Development of Synergic Mixed Metal Oxides for the Combined Catalytic-Absorptive Removal of Nitric Oxide from Diesel Exhaust

The no removal over oxide sorbents (k2o/al2o3 , cao/al2o3 and bao/al2o3) at a loading of up to 25 wt.% was investigated using a synthetic diesel exhaust gas containing 1,000 ppm no, 1000 ppm iso-butane (i-c4h10), 8% o2 and n2 balance. the reactor was operated at 250 oc to 450 oc for the activity study. no was effectively stored (removal efficiencies between 30-60 %) as nitrate under experimental conditions after surface oxidation to no2; and the maximum removal efficiency decreased in the order of k2o/al2o3 (55.4 %) > bao/al2o3 (39.0 %) > cao/al2o3 (37.0 %). k2o/al2o3 had higher mobility; but loadings higher than 15 wt.% were detrimental to the morphological properties. despite higher basicity, cao/al2o3 showed lower removal efficiency of no compared to bao(10)/al2o3 due to low catalytic no2 formation activity. unlike k2o(10)/al2o3, bao(10)/al2o3 showed increasing no removal between 350 oc and 450 oc. k2o(5)bao(5)/al2o3 resulted in better surface area and volume leading to about 65 % of no removal. this was attributed to synergic effects between physicochemical, catalytic and no removal properties of the components. the high performance of k2o(5)bao(5)/al2o3 was successfully elucidated based on the characteristics of the sorbent.