碱金属氢氧化物对Al_2O_3表面性质的调变效应

Change of Surface Properties of Al_2O_3 with Alkaline Metal Hydroxides

采用将 Al_2O_3浸渍 NaOH 和 LiOH 的方法,对其表面性质进行调变。处理后样品的 X-射线衍射物相分析,BET 比表面的测定以及表面酸度和相对酸强度分布的测定表明,NaOH、LiOH与γ-Al_2O3 作用分别生成了β-NaAlO_2和β-LiAlO_2,从而调变了 Al_2O_3表面酸度和酸强度分布。当碱金属加入量较少时,主要抑制强酸中心,使其明显减少,同时弱酸中心有所增多,当进一步增加碱金属加入量时,不但强酸中心逐渐消失,弱酸中心也开始减少。Al_2O_3表面碱度随碱金属的加入量而增加,加入 NaoH 后,Al_2O_3的比表面降低;而加入 LiOH,在一定含量范围内,对比表面影响不大.

The surface properties of Al_2O_3 are changed by immersing it in NaOH andLiOH.XRD analysis,determination by BET of specific surface area,and surfaceacid and basic property measurement indicate that β-NaAlO_2 and β-LiAlO_2 areformed,and surface acidity and relative acid strength distribution of catalyts arechanged by reaction of NaOH,LiOH with γ-Al_2O_3.When alkaline metal is addedinsmall amount,the number of strong acid site abviously decreases and,in themean time that of relatively weak acid site increases.When the amount of alkalinemetal added is farther increased,the strong acid site disappears gradually,andthe weak acid site also diminishes.The surface basicity of catalysts increaseswith increasing NaOH,LiOH.The specific surface area however,deminishes asNaOH is added,but little effect is observed when a limited amount of LiOH isadded.