過渡金屬離子交換型沸石之酸性與氧化還原性探討

Acidity and Redox Properties of Transition Metal Cation-Exchanged Zeolites

吳榮宗(Jung-Chung Wu) ； 施呈杰(Cheng-Jec Shih) ； 李秋萍(Chiu-Ping Li)

《化學》 54卷1期 (1996/03) Pp. 44-54

https://doi.org/10.6623/chem.1996007

摘要

本研究係探討沸石經離子交換反應後，沸石之酸性及金屬離子之氧化還原性之變化情形，此兩種特性在選擇性催化脫硝(SCR DeNOx)反應上扮演重要之角色。其中金屬離子包括鐵、鈷及銅等，而沸石包括Y, Mordenite, ZSM-5, Beta, L及Ferrierite等，改變離子交換程度及沸石之Si/Al比值，利用pyridine-FT-IR測定路易士酸及布侖斯特酸，NH_3-TPD測定酸量及酸強度變化，CO/O_2 redox cycle測定金屬離子氧化還原特性。實驗結果顯示，Cu(II)於加熱活化石還原成Cu(I)並可強吸附CO分子，Fe(III)則容易被CO還原成Fe(II)或Fe金屬原子，同時升成類似iron carbide物質。文中將探討不同沸石、不同Si/Al比值及不同離子交換程度對金屬離子之氧化還原性及沸石酸性之影響。

關鍵字

沸石 ； 選擇性催化脫硝 ； 氮氧化物 ； 路易士酸 ； 布侖斯特酸 ； 氧化還原

並列摘要

A series of transition metal cation-exchanged zeolites were prepared and characterized . Acidity of the ion-exchanged zeolites was measured by pyridine FT-IR and NH_3-TPD methods. Redox properties were invesFigated by CO/O_2 redox cycle. Cations of Fe, Co, and Cu, and zeolites of Y. Mordcnitc, ZSM-5. Beta. L and ferricrite with various Si/AI ratios were used. The results showed that Cu(ll) ion could be reduced to Cu (I) by calcination. CO was found to be strongly adsorbed on Cu(I) ion and reoxidized to CO_2 by O_2 rapidly. The result s did not show any auto-reduction for Fe(III) ion . However. Fe(III) ion was found to be reduced to Fe(ll) or Fe metal by CO rapidly. We also found the formation of iron carbide species during the treatment with CO stream. The effects of zeolite. Si/AI ratio and exchange level on the acidity and redox properties of cation-exchanged zeolites will be discussed.

並列關鍵字

Zeolite(Y. Mordenite, ZSM-5, Beta. L, Ferrierite) ； Selective catalytic reduction(SCR) DeNOx ； NOx ； Lewis acid ； Bronsted acid ； Redox