Complete Conversion of NO with NH3 over the Composite Catalyst Supported on Active Carbon

Abstract

Composite catalysts composed of iron group metals, rare eath oxides and noble metals were previously found to be active for the direct reduction of NO with active carbon as the catalyst support. In this paper, we inspected the catalytic reduction of NO with NH3 on the same catalyst system.An ordinary flow reaction apparatus was used at atmospheric pressure. The reaction gas containing 1.4% of NO and 4.0% of NH3 was allowed to flow through a 70 mg portion of the catalyst under the condition of a 37, 000 hourly space velocity.Among various composite catalysts, 5.0% Co-2.7% La2O3-0.70% Pt catalyst showed the best performance, on which NO was completely converted at 270°C. Synergistic effect of each component was commonly observed in the composite catalysts. This reaction was extensively studied for higher space velocity up to 320, 000h-1 which was achieved by varying the amount of catalyst under the constant flow condition. The higher limit of space velocity for complete NO conversion; (SV) c was expressed as the function of the reaction temperature (T) as follows;(SV) c=10 (0.023T-1.3) (SV≤105h-1)(SV) c=2.1×103T-4.8×105 (SV≥105h-1)T=°CKinetic analysis of this reaction showed that the reaction proceeded by the Langmuir-Hinshelwood mechanism. This reaction was also enhanced by oxygen, and 100% of NO conversion was obtained at 190°C for the same catalyst.