NiMg AlO-F催化剂的物化性能及其在甲烷部分氧化制合成气中的应用

用共沉淀法合成了NiMgAl类水滑石,并利用水滑石的"记忆效应"成功地将F-添加到该类水滑石中,经1073K焙烧后得到NiMgAIO-F催化剂,采用XRD、EXAFS、TG、ICP、H_2-TPR和N_2吸附-脱附等手段对其物化性能进行了表征。表征结果显示,添加F-前后的类水滑石前体经过焙烧后所得的催化剂均为方镁石结构,但NiMgAlO-F比不含F-的复合氧化物NiMgAlO具有更小的比表面积、晶粒度和结晶度。NiMgAlO-F催化剂在甲烷部分氧化反应中表现出更高的活性和稳定性,甲烷转化率达到95%,CO和H_2的选择性分别达到95%和99%,且反应120h后催化剂活性没有下降,这是因为F-的引入提高了催化剂的可还原性、碱性和活性组分Ni的分散性,进而改善了催化剂的活性和抗积碳能力。

Physicochemical Properties of NiMgAlO-F Catalyst and Its Application to Partial Oxidation of Methane

Fluorine-modified NiMgAl composite oxide NiMgA10-F was prepared by thermal decomposition of hydrotalcite-type precursor and was characterized by means of XRD,EXAFS,TG, ICP,H_2-TPR and N_2 adsorption/desorption technique.The composite oxide was used as the catalyst in the partial oxidation of methane(POM)to syngas.The results revealed that fluorine was successfully introduced into the NiMgAl composite oxide via high dispersion of MgF_2,which led to formation of the periclase-type catalyst with mesoporous structure.Compared with the composite oxide NiMgAlO, both specific surface area and crystallization of the NiMgAlO-F were low and its particle size was small,but its basicity was strong.As a result,NiMgAlO-F showed a higher activity in POM without deactivation even after running at 1053 K for 120 h with CH_4 conversion of 95%,CO selectivity of 95% and H_2 selectivity of 99%.This could be attributed to the high dispersion of nickel due to the introduction of F-anions,which improved resistance to coking.