Thermal durability of Cu-CHA NHb>3b>-SCR catalysts for diesel NOb>xb> reduction

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• 作者：Steven J. Schmieg^a ; ^{steven.j.schmieg@gm.com} ; Se H. Oh^a ; ¹ ; ^{se.h.oh@gm.com} ; Chang H. Kim^a ; ² ; ^{chang.h.kim@gm.com} ; David B. Brown^b ; ³ ; ^{david.b.brown@gm.com} ; Jong H. Lee^c ; ⁴ ; ^{jong.lee@pnl.gov} ; Charles H.F. Peden^c ; ⁵ ; ^{chuck.peden@pnl.gov} ; Do Heui Kim^c ; ^d ; ^{dohkim@snu.ac.kr}
• 关键词：Selective catalytic reduction ; NH3-SCR ; Cu-chabazite ; Deactivation ; Laboratory aging ; Vehicle aging
• 刊名：Catalysis Today
• 出版年：2012
• 期刊代码：13_09205861
• 类别：ce
• 出版时间：30 April, 2012
• 卷：184
• 期：1
• 页码：252-261
• 文件大小：2709 K

摘要

Multiple catalytic functions (NOb>xb> conversion, NO and NHb>3b> oxidation, NHb>3b> storage) of a commercial Cu-chabazite (CHA) urea/NHb>3b>-SCR catalyst were assessed in a laboratory fixed-bed flow reactor system after differing degrees of hydrothermal aging. Catalysts were characterized by using X-ray diffraction (XRD), ²⁷Al solid state nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM)/energy dispersive X-ray (EDX) spectroscopy to develop an understanding of degradation mechanisms during catalyst aging. The catalytic reaction measurements of laboratory-aged catalysts were performed, which allows us to obtain a universal curve for predicting the degree of catalyst performance deterioration as a function of time at each aging temperature. Results show that as the aging temperature becomes higher, the zeolite structure collapses in a shorter period of time after an induction period. The decrease in SCR performance was explained by zeolite structure destruction and/or Cu agglomeration, as detected by XRD/²⁷Al NMR and by TEM/EDX, respectively. Destruction of the zeolite structure and agglomeration of the active phase also results in a decrease in NO/NHb>3b> oxidation activity and NHb>3b> storage capacity of the catalyst. Laboratory aging conditions (16 h at 800 掳C) compare well with a 135,000 mile vehicle-aged catalyst, except for the chemically poisoned inlet section of the vehicle-aged catalyst.