Mechanochemical and wet chemical syntheses of CaIn-layered double hydroxide and its performance in a transesterification reaction compared to those of other Ca2M(III) hydrocalumites (M: Al, Sc, V, Cr, Fe, Ga) and Mg(II)-, Ni(II)-, Co(II)- or Zn(II)-based hydrotalcites
Márton Szabados, Anna Adél Ádám, Péter Traj, Szabolcs Muráth, Kornélia Baán, Péter Bélteky, Zoltán Kónya, Ákos Kukovecz, Pál Sipos, István Pálinkó
Abstract
The feasibility of indium introduction into the hydrocalumite group of layered double hydroxides (LDHs) was investigated for the first time. Mechanochemical and co-precipitation techniques were applied in the syntheses. During the development of preparation, a yet unknown CaIn chloride-hydroxide solid side-product was found and synthesized in phase-pure state. The as-prepared materials were characterized by X-ray diffractometry, Fourier-transform infrared, Raman, and UV–Vis diffuse reflectance spectroscopies. Their thermal behavior was mapped up to 900 °C, while the surface and textural attributes were studied by scanning and transmission electron microscopies, specific surface area measurements and pore size analysis. For the LDH, the Ca2.3InCl(OH)6.6·4H2O and for the side-product, the Ca3In4Cl2(OH)16·6H2O stoichiometric formula was calculated. Various further hydrocalumites (M(III): Al3+, Sc3+, V3+, Cr3+, Fe3+, Ga3+) were synthesized, their surface basicity was investigated by CO2 temperature programmed desorption. These materials and the indium-containing phases were tested as catalysts in the transesterification reactions of dimethyl carbonate with glycerol. All solids proved to be active: their glycerol conversion capabilities and recycling abilities were determined and compared to the well-known Mg-, Ni-, Co–, Zn-based hydrotalcites.