Abstract
Thermo-Raman spectroscopy was used to monitor the dehydration and phase transformations of Bi 2 Mo 3 O 12 ·5H 2 O. The hydrated forms Bi 2 Mo 3 O 12 ·5H 2 O, Bi 2 Mo 3 O 12 ·4.75H 2 O, Bi 2 Mo 3 O 12 ·3H 2 O, Bi 2 Mo 3 O 12 ·2H 2 O, and anhydrous Bi 2 Mo 3 O 12 were observed during dehydration in the wave-length range from 200 to 1400 cm -1 . Representative Raman spectra of these compounds are reported for the first time. The thermo-Raman intensity thermogram showed a systematic dehydration in four steps, and the differential thermo-Raman intensity thermogram confirmed this. Thermogravimetry, differential thermogravimetry, and differential scanning calorimetry results were in harmony with the results of the thermo-Raman spectroscopy. Additionally, the dehydration resulting in formation of anhydrous Bi 2 Mo 3 O 12 (amorphous Bi 2 Mo 3 O 12 phase) and the final transformation into the α-Bi 2 Mo 3 O 12 phase was observed to be a dynamic thermal process. The slow, controlled heating rate produced α-Bi 2 Mo 3 O 12 catalyst with a particle size averaging 200 nm. The catalyst formed was further characterized by Fourier transform infrared spectroscopy, X-ray diffraction, time of flight SIMS, transmission electron microscopy, and energy-dispersive X-ray analysis. © Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.