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%。     

Soybean lipoxygenase-promoted oxidation of free and esterified linoleic acid in the presence of deoxycholate

Lipoxygenase (EC 1.13.11.12) catalyzes the reaction between oxygen and polyunsaturated fatty acids to give fatty acid hydroperoxides. Recent work showed that soybean lipoxygenase 1 can oxidize diacylglycerols when deoxycholate is present in the reaction medium. Conditions were sought to maximize 1,3-dilinolein oxidation with a commercial soybean lipoxygenase preparation. It was found that dilinolein was oxidized most rapidly in a multicomponent buffer medium that contained 10 mM deoxycholate between pH 8 and 9. When dilinolein oxidation was conducted in the individual components of the multicomponent buffer, the oxidation rate decreased two- to threefold. Addition of 0.2 M NaCl to one of the components, Tricine buffer, caused a twofold increase in the oxidation rate, demonstrating that high ionic strength is a major factor promoting rapid oxidation in the multicomponent buffer. In the deoxycholate multicomponent buffer, the order of reactivity toward oxidation was monolinolein>methyl linoleate≈ linoleic acid>dilinolein. Competition experiments in which mixtures of the substrates were presented simultaneously to lipoxygenase in the presence of deoxycholate showed that linoleic acid was the most reactive substrate. When no surfactant was present or when the surfactant was Tween 20, linoleic acid was the most rapidly oxidized substrate. Overall, the results demonstrate that monolinolein and methyl linoleate are just as reactive, or more so, as linoleic acid to oxidation by lipoxygenase under specified reaction conditions. In competition experiments, linoleic acid oxidation predominates, probably because its free carboxyl functionality allows it to be preferentially bound to the active site of lipoxygenase.     

Lipoxygenase as a versatile biocatalyst

This review of lipoxygenase and lipoxygenase pathway enzymes focuses on the potential for the efficient production of useful compounds. Although the existence of lipoxygenase has been inown for many years, only recently has there been progress toward understanding the conditions required to improve yields and immobilize its activity. Maintaining a high O₂ tension is necessary to obtain good yeilds of hydroperoxides; whereas, partial anaerobic conditions can lead to hydroperoxide decomposition. Fatty hydroperoxides, obtained from lipoxygenase action, can serve as precursors for further transformation by either enzymes or chemical reactions. Well over one-hundred products from lipoxygenase-generated hydroperoxides of linoleic acid alone have been described. Examples will be given of the formation of fatty acids with epoxide, hydroxy, ketone, cyclic, and multiple functional groups. The cleavage of fatty hydroperoxides into short-chain aldehydes and alcohols also will be described. Many of the products have biological activity, suggesting a significant physiological function for lipoxygenase.     

Epoxidation of methallyl chloride with t-butyl hydroperoxide

By applying a statistical method of experiment planning the optimum conditions of methallyl chloride epoxidation with t-butyl hydroperoxide have been determined. The influences of the temperature, molar ratio of the methallyl chloride to t-butyl hydroperoxide, catalyst concentration and reaction time on the selectivity of the synthesis of methylglycerol epichlorohydrine in relation to reacted t-butyl hydroperoxide have been examined.     

微量Cu2+对过氧化氢异丙苯热稳定性的影响

为研究微量铜离子（Cu2+）对过氧化氢异丙苯（CHP）热分解的影响,采用绝热加速量热仪（ARC）对CHP及含两种不同浓度Cu2+的CHP进行了绝热分解测试,研究了不同浓度Cu2+对CHP起始的分解温度（To）、最高分解温度（Tf）、绝热温升（△Tad）、最大温升速率（mm）等热力学参数及分解活化能（Ea）的影响,并利用热惰性因子（Φ）对实验数据进行了修正。结果表明：微量Cu2+的加入对CHP分解的热力学参数有影响,而且浓度不同影响不同。如CHP的校正起始分解温度（To,s）和Ea分别为111.28 ℃和170.93 kJ/mol,而加入（1.85×10-3）%或（3.70×10-3）% Cu2+后,相应的参数分别为104.26 ℃、164.73 kJ/mol和98.87 ℃、145.63 kJ/mol。表明微量Cu2+的存在能降低CHP的起始分解温度To,s和活化能Ea,且浓度越高,降低越明显,从而增加了CHP的热分解风险。     

氢氧化钠催化过氧化氢异丙苯分解研究

捅要：为研究过氧化氢异丙苯（CHP）的热稳定性,本文利用C600微型量热仪对CHP和CHP与NaOH的混合物在空气中受热分解的反应和放热特性进行了实验研究。同时通过GC／MS分析了CHP和不同浓度NaOH混合后的产物组成,并利用气相色谱仪对各产物进行了定量分析,结果得出高浓度氢氧化钠催化CHP分解产物主要是2一苯基一2一丙醇,低浓度时的主要产物是乙酰苯。氢氧化钠催化CHP分解产物的组成与其浓度相关。     

The Effect of Pd Precursors on the Catalytic Activity of a Pd/Al2O3 Catalyst for Cumene Hydroperoxide Hydrogenation

Abstract

Abstract Pd/Al₂O₃ catalysts were prepared by wet impregnation using K₂PdCl₄, (NH₄)₂PdCl₄, and Pd(NO₃)₂ as precursors. All catalysts were characterized by means of inductively coupled plasma-atomic emission spectroscopy (ICP-AES), temperature-programmed reduction (TPR), X-ray diffraction (XRD), and CO chemisorption. The results obtained in the hydrogenation of cumene hydroperoxide (CHP) to α-cumyl alcohol (CA) showed that Pd/Al₂O₃ catalyst prepared from Pd(NO₃)₂ exhibited the highest turnover frequency (TOF) value and the greatest deactivation extent, whereas Pd/Al₂O₃ catalyst prepared from (NH₄)₂PdCl₄ displayed the lowest TOF value but the best stability.     

缚酸剂对合成N,N′-二环己基对苯二甲酰胺的影响及其应用

以对苯二甲酰氯和环己胺为原料,添加缚酸剂,合成了N,N′-二环己基对苯二甲酰胺。考察了缚酸剂的种类及用量对产物收率的影响;并以N,N′-二环己基对苯二甲酰胺为β成核剂对聚丙烯进行改性,考察其对聚丙烯性能的影响。实验结果表明,以甲苯为溶剂,以吡啶、三乙胺或三乙胺-吡啶(n(吡啶)∶n(三乙胺)=0.10)为缚酸剂时,适宜的合成条件为:110.6℃、6.0⁶.5 h、n(甲苯)∶n(对苯二甲酰氯)=36.2、n(缚酸剂)∶n(对苯二甲酰氯)=2.46.5 h、n(甲苯)∶n(对苯二甲酰氯)=36.2、n(缚酸剂)∶n(对苯二甲酰氯)=2.4².8;以吡啶为溶剂(又为缚酸剂)时,适宜的合成条件为:115.2℃、4.5 h、n(吡啶)∶n(对苯二甲酰氯)=20.0;与不使用缚酸剂相比,添加缚酸剂可使产物收率从58.0%提高至75.9%2.8;以吡啶为溶剂(又为缚酸剂)时,适宜的合成条件为:115.2℃、4.5 h、n(吡啶)∶n(对苯二甲酰氯)=20.0;与不使用缚酸剂相比,添加缚酸剂可使产物收率从58.0%提高至75.9%⁸1.7%;采用添加缚酸剂合成的N,N′-二环己基对苯二甲酰胺为β成核剂时,可使聚丙烯的抗冲强度从3.95 kJ/m2提高至15.80 kJ/m2。     

苯丙乳液降低残单方法的研究

乳液残余单体含量是评判其品质的一项重要指标。通过不同的后处理剂和不同的滴加工艺,以及不同的方法对同一款苯丙乳液进行处理,分析其残单含量和外观变化,结果表明:采用叔丁基过氧化氢与FF6搭配,以及抽真空的方式能得到最为理想的乳液,其残余单体含量最低。     

过氧化氢氧化-亚铁盐沉淀联合工艺处理含氰尾矿试验研究

某金精矿冶炼企业含氰尾矿中总氰化合物及砷含量较高,采用过氧化氢氧化—亚铁盐沉淀联合工艺对其进行无害化处理,并对试验条件进行了优化。最佳试验参数:除氰阶段为过氧化氢用量2.0 mL/L,pH值6.0~6.5,反应时间2 h;除砷阶段为七水硫酸亚铁用量0.50 g/L,过氧化氢用量1.0 mL/L,pH值6.0~6.5,反应时间1 h。处理后的含氰尾矿压滤渣毒性浸出液中的总氰化合物和砷质量浓度均稳定低于HJ 943—2018《黄金行业氰渣污染控制技术规范》尾矿库处置标准要求,实现尾矿库堆存。