PS负载acac系列钼配合物的合成、表征及其催化性能

以二乙烯苯交联的大孔聚苯乙烯树脂(PS)为载体,首次制备了高分子配体PS-(OCH2CH2)n-acac(n=0,1,2),并在其上组装入了Mo活性中心而成为催化剂--PS-(OCH2CH2)n-acac-Mo(n=0,1,2);用红外光谱分别对高分子配体及催化剂的结构进行了表征.XPS表征证实催化剂中钼以Mo(Ⅵ)价态存在,此外还对催化剂可能存在的结构进行了分析.实验检测了PS-(OCH2CH2)n-acac-Mo (n=0,1,2)在以n(t-BuOOH)=0.1 mol计,n( (◇)):n(t-BuOOH)=3:1,溶剂用量～10 mL,反应温度～80℃,时间～60 min条件下的催化性能.结果表明,在大孔PS载体上,活性组分与载体间增加2个-(OCH2CH2)-距离的臂长,对催化剂催化性能无明显影响;PS-(OCH2CH2)n-acac-Mo催化剂(n=0,1,2)催化环己烯环氧化活性和选择性优异,其中以PS-acac-Mo催化剂最优,环氧环己烷收率在99.5%以上.用于环己烯环氧化反应经循环使用5次后,t-BuOOH转化率仍高达99%以上,催化选择性并未发现明显减低,仍保持在99%以上.     

Optimisation of olefin epoxidation catalysts with the application of high-throughput and genetic algorithms assisted by artificial neural networks (softcomputing techniques)

An olefin epoxidation Ti catalyst has been optimised by means of high-throughput experimentation involving materials synthesis, postsynthesis treatments, and catalytic testing. Softcomputing techniques for advanced experimental design have been used. The variables explored in the hydrothermal synthesis of Ti-silicate-based catalysts were: concentration of OH⁻, titanium, and surfactant. The probe reaction employed for the optimisation was the solvent-free epoxidation of cyclohexene, with tert-butylhydroperoxide as oxidant. The different catalyst groups detected by clustering analysis were studied by XRD and UV diffuse reflectance. Ti-mesoporous MCM-41 and MCM-48 molecular sieves were among the most active catalysts. The best performing catalysts were tested for epoxidation of different linear olefins.     

Salen-Mn(Ⅲ)和Salen-Mo(Ⅳ)配合物在介孔硅胶上接枝及烯烃环氧化催化性能

通过肽键作用将Salen型金属配合物接枝到介孔硅胶孔道中生成固相催化剂,采用红外光谱、热重分析和元素分析等对制备的固相催化剂进行表征,结果证实,Salen型金属配合物成功接枝到介孔硅胶载体上。以环辛烯和环己烯为反应底物,叔丁基过氧化氢和过氧化氢为氧化剂,比较均相Salen型催化剂和多相Salen型催化剂的催化活性。制备的均相Salen型催化剂和利用肽键键合制备的固相催化剂均具有一定的催化性能,Mo-Salen催化活性更高,是因为叔丁基过氧化氢在Mo-Salen存在下易分解。固相催化剂活性≤75℃时稳定,在氧化剂叔丁基过氧化氢和过氧化氢作用下具有较好的稳定性能。重复实验中,金属离子流失量很小,催化活性和TOF值未降低,表明利用肽键制备的固相催化剂催化活性稳定,为固相催化剂的制备开辟新思路。     

Dendronized polyamides supports for Mo catalysts

Dendronized polyamides of generations 1 and 2 were grafted with ethylenediamine (en) ligands at their peripheries by the condensation of chloromethyl groups and en molecules. The obtained dendronized complexes were further equipped with MoO₂acac₂ to form the catalysts PGn‐en‐Mo. The results of FT‐IR and thiocyanate photometric analysis confirmed the successful immobilization of Mo catalysts on dendronized polyamides. The catalytic properties of PGn‐en‐Mo were first studied in the epoxidation of cyclohexene with tert‐butyl hydroperoxide and exhibited high catalytic activity and selectivity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

环己烯催化环氧化反应的研究新进展

综述了环己烯催化氧化法合成环氧环己烷的最新研究进展。近年来,催化环己烯环氧化越来越受到关注,因为它采用了来源方便和具有环保性质的氧化剂。介绍了环己烯催化环氧化的一些新进展。反应中采用了各种氧化剂如过氧化氢(双氧水),叔丁基过氧化氢(TBHP)和分子氧(O2),以及各种含有各种配体(如席夫碱、卟啉、酞菁和杂多酸)的过渡金属催化剂。对有关反应的机理进行了讨论。     

Epoxidation of cyclohexene over basic mixed oxides derived from hydrotalcite materials: Activating agent, solvent and catalyst reutilization

Synthesis and characterization of basic hydrotalcite-like derived catalysts were carried out and the resulting materials were tested in cyclohexene epoxidation. The reaction being dependent on the activating agent and the solvent of the reaction. Several nitriles and amides were used as activating agents and various compounds of different nature (protic and aprotic, polar and apolar) were analyzed as epoxidation solvents. The highest epoxide yield and cyclohexene conversion were achieved by using benzonitrile and methanol as activating agent and solvent, respectively. In the present work the reutilization of these solids in cyclohexene epoxidation has been tested by regeneration. The catalyst washed with the solvent after one reaction did not enhance the catalytic properties of the fresh solid. Nevertheless the activation of the solid up 600 °C provided a good activity after four runs.     

Grafting polyethylene glycols molybdenum(VI) complexes on ZSPP and their catalytic epoxidation of cyclohexene

A new type of inorganic–organic hybrid materials – zirconium oligo-styrenyl phosphonate hydrogen phosphate (ZSPP) was used to prepare heterogeneous catalysts for olefin epoxidation by grafting polyethylene glycols on ZSPP and subsequently coordinating with MoO₂(acac)₂. The catalysts were characterized by IR, Raman, XPS, XRD, TG, BET and elemental analysis. The catalytic activities of the prepared catalysts were evaluated through the epoxidation of cyclohexene using TBHP as oxidant. The results indicated that conversion and selectivity increased at first and then decreased with increasing numbers of O atoms in the ligands, and the catalyst 2b gave the best catalytic results that the conversion and selectivity was up to 98.9% and 97.4%, respectively.     

Recyclable Pd supported catalysts with low loading for efficient epoxidation of olefins at ambient conditions

Epoxides are a kind of useful synthetic intermediates. This work reports that activated carbon-supported Pd nanoparticles (Pd/C) efficiently catalyzed cyclohexene epoxidation in the presence of molecular oxygen and isobutyraldehyde with 91.5% conversion, 95.6% selectivity to cyclohexene oxide, ~ 400 h^− 1 activity and excellent stability for at least 5 catalytic runs. The epoxidation was examined on Pd catalysts supported on seven supports, and Pd/C exhibited superior catalytic performance possibly due to the inert support surface. The epoxidation reaction on Pd/C is via radical intermediate. Pd/C is also applicable to catalyze other olefins epoxidation.     

新型钨基催化剂上环己烯环氧化反应

烯烃环氧化在现代化学中具有重要的学术和工业价值,但采用绿色氧化剂过氧化氢仍面临传质的挑战。采用过氧缩合法制备了一种新型钨基催化剂,用于过氧化氢与环己烯环氧化研究,环己烯的转化率为51.2%,环氧环己烷的选择性为69.2%。结果显示该催化剂催化活性高,环氧环己烷的选择性好,反应条件温和,工艺无溶剂且绿色环保。     

A high-throughput experimentation study of the epoxidation of alkenes with transition-metal-free heterogeneous catalysts

A set of transition-metal-free heterogeneous catalysts for the epoxidation of alkenes with hydrogen peroxide was studied by means of high-throughput experimentation. The catalysts were tested with a range of substrates. Gallium oxide displayed the highest epoxidation activity with all tested alkenes, followed by Ga-MCM-41. The reaction conditions were optimised by investigating the effect of the solvent in which the epoxidation takes place. Considerable improvements in the epoxide yields were obtained in the processes catalysed by Al-MCM-41, Ga-MCM-41 and zeolite USY_(2.6). This work confirms the versatility of HTE for studying catalytic systems.     

硅烷化含钛介孔分子筛催化环己烯环氧化动力学

研究了气相沉积法制备的硅烷化含钛介孔分子筛(Ti/HMS)催化环己烯与异丙苯过氧化氢(CHP)的环氧化反应的宏观动力学.结果表明:环己烯与CHP的环氧化反应对催化剂的量表现为1级;对于环己烯和氧化剂CHP,随着浓度的增加,反应随之由1级向0级过渡,根据实验结果和反应机理,运用Rideal-Eley方法,提出了硅烷化Ti/HMS催化环己烯与CHP环氧化反应的动力学方程.     

Preparation of Titanium-Containing Carbon–Silica Composite Catalysts and Their Liquid-Phase Epoxidation Activity

Titanium-containing catalysts have been prepared by two different post-synthesis methods using activated carbon and carbon-silica composite as catalyst supports. They have been applied to the liquid-phase epoxidation of cyclohexene with tert-butyl hydroperoxide (TBHP) and H₂O₂. The carbon-silica composite catalyst showed a high conversion and selectivity to epoxide compared to the Ti-carbon catalyst and silica-based catalysts for the cyclohexene epoxidation with H₂O₂. The highest values of cyclohexene conversion and epoxide selectivity were obtained with the carbon-silica composite catalyst having a titanium content of 3 wt%.     

The epoxidation of cyclohexene by dioxiranes over ketone catalysts

In this work, the dioxirane system has been applied to the epoxidation of cyclohexene. The catalytic activity of acetone, butan-2-one and pentan-2-one presented as homogeneous catalysts or supported on inorganic and polymer materials was investigated. It was found that the rate of cyclohexene oxide formation increased in proportion to increasing ketone concentrations using acetone and butan-2-one. Because of the advantages of supported catalysts, ketones were chemisorbed or grafted onto a range of different supports including different forms of silica and various polymers. The presence of carbonyl groups on the surface of the supports was confirmed and their catalytic activity was evaluated. The turnover frequency of the grafted ketones were compared with that of the homogeneous catalysts and design criteria for the further development of supported ketone catalysts were established.     

Synthesis, characterization of high Ti-containing Ti-MCM-41 catalysts and their activity evaluation in oxidation of cyclohexene and epoxidation of higher olefins

A series of titanium rich isomorphous substituted Ti MCM-41 and HMS materials have been synthesized with different Si/Ti ratios. The highest amount of Ti incorporated in synthesis gel is in TiMCM-41 (Si/Ti = 10). Whereas for TiHMS catalysts, Ti is incorporated up to Si/Ti = 50 successfully without forming any extra framework TiO₂. Cyclohexene epoxidation reaction with dry tert-butyl hydroperoxide (TBHP) as an oxidant has been studied to evaluate the catalytic properties of Ti substituted mesoporous catalysts. The effect of molar ratio of substrate:oxidant in this reaction has been studied and high conversion, high selectivity were achieved at 2: 1 molar ratio with TiMCM-41 (Si/Ti =25). Dry TBHP (in dichloromethane) and chloroform were found as good oxidant and solvent system for this reaction. Pure siliceous mesoporous silica and low `Ti' substituted mesoporous silicas were found to be efficient catalysts for oxidation of cyclohexene. An interesting variation of the selectivity from allylic oxidation to epoxidation during oxidation of cyclohexene was observed with an increase in the Ti amount in the mesoporous framework. The allylic oxidation of cyclohexene has been carried out using molecular oxygen as an oxidant and in the presence of a small amount of TBHP as initiator. Siliceous HMS materials gave better conversion compared to MCM-41 type of materials and other conventional silicas like silica gel, fumed silica etc. in allylic oxidation of cyclohexene. Epoxidation of higher cyclic olefins like cyclooctene, cyclododecene, cis-cyclododecene and linear olefins 1-Heptene, cis-2-hexene, 1-undecene was carried out over TiMCM-41 (Si/Ti = 25). Ti substituted mesoporous catalysts were characterized by elemental analysis, XRD, FTIR, UVDRS, ²⁹SiMASNMR, BET surface area and pore size distribution techniques.     

Catalytic activity of ethylene oxidation over Au,Ag and Au–Ag catalysts: Support effect

Au, Ag and Au–Ag catalysts on different supports of alumina, titania and ceria were studied for their catalytic activity of ethylene oxidation reactions. An addition of an appropriate amount of Au on Ag/Al₂O₃ catalyst was found to enhance the catalytic activity of the ethylene epoxidation reaction because Au acts as a diluting agent on the Ag surface creating new single silver sites which favor molecular oxygen adsorption. The Ag catalysts on both titania and ceria supports exhibited very poor catalytic activity toward the epoxidation reaction of ethylene, so pure Au catalysts on these two supports were investigated. The Au/TiO₂ catalysts provided the highest selectivity of ethylene oxide with relatively low ethylene conversion whereas, the Au/CeO₂ catalysts was shown to favor the total oxidation reaction over the epoxidation reaction at very low temperatures. In comparisons among the studied catalysts, the bimetallic Au–Ag/Al₂O₃ catalyst is the best candidate for the ethylene epoxidation. The catalytic activity of the gold catalysts was found to depend on the support material and catalyst preparation method which govern the Au particle size and the interaction between the Au particles and the support.     

In-situ epoxidation using dioxiranes: Evaluation of reactivity and selectivity

The epoxidation of cyclohexene to cyclohexene oxide by dioxiranes in the ketone/oxone system was studied. The catalytic activities of acetone, butan-2-one, pentan-2-one and 1,1,1-trifluoroacetone were investigated. A monophasic and a biphasic system were investigated for this reaction, namely tetrahydrofuran (THF)/water and dichloromethane/water. The THF/water system was found to be more efficient at converting cyclohexene to cyclohexene oxide. It was found that the rate of cyclohexene oxide formation increased in proportion to increasing ketone concentration using 1,1,1-trifluoroacetone, acetone and butan-2-one. Turnover frequencies were in the range 0–2·75 h⁻¹, in sharp contrast to the perceived reactivity of this system. The greater the solubility of a ketone in water the greater its catalytic activity. The selectivity in terms of cyclohexene conversion to cyclohexene oxide was always 100% but the selectivity in terms of KHSO₅ utilisation was generally less than 60%, even in the best experimental conditions. © 1998 SCI     

Synthesis and Characterization of Dendrimer-Templated Mesoporous Oxidation Catalysts

We report here the use of 4th and 5th generation dendrimers poly(propylene)imine (CU-D32 and CU-D64) as templating agents for the synthesis of mesoporous titanosilicate and vanadosilicate oxidation catalysts via solgel techniques. The physical properties of these mesoporous materials were characterized by TGA, BET, PXD and SEM/EDX analyses and these showed that the transition metals are evenly distributed throughout these silicates, which have interconnected spherical pores (approx. 12Å in diameter) and high surface areas of about 650m²g^–1. Kinetic studies showed that all transition metal-doped catalysts were highly selective at oxidizing cyclohexene to the corresponding epoxide. Additionally, CU-D64-templated catalysts were more catalytically active for cyclohexene epoxidation than CU-D32-templated catalysts as a result of differences in pore size. All CU-D64-templated catalysts exhibited epoxidation catalytic activity comparable to that of titanium doped MCM-41 materials.     

Über die Katalyse der PRILEŽAEV-Reaktion

About the Catalysis of the PRILEŽAEV Reaction It is shown that a catalysis of the PRILEŽAEV reaction exists. We investigated the influence of homogeneous molybdenum catalysts on the epoxidation reaction of olefins with percarboxylic acids kinetically. The second order reaction rate data show that the MoO₂(acac)₂ catalyzed cyclohexene epoxidation with peracetic acid runs two times faster than the uncatalyzed reaction and the same epoxidation of oct-1-ene runs 15 to 30 times faster. In the same way the reduction of activation parameters in the catalytic reaction proves the catalytic effect. An influence of catalyst concentration and a formation period at the beginning of the catalytic reaction were observed. The influence of the structure of olefin and of the kind of catalyst were investigated and discussed. A formulation of the transition state is given and discussed in relation to the uncatalyzed PRILEŽAEV reaction and to the Halcon reaction.     

清洁催化氧化合成己二酸的研究进展

综述了近年来以环己烯、环己酮、环己醇或其混合物为原料,以过氧化氢或空气为氧源,用不同催化剂及其配体催化氧化合成己二酸.     

分子筛固载希夫碱锰配合物催化环己烯环氧化

研究了在Mnsalophen／ZSM-5催化剂的作用下,分子氧环氧化环己烯合成1,2-环氧环己烷的反应。结果表明,利用柔性配体法在ZSM-5型分子筛上固载Mnsalphen配合物,随着反应时间的延长和反应温度的提高,环己烯的转化率逐渐增加;1,2-环氧环己烷的收率为先增加后降低,环氧环己烷的最高收率可达到83．38％;催化剂重复使用3次后,其催化活性仅降低了2％。