High surface area carbides and nitrides have been synthesized and tested for hydrodenitrogenation activity. Some of the novel materials, particularly Mo2C and Mo2N, provided hydrodenitrogenation activity of the same magnitude as commercial sulfided Ni-Mo/Al203.
Because the exhaust composition in closed-loop emission control systems fluctuates about the stoichiometric set point, there is considerable interest in understanding and improving catalyst behavior in this oscillating environment. We have measured adsorption capacities, responses to step changes in feedstream composition, and performance in cycled laboratory feedstreams in order to clarify features of the transient response of three-way catalysts. Our laboratory results are best explained on the basis of a temporary increase in water-gas shift activity rather than the more common oxygen storage explanation. The phenomenon is associated with the presence of rhodium in the catalyst and Is enhanced when cerium is also present. Sulfur dioxide in the feedstream was highly detrimental to the water-gas shift reaction; so the applicability of these results to the exhaust environment remains an open question.
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