离子液体功能化salen Mn催化苯乙烯与CO2一锅合成碳酸苯乙烯酯

合成了咪唑离子液体功能化salen Mn配合物(IL-salen Mn),并作为催化剂应用于苯乙烯与CO2一锅合成碳酸苯乙烯酯反应中.以尿素过氧化氢(UHP)为氧化剂、吡啶氮氧化物(PyNO)为助剂,催化苯乙烯高效制备环氧苯乙烷,继而催化环氧苯乙烷与CO2发生环加成反应合成碳酸苯乙烯酯.考察了催化剂种类和用量、助剂用量、氧化剂种类和用量、反应时间、反应温度及CO2压力对上述反应的影响.结果表明,当催化剂IL-salen Mn用量为苯乙烯物质的量的8％、n(苯乙烯):n(UHP):n(PyNO)=1.0:3.0:0.2、环氧化反应温度和时间分别为30℃和5 h、环加成反应温度和时间分别为80℃和12 h、CO2压力为1.0 MPa时,苯乙烯的转化率为90％,碳酸苯乙烯酯收率达到32％.结合前期研究与反应时间动力学结果,推测了该一锅反应的可能机理.     

离子液体功能化salen Mn催化苯乙烯与CO2一锅合成碳酸苯乙烯酯

合成了咪唑离子液体功能化salen Mn配合物(IL-salen Mn),并作为催化剂应用于苯乙烯与CO2一锅合成碳酸苯乙烯酯反应中.以尿素过氧化氢(UHP)为氧化剂、吡啶氮氧化物(PyNO)为助剂,催化苯乙烯高效制备环氧苯乙烷,继而催化环氧苯乙烷与CO2发生环加成反应合成碳酸苯乙烯酯.考察了催化剂种类和用量、助剂用量、氧化剂种类和用量、反应时间、反应温度及CO2压力对上述反应的影响.结果表明,当催化剂IL-salen Mn用量为苯乙烯物质的量的8％、n(苯乙烯):n(UHP):n(PyNO)=1.0:3.0:0.2、环氧化反应温度和时间分别为30℃和5 h、环加成反应温度和时间分别为80℃和12 h、CO2压力为1.0 MPa时,苯乙烯的转化率为90％,碳酸苯乙烯酯收率达到32％.结合前期研究与反应时间动力学结果,推测了该一锅反应的可能机理.     

离子液体功能化salen Mn催化苯乙烯与CO2一锅合成碳酸苯乙烯酯

合成了咪唑离子液体功能化salen Mn配合物(IL-salen Mn),并作为催化剂应用于苯乙烯与CO2一锅合成碳酸苯乙烯酯反应中.以尿素过氧化氢(UHP)为氧化剂、吡啶氮氧化物(PyNO)为助剂,催化苯乙烯高效制备环氧苯乙烷,继而催化环氧苯乙烷与CO2发生环加成反应合成碳酸苯乙烯酯.考察了催化剂种类和用量、助剂用量、氧化剂种类和用量、反应时间、反应温度及CO2压力对上述反应的影响.结果表明,当催化剂IL-salen Mn用量为苯乙烯物质的量的8％、n(苯乙烯):n(UHP):n(PyNO)=1.0:3.0:0.2、环氧化反应温度和时间分别为30℃和5 h、环加成反应温度和时间分别为80℃和12 h、CO2压力为1.0 MPa时,苯乙烯的转化率为90％,碳酸苯乙烯酯收率达到32％.结合前期研究与反应时间动力学结果,推测了该一锅反应的可能机理.     

离子液体催化二氧化碳合成环状碳酸酯的研究进展

概述了以离子液体作为催化剂或作为反应介质,用CO2合成环状碳酸酯的研究进展。离子液体是固定CO2产生环状碳酸酯的适宜催化剂和溶剂,离子液体的话性可以通过添加本身并无活性或低活性的Lewis酸性金属卤化物或金属配合物得到改善。使用离子液体使得合成过程变得更加绿色和简单,因为产品易分离,催化剂可以循环利用,而且不必使用挥发性有害的有机溶剂。     

离子液体中电活化CO2合成有机碳酸酯的研究进展

综述了近年来离子液体介质中CO₂电活化合成有机碳酸酯的研究进展, 着重概述了电催化合成碳酸二甲酯(DMC)和环状碳酸酯的研究现状, 并简述了CO₂间接电活化和直接电活化技术, 以及反应介质、电极材料等因素对反应产物的影响, 对电催化还原CO₂的关键技术和今后研究重点进行了探讨。离子液体具有不易挥发、可循环使用、导电性好、对CO₂有较高溶解度等优点, 在CO₂固定和有机资源化研究中日益受到重视。电化学作为一种环境友好的绿色合成新技术, 在CO₂有机资源化方面有很好的应用前景, 对缓解日益严峻的温室效应、实现CO₂的资源化利用具有十分重要的现实意义。     

钴卟啉-四丁基溴化铵串联催化苯乙烯在氧气和二氧化碳中合成碳酸苯乙烯酯

通过仿生催化,将苯乙烯、氧气(O₂)和二氧化碳(CO₂)直接合成环状碳酸酯在现代化学中极具学术研究意义和工业应用价值。采用钴卟啉-四丁基溴化铵为双组分催化剂,以2-氧代环戊烷羧酸甲酯为助剂,在O₂和CO₂条件下,直接将苯乙烯转化为碳酸苯乙烯酯。系统考察了催化剂用量等因素对催化性能的影响。在最佳反应条件下,苯乙烯的转化率高达99%,环状碳酸酯的收率可达35%。利用在线紫外与在线红外探讨了该串联反应可能的机理。结果表明,钴中心与2-氧代环戊烷羧酸甲酯的环内氧原子配位后活化氧气形成过氧活性物种,进而形成高价钴-氧中间体,其通过传递氧原子给苯乙烯而生成环氧苯乙烷。而后,环氧苯乙烷在四丁基溴化铵的催化作用下开环,并通过CO₂插入反应和分子内闭环反应最终生成环状碳酸酯。     

离子液体和低共熔溶剂催化二氧化碳合成有机碳酸酯的研究进展

离子液体和低共熔溶剂因其良好的溶解与催化能力,可催化CO₂转化为高附加值化学品。本文综述了离子液体和低共熔溶剂催化CO₂转化为有机碳酸酯的研究进展,分析了CO₂与醇生成直链碳酸酯以及与环氧化物生成环状碳酸酯的反应机理;介绍了传统型、质子型、功能化离子液体以及由氯化胆碱、季铵盐与季膦盐、有机碱等作为氢键受体组成的低共熔溶剂,及其在CO₂转化为直链和环状碳酸酯反应中的催化性能;总结了此两类反应中离子液体和低共熔溶剂设计的基本规律;指出了CO₂转化反应中离子液体与低共熔溶剂存在的催化效率低、稳定性不高、后续分离困难等问题,后续研究可结合计算机辅助设计方法,探索更合适的阴阳离子/氢键供受体组合,获得更高效的催化体系。     

功能化离子液体催化合成辛酸苄酯

以苯甲醇与正辛酸为原料合成了辛酸苄酯,咪唑类和吡啶类具有PS(丙烷磺酸基)功能基团的离子液体作催化剂,考察了其阴、阳离子对催化活性的影响。并选择[PSPy]HSO4为催化剂,研究了酸醇摩尔比、催化剂用量、反应温度和反应时间等对酯化率的影响,实验结果表明,催化剂用量为正辛醇的20%(摩尔分数),反应温度120℃,反应时间2.5h,酯化率达95.3%;此外,该催化剂重复使用10次后,酯化率达94.2%。     

离子液体催化碳酸二甲酯和乙醇酯交换合成碳酸甲乙酯

考察了碱性离子液体催化碳酸二甲酯和乙醇酯交换反应合成碳酸甲乙酯的过程, 筛选出催化性能较好的离子液体1-丁基-3-甲基咪唑溴盐（［Bmim］Br）作为催化剂, 并对酯交换反应条件进行优化。结果表明,［Bmim］Br对反应表现出优异的催化性能,在常压、反应温度90 ℃、反应时间12 h、n(碳酸二甲酯)∶n(乙醇)=1∶1和［Bmim］Br用量为碳酸二甲酯质量的2%条件下,碳酸二甲酯转化率为71.1%,碳酸甲乙酯选择性为81.8%。经回收和循环利用 3次,催化剂仍保持较好的催化活性。     

CoTPP-TBAB catalyzed tandem transformation of styrene carbonate from styrene in the presence of O2 and CO2

The direct synthesis cyclic carbonate from styrene, O₂ and CO₂ is of great academic attraction and industrial value in modern chemistry. The metalloporphyrin/tetrabutylammonium bromide was employed as binary catalyst for this reaction in the presence of O₂ and CO₂ by using methyl 2-cyclopentanone-carboxylate as co-catalysts. The effects of reaction parameters on catalytic performance were investigated systematically. Under the optimal reaction conditions, conversion of styrene (99%) and selectivity to cyclic carbonate (35%) were obtained. The possible mechanism of cascade reaction was proposed by using in-situ ultraviolet and infrared spectroscopy. The results show that the cobalt center is coordinated with the ring oxygen atom of methyl 2-oxocyclopentanecarboxylate to activate oxygen to form a peroxy active species, thereby forming a high-valent cobalt-oxygen intermediate, which passes oxygen atoms to styrene and generate epoxy styrene. Then, styrene oxide opened ring under the catalysis of tetrabutylammonium bromide, and finally formed cyclic carbonate through CO₂ insertion reaction and intramolecular ring-closing reaction.     

Polyethylene glycol-supported ionic liquid as a highly efficient catalyst for the synthesis of propylene carbonate under mild conditions

The coupling reaction of propylene and CO₂ to form propylene carbonate (PC) was promoted by an ionic liquid (IL) covalently bound to polyethylene glycol (PEG). The supported ionic liquid, which has both acidic and basic components, proved to be an active catalyst for PC synthesis under mild conditions. The effects of different cations and anions, reaction temperature, CO₂ pressure, and reaction time were investigated. It was demonstrated that the acid group in the catalyst plays an important role in the reaction. With this system, a high PC yield (95%) was achieved under mild conditions (3.0 MPa, 120°C and 4 h) without a co-solvent. In addition, the catalyst was readily recovered and reused. Based on the experimental results, a plausible mechanism for the catalyst was proposed.     

Electrochemical synthesis of dimethyl carbonate from methanol,CO2 and propylene oxide in an ionic liquid

BACKGROUND: Dimethyl carbonate (DMC) can be used effectively as an environmentally benign substitute for highly toxic phosgene and dimethyl sulfate in carbonylation and methylation, as well as a promising octane booster owing to its high oxygen content. Two‐step transesterification from epoxide, methanol, and CO₂ is widely used in the bulk production of DMC. However, major disadvantages of this process are high energy consumption, and high investment and production costs. A one pot synthesis of DMC from carbon dioxide, methanol, and epoxide was, therefore, developed. But the yields of DMC are below 70% due to the thermodynamic limitation. RESULTS: Electrochemical synthesis of DMC was conducted with platinum electrodes from methanol, CO₂ and propylene oxide in an ionic liquid was conducted. The bmimBr (1‐butyl‐3‐methylimidazolium bromide)‐methanol‐propylene oxide system with CO₂ bubbling allows DMC to be effectively synthesized and a high yield (75.5%) was achieved. CONCLUSION: In this electrolysis, redox reactions of substrates, CO₂, methanol, and propylene oxide, on Pt electrodes were carried out, producing the activated particles, CH₃O^?, CH₃OH⁺, CO₂^? and PO^?, resulting in the effective synthesis of DMC with a 75.5% yield in an ionic liquid (bmimBr). Finally, a mechanism for this synthesis reaction was proposed, which is very different from those reported in the literature. Copyright © 2011 Society of Chemical Industry     

Immobilization of new Mn(salen) complex over MCM-41 and its activity in asymmetric epoxidation of styrene

New tetradentate chelates of bis-Schiff bases were synthesized and then these chiral salen ligands were immobilized over mesoporous MCM-41 by using the ion-exchange method. The efficiency of the chiral catalyst was examined in the asymmetric epoxidation of styrene. Chiral Mn(salen) complexes immobilized onto mesoporous MCM-41 were stable during the reaction without any leaching and exhibited relatively high enantioselectivity for epoxidation as compared with homogeneous complexes. This revised version was published online in August 2006 with corrections to the Cover Date.     

碱性嫁接型离子液体催化二氧化碳环加成反应

采用后嫁接法将不同量的1-甲基-3-丙基(三乙氧基硅基)咪唑的氢氧化物(［Smim］OH)嫁接到介孔硅胶(SiO₂)上,采用傅里叶变换红外光谱、元素分析、硅核磁共振及热重分析等技术对所制备的材料进行表征。在无溶剂、温和的条件下,将碱性嫁接型离子液体用于CO₂与环氧丙烷(PO)合成碳酸丙烯酯(PC)的环加成反应来考察其催化活性。结果表明,离子液体［Smim］OH成功地以共价键嫁接到介孔硅胶上得到碱性嫁接型离子液体(GILs),但不同量的［Smim］OH嫁接程度有所不同;在优化条件下,PO的转化率为99.5%,选择性为100%。反应后催化剂经过滤即可分离回收利用,且多次使用仍保持较高的反应活性。