An investigation on structure and texture of silica-magnesia xerogels

Silica-magnesia xerogels were prepared by reacting tetraethoxysilane (TEOS) and magnesium chloride (MgCl₂) under acidic conditions. The TEOS/MgCl₂ molar ratio was varied from 1:0 to 0:1. The xerogels were characterized by a set of complementary techniques, namely, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), nitrogen adsorption, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). Magnesium contents of silica-magnesia xerogels were between 1.3 and 16.0 wt%. Increasing TEOS/MgCl₂ molar ratio affords higher homogeneity and crystallinity. The presence of low Mg content (<5%) increases specific surface area compared to bare silica. A cubic grain morphology was observed for xerogels with higher Mg content.