焙烧温度对甲醇氧化制甲醛铁钼催化剂结构及性能的影响

Effect of calcination temperature on structure and activity of iron-molybdenum catalysts for methanol oxidation to formaldehyde

以Fe(NO_(3))_(3)·9H_(2)O和(NH_(4))6Mo_(7)O_(2)4·4H_(2)O为Fe源和Mo源,通过共沉淀法制备了系列不同焙烧温度的铁钼催化剂,并考察了催化剂对甲醇氧化制甲醛反应性能的影响。结果表明,400℃焙烧的铁钼催化剂具有最佳催化性能,其甲醇转化率为96.6%、甲醛收率为87.6%、甲醛选择性为80.7%。进一步通过BET、XRD、Raman、SEM、XPS及H_(2)-TPR对催化剂进行表征,发现焙烧温度对催化剂的织构、形貌、晶相结构以及表面Fe、Mo、O物种的种类和分布具有显著影响。当焙烧温度从350℃提升至400℃时,催化剂中钼氧化物由六方相h-MoO_(3)转变为正交相α-MoO_(3),催化剂表面Mo^(5+)和晶格氧含量增加是催化性能提升的主要原因。

Using Fe(NO_(3))_(3)·9H_(2)O and(NH_(4))6Mo_(7)O_(2)4·4H_(2)O as Fe source and Mo source,a series of iron-molybdenum catalysts calcined at different calcination temperatures were prepared by co-precipitation,and the effect of the catalysts on the reaction performance of methanol oxidation to formaldehyde was investigated.The results show that the iron-molybdenum catalyst calcined at 400℃has the best catalytic performance,with methanol conversion rate of 96.6%,formaldehyde yield of 87.6%and formaldehyde selectivity of 80.7%.Furthermore,the catalysts were characterized by BET,XRD,Raman,SEM,XPS and H_(2)-TPR,and it was found that the calcination temperature has significantly effects on the texture,morphology,crystal phase structure and the types and distribution of Fe,Mo,and O species on the surface of the catalysts.When the calcination temperature is increased from 350℃to 400℃,the molybdenum oxide in the catalyst changes from the hexagonal phase h-MoO_(3) to the orthogonal phaseα-MoO_(3),and the increase of content of Mo^(5+)and lattice oxygen on the catalyst surface are the main reasons for the improvement of the catalytic performance.