Synthesis of cordierite by dolomite and kaolinitic clay chlorination. Study of the phase transformations and reaction mechanism

The focus of analysis in this work has been the study of the synthesis of cordierite using a pyrometallurgical route which involved thermal treatment in a chlorine atmosphere of a kaolinitic clay and dolomite mixture as raw material. The reaction mechanism was also investigated. Isothermal and non-isothermal chlorination assays were conducted in experimental equipment adapted for working in corrosive atmospheres. The temperature effect on the reactions yielding cordierite were studied. Both reagents and products were analyzed by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). The experimental results have shown that cordierite starts to be produced at 700 °C, and that the elimination of iron, which is present as an impurity, begins at about 700 °C. The most favorable chlorination temperature was 900 °C, since at this temperature a selective production of cordierite and an efficient elimination of iron were achieved.