Time resolved in situ X-ray diffraction study of crystallisation processes of large pore nanoporous aluminophosphate materials

Abstract

Time resolved high-resolution X-ray powder diffraction was utilized to obtain detailed changes in the crystal structure parameters during the hydrothermal crystallization process of the nanoporous aluminophosphate AlPO-5 (AFI) structure. This in situ study offered not only the influence of metal ions on the onset of crystallization and estimation of the activation energy of the process, but also allowed us to determine in detail the changes in lattice parameters during this process. More importantly the time-resolved study clearly showed the lattice expansion in the divalent metal ions substituted system right from the on-set of crystallization process, compared to the one without any dopant ions, which suggest that an amorphous or poorly crystalline network is formed prior to crystallization that contains the large divalent ions (compared to Al(iii), the substituting element), which is in agreement with the combined XAS/XRD study reported earlier. A mechanism based on this and the earlier study is suggested.

Metal-Substituted Microporous Aluminophosphates

“…Some of the reasons are that they may not be ordered and also that in the majority of the cases, the concentration of the metal ions is too small to show any effect. However, Simmance et al [99,100] indeed show that there are specific lattice expansions in certain directions, in cobalt and zinc substituted aluminophosphates. Despite this observation, it is difficult to determine the local structure of the substituted metal ions unless a more specific local structural tool is used, specifically adaptable to systems with low concentrations of heteroatoms.…”

Molecular Orientation of Intercalants Stabilized in the Interlayer Space of Layered Ceramics: 1-D Electron Density Simulation

“…Recently, a time-resolved in situ energy dispersive X-ray diffraction (EDXRD) experiment was developed using a synchrotron X-ray device. 26,[74][75][76] This is a very useful tool for investigating the intercalation mechanism and its kinetics, since the intercalation reactions can be simultaneously traced as soon as the guest species is added to the host suspension. From this time-resolved in situ EDXRD, Taviot-Gueho et al clarified the second-stage phenomena (the interstratified structure) during the intercalation of tartrate into Zn 2 Cr-Cl LDH.…”

Systematic study of the crystallization process of CrAPO-5 using in situ high resolution X-ray diffraction

“…7 -substituted aluminophosphates. 41 Compared to un-substituted AlPO 4 -5, 13.716 A, the greater a (¼b) parameters indicated that the metal ions was part of the framework, which could result in the lattice expansion. Furthermore, the lattice expansion was limited, which might relate to the amount of Cr 3+ interacted with the framework was limited.…”

“…The increase in c parameter during the crystallization process could be ascribed to the uptake of water molecular and the template orientation, as explained by Sankar. 41 The increase in the c parameter, over the crystallization time, was due to the uptake of water molecules which may coordinate to Al 3+ ions accessible in the channel direction, 59 ) should therefore show a larger increase in the c parameter compared to MeAPO-5. On the other hand the template orientation within the structure could also play a role in this change in c parameter and cell volume.…”

“…The in situ methods had been widely used on Co, Zn and Mn substituted aluminophosphate molecular sieves. 5,[32][33][34][36][37][38][39][40][41] However, there is no report so far on the in situ study of the crystallization process of CrAPO-5. We present here an in situ study of the hydrothermal crystallization of CrAPO-5 starting from the precursor gel prepared with the classical method to the crystalline material using the high resolution synchrotron powder X-ray diffraction (HRXRD).…”