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

9^th World Congress on Green Chemistry and Technology

September 17-19, 2018 | Amsterdam, Netherlands

Chen Wang and Xue Kang

North University of China, China

Posters & Accepted Abstracts: J Environ Anal Chem

Abstract :

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° and 600°. 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. 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.

Biography :

E-mail: chenwang87@nuc.edu.cn