丙三醇制丙三醇碳酸酯催化研究进展

以丙三醇为原料可通过多种途径制备丙三醇碳酸酯,包括丙三醇与尿素的醇解反应、与碳酸酯的酯交换反应以及与CO、CO_2的羰基化反应等。对丙三醇碳酸酯的合成途径、所用催化剂的性能进行综述,并对其未来进行了展望。     

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。     

碘化铯催化二氧化碳与甘油合成甘油碳酸酯

以不同碱金属(铵)卤化物为催化剂,考察了其在二氧化碳与甘油合成甘油碳酸酯反应中的活性。采用环氧丙烷为溶剂及耦合剂,极大提高了反应的转化率。实验结果发现碘化物具有较好的催化活性。以碘化铯为催化剂,考察了反应温度、反应时间、反应压力、反应物摩尔比和催化剂用量对反应结果的影响。在最佳反应条件下(环氧丙烷0.3 mol,甘油0.1 mol,反应温度120℃,反应时间1.5 h,反应压力3.0 MPa,催化剂用量0.15 g),甘油的转化率为86.5%,甘油碳酸酯的产率为81.6%。     

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。     

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。     

负载型碘化钾催化合成甘油碳酸酯

采用浸渍法制备了负载型碘化钾催化剂,并通过二氧化碳、环氧丙烷和甘油合成甘油碳酸酯反应评价其催化活性,发现KI/γ-Al2O3具有最高的活性,甘油的转化率为58.5%,甘油碳酸酯的产率为54.6%。其中,不同比表面积的γ-Al2O3载体对于活性组分负载量具有一定的影响,通过BET、XRD法对催化剂进行了表征,进一步说明了大比表面积的γ-Al2O3载体有利于KI高度分散。实验考察了反应温度、反应物摩尔比、KI负载量对反应结果的影响,得到最佳实验参数为:反应温度130℃,环氧丙烷与甘油的摩尔比3∶1,KI负载量1.5 mmol/g。催化剂KI/γ-Al2O3经过5次使用后,甘油碳酸酯的产率仍在50%以上,具有较好的稳定性。     

负载型KI催化甘油与CO2合成甘油碳酸酯

添加不同组分对氧化铝载体进行调变改性,再以改性氧化铝为载体,负载KI制备了一系列负载型催化剂KI/Al₂O₃-MgO、KI/Al₂O₃-ZnO、KI/Al₂O₃-TiO₂和KI/Al₂O₃-ZrO₂,并通过CO₂、环氧丙烷和甘油合成甘油碳酸酯反应评价其催化活性,发现KI/Al₂O₃-MgO具有最高的活性。由不同载体的CO₂-TPD分析可以发现,载体表面少量碱性位的存在有利于反应进行。实验研究了不同负载量KI/Al₂O₃-MgO的活性及稳定性,发现KI负载量为1.5mmol/g较为适宜。同时,实验又通过N₂吸附/脱附(BET)、X射线衍射(XRD)等手段对不同负载量的KI/Al₂O₃-MgO进行了表征,进一步说明了负载量过多会导致KI晶粒团聚,并阻塞载体孔道。优化了反应条件,在最佳条件下(环氧丙烷0.3mol,甘油0.1mol,反应温度130℃,反应时间2h,反应压力6.0MPa),甘油的转化率为65.5%,甘油碳酸酯的产率为60.8%。     

碳酸丙二醇酯的新法合成

在ＫＩ配合物的催化下，环氧丙烷和二氧化碳反应生成碳酸丙二醇酯。ＫＩ配合物的催化作用与１８－冠－６相当，反应压力为以［（１４．７０～１８．３８）×１０－３ＭＰａ］，温度为８０～１００℃，时间１ｈ２０ｍｉｎ。产品收率可达９９．９％，催化剂可循环使用。     

多孔有机聚合物催化二氧化碳合成环状碳酸酯研究进展

二氧化碳（CO₂）捕集、利用和储存（CCUS）在全球能源结构转型中是一种极具潜力的策略,能够实现能源供给、基础原料产出以及限制气候变化。多孔有机聚合物（POPs）具有高CO₂吸附容量和吸附选择性、突出的结构特性以及优异的化学可调控性,其作为极具潜力的材料广泛应用于催化CO₂参与的有机反应中。其中,CO₂与环氧化物环加成生成环状碳酸酯的反应具有100%的原子经济性,且其产物也极具工业价值。本文基于CO₂环加成反应催化机制,从催化剂的合成方法、结构性质与组成特性角度出发,综述了POPs在CO₂/环氧化物环加成反应的研究进展,包括金属配合物类、氢键供体类、离子液体类、金属配合物/离子液体和氢键供体/离子液体等有机多孔聚合物体系。通过阐述POPs在催化CO₂制备高附加值环状碳酸酯反应中的研究现状和发展趋势,为POPs的开发与应用以及CO₂综合利用的工业化探索提供具有建设性的指导意见。     

二氧化碳合成碳酸二甲酯催化剂的研究进展

碳酸二甲酯是一种用途广泛的环境友好有机介成中间体,利用CO2合成碳酸二甲酯能有效利用C02资源,在环境保护和绿色合成化学方面具有重要的意义.综述了利用CO2合成碳酸二甲酯有机金属催化剂、氧化物催化剂、碱催化剂、负载型金属催化剂、醋酸盐催化剂及催化反应机理的研究进展,并展望了未来的发展方向.     

锌基催化剂制备及其催化合成碳酸丙烯酯

通过尿素沉淀法制备了以锌基为主要活性组分的不同的复合型氧化物催化剂,考察了尿素与1,2-丙二醇（PG）合成碳酸丙烯酯（PC）反应的催化性能。用XRD,SEM,BET,CO2-TPD等技术对催化剂进行了表征。结果表明,催化剂的强碱性位数量可能是影响催化活性的关键因素, 在此基础上推出碱催化机理：较强的碱强度有利于降低中间产物羟丙基氨基甲酸酯（HPC）转化为PC的活化能。在反应温度170℃,反应时间1h, PG/尿素摩尔比1.5, 0.6g催化剂(尿素质量的2%),反应压力300mmHg的条件下, PC收率高达99.8%.锌/镁1:4催化剂经过五次再生,PC收率降低了2.2%。     

甲醇和二氧化碳合成碳酸二甲酯催化剂的研究进展

碳酸二甲酯是一种重要的绿色化工产品,甲醇和二氧化碳直接合成碳酸二甲酯是符合"绿色化学"的合成路线。综述了近年来该路线合成碳酸二甲酯催化剂的研究进展,简述了各类催化剂的催化机理、催化效能及发展趋势。     

An in situ Raman study of dimethyl carbonate synthesis from carbon dioxide and methanol over zirconia

In situ Raman spectroscopy has been used to investigate the mechanism of dimethyl carbonate (DMC) synthesis via the reaction of methanol with carbon dioxide over zirconia. Methanol adsorption leads to the appearance of adsorbed methoxide groups, whereas CO₂ adsorption leads to the formation of carbonate species. Monomethyl carbonate species, (CH₃O)COO(Zr)₂, are formed by the reaction of methoxide and monodentate carbonate species and DMC is formed via the further reaction of monomethyl carbonate species with methanol. This sequence is supported by evidence that DMC decomposition on zirconia proceeds via the reverse of the proposed mechanism.     

Chemical fixation of carbon dioxide to propylene carbonate over amine-functionalized silica catalysts

Amine-functionalized silica catalysts (NH₂/SiO₂, NH(CH₂)₂NH₂/SiO₂ and 1,5,7-triazabicyclo[4,4,0]dec-5-ene/SiO₂ (TBD/SiO₂)), which were characterized by ²⁹Si NMR, elemental analysis, N₂ adsorption–desorption method and indicator dye adsorption, were prepared by ultrasonic technique under mild conditions. Such hybrid solid bases showed high catalytic activity towards CO₂ coupling with epoxide. However, it was found that the reaction conditions had a great influence on the performance. Furthermore, silanols on the surface played an important role in the chemical fixation of CO₂. Based on these, the possible reaction mechanism was proposed for CO₂ coupling with epoxide over such type of catalysts.     

Synergism in methanol synthesis from carbon dioxide over gold catalysts supported on metal oxides

Gold deposited on various oxides with high dispersion was found to be active for the hydrogenation of CO₂ at temperatures between 150 and 400°C. Product selectivities greatly depended on the nature of support oxide. Acidic oxides like TiO₂ gave higher CO₂ conversions but low methanol yields. Zinc oxide component was indispensable for selective methanol synthesis. Significantly, large particle size effect of gold was observed and smaller gold particles gave higher methanol productivity per exposed surface area of gold. This can be explained by an increase in the perimeter area of gold particles with a decrease in particle size. Methanol yield was greatly enhanced in a Au/ZnO---TiO₂ catalyst probably due to an increase in gold-zinc oxide interface.     

Synthesis of glycerol carbonate from ethylene carbonate and glycerol using immobilized ionic liquid catalysts

In this study, ionic liquids immobilized on mesoporous MCM41 were prepared and their catalytic performance was tested in the synthesis of glycerol carbonate from transesterification of ethylene carbonate with glycerol. The ionic liquids were generated on chloropropyl functionalized MCM41 (CP-MCM41) via the immobilization of trialkylamines. The quaternary salt ionic liquid immobilized on MCM41 (RNX-MCM41) was characterized using a number of physical–chemical measurements including XRD, BET, ¹³C and ²⁹Si MAS-NMR. Their catalytic performances were tested in a batch reactor. The influence of the structure of the quaternary ammonium salt and reaction parameters like temperature and reaction time was investigated. It was found that RNX-MCM41 with a longer alkyl chain length showed much better catalytic activity. High temperature and longer reaction time were favorable for the reactivity of RNX-MCM41. The catalyst can be reused for the reaction up to three consecutive runs without any considerable loss of its initial activity.     

Efficient synthesis of glycerol carbonate from glycerol and urea with lanthanum oxide as a solid base catalyst

Lanthanum oxide catalyst prepared by precipitation method and calcined at 600 °C exhibited better catalytic activity in the catalytic synthesis of glycerol carbonate from glycerol and urea with TOF up to 1506 mmol/g·h. It was proposed that the lanthanum oxide catalyst with more strong basic sites (T_d > 400 °C) exhibited higher catalytic activity. Accordingly, the catalyst containing appropriate amount of La₂O₂CO₃ phase exhibited higher catalytic activity. Moreover, the recycling experiments demonstrated that the catalytic activity can be essentially preserved during the recycling tests investigated.     

A new process for the synthesis of diphenyl carbonate from dimethyl carbonate and phenol over heterogeneous catalysts

The two-step synthesis of diphenyl carbonate (DPC) from dimethyl carbonate (DMC) and phenol has been compared in liquid phase and gas phase, both over heterogeneous catalysts. In the first step, equilibrium yields of methyl phenyl carbonate (MPC) in the transesterification of DMC and phenol were very low at low temperatures in the liquid phase although reaction rates were fast. This endothermic reaction was more favorable at high temperatures in the gas-phase reaction. Titanium oxide catalysts supported on SiO₂ or activated carbon were found to be effective in a continuous gas flow reactor. In case of the second step, the disproportionation of MPC, selective formation of DPC was not feasible in the gas-phase reaction due to extensive side reactions. However, there was no by-product in the liquid-phase reaction over the TiO₂/SiO₂ catalyst. Therefore, our proposed two-step synthesis process consists of the gas-phase transesterification of DMC and phenol followed by the liquid-phase disproportionation of MPC to DPC, both over the TiO₂/SiO₂ catalyst. This revised version was published online in July 2006 with corrections to the Cover Date.