Characterization of Microporous Amorphous Alumina-Boria.

Alumina-boria samples with B : (B + Al) 0–50 atom% have been prepared by an unconventional procedure consisting of the reductive decomposition of the mixture of nitrates in the presence of glycerol X-ray diffraction (XRD)-amorphous samples having surface areas of 380–470 m2 g–1 were obtained after calcination at 673 K. Their thermal stability has been studied by differential thermal analysis (DTA) and XRD analysis, showing that crystallization occurred in all cases above 1150 K. FTIR data show the predominance of octahedral Al3+ and triangular B3+ both in the bulk and on the surface. Correspondingly, all samples show lower catalytic activity in methanol dehydration compared with γ-alumina. It was concluded that boron tends to hinder crystallization of amorphous alumina, to increase its surface area and to further decrease it surface acidity.