层状K/Mg-Fe-Al催化剂的制备及其CO加氢性能研究  

Preparation of layered K/Mg-Fe-Al catalysts and its catalytic performances in CO hydrogenation

作　　者：张建利[1] 王旭[1] 马丽萍[1] 于旭飞 马清祥[1] 范素兵[1] 赵天生[1] 

机构地区：[1]宁夏大学省部共建煤炭高效利用与绿色化工国家重点实验室,宁夏银川750021

出　　处：《燃料化学学报》2017年第12期1489-1498,共10页Journal of Fuel Chemistry and Technology

基　　金：国家自然科学基金(21666030;21366025);"化学工程与技术"国内一流学科建设项目资助~~

摘　　要：采用共沉淀法制备了系列不同Mg/Fe/Al配比MgFeAl-HTLcs前驱体,经焙烧、浸渍K改性、二次焙烧后用于CO加氢反应。采用N2吸附-脱附、SEM、TG、XRD、H2-TPR、XPS等手段对催化剂进行了表征。结果表明,共沉淀法制备的不同配比MgFeAl-HTLcs类水滑石前躯体均具有典型层状结构;焙烧后生成MgO、Fe2O3以及少量MgFeAlO4物相,三组元间相互作用增强,反应后以MgCO3和Fe3O4物相为主,同时出现较弱的Fe5C2相;K改性后发生结构重构,热稳定性增强,且随Al含量增加,比表面积显著单调下降;与K/Mg-Fe相比,K/Mg-Fe-Al样品中Fe2O3到Fe3O4的还原受到抑制;二次焙烧后,反应前表面相对富Fe,反应后表面富K。在CO加氢反应中,K/Mg-Fe-Al系列催化剂均表现出较高的反应活性以及烯烃选择性,随Fe/Al配比相对增加,C5+含量呈降低趋势,O/P值增加;与K/1.5Mg-0.67Fe相比,K/1.5Mg-0.67Fe-0.33Al催化剂C5+含量由22.17%降至10.90%,C=2-4含量由40.98%提高至47.28%。A series of K promoted K/MgFeAl-HTLcs catalysts with different Mg/Fe/Al molar ratios were prepared by means of coprecipitation and impregnation method for direct synthesis of light olefins from CO hydrogenation. The samples were characterized by XRD,N2 adsorption-desorption,SEM,TG,H2-TPR and XPS measurements. The results show that MgFeAl-HTLcs catalyst precursors has typical layered structure. MgO,Fe2 O3 and small amount of MgFeAlO4 are formed after calcination. MgCO3 and Fe3 O4 could be observed after reaction,and a little Fe5 C2 iron carbide with broad and weak peaks appear simultaneously. Thermal stability of K/MgFeAl-HTLcs is improved due to recovery of hydrotalcite-like structure after K promotion. With increase of Al content, specific surface area of the precursors decreases monotonically after structure reconstruction.Reduction of Fe2 O3 to Fe3 O4 is inhibited with addition of Al,compared with K/Mg-Fe sample. Fe enrichment before reaction and K enrichment after reaction are observed on secondary calcination samples. During CO hydrogenation,the prepared samples show high activity and C =2-4 selectivity with low C5＋ weight fraction. C5＋hydrocarbons decrease and olefin selectivity increases with increasing Fe/Al molar ratio. The C5＋ decreases from22.17% to 10.90%,and C =2-4 weight content increases from 40.98% to 47.28% on K/1.5 Mg-0.67 Fe-0.33 Al sample compared with that of K/1.5 Mg-0.67 Fe sample.

关 键 词：费托合成 K/Mg-Fe-Al催化剂 CO加氢 低碳烯烃 

分 类 号：O643[理学—物理化学]