Abstract
AbstractWe have studied the structural behavior of SAPO-37 during calcination using simultaneous in situ powder X-ray diffraction (PXRD) and mass spectroscopy (MS) in addition to ex situ thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). A spike in the unit cell volume corresponding to template removal (tracked using the occupancy of the crystallographic sites in the SAPO-37 cages) is revealed from the XRD data and is strongly correlated with the DSC curve. The occupancy of the different template molecules in the faujasite (FAU) and sodalite (SOD) cages is strongly related to the two mass loss steps observed in the TGA data. The templates act as a physical stabilizing agent, not allowing any substantial unit cell response to temperature changes until they are removed. The FAU cages and SOD cages have different thermal response to the combustion of each template. The FAU cages are mainly responsible for the unit cell volume expansion observed after the template combustion. This e...
Highlights
Due to their acidic and shape-selective properties, zeolites have found widespread applications in catalytic, ion-exchange and separation processes in several industries [1]
In situ synchrotron radiation powder XRD (SR-PXD) during calcination of SAPO-37 reveals a spike in unit cell volume at the temperature at which the oxidative thermal decomposition of template takes place (Figure 2, top)
We have found evidence from several techniques that the two template types used to form the two different cages of SAPO-37 exhibit significantly different thermal behavior, and that their removal seems to be to some extent interdependent
Summary
Due to their acidic and shape-selective properties, zeolites have found widespread applications in catalytic, ion-exchange and separation processes in several industries [1]. In situ SR-PXD during calcination of SAPO-37 reveals a spike in unit cell volume at the temperature at which the oxidative thermal decomposition of template takes place (Figure 2, top). The values of SAPO-37 unit cell volume are presented in relation with the oxygen and T-atoms thermal parameter B-iso (left) and the occupancy of the dummy atom corresponding to each template, TMA+ in blue and TPA+ in red, respectively (right).
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