title: Propene poisoning on three typical Fe-zeolites for SCR of NOχ with NH₃: from mechanism study to coating modified architecture.
abstract: Application of Fe-zeolites for urea-SCR of NO(x) in diesel engine is limited by catalyst deactivation with hydrocarbons (HCs). In this work, a series of Fe-zeolite catalysts (Fe-MOR, Fe-ZSM-5, and Fe-BEA) was prepared by ion exchange method, and their catalytic activity with or without propene for selective catalytic reduction of NO(x) with ammonia (NH(3)-SCR) was investigated. Results showed that these Fe-zeolites were relatively active without propene in the test temperature range (150-550 °C); however, all of the catalytic activity was suppressed in the presence of propene. Fe-MOR kept relatively higher activity with almost 80% NO(x) conversion even after propene coking at 350 °C, and 38% for Fe-BEA and 24% for Fe-ZSM-5 at 350 °C, respectively. It was found that the pore structures of Fe-zeolite catalysts were one of the main factors for coke formation. As compared to ZSM-5 and HBEA, MOR zeolite has a one-dimensional structure for propene diffusion, relatively lower acidity, and is not susceptible to deactivation. Nitrogenated organic compounds (e.g., isocyanate) were observed on the Fe-zeolite catalyst surface. The site blockage was mainly on Fe(3+) sites, on which NO was activated and oxidized. Furthermore, a novel fully formulated Fe-BEA monolith catalyst coating modified with MOR was designed and tested, the deactivation due to propene poisoning was clearly reduced, and the NO(x) conversion reached 90% after 700 ppm C(3)H(6) exposure at 500 °C.
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Ma
authors.forename: Junhua
authors.initials: J
authors.lastname: Li
authors.forename: Yisun
authors.initials: Y
authors.lastname: Cheng
authors.forename: Christine K
authors.initials: CK
authors.lastname: Lambert
authors.forename: Lixin
authors.initials: L
authors.lastname: Fu
mesh_terms: D000397:Air Pollution / Q000517:prevention & control*; D000475:Alkenes / Q000737:chemistry*; D000641:Ammonia / Q000737:chemistry; D002384:Catalysis; D007474:Ion Exchange; D007501:Iron / Q000737:chemistry*; D009589:Nitrogen Oxides / Q000737:chemistry*; D010084:Oxidation-Reduction; D013696:Temperature; D001335:Vehicle Emissions / Q000032:analysis / Q000517:prevention & control*; D017641:Zeolites / Q000737:chemistry*
chemical_list: D000475:Alkenes; D009589:Nitrogen Oxides; D001335:Vehicle Emissions; D017641:Zeolites; D000641:Ammonia; C013658:propylene; D007501:Iron