有机添加剂对抑制锌粉催化合成炔基硅烷副产物的影响

锌粉催化苯乙炔与氯硅烷的硅烷化反应产物中会形成约33%端烯副产物。通过添加有机物作为H捕捉剂,利用气相色谱对产物进行分析,研究其对抑制端烯副产物形成的影响。实验结果表明,当使用吡啶和1,8-二氮杂二环十一碳-7-烯（DBU）时,可有效提高选择性。分别对有机添加剂的浓度、反应时间和温度进行了优化。浓度优化结果表明,添加6 mol吡啶或DBU时,副产物含量均明显降低,转化率相对提高,且添加吡啶时效果更显著。添加6 mol吡啶时,继续考察反应时间和温度的影响,结果发现,反应20 h后,转化率较高,延长反应时间不再明显提高反应的选择性和转化率;提高温度有利于提高转化率,但不利于提高选择性,110℃下反应转化率较高,100℃反应时选择性最好。     

Current approaches to the electrochemical synthesis of organo-fluorine compounds

Recent trends in the synthesis of organo-fluorine compounds using the conventional selective electrochemical fluorination (SEF) route as well as other novel synthetic approaches are presented. In the conventional SEF route, fluorinations of the active methylene group in the side chain as well as unsaturated alkenes have been achieved. In the case of heterocycles, nuclear fluorination is the predominant process. In aromatic compounds, nuclear substitution as well as addition proceeds simultaneously, leading to the formation of a mixture of products. The influence of solvents, supporting electrolytes and adsorption on product yield and selectivity has also been evaluated in recent studies. DME is found to be a superior solvent for the above processes. In the SEF process itself, redox mediators have been employed to minimize passivation and achieve better current efficiencies. Nitrogen bases containing perfluoro alkyl unit have been synthesized using redox catalysts as mediators and trifluoromethylation was achieved by the sacrificial anode technique. The introduction of the trimethyl silyl (TMS) group into the −CF₃ moiety to form very reactive −CF₂—TMS synthon, leads to the synthesis of interesting organic molecules. A brief summary of important biologically active fluoro organic molecules that have been prepared by the electrochemical route is also provided.     

单组分硅烷化聚氨酯密封胶的研制

通过改变SPU预聚体合成的工艺条件、原材料及配比,对单组分硅烷化聚氨酯密封胶的机械性能进行研究。结果发现:在600℃左右,4000分子量的聚醚与MDI反应,再用自制的LZ001偶联剂进行封端,在NCO/OH=1.5-1.8的范围内得到的预聚体,给密封胶带来很好的机械性能。     

一种制作亚微米线条的有效方法

本文介绍利用普通接触式曝光系统和等离子刻蚀机来制作亚微米线条。基本工艺是用深紫外线作为光源，对曝光后的光刻胶在ＨＭＤＳ或ＴＭＤＳ气氛下加热处理，然后采用氧反应离子刻蚀，结果可得到０．７微米的光刻胶线条，其端面完整、侧壁陡直，非常适合于大规模集成电路制造中的剥离工艺。     

Ti-HMS分子筛的合成和气相硅烷化

以工业级正十六胺为模板剂,采用水热法合成了不同Ti含量的Ti-HMS分子筛,并用六甲基二硅氮烷对其进行气相硅烷化。采用X射线衍射、N2吸附、傅里叶变换红外光谱、交叉极化/魔角旋转29Si核磁共振、紫外-可见光谱和电感耦合等离子体原子发射光谱(ICP-AES)对试样进行了表征。以过氧化氢异丙苯(CHP)为氧化剂,用环己烯的环氧化反应考察了Ti-HMS分子筛的催化性能。实验结果表明,合成的Ti-HMS分子筛试样具有典型的六方介孔特征,Ti主要以骨架四配位状态存在,硅烷化显著增加了Ti-HMS分子筛表面的疏水性。以不同Ti含量的Ti-HMS分子筛为催化剂,产物环氧环己烷(CHO)的选择性都超过90%,以凝胶中n(Si)∶n(Ti)=50时所合成的Ti-HMS分子筛为催化剂CHP转化率最高(75.9%)。以硅烷化后的Ti-HMS分子筛为催化剂,CHP转化率和CHO选择性有较大幅度的提高,分别达到80.3%和97.8%。     

A new route for preparation of sodium-silicate-based hydrophobic silica aerogels via ambient-pressure drying

Abstract

An in-depth investigation into the synthesis of hydrophobic silica aerogels prepared by the surface derivatization of wet gels followed by subsequent drying at ambient pressure is reported. The following sol–gel parameters were examined for their effect on the physical properties of the derived aerogels: number of gel washings with water, percentage of hexane or methanol in silylating mixture, molar ratio of tartaric acid: Na₂SiO₃, gel aging period, weight% of silica, trimethylchlorosilane (TMCS) percentage, and silylation period. These parameters were varied from 1 to 4, 0 to 100%, 0.27 to 1.2, 0 to 4 h, 1.5 to 8 wt.%, 20 to 40% and 6 to 24 h, respectively. The properties of hydrophobic silica aerogels synthesized by this new route were investigated in terms of bulk density, percentage volume shrinkage, percentage porosity, thermal conductivity and contact angle with water, and by Fourier transform infrared spectroscopy (FTIR). The as-prepared hydrophobic silica aerogels exhibited high temperature stability (up to approximately 435 °C) as measured by thermogravimetric/differential thermal analysis (TGA-DTA). The optimal sol-gel parameters were found to be a molar ratio of Na₂SiO₃:H₂O : tartaric acid : TMCS of 1 : 146.67 : 0.86 : 9.46, an aging period of 3 h, four washings with water in 24 h and the use of a 50% hexane- or methanol-based silylating mixture. Aerogels prepared with these optimal parameters were found to exhibit 50% optical transparency in the visible range, 84 kg m^?3 density, 0.090 W mK^?1 thermal conductivity, 95% porosity and a contact angle of 146° with water.     

Improved Synthesis of 1,2‐Bis(trimethylsilyl)benzenes using Rieke‐Magnesium or the Entrainment Method

1,2‐Bis(trimethylsilyl)benzene is the key starting material for the synthesis of efficient benzyne precursors and certain luminescent π‐conjugated materials. We now report that it can be conveniently prepared in tetrahydrofuran from 1,2‐dibromobenzene, chlorotrimethylsilane, and either Rieke‐magnesium (Mg^R) or magnesium turnings in the presence of 1,2‐dibromoethane as an entrainer (Mg^e). The most important advantages of these new protocols over the currently best‐established procedure (1,2‐dichlorobenzene, chlorotrimethylsilane, magnesium turnings, hexamethylphosphoramide) lie in the milder reaction conditions (Mg^R: 0 °C, 2 h; Mg^e: room temperature, 30 min vs. 100 °C, 2 days) and in the fact that the cancerogenic solvent hexamethylphosphoramide is avoided. Moreover, the improved protocols are also applicable for the high‐yield synthesis of 1,2,4,5‐tetrakis(trimethylsilyl)benzene, 4‐fluoro‐1,2‐bis(trimethylsilyl)benzene, 4‐chloro‐1,2‐bis(trimethylsilyl)benzene, and 4,5‐dichloro‐1,2‐bis(trimethylsilyl)benzene.     

过氧化氢异丙苯生产环氧丙烷和过氧化二异丙苯的研究

用水热晶化法合成了Ti-MCM-41分子筛,并对其进行甲基硅烷化改性。用X射线衍射、傅里叶变换红外光谱和紫外漫反射光谱等手段对其结构进行了表征,在过氧化氢异丙苯做氧化剂催化环氧化丙烯制环氧丙烷的反应中,考察了催化剂的环氧化性能。结果表明：甲基硅烷化增强了Ti-MCM-41分子筛的表面疏水性,但分子筛的介孔特征仍然保持,...     

The effect of 3-(triethoxy silyl) propyl amine concentration on surface modification of multiwall carbon nanotubes

Abstract

The influence of 3-(triethoxy silyl) propyl amine (TESPA) concentration on Multi Wall Carbon Nanotubes (MWCNTs) modification, is experimentally investigated. The MWCNTs modification were performed by 150, 75 and 25 weight percent (wt.%) of TESPA with respect to MWCNTs weight and the properties of the prepared samples were compared with each other and pristine MWCNTs. The MWCNTs silylation has been confirmed by Fourier Transformation Infrared Spectroscopy due to O-H stretching absorption peak disappearing. The 75?wt.% silyl grafted MWCNTs with increasing at about 26.7% in mean value diameters size owns more uniform morphology among the samples based on Scanning Electron Microscopy images. Also, Thermo Gravimetric Analysis shows that this sample has higher thermal stability because of lower weight loss (9.97%) in coupling agent decomposition temperature range at about 119.5–480?°C. Furthermore, X-Ray Diffraction indicates that the mentioned sample has higher level of amorphous structure with 39% reduction in crystallite size in comparison with the pristine MWCNTs. So, the 75?wt.% of TESPA introduced as the optimal concentration for this type of MWCNTs modification.

• Highlights

• Introduction of silyl compounds as a proper coupling agent to modify the carbon nanotube surfaces

• Determination of optimal silyl compounds concentration to modify the carbon nanotube surface

• Cristallinity in XRD pattern can determine the success of CNTs grafted with silyl compounds

     

硅改性对Zn-IM5分子筛及其丁烷芳构化性能的影响

本文研究了硅改性对于Zn-IM5催化剂表面性质及其丁烷芳构化性能的影响。NH3-TPD表征发现,硅改性不仅减小了强酸以及弱酸的量,而且减弱了催化剂上原有弱酸的强度。硅改性处理削弱了催化剂的酸性、收缩了孔道,因此裂解反应得到抑制,BTX选择性得以提高。本文还研究了硅负载温度以及负载量,最佳条件为50℃,二氧化硅负载量为4.0wt%。