Si-VPI-5分子筛的多核固体NMR研究

磷酸铝类分子筛是近年来继Y型和ZSM七分子筛之后的第三代合成分子筛材料，其骨架由A10。和P0。四面体均匀交替地组成问．由于带负电行的A10。和带正电荷的PO。四面体数目相等，整个骨架呈电中性，所以这类分子筛本身无离子交换能力和催化活性．当用硅或某些金属离子（如Mg、Fe、Co、Zn等）对磷酸铝分子筛进行同晶取代，就会在骨架上造成电行不平衡，从而使这类分子筛具有一定的离子交换能力和酸性【习．因而对硅或金属离子在磷酸错类分子筛中取代机理的研究一直是人们感兴趣的问题问．Vpl－5是最近才合成出来的具有18圆环一维孔结构的…     

硅源对MCM-22分子筛合成及物化性质的影响

在动态水热条件下,研究了硅溶胶、白炭黑、硅酸及硅胶为硅源时对MCM-22分子筛合成及物化性质的影响。以硅溶胶、白炭黑、硅酸三种硅源均可合成出高结晶度且无杂晶的片状MCM-22分子筛,其平均粒径分别为190、220和750 nm。硅源影响分子筛的聚集形态,三种硅源分别形成晶粒分散、晶粒半分散及晶粒聚集形态。三组样品的酸强度分布基本一致,都具有较多的中强酸分布,由硅溶胶和硅酸所得MCM-22分子筛在中强酸范围具有更高的B/L酸比值,以白炭黑合成的分子筛总酸量最高。NMR结果表明,样品中的铝以骨架铝为主,不存在明显的非骨架铝。由于硅胶对合成体系中游离水的吸附作用,水热反应难以发生,不能得到MCM-22分子筛,硅胶作为分子筛合成硅源时需要选择合适的反应条件。     

Asymmetric Catalysis with Silicon‐Based Cuprates: Enantio‐ and Regioselective Allylic Substitution of Linear Precursors

An enantio‐ and regioselective allylic silylation of linear allylic phosphates that makes use of catalytically generated cuprate‐type silicon nucleophiles is reported. The method relies on soft bis(triorganosilyl) zincs as silicon pronucleophiles that are prepared in situ from the corresponding hard lithium reagents by transmetalation with ZnCl₂. With a preformed chiral N‐heterocyclic carbene–copper(I) complex as catalyst, exceedingly high enantiomeric excesses are achieved. The new method is superior to existing ones using a silicon–boron reagent as the source of the silicon nucleophile.     

无机原料体系合成TS-1影响因素的研究

以廉价的硅溶胶和三氯化钛分别作为硅源和钛源,四丙基溴化铵(TPABr)为模板剂,二乙胺、正丁胺、氨水等作为碱源,在无机体系中合成了TS-1分子筛。采用XRD,IR,UV-vis,SEM,元素分析和N2吸附/脱附等对合成的分子筛进行了表征。详细考察了碱源、硅钛比N2保护、晶种、模板剂用量、硅源及晶化时间等因素对分子筛合成的影响。结果表明,以无机原料合成的TS-1与用传统有机原料合成的TS-1具有同样的特征。碱度的控制是合成的关键,配胶时需N2保护,加入晶种对合成有明显的导向作用,模板剂最低用量有一临界值,硅溶胶作硅源合成的TS-1晶粒比较大。     

以天然矿物为全部硅铝源低成本绿色合成ZSM-5分子筛的研究

ZSM-5分子筛被广泛地应用于催化、吸附分离、离子交换和绿色化工等领域,但目前其合成主要是以无机化学品为硅铝源,从源头来看是非绿色化的过程.我们以热活化的硅藻土和亚熔盐活化的累托土为全部硅铝源,通过调变两种矿物的加入比例调变合成体系的硅铝比,在水热合成体系中制备ZSM-5分子筛.系统地考察模板剂用量、碱度、投料硅铝比、晶化时间等合成条件对产物结构和性质的影响,并对在最优条件下合成的ZSM-5分子筛的物化性质进行了详细地表征,结果表明：以天然矿物为全部硅铝源可以合成出具有较高结晶度、晶粒尺寸约为4 μm的六面体挛晶形貌的ZSM-5分子筛,该分子筛比商业ZSM-5分子筛具有更高的水热稳定性和更优的加氢异构性能.     

Dislocations as active centers in topochemical reactions

The kinetics and mechanism are discussed for the topochemical reaction of Al with Si produced by heat and localized pressure. The structure of the contact zone at the surface of the silicon is used to discuss the role of dislocations as active centers. The activations conditions for the silicon are deduced, together with the effective area of a center. The possible source of dislocations in deformed solids is discussed.     

Silicon Effect on the Enantioselective Transcyanation of Acetyltrimethylsilane Examined by Different Oxynitrilases

The synthesis of optically active （R）- and （S）-2-trimethylsilyl-2-hydroxyl propionitrile by enantioselective transcyanation of acetyltrimethylsilane with acetone cyanohydrin was successfully carded out using defatted plum, loquat , peach, almond or apple seed meals as （R）-oxynitrilase source and using Manihot esculenta leaves as （S）-oxynitrilase source in a biphasic system with good conversion and high enantiomeric excess. Comparative study demonstrated that silicon atom in substrate showed great effect on the reaction and due to the unique characteristics of silicon atom, both the substrate conversion and the product e.e. of the transcyanation of acetyltrimethylsilane were much higher than those of its carbon counterpart 3,3-dimethyl-2-butanone for all examined oxynitrilases.     

The Effects of Various Sources and Templates on the Microwave‐assisted Synthesis of BZSM‐5 Zeolite

Isomorphic substitution of boron into ZSM‐5 zeolite under microwave‐assisted hydrothermal conditions was systematically studied. When microwave treatment and conventional heating were used, BZSM‐5 zeolite could be obtained within one day, whereas the synthesis of BZSM‐5 under conventional hydrothermal conditions took five days at 180 °C. Various parameters that affect the crystallization of BZSM‐5, such as templates, crystallization time, the silicon source and the Si/B ratio were investigated. Systematic variations of these parameters revealed that this zeolite can be obtained from the reaction mixture with optimized ratios of Si/B > 0.6. Among various tested sources, tetraethylorthosilicate (TEOS) turned out to be the best source for synthesis of borosilicate zeolite and further investigations were done with TEOS as silicon source. The obtained products were characterized by XRD, SEM, and IR spectroscopic techniques.     

YOx -MCM-41介孔分子筛的合成与表征

以十六烷基三甲基溴化铵为模板剂,偏硅酸钠为硅源,硝酸钇为钇源,用水热法合成了YOx-MCM-41介孔分子筛,经X射线粉末衍射法,FT-IR,热重分析,紫外漫反射法及N2吸附-脱附法表征。结果表明,该分子筛具有热稳定性好、比表面积大、孔道均一等典型的MCM-41介孔分子筛的特征。     

The Cp*Si+ cation as a stoichiometric source of silicon

The Cp*Si(+) cation acts as a stoichiometric source of silicon in the reaction with the disilenide Tip(2)Si=Si(Tip)Li (Tip = 2,4,6-(i)Pr(3)C(6)H(2)) affording known neutral unsaturated silicon clusters. It thereby provides a conceptually different approach to this novel class of compounds. The proposed mechanism involves a Cp*-substituted cyclotrisilene in which Cp*(-) acts as a leaving group upon single electron reduction or in a nucleophilic substitution step.     

The effect of silicon sources on the mechanism of phosphorus–silicon synergism of flame retardation of epoxy resins

The effect of silicon source on the mechanism and efficiency of silicon–phosphorus synergism of flame retardation was studied. The studied systems composed of a phosphorus-containing epoxy resin and various types of silicon additives including nanoscale colloidal silica (CS), tetraethoxysilane (TEOS), and diglycidylether terminated polydimethylsiloxane (PDMS-DG). Thermal stability and degradation kinetics of cured epoxy resins, elemental analysis of degraded residues, and evolved gases analysis of degradation reactions were conducted with a thermogravimetric analyser, energy-dispersive X-ray spectrometry, and gas chromatography–mass spectrometry, respectively. Addition of silicon compounds showed significant effect on enhancing the thermal stability and char yields of the cured epoxy resins. During thermal degradation, TEOS and PDMS-DG exhibited silicon migration to sample surface and CS did not. Self-degradation of PDMS-DG resulted in a silicon loss for PDMS-DG-containing epoxy resin. From the results it was concluded that using TEOS as an additive for epoxy resins and formation of epoxy-silica hybrid structure through sol–gel reactions was a good approach for achieving phosphorus–silicon synergism in flame retardation.     

钛硅分子筛TS-1的合成、表征及催化性能

钛硅分子筛TS-1自Taramasso等［1］首次报道合成以来,由于其优异的选择氧化催化 性能及其催化的反应具有对环境污染轻,反应条件温和等优点而备受关注. 钛硅分子筛的制 备及应用研究是分子筛催化领域中的热点之一. 在经典的合成体系中,四丙基氢氧化铵(TPAO H)常被用作模板剂［2］,这是钛硅分子筛价格较为昂贵的主要原因之一. 国内外学者 都致力于廉价合成体系的开发,Müller等［3］报道了以四丙基溴化铵(TPABr)作模板 剂合成钛硅分子筛. 对于钛源和硅源,人们往往都采用水解趋势较为缓和的钛酯和硅酯,以达 到钛源和硅源的匹配;在合成过程中,要预先将钛酯加入到乙酰丙酮或异丙醇溶剂中进行稀释 ,并对胶液进行蒸醇处理［2,3］. 这使得钛硅分子筛的合成过程更加复杂,并提高了 其合成费用. 本文以钛酸四丁酯(TBOT)和四氯化钛混合原料作钛源,成功地合成出对丙烯环 氧化具有优异催化性能的钛硅分子筛TS-1,避免了上述的复杂步骤,并降低了钛硅分子筛的成本.     

From sand to fast and stable silicon anode: Synthesis of hollow Si@void@C yolk–shell microspheres by aluminothermic reduction for lithium storage

We report aluminothermic reduction enabled synthesis of hollow silicon microspheres from sand, which are further encaged in a carbon shell, resulting in hollow Si@void@C yolk-shell microspheres. The hollow Si@void@C yolk-shell microspheres exhibit superior long-term cyclability and rate capability, which lay a basis for the development of high-performance silicon anode of advanced LIBs.     

Atomically Precise Expansion of Unsaturated Silicon Clusters

Small‐ to medium‐sized clusters occur in various areas of chemistry, for example, as active species of heterogeneous catalysis or as transient intermediates during chemical vapor deposition. The manipulation of stable representatives is mostly limited to the stabilizing ligand periphery, virtually excluding the systematic variation of the property‐determining cluster scaffold. We now report the deliberate expansion of a stable unsaturated silicon cluster from six to seven and finally eight vertices. The consecutive application of lithium/naphthalene as the reducing agent and decamethylsilicocene as the electrophilic source of silicon results in the expansion of the core by precisely one atom with the potential of infinite repetition.     

以SBA-15为硅源合成多级孔SAPO-11分子筛及其在正十二烷临氢异构化中的应用

以脱除模板剂后的SBA-15为硅源和间接模板剂,在水热条件下制备多级孔SAPO-11分子筛,并通过XRD、SEM、红外光谱、氮气物理吸附-脱附等表征手段对样品的晶相、形貌、酸性和织构性质进行表征。结果表明,以焙烧后的SBA-15为硅源合成出纯相的SAPO-11分子筛,且SBA-15已完全转化。合成的SAPO-11样品呈空心的近方柱体形貌,由宽度为100 nm左右的细条聚集而成,晶粒粒径为1-3 μm。与白炭黑、硅溶胶合成的常规SAPO-11分子筛对比发现,添加SBA-15可在SAPO-11中引入介孔孔道,孔径为5-10 nm,且样品以中强度的Brønsted酸为主,弱Brønsted酸相对较少。以正十二烷为探针分子,考察Pt/SAPO-11催化剂的临氢异构化反应性能。结果表明,多级孔Pt/SAPO-11催化剂具有优良的异构化反应性能。催化剂的高活性和选择性与SAPO-11分子筛的酸性质和孔道结构密切相关,中强度的Brønsted酸量的增加有助于活性提高,同时介孔孔道有利于产物扩散,异构产物的选择性明显提高。     

Ag/SBA-15表面催化过程的现场SERS研究

以三嵌段共聚物P₁₂₃为模板剂, 正硅酸乙酯为硅源, 水热合成了介孔分子筛SBA-15, 通过对SBA-15内外表面修饰, 使用银氨溶液和硝酸银溶液作为金属源合成Ag/SBA-15, 透射电镜(TEM)研究表明在SBA-15孔道内较好地分散了颗粒状和棒状的Ag纳米粒子. 以苯硫酚作为探针分子, 研究了负载Ag纳米粒子的SBA-15的SERS效应, 结果表明Ag/SBA-15具有良好的SERS活性. 另外, 该材料对催化硼氢化钠还原对硝基苯酚具有良好的催化效果, 通过结合现场SERS技术, 研究了该催化过程的机理.     

Simultaneous determination of silicon and aluminium in ferrosilicon by instrumental neutron activation analysis with the aid of an Ac-Be isotopic neutron source

A method has been developed for the accurate determination of silicon and aluminium by instrumental neutron activation analysis with the aid of an²²⁷Ac-Be isotopic neutron source. The samples are pellets made of 4.6 g of ferrosilicon and 0.9 g of a pelletizing agent. Each pellet is irradiated twice at two different fast-to-thermal neutron flux ratios. Each irradiation is followed by two integral mode countings. This allows correction for manganese activities and calculation of the fraction of the aluminium activity induced in silicon and aluminium. The method has been tested with laboratory-prepared synthetic samples as well as commercially certified ferrosilicon. For ferrosilicon containing 75% Si, a relative precision of 0.7% for the results of the silicon concentration has been obtained. For aluminium the relative precision varied from 2 to 7% for concentrations of 3.5 to 1.5%.     

Preparation of SiBN films deposited by MOCVD

SiBN films were prepared by the MOCVD method using triethylsilane and triethylboron as source materials. The SiBN films were a mixture of boron nitride and silicon nitride determined by IR spectra. The relationship between the ratio of mixture and the preparation condition is clarified. The ratio of silicon nitride to boron nitride in the films was proportional to the ratio of triethylsilane to triethylboron under a large excess of ammonia flow condition. The reaction temperature also influenced the ratio of boron nitride and silicon nitride in the films. The deposition rate of the film increased up to 800°C with a maximum at 1000°C, and decreased up to 1300°C with small value. The crystallinity of SiBN films was very poor because the crystal growth was obstructed.     

Boraformylation and Silaformylation of Allenes

The boraformylation of allenes with B₂(pin)₂ and a formate ester as boron and formyl source, respectively, proceeds in the presence of a copper catalyst. The reaction selectively affords the corresponding β‐boryl β,γ‐unsaturated aldehydes in good to high yields. Furthermore, the silaformylation of allenes was achieved with a formate ester and PhMe₂Si−B(pin) as the silicon source.     

Metallization of dna on the surface

A method to develop DNA fibrils with a length more than a few tens of micrometers, oriented in one direction on the n- and p-type silicon surface is described. A new simple and effective technique is proposed to produce silver nanowires by electrochemical reduction of silver ions bound to DNA using the obtained fibrils as a template, as a result of which DNA molecules fixed on the surface of the n-type silicon single crystal are uniformly covered by silver clusters with a size of about 30 nm. The proposed metallization procedure of DNA on the n-type silicon surface has an advantage in comparison with a similar one for macromolecules fixed on freshly cleaved mica, glass surface, and p-type silicon. n-Type silicon is not only a substrate, but also a source of electrons for silver reduction. The absence of an additional chemical component (reducer) principally distinguishes the proposed method from the others currently known. Atomic force microscopic images of fixed DNA molecules and prepared nanowires are obtained.