摘要
由二交二焙工艺及液-固工艺制备LaY沸石,采用多晶XRD结合Rietveld结构精修确定了La离子在Y沸石骨架外的分布。结果表明,进入方钠石笼的La离子定位于SⅠ’位置,与骨架O3形成配位,从而稳定沸石骨架,提高沸石水热稳定性。采用液-固工艺制备的LaY沸石中La离子与O3的距离比采用二交二焙工艺制备的LaY沸石中La离子与O3的距离要短。因此,前者La离子与O3的作用更强。采用液-固工艺制备的LaY沸石中,每个La离子除与3个O3配位外,还与2个羟基配位,La离子以[La(OH)2]+形式存在。2种工艺制备的样品中,均有少量Na+定位于六方柱笼SⅠ位置。采用二交二焙工艺制备的LaY沸石中,沸石骨架有轻微脱Al,有少量Al3+定位于SⅡ’位置。
LaY samples were prepared by double exchange double calcinations （DEDC） method and liquid-solid phase exchange （LSPE） method. The position, occupation and coordination of La^3＋ outside the framework of Y zeolite were determined by polycrystalline XRD with the Rietveld method. La^3＋ situate at S I＇ sites and coordinate with framework oxygen （03）. As a result, they made the framework of Y zeolite more stable and the hydrothermal stability improved. In samples prepared by LSPE method, the interaction between La^3＋ and 03 was stronger because the bond distance from La^3＋ to 03 was shorter than that in samples prepared by DEDC method. In samples prepared by LSPE method, La cation existed in the form of [-La（OH）2]^＋ because each La^3＋ coordinated with two hydroxyl besides three 03. There were a small amount of Na^＋ located at S sites inside hexagonal prism in samples prepared by both methods. In samples prepared by DEDC method, there were a few AP^＋ locate at S Ⅱ’ sites due to slight dealumination during preparation process.
出处
《石油学报（石油加工）》
EI
CAS
CSCD
北大核心
2007年第3期87-91,共5页
Acta Petrolei Sinica(Petroleum Processing Section)
基金
国家重点基础研究发展规划"973"项目(G2000048001)资助
关键词
LaY沸石
镧
稀土
结构精修
稀土离子位置
LaY zeolite
lanthanum
rare earth
Rietveld refinement
rare earth cation site
