溶胶-凝胶法制备Na_2WO_4~-Mn/SiO_2催化剂及其甲烷氧化偶联反应性能的研究

采用溶胶-凝胶法制备了一系列5%Na2WO4-2%Mn/SiO2催化剂;用XRD、XPS、BET、O2-TPD和CO2-TPD等方法对催化剂进行了表征,并考察了对甲烷氧化偶联反应的催化性能。结果表明,与常规浸渍法相比,采用溶胶-凝胶法制备的Na2WO4-Mn/SiO2催化剂中W和Mn的原子浓度在催化剂表面和体相分布较为接近,而且两种制备方法所得的催化剂具有相似的催化性能,Na2WO4与α-方石英之间的相互作用,催化剂释放晶格氧的能力,碱性强弱是影响甲烷氧化偶联活性的关键因素。

Oxidative Coupling of Methane over Na2WO4-Mn/SiO2 Catalysts Prepared by Sol-gel method

A series of 5wt% Na_2WO_4-2wt% Mn/SiO_2 catalysts were prepared by sol-gel method.The structure and physical chemistry properties of these catalysts were characterized by XRD,XPS,BET,O_2-TPD and CO_2-TPD techniques,and their catalytic performances for the oxidative coupling of methane(OCM) were evaluated in a continuous micro-reactor.The results of X-ray diffraction(XRD) studies indicate that the main crystallite phases are Mn_2O_3,Na_2WO_4 and α-cristobalite,and the precursors of silica are transformed ultimately into highly crystallite α-cristobalite.O_2-TPD,CO_2-TPD and XPS results show that there is a synergic effect of lattice oxygen,basicity and elemental concentrations on surface,which is responsible to the high activity for the oxidative coupling of methane.