promotion of Pt/Al 2 O 3 for the water–gas shift reaction. United States: N. p., 2016. Web. doi:10.1016/j.jcat.2016.04.018.
Cybulskis, Viktor J., Wang, Jun, Pazmiño, Jorge H., Ribeiro, Fabio H., & Delgass, W. Nicholas. Isotopic transient studies of sodium promotion of Pt/Al 2 O 3 for the water–gas shift reaction. United States. doi:10.1016/j.jcat.2016.04.018.
Cybulskis, Viktor J., Wang, Jun, Pazmiño, Jorge H., Ribeiro, Fabio H., and Delgass, W. Nicholas. Fri . "Isotopic transient studies of sodium promotion of Pt/Al 2 O 3 for the water–gas shift reaction". United States. doi:10.1016/j.jcat.2016.04.018.
@article{osti_1341151,
title = {Isotopic transient studies of sodium promotion of Pt/Al 2 O 3 for the water–gas shift reaction},
author = {Cybulskis, Viktor J. and Wang, Jun and Pazmiño, Jorge H. and Ribeiro, Fabio H. and Delgass, W. Nicholas},
abstractNote = {},
doi = {10.1016/j.jcat.2016.04.018},
journal = {Journal of Catalysis},
number = C,
volume = 339,
place = {United States},
year = {Fri Jul 01 00:00:00 EDT 2016},
month = {Fri Jul 01 00:00:00 EDT 2016}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.jcat.2016.04.018

Citation Metrics:
Cited by: 4works
Citation information provided by
Web of Science

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  • An investigation of La{sup 3+} promotion of 20 wt% Co/Al{sub 2}O{sub 3} [(La/Co){sub atomic}=0, 0.05., 0.10, and 1.0] for CO hydrogenation at 463-503 K and 1.8 atm has been carried out in order to develop a better understanding of the mechanism and effects of promotion. Chemisorption results show that at lower La{sup 3+} loadings there was a more significant effect on H{sub 2} adsorption blockage. La{sup 3+} promotion enhanced the selectivity for high hydrocarbons during CO hydrogenation, as has previously been observed for La{sup 3+}-promoted Co catalysts at lower metal loadings, while the overall activity went through a maximum formore » La/Co = 0.05. Steady-state isotopic transient kinetic analysis (SSITKA) with carbon tracing was used to decouple the effects of La{sup 3+} on methane-producing sites during CO hydrogenation. The SSITKA results indicate that both a measure of the average methanation site/intermediate activity (1/{tau}m) and the concentration of active surface intermediates leading to CH{sub 4} (N{sub M}) increased upon initial La{sup 3+} promotion. At higher La{sup 3+} content the concentration of active surface intermediates leading to CH{sub 4} decreased; however, the average site/intermediate activity remained essentially constant, resulting in a lower rate of methane formation. Deconvolution results indicate that La{sup 3+} promotion affected methane site activity by increasing the reactivity of the most active pool of intermediates. Increasing the H{sub 2}/CO inlet ratio at constant temperature and CO partial pressure led to an increase in the observed average site/intermediate activity, indicating a dependence on the concentration of surface hydrogen. One can conclude that while La{sup 3+} species block some of the Co surface, promotion results in the creation of more sites/intermediates on the surface having higher activities and probably results in a modification of the hydrogen surface concentration. 26 refs., 10 figs., 2 tabs.« less
  • Steady-state isotopic transient kinetic analysis (SSITKA) of the NO/C{sub 3}H{sub 6}/O{sub 2} reaction, using {sup 14}NO {r_arrow} {sup 15}NO switches, has been carried out over a 1% Pt-SiO{sub 2} catalyst at four different temperatures. The results indicate that below the temperature of the maximum NO{sub x} conversion there are no NO adsorption/desorption processes taking place under these steady-state conditions. Moreover, less than 15% of the catalyst surface is covered with N{sub 2} or N{sub 2}O precursors. N{sub 2}O is the isotopically first product while N{sub 2} is the second. The surface lifetime of N{sub 2}O precursors is relatively short whilemore » the surface lifetime of N{sub 2} precursors is significantly longer. The production of N{sub 2} and N{sub 2}O are both increased by raising the temperature. In the case of N{sub 2}O, this seems to be solely due to an increase in the concentration of active sites on the catalyst while in the case of N{sub 2} the increase in the number of active sites is accompanied by an increase in their intrinsic activity. At temperatures above the maximum in the NO{sub x} conversion that is a discernible amount of NO desorption taking place under steady-state conditions. This is rationalized by the formation of NO{sub 2(ads)} species on the now-oxidized Pt surface. The SSITKA results are found to support the previously proposed reaction mechanism for the NO/C{sub 3}H{sub 6}/O{sub 2} reaction over Pt-based catalysts. Finally, a general form for the calculation of concentrations of adsorbed species from any SSITK analysis is presented.« less
  • A detailed reaction network, derived from literature data and the authors own experimental work, is used as a basis for the development of a steady-state kinetic model for methanol synthesis and the water gas shift reaction on a commercial Cu/ZnO/Al{sub 2}O{sub 3} catalyst. Experimental data, obtained in a bench scale setup, operating between 180 and 280{degrees} C and at pressures up to 51 bar, are subsequently used for the estimation of the parameters in the proposed model. The result is a mechanistically sound kinetic model, comprising a set of statistically significant and physically meaningful parameter groups. It accurately predicts themore » experimentally obtained conversions, even upon extrapolation outside the originally applied experimental window. using this model, the influence of inlet temperature, pressure, and the ratio of p{sub CO} and p{sub CO{sub 2}} are briefly illustrated. 36 refs., 8 figs., 3 tabs.« less
  • While it is long known that different types of support oxides have different capabilities to anchor metals and thus tailor the catalytic behavior, it is not always clear whether the support is a mere carrier of the active metal site, itself not participating directly in the reaction pathway. We report that catalytically similar single-atom centric Pt sites are formed by binding to sodium ions through ?O ligands, the ensemble being equally effective on supports as diverse as TiO2, L-zeolites, and mesoporous silica MCM-41. Loading of 0.5 wt.% Pt on all these supports, preserves the Pt in atomic dispersion as Pt(II),more » the Pt-O(OH)x- species catalyzing the water-gas shift reaction (WGS) from ~120 to 400 oC. Since the effect of support is ?indirect,? these findings pave the way for the use of a variety of earth-abundant supports as carriers of atomically dispersed platinum for application to catalytic fuel-gas processing.« less