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以十六烷基三甲基溴化铵(CTAB)为模板剂, 钛酸异丙酯为钛源, 通过水热法合成了Ti-MCM-41分子筛催化剂并对其进行了表征, 结果表明, Ti-MCM-41催化剂具有介孔结构, 其孔径约2.0~4.0 nm. 考察了无溶剂条件下Ti-MCM-41对环氧化合物与胺的开环反应的催化性能. 结果表明, 当反应温度和压力分别为145 ℃和2.5 MPa时, Ti-MCM-41(5)对环氧乙烷(EO)与二甲胺(DMA)的反应具有良好的催化性能, 环氧乙烷的转化率和N,N-二甲基乙醇胺的选择性分别为98.37%和86.68%. 表征结果表明, 催化剂骨架中四配位结构的Ti使其表面具有丰富的路易斯酸性位, 该酸性位对环氧化合物与胺的开环反应具有重要促进作用. 此外, 还对Ti-MCM-41催化环氧乙烷与二甲胺开环反应的机理进行了初步探讨. 相似文献
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作为有机强碱,胍类化合物可用于催化多种反应[1 5],并且反应可以在均相、无水条件下进行,不需要相转移催化剂。本文探讨用胍催化邻苯二甲酰亚胺对环氧化合物进行开环。用三光气将二乙胺转变为四乙基脲1,后者用五氯化磷和叔丁胺处理得到1,1,3,3 四乙基 2 叔丁基胍2。用2催化邻苯二甲酰亚胺与末端环氧化合物的反应,实现了环氧化合物的区域选择性开环。合成路线如下:1 实验部分1 1仪器与试剂WC 1型显微熔点仪(四川大学科仪厂),温度计未校正;Carlo ErbaModel1110自动元素分析仪,Varian400MHz核磁共振仪。溶剂和试剂经干燥、重蒸后使用… 相似文献
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报道了一种在水和1,4-二氧六环混合溶剂体系中进行环氧开环反应的有效方法,水和其他的亲核试剂(胺类、叠氮化钠、苯硫酚)在该体系中都可以进攻疏水性的环氧化合物,并以很高的收率得到相应的开环产物.我们认为在该反应中水是一种温和的BrФnsted酸,在反应过程中起着酸催化的作用. 相似文献
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取代脲促进环氧树脂/双氰胺固化体系反应机理 总被引:5,自引:0,他引:5
双氰胺作为环氧树脂的固化剂,由于固化产物具有优良的机械和电性能,广泛应用在汽车、航天及电子等领域中.但由于其固化温度高达180C以上,使应用范围受到很大限制.专利文献曾报道晚衍生物作为环氧树脂/双氰胺固化体系的促进剂,可以使体系的固化温度降低到130~140oC,并且在室温下仍保持一定的潜伏性[‘,’].在以往的研究中,认为取代脉的促进作用在于其与环氧发生反应生成环状化合物2一心竣烷酮和仲胺,仲胺与环氧基进一步反应生成的叔胺可以催化环氧发生阴离子聚合[’~’].实验表明,环氧树脂/双氰胺/取代脉体系的固化温… 相似文献
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The reaction kinetics of bisphenol-S epoxy resin with methyl-acrylic acid in the presence of quaternary ammonium salt catalyst was studied. The reaction rate constants at different temperatures were determined. The reaction is first order with respect to epoxy group, zero order with respect to methylacrylic acid and 0.71 order with respect to quaternary ammonium salt catalyst, respectively. The mechanism of this reaction was discussed. 相似文献
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Carole Rais-Beghdadi Mario A. Roggero Nicolas Fasel Christophe D. Reymond 《Applied biochemistry and biotechnology》1998,74(2):95-103
The efficient removal of a N-or C-terminal purification tag from a fusion protein is necessary to obtain a protein in a pure
and active form, ready for use in human or animal medicine. Current techniques based on enzymatic cleavage are expensive and
result in the presence of additional amino acids at either end of the proteins, as well as contaminating proteases in the
preparation. Here we evaluate an alternative method to the one-step affinity/protease purification process for large-scale
purification. It is based upon the cyanogen bromide (CNBr) cleavage at a single methionine placed in between a histidine tag
and aPlasmodium falciparum antigen. The C-terminal segment of the circumsporozoite polypeptide was expressed as a fusion protein with a histidine tag
inEscherichia coli purified by Ni-NAT agarose column chromatography and subsequently cleaved by CNBr to obtain a polypeptide without any extraneous
amino acids derived from the cleavage site or from the affinity purification tag. Thus, a recombinant protein is produced
without the need for further purification, demonstrating that CNBr cleavage is a precise, efficient, and low-cost alternative
to enzymatic digestion, and can be applied to large-scale preparations of recombinant proteins. 相似文献
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Jun LIU Qing Hua BIAN Ming An WANG Hong Chao GUO Min WANG 《中国化学快报》2006,17(5):606-608
Optically active TADDOL (α, α, α′, α′-tetraaryl-1, 3-dioxolane-4, 5-dimethanol) and the related ligands have played a significant role in asymmetric reactions1. Although several hundreds of different TADDOLs and TADDOL analogues have already been de 相似文献
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螯合金属离子亲和色谱法分离α-氨基酸和肽 总被引:1,自引:0,他引:1
以SephadexG10为基质螯合二价铜离子的亲和色谱法分离α-氨基酸和肽,使之得以完全分离。对分离过程的原理进行了讨论。 相似文献