负载型磷酸氧钒低温脱硝催化剂的制备及其抗硫抗水性能

Preparation of low-temperature DeNO_x catalyst of supported vanadium phosphate and its resistance to sulfur dioxide and water vapor

针对目前低温脱硝催化剂抗硫抗水性较差的不足,以TiO_2为载体负载活性组分V_2O_5,利用磷酸调控表面酸性,制备了磷酸氧钒催化剂VPO/TiO_2,并实验研究了SO_2和水蒸气对其脱硝活性的影响。结果表明:控制P与V的摩尔比为1/5,活性组分(VPO)负载量为10%,焙烧温度为400℃时,催化剂脱硝性能最好,180～400℃温度范围内脱硝率高于98%;反应温度为200℃,烟气中SO_2体积分数为200×10^(-6)～800×10^(-6)和水蒸气体积分数为4%时,催化剂的活性无明显下降。添加磷酸能够促使催化剂表面生成VOPO_4、(VO)_2P_2O_7及V^(4+)/V^(5+)氧化还原电对,提高了催化剂的低温脱硝活性。磷酸可增强催化剂的表面酸性,减少了SO_2的表面吸附及其与活性组分的反应。另外,催化剂表面以介孔为主,可提高未被水分子占据的活性位点量,FT-IR图谱显示抗硫抗水测试后的VPO/TiO_2表面未发现有硫酸根生成,VPO/TiO_2表现出较强的抗SO_2和水蒸气毒化的性能。负载型磷酸氧钒催化剂具有较高的脱硝活性和较强的抗硫抗水性能。

In view of poor resistance to sulfur and water vapor for the low temperature DeNOx catalyst, a type ofvanadium phosphate catalyst VPO/TiO2 was prepared through doping active constituent V2O5 on TiO2 andregulating the surface acidity with phosphoric acid in this study, and the effects of SO2 and water vapor on itsDeNOx activity were studied. The results showed that the best DeNOx performance of this vanadium phosphatecatalyst was obtained at P/V molar ratio of 1/5, 10% active component(VPO) loading and the calcinationtemperature of 400 ℃, and the corresponding DeNOx efficiency was above 98% at the temperature range of 180~400 ℃. The DeNOx efficiency didn’t decrease at reaction temperature of 200 ℃ when the volume fractions of SO2 and water vapor were 200 × 10-6~800 × 10-6 and 4%, respectively. The addition of phosphoric acid couldpromote the formation of VOPO4,(VO)2P2O7 and redox couples V4+/V5+, which led to the improvement on the lowtemperature DeNOx activity of the catalyst. Phosphoric acid addition could enhance the surface acidity ofvanadium-based catalyst, suppressed SO2 adsorption on the catalyst surface and their reaction to activeconstituent. In addition, the catalyst surface mainly contained mesoporous structure, which caused the increaseof the amount of active sites unoccupied by the water molecules. The FT-IR spectra show that sulfate was notproduced on the surface of tested VPO/TiO2 in the presence of SO2 and water vapor. The VPO/TiO2 catalystsshow a strong resistance to SO2 and water vapor. Accordingly, the supported vanadium phosphate catalyst in thisstudy had a high catalytic activity and strong sulfur and water resistance.