Synthesis and characterization of a novel nano-scale magnetic solid base catalyst involving a layered double hydroxide supported on a ferrite core

Abstract

A nano-scale magnetic solid base catalyst MgAl-OH-LDH/MgFe 2O 4 (where LDH denotes layered double hydroxide) composed of MgAl-OH-LDH Brønsted base catalytic layers coated on MgFe 2O 4 spinel cores has been prepared. A magnetic precursor MgAl-CO 3-LDH/MgFe 2O 4 was prepared by a method involving separate nucleation and aging steps, and subsequently calcined to give a mixed metal oxide composite MgAl(O)/MgFe 2O 4 which was rehydrated to give MgAl-OH-LDH/MgFe 2O 4. The structure and magnetic properties of the nano-scale magnetic solid base MgAl-OH-LDH/MgFe 2O 4, together with those of the magnetic precursor MgAl-CO 3-LDH/MgFe 2O 4 and MgFe 2O 4 were characterized by XRD, XPS, low temperature N 2 adsorption and vibrating sample magnetometry (VSM). The MgAl-OH-LDH/MgFe 2O 4 composite possesses a mesoporous structure with pore size ranging from 2 to 20 nm with particle size mainly in the range 35–130 nm. The catalytic properties of MgAl-OH-LDH/MgFe 2O 4 were evaluated using the self-condensation of acetone at 273 K as a probe reaction. The results showed that the conversion of acetone to diacetone alcohol reached the thermodynamic equilibrium value of 23% at 273 K. The catalyst was easily recovered through application of an external magnetic field, and when the reclaimed catalyst was used in a second run for the same reaction, the reactivity remained unchanged.