Natural Mg silicates with different structures and morphologies: Reaction with K to produce K 2 MgSiO 4 catalyst for biodiesel production

In this work, different magnesium silicate mineral samples based on antigorite, lizardite, chrysotile (which have the same general formula Mg 3 Si 2 O 5 (OH)4), and talc (Mg 3 Si 4 O 10 (OH) 2 ) were reacted with KOH to prepare catalysts for biodiesel production. Simple impregnation with 20wt% K and treatment at 700-900°C led to a solid-state reaction to mainly form the K 2 MgSi0 4 phase in all samples. These results indicate that the K ion can diffuse into the different Mg silicate structures and textures, likely through intercalation in the interlayer space of the different mineral samples followed by dehydroxylation and K 2 MgSi0 4 formation. All the materials showed catalytic activity for the transesterification of soybean oil (1:6 of oil: methanol molar ratio, 5wt% of catalyst, 60°C). However, the best results were obtained for the antigorite and chrysotile precursors, which are discussed in terms of mineral structure and the more efficient formation of the active phase K 2 MgSi0 4 .