合成气制低碳烯烃串联反应中Zn-Al氧化物的制备及性能

Study on preparation and catalytic performance of Zn-Al oxides for tandem reaction of syngas conversion into light olefins

  • 摘要: 以工业拟薄水铝石为铝源,通过微波辅助蒸发诱导自组装(M-EISA)法制备了一系列不同Zn/Al原子比的Zn-Al氧化物,并与SAPO-18分子筛物理混合后考察其催化合成气制低碳烯烃(\rmC_2^= -\rmC_4^=)反应性能。采用X射线衍射(XRD)、透射电镜(TEM)、N2吸附-脱附、CO和H2程序升温脱附(CO-TPD、H2-TPD)、X射线光电子能谱(XPS)等进行表征。M-EISA法制备的Zn-Al氧化物随Zn/Al原子比的增加,比表面积和孔容逐渐下降,平均孔径先增大后降低。与浸渍(IP)法制备的ZnAl-IP相比,Zn/Al原子比为1∶2的ZnAl2Ox样品中Zn分散度高,形成的ZnAl2O4尖晶石结构产生了更多的氧空位。催化结果表明,M-EISA法制备的Zn-Al样品活性随Zn/Al原子比的增加而先增加后减小,\rmC_2^= -\rmC_4^= 选择性逐渐降低。ZnAl2Ox样品的CO转化率最高(34.8%),且反应50 h未见明显失活,催化性能明显优于ZnAl-IP样品。

     

    Abstract: A series of Zn-Al oxides with different Zn/Al atomic ratios were prepared by the microwave-assisted evaporation-induced self-assembly (M-EISA) method, using industrial pseudo-boehmite as aluminum source. The prepared Zn-Al oxides were physically mixed with SAPO-18 zeolite and applied in tandem reaction for direct conversion of syngas to light olefins (\rmC_2^= -\rmC_4^= ). X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption-desorption, CO and H2 temperature-programmed desorption (CO-TPD, H2-TPD) and X-ray photoelectron spectroscopy (XPS) were selected for characterization. As the increase of Zn/Al ratio, the specific surface area and pore volume of Zn-Al oxides gradually decreased, while the average pore diameter firstly increased and then decreased. Compared with the ZnAl-IP prepared by the impregnation (IP) method, the ZnAl2Ox with the Zn/Al ratio of 1∶2 had a high dispersion of Zn and formed the ZnAl2O4 spinel structure that produced more oxygen vacancies. The catalytic results showed that the activity of Zn-Al samples prepared by M-EISA method firstly increased and then decreased as the Zn/Al ratio rose, while the \rmC_2^= -\rmC_4^= selectivity gradually decreased. ZnAl2Ox sample exhibited the highest CO conversion of 34.8% and almost no obvious deactivation after 50 h reaction, furthermore, its catalytic performance was much better than that of ZnAl-IP sample.

     

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