制备了可用于固定床反应器中甲醇脱水制备二甲醚的Al2O3-HZSM-5组合固体酸催化剂系列,并采用X射线衍射、扫描电镜、N2物理吸附和氨气程序升温脱附等对其进行了表征.结果表明,在浸渍法制备的组合Al2O3-HZSM-5催化剂中,细小的氧化铝颗粒高度分散在HZSM-5分子筛的周围;在化学沉淀法制备的组合Al2O3-HZSM-5催化剂中,一层氧化铝膜覆盖在HZSM-5分子筛的颗粒外层.所制备的催化剂都具有较多的大孔和介孔比表面积,在低温(235℃)和高空速(30h-1)条件下具有较高的甲醇脱水反应活性和稳定性,其中在化学沉淀法制备的组合Al2O3-HZSM-5催化剂上,二甲醚产率达到13.5g/(g·h).
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, N2 adsorption, and NH3 temperature-programmed desorption. Al2O3 was highly dispersed in Al2O3-HZSM-5 afier 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 ℃) and a higher LHSV (30 h-1). The stable DME productivities for Al2O3-HZSM-5-IM and Al2O3-HZSM-5-CP at 235℃ reaches 12.7 and 13.5g(g·h),respectively.
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