Effect of C16TMA contents on the thermal stability of organo-bentonites: In situ X-ray diffraction analysis

Different concentrations of cetyl trimethylammonium bromide solutions were cation exchanged with bentonite clay mineral, at room temperature. The resulting organoclays were characterized by elemental analysis C and N, X-ray diffraction and thermal gravimetric analysis. The evolved gases during the calcination of organoclays were identified by online mass spectrometry coupled with thermal gravimetry technique. Meanwhile, in situ X-ray diffraction was used to have insight on the thermal stability of the organoclays in air atmosphere. X-ray diffraction at room temperature indicated that a disorder transition phase from bilayer to paraffin configuration occurred at higher surfactant-cation exchange capacity ratios, with two phases at 3.25 and 2.00 nm, respectively. The in situ X-ray diffraction confirmed the presence of these two phases with improved reflections intensities in the range of 100–200 °C. Above this temperature, both phases collapsed due to the decomposition of the surfactants as recorded by mass spectrometry thermal gravimetric analysis.

► Organo-bentonites were prepared at C16TMABr/CEC ratios up to 11. ► Disorder configuration of C16TMA cations was observed at higher C16TMABr/CEC ratios. ► The evolved gases during the calcinations of organoclays were analyzed by MS-TG. ► In situ XRD technique detected clearly the phase disorder in the range 50–150 °C. ► Collapse of organoclays depended on the temperature and the used atmospheres.