Selective copolymerization of carbon dioxide with propylene oxide catalyzed by a nanolamellar double metal cyanide complex catalyst at low polymerization temperatures

Traditional cobalt-zinc double metal cyanide complex [Zn-Co(III)DMCC] catalysts could catalyze the copolymerization of carbon dioxide (CO₂) with propylene oxide (PO) to afford poly (propylene carbonate) (PPC) with high productivity. But the molecular weight (MW) of PPC and the polycarbonate selectivity were not satisfied. In this work, by using a nanolamellar Zn-Co(III) DMCC catalyst, the CO₂-PO copolymerization was successfully performed to yield PPC with high molecular weight (M_n: 36.5 kg/mol) and high molar fraction of CO₂ in the copolymer (FCO₂: 74.2%) at low polymerization temperatures (40∼80 °C). Improved selectivity (FCO₂: 72.6%) and productivity of the catalyst (6050 g polymer/g Zn) could be achieved at 60 °C within 10 h. The influences of water content on CO₂-PO copolymerization were quantitatively investigated for the first time. It was proposed that trace water in the reaction system not only acted as an efficient chain transfer agent, which decreased MW of the resultant copolymer, but also strongly interacted with zinc site of the catalyst, which led to low productivity of PPC and more amounts of cyclic propylene carbonate (cPC). These conclusions were also supported by the apparent kinetics of CO₂-PO copolymerization. ESI-MS results showed that all polymers have two end alkylhydroxyl groups. It was thus proposed that the alkylhydroxyl groups came from the initiation reaction of Zn-OH in the catalyst and the chain transfer reaction by H₂O. The proposed mechanism of chain initiation, propagation and chain transfer reaction were proved by the experimental results.     

锌/钴双金属氰化络合物催化环氧丙烷聚合机理

用以二乙二醇二乙醚为有机配体的锌／钴双金属氰化络合物进行了环氧丙烷的聚合,并用扩展X射线精细结构分析方法研究了催化剂激活和环氧丙烷聚合过程中锌离子和钴离子的区域结构变化。结果表明,锌／钴双金属氰化络合物催化环氧丙烷的聚合是一个活性聚合体系。在环氧丙烷聚合过程中锌离子由与3．0个氧原子配位转变为与5．7个氧原子配位,表明聚合活性中心为5．0个氧原子配位的螯合锌离子。     

Polymerization of propylene oxide by using double metal cyanide catalysts and the application to polyurethane elastomer

Polymerizations of propylene oxide have been carried out by using double metal cyanide (DMC) catalysts based on Zn₃[Co(CN)₆]₂. By controlling the type and the amount of complexing agent during preparation of catalyst the catalytic activity, initiation time, and the unsaturation level in polyether polyols could be tuned. Various catalysts prepared by changing the complexing and co-complexing agents were characterized by x-ray photoelectron spectroscopy, infrared spectroscopy, and X-ray powder diffraction. Highly active catalyst prepared by choosing a polytetramethylene ether glycol as a co-complexing agent resulted in polyoxypropylenes (POP) with low very low unsaturation level (0.003-0.006 meq/g) and with narrow molecular weight distribution (MWD=1.02-1.04). The active sites of DMC-catalyzed polymerization of propylene oxide have both cationic and coordinative characters. ¹³C NMR analysis showed that the polyols have a random distribution of the configurational sequences and head-to-tail regiosequence, even if the amount of [rr] triad of polyol produced by DMC catalyst was larger than that of polyol by conventional KOH catalyst. The distortionless enhancement by polarization transfer analysis showed that there exist regioirregular sequences as well. The stress-strain curves of methylene diisocyanate/1,4-butanediol cured POP-based polyurethane elastomers showed that the unsaturation content contained in POP showed a dramatic effect on the mechanical properties.     

Tuning of activity, induction period and polymer properties of double metal cyanide catalyzed ring-opening polymerizations of propylene oxide by using quaternary ammonium salts

Polymerizations of propylene oxide (PO) have been carried out by using double metal cyanide (DMC) catalyst prepared by reacting ZnCl₂ and K₃[Co(CN)₆] in the presence of tert-butyl alcohol (^tBuOH) as a complexing agent. The catalytic activity and the induction period for PO polymerizations catalyzed by DMC are tunable by using various quaternary ammonium salts (QAS) as external additives. The DMC/QAS binary catalyst improves polymer properties as well such as molecular weight, molecular weight distribution, viscosity, and unsaturation level.     

双金属氰化物催化环氧化物开环聚合的研究进展

综述了近年来双金属氰化物催化剂制备聚醚多元醇的研究进展,详细介绍了双金属氰化物催化剂的制备及其催化环氧化物的聚合机理、聚合工艺方面的研究现状,并展望了催化剂制备及其催化环氧化物合成聚醚今后的研究方向。     

Multi-metal cyanide catalysts for ring-opening polymerization of propylene oxide

Polymerizations of propylene oxide (PO) have been carried out by using a series of multi-metal metal cyanide (MMC) catalysts prepared by reacting ZnCl₂ and K₃[Co(CN)₆]₂, K₄Fe(CN)₆, K₃Fe(CN)₆ and/or K₂Ni(CN)₄ in the presence of tert-butyl alcohol and polytetramethylene ether glycol as complexing agents. The resulting MMC catalysts are characterized by elemental analysis, X-ray photoelectron spectroscopy, infrared spectroscopy and X-ray powder diffraction. The structure of MMC catalysts with broadened X-ray diffraction peaks is different from that of highly crystalline Prussian blue analogues of microporous crystalline materials due to the coordination of complexing agents. The PO polymerization behavior was tunable by changing with various metal cyanide salts after fixing a main catalyst component as ZnCl₂. Even if the basic structure of the MMC complexes is different each other, i.e. orthorhombic for Zn₂[Fe(CN)₆] and monoclinic for Zn₃[Fe(CN)₆]₂ and Zn₃[Co(CN)₆]₂, the chemical formulations become more complicated by forming MMC complexes through cyano bridges and complexing agents’ coordination and the structure more distorted from the defined crystal structures. All catalysts prepared by using K₃[Co(CN)₆]₂ showed very high activity once they were activated. Simply changing catalyst formulation by choosing different metal cyanide salts, catalytic activity, induction period, polymer molecular weight and its distribution and polymer viscosity could be tuned.     

双金属氰化物催化剂在外循环反应器中的应用研究

介绍了双金属氰化物催化剂在1.5m3外循环生产装置上的工业应用试验情况。结果表明,该催化剂活性高,诱导期短,缩短了生产周期,提高了产品质量。     

双金属氰化络合催化剂催化环氧烷烃与二氧化碳共聚研究进展

针对CO₂与环氧烷烃共聚制备脂肪族聚碳酸酯反应体系,本文在综合分析脂肪族聚碳酸酯应用前景的基础上,着重介绍了双金属氰化络合催化剂在该工艺中的研究进展,并对不同种类活性中心金属的组合在不同反应体系中的催化效果进行了分析。共沉淀法制得的Zn-Co双金属氰化络合催化剂在CO₂与环氧烷烃的催化体系中,通过改变制备方法、配体等条件可以实现对催化剂形貌的控制,有利于催化活性的提升。Zn-Fe双金属氰化络合催化剂对于环氧丙烷开环活性较好。同时还介绍了采用其他活性中心金属组合制得的双金属氰化络合催化剂,发现对于CO₂与环氧烷烃共聚活性受中心金属及配体的影响较大。最后,对该共聚反应的机理进行了分析,为双金属氰化络合催化剂的设计研究指明了方向。     

Effect of polymerization conditions on the polymer properties of CO2-cyclohexene oxide copolymer prepared by double metal cyanide catalyst

The effect of polymerization parameters such as polymerization time, temperature, pressure and the amount of catalyst amount in CO₂-cyclohexene copolymerizations with double metal cyanide (DMC) catalyst were investigated in detail. Especially, the effect of polymerization conditions on the polydispersity index (PDI) and glass transition temperature (T_g) were deeply examined. Increases in polymerization time, pressure, temperature and the amount of catalyst in feed increased the activity of the DMC catalyst. The molecular weight (MW), PDI and glass transition temperature (T_g) were affected by the polymerization time, temperature, pressure and the amount of catalyst in the feed.     

Ring‐opening copolymerization of maleic anhydride with propylene oxide by double‐metal cyanide

Ring‐opening copolymerization of maleic anhydride (MA) with propylene oxide (PO) was successfully carried out by using double‐metal cyanide (DMC) based on Zn₃[Co(CN)₆]₂. The characteristics of the copolymerization are presented and discussed in this article. The structure of the copolymer was characterized with IR and ¹H‐NMR. Number‐average molecular weight (M_n) and molecular weight distribution (MWD) of the copolymer were measured by GPC. The results showed that DMC was a highly active catalyst for copolymerization of MA and PO, giving high yield at a low catalyst level of 80 mg/kg. The catalytic efficiency reached 10 kg polymer/g catalyst. Almost alternating copolymer was obtained when monomer charge molar ratio reached MA/PO ≥ 1. The copolymerization can be also carried out in many organic solvents; it was more favorable to be carried in polar solvents such as THF and acetone than in low‐polarity solvents such as diethyl ether and cyclohexane. The proper reaction temperature carried in the solvents was between 90 and 100 °C. The M_n was in the range of 2000–3000, and it was linear with the molar ratio of conversion monomer and DMC catalyst. The reactivity ratio of MA and PO in this reaction system was given by the extended Kelen–Tudos equation: η=[r₁+(r₂/α)]ξ?(r₂/α) at some high monomer conversion. The value of reactivity ratio r₁(MA) = 0 for MA cannot be polymerized itself by DMC catalyst, and r₂(PO) = 0.286. The kinetics of the copolymerization was studied. The results indicated that the copolymerization rate is first order with respect to monomer concentration. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1788–1792, 2004     

Tuning of the activity and induction period of double metal cyanide catalyzed ring-opening polymerizations of propylene oxide by using ionic liquids

Polymerizations of propylene oxide (PO) have been carried out by using double metal cyanide (DMC) catalyst prepared by reacting ZnCl₂ and K₃[Co(CN)₆] in the presence of tert-butyl alcohol as a complexing agents. The DMC catalyst of the molecular formula, Zn_2.3Cl_1.0[Co(CN)₆]_1.0·2.0 ^tBuOH·1.0H₂O, is characterized by gas sorption measurements, infrared spectroscopy and X-ray powder diffraction. The structure of DMC catalyst with negligible surface area and broadened X-ray diffraction peaks is different from that of Prussian blue analogue, Zn₃[Co(CN)₆]₂·12H₂O of microporous crystalline materials. The PO polymerization behavior is tunable by combining it with various imidazolium based ionic liquids (ILs) as external additives. Thus, (1) they make the zinc-monomer bond faster activated during the initial stage of polymerization, (2) they make the zinc-monomer bond more active, (3) they stabilize the polymerization centers and prevent their decomposition, and (4) they improve important polymer properties such as molecular weight, viscosity and unsaturation level. The maximum rate of polymerization (R_p,max) of DMC catalyst increases from 2587 to 27,222 g-polymer/g-cat h by combining with 1-ethyl-3-methylimidazolium chloride (emimCl, [emimCl]/[Zn] = 1.25) at 115 °C. The induction period as the time to reach R_p,max becomes short from 321 min for DMC catalyst to 29 min for DMC/emimCl binary catalyst. The unsaturation value of polyol (0.017 mequiv./g) produced by DMC decreases to 0.005 mequiv./g by simply combining with IL. The molecular weight polyol produced by DMC catalyst increases from M_n = 3700 to more than 6000, and the viscosity of polyol decreases by combining with ILs.     

One-pot terpolymerization of CO2, cyclohexene oxide and maleic anhydride using a highly active heterogeneous double metal cyanide complex catalyst

This paper describes a convenient one-pot terpolymerization of CO₂, cyclohexene oxide (CHO) and maleic anhydride (MAH) to afford a poly (ester-carbonate) with a low content of ether units (2.9-4.3 mol%) using a highly active Zn-Co(III) double metal cyanide complex (DMCC) catalyst. Terpolymerization was carried out in tetrahydrofuran (THF) at 75-90 °C and 1.0-4.0 MPa and no cyclic carbonate was observed in NMR spectra. The number-average molecular weight (M_n) of the terpolymer was up to 14.1 kg/mol with a narrow molecular weight distribution of 1.4-1.7. The apparent efficiency of the catalyst was up to 12.7 kg polymer/g Zn, representing the highest catalytic activity for terpolymerization of CO₂, epoxides and cyclic anhydrides to date. THF dramatically inhibited polyether formation in this terpolymerization owing to its nucleophilicity towards the Zn²⁺ center of Zn-Co (III) DMCC. This presents the first example of solvent-assisted selectivity for inhibiting ether units in CO₂ polymerization catalyzed by a heterogeneous system. Kinetic analyses of MAH/CHO/CO₂ terpolymerization (MAH/CHO 0.2) suggested that polyester production was slightly faster than polycarbonate production in the early stage. A mechanism for this terpolymerization catalyzed by Zn-Co (III) DMCC catalyst was proposed. Moreover, addition of small amounts of MAH (MAH/CHO molar ratio ≤0.2) during CO₂/CHO copolymerization can improve the thermal properties of the resultant terpolymers.     

DMC催化马来酸酐与环氧丙烷开环共聚行为类型及动力学的研究

研究了双金属氰化络合物（DMC）催化剂催化马来酸酐（MAn）与环氧丙烷（PO）开环共聚行为类型及动力学特征.用IR和1H-NMR表征了共聚物结构,结果表明MAn单体在DMC催化剂催化下不能开环均聚合,聚合为交替共聚.开环共聚合行为类型研究表明,以DMC催化剂催化MAn-PO开环共聚合中,PO单体竞聚率r1〉0、MAn单体竞聚率r2=0,进一步证明此聚合为交替共聚.以共聚行为类型为依据,对聚合动力学进行了研究,结果表明：共聚合反应动力学方程式为Rp=K[C][M],聚合反应速率与单体浓度及催化剂浓度均成一次方关系.     

Aliphatic polycarbonate synthesis by copolymerization of carbon dioxide with epoxides over double metal cyanide catalysts prepared by using ZnX2 (X = F, Cl, Br, I)

As means of the chemical fixation of carbon dioxide and the synthesis polycarbonates, copolymerizations of carbon dioxide with various epoxides, such as cyclohexene oxide, cyclopentene oxide and propylene oxide were investigated in the presence of double metal cyanide (DMC) catalysts. The DMC catalysts were prepared by reacting K₃Co(CN)₆ with ZnX₂ (X = F, Cl, Br, I) together with tertiary butyl alcohol and poly(tetramethylene ether glycol) as complexing reagents and were characterized by various spectroscopic methods. The DMC catalysts showed high activity for epoxides and CO₂ copolymerization to yield aliphatic polycarbonates of narrow polydispersity and moderate molecular weight.     

双金属氰化络合物(DMC)催化剂的合成及应用研究进展

从催化剂的结构、制备工艺、配位体等方面讨论了催化剂合成、催化机理和低不饱和度聚醚的制备方法的研究进展。催化剂的制备工艺及小分子配位体的加入顺序影响催化剂的晶体结构和催化剂的活性。配位体的类型对催化剂活性有显著影响,寻找更有效的配位体是提高催化剂性能的有效途径。     

Bis(imino)pyridyl Co(II) and Fe(II) catalysts immobilized on SBA-15 mesoporous material: new highly active supported catalysts for the polymerization of ethylene

A series of bis(imino)pyridyl Co(II) and Fe(II) complexes containing allyloxy group on the pyridine ring were prepared. These metal complexes were heterogenized covalently immobilizing on modified SBA-15 mesoporous material in the presence of Karstedt catalyst. This immobilization technique was demonstrated to be an ideal one since the resulting supported catalysts resembled closely their homogeneous counterparts, mirroring the feature of active sites.     

Advanced metal oxide (supported) catalysts: Synthesis and applications

A variety of metal oxides catalysts are used in heterogeneous catalysis for chemical processes and have now been developed for their catalytic performance and durability. The heterogeneous catalysis is the most important technology in chemical industry as well as other environmental, energy applications, etc. This review examines recent advances at the preparation and applications of metal oxide particles, especially pertaining to catalytic enhancements for current and future chemical process such as Fischer–Tropsch process, alkylation, and transesterification and environmental applications such as the oxidation of volatile organic compounds and the reduction of NO_x.     

Supported catalysts based on 2,6-bis(imino)pyridyl complex of Fe(II): DRIFTS study of the catalyst formation and data on ethylene polymerization

The supported catalysts for ethylene polymerization were prepared by interaction of 2,6-bis[1-(2,6-dimetilphenylimino)-ethyl]pyridineiron(II) dichloride (LFeCl₂) with silica and alumina. The catalysts exhibit high and stable activity at ethylene polymerization in presence of Al(i-Bu)₃ as co-catalyst. LFeCl₂ interaction with surface functional groups of the supports was studied by means of DRIFTS. LFeCl₂ adsorbed on the support surface mainly retains its structure. LFeCl₂ is strongly bounded to the support due to formation of multiple bonds between LFeCl₂ and surface functional groups of the supports. DRIFTS data on the state of the surface iron compounds have been obtained using CO as probe molecule.     

Synthesis,characterization, and catalytic activity of 4 mol % N,N′‐methylene bisacrylamide crosslinked poly(acrylic acid)–metal complexes

The metal‐ion complexation behavior and catalytic activity of 4 mol % N,N′‐methylene bisacrylamide crosslinked poly(acrylic acid) were investigated. The polymeric ligand was prepared by solution polymerization. The metal‐ion complexation was studied with Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), and Zn(II) ions. The metal uptake followed the order: Cu(II) > Cr(III) > Mn(II) > Co(II) > Fe(III) > Zn(II) > Ni(II). The polymeric ligand and the metal complexes were characterized by various spectral methods. The catalytic activity of the metal complexes were investigated toward the hydrolysis of p‐nitrophenyl acetate (NPA). The Co(II) complexes exhibited high catalytic activity. The kinetics of catalysis was first order. The hydrolysis was controlled by pH, time, amount of catalyst, and temperature. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 272–279, 2004     

Hydrothermal synthesis and crystal structure of a novel cyanide-bridged double helical copper(I) coordination polymer [Cu3(CN)3(phen)]n

Hydrothermal reaction of CuCN, K₃[Fe(CN)₆] and 1,10-phenanthroline affords a novel cyanide-bridged copper(I) coordination polymer [Cu₃(CN)₃(phen)]_n (1). The complex displays an interesting one-dimensional neutral double helical framework with (phen)Cu–CN– side-arms as interchain bridges. The double helical chains are close packed in a parallel fashion, and the phen ligands stack in an interpenetrating mode, which leads to π–π interactions between parallel phen planes. The thermal stability and fluorescent property have also been investigated.