丙烯酰胺的oxa-Michael加成:β-烷氧基丙酰胺的合成

本文利用醇与丙烯酰胺的oxa-Michael加成,合成了一系列β-烷氧基丙酰胺类化合物。通过NMR、HRMS表征了产物的结构。考察了催化剂、反应温度、原料配比对反应的影响。在40℃下,5(mol)%的活化碳酸钾能催化伯醇与丙烯酰胺发生oxa-Michael加成,仲醇的反应活性较低,叔醇及苯酚几乎不反应。温度升高及强碱会导致丙烯酰胺自身aza-Michael加成反应形成二聚体。醇与丙烯酰胺可以在等官能团比的无溶剂条件下反应。分子内的氢键有利于提高仲羟基的反应活性。     

二氧化硅包覆的杂多酸在双氧水存在条件下催化氧化甘油

催化剂的酸性和氧化还原性在催化生物质平台分子转化过程中起着非常重要的作用,杂多酸具有较强的酸性以及优良的氧化还原性,因而杂多酸在生物质催化转化领域备受关注。本文利用溶胶-凝胶法和硅烷化方法将杂多酸催化剂封装在二氧化硅载体内部,随后以傅立叶红外光谱、X-射线衍射仪、热重分析仪、透射电子显微镜、扫描电镜等手段对合成的材料进行了表征。红外光谱表明杂多酸在催化剂中保持了其完整结构,X-射线衍射表明杂多酸高度分散在二氧化硅载体上,电镜表征显示催化剂呈球形纳米颗粒形貌。基于以上表征结果,我们将包覆的杂多酸催化剂应用于甘油氧化,在以过氧化氢为氧化剂,温和反应条件下,合成的材料对甘油氧化具有良好的催化活性,其中对甲酸的选择性大约为70%,对乙醇酸的选择性大约为27%。硅烷化过程对于催化剂循环起着重要的作用,单纯二氧化硅的比表面积为287 m²·g^-1,二氧化硅包覆杂多酸经过硅烷化后,其比表面积降为245 m²·g^-1,而且孔径也有所降低。单纯二氧化硅与水的接触角为0°,而二氧化硅包覆的杂多酸在硅烷化之后的催化剂具有很强的疏水性,与水的接触角为137°。根据这些催化剂表征数据说明硅烷化过程不仅可以显著提高催化剂的疏水性,而且同时限制了载体孔径,阻止杂多酸流失到反应体系中,与传统的浸渍法将杂多酸负载在二氧化硅载体上得到的催化剂相比,催化剂的循环利用性显著提高。反应后的催化剂结构与新鲜催化剂相比,并没有发生明显变化。催化剂经过一次循环后,表面暴露了更多的活性中心,活性稍有提高。催化剂在反应体系中加入强质子酸可以显著提高反应的催化性能,揭示了Bronsted酸在甘油氧化过程中对甘油分子的活化起着重要的作用。     

铯钨青铜的合成及其对甘油脱水制丙烯醛的催化性能

以仲钨酸铵、硝酸铯为原料,乙二胺四乙酸(EDTA)为模板剂和还原剂,采用水热法合成了铯钨青铜,考察了EDTA用量、水热前驱液浓度、铯钨比等条件对水热产物组成及形貌的影响,并以所得产物为催化剂在固定床反应器中进行甘油脱水制丙烯醛的反应研究,发现铯含量对催化性能有较大影响,在Cs/W摩尔比为0. 2∶1时催化性能最好,甘油转化率达到81. 3%,丙烯醛的选择性达到92. 9%。     

Enhancement of oxygen transfer by pressure pulsation in aqueous glycerol fermentation

Aeration plays an important role in the production of glycerol by fermentation with yeast. Effective aeration depends on a number of factors, such as amount of air, fineness of air dispersion, rate of agitation, and time of gasliquid contact. This investigation dealt with the effect of periodic variation in gas pressure on oxygen transfer measured by sulfite oxidation and glycerol fermentation in stirred tanks. The oxygen transfer rate measured with the sulfite oxidation method was improved by 20–30% under the condition of pressure pulsation (PP) at 30°C. The yield and productivity of glycerol were increased by about 26 and 6.8%, respectively, in 48 h by employing a glucose concentration of 250 g/L with PP at 30°C.     

Polymerization of brightly colored emulsions in a glycerol suspension medium

Upon emulsification of a mixture of methyl methacrylate or methacrylic acid monomer, along with divinylbenzene crosslinker and octane porogen into a glycerol suspension medium, brightly colored emulsions form. The bright colors of the emulsion originate from an exact matching of the refractive index of the emulsion droplets with that of the glycerol medium only at certain wavelengths of light – other wavelengths of light scatter. Polymerization of the brightly colored emulsions yields three different latex morphologies depending upon the polymerization temperature and the type of emulsifier, monomer, initiator, or hydrocarbon applied. The latex morphologies obtained range from large porous latex (1–10 μm in size) to medium-sized porous latex (0.1–1 μm in size) to small latex (up to 0.1 μm in size). Electronic Publication     

磷酸锆催化甘油气相脱水制备丙烯醛

以沉淀法、水热合成法和浸渍法制备了磷酸锆催化剂,通过X射线衍射、热重分析、氮气物理吸附、红外光谱和Hammett指示剂法对催化剂进行了表征,并将该催化剂用于甘油气相脱水反应.研究表明,由沉淀法得到的磷酸锆经过400℃焙烧后能达到最佳催化活性,在温和条件下,甘油可完全转化,丙烯醛选择性为81%,反应24h内催化剂失活不明显.不同方法制备的磷酸锆其结构和表面酸性显著不同,催化剂表面酸性对催化剂活性、丙烯醛选择性和催化剂的寿命均有较大影响.     

Telomerization of 1,3-butadiene with glycerol carbonate and subsequent ring-opening lactone co-polymerization

Glycerol carbonate, straightforwardly issued from glycerol, is functionalized by telomerization with 1,3-butadiene by means of a palladium catalyst, to selectively afford the linear octadienylglyceryl carbonate. Further hydrogenation of the double bonds gives the saturated functionalized product. The resulting glyceryl carbonate ethers are tentatively co-polymerized with lactones in the presence of a neodymium initiator. Copolymers with up to ca 4 mol % of inserted carbonate are received. The rather low amount of inserted co-monomer is found sufficient to modulate the thermal behavior of polycaprolactone.     

Glycerol as a promoting medium for cross-coupling reactions of diaryl diselenides with vinyl bromides

We described herein the use of glycerol as a novel solvent in the cross-coupling reaction of diaryl diselenides with vinyl bromides catalyzed by CuI. This cross-coupling reaction was performed with diaryl diselenides and (Z)- or (E)-vinyl bromides bearing electron-withdrawing and electron-donating groups, affording the corresponding vinyl selenides in good to excellent yields. The mixture glycerol/catalyst can be directly reused for further cross-coupling reactions.