ABSTRACT
In diesel exhaust emissions the hydrocarbon available for reduction varies significantly in carbon number and concentration and is acknowledged to be considerably different than that obtained from conventional gasoline fueled engines. This chapter examines the NOx reduction over a variety of previously reported metal loaded zeolites in separate catalytic efficiency tests using propane/propylene versus isobutane hydrocarbon reductant feed streams. A series of zeolites and silicoaluminophosphates (SAPOs) have been either synthesized or procured from commercial sources for catalytic screening. Zeolites were washed with aqueous NH4 F solutions to remove extra-lattice aluminum. Conventional aqueous ion exchange, solid-state techniques, or a combination of the two were used to prepare catalysts. Effluent gas analysis was performed using a flame ionization detector for hydrocarbons and a chemiluminescent NOx analyzer. Catalytic activity data were acquired in a ramp down mode from 700°C in 50° increments with the same catalysts used in separate trials for each different gas mixture.
