菱钾沸石中铝在不等价四面体位上分布的~29Si MAS NMR谱研究

根据菱钾沸石^(29)Si MAS NMR实验讨论了骨架Si/Al比(R)和Al在两种不等价四面体位分配比率(r)二者之间必须满足的关系,对于合成原粉,Al择优占据T_B位;用(NH_4)_2SiF_6同晶取代脱铝,T_B位上的Al择优解脱.

菱钾沸石(OFF)的离子交换及对SO_2气体吸附性能研究

采用水热合成法制备了菱钾沸石(OFF),通过离子交换得到了H-OFF,L i-OFF,N a-OFF,K-OFF和C s-OFF.用XRD,SEM,TG,DTA,固体1H NM R,FT IR和低温氮吸附等手段研究了离子交换性质,发现其晶体结构和晶貌在离子交换过程中基本不变,热力学性质随阳离子类型的改变而发生很大变化.样品的比表面积和孔体积随阳离子的增大而减小,B酸随阳离子半径的增大而减小,L酸反之.测定沸石样品对酸性气体SO2的吸附结果表明,L i-OFF在低分压下对SO2有很好的吸附性能.

一种新型共生沸石(T-L)的合成与表征

在Na2O-K2O-Al2O3-SiO2-H2O体系中水热合成了一种新型的共生沸石,它由L型沸石生长在T型沸石的一端而形成,称之为T-L型沸石.通过XRD,SEM,TEM,EDX,IR等手段对其进行了初步的表征.SEM相片表明这种沸石具有特殊的铆钉状外形;在TEM相片上可以清楚地看到L型沸石的大孔道,此孔道与L型沸石的表面垂直.通过EDX的数据计算发现共生沸石的两相有不同的骨架硅铝比:T型沸石部分Si/Al=3.71,L型沸石部分Si/Al=3.41.在该样品中B酸大于L酸.

微波加热法快速合成T型分子筛

Zeoilte T crystals were synthesized by microwave heating and could be crystallized well within 8 h when the template was added in the gel. Compared with the conventional heating method, not only was crystallization time reduced over 80%, but also the crystallinity and surface area of crystals were improved. Similar phenomenon occurred in the presence of seeds. In addition to shorter synthesis time, the smaller crystals with narrower particle size distribution were obtained by the title method. These could be attributed to high heating rate, fast dissolution of gel and homogeneous heating of microwave irradiation.

合成条件对T型分子筛晶化的影响

采用XRD、SEM和ICP表征了合成的T型分子筛样品,考察了水热合成条件对T型分子筛晶化的影响.结果表明,硅源、n(SiO2)/n(Al2O3)、n(Na2O+K2O)/n(SiO2)对结晶的影响很大.当n(SiO2)/n(Al2O3)为16～30和n(Na2O+K2O)/n(SiO2)为0.25～0.40,采用n(SiO2):n(Al2O3):n(Na2O+K2O):n(H2O):n(TMAOH)=1:0.055:0.31:11.67:0.045的初始硅铝溶胶,在温度100℃下反应2 d,可得到高结晶度的T型分子筛.加入晶种、模板剂或控制较低的碱浓度均可以合成以菱钾沸石为主体的T型分子筛.