Abstract:
Dehydration of methanol to dimethyl ether (DME) was investigated over nanocrystalline γ-Al₂O₃, χ-Al₂O₃ and mixed γ- and χ-crystalline phases with various ratios. The catalysts were characterized by X-ray diffraction (XRD), N₂ physisorption, NH₃-temperature programmed desorption (NH₃-TPD), and ion-exchange titration. Firstly, It was found that the NH₃-TPD results revealed that γ-Al₂O₃ with synthesized by solvothermal method had higher acidity than commercial exhibited the higher yield. Secondly, the NH₃-TPD and ion-exchange titration results revealed that the existence of 20 wt% χ-phase in γ-Al₂O₃ with synthesized by solvothermal method increased significantly both the density and the strength of surface acidity of alumina. γ-Al₂O₃ catalyst containing 20 wt% of x-phase with synthesized by solvothermal method exhibited the highest yield (86%) with good stability for DME synthesis. Lastly, It was found that the NH₃-TPD and ion-exchange titration results revealed that 20 wt% χ-phase in γ-Al₂O₃ with synthesized by solvothermal method had higher acidity than 20 wt% χ-phase in γ-Al₂O3 with synthesized by physical mixture method exhibited the higher yield. Therefore, the appropriate catalyst was 20 wt% χ-phase in γ-Al₂O₃ catalyst with synthesized by solvothermal method.
