Unexpected reduction pathway of a Co(2+) salt to [HCo(CO)(4)] via [Co(2)(CO)(8)] in an ionic liquid

In the 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ionic liquid ([BMI][NTf(2)]), [Co(NTf(2))(2)] is reduced under 5.5 MPa of H(2)-CO to [Co(2)(CO)(8)] prior to [HCo(CO)(4)], provided a pyridine ligand is present in the medium.     

Temperature-dependent Crystallization and Phase Transition of Poly(L-lactic acid)/CO_2 Complex Crystals

Semicrystalline polymers can crystallize in the unique crystalline polymorph and show different phase behaviors under the highpressure CO_2 treatment. Understanding such unique crystallization and phase transition behavior is of fundamental importance for the CO_2-assisited processing of semicrystalline polymers. Herein, we investigated the polymorphic crystalline structure, phase transition, and structureproperty relationships of poly(L-lactic acid)(PLLA) treated by CO_2 at different pressures(1-13 MPa) and crystallization temperatures(T_c's, 10-110 °C). PLLA crystallized in the PLLA/CO_2 complex crystals under 7-13 MPa CO_2 at T_c≤50 °C but the common α crystals under the high-pressure CO_2 at T_c≥70 °C. Solid-state nuclear magnetic resonance analysis indicated that the PLLA/CO_2 complex crystals possessed weaker interactions between the PLLA chains than the common α crystals. The PLLA/CO_2 complex crystals were metastable and transformed into the thermally stableα crystals via the solid-to-solid route during heating or annealing at the temperature above 50 °C. The complex crystals of PLLA produced at low T_c was more ductile than the α crystals due to the lower crystallinity and the plasticizing effect of CO_2.     

Clathrate hydrate formation after CO2-H2O vapour deposition

We study vapour condensation of carbon dioxide and water at 77 K in a high-vacuum apparatus, transfer the sample to a piston-cylinder apparatus kept at 77 K and subsequently heat it at 20 MPa to 200 K. Samples are monitored by in situ volumetric experiments and after quench-recovery to 77 K and 1 bar by powder X-ray diffraction. At 77 K a heterogeneous mixture of amorphous solid water (ASW) and crystalline carbon dioxide is produced, both by co-deposition and sequential deposition of CO(2) and H(2)O. This heterogeneous mixture transforms to a mixture of cubic structure I carbon dioxide clathrate and crystalline carbon dioxide in the temperature range 160-200 K at 20 MPa. However, no crystalline ice is detected. This is, to the best of our knowledge, the first report of CO(2) clathrate hydrate formation from co-deposits of ASW and CO(2). The presence of external CO(2) vapour pressure in the annealing stage is not necessary for clathrate formation. The solid-solid transformation is accompanied by a density increase. Desorption of crystalline CO(2) atop the ASW sample is inhibited by applying 20 MPa in a piston-cylinder apparatus, and ultimately the clathrate is stabilized inside layers of crystalline CO(2) rather than in cubic or hexagonal ice. The vapour pressure of carbon dioxide needed for clathrate hydrate formation is lower by a few orders of magnitude compared to other known routes of CO(2) clathrate formation. The route described here is, thus, of relevance for understanding formation of CO(2) clathrate hydrates in astrophysical environments.     

Study on the phase behaviors,viscosities, and thermodynamic properties of CO2/[C(4)mim][PF(6)]/methanol system at elevated pressures

An apparatus to determine the vapor-liquid equilibria of CO(2)/ionic liquid (IL)/organic solvent multisystems and the viscosity of the liquid phase at elevated pressures has been constructed. The solubility of CO(2) in 3-butyl-1-methyl-imidazolium hexafluorophosphate ([C(4)mim][PF(6)]) and the viscosity of CO(2)-saturated [C(4)mim][PF(6)] have been studied at 313.15, 323.15, and 333.15 K and at pressures up to 12.5 MPa. The phase behavior of CO(2)/[C(4)mim][PF(6)]/methanol ternary mixture and the viscosity of the liquid phases at equilibrium condition have also been determined at 313.15 K and at 7.15 and 10.00 MPa. The partition coefficients of the components in the ternary system are calculated. Peng-Robinson equation of state and some thermodynamic functions are combined to calculate the fugacity coefficients of the components in the system. It demonstrates that the viscosity of the IL-rich phase decreases significantly with increasing pressure of CO(2), and the effect of temperature on the viscosity of CO(2)/IL mixture is not noticeable at high pressure, although the viscosity of the CO(2)-free IL decreases dramatically with increasing temperature. Compressed CO(2) may become an attractive reagent for reducing the viscosity of ILs in many applications. The mole fraction of methanol in the CO(2)-rich phase is much lower than that in the IL-rich phase; this indicates that the interaction between the IL and methanol is stronger than that between CO(2) and methanol. The fugacity coefficient of CO(2) in IL-rich phase is larger than unity, while that of methanol is much small than unity, which further suggests that methanol-IL interaction is much stronger than CO(2)-IL interaction. However, the CO(2)-IL interaction is stronger than the CO(2)-methanol interaction.     

CO2 capture from binary mixture via forming hydrate with the help of tetra-n-butyl ammonium bromide

Hydrate formation rate and separation effect on the capture of CO2 from binary mixture v/a forming hydrate with 5 wt% tetra-n-butyl ammonium bromide (TBAB) solution were studied.The results showed that the induction time was 5 min,and the hydrate formation process pressure of 7.30 MPa.The CO2 recovery was about 45% in the feed pressure range from 4.30 to 7.30 MPa.Under the feed pressure of 4.30 MPa,the maximum separation factor and CO2 concentration in hydrate phase were 7.3 and 38.2 tool%,respectively.The results demonstrated that TBAB accelerated hydrate formation and enriched CO2 in hydrate phase under the gentle condition.     

超临界条件下CO2和丙烯直接合成甲基丙烯酸Ni2(OCH3)2/SiO2催化剂

超临界反应;负载型催化剂;双核桥联配合物;配合物;超临界条件下CO2和丙烯直接合成甲基丙烯酸Ni2(OCH3)2/SiO2催化剂     

HYDROFORMYLATION OF PROPYLENE AND ETHYLEN'E CATALYZED BY WATER-SOLUBLERu_3(CO)_9(TPPMS)_3 CATALYST

IntroductionRutheniumcarbonylclustercomplexes,Ru3(CO)12,ruRu4(CO)12,[PPNlgu3(CO)llland[PPN][H3Ru4(CO)12]havebeenreportedtocatalyseavarietyofCOThisProjectissuPPortedbytheNationalNaturalScienceFoundationofChinaandtheResearchFoundationofSino-PEC.tranSfonnati…     

Rh/SiO~2和Rh/NaY催化剂上合成气反应的高压原位 红外光谱研究

采用高压原位FT-IR技术,对比研究了CO加H~2反应条件下Rh/SiO~2和Rh/NaY催化剂表面反应中间物种。在Rh/SiO~2表面上,无论在常压还是在1.0MPa合成气中,只观察到线式和桥式吸附CO。而在常压合成气中,Rh/NaY上不仅存在上述CO吸附物种,而且还有孪生型的Rh(Ⅰ)(CO)~2和少量Rh~6(CO)~1~6;当合成气压力升至1.0MPa后,Rh(Ⅰ)(CO)~2迅速转化成Rh~6(CO)~1~6和在2042cm^-^1产生吸收的单核羰基Rh物种,与此同时催化剂表面还生成了单齿和双齿乙酸根物种;这些在高压下生成的物种在合成气压力重新降回到常压时依然稳定存在。研究Rh/NaY上合成气反应表面物种与H~2的反应行为表明单齿乙酸根很可能是反应的活性中间物。这些结果说明Rh/NaY催化剂在高压合成气中的重构是诱发选择生成乙酸反应的基础。     

吡啶-2-羧酸钴的CO加合性能与催化羰化合成苯乙酸研究

吡啶羧酸与过渡金属离子形成的配合物是一类重要的均相氧化、羰化、聚酮反应催化剂 ,这些催化剂对ＣＯ、Ｏ2 、ＲＣＨ =ＣＨ2 、ＲＸ、ＣＨ3ＯＨ等小分子均具有良好的活化功能 ,此类小分子均能在配合物分子中进行氧化加成插入、转位及还原消除等过程合成相应的有机化合物 ,其中吡啶 - 2 -羧酸钴对氧化羰化合成碳酸酯、聚酮显示出较好的催化活性[1,2 ] 。苯乙酸是医药、农药及香料合成的重要中间体 ,传统的合成路线为苯乙氰水解法。自本世纪 6 0年代以来 ,过渡金属配合物催化卤苄羰化合成苯乙酸的新方法引起了人们的极大兴趣。迄今 ,见诸文献…     

氨基硅烷修饰的SBA-15用于CO2的吸附

以3-丙胺基三乙氧基硅烷(APTES)为硅烷化试剂,分别采用后修饰法和一步嫁接法将其嫁接到SBA-15的孔内,形成了功能化的介孔分子筛用于CO2吸附.利用X射线衍射和氮气物理吸附等方法考察了嫁接前后SBA-15的孔结构变化,用静态吸附天平考察了不同温度和不同分压下CO2的吸附行为.实验结果表明,一步嫁接法比后修饰法更有利于实现APTES在SBA-15上的嫁接.与传统的活性炭吸附剂相比,该种介孔分子筛更有利于较低分压下CO2的吸附脱除.     

Molecular dynamics computations of brine-CO(2) interfacial tensions and brine-CO(2)-quartz contact angles and their effects on structural and residual trapping mechanisms in carbon geo-sequestration

In the context of carbon geo-sequestration projects, brine-CO(2) interfacial tension γ and brine-CO(2)-rock surface water contact angles θ directly impact structural and residual trapping capacities. While γ is fairly well understood there is still large uncertainty associated with θ. We present here an investigation of γ and θ using a molecular approach based on molecular dynamics computer simulations. We consider a system consisting of CO(2)/water/NaCl and an α-quartz surface, covering a brine salinity range between 0 and 4molal. The simulation models accurately reproduce the dependence of γ on pressure below the CO(2) saturation pressure at 300K, and over predict γ by ～20% at higher pressures. In addition, in agreement with experimental observations, the simulations predict that γ increases slightly with temperature or salinity. We also demonstrate that for non-hydroxylated quartz surfaces, θ strongly increases with pressure at subcritical and supercritical conditions. An increase in temperature significantly reduces the contact angle, especially at low-intermediate pressures (1-10MPa), this effect is mitigated at higher pressures, 20MPa. We also found that θ only weakly depends on salinity for the systems investigated in this work.     

固定床反应器中添加CO2对费托合成反应的影响

用固定床反应器研究了Fe-Mn催化剂上原料气中添加CO2对费托合成反应的影响.结果表明,在533K与反应总压为1.50MPa时,大量CO2的添加使得生成CO2的选择性迅速降低,烃的生成速率降低,烃的收率也有所降低,产物向轻组分方向偏移,有机含氧化合物的生成速率降低;在593K与合成气(H2 CO)分压为1.50MPa时,随着CO2分压的增加,CO消耗速率变化不大,而烃的生成速率缓慢升高,烃的收率有所升高,CO2的生成速率缓慢降低,H2O的生成速率明显加快.由于CO2的添加,促使水煤气变换反应向逆反应方向进行,降低了催化剂表面氢物种浓度,抑制了加氢反应,低碳烃的烯/烷比有所增大,同时提高了重质烃的选择性,且随着CO2分压的增加,有机含氧化合物的生成速率呈上升的趋势.     

二氧化碳和丙烯在Cu2(OEt)2/SiO2催化下超临界合成甲基丙烯酸

负载型双核金属乙氧基配合物催化剂Cu2(OEt)2／SiO2采用表面改性法制备。运用滴定、IR、DSC和超临界反应技术对催化剂的表面结构、化学吸附性质和反应性能进行了研究。结果表明：负载型双核金属乙氧基配合物Cu2(OEt)2／SiO2中Cu”与载体SiO2表面O^2-以双齿配位形式键合,存在Cu2(OEt)2双核结构;二氧化碳在催化剂表面吸附形式形成桥式和乙氧碳酸酯基物种两种吸附态,丙烯则只有一种分子吸附态;在超临界的反应条件下,二氧化碳和丙烯在Cu2(OEt)2／SiO2催化剂上可以高选择性地合成甲基丙烯酸;反应物分子共吸附于催化剂表面,同一活性基元以及羧酸根与丙烯解离吸附态的形成是反应顺利进行的关键因素。     

Metal ion extraction using newly-synthesized bipyridine derivative as a chelating reagent in supercritical CO(2).

4,4'-Bis(dihexylaminocarbonyl)-2,2'-bipyridine (BDC-Bipy) was synthesized and studied systematically as a chelating reagent for metal ions extraction in supercritical CO(2). The compound showed high extraction efficiency for Co(2+) (100%), Cu(2+) (100%), Cd(2+) (98.2%), and Zn(2+) (100%) ions and good extraction efficiency for Sr(2+) (79.4%) and Pb(2+) (89.8%) when the extraction was performed in supercritical CO(2) at 313 K and 25 MPa with the system of BDC-Bipy, deionized water and perfluoro-1-octanesulfonic acid tetraethylammonium salt. The recoveries of mixed metal ions were also measured; unfortunately, the system of extraction has no selectivity for the metal ions.     

Liposome fluidization and melting point depression by pressurized CO2 determined by fluorescence anisotropy

The influence of CO2 on the bilayer fluidity of liposomes, which are representative of model cellular membranes, was examined for the first time at the elevated pressures (up to 13.9 MPa) associated with CO2-based processing of liposomes and microbial sterilization. Fluidization and melting point depression of aqueous dipalmitoylphosphatidylcholine (DPPC) liposomes by pressurized CO2 (present as an excess phase) were studied by steady-state fluorescence anisotropy using the membrane probe 1,6-diphenyl-1,3,5-hexatriene (DPH). Isothermal experiments revealed reversible, pressure-dependent fluidization of DPPC bilayers at temperatures corresponding to near-gel (295 K) and fluid (333 K) phases at atmospheric pressure, where the gel-to-fluid phase transition (Tm) occurs at approximately 315 K. Isobaric measurements (PCO2 =1.8, 7.0, and 13.9 MPa) of DPH anisotropy demonstrate substantial melting point depression (DeltaTm = -4.8 to -18.5 K) and a large broadening of the gel-fluid phase transition region, which were interpreted using conventional theories of melting point depression. Liposome fluidity is influenced by CO2 accumulation in the hydrocarbon core and polar headgroup region, as well as the formation of carbonic acid and/or the presence of buffering species under elevated CO2 pressure.     

Enhancing reaction rate of transesterification of glycerol monostearate and methanol by CO(2)

The effect of CO2 as a green additive on the reaction rate of transesterification of glycerol monostearate with methanol was studied at 333.15 and 343.15 K up to 10.5 MPa. It was demonstrated that addition of CO2 in the reaction system could increase the reaction rate significantly. The phase behavior of the CO2+methanol+ glycerol monostearate ternary system was also determined at 333.15 and 343.15 K. It is shown that addition of CO2 can enhance the miscibility of the reactant. The main reasons for the reaction rate enhancement are that CO2 can enhance the miscibility of the reactants, reduce the viscosity of the reaction mixture, and increase the diffusion coefficients of the reactants.     

双金属氰化物催化二氧化碳与环氧丙烷聚合

研究了双金属氰化配合物(DMC)催化剂催化二氧化碳(CO2)与环氧丙烷(PO)的共聚及PO的均聚反应,考察了DMC催化剂的诱导现象。结果表明,共聚时DMC催化的诱导期比均聚短,尤其是在低CO2压力(1.0MPa)下更明显,诱导期由均聚时的45min缩短为共聚时的15min。共聚时诱导期随CO2压力升高而增加,当反应压力由1.0MPa升高至7.0MPa时,诱导期由15min增至40min。PO与CO2共聚时的引发现象不同于PO均聚:共聚引发时温度和压力突然异常升高并迅速降低至引发前的状态,而均聚引发时温度突然升高后逐渐下降。由此可知CO2能促进DMC催化剂的活化。     

Oxygenated hydrocarbon ionic surfactants exhibit CO2 solubility

Several oxygenated hydrocarbons, including acetylated sugars, poly(propylene glycol), and oligo(vinyl acetate), have been used to generate CO2-soluble ionic surfactants. Surfactants with vinyl acetate tails yielded the most promising results, exhibiting levels of CO2 solubility comparable to those associated with fluorinated ionic surfactants. For example, a sodium sulfate with single, oligomeric vinyl acetate (VAc) tails consisting of 10 VAc repeat units was 7 wt % soluble in CO2 at 25 degrees C and 48 MPa. Upon introduction of water to these systems, only surfactants with the oligomeric vinyl acetate tails exhibited spectroscopic evidence of a polar environment that was capable of solubilizing the methyl orange into the CO2-rich phase. For example, a single-phase solution of CO2, 0.15 wt % sodium bis(vinyl acetate)8 sulfosuccinate, and water, at water loading (W) values ranging from 10 to 40 at 25 degrees C and 34.5 MPa, exhibited a methyl orange peak at 423 nm. This result indicated that the core of a reverse micelle provided a microenvironment with a polarity similar to that of methanol. Quantum chemical calculations indicate that the acetylated sugars may be too hydrophilic to readily form reverse micelles, whereas the VAc-based surfactants appear to have the correct balance of hydrophilic and hydrophobic forces necessary to form reverse micelles.     

Speciation and kinetics related to catalytic carbonylation in the presence of cis-[Ir(CO)2I2]P(C6H5)4 under CO and H2 pressures

The differences in the reactivities of the square-planar complexes cis-[Rh(CO)2I2]- (1) and cis-[Ir(CO)2I2]- (2), involved in the catalytic carbonylation of olefins, are investigated, with P(C6H5)4+ as the counterion, by ambient- and high-pressure NMR and IR spectroscopy. Under an elevated pressure of CO, 1 and 2 form the [M(CO)3I] complexes with the equilibrium constants KIr approximately 1.8 x 10(-3) and KRh approximately 4 x 10(-5). The ratio KIr/KRh close to 50 shows that, under catalytic conditions (a few megapascals), only complex 1 remains in the anionic form, while a major amount of the iridium analogue 2 is converted to a neutral species. The oxidative addition reactions of HI with 1 and 2 give two monohydrides of different geometries, mer,trans-[HRh(CO)2I3]- (3) and fac,cis-[HIr(CO)2I3]- (4), respectively. Both hydrides are unstable at ambient temperature and form, within minutes for Rh and within hours for Ir, the corresponding cis-[M(CO)2I2]- (1 or 2) and [M(CO)2I4]- (5 or 6) species and H2. When an H2 pressure of 5.5 MPa is applied to a nitromethane solution of complex 2, ca. 50% of 2 is transformed to cis-dihydride complexes. The formation of cis,cis,cis-[IrH2(CO)2I2]- (8a) is followed by intermolecular rearrangements to form cis,trans,cis-[IrH2(CO)2I2]- (8b) and cis,cis,trans-[IrH2(CO)2I2]- (8c). A small amount of a dinuclear species, [Ir2H(CO)4I4]x- (9), is also observed. The formation rate constants for 8a and 8b at 262 K are k1(262) = (4.42 +/- 0.18) x 10(-4) M-1 s-1, k-1(262) = (1.49 +/- 0.07) x 10(-4) s-1, k2(262) = (2.81 +/- 0.04) x 10(-5) s-1, and k-2(262) = (5.47 +/- 0.16) x 10(-6) s-1. The two equilibrium constants K1(262) = [8a]/([2][H2]) = 2.97 +/- 0.03 M-1 and K2(262) = [8b]/[8a] = 5.13 +/- 0.10 show that complex 8b is the thermodynamically stable addition product. However, no similar H2 addition products of the rhodium analogue 1 are observed. The pressurization with H2 of a solution containing 2 and 6 give the monohydride 4, the dihydrides 8a and 8b, the dinuclear complex 9, and the two new complexes [Ir(CO)2I3] (10) and [HIr(CO)2I2] (11). The reactions of the iridium complexes with H2 and HI are summarized in a single scheme.     

Phase separation of the reaction system induced by CO2 and conversion enhancement for the esterification of acetic acid with ethanol in ionic liquid

The effect of CO2 on the phase behavior of the reaction system and equilibrium conversion for esterification of acetic acid and ethanol in ionic liquid (1-butyl-3-methylimidazolium hydrogen sulfate, [bmim][HSO4]) was studied at 60.0 degrees C up to 15 MPa. It was demonstrated that there was only one phase in the reaction system in the absence of CO2. The reaction system underwent two-phase-->three-phase-->two-phase transitions with increasing pressure. The pressure of CO2 or the phase behavior of the system affected the equilibrium conversion of the reaction markedly. As the pressure was less than 3.5 MPa, there were two phases in the system, and the equilibrium conversion increased as pressure was increased. In the pressure range of 3.5-9.5 MPa, there existed three phases, and the equilibrium conversion increased more rapidly with increasing pressure. As the pressure was higher than 9.5 MPa, the reaction system entered another two-phase region and the equilibrium conversion was nearly independent of pressure. The total equilibrium conversion was 64% without CO2 and could be as high as 80% as pressure was higher than 9.0 MPa. The apparent equilibrium constants (K(x)) in different phases were also determined, showing that the K(x) in the middle phase or top phase was much greater than that in the bottom phase.