Catalytic Activities of Supported Nickel Catalysts for Reduction of Nitrogen Monoxide

Abstract

Activity and selectivity of nickel catalysts in the reduction of NO with H2 was investigated. Eight nickel catalysts were reduced at different temperatures by hydrogen and used for the hydrogenation of nitrogen monoxide to yield N₂, N₂O and NH₃. These catalysts were reference catalysts of Catalyst Society of Japan, and were different in support material, nickel content and preparation method. The results are summarized as follows: 1) The maximum activity of Ni/SiO₂ catalysts were about one hundred times more active than that of Ni/Al₂O₃catalysts.2) Such effects as the starting material for the preparation of nickel catalysts, (nitrate or sulfate), and the preparing method, (impregnation or precipitation), on the catalytic activity are masked by the stronger effect of the supporting material.3) Reduction of nickel ion to metallic nickel is essential for the catalytic activity, but the amount of carbon monoxide absorbed is not a measure of the catalytic activity, though it may be a measure of the degree of reduction of nickel. Based on the fact that the selectivity to NH₃ is well correlated to the catalytic activity, a hypothesis is proposed that the catalytic activity for the hydrogenation of nitrogen monoxide is governed by the relative strength of the intteractions of H₂ and NO with nickel.