NH_3-SCR反应中Fe-ZSM-5的Fe物种分布和酸性位对其水热稳定性及抗硫和抗碳氢性能的影响(英文)

The effect of Fe species distribution and acidity of Fe-ZSM-5 on the hydrothermal stability and SO_2 and hydrocarbons durability in NH_3-SCR reaction

以Na+型和H+型ZSM-5为载体制备了Fe-ZSM-5催化剂并用于氨选择性催化还原(NH3-SCR)氮氧化物.Fe-H-ZSM-5在新鲜时和750 oC含10%水的空气中老化后,其SCR活性均优于Fe-Na-ZSM-5.表征结果显示,Fe-H-ZSM-5和Fe-Na-ZSM-5的Fe物种分布和酸性位有所不同.高温水热老化后Fe-H-ZSM-5分子筛骨架的脱铝较Fe-Na-ZSM-5严重.水和硫的存在对Fe-H-ZSM-5和Fe-Na-ZSM-5的SCR活性的影响相似,即降低了低温活性,略提高了高温活性.Fe-Na-ZSM-5表现出比Fe-H-ZSM-5更好的抗碳氢中毒性能.这两种催化剂的SO2和碳氢中毒是可逆的.

Fe-exchanged ZSM-5 catalysts prepared from Na＋ and H＋ forms of ZSM-5 were evaluated for the selective catalytic reduction of NOx by NH3（NH3-SCR）. Fe-H-ZSM-5 showed higher SCR activity than Fe-Na-ZSM-5 both when fresh and after hydrothermal aging at 750 ℃ in 5% H2O/air. The Fe species distribution and acidity of Fe-H-ZSM-5 and Fe-Na-ZSM-5 were found to be different. The dealumina-tion of the zeolite framework of Fe-H-ZSM-5 during hydrothermal aging was found to be more se-vere compared with that of Fe-Na-ZSM-5. The durability of Fe-H-ZSM-5 and Fe-Na-ZSM-5 in NH3-SCR was compared using SO2 tolerance and hydrocarbon resistance experiments. The effect of water and SO2 on the activity of the two catalysts was similar, such that their activity decreased at low temperatures and increased at high temperatures. Fe-Na-ZSM-5 showed better propene re-sistance than Fe-H-ZSM-5. The SO2 and propene poisoning of the two Fe-ZSM-5 catalysts were found to be reversible.