A rapid microwave-assisted derivatization process for the determination of phenolic acids in brewer’s spent grains

A simple and fast method for the TMS derivatization of phenolic acids in a closed vial using microwave irradiation followed by GC/MS analysis is proposed. A full factorial design was used to investigate the effects of two independent variables, namely, time and power of microwave irradiation, on the yield of silylation reaction. The optimal conditions were tested against the classical heating derivatization procedure. No significant differences were found between the classical heating and microwave-assisted derivatization. Chromatographic separation of the nine phenolic acids examined was achieved in 16 min. The mass spectral fragmentation patterns of the derivatives obtained by the proposed method were identical to those from the classical heating. Four different batches of brewer’s spent grain were extracted and analyzed for the total phenolic acid content. Significant differences between the batches of spent grains were found for all analytes. The total phenolic acid content varied between 2688 and 4884 μg/g.     

共沸物分离及深加工

介绍了甲基氯硅烷合成中的副产共沸物[SiCl4(CH3)3SiCl]的主要分离方法:恒沸精馏法和酯化分离法,并分述了共沸物分离后三甲基氯硅烷和四氯化硅的深加工方法。三甲基氯硅烷可用来制备六甲基二硅氧烷、六甲基二硅氮烷、六甲基二硅烷等;四氯化硅可用来制备四丁酮肟基硅烷、四乙酰氧基硅烷、正硅酸乙酯及其缩聚物、烧制气相法白炭黑等。     

Effect of sodium bicarbonate solution on methyltrimethoxysilane-derived silica aerogels dried at ambient pressure

Here we present an economical ambient pressure drying method of preparing monolithic silica aerogels from methyltrimethoxysilane precursor while using sodium bicarbonate solution as the exchanging solvent. We prepared silica aerogels with a density and a specific surface area of 0.053 g∙cm⁻³ and 423 m²∙g⁻¹, respectively. The average pore diameter of silica aerogels is 23 nm as the pore specific volume is 1.11 cm³∙g⁻¹. Further, the contact angle between water droplet and the surface of silica aerogels in specific condition can be as high as 166°, which indicates a super-hydrophobic surface of aerogels.     

活性炭负载AlCl3固体酸催化甲基氯硅烷再分配反应性能与结构研究

以活性炭为载体，采用浸渍蒸发煅烧法制备了负载型AlCl₃固体酸催化剂，并以甲基三氯硅烷(M₁)和三甲基氯硅烷(M₃)的再分配反应为模型反应，在φ20 mm×800 mm的固定床反应器中，310℃、n (M₁/M₃)=1.0、液时空速1.5 h^-1下考察了催化剂的制备条件对其反应活性的影响，并对催化剂的稳定性进行了初步考察.运用N2等温吸附-脱附法、XRD、TG-DSC和吡啶吸附Raman光谱等手段对催化剂的结构和酸性进行了表征.结果表明，较佳的催化剂制备条件为：活性炭经过2.0 mol·L^-1盐酸溶液处理6 h，AlCl₃负载量为1.87 mmol·g^-1，450～500℃焙烧活化;催化剂在100 h内表现出良好的催化稳定性.催化剂的XRD和TG-DSC表征结果表明，AlCl₃负载到活性炭载体上经活化后不再以AlCl₃晶相存在，催化剂在485～600℃时活性组分出现分解;吡啶吸附Raman光谱分析表明催化剂的活性组分为Lewis酸.     

三氯化铝催化有机硅单体副产共沸物歧化反应密度泛函理论研究

AlCl₃催化(CH₃)₃SiCl和SiCl₄的歧化反应体系中可能存在(CH₃)₃SiCl与SiCl₄生成(CH₃)₂SiCl₂与CH₃SiCl₃(反应1),(CH₃)₂SiCl₂与SiCl₄生成CH₃SiCl₃(反应2)和(CH₃)₃SiCl与CH₃SiCl₃生成(CH₃)₂SiCl₂(反应3)等反应。本文采用密度泛函理论对这3种反应进行了研究。结果发现在AlCl₃ 催化剂上,可能发生CH₃AlCl₂中间体生成的分步反应和反应物共吸附反应,对两种情况下3种反应的反应路径均进行了计算,发现3种反应均偏向于以双分子共吸附机理进行。3种反应的能垒排序是反应2 >反应1 >反应3。同时,热力学数据分析发现,在543.15～593.15 K之间,温度变化对反应2的摩尔Gibbs反应能变基本无影响,但在593.15 K时,反应1和反应3的Gibbs自由能变显著减小。这些计算结果显示,如果适当调控反应温度,就能够在保证反应1和3进行的同时,抑制反应2的进行,从而实现歧化产物组成的调控,有利于(CH₃)₂SiCl₂的生成。     

7-ADCA的溶解性研究

经研究确定了7-ADCA最佳溶解路线。     

金属铟促进下有机相中合成高烯丙基醇

主要研究了以四氢呋喃作为反应溶剂,三甲基氯硅烷作为活化剂,金属铟促进下醛与烯丙基溴生成高烯丙基醇的反应。讨论了三甲基氯硅烷的用量及了不同反应底物对反应的影响,得出反应的最佳条件是三甲基氯硅烷与醛的比2/1,并且发现只有吸电子基及卤素取代的芳香醛反应速度较快,收率好,其它醛的反应较复杂。     

聚二甲基硅氧烷薄膜的衬底硅烷化及测试分析

聚二甲基硅氧烷(PDMS)微薄膜可作为高灵敏生物传感器的敏感单元.为了实现敏感单元的制备,往往需要进行揭膜.采用对衬底硅烷化的方法,研究了PDMS微薄膜的揭膜工艺.通过测试其旋涂衬底:玻璃片、Si片的表面静态接触角,实验证明三甲基氯硅烷(TMCS)可改善衬底疏水特性,在硅烷化10 min后,PDMS微米级薄膜可从衬底完整揭下.同时,研究表明浓硫酸和过氧化氢混合液可增强玻璃片亲水性并促进硅烷化,以及在氢氟酸处理Si片时,Si片疏水性随浸泡时间先增强后减弱.     

PE/OMMT nanocomposites prepared by in situ polymerization approach: Effects of OMMT‐intercalated catalysts and silicate modifications

In this article, the surfactants, (2‐hydroxylethyl) octadecyl dimethylammonium nitrate (OH‐C18), hexadecyltrimethylammonium bromide(C16), and mixture of trimethylchlorosilane (TM) and OH‐C18 were ion‐exchanged with cations in the montmorillonite (MMT) to generate three organic MMTs (named as OH‐C18‐MMT, C16‐MMT, and MMMT), leading to different environments of catalyst species in MMT interlayer gallery. Et[Ind]₂ZrCl₂ (abbreviated as EI) was supported on the above three types of OMMTs to prepare the PE/OMMT nanocomposites via in situ polymerization. By contrast, EI/MMMT showed higher activity than EI/OH‐C18‐MMT and EI/C16‐MMT under the same polymerization conditions. The other two types of catalysts, such as [(tert‐Bu)NSi(Me₂)C₅Me₄]TiCl₂ (CGCT) and Bis[N‐(3‐tert‐butylsalicylidene)anilinato] titanium (IV) dichloride (FI) were also supported on the OH‐C18‐MMT for in situ ethylene polymerization. It was found that the activity of FI/OH‐C18‐MMT for ethylene polymerization was much lower than the other two corresponding catalysts under the similar reaction conditions. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Trimethylchlorosilane and Silicon Tetrachloride in Two Novel Methodologies for the Efficient and Mild Aldol Addition of β‐Keto Esters and Malonates to Aldehydes

Efficient and mild aldol additions of β‐keto esters and malonates to aldehydes are described using two novel protocols in the presence of silicon tetrachloride and trimethylchlorosilane, respectively. Scope and limitations of the methods have been discussed. Moreover the stability of the obtained products, trimethylsilyl protection of the hydroxy group, as well as the role of both silicon tetrachloride and trimethylchlorosilane in attaining the final products have been analyzed.