Intrinsic kinetics study of dimethyl ether synthesis from methanol on γ-Al2 O3 catalysts

A series of commercially available gamma-Al2O3 samples were tested for vapor-phase dehydration of methanol to dimethyl ether (DME). The samples were characterized using X-ray diffraction (XRD), temperature-programmed desorption of ammonia (NH3-TPD), and Brunauer-Emmett-Teller (BET) surface area techniques. The catalysts were determined to be highly amorphous with similar porous structures. Catalyst screening tests were performed in a fixed-bed reactor under the same operating conditions (temperature, T 573 K; pressure, P = 16 bar (gauge); weight hourly space velocity, WHSV = 26.07 h(-1)). The influence of operation conditions on catalyst performance, as well as the stability of catalysts toward water, was also studied. It was determined that gamma-Al2O3 catalysts with acidic sites whose acidity is very weak and/or moderate exhibit the best catalytic performance and stability. A new kinetics expression was developed for the dehydration of methanol to DME. The kinetics was observed to fit the experimental data accurately. An activation energy of 57.7 kJ/mol was obtained for the catalyst with the best performance.