Synthesis of Dimethyl Ether via Methanol Dehydration over Combined Al2O3-HZSM-5 Solid Acids

Combined Al2O3-HZSM-5 solid acids were prepared and used for methanol dehydration to dimethyl ether (DME) in a fixed-bed reactor The physicochemical properties of the combined solid acids were characterized by X-ray diffraction, field emission scanning electron microscopy, N-2 adsorption, and NH3 temperature-programmed desorption Al2O3 was highly dispersed in Al2O3-HZSM-5 after impregnation (Al2O3-HZSM-5-IM); while a layered Al2O3-covered HZSM-5 structure solid acid was synthesized via chemical precipitation (Al2O3-HZSM-5-CP) Both the combined Al2O3-HZSM-5 solid acids prepared by Impregnation and chemical precipitation have a higher surface area and more meso- and macropores The combined Al2O3-HZSM-5 solid acids exhibit higher methanol dehydration activity than pure Al2O3 and it possesses higher stability than pure HZSM-5 at a lower temperature (235 degrees C) and a higher LHSV (30 h(-1)) The stable DME productivities for Al2O3-HZSM-5-IM and Al2O3-HZSM-5-CP at 235 degrees C reached 12 7 and 13 5 g/(g h), respectively