Heterogeneous Selective Oxidation of Alkenes to α,β‐ Unsaturated Ketones over Coordination Polymer MIL‐101

The mesoporous metal‐organic framework MIL‐101 is an efficient heterogeneous catalyst for the selective allylic oxidation of alkenes with tert‐butyl hydroperoxide. The selectivity towards α,β‐unsaturated ketones reaches 86–93%. The temperature of the catalyst activation strongly affects the ketone yield. MIL‐101 is stable to chromium leaching, behaves as a true heterogeneous catalyst, can be easily recovered by filtration, and can be reused several times without loss of the catalytic performance.     

反-4-(反-4'-正丙基环己基)-环己基乙烯的合成

以顺/反-4-(反-4'-正丙基环己基)-环己基甲酸为起始原料,经酰化、还原、异构化、Wittig反应得到色谱纯度99.9%以上的反-4-(反-4'-正丙基环己基)-环己基乙烯,总收率74.9%。目标产物结构经IR、GC-MS及1HNMR确认。     

A Hydrophobic Gel for Epoxidation of Olefins with Organic Peroxides

The epoxidation of cyclooctene by tert-butyl hydroperoxide (t-BuOOH) over a TiO₂–SiO₂ xerogel made from a permethylated cyclooligosiloxane, tetraethylorthosilicate, and a Ti chloroalkoxide, was carried out in acetonitrile as the reaction solvent. The organic moieties of the hybrid gel (in this case, –CH₃ groups) and the Ti content of the catalyst appear to be stable on prolonged exposure to the reaction medium. Besides very good stability, the hybrid catalyst in this study displays 100% selectivity toward cyclooctene epoxide production. Solid state ²⁹Si magic angle spinning NMR (²⁹Si MASNMR), diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), and chemical analysis were used to monitor the stability of the hybrid material. The kinetics of olefin epoxidation was studied in a batch reactor in the 313–343 K range.     

环己甲醇合成方法和应用

本文介绍了羧酸或其酯还原成醇类的一些还原剂，主要介绍了环己甲醇的一些合成方法和其主要应用考虑到经济性问题，提出了由硼氢化钾或钠作为还原剂的合成路线。     

Laboratory‐Scale Studies of the Impact of Oxygen on Mashing

An assessment of the impact of oxygen and hydrogen peroxide on mashing and wort parameters has been made on a laboratory scale. Oxygen has been stridently eliminated by using an anaerobic chamber during mash analysis. Additionally the relative importance of proanthocyanidin species has been assessed by comparing the behaviour of “conventional” malt and a malt produced from a low proanthocyanidin variety. It seems that oxygen and peroxide act independently in causing the oxidation of thiol‐containing materials and polyphenols in mashes and that oxygen is not primarily exerting its impacts through the intermediacy of peroxide. The removal of thiols (presumably at least in part through the production of disulphide bridges between proteins) and of polyphenols (presumably via polymerisation) both contribute to increased wort turbidity and decreased rates of wort separation after mashing. Three inhibitors (nordihydroguaiaretic acid, ethylenediamenetetraacetate and potassium cyanide) have been employed in an attempt to differentiate between enzymic and non‐enzymic events and also to identify whether lipoxygenase and peroxidase are catalysing key events. Whilst it seems that peroxidase has a key role in catalysing the oxidation of polyphenols by H₂O₂, it does not appear that either peroxidase or lipoxygenase is involved in the removal of measurable thiol. Nonetheless a significant proportion of the thiol elimination is likely enzyme‐catalysed. We have been unable to demonstrate the production of hydroperoxides in mashes, but added hydroperoxide is undetectable, which suggests that these materials are either lost by onward conversion or by adsorption onto spent grains.     

12-磷钨酸催化叔丁醇氧化制备叔丁基过氧化物

以12-磷钨酸作为催化剂,双氧水氧化叔丁醇制备了叔丁基过氧化氢和二叔丁基过氧化物,通过单因素法和正交设计法考察了温度、反应时间、催化剂用量、原料配比等因素对反应的影响,当叔丁醇与双氧水的摩尔比为0.7∶1,叔丁醇与磷钨酸的摩尔比为298.8∶1,反应温度83℃,反应时间3 h时,叔丁醇的转化率可达到95%以上,叔丁基过氧化氢的产率和选择性分别为75.9%和79.6%。     

Ti-MSU分子筛催化1-丁烯氧化制环氧丁烷的研究

通过液相浸渍法制备Ti质量分数为5.5%的Ti-MSU分子筛催化剂,并采用X射线衍射、N2吸附-脱附对催化剂样品进行表征。考察了Ti-MSU催化剂对以过氧化氢异丙苯(CHP)、1-丁烯为原料制备环氧丁烷的反应工艺条件的影响。结果表明,当催化剂床层温度为100℃、反应压力为3.0 MPa、1-丁烯/CHP摩尔比为10∶1、CHP空速为2 h-1时,CHP的转化率达到81.2%,1,2-环氧丁烷(BO)选择性为60.2%,苄醇(DMBA)选择性为87.2%。     

Comparative study of poly(2,3 and 4 methyl cyclohexyl methacrylate)s. Dielectric relaxation spectroscopy (DRS)

The relaxation properties of poly(methyl cyclohexyl methacrylate)s (P2MCHMA), (P3MCHMA), (P4MCHMA) were analyzed. Dielectric spectroscopy (DS) techniques were used for this purpose. These polymers exhibit prominent α peaks, associated to the dynamic glass transitions, and then poorly defined β-relaxations and two other relaxation zones labelled as γ- and δ-relaxation in order of decreasing temperatures. The α relaxation processes were analyzed by means of the free volume theory, using the Vogel-Fulcher-Tammann-Hesse (VFTH) equation and in terms of the Havriliak-Negami (HN) empirical equation. Previously to these analyses, conductive contributions to the loss permittivity were subtracted. The apparent activation energies for the secondary processes under study have been calculated by means of Arrhenius. Comparison with previous relaxation results of poly(cyclohexyl methacrylate) (PCHMA), i.e. the polymer without substituents in the cyclohexyl ring, has been also carried out. In this way, changes in the glass transition absorptions as well as in the secondary processes have been discussed.     

Thermal degradation of single methyl oleate hydroperoxides obtained by Photosensitized oxidation

A peroxidation mixture containing methyl 9- and 10-hydroperoxy-trans-octadecenoates (MOHP) was obtained by singlet oxygen oxidation of methyl oleate. The two hydroperoxides were collected by solid phase extraction and purified separately by high-performance liquid chromatography. Identification and single-isomer purity evaluations were carried out by comparing the chromatographic and gas chromatography-mass spectrometry parameters of the corresponding reduced hydroxy derivatives. Each purified MOHP was thermally degraded and new reaction mechanisms were proposed from the identification of the degradation products. Thermal rearrangement of each hydroperoxide isomer involved an allylic 3-carbon intermediate before further degradation steps. The two MOHP isomers obtained from singlet oxygen oxidation produced all eight hydroperoxide isomers by thermal degradation in the condensed phase at high temperature (200°C). This result supports the assumption of singlet oxygen as a promoter of the first steps of oxidation of food lipids and also reconsiders the Khan mechanism.     

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%。