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Extraordinarily effective promotion by sodium in emission control catalysis: NO reduction by propene over Na-promoted Pt/γ-Al2O3

Gentekakis Ioannis, Konsolakis Michail, Lambert Richard M., Macleod Norman , Nalbantian L.

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Περίληψη

The catalytic activity and selectivity of Pt dispersed on γ-Al2O3, for the reduction of NO by propene is promoted extremely strongly by sodium in the temperature range 470–770 K. Remarkable and unprecedented effects on both activity and selectivity are found. Rate increases by two orders of magnitude are achievable, while the selectivity towards to N2 is improved from ∼20% over the Na-free unpromoted Pt catalyst, to >95% over the optimally Na-promoted catalyst. The Na-free Pt is almost ineffective for the NO + C3H6 reaction over the gas composition and temperature range of this investigation. The promoting effect is due to a sodium-induced increase in the strength of Pt–NO chemisorption relative to propene on a catalyst surface predominantly covered by propene and its fragments. This is accompanied by weakening of the N–O bond, thus facilitating NO dissociation, which process is proposed as the critical reaction initiating step.

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