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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Detailed Determination of the Tl~+ Positions in Zeolite Tl-ZSM-5. Single-Crystal Structures of Fully Dehydrated Tl-ZSM-5 and H-ZSM-5 (MFI, Si/Al = 29). Additional Evidence for a Nonrandom Distribution of Framework Aluminum
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Detailed Determination of the Tl~+ Positions in Zeolite Tl-ZSM-5. Single-Crystal Structures of Fully Dehydrated Tl-ZSM-5 and H-ZSM-5 (MFI, Si/Al = 29). Additional Evidence for a Nonrandom Distribution of Framework Aluminum

机译：Tl-ZSM-5沸石中Tl〜+位置的详细测定。完全脱水的T1-ZSM-5和H-ZSM-5的单晶结构（MFI，Si / Al = 29）。框架铝的非随机分布的其他证据

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The structures of the fully exchanged, fully dehydrated zeolites Tl-ZSM-5 (a = 20.064(1), b = 19.946(1), c = 13.416(1) A) and H-ZSM-5 (a = 20.079(1), b = 19.948(1), c = 13.419(1) A) have been determined crystallographically using modestly twinned single crystals and synchrotron X-radiation. They were refined in the orthorhombic space group Pnma to R1 = 0.071 and 0.066 with 3962 and 4278 reflections, respectively, for which F_o > 4σ(F_o). The geometry of the zeolite framework in both crystals (MFI, Al_(3.2)Si_(92.8)O_(192), Si/Al = 29) is very similar to that in earlier determinations. The ZSM-5 framework and Tl~+ positions are described using the four nonequivalent partially overlapping 10-rings (R), the two channel systems (C), the channel intersection volume, and the cove of the ZC. The latter two comprise the conventionally defined cavity. The zigzag (sinusoidal) channel (ZC) passes through Rl, R3, and R4; the straight channel (SC) passes through R2. A total of 3.3(2) Tl~+ ions per unit cell were found scattered among 18 crystallographically distinct positions. Based on their positions near Rl, R2, and R3, these positions may be classified into three groups (Gn, n = 1-3), each with two general cation sites (Sn and Sn'). Of the 18 Tl~+ positions, six are in the intersection volume (at S2' in G2), 11 are elsewhere in the ZC (in G1 and G3), and one is elsewhere in the SC (at S2) just outside the intersection volume. Among the six general cation sites, S1' at the mouth of the cove has the highest Tl~+ population, 28% of the total. Of the 18 Tl~+ positions, 14 bond strongly to framework oxygen atoms with 2.68(4) < Tl-O < 2.87(5) A (Tl~+ + O~(2-) radii = 2.79 A); three other shortest distances range upward to 2.97(5) A; one at 3.18(10) A appears to be an unresolved position. The framework sites (T) that Al atoms preferentially occupy are identified from Tl~+ occupancies and Tl-O bond distances. Using Tl-O < 2.70 A, the order is T10 (most preferred) > T6. The preference of Al for the T10 site remains when longer, less reliable but more comprehensive, Tl-O bond length criteria are used. Using Tl-O < 2.80 A, the order is T10 > T6 ~ T9 > T5 > T4 > T2 > T12 > T7 > T11, and with Tl-O < 2.90 A, the preference order includes all 12 T sites: T10 > T3 > T2 > T12 > T6 ~ T9 > T5 > T4 > T8 > T7 > T11 > Tl. T10 is a member of R4, the 10-ring that is common to the intersection volume and the cove.
机译：完全交换，完全脱水的沸石T1-ZSM-5（a = 20.064（1），b = 19.946（1），c = 13.416（1）A）和H-ZSM-5（a = 20.079（1） ），b = 19.948（1），c = 13.419（1）A）已使用适度孪生的单晶和同步加速器X射线进行了晶体学测定。在正交空间群Pnma中将它们精炼为R1 = 0.071和0.066，分别反射3962和4278，其中F_o>4σ（F_o）。两种晶体（MFI，Al_（3.2）Si_（92.8）O_（192），Si / Al = 29）中沸石骨架的几何形状与早期测定中的非常相似。使用四个非等效的部分重叠的10环（R），两个通道系统（C），通道相交体积和ZC的凹口来描述ZSM-5框架和T1 +位置。后两个包括常规限定的腔。锯齿形（正弦）通道（ZC）穿过R1，R3和R4;直通道（SC）穿过R2。每个晶胞中共有3.3（2）个Tl〜+离子散布在18个晶体学上不同的位置之间。基于它们在R1，R2和R3附近的位置，可以将这些位置分为三组（Gn，n ＝ 1-3），每组具有两个一般的阳离子位点（Sn和Sn'）。在18个Tl〜+位置中，有六个位于交叉点体积中（在G2中的S2'），有11个位于ZC中的其他地方（在G1和G3中），而一个位于SC中其他地方（在S2中）就在交叉点之外卷。在六个一般阳离子位点中，海湾口处的S1'具有最高的Tl +种群，占总数的28％。在18个Tl〜+位置中，有14个与骨架氧原子牢固键合，其2.68（4） T6〜T9> T5> T4> T2> T12> T7> T11，并且在T1-O <2.90 A时，优先顺序包括所有12个T位点：T10> T3 > T2> T12> T6〜T9> T5> T4> T8> T7> T11> T1 T10是R4的成员，R4是相交体积和海湾共用的10环。

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