三元硅酸盐玻璃相中Al^(3+)离子结构状态的MAS NMR谱研究

采用魔角旋转核磁共振谱 (MASNMR)技术对CaO Al2 O3 SiO2 三元铝硅酸盐玻璃 (简称CAS)中Al3+离子的占位进行了系统的定量研究 ,获得下列结论 :1 .Al3+在硅酸盐熔体中 ,大部分进入四面体替代 [SiO4]4- 中的Si,成为网络形成子 .另有小部分Al3+在网络骨架之间 ,以六配位、五配位和其他配位形式成为网络的修饰子 .2 .设 η =N(Al3+IV) /N(ΣAl) ,即考察区域内 ,四配位Al3+离子数与全部Al3+离子数之比 .设γ =N(ΣAl) /N(ΣSi) ,即考察区域内全部Al3+离子数与全部Si4+离子数之比 .则单位四面体的非桥氧数 (Onb/T)与 η成反比 .对于不同的γ值 ,Onb/T下降的速率不同 .γ值越大 ,下降的速率也越大 .

^(27)Al和^(29)Si MAS-NMR对Mo/HZSM-5催化剂的研究

使用29Si和27Al固体高分辨核磁技术对甲烷无氧芳构化催化剂Mo／HZSM－5分子筛进行了研究，发现HZSM－5分子筛本体中仅含有少量非骨架Al，Mo物种与分子筛骨架Al及骨架外Al的相互作用随Mo担载量以及焙烧温度的升高而增加，在高温焙烧下，Mo物种会使分子筛骨架严重脱铝，并且生成Al2（MoO4）3新相，最终导致分子筛骨架塌陷，催化性能下降.

煅烧高岭土的NMR研究

采用29Si、27AlMASNMR谱对不同产地高岭在同一煅烧温度及同一产地高岭土在不同煅烧温度的煅烧产物进行了研究.实验结果表明:不同产地高岭土在同一煅烧温度煅烧产物的29SiMASNMR相似,27AlMASNMR谱有所区别,煅烧温度对煅烧产物的29Si、27AlMASNMR有一定影响.

丝光沸石水蒸气/酸浸渍脱铝的多核固体核磁共振研究

采用 1 H,2 9Si,2 7Al魔角旋转固体核磁共振 ( MAS NMR)及 1 H-2 9Si交叉极化 ( CP)技术研究丝光沸石水蒸气 /酸浸渍脱铝过程中各种铝物质的结构与性质 .结果表明 ,丝光沸石上骨架铝原子在水分子作用下 ,生成非骨架四配位铝物质 [Al( OH) 3( H2 O) ],分别在 2 7Al谱 δ45和 1 H谱 δ3 .0处出现共振信号 ,这种铝物质不同于扭曲四配位铝 ,在高温下进一步水合生成 Al( OH) 3( H2 O) 2 和 Al( OH) 3( H2 O) 3,即非骨架五配位和六配位铝物质 .1 H-2 9Si CP和1 H谱证实 ,水蒸气脱铝使丝光沸石产生了大量的硅羟基和铝羟基 .

以四丙基溴化铵为模板剂合成TS-1分子筛的研究

运用1H→13CCP／MASNMR、29SiMASNMR、IR、XRD和元素分析等表征方法，研究了以四丙基溴化铵（TPABr）为模板剂的合成体系中，Ti酯和模板剂用量以及不同碱源对TS-1分子筛的影响，考察了不同Ti含量固体样品催化丙烯环氧化反应．实验结果表明：随着凝胶中Ti酯用量的增加，制得的分子筛结构对称性由单斜晶系逐渐向正交晶系转变，其丙烯环氧化活性也相应增加．尽管凝胶中所加减源只调变凝胶碱度而不起模板剂作用，然而凝胶的强碱环境对骨架钛原子引入有利．当凝胶中TPABr／SiO2摩尔比值在0．05－0.25之间时，TPABr加入量的变化不影响TS－1分子筛中骨架钛含量．

FER型沸石的合成、结构与吸附性质(英文)

在TMEDA(四甲基乙基二胺)-Na_2O-SiO_2-Al_2O_3-H_2O体系(Ⅰ),Na_2O-K_2O-Al_2O_3-SiO_2-H_2-HCO_3^-CO_3^(2-) (Ⅱ)及Py(吡啶)-PrNH_2(正丙胺)-HF-SiO_2-H_2O体系(Ⅲ)中,分别合成了纯相FER沸石及FER硅沸石.用粉末XRD,FT-IR,^(29)Si MAS NMR及TG/DTA等表征其结构性质,并用超微量电子真空吸附天平测定这些沸石样品对正己烷,甲醇和水的吸附等温线.结果表明:各体系合成的样品虽然结晶度高,呈现出FER沸石的典型结构特征,但由于它们的组成和晶格微结构不同,热稳定性与吸附性质有明显的差异.在(Ⅰ)体系中合成的FER沸石层错缺陷少,晶格完美,正己烷与甲醇的吸附量可达到理论值,结构破坏温度为1190℃.红外精细谱及^(29)Si MAS NMR高分辨谱证明FER硅沸石具有十分完美的骨架结构.由于晶胞收缩,它对正己烷与甲醇吸附量略低于理论值,并呈现出高度的疏水性.它的结构破坏温度高于1300℃.在(Ⅱ)体系中合成的FER型沸石结构缺陷多,沸石孔中的钾离子不易被质子完全交换.它的正己烷与甲醇吸附量均较低,而水的吸附量相对较高.吸附现象表明,正己烷和甲醇都被吸附于FER沸石的十元环主孔道中,分压较高时,甲醇可通过八元环进入小笼,而水的吸附性质则主要与各样品的Si-OH缺陷及骨架中的阳离子含量有关.

MFI沸石上对二甲苯的热脱附

The structures of silicalite-1 and H、 Na form of ZSM-5 with various SiO2/Al2O3 ratios were characterized by powder XRD, 29Si MAS NMR, and the desorption process of р-xylene (p-x) on the zeolites was investigated by using TG/DTG/DTA. SiOH defects of ZSM-5 have no relation with the content of structural Al. Silicalite-1 possesses perfect framwork structure without SiOH defects and structural Al. On a curve of TG/DTG/DTA, p-x adsorbed by silicalite completely desorbs in the range of 57-174℃by two steps, accompaned with endothermal effect. While on the TG/DTG/DTA curves of H, Na-ZSM-5, there is a third desorption step of p-x in the range of 180-600℃ with exothermic effect. Below 180℃ the number of desorbed p-x molecules is related to pore space, but over 180℃，it is related to SiOH and positive ion linking with the structural Al.

焙烧对HZSM－5分子筛结构的影响

运用魔角自转固态核磁共振谱（ＭＡＳ－ＮＭＲ），研究了焙烧对ＨＺＳＭ－５分子筛结构的影响．结果表明，高温焙烧将引起ＨＺＳＭ－５分子筛骨架的脱铝，当焙烧温度从５００℃增加到７００℃时，ＨＺＳＭ－５的骨架Ｓｉ／Ａｌ比由１６．７增加至２２．７；而当焙烧温度由７００℃到８００℃时，骨架Ｓｉ／Ａｌ比则由２２．７增加到了４８．５．２７Ａｌ－ＭＡＳＮＭＲ结果表明，从骨架上脱下来的铝，部分地形成了ＮＭＲ不可见的无定形态．随着焙烧温度的升高。

New evidence for microstructural evolution model of acid-activated montmorillonite

Ca-montmorillonite samples from Choushan treated at various acid concentrations were studied using chemical analysis, XRD, 29Si and 27A1 MAS NMR, to investigate the microstructure of the activated montmorillonites. With the increase of acid concentration and dissolution of cations of montmorillonite, the intensity of d(001) decreased obviously and significant changes of the microstructure of Si and Al occurred. There were two new types of structural units of Si atoms formed: (SiO)3SiOH units and Q4(0A1) units. For Al atoms, in the course of activation, the removal of one of a pair of octahedral aluminium atoms from montmorillonite removed two hydroxyl groups and left the other aluminum of the pair in the four-fold coordination. The 27A1 signal at 5 54.0 corresponding to AlIV arose from the four-coordinated Al in the octahedral sheet. This study first confirmed, by 29Si and 27A1 MAS NMR spectra, that the model of microstructural evolution for activated montmorillonite postulated by Thomas et al. (1950)

Studies on Natural CXN Zeolite: Modification, Framework De-alumination and Ion-exchange

A natural CXN zeolite (stilbite, type code-STI) discovered in China was modified with +4NH exchange by using ammonium salt and calcinations (procedure I), or with +4NH exchange followed by treatment with acid (procedure II). The coordination state of Si and Al atoms in the framework, the property of ion exchange, and the adsorption of the H-STI zeolite samples prepared by different modification procedure were investigated with XRD, EDX, 29Si and 27Al MAS NMR, Ag+ ion exchange and N2 adsorption. The results of the investigations indicate that different procedure of the modification made variety on the distribution of the framework Si atoms and Al atoms, the content of non-framework aluminum, and the blocking channels and the shielding effect to the positions of the exchangeable cations. The H-STI zeolite prepared by the procedure II possesses high ion exchange capacity, open and perfect pore system, and high thermal stability.