Martucci Annalisa, Alberti Alberto, Cruciani Giuseppe, Frache Alberto, Marchese Leonardo, Pastore Heloise O
Dipartimento di Scienze della Terra, Sezione di Mineralogia, Petrografia e Geofisica, Via Saragat 132, I-44100 Ferrara, Italy.
J Phys Chem B. 2005 Jul 21;109(28):13483-92. doi: 10.1021/jp050777k.
Thermally induced processes of CoAPO-34, an aluminophosphate molecular sieve with chabasite-type structure, synthesized in the presence of morpholine as a structure-directing agent and HF as a mineralizing agent, have been studied by in situ X-ray synchrotron powder diffraction augmented with Fourier transform (FT) IR analysis. A time-resolved experiment was performed using a translating imaging plate system. At room temperature, the structure refinement by full-profile Rietveld analysis showed P-1 symmetry and the presence of one Al site with sixfold coordination. At around 400 degrees C, both fluorine and morpholine are lost, and the four-connected chabazite (CHA)-type topology is restored. Notwithstanding the metrically rhombohedral values of the cell parameters, the symmetry remains triclinic P-1. Inhomogeneous dealumination of the framework begins at 725 degrees C, accompanied by a strong triclinization of the unit cell and followed by the collapse of the structure above 775 degrees C. The insertion of cobalt ions within the CHA framework was monitored by FTIR spectroscopy, which showed that bridged Co(2+)-O(H)-P hydroxyls are present after morpholine removal.
以吗啉为结构导向剂、HF为矿化剂合成的具有菱沸石型结构的磷酸铝分子筛CoAPO-34的热诱导过程，已通过结合傅里叶变换（FT）红外分析的原位X射线同步辐射粉末衍射进行了研究。使用平移成像板系统进行了时间分辨实验。在室温下，通过全谱Rietveld分析进行的结构精修显示出P-1对称性以及存在一个具有六重配位的铝位点。在约400℃时，氟和吗啉均损失，并且恢复了四连接的菱沸石（CHA）型拓扑结构。尽管晶胞参数在度量上为菱面体值，但对称性仍为三斜P-1。骨架的不均匀脱铝在725℃开始，伴随着晶胞的强烈三斜化，随后在775℃以上结构坍塌。通过FTIR光谱监测了钴离子在CHA骨架中的插入，结果表明在吗啉去除后存在桥连的Co(2+)-O(H)-P羟基。
