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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Electron Paramagnetic Resonance Spectroscopy of Chromium i CrAPO-5 Molecular Sieves
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Electron Paramagnetic Resonance Spectroscopy of Chromium i CrAPO-5 Molecular Sieves

机译：铬i CrAPO-5分子筛的电子顺磁共振波谱

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A new synthesis strategy with the use of a co-template allowed for the framework substitution of chromium and the preparation of CrAPO-5 with high sorption capacities for nitrogen and benzene (HS samples). FN~materials as well as for those synthesized with classical methods and exhibiting low sorption capacities ~. X-band electron paramagnetic resonance (EPR) spectra were measured at room and liquid wawres. The spectra of the as-synthesized HS and LS samples consist of a broad intense hiwAJI~ 500 G) with a positive lobe at g~~ff — 5.15 + 0.01. assigned to the Cr~ (3d3.(~h~mbicl distorted octahedral coordination. The calcined samples show an additional~uy with g = 1.971 ± 0.001 and g~ 1.959 ± 0.001 that is assigned to the C ~l ~ordinanon as v~ell. The HS samples heated under a vacuum exhibit a decrease in irne tyc*~C~Isas well as several new s±nals. Two of these signals are characterized by an axially symincuic g I~mc~ mad ~u.g to the Cr5~ centers in square pyramidal and tetrahedral coordinations. The third signal may he assigned to the Cr’ 3d~. ~Ss.c, ions. The spectra of the LS samples heated under a vacuum show a strong decrease in intensity of the Cr~ lines and only the two signals of the CrSt centers in the same coordinations. Their g factors are similar to those in the HS samples. The thermal treatments under oxidative (02) and reductive (H2) atmospheres reveal reproducible redox properties of the Cr5t ions and a high stability of the Cr3t ones, especially in the HS samples. The EPR results gi~e strong support for the framework incorporation of the Cr3t ions in the HS materials.
机译：使用共模板的新合成策略可用于铬的构架取代和对氮和苯具有高吸附能力的CrAPO-5的制备（HS样品）。 FN〜材料以及那些用经典方法合成的材料都具有较低的吸附能力。 X波段电子顺磁共振（EPR）光谱是在室温和液态时测量的。合成后的HS和LS样品的光谱由宽的强烈hiwAJI（500 G）和正的波瓣在g〜ff_ 5.15 + 0.01组成。分配给Cr〜（3d3。（〜h〜mbicl扭曲了八面体配位。煅烧后的样品显示出一个附加的uy，g = 1.971±0.001和g〜1.959±0.001）被分配给C〜l〜ordinanon作为v〜真空加热的HS样品的irn tyc *〜C_Is降低，并且出现几个新的信号，其中两个信号的特征是对Cr5〜的轴向共轭I〜mc_mad。第三个信号可能是Cr'3d〜。〜Ss.c，离子，在真空下加热的LS样品的光谱显示Cr〜线和只有CrSt的两个信号在相同的配位中心，它们的g因子与HS样品中的g因子相似在氧化（02）和还原（H2）气氛下进行的热处理显示Cr5t离子具有可重现的氧化还原特性，并且高Cr3t的稳定性，特别是在HS样品中。EPR结果为f在HS材料中进行Cr3t离子的网状掺入。

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