模板剂四乙基氢氧化铵的用量对合成的β沸石结构及脱胺的影响

研究四乙基氢氧化铵（TEA-OH）模板剂用量对合成的β沸石的结构及脱胺行为的影响。合成β沸石的模板剂的较佳用量(TEA+/Al)为2.10～1.68,合成的β沸石的相对结晶度均大于84%;β沸石中的铝含量(Al/Al+Si)及骨架铝含量(TdAl/TdAl+OhAl)随晶化混合液的TEA+/Al而变,存在最佳TEA+/Al点为1.9,此时合成的β沸石非骨架铝量最少,结构硅铝比最高;含TEA的β沸石脱胺过程为Hofmann降解反应,TGA测定的失重量、DSC测定的吸热量与β沸石中TEA含量密切相关.     

XRD和FTIR对沸石合成机制的光谱学解析

以粉煤灰为原料,采用优化的水热晶化一步法合成沸石。比较晶化反应过程沸石产物CEC值及化学成分的变化,推断固液体系中物质转换及元素迁移方式和途径。借助XRD,SEM,FTIR等表征反应过程沸石的晶型变化及成核特性,提出可能存在的沸石生成机制。合成产物主要为NaP1型沸石,反应24h后CEC值最大为135mmol/100g。12h后,产物中初步发现NaP1沸石相特征峰和亚晶结构,48h后出现羟基方钠石的特征弱峰。沸石生成过程涉及到固液体系间的物质流动:碱熔融作用将粉煤灰组分侵蚀进入液相体系,为沸石形成提供了原料组分,而固相体系为沸石生长提供骨架结构,液相体系和固相体系分别为晶化反应的"源"和"汇",这是液相转化机制和固相转化机制的客观反映。     

高铁高砂煤矸石合成4A沸石分子筛

以六盘水矿区的高铁高砂煤矸石为原料合成4A沸石分子筛,将煤矸石低温焙烧、盐酸酸浸除铁、高温焙烧后再碱融活化获得了活性原料,最后采用水热晶化的方法,合成了4A沸石分子筛产品.本研究采用单因素实验的方法,考察了合成条件对4A沸石分子筛性能的影响,并运用XRD和SEM对产品进行了表征,结果表明所得产品为4A沸石分子筛,粒度分...     

导向剂法合成U沸石的光谱研究

采用导向剂法合成了β沸石。ＸＲＤ光谱测定表明,导向剂的成活以及β沸石的形成被局限于相对较窄的相区范围内。β沸石的２９Ｓｉ和２７Ａｌ－ＮＭＲ 光谱表征进一步说明β沸石骨架硅铝四面体的排列较为规整,其中Ｎａ＋ 离子起着平衡沸石骨架负电荷的作用。     

导向剂法合成β沸石的光谱研究

采用导向剂法合成了β沸石。ＸＲＤ光谱测定表明,导向剂的成活以及β沸石的形成被局限于相对较窄的相区范围内。β沸石的＾２９Ｓｉ和＾２７Ａｌ－ＮＭＲ光谱表征进一步说明β沸石骨架硅铝四面体的排列较为规整,其中Ｎａ＾＋离子起着平衡沸石骨架负电荷的作用。     

红辉沸石合成A型分子筛的红外光谱研究

以天然红辉沸石合成了A型分子筛，通过XRD、IR光谱研究了其晶化过程。发现在1000-950cm^-1、750一600cm^-1、560cm^-1、460cm^-1处的红外吸收峰随结晶度有规律的变化，初步探讨其反应机理。     

FTIR和XPS对沸石合成特性及Cr(Ⅲ)去除机制的谱学表征

以粉煤灰为原料,采用优化的水热晶化法合成沸石,使用XRD,SEM和ζ电位分析沸石产品的组成特性,借助FTIR和XPS等揭示废水中Cr(Ⅲ)的去除机制。合成产品主要为NaP1型沸石,在pH值8～12区间内,ζ电位由-8.72mV降到-24.46mV。准二级方程和Langmuir等温线对试验的拟合效果更好,理论饱和吸附量为33.557 0mg.g-1。FTIR图谱表明—OH和Si—O类官能团在反应过程中有重要贡献。XPS全谱发现:结合能576.45eV为Cr(2p3/2)的特征峰,揭示了吸附过程的有效性。吸附Cr(Ⅲ)后,沸石中Si—Si和Si—O对应的结合能增加了0.25和0.60eV,含Si官能团可能与Cr(Ⅲ)发生了配位反应。O(1s)的结合能在反应后变得更低。这些证据表明:沸石对Cr(Ⅲ)的去除过程是物理吸附和化学吸附共同作用的结果。     

抑制β沸石骨架脱铝的焙烧研究

研究了因焙烧过程升温速率对β沸石模板剂的热分解过程的影响 ,不同升温速率下Naβ沸石焙烧的尾气组成 ;还测定了Naβ沸石的TG -DTG谱 ,40 0℃下Naβ沸石的FTIR谱图 ,以及在不同温度下焙烧 4h后的XRD谱图及2 9Si、2 7Al的NMR结果 .根据这些结果 ,提出了分段焙烧脱胺方法 ,使有机胺在 2 6 0～ 42 0℃间的两个恒温段充分发生Hofmann降解反应 ,从而使分解产生的乙烯和水蒸气能够随空气流自然排出焙烧体系 ,可使焙烧过程中产生的热能得到分阶段逐步地释放 ,同时可避免高温下沸石骨架水热脱铝的负作用 ,得到骨架脱铝少、结晶度高的脱胺 β沸石 .     

Pb液滴在Ni基底润湿铺展行为的分子动力学模拟

采用分子动力学方法研究了Pb液滴在Ni(100)晶面、(110)晶面和(111)晶面的铺展润湿行为. 结果表明: Pb液滴在Ni(100)及(111)基底上的润湿铺展现象呈各向同性, 而在Ni(110)基底上的润湿铺展现象呈明显的各向异性, 且这种各向异性源于Ni(110)晶面点阵结构上Pb原子沿不同晶向的扩散机制及速度的明显差异; Pb液滴在Ni(111)晶面上铺展时, 未发生表面合金化, 液滴铺展动力学描述近似满足 R² ∝ t, 而液滴在(100)晶面和(110)晶面上铺展时表面产生合金化现象, 铺展动力学关系近似满足 R⁴ ∝ t, 且液滴在(100)晶面上的铺展速度高于(110)晶面上的铺展速度. 关键词： 分子动力学 润湿各向异性 铺展膜 扩散机制     

一元溶剂体系β-HMX球形化结晶形貌的分子动力学模拟

奥克托金(β-HMX)晶体形貌在很大程度上影响其安定性能、流散性和能量输出,其中溶剂对晶习的影响起着很关键的作用,因此研究溶剂对β-HMX结晶形貌影响的微观机理具有很重要的意义.运用分子动力学方法计算了五种溶剂作用下β-HMX五个重要的晶面层与溶剂层的相互作用能,对附着能进行了修正,预测了不同溶剂作用下β-HMX的晶体形貌.结果表明,β-HMX重要晶面与五种溶剂都呈吸引作用,五种溶剂都会对晶面的附着能产生很大影响,抑制晶面的生长速率,除N-甲基吡咯烷酮(NMP)外,其余四种溶剂作用下(020)面的相对生长速率都是最快的,在晶体的最终形貌中消失.二甲基亚砜(DMSO)溶剂作用下的晶体形貌相对比较好, N,N-二甲基甲酰胺(DMF)、环己酮(CH)和NMP溶剂作用下的晶体形貌次之,γ-丁内酯(GBL)溶剂作用下的晶体形貌球形度最差.     

Nanocrystalline zeolite beta and zeolite Y as catalysts in used palm oil cracking for the production of biofuel

Nanocrystalline zeolites with crystal size smaller than 100 nm are potential replacement for conventional zeolite catalysts due to their unique characteristics and advantages. In this study, the synthesis of nanocrystalline zeolite Y (FAU) and nanocrystalline zeolite beta (BEA) under hydrothermal conditions is reported. The effect of crystal size on the physico-chemical characteristics of the zeolite, Y (FAU), and beta (BEA) is reported. The properties of nanocrystalline zeolites Y and Beta with crystal size around 50 nm are compared with the microcrystalline zeolite Y and microcrystalline zeolite beta, respectively. The performance of the nanocrystalline zeolite as a catalyst was investigated in the cracking of used palm oil for the production of biofuel. The nanocrystalline zeolite catalytic activity was compared with the activity of microcrystalline zeolite in order to study the effect of crystal size on the catalytic activity. Both nanocrystalline zeolites gave better performance in terms of conversion of used palm oil as well as selectivity for the formation of gasoline fraction. The increase in surface area and improved accessibility of the reactant in nanocrystalline zeolites enhanced the cracking activity as well as the desired product selectivity.     

Facile synthesis of mesoporous ZSM-5 aided by sonication and its application for VOCs capture

Application of ultrasound power to the mother liquor is popular pretreatment for zeolite synthesis which offers a simple way of accelerating crystallization process and finetuning the properties of nanocrystalline zeolites. In this work, sonication-aided synthesis of mesoporous ZSM-5 at low temperature and ambient pressure was systematically studied, in an attempt to reach efficient and benign synthesis of zeolites with hierarchical pore structure, which has wide applications as catalysts and sorbents. The effects of sonication duration, power density, sonication temperature and seeding on the crystallization of ZSM-5 were investigated. The obtained samples were characterized by XRD, SEM, BET and VOCs capture. High quality mesoporous ZSM-5 can be obtained by a facile 5 d synthesis at 363 K, much faster than conventional hydrothermal synthesis. The reduced synthesis time was mainly attributed to the enhanced crystallization kinetics caused by the fragmentation of seeds and nuclei, while sonication radiation had little impact on the nucleation process. Compared with control sample, mesoporous ZSM-5 prepared by sonochemical method had higher surface area and mesoporosity which demonstrated improved adsorption performance for the capture of isopropanol.     

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。     

模板剂在沸石合成过程中的作用机理研究

通过分子模拟途径,对有机模板剂的分子与沸石骨架间非成键互作用的能学分析,论证不同工的双季铵盐「（ＣＨ３）３＋／Ｎ（ＣＨ２）ｎＮ＋／ｎ（ＣＨ３）３」２Ｂｒ在四种沸石（ＺＳＭ－５０、ＺＳＭ－１２、ＮＵ－８７和ＺＳＭ－２３）合成中所超的模板作用。主为这种模板作用可用非成键互作用能定量表达;在一定程度上解释了Ｍ等人固定胶凝条件、实验考察以双季铵盐系列作为模板剂的合成结果。     

Key factor affecting the structural and textural properties of ZSM-5/MCM-41 composite

ZSM-5/MCM-41 micro/mesoporous composite materials were synthesized by the hydrothermal technique with alkali-treated ZSM-5 zeolite as source of silica and aluminum and characterized by various physico-chemical techniques such as X-ray diffraction (XRD), nitrogen sorption at 77 K, transmission electronic microscopy (TEM), FTIR spectroscopy and NH₃ temperature programmed desorption (TPD) techniques. The effect of concentration of CTAB in the synthesis of these solids has been investigated, the mesopore volume, surface area and surface acidity decrease with increasing the concentration of CTAB. Increasing the CTAB concentration causes the recrystallization of zeolite ZSM-5 and it disadvantage the formation of mesoporous materials MCM-41. The catalytic activity of ZSM-5/MCM-41 materials has been evaluated in the Friedel–Crafts acylation of anisole with benzoyl chloride as alkylating agent. The results revealed the reaction to be influenced by surface area, pore volume and surface acidity.     

Ultrasound-assisted rapid hydrothermal design of efficient nanostructured MFI-Type aluminosilicate catalyst for methanol to propylene reaction

The influence of ultrasound-assisted rapid hydrothermal synthesis of aluminosilicate ZSM-5 catalysts was examined in this work. A series of MFI-type nanostructured materials with sonochemical approach and conventional heating were synthesized and evaluated for conversion of methanol to propylene reaction. The prepared samples were tested by characterization analyses such as XRD, FESEM, BET-BJH, FTIR, TPD-NH₃ and TG/DTG. The obtained results confirmed that ultrasound treatment enhanced the nucleation process and crystal growth for ZSM-5 sample synthesized at moderate temperature of 250 °C. Therefore, it was found the formation of pure MFI zeolite with high crystallinity and improved textural, structural and acidic properties for ZSM-5(UH-250) sample compared with the other zeolites. This observation was attributed to the relationship between the perfect crystallization mechanism and catalytic properties, which led to producing an efficient MFI zeolite toward the optimal catalytic performance. In this manner, the methanol conversion and products selectivity of prepared materials were carried out in MTP reaction at 460 °C and atmospheric pressure. The ZSM-5(UH-250) zeolite with slower deactivation regime exhibited the constant level of methanol conversion (84%) and high propylene selectivity (78%) after 2100 min time on stream. Moreover, the synthesis pathway for MFI zeolite at moderate temperature and also deactivation mechanism of improved sample were proposed.     

Successive,Seed‐Mediated Growth for the Synthesis of Single‐Crystal Gold Nanospheres with Uniform Diameters Controlled in the Range of 5–150 nm

A simple and robust route is described to the synthesis of single‐crystal Au nanospheres with diameters controlled in the range of 5 nm to 150 nm. The success of this synthesis relies on the use of single‐crystal Au spheres with different diameters as the seeds for successive growth and the use of a slow injection rate for the precursor to enable surface diffusion for the atoms added onto the surface of a seed. The diameters could be precisely controlled by varying the size and/or number of the seeds. The products exhibit excellent uniformity in terms of both size and shape and they are expected to find widespread use in a number of applications, including self‐assembly, fabrication of metallodielectric photonic crystals, plasmonics, and biomedical research.     

氢在A、X及ZSM-5型沸石上的高压物理吸附

采用常规体积吸附装置测定了77、195、293K和7MPa的条件下氢在A、X及ZSM-5沸石上的吸附特性和吸附容量．所有的氢吸附等温线基本符合Ⅰ型等温线,但在77K,压力为2-5MPa的等温线上观察到了超临界高压吸附所特有的最大吸附量．从等温线确定了等量吸附热并讨论了其影响因素．根据骨架结构和所含阳离子类型的差异,各种沸石表现出不同的氢吸附量．其中NaX沸石在77K/4MPa下的重量储氢分数为2．55％,是该实验中所测得的最高吸附量．CaA、NaX和ZSM-5沸石的氢吸附量与其比表面积成正比,这与沸石中的可用空穴容积有关．然而NaA和KA沸石不存在这种线性关系．实验中还观察到,NaA与KA沸石间出现氢吸附量的临界值是由KA沸石中较大的阳离子堵塞效应引起的．该实验将吸附质分了的动力学直径与沸石主晶孔的有效直径之比用于判断物理吸附中的堵塞效应．     

CuCoMn-zeolite双功能催化剂转化生物质基合成气制取液态烃

选用四种不同的分子筛(SAPO-34, ZSM-5, Y, MCM-41)与CuCoMn(高醇合成组元)构成双功能催化剂,利用N₂吸脱附、H₂-TPR、XRD、NH₃-TPD等表征了催化剂的结构性质. 研究了催化剂在生物质基合成气一段法制取液态烃燃料的应用. 相比于CuCoMn催化剂,加入分子筛的双功能催化剂均不同程度地提高了液体烃燃料的选择性及收率,且收率按顺序递减呈CCM-ZSM-5>CCM-SAPO-34>CCM-Y>CCM-MCM-41. 同时,共沉淀法制备的CuCoMn-ZSM-5 (20wt%, Si/Al=100) 具有最佳的CO转化率(76%)及液体产物收率(30%). 相比于CuCoMn氧化物,双功能催化剂的比表面及孔容均得到提高. CCM-ZSM-5具有适中的微孔尺寸和中等强度的酸性,增加CCM-ZSM-5中ZSM-5含量或降低ZSM-5中的Si/Al比,均有利于提高酸性位的数量,主要是较弱的酸性位. 而共沉淀法制备的CCM-ZSM-5具有更好的金属分散性及还原性能.     

The improvement of gas-sensing properties of SnO<Subscript>2</Subscript>/zeolite-assembled composite

SnO₂-impregnated zeolite composites were used as gas-sensing materials to improve the sensitivity and selectivity of the metal oxide-based resistive-type gas sensors. Nanocrystalline MFI type zeolite (ZSM-5) was prepared by hydrothermal synthesis. Highly dispersive SnO₂ nanoparticles were then successfully assembled on the surface of the ZSM-5 nanoparticles by using the impregnation methods. The SnO₂ nanoparticles are nearly spherical with the particle size of ~?10 nm. An enhanced formaldehyde sensing of as-synthesized SnO₂-ZSM-5-based sensor was observed whereas a suppression on the sensor response to other volatile organic vapors (VOCs) such as acetone, ethanol, and methanol was noticed. The possible reasons for this contrary observation were proposed to be related to the amount of the produced water vapor during the sensing reactions assisted by the ZSM-5 nanoparticles. This provides a possible new strategy to improve the selectivity of the gas sensors. The effect of the humidity on the sensor response to formaldehyde was investigated and it was found the higher humidity would decrease the sensor response. A coating layer of the ZSM-5 nanoparticles on top of the SnO₂-ZSM-5-sensing film was thus applied to further improve the sensitivity and selectivity of the sensor through the strong adsorption ability to polar gases and the “filtering effect” by the pores of ZSM-5.