New mixed lanthanum- and alkaline-earth cation-containing basic catalysts obtained by an alginate route

A new route using mixed ionotropic gels of the natural block copolymer alginate as precursor has been used for the preparation of basic catalysts. Gelification of the alginate has been performed with lanthanum which has been then exchanged by a second alkaline-earth cation. The amount of both type of cations was controlled by the pre-determined relative affinity of the lanthanum containing hydrogels for the alkaline-earth cations which trend is as follows: Ba2+ > Sr2+ > Ca2+ > Mg2+. The surface areas of the materials obtained after thermal decomposition of the ex-alginate samples dried under supercritical CO2 conditions are greatly improved compared to samples with similar composition obtained by coprecipitation. The catalytic test reaction of 2-Methylbut-3-yn-2-ol decomposition reveals the basic properties of the ex-alginate samples. They range as follows in function of the alkaline-earth cation: Mg > Ba > Sr > Ca. This emphasizes the very attractive properties of the Mg-containing catalysts obtained through the alginate route due to their high basic strength and surface areas.