Reduction of Nitric Oxide by Ammonia over Precipitated Alumina Base Catalysts (II):Several Factors which Affect NO-NH3 Reaction over Copper-Alumina Catalysts

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Operational factors affecting the reduction of nitric oxide (NO) by ammonia on precipitated copper oxide-alumina catalysts were studied. On a sulfate ion free catalyst the reaction rate reached maximum at about 280°C giving rise to nearly complete NO conversion. At the higher temperature the conversion of NO declined due to oxidative decomposition of NH3. The catalyst which was of copper sulfate and contained sulfate ion exhibited a high activity above 300°C and the conversion of NO on the catalyst was always more than 99% under the following condition: NH3/NO= 1.5-4.0 (mol ratio), space velocity= 20, 000 cc/g-hr (STP), reaction temperature= 300-400°C. Oxygen in the gas phase accelerated the NO conversion rate more than ten times at around 250°C. Sulfur dioxide in the gas phase inhibited, to some extent, the reac-tion in the concentration range from 0 to 2, 000ppm. Steam, in the concentration range of 1-20vol%, suppressed the reaction greatly. However, if sulfate ion existed in the catalyst, the suppression by steam was fairly mild, and if sulfur dioxide is added in the gas phase steam showed little effect on the reaction. Reaction order with respect to NO ranged between 0.62 to 0.93 depending on the catalyst and the reaction condition. The catalyst containing sulfate ion exhibited the high reaction order. The reaction rate was independent of the concentration of NH3 in large excess.
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