Influence of preparation parameters of γ-Al۲O۳ catalysts on itsperformance in methanol dehydration to dimethyl ether

A series of γ-Al۲O۳ catalysts were prepared by precipitation of Al(OH)۳ from aluminum nitratesolutions, using NaOH as precipitating agent, followed by filtering and calcination at ۵۰۰ °C. Theresulting powder was formed as extrudates and tablets prior to performance test. The catalyst weretested in a fixed-bed reactor for dehydration of methanol to dimethyl ether (DME), an alternativeand environmental benign fuel and chemical [۱]. The effect of preparation conditions such asNaOH concentration (۱-۴ M) and forming on catalyst performance were examined. The resultsshowed that higher NaOH concentrations increased the surface area (and thus catalytic activity) ofthe samples (Fig. ۱a) due to increased supersaturation [۲]. A higher NaOH concentration is ofeconomic benefit as it reduces the size of precipitation reactor. Above ۲۷۰°C the reaction wasequilibrium limited, and because of a high DME selectivity (≈۱۰۰%) for all samples, thistemperature is the optimum one in terms of DME yield. When formed as pellets, the extrudatedsample showed higher conversion compared to tableted sample, due to more reduction of porevolume in the latter as a result of much higher pressure applied. The results were compared with acommercial sample and a higher yield was observed for the extrudate sample (Fig. ۱b).

Keywords:

Methanol dehydration , dimethyl ether , γ-Al۲O۳ Catalyst , precipitation , catalyst forming