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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. 2016. "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 = 2016,
month = 7
}

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

Citation Metrics:
Cited by: 1work
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  • Li promotion is known to greatly enhance the rate of methanol synthesis on Pd. The mechanism of Li promotion of Pd/SiO{sub 2} at 483-563 K and 1.8 atm was studied using isotopic transient kinetic analysis (ITKA) with carbon tracing to decouple the effects of Li on the methanol-producing sites during the initial period (at 10 min) of reaction. ITKA results indicate that the concentration of active surface intermediates leading to CH{sub 3}OH increased upon Li promotion, indicating that the number of active sites increased or that the coverage of active sites by surface intermediates increased. This increase in concentration ofmore » active intermediates was not due to any effect of the Li on the Pd dispersion. On the other hand, a measure of the average intrinsic k for methanol formation (k{sub meOH}) approximated using the reciprocal of the surface residence time of MeOH intermediates was lower for the Li-promoted than the unpromoted catalyst. Because of the greater importance of the increase in the concentration of surface intermediates, the overall effect was that the Li-promoted catalyst was more active for methanol synthesis. 18 refs., 9 figs., 3 tabs.« less
  • 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
  • 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
  • Iron carbonyls Fe(CO)/sub 5/, Fe/sub 2/(CO)/sub 9/, and Fe/sub 3/(CO)/sub 12/ have been introduced into a hydrated Na-Y zeolite. Fe(CO)/sub 5/ was only weakly adsorbed on the zeolite. Fe/sub 2/(CO)/sub 9/ and Fe/sub 3/(CO)/sub 12/ were reactive in the hydrated zeolite cages to yield a hydride anion species HFe/sub 3/(CO)/sub 11//sup -/ which was characterized by IR absorption bands at 2044, 1987, 1950, and 1645 cm/sup -1/, UV-vis spectrum at 540 nm, and gas-phase analyses. The red shift of absorption band of the bridging carbonyl indicated ionic interaction of a bridging carbonyl with an Al/sup 3 +/ ion in themore » zeolite matrix. The formation of the anion species was not observed in a dehydrated Na-Y zeolite, indicating the importance of water or a surface hydroxyl group n the reaction. The reaction course from di- or trinuclear iron carbonyl to the hydride anion has been studied by an ESR technique. Fe/sub 2/(CO)/sub 8//sup -/, Fe(CO)/sub 4//sup -/, and Fe/sub 3/(CO)/sub 11//sup -/ species were detected as intermediates, and reaction schemes have been proposed. The resulting HFe/sub 3/(CO)/sub 11//sup -/ was stable at or below 413 K both in a vacuum or in a CO atmosphere. Above this temperature it was gradually decomposed. Catalytic activity of the HFe/sub 3/(CO)/sub 11//sup -/ species was examined for water-gas-shift reaction at 333-453 K and atmospheric pressure. The activity was very high and comparable to that reported in the homogeneous phase at high pressure. Kinetics and spectroscopic studies indicated that the reaction between HFe/sub 3/(CO)/sub 11//sup -/ and H/sub 2/O would be rate-determining.« less
  • The mechanism of nitric oxide reduction with ammonia to form N/sub 2/, H/sub 2/O and N/sub 2/O both in the presence and in the absence of O/sub 2/ over the following series of catalysts, unsupported V/sub 2/O/sub 5/, V/sub 2/O/sub 5/ on TiO/sub 2/, V/sub 2/O/sub 5/ on SiO/sub 2//Al/sub 2/O/sub 3/, and V/sub 2/O/sub 5/ on Al/sub 2/O/sub 3/, has been investigated with the aid of labeled O/sub 2/ and labeled NH/sub 3/ at 400/sup 0/C. The behavior of ammonia was studied both in the presence and in the absence of O/sub 2/. The presence of labeled O/sub 2/more » gives extra information about the product distribution and the reaction mechanism. Evidence is given that ammonia does not react with O/sub 2/ or O from any source during the reaction, but that nitrogen and nitrous oxide were produced by a reaction involving all three species, NO, NH/sub 3/, and/or O/sub 2/. Nitrous oxide and water are both formed at two different sites of the catalyst. A series of transient tracing studies were performed in a plug-flow reactor using /sup 15/NH/sub 3/ and /sup 18/O/sub 2/. Both /sup 15/NN and /sup 15/NNO were produced on the unsupported V/sub 2/O/sub 5/, V/sub 2/O/sub 5/ on TiO/sub 2/, V/sub 2/O/sub 5/ on SiO/sub 2//Al/sub 2/O/sub 3/, and V/sub 2/O/sub 5/ on Al/sub 2/O/sub 3/ with very high selectivities. The mechanism of the reaction of NO, NH/sub 3/, and O/sub 2/, proposed in a previous paper, is further evaluated on the basis of this new experimental evidence.« less