Iv. Yentekakis et al., Extraordinarily effective promotion by sodium in emission control catalysis: NO reduction by propene over Na-promoted Pt/gamma-Al2O3, APP CATAL B, 22(2), 1999, pp. 123-133
Citations number
31
Categorie Soggetti
Physical Chemistry/Chemical Physics","Environmental Engineering & Energy
The catalytic activity and selectivity of Pt dispersed on gamma-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 bo
th activity and selectivity are found. Rate increases by two orders of magn
itude are achievable, while the selectivity towards to N-2 is improved from
similar to 20% over the Na-free unpromoted Pt catalyst, to >95% over the o
ptimally 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 surfa
ce predominantly covered by propene and its fragments. This is accompanied
by weakening of the N-O bond, thus facilitating NO dissociation, which proc
ess is proposed as the critical reaction initiating step. (C) 1999 Elsevier
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