Correlation between acidity and catalytic activity for the methanol dehydration over various aluminum oxides

摘要

Dehydration of methanol into dimethyl ether (DME) was carried outover aluminum oxides with different crystalline phases, viz. η-Al_20_3, γ- Al_2O_3, θ-Al_20_3, (X+γ)-Al_20_3,δ-Al_20_3, α-Al_20_3, and K-Al_20_3. The catalytic activity decreased in the following order: η-Al_20_3 > γ-Al_20_3 θ-Al_2 0_3 (X+γ)-Al_20_3 (δ-Al_20_3 > α-Al_2O_3≈K-Al_2O_3. Several techniques: N_2 physisorption, X-ray diffraction (XRD), temperature-programmed desorption ( TPD) of NH3, and FT-IR spectroscopy after pyridine adsorption were employed to characterize these solid acid catalysts. The good correlation can be found between the catalytic activity and the amount of Lewis acid site determined by the FTIR spectra after pyridine adsorption