Effect of surface acidity on the catalytic activity and deactivation of supported sulfonic acids during dehydration of methanol to DME

The influence of catalyst's surface acidity on the catalytic activity and deactivation in the dehydration of methanol to DME was investigated. Different materials including propylsulfonic acid functionalized silica at different Bronsted acidity, silica-alumina, propyl and phenylsulfonic acid functionalized silica-alumina catalysts were prepared. All samples were characterized by XRD, TGA, XPS, N2-sorption, ICP-OES and SEM analysis. It was found that the Bronsted and Lewis acidity of SiO2/Al2O3-PhSO3H catalyst played a critical role in the performance of methanol to DME catalyst. The grafting of sulfonic acid groups on the silica-alumina enhanced the surface Brønsted acidity and also the reaction activity and selectivity for the dehydration of methanol to DME. In addition, phenylsulfonic acid functionalized silica-alumina catalyst exhibited the highest activity and stability for the dehydration reaction at relatively low temperatures at which the γ-Al2O3, commercial reference, displayed the low dehydration activity. The water effect was also investigated because in the indirect process to produce DME using acidic -alumina, has the most important effect on catalyst deactivation. As a result, the water had a positive effect on methanol dehydration over SiO2/Al2O3-PhSO3H catalyst contrary to of γ-Al2O3 that was rapidly deactivated. Thus, the Brønsted and Lewis acid sites with suitable strength may be responsible for the effective conversion of methanol to DME with high stability and selectivity