Investigation on catalytic reduction of NO with methane over metal catalysts

Abstract

Catalytic reduction of NO with methane over Pd/ MgO, Pd/A1₂O₃, Co/MgO and Pt/ A1₂O₃ catalysts has been studied using a closed circulation apparatus. The reaction activities of catalysts are: Pd/MgO &gt; Pd/ AI₂O₃] &gt;Pt/ Al₂O₃ &gt; Co/MgO. The mol. ratio of CO₂ and N₂ in the products is near 1/2, which indicates that the reaction can be described as 4NO +CH₄->2N₂ + CO₂+2 H₂O. With N₂O as an intermediate, the reaction mechanism can be described as NO^<i>k</i> -> ¹N₂O²^<i>k</i> -> ²N₂. The value of <i>k₁ </i>and <i>k₂ </i> for the catalysts used are related as follows: Co/MgO catalyst, <i>k₁ «k₂ </i> at 600°C; Pd/ MgO catalyst, <i>k </i>₁ » <i>k₂ </i> at 420°C; and Pd/ Al₂O₃ catalyst, <i>k₁ » k₂ </i> at 420°C. Methane can be used as reductant to remove the emission under mild reaction condition. CO is detected when NO + CH₄ reacts on Pd/ Al₂O₃ It is assumed t at the excess CH₄ would react further with the reaction product CO₂ to produce CO.