氧化铝表面碱性与钼金属负载研究

Study on surface alkalinity of alumina and molybdenum metal loading

制备了氧化铝负载的钼金属催化剂,采用FTIR,CO2-TPD,NH3-TPD,TEM,H2-TPR等分析方法对钼金属催化剂试样进行表征,考察了钼金属在氧化铝上的负载机理及氧化铝负载钼金属后碱性质的变化。实验结果表明,氧化铝的表面以弱碱性为主,钼金属优先负载到氧化铝的弱碱性位,钼金属是以氧化钼纳米簇形式负载到氧化铝上的,纳米簇中体相氧化钼优先还原,纳米簇底部氧化铝较难还原;随着钼负载量的增加,氧化钼纳米簇的面积和厚度增加,氧化铝不同羟基FTIR的峰强度改变,弱碱性逐渐消失。

Molybdenum catalysts supported on alumina were prepared and characterized by FTIR,CO2-TPD,NH3-TPD TEM and H2-TPR.The mechanism of molybdenum supported on alumina and the change of base properties were investigated.The result shows that the surface basicity of alumina is mainly weak.Molybdenum is preferentially loaded to the weak basicity site of alumina.Molybdenum is supported on alumina in the form of molybdenum oxide nanoclusters.The bulk phase of molybdenum oxide in the nanoclusters is preferentially reduced,while molybdenum oxide at the bottom of the nanoclusters is difficult to be reduced.With the increase of molybdenum loading,the area and thickness of molybdenum oxide nanoclusters increase,the intensity of different hydroxyl infrared peaks of alumina changes,and the weak basicity disappears gradually.