CuO改性商用选择性催化还原催化剂催化氧化单质汞性能

Catalytic oxidation of elemental mercury over CuO modified commercial SCR catalyst

燃煤烟气中单质汞(Hg^0)的高效氧化是提高燃煤电厂脱汞效率的关键,为提高传统选择性催化还原(SCR)催化剂氧化Hg^0的性能,本文采用溶液浸渍法制备了CuO-SCR催化剂,在固定床反应装置上考察了其脱硝协同氧化单质汞性能,并借助BET、XRD和XPS等分析技术对催化剂进行表征。结果表明,CuO的掺杂显著提高了商用SCR催化剂的Hg^0氧化性能和低温脱硝活性;在200~400℃内,随着反应温度升高和NO+NH_3浓度增大,NH_3对CuO-SCR催化剂的Hg^0氧化性能抑制作用加强;在350℃、模拟燃煤烟气条件下,随着空速比的减小,催化剂的Hg^0氧化性能显著提高,NH3对Hg^0氧化的抑制作用明显减弱。催化剂表征结果表明,CuO-SCR催化剂表面存在氧化还原反应V4++Cu2+V5++Cu+,增强了催化剂的催化活性。Hg^0在CuO-SCR催化剂表面的氧化过程遵循Mars-Maessen机制,能够有效增强催化剂的Hg^0氧化性能。

Efficient oxidation of elemental mercury(Hg0)in coal-fired flue gas is the key technology to control the mercury emission in coal-fired power plants.To improve the Hg0 oxidation activity of the traditional SCR catalyst,the CuO-SCR catalysts were prepared by an improved impregnation method and then were used for simultaneous NO removal and Hg0 oxidation to evaluate the catalytic performance.BET,XRD and XPS were used to characterize the catalysts.The results showed that the Hg0 oxidation activity and low-temperature NO removal activity of the commercial SCR catalyst were significantly improved by the addition of CuO.The presence of NO and NH3 could inhibit the Hg0 oxidation activity over CuO-SCR catalyst at 200-400℃,and the effect was enhanced with increased temperature and NH3 content.At 350°C,the Hg0 oxidation activity over CuO-SCR catalyst was remarkably enhanced with the decrease of GHSV under simulated coal-fired flue gas,and the inhibiting effect of NH3 was also diminished.The characterization results suggested that there could be a redox cycle of V4++Cu2+V5++Cu+in the CuO-SCR catalyst which enhanced the catalytic activity.Moreover,the Hg0 oxidation on the CuO-SCR catalyst agreed with the Mars-Maessen mechanism.