不同支撑材料对Na-Mn_(2)O_(3)载氧体化学链甲烷氧化偶联性能的影响

Effects of different supports on performance of Na-Mn_(2)O_(3)oxygen carrier for chemical-looping oxidative coupling of methane

采用浸渍法制备了3种具有稳定多孔结构的支撑材料(SiO_(2),Mg O,TiO_(2))负载的Na-Mn_(2)O_(3)载氧体,采用XRD、N2吸附-脱附、SEM、H_(2)-TPR等方法对载氧体的微观结构进行表征,研究了不同还原温度下各种支撑材料对Na-Mn_(2)O_(3)载氧体化学链甲烷氧化偶联性能的影响。实验结果表明,支撑材料主要影响载氧体的催化活性和储氧能力,SiO_(2)比MgO和TiO_(2)具有更发达的孔结构和更高的比表面积,Na-Mn_(2)O_(3)/Si O_(2)的催化性能最佳,在800℃下C2选择性达74.25%、C2产率为14.12%;Na-Mn_(2)O_(3)/SiO_(2)和Na-Mn_(2)O_(3)/MgO具有较好的结构稳定性,活性组分具有较好的晶格氧稳定性;MgO与Mn_(2)O_(3)的前体在载氧体制备过程中化学反应最显著,形成了Mg_(6)MnO_(8)并产生较高的储氧能力。

Three Na-Mn_(2)O_(3)oxygen carriers(OCs)supported by different inert supports(SiO_(2),MgO,TiO_(2))with stable porous structure were prepared by impregnation method.The microstructures of OCs were characterized by XRD,N2 adsorption-desorption,SEM and H_(2)-TPR.The effects of supports on the performance of Na-Mn_(2)O_(3)OCs in chemical-looping oxidative coupling of methane were investigated at various temperatures.The experimental results show that the supports exhibited strong influences on the catalytic activity and oxygen transport capacity of OCs.SiO_(2)possesses a more porous structure and higher specific surface area as compared to MgO and TiO_(2).Na-Mn_(2)O_(3)/SiO_(2)exhibits the best catalytic performance with 74.25%of C2 selectivity and 14.12%of C2 yield at 800℃.Na-Mn_(2)O_(3)/SiO_(2)and Na-Mn_(2)O_(3)/MgO show good structural stability and lattice oxygen stability.During the preparation of OCs,the precursor of MgO supports strongly interact with the precursor of Mn_(2)O_(3),forming Mg_(6)MnO_(8) and resulting in higher oxygen storage capacity.