模板剂合成ZSM-35动力学模拟计算

通过分子模拟途径,将吡咯烷、乙二胺、正丁胺三种有机模板剂与ZSM-35沸石骨架间非成键互作用的能学分析分别于它们的合成实验结果进行对照,论证模板剂与沸石间非键相互作用能与合成速率的关联。发现处于十员环孔道中的上述三种模板剂与ZSM-35骨架间非成键互作用能从小到大的顺序与晶化速率从快到慢的顺序一致。     

模板剂在分子筛合成过程中的作用机理

启用分子模拟途径,通过Lennard-Jones势对模板剂分子与分子筛骨架间非成键作用的能学分析,论证n=5、6的双季铵盐［(CH₃)₃N(CH₂)_nN(CH₃)₃］Br₂在ZSM-50分子筛骨架合成过程中所起的模板作用。     

丙烯在ZSM-5沸石上齐聚反应的研究Ⅰ. 模板剂用量对丙烯齐聚反应的影响

考察了不同正丁胺(NBA)模板剂用量合成ZSM-5沸石的物化特性和催化性能.采用XRD、SEM、NH3-TPD和BET等手段对合成样品的物化特性进行了表征.结果表明,模板剂与SiO2摩尔比在0.67～0.22时合成的ZSM-5沸石结晶度高于90%;随着模板剂用量的减少,ZSM-5沸石的平均粒径减小,强酸量也存在相同的趋势.丙烯齐聚反应评价结果显示,模板剂用量对合成ZSM-5沸石的催化活性有显著影响,模板剂与SiO2摩尔比在0.67～0.45之间合成的沸石催化性能较好.     

以一种新型Gemini表面活性剂作为介孔模板剂通过转晶过程合成介孔ZSM-5分子筛

将一种新型Gemini表面活性剂,丙撑基双(十八烷基二甲基氯化铵)[C18H37(CH3)2–N+–(CH2)3–N+–(CH3)2C18H37]Cl2(C18-3-18),作为介孔模板剂用于水热法合成介孔ZSM-5分子筛.结果表明,在130 oC低温晶化即可高效合成介孔ZSM-5分子刷.C18-3-18的加入量可影响到所合成介孔ZSM-5分子筛的相对结晶度和织构性质,它的形成遵从一个转晶过程.在合成初期,凝胶中介孔模板剂C18-3-18的使用导向了介孔材料的生成;随后在TPABr的模板作用下,介孔材料慢慢转晶生成具有MFI结构的介孔ZSM-5;然后所合成的介孔ZSM-5晶粒进一步长大并聚集形成块状颗粒,同时产生晶间介孔.C18-3-18作为介孔导向剂不仅可用于合成介孔ZSM-5分子筛,也可用于其它介孔分子筛的合成中.     

丙烯在ZSM-5沸石上齐聚反应的研究 Ⅰ. 模板剂用量对丙烯齐聚反应的影响

考察了不同正丁胺（NBA）模板剂用量合成ZSM-5沸石的物化特性和催化性能。采用XRD、SEM、NH3-TPD和BET等手段对合成样品的物化特性进行了表征。结果表明，模板剂与SiO2摩尔比在0.67～0.22时合成的ZSM-5沸石结晶度高于90%；随着模板剂用量的减少，ZSM-5沸石的平均粒径减小，强酸量也存在相同的趋势。丙烯齐聚反应评价结果显示,模板剂用量对合成ZSM-5沸石的催化活性有显著影响，模板剂与SiO2摩尔比在0.67～0.45之间合成的沸石催化性能较好。     

高硅沸石合成中四氢呋喃模板作用的初步研究

在四氢呋喃(THF)-Na~2O-SiO~2-Al~2O~3-H~2O体系中,水热条件下合成出的沸石相,随配料硅铝比提高,依次为MOR(丝光沸石),ZSM-35,ZSM-5和ZSM-39,1^3^CCP/MASNMR谱,TG/DTG/DTA和EDX成分分析方法对沸石中的THF进行表征,1^3^C谱化学位移的显著变化,以及THF高的脱除温度,证明作为模板剂的THF分子进入所合成的沸石结构,并与骨架发生强的相互作用。     

不同硅铝比Cu-ZSM-5纳米片上N2O催化分解

以双季铵盐表面活性剂为模板剂,水热条件下合成了硅铝比(nSi/nAl)为18、26和95的ZSM-5沸石纳米片,采用离子交换方法制备了铜改性的ZSM-5纳米片样品,并测试了其催化分解N_2O性能。结合X射线衍射(XRD)、N_2吸附/脱附、X射线荧光光谱(XRF)、扫描电镜(SEM)、透射电镜(TEM)、氢气程序升温还原(H_2-TPR)、氧气程序升温脱附(O_2-TPD)和原位红外漫反射光谱(CODRIFT)等表征结果 ,探讨了沸石硅铝比对于催化剂N_2O分解性能的影响及其原因。结果表明,ZSM-5纳米片硅铝比越低,CuZSM-5纳米片催化剂的活性越高。催化活性的提高归因于低硅铝比催化剂上Cu~+活性物种可还原性的增强和吸附氧脱附能力的提高。     

模板剂对ZSM—5分子筛的成孔作用

用不同模板剂合成出不同硅铝比的ZSM-5沸石分子筛。在560℃赶除模板剂,经饱合吸冰后,应用多晶X射线衍射测定各样品的结晶度和晶胞体积。实验结果表明,合成氧化铝含量相同的ZSM-5分子筛时,加入不同的模板剂所得分子筛的晶胞体积不等(或称孔体积不等)。据此可以推测,模板剂对合成分子筛的造孔起支撑和定位的作用。     

单一模板线性多胺一步合成多级孔ZSM-5沸石微球

线性多胺模板剂(二乙烯三胺(DETA)、三乙烯四胺(TETA)、四乙烯五胺(TEPA))作为单一模板合成了均匀的10-15 μm的多级孔沸石ZSM-5微球. 实验发现, 在水热过程中, 50 nm纳米的沸石晶体粒子自发地堆积成微球, 并且这些微球具有较大的介孔体积, 在傅-克烷基化反应中具有高的催化活性. 同时,我们发现线性多胺起到了模板剂和空隙填充剂的多重功能,这点明显不同于以前我们报道的线性二胺作为模板剂在合成ZSM-5沸石时,主要是起模板剂的作用.     

模板分子TMEDA在CF-3及ZSM-39沸石笼中的位置及其与骨架的相互作用

用XRD、FTIR、IG-DTA、~(13)C魔角固体核磁共振表征了用四甲基乙基二胺(TMEDA)为结构异向剂合成的高硅沸石CF-3及ZSM-39.TMEDA不同基团的~(13)C化学位移,共振峰相对强度在交叉极化(CP)及高功率去偶(HPDEC)核磁共振谱中的变化,揭示出模板分子在尺寸不同的沸石笼中的位置、运动状态及其与骨架的相互作用.在ZSM-39沸石中的TMEDA分子,它的-C_2H_4-基团~(13)C共振峰明显窄化,向高场的异常位移以及它与-CH_3基团~(13)C共振峰相对强度在CP及HPDEC谱中的明显变化,说明为2个相邻的[5~(12)6~4]笼所共有的TMEDA分子,其-C_2H_4-基团与这2个笼所共用的六氧元环的氧原子有强烈的相互作用.     

Synthesis and catalytic performance of ZSM-5/MCM-41 composite molecular sieve from palygorskite

ZSM-5/MCM-41 composite molecular sieve has been hydrothermally synthesized through a two-step crystallization process using palygorskite (PAL) as silicon and aluminum source. The products were characterized by various means and their catalytic properties for acetalization of cyclohexanone and esterification of acetic acid and n-butanol were also investigated. In the first step ZSM-5 zeolite could be formed from the acid-treated PAL after hydrothermal treatment using tetrapropylammonium bromide as template. XRD patterns, N₂ adsorption and desorption data, and TEM images show that the composite obtained in the secondary step had a well-ordered mesoporous MCM-41 phase and a microporous ZSM-5 zeolite phase. Compared with ZSM-5, ZSM-5/MCM-41 composite possessed more total acid amount, weak acid sites and large pore structure due to the formation of MCM-41 and exhibited higher catalytic activity for the acetalization and esterification reaction.     

Controllable synthesis of composites of ZSM-5 and KIT-1 using an ionic liquid as template

ZSM-5/KIT-1 composites were synthesized using an ionic liquid as a template. The structures and morphologies of as-obtained products were characterized using an infrared spectroscopy, X-ray diffractometer, N₂ adsorption/desorption, scanning electron microscopy and transmission electron microscopy. The resultant zeolites show a fully crystalline microporous MFI zeolite framework and a three-dimensional network of short worm-like channels. Mesopores and microspores of 4.2 and 0.8 nm in diameter coexist in the zeolite composites. Moreover, the ratio of ZSM-5 and KIT-1 could be simply adjusted by controlling the pre-crystalline time. We believe that the strategy for fabricating ZSM-5/KIT-1 through a simple method could potentially promote the large-scale production of zeolite composites.     

ZSM-5分子筛的粒径可控合成及其在甲醇转化中的催化作用

以四丙基氢氧化胺为模板剂、聚乙二醇为添加剂,水热合成了粒径在0.1～14 μm且分布均一的ZSM-5分子筛,并采用XRD、SEM、BET、Py-IR、NH₃-TPD和ICP等技术对其进行了表征,考察了不同粒径分子筛在甲醇转化制碳氢化合物反应中的催化作用。结果表明,通过调变PEG添加量、硅源种类和水含量以及控制陈化和晶化条件,可以在较大范围内调变分子筛晶粒尺寸。随着粒径的减小,ZSM-5晶粒的聚集程度、比表面积和Si/Al比提高,而结晶度、BrØnsted酸浓度和总酸量有所下降。在甲醇催化转化制碳氢化合物的反应中,粒径为0.1 μm的分子筛催化稳定性最好;随着粒径的增大,其稳定性逐渐下降,粒径为14 μm的分子筛催化剂寿命明显降低。同时,粒径对甲醇转化产物分布也有较大影响;小粒径分子筛有利于生成轻质烃类(C₁～C₄),而大粒径分子筛对C₅以上烷烃和芳烃的选择性较高。     

ZSM-5、ZSM-57分子筛和丝光沸石间的转晶规律

考察了硅铝比、碱度、有机胺模板剂、晶化时间及温度等合成条件对ZSM-5、ZSM-57 分子筛和丝光沸石之间相互转晶的影响. 发现较高的碱度、较长的晶化时间有利于合成丝光沸石；较低的碱度、较高的诱导晶化温度、较长的晶化时间有利于合成低硅铝比的ZSM-57 分子筛；合成低硅铝比的ZSM-5分子筛则需要在能合成丝光沸石和ZSM-57 分子筛的碱度区间内精确调节碱度, 缩短晶化时间、降低诱导晶化温度、加入适当晶种, 有利于合成低硅铝比的ZSM-5 分子筛. 合成条件稍微改变, 会导致各种沸石之间发生转晶, 晶化产物出现两种或两种以上的晶型.     

Sustainable Synthesis of Core-Shell Structured ZSM-5@Silicalite-1 Zeolite

Core-shell structured ZSM-5@Silicalite-1 zeolite could effectively hinder the deactivation of catalyst surface. Currently, organic structure directing agents(OSDAs) are necessary in the conventional route for the synthesis of this core-shell zeolite under hydrothermal conditions, which is costly and environmental-unfriendly. In this research, a synthesis of the core-shell structured ZSM-5@Silicalite-1 zeolite with a strategy of alcohol filling and zeolite seeding without any organic template or solvent is exhibited. The obtained products are well characterized by X-ray powder diffractometer(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), N₂ sorption isotherms, solid magic angle spinning(MAS) NMR, temperature-programmed-desorption of ammonia(NH₃-TPD), and X-ray photoelectron spectroscopy(XPS) techniques, in order to confirm the core-shell structure. More importantly, the core-shell structured ZSM-5@Silicalite-1 zeolite exhibits a long lifetime and a high p-xylene selectivity in the alkylation of toluene with methanol, compared with the conventional ZSM-5 catalyst.     

ZSM-34分子筛的合成及其催化甲醇转化制烯烃反应性能

以氯化胆碱为模板剂,采用水热合成法在较短的晶化时间内合成了OFF/ERI共晶体ZSM-34,考察了各种合成条件对产物的影响.通过调变合成参数可以获得不同ERI含量的ZSM-34.用X射线衍射、扫描电子显微镜和X射线荧光分析等对合成产物进行了表征.吸附实验显示,所合成的分子筛具有较大的孔容,其对正己烷的吸附容量为11.4%.HZSM-34分子筛对甲醇转化制烯烃(MTO)反应具有良好的催化活性和高的乙烯选择性,低碳烯烃(乙烯 丙烯)选择性高达86.0%,并且在反应过程中始终维持在较高的水平,不受甲醇转化率降低的影响.高温水蒸气处理后的分子筛酸性降低,大大抑制了MTO初始反应中丙烷的选择性,而初始低碳烯烃的选择性则明显提高.     

DRY METHOD SYNTHESIS OF PURE SILICEOUS FORM OF ZEOLITE ZSM-35

IntroductionZeoliteZSM-35isclassifiedasfcrricritc(FER)t\pc.x'hicllalsoincludesZSM-ZI.ZSM-38andFER.Zeolitesofthist}'pcha\lcrclatit'CI}UlldiscrinlinablcXRDpattcnlswhichindicatetheirsinlilarit\'illst,u.tu,.,I11.Thehighsiliceousfonllsofthesezeolitesarcgcllcra…     

Preparation and characterization of nanosized ZSM-5 zeolite using kaolin and investigation of kaolin content, crystallization time and temperature changes on the size and crystallinity of products

Nano sized ZSM-5 zeolite samples were synthesized successively from kaolin clay as alumina source having a large amount of quartz (39%) and silicic acid as silica source by hydrothermal treatment with NaOH in the presence of tetrapropylammonium hydroxide as a template. Then the effect of kaolin content, crystallization temperature and time on the size and crystallinity of the products were investigated. The prepared samples were characterized using XRD, SEM, EDS and FT-IR techniques. The results showed that the synthesized ZSM-5 zeolite samples were almost pure and their crystallization was almost complete. The average particle size, as determined by Debye-Scherrer equation, was in the range of 20-42 nm. Increasing kaolin content on crystal size was more effective than increase in crystallization temperature and time. Additional evidences for the nano sized ZSM-5 zeolite were the asymmetric stretch vibration band at 1225 cm^-1 in the FT-IR spectra and TEM images. The scanning electron micrographs of the synthesized zeolites showed that they are spherical shape crystals.