合成气直接转化制低碳烯烃催化剂设计及反应条件优化

采用水热法合成了相同粒径、不同硅铝比的ZSM-5分子筛，并通过浸渍法将Fe基（Fe-Cu-K）催化剂负载于ZSM-5上，系统考察了分子筛硅铝比变化对合成气制烯烃（FTO）反应的影响。结果表明，反应条件、分子筛酸性对CO转化率和低碳烯烃选择性有显著影响。当ZSM-5分子筛硅铝比为50时负载型催化剂有着最高的CO转化率（84.71%）和低碳烯烃选择性（32.08%）。H₂-TPR结果表明，硅铝比为50的Z50/FeCuK中Fe物相的还原度最高。原位漫反射红外光谱（DRIFTS）、热重差热分析（TG-DTA）、X射线粉末衍射（XRD）等结果表明，Z50/FeCuK催化剂表面吸附的碳酸盐和烃类吸附物种最多，且其反应后形成了较多的FeC_x晶相。最后对反应条件进行了优化，结果表明，温度为310 ℃，H₂/CO （volume ratio）=2和压力为1.0 MPa时FTO的催化性能最优。

Design of the catalysts for direct conversion of syngas to light olefins and optimization of the reaction conditions

ZSM-5 catalysts with same particle size and different Si/Al molar ratio were synthesized successfully by hydrothermal synthesis method, and then, Fe-Cu-K-containing ZSM-5 samples were prepared via aqueous incipient wetness impregnation. The effect of Si/Al molar ratio on the FTO reaction was systematically investigated. The results indicated that the conversion of CO and selectivity to light olefins strongly depended on the reaction conditions and the acidic properties of the zeolite. The ZSM-5/FeCuK catalyst with a Si/Al molar ratio of 50 possessed the highest CO conversion (84.71%) and selectivity to light olefins (32.08%) compared with others. H₂-TPR results showed that the reduction of Fe phase in Z50/FeCuK was the highest. With the combination of DRIFTS, TG-DTA and XRD techniques, it was found that there were more carbonate and hydrocarbon species adsorbed on the surface of Z50/FeCuK and more FeC_x phases were formed after reaction compared with the other catalysts. Finally, the reaction conditions were optimized and the results showed that the catalyst had the best performance at 310 ℃, H₂/CO(volume ratio)=2 and 1.0 MPa.