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Chen Wang

Chen Wang

North University of China, China

Title: The reliability study on the Cu/CHA NH3-SCR Catalysts: SO3 and Na ions poisoning

Biography

Biography: Chen Wang

Abstract

Part 1:

The deactivation mechanism of Cu/CHA ammonia selective catalytic reduction catalysts by SO3 poisoning has been systematically investigated using a range of analytical techniques. In order to study the influence of SO3 poisoning on active Cu2+ ions and the zeolite framework, different sulfate samples were prepared with different contents of SO3 (0 ~ 20%) in SOx under same poisoning condition. The results reveal the NO conversion of samples poisoned by SO3 decreased more than that poisoned by SO2 when temperature ranged between 100 oC and 600 oC. The TPR and EPR results demonstrate that SO3 poisoning does a significant influence on the amount of active Cu2+ ions than SO2 does. The kinetic results illustrate the SO3 poisoning has no impact on the apparent activation energy (Ea) of NH3-SCR reaction over Cu/CHA catalysts. The reason of NH3-SCR activity declining is the reduction of the number of isolated Cu2+ ions among the kinetic temperature regions. The ex-situ DRIFTs and BET results expose that the SO3 poisoning could decrease the crystallization by damaging Si-OH-Al structure. The NH3-SCR activity at high temperature decline because of the NH3 migration difficulty resulted by structure damaging.

Part 2:

Cu/CHA catalysts have been found to be affected by alkali and alkali earth ions; however, the poisoning mechanism is still unclear. In order to investigate Na poisoning effects and its mechanism on Cu/SAPO-34 and Cu/SSZ-13, five samples with different Na contents were synthesized. The Na effects on the structure, Cu species, and NH3-SCR reaction over Cu/CHA were characterized through XRD, BET, NH3-TPD, ex-DRIFTS, H2-TPR, EPR, activity tests and kinetic experiments, and CO2-DRIFTS were used to probe the types of Na species. The results indicate that the introduced Na+ exchanged with H+ and Cu2+, and it mainly substituted H+ from Si-OH-Al, then H+ from surface OH, finally isolated Cu2+. The exchanged H+ led to the structure damaging of Cu/CHA by dealumination, and the exchanged Cu2+ aggregated and formed CuOx species. The NH3-SCR activity decreased with Na contents, and the loss of isolated Cu2+ and CHA structure was responsible for the performance deactivation.