摘要
锰钾矿八面体分子筛(OMS-2)材料是一种孔径为4.6?×4.6?的一维隧道结构锰氧化物,锰离子以混合价态(Mn~(2+),Mn~(3+),Mn~(4+))存在于OMS-2的骨架结构中,钾离子位于OMS-2结构的一维隧道中,起到中和多余负电荷的作用,除此之外,孔道中还有少量的水分子来维持结构稳定[1-4]。臭氧分解主要是氧化还原反应,因此多种价态锰的存在有利于臭氧的催化分解。本文分别以乙酸锰、硝酸锰和氯化锰为Mn~(2+)的前驱体,考察了不同前驱体制备的催化剂在高湿度条件下对臭氧的催化活性,并讨论活性与催化剂结构性质之间的关系。采用乙酸锰为前驱体合成的OMS-2-Ac催化剂在相对湿度为90%,空速为600000 h-1的条件下,表现出比较优越的臭氧催化活性,转化率为80%左右,性能优于以硝酸锰的OMS-2-NO_3和以氯化锰合成的OMS-2-Cl催化剂。合成过程中乙酸根的存在能够阻止锰氧化物之间的富集,提供更多的表面缺陷位。各种物理化学表征发现大的表面积、更高含量的Mn~(3+)是促进臭氧催化分解的关键影响因素。该研究结果能够提高我们对臭氧催化分解的理解,并且可以指导高活性臭氧催化分解催化剂的合成。
The effects of Mn~(2+) precursors on the structure and ozone decomposition activity of cryptomelane-type manganese oxide(OMS-2) catalysts were investigated under high-humidity conditions.The OMS-2-Ac synthesized using Mn Ac2 as a Mn~(2+) precursor showed the best catalytic activity for ozone decomposition(80%) under RH = 90% and space velocity of 600000 h-1 and is a promising catalyst for purifying waste gases containing ozone under high-humidity conditions.Acetate groups could prevent the aggregation of manganese oxide particles,which may introduce more crystalline defects.On the basis of the characterization results,it is supposed that the greater surface area and higher amount of Mn~(3+) are the main factors that contribute to the excellent performance of OMS-2-Ac.This study can improve our understanding of ozone decomposition on OMS-2 catalysts and serve as a guide in using OMS-2 for ozone removal.
引文
[1]Wang,R.H.;Li,J.H.Environ.Sci.Technol.2010,44:4282.
[2]Huang,H.;Meng,Y.;Labonte,A.;Dobley,A.;Suib,S.L.J.Phys.Chem.C 2013,117:25352.
[3]Hou,J.T.;Liu,L.L.;Li,Y.Z.;Mao,M.Y.;Lv,H.Q.;Zhao,X.J.Environ.Sci.Technol.2013,47:13730.
[4]Genuino,H.C.;Dharmarathna,S.;Njagi,E.C.;Mei,M.C.;Suib,S.L.J.Phys.Chem.C 2012,116:12066.