Copolymerization of propylene oxide and carbon dioxide in the presence of diphenylmethane diisoyanate

To improve the thermal and mechanical properties of poly(propylene carbonate) (PPC), the copolymerization of CO₂ with PO was successfully carried out in the presence of a third monomer, 4,4′-diphenylmethane diisocyanate (MDI) using supported multi-component zinc dicarboxylate as catalyst. Chemical structure, the molecular weight, as well as thermal and mechanical properties of the resulting new copolymers were fully investigated. The experimental results show that the yield increases with increasing MDI feed content from 0 to 2 wt.%. The introduction of MDI leads to an increase in the molecular weight of PPC with light crosslinking. When the MDI feed content is lower than 3 wt.%, the PPC copolymers have number average molecular weight (Mn) ranging from 153 K to 424 K g/mol and molecular weight distribution (MWD) values ranging from 1.71 to 2.79. The resulting PPC copolymers show higher glass transition temperature (Tg) and decomposition temperature compared with poly(propylene carbonate) (PPC) without MDI. Considering the gel content of the resulting copolymers, the optimized MDI feed content should be smaller than 1.5 wt.% based on PO content. The introduction of small amount of MDI provides a very effective way to improve the mechanical properties and thermal stabilities of PPC due to the increase in its molecular weight.     

Copolymerization of carbon dioxide and propylene oxide with zinc glutarate as catalyst in the presence of compounds containing active hydrogen

To enhance the catalytic copolymerization of CO₂ and propylene oxide catalyzed by zinc glutarate, the influence of trace of water, ethanol, and propanal on the catalytic activity, the resulted copolymer structure, and the molecular weight and molecular weight distribution of the copolymer were investigated extensively. The experimental results showed that the catalytic activity decreased remarkably in the presence of either trace of ethanol or water, but increased in the presence of trace of propanal. Both ¹H‐NMR and ¹³C‐NMR spectra suggested that the content of carbonate linkages of resulted copolymer was not effected obviously in the presence of above‐mentioned impurities, giving completely alternating poly(propylene carbonate) (PPC). GPC results indicated that these impurities reduced the molecular weights but broadened the molecular weight distributions of resulted copolymers. Finally, the byproduct contents including both propylene carbonate determined by GC and polyether increased with the increase of three impurity concentrations. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Copolymerization of carbon dioxide and propylene oxide with neodymium trichloroacetate-based coordination catalyst

The copolymerizations of carbon dioxide (CO₂) and propylene oxide (PO) were performed using new ternary rare-earth catalyst. It was found that the rare-earth coordination catalyst consisting of Nd(CCl₃COO)₃, ZnEt₂ and glycerine was very effective for the copolymerization of PO with CO₂. The effects of the relative molar ratio and addition order of the catalyst components, copolymerization reaction time, and operating pressure as well as temperature on the copolymerization were systematically investigated. At an appropriate combination of all variables, the yield could be as high as 6875 g/mol Nd per hour at 90 °C in a 8 h reaction period.     

Kinetics of carbon dioxide reaction with diethylaminoethanol in aqueous solutions

Differential rates of CO₂ adsorption into 0.90, 0.47 and 0.24 M aqueous solutions of 2-(diethylamino)ethanol (DEAE) were measured at 323 K over a wide range of carbonation ratios. A rigorous thermodynamic model was used to define species activities which were coupled with Danckwerts' gas-liquid reaction model to deduce the kinetics. The reaction of CO₂ with this highly basic tertiary amine occurs by two pathways: (1) a minor path via the CO₂ reaction with hydroxide ion and (2) a predominant reaction pathway that can be characterized by its first order dependency on the free amine concentration. The second reaction was proposed to involve an internal salt-like intermediate,.     

Kinetics of the reaction between carbon dioxide and methyldiethanolamine

A stirred cell gas-liquid contactor was used to investigate the kinetics of the reaction between carbon dioxide and methyldiethanolamine (MDEA) in aqueous solutions. Experiments were conducted over the temperature range 15–35°C and for MDEA concentrations from 0.85 to 1.70 g mol/l. The kinetic data support a previously proposed mechanism in which MDEA acts as a homogeneous catalyst for CO₂ hydrolysis. The second-order rate constant was found to have a value of 2/47 l/g mols at 25°C, in good agreement with existing literature values. The second-order rate constant is correlated well by the Arrhenius expression

     

CO_2/环氧丙烷共聚合成聚碳酸亚丙酯多元醇

利用双金属氰化物作为催化剂,催化CO2/环氧丙烷调节共聚制备聚碳酸亚丙酯多元醇(PPC),详细考察了催化剂用量、相对分子质量调节剂及其用量、CO2用量等对聚合的影响.研究发现PPC的相对分子质量与相对分子质量调节剂的用量成线性关系,可以根据需要合成具有规定相对分子质量的PPC树脂.最后提出聚合过程中碳酸丙烯酯可能按照解拉链的方式生成.     

Fluid phase equilibria during propylene carbonate synthesis from propylene oxide in carbon dioxide medium

In the present study the influence of the amount of carbon dioxide on the catalytic performance during the propylene carbonate synthesis from propylene oxide and CO₂ was investigated. The reaction was performed in high-pressure batch autoclaves using immobilized 1-hydroxyethyl-9-propyl-cyclic guanidinium bromide on SBA-15 (HEPCGBr/SBA-15) as catalyst in the absence of any co-catalyst. It was found that the yield was strongly dependent on the amount of CO₂ added to the system and that the phase behavior strongly changes along the reaction pathway. The Cubic-Plus-Association (CPA) equation of state was used to predict the phase behavior during the reaction and the number and composition of coexisting phases in the multicomponent reaction system were determined. In accordance with the experimental data, the maximum conversion was achieved in the transition region between the two- and the one-phase region where a CO₂-expanded reactant/product phase (larger volume due to the dissolution of carbon dioxide in the liquid phase) is present. Optimal conditions for performing the reaction have been derived which requires consideration not only of the phase behavior of the starting phase but also of the mixture during reaction.     

Water-tolerant graphene oxide as a high-efficiency catalyst for the synthesis of propylene carbonate from propylene oxide and carbon dioxide

Graphene oxide (GO) was found to be a metal-free, water-tolerant and high-efficiency catalyst towards the cycloaddition of carbon dioxide (CO₂) to propylene oxide (PO) for the synthesis of propylene carbonate (PC) at room temperature (RT) and atmospheric pressure without the need for a solvent. Using GO as catalyst and tetrabutylammonium bromide (Bu₄NBr) as co-catalyst, PO is rapidly converted to PC with 96% yield and 100% selectivity under relatively mild conditions (100 °C, 2.25 MPa, 1 h). The effects of catalyst amount, temperature, time and water (H₂O) addition on the reaction were investigated. It is found that the presence of a proper amount of H₂O enhances the conversion of epoxide remarkably. A comparison of the catalytic activities of a number of reduced graphene oxide (r-GO) samples under similar reaction conditions revealed that it is the hydroxyl groups (rather than the carboxyl groups) on GO that form hydrogen bonds with PO, and act synergistically with halide anions to promote the cycloaddition reaction. A possible mechanism is proposed.     

Synthesis and characterization of alternating copolymer from carbon dioxide and propylene oxide

High yield and pure zinc glutarate catalysts used for copolymerization of carbon dioxide and propylene oxide have been synthesized in different solvents by ultrasonic methodology. For the purposes of comparison, low‐yield zinc glutarates were also synthesized via mechanical stirring method with other synthetic conditions remaining unchanged. Fourier Transform Infrared Spectroscopy and wide‐angle X‐ray diffraction techniques confirmed the presence of high‐quality zinc glutarate catalysts. Accordingly, poly(propylene carbonate) (PPC) can be synthesized from carbon dioxide and propylene oxide using the zinc glutarate catalysts. It was confirmed that the as‐prepared PPC had an alternating copolymer structure together with high molecular weight. The thermal and mechanical properties of the obtained PPC copolymer were determined by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile test. DSC and TGA results showed that the PPC copolymer exhibited high glass transition temperature (39.39°C) and decomposition temperature (278°C) when compared to their corresponding values reported in the literature. Tensile test showed that the PPC film exhibited superior mechanical strength. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2327–2334, 2002     

复合催化剂下二氧化碳与环氧丙烷共聚的研究

制备了钴锌双金属氰化物/戊二酸锌复合催化剂(DMC/ZnGA),研究了催化剂的组成对CO₂与环氧丙烷共聚反应的影响;采用凝胶渗透色谱、核磁共振谱、红外光谱和热重分析对共聚产物进行了表征,结果表明,钴锌双金属氰化物/戊二酸锌复合催化剂表现出明显的协同效应,能高效催化CO₂与环氧丙烷的共聚反应,共聚产物的数均分子量在18 000~31 000;通过调节催化剂的配比,最高催化效率达到168 g-聚合物·(g-催化剂)^-1,反应生成共聚产物的反应选择性大于97%。     

Kinetics of the liquid phase reaction between carbon dioxide and diethanolamine

The kinetics of the reaction between carbon dioxide in aqueous solution and aqueous diethanolamine have been studied using the thermal flow method. The data indicate that the kinetics of the reaction is complex. The particular mechanism proposed consists of two reactions which initially compete for the available carbon dioxide. One of these reactions is reversible, and regenerates carbon dioxide as the overall reaction proceeds. The species participating in the proposed reversible reaction were not identifiable from the data obtained.     

Novel ternary block copolymerization of carbon dioxide with cyclohexene oxide and propylene oxide using zinc complex catalyst

Block copolymers of poly (propylene carbonate—cyclohexyl carbonate) (PPC-PCHC) were successfully synthesized by a one-pot method with the zinc complex catalyst (Zn2G). The IR and ¹H-NMR and ¹³C-NMR spectra verified the introducing of PCHC segments in the copolymers. The GPC curves of the copolymers appeared only one peak and the DSC results showed three glass transition temperatures at 40 °C, 66 °C and 115 °C, indicating the three-block copolymer structure. TGA tests revealed that the thermal decomposition temperature of the synthesized block copolymers increased up to about 300 °C. The mechanical properties proved to be also enhanced greatly as evidenced by static and dynamic mechanical tests. The thermal and mechanical properties of the resultant block copolymers lay between those of PPC and PCHC, demonstrating the desired properties of a polymer can be achieved via block copolymerization.     

Kinetics of the liquid phase reaction between carbon dioxide and diethanolamine

The kinetics of the reaction between carbon dioxide in aqueous solution and aqueous diethanolamine have been studied using the thermal flow method. The data indicate that the kinetics of the reaction is complex. The particular mechanism proposed consists of two reactions which initially compete for the available carbon dioxide. One of these reactions is reversible, and regenerates carbon dioxide as the overall reaction proceeds. The species participating in the proposed reversible reaction were not identifiable from the data obtained.     

Copolymerization of carbon dioxide and propylene oxide using zinc adipate as catalyst

Zinc adipate was synthesized from zinc oxide with adipic acid by different methods. Their chemical structure and crystalline morphology were determined by Fourier transform infrared spectroscopy (FTIR), wide‐angle X‐ray diffraction (WXRD), and scanning electron microscopy (SEM) techniques. The results showed that the zinc adipate synthesized under magnetic stirring possessed higher degree of crystallinity than that synthesized under mechanical stirring due to the different stirring strength, and therefore exhibited greater catalytic activity for the copolymerization between CO₂ and propylene oxide (PO). The optimum condition for the copolymerization of CO₂ and PO was also investigated. Very high catalytic activity of 110.4 g polymer/g catalyst was afforded under optimizing copolymerization condition. NMR spectra revealed that the synthesized poly(propylene carbonate) (PPC) had a highly alternating copolymer structure. DSC and TGA examinations showed that the glass transition temperature and decomposition temperature of the PPC with M_n = 41,900 Da were 27.7 and 248°C, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 200–206, 2006     

Chemically foaming of biodegradable poly(propylene carbonate) derived from carbon dioxide and propylene oxide

A composite chemical blowing agent PU8, composed of azodiformamide (AC), N,N′‐dinitroso pentamethylene tetramine (H) and other chemicals, was used to prepare the poly(propylene carbonate) foam material. The decomposition behavior of the blowing agent was investigated. The effect of blowing agent content and the foaming condition on the foaming of poly(propylene carbonate) was studied in detail. The results suggested that 10 phr PU8 is the optimum formulation to afford a desired poly(propylene carbonate) foam. The morphologies and compression strength of the poly(propylene carbonate) foam were studied using a scanning electron microscope and tensile tester, respectively. The foam with a blowing ratio of 16 can be obtained under an optimum foaming condition at 160°C for 30 min. POLYM. ENG. SCI. 46:153–159, 2006. © 2005 Society of Plastics Engineers     

无溶剂下负载离子液体催化合成碳酸丙烯酯

研究了在无溶剂条件下,利用负载型离子液体催化二氧化碳和环氧丙烷合成碳酸丙烯酯的反应.在4 MPa、130℃反应2 h后,BMImBF4离子液体催化活性要远大于Ⅺ的催化活性.BMImBF4/SiO2负载型离子液体的催化活性要略低于BMImBF4离子液体,但负载后更有利于反应产物的分离.并研究了反应时间、反应压力和反应温度对碳酸丙烯酯产率和选择性的影响.     

Kinetics of the reaction of carbon dioxide with aqueous sodium and potassium carbonate solutions

Kinetics for CO₂ absorption into 5–30 wt-% sodium carbonate solutions and 5–50 wt-% potassium carbonate solutions up to 70 °C were studied in a string of discs apparatus under conditions, in which the reaction of CO₂ could be assumed pseudo-first-order. The experimental data were evaluated based on the use of activities in the reaction rate expressions. The second order kinetic constant for the CO₂ reaction CO₂+OH^??HCO₃^? at infinite dilution is discussed and an expression for it is obtained up to 70 °C.The difference between the activity and concentration based kinetic constants were found to be small at low concentrations, where the apparent Henry’s law constant is close to that at infinite dilution in water. However, at high concentrations (high apparent Henry’s law constants), the difference was bigger. Using the activity based approach, the second order kinetic constant was calculated, compared to the second order kinetic constant in infinite dilution and found to be independent of both carbonate concentration and the cation present in the solution.     

Synthesis and degradation behavior of poly(propylene carbonate) derived from carbon dioxide and propylene oxide

High molecular weight and regular molecular structure poly(propylene carbonate) (PPC) was successfully synthesized from carbon dioxide and propylene oxide. The PPC copolymer structure was an exact alternating copolymer as evidenced by the ¹³C‐NMR technique. Degradative behavior of the PPC was conducted by soil burial and buffer solution immersion (pH = 6) tests, respectively. The results showed that the weight loss of soil buried in PPC films increased more slowly than that immersed in the buffer solution after 6‐month exposure. However, the weight loss of sample immersed in the buffer solution increased rapidly during the first 2 months and reached a value of 4.59%. Water sorption measurement also revealed that the PPC membranes immersed in buffer solution were more hydrophilic than those in soil burial tests. The degradation mechanism of PPC membranes was correlated with the sample morphologies, FTIR, and ¹H‐NMR spectra. The SEM morphologies were consistent with the weight loss and water sorption measurements. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1840–1846, 2004