Crystallization in Nonaqueous Media of Co- and Mn-Substituted Microporous Aluminophosphates Investigated by in Situ Synchrotron X-ray Powder Diffraction

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Abstract
In situ synchrotron X-ray powder diffraction was used to investigate the crystallization of microporous transition metal-substituted aluminophosphates from nonaqueous media. The gels contained ethylene glycol and triethylamine as the template and were heated in quartz glass capillaries at temperatures up to 200 °C. The following crystalline products were formed: MnAPO-5, [AFI], CoAPO-5, [AFI], and AlPO4-5, [AFI]. Three nonaqueous systems were investigated in situ, where the crystallization of MAPO-5-type materials were followed. Solvothermal crystallization of MnAPO-5 and CoAPO-5 was studied, and the effect of adding HF as a mineralizing agent was investigated. Time-resolved powder diffraction data were collected using a translating imaging plate (TIP) camera, and crystallization curves were extracted using integrated diffraction peaks. Kinetic analysis of the crystallization curves was performed using an Avrami-type expression, α(t) = exp(−(kt)n). Apparent activation energies were determined from Arrhenius plots: MnAPO-5, 94 kJ/mol; MnAPO-5(HF), 68 kJ/mol; CoAPO-5, 61 kJ/mol. Crystallization of CoAPO-5 is faster than for MnAPO-5, and the values for n obtained by fitting with the Avrami-type expression were significantly lower for CoAPO-5 than for MnAPO-5.