Performance, selectivity, and deactivation of Pt-ZSM-5 catalysts for selective catalytic reduction of NO

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:214809

Kharas, K C.C.; Robota, H J ^[1]

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1. AlliedSignal Environmental Catalysts, Tulsa, OK (United States)

It is well known that precious metal catalysts can effectively oxidize CO and hydrocarbons under oxidizing conditions. Reduction of NO under net oxidizing conditions remains a significant industrial challenge. Fresh Pt-ZSM-5 is quite effective at using hydrocarbons to reduce NO at relatively low temperatures, between about 100{degrees}C and 350{degrees}C. Interesting interactions are observed using multicomponent synthetic exhaust gas mixtures chosen to model some aspects of diesel exhaust. The presence of H{sub 2}O strongly affects conversion of propene and CO over this noble metal catalyst. The selectivity of NO reduction, either to N{sub 2}O or to N{sub 2}, is highly dependent on the types of reducing agents present. EXAFS analysis of the fresh material reveals the platinum to occur as highly oxidized species that are either amorphous or highly dispersed. TEM analysis shows the dispersion of at least some of the Pt in the fresh catalyst to be low. One hour of catalysis under oxidizing conditions at 700{degrees}C to 800{degrees}C can result in significant deactivation. A number of physicochemical changes occur in the catalyst, some of which may be relevant to deactivation. In particular, very thin films covering Pt can be observed in deactivated catalysts.

• OSTI ID: 214809
• Report Number(s): CONF-950801--
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
54 ENVIRONMENTAL SCIENCES
CATALYSTS
CATALYTIC EFFECTS
COMBUSTION PRODUCTS
DEACTIVATION
NITROGEN OXIDES
PLATINUM
REDUCING AGENTS
SELECTIVE CATALYTIC REDUCTION
THIN FILMS
ZEOLITES