Synthesis and characterization of porous magnesium aluminate spinel by hydrothermal process

Magnesium aluminate spinel has a great prospect in catalyst supports due to porous structure, good catalytic activity, high thermal stability and two active centers as acid and alkaline. The magnesium aluminate spinel powders synthesized by hydrothermal process were characterized by scanning electron microscope, transmission electron microscope, X-ray diffraction and N2 adsorption-desorption isotherms. The particle surface is made up of laminated structure and it grows bigger with the increase of hydrothermal temperature and hydrothermal time. The spinel has wormlike porous structures and these structures grow smaller and better distributed at Hexadecyl trimethyl ammonium Bromide (CTAB) condition. The spinel phase emerges at 450 °C and the perfect crystalline structure emerges at 600 °C. The percent of MgAl2O4 spinel goes up with the increase of heat treatment temperature. The spinel has a large BET surface area and its special surface area diminishes continuously from 245.68 m2/g to 58.65 m2/g when the calcinating temperature increases from 500 °C to 1200 °C. Moreover, it reaches the maximum surface area of 195.1 m2/g with the addition of 1% CTAB according to BET analysis, yet excess of it has an adverse effect.