In situ molecular spectroscopic evidence for CO2 intercalation into montmorillonite in supercritical carbon dioxide

The interaction of anhydrous supercritical CO(2) (scCO(2)) with both kaolinite and ~1W (i.e., close to but less than one layer of hydration) calcium-saturated montmorillonite was investigated under conditions relevant to geologic carbon sequestration (50 °C and 90 bar). The CO(2) molecular environment was probed in situ using a combination of three novel high-pressure techniques: X-ray diffraction, magic angle spinning nuclear magnetic resonance spectroscopy, and attenuated total reflection infrared spectroscopy. We report the first direct evidence that the expansion of montmorillonite under scCO(2) conditions is due to CO(2) migration into the interlayer. Intercalated CO(2) molecules are rotationally constrained and do not appear to react with waters to form bicarbonate or carbonic acid. In contrast, CO(2) does not intercalate into kaolinite. The findings show that predicting the seal integrity of caprock will have complex dependence on clay mineralogy and hydration state.     

The use of a new carboranylamidophosphite ligand in the asymmetric Pd-catalysed allylic alkylation in organic solvents and supercritical carbon dioxide

A novel P-monodentate ligand based on carboranyl alcohol and (S)-2-(anilinomethyl)pyrrolidine provides high enantioselectivities (ee’s up to 95%) in the Pd-catalyzed allylic alkylation of (E)-1,3-diphenylallyl acetate. The first example of the Pd-catalysed allylic alkylation in supercritical carbon dioxide is also described.     

Dispersion of organic pigments using supercritical carbon dioxide

This research describes dispersion of organic pigments using supercritical fluids. With low surface tension and high diffusivity of fluids in supercritical states, aggregated particles may be effectively wetted and swelled to form the primary constituent of the dispersing solution by volume. In this paper, the conditions of temperature and pressure are used to control the density of supercritical carbon dioxide subject to PGMEA as cosolvent for dispersing organic powder in a solution. As shown from measurement with a laser scattering particle analyzer, the average diameter of phthalocyanine green 36 with the haloid structure can be significantly reduced to 93.5 nm; for aminoanthraquinone red containing and amino group (-NH(2)) and phthalocyanine blue 15:6 with symmetry benzene and inner hydrogen bond, the mean particle sizes are 178.5 and 188.7 nm, respectively, using supercritical CO(2). Additionally, the transmittance of UV light is used to confirm the dispersing performance in this study.     

X-ray studies of carbon dioxide intercalation in Na-fluorohectorite clay at near-ambient conditions

We show experimentally that gaseous CO(2) intercalates into the interlayer space of the synthetic smectite clay Na-fluorohectorite at conditions not too far from ambient. The mean interlayer repetition distance of the clay when CO(2) is intercalated is found to be 12.5 ? for the conditions -20 °C and 15 bar. The magnitude of the expansion of the interlayer upon intercalation is indistinguishable from that observed in the dehydrated-monohydrated transition for H(2)O, but the possibility of water intercalation is ruled out by a careful analysis of the experimental conditions and repeating the measurements exposing the clay to nitrogen gas. The dynamics of the process is observed to be dependent on the pressure, with a higher intercalation rate at increased pressure. The rate of CO(2) intercalation at the studied conditions is found to be several orders of magnitude slower than the intercalation rate of water or humidity at ambient pressure and temperature.     

Three-metal-center spin interactions through the intercalation of metal azaporphines and porphines into an organic pillared coordination box

Discrete homo Cu-Cu-Cu and hetero Cu-Pd-Cu or Cu-Co-Cu metal arrays are prepared within an organic-pillared coordination box by inserting M(ii)-azaporphine/porphine cartridges (M = Cu(ii), Pd(ii) or Co(ii)), where the metal arrays show unique spin interactions in ESR: in particular, Deltam(s) = 3 for the Cu-Cu-Cu array.     

Flexible biradicals in liquid and supercritical carbon dioxide: the exchange interaction, the chain dynamics, and a comparison with conventional solvents

X-band time-resolved electron paramagnetic resonance (TREPR) spectra of three flexible biradicals of varying chain length and structure were obtained in liquid and supercritical carbon dioxide (CO2) solutions and compared to conventional solvents. For C16 acyl-alkyl biradical 1a, an average spin exchange interaction between the radical centers, J(avg), was obtained by spectral simulation using a simple model for spin-correlated radical pairs (SCRPs) and a small amount of T2 relaxation from a previously established J modulation mechanism. A large solvent effect on J(avg) was observed for the first time, varying by almost 1 order of magnitude from CO2 (J(avg) = -120 +/- 10 MHz) to heavy mineral oil (-11 +/- 3 MHz) for 1a. For C15 bis(alkyl) biradical 1b, spectra obtained under supercritical conditions are only slightly different from those detected in liquid CO2 but differ from spectra taken in benzene. For C10 acyl-alkyl biradical 2a, more emissive spin polarization due to S-T- mixing is observed in CO2 than in benzene. These results are discussed in terms of solvent properties such as dielectric constant, viscosity, and specific interactions. Both chain dynamics and changes to the equilibrium distribution of end-to-end distances can alter J(avg) and the observed ratio of S-T0 to S-T- mixing; however, faster chain dynamics is concluded to be the most likely cause of the observed effects in these systems.     

A comparison of the extraction of clove buds with supercritical carbon dioxide and superheated water

Supercritical carbon dioxide and superheated water (subcritical water above 100 °C under pressure) have both been used to extract the buds of cloves (Syzygium aromaticum). The yields of eugenol and eugenyl acetate obtained by these methods and also by steam distillation and liquid solvent (Soxhlet) extraction are similar, but the yields of caryophyllene were lower for the methods using water. Received: 23 December 1998 / Revised: 26 March 1999 / Accepted: 31 March 1999     

A comparison of the extraction of clove buds with supercritical carbon dioxide and superheated water

Supercritical carbon dioxide and superheated water (subcritical water above 100 °C under pressure) have both been used to extract the buds of cloves (Syzygium aromaticum). The yields of eugenol and eugenyl acetate obtained by these methods and also by steam distillation and liquid solvent (Soxhlet) extraction are similar, but the yields of caryophyllene were lower for the methods using water. Received: 23 December 1998 / Revised: 26 March 1999 / Accepted: 31 March 1999     

Enhanced cage effects in supercritical fluid solvents. the behavior of diffusive and geminate caged-pairs in supercritical carbon dioxide

The behavior of geminate and diffusive radical caged-pairs arising from the photolysis of dicumyl ketone in conventional and supercritical carbon dioxide (SC--CO(2)) solvents has been examined. The results suggest that locally enhanced solvent density about a solute (solvent/solute clustering) can lead to an enhanced cage effect near the critical pressure in supercritical fluid solvents. This enhanced cage effect is similar in magnitude for both diffusive and geminate caged-pairs.     

Photoluminescent phenylated polyfluorenes synthesized in an organic solvent and supercritical carbon dioxide

A number of new phenylated polyfluorenes with blue emission are synthesized via the Diels-Alder reaction in chloronaphthalene and supercritical carbon dioxide. It is shown that these polymers are thermally stable. A comparative analysis of their properties shows that a ??green?? solvent is a suitable alternative to organic solvents for obtaining phenyl-substituted polyfluorenes via the Diels-Alder reaction.     

Measurements for the solid solubilities of antipyrine, 4-aminoantipyrine and 4-dimethylaminoantipyrine in supercritical carbon dioxide

The solid solubilities of three active pharmaceutical ingredients (APIs) of antipyrine, 4-aminoantipyrine and 4-dimethylaminoantipyrine in supercritical carbon dioxide were measured by a semi-flow apparatus. The experiments were taken at 308.2, 318.2 and 328.2 K. The pressure range was from 10 to 22 MPa. These experimental results were correlated by the semi-empirical models of Mendez–Santiago–Teja and Chrastil. A solution model was also employed to fit the measured data. The average absolute relative deviation in solid solubility from semi-empirical models was 4–6%, and that from the solution model was 5–8%. The measured data satisfied the self-consistency test, and the parameters in the semi-empirical models are feasible for data extrapolation.     

Extraction of brominated flame retardants from polymeric waste material using different solvents and supercritical carbon dioxide

Different procedures were examined to extract pure and high concentrations of a series of brominated flame retardants from various polymer materials. These procedures include supercritical carbon dioxide (sc-CO₂), modified sc-CO₂, solvent and soxhlet extraction. Extraction with sc-CO₂ gave low extraction efficiencies (between 6 and 20%) probably due to the low pressure of sc-CO₂ used. The use of toluene, acetonitrile and THF as modifier in sc-CO₂ raised the extraction efficiencies for many flame retardants. High extraction efficiencies were achieved for tetrabromobisphenol A (TBBPA), TBBPA-bis-(2,3-dibromopropylether) (TBBPA-dbp), TBBPA-carbonatoligomer (TBBPA-co) and decabromodiphenylether (DECA) (between 93 and 100%) by using 1-propanol as solvent during soxhlet extraction. Toluene instead of 1-propanol was used where insufficient extraction of the flame retardant occurred. The materials (before and after extraction) were analysed with energy dispersive X-ray fluorescence analysis (EDXRF), high performance liquid chromatography with ultraviolet detection (HPLC/UV), gas chromatography/mass spectrometry (GC/MS) and infrared spectroscopy (IR) techniques. The properties of the extracted flame retardants such as TBBPA, TBBPA-dbp and 1,2-bis(tribromophenoxy)-ethane (TBPE) are in good agreement with those of standard reference materials.     

Partitioning effect of nitrogen catalyst into polymerizing particles on dispersion reversible chain transfer catalyzed polymerization (dispersion RTCP) of methyl methacrylate in supercritical carbon dioxide and organic solvents

Reversible chain transfer catalyzed polymerization (RTCP) in dispersion polymerization system (dispersion RTCP) of methyl methacrylate (MMA) was performed with N‐iodosuccimide (NIS) as a nitrogen catalyst in supercritical carbon dioxide (scCO₂). The solubility of NIS in scCO₂ can be controlled by tuning the pressure, and this led to promote NIS partitioning into polymerizing particles. As a result, the molecular weight distribution control was successfully improved by decreasing the NIS solubility in the medium by tuning the scCO₂ at a low pressure of 20 MPa. On the other hand, at the same NIS concentration, a solution RTCP of MMA in toluene as a homogeneous polymerization system did not proceed with a controlled/living manner. The importance of NIS partitioning into the polymerizing particles was also confirmed in hexane as well as scCO₂ medium. From these results, it was clarified that the NIS catalyst partitioning into the polymerizing particles as main polymerization loci is a key factor to control the molecular weight distribution in the dispersion RTCP of MMA in scCO₂. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 613–620     

Dry ice-originated supercritical and liquid carbon dioxide extraction of organic pollutants from environmental samples

Packed in a high-pressure vessel and under calculated conditions, dry ice can be used as a source of carbon dioxide for supercritical CO₂ extraction or liquid CO₂ of organic compounds from environmental samples. Coupled with a fluid modifier such as toluene, dry ice-originated supercritical CO₂ (Sc CO₂) achieves quantitative extraction of many volatile organic compounds (VOCs) and semivolatile organic compounds (SOCs) including polycyclic aromatic hydrocarbons (PAHs), n-alkanes, and polychlorinated biphenyls (PCBs) from solid matrices. Compared to contemporary manual or automated supercritical fluid extraction (SFE) technologies, this novel technique simplifies SFE to a minimum requirement by eliminating the need of a high-pressure pump and any electrical peripherals associated with it. This technique is highly suitable to analytical areas where sample preservation is essential but difficult in the sampling field, or where sample collection, sample preparation, and analysis are to be done in the field.     

Synthesis of fluorinated oligomers for supercritical carbon dioxide applications

Syntheses of various fluorine‐based surfactants, namely fluorinated‐segment‐containing block co‐oligomers, were achieved by the radical polymerization of mainly acrylate‐based monomers. These types of surfactants serve as stabilizers for supercritical carbon dioxide (scCO₂) media based applications, for which the effective solubilization of materials in the supercritical phase is generally not possible because of solubility problems faced when CO₂ is involved. Initially, a difunctional fluorinated initiator was synthesized in two steps. First, 4,4′‐azobis‐4‐cyanovaleric acid was chlorinated with SOCl₂, and then the product, 4,4′‐azobis‐4‐cyanovaleryl chloride, was reacted with a fluorinated alcohol to obtain the initiator for the polymerization reactions. The synthesized triblock co‐oligomers consisted of fluorinated side blocks and a hydrocarbon intermediate block. Efficient solubilization of the materials in scCO₂ was observed. It was experimentally shown that the solubility efficiency was affected by specific interactions between CO₂ and the oligomers, and these were determined by the nature and size of the inner block and by the chain length of the fluorinated side blocks in comparison with the inner block. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5312–5322, 2005     

High-pressure phase studies on fluid mixtures of low-volatile organic substances with supercritical carbon dioxide

Two high-pressure phase equilibrium cells working according to the analytical method in the temperature range 300 to 450 K and up to 200 MPa have been developed. In the first cell p,T,x,y equilibrium data can be determined by sampling and GC analysis. With this cell the gas-liquid phase behaviour of the ternary systems carbon dioxide + tridecane + hexadecane and carbon dioxide + tridecane + 1-hexadecanol were determined at 423.4 K and between 8 and 35 MPa. For the second apparatus a spectroscopic high-pressure cell fitted with two pairs of sapphire windows was developed. Molar absorptivities are obtained from calibration runs in the homogeneous region. Gasliquid phase equilibria in the system decane + CO₂ were investigated from 342.8 to 400.2 K and between 10 and 20 MPa; here absorption data were measured in the NIR region.     

Efficient catalyst-free chemical fixation of carbon dioxide into 2-oxazolidinones under supercritical condition

4-Methylene-1,3-oxazolidin-2-ones can be synthesized from propargylic alcohols,primary amines and carbon dioxide under supercritical condition in the absence of any additional catalyst and solvent.Various propargylic alcohols and primary amines were examined.