Selective catalytic reduction of nitric oxide by hydrogen over NiFe2-xPdxO4 catalysts at low temperature

Selective catalytic reduction of NOx to nitrogen by hydrogen (H-2-SCR) does not result in any secondary pollutants and can reduce NOx at the lowest possible temperatures. To achieve this goal, proper catalysts are critical. In this paper, NiFe2-xPdxO4 catalysts were prepared using a sal-gel auto-ignition method for the selective catalytic reduction of NO with hydrogen (H-2-SCR) in the presence of oxygen at 150-250 degrees C. The NiFe2-xPdxO4 catalysts exhibited high SCR activity providing 100% NO conversion at 190 degrees C, and the activity improved as the palladium content increased. NiFe1.90Pd0.10O4 exhibited a slightly lower activity in the 180-220 degrees C range. NiFe1.93Pd0.07O4 and NiFe1.95Pd0.05O4 exhibited larger acidity, higher level of reducibility and catalytic activity, which was validated through NH3-TPR, H-2-TPR analysis and SCR activity tests. The XRD results indicated that the samples had a spinet cubic structure with good crystallization. The EDS results indicated that the Fe/Ni and Pd/Ni atomic ratio in the samples were consistent with the theoretical molecular formula (i.e., NiFe2-xPdxO4). The effects of GHSV, H-2/NO ratios and O-2 feed concentration on the NO conversion over the NiFe1.95Pd0.05O4 catalyst were also investigated. An increase in the 02 concentration from 0% to 6% and a decrease in the H-2/NO ratio from 10:1 to 5:1 produced only a slight decrease in the NO conversion. Studies on the effect of 3% and 5% H2O on the SCR activity concluded that the slight activity decrease, was due to reversible inhibition and weakly irreversible deactivation, and that the catalysts contained excellent water tolerance. (C) 2015 Elsevier B.V. All rights reserved.