Evaluation of the microporosity of aluminium pillared montmorillonite: Optimisation of the exchange process

Aluminium pillared clays were synthesised under various experimental condit ions starting from a sodium montmorillonite clay (Hithix). The influence of sonication, successive exchange and a constant pH during and after the int ercalation process were investigated as important synthesis parameters in t he optimisation of these materials. The concentration of aluminium in the p illaring solution, the ratio of Al/clay and the aging time and temperature were kept constant throughout this work. This optimisation is necessary in order to obtain high-quality Al-PILCs, as could be deduced from a theoretic al study on the potential and limitations of pillared clay substrates. The ultrasonic treatment of the suspension during the synthesis is responsible for a significant increase in porosity. Despite the promising nature of the successive exchange technique, a reduction of the porosity is observed. In stead of a homogenisation process, an accumulation of aluminium in the inte rlayer space occurred. This expected homogenisation takes place when the sy nthesis of the pillared clay was carried out at constant pH. In this case, nitrogen BET surface areas of 458 m(2)/g and micropore volumes of 0.17 cm(3 )/g were obtained after calcination of the intercalated clays at 400 degree s C.