Reduction of nitric oxide by carbon monoxide over a silica supported platinum catalyst: infrared and kinetic studies

Technical Report · Sat Jul 01 04:00:00 EDT 1978

OSTI ID:6710856

Lorimer, D H

The reduction of nitric oxide by carbon monoxide over a 4.5 weight percent platinum catalyst supported on silica was studied at 300/sup 0/C. Reaction rate data was obtained together with in situ infrared spectra of species on the catalyst surface. The kinetics of the system were found to exhibit two distinct trends, depending on the molar ratio of CO/NO in the reactor. For net reducing conditions (CO/NO greater than 1) the catalyst underwent a transient deactivation, the extent of which was dependent on the specific CO/NO ratio during reaction. Reactivation of the catalyst was obtained with both oxidizing and reducing pretreatments. A reaction mechanism based on the dissociation of nitric oxide as the rate-limiting step was used to correlate nitric oxide reaction rates and nitrous oxide selectivities observed under reducing conditions. As part of this mechanism it is assumed that nitrous oxide is formed via a Langmuir-Hinshelwood process in which an adsorbed nitrogen atom reacts with an adsorbed nitric oxide molecule. The nitric oxide reaction rate was found to be first order in nitric oxide partial pressure, and inverse second order in carbon monoxide partial pressure. A mechanism is proposed to qualitatively explain the deactivation process observed under reducing conditions. The essential part of this mechanism is the formation of an isocyanate species on the Pt crystallites of the catalyst and the subsequent transient diffusion of these species to the silica support. The deactivation is believed to result from the build-up of NCO on vacant sites necessary for the dissociation of nitric oxide.

• Research Organization: California Univ., Berkeley (USA). Lawrence Berkeley Lab.
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6710856
• Report Number(s): LBL-8007
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
025000* -- Petroleum-- Combustion
33 ADVANCED PROPULSION SYSTEMS
330700 -- Advanced Propulsion Systems-- Emission Control
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
AUTOMOBILES
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
ELEMENTS
GASEOUS WASTES
KINETICS
METALS
MINERALS
NITRIC OXIDE
NITROGEN COMPOUNDS
NITROGEN OXIDES
OXIDES
OXYGEN COMPOUNDS
PLATINUM
PLATINUM METALS
REACTION KINETICS
REDUCTION
REGENERATION
SILICA
SILICON COMPOUNDS
SILICON OXIDES
TRANSITION ELEMENTS
VEHICLES
WASTES