氟修饰的含Ni类水滑石在甲烷部分氧化制合成气中的应用研究

摘要

通过共沉淀法合成了含Ni/Mg/Al的类水滑石,并利用水滑石的“重构性能”将F-引入到水滑石层间.焙烧该类水滑石后得到Ni/Mg/Al/O-F催化剂,采用XRD、SEM、CO2 -TPD、H2 -TPR、N2吸附-脱附等手段对其结构进行了表征.结果表明,焙烧后的催化剂为方镁石结构,并具有丰富的介孔,Ni/Mg/Al/O-F较之不含F-的复合氧化物Ni/Mg/AlO具有更小的比表面积、颗粒粒径和结晶度,但是碱密度明显增大,并且在甲烷部分氧化(POM)反应中表现出更高的活性和稳定性,反应120h后,活性没有下降.这是因为F-的引入提高了催化剂碱性和活性组分Ni的分散,从而改善了催化剂的抗积炭和烧结能力.%Fluorine-modified Ni-Mg-Al mixed oxides (Ni/Mg/Al/O-F) prepared from thermal decomposition of hydrotalcite-type (HT) precursor was characterized by XRD, SEM, CO2-TPD, H2-TPR, and N2 sorption and used as catalyst in partial oxidation of methane (POM) to syngas. The results indicated that Ni/Mg/Al/O-F catalyst after calcination takes the mesoporous structure of periclase. Compared with the non-modified Ni-Mg-Al mixed oxides (Ni/Mg/Al/O), Ni/Mg/Al/O-F exhibits lower surface area, lower crystallinity and smaller particle size, but higher basicity of moderate and strong intensity. Ni/Mg/Al/O-F exhibits high activity and stability in POM; the activity at 1 053 K retains without deactivation even after 120 h on stream. The presence of the F-anions can enhance the dispersion of active nickel species and their resistance to coking, which may contribute to the high performance of Ni/Mg/Al/O-F catalyst.