以NaY分子筛为原料,采用二次交换二次焙烧工艺,制得了LaNH4Y-1,LaY-1,LaNH4Y-2和LaY-2四种分子筛样品.采用粉末X射线衍射结合Rietveld结构精修确定了La离子在分子筛中的分布.结果表明,在离子交换过程中,La离子首先定位于分子筛超笼里；经焙烧脱水后,La离子迁移到分子筛方钠石笼并定位在SI'位置.T-O-T键角的变化表明,LaNH4Y-1表现出最大的骨架扭曲性和结构不稳定性.La离子定位在SI'位置与O3配位,增加了T-O3的键长,表明稀土离子不仅通过控制骨架脱铝抑制晶胞收缩,还可能通过影响T-O3键长使晶胞增大.在REY分子筛中,稀土的主要作用是稳定分子筛结构,从而调节其酸性和催化活性.采用红外光谱和NH3程序升温脱附考察了La离子和NH4+对分子筛酸性的影响,并总结了稀土离子稳定Y型分子筛的机理.
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