Synthesis and monitoring of α-Bi2Mo3O12 catalyst formation using thermo-Raman spectroscopy

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 wavelength 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 alpha-Bi(2)Mo(3)O(12) phase was observed to be a dynamic thermal process. The slow, controlled heating rate produced alpha-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. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).