Preparation of thermally stable geopolymers as new catalysts or supports

Geopolymers are alkali bonded ceramics (ABC's) and are produced using an energy saving process involving chemical reactions in aqueous medium at T < 120°C. Thermally stable geopolymers may have many industrial applications, considering that their preparation allows to produce near-net-shape pieces, also simultaneously to the foaming. ABC's have a three-dimensional aluminosilicate network, in which polymeric Si-O-Al-O bonds form under alkaline conditions in presence of aluminosilicates. The final structure of a fully reacted ABC consists of nanoparticulates ranging from 5 to 15 nm, pores of 3 to 10 nm with specific surface area in the range 20-140 m2/g. Finally, the functional and structural properties of the ABC's can be tailored by introducing specific ceramic fillers. The geopolymer network and the zeolite framework have close similarity in the exchange with charge balancing cations; ABC's network also enables incorporation of transition metal ions or protonic extra-network sites as active centres for catalytic reactions. However, it must be noted that geopolymers posses some advantages in comparison to zeolites, such as formation at room or low temperature, mesoporosity and low preparation cost, opening potential interests for the synthesis of new robust catalysts for heterogeneous reactions. Aim of this study was to set up the preparation method for new geopolymers (pellets and/or foams) to be applied as catalysts or supports