Recent advances in metal-free catalysts for the synthesis of cyclic carbonates from CO_2 and epoxides

The aim of ＂green chemistry＂ and ＂atom economy＂ is to utilize carbon dioxide and replace harmful reactants such as CO and phosgene for the production of cyclic carbonates. In this paper, metal-free catalysts including organic bases, ionic liquids, supported catalysts, organic copolymers and carbon materials for the synthesis of cyclic carbonates by the cycloaddition of carbon dioxide to epoxides are reviewed. Recent advances in the design of the catalysts and the understanding of the reaction mechanism are summarized and discussed. The synergistic effects of organic bases and hydrogen bond donors, organic bases and nucleophilic anions, hydrogen bond donors and nucleophilic anions and active components and supports are highlighted. The challenge is to develop metal-free catalysts suitable for carbon dioxide capture and fixation. The ultimate goal is to synthesize cyclic carbonates in a flow reactor directly using carbon dioxide from industrial flue gas at ambient temperature and atmospheric pressure. By using synergetic effects, a multi-functional approach can meet the design strategy of metal-free catalysts for carbon dioxide adsorption and activation as well as epoxide ring opening.

Polymeric Catalyst with Discrete Distributed Active Centers for Regulating Backbone Structure of Poly(propylene carbonate)

Converting CO_(2) into valuable chemicals is an effective means to alleviate environmental pressure and the depletion of oil resources.Among them,polymers derived from the copolymerization of PO and CO_(2) have been widely studied because of their excellent properties.To meet the expansion of the application range of CO_(2)-based polymers,regulation of the CU in the polymer is imperative.Based on the understanding of the relationship between catalyst synergy and structure,we designed a new generation of polyester-based polymeric catalysts APEPC-R and RPEPC-N with discretely distributed active centers to achieve the synthesis of CO_(2)-based polymers with regulated CU(from 50%to 90%).The discrete arrangement of catalyst active centers was demonstrated by 1H NMR and UV-vis characterization.Benefiting from multi-site synergy,high molecular weight(M_(n)>100 kg/mol)CO_(2)-based copolymers with CU among 50%—90%were successfully synthesized and their properties were firstly investigated.This work not only contributes to enriching the scope of the application of CO_(2)-based copolymers but also provides a new platform for the development of a new generation of catalysts.

Polystyrene-supported Phenol/DMAP： an Efficient Binary Catalyst System for CO2 Fixation to Give Cyclic Carbonates

Polystyrene-supported phenol （PS-PhOH） was successfully synthesized by alkylation reaction of phenol with 2% DVB cross-linked chloromethylated polystyrene and characterized by IR spectra and elemental analysis. In conjunction with an organic base such as DMAP, DBU, triethylamine （Et3N）, diethylamine （Et2NH） or pyridine, the PS-PhOH could effectively catalyze the coupling reaction of carbon dioxide with epoxides to give cyclic carbonates in high yield and selectivity under mild conditions. The binary catalyst system of the PS-PhOH/DMAP was found to be the most active. The influence of reaction temperature, carbon dioxide pressure and reaction time on the yield of product was carefully investigated. The PS-PhOH could be recycled by simple filtration for at least up to ten times without loss of catalytic activity.

Synthesis of Polycarbonate Block Terpolymers Using Robust Cobalt Catalyst Systems

This contribution reports an efficient approach for preparing polycarbonate block terpolymers by immortal stepwise copolymerization of CO2 with different epoxides in the presence of enol chain transfer,mediated by robust cobalt catalyst systems consisting of the fluorine substituted salen Co(Ⅲ)NO3 or biphenol-linker bimetallic Co(Ⅲ)complex in conjunction with an ionic cocatalyst,PPNX(PPN=bis(triphenylphosphine)iminium,X=NO3–or 2,4-dinitrophenoxide).Various polycarbonate block terpolymers were obtained in perfectly unimodal distribution of their molecular weights with narrow polydispersity.They all possessed only one broad glass transition temperature,which could be adjusted by altering the length of different polycarbonate segments.

Polymeric catalyst with polymerization-enhanced Lewis acidity for CO_(2)-based copolymers

Ring-opening copolymerization of CO_(2) and epoxides is a promising way to manufacture high value-added materials.Despite a variety of catalyst systems have been reported,the reaction is still limited by low activity and polymer selectivity.Herein,a strategy of polymerization-enhanced Lewis acidity is reported to construct a series of highly efficient polymeric aluminum porphyrin catalysts(PAPCs).The characterization of the coordination equilibrium constant(K_(eq))showed significantly enhanced Lewis acidity of PAPC(K_(eg)=18.2 L/mol)compared to the monomeric counterpart(K_(eq)=6.4 L/mol),accompanied with increased turnover frequency(TOF)from 136 h^(-1) to 5500 h^(-1).Through detailed regulation of Lewis acidity,the highly Lewis acidic PAPC-OTs displayed a record high TOF of 30,200 h^(-1) with polymer selectivity of up to 99%.

The Effect of Oxygen to Salen-Co Complexes for the Copolymerization of PO/C02

A series of Salen-Co(Ⅱ)complexes were synthesized to study the effect of O2 on the catalytic performance of Salen-Co complexes for the copolymerization of PO/CO2 The Salen-Co(Ⅱ) complexes showed low activity on the cyclo addition of CO2 to PO with the aid of a cocatalyst such as PPNCI Unexpectedly,with the addition of O2 the activity of Salen-C(Ⅱ)complexes was obviously increased and 100%cylic carbonate was obtained.As the pressure of O2 increased,the activity of the complex also increased.With the existence of 02 the activity of the complexes was influenced by their structures and the pressure of 02,and the camplexes with the conjugated structure showed higher activity.The structures of cocatalyst also played a crucial role as for the change of the activity By altering the electrophilit of Salen-Co(Ⅲ),O2 can also be used as cocatalyst for the copolymerization of PO/CO2。

CO_(2)与环氧化物耦合制备环状碳酸酯的多相催化体系研究进展

作为最主要的温室气体,二氧化碳(CO_(2))的过度排放已导致了严重的环境问题。同时,CO_(2)也属于储量丰富、廉价、安全和可再生利用的C1资源,被认为是有机合成的理想碳材料。高效且绿色的化学固定CO_(2)耦合制备具有高沸点、高极性、低挥发性和可生物降解性等优点的环状碳酸酯是CO_(2)资源化利用的有效方式,已引起社会各界的广泛关注。本文首先简述了目前合成环状碳酸酯的现有反应路径。然后,以CO_(2)和环氧化物的耦合反应为出发点,着重分析了该反应发生所涉及的反应机理以及催化该反应时多相催化体系的设计思路和当前研究进展。同时,综合比较了不同多相催化体系的催化条件、催化活性及循环使用性等催化参数的优缺点。最后,基于上述分析,本文总结了不同多相催化体系的应用前景并建议其后续发展应与均相催化体系相结合,利用两者的优势高效活化CO_(2)与环氧化物,以实现温和条件下催化耦合反应。

均相与多相催化剂在CO_(2)环加成反应中的研究进展

二氧化碳(CO_(2))是一种主要的人为温室气体,主要由化学、热电和钢铁工业以及运输等部门产生。大气层中CO_(2)浓度的增加是导致诸多环境问题的主要原因,如全球变暖、海平面上升和全球气温升高。然而,CO_(2)作为一种可再生、廉价和无毒的化学原料,可用来生产具有高附加值的化学品,进而降低碳浓度。五元环碳酸酯由于其优越的物理化学特性,如高沸点、高偶极矩和生物降解等性能而被广泛应用。由环氧化合物和CO_(2)合成环碳酸酯是迄今为止研究较多的方法。然而,由于CO_(2)的高热稳定性和动力学惰性,使其作为反应原料需要大量的能量投入,可能导致的结果是CO_(2)浓度是一个净增长过程。因此,利用CO_(2)作为C1构筑单元是一个长期的挑战。本工作基于CO_(2)固定反应机制,概述了各种类型的均相和多相催化剂在CO_(2)固定反应合成精细化学品环状碳酸酯中的研究进展,包括有机催化剂、离子液体、金属有机框架化合物、多孔有机聚合物等。目前,几乎所有类别催化剂均可以在室温和低压力下,以实验室规模成功地使用纯CO_(2)将其固定到末端环氧化合物上,对于非末端环氧化合物通过更高的温度和压力以实现相应转化。同时,分析了催化剂在多取代环氧化合物或生物衍生环氧化合物转化、低浓度CO_(2)转化和实现工业化三个方面所面临的挑战,并提出了未来相关研究努力的方向。

二氧化碳与环氧化物交替共聚催化剂的最新研究

自1969年科学家Inoue用ZnEt2/H2O的混合物作催化剂由CO2与环氧化物合成聚碳酸酯以来,科学家们在催化剂体系的设计方面进行了大量研究。在此基础上,本文就最近几年CO2与环氧化物交替共聚的催化剂体系进行了详细的叙述和概括。

二氧化碳与环氧化合物共聚反应催化剂的研究进展

二氧化碳综合利用对于减轻温室效应和开发有机化工新碳源都具有重要价值。本文简要介绍了二氧化碳化学转化的研究意义,总结了其参与化学反应的主要途径,对比了二氧化碳基聚碳酸酯与双酚A型聚碳酸酯,指出开发催化二氧化碳与环氧化合物共聚反应的高效催化剂是该领域研究的重点。重点综述了二氧化碳与环氧化合物共聚各类催化剂的研究进展,并探讨了其优缺点。分析得出该研究领域进一步发展面临的主要问题是催化剂效率和共聚产物的性能与应用。产品由于具有生物降解性且其原料为储量丰富的二氧化碳,因而具有广阔的应用前景。

二氧化碳与环氧化物的共聚反应

自1969年Inoue用ZnEt2/H2O的混合物作催化剂由二氧化碳与环氧化物合成聚碳酸酯以来,化学家们在催化剂体系的设计与合成方面进行了大量研究。目前,这条合成聚碳酸酯的绿色合成路线已日渐成熟。本文综述了近5年来环氧化物与二氧化碳反应合成聚碳酸酯的研究成果,主要考察催化剂的催化活性对共聚反应的影响以及反应机理研究。

CO_2与环氧化合物共聚用的泡沫负载PBM催化剂

PBM催化剂是非常有效的CO2和环氧化物共聚催化剂,但从产物中回收困难。本文尝试分别用环氧树脂、酚醛树脂和聚氨酯泡沫作为载体将PBM催化剂负载,再催化环氧化物和CO2共聚,并通过IR、1HNMR对共聚产物进行表征分析。结果显示,聚氨酯泡沫负载的PBM成功地催化了CO2和环氧丙烷、环氧乙烷以及氧化环已烯的共聚反应,尤其是在催化CO2和环氧丙烷的共聚中显示了较好的催化效率(28g/g),而且负载催化剂循环使用三次后仍有催化活性,有利于实现反应工艺的连续化。

二氧化碳与环氧化合物直接制备聚碳酸酯

综述了近几年来发展的用于二氧化碳与环氧化合物直接催化合成聚碳酸酯的各类催化剂,并详细讨论了其催化反应机理。利用二氧化碳与环氧化合物来合成聚碳酸酯,对于高分子合成化学、碳资源利用和环境保护都具有重大意义。它是发展聚碳酸酯生产的一个具有很大潜力的方面。

缩酮胺合锌催化二氧化碳和氧化环己烯共聚

Two catalyst precursors—DPB ( N,N′ diphenyl 2,3 butadiimine) and PDP ( N phenyl 2,5 dimethyl pyrrole) were synthesized by reactions of diketones and aniline in alcohol. N,N′ diphenyl 2,3 butadiimine and N phenyl 2,5 dimethyl pyrrole were characterized by IR, 1H NMR and MS, and were found to have diimine and substituted pyrrole ring structure, respectively. The condensates N,N′ diphenyl 2,3 butadiimine and N phenyl 2,5 dimethyl pyrrole both were treated with ZnEt\-2 and then with methnol, resulting in Zn complexes with the diketone\|aniline condensates (DPBZn and PDPZn). The two complexes were applied as catalysts for the copolymerization of CO 2 and cyclohexene oxide. One mole of DPBZn and DPDZn may generate 3000 and 16800 g of polymers, respectively. The obtained copolymers were also determined to have CO 2 fractions of 0 424～0 476 (by 1H NMR) and instrinsic viscosity [ η] of 0 115～0 368?dL/g in chloroform at 30℃.

CO_2在Ag－Ba－Ca－K／α－Al_2O_3上的吸附及其在乙烯环氧化反应

应用ＦＴＩＲ和脉冲反应技术研究了ＣＯ_２和Ｏ_２在Ａｇ－Ｂａ－Ｃａ－Ｋ／α－Ａｌ２Ｏ３上的吸附及ＣＯ２对Ｃ２Ｈ４环氧化、完全氧化及环氧乙烷（ＥＯ）深度氧化反应的影响．研究结果表明，ＣＯ２和表面吸附氧在负载银催化剂表面存在竞争吸附，ＣＯ２对表面吸附氧有置换作用，该作用降低了银催化剂表面吸附氧的浓度，并且所形成的碳酸根物种改善了乙烯环氧化反应活住氧种的表面分布，对Ｃ_２Ｈ_４的环氧化反应有一定的抑制作用，但是对Ｃ２Ｈ４和ＥＯ的深度氧化反应的抑制作用更强，使得乙烯环氧化反应的选择性得到改善．

席佛碱催化剂(Salen Co(Ⅲ))催化二氧化碳和环氧氯丙烷的共聚

利用席佛碱催化体系催化二氧化碳(CO2)和环氧氯丙烷(ECH)共聚反应,合成出新型环状碳酸酯(ECHCO2)。利用红外光谱、核磁等方法对产物进行了表征。结果表明,最优化的试验温度是60℃,这一催化剂体系催化的活性高达920 polymer/(mol Co h),并且有较高的选择性,高达99%。

戊二酸锌体系催化合成二氧化碳基聚碳酸酯研究进展

二氧化碳(CO_(2))是一种无毒无害、性质稳定、可再生的C1资源.近年来,以CO_(2)为原料合成的CO_(2)基聚酯受到了广泛关注.其中,戊二酸锌催化CO_(2)和环氧化物共聚生成聚碳酸酯成为CO_(2)高值转化的途径之一(特别是戊二酸锌催化CO_(2)和环氧化物共聚,包括引入酸酐、环酯等三元共聚).我们综述了近年来戊二酸锌催化CO_(2)基聚合反应的研究进展,对催化剂发展、结构、活性和产物性能等进行了系统的总结,分析了戊二酸锌催化剂在聚合反应过程中的优势和不足,最后对戊二酸锌催化剂的发展、挑战等进行了展望分析.

二氧化碳与环氧化合物共聚催化剂研究进展

二氧化碳是一种廉价、低毒、资源丰富的可用于有机合成的理想原料。由二氧化碳和环氧化合物共聚合成的脂肪族聚碳酸酯具有生物可降解性。自1969年井上祥平等发现二氧化碳和环氧化合物通过共聚反应合成脂肪族聚碳酸酯以来,利用二氧化碳制备高分子材料一直备受人们注目。该过程的关键是寻找具有高选择性的高效催化剂,三十余年来通过各国科学家的不懈努力已取得了不少成果,本文对其研究的最新进展进行了综述。

稀土络合催化二氧化碳合成脂肪族聚碳酸酯

利用稀土磷酸酯盐和三异丁基铝组成的催化剂催化二氧化碳和环氧氯丙烷 (ECH)共聚反应 ,合成出新型高分子材料脂肪族聚碳酸酯 (ECHCO2 )。考察不同稀土元素对组成的催化剂活性和共聚物分子量的影响。同时还研究了催化剂用量、1 ,4 二氧六环的用量、溶剂种类、反应温度、反应时间、水量及加水方式等对该反应的影响。