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1.
A series of single-component cobalt salen complexes, N,N′-bis(salicylidene)-1,2phenylenediamino cobaltIII X (X = Cl (1a), Br (1b), NO3 (1c), CF3COO (1d), BF4 (1e), and N3 (1f)) (SalphCoX), were prepared for alternating copolymerization of carbon dioxide and propylene oxide(PO) under mild condition. The axial anion X group of the SalenphCoX played important role in tailoring the catalytic activity, polymeric/cyclic carbonate selectivity, as well as stereochemistry of carbonate unit sequence in the polymer chain. SalenphCoX with an electron-withdrawing axial X group (complex 1c) was an ideal catalyst for the copolymerization of CO2 and PO to selectively produce polycarbonate with ∼99% carbonate linkage and over 81% head-to-tail structure.  相似文献   

2.
A series of chromium/Schiff base complexes N,N′-bis(salicylidene)-1,2-phenylenediamino chromiumIII X were prepared and employed for the alternating copolymerization of carbon dioxide with racemic propylene oxide in the presence of (4-dimethylamino)pyridine. The effect of the complex structure and reaction conditions on the catalytic activity, the poly(propylene carbonate)/cyclic carbonate (PPC/PC) selectivity, and the polymer head-to-tail linkages was examined. The experiments indicated that N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-phenylenediamino chromiumIII (NO3) exhibited the highest PPC/PC selectivity as well as polymer head-to-tail linkages and N,N′-bis(3,5-dichlorosalicylidene)-1,2-phenylenediimino chromiumIII (NO3) possessed the highest catalytic activity among these chromium/Schiff base complexes. The structure of the produced copolymer was characterized by the IR, 1H NMR, and 13C NMR measurements. Almost 100% carbonate content of the resulting polycarbonate were obtained with the help of these effective catalyst systems under facile conditions.  相似文献   

3.
Xiaoqin Xu  Haoran Li  Yong Wang  Zhiquan Shen 《Polymer》2007,48(14):3921-3924
Imidazolium salts, most of which are room temperature ionic liquids (ILs), have been introduced as effective and tunable cocatalysts in the copolymerization of CO2 with epoxides catalyzed by (salen)CrIIICl complex for the first time. Effects of imidazolium salts with different alkyl chains as well as with different anions on the copolymerization were investigated. The results showed that the copolymerization was influenced obviously by the property of anion. In addition, the cation of imidazolium salts with longer alkyl chain length such as n-dodecyl (TOF, 242.5 h−1, carbonate linkages > 99%) displays better activities and selectivity in the copolymerization as compared with N-MeIm (TOF, 72.5 h−1, carbonate linkages 94%). These results are instructive for further design of task-specific ILs as effective cocatalysts to improve the copolymerization of CO2 with epoxides.  相似文献   

4.
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 (Mn: 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.  相似文献   

5.
Shang Chen 《Polymer》2004,45(19):6519-6524
Copolymerization of propylene oxide and carbon dioxide was successfully carried out by using double metal cyanide complex (DMC) based on Zn3[Co(CN)6]2. It has been found that this catalyst demonstrated highly enhanced catalytic activity over 1000 g copolymer per gram of Zn3[Co(CN)6]2 compared with its analog based on Zn3[Fe(CN)6]2. The copolymers prepared were characterized by IR, 1H NMR, the molar fraction of CO2 (FCO2) for copolymer was as high as 0.31 under optimum condition. Propylene carbonate was also identified as co-product by the spectrometry. The study showed that lower temperature is favorable for incorporation of CO2 into copolymer instead of propylene carbonate, and FCO2 is significantly influenced by amount of catalyst used. The kind of complexing agent employed in preparation impacted on the catalytic activity, but not yet for FCO2.  相似文献   

6.
The copolymerization of phenyl glycidyl ether (PGE) and carbon dioxide was performed without any solvent in the presence of ionic liquid as catalyst. The reaction was carried out in a batch autoclave reactor. The carbonate content of polycarbonate was affected by the structure of imidazolium salt ionic liquid; the one with the cation of bulkier alkyl chain length and with more nucleophilic anion showed better reactivity. However, the yield of carbon dioxide addition decreased when hexyl or octyl containing ionic liquids were used in place of butyl group in 1-alkyl-3-methyl imidazolium salts. The carbonate content and turnover number (TON) of the polycarbonate increased as the reaction temperature increased from 40 to 80 ‡C. However, the carbonate content decreased with increasing reaction time.  相似文献   

7.
Cailiang Zhang 《Polymer》2011,52(8):1847-1855
Carbon particles such as platelet-like graphite (GR), spherically shaped activated carbon (AC), and tubular carbon nanofiber (CNF) were used as additives in extruded polystyrene (PS) foams with carbon dioxide (CO2) and water as co-blowing agents. It was found that GR is the best additive for improving the thermal insulation performance of CO2 based foam samples because of GR’s good absorption and reflectivity of infrared (IR) radiation. However, when the GR concentration was higher than 0.5 wt.%, the extruded foams exhibited large bubbles in the center of the foam and the extrusion line became unstable. By adding water carried by AC as a co-blowing agent, it was able to decrease the temperature in the center of the extruded foam, which successfully eliminated the bubble problem and achieved stable foam extrusion with good control of the foam density and cell morphology. Moreover, water carried by AC could also improve the mechanical performance of extruded foams containing CNF or GR. Water was not found in the extruded foams and the presence of water during extrusion did not affect the molecular weight and glass transition temperature of PS. Our results showed that a combination of AC as a water carrier and GR as an absorber and reflector of IR radiation can produce CO2 based PS foams with good thermal insulation and mechanical properties, particularly with the presence of a small amount of CNF nanoparticles.  相似文献   

8.
Ken-ichi Tominaga   《Catalysis Today》2006,115(1-4):70-72
A mixed ionic liquid [bmim][Cl + NTf2] system was successfully used as a reaction medium for Ru-catalyzed hydroformylation of 1-hexene with carbon dioxide in the absence of toxic CO and any volatile organic solvents. The yields and TONs are higher than those reported previously using conventional organic solvents. The product can be readily separated by distillation, and the reaction medium containing the Ru-catalyst was successfully recycled.  相似文献   

9.
An organic modification of the surface of titanium dioxide particles precoated with SiO2 and Al2O3 films in a CO2 medium is performed, where CO2 of different phases is used as the solvent and a titanate coupling reagent (CH3)2CHOTi(OP(O)(OH)OP(O)(OC8H17)2)3 is the modification reagent. The results are compared with the modification carried out in a conventional organic solvent. The interaction between the functional groups of the modification reagent and the hydroxyl groups on the surface of the particles is analyzed. Experimental results indicate that the surface of particles is modified efficiently when the CO2 solvent is in a supercritical or liquid state. The particles are remarkably changed from hydrophilic to hydrophobic by the modification. A chemical bond of AlOTi is likely formed between the molecules of the organic modification reagent (CH3)2CHOTi(OP(O)(OH)OP(O)(OC8H17)2)3 and the particle surface. The actual maximum quantity order of organic modification reagent reacted on the particle surface is about 7.08×10−7 mol/m2 (1.73% by weight) from thermogravimetric analysis. The organic modification process using supercritical or liquid CO2 as the solvent has the advantages of being simple, effective, and green.  相似文献   

10.
Cerium dioxide microspheres were successfully prepared by internal gelation process with copolymerization using acrylic acid. The effects of acrylic acid (AA)/hexamethylenetetramine (HMTA) molar ratio and concentration of solution containing urea and HMTA on the stability of precursor solution and on the prepared microspheres were investigated. The results indicated that acrylic acid could modify the urea resin and slow down the decomposition of urea resin. The stability of precursor solutions was improved with the increase of AA/HMTA molar ratio, but the surfaces of gelled microspheres became rough and cracked when the ratio was greater than 1. The solution containing urea and HMTA had a significant effect on the stability of precursor solution and on the surface morphology, specific surface area, pore volume and average pore diameter of the microspheres. The porous CeO2 microspheres were obtained by heat treatment at 600?°C for 2?h.  相似文献   

11.
碳酸酐酶(CA)可以加速捕集化石燃料燃烧产生的二氧化碳,从而降低CO2的排放量。主要介绍了CA的来源、活性、稳定性及作用。分析了使用新型生物方法对二氧化碳进行捕集和储存的优缺点,并对下一步的工作进行了展望。  相似文献   

12.
Copolymerization of carbon dioxide and propylene oxide was carried out employing (RC6H4COO)3Y/glycerin/ZnEt2 (R=-H, -CH3, -NO2, -OH) ternary catalyst systems. The feature of yttrium carboxylates (ligand, substituent and its position on the aromatic ring) is of great importance in the final copolymerization. Appropriate design of substituent and position of the ligand in benzoate-based yttrium complex can adjust the microstructure of aliphatic polycarbonate in a moderate degree, where the head-to-tail linkage in the copolymer is adjustable from 68.4 to 75.4%. The steric factor of the ligand in the yttrium complex is crucial for the molecular weight distribution of the copolymer, probably due to the fact that the substituent at 2 and 4-position would disturb the coordination or insertion of the monomer, lead the copolymer with broad molecular distribution. Based on the study of ultraviolet-visible spectra of the ternary catalyst in various solvents, it seems that the absorption band at 240-255 nm be closely related to the active species of the rare earth ternary catalysts.  相似文献   

13.
CO_2加氢合成甲醇反应及其催化剂研究进展   总被引:3,自引:0,他引:3  
介绍了CO2加氢合成甲醇的反应机理和特点,对所用催化剂的研究进展以及工业应用情况等作了概述。  相似文献   

14.
The coordination system, Y(CF3CO2)3 (I)-Zn(Et)2 (II)-m-hydroxybenzoic acid (III), was found to be the most active catalyst to generate poly(propylene carbonate) (PPC) from carbon dioxide and propylene oxide (PO) in 1,3-dioxolane. A high yield and a high molecular weight could be obtained at the conditions of a II/I molar ratio of 20, a III/II molar ratio of 1.0, a temperature of 60 °C, and a pressure of 2.76 MPa. The carbonate content in the resultant PPC was found to be nearly 100%.The block copolymerization in the based PPC was carried out by in situ introducing an epoxide other than PO right after the copolymerization of carbon dioxide with PO using the same catalyst system. The IR and 1H NMR spectra as well as the measured molecular weights verified the resulting copolymers were block copolymers. For the block copolymerization of CO2 with cyclohexene oxide and CO2 with 4-vinyl-1-cyclohexene-1,2-epoxide in the based PPC, the yield as well as the cyclohexene carbonate and the 4-vinyl-1-cyclohexene carbonate contents were found to increase with increasing temperature. The most appropriate temperature was around at 80 °C. The weight-average molecular weights of the block copolymers lay in a range from 2.44×105 to 3.16×105, the polydispersity in a range from 5.0 to 6.3, and the 10% weight loss temperature in a range from 226 to 253 °C. The thermal and mechanical properties of the resultant block copolymers lay between those of PPC, poly(cyclohexene carbonate), and poly(4-vinyl-1-cyclohexene carbonate), indicating the desired properties of a polymer can be achieved via block copolymerization.  相似文献   

15.
Use of carbon dioxide as a reactant instead of toxic carbon monoxide in the hydroaminomethylation reaction sequence is demonstrated for the first time. The present Ru3(CO)12-catalyzed one-pot protocol includes reverse-water–gas-shift (RWGS) reaction, hydroformylation reaction and reductive amination which finally leads to secondary and tertiary amine. The influence of various reaction parameters including the effects of catalytic promotors and phase-transfer-catalysts has been investigated. Finally, an optimum reaction conditions were found by suppressing the major side products to have a variety of amines in excellent yields (up to 98%).  相似文献   

16.
The catalyst system consisting of Y(CF3CO2)3, Zn(Et)2, and pyrogallol in the solvent of 1,3-dioxolane was found to be effective for the copolymerization of allyl glycidyl ether with carbon dioxide at 60 °C and 400 psi. The IR, 1H-NMR, and 13C-NMR spectra as well as the element analysis indicated that the resulting copolymer was an alternating polyethercarbonate with the carbonate content higher than 97.5%. The resulting polyethercarbonate could react with 3-(trimethoxysilyl)propyl methacrylate via a free radical reaction to generate the alkoxysilane-containing copolymer precursors that were used in the subsequent sol-gel process to result in the polyethercarbonate-silica nanocomposite. The generated nanocomposite was characterized by 13C-NMR, 29Si-NMR, SEM, DSC, TGA, ESCA, and UV-Vis. The mechanical properties were also measured. A good compatibility between polyethercarbonate and silica and a SiO2 network with silica particles less than 100 nm in the nanocomposite were observed. Both the thermal and mechanical properties of the resulting polyethercarbonate-silica nanocomposite were found to enhance with silica content. The optical transparency of the generated nanocomposite was comparable to that of the based polyethercarbonate.  相似文献   

17.
The addition of carbon dioxide to allyl glycidyl ether (AGE) was investigated without using any solvent in the presence of ionic liquid as catalyst. Ionic liquids based on 1-ethyl-3-methylimidazolium (EMIm), 1-butyl-3-methylimidazolium (BMIm), and 1-hexyl-3-methylimidazolium (HMIm) with different anions such as Cl, BF4, PF6 were used as catalysts. The reaction was performed in a 50 mL stainless steel autoclave. The conversion of allyl glycidyl ether was affected by the structure of imidazolium salt ionic liquids; the one with the cation of bulkier alkyl chain length and with more nucleophilic anion showed better reactivity. Reaction temperature and carbon dioxide pressure enhanced the addition of carbon dioxide to AGE.  相似文献   

18.
A binary catalyst system composed of n-Bu4NBr3/n-Bu4NBr was developed for facile synthesis of 5-substituted 2-oxazolidinones with perfect regioselectivity in a single operation directly from olefins, chloramine-T and CO2. The choice of efficient binary catalysts for two steps, i.e. aziridination and cycloaddition, and the optimization of reaction condition are keys to the one-pot synthesis of 5-substituted 2-oxazolidinones. A possible mechanism for the present one-pot synthesis of oxazolidinones was also proposed.  相似文献   

19.
Two kinds of Cr-based mesoporous materials, Cr incorporated and supported silicate MSU-1, were synthesized at room temperature and characterized with XRD, N2 adsorption–desorption, FT-IR, DR UV–vis and H2-TPR techniques. Both Cr-based catalysts exhibited similar mesoporous channels and textural properties. The catalytic performances of two catalysts for the oxidative dehydrogenation of ethane to ethylene with CO2 were investigated. They both showed high activities, providing 58.0 and 68.1% ethane conversion and 53.4 and 55.6% ethylene yield at 700 °C, respectively. The catalysts were prone to deactivate in the reaction but could be partially regenerated by oxygen. Cr species formed in high oxidation state were reduced during the reaction. It was proposed that these high-valent Cr species were responsible for the high activities of catalysts.  相似文献   

20.
In this work, the solubility of carbon dioxide, CO2, in pentaerythritol tetraheptanoate (PEC7) and in pentaerythritol tetranonanoate (PEC9) has been performed from 283 to 348 K and pressures up to 7.5 MPa in an isochoric high-pressure gas solubility apparatus. The solubility values are very similar in terms of mole fractions of CO2 in both pentaerythritol esters. The experimental gas solubility data, together with those available in the literature for other CO2 + pentaerythritol tetraester systems, were satisfactorily correlated with the PC-SAFT equation of state. The average absolute deviations of the gas solubility correlations were less than 3.9% for all the systems. In addition, PC-SAFT model was applied in a semi-predictive manner: the pure component's molecular parameters and the binary interaction parameter optimized from solubility data were used to calculate the types of the phase diagram as well as the densities and excess molar volumes in broad temperature and pressure ranges. The results obtained show the robustness of the model and these parameters to calculate properties not included in the fitting procedure.  相似文献   

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