Figure 1

X-ray diffractograms of HSiW/X recorded under air atmosphere between 25 and 550 °C. Purple: H₄SiW₁₂O₄₀·(6-21)H₂O; blue: H₄SiW₁₂O₄₀·6H₂O; orange: H₄SiW₁₂O₄₀; red: WO₃; green: unidentified pattern. The diffractograms for the support are shown as black lines on each set of diffractograms.