碱金属对铈钨复合氧化物SCR脱硝催化剂性能影响

The Effect of Alkali Metals on the Performance of Cerium Tungsten Composite Oxide SCR Denitrification Catalyst

选择性催化还原(SCR)法是目前公认的脱硝效率最高、最为成熟的脱硝技术,其中催化剂是该技术的核心所在。铈钨复合氧化物是一种非钒SCR催化剂,为了使得该催化剂能够长期保持高效且稳定的脱硝活性,对其中毒机理进行深入研究,具有非常重要的意义。采用共沉淀法制备了CeWO_(x)复合氧化物脱硝催化剂,考察了碱金属种类(Na_(2)O和K_(2)O)对催化活性的影响,利用N_(2)-BET、XR D、NH_(3)-TPD和H_(2)-TPR对催化剂中毒原因进行了分析。活性评价结果表明:碱金属毒化后催化剂脱硝活性受到明显抑制,K_(2)O引起的失活程度要远大于Na_(2)O,在150~400℃的反应温度范围内,质量分数1%K_(2)O中毒的CeWO_(x)相比新鲜催化剂NO_(x)转化率下降了52%~84%。N_(2)-BET结果表明:碱金属沉积会导致催化剂的比表面积降低;XRD结果表明:碱金属的引入导致催化剂上CeO_(2)的晶粒尺寸增大;NH_(3)-TPD和H_(2)-TPR结果表明:碱金属的表面掺杂会导致催化剂的表面酸性和氧化还原性能会受到明显抑制。

Selective catalytic reduction(SCR)is currently recognized as the most efficient and mature denitrification technology,with the catalyst being the core of this technology.Cerium tungsten composite oxide is a non vanadium SCR catalyst.In order to maintain its efficient and stable denitrification activity for a long time,it is of great significance to conduct in-depth research on its poisoning mechanism.CeWO_(x) composite oxide denitrification catalyst was prepared by co precipitation method,and the influence of alkali metal species(Na_(2)O and K_(2)O)on catalytic activity was investigated.The reasons for catalyst poisoning were analyzed using N2-BET,XRD,NH_(3)-TPD,and H_(2)-TPR.The activity evaluation results showed that the denitrification activity of the catalyst was significantly inhibited after alkali metal poisoning,and the degree of deactivation caused by K_(2)O was much greater than that caused by Na_(2)O.Within the reaction temperature range of 150~400℃,the NO_(x) conversion rate of CeWO_(x) poisoned by 1%K_(2)O decreased by 52%~84%compared to fresh catalyst.The N2-BET results indicate that alkali metal deposition leads to a decrease in the specific surface area of the catalyst.The XRD results indicate that the introduction of alkali metals leads to an increase in the grain size of CeO_(2) on the catalyst.The NH_(3)-TPD and H_(2)-TPR results indicate that surface doping of alkali metals can significantly suppress the surface acidity and redox performance of the catalyst.