水热条件下坡缕石在NaOH溶液中的行为及结构变化

分别用1,2和3 mol·L^-1的NaOH溶液,在不同的温度条件下对坡缕石进行了侵蚀实验。对反应后的固相产物进行了XRD和SEM分析,对浸出液中的金属阳离子进行了原子吸收光谱分析。讨论了反应温度和碱溶液浓度对碱溶后产物的影响。XRD和SEM结果表明,c_NaOH≤2 mol·L^-1时,坡缕石经碱溶液侵蚀后,可以生成蒙脱石和方沸石,其中反应温度的升高有利于方沸石的形成,碱溶液浓度的升高有利于蒙脱石的形成。当碱溶液浓度达到3 mol·L^-1,反应温度为200 ℃时,最终产物为SiO₂。浸出液的定量分析结果显示,坡缕石与碱溶液的反应过程中,Na⁺对八面体阳离子的置换具有选择性,置换顺序为：Al³⁺＞Fe³⁺(Fe²⁺)＞Mg²⁺。     

The structure of dehydrated (Li<Subscript>0.7</Subscript>Na<Subscript>0.3</Subscript>)-analcime: Trigonal deformation of the ANA framework and new low coordinated non-framework positions

The dehydrated form of (Li,Na)-substituted analcime, Li_1.30Na_0.53[Al_1.83Si_4.17O₁₂], has been prepared and investigated with single crystal X-ray diffraction: a = 32.167(6) Å, b = 18.551(2) Å, c = 11.693(2) Å; β = 90.06(1)°, V = 6978(1) ų, Z = 24, space group C2. The structure was analyzed through considering the aluminosilicate framework as a system of tubes composed from corrugated 6-membered rings joint by triples of tetrahedra. Volume decrease by 6.5% and trigonal distortion of the structure are explained by the localization of the non-framework cations in new unusual positions. On dehydration of Li, Na-analcime, 67% of Na⁺ and 20% of Li⁺ migrated from the standard M-positions at the periphery of the tubes into essentially different positions Na^W and Li^L situated on the axes of the tubes. Among the total of the fixed tube positions— 12Na^W and 16Li^L — one half is aggregated in the tubes parallel to [001] and has a planar three-fold coordination by framework O-atoms. The configuration and cation population of the tubes in other directions follow the motif of the “basic” system.     

Na_2O-SiO_2-Al_2O_3-NaCl-H_2O体系中ANA和SOD沸石膜的水热合成

Na2 O SiO2 Al2 O3 NaCl H2 O体系中,以水玻璃和准一水软铝石为原料,分别在堇青石和玻璃载体上水热合成方沸石(ANA)与方钠石(SOD)沸石膜.研究水含量、反应温度、反应时间与多次合成对膜结晶的影响.用XRD,SEM,EDX表征膜的晶相、形貌和化学组成.堇青石负载方沸石膜在对 95 %(wt.)乙醇水溶液的渗透蒸发实验中,水优先透过沸石膜的选择性显示了晶间孔的醇/水分离作用.非计量的NaCl进入到在玻璃载体上成膜的方钠石笼中,致使该膜显示光致变色效应     

Micro‐Raman spectroscopy on analcime and pollucite in comparison to X‐ray diffraction

Natural and synthetic samples of analcime and pollucite (both zeolites belonging to the analcime group) were studied by means of micro‐Raman spectrometry, X‐ray fluorescence analysis (XFA) and X‐ray diffraction (XRD). On knowing the chemical and structural characteristics of each solid‐solution member, the observed shift in the spectral position of the Raman active modes can be explained and used for phase determination. As shown, the distinction between members of the analcime–pollucite solid‐solution series using Raman spectroscopy is significantly more conclusive than the corresponding XRD findings. Also, information about the structurally bound water inside the zeolite structure can be gained using Raman spectroscopy as long as a suitable exciting wavelength is selected. Copyright © 2008 John Wiley & Sons, Ltd.