CeO2 promoted with either 1 wt% Pt or 1 wt% Pd was evaluated as a model system for passive NO
 x
 adsorber applications. According to NO
 x
 storage experiments conducted over the temperature range 80–160 °C, promotion with Pt resulted in higher NO
 x
 storage efficiencies than for the Pd-promoted material. However, for NO
 x
 storage at 80 and 120 °C, the latter released more NO
 x
 below 350 °C during temperature-programmed desorption in relative and absolute terms, the Pt analog releasing most of its stored NO
 x
 above 350 °C. DRIFT spectra showed that the use of Pd leads to preferential adsorption of NO
 x
 in the form of nitrites, while predominately nitrate formation is observed over the Pt promoted material. Overall, the use of Pd promoted CeO2 is preferred for low temperature NO
 x
 storage and release due to its ability to store NO
 x
 as thermally labile nitrites.

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Ceria-Based Catalysts for Low Temperature NO x Storage and Release

In late 1979, Engelhard renewed development efforts directed at vanadia type catalysts which were initially used in Europe for nitric acid plants, and vanadia-titania catalysts which were later used extensively in Japan for power plants The vanadia-titania basic composition was combined with the earlier extensive Engelhard experience developed during the commercial pioneering effort which resulted in the practical catalyzing of ceramic honeycomb supports The result was the high activity, high cell density, coated ceramic honeycomb catalyst, now available for use downstream of utility FGD units, gas turbines, stationary engines, industrial heaters and boilers This paper reports key performance characteristics of Engelhard vandia-titania based catalyst The results of commercial systems using this catalyst demonstrating favorable long-term operation is also discussed along with comparisons of published results for other catalysts

R.M. Heck

Papers

Catalytic air pollution controls commercial development of selective catalytic reduction for NOx