A study of thermally activated Mg-Fe layered double hydroxides as potential environmental catalysts

Abstract

Layered double hydroxides (LDHs) and mixed oxides derived after thermal decomposition of LDH with different Mg-Fe content were investigated. These materials were chosen because of the possibility to tailor their various properties, such as ion-exchange capability, redox and acid-base properties and surface area. Layered double hydroxides, [Mg1-x Fex (OH)2](CO3)x/2 ? m H2O, (where x presents the content of trivalent ions, x = M(III)/[M(II) + M(III)]) were synthesized, using low supersaturation precipitation method. The influence of different Mg/Fe ratio on the structure and surface properties of LDH and derived mixed oxides was investigated in correlation to catalytic properties in chosen test reaction (Fischer-Tropsch synthesis). It was determined that the presence of active sites in the mixed oxides is influenced by structural properties of the initial LDH and by the presence of additional Fe phases. Furthermore, the synthesis outside the optimal range for the synthesis of single phase LDHs leads to the formation of metastable, multiphase systems with specific characteristics and active sites.