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Density Functional Calculations on the Distribution, Acidity, and Catalysis of Ti-IV and Ti-III Ions in MCM-22 Zeolite
Yang, Gang1,2; Zhou, Lijun2; Liu, Xianchun1; Han, Xiuwen1; Bao, Xinhe1
关键词C-h Activation Density Functional Calculations Lewis Acidity Titanium Zeolites
刊名CHEMISTRY-A EUROPEAN JOURNAL
2011
DOI10.1002/chem.201002241
17期:5页:1614-1621
收录类别SCI
文章类型Article
WOS标题词Science & Technology ; Physical Sciences
类目[WOS]Chemistry, Multidisciplinary
研究领域[WOS]Chemistry
关键词[WOS]DIRECT BENZENE HYDROXYLATION ; NITROUS-OXIDE DECOMPOSITION ; TITANIUM SILICALITE ; ACTIVE-SITES ; HYDROGEN-PEROXIDE ; MOLECULAR-SIEVES ; SELECTIVE-OXIDATION ; REACTION-MECHANISMS ; TS-1 ZEOLITES ; TITANOSILICATE
英文摘要Isolated Ti species in zeolites show unique catalytic activities for a variety of chemical reactions. In this work, density functional calculations were used to explore three current concerns: 1) the distributions of Ti-IV and Ti-III ions in the MCM-22 zeolite; 2) the Lewis acidity of the Tilv and Ti-III sites; and 3) activation of alkane C-H bonds by photocatalysis with Ti-doped zeolites. Neither the Ti-IV nor Ti-III ions are randomly distributed in the MCM-22 zeolite. The orders of relative stability are very close for the eight Ti-IV and Ti-III sites, and the T3 site is the most probable in both cases. The wavelengths for Ti-IV-Ti-III excitations were calculated to lie in the range lambda=246.9-290.2 nm. The Ti3(IV) site shows Lewis acidity toward NH3 in two different modes, and these two modes can coexist with each other. The calculated Tilv coordination numbers, Ti-IV-O bond elongations, and charge transfers caused by NH3 adsorption are in good agreement with previous results. Similarly, two different NH3 adsorption modes exist for the Ti3(III) site; the site that exhibits radical transfer from the lattice O to N atoms is preferred due to the higher adsorption energy. This indicates that the Ti3(III) site does not show Lewis acidity, in contrast to the Ti3(IV) site. At the Ti3(III) site, the energy barrier for activating the methane C-H bond was calculated to be 33.3 kJ mol(-1) and is greatly reduced by replacing the hydrogen atoms with methyl groups. In addition, the reactivity is improved when switching from MCM-22 to TS-1 zeolite. The studies on the various Ti species reveal that lattice O atoms rather than Ti-III radicals are crucial to the activation of alkane C-H bonds. This work provides new insights into and aids understanding of the catalysis by isolated Ti species in zeolites.
语种英语
WOS记录号WOS:000287555600027
引用统计
被引频次:20[WOS]   [WOS记录]     [WOS相关记录]
文献类型期刊论文
条目标识符http://cas-ir.dicp.ac.cn/handle/321008/142622
专题中国科学院大连化学物理研究所
作者单位1.Chinese Acad Sci, State Key Lab Catalysis, Dalian Inst Chem Phys, Dalian 116023, Peoples R China
2.NE Forestry Univ, Key Lab Forest Plant Ecol, Minist Educ, Harbin 150040, Peoples R China
推荐引用方式
GB/T 7714
Yang, Gang,Zhou, Lijun,Liu, Xianchun,et al. Density Functional Calculations on the Distribution, Acidity, and Catalysis of Ti-IV and Ti-III Ions in MCM-22 Zeolite[J]. CHEMISTRY-A EUROPEAN JOURNAL,2011,17(5):1614-1621.
APA Yang, Gang,Zhou, Lijun,Liu, Xianchun,Han, Xiuwen,&Bao, Xinhe.(2011).Density Functional Calculations on the Distribution, Acidity, and Catalysis of Ti-IV and Ti-III Ions in MCM-22 Zeolite.CHEMISTRY-A EUROPEAN JOURNAL,17(5),1614-1621.
MLA Yang, Gang,et al."Density Functional Calculations on the Distribution, Acidity, and Catalysis of Ti-IV and Ti-III Ions in MCM-22 Zeolite".CHEMISTRY-A EUROPEAN JOURNAL 17.5(2011):1614-1621.
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