Search

The combined catalysts Mn/Ba/Al2O3-Pt/Ba/Al2O3and Mn/Ba/Al2O3+Pt/Ba/Al2O3for NOxstorage-reduction were investigated. Mn/Ba/Al2O3indicated high activity of NO oxidation and NOxstorage in the oxidation-storage reaction and certain reduction activity in the storage-reduction reaction. The combination of Pt/Ba/Al2O3with Mn/Ba/Al2O3could enhance the activity of NOxstorage-reduction under dynamic lean-rich burn conditions. Compared to Pt/Ba/Al2O3catalyst, although the Pt content decreased half over Mn/Ba/Al2O3-Pt/Ba/Al2O3and Mn/Ba/Al2O3+Pt/Ba/Al2O3, the NOxconversion increased 9.4% and 6.3% at 350 °C. The pollutions such as NOxand CO could be eliminated effectively over two combined catalysts with low Pt content under dynamic lean-rich burn conditions.

NiMgAlO catalysts were prepared by two methods: coprecipition and impregnation. They were used to simultaneously adsorb SO2 and NO with O2 in a fixed bed at atmospheric pressure. Typically the molar composition of the feed gas was 1% SO2, 0.2% NO and O2 with ultra-high purity Ar as the diluent. The results showed the catalysts were excellent materials for the simultaneous oxidation adsorption of SO2 and NOx. The two kinds of catalysts were compared for the SO2 and NOx adsorption capacity. The NiMgAlO catalyst prepared by coprecipition had better adsorption than impregnation. When NiMgAlO catalysts with 10 wt-% Ni content were calcined at 550°C, adsorption capacity was the largest at 120°C adsorption temperature: 1.392 mmol SO2 and 0.213 mmol NOx were adsorbed on 1 g catalyst prepared by the coprecipition method. The causes are seen by the XRD, surface area and porous size analysis.

The solid state reaction method, coprecipitation method and citric acid method were employed for the preparation of Cr-Mn mixed-oxide catalysts. Experimental results showed that this catalytic system has good selective catalytic reduction (SCR) properties of NOxby ammonia in the presence of excess oxygen at low temperature (80-220°C). 97.8% conversion of NOxwith 100% selectivity of N2had been achieved on Cr-MnOxmixed oxide prepared by the citric acid method at 120°C with the space velocity of 30,000 h-1. X-ray diffraction, BET were adopted for the characterization of the active phase. The characterization results showed that a new crystal phase CrMn1.5O4generated in mixed oxides which was the active center of the Cr-Mn catalysts.