Pr/Zr原子比对Pr_(x)Zr_(1−x)O_(2−δ)催化氧化脱硝活性的影响

Effect of Pr/Zr atomic ratio on the activity of catalytic oxidation denitration of Pr_(x)Zr_(1−x)O_(2−δ)

采用溶胶-凝胶法制备了不同Pr/Zr原子比的Pr_(x)Zr_(1−x)O_(2−δ)催化剂用于催化氧化脱硝。结果表明,催化氧化脱硝效率随Pr原子比的增加而先提高后降低;当Pr/Zr原子比为5∶5时,在250°C下,最佳脱硝活性可达94.62%。采用SEM、N_(2)吸附-脱附、XRD、XPS、H_(2)-TPR和FT-IR对催化剂进行了表征。结果表明,活性最好的催化剂(Pr_(0.5)Zr_(0.5)O_(2−δ))具有“层状”形貌,表面孔隙多,比表面积大,孔体积分别为77.74 m^(2)/g和0.66 cm^(3)/g。此外,随着Pr原子的增加,晶相从c-ZrO_(2)转变为Pr_(2)Zr_(2)O_(7)。XPS和H_(2)-TPR结果表明,表面化学吸附氧和表面Pr^(4+)氧化物增加,Pr原子比的上升有利于产生氧空位(Vӧ),有利于提高催化氧化脱硝效率。FT-IR表征结果表明,Pr_(0.5)Zr_(0.5)O_(2−δ)固溶体具有较高的NO选择性,有利于NO的催化氧化。抗SO_(2)和H_(2)O毒性实验表明,5∶5的Pr/Zr原子比的催化剂具有更好的抗毒性。此外,利用IC分析吸收产物,结果表明,吸收液中的主要产物是NO_(2)^(-)和NO_(3)^(-)。

The Pr_(x)Zr_(1−x)O_(2)-δcatalyst with different atom ratio of Pr/Zr was prepared by the sol-gel to catalytic oxidation denitration.Results showed that the efficiency of catalytic oxidation denitration increased initially and decreased afterward with the ratio of Pr atom increased.And the optimum denitration activity could achieve 94.62%at 250°C when the atom ratio of Pr/Zr was 5∶5.The catalysts were characterized by SEM,N_(2)adsorption-desorption,XRD,XPS,H_(2)-TPR,and FT-IR.The results illustrated that the catalyst(Pr_(0.5)Zr_(0.5)O_(2−δ))with the best activity has a“layered”morphology,many pores on the surface,and it has a large specific surface area and pore volume of 77.74 m^(2)/g and 0.66 cm^(3)/g,respectively.Furthermore,the crystalline phase transforms from c-ZrO_(2)to Pr_(2)Zr_(2)O_(7)with the increasing of Pr atom.XPS and H_(2)-TPR results showed that the surface chemosorption oxygen and surface Pr^(4+)oxides increased,and the rising of Pr atom ratio was beneficial to produce oxygen vacancy(Vӧ)site which advantageous to improve the efficiency of catalytic oxidation denitration.FT-IR characterization results indicated that Pr_(0.5)Zr_(0.5)O_(2−δ)solid solution had better NO selectivity,which was conducive to the catalytic oxidation of NO.The anti-SO_(2)and H_(2)O toxicity experiments showed that Pr/Zr atomic ratio at 5∶5 had better anti-toxicity than other ratios.In addition,using IC to analysis absorption products,the result showed that no2-and NO_(2)^(-)were the main products in the absorption solution.