(134g) Water-Gas Shift Activity of Platinum Promoted by Alkali Ions

Authors: 
Zhai, Y. - Presenter, Tufts University
Pierre, D. - Presenter, Tufts University
Si, R. - Presenter, Brookhaven National Lab
Deng, W. - Presenter, Tufts University
Ferrin, P. - Presenter, University of Wisconsin - Madison
Mavrikakis, M. - Presenter, University of Wisconsin - Madison


Alkali additives have been widely used as promoters for Pt based catalysts in industrial catalysts such as the synthesis of ammonia[1], automotive emission control, CO hydrogenation, and recently PROX and WGSR[ 2,3]. The presence of alkali ions (Na, K) added in small amounts significantly promotes the activity of platinum for the low-temperature WGS reaction. Remarkably, low content (<1 at%) platinum on various oxide supports modified by a small amount (1 ? 9 at%) of alkali metals shows catalytic performance comparable to Pt on ceria, the most ?active? support reported to date[8].

The introduction of alkali metals on the Pt- free or doped support changes the surface of the supports; it provides reducible surface oxygen at low temperatures (<200oC) and active OH groups (~150oC). On the other hand, alkali dopants suppress the sintering of Pt particles and maintain most of the Pt in oxidized state. The CO-Pt bond is weaker when Pt is more electron-deficient, thus CO is more active to involve in the reaction pathway. These findings, supported by DFT calculations, and detailed characterization of the active catalysts will be presented.

References

[1] Y. Larichev, D. Shlyapin, P. Tsyrul'nikov, V. Bukhtiyarov, Catal. Lett. 120 (2008) 204-209.

[2] H. Evin, G. Jacobs, J. Ruiz-Martinez, G. Thomas, B. Davis, Catal. Lett. 120 (2008) 166-178.

[3] A. Hagemeyer, et al. ; HONDA GIKEN KOGYO KK (HOND) SYMYX TECHNOLOGIES INC. PCT, 2006

[4] D. Pierre, W. Deng, M. Flytzani-Stephanopoulos, Topics in Catalysis 46 (2007) 363-373.