Poison-resistant catalysts for the simultaneous control of hydrocarbon, carbon monoxide and nitrogen oxide emissions

Conference · Fri Sep 01 00:00:00 EDT 1978 · Prepr., Div. Pet. Chem., Am. Chem. Soc.; (United States)

OSTI ID:6261930

Hegedus, L L; Summers, J C; Schlatter, J C; Baron, K

Experiments designed to answer certain questions about the mechanism of operation and of deactivation of catalysts near stoichiometric conditions were carried out. This involved special catalysts preparations tested in laboratory equipment and in vehicles. We concluded that the poisoning process at exhaust stoichiometry appears to be very similar to the poisoning process under net oxidizing conditions; that is, only a sharply defined outer shell of the pellets is poisoned, this shell progressing inward as time elapses. Based on these experiments, the following catalyst design concept was developed: To utilize the different properties of Pt, Pd and Rh, all three will have to be employed in a special design corresponding to their ratio in ores. To avoid interferences, they should not be coimpregnated over the same support surface; one way to avoid coimpregnation is to impregnate them in separate layers in the catalyst pellets. Due to its relative poison insensitivity Pt should be the outer layer, while Pd and Rh should be protected from the poison front. Consequenty, the Pt impregnation depth (from the outer surface) is given by the depth to which the poisons penetrate. Due to the importance of Rh in catalyzing the NO reduction reaction at the (diffusion controlled) rich end of the A/F scale, Rh should be impregnated as close to the surface of the pellet as possible, while still being protected from poisoning. Consequently, Rh should be impregnated right below the Pt layer and Pd underneath the Rh layer. Due to the transient nature of the feedstream's A/F, it appears to be beneficial to include an agent in catalyst formulations which, by storing and slowly releasing some of the components from the surface, tends to smooth out the effects of A/F oscillations. The results are encouraging; real-time engine dynamometer and vehicle aging tests are required, however, to prove their durability in actual automobile service.

• Research Organization: General Motors Research Labs., Warren, MI
• OSTI ID: 6261930
• Report Number(s): CONF-780902-P4
• Journal Information: Prepr., Div. Pet. Chem., Am. Chem. Soc.; (United States), Vol. 23:4; Conference: American Chemical Society meeting, Miami, FL, USA, 10 Sep 1978
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
AUTOMOBILES
CATALYTIC CONVERTERS
EXHAUST GASES
CATALYSTS
CHEMICAL PREPARATION
POISONING
DESIGN
PERFORMANCE TESTING
CERIUM
CATALYTIC EFFECTS
PALLADIUM
PLATINUM
RHODIUM
AIR POLLUTION CONTROL
CARBON MONOXIDE
DEACTIVATION
ELECTRON MICROPROBE ANALYSIS
FUEL-AIR RATIO
HYDROCARBONS
LEAD
NITRIC OXIDE
PHOSPHORUS
X-RAY FLUORESCENCE ANALYSIS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL ANALYSIS
ELEMENTS
EQUIPMENT
GASEOUS WASTES
METALS
MICROANALYSIS
NITROGEN COMPOUNDS
NITROGEN OXIDES
NONDESTRUCTIVE ANALYSIS
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
POLLUTION CONTROL
POLLUTION CONTROL EQUIPMENT
RARE EARTHS
REFRACTORY METALS
SYNTHESIS
TESTING
TRANSITION ELEMENTS
VEHICLES
WASTES
X-RAY EMISSION ANALYSIS
330700* - Advanced Propulsion Systems- Emission Control