New catalyst systems of heteropoly compounds
as functional material for the adsorptiondecomposition of NO_x

Several catalysts of heteropoly compounds (HPCs) with the performance of NO_x adsorption-decomposition were prepared by means of ethanol-extraction and impregnation. The catalysts were characterized by IR, XRD and TEM and evaluated in a fixedbed reactor. The results showed that tungsten containing HPCs were superior to molybdenum containing HPCs for NO_x adsorption; with the increase of the number of molybdenum atoms substituted by tungsten in H₃PMo_12-xW_xO₄₀（x=1、3、6、12）, its NO_x adsorption efficiency increased. Titania and carbon nanotube (CNT) were good supports for H₃PW₁₂O₄₀(HPW); CNT performed better than titania on the adsorption of NO_x. When TiO₂ was calcinated at 500℃ and the HPW loading was 20%, the NO_x adsorption efficiency of HPW/TiO₂ reached 62.8%. Mixed HNO₃/H₂SO₄ with a volume ratio of 1∶ 3 could produce functional groups such as COO- and C-O on the surface of CNT, which could enhance the dispersion of CNT in the aqueous solution. HPW/CNT catalyst prepared with HNO₃/H₂SO₄modified CNT as support and using water as impregnation solvent was superior to that using ethanol as impregnation solvent; with the HPW loading of 70%, the adsorption efficiency of NO_x by HPW/CNT reached 73.5%. The process effectiveness for NO_x decomposition into N₂ was confirmed by GC-MS analysis.